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Mineralocorticoid receptor in adipocytes and macrophages: A promising target to fight metabolic syndrome
... Mineralocorticoid receptors are also found in non-epithelial tissues such as the retina, brain, myocardium, vascular smooth muscle cells, macrophages, fibroblasts, and adpiocytes. [46][47][48][49][50] Aldosterone's effects are therefore wide spread, extending well beyond its role as a "renal hormone." Specifically, aldosterone is thought to mediate inflammation and affect energy metabolism in non-epithelial tissues. ...
... Specifically, aldosterone is thought to mediate inflammation and affect energy metabolism in non-epithelial tissues. 50 The unbound MR is primarily located in the cytoplasm, and when bound by ligand, it is shuttled to the nucleus where it acts as a transcription factor. 51 Some actions of aldosterone are non-genomic and occur relatively rapidly. ...
Chronic activation of the renin‐angiotensin‐aldosterone system (RAAS) promotes and perpetuates the syndromes of congestive heart failure, systemic hypertension, and chronic kidney disease. Excessive circulating and tissue angiotensin II (AngII) and aldosterone levels lead to a pro‐fibrotic, ‐inflammatory, and ‐hypertrophic milieu that causes remodeling and dysfunction in cardiovascular and renal tissues. Understanding of the role of the RAAS in this abnormal pathologic remodeling has grown over the past few decades and numerous medical therapies aimed at suppressing the RAAS have been developed. Despite this, morbidity from these diseases remains high. Continued investigation into the complexities of the RAAS should help clinicians modulate (suppress or enhance) components of this system and improve quality of life and survival. This review focuses on updates in our understanding of the RAAS and the pathophysiology of AngII and aldosterone excess, reviewing what is known about its suppression in cardiovascular and renal diseases, especially in the cat and dog.
... Increasing evidence shows a link between obesity, hypertension and hyperaldosteronism, and clinical studies have established a positive correlation between visceral obesity, CMS or BMI and plasma levels of aldosterone (Goodfriend et al. 1999, Fallo et al. 2006, Ingelsson et al. 2007, Rossi et al. 2008. Aldosterone mediates deleterious effects in adipose tissue through genomic and non-genomic pathways, leading not only to alteration of glucose metabolism and insulin sensitivity (Luo et al. 2013, Feliciano Pereira et al. 2014, Luther 2014, Marzolla et al. 2014, Urbanet et al. 2015, but also to inflammation, oxidative stress, endothelial dysfunction and vasoconstriction, as adipose tissue is intimately associated with structural and physiological functions of the vasculature (Guo et al. 2008, Tirosh et al. 2010, Nguyen Dinh Cat et al. 2016. ...
... One of the possible explanation would be an intrinsic difference between species, but this issue is addressed as treatment with the MR antagonist drospirenone inhibited adipogenesis in human pre-adipocytes (Caprio et al. 2011). Taken altogether, these studies suggest that GR and MR could be implicated at different stages of differentiation and play a specific role depending on the fat depot or on the health status of the patient (obese vs lean) (Armani et al. 2014). Further studies are necessary to identify the precise roles of each corticosteroid receptors and to better understand the interactions between MR and GR in the regulation of adipogenesis. ...
Obesity is a multifaceted, chronic, low-grade inflammation disease characterized by excess accumulation of dysfunctional adipose tissue. It is often associated with the development of cardiovascular disorders, insulin resistance and diabetes. Under pathological conditions like in obesity, adipose tissue secretes bioactive molecules called "adipokines", including cytokines, hormones and reactive oxygen species (ROS). There is evidence suggesting that oxidative stress, in particular the ROS imbalance in adipose tissue, may be the mechanistic link between obesity and its associated cardiovascular and metabolic complications. Mitochondria in adipose tissue are an important source of ROS and their dysfunction contributes to the pathogenesis of obesity-related type 2 diabetes. Mitochondrial function is regulated by several factors in order to preserve mitochondria integrity and dynamics. Moreover, the renin-angiotensin-aldosterone system is over-activated in obesity. In this review, we focus on the pathophysiological role of the mineralocorticoid receptor in the adipose tissue and its contribution to obesity-associated metabolic and cardiovascular complications. More specifically, we discuss whether dysregulation of the mineralocorticoid system within the adipose tissue may be the upstream mechanism and one of the early events in the development of obesity, via induction of oxidative stress and mitochondrial dysfunction, thus impacting on systemic metabolism and the cardiovascular system.
... Recent studies have also demonstrated the implication of MR from immune cells in these pathologies [18,[38][39][40]. Mϕ mediate inflammation contributing to endorgan damage [41]. It is well establish that MR is expressed in Mϕ [41]. ...
... Mϕ mediate inflammation contributing to endorgan damage [41]. It is well establish that MR is expressed in Mϕ [41]. Interestingly, it has been demonstrated that MR signaling regulates Mϕ function since its depletion from Mϕ protects against cardiac fibrosis and hypertension induced by deoxycorticosterone/salt in mice [38]. ...
Immune system activation is involved in cardiovascular (CV) inflammation and fibrosis, following activation of the mineralocorticoid receptor (MR). We previously showed that Neutrophil Gelatinase-Associated Lipocalin (NGAL) is a novel target of MR signaling in CV tissue and plays a critical role in aldosterone/MR-dependent hypertension and fibrosis. We hypothesized that the production of NGAL by immune cells may play an important part in the mediation of these deleterious mineralocorticoid-induced effects. We analyzed the effect of aldosterone on immune cell recruitment and NGAL expression in vivo. We then studied the role of NGAL produced by immune cells in aldosterone-mediated cardiac inflammation and remodeling using mice depleted for NGAL in their immune cells by bone marrow transplantation and subjected to mineralocorticoid challenge NAS (Nephrectomy, Aldosterone 200 μg/kg/day, Salt 1%). NAS treatment induced the recruitment of various immune cell populations to lymph nodes (granulocytes, B lymphocytes, activated CD8⁺ T lymphocytes) and the induction of NGAL expression in macrophages, dendritic cells, and PBMCs. Mice depleted for NGAL in their immune cells were protected against NAS-induced cardiac remodeling and inflammation.
We conclude that NGAL produced by immune cells plays a pivotal role in cardiac damage under mineralocorticoid excess. Our data further stressed a pathogenic role of NGAL in cardiac damages, besides its relevance as a biomarker of renal injury.
... might play a role in inflammation. Furthermore, MR blockade in macrophages suppresses the pro-inflammatory M1 phenotype, with beneficial effects in terms of attenuated fibrotic responses and protection from high blood pressure 3 . Studies have demonstrated that aldosterone affects the expression of inflammatory mediators as well as the final fibrosis process, given that hypertension induced by aldosterone causes cardiac inflammation with remodeling of the right and left ventricles [4][5][6] . ...
The immunotropic effects of aldosterone might play a role in COVID-19, as SARS-CoV-2 reportedly uses angiotensin-converting enzyme 2 receptors as an entry point into cells. Aldosterone function is closely linked to its action on mineralocorticoid receptors in kidneys; it increases the renal retention of sodium and the excretion of potassium, which increases blood pressure. Despite the large number of studies examining the effect of Ang-II and its blockers on the course of COVID-19 infection, there is still uncertainty about the role of aldosterone. The aim of the study was to assess the correlation of aldosterone, urea, creatinine, C-reactive protein (CRP), and procalcitonin (PCT) levels with 28 days of mortality in patients treated for COVID19 in an intensive care unit (ICU). This cross-selection study involved 115 adult patients who were divided into two groups: those who died within a 28-day period (n = 82) and those who survived (n = 33). The correlation of aldosterone, urea, creatinine, C-reactive protein (CRP), and procalcitonin (PCT) levels with 28 days of mortality in patients treated for COVID-19 were performed. The patients’ age, sex, scores from the APACHE II, SAPS II, and SOFA scales and comorbidities like HA, IHD and DM were also analyzed. Remarkably, the individuals who survived for 28 days were of significantly lower mean age and achieved notably lower scores on the APACHE II, SAPS II, and SOFA assessment scales. Statistically significantly higher CRP levels were observed on days 3, 5, and 7 in individuals who survived for 28 days. Creatinine levels in the same group were also statistically significantly lower on days 1, 3, and 5 than those of individuals who died within 28 days. The investigation employed both univariate and multivariate Cox proportional hazard regression models to explore factors related to mortality. In the univariate analysis, variables with a p value of less than 0.50 were included in the multivariate model. Age, APACHE II, SAPS II, and SOFA demonstrated significance in univariate analysis and were considered to be associated with mortality. The outcomes of the multivariate analysis indicated that age (HR = 1.03, p = 0.033) served as a robust predictor of mortality in the entire study population. In conclusion the plasma aldosterone level is not associated with ICU mortality in patients with COVID-19. Other factors, including the patient’s age, creatinine or CRP contribute to the severity and prognosis of the disease. This study was retrospectively registered in the Australian New Zealand Clinical Trials Registry (ANZCTR) with registration no. ACTRN12621001300864 (27/09/2021: https://www.anzctr.org.au/Trial/Registration/TrialReview.aspx?id=382563&isReview=true).
... Поэтому эффекты ALD широко распространены, выходя далеко за рамки его роли в качестве «почечного гормона». В частности, считается, что ALD опосредует воспаление и влияет на энергетический обмен в неэпителиальных тканях [11]. ...
The angiotensin-converting enzyme (ACE) was discovered in 1956 and has been actively studied to date. It has a unique structure of two homologous domains, each containing a catalytic zinc ion. Domains have different substrate specificity. In terms of function, ACE is a zinc metallopeptidase widely present on the surface of endothelial and epithelial cells. The gene encoding ACE is located on the long arm of chromosome 17 (17q23) and is 21 kb long, including 26 exons and 25 introns. The structure of ACE may be the result of an ancient gene duplication that occurred approximately 700 million years ago. The main function of ACE is the conversion of AngI to the vasoconstrictor AngII, which is the main active product. In addition, ACE metabolizes bradykinin, which is a potent vasodilator. ACE is involved in the metabolism of other angiotensins, in particular Ang(1–7), forming, together with ACE 2 and other components of the renin-angiotensin-aldosterone system (RAAS), a complex balanced system for maintaining blood pressure, water and electrolyte balance, and many other components of systemic, tissue and cellular homeostasis that have not yet been fully studied. More data are accumulating confirming the role of ACE for the renal development, early hematopoiesis, normal male fertility, erythropoiesis, myelopoiesis. ACE plays important roles in the immune response, intracellular signaling.
... MR expression in the periphery is predominant in epithelial tissues such as distal parts of the nephron, liver, distal colon, airway, sweat glands, inner ear, etc. (Gorini et al., 2019). in epithelial tissues, where cortisol has a low affinity for MR, the conversion of cortisol to corticosterone can be accomplished by 11β-HSD2, thus ensuring that aldosterone, the main physiological ligand in epithelial tissues, can bind to MR to exert its proper physiological effects (edwards et al., 1988). in addition, many non-epithelial tissues such as cardiovascular, skin, placenta, ovary and testis, adipose tissue and the brain have been identified as expressing MR (Cole & Young, 2017). in contrast to epithelial tissues, the expression of 11β-HSD2 is almost absent or relatively low in many of these tissues. Thus, glucocorticoids become the main ligands for MR in most non-epithelial tissues (Marzolla et al., 2014). Differences in the tissue distribution of MR and GR were also related to receptor selectivity, and MR and GR are expressed at varying amounts on various cell types. ...
Stress is a normal response to situational pressures or demands. Exposure to stress activates the hypothalamic-pituitary-adrenal (HPA) axis and leads to the release of corticosteroids, which act in the brain via two distinct receptors: mineralocorticoid receptors (MR) and glucocorticoid receptors (GR). Persistent HPA axis overactivation or dysregulation can disrupt an individual’s homeostasis, thereby contributing to an increased risk for mental illness. On the other hand, successful coping with stressful events involves adaptive and cognitive processes in the brain that render individuals more resilient to similar stressors in the future. Here we review the role of the MR in these processes, starting with an overview of the physiological structure, ligand binding, and expression of MR, and further summarizing its role in the brain, its relevance to psychiatric disorders, and related rodent studies. Given the central role of MR in cognitive and emotional functioning, and its importance as a target for promoting resilience, future research should investigate how MR modulation can be used to alleviate disturbances in emotion and behavior, as well as cognitive impairment, in patients with stress-related psychiatric disorders.
... This may have potential therapeutic implications, suggesting a possible role of mineralocorticoid receptor antagonists (MRAs), such as spironolactone, eplerenone, canrenone, and potassium canrenoate in obese patients. Often adopted for the treatment of arterial hypertension or heart failure, these drugs could be effective in ameliorating metabolic parameters in patients with obesity [24][25][26]. ...
The mineralocorticoid receptor (MR) acts as an essential regulator of blood pressure, volume status, and electrolyte balance. However, in recent decades, a growing body of evidence has suggested that MR may also have a role in mediating pro-inflammatory, pro-oxidative, and pro-fibrotic changes in several target organs, including the adipose tissue. The finding that MR is overexpressed in the adipose tissue of patients with obesity has led to the hypothesis that this receptor can contribute to adipokine dysregulation and low-grade chronic inflammation, alterations that are linked to the development of obesity-related metabolic and cardiovascular complications. Moreover, several studies in animal models have investigated the role of MR antagonists (MRAs) in preventing the metabolic alterations observed in obesity. In the present review we will focus on the potential mechanisms by which MR activation can contribute to adipose tissue dysfunction in obesity and on the possible beneficial effects of MRAs in this setting.
... However, the MR is also expressed in non-epithelial cells such as neurons, adipocytes, macrophages, fibroblasts, endothelial cells, and vascular smooth muscle cells. Here, MR functions are heterogeneous, and include development and differentiation as well as inflammatory response and stress adaptation [3][4][5]. Next to its important homeostatic function, inappropriate activation of the MR can also lead to pathological effects. ...
The mineralocorticoid receptor (MR) is a member of the steroid receptor family and acts as a ligand-dependent transcription factor. In addition to its classical effects on water and electrolyte balance, its involvement in the pathogenesis of cardiovascular and renal diseases has been the subject of research for several years. The molecular basis of the latter has not been fully elucidated, but an isolated increase in the concentration of the MR ligand aldosterone or MR expression does not suffice to explain long-term pathologic actions of the receptor. Several studies suggest that MR activity and signal transduction are modulated by the surrounding microenvironment, which therefore plays an important role in MR pathophysiological effects. Local changes in micromilieu, including hypoxia, ischemia/reperfusion, inflammation, radical stress, and aberrant salt or glucose concentrations affect MR activation and therefore may influence the probability of unphysiological MR actions. The surrounding micromilieu may modulate genomic MR activity either by causing changes in MR expression or MR activity; for example, by inducing posttranslational modifications of the MR or novel interaction with coregulators, DNA-binding sites, or non-classical pathways. This should be considered when developing treatment options and strategies for prevention of MR-associated diseases.
... Acting via the mineralocorticoid receptor (MR), aldosterone modulates the expression of ion channels, pumps and exchangers in epithelial tissues (kidney, colon and salivary and sweat glands). This ultimately leads to an increase in transepithelial Na + and water reabsorption and K + excretion [39]. Mineralocorticoid receptors are also found in non-epithelial tissues such as the retina, brain, myocardium, vascular smooth muscle cells, macrophages, fibroblasts and adipocytes. ...
In March 2020, coronavirus disease 2019 (COVID-19) caused by SARS-CoV-2 was declared a global pandemic by the World Health Organization (WHO). The clinical course of the disease is unpredictable but may lead to severe acute respiratory infection (SARI) and pneumonia leading to acute respiratory distress syndrome (ARDS). It has been shown that pulmonary fibrosis may be one of the major long-term complications of COVID-19. In animal models, the use of spironolactone was proven to be an important drug in the prevention of pulmonary fibrosis. Through its dual action as a mineralocorticoid receptor (MR) antagonist and an androgenic inhibitor, spironolactone can provide significant benefits concerning COVID-19 infection. The primary effect of spironolactone in reducing pulmonary edema may also be beneficial in COVID-19 ARDS. Spironolactone is a well-known, widely used and safe anti-hypertensive and antiandrogenic medication. It has potassium-sparing diuretic action by antagonizing mineralocorticoid receptors (MRs). Spironolactone and potassium canrenoate, exerting combined pleiotropic action, may provide a therapeutic benefit to patients with COVID-19 pneumonia through antiandrogen, MR blocking, antifibrotic and anti-hyperinflammatory action. It has been proposed that spironolactone may prevent acute lung injury in COVID-19 infection due to its pleiotropic effects with favorable renin–angiotensin–aldosterone system (RAAS) and ACE2 expression, reduction in transmembrane serine protease 2 (TMPRSS2) activity and antiandrogenic action, and therefore it may prove to act as additional protection for patients at highest risk of severe pneumonia. Future prospective clinical trials are warranted to evaluate its therapeutic potential.
... A recent study reported that MR signaling was involved at multiple levels in the metabolic, inflammatory, and fibrotic pathways of nonalcoholic steatohepatitis and other manifestations of metabolic syndrome. 8 In several animal models of liver disease, including diet-induced nonalcoholic steatohepatitis, MR antagonist treatment reduced glucose and lipid metabolism, steatosis, and inflammation and had a robust antifibrotic effect. 9e11 There is evidence of the efficacy of MR antagonists in the treatment of these various types of diseases, and of their utility in combination with various other drugs. ...
Purpose
To characterize the clinical relevance of in vitro drug–drug interaction findings with apararenone (MT-3995), the effects of apararenone on the sensitive substrates of cytochrome P450 3A4 (midazolam) and 2C9 (warfarin), and P-glycoprotein (digoxin), were assessed through a series of studies conducted in healthy volunteers.
Methods
Three studies were conducted in 56 healthy adults. Study 1 investigated the effects of the administration of apararenone with midazolam; apararenone was administered on days 2 (320 mg) and days 3–15 (20 mg/d), and midazolam 2 mg, on days 1 and 15. Study 2 investigated the effects of the administration of apararenone with warfarin; apararenone was administered on days 8–11 (40 mg/d) and days 12–27 (10 mg/d), and warfarin 25 mg, on days 1 and 21. Study 3 assessed the effects of the administration of apararenone with digoxin; apararenone was administered on days 11 (160 mg) and days 12–28 (10 mg/d), and digoxin 0.5 mg, on days 1 and 24. Pharmacokinetic parameters included Cmax, AUC0–t, and AUC0–∞. The safety profile was evaluated based on adverse events from spontaneous reports and clinical findings.
Findings
After the administration of midazolam together with apararenone, compared with midazolam alone, the midazolam ± apararenone treatment ratios (90% CIs) of the geometric least squares (LS) mean Cmax, AUC0–t, and AUC0–∞ values were 1.263 (1.147–1.392), 1.342 (1.220–1.477), and 1.370 (1.225–1.534), respectively. After the administration of warfarin ± apararenone, the R-warfarin ± apararenone treatment ratios (90% CIs) of the geometric LS mean Cmax, AUC0–t, and AUC0–∞ values were 1.008 (0.934–1.089), 1.078 (1.029–1.129), and 1.110 (1.056–1.166). Corresponding values for S-warfarin were 1.025 (0.941–1.117), 1.024 (0.979–1.071), and 1.031 (0.984–1.080). After the administration of digoxin ± apararenone, the digoxin ± apararenone treatment ratios (90% CIs) of the geometric LS mean Cmax, AUC0–t, and AUC0–∞ values were 0.929 (0.789–1.093), 0.894 (0.797–1.033), and 0.887 (0.805–0.977), respectively. Treatment-emergent adverse events were generally of mild to moderate intensity, and no serious adverse events of any kind were reported.
Implications
The findings from this analysis of data from healthy volunteers suggest minimal risk for potential drug–drug interactions between apararenone and other drugs that are likely to be used concurrently in patients. ClinicalTrials.gov identifier: NCT02531568.
... In another study, cold exposure produced a translocation in transporter type 4 (GLUT4) and increased glucose uptake in skeletal muscle [247]. Adipose-derived stem cells can be induced to differentiate to beige adipocytes in many ways, and the results of a large amount of research in this area suggest that a substantial number of potential drugs will become available in the next few years [248][249][250][251][252][253][254]. Although many effects remains to be clarified, it is evident that the increase in the activity of beige adipocytes is a consistent mechanism to increase glucose metabolism, supporting its role in treating obesity and related metabolic disorders in humans, especially for type 2 diabetes mellitus [255], which has two key pathophysiological components: peripheral resistance to the action of insulin especially in muscular cells and adipocytes and reduction in insulin secretion in β-pancreatic cells. ...
Adipose tissue is the largest endocrine organ in humans and has an important influence on many physiological processes throughout life. An increasing number of studies have described the different phenotypic characteristics of fat cells in adults. Perhaps one of the most important properties of fat cells is their ability to adapt to different environmental and nutritional conditions. Hypothalamic neural circuits receive peripheral signals from temperature, physical activity or nutrients and stimulate the metabolism of white fat cells. During this process, changes in lipid inclusion occur, and the number of mitochondria increases, giving these cells functional properties similar to those of brown fat cells. Recently, beige fat cells have been studied for their potential role in the regulation of obesity and insulin resistance. In this context, it is important to understand the embryonic origin of beige adipocytes, the response of adipocyte to environmental changes or modifications within the body and their ability to transdifferentiate to elucidate the roles of these cells for their potential use in therapeutic strategies for obesity and metabolic diseases. In this review, we discuss the origins of the different fat cells and the possible therapeutic properties of beige fat cells.
... This effect can be accomplished in different ways by modulating specific transcription factors. The large number of investigations in this area suggests a high possibility that numerous potential drugs will be tested in the upcoming years [149][150][151][152][153][154][155] . Despite the fact that the mechanisms by which these effects are produced have not been sufficiently elucidated, the use of modulation of beige adipocytes in adipose cell progenitors in adults is clearly a therapeutic approach, especially for obesity and type 2 diabetes 156 . ...
Adipose tissue is the most abundant endocrine organ in humans with an important influence on many events throughout life. Many studies that highlight the different phenotypic characteristics of fat cells in adults are becoming more frequent. Perhaps, one of the most important properties of fat cells is their flexibility to adapt to different environmental and nutritional conditions. White adipocytes can receive hormonal stimuli from other tissues and differentiate into cells with a greater thermogenic potential. In this process, lipid inclusion changes and the number of mito-chondria increases, leading to functional characteristics similar to those of brown adipocytes. Recently, beige fat cells have been studied in the attempt to elucidate their role in the regulation of obesity and insulin resistance. Therefore, understanding the beige adipocyte embryonic origin and the ability of these cells to transdifferentiate is a major research challenge, with the aim of elucidating the role of these cells as a possible therapeutic strategy for obesity and metabolic diseases. In this manuscript, we will focus on the origins of the different fat cells and the possible therapeutic properties of beige fat cells.
... Significantly, analysis of terminally differentiated 3T3-L1 adipocytes treated with aldosterone and a MR antagonist, demonstrated that the MR modulates the expression of proinflammatory adipokines (Tnfa, IL6, and Mcp1), peroxisome proliferator-activated receptor gamma (PPARg), adiponectin and enzymes involved in reactive oxygen species (ROS) production, suggesting that MR function has a fundamental role in modulating the activity of mature adipocytes. Furthermore, MR blockade has also been shown to reduce ROS levels and inflammation in mature adipocytes (6,10). ...
Introduction: Mineralocorticoid receptor (MR) activation within adipose tissue, triggers inflammation and metabolic syndrome development. The pharmacological blockade of MR provides beneficial effects for adipose tissue. Our study evaluates the impact of eplerenone implantation upon obesity. Experimental approach: A group of mice with implanted placebo pellets were fed using two types of diet, a normal (ND) or a high fat (HFD) diet. Additionally, a group of mice fed HFD were implanted with an eplerenone pellet. Metabolic and biochemical parameters were assessed in each animal group. Adipocyte size and lipid accumulation were investigated in the liver and adipose tissue. We evaluated the components of renin-angiotensin-aldosterone system (RAAS) locally in adipose tissue. Key results: Eplerenone reduced HFD-induced body weight gain, fasting glucose levels, fat accumulation, HFD-induced adipocyte size and liver lipid accumulation and improved glucose tolerance. In the adipose tissue, HFD significantly increased the mRNA levels of the RAAS molecules relative to the ND group. Eplerenone lowered RAAS mRNA levels, components of lipid metabolism and markers of inflammation in HFD-fed animals. Conclusion: MR antagonism with eplerenone diminishes insulin resistance that is related to obesity partly via a reduction of RAAS activation, inflammatory progression and cytokines induction. This suggests that eplerenone should be further studied as a therapeutic option for obesity and overweight.
... Thus, in vivo adipogenesis is likely regulated by GCs. In AT, active GC bioavailability is also affected by the enzyme 11beta-hydroxysteroid dehydrogenase type I (11b-HSD1) which converts cortisone to cortisol (in humans), and 11-dehydrocorticosterone to corticosterone (in rodents) [101]. ...
Over the past decade, several studies have shown that activity of extra-renal mineralocorticoid receptors (MR) regulates vascular tone, adipogenesis, adipose tissue function, and cardiomyocyte contraction. In mice, abnormal activation of MR in the vasculature and in adipose tissue favors the occurrence of several components of the metabolic syndrome (MetS), such as hypertension, obesity, and glucose intolerance. Accordingly, high levels of aldosterone are associated with obesity and MetS in humans, suggesting that altered activation of aldosterone-MR system in extra-renal tissues leads to profound metabolic dysfunctions. In this context, in addition to the classical indications for heart failure and hypertension, MR antagonists (MRAs) nowadays represent a promising approach to tackle cardiovascular and metabolic disorders occurring in the MetS.
... In the end of 1990th Pitt and coll. confirmed the importance of MR blockers to prevent cardiovascular complications and cerebrovascular accidents even in patients with normal values of Aldo (16,17) and several studies are evaluating a possible terapeuthic role of MR blockers to treat obesity and metabolic disorders (18). ...
Aldosterone is the main mineralocorticoid hormone, responsible of the regulation of fluid and electrolyte balance and blood pressure. It acts also as a pro-inflammatory factor responsible of an increased cardiovascular risk, independent from blood pressure values. After the discovery of mineralocorticoid receptor (MR) in mononuclear leukocytes, further studies supported its role in inflammatory and even autoimmune mechanisms underlying several diseases. In particular, recent studies reported a possible involvement of aldosterone in some gynecological conditions and diseases, characterized by inflammation, hypertension and increased cardio-metabolic risk, such as use of hormonal contraceptives, preeclampsia, polycystic ovary syndrome, uterine fibroids, and endometriosis. The aim of this mini-review is to report the possible involvement of aldosterone in all these gynecological conditions, suggesting different pathogenetic mechanisms and new target treatments of MR blockers for these diseases.
... Accordingly, MR antagonism upregulated the expression of some anti-inflammatory factors while downregulating the expression of proinflammatory cytokines in wound tissues. This is consistent with previous findings that showed the role of MR activation in various diseases involving chronic inflammation, including diabetes (Guo et al., 2008;Jaisser and Farman, 2015;Marzolla et al., 2014). Previous studies reported a central role of MR overactivation in sustained macrophage polarization after renal injury induced by ischemia-reperfusion ( Barrera-Chimal et al., 2018). ...
Skin ulcers resulting from impaired wound healing are a serious complication of diabetes. Unresolved inflammation, associated with the dysregulation of both the phenotype and function of macrophages, is involved in the poor healing of diabetic wounds. Here, we report that topical pharmacological inhibition of the mineralocorticoid receptor (MR) by canrenoate or MR small interfering RNA can resolve inflammation to improve delayed skin wound healing in diabetic mouse models; importantly, wounds from normal mice are unaffected. The beneficial effect of canrenoate is associated with an increased ratio of anti-inflammatory M2 macrophages to proinflammatory M1 macrophages in diabetic wounds. Furthermore, we show that MR blockade leads to downregulation of the MR target, LCN2, which may facilitate macrophage polarization toward the M2 phenotype and improve impaired angiogenesis in diabetic wounds. Indeed, diabetic LCN2-deficient mice showed improved wound healing associated with macrophage M2 polarization and angiogenesis. In addition, recombinant LCN2 protein prevented IL-4-induced macrophage switch from M1 to M2 phenotype. In conclusion, topical MR blockade accelerates skin wound healing in diabetic mice via LCN2 reduction, M2 macrophage polarization, prevention of inflammation, and induction of angiogenesis.
... In mammals, a regulatory role for MR has been described in both adipocyte tissue differentiation and adipose tissue inflammation (adipokine production); however, a role for MR-mediated adipogenesis during early development has not yet been described (Marzolla et al. 2012). While mice overexpressing MR were resistant to a high fat diet in vivo (Kuhn et al. 2014), there is clear evidence that MR has a primarily anabolic effect and promotes adipogenesis in mammals (reviewed by Marzolla et al. 2012Marzolla et al. , 2014Armani et al. 2014). This was also clearly evident in our study where MR activation led to the accumulation of TG, glycerol and cholesterol levels in zebrafish larvae postnatally (Fig. 2). ...
Key points
Glucocorticoids (GCs) either enhance or reduce obesity in mammals, but limited information exists on the role of corticosteroid receptors in mediating the effect of GCs on lipid metabolism during postnatal development.
Mineralocorticoid receptor (MR) activation leads to triglyceride (TG) accumulation post‐feeding, whereas glucocorticoid receptor (GR) activation reduces TG levels.
The TG profile was inversely related to the lipoprotein lipase (lpl) transcript abundance, and this gene was downregulated by MR activation.
Cortisol plays an important role in adipogenesis during postnatal development in zebrafish, and this includes gene/pathway‐specific signalling by GR, MR and GR/MR interactions.
Ubiquitous MR and GR knockout in zebrafish provides an excellent model to study the mode of action of GCs in regulating lipid metabolism.
Abstract
Glucocorticoids (GCs) act through two receptors, the mineralocorticoid receptor (MR) and the glucocorticoid receptor (GR), which differ in both their affinity to bind GCs and their function. As MR has 10‐fold higher affinity for GCs compared to GR, it has been postulated that MR activation occurs at basal levels, while stress levels of these steroid hormones activate GR signalling. There is a growing body of evidence that both these receptors are involved in GC‐mediated lipid metabolism. However, the role of GCs in lipogenesis and lipolysis is controversial, as these steroids appear to both enhance and reduce obesity. As lipid synthesis is a critical part of early development, we hypothesized that both MR and GR contribute to lipid regulation by GCs during postnatal growth. Using MR and GR knockout zebrafish, we demonstrate that MR activation, but not GR activation, is involved in triglyceride (TG) accumulation during the larval development post feeding. Lack of MRs did not affect the gene expression of fatty acid synthase (fas), or acyl‐CoA:diacylglycerol acyltransferase 2 (dgat2), but increased lipoprotein lipase (lpl) transcript abundance. Activation of GR with exogenous cortisol decreased TG levels and increased lpl mRNA levels, but these responses require the presence of MR. Larval transcriptome revealed that MR was the primary regulator of genes involved in lipid synthesis, while GR activation favoured lipid catabolism. Our results underscore a key role for MR activation in mediating postnatal lipid accumulation, as well as cooperatively regulating GR‐mediated lipolysis during postnatal stress.
... While the MR is typically activated by aldosterone, it has equal affinity for both cortisol and aldosterone (29). GCs exert their anti-inflammatory effects through the GR, while GC activation of the MR promotes release of pro-inflammatory cytokines from M1/metabolically activated macrophages in adipose tissue leading to downstream insulin resistance (30). Animals treated with MR antagonists have decreased expression of M1 markers and thus decreased pro-inflammatory cytokines (31,32). ...
Context
While glucocorticoids (GCs) have potent anti-inflammatory actions, patients with hypercortisolism due to Cushing’s disease (CD) have increased circulating pro-inflammatory cytokines that may contribute to their insulin resistance and cardiovascular disease. The mechanisms and tissues that account for the increased systemic inflammation in patients with CD are unknown.
Objective
To determine if chronic endogenous GC exposure due to CD is associated with adipose tissue (AT) inflammation in humans.
Design, Setting, Participants
Abdominal subcutaneous AT samples from 10 patients with active CD and 10 age, gender, and BMI-matched healthy subjects were assessed for macrophage infiltration and mRNA expression of pro-inflammatory cytokines.
Main Outcome Measure
Using immunohistochemistry, AT samples were analyzed for the expression of Vimentin, caspase, CD3, CD4, CD8, CD11c, CD20, CD31, CD56, CD68, and CD163. Quantitative PCR was used to assess the mRNA gene expression of arginase, CD11b, CD68, EMR-1, IL-6, IL-10, MCP-1, and TNF-α.
Results
Immunohistochemistry revealed higher mean percent infiltration of CD68+ macrophages and CD4+ T lymphocytes, increased mean area of CD11c+ M1 macrophages, higher number of CD11c+ crown-like structures, and decreased Vimentin in the AT of patients with active CD compared to controls. PCR revealed no differences in mRNA expression of any analyzed markers in patients with CD.
Conclusions
Chronic exposure to GCs due to CD increases the presence of AT macrophages, a hallmark of AT inflammation. Hence, AT inflammation may be the source of the systemic inflammation seen in CD, which in turn may contribute to the obesity, insulin resistance, and cardiovascular disease in these patients.
... Accordingly, in murine models of obesity MR pharmacological blockade has markedly reduced the total number of hypertrophic adipocytes, thus affecting adipocyte secretory capacity. This change in adipocyte morphology was accompanied by a marked reduction in the levels of pro-inflammatory cytokines, along with a significant increase in adiponectin expression and suppression of macrophage infiltration in adipose tissue of such animals (Guo et al., 2008;Hirata et al., 2009;Hoppmann et al., 2010;Marzolla et al., 2014). Moreover, MR is also able to affect macrophages polarization. ...
Mineralocorticoid receptor (MR) has been recently identified in adipose tissue, where its excessive activation contributes to several metabolic derangements often observed in obesity and metabolic syndrome. Recent findings support the existence of a bidirectional cross-talk between adipose tissue and adrenal glands, contributing to obesity-related hyperaldosteronism and subsequent adipocyte MR excessive activation. In this regard, MR pharmacological blockade has led to prevention of weight gain and metabolic benefits in murine models of genetic or diet-induced obesity. However, there is still a lack of knowledge on the potential metabolic effects of MR antagonists in clinical settings. Hence, larger clinical studies are deemed necessary to clarify the role of MR antagonism in obesity and metabolic syndrome in humans.
... This review focuses on the role of vascular MR yet it should be noted that MR signaling in myeloid cells also impacts vascular inflammation and function and has recently been reviewed elsewhere. [18][19][20][21] Here, we summarize recent advances in our understanding of how MR activation in SMC and EC under conditions of vascular injury/ damage contributes to: (i) vascular tone, (ii) thrombosis, (iii) inflammation, and (iv) wound healing with fibrosis. It is concluded that while all of these processes could be lifesaving in the aftermath of an encounter with a saber-toothed cat, they become maladaptive in an environment where our most dangerous predator is our modern lifestyle ( Figure 1). ...
The mineralocorticoid receptor(MR) is indispensable for survival through its critical role in maintaining blood pressure in response to sodium scarcity or bleeding. Activation of MR by aldosterone in the kidney controls water and electrolyte homeostasis. This review summarizes recent advances in our understanding of MR function specifically in vascular endothelial and smooth muscle cells. The evolving roles for vascular MR are summarized in the areas of: (1)vascular tone regulation, (2)thrombosis; (3)inflammation; and (4)vascular remodeling/fibrosis. Synthesis of the data supports the concept that vascular MR does not contribute substantially to basal homeostasis but rather, MR is poised to be activated when the vasculature is damaged to coordinate blood pressure maintenance and wound healing. Specifically, MR activation in the vascular wall promotes vasoconstriction, inflammation, and exuberant vascular remodeling with fibrosis. A teleological model is proposed in which these functions of vascular MR may have provided a critical evolutionary survival advantage in the face of mechanical vascular injury with bleeding. However, modern lifestyle is characterized by physical inactivity and high fat/high sodium diet resulting in diffuse vascular damage. Under these modern conditions, diffuse, persistent and unregulated activation of vascular MR contributes to post-reproductive cardiovascular disease in growing populations with hypertension, obesity and advanced age.
... Cortisol and aldosterone display similar affinity and specificity for the MR [4]. In tissues with low 11β-hydroxysteroid dehydrogenase type 2 (11β-HSD2) activity, which converts cortisol to inactive cortisone, MR activation is mainly regulated by circulating glucocorticoids [5]. ...
The mineralocorticoid receptor (MR) was first identified as a blood pressure regulator, modulating renal sodium handling in response to its principal ligand aldosterone. The mineralocorticoid receptor is also expressed in many tissues other than the kidney, such as adipose tissue, heart and vasculature. Recent studies have shown that MR plays a relevant role in the control of cardiovascular and metabolic function, as well as in adipogenesis. Dysregulation of aldosterone/MR signaling represents an important cause of disease as high plasma levels of aldosterone are associated with hypertension, obesity and increased cardiovascular risk. Aldosterone displays powerful vascular effects and acts as a potent pro-fibrotic agent in cardiovascular remodeling. Mineralocorticoid receptor activation regulates genes involved in vascular and cardiac fibrosis, calcification and inflammation. This review focuses on the role of novel potential biomarkers related to aldosterone/MR system that could help identify cardiovascular and metabolic detrimental conditions, as a result of altered MR activation. Specifically, we discuss: (1) how MR signaling regulates the number and function of different subpopulations of circulating and intra-tissue immune cells; (2) the role of aldosterone/MR system in mediating cardiometabolic diseases induced by obesity; and (3) the role of several MR downstream molecules as novel potential biomarkers of cardiometabolic diseases, end-organ damage and rehabilitation outcome.
... In this context, MR antagonists have been shown to display complex and pleiotropic effects at the level of the adipose organ, which prevents white adipocyte hypertrophy (105), reduces inflammation (106), and restores a normal expression of adipocytokines (107). In addition, MR antagonists have well-established beneficial effects at the vascular and cardiac levels, which supports the notion that MR antagonists act at a multisystemic level, reducing blood pressure, tissue fibrosis, oxidative stress, insulin resistance, and adipose mass expansion, with potential global protective effects on MetS (108). Indirect evidence emerges from clinical studies that demonstrate that the prevalence of MetS is higher in primary aldosteronism than in essential hypertension (109), mostly for a detrimental effect of aldosterone excess on glucose metabolism and on adipose tissue physiology (110,111). ...
The metabolic syndrome (MetS) is defined as a cluster of 3 or more metabolic and cardiovascular risk factors and represents a serious problem for public health. Altered function of adipose tissue has a significant impact on whole-body metabolism and represents a key driver for the development of these metabolic derangements, collectively referred as to MetS. In particular, increased visceral and ectopic fat deposition play a major role in the development of insulin resistance and MetS. A large body of evidence demonstrates that aging and MetS share several metabolic alterations. Of importance, molecular pathways that regulate lifespan affect key processes of adipose tissue physiology, and transgenic mouse models with adipose-specific alterations in these pathways show derangements of adipose tissue and other metabolic features of MetS, which highlights a causal link between dysfunctional adipose tissue and deleterious effects on whole-body homeostasis. This review analyzes adipose tissue-specific dysfunctions, including metabolic alterations that are related to aging, that have a significant impact on the development of MetS.-Armani, A., Berry, A., Cirulli, F., Caprio, M. Molecular mechanisms underlying metabolic syndrome: the expanding role of the adipocyte.
... Physiological doses of 1,25(OH) 2 D 3 inhibit cytokine production by Th1 and Th17 cells in a VDR-dependent manner [26], whereas aldosterone can induce the priming to Th17 cells that are involved in autoimmune reaction [27]. Moreover, MR drives macrophage polarization towards a pro-inflammatory phenotype, as demonstrated by the fact that macrophage-specific MR genetic deletion and pharmacological antagonism in vitro are both able to induce a switch from a pro-inflammatory (M1) into an anti-inflammatory (M2) phenotype [28]. ...
Vitamin D is a fat-soluble vitamin and a steroid hormone that plays a central role in maintaining calcium-phosphorus and bone homeostasis in close interaction with parathyroid hormone, acting on its classical target tissues, namely, bone, kidney, intestine, and parathyroid glands. However, vitamin D endocrine system regulates several genes (about 3 % of the human genome) involved in cell differentiation, cell-cycle control, and cell function and exerts noncalcemic/pleiotropic effects on extraskeletal target tissues, such as immune and cardiovascular system, pancreatic endocrine cells, muscle, and adipose tissue. Several studies have demonstrated the role of vitamin D supplementation in the prevention/treatment of various autoimmune diseases and improvement of glucose metabolism, muscle, and adipose tissue function. Hence, this review aims to elucidate the effects of vitamin D on extraskeletal target tissues and to investigate the potential therapeutic benefit of vitamin D supplementation among a broad group of pathological conditions, especially with regard to metabolic and autoimmune diseases. In addition, we focused on the best daily intakes and serum levels of vitamin D required for extraskeletal benefits which, even if still controversial, appear to be higher than those widely accepted for skeletal effects.
... Deletion of the mineralocorticoid receptor protected against cardiac fibrosis after angiotensin II challenge or thoracic aortic constriction [17,18]. Aldosterone may directly influence a switch in macrophage polarization and the differentiation of monocytes into an inflammatory phenotype [19]. Besides monocytes, it seems that T-cells are also involved in aldosterone-induced microinflammation. ...
Aldosterone binds to the mineralocorticoid receptor and has an important regulatory role in body fluid and electrolyte balance. It also influences a variety of different cell functions such as oxidative stress, inflammation and organ fibrosis. The important role of the tissue-specific mineralocorticoid receptors in cardiovascular and renal injury has been shown in knockout animals and in clinical studies Mineralocorticoid receptor antagonists seem to exert their beneficial effects via anti-oxidative, anti-inflammatory and anti-fibrotic effects. Spironolactone and eplerenone were the first steroidal mineralocorticoid receptor antagonist. The established steroidal mineralocorticoid receptor antagonists show important therapeutic effects but are hampered by a variety of side effects, most importantly clinically significant hyperkaliemia. Selective non-steroidal mineralocorticoid receptor antagonists have been recently developed and demonstrate effectiveness in early clinical trials. Finereroneholds promise for the future application of this new mineralocorticoid receptor antagonist class in patients with chronic kidney disease since it has shown a significant reduction in UACR combined with a safety profile similar to that in the placebo group. However, further long-term studies investigating relevant clinical end points like reduction in cardiovascular or renal event rate are warranted.
... Although this is a common characteristic of GCs, there are many instances where GCs fail to function in this capacity. It is tempting to speculate that this failure may be due to activation of MR, which we now know promotes the expression of inflammatory cytokines in adipose tissue in response to both aldosterone and GCs like cortisol (44). Therefore, this mechanism may underlie several heretofore incongruous reports. ...
Glucocorticoid hormones (GCs) are important regulators of lipid metabolism, promoting lipolysis with acute treatment but lipogenesis with chronic exposure. Conventional wisdom posits that these disparate outcomes are mediated by the classical glucocorticoid receptor GRα. There is insufficient knowledge of the GC receptors (GRα and GRβ) in metabolic conditions such as obesity and diabetes. We present acute models of GC exposure that induce lipolysis, such as exercise, as well as chronic-excess models that cause obesity and lipid accumulation in the liver, such as hepatic steatosis. Alternative mechanisms are then proposed for the lipogenic actions of GCs, including induction of GC resistance by the GRβ isoform, and promotion of lipogenesis by GC activation of the mineralocorticoid receptor (MR). Finally, the potential involvement of chaperone proteins in the regulation of adipogenesis is considered. This re-evaluation may prove useful to future studies on the steroidal basis of adipogenesis and obesity.
... Experimental and clinical studies have highlighted aldosterone as a potential risk factor for diabetes and metabolic syndrome (MetS), through mechanisms at least partially independent of hypertension (Whaley-Connell et al., 2010). A new role for aldosterone/MR activation in adipose tissue has been highlighted (Zennaro et al., 2009;Marzolla et al., 2014;Gomez-Sanchez, 2015 ). MR is involved in the plasticity of white adipocyte and MR antagonism promotes "browning" of the white adipose tissue (i.e., increased presence of brown adipocytes within the white adipose tissue) through direct control of autophagy promoting increased metabolic activity of adipose depots . ...
The mineralocorticoid receptor (MR) and its ligand aldosterone are the principal modulators of hormone-regulated renal sodium reabsorption. In addition to the kidney, there are several other cells and organs expressing MR, in which its activation mediates pathologic changes, indicating potential therapeutic applications of pharmacological MR antagonism. Steroidal MR antagonists have been used for decades to fight hypertension and more recently heart failure. New therapeutic indications are now arising, and nonsteroidal MR antagonists are currently under development. This review is focused on nonclassic MR targets in cardiac, vascular, renal, metabolic, ocular, and cutaneous diseases. The MR, associated with other risk factors, is involved in organ fibrosis, inflammation, oxidative stress, and aging; for example, in the kidney and heart MR mediates hormonal tissue-specific ion channel regulation. Genetic and epigenetic modifications of MR expression/activity that have been documented in hypertension may also present significant risk factors in other diseases and be susceptible to MR antagonism. Excess mineralocorticoid signaling, mediated by aldosterone or glucocorticoids binding, now appears deleterious in the progression of pathologies that may lead to end-stage organ failure and could therefore benefit from the repositioning of pharmacological MR antagonists.
... Гипертензия у больных с ожирением во многом обусловлена повышенным уровнем альдостерона, что доказывается улучшением состояния пациентов при назначении блокаторов рецепторов альдостерона [16][17][18]. Кроме этого, у больных с повышенным уровнем альдостерона обнаружено снижение выброса инсулина и уменьшение чувствительности к нему [19]. Значительный интерес представляют результаты наблюдения за мужчинами 45-65 лет с ожирением, МС, стабильной ИБС, гипертонией II-III стадии и андрогенным дефицитом. ...
The objective of the present study was to elucidate the peculiar features of hormonal and metabolic imbalance in the young and adult men depending on the time of obesity manifestation, that is in adolescence or in the mature age. It was shown that over 40% of the young and adult men with obesity developed the well-apparent testosterone deficiency regardless of the time of obesity manifestation (Me 11.2-11.7 nmol/l). The overwhelming majority of the patients showing testosterone deficiency (60-80%) made up subgroups with metabolic syndrome (MS). The young and adult men in whom obesity began to develop in adolescence exhibited a more pronounced increase of fasting blood insulin level and HOMA-IR index than the men who developed obesity in the adulthood. Only in both young and adult men who began to develop obesity in adolescence, the blood aldosterone and cortisol levels were higher than in the age-matched normal subjects. These men, unlike those with obesity starting to develop in the adulthood, had the blood aldosterone and cortisol levels shifted to the upper limit of the reference values
... Conversely, aldosterone directly stimulates adipocyte expansion, increases leptin expression, and impairs adipocyte function in culture systems [7,8]. Decreased circulating adiponectin concentration is associated with insulin resistance, obesity, and endothelial dysfunction [9]. ...
Purpose of review:
This review will highlight recent developments in mineralocorticoid receptor research which impact aldosterone-associated vascular and cardiometabolic dysfunction.
Recent findings:
The mineralocorticoid receptor is also expressed in vascular smooth muscle and vascular endothelium, and contributes to vascular function and remodeling. Adipocyte-derived leptin stimulates aldosterone secretion, which may explain the observed link between obesity and hyperaldosteronism. Adipocyte mineralocorticoid receptor overexpression produces systemic changes consistent with metabolic syndrome. Ongoing studies with novel nonsteroidal mineralocorticoid receptor antagonists may provide a novel treatment for diabetic nephropathy and heart failure in patients with chronic kidney disease, with reduced risk of hyperkalemia.
Summary:
Ongoing research continues to demonstrate novel roles of the vascular and adipocyte mineralocorticoid receptor function, which may explain the beneficial metabolic and vascular benefits of mineralocorticoid receptor antagonists.
... Task1null mice displayed a peculiar phenotype of sex-and agedependent primary hyperaldosteronism confined to adult female mice (22), caused by a surprising defect in functional zonation of the adrenal glands, resulting in permanent mineralocorticoid hormone production, independent of salt intake, and high blood pressure (23). Besides its effect on salt balance, aldosterone is also known to exert a detrimental effect on adipose tissue function and the development of metabolic dysfunctions (24). As an example, aldosterone has been demonstrated, via the activation of its receptor [mineralocorticoid receptor (MR)], to promote adipogenesis (25) and adipocyte hypertrophy and inflammation (26) and to be related to glucose metabolism disturbance (27). ...
Brown adipose tissue (BAT) is essential for adaptive thermogenesis and dissipation of caloric excess through the activity of uncoupling protein (UCP)-1. BAT in humans is of great interest for the treatment of obesity and related diseases. In this study, the expression of Twik-related acid-sensitive K(+) channel (TASK)-1 [a pH-sensitive potassium channel encoded by the potassium channel, 2-pore domain, subfamily K, member 3 (Kcnk3) gene] correlated highly with Ucp1 expression in obese and cold-exposed mice. In addition, Task1-null mice, compared with their controls, became overweight, mainly because of an increase in white adipose tissue mass and BAT whitening. Task1(-/-)-mouse-derived brown adipocytes, compared with wild-type mouse-derived brown adipocytes, displayed an impaired β3-adrenergic receptor response that was characterized by a decrease in oxygen consumption, Ucp1 expression, and lipolysis. This phenotype was thought to be caused by an exacerbation of mineralocorticoid receptor (MR) signaling, given that it was mimicked by corticoids and reversed by an MR inhibitor. We concluded that the K(+) channel TASK1 controls the thermogenic activity in brown adipocytes through modulation of β-adrenergic receptor signaling.-Pisani, D. F., Beranger, G. E., Corinus, A., Giroud, M., Ghandour, R. A., Altirriba, J., Chambard, J.-C., Mazure, N. M., Bendahhou, S., Duranton, C., Michiels, J.-F., Frontini, A., Rohner-Jeanrenaud, F., Cinti, S., Christian, M., Barhanin, J., Amri, E.-Z. The K(+) channel TASK1 modulates β-adrenergic response in brown adipose tissue through the mineralocorticoid receptor pathway.
... Interestingly, mice with macrophage-specific deletion of the MR gene display increased M2 polarization and cardio-protective effects; however, the metabolic profile and adipose tissue function of these mice has still not been investigated (Rickard et al. 2009, Usher et al. 2010. Indeed, as discussed by Marzolla et al. (2014), regulation of macrophage polarization by MR might have a role in regulating development, inflammatory state and insulin sensitivity of adipose tissue. ...
In addition to the well-documented expression and activity of the mineralocorticoid receptor (MR) in the kidney, in the last decade research on MR has also revealed its important role in regulating functions of extrarenal tissues, including adipose tissue, where MR is involved in adipocyte fundamental processes such as differentiation, autophagy and adipokine secretion. MR expression is increased in adipose tissue of murine models of obesity and in obese human subjects, suggesting that over-activation of the mineralocorticoid signaling leads to dysfunctional adipocyte and associated metabolic disorders. Notably, pharmacological blockade of MR prevents metabolic dysfunctions observed in obese mice and suggests a potential therapeutic use of MR antagonists in the treatment of obesity and metabolic syndrome. However, the molecular pathways affected by MR blockade have been poorly investigated. This review summarizes the functions of MR in the adipocyte, discusses potential signaling pathways mediating MR action, and describes post-translational modifications regulating its activity.
The overactivation of the mineralocorticoid receptor (MR) promotes pathophysiological processes related to multiple physiological systems, including the heart, vasculature, adipose tissue and kidneys. The inhibition of the MR with classical MR antagonists (MRA) has successfully improved outcomes most evidently in heart failure. However, real and perceived risk of side effects and limited tolerability associated with classical MRA have represented barriers to implementing MRA in settings where they have been already proven efficacious (heart failure with reduced ejection fraction) and studying their potential role in settings where they might be beneficial but where risk of safety events is perceived to be higher (renal disease). Novel non-steroidal MRA have distinct properties that might translate into favourable clinical effects and better safety profiles as compared with MRA currently used in clinical practice. Randomised trials have shown benefits of non-steroidal MRA in a range of clinical contexts, including diabetic kidney disease, hypertension and heart failure. This review provides an overview of the literature on the systemic impact of MR overactivation across organ systems. Moreover, we summarise the evidence from preclinical studies and clinical trials that have set the stage for a potential new paradigm of MR antagonism.
Graphical Abstract
Fibrosis can occur in all major organs with relentless progress, ultimately leading to organ failure and potentially death. Unfortunately, current clinical treatments cannot prevent or reverse tissue fibrosis. Thus, new and effective antifibrotic therapeutics are urgently needed. In recent years, a growing body of research shows that macrophages are involved in fibrosis. Macrophages are highly heterogeneous, polarizing into different phenotypes. Some studies have found that regulating macrophage polarization can inhibit the development of inflammation and cancer. However, the exact mechanism of macrophage polarization in different tissue fibrosis has not been fully elucidated. This review will discuss the major signaling pathways relevant to macrophage-driven fibrosis and profibrotic macrophage polarization, the role of macrophage polarization in fibrosis of lung, kidney, liver, skin, and heart, potential therapeutics targets, and investigational drugs currently in development, and hopefully, provide a useful review for the future treatment of fibrosis.
Cancer is a chronic illness that directly or indirectly affects many individuals worldwide. As the second most commonly diagnosed cancer worldwide, breast cancer is a major public health concern affecting 1 in 8 women in their lifetime. Breast cancer, along with many other cancers, is typically treated using a combination of surgery, chemotherapy, radiation, and/or targeted therapies. Despite the beneficial effects of anti-cancer therapy in reducing overall patient morbidity and mortality, these treatments are associated with cardiotoxic side effects. Although the renin-angiotensin system (RAS) plays an important role in cardiovascular and renal homeostasis, RAS inhibitors (RASi) may be used in the treatment of cancer and chemotherapy mediated cardiotoxicity. The following chapter explores the role of various RASi as adjunctive treatment options for women with breast cancer and as future anti-cancer agents with a potential use in both the prevention and treatment of chemotherapy mediated cardiotoxicity.KeywordRenin-angiotensin-systemCancerBreast cancerChemotherapyAnthracyclineAngiotensin converting enzyme inhibitorCardiotoxicityCardio-Oncology
Introduction:
Diabetic kidney disease (DKD) represents a leading cause of morbidity and mortality in subjects with diabetes and develops in more than one third of diabetic patients. Steroidal mineralocorticoid receptor antagonists (MRAs - eplerenone and spironolactone) reduce mortality in patients with heart failure with reduced ejection fraction (HFrEF). However, in clinical practice the use of steroidal MRAs is limited by the significant risk of hyperkalaemia, especially in patients with impaired renal function. Finerenone, a novel nonsteroidal MRA, shows a higher selectivity and binding affinity for mineralocorticoid receptor (MR) compared to steroidal MRAs and has been shown to reduce chronic kidney disease (CKD) progression and cardiovascular mortality in patients with CKD and T2DM.
Areas covered:
This review summarizes the current evidence on efficacy and safety of finerenone in the treatment of patients with CKD and T2DM, and discusses its mechanisms of action investigated in preclinical studies.
Expert opinion:
Pharmacological properties of finerenone and its unique tissue distribution are responsible for a lower risk of hyperkalaemia. Therefore, finerenone represents a valuable therapeutic tool in patients with CKD/diabetic kidney disease (DKD). Recent studies have shown that finerenone delays the progression of CKD and reduce cardiovascular events in patients with DKD, highlighting its safety and efficacy in this high-risk population.
Background
Esaxerenone is a novel, non-steroidal selective mineralocorticoid receptor (Csige et al.) blocker. MR activation plays a crucial role in the development of cardiovascular and metabolic diseases. In this study, we investigated the effects of esaxerenone on various metabolic parameters in mice.
Materials and methods
Esaxerenone (3 mg/kg/day) was orally administered to high-fat diet (HFD)-fed male C57BL/6 mice. Mice fed a normal diet (ND) served as controls. Glucose and insulin tolerance, plasma lipid levels, and transaminase levels were assessed as metabolic parameters. Macrophage accumulation in the adipose tissue was evaluated using histological analysis. 3T3-L1 adipocytes, HepG2 cells, and C2C12 myotubes were used for in vitro experiments. Gene expression and insulin signaling were examined using quantitative RT-PCR and western blotting, respectively.
Results
HFD successfully induced insulin resistance compared with that in ND. Esaxerenone ameliorated insulin resistance (P < 0.05) without altering other metabolic parameters, such as the lipid profile. Esaxerenone administration tended to decrease plasma transaminase levels compared with those in the non-treated group. In the adipose tissue, esaxerenone decreased macrophage accumulation (P < 0.05) and increased the expression levels of adiponectin and PPARγ. Aldosterone significantly decreased the expression levels of PPARγ and adiponectin in 3T3-L1 adipocytes. Furthermore, aldosterone attenuated insulin-induced Akt phosphorylation in 3T3-L1 adipocytes, HepG2 cells, and C2C12 myotubes in a dose-dependent manner (P < 0.01). These effects were ameliorated by pretreatment with esaxerenone.
Conclusion
Esaxerenone ameliorated insulin resistance in HFD-fed mice. Reduction of inflammation and improvement in insulin signaling may underlie the beneficial effects of esaxerenone.
Obesity is an emerging non-communicable disease associated with chronic low-grade inflammation and oxidative stress, compounded by the development of many obesity-related diseases, such as cardiovascular disease, type 2 diabetes mellitus, and a range of cancers. Originally developed for the treatment of epilepsy in drug non-responder children, the ketogenic diet (KD) is being increasingly used in the treatment of many diseases, including obesity and obesity-related conditions. The KD is a dietary pattern characterized by high fat intake, moderate to low protein consumption, and very low carbohydrate intake (<50 g) that has proved to be an effective and weight-loss tool. In addition, it also appears to be a dietary intervention capable of improving the inflammatory state and oxidative stress in individuals with obesity by means of several mechanisms. The main activity of the KD has been linked to improving mitochondrial function and decreasing oxidative stress. β-hydroxybutyrate, the most studied ketone body, has been shown to reduce the production of reactive oxygen species, improving mitochondrial respiration. In addition, KDs exert anti-inflammatory activity through several mechanisms, e.g., by inhibiting activation of the nuclear factor kappa-light-chain-enhancer of activated B cells, and the inflammatory nucleotide-binding, leucine-rich-containing family, pyrin domain-containing-3, and inhibiting histone deacetylases. Given the rising interest in the topic, this review looks at the underlying anti-inflammatory and antioxidant mechanisms of KDs and their possible recruitment in the treatment of obesity and obesity-related disorders.
Since the discovery of renin in 1898 as a “pressor hormone” the renin-angiotensin aldosterone system (RAAS) has evolved into an increasingly complex, pleiotropic regulatory system affecting fluid and electrolyte balance; cell proliferation, hypertrophy, survival and death; cognition and neurodegeneration; promoting inflammation and fibrosis; exacerbating co-morbid diseases such as diabetes mellitus; and secondarily the actions of aldosterone, for which angiotensin peptides are the primary activator. The metabolic pathways by which the angiotensin peptides are produced and modified involve an ever-increasing number of enzymes, with an ever-increasing number of receptors mediating effects of the various angiotensin peptides, aldosterone; even those of renin and its precursor prorenin. Given the predominant pathophysiological actions of RAAS, several classes of drugs have been developed to counteract these morbidities; renin and angiotensin-converting enzyme (ACE or ACE-1) inhibitors, AT1 type angiotensin II receptor antagonists, and aldosterone receptor antagonists. With the discovery of multiple angiotensin receptor types came the recognition of a second, counterregulatory arm of the RAAS involving the AT2 type receptor, the enzyme ACE-2, Mas, and Mas-related G protein-coupled receptors (Mrgs). Drugs under development include AT2 receptor agonists, Mas agonists and ACE-2 activators. With the discovery that ACE-2 is the primary receptor by which SARS-CoV-1 and 2 infects cells, its role as a COVID-19 facilitator versus its role as a counterregulator of the RAAS, has initiated considerable scientific debate.
The molecular processes of immune responses in mucosal tissues such as fish gills under environmental stress are poorly understood. In the present study, pro-inflammatory response under hyposaline stress and its regulation by cortisol/corticosteroid receptors (CRs) in gill epithelial cells of the spotted scat Scatophagus argus were analyzed. The fish were transferred to freshwater for 6 days (144 hours) of acclimation. Following freshwater exposure, the cortisol concentration increased transiently before returning to the control level over time. mRNA expression of pro-inflammatory cytokines (TNF-a, IL-1b and IL-6) was stimulated by cortisol through CR signals at early stages of acclimation, but hyposaline stress inhibited their levels by the end of the experimental period. The transcriptional profile of anti-inflammatory cytokine IL-10 was quite different from these pro-inflammatory cytokines, and its value fluctuated within a narrow range during the experimental period. Full-length cDNAs of mineralocorticoid receptor (MR) and glucocorticoid receptor 1(GR1) (different kinds of CRs) were cloned from the gills. Our results showed that MR and GR displayed mutually antagonistic effects during hyposaline stress. MR responded quickly at early stages, and its expression decreased with the drop of cortisol concentration. By contrast, GR expression was maintained at high levels after the acclimation of freshwater exposure. The tight coordination of GR and MR helps to shape the effects of stress on the immune system, which in turn, regulates the stress response. Our results confirm the interaction between endocrine and cytokine messengers and a clear difference in the sensitivity of GR and MR during the hyposaline challenge in gill epithelial cells of the spotted scat Scatophagus argus.
Background
Dysregulation of glucocorticoid metabolism is known to be a causative factor of obesity. However, only a few studies have evaluated the enzymatic activities involved in glucocorticoid metabolism in the pediatric population.
Objective
To examine whether circulating glucocorticoid metabolites and their ratios reflecting the activities of metabolic enzyme are associated with obesity and body composition in girls.
Methods
A total of 227 girls aged 7–13 years (131 control, 45 overweight, 51 obese) were enrolled in this study. Serum concentrations of glucocorticoids (11-deoxycortisol, cortisol, tetrahydrocortisol [THF], allo-THF, allo-dihydrocortisol [allo-DHF], and cortisone) were evaluated by gas chromatography-mass spectrometry. Enzyme activities corresponding to the ratios of cortisol and cortisone to their respective precursors and metabolites were also assessed.
Results
Serum levels of allo-THF were significantly higher in obese girls compared with those in overweight and control girls (P = 0.018); however, concentrations of other cortisol metabolites were not significantly different between the groups studied. According to the severity of obesity, increasing trends in the metabolic ratios reflecting the activity of 11β-hydroxysteroid dehydrogenase type 1 (11β-HSD1) [(cortisol + allo-DHF + allo-THF + THF)/cortisone], relative 5α/5β-reductase [allo-THF/THF] activity, and 3α-HSD [allo-THF/allo-DHF] activity, were noted (P-for-trend <0.05). Body fat percentage and waist-to-height ratio positively correlated with the activities of 11β-HSD1 and 3α-HSD (P < 0.05). Following covariate control, girls with central obesity demonstrated significantly higher metabolic ratios reflecting 11β-HSD1, relative 5α/5β-reductase, and 3α-HSD activities (P < 0.05).
Conclusions
We found an altered glucocorticoid metabolism suggesting increased production of cortisol by 11β-HSD1 and increased metabolic clearance of cortisol catalyzed by 3α-HSD in girls with central obesity.
Progression of chronic kidney disease (CKD) to uremia is often accompanied by varying degrees of lung damage and this is also an important cause of death. Although there are many studies on the mechanism of lung injury, it is not clearly understood. Inflammatory macrophages may associated with fibrosis in the lungs. Here, we investigated the role of macrophage-myofibroblast transition (MMT) in lung fibrosis with unilateral ureteral obstruction (UUO) rats. We found that cells undergoing MMT accounted for an important part of the myofibroblast population, and correlated with lung fibrosis, MMT cells in lungs have a predominant M2 phenotype, and this process was attenuated after treatment with eplerenone. In conclusion, our studies provide a possible mechanism for UUO-induced kidney damage and lung injury, indicating the possibility of using eplerenone, a mineralocorticoid receptor blocker, to treat UUO to reduce kidney damage and protect lung function.
Context
Not all obese individuals develop cardiovascular disease (CVD). Hyperaldosteronism is suggested to cause inflammation and metabolic dysregulation, and might contribute to CVD development in obese individuals.
Objective
We aimed to investigate the association of aldosterone concentrations with inflammation, metabolic disturbances, and atherosclerosis in overweight and obese individuals. Additionally, we measured renin concentrations, to investigate if the observed effects reflected general activation of the renin-angiotensin-aldosterone system (RAAS).
Design
Cross-sectional cohort study (300-OB study). Various inflammatory parameters, traits of the metabolic syndrome, lipidome and metabolome parameters, fat distribution, and carotid atherosclerosis were associated with plasma aldosterone and renin levels.
Setting
Radboudumc, the Netherlands.
Patients
302 individuals with a BMI≥27kg/m2.
Main outcome measures and results
Aldosterone associated with various markers of inflammation and metabolic dysregulation, which partly differed from the associations observed for renin. While both associated with inflammatory cell numbers, only renin associated with classical markers of systemic inflammation. Both associated with the metabolic syndrome and hepatic steatosis. Of the traits that constitute the metabolic syndrome, aldosterone, but not renin, associated with triglyceride concentrations. In line, aldosterone associated with large VLDL particles; metabolomics studies further associated aldosterone with urate concentrations and derivatives of the linoleic acid metabolism pathway. Neither aldosterone nor renin associated with atherosclerotic plaque thickness.
Conclusions
aldosterone is not an important driver of systemic inflammation in the obese, while aldosterone concentrations and metabolic dysregulation are strongly intertwined in these individuals. Although prospective studies are necessary to validate these results, the independent effects of aldosterone on carotid atherosclerosis appear modest.
Aim. To characterize the peculiarities of the dynamics of the level of corticosteroid receptors in the myocardium of animals with different resistance to hypoxia in the post-resuscitation period.
Methods. Experimental studies were carried out on male non-inbred white rats, divided into 2 groups by hypoxia resistance. A 5-minute arrest of the systemic circulation was modeled under ether anesthesia with intrathoracic clamping of the cardiovascular cluster with subsequent resuscitation. The observation period was 35 days. The content of corticosterone and aldosterone was determined in the blood plasma, the concentration of glucocorticoid and mineralocorticoid receptors in myocard homogenates was determined as well.
Results. On days 1 to 3 of the post-resuscitation period in rats highly resistant to hypoxia, the dynamics of plasma corticosterone concentration and the content of corticosteroid receptors was unidirectional. Starting from the 5th day, against the background of a statistically significant decrease in the level of plasma corticosterone, a gradual increase in the density of corticosteroid receptors, mostly glucocorticoid, was observed, most pronounced on the 14th day and remaining until the end of the observation. In animals with low resistance to hypoxia, the dynamics of corticosteroid receptors was characterized by a predominance of mineralocorticoid content in almost all periods of observation. On days 13 of post-resuscitation period on the background of high concentrations of corticosteroid hormones, the minimum content of glucocorticoid receptors was noted. A decrease in the mineralocorticoid receptor level was recorded only on the first day, and in all subsequent periods of the experiment, the control indicators were significantly higher by 1.41.6 times. Strengthened mineralocorticoid signaling in the myocardium, characteristic of animals with low resistance to hypoxia, may be associated with the development of hypertrophy and fibrosis, inflammation, impaired electrical function. An increase in glucocorticoid receptors, characteristic of animals with a high resistance to hypoxia, has an adaptive effect, limiting the inflammatory response, the potential mechanism may be associated with increased expression of type 11-hydroxysteroid dehydrogenase.
Conclusion. The identified features can have a significant influence on the course of the post-resuscitation period and determine the long-term forecast.
Mineralocorticoid excess produces inflammation, hypertrophy, and fibrosis independently of its effects on sodium balance and blood pressure. Mineralocorticoids act through the mineralocorticoid receptor (MR) which mediates transcriptional and rapid non-genomic effects in non-epithelial cells including cardiomyocytes, vascular endothelial and smooth muscle cells, macrophages and T-cells, and neurons. DOCA, an inactive pro-drug, is converted to DOC with variable efficiency in different cells types. The affinities of DOC and aldo for the MR are similar; the affinity of DOC for the glucocorticoid receptor (GR) is greater than that of aldosterone. As DOC is rapidly inactivated in the kidney, doses of DOCA required to increase renal sodium and water resorption produce relatively greater non-renal effects and concentrations of DOC that activate both MR and GR. Thus the DOCA excess is not equivalent to endogenous aldosterone excess. Nonetheless, the mechanisms of both steroids that produce cardiovascular inflammation and remodeling are direct and independent of hypertension, as well as indirect, through increased blood pressure.
The mineralocorticoid receptor (MR) was originally identified as a regulator of blood pressure, able to modulate renal sodium handling in response to its principal ligand aldosterone. MR is expressed in several extra-renal tissues, including the heart, vasculature, and adipose tissue. More recent studies have shown that extra-renal MR plays a relevant role in the control of cardiovascular and metabolic functions and has recently been implicated in the pathophysiology of aging. MR activation promotes vasoconstriction and acts as a potent pro-fibrotic agent in cardiovascular remodeling. Aging is associated with increased arterial stiffness and vascular tone, and modifications of arterial structure and function are responsible for these alterations. MR activation contributes to increase blood pressure with aging by regulating myogenic tone, vasoconstriction, and vascular oxidative stress. Importantly, aging represents an important contributor to the increased prevalence of cardiometabolic syndrome. In the elderly, dysregulation of MR signaling is associated with hypertension, obesity, and diabetes, representing an important cause of increased cardiovascular risk. Clinical use of MR antagonists is limited by the adverse effects induced by MR blockade in the kidney, raising the risk of hyperkalaemia in older patients with reduced renal function. Therefore, there is an unmet need for the enhanced understanding of the role of MR in aging and for development of novel specific MR antagonists in the context of cardiovascular rehabilitation in the elderly, in order to reduce relevant side effects.
Context
Adrenal insufficiency (AI) requires life-long glucocorticoid replacement. Conventional therapies fail to mimic the endogenous cortisol circadian rhythm. Clock genes are essential components of the molecular machinery controlling an organ’s circadian function and are influenced by glucocorticoids. However, clock gene expression has never been investigated in AI patients.
Objective
To evaluate the effect of the timing of glucocorticoid administration on circadian gene expression in peripheral blood mononuclear cells (PBMCs) of AI patients from the DREAM trial.
Design
Outcome assessors blinded, randomized, active comparator clinical trial.
Participants and Intervention
Eighty-nine AI patients taking glucocorticoids were randomly assigned to continue their multiple daily doses, or switch to an equivalent dose of once-daily modified-release hydrocortisone, and compared to 25 healthy controls: 65 AI patients and 18 controls consented gene expression analysis by real-time qRT-PCR.
Results
Compared to healthy controls, 19 of the 68 genes were found differentially expressed in AI patients at baseline, 18 of which were restored to control levels 12 week after switching therapy, comprising: ARNTL[BMAL] (P=0.024), CLOCK (P=0.016), PER3 (P<0.001), TIMELESS (<0.001), AANAT (p=0.021), CAMK2D (p<0.001), CREB1 (p=0.010), CREB3 (p=0.037), MAPK1 (p<0.001), MAT2A (p=0.013), PRKAR1A (p=0.006), PRKAR2A (p=0.006), PRKCB (p=0.006); SP1 (p<0.001), WEE1 (p<0.001), CSNK1A1 (p<0.001), ONP3 (p<0.001) and PRF1 (p<0.001). Changes in WEE1, PRF1 and PER3 expression correlated with glycated hemoglobin, inflammatory monocytes and CD16+ NK cells.
Conclusions
AI patients on standard therapy exhibit a dysregulation of circadian genes in PBMCs. The once-daily administration reconditions peripheral tissue gene expression to levels close to healthy controls, paralleling the clinical outcomes of the DREAM trial [NCT02277587].
L’utilisation d’antagonistes du récepteur aux minéralocorticoïdes (ARM) a prouvé son efficacité dans le traitement de l’insuffisance cardiaque (IC). Un des facteurs de risque majeur de l’IC, le syndrome métabolique (SMet), est également associé à une production augmentée d’aldostérone et une activation excessive de son récepteur. Dans ce contexte, nous avons émis l’hypothèse que l’utilisation des ARM pouvait être appliquée pour cibler les facteurs de risques du SMet et prévenir la progression subséquente vers l’IC. Dans ce projet, des rats Spontanément Hypertendus et développant une IC (rats SHHF) portant ou non une mutation du récepteur de la leptine (« cp ») conduisant à un SMet (respectivement SHHFcp/cp et SHHF+/+) ont été utilisés comme modèle expérimental. Les animaux ont reçu soit un placebo soit le traitement ARM (Eplérénone, Eplé) dès l’âge de 1.5 à 12.5 mois et leurs paramètres métaboliques et cardiovasculaires ont été régulièrement évalués. Les fonctions moléculaires altérées dans le coeur et le tissu adipeux lors du développement du SMet et la progression de l’IC, ainsi que celles modulées par l’action de l’Eplé ont été caractérisées par l’analyse du transcriptome et miRNome des animaux. Nos résultats montrent que les rats SHHFcp/cp développent à 12.5 mois une hypertrophie cardiaque excentrique associée à une dilatation du ventricule gauche (VG) et une fraction d’éjection diminuée comparés aux SHHF+/+. Alors que l’Eplé ne modifie pas les paramètres métaboliques et cardiovasculaires des SHHF+/+, Les rats Eple-SHHFcp/cp présentent une moindre prise de masse corporelle ainsi qu’une moindre dyslipidémie. Sans effet sur la pression artérielle (PA), ni le transcriptome et miRNome adipeux, les animaux SHHFcp/cp traités présentent en outre une moindre dilatation et hypertrophie de leur VG, une fraction d’éjection, un temps de relaxation isovolumique et un ratio E/A plus élevés. Les analyses du transcriptome et miRNome cardiaques révèlent que l’Eplé induit une diminution significative de l’expression de gènes impliqués dans le remodelage et l’inflammation myocardiques ainsi qu’une augmentation de l’expression de gènes relatifs à l’oxydation des acides gras dans le coeur. L’intégration et l’exploration bioinformatique des profils d’expression du transcriptome et du miRNome ont permis d’établir des réseaux de régulation de l’expression génique potentiellement impliqués dans les mécanismes physiopathologiques à l’oeuvre chez les rats SHHF obèses et dans ceux impactés par le traitement. Dans leur ensemble, nos données montrent que l’initiation d’un traitement ARM lors du développement du SMet permet d’atténuer l’obésité et la dyslipidémie et d’améliorer les paramètres de structure et fonction cardiaque. De façon intéressante, ces effets cardioprotecteurs sont obtenus via des mécanismes indépendants de la diminution de la PA, les analyses du transcriptome/miRNome cardiaque indiquent un mécanisme basé sur une diminution des processus de remodelage et d’inflammation ainsi qu’ une restauration de la fonction de métabolisme énergétique des acides gras au niveau myocardique
Glucocorticoids act via multiple mechanisms to mobilize energy for in maintenance and restoration of homeostasis. In adipose tissue, glucocorticoids can promote lipolysis and facilitate adipocyte differentiation/growth, serving both energy-mobilizing and restorative processes during negative energy balance. Recent data suggest that adipose-dependent feedback may also be involved in regulation of stress responses. Adipocyte glucocorticoid receptor (GR) deletion causes increased HPA axis stress reactivity, due to a loss of negative feedback signals into the CNS. The fat-to-brain signal may be mediated by neuronal mechanisms, release of adipokines or increased lipolysis. The ability of adipose GRs to inhibit psychogenic as well as metabolic stress responses suggests that 1) feedback regulation of the HPA axis occurs across multiple bodily compartments, and 2) fat tissue integrates psychogenic stress signals. These studies support a link between stress biology and energy metabolism, a connection that has clear relevance for numerous disease states and their comorbidities.
La découverte récente d'adipocytes bruns fonctionnels chez les humains adultes a conduit à envisager leur utilisation afin d’augmenter la dépense énergétique dans de potentiels traitements contre l'obésité et les maladies associées. Par ailleurs, des ilots d’adipocytes bruns, appelés adipocytes "brite" (brown in white), émergent dans le tissu adipeux blanc après une exposition au froid ou une stimulation des récepteurs β3-adrénergiques. En utilisant les cellules hMADS, nous avons identifié plusieurs miARNs régulés pendant le « britening ». miR-125b et let-7i ont des niveaux d’expression plus bas dans les adipocytes « brites ». Des analyses fonctionnelles utilisant un « mimic » de miR-125b ou un inhibiteur ont révélé que miR-125b agit comme un frein sur le « brunissage » des cellules hMADS en altérant leur respiration ainsi que leur contenu mitochondrial. In vivo, nous avons montré que miR-125b et let-7i sont moins exprimés dans le tissu adipeux brun par rapport au tissu adipeux blanc. La stimulation des récepteurs β3-adrénergiques ou l'exposition au froid induit une diminution d’expression des miARNs dans les deux tissus et est associée à l'activation du tissu adipeux brun et au recrutement des adipocytes « brites ». Nous avons constaté que l’injection de miR-125b ou let-7i dans le tissu adipeux blanc sous-cutané inhibait l’expression de gènes du « brunissage » induite par la stimulation de la voie β3-adrénergique. En conclusion, nos observations ont montré que miR-125b et let-7i jouaient un rôle important dans la modulation des adipocytes « brites » et des adipocytes « bruns » en ciblant l’expression de gènes mitochondriaux et en diminuant la biogenèse mitochondriale.
The mineralocorticoid receptor (MR) controls adipocyte function, but its role in the conversion of white adipose tissue (WAT) into thermogenic fat has not been elucidated. We investigated responses to the MR antagonists spironolactone (spiro; 20 mg/kg/d) and drospirenone (DRSP; 6 mg/kg/d) in C57BL/6 mice fed a high-fat (HF) diet for 90 d. DRSP and spiro curbed HF diet-induced impairment in glucose tolerance, and prevented body weight gain and white fat expansion. Notably, either MR antagonist induced up-regulation of brown adipocyte-specific transcripts and markedly increased protein levels of uncoupling protein 1 (UCP1) in visceral and inguinal fat depots when compared with the HF diet group. Positron emission tomography and magnetic resonance spectroscopy confirmed acquisition of brown fat features in WAT. Interestingly, MR antagonists markedly reduced the autophagic rate both in murine preadipocytes in vitro (10(-5) M) and in WAT depots in vivo, with a concomitant increase in UCP1 protein expression. Moreover, the autophagy repressor bafilomycin A1 (10(-8) M) mimicked the effect of MR antagonists, increasing UCP1 protein expression in primary preadipocytes. Hence, we showed that adipocyte MR regulates brown remodeling of WAT through a modulation of autophagy. These results provide a rationale for the use of MR antagonists to prevent the adverse metabolic consequences of adipocyte dysfunction.-Armani, A., Cinti, F., Marzolla, V., Morgan, J., Cranston, G. A., Antelmi, A., Carpinelli, G., Canese, R., Pagotto, U., Quarta, C., Malorni, W., Matarrese, P., Marconi, M., Fabbri, A., Rosano, G., Cinti, S., Young, M. J., Caprio, M. Mineralocorticoid receptor antagonism induces browning of white adipose tissue through impairment of autophagy and prevents adipocyte dysfunction in high-fat-diet-fed mice.
International Journal of Obesity is a monthly, multi-disciplinary forum for papers describing basic, clinical and applied studies in biochemistry, genetics and nutrition, together with molecular, metabolic, psychological and epidemiological aspects of obesity and related disorders
The mineralocorticoid receptor (MR) exerts pro-adipogenic and anti-thermogenic effects in vitro, yet its in vivo metabolic impact remains elusive. Wild type (WT) and transgenic (Tg) mice overexpressing human MR were subjected to standard chow (SC) or high fat diet (HFD) for 16 wks. Tg mice had a lower body weight gain than WT animals, and exhibited a relative resistance to HFD-induced obesity. This was associated with a decrease of fat mass, an increased population of smaller adipocytes, and an improved glucose tolerance compared to WT animals. Quantitative RT-PCR studies revealed decreased expression of PPARγ2, a master adipogenic gene, and of glucocorticoid receptor and 11β-hydroxysteroid dehydrogenase type 1, consistent with an impaired local glucocorticoid signaling in adipose tissues (AT). This paradoxical resistance to HFD-induced obesity was not related to an adipogenesis defect since differentiation capacity of Tg preadipocytes isolated from stroma-vascular fractions was unaltered, suggesting that other non-adipocyte factors might compromise AT development. While AT macrophage infiltration was not different between genotypes, Tg mice exhibited a distinct macrophage polarization as revealed by FACS analysis and CD11c/CD206 expression studies. We further demonstrated that Tg macrophage-conditioned medium partially impaired preadipocyte differentiation. Therefore we propose that modification of M1/M2 polarization of hMR-overexpressing macrophages could account in part for the metabolic phenotype of Tg mice. Collectively, our results provide evidence that MR exerts a pivotal immunometabolic role by directly controlling adipocyte differentiation processes but also indirectly through macrophage polarization regulation. Our findings should be taken into account for the pharmacological treatment of metabolic disorders.
Because the renin-angiotensin-aldosterone system has been implicated in the development of insulin resistance and promotion of fibrosis in some tissues, such as the vasculature, we examined the effect of eplerenone, a selective mineralocorticoid receptor (MR) antagonist, on non-alcoholic steatohepatitis (NASH) and metabolic phenotypes in a mouse model reflecting metabolic syndrome in humans. We adopted liver-specific transgenic mice overexpressing the active form of sterol response element binding protein 1c (SREBP1c) fed a high-fat and fructose diet (HFFD) as the animal model in the present study. When wild-type (WT) C57BL/6 and liver-specific SREBP1c transgenic (Tg) mice grew while being fed HFFD for 12 weeks, body weight and epididymal fat weight increased in both groups with an elevation in blood pressure and dyslipidemia. Glucose intolerance and insulin resistance were also observed. Adipose tissue hypertrophy and macrophage infiltration with crown-like structure formation were also noted in mice fed HFFD. Interestingly, the changes noted in both genotypes fed HFFD were significantly ameliorated with eplerenone. HFFD-fed Tg mice exhibited the histological features of NASH in the liver, including macrovesicular steatosis and fibrosis, whereas HFFD-fed WT mice had hepatic steatosis without apparent fibrotic changes. Eplerenone effectively ameliorated these histological abnormalities. Moreover, the direct suppressive effects of eplerenone on lipopolysaccharide-induced TNFalpha production in the presence and absence of aldosterone were observed in primary-cultured Kupffer cells and bone marrow-derived macrophages. These results indicated that eplerenone prevented the development of NASH and metabolic abnormalities in mice by inhibiting inflammatory responses in both Kupffer cells and macrophages.
Obese individuals have high aldosterone levels that may contribute to insulin resistance (IR) and endothelial dysfunction leading to obesity induced cardiovascular disease. We conducted a study to evaluate the effect of mineralocorticoid receptor antagonism on IR and endothelial function in obese individuals.
This was a placebo-controlled, double blind, randomized, parallel-group study (NCT01406015).
Thirty two non-diabetic, obese subjects (BMI 30 to 45 kg/m(2) ) with no other medical problems were randomized to six weeks of treatment with spironolactone 50 mg daily or placebo. Insulin sensitivity index (ISI) was assessed by Matsuda method, endothelial function by flow mediated vasodilatation (FMD) of brachial artery and renal plasma perfusion by clearance of para-aminohippurate (PAH).
There was no change in weight, BMI or plasma potassium during the study period. Treatment with spironolactone led to increases in serum aldosterone (7.6 ± 6.6 Vs 3.2 ± 1.3 ng/dL; p <0.02, post-treatment Vs baseline) and urine aldosterone (11.0 ± 7. Vs 4.8 ± 2.4 µg/G creatinine; p < 0.01) and decreases in systolic blood pressure (116 ± 11 Vs 123 ± 10 mmHg; p < 0.001). There were no changes in these variables in the placebo group. Neither spironolactone nor placebo treatment had a significant effect on ISI or other indices of glucose metabolism (HOMA, area under the curve for insulin, area under the curve for glucose), brachial artery reactivity or the renal plasma perfusion values. Changes in these variables were similar in two groups.
We conclude that six weeks of treatment with spironolactone does not change insulin sensitivity or endothelial function in normotensive obese individuals with no other comorbidities.
Mineralocorticoid Receptor (MR) activation is involved in blood pressure regulation and the pathogenesis of cardiovascular diseases, such as cardiac fibrosis, vascular inflammation and arterial aging. Recent investigations suggest a role for MR activation in metabolic dysregulation.Objective
To test the effect of MR blockade on basal and postprandial glucose and lipid levels after a meal high in fat and glucose in healthy males.Subjects and methodsA prospective, self-controlled study was performed in 13 healthy adult males aged 18–45 years. Blood was drawn before, 2 h, and 4 h after a high fat/high glucose meal (50 g fat, 75 g glucose), followed by low-dose eplerenone treatment (50 mg daily) for 14 days. Subjects returned for a second high fat/high glucose meal after the medication period. Basal and postprandial blood glucose and lipid levels were compared before and after eplerenone treatment.ResultsEplerenone treatment affected neither basal nor postprandial glucose and lipid levels in our study population.Conclusion
Our results suggest that low-dose, non-blood pressure-affecting, MR blockade does not alter postprandial lipid and glucose homeostasis in healthy adult subjects.
Aldosterone is important in the pathophysiology of heart failure. In a doubleblind study, we enrolled 1663 patients who had severe heart failure and a left ventricular ejection fraction of no more than 35 percent and who were being treated with an angiotensin-converting-enzyme inhibitor, a loop diuretic, and in most cases digoxin. A total of 822 patients were randomly assigned to receive 25 mg of spironolactone daily, and 841 to receive placebo. The primary end point was death from all causes.
The trial was discontinued early, after a mean follow-up period of 24 months, because an interim analysis determined that spironolactone was efficacious. There were 386 deaths in the placebo group (46 percent) and 284 in the spironolactone group (35 percent; relative risk of death, 0.70; 95 percent confidence interval, 0.60 to 0.82; P<0.001). This 30 percent reduction in the risk of death among patients in the spironolactone group was attributed to a lower risk of both death from progressive heart failure and sudden death from cardiac causes. The frequency of hospitalization for worsening heart failure was 35 percent lower in the spironolactone group than in the placebo group (relative risk of hospitalization, 0.65; 95 percent confidence interval, 0.54 to 0.77; P<0.001). In addition, patients who received spironolactone had a significant improvement in the symptoms of heart failure, as assessed on the basis of the New York Heart Association functional class (P<0.001). Gynecomastia or breast pain was reported in 10 percent of men who were treated with spironolactone, as compared with 1 percent of men in the placebo group (P<0.001). The incidence of serious hyperkalemia was minimal in both groups of patients.
Blockade of aldosterone receptors by spironolactone, in addition to standard therapy, substantially reduces the risk of both morbidity and death among patients with severe heart failure.
Type 2 diabetes mellitus is the result of interaction between genetic and environmental factors, leading to heterogeneous and progressive pancreatic β-cell dysfunction. Overweight and obesity are major contributors to the development of insulin resistance and impaired glucose tolerance. The inability of β cells to secrete enough insulin produces type 2 diabetes. Abnormalities in other hormones such as reduced secretion of the incretin glucagon-like peptide 1 (GLP-1), hyperglucagonemia, and raised concentrations of other counterregulatory hormones also contribute to insulin resistance, reduced insulin secretion, and hyperglycaemia in type 2 diabetes. Clinical-overt and experimental cortisol excess is associated with profound metabolic disturbances of intermediate metabolism resulting in abdominal obesity, insulin resistance, and low HDL-cholesterol levels, which can lead to diabetes. It was therefore suggested that subtle abnormalities in cortisol secretion and action are one of the missing links between insulin resistance and other features of the metabolic syndrome. The aim of this paper is to address the role of glucocorticoids on glucose homeostasis and to explain the relationship between hypercortisolism and type 2 diabetes.
Brown adipose tissue (BAT) is known to function in the dissipation of chemical energy in response to cold or excess feeding, and also has the capacity to modulate energy balance. To test the hypothesis that BAT is fundamental to the regulation of glucose homeostasis, we transplanted BAT from male donor mice into the visceral cavity of age- and sex-matched recipient mice. By 8-12 weeks following transplantation, recipient mice had improved glucose tolerance, increased insulin sensitivity, lower body weight, decreased fat mass, and a complete reversal of high-fat diet-induced insulin resistance. Increasing the quantity of BAT transplanted into recipient mice further improved the metabolic effects of transplantation. BAT transplantation increased insulin-stimulated glucose uptake in vivo into endogenous BAT, white adipose tissue (WAT), and heart muscle but, surprisingly, not skeletal muscle. The improved metabolic profile was lost when the BAT used for transplantation was obtained from Il6-knockout mice, demonstrating that BAT-derived IL-6 is required for the profound effects of BAT transplantation on glucose homeostasis and insulin sensitivity. These findings reveal a previously under-appreciated role for BAT in glucose metabolism.
Background
Microglia, the resident macrophage-like cells in the brain, regulate innate immune responses in the CNS to protect neurons. However, excessive activation of microglia contributes to neurodegenerative diseases. Corticosteroids are potent modulators of inflammation and mediate their effects by binding to mineralocorticoid receptors (MR) and glucocorticoid receptors (GR). Here, the coordinated activities of GR and MR on the modulation of the nuclear factor-κB (NF-κB) pathway in murine BV-2 microglial cells were studied.
Methods
BV-2 cells were treated with different corticosteroids in the presence or absence of MR and GR antagonists. The impact of the glucocorticoid-activating enzyme 11β-hydroxysteroid dehydrogenase type 1 (11β-HSD1) was determined by incubating cells with 11-dehydrocorticosterone, with or without selective inhibitors. Expression of interleukin-6 (IL-6), tumor necrosis factor receptor 2 (TNFR2), and 11β-HSD1 mRNA was analyzed by RT-PCR and IL-6 protein expression by ELISA. NF-κB activation and translocation upon treatment with various corticosteroids were visualized by western blotting, immunofluorescence microscopy, and translocation assays.
Results
GR and MR differentially regulate NF-κB activation and neuroinflammatory parameters in BV-2 cells. By converting inactive 11-dehydrocorticosterone to active corticosterone, 11β-HSD1 essentially modulates the coordinated action of GR and MR. Biphasic effects were observed for 11-dehydrocorticosterone and corticosterone, with an MR-dependent potentiation of IL-6 and tumor necrosis factor-α (TNF-α) expression and NF-κB activation at low/moderate concentrations and a GR-dependent suppression at high concentrations. The respective effects were confirmed using the MR ligand aldosterone and the antagonist spironolactone as well as the GR ligand dexamethasone and the antagonist RU-486. NF-κB activation could be blocked by spironolactone and the inhibitor of NF-κB translocation Cay-10512. Moreover, an increased expression of TNFR2 was observed upon treatment with 11-dehydrocorticosterone and aldosterone, which was reversed by 11β-HSD1 inhibitors and/or spironolactone and Cay-10512.
Conclusions
A tightly coordinated GR and MR activity regulates the NF-κB pathway and the control of inflammatory mediators in microglia cells. The balance of GR and MR activity is locally modulated by the action of 11β-HSD1, which is upregulated by pro-inflammatory mediators and may represent an important feedback mechanism involved in resolution of inflammation.
Several clinical and experimental lines of evidence have highlighted the detrimental effects of visceral adipose tissue excess on cardiometabolic parameters. Besides, recent findings have shown the effects of gluco-and mineralocorticoid hormones on adipose tissue and have also underscored the interplay existing between such adrenal steroids and their respective receptors in the modulation of adipose tissue biology. While the fundamental role played by glucocorticoids on adipocyte differentiation and storage was already well known, the relevance of the mineralocorticoids in the physiology of the adipose organ is of recent acquisition. The local and systemic renin-angiotensin-aldosterone system (RAAS) acting on adipose tissue seems to contribute to the development of the cardiometabolic phenotype so that its modulation can have deep impact on human health. A better understanding of the pathophysiology of the adipose organ is of crucial importance in order to identify possible therapeutic approaches that can avoid the development of such cardiovascular and metabolic sequelae.
Mineralocorticoid receptor (MR) activation promotes the development of cardiac fibrosis and heart failure. Clinical evidence demonstrates that MR antagonism is protective even when plasma aldosterone levels are not increased. We hypothesize that MR activation in macrophages drives the profibrotic phenotype in the heart even when aldosterone levels are not elevated. The aim of the present study was to establish the role of macrophage MR signaling in mediating cardiac tissue remodeling caused by nitric oxide (NO) deficiency, a mineralocorticoid-independent insult. Male wild-type (MRflox/flox) and macrophage MR-knockout (MRflox/flox/LysMCre/+; mac-MRKO) mice were uninephrectomized, maintained on 0.9% NaCl drinking solution, with either vehicle (control) or the nitric oxide synthase (NOS) inhibitor NG-nitro-l-arginine methyl ester (L-NAME; 150 mg/kg/d) for 8 wk. NO deficiency increased systolic blood pressure at 4 wk in wild-type L-NAME/salt-treated mice compared with all other groups. At 8 wk, systolic blood pressure was increased above control in both L-NAME/salt treated wild-type and mac-MRKO mice by approximately 28 mm Hg by L-NAME/salt. Recruitment of macrophages was increased 2- to 3-fold in both L-NAME/salt treated wild-type and mac-MRKO. Inducible NOS positive macrophage infiltration and TNFα mRNA expression was greater in wild-type L-NAME/salt-treated mice compared with mac-MRKO, demonstrating that loss of MR reduces M1 phenotype. mRNA levels for markers of vascular inflammation and oxidative stress (NADPH oxidase 2, p22phox, intercellular adhesion molecule-1, G protein-coupled chemokine receptor 5) were similar in treated wild-type and mac-MRKO mice compared with control groups. In contrast, L-NAME/salt treatment increased interstitial collagen deposition in wild-type by about 33% but not in mac-MRKO mice. mRNA levels for connective tissue growth factor and collagen III were also increased above control treatment in wild-type (1.931 ± 0.215 vs. 1 ± 0.073) but not mac-MRKO mice (1.403 ± 0.150 vs. 1.286 ± 0.255). These data demonstrate that macrophage MR are necessary for the translation of inflammation and oxidative stress into interstitial and perivascular fibrosis after NO deficiency, even when plasma aldosterone is not elevated.
Aldosterone blockade reduces mortality and morbidity among patients with severe heart failure. We conducted a double-blind, placebo-controlled study evaluating the effect of eplerenone, a selective aldosterone blocker, on morbidity and mortality among patients with acute myocardial infarction complicated by left ventricular dysfunction and heart failure.
Patients were randomly assigned to eplerenone (25 mg per day initially, titrated to a maximum of 50 mg per day; 3319 patients) or placebo (3313 patients) [correction] in addition to optimal medical therapy. The study continued until 1012 deaths occurred. The primary end points were death from any cause and death from cardiovascular causes or hospitalization for heart failure, acute myocardial infarction, stroke, or ventricular arrhythmia.
During a mean follow-up of 16 months, there were 478 deaths in the eplerenone group and 554 deaths in the placebo group (relative risk, 0.85; 95 percent confidence interval, 0.75 to 0.96; P=0.008). Of these deaths, 407 in the eplerenone group and 483 in the placebo group were attributed to cardiovascular causes (relative risk, 0.83; 95 percent confidence interval, 0.72 to 0.94; P=0.005). The rate of the other primary end point, death from cardiovascular causes or hospitalization for cardiovascular events, was reduced by eplerenone (relative risk, 0.87; 95 percent confidence interval, 0.79 to 0.95; P=0.002), as was the secondary end point of death from any cause or any hospitalization (relative risk, 0.92; 95 percent confidence interval, 0.86 to 0.98; P=0.02). There was also a reduction in the rate of sudden death from cardiac causes (relative risk, 0.79; 95 percent confidence interval, 0.64 to 0.97; P=0.03). The rate of serious hyperkalemia was 5.5 percent in the eplerenone group and 3.9 percent in the placebo group (P=0.002), whereas the rate of hypokalemia was 8.4 percent in the eplerenone group and 13.1 percent in the placebo group (P<0.001).
The addition of eplerenone to optimal medical therapy reduces morbidity and mortality among patients with acute myocardial infarction complicated by left ventricular dysfunction and heart failure.
Although some clinical studies have suggested that spironolactone (SPL), a mineralocorticoid receptor (MR) antagonist, appears to increase the blood glucose levels, experimental studies have not supported this notion. Here, we investigated the effect of SPL on blood glucose levels in SHR/NDmcr-cp(cp/cp) (ND) rats, an animal model of metabolic syndrome, in comparison with that of eplerenone (EPL), another MR antagonist. At the same dose of 100 mg/kg, SPL and EPL increased the urinary sodium-to-potassium ratio to a comparable extent, indicating that both agents have similar renal MR antagonistic efficacy in ND rats. Interestingly, SPL but not EPL significantly increased the level of blood glucose. The oral glucose tolerance test revealed that treatment with SPL led to glucose intolerance. The levels of serum insulin and adiponectin, regulators of the blood glucose level, were virtually unaffected by treatment with SPL. On the other hand, SPL induced a marked increase in the blood level of aldosterone, known to be a risk factor for insulin resistance. These results demonstrate that in comparison with EPL, SPL characteristically impairs glucose tolerance in an animal model of metabolic syndrome, in association with a higher blood level of aldosterone.
Aldosterone has been linked to the deleterious cardiovascular effects of obesity in humans. The association of aldosterone with obesity in rodents is less well defined, particularly in models of diet-induced obesity. We hypothesized that adrenal aldosterone production and aldosterone synthase expression would be increased in rats with obesity-induced hypertension. Male Sprague Dawley rats were fed a high-fat (HF: 36% fat) or control diet from 3 wk of age, and mean arterial pressure (MAP) was measured by telemetry. MAP was increased after 4 wk of HF diet; this was 6 wk before changes in body weight. Mineralocorticoid receptor antagonism did not prevent the HF-induced increase in MAP. After 17 wk on the diets, HF rats had increased body and fat weights (abdominal and epididymal) and were insulin resistant (Homeostasis Model Assessment index: 3.53 ± 0.43 vs. 8.52 ± 1.77; control vs. HF, P < 0.05). Plasma aldosterone levels were increased in the HF rats (64.14 ± 14.96 vs. 206.25 ± 47.55 pg/ml; control vs. HF, P < 0.05). This occurred independently of plasma renin activity (4.8 ± 0.92 vs. 4.73 ± 0.66 ng/ml/h, control vs. HF). The increase in aldosterone was accompanied by a 2-fold increase in adrenal aldosterone synthase mRNA expression and zona glomerulosa hypertrophy. Rats were also studied after 8 wk of HF diet, a time when MAP, but not body weight, was increased. At this time plasma aldosterone was unchanged but plasma renin activity was increased (4.4 ± 0.5 vs. 8.1 ± 1.3 ng/ml/h; control vs. HF, P < 0.05). These studies suggest that rats fed a HF diet from weaning may be a useful model for studying obesity-associated hyperaldosteronism.
Aldosterone is a major regulator of salt balance and blood pressure, exerting its effects via the mineralocorticoid receptor (MR). To analyze the regulatory mechanisms controlling tissue-specific expression of the human MR (hMR) in vivo, we have developed transgenic mouse models expressing the SV40 large T antigen (TAg) under the control of each of the two promoters of the hMR gene (P1 or P2). Unexpectedly, all five P1-TAg founder animals died prematurely from voluminous malignant liposarcomas originating from brown adipose tissue, as evidenced by the expression of the mitochondrial uncoupling protein ucp1, indicating that the proximal P1 promoter was transcriptionally active in brown adipocytes. No such hibernoma occurred in P2-TAg transgenic mice. Appropriate tissue-specific usage of P1 promoter sequences was confirmed by demonstrating the presence of endogenous MR in both neoplastic and normal brown adipose tissue. Several cell lines were derived from hibernomas; among them, the T37i cells can undergo terminal differentiation into brown adipocytes, which remain capable of expressing ucp1 upon adrenergic or retinoic acid stimulation. These cells possess endogenous functional MR, thus providing a new model to explore molecular mechanisms of mineralocorticoid action. Our data broaden the known functions of aldosterone and suggest a potential role for MR in adipocyte differentiation and regulation of thermogenesis.
To compare the risk of non-fatal venous thromboembolism in women receiving oral contraceptives containing drospirenone with that in women receiving oral contraceptives containing levonorgestrel.
Nested case-control and cohort study.
The study was based on information from PharMetrics, a United States based company that collects information on claims paid by managed care plans.
The study encompassed all women aged 15 to 44 years who received an oral contraceptive containing either drospirenone or levonorgestrel after 1 January 2002. Cases were women with current use of a study oral contraceptive and a diagnosis of venous thromboembolism in the absence of identifiable clinical risk factors (idiopathic venous thromboembolism). Up to four controls were matched to each case by age and calendar time.
Odds ratios comparing the risk of non-fatal venous thromboembolism in users of the two contraceptives; incidence rates and rate ratios of non-fatal venous thromboembolism for users of each of the study contraceptives.
186 newly diagnosed, idiopathic cases of venous thromboembolism were identified in the study population and matched with 681 controls. In the case-control analysis, the conditional odds ratio for venous thromboembolism comparing use of oral contraceptives containing drospirenone with use of those containing levonorgestrel was 2.3 (95% confidence interval 1.6 to 3.2). The incidence rates for venous thromboembolism in the study population were 30.8 (95% confidence interval 25.6 to 36.8) per 100,000 woman years among users of oral contraceptives containing drospirenone and 12.5 (9.61 to 15.9) per 100,000 woman years among users of oral contraceptives containing levonorgestrel. The age adjusted incidence rate ratio for venous thromboembolism for current use of oral contraceptives containing drospirenone compared with those containing levonorgestrel was 2.8 (2.1 to 3.8).
The risk of non-fatal venous thromboembolism among users of oral contraceptives containing drospirenone seems to be around twice that of users of oral contraceptives containing levonorgestrel, after the effects of potential confounders and prescribing biases have been taken into account.
To examine the risk of non-fatal idiopathic venous thromboembolism in current users of a combined oral contraceptive containing drospirenone, relative to current users of preparations containing levonorgestrel.
Nested case-control study.
UK General Practice Research Database.
Women aged 15-44 years without major risk factors for venous thromboembolism who started a new episode of use of an oral contraceptive containing 30 µg oestrogen in combination with either drospirenone or levonorgestrel between May 2002 and September 2009. Cases were women with a first diagnosis of venous thromboembolism; up to four controls, matched by age, duration of recorded information, and general practice, were randomly selected for each case.
Odds ratios and 95% confidence intervals estimated with conditional logistic regression; age adjusted incidence rate ratio estimated with Poisson regression.
61 cases of idiopathic venous thromboembolism and 215 matched controls were identified. In the case-control analysis, current use of the drospirenone contraceptive was associated with a threefold higher risk of non-fatal idiopathic venous thromboembolism compared with levonorgestrel use; the odds ratio adjusted for body mass index was 3.3 (95% confidence interval 1.4 to 7.6). Subanalyses suggested that referral, diagnostic, first time user, duration of use, and switching biases were unlikely explanations for this finding. The crude incidence rate was 23.0 (95% confidence interval 13.4 to 36.9) per 100,000 woman years in current users of drospirenone and 9.1 (6.6 to 12.2) per 100,000 woman years in current users of levonorgestrel oral contraceptives. The age adjusted incidence rate ratio was 2.7 (1.5 to 4.7).
These findings contribute to emerging evidence that the combined oral contraceptive containing drospirenone carries a higher risk of venous thromboembolism than do formulations containing levonorgestrel.
Mineralocorticoid receptor (MR) activation is proinflammatory and proatherogenic. Antagonism of MR improves survival in humans with congestive heart failure caused by atherosclerotic disease. In animal models, activation of MR exacerbates atherosclerosis. The enzyme 11β-hydroxysteroid dehydrogenase type 2 (11β-HSD2) prevents inappropriate activation of the MR by inactivating glucocorticoids in mineralocorticoid-target tissues. To determine whether glucocorticoid-mediated activation of MR increases atheromatous plaque formation, we generated Apoe(-/-)/11β-HSD2(-/-) double-knockout (E/b2) mice. On chow diet, E/b2 mice developed atherosclerotic lesions by 3 months of age, whereas Apolipoprotein E (Apoe(-/-)) mice remained lesion free. Brachiocephalic plaques in 3-month-old E/b2 mice showed increased macrophage and lipid content and reduced collagen content compared with similar sized brachiocephalic plaques in 6-month-old Apoe(-/-) mice. Crucially, treatment of E/b2 mice with eplerenone, an MR antagonist, reduced plaque development and macrophage infiltration while increasing collagen and smooth muscle cell content without any effect on systolic blood pressure. In contrast, reduction of systolic blood pressure in E/b2 mice using the epithelial sodium channel blocker amiloride produced a less-profound atheroprotective effect. Vascular cell adhesion molecule 1 expression was increased in the endothelium of E/b2 mice compared with Apoe(-/-) mice. Similarly, aldosterone increased vascular cell adhesion molecule 1 expression in mouse aortic endothelial cells, an effect mimicked by corticosterone only in the presence of an 11β-HSD2 inhibitor. Thus, loss of 11β-HSD2 leads to striking atherogenesis associated with activation of MR, stimulating proinflammatory processes in the endothelium of E/b2 mice.
The mineralocorticoid receptor (MR) mediates aldosterone- and glucocorticoid-induced adipocyte differentiation. Drospirenone (DRSP) is a potent synthetic antimineralocorticoid with progestogenic and antiandrogenic properties, which is widely used for contraception and hormone replacement therapy. We investigated its potential role on adipocyte differentiation. The effects of DRSP were studied in murine preadipocyte cell lines and primary cultures of human preadipocytes. Differentiation markers and mechanisms underlying phenotypic variations in response to DRSP were explored. Early exposure to DRSP during differentiation led to a marked dose-dependent inhibition of adipose differentiation and triglyceride accumulation in 3T3-L1 and 3T3-F442A cells. DRSP also markedly inhibited adipose conversion of human primary preadipocytes derived from visceral (mesenteric and epicardial) and subcutaneous fat. This effect was MR-dependent and did not involve the glucocorticoid, androgen, or progesterone receptors. DRSP inhibited clonal expansion of preadipocytes and decreased expression of PPARγ, a key transcriptional mediator of adipogenesis, but had no effect on lipolysis, glucose uptake, and PPARγ binding to its ligands. DRSP exerts a potent antiadipogenic effect that is related to an alteration of the transcriptional control of adipogenesis via an antagonistic effect on the MR. Selective MR blockade therefore has promise as a novel therapeutic option for the control of excessive adipose tissue deposition and its related metabolic complications.
Inappropriate excess of the steroid hormone aldosterone, which is a mineralocorticoid receptor (MR) agonist, is associated with increased inflammation and risk of cardiovascular disease. MR antagonists are cardioprotective and antiinflammatory in vivo, and evidence suggests that they mediate these effects in part by aldosterone-independent mechanisms. Here we have shown that MR on myeloid cells is necessary for efficient classical macrophage activation by proinflammatory cytokines. Macrophages from mice lacking MR in myeloid cells (referred to herein as MyMRKO mice) exhibited a transcription profile of alternative activation. In vitro, MR deficiency synergized with inducers of alternatively activated macrophages (for example, IL-4 and agonists of PPARgamma and the glucocorticoid receptor) to enhance alternative activation. In vivo, MR deficiency in macrophages mimicked the effects of MR antagonists and protected against cardiac hypertrophy, fibrosis, and vascular damage caused by L-NAME/Ang II. Increased blood pressure and heart rates and decreased circadian variation were observed during treatment of MyMRKO mice with L-NAME/Ang II. We conclude that myeloid MR is an important control point in macrophage polarization and that the function of MR on myeloid cells likely represents a conserved ancestral MR function that is integrated in a transcriptional network with PPARgamma and glucocorticoid receptor. Furthermore, myeloid MR is critical for blood pressure control and for hypertrophic and fibrotic responses in the mouse heart and aorta.
Although brown adipose tissue in infants and young children is important for regulation of energy expenditure, there has been considerable debate on whether brown adipose tissue normally exists in adult humans and has physiologic relevance in this population. In the last decade, radiologic studies in adults have identified areas of adipose tissue with high 18F-fluorodeoxyglucose (18F-FDG) uptake, putatively identified as brown fat. This radiologic study assessed the presence of physiologically significant brown adipose tissue among 1972 adult patients who had 3640 consecutive 18F-FDG positron-emission tomographic and computed tomographic whole-body scans between 2003 and 2006. Brown adipose tissue was defined as areas of tissue that were more than 4 mm in diameter, had the CT density of adipose tissue, and had maximal standardized uptake values of 18F-FDG of at least 2.0 gm per mL. A sample of 204 date-matched patients without brown adipose tissue served as the control group. Using these criteria, positron-emission tomographic and computed tomographic scans identified brown adipose tissue in 106 of the 1972 patients (5.4%). The most common location for substantial amounts of brown adipose tissue was the region extending from the anterior neck to supraclavicular region. Immunohistochemical staining for uncoupling protein 1 in this region confirmed the identity of immunopositive, multilocular adipocytes as brown adipose tissue. More brown adipose tissue was detected in women (7.5% [76/1013]) than in men (3.1% [30/959]); the female:male ratio was 2.4:1.0 (P 64) (P 64 years) (P for trend = 0.007). These findings show that functional brown adipose tissue is prevalent in adult humans, and significantly more frequently in women. The inverse correlation of body mass index with the amount of brown adipose tissue, especially in older patients, suggests to the investigators a possible role of brown adipose tissue in protecting against obesity.
Expression of the macrophage mannose receptor is inhibited by interferon gamma (IFN-gamma), a T helper type 1 (Th-1)-derived lymphokine. Interleukin 4 (IL-4), a Th-2 lymphocyte product, upregulates major histocompatibility class II antigen expression but inhibits inflammatory cytokine production by macrophages. We have studied the effect of IL-4 on expression of the macrophage mannose receptor (MMR) by elicited peritoneal macrophages. We found that recombinant murine IL-4 enhances MMR surface expression (10-fold) and activity (15-fold), as measured by the respective binding and degradation of 125I-mannose-bovine serum albumin. Polymerase chain reaction analysis of cDNAs from purified primary macrophage populations revealed that MMR, but not lysozyme or tumor necrosis factor alpha, mRNA levels were markedly increased by IL-4. The above effects were associated with morphologic changes. These data establish IL-4 as a potent and selective enhancer of murine MMR activity in vitro. IL-4 induces inflammatory macrophages to adopt an alternative activation phenotype, distinct from that induced by IFN-gamma, characterized by a high capacity for endocytic clearance of mannosylated ligands, enhanced (albeit restricted) MHC class II antigen expression, and reduced proinflammatory cytokine secretion.
Background:
Metabolic syndrome is becoming a common disease due to a rise in obesity rates among adults.
Objectives:
The aim was to evaluate the effects of canrenone compared to placebo on metabolic and inflammatory parameters in patients affected by metabolic syndrome. A total of 145 patients were treated with placebo or canrenone, 50 mg/day, for 3 months and then 50 mg b.i.d. till the end of the study. Blood pressure, body weight, body mass index, fasting plasma glucose (FPG), fasting plasma insulin, HOMA-IR, lipid profile, plasma aldosterone, brain natriuretic peptide, high-sensitivity C-reactive protein (Hs-CRP), tumor necrosis factor-α (TNF-α) and M value were evaluated.
Results:
A decrease of blood pressure was observed in canrenone group compared to baseline; moreover, systolic blood pressure value recorded after 6 months of canrenone therapy was lower than the one recorded with placebo. Canrenone gave a significant decrease of FPI and HOMA index, and an increase of M value both compared to baseline and to placebo. Canrenone also decreased triglycerides and FPG was not observed with placebo. Canrenone also decreased plasma aldosterone, Hs-CRP and TNF-α compared to baseline and to placebo.
Conclusion:
Canrenone seems to be effective in reducing some factors involved in metabolic syndrome and in improving insulin-resistance and the inflammatory state observed in these patients.
Background:
In this study, we have analyzed the response of human monocyte-derived macrophages to mineralocorticoid axis modulators.
Methods:
Human monocyte-derived macrophages were incubated with aldosterone alone, eplerenone alone, and the combination of aldosterone and eplerenone. The analyzed variables were nitric oxide and reactive oxygen species production, and the gene and protein expression of inducible nitric oxide synthase, arginase I, and mannose receptor.
Results:
We showed that aldosterone promotes a classic inflammatory response in macrophages, whereas its antagonist, eplerenone, attenuates aldosterone-induced activity.
Conclusion:
Eplerenone did not quantitatively weaken the response of macrophages to aldosterone but instead qualitatively changed their behavior.
It has been increasingly accepted that chronic subacute inflammation plays an important role in the development of insulin resistance and type 2 Diabetes in animals and humans. Particularly supporting this is that suppression of systemic inflammation in type 2 Diabetes improves glycemic control; this also points to a new potential therapeutic target for the treatment of type 2 Diabetes. Recent studies strongly suggest that obesity-induced inflammation is mainly mediated by tissue resident immune cells, with particular attention being focused on adipose tissue macrophages (ATMs). This review delineates the current progress made in understanding obesity-induced inflammation and the roles ATMs play in this process.
The macrophage, a versatile cell type prominently involved in host defense and immunity, assumes a distinct state of alternative activation in the context of polarized type 2 immune responses such as allergic inflammation and helminth infection. This alternatively activated phenotype is induced by the canonical type 2 cytokines interleukin (IL)-4 and IL-13, which mediate expression of several characteristic markers along with a dramatic shift in macrophage metabolic pathways that influence surrounding cells and tissues. We discuss recent advances in the understanding of IL-4- and IL-13-mediated alternatively activated macrophages and type 2 immune responses; such advances have led to an expanded appreciation for functions of these cells beyond immunity, including maintenance of physiologic homeostasis and tissue repair. Expected final online publication date for the Annual Review of Immunology Volume 31 is March 19, 2013. Please see http://www.annualreviews.org/catalog/pubdates.aspx for revised estimates.
BACKGROUND AND METHODS: Aldosterone is important in the pathophysiology of heart failure. In a doubleblind study, we enrolled 1663 patients who had severe heart failure and a left ventricular ejection fraction of no more than 35 percent and who were being treated with an angiotensin-converting-enzyme inhibitor, a loop diuretic, and in most cases digoxin. A total of 822 patients were randomly assigned to receive 25 mg of spironolactone daily, and 841 to receive placebo. The primary end point was death from all causes. RESULTS: The trial was discontinued early, after a mean follow-up period of 24 months, because an interim analysis determined that spironolactone was efficacious. There were 386 deaths in the placebo group (46 percent) and 284 in the spironolactone group (35 percent; relative risk of death, 0.70; 95 percent confidence interval, 0.60 to 0.82; P0.001). This 30 percent reduction in the risk of death among patients in the spironolactone group was attributed to a lower risk of both death from p
We reported aldosterone as a novel adipocyte-derived factor that regulates vascular function. We aimed to investigate molecular mechanisms, signaling pathways, and functional significance of adipocyte-derived aldosterone and to test whether adipocyte-derived aldosterone is increased in diabetes mellitus-associated obesity, which contributes to vascular dysfunction. Studies were performed in the 3T3-L1 adipocyte cell line and mature adipocytes isolated from human and mouse (C57BL/6J) adipose tissue. Mesenteric arteries with and without perivascular fat and mature adipocytes were obtained from obese diabetic db/db and control db/+ mice. Aldosterone synthase (CYP11B2; mRNA and protein) was detected in 3T3-L1 and mature adipocytes, which secrete aldosterone basally and in response to angiotensin II (Ang II). In 3T3-L1 adipocytes, Ang II stimulation increased aldosterone secretion and CYP11B2 expression. Ang II effects were blunted by an Ang II type 1 receptor antagonist (candesartan) and inhibitors of calcineurin (cyclosporine A and FK506) and nuclear factor of activated T-cells (VIVIT). FAD286 (aldosterone synthase inhibitor) blunted adipocyte differentiation. In candesartan-treated db/db mice (1 mg/kg per day, 4 weeks) increased plasma aldosterone, CYP11B2 expression, and aldosterone secretion were reduced. Acetylcholine-induced relaxation in db/db mesenteric arteries containing perivascular fat was improved by eplerenone (mineralocorticoid receptor antagonist) without effect in db/+ mice. Adipocytes possess aldosterone synthase and produce aldosterone in an Ang II/Ang II type 1 receptor/calcineurin/nuclear factor of activated T-cells-dependent manner. Functionally adipocyte-derived aldosterone regulates adipocyte differentiation and vascular function in an autocrine and paracrine manner, respectively. These novel findings identify adipocytes as a putative link between aldosterone and vascular dysfunction in diabetes mellitus-associated obesity.
The discovery of leptin in the mid-1990s has focused attention on the role of proteins secreted by adipose tissue. Leptin has profound effects on appetite and energy balance, and is also involved in the regulation of neuroendocrine and immune function. Sex steroid and glucocorticoid metabolism in adipose tissue has been implicated as a determinant of body fat distribution and cardiovascular risk. Other adipose products, for example, proinflammatory cytokines, complement factors and components of the coagulation/fibrinolytic cascade, may mediate the metabolic and cardiovascular complications associated with obesity.
All homeotherms use thermogenesis to maintain their core body temperature, ensuring that cellular functions and physiological processes can continue in cold environments. In the prevailing model of thermogenesis, when the hypothalamus senses cold temperatures it triggers sympathetic discharge, resulting in the release of noradrenaline in brown adipose tissue and white adipose tissue. Acting via the β(3)-adrenergic receptors, noradrenaline induces lipolysis in white adipocytes, whereas it stimulates the expression of thermogenic genes, such as PPAR-γ coactivator 1a (Ppargc1a), uncoupling protein 1 (Ucp1) and acyl-CoA synthetase long-chain family member 1 (Acsl1), in brown adipocytes. However, the precise nature of all the cell types involved in this efferent loop is not well established. Here we report in mice an unexpected requirement for the interleukin-4 (IL-4)-stimulated program of alternative macrophage activation in adaptive thermogenesis. Exposure to cold temperature rapidly promoted alternative activation of adipose tissue macrophages, which secrete catecholamines to induce thermogenic gene expression in brown adipose tissue and lipolysis in white adipose tissue. Absence of alternatively activated macrophages impaired metabolic adaptations to cold, whereas administration of IL-4 increased thermogenic gene expression, fatty acid mobilization and energy expenditure, all in a macrophage-dependent manner. Thus, we have discovered a role for alternatively activated macrophages in the orchestration of an important mammalian stress response, the response to cold.
Several lines of evidence suggest a detrimental effect of aldosterone excess on the development of metabolic alterations. Glucose metabolism derangements due to aldosterone action are frequently observed not only in patients with primary aldosteronism but also in patients with obesity. A contribution to the hyperaldosteronism observed in obese subjects can be attributed, at least in part, to the action of still unidentified adipocyte-derived factor. Aldosterone, through genomic and non-genomic actions contributes to induce several abnormalities: pancreatic fibrosis, impaired beta cell function, as well as reduced skeletal muscle and adipose tissue insulin sensitivity. Oxidative stress, systemic inflammation, together with these metabolic alterations may explain the appearance of the cardiometabolic syndrome and the progression of cardiovascular and renal diseases, in the presence of inappropriate aldosterone levels. The biological actions of aldosterone are mediated by mineralocorticoid receptor (MR), although MR can be activated through an aldosterone independent fashion. Besides salt-water homeostasis, MR activation promotes inflammation, endothelial dysfunction, cardiovascular remodelling and affects adipose tissue differentiation and function. Clinical and experimental studies have shown that MR blockade is able to suppress inflammation, to improve endothelium- dependent vasorelaxation, but most interestingly, to improve pancreatic insulin release as well as insulin-mediated glucose utilization. These actions indicate MR antagonists as a useful therapeutic tool able not only to reduce cardiovascular risk and renal damage, but also to improve metabolic sequaelae.
Metabolism and immunity are two fundamental systems of metazoans. The presence of immune cells, such as macrophages, in metabolic tissues suggests dynamic, ongoing crosstalk between these two regulatory systems. Here, we discuss how changes in the recruitment and activation of macrophages contribute to metabolic homeostasis. In particular, we focus our discussion on the pathogenic and protective functions of classically and alternatively activated macrophages, respectively, in experimental models of obesity and metabolic disease.
Aldosterone controls blood pressure by binding to the mineralocorticoid receptor (MR), a ligand-activated transcription factor which regulates critical genes controlling salt and water homeostasis in the kidney. In recent years, inappropriate MR activation has been shown to trigger deleterious responses in various tissues, including vessels, heart and brain, hence promoting vascular inflammation, cardiovascular remodeling, endothelial dysfunction, and oxidative stress. Moreover, epidemiological studies have shown a clear association between aldosterone levels and the incidence of metabolic syndrome. In particular, recent work has revealed functional MRs in adipose tissue, where they mediate the effects of aldosterone and glucocorticoids, displaying important and specific functions involving adipose differentiation, expansion and proinflammatory capacity. This recent evidence finally moved MR out of the shadow of the glucocorticoid receptor (GR), which had previously been considered the only player mediating corticosteroid action in adipose tissue. This has opened a new era of research focusing on the complexity and selectivity of MR function in adipocyte biology. The aim of this review is to summarize the latest concepts on the role of MR in white and brown adipocytes, and to discuss the potential benefits of tissue-selective MR blockade in the treatment of obesity and metabolic syndrome.
Obesity is one major risk factor for the development of arterial hypertension, and the development of obesity-related hypertension has been associated with increased plasma aldosterone levels. Our previous work shows a direct stimulatory effect of adipokines on aldosterone secretion from human adrenocortical cells, mediated via ERK1/2-dependent upregulation of steroid acute regulatory protein (StAR) activity. Recent evidence also indicates the involvement of the Wnt-signaling pathway in fat cell-mediated aldosterone secretion. Wnt-signaling molecules are secreted by adipocytes and regulate the activity of SF-1, a key transcription factor in adrenal steroidogenesis. The goal of this study was to investigate the cellular mechanisms of adipocyte-induced aldosterone secretion in detail, and to evaluate effects and possible interactions of the ERK1/2 MAPK- and the Wnt-signaling pathways on adipocyte-induced adreno-cortical aldosterone secretion. Our results show that, similar to adipocyte-conditioned medium (ACM), β-catenin, which is an intracellular mediator of canonical Wnt-signaling, induced StAR promotor activity in human NCI-H295R adrenocortical cells, and ACM-induced StAR promotor activity depended on intact SF-1 binding sites. Wnt antagonist sFRP-1 inhibited adipokine-mediated StAR activity, but did not affect ERK1/2 MAPK activation. Accordingly, Wnt did not stimulate ERK1/2 phosphorylation in adrenocortical cells, indicating that ERK1/2 MAPK and Wnt signaling pathways are independently involved in adipocyte-mediated aldosterone secretion.
Several large clinical studies have demonstrated the important benefit of mineralocorticoid receptor (MR) antagonists in patients with heart failure, left ventricular dysfunction after myocardial infarction, hypertension or diabetic nephropathy. Aldosterone adjusts the hydro-mineral balance in the body, and thus participates decisively to the control of blood pressure. This traditional view of the action of aldosterone restricted to sodium reabsorption in epithelial tissues must be revisited. Clinical and experimental studies indicated that chronic activation of the MR in target tissues induces structural and functional changes in the heart, kidneys and blood vessels. These deleterious effects include cardiac and renal fibrosis, inflammation and vascular remodeling. It is important to underscore that these effects are due to elevated MR activation that is inadequate for the body salt requirements. Aldosterone is generally considered as the main ligand of MR. However, this is a matter of debate especially in heart. Complexity arises from the glucocorticoids with circulating concentrations much higher than those of aldosterone, and the fact that the MR has a high affinity for 11β-hydroxyglucocorticoids. Nevertheless, the beneficial effects of MR inhibition in patients with heart failure emphasize the importance of this receptor in cardiovascular tissue. Diverse experimental models and strains of transgenic mice have allowed to dissect the effects of aldosterone and the MR in the heart. Taken together experimental and clinical data clearly highlight the deleterious cardiovascular effects of MR stimulation.
Macrophage infiltration and activation in metabolic tissues underlie obesity-induced insulin resistance and type 2 diabetes. While inflammatory activation of resident hepatic macrophages potentiates insulin resistance, the functions of alternatively activated Kupffer cells in metabolic disease remain unknown. Here we show that in response to the Th2 cytokine interleukin-4 (IL-4), peroxisome proliferator-activated receptor delta (PPARdelta) directs expression of the alternative phenotype in Kupffer cells and adipose tissue macrophages of lean mice. However, adoptive transfer of PPARdelta(-/-) (Ppard(-/-)) bone marrow into wild-type mice diminishes alternative activation of hepatic macrophages, causing hepatic dysfunction and systemic insulin resistance. Suppression of hepatic oxidative metabolism is recapitulated by treatment of primary hepatocytes with conditioned medium from PPARdelta(-/-) macrophages, indicating direct involvement of Kupffer cells in liver lipid metabolism. Taken together, these data suggest an unexpected beneficial role for alternatively activated Kupffer cells in metabolic syndrome and type 2 diabetes.
Recent evidence suggests that treatment with mineralocorticoid receptor antagonist suppressed local inflammation in vascular tissues or cardiomyocytes; therefore, we examined the effect of spironolactone on glucose and lipid metabolism in a mouse model with diet-induced diabetes and nonalcoholic fatty liver disease. C57BL/6 mice were fed either the control diet, 60% fat diet with 30% fructose water (HFFD), or HFFD with spironolactone for 8 wk. HFFD mice demonstrated apparent phenotypes of metabolic syndrome, including insulin resistance, hypertension, dyslipidemia, and fatty liver. Although treatment with spironolactone did not affect the increased calorie intake and body weight by HFFD, the increments of epididymal fat weight, blood pressure, serum triglyceride, free fatty acids, leptin, and total cholesterol levels were significantly suppressed. Elevation of blood glucose during glucose and insulin tolerance tests in HFFD mice was significantly lowered by spironolactone. Notably, increased glucose levels during pyruvate tolerance test in HFFD mice were almost completely ameliorated to control levels by the treatment. Staining with hematoxylin-eosin (HE) and Oil-red-O demonstrated marked accumulation of triglycerides in the centrilobular part of the hepatic lobule in HFFD mice, and these accumulations were effectively improved by spironolactone. Concomitantly HFFD feeding markedly up-regulated hepatic mRNA expression of proinflammatory cytokines (TNFalpha, IL-6, and monocyte chemoattractant protein-1), gluconeogenic gene phosphoenolpyruvate carboxykinase, transcription factor carbohydrate response element binding protein, and its downstream lipogenic enzymes, all of which were significantly suppressed by spironolactone. These results indicate that inhibition of mineralocorticoid receptor might be a beneficial therapeutic approach for diet-induced phenotypes of metabolic syndrome and fatty liver.
Glucocorticoids contribute to the maintenance of basal and stress-related homeostasis in all higher organisms, and influence a large proportion of the expressed human genome, and their effects spare almost no organs or tissues. Glucocorticoids regulate many functions of the central nervous system, such as arousal, cognition, mood, sleep, the activity and direction of intermediary metabolism, the maintenance of a proper cardiovascular tone, the activity and quality of the immune and inflammatory reaction, including the manifestations of the sickness syndrome, and growth and reproduction. The numerous actions of glucocorticoids are mediated by a set of at least 16 glucocorticoid receptor (GR) isoforms forming homo- or hetero-dimers. The GRs consist of multifunctional domain proteins operating as ligand-dependent transcription factors that interact with many other cell signaling systems, including large and small G proteins. The presence of multiple GR monomers and homo- or hetero-dimers expressed in a cell-specific fashion at different quantities with quantitatively and qualitatively different transcriptional activities suggest that the glucocorticoid signaling system is highly stochastic. Glucocorticoids are heavily involved in human pathophysiology and influence life expectancy. Common behavioral and/or somatic complex disorders, such as anxiety, depression, insomnia, chronic pain and fatigue syndromes, obesity, the metabolic syndrome, essential hypertension, diabetes type 2, atherosclerosis with its cardiovascular sequelae, and osteoporosis, as well as autoimmune inflammatory and allergic disorders, all appear to have a glucocorticoid-regulated component.
Increased mineralocorticoid levels plus high salt promote vascular inflammation and cardiac tissue remodeling. Mineralocorticoid receptors are expressed in many cell types of the cardiovascular system, including monocytes/macrophages and other inflammatory cell types. Although mineralocorticoid receptors are expressed in monocytes/macrophages, their role in regulating macrophage function to date has not been investigated. We, thus, used the Cre/LoxP-recombination system to selectively delete mineralocorticoid receptors from monocytes/macrophages with the lysozyme M promoter used to drive Cre expression (MR(flox/flox)/LysM(Cre/-) mice). Male mice from each genotype (MR(flox/flox) or wild-type and MR(flox/flox)/LysM(Cre/-) mice) were uninephrectomized, given 0.9% NaCl solution to drink, and treated for 8 days or 8 weeks with either vehicle (n=10) or deoxycorticosterone (n=10). Equivalent tissue macrophage numbers were seen for deoxycorticosterone treatment of each genotype at 8 days; in contrast, plasminogen activator inhibitor type 1 and NAD(P)H oxidase subunit 2 levels were increased in wild-type but not in MR(flox/flox)/LysM(Cre/-) mice given deoxycorticosterone. Baseline expression of other inflammatory genes was reduced in MR(flox/flox)/LysM(Cre/-) mice compared with wild-type mice. At 8 weeks, deoxycorticosterone-induced macrophage recruitment and connective tissue growth factor and plasminogen activator inhibitor type 1 mRNA levels were similar for each genotype; in contrast, MR(flox/flox)/LysM(Cre/-) mice showed no increase in cardiac fibrosis or blood pressure, as was seen in wild-type mice at 8 weeks. These data demonstrate the following points: (1) mineralocorticoid receptor signaling regulates basal monocyte/macrophage function; (2) macrophage recruitment is not altered by loss of mineralocorticoid receptor signaling in these cells; and (3) a novel and significant role is seen for macrophage signaling in the regulation of cardiac remodeling and systolic blood pressure in the deoxycorticosterone/salt model.