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Prenatal programming of hepatocyte nuclear factor 4?? in the rat: A key mechanism in the 'foetal origins of hyperglycaemia'?
Abstract
Prenatal glucocorticoid exposure causes lifelong hyperglycaemia in rat offspring, associated with permanently increased hepatic phosphoenolpyruvate carboxykinase 2 (PCK2), the rate-controlling enzyme of gluconeogenesis. To elucidate the mechanisms underlying the 'programming' of PCK2, this study examined the effect of prenatal dexamethasone treatment on expression of transcription factors that regulate Pck2.
Real-time RT-PCR and in situ hybridisation were used to measure and localise hepatic mRNA transcribed from the genes for PCK2, hepatocyte nuclear factor 4, alpha (HNF4A), transcription factor 1 (TCF1), CCAAT/enhancer binding protein, alpha (CEBPA), CEBPB, the glucocorticoid receptor (NR3C1) and peroxisome proliferative activated receptor, gamma, coactivator 1 alpha (PPARGC1A) in foetal and adult offspring of dams treated with dexamethasone or vehicle during the last week of gestation.
Prenatal dexamethasone exposure significantly elevated Hnf4a mRNA expression in foetal and adult liver. This resulted from increased expression of isoforms derived from the 'adult' (P1) Hnf4a promoter. In contrast, isoforms from the 'foetal' (P2) promoter were markedly suppressed by dexamethasone. Like Pck2, the increase in hepatic Hnf4a mRNA occurred exclusively in the periportal zone. Foetal Tcf1 expression was also increased by dexamethasone treatment, but this did not persist into adulthood. Prenatal dexamethasone did not affect the amounts of foetal and/or adult Cebpa, Cebpb, Nr3c1 or Ppargc1a mRNA.
Prenatal dexamethasone exposure caused a permanent increase in hepatic Hnf4a mRNA. This increase, which was associated with a premature switch from foetal to adult promoter predominance, was congruent with changes in Pck2 expression. These data suggest that HNF4A might mediate Pck2 overexpression and subsequent hyperglycaemia.
... Similarly, some of the functional changes observed at the cellular level in fetal A. L. tissues after glucocorticoid treatment are also present in the tissues of the adult offspring (Table 2). Increases in the hepatic glucogenic capacity induced in utero by maternal glucocorticoid administration late in gestation persist after birth and are associated with glucose intolerance in the adult offspring (Nyirenda et al. 1998(Nyirenda et al. , 2006Franko, 2007). In some tissues, maternal glucocorticoid administration has opposite effects in the fetus and adult offspring (Table 2). ...
... The phenotypical outcome of prenatal glucocorticoid administration also depends, in part, on gestational age at treatment and whether exposure is to natural or synthetic glucocorticoids (Fowden et al. 1998a;Moritz et al. 2005). In rats, hepatic phosphoenolpyruvate caboxykinase (PEPCK) expression is upregulated in the adult offspring after maternal dexamethasone treatment in the third but not the first or second week of pregnancy (Nyirenda et al. 2006). Similarly, in sheep, maternal treatment with synthetic glucocorticoids early in gestation leads to adult hypertension but not glucose tolerance, whereas treatment later in gestation has the opposite effects in the adult offspring (Gatford et al. 2000;Moss et al. 2001). ...
... At the transcriptional level, hormones can alter gene expression by changes in transcription factor abundance, RNA stability and/or promotor usage and differential splicing. In fetal liver, glucocorticoids have been shown to influence promotor usage of several genes with multiple mRNA transcripts, including the GR, growth hormone receptor (GHR), IGF-I and Hnf4a genes (Li et al. 1996, Exp Physiol 94.6 pp 607-625 1998McCormick et al. 2000;Nyirenda et al. 2006). This leads to alternative slicing of the exons and differences in the 5 untranslated end of the mRNA transcripts, which may influence their translation. ...
In mammals, including man, epidemiological and experimental studies have shown that a range of environmental factors acting during critical periods of early development can alter adult phenotype. Hormones have an important role in these epigenetic modifications and can signal the type, severity and duration of the environmental cue to the developing feto-placental tissues. They affect development of these tissues both directly and indirectly by changes in placental phenotype. They act to alter gene expression, hence the protein abundance in a wide range of different tissues, which has functional consequences for many physiological systems both before and after birth. By producing an epigenome specific to the prevailing condition in utero, hormones act as epigenetic signals in developmental programming, with important implications for adult health and disease. This review examines the role of hormones as epigenetic signals by considering their responses to environmental cues, their effects on phenotypical development and the molecular mechanisms by which they programme feto-placental development, with particular emphasis on the glucocorticoids.
... In this issue of Diabetologia, Nyirenda et al. [17] report an exciting new potential mechanism for glucocorticoidinduced foetal programming of hyperglycaemia. The authors' previous work demonstrated that exposure to prenatal dexamethasone resulted in persistent upregulation of the mRNA and activity of the cytosolic form of the gluconeogenic enzyme phosphoenolpyruvate carboxykinase (PCK) in adult offspring [18]. ...
... Furthermore, these changes in PCK expression in adult offspring could not be attributed to altered postnatal maternal behaviour, suggesting that excess foetal glucocorticoid exposure has a permanent effect, programming increased gluconeogenesis [19]. Nyirenda et al. [17] have now followed up this work by investigating the effects of supraphysiological levels of glucocorticoids, administered to female rats during the last week of pregnancy, on key hepatic transcription factors known to regulate PCK expression in the rat foetus and adult offspring. Prenatal dexamethasone resulted in an early increase in the transcription of the gene encoding foetal hepatic nuclear factor 4 (Hnf4a), which remained elevated into adulthood, and paralleled the rise in Pck1 expression and hyperglycaemia. ...
... HNF4A has been associated with recruiting coactivator protein (CREB binding protein/ p300) and the ability to mediate chromatin remodelling [26][27][28]. Whether these other regulators are also involved in stimulating PCK gene transcription directly in response to early glucocorticoid exposure was not explored in the report by Nyirenda et al. [17]. A more thorough and direct analysis of the DNA binding factors at the protein level could be explored using foetal rat liver nuclear extracts and DNA binding assays. ...
... 8 In rats, a positive correlation between dexamethasone exposure and an elevated expression of hepatocyte nuclear factor 4α (HNF4α), together with its regulated phosphoenolpyruvate carboxykinase 2 (PEPCK, encoded by pck1/pck2) was identified in the fetal liver. 9 Hnf4α encodes a transcription factor essential for hepatocyte differentiation and maturation, both morphologically and functionally. It also acts to regulate expression of key gluconeogenic genes, including Pck1 and glucose-6phosphatase (G6pc). ...
... 29,30 However, premature activation of the gluconeogenic pathway, especially an increase in expression of Hnf4α and Pck1/Pck2, in fetuses exposed in utero to dexamethasone or to maternal HFD, has been associated with adulthood diabetic symptoms in both rodents and monkeys. 9,31,32 This suggests that gluconeogenic gene activation before birth may be a common underlying mechanism for fetal programming of adult metabolic diseases. Indeed, a significant induction of Hnf4α has been seen in all three cases: gestational exposure to metformin (this report); to dexamethasone; 9 or to maternal HFD. 31 While previous studies reported an increase in expression of Pck1 in maternal HFD 31,32 or Pck2 9 in dexamethasone-9 exposed fetuses, we did not observe such an effect in metformin-exposed fetal liver (Figures 2d and e). ...
Metformin is the most widely used anti-diabetic medication worldwide. However, human and animal studies suggest that prenatal metformin exposure may increase the risk of metabolic disorders in adult offspring, yet the underpinning mechanism remains unclear. Here we report that metformin-exposed mouse fetuses exhibit elevated expression of the H19 long noncoding RNA, which induces hypomethylation and increased expression of hepatocyte nuclear factor 4α (HNF4α). As a transcription factor essential for morphological and functional differentiation of hepatocytes, HNF4α also has an indispensable role in the regulation of expression of gluconeogenic genes. Consistently, H19 overexpression in a human liver cell line leads to decreased methylation and increased expression of Hnf4α, with concomitant activation of the gluconeogenic program. Mechanistically, we show that the methylation change of Hnf4α is induced by H19-mediated regulation of S-adenosylhomocysteine hydrolase. We also provide evidence that altered H19 expression is a direct effect of metformin in the fetal liver. Our results suggest that metformin from the mother can directly act upon the fetal liver to modify Hnf4α expression, a key factor for both liver development and function, and that perturbation of this H19/Hnf4α-mediated pathway may contribute to the fetal origin of adult metabolic abnormalities.
... The transcription factor HNF4a encoded by HNF4A, is a master regulator of the hepatocyte phenotype [24][25][26]. During development there is a switch from an upstream immature P2 promoter to a downstream 'liver' P1 promoter, generating alternative first exons of the HNF4A gene [27,28]. This was mirrored in our cultures: in DE-like cells, HNF4A was expressed from the 'immature' P2 promoter; however, in HLCs the downstream first exon was preferentially transcribed from the P1 'liver' promoter ( Supplementary Fig. 2C, red boxes). ...
... The high rates of proliferation and apoptosis during this phase of differentiation match those seen previously [25] and are consistent with the major remodelling that characterizes embryogenesis. We mimicked the change in HNF4A promoter usage during embryonic development [27,28]. Finally, despite some unexpected individual proteins, we demonstrated that the HLC proteome had more in common with human liver than any other organ tested. ...
Background & aims
Hepatocyte-like cells (HLCs) differentiated from pluripotent stem cells by the use of soluble factors can model human liver function and toxicity. However, at present HLC maturity and whether any deficit represents a true fetal state or aberrant differentiation is unclear and compounded by comparison to potentially deteriorated adult hepatocytes. Therefore, we generated HLCs from multiple lineages and two different protocols for direct comparison with fresh fetal and adult hepatocytes.
Methods
Protocols were developed for robust differentiation. Multiple transcript, protein and functional analyses compared HLCs to fresh human fetal and adult hepatocytes.
Results
HLCs were comparable to those of other laboratories by multiple parameters. Transcriptional changes during differentiation mimicked human embryogenesis and showed more similarity to pericentral than periportal hepatocytes. Unbiased proteomics demonstrated greater proximity to liver than 30 other human organs or tissues. However, by comparison to fresh material HLC maturity was proven by transcript, protein and function to be fetal-like and short of the adult phenotype. Expression of 81% of phase 1 enzymes in HLCs was significantly upregulated and half were statistically no different from in fetal hepatocytes. HLCs secreted albumin and metabolized testosterone (CYP3A) and dextrorphan (CYP2D6) like fetal hepatocytes. In seven bespoke tests devised by principal components analysis to distinguish fetal from adult hepatocytes HLCs from two different source laboratories consistently demonstrated fetal characteristics.
Conclusions
HLCs from different sources are broadly comparable with unbiased proteomic evidence for faithful differentiation down the liver lineage. This current phenotype mimics human fetal rather than adult hepatocytes.
... These observations suggest that changes in PEPCK activity programmed in utero are more evident at times of major changes in nutrition at birth and weaning. However, hepatic PEPCK activity was higher in the adult offspring of the dex-treated dams than in those of the saline-treated dams as reported previously for offspring of dex-and vehicle-injected dams (Nyirenda et al. 1998(Nyirenda et al. , 2006. This glucocorticoid programmed upregulation of adult hepatic PEPCK activity is associated with increased expression of hepatocyte nuclear factor 4, a known transcription factor for the Pck2 promoter (Nyirenda et al. 2006). ...
... However, hepatic PEPCK activity was higher in the adult offspring of the dex-treated dams than in those of the saline-treated dams as reported previously for offspring of dex-and vehicle-injected dams (Nyirenda et al. 1998(Nyirenda et al. , 2006. This glucocorticoid programmed upregulation of adult hepatic PEPCK activity is associated with increased expression of hepatocyte nuclear factor 4, a known transcription factor for the Pck2 promoter (Nyirenda et al. 2006). In the current study, the difference in hepatic PEPCK activity between offspring of the saline-and dex-treated dams was observed in both adult males and females, whereas previously, this effect was observed only in males (Nyirenda et al. 1998, O'Regan et al. 2004. ...
Glucocorticoid administration during pregnancy programmes cardiovascular and metabolic functions in the adult offspring. Often, the control procedures are stressful per se and raise maternal glucocorticoid concentrations. This study compared the effects of maternal injection with dexamethasone (dex, 200 microg/kg) or saline with no treatment from 15 to 20 days of rat pregnancy on offspring growth and glucose metabolism. Near term, maternal corticosterone concentrations were higher in the saline-treated dams and lower in the dex-treated dams relative to untreated animals. In both male and female offspring, growth rate was measured for 14 weeks, and glucose tolerance was assessed between 12 and 13 weeks together with body fat content and plasma concentrations of insulin, leptin, and corticosterone between 14 and 15 weeks. Offspring liver was collected at different ages and was analyzed for glycogen content and gluconeogenic enzyme activity. Compared with untreated animals, both dex and saline treatments altered postnatal growth although adult body weight was unaffected. The two treatments had different effects on adult insulin concentrations and on hepatic glycogen content and gluconeogenic enzyme activities both pre- and postnatally. Relative to untreated animals, adult glucose tolerance was improved by maternal saline injection in males but not in females, while it was impaired in female offspring but not in male offspring of the dex-treated dams. Adult glucose tolerance was related to male body fat content but not to female body fat content. Dex and saline treatments of pregnant rats have differential sex-linked effects on the growth and glucose metabolism of their offspring, which indicates that the programming actions of natural and synthetic glucocorticoids may differ.
... It is The copyright holder for this preprint this version posted April 30, 2022. ; upstream (termed developmental, P2) to proximal (termed mature, P1) elements ( Supplementary Fig. S1) [28,29]. We hypothesised that this reduced expression of HNF4A and CEBPA would likely compromise HLC maturation and was due to under-representation of important gene networks normally active in mature adult hepatocytes. ...
Hepatocytes derived from human pluripotent stem cells (PSCs) hold great promise for modeling human liver disease, in vitro hepatotoxicity testing, and future cellular therapy. However, current protocols generate hepatocyte-like cells (HLCs) that resemble fetal hepatocytes, and thus do not accurately recapitulate the molecular identity and functions of the adult liver. To address this, we compared the transcriptomes of human fetal and adult liver to PSC-derived HLCs during progressive stages of in vitro differentiation. This revealed that during the final stages of in vitro differentiation the hepatic transcription factors HNF4A and CEBPA were sub-optimally expressed. Computational analyses predicted that ALK5i II (TGF-β receptor inhibitor) and thyroid hormone (T3) would be able to rectify this and improve HLC maturation. We next show that application of these molecules during hepatocyte differentiation indeed increases CEBPA and HNF4A mRNA and protein expression, and that these HLCs show enhanced albumin secretion, a 25-fold increase in CYP3A4 activity, and 10 to 100-fold increased expression of mature hepatic markers. We demonstrate that this improved maturation is effective across different cell lines and HLC differentiation protocols, and exemplifies that our approach provides a tractable template for identifying and targeting additional factors that that will fully mature human liver cells from human pluripotent stem cells.
... Prenatal DEX administration also increased their levels in the liver of 19F and 21F rats. Nyirenda et al. reported that continuous administration of prenatal DEX increased HNF4α mRNA expression in rat livers [47]. Our results are consistent with those obtained by Nyirenda et al. ...
Background
Prenatal glucocorticoid (GC) is clinically administered to pregnant women who are at risk of preterm birth for the maturation of cardiopulmonary function. Preterm and low-birth-weight infants often experience liver dysfunction after birth because their livers are immature. However, the effects of prenatal GC administration on the liver remain unclear. We aimed to investigate the effects of prenatal GC administration on the maturation of liver hepatocytes in preterm rats.
Methods and results
Dexamethasone (DEX) was administered to pregnant Wistar rats on gestational days 17 and 19 before cesarean section. Real-time reverse transcription-polymerase chain reaction (RT-PCR) was performed to determine the mRNA levels of albumin, hepatocyte nuclear factor-4 alpha (HNF4α), hepatocyte growth factor (HGF), thymus cell antigen 1 (Thy-1), cyclin B, and Cyclin-dependent kinase 1 (CDK1) in the liver samples. Immunohistochemical staining and enzyme-linked immunosorbent assay were performed to examine protein production. The hepatocytes enlarged because of growth and prenatal DEX administration. Albumin, HNF4α, and HGF levels increased secondary to growth and prenatal DEX administration. The levels of the cell cycle markers cyclin B and CDK1 gradually decreased during growth and with DEX administration.
Conclusions
The results suggest that prenatal GC administration leads to hepatocyte maturation via expression of HNF4α and HGF in preterm fetuses.
... Prenatal DEX administration also increased their levels in the liver of 19F and 21F rats. Nyirenda et al. reported that continuous administration of prenatal DEX increased HNF4α mRNA expression in rat livers [41]. Our results are close to clinical therapeutics and are consistent with those obtained by Nyirenda et al. ...
Prenatal glucocorticoid (GC) is clinically administered to pregnant women who are at risk of preterm birth for maturation of cardiopulmonary function. Preterm and low-birth-weight infants often experience liver dysfunction after birth because the liver is immature. However, the effects of prenatal GC administration on the liver remain unclear. We aimed to investigate the effects of prenatal GC administration on the maturation of liver hepatocytes in preterm rats.
Dexamethasone (DEX) was administered to pregnant Wistar rats on gestational days 17 and 19 before cesarean section. Real time-polymerase chain reaction (RT-PCR) was performed to determine the mRNA levels of albumin, HNF4α, HGF, Thy-1, cyclin B, and CDK1 in the liver samples. Immunohistochemical staining and enzyme-linked immunosorbent assay were performed to examine protein production.
The hepatocytes enlarged because of growth and prenatal DEX administration. Albumin, HNF4α, and HGF levels increased secondary to growth and prenatal DEX administration. The levels of the cell cycle markers cyclin B and CDK1 gradually decreased during growth and with DEX administration.
The results suggest that prenatal GC administration leads to hepatocyte maturation via expression of HNF4α and HGF in premature fetuses.
... Prenatal DEX administration also increased their levels in 19F and 21F livers. Nyirenda et al. (2006) The obtained all data was compared using a two-way ANOVA variance test to detect any differences between groups, considering in the age, DEX treatment, and both factors. Almost the gene and protein levels, except for some gene and protein were signi cant differences between the age or DEX treatment. ...
Prenatal glucocorticoid (GC) is clinically administered to pregnant women at risk of preterm birth for maturation of the cardiopulmonary function. Preterm and low birth weight infants often experience liver dysfunction after birth because the liver is immature. However, the effects of prenatal GC administration on the liver remain unclear. We aimed to investigate the effects of prenatal GC administration regarding maturity of the liver in preterm rats.
Dexamethasone (DEX) was administered to pregnant Wistar rats on gestational day 17 and 19 before cesarean section. Real time polymerase chain reaction (RT-PCR) was then used to analyze the mRNA levels (albumin, HNF4α, HGF, Thy-1, cyclin B, and CDK1) in the liver samples. Immunohistochemical staining and enzyme-linked immunosorbent assay (ELISA) were used to analyze protein production.
Hepatocyte size enlarged because of growth and administration of prenatal DEX. Albumin, HNF4α, and hepatocyte growth factor (HGF) increased secondary to growth and administration of prenatal DEX. Cell cycle markers, cyclin B, and CDK1 gradually decreased during growth and by administration of DEX.
These results suggest that prenatal GC administration achieves hepatocyte maturation via expression of HNF4α and HGF in premature fetuses.
... Metformin is one of drugs that can overcome the placental barrier, get significant concentrations in fetus and therefore can have a direct or indirect effect on it. A correlation between hyperglycemia with consequent glucose intolerance and pharmacological treatment during pregnancy has recently been demonstrated for dexamethasone, which increases Hnf4α factor expression and deregulates PEPCK in fetal liver 99 . Hnf4α encodes for a key factor in differentiation, maturation and liver architecture, and regulates gluconeogenesis genes like PEPCK and G6Pase 100 . ...
This review aims at presenting an overview on metformin effects in diabetic and pre-diabetic states as well as in Polycystic Ovary Syndrome. The molecular mechanisms in which metformin is involved are discussed in depth. Particular attention is paid to the metabolic
alterations and infertility which are important aspects characterizing PCOS. The part devoted to the molecular mechanisms underlying the metformin activity is a necessary introduction to the following sections and helps explaining its therapeutic activity in disorders
where the common denominator is insulin resistance. The review also compares the effects of metformin with those of other therapeutic
molecules. An important part is also dedicated to the side effects and limitations in the use of this drug, with a particular attention to the
long-term effects. Metformin exerts multiple activities at the molecular level, still partly to be clarified, and induces a number of side effects. For these reasons, it should be administered with caution and always under careful control to patients suffering from diabetic and pre-diabetic states, and from PCOS. Furthermore, wherever possible it would be necessary to prefer the use of safer molecules.
... Animal research in rodents and non-human primates provides a number of plausible mechanisms for how prenatal events can program the fetus for later adversity in adolescence and adult life. Specifically, prenatal events can have functional and structural effects on the brain, resulting in altered behaviors and responses to stress in addition to metabolic changes and even effects on whole genome methylation (Crudo et al., 2012;Drake et al., 2010;Drake and Walker, 2004;Harris and Seckl, 2011;Iqbal et al., 2012;Nyirenda et al., 2006;Seckl, 2004). ...
Prenatal dexamethasone (DEX) treatment in congenital adrenal hyperplasia (CAH) is effective in reducing virilization in affected girls, but potential long-term adverse effects are largely unknown. In this report we intended to explore potential side effects of DEX therapy to enhance the adequacy of future risk benefit analyses of DEX treatment. We investigated the long-term effects of first trimester prenatal DEX treatment on behavioral problems and temperament in children and adolescents aged 7-17 years. The study included 34 children and adolescents, without CAH, who had been exposed to DEX during the first trimester and 67 untreated controls. Standardized parent-completed questionnaires were used to evaluate adaptive functioning and behavioral/emotional problems (CBCL), social anxiety (SPAI-C-P), and temperament (EAS) in the child. Self-reports were used to assess the children's perception of social anxiety (SASC-R). No statistically significant differences were found between DEX-treated and control children and adolescents, suggesting that, in general, healthy children treated with DEX during early fetal life are well adjusted.
... Alterations in maternal DNA methylation may also indirectly affect the fetus through changes in the maternal environment. Changes in the maternal environment can result in direct changes in gene expression in the developing fetus [44], and if certain harmful exposures occur during organogenesis, various structural anomalies may occur [13]. Alterations in maternal methylation in genes involved in the maintenance of the intrauterine environment may lead to an increased susceptibility to teratogenic agents. ...
... Animal research in rodents and non-human primates provides a magnitude of plausible mechanisms indicating how prenatal events can program the fetus for later adversity during adolescence and adult life (Harris and Seckl, 2011). Specifically, prenatal events can have functional and structural effects on the brain resulting in altered behaviors as well as metabolic changes and hypertension, hyperlipidemia and hyperglycemia in rats (Drake et al., 2010;Nyirenda et al., 2006). Altered responses to stress and even transgenerational whole genome methylation changes have been reported in off-spring to guinea pigs treated during the end of pregnancy (Crudo et al., 2012;Iqbal et al., 2012). ...
This article has been retracted: please see Elsevier Policy on Article Withdrawal (http://www.elsevier.com/locate/withdrawalpolicy).
This article has been retracted at the request of the authors due to technical errors that have called into question the reliability of the data used to inform the author's conclusions.
All data on cognitive and behavioral outcomes in CAH and non–CAH cases, treated or not treated with DEX prenatally, were put into a single Excel database. The authors had in total four different patient groups for each age group (5–6 y, 7–17 y and 18-35 y). The database consisted of 237 cases in total and there were multiple columns for the different outcome measures.
When the behavioral data for the sub-cohort described in this paper (first trimester treated non-CAH cases and healthy population controls, age 7–17 y) were copied to another sheet and compressed/modified in preparation for statistical analysis in SPSS, an error occurred. This technological issue caused rows to shift and the data from the different groups got mixed up. In particular, the non–CAH group versus the control group were "contaminated" with cases from the wrong patient group.
The authors discovered this mistake when they started to analyse the data from the other sub–groups of patients, the CAH cases and the adult cohort, which was after their original results had already been published in Hormones and Behavior in this manuscript "Evaluation of behavioral problems after prenatal dexamethasone treatment in Swedish adolescents at risk of CAH".
It then became apparent that the entire data set was unreliable and needed to be re–analysed which is what has motivated the retraction of this article. The authors have recently completed this re–analysis and the results have been published here: https://www.sciencedirect.com/science/article/pii/S0018506X17300752
... Overall, these interventions have resulted in offspring with lower birth weight, dysregulated HPA axis, anxiety phenotype and an adverse metabolic profile in adult life [38]. Ex vivo analysis has shown that prenatal glucocorticoid treatment alters hepatic gene expression, leading to enhanced hepatic gluconeogenesis and insulin resistance (IR) [39][40][41]. Additionally, high fasting and postprandial blood glucose have been found in neonatal rats treated with glucocorticoids, metabolic disruptions combined with IR and lipid disorder in later life [42]. ...
Glucococorticoids play a critical role in the developmental programming and fetal growth. Key molecules mediating and regulating tissue-specific glucocorticoid actions are 11beta-hydroxysteroid dehydrogenase (11beta-HSD) type 1 and 2 isozymes, both of which are expressed in the placenta and the fetal membranes. 11beta-HSD1 is implicated in the pathogenesis of metabolic syndrome and its dysregulation has been observed in pregnancy-related complications (pre-eclampsia, intrauterine growth restriction). Interestingly, preliminary clinical data have associated certain 11beta-HSD1 gene polymorphisms with hypertensive disorders in pregnancy, suggesting, if confirmed by further targeted studies, its potential as a putative prognostic marker. Animal studies and observations in humans have confirmed that 11beta-HSD2 insufficiency is related with pregnancy adversity (pre-eclampsia, intrauterine growth restriction, preterm birth). Importantly, down-regulation or deficiency of placental 11beta-HSD2 is associated with significant restriction in fetal growth and low birth weight, and unfavourable cardio-metabolic profile in adulthood. The potential association of 11beta-HSD1 tissue-specific dysregulation with gestational diabetes, as well as the plausible utility of 11beta-HSD2 as a biomarker of pregnancy adversity and later life morbidity, are emerging areas of intense scientific interest and future investigation.
... The mechanisms responsible for increased HGP and the inability of insulin to suppress HGP in the IUGR fetus may include the combined effects of endocrine cues and associated changes in hormone and nutrient signaling pathways. The IUGR fetal liver has increased expression of PGC1A mRNA, nuclear hepatic nuclear factor (HNF4α), and phosphorylation of cAMP regulated binding protein (CREB) supporting the potential role of cAMPdependent signaling in mediating HGP , Nyirenda et al., 2006, Rhee et al., 2003, Thorn et al., 2009. AMPK activated protein kinase (AMPK) is a key nutrient sensor of decreased energy state and activation of AMPK (phosphorylation) decreases HGP in rodents (Shaw et al., 2005, Zhou et al., 2001. ...
Glucose is the major fuel for fetal oxidative metabolism. A positive maternal-fetal glucose gradient drives glucose across the placenta and is sufficient to meet the demands of the fetus, eliminating the need for endogenous hepatic glucose production (HGP). However, fetuses with intrauterine growth restriction (IUGR) from pregnancies complicated by placental insufficiency have an early activation of HGP. Furthermore, this activated HGP is resistant to suppression by insulin. Here, we present the data demonstrating the activation of HGP in animal models, mostly fetal sheep, and human pregnancies with IUGR. We also discuss potential mechanisms and pathways that may produce and support HGP and hepatic insulin resistance in IUGR fetuses.
... Un taux trop élevé de glucocorticoïdes a été corrélé dans de nombreuses études au développement d'une résistance à l'insuline, précédent l'installation du diabète de type II. L'exposition foetale aux glucocorticoïdes entraîne un changement précoce des isoformes foetales vers celles adultes entraînant ainsi une augmentation de l'expression du gène PEPCK (Nyirenda et al., 2006). ...
Mitochondria are integrators of intracellular signaling (adjusting its functioning to cellular energy demand) and initaitors of retrograde pathways (triggering cellular response to variations of functional status of mitochondria). This work focus on oxidative mitochondrial metabolism and signaling pathways, in HepG2 cells, in response of two energetic stresses : mitochondrial uncoupling and glucocorticoids treatement. Mitochondrial uncoupling triggers an increase in oxidative metabolism without any change in glycolysis (notably by a stimulation of nuclear transcription of genes encoding mitonchondrial proteins). Mitochondria are also one of targets of glucocorticoids, homones tht induce short term and long term effects. Rapid effects (modification of respiratory chain complexes I, II and III activities) involve dexamethasone binding on a membrane glucocorticoid receptor. These effects are mediated by calcium dependent activation of p38MAPK. Long term genomic effects (increase in respiratory chain capacity) implicate the classical intracellular glucocorticoid receptor. Modifications of the respiratory chain functioning induced by glucocorticoids involve the gradual recruitement of glucocorticoid binding sites (located in plasma membrane or in cytosol).
... One rate-controlling enzyme of gluconeogenesis (Nyirenda et al., 2006), namely phosphoenolpyruvate carboxykinase (PCKGM), was up-regulated in response to ZEA treatment. ...
... However, concerns have already emerged about the metabolic disorders caused by prenatal glucocorticoids excess. Studies from animal models have found that prenatal glucocorticoids treatment leads to increased hepatic gene expression of hepatocyte nuclear factor 4 alpha [85], phosphoenolpyruvate carboxykinase [86], and glucose-6-phosphatase [87] in the offspring, indicating elevated hepatic gluconeogenesis and hepatic insulin resistance. Nyirenda et al. also found that prenatal dexamethasone administration during late gestation may result in elevated 11 beta-HSD1 [88] and glucocorticoids receptor [86] expression in the liver, which may cause insulin resistance by increasing local glucocorticoids level [89] or activity. ...
Type 2 diabetes mellitus (T2DM) is a multifactorial disease, and its aetiology involves a complex interplay between genetic, epigenetic, and environmental factors. In recent years, evidences from both human and animal experiments have correlated early life factors with programming diabetes risk in adult life. Fetal and neonatal period is crucial for organ development. Many maternal factors during pregnancy may increase the risk of diabetes of offsprings in later life, which include malnutrition, healthy (hyperglycemia and obesity), behavior (smoking, drinking, and junk food diet), hormone administration, and even stress. In neonates, catch-up growth, lactation, glucocorticoids administration, and stress have all been found to increase the risk of insulin resistance or T2DM. Unfavorable environments (socioeconomic situation and famine) or obesity also has long-term negative effects on children by causing increased susceptibility to T2DM in adults. We also address the potential mechanisms that may underlie the developmental programming of T2DM. Therefore, it might be possible to prevent or delay the risk for T2DM by improving pre- and/or postnatal factors.
... These data suggest that Hnf4-a might mediate Pck2 overexpression and thus hyperglycaemia. It remains to be established whether the change in Hnf4-a expression is the primary effect of prenatal dexamethasone treatment or is secondary to alterations in the expression and/or function of other genes involved in the glucose metabolism/insulin signalling system [52]. Intriguingly, these effects are transmitted across generations without further exposure to glucocorticoids, which suggests an epigenetic mechanism. ...
Our purpose was to conduct a systematic review of the literature to determine whether synthetic pharmaceutical glucocorticoids (betamethasone and dexamethasone) are safe as well as effective in reducing neonatal respiratory morbidity at term of pregnancy prior to elective caesarean section. The overall incidence of respiratory disorders is estimated at 2.8 %, and the main risk factors are gestational age and mode of delivery. Newborns delivered by elective caesarean section (CS after 37 weeks) are more susceptible to serious respiratory complications than babies born by vaginal delivery. Neonatal respiratory morbidity at term of pregnancy is low but not negligible. Further, it is increasing due to a drastic decline in trial of labour in those pregnant women who underwent a caesarean section in the past. Because prophylaxis is inexpensive, easy to administer, and safe, other studies should be conducted to confirm its effectiveness.
We conducted a systematic review of literature since 1965 on the discovery of action mechanisms, pharmaceutical development, proper dosage, and potential side effects of corticosteroids on the mother and offspring to extrapolate their efficacy as no clinical trial has directly demonstrated it.
We extrapolated no negative effects on mother and foetus behaviour.
Human studies suggest that corticosteroid administration may become a proper clinical indication prior to caesarean section in the reduction of neonatal respiratory problems.
... The mechanisms of these programmed effects are tissuespecific and involve glucocorticoid-driven changes in target organ structure, gene expression, and function. Epigenetic mechanisms to maintain such effects have been advocated (167,523,524,623,755,760,761,781,782). Indeed, the key HPA axis drivers, corticotropin releasing hormone (CRH) and arginine vasopressin (AVP), and feedback receptor, glucocorticoid receptor (GR), show altered expression in models of programming and the promoters of all three encoding genes show persisting changes in methylation in response to early life environmental challenges (496,500,756). ...
Glucocorticoid action on target tissues is determined by the density of "nuclear" receptors and intracellular metabolism by the two isozymes of 11β-hydroxysteroid dehydrogenase (11β-HSD) which catalyze interconversion of active cortisol and corticosterone with inert cortisone and 11-dehydrocorticosterone. 11β-HSD type 1, a predominant reductase in most intact cells, catalyzes the regeneration of active glucocorticoids, thus amplifying cellular action. 11β-HSD1 is widely expressed in liver, adipose tissue, muscle, pancreatic islets, adult brain, inflammatory cells, and gonads. 11β-HSD1 is selectively elevated in adipose tissue in obesity where it contributes to metabolic complications. Similarly, 11β-HSD1 is elevated in the ageing brain where it exacerbates glucocorticoid-associated cognitive decline. Deficiency or selective inhibition of 11β-HSD1 improves multiple metabolic syndrome parameters in rodent models and human clinical trials and similarly improves cognitive function with ageing. The efficacy of inhibitors in human therapy remains unclear. 11β-HSD2 is a high-affinity dehydrogenase that inactivates glucocorticoids. In the distal nephron, 11β-HSD2 ensures that only aldosterone is an agonist at mineralocorticoid receptors (MR). 11β-HSD2 inhibition or genetic deficiency causes apparent mineralocorticoid excess and hypertension due to inappropriate glucocorticoid activation of renal MR. The placenta and fetus also highly express 11β-HSD2 which, by inactivating glucocorticoids, prevents premature maturation of fetal tissues and consequent developmental "programming." The role of 11β-HSD2 as a marker of programming is being explored. The 11β-HSDs thus illuminate the emerging biology of intracrine control, afford important insights into human pathogenesis, and offer new tissue-restricted therapeutic avenues.
... Dexamethasone-induced programming of later hyperglycaemia was also previously demonstrated to be fetus-focused [34] , sex- dependent [35] and transgenerational [36]. Mechanistically, this programming process involved elevated Hnf4a gene expression due to a shift from its fetal to adult promoter utilization occurring in the liver periportal zone [37]. We also presently report that DEX and UN pups show an early intolerance to glucose administration observable as soon as PND21. ...
Poor fetal growth, also known as intrauterine growth restriction (IUGR), is a worldwide health concern. IUGR is commonly associated with both an increased risk in perinatal mortality and a higher prevalence of developing chronic metabolic diseases later in life. Obesity, type 2 diabetes or metabolic syndrome could result from noxious "metabolic programming." In order to better understand early alterations involved in metabolic programming, we modeled IUGR rat pups through either prenatal exposure to synthetic glucocorticoid (dams infused with dexamethasone 100 µg/kg/day, DEX) or prenatal undernutrition (dams feeding restricted to 30% of ad libitum intake, UN). Physiological (glucose and insulin tolerance), morphometric (automated tissue image analysis) and transcriptomic (quantitative PCR) approaches were combined during early life of these IUGR pups with a special focus on their endocrine pancreas and adipose tissue development. In the absence of catch-up growth before weaning, DEX and UN IUGR pups both presented basal hyperglycaemia, decreased glucose tolerance, and pancreatic islet atrophy. Other early metabolic defects were model-specific: DEX pups presented decreased insulin sensitivity whereas UN pups exhibited lowered glucose-induced insulin secretion and more marked alterations in gene expression of pancreatic islet and adipose tissue development regulators. In conclusion, these results show that before any catch-up growth, IUGR rats present early physiologic, morphologic and transcriptomic defects, which can be considered as initial mechanistic basis of metabolic programming.
... Rats exposed to dexamethasone in utero have lifelong elevated levels of PEPCK mRNA and enzyme activity 23 and this may be a consequence of the increase in expression of key transcription factors that bind to recognition motifs in the PEPCK promoter region, notably GR 23,65 and hepatocyte nuclear factor 4a (HNF4a). 66 Increased GR expression is also observed in other models of programming of hyperglycemia using protein restriction and/or uterine artery ligation 67 and these observations indicate that changes in transcription factors such as GR may provide a common mechanism through which intrauterine environmental insults might lead to persistent derangements in metabolic control. ...
Epidemiological evidence suggests that exposure to an adverse environment in early life is associated with an increased risk of cardio-metabolic and behavioral disorders in adulthood, a phenomenon termed 'early life programming'. One major hypothesis for early life programming is fetal glucocorticoid overexposure. In animal studies, prenatal glucocorticoid excess as a consequence of maternal stress or through exogenous administration to the mother or fetus is associated with programming effects on cardiovascular and metabolic systems and on the brain. These effects can be transmitted to subsequent generations. Studies in humans provide some evidence that prenatal glucocorticoid exposure may exert similar programming effects on glucose/insulin homeostasis, blood pressure and neurodevelopment. The mechanisms by which glucocorticoids mediate these effects are unclear but may include a role for epigenetic modifications. This review discusses the evidence for glucocorticoid programming in animal models and in humans.
... Expression of PGC1A mRNA, nuclear HNF4a, and p-CREB are increased in the IUGR liver during basal and hyperinsulinemic conditions, supporting the potential role of cAMP-dependent signaling in mediating glucose production (6,7,18,45). IUGR fetuses have increased cortisol concentrations, and cortisol and norepinephrine concentrations positively correlate with GPR, suggesting that these hormones may potentiate glucose production. ...
Intrauterine growth restriction (IUGR) increases the risk for metabolic disease and diabetes, although the developmental origins of this remain unclear. We measured glucose metabolism during basal and insulin clamp periods in a fetal sheep model of placental insufficiency and IUGR. Compared with control fetuses (CON), fetuses with IUGR had increased basal glucose production rates and hepatic PEPCK and glucose-6-phosphatase expression, which were not suppressed by insulin. In contrast, insulin significantly increased peripheral glucose utilization rates in CON and IUGR fetuses. Insulin robustly activated AKT, GSK3β, and forkhead box class O (FOXO)1 in CON and IUGR fetal livers. IUGR livers, however, had increased basal FOXO1 phosphorylation, nuclear FOXO1 expression, and Jun NH(2)-terminal kinase activation during hyperinsulinemia. Expression of peroxisome proliferator-activated receptor γ coactivator 1α and hepatocyte nuclear factor-4α were increased in IUGR livers during basal and insulin periods. Cortisol and norepinephrine concentrations were positively correlated with glucose production rates. Isolated IUGR hepatocytes maintained increased glucose production in culture. In summary, fetal sheep with IUGR have increased hepatic glucose production, which is not suppressed by insulin despite insulin sensitivity for peripheral glucose utilization. These data are consistent with a novel mechanism involving persistent transcriptional activation in the liver that seems to be unique in the fetus with IUGR.
... Alterations in maternal DNA methylation may also indirectly affect the fetus through changes in the maternal environment. Changes in the maternal environment can result in direct changes in gene expression in the developing fetus [44], and if certain harmful exposures occur during organogenesis, various structural anomalies may occur [13]. Alterations in maternal methylation in genes involved in the maintenance of the intrauterine environment may lead to an increased susceptibility to teratogenic agents. ...
The majority of congenital heart defects (CHDs) are thought to result from the interaction between multiple genetic, epigenetic, environmental, and lifestyle factors. Epigenetic mechanisms are attractive targets in the study of complex diseases because they may be altered by environmental factors and dietary interventions. We conducted a population based, case-control study of genome-wide maternal DNA methylation to determine if alterations in gene-specific methylation were associated with CHDs. Using the Illumina Infinium Human Methylation27 BeadChip, we assessed maternal gene-specific methylation in over 27,000 CpG sites from DNA isolated from peripheral blood lymphocytes. Our study sample included 180 mothers with non-syndromic CHD-affected pregnancies (cases) and 187 mothers with unaffected pregnancies (controls). Using a multi-factorial statistical model, we observed differential methylation between cases and controls at multiple CpG sites, although no CpG site reached the most stringent level of genome-wide statistical significance. The majority of differentially methylated CpG sites were hypermethylated in cases and located within CpG islands. Gene Set Enrichment Analysis (GSEA) revealed that the genes of interest were enriched in multiple biological processes involved in fetal development. Associations with canonical pathways previously shown to be involved in fetal organogenesis were also observed. We present preliminary evidence that alterations in maternal DNA methylation may be associated with CHDs. Our results suggest that further studies involving maternal epigenetic patterns and CHDs are warranted. Multiple candidate processes and pathways for future study have been identified.
... In contrast, late pregnancy administration of metyrapone, an inhibitor of adrenal glucocorticoid synthesis, increases fetal and placental weight [35]. Mechanisms involving glucocorticoid-driven changes in target organ structure, gene expression and function have been demonstrated and epigenetic process maintaining such effects advocated [64,197,198,240,296,298,299,306,307]. Interestingly, in programming models involving maternal low-protein diet there is an increase in maternal and fetal glucocorticoid levels [89,148] in addition to a decrease in placental 11β-HSD2 activity [142]. ...
Glucocorticoids have profound effects on brain development and adult CNS function. Excess or insufficient glucocorticoids cause myriad abnormalities from development to ageing. The actions of glucocorticoids within cells are determined not only by blood steroid levels and target cell receptor density, but also by intracellular metabolism by 11β-hydroxysteroid dehydrogenases (11β-HSD). 11β-HSD1 regenerates active glucocorticoids from their inactive 11-keto derivatives and is widely expressed throughout the adult CNS. Elevated hippocampal and neocortical 11β-HSD1 is observed with ageing and causes cognitive decline; its deficiency prevents the emergence of cognitive defects with age. Conversely, 11β-HSD2 is a dehydrogenase, inactivating glucocorticoids. The major central effects of 11β-HSD2 occur in development, as expression of 11β-HSD2 is high in fetal brain and placenta. Deficient feto-placental 11β-HSD2 results in a life-long phenotype of anxiety and cardiometabolic disorders, consistent with early life glucocorticoid programming.
... Prenatal stress also impacts upon the development of CRH neurons in the PVN (Fujioka et al., 1999;Shoener et al., 2006) with greater vulnerability to PVN cell death (Tobe et al., 2005), which has implications for HPA axis programming. The resulting mild chronic glucocorticoid excess can be further exacerbated by increased hepatic and visceral adipose tissue glucocorticoid activity due to increased tissue levels of 11ß-hydroxysteroid dehydrogenase type 1 (HSD1) (Cleasby et al., 2003;Nyirenda et al., 2009Nyirenda et al., , 2006. HSD1 catalyzes the reverse reaction to HSD2, thus regenerating active glucocorticoids from inert 11-keto metabolites (Rajan et al., 1996;Yau et al., 2001) in CNS and peripheral metabolic organs (e.g. ...
An adverse foetal environment is associated with increased risk of cardiovascular, metabolic, neuroendocrine and psychological disorders in adulthood. Exposure to stress and its glucocorticoid hormone mediators may underpin this association. In humans and in animal models, prenatal stress, excess exogenous glucocorticoids or inhibition of 11β-hydroxysteroid dehydrogenase type 2 (HSD2; the placental barrier to maternal glucocorticoids) reduces birth weight and causes hyperglycemia, hypertension, increased HPA axis reactivity, and increased anxiety-related behaviour. Molecular mechanisms that underlie the 'developmental programming' effects of excess glucocorticoids/prenatal stress include epigenetic changes in target gene promoters. In the case of the intracellular glucocorticoid receptor (GR), this alters tissue-specific GR expression levels, which has persistent and profound effects on glucocorticoid signalling in certain tissues (e.g. brain, liver, and adipose). Crucially, changes in gene expression persist long after the initial challenge, predisposing the individual to disease in later life. Intriguingly, the effects of a challenged pregnancy appear to be transmitted possibly to one or two subsequent generations, suggesting that these epigenetic effects persist.
... Permanent and sometimes progressive changes in gene expression have been observed in multiple tissues as a consequence of IUGR [16,17,20,21]. Dysregulation of the epigenome may explain changes that are propagated from parent to daughter cells in IUGR offspring throughout life. ...
Perturbations of the intrauterine environment can affect fetal development during critical periods of plasticity, and can increase susceptibility to a number of age-related diseases (e.g., type 2 diabetes mellitus; T2DM), manifesting as late as decades later. We hypothesized that this biological memory is mediated by permanent alterations of the epigenome in stem cell populations, and focused our studies specifically on DNA methylation in CD34+ hematopoietic stem and progenitor cells from cord blood from neonates with intrauterine growth restriction (IUGR) and control subjects.
Our epigenomic assays utilized a two-stage design involving genome-wide discovery followed by quantitative, single-locus validation. We found that changes in cytosine methylation occur in response to IUGR of moderate degree and involving a restricted number of loci. We also identify specific loci that are targeted for dysregulation of DNA methylation, in particular the hepatocyte nuclear factor 4alpha (HNF4A) gene, a well-known diabetes candidate gene not previously associated with growth restriction in utero, and other loci encoding HNF4A-interacting proteins.
Our results give insights into the potential contribution of epigenomic dysregulation in mediating the long-term consequences of IUGR, and demonstrate the value of this approach to studies of the fetal origin of adult disease.
... compelling new evidence on the mechanism of fetal programming of gluconeogenesis by glucocorticoid administration during the last third of pregnancy in rats [1], a study that is commented on by McCurdy and Friedman [2]. Nyirenda et al. focus on a fluxgenerating enzyme of gluconeogenesis (phosphoenolpyruvate carboxykinase [PCK]) and the factors involved in its transcription, showing how PCK mRNA and that of its controlling transcription factors are localised within the hepatic acinus. ...
... PEPCK gene regulation is complex and involves interplay among insulin, glucocorticoids, and other counterregulatory hormones (60). In rats, several transcription factors involved in PEPCK control are altered by antenatal dexamethasone (61). We suggest that the changes in PEPCK in vervet offspring reflect this interplay and that reduced PEPCK may ameliorate any tendency toward fasting hyperglycemia in these animals. ...
Prenatal stress or glucocorticoid administration has persisting "programming" effects on offspring in rodents and other model species. Multiple doses of glucocorticoids are in widespread use in obstetric practice. To examine the clinical relevance of glucocorticoid programming, we gave 50, 120, or 200 microg/kg/d of dexamethasone (dex50, dex120, or dex200) orally from mid-term to a singleton-bearing nonhuman primate, Chlorocebus aethiops (African vervet). Dexamethasone dose-dependently reduced maternal cortisol levels without effecting maternal blood pressure, glucose, electrolytes, or weight gain. Birth weight was unaffected by any dexamethasone dose, although postnatal growth was attenuated after dex120 and dex200. At 8 months of age, dex120 and dex200 offspring showed impaired glucose tolerance and hyperinsulinemia, with reduced (approximately 25%) pancreatic beta cell number at 12 months. Dex120 and dex200 offspring had increased systolic and diastolic blood pressures at 12 months. Mild stress produced an exaggerated cortisol response in dex200 offspring, implying hypothalamic-pituitary-adrenal axis programming. The data are compatible with the extrapolation of the glucocorticoid programming hypothesis to primates and indicate that repeated glucocorticoid therapy and perhaps chronic stress in humans may have long-term effects.
... The increase in HNF4a is associated with a premature switch from fetal to adult promoter predominance. Therefore, HNF4a might mediate PCK2 overexpression and subsequent lifelong hyperglycaemia in the rats exposed in utero to dexamethasone [73]. The increase in the hepatic GR mRNA expression alongside the increased plasma glucose responses to exogenous corticosterone implicate increased tissue sensitivity to glucocorticoids [66]. ...
It is widely accepted that an association exists between the intrauterine environment in which a fetus grows and develops and the subsequent development of type 2 diabetes. Any disturbance in maternal ability to provide nutrients and oxygen to the fetus can lead to fetal intrauterine growth restriction (IUGR). Here we will review IUGR in rodent models, in which maternal metabolism has been experimentally manipulated to investigate the molecular basis of the relationship between IUGR and development of type 2 diabetes in later life, and the identification of the molecular derangements in specific metabolically - sensitive organs/tissues.
... PEPCK is a key regulator of gluconeogenesis and hyperglycemia is a well-known side effect of steroid use. Antenatal DEX treatment has been shown to up-regulate hepatocyte nuclear factor 4 alpha which in turn up-regulates PEPCK gene and this phenomenon has been linked to prenatal foetal programming and hyperglycemia later in life [52]. ...
Antenatal steroids like dexamethasone (DEX) are used to augment fetal lung maturity and there is a major concern that they impair fetal growth. If delivery is delayed after using antenatal DEX, placental function and hence fetal growth may be compromised even further. To investigate the effects of DEX on placental function, we treated 9 pregnant C57/BL6 mice with DEX and 9 pregnant mice were injected with saline to serve as controls. Placental gene expression was studied using microarrays in 3 pairs and other 6 pairs were used to confirm microarray results by semi-quantitative RT-PCR, real-time PCR, in situ hybridization, western blot analysis and Oligo ApopTaq assay. DEX-treated placentas were hydropic, friable, pale, and weighed less (80.0+/-15.1mg compared to 85.6.8+/-7.6mg, p=0.05) (n=62 placentas). Fetal weight was significantly reduced after DEX use (940+/-32mg compared to 1162+/-79mg, p=0.001) (n=62 fetuses). There was >99% similarity within and between the three gene chip data sets. DEX led to down-regulation of 1212 genes and up-regulation of 1382 genes. RT-PCR studies showed that DEX caused a decrease in expression of genes involved in cell division such as cyclins A2, B1, D2, cdk 2, cdk 4 and M-phase protein kinase along with growth-promoting genes such as EGF-R, BMP4 and IGFBP3. Oligo ApopTaq assay and western blot studies showed that DEX-treatment increased apoptosis of trophoblast cells. DEX-treatment led to up-regulation of aquaporin 5 and tryptophan hydroxylase genes as confirmed by real-time PCR, and in situ hybridization studies. Thus antenatal DEX treatment led to a reduction in placental and fetal weight, and this effect was associated with a decreased expression of several growth-promoting genes and increased apoptosis of trophoblast cells.
Water pollution caused by widely used agricultural pesticide chlorpyrifos (CPF) has aroused extensive public concern. While previous studies have reported on toxic effect of CPF on aquatic animal, little is known about its effect on common carp (Cyprinus carpio L.) livers. In this experiment, we exposed common carp to CPF (11.6 μg/L) for 15, 30, and 45 days to establish a poisoning model. Histological observation, biochemical assay, quantitative real-time polymerase chain reaction (qRT-PCR), Western blot, and integrated biomarker response (IBR) were applied to assess the hepatotoxicity of CPF in common carp. Our results displayed that CPF exposure damaged histostructural integrity and induced liver injury in common carp. Furthermore, we found that CPF-induced liver injury may be associated with mitochondrial dysfunction and autophagy, as evidenced by swollen mitochondria, broken mitochondrial ridges, and increased the number of autophagosomes. Moreover, CPF exposure decreased the activities of ATPase (Na+/K+-ATPase, Ca2+-ATPase, Mg2+-ATPase, and Ca2+Mg2+-ATPase), altered glucose metabolism-related genes (GCK, PCK2, PHKB, GYS2, PGM1, and DLAT), and activated energy-sensing AMPK, indicating that CPF caused energy metabolism disorder. The activation of AMPK further induced mitophagy via AMPK/Drp1 pathway, and induced autophagy via AMPK/mTOR pathway. Additionally, we found that CPF induced oxidative stress (abnormal levels of SOD, GSH, MDA, and H2O2) in common carp livers, which further contributed to the induction of mitophagy and autophagy. Subsequently, we confirmed a time-dependent hepatotoxicity caused by CPF in common carp via IBR assessment. Our findings presented a new insight into molecular mechanism of CPF induced-hepatotoxicity in common carp, and provided a theoretical basis for evaluating CPF toxicity to aquatic organisms.
Early-life environmental factors can have persistent effects on physiological functions by altering developmental procedures in various organisms. Recent experimental and epidemiological studies now further support the idea that developmental programming is also present in mammals, including humans, influencing long-term health. Although the mechanism of programming is still largely under investigation, the role of endocrine glucocorticoids in developmental programming is gaining interest. Studies found that perinatal glucocorticoids have a persistent effect on multiple functions of the body, including metabolic, behavioral, and immune functions, in adulthood. Several mechanisms have been proposed to play a role in long-term programming. In this review, recent findings on this topic are summarized and the potential biological rationale behind this phenomenon is discussed.
Substantial epidemiological evidence suggests that exposure to an adverse environment in early life is associated with an increased risk for cardio-metabolic and neuroendocrine disorders in adulthood, a phenomenon termed “early life programming.” One of the major hypotheses advanced to explain early life programming is fetal glucocorticoid overexposure occurring as a consequence of maternal stress, exogenous administration or dysfunction of the placental gluco-corticoid barrier. There is evidence from both human and animal studies for an association between prenatal glucocorticoid overexposure and programming effects on cardiovascular and metabolic systems and on the brain. There is much interest in the potential for programmed effects to be transmitted across generations, including the effects of glucocorticoid programming. This review discusses the evidence for glucocorticoid programming and intergenerational effects in animal models and in humans.
The notion that the environment in which a fetus develops is critical for long-term health and optimal developmental outcome is well supported by research. The adaptation of the pregnant mother to psychological challenges or threats to homeostasis can have adverse effects on the offspring's development. Moreover, the pathways that link prenatal stress to suboptimal development in the offspring remain uncertain. Recent data suggest that stressful experiences in the life of the pregnant mother may be incorporated into the offspring's biology by altering both neural and hormonal processes. This chapter reviews the evidence establishing a relationship between prenatal stress, birth outcomes, and child behavior problems in humans. It describes the evidence that prenatal stress compromises birth weight, infant neurobehavior, behavioral/hypothalamic-pituitary-adrenal (HPA) axis reactivity to challenge, response to sensory stimulation, and dopaminergic function in rhesus monkey offspring. The effects found in the primate studies include reduced birth weight, altered HPA axis regulation, enhanced sensitization to tactile stimuli, and altered dopaminergic system function. Early gestation appears to be a sensitive period for these effects, and some of the effects seem to be compounded by other factors including exposure to alcohol consumption during pregnancy.
Europe has the highest proportion of elderly people in the world. Cardiovascular disease, type 2 diabetes, sarcopenia and cognitive decline frequently coexist in the same aged individual, sharing common early risk factors and being mutually reinforcing. Among conditions which may contribute to establish early risk factors, this review focuses on maternal obesity, since the epidemic of obesity involves an ever growing number of women of reproductive age and children, calling for appropriate studies to understand the consequences of maternal obesity on the offspring's health and for developing effective measures and policies to improve people's health before their conception and birth. Though the current knowledge suggests that the long-term impact of maternal obesity on the offspring's health may be substantial, the outcomes of maternal obesity over the lifespan have not been quantified, and the molecular changes induced by maternal obesity remain poorly characterized. We hypothesize that maternal insulin resistance and reduced placental glucocorticoid catabolism, leading to oxidative stress, may damage the DNA, either in its structure (telomere shortening) or in its function (via epigenetic changes), resulting in altered gene expression/repair, disease during life, and pathological ageing. This review illustrates the background to the EU-FP7-HEALTH-DORIAN project. © 2014 S. Karger GmbH, Freiburg.
Compelling epidemiological evidence suggests that the early environment is an important determinant of later risk of disease. In particular, low birth weight has been associated with an increased risk of cardiovascular and metabolic disorders, including hypertension, Type 2 diabetes mellitus and ischemic heart disease, independent of classical adult lifestyle risk factors such as smoking, adult weight, social class, excess alcohol intake and sedentary lifestyle. These observations have led to a revolutionary concept of early life physiological programming. The molecular mechanisms that underlie this relationship remain unclear, but one major hypothesis implicates fetal overexposure to glucocorticoid stress hormones. This article will review evidence for this hypothesis.
Compelling epidemiological evidence linking exposure to an adverse intrauterine environment with a markedly elevated risk
of cardiometabolic disorders in adulthood has led to the concept of “developmental programming”. One major hypothesis for
early life physiological programming implicates fetal overexposure to glucocorticoids. In animal studies, prenatal glucocorticoid
excess as a consequence of maternal stress, exogenous administration, or dysfunction of the placental enzyme 11β-hydroxysteroid
dehydrogenase type 2 (the placental glucocorticoid “barrier”) reduces birthweight and is associated with programming effects
in the offspring. Prenatal glucocorticoid overexposure is associated with persistent elevations in blood pressure, potentially
secondary to effects on nephron number, renal glucocorticoid sensitivity, the renin–angiotensin system, and vascular responsiveness.
Additionally, offspring exposed to excess glucocorticoid in utero have altered glucose and insulin homeostasis in adulthood,
with insulin resistance and hyperglycemia, which may result from programming effects on specific genes in liver and pancreas.
The long-term effects of prenatal glucocorticoid overexposure in humans have been poorly investigated thus far, although some
studies have shown prenatal glucocorticoid administration to be associated with increased blood pressure, altered renal function,
and insulin resistance in early adulthood. In this chapter we review the evidence for early life glucocorticoid effects on
the programming of cardiometabolic risk and discuss the potential mechanisms, including alterations in organ size or cell
number, changes in gene expression, altered target organ responsiveness, and epigenetic modifications.
Cytochrome P450 (CYP) enzymes are important for the metabolism of many drugs. While there is information on their identity and ontogeny in humans and rodents, similar data in sheep are lacking. In the present study, cDNA sequences of several CYP enzymes (CYP2A6, CYP2C19, CYP2D6) were cloned by rapid amplification of cDNA ends. In adult, newborn and fetal sheep the mRNA and protein levels of these CYPs and the regulatory factor, hepatic nuclear factor 4α (HNF4α) were determined in liver samples using real-time PCR and western blotting. The effect of antenatal glucocorticoid on these enzymes was also studied by i.v. infusion of cortisol (0.45 mgh(-1); 80 h) to another group of fetuses. The mRNA and protein levels of the CYPs and HNF4α were low or absent in the fetus, followed by increasing levels in the newborn and adult. Fetal cortisol administration significantly increased the mRNA and protein levels of CYP2D6. Moreover, the correlation observed between the CYP and HNF4α mRNA levels suggests a possible regulatory role for this transcription factor. The findings suggest that fetal and newborn lambs have a low ability to metabolise drugs that are substrates of these enzymes, and that this ability increases with advancing postnatal age, similar to the situation in humans.
Glucocorticoids promote maturation of fetal systems, including erythropoiesis, in preparation for extrauterine life. However, recent studies have shown that prenatal glucocorticoid excess can cause long-term deleterious cardiometabolic and other consequences to the offspring. Here, we examined the effect of prenatal treatment with the synthetic glucocorticoid dexamethasone (DEX) during the last week of gestation on red blood cell (RBC) mass in the rat offspring. DEX-treated offspring at 9 months of age had significantly higher RBC count (9.4 ± 0.1 vs. 8.8 ± 0.2 × 10(12) liter; P = 0.02), hematocrit (50.0 ± 0.5 vs. 46.7 ± 0.7%; P=0.004), hemoglobin (17.3 ± 0.2 vs. 16.2 ± 0.2 g/dl; P = 0.02) and number of reticulocytes (258.2 ± 8.8 vs. 235.7 ± 5.6 × 10(9) liter; P = 0.04), compared with offspring of vehicle-treated control pregnancies. White blood cells and platelets were unaltered. Renal mRNA expression and plasma concentrations of erythropoietin, the main regulator of erythropoiesis, were increased by nearly 100% in both newborn and adult DEX-treated rats (P < 0.01). This increase was accompanied by marked elevation in renal expression of hepatocyte nuclear factor 4α mRNA, whereas other erythropoietin-regulating transcription factors, such as hypoxia-inducible factor 1, hypoxia-inducible factor 2, and GATA2 were unchanged. These data indicate that RBC mass can be programmed by prenatal glucocorticoid excess, and if extrapolatable to humans, provide a novel mechanism for fetal origins of polycythemia and its associated complications.
Developmental insults during gestation, such as under-nutrition, are known to restrict the number of beta cells that form in the fetal pancreas and are maintained in adulthood, leading to increased risk of type 2 diabetes. There are now substantial data indicating that glucocorticoids mediate this effect of under-nutrition on beta cell mass and that even at physiological levels they restrain fetal beta cell development in utero. There are emerging clues that this occurs downstream of endocrine commitment by neurogenin 3 but prior to terminal beta cell differentiation. Deciphering the precise mechanism will be important as it might unveil new pathways by which to manipulate beta cell mass that could be exploited as novel therapies for patients with diabetes.
For many years glucocorticoids have been used world-wide in pregnant women for treatment of a variety of medical disorders, from bronchial asthma to systemic lupus erythematosous, to renal transplant. More recently their administration has been successfully addressed to the prevention of congenital fetal diseases. In some of these, such as for instance the 21-hydroxylase deficiency leading to congenital adrenal hyperplasia, the pathogenic mechanism is well known, while in others, such as the cystic adenomatoid malformation of the lung, it is not yet understood. Besides these types of diseases, there are acquired inflammatory conditions impairing the physiologic evolution of pregnancy that benefit from glucocorticoid administration. This is the case in recurrent miscarriage due to increased concentration of decidual Natural Killer cells, as well as in the Romero's syndrome, leading to premature parturition and related life threatening fetal complications. However, in spite of its prominent efficacy, the therapy is generally viewed with some suspicion because of possible fetal and maternal adverse effects. With the aim to contribute to a better knowledge of the basic mechanisms of glucocorticoid protection, we reviewed the regulation of their trans-placental passage, their biological effects on gestational environment, their possible 'programming' and teratogenic action, and their accepted use for prevention and cure of pregnancy complications. We believe that a more qualified and liberal use of these compounds will lead in many cases to a significant improvement of fetal and maternal prognosis.
Hepatocyte nuclear factor 4-alpha (HNF4-alpha) regulates expression of a number of genes in several metabolic organs. The HNF4-alpha gene has two promoters and encodes at least nine isoforms through differential splicing. In mouse liver, transcription initiates at promoter 2 (P2) during fetal life, but switches to P1 at birth. Developmental and tissue-specific expression of HNF4-alpha in other organs is largely unknown. Here, we examined expression of P1- and P2-derived transcripts in a number of mouse and rat tissues. Both P1 and P2 were active in mouse fetal liver, but P2-derived isoforms were detected 50% more abundantly than P1 transcripts. Conversely, the adult mouse liver expressed significantly higher levels of P1- than P2-derived mRNA. In contrast, in the rat, P1 was used more predominantly in both fetal and adult liver. Exposure of fetal rats to the synthetic glucocorticoid dexamethasone caused suppression of P2 while enhancing hepatic expression of transcripts from P1. This was associated with increased expression of erythropoietin and phosphoenolpyruvate carboxykinase, which are key HNF4-alpha targets in the liver. Unlike liver, the kidney and stomach used promoters more selectively, so that only P1-derived isoforms were detected in fetal and adult kidneys in mice or rats, whereas the stomach in both species expressed P2-derived transcripts exclusively. No significant HNF4-alpha mRNA was detected in the spleen. These data reveal striking developmental and tissue-specific variation in expression of HNF4-alpha, and indicate that this can be influenced by environmental factors (such as exposure to glucocorticoid excess), with potential pathophysiological consequences.
Nutrition during fetal and early postnatal development can have permanent effects on physiology resulting in an increased risk for disease in later life. The aim of this study was to explore changes in gene expression related to maternal energy restriction during pregnancy in rat fetuses and in neonatal rat offspring.
From day 4 of gestation until parturition, energy-restricted dams received either 75 or 50% of ad libitum food intake. Microarray analyses were performed on whole 13- and 17-day fetuses and 1-day-old pups. Protein and fat contents of the dams' milk were analyzed in the different feeding groups.
A surprisingly small number of genes were differentially expressed between the groups, probably due to the strict control of fetal development. Interestingly, the expressions of many pancreatic digestion enzymes were reduced in the 1-day-old pups of the energy-restricted dams. A statistically significant difference in milk protein content was observed on day 1 post-partum between the gestationally food-restricted groups.
The expressions of several genes that may have an important role in the normal development of organs were affected by undernutrition during fetal development. In addition, undernutrition may have affected the function of the exocrine pancreas.
Epidemiological studies have shown that low birthweight is associated with increased risk of development of diabetes and obesity in later life. Over-exposure of the developing fetus to glucocorticoids is one of the major hypotheses that has been proposed to explain this association. In animal models, a range of manipulations that increase fetal glucocorticoid load, 'programme' permanent changes in glucose and insulin metabolism and adiposity. This may be mediated by alterations in regulation of the hypothalamic-pituitary-adrenal (HPA) axis. In humans, low birthweight is associated with increased circulating glucocorticoid levels, and an increased cortisol response to physiological and psychosocial stressors, in child- and adulthood. This activation of the HPA axis is also associated with increased risk of development of diabetes and obesity in later life.
Low birth weight in humans is predictive of hypertension in adult life, and while the mechanisms underlying this link remain unknown, fetal overexposure to glucocorticoids has been implicated. We have previously shown that prenatal dexamethasone (DEX) exposure in the rat lowers birth weight and programmes adult hypertension. This current study aimed to unravel the molecular nature of this hypertension. However, unknowingly, post hoc investigations revealed that our animals had been subjected to environmental noise stresses from an adjacent construction site, which were sufficient to confound our prenatal DEX-programming experiments. This perinatal stress successfully established low birth weight, hypercorticosteronaemia, insulin resistance, hypertension and hypothalamic-pituitary-adrenal axis dysfunction in vehicle (VEH)-treated offspring, such that the typical distinctions between both treatment groups were ameliorated. The lack of an additional effect on DEX-treated offspring is suggestive of a maximal effect of perinatal stress and glucocorticoids, serving to prevent against the potentially detrimental effects of sustained glucocorticoid hyper-exposure. Finally, this paper serves to inform researchers of the potential detrimental effects of neighbouring construction sites to their experiments.
Epidemiological evidence suggests that an adverse prenatal environment permanently 'programs' physiology and increases the risk of cardiovascular, metabolic, neuroendocrine and psychiatric disorders in adulthood. Prenatal stress or exposure to excess glucocorticoids might provide the link between fetal maturation and adult pathophysiology. In a variety of animal models, prenatal stress, glucocorticoid exposure and inhibition (or knockout of) 11beta-hydroxysteroid dehydrogenase type 2 (11beta-HSD2)--the fetoplacental barrier to maternal glucocorticoids--reduce birth weight and cause increases in adult blood pressure, glucose levels, hypothalamic-pituitary-adrenal (HPA) axis activity and anxiety-related behaviors. In humans, mutations in the gene that encodes 11beta- hydroxysteroid dehydrogenase type 2 are associated with low birth weight. Babies with low birth weight have higher plasma cortisol levels throughout life, which indicates HPA-axis programming. In human pregnancy, severe maternal stress affects the offspring's HPA axis and is associated with neuropsychiatric disorders; moreover, maternal glucocorticoid therapy alters offspring brain function. The molecular mechanisms that underlie prenatal programming might reflect permanent changes in the expression of specific transcription factors, including the glucocorticoid receptor; tissue specific effects reflect modification of one or more of the multiple alternative first exons or promoters of the glucocorticoid receptor gene. Intriguingly, some of these effects seem to be inherited by subsequent generations that are unexposed to exogenous glucocorticoids at any point in their lifespan from fertilization, which implies that these epigenetic effects persist.
Environmental effects on the materno-foetal interaction determine birth outcomes that predict health over the lifespan. Thus, maternal undernutrition or stress associate with low birth weight, leading to an increased risk of metabolic and cardiovascular illness in the offspring. We argue that these effects are, in part, mediated by direct and indirect effects on the hypothalamic-pituitary-adrenal (HPA) axis such that (i) the effect of maternal adversity on foetal growth is mediated by adrenal glucocorticoids and (ii) environmental adversity alters maternal physiology and behaviour, which then programs HPA activity in the offspring.
THE disease non-insulin-dependent (type 2) diabetes mellitus (NIDDM) is characterized by abnormally high blood glucose resulting from a relative deficiency of insulin(1). It affects about 2% of the world's population and treatment of diabetes and its complications are an increasing health-care burden(2). Genetic factors are important in the aetiology of NIDDM, and linkage studies are starting to Localize some of the genes that influence the development of this disorder(3). Maturity-onset diabetes of the young (MODY), a single-gene disorder responsible for 2-5% of NIDDM, is characterized by autosomal dominant inheritance and an age of onset of 25 years or younger(4-6). MODY genes have been localized to chromosomes 7, 12 and 20 (refs 5, 7, 8) and clinical studies indicate that mutations in these genes are associated with abnormal patterns of glucose-stimulated insulin secretion(1,9). The gene on chromosome 7 (MODY2) encodes the glycolytic enzyme glucokinase(5) which plays a key role in generating the metabolic signal for insulin secretion and in integrating hepatic glucose uptake. Here we show that subjects with the MODY3-form of NIDDM have mutations in the gene encoding hepatocyte nuclear factor-1 alpha (HNF-1 alpha, which is encoded by the gene TCF1). HNF-1 alpha is a transcription factor that helps in the tissue-specific regulation of the expression of several liver genes(10,11) and also functions as a weak transactivator of the rat insulin-I gene(12). Peer Reviewed http://deepblue.lib.umich.edu/bitstream/2027.42/62900/1/384455a0.pdf
The metabolic response to the first fast experienced by all mammals has been studied in the newborn rat. Levels of fuels and hormones have been compared in the fetal and maternal circulations at term. Then, after cesarean section just before the normal time of birth, sequential changes in the same parameters were quantified during the first 16 h of the neonatal period. No caloric intake was permitted, and the newborns were maintained at 37 degrees C. Activities of three key hepatic enzymes involved in glucose production were estimated. Marked differences in maternal and fetal hormones and fuels were observed. Lower levels of glucose, free fatty acids, and glycerol but higher levels of lactate, alpha-amino nitrogen, alanine, and glutamine were present in the fetus. Pyruvate, glutamate, and ketone bodies were not significantly different. The combination of a strikingly higher fetal immunoreactive insulin and a slightly lower immunoreactive glucagon (pancreatic) resulted in a profound elevation in the insulin-to-glucagon ratio, a finding consistent with an organism in an anabolic state. The rat at birth presents a body composition with respect to fuels available for mobilization and conversion which is dominated by carbohydrate and protein, since little fat is present. However, at birth a transient period of hypoglycemia occurred, associated with a rapid fall in insulin and rise in glucagon, causing reversal of the insulin-to-glucagon relationship toward ratios such as were observed in the mother. After a lag period, hepatic activities of phosphorylase, glucose-6-phosphatase, and phosphoenolpyruvate carboxykinase increased. Concurrent with these enzyme changes, the blood glucose returned to levels at or above those of the fetus. Interestingly, the fall observed in levels of the gluconeogenic precursors, lactate and amino acids, preceded the rise in enzyme activities and restoration of blood glucose. After 4 h, however, hypoglycemia recurred, during a period of decreasing hepatic glycogen content and blood lactate, pyruvate, and glycerol levels but of stable or increasing amino acid concentrations. Hepatic gluconeogenesis in this phase of depleted glycogen stores was insufficient to maintain euglycemia. Substrates derived from fat showed early changes of smaller magnitude. The rise in free fatty acids which occurred was less than twofold the value at birth, though this rise persisted up to 6 h. Whereas glycerol rose transiently, acetoacetate did not change and beta-hydroxybutyrate concentration fell. Both ketone bodies showed a marked rise at 16 h. at a time of diminished free fatty acid levels. Plasma growth hormone, though higher in the fetal than the maternal circulation, showed no consistent change during the period of observation. The changes in levels of the endocrine pancreatic hormones at birth were appropriate in time, magnitude, and direction to be implicated as prime regulators of the metabolic response during the neonatal period in the rat.
Hepatocyte nuclear factor 4 (HNF4) was first identified as a DNA binding activity in rat liver nuclear extracts. Protein purification had then led to the cDNA cloning of rat HNF4, which was found to be an orphan member of the nuclear receptor superfamily. Binding sites for this factor were identified in many tissue-specifically expressed genes, and the protein was found to be essential for early embryonic development in the mouse. We have now isolated cDNAs encoding the human homolog of the rat and mouse HNF4 splice variant HNF4 alpha 2, as well as a previously unknown splice variant of this protein, which we called HNF alpha 4. More importantly, we also cloned a novel HNF4 subtype (HNF4 gamma) derived from a different gene and showed that the genes encoding HNF 4 alpha and HNF4 gamma are located on human chromosomes 20 and 8, respectively. Northern (RNA) blot analysis revealed that HNF4 GAMMA is expressed in the kidney, pancreas, small intestine, testis, and colon but not in the liver, while HNF4 alpha RNA was found in all of these tissues. By cotransfection experiments in C2 and HeLa cells, we showed that HNF4 gamma is significantly less active than HNF4 alpha 2 and that the novel HNF4 alpha splice variant HNF4 alpha 4 has no detectable transactivation potential. Therefore, the differential expression of distinct HNF4 proteins may play a key role in the differential transcriptional regulation of HNF4-dependent genes.
The disease non-insulin-dependent (type 2) diabetes mellitus (NIDDM) is characterized by abnormally high blood glucose resulting from a relative deficiency of insulin. It affects about 2% of the world's population and treatment of diabetes and its complications are an increasing health-care burden. Genetic factors are important in the aetiology of NIDDM, and linkage studies are starting to localize some of the genes that influence the development of this disorder. Maturity-onset diabetes of the young (MODY), a single-gene disorder responsible for 2-5% of NIDDM, is characterized by autosomal dominant inheritance and an age of onset of 25 years or younger. MODY genes have been localized to chromosomes 7, 12 and 20 (refs 5, 7, 8) and clinical studies indicate that mutations in these genes are associated with abnormal patterns of glucose-stimulated insulin secretion. The gene on chromosome 7 (MODY2) encodes the glycolytic enzyme glucokinases which plays a key role in generating the metabolic signal for insulin secretion and in integrating hepatic glucose uptake. Here we show that subjects with the MODY3-form of NIDDM have mutations in the gene encoding hepatocyte nuclear factor-1alpha (HNF-1alpha, which is encoded by the gene TCF1). HNF-1alpha is a transcription factor that helps in the tissue-specific regulation of the expression of several liver genes and also functions as a weak transactivator of the rat insulin-I gene.
The transcription factor hepatocyte nuclear factor 4α (HNF4α) is a tissue specific transcription factor mainly expressed in
the liver, kidney, intestine and the endocrine pancreas, but is also an essential regulator for early embryonic events. Based
on its protein structure HNF4α is classified as an orphan member of the nuclear receptor superfamily. Comparing HNF4α transcription
factors in the differentiated and dedifferentiated murine hepatocyte cell line MHSV-12 we identified in dedifferentiated cells
the novel splice variant HNF4α7. This variant is characterized by an alternative first exon and has a lower transactivation
potential in transient transfection assays using HNF4 dependent reporter genes. HNF4α7 mRNA and the corresponding protein
are expressed in the undifferentiated pluripotent embryonal carcinoma cell line F9, whereas HNF4α1 only appears after differentiation
of F9 cells to visceral endoderm. HNF4α7 mRNA is also found in totipotent embryonic stem cells. However, the function of HNF4α7
seems not to be restricted to embryonic cells as the HNF4α7 mRNA is also present in adult tissues, most notably the stomach.
All these features suggest that the presence of distinct splice variants of HNF4α modulates the activity of HNF4α in a cell
type specific way.
Low birth weight in humans is predictive of insulin resistance and diabetes in adult life. The molecular mechanisms underlying this link are unknown but fetal exposure to excess glucocorticoids has been implicated. The fetus is normally protected from the higher maternal levels of glucocorticoids by feto-placental 11β-hydroxysteroid dehydrogenase type-2 (11β-HSD2) which inactivates glucocorticoids. We have shown previously that inhibiting 11β-HSD2 throughout pregnancy in rats reduces birth weight and causes hyperglycemia in the adult offspring. We now show that dexamethasone (a poor substrate for 11β-HSD2) administered to pregnant rats selectively in the last week of pregnancy reduces birth weight by 10% (P < 0.05), and produces adult fasting hyperglycemia (treated 5.3±0.3; control 4.3±0.2 mmol/liter, P = 0.04), reactive hyperglycemia (treated 8.7±0.4; control 7.5±0.2 mmol/liter, P = 0.03), and hyperinsulinemia (treated 6.1±0.4; control 3.8±0.5 ng/ml, P = 0.01) on oral glucose loading. In the adult offspring of rats exposed to dexamethasone in late pregnancy, hepatic expression of glucocorticoid receptor (GR) mRNA and phosphoenolpyruvate carboxykinase (PEPCK) mRNA (and activity) are increased by 25% (P = 0.01) and 60% (P < 0.01), respectively, while other liver enzymes (glucose-6- phosphatase, glucokinase, and 11β-hydroxysteroid dehydrogenase type-1) are unaltered. In contrast dexamethasone, when given in the first or second week of gestation, has no effect on offspring insulin/glucose responses or hepatic PEPCK and GR expression. The increased hepatic GR expression may be crucial, since rats exposed to dexamethasone in utero showed potentiated glucose responses to exogenous corticosterone. These observations suggest that excessive glucocorticoid exposure late in pregnancy predisposes the offspring to glucose intolerance in adulthood. Programmed hepatic PEPCK overexpression, perhaps mediated by increased GR, may promote this process by increasing gluconeogenesis.
In the liver, glucocorticoids induce a 10–15-fold increase in the rate of transcription of the phosphoenolpyruvate carboxykinase
(PEPCK) gene, which encodes a key gluconeogenic enzyme. This induction requires a multicomponent glucocorticoid response unit
(GRU) comprised of four glucocorticoid accessory factor (AF) elements and two glucocorticoid receptor binding sites. We show
that the AFs that bind the gAF1, gAF2, and gAF3 elements (hepatocyte nuclear factor [HNF]4/chicken ovalbumin upstream promoter
transcription factor 1 and HNF3β) all interact with steroid receptor coactivator 1 (SRC1). This suggests that the AFs function
in part by recruiting coactivators to the GRU. The binding of a GAL4-SRC1 chimeric protein completely restores the glucocorticoid
induction that is lost when any one of these elements is replaced with a GAL4 binding site. Thus, when SRC1 is recruited directly
to gAF1, gAF2, or gAF3, the requirement for the corresponding AF is bypassed. Surprisingly, glucocorticoid receptor is still
required when SRC1 is recruited directly to the GAL4 site, suggesting a role for the receptor in activating SRC1 in the context
of the GRU. Structural variants of GAL4-SRC1 were used to identify requirements for the basic-helix-loop-helix and histone
acetyltransferase domains of SRC1, and these are specific to the region of the promoter to which the coactivator is recruited.
Blood glucose levels are maintained by the balance between glucose uptake by peripheral tissues and glucose secretion by the liver. Gluconeogenesis is strongly stimulated during fasting and is aberrantly activated in diabetes mellitus. Here we show that the transcriptional coactivator PGC-1 is strongly induced in liver in fasting mice and in three mouse models of insulin action deficiency: streptozotocin-induced diabetes, ob/ob genotype and liver insulin-receptor knockout. PGC-1 is induced synergistically in primary liver cultures by cyclic AMP and glucocorticoids. Adenoviral-mediated expression of PGC-1 in hepatocytes in culture or in vivo strongly activates an entire programme of key gluconeogenic enzymes, including phosphoenolpyruvate carboxykinase (PEPCK) and glucose-6-phosphatase, leading to increased glucose output. Full transcriptional activation of the PEPCK promoter requires coactivation of the glucocorticoid receptor and the liver-enriched transcription factor HNF-4alpha (hepatic nuclear factor-4alpha) by PGC-1. These results implicate PGC-1 as a key modulator of hepatic gluconeogenesis and as a central target of the insulin-cAMP axis in liver.
Hepatocyte nuclear factor 4α (HNF-4α), a liver-specific transcription factor, plays a significant role in many liver-specific
functions, including lipid, glucose, drug, and ammonia metabolism, and also in embryonal liver development. However, its functions
and regulation are not yet clearly understood. In this study, we constructed an adenovirus vector carrying rat HNF-4α cDNA
and transfected the adenovirus to human hepatoma cells, HuH-7, to enforce expression of the exogenous HNF-4α gene. We analyzed
HNF-4α-induced genes using cDNA microarray technology, which included over 9000 genes. As a result, 62 genes showed a greater
than 2.0-fold change in expression level after the viral transfection. Fifty-six genes were consistently induced by HNF-4α
overexpression, and six genes were repressed. To assess HNF-4α function, we attempted to classify the genes, which had been
classified by their encoding protein functions in a previous report. We could classify 45 genes. The rest of the HNF-4α-sensitive
genes were unclassified (4 genes) or not identified (13 genes). Among the classified genes, almost half of the induced genes
(26 of 40) were related to metabolism genes and particularly to lipid metabolism-related genes. This cDNA microarray analysis
showed that HNF-4α is one of the central liver metabolism regulators.
The liver plays several critical roles in the metabolic adaptation to fasting. We have shown previously that the transcriptional coactivator peroxisome proliferator-activated receptor gamma coactivator-1alpha (PGC-1alpha) is induced in fasted or diabetic liver and activates the entire program of gluconeogenesis. PGC-1alpha interacts with several nuclear receptors known to bind gluconeogenic promoters including the glucocorticoid receptor, hepatocyte nuclear factor 4alpha (HNF4alpha), and the peroxisome proliferator-activated receptors. However, the genetic requirement for any of these interactions has not been determined. Using hepatocytes from mice lacking HNF4alpha in the liver, we show here that PGC-1alpha completely loses its ability to activate key genes of gluconeogenesis such as phosphoenolpyruvate carboxykinase and glucose-6-phosphatase when HNF4alpha is absent. It is also shown that PGC-1alpha can induce genes of beta-oxidation and ketogenesis in hepatocytes, but these effects do not require HNF4alpha. Analysis of the glucose-6-phosphatase promoter indicates a key role for HNF4alpha-binding sites that function robustly only when HNF4alpha is coactivated by PGC-1alpha. These data illustrate the involvement of PGC-1alpha in several aspects of the hepatic fasting response and show that HNF4alpha is a critical component of PGC-1alpha-mediated gluconeogenesis.
Mutations in hepatocyte nuclear factor (HNF)-4alpha gene cause a form of maturity-onset diabetes of the young (MODY1). The T130I mutation is a rare missense mutation, which affects a conserved amino acid in a DNA binding domain. This mutation can be found in the general population, so this variant alone does not cause MODY. However, its significance in the development of late-onset Type 2 diabetes is not known.
We screened 423 unrelated Japanese patients with late-onset Type 2 diabetes and 354 unrelated non-diabetic control subjects for the T130I mutation in the HNF-4alpha gene. The transactivation ability of T130I-HNF-4alpha was assessed using reporter gene assay.
The frequency of the T130I mutation was higher in Type 2 diabetic patients ( p=0.015, odds ratio 4.3, 95%CI 1.24-14.98) than control subjects. The serum HDL-cholesterol concentration was lower in Type 2 diabetic patients with the T130I mutation compared with those without this mutation ( p=0.006). Reporter gene analysis showed that T130I-HNF-4alpha transcriptional activity was not impaired compared with wild-type HNF-4alpha in Hela and MIN6 cells, but it was reduced in HepG2 and primary cultured mouse hepatocytes (27-78% of wild type, p<0.05).
Our findings suggest that T130I-HNF-4alpha is a loss-of-function mutation in hepatocytes and that this mutation is associated with late-onset Type 2 diabetes in Japanese subjects. The T130I mutation in the HNF-4alpha gene might be involved in the development of Type 2 diabetes in the Japanese population.
The Finland-United States Investigation Of NIDDM Genetics (FUSION) study aims to identify genetic variants that predispose to type 2 diabetes by studying affected sibling pair families from Finland. Chromosome 20 showed our strongest initial evidence for linkage. It currently has a maximum logarithm of odds (LOD) score of 2.48 at 70 cM in a set of 495 families. In this study, we searched for diabetes susceptibility variant(s) at 20q13 by genotyping single nucleotide polymorphism (SNP) markers in case and control DNA pools. Of 291 SNPs successfully typed in a 7.5-Mb interval, the strongest association confirmed by individual genotyping was with SNP rs2144908, located 1.3 kb downstream of the primary beta-cell promoter P2 of hepatocyte nuclear factor-4 alpha (HNF4A). This SNP showed association with diabetes disease status (odds ratio [OR] 1.33, 95% CI 1.06-1.65, P = 0.011) and with several diabetes-related traits. Most of the evidence for linkage at 20q13 could be attributed to the families carrying the risk allele. We subsequently found nine additional associated SNPs spanning a 64-kb region, including the P2 and P1 promoters and exons 1-3. Our results and the independent observation of association of SNPs near the P2 promoter with diabetes in a separate study population of Ashkenazi Jewish origin suggests that variant(s) located near or within HNF4A increases susceptibility to type 2 diabetes.
Variants in hepatocyte nuclear factor-4 alpha (HNF4 alpha), a transcription factor that influences the expression of glucose metabolic genes, have been correlated with maturity-onset diabetes of the young, a monogenic form of diabetes. Previously, in a genome scan of Ashkenazi Jewish type 2 diabetic families, we observed linkage to the chromosome 20q region encompassing HNF4 alpha. Here, haplotype-tag single nucleotide polymorphisms (htSNPs) were identified across a 78-kb region around HNF4 alpha and evaluated in an association analysis of Ashkenazi Jewish type 2 diabetic (n = 275) and control (n = 342) subjects. We found that two of nine htSNPs were associated with type 2 diabetes: a 3' intronic SNP, rs3818247 (29.2% case subjects vs. 21.7% control subjects; P = 0.0028, odds ratio [OR] 1.49) and a 5' htSNP located approximately 3.9 kb upstream of P2, rs1884614 (26.9% case subjects vs. 20.3% control subjects; P = 0.0078, OR 1.45). Testing of additional SNPs 5' of rs1884614 revealed a >10-kb haplotype block that was associated with type 2 diabetes. Conditioning on the probands' rs1884614 genotype suggested that the chromosomal region identified by the htSNP accounted for the linkage signal on chromosome 20q in families in which the proband carried at least one risk allele. Notably, the associations and the partitioned linkage profiles near P2 were independently observed in a Finnish sample, suggesting the presence of potential regulatory element(s) that may contribute to the risk for type 2 diabetes.
Many plants and animals are capable of developing in a variety of ways, forming characteristics that are well adapted to the environments in which they are likely to live. In adverse circumstances, for example, small size and slow metabolism can facilitate survival, whereas larger size and more rapid metabolism have advantages for reproductive success when resources are more abundant. Often these characteristics are induced in early life or are even set by cues to which their parents or grandparents were exposed. Individuals developmentally adapted to one environment may, however, be at risk when exposed to another when they are older. The biological evidence may be relevant to the understanding of human development and susceptibility to disease. As the nutritional state of many human mothers has improved around the world, the characteristics of their offspring--such as body size and metabolism--have also changed. Responsiveness to their mothers' condition before birth may generally prepare individuals so that they are best suited to the environment forecast by cues available in early life. Paradoxically, however, rapid improvements in nutrition and other environmental conditions may have damaging effects on the health of those people whose parents and grandparents lived in impoverished conditions. A fuller understanding of patterns of human plasticity in response to early nutrition and other environmental factors will have implications for the administration of public health.
The hepatic transcriptional regulation by glucocorticoids of the cytosolic form of phosphoenolpyruvate carboxykinase (PEPCK-C) gene is coordinated by interactions of specific transcription factors at the glucocorticoid regulatory unit (GRU). We propose an extended GRU that consists of four accessory sites, two proximal AF1 and AF2 sites and their distal counterpart dAF1 (-993) and a new site, dAF2 (-1365); together, these four sites form a palindrome. Sequencing and gel shift binding assays of hepatic nuclear proteins interacting with these sites indicated similarity of dAF1 and dAF2 sites to the GRU proximal AF1 and AF2 sites. Chromatin immunoprecipitation assays demonstrated that glucocorticoids enhanced the binding of FOXO1 and peroxisome proliferator-activated receptor-alpha to AF2 and dAF2 sites and not to dAF1 site but enhanced the binding of hepatic nuclear transcription factor-4alpha only to the dAF1 site. Insulin inhibited the binding of these factors to their respective sites but intensified the binding of phosphorylated FOXO1. Transient transfections in HepG2 human hepatoma cells showed that glucocorticoid receptor interacts with several non-steroid nuclear receptors, yielding a synergistic response of the PEPCK-C gene promoter to glucocorticoids. The synergistic stimulation by glucocorticoid receptor together with peroxisome proliferator-activated receptor-alpha or hepatic nuclear transcription factor-4alpha requires all four accessory sites, i.e. a mutation of each of these markedly affects the synergistic response. Mice with a targeted mutation of the dAF1 site confirmed this requirement. This mutation inhibited the full response of hepatic PEPCK-C gene to diabetes by reducing PEPCK-C mRNA level by 3.5-fold and the level of circulating glucose by 25%.
In a previous study, we showed that exposure of rats to dexamethasone (Dex) selectively in late pregnancy produces permanent induction of hepatic phosphoenolpyruvate carboxykinase (PEPCK) expression and hyperglycaemia in the adult offspring. The mechanisms by which glucocorticoids cause this programming are unclear but may involve direct actions on the fetus/neonate, or glucocorticoids may act indirectly by affecting maternal postnatal nursing behaviour. Using a cross-fostering paradigm, the present data demonstrate that switching the offspring at birth from Dex-treated dams to control dams does not prevent induction of PEPCK or hyperglycaemia. Similarly, offspring born to control dams but reared by Dex-treated dams from birth maintain normal glycaemic control. During the neonatal period, injection of saline per se was sufficient to cause exaggeration in adult offspring responses to an oral glucose load, with no additional effect from Dex. However, postnatal treatment with either saline or Dex did not alter hepatic PEPCK activity. Prenatal Dex permanently raised basal plasma corticosterone levels, but under stress conditions there were no differences in circulating corticosterone levels. Likewise, Dex-exposed rats had similar plasma catecholamine concentrations to control animals. These findings show that glucocorticoids programme hyperglycaemia through mechanisms that operate on the fetus or directly on the neonate, rather than via effects that alter maternal postnatal behaviour during the suckling period. The hyperglycaemic response does not appear to result from abnormal sympathoadrenal activity or hypothalamic-pituitary-adrenal response during stress.
Summary There is a significant body of evidence which suggests that the α-isoform of the CCAAT/enhancer binding protein (C/EBPα)
plays a central regulatory role in energy metabolism in the liver. However, there is little information available regarding
regulation of its expression in this tissue. In this study, we examined the effect of hormones and diabetes on its expression
in rat H4IIE hepatoma cells and in rat liver. Treatment of H4IIE cells with dexamethasone led to a threefold increase in C/EBPα
mRNA within 4 h. Insulin treatment produced a bi-phasic response, initially reducing mRNA levels up to the 4 h time point,
but after 8 h a twofold increase in C/EBPα mRNA was observed. Treatment with 8-chlorophenylthio-cAMP produced a twofold induction
of C/EBPα mRNA after 8 h. Western analysis indicated that the changes in mRNA in response to hormonal treatment generally
resulted in corresponding alterations in C/EBPα protein levels. Finally, we observed an inhibition of C/EBPα gene expression
in streptozotocin-diabetic rat liver, reflected by a decrease in both mRNA and protein levels that were partially reversed
by insulin treatment. These results indicate that the expression of C/EBPα in liver is under complex control by both hormonal
and metabolic signals, which is consistent with its role as a trans -regulator of genes which play a role in energy metabolism. [Diabetologia (1997) 40: 1117–1124]
Hepatocyte nuclear factors (HNFs) are a heterogeneous class of evolutionarily conserved transcription factors that are required
for cellular differentiation and metabolism. Mutations in HNF-1αand HNF-4α genes impair insulin secretion and cause type 2 diabetes. Regulation of HNF-4/HNF-1 expression byHNF-3α and HNF-3β was studied in embryoid bodies in which one or both HNF-3α or HNF-3βalleles were inactivated. HNF-3β positively regulated the expression of HNF-4α/HNF-1α and their downstream targets, implicating a role in diabetes. HNF-3β was also necessary for expression of HNF-3α. In contrast, HNF-3α acts as a negative regulator of HNF-4α/HNF-1α demonstrating thatHNF-3α and HNF-3β have antagonistic transcriptional regulatory functions in vivo. HNF-3α does not appear to act as a classic biochemical repressor but rather exerts its negative effect by competing for HNF-3 binding
sites with the more efficient activatorHNF-3β. In addition, the HNF-3α/HNF-3β ratio is modulated by the presence of insulin, providing evidence that the HNF network may have important roles in mediating
the action of insulin.
Corticosteroids exert effects on the hippocampus by binding to intracellular glucocorticoid and/or mineralocorticoid receptors, but the relative importance of each receptor type in mediating corticosteroid effects is poorly understood. There is an extensive serotoninergic (5-HT) innervation of the hippocampus which interacts with corticosteroid-sensitive cells. We have investigated the effect of intracerebroventricular 5,7-dihydroxytryptamine lesions of 5-HT neurons on glucocorticoid and mineralocorticoid receptor messenger ribonucleic acid (mRNA) expression in the rat hippocampus using in situ hybridization histochemistry. In controls, glucocorticoid receptor mRNA was highly expressed in dentate gyrus granule cell neurons, and in pyramidal cells of CA1 and CA2, but levels in CAS and CA4 were significantly lower. 5,7-dihydroxytryptamine-lesioned animals showed significantly less glucocorticoid receptor mRNA in the dentate gyrus (76% decrease), CA1 (42% decrease) and CA2 (52% decrease; all P<0.05 compared with controls). Mineralocorticoid receptor mRNA was expressed at a similar level in all hippocampal subregions in control rats. 5,7-dihydroxytryptamine lesioning led to a significant decrease in mineralocorticoid receptor mRNA expression in CA3 (56% fall) and CA4 (45% fall; both P<0.05), but not in the other subregions. Thus the 5-HT innervation regulates hippocampal corticosteroid receptor mRNA expression.
Hepatic gluconeogenesis in the rat does not begin until birth. The enzyme P-enolpyruvate carboxykinase appears initially at birth and is the final enzyme in the gluconeogenic sequence to develop. The appearance of this enzyme in the cytosol of rat liver is caused by the stimulation of enzyme synthesis, probably due directly to an increase in the hepatic concentration of cAMP. Enzyme degradation does not begin until 36 hours after birth. Studies with fetal rats in utero have shown that dibutyryl cAMP or glucagon will stimulate P-enolpyruvate carboxykinase synthesis and that this effect can be blocked by insulin. Insulin is known to depress the synthesis of P-enolpyruvate carboxykinase in adult rat liver and in Reuber H-35 liver cells in culture. The glucocorticoids are without effect on the synthesis of the enzyme in fetal rat liver. Work by Girard et al. (J. Clin. Invest. 52: 3190, 1973) has established that the molar ratio of insulin to glucagon drops from 10 immediately after birth, to 1 after one hour. This is due to both a rise in glucagon and a fall in insulin concentrations at birth. These studies, together with our work on the synthesis of P-enolpyruvate carboxykinase, indicate that the sharp drop in the concentration of insulin may relieve the normal inhibition of enzyme synthesis. This would allow the initial stimulation of enzyme synthesis by the glucagon-mediated rise in the concentration of CAMP.
Although transcriptional hierarchies have been extensively studied in invertebrates, their involvement in mammalian cell-type specification is poorly understood. Here we report a hepatocyte transcriptional cascade suggested by the expression patterns of hepatic transcription factors in dedifferentiated hepatomas and hepatocyte: fibroblast hybrids in which the liver phenotype was extinguished. These results indicated that the homeoprotein hepatocyte nuclear factor-1 alpha (HNF-1 alpha), and HNF-4, a member of the steroid hormone receptor superfamily, were regulated coordinately or in a hierarchy by a higher-order locus, independently of other hepatic transactivators. HNF-4 was implicated as an essential positive regulator of HNF-1 alpha, as deletion of an HNF-4 binding site in the HNF-1 alpha promoter abolished promoter activity, and HNF-4 potently transactivated the HNF-1 alpha promoter in cotransfection assays. Moreover, genetic complementation of dedifferentiated hepatomas with HNF-4 complementary DNA rescued expression of endogenous HNF-1 alpha messenger RNA and DNA-binding activity. Our studies therefore define an HNF-4----HNF-1 alpha (4----1 alpha) transcriptional hierarchy operative in differentiated hepatocytes but selectively inhibited by an extinguishing locus and somatic mutations which antagonize the liver phenotype.
Hepatocyte nuclear factor 1 (HNF-1) is a transcriptional regulatory protein possibly involved in the activation of many liver-specifically expressed genes. HNF-1 mRNA is restricted to a small number of tissues, suggesting that the HNF-1 gene itself is regulated at the transcriptional level. We have isolated and characterized the promoter region of this gene and have determined its transcriptional potential in several cell types by cell-free transcription and transient transfection experiments. In in vitro transcription assays, an HNF-1 promoter is active in nuclear extracts from liver and kidney, two tissues that contain HNF-1, but silent in nuclear extracts from spleen and lung, which are devoid of this transcription factor. Likewise, in transfection experiments, HNF-1 promoter-chloramphenicol acetyltransferase (CAT) fusion genes are expressed in Hep G2 cells, which express HNF-1, but not in mouse L cells or Hela cells, which do not express HNF-1. In both cell-free transcription and transient transfection assays, a relatively short promoter segment located between positions -82 and -40 is necessary and sufficient to direct cell type-specific HNF-1 transcription. This region contains a single site for a DNA-binding protein that has been tentatively identified as hepatocyte nuclear factor 4, a member of the steroid hormone receptor family.
Increased hepatic glucose output is the main cause of fasting hyperglycemia in non-insulin dependent diabetes mellitus. Due to difficulties in obtaining a quantitative estimate of gluconeogenesis in vivo, the relative contribution of gluconeogenesis and glycogenolysis to this increased hepatic glucose output was unknown. The application in vivo of a new isotopic approach based on a mathematical model of the Krebs cycle enabled us to obtain a quantitative estimate of gluconeogenesis in vivo. Using this approach, gluconeogenesis was found to account for approximately 28% and approximately 97% of overall hepatic glucose output in healthy volunteers in the postabsorptive and in the fasted state respectively. When this technique was used to compare gluconeogenesis rates in non-insulin dependent diabetes mellitus and nondiabetic patients, gluconeogenesis was found to be increased threefold in the patients with non-insulin dependent diabetes mellitus (12.7 +/- 1.6 mu vs 3.6 +/- 0.6 mumol/Kg/min) and to be significantly correlated with fasting plasma glucose. Furthermore, the increase in gluconeogenesis could explain more than 80% of the increase in overall hepatic glucose output in patients with non-insulin dependent diabetes mellitus. In conclusion, in non-insulin dependent diabetes mellitus, gluconeogenesis, as measured by a new isotopic technique, is increased and this increase represents the main cause for increased overall hepatic glucose output and fasting hyperglycemia.
Seventeen-day-old fetal rat hepatocytes were employed to examine factors required to promote differentiation in vitro. In the absence of effectors, primary fetal hepatocytes dedifferentiated, as characterized by the rapid decline in synthesis of fetal alpha-fetoprotein (AFP), albumin, and transferrin. On the other hand, cells maintained in the presence of glucocorticoid hormone produced high levels of albumin and transferrin. Glucocorticoid could not prevent the decline in fetal AFP synthesis, but induced synthesis of the 65K variant AFP--the major AFP species produced by adult rat liver. Fetal hepatocytes maintained in the presence of 8-bromo-cAMP (8-BrcAMP), or methyl isobutyl xanthine (MIX), an agent that increases intracellular cAMP levels, synthesized high levels of fetal AFP and albumin but reduced levels of transferrin. Both glucocorticoid and 8-BrcAMP or MIX induced expression of adult liver-specific genes such as tyrosine aminotransferase (TAT) and phosphoenolpyruvate carboxykinase (PEPCK), suggesting that these fetal hepatocytes have matured. Cells maintained in the presence of glucocorticoid hormone and MIX (or 8-BrcAMP) contained more albumin, TAT, and PEPCK mRNAs and synthesized increased amounts of the 65K variant AFP than those with either agent alone. However, the glucocorticoid/MIX cells produced intermediate levels of the fetal AFP and transferrin. Our data indicate that both glucocorticoid hormone and cAMP are necessary for optimal differentiation of fetal hepatocytes in vitro.
1. Administration of glucagon to foetal rats produced a 10-15-fold increase in hepatic phosphoenolpyruvate carboxykinase activity together with a similar increase in the overall pathway of pyruvate conversion into glycogen in liver slices. 2. Glucagon was without effect on gluconeogenesis in vivo, which remained at approx. 0.1% of the incorporation as measured in newborn animals. 3. The apparent discrepancy between these results was due to the ether anaesthesia that was required for experimentation in vivo. Under conditions when minimal ether was used, the rates of labelling of glycogen from [3-(14)C]pyruvate in vivo were increased 10-20-fold and there was an additional stimulus by glucagon. 4. Ether anaesthesia produced a more reduced redox state of the foetal liver cytosol and lowered the ATP/ADP concentration ratio. 5. It is proposed that these effects are significant in the limitation of gluconeogenesis in the foetal rat liver, so that only with high phosphoenolpyruvate carboxykinase activity, high ATP concentration and a relatively oxidized cytosol redox state will a functional gluconeogenic pathway be present.
1. Phosphoenolpyruvate carboxykinase and pyruvate carboxylase were measured in foetal, newborn and adult rat liver extracts by a radiochemical assay involving the fixation of [(14)C]bicarbonate. 2. Pyruvate-carboxylase activity in both foetal and adult liver occurs mainly in mitochondrial and nuclear fractions, with about 10% of the activity in the cytoplasm. 3. Similar studies of the intracellular distribution of phosphoenolpyruvate carboxykinase show that more than 90% of the activity is in the cytoplasm. However, in the 17-day foetal liver about 90% of the activity is in mitochondria and nuclei. 4. Pyruvate-carboxylase activity in both particulate and soluble fractions is very low in the 17-day foetal liver and increases to near adult levels before birth. 5. Phosphoenolpyruvate-carboxykinase activity in the soluble cell fraction increases 25-fold in the first 2 days after birth. This same enzyme in the mitochondria has considerable activity in the foetal and adult liver and is lower in the newborn. 6. Kinetic and other studies on the properties of phosphoenolpyruvate carboxykinase have shown no differences between the soluble and mitochondrial enzymes. 7. It is suggested that the appearance of the soluble phosphoenolpyruvate carboxykinase at birth initiates the rapid increase in overall gluconeogenesis at this stage.
Hepatocyte nuclear factor 4 (HNF-4) is a liver-enriched transcription factor and a member of the steroid hormone receptor
superfamily. HNF-4 is required for the hepatoma-specific expression of HNF-1 alpha, another liver-enriched transcription factor,
suggesting the early participation of HNF-4 in development. To prepare for further study of HNF-4 in development, the tissue-specific
expression of the mouse HNF-4 gene was studied by analyzing the promoter region for required DNA elements. DNase-hypersensitive
sites in the gene in liver and kidney tissues were found in regions both distal and proximal to the RNA start that were absent
in tissues in which HNF-4 expression did not occur. By use of reporter constructs in transient-transfection assays and with
transgenic mice, a region sufficient to drive liver-specific expression of HNF-4 was identified. While an HNF-1 binding site
between bp -98 and -68 played an important role in the hepatoma-specific promoter activity of HNF-4 in transient-transfection
assays, it was not sufficient for the liver-specific expression of a reporter gene in transgenic mice. Distal enhancer elements
indicated by the presence of DNase I-hypersensitive sites at kb -5.5 and -6.5, while not functional in transient-transfection
assays, were required for the correct expression of the mouse HNF-4 gene in animals.
An increase in hepatic gluconeogenesis is believed to be an important factor responsible for the fasting hyperglycemia detected in patients with non-insulin-dependent diabetes mellitus (NIDDM). Phosphoenolpyruvate carboxykinase (GTP) (PEPCK; EC 4.1.1.32) is a regulatory enzyme of gluconeogenesis. To study the role of the expression of PEPCK gene in the development of NIDDM, we have produced lines of transgenic mice expressing a PEPCK minigene under control of its own promoter. Transgenic mice were hyperglycemic and had higher serum insulin concentrations. In addition, alterations in liver glycogen content and muscle glucose transporter GLUT-4 gene expression were detected. The overexpression of the PEPCK gene led to an increase in glucose production from pyruvate in hepatocytes in primary culture. When intraperitoneal glucose tolerance tests were performed, blood glucose levels were higher than those detected in normal mice. This animal model shows that primary alterations in the rate of liver glucose production may induce insulin resistance and NIDDM.
The expression of genes in the liver is mostly controlled at the transcriptional level and depends on the regulatory interactions between cis-acting sequences and trans-acting molecules. Proximal promoters and distant enhancers in combination with a number of hepatocyte-enriched DNA-binding proteins and general transcription factors interact specifically with these elements and control the expression of liver-specific genes. Hepatocyte-enriched regulatory proteins have been isolated from liver nuclear extracts, characterized, and their corresponding genes have been cloned. These include the hepatocyte nuclear factors 1, 3, 4 (HNF-1,3,4), some members of the CAAAT/enhancer binding protein (C/EBP) family, and D site binding protein (DBP). These factors belong to larger families and are able to form heterodimers, perhaps with the exception of the HNF-3 family, with other members of the same family. Interestingly, the majority of the genes encoding such proteins are themselves regulated at the transcriptional level, although both transcriptional and post-transcriptional events modulate their expression during development, hepatocyte differentiation and disease, suggesting that a transcriptional cascade may play a critical role in mammalian liver development and differentiation.
Summary Recent human epidemiological studies have linked low birth weight with a substantially increased risk of non-insulin-dependent
diabetes mellitus in later life. These data suggest that the intrauterine environment plays a crucial role in determining
later glucose homeostasis, but the mechanism is unknown. We have proposed that exposure of the fetus to excess maternal glucocorticoids
may underpin the epidemiological findings. Normally placental 11 β -hydroxysteroid dehydrogenase type 2 (11 β -HSD-2) protects the fetus from the normally higher maternal levels of glucocorticoids by inactivating corticosterone and
cortisol to inert 11-keto products. Here we show that administration of carbenoxolone, an inhibitor of placental 11 β -HSD 2, to pregnant rats, leads to a significant reduction in average birth weight (20 % fall). At 6 months of age, the male
offspring of carbenoxolone-treated pregnancies had similar weights to controls, but showed significantly higher fasting plasma
glucose (6.0 ± 0.3 vs 4.8 ± 0.2 mmol/l; p < 0.01) and exhibited significantly greater plasma glucose (10 % higher) and insulin (38 % higher) responses to an oral glucose
load. These effects of carbenoxolone require intact maternal adrenal glands suggesting that inhibition of feto-placental 11 β -HSD 2 is key. These data support the notion that defiency of placental 11 β -HSD, by exposing the fetus to excess maternal glucocorticoids, reduces growth and predisposes to hyperglycaemia in later
life. [Diabetologia (1996) 39: 1299–1305]
The disease maturity-onset diabetes of the young (MODY) is a genetically heterogeneous monogenic form of non-insulin-dependent (type 2) diabetes mellitus (NIDDM), characterized by early onset, usually before 25 years of age and often in adolescence or childhood, and by autosomal dominant inheritance. It has been estimated that 2-5% of patients with NIDDM may have this form of diabetes mellitus. Clinical studies have shown that prediabetic MODY subjects have normal insulin sensitivity but suffer from a defect in glucose-stimulated insulin secretion, suggesting that pancreatic beta-cell dysfunction rather than insulin resistance is the primary defect in this disorder. Linkage studies have localized the genes that are mutated in MODY on human chromosomes 20 (MODY1), 7 (MODY2) and 12 (MODY3), with MODY2 and MODY3 being allelic with the genes encoding glucokinase, a key regulator of insulin secretion, and hepatocyte nuclear factor-1alpha (HNF-1alpha), a transcription factor involved in tissue-specific regulation of liver genes but also expressed in pancreatic islets, insulinoma cells and other tissues. Here we show that MODY1 is the gene encoding HNF-4alpha (gene symbol, TCF14), a member of the steroid/thyroid hormone receptor superfamily and an upstream regulator of HNF-1alpha expression.
Human epidemiological data show a strong association between low birth weight and hypertension in adulthood, an effect that has been ascribed to ‘fetal programming’. In rats, fetoplacental exposure to maternally administered dexamethasone throughout gestation reduces birth weight and produces hypertensive adult offspring, though the mechanism is unclear. Pre- and postnatal stress programmes hypothalamic-pituitary-adrenal (HPA) axis responses throughout the lifespan, an effect thought to be mediated via permanent effects on glucocorticoid receptor (GR) and/or mineralocorticoid receptor (MR) gene expression in the hippocampus. Corticosteroids also have specific central effects on blood pressure control mediated by GR and MR. This study investigated corticosterone (CORT) responses to restraint stress and GR and MR gene expression in areas of the brain postulated to mediate the central effects of corticosteroids on (i) HPA axis suppression (hippocampus), and (ii) blood pressure (organ vasculosum of the lamina terminalis (OVLT), sub-commissural organ, area postrema and nucleus tractus solitarius). Pregnant Wistar rats received dexamethasone (100 µg/kg·day–1) or vehicle on days 15–20 of gestation. This reduced birth weight by 11 %. When the offspring were 16 weeks old, blood pressure was recorded directly and plasma CORT measured basally (AM) and after 30 min restraint. GR and MR mRNA expression were determined by in situ hybridization. Blood pressure was significantly elevated in the adult offspring of dexamethasone-treated pregnancies (dexamethasone 144 ± 2/125 ± 2 mm Hg vs. control 133 ± 2.7/ 112 ± 2.8 mm Hg; both p
Within the liver acinus the majority of genes are expressed in an ascending or descending gradient from the portal to the central vein. The regulatory factors involved in this spatial pattern of gene expression are still poorly understood. Many liver genes are regulated by liver-enriched transcription factors. Here we report on mRNA distribution of four transcription factors in cell lysates obtained from either the periportal or the perivenous region after zone-specific digitonin infusion and by in-situ hybridization. Northern blot analysis revealed that there were slightly more transcripts of C/EBP, HNF1 beta (n.s.) and HNF4 (p < 0.05), but fewer of HNF3 gamma (n.s.), in perivenous than in periportal lysates. A somewhat stronger staining in the perivenous region of HNF4 was also seen by in-situ hybridization. The moderate acinar zonation of the mRNAs of these transcription factors suggests that at best they could modulate but not govern the zonated expression of liver genes in the mature liver.
1.Many human fetuses have to adapt to a limited supply of nutrients. In doing so they permanently change their structure and metabolism.
2.These ‘programmed' changes may be the origins of a number of diseases in later life, including coronary heart disease and the related disorders stroke, diabetes and hypertension.
3.This review examines the evidence linking these diseases to fetal undernutrition and provides an overview of previous studies in this area.
Hepatocyte nuclear factor (HNF)-4alpha is a transcription factor that plays an important role in regulation of gene expression in pancreatic beta-cells and in the liver. Heterozygous mutations in the HNF-4alpha gene are responsible for maturity-onset diabetes of the young 1 (MODY1), which is characterized by pancreatic beta-cell-deficient insulin secretion. HNF-4alpha is a major transcriptional regulator of many genes expressed in the liver. However, no liver defect has been identified in individuals with HNF-4alpha mutations. In this study, we have identified HNF-4alpha target genes that are mainly expressed in the liver, including alpha1-antitrypsin, alpha1-antichymotrypsin, alpha-fetal protein, ceruloplasmin, IGF binding protein 1, transferrin, apolipoprotein(AI) [apo(AI)], apo(AII), apo(B), and apo(CIII). Serum levels of these proteins and Lp(a) and triglycerides were measured in 24 members of the HNF-4alpha/MODY1 RW pedigree (Q268X mutation), including 12 diabetic patients with HNF-4alpha mutations (D-HNF4+/-), 6 nondiabetic subjects with HNF-4alpha mutations (N-HNF4+/-), 6 normal relatives (N-HNF4+/+), 6 unrelated normal matched control subjects (N-HNF4+/+), and 12 matched diabetic (non-MODY1-5) patients (D-HNF4+/+). Serum levels of apo(AII), apo(CIII), lipoprotein(a) [Lp(a)], and triglyceride were significantly reduced in HNF4+/- subjects (26.9, 19.8, 12.1, and 72.1 mg/dl, respectively) compared with HNF4+/+ subjects (37.4, 26.5, 45.2, and 124.2 mg/dl, respectively) (P = 0.00001, P = 0.01, P = 0.00006, and P = 0.000003, respectively). This reduction was not found when apo(AII), apo(CIII), Lp(a), and triglyceride levels were compared in D-HNF4+/- versus N-HNF4+/- or in D-HNF4+/+ versus N-HNF4+/+ subjects, which indicates that HNF-4alpha haploinsufficiency rather than hyperglycemia is the primary cause of decreased serum protein and triglyceride concentrations. Furthermore, we determined that genetic or environmental modifiers other than HNF-4alpha do not appear to contribute to the observed decrease of HNF-4alpha-regulated serum proteins. This study demonstrates that a heterozygous HNF-4alpha mutation leads to an HNF-4alpha-dependent hepatocyte secretory defect of liver-specific proteins.
The numerous functions of the liver are controlled primarily at the transcriptional level by the concerted actions of a limited number of hepatocyte-enriched transcription factors (hepatocyte nuclear factor 1α [HNF1α], -1β, -3α, -3β, -3γ, -4α, and -6 and members of the c/ebp family). Of these, only HNF4α (nuclear receptor 2A1) and HNF1α appear to be correlated with the differentiated phenotype of cultured hepatoma cells. HNF1α-null mice are viable, indicating that this factor is not an absolute requirement for the formation of an active hepatic parenchyma. In contrast, HNF4α-null mice die during embryogenesis. Moreover, recent in vitro experiments using tetraploid aggregation suggest that HNF4α is indispensable for hepatocyte differentiation. However, the function of HNF4α in the maintenance of hepatocyte differentiation and function is less well understood. To address the function of HNF4α in the mature hepatocyte, a conditional gene knockout was produced using the Cre-loxP system. Mice lacking hepatic HNF4α expression accumulated lipid in the liver and exhibited greatly reduced serum cholesterol and triglyceride levels and increased serum bile acid concentrations. The observed phenotypes may be explained by (i) a selective disruption of very-low-density lipoprotein secretion due to decreased expression of genes encoding apolipoprotein B and microsomal triglyceride transfer protein, (ii) an increase in hepatic cholesterol uptake due to increased expression of the major high-density lipoprotein receptor, scavenger receptor BI, and (iii) a decrease in bile acid uptake to the liver due to down-regulation of the major basolateral bile acid transporters sodium taurocholate cotransporter protein and organic anion transporter protein 1. These data indicate that HNF4α is central to the maintenance of hepatocyte differentiation and is a major in vivo regulator of genes involved in the control of lipid homeostasis.
We have characterized a 700 bp enhancer element around –6 kb relative to the HNF4α1 transcription start. This element increases
activity and confers glucocorticoid induction to a heterologous as well as the homologous promoters in differentiated hepatoma
cells and is transactivated by HNF4α1, HNF4α7, HNF1α and HNF1β in dedifferentiated hepatoma cells. A 240 bp sub-region conserves
basal and hormone-induced enhancer activity. It contains HNF1, HNF4, HNF3 and C/EBP binding sites as shown by DNase I footprinting
and electrophoretic mobility shift assays using nuclear extracts and/or recombinant HNF1α and HNF4α1. Mutation analyses showed
that the HNF1 site is essential for HNF1α transactivation and is required for full basal enhancer activity, as is the C/EBP
site. Glucocorticoid response element consensus sites which overlap the C/EBP, HNF4 and HNF3 sites are crucial for optimal
hormonal induction. We present a model that accounts for weak expression of HNF4α1 in the embryonic liver and strong expression
in the newborn/adult liver via the binding sites identified in the enhancer.
In a previous study, we showed that exposure of rats to dexamethasone (Dex) selectively in late pregnancy produces permanent induction of hepatic phosphoenolpyruvate carboxykinase (PEPCK) expression and hyperglycaemia in the adult offspring. The mechanisms by which glucocorticoids cause this programming are unclear but may involve direct actions on the fetus/neonate, or glucocorticoids may act indirectly by affecting maternal postnatal nursing behaviour. Using a cross-fostering paradigm, the present data demonstrate that switching the offspring at birth from Dex-treated dams to control dams does not prevent induction of PEPCK or hyperglycaemia. Similarly, offspring born to control dams but reared by Dex-treated dams from birth maintain normal glycaemic control. During the neonatal period, injection of saline per se was sufficient to cause exaggeration in adult offspring responses to an oral glucose load, with no additional effect from Dex. However, postnatal treatment with either saline or Dex did not alter hepatic PEPCK activity. Prenatal Dex permanently raised basal plasma corticosterone levels, but under stress conditions there were no differences in circulating corticosterone levels. Likewise, Dex-exposed rats had similar plasma catecholamine concentrations to control animals. These findings show that glucocorticoids programme hyperglycaemia through mechanisms that operate on the fetus or directly on the neonate, rather than via effects that alter maternal postnatal behaviour during the suckling period. The hyperglycaemic response does not appear to result from abnormal sympathoadrenal activity or hypothalamic-pituitary-adrenal response during stress.
Hepatocyte nuclear factor 4alpha (HNF4alpha) is essential for the establishment and maintenance of liver-specific gene expression. The HNF4alpha gene codes for several isoforms whose developmental and physiological relevance has not yet been explored. HNF4alpha1 and HNF4alpha7 originate from different promoters, while alternative splicing in 3' leads to HNF4alpha2 and HNF4alpha8, respectively. HNF4alpha7/alpha8 were abundantly expressed in embryonic liver and fetal-like hepatoma cells. HNF4alpha1/alpha2 transcripts were up-regulated at birth and represented the only isoforms in adult-like hepatoma cells. In line with its expression profile, HNF4alpha7 activated more avidly than HNF4alpha1 reporter plasmids for genes that are expressed early. The expression patterns of both isoforms together with the differences observed in their transcriptional activities provide elements accounting for fine-tuning of the activity of HNF4alpha. The sequential expression of HNF4alpha7/alpha8 and HNF4alpha1/alpha2 during mouse liver development is the only modification in liver-enriched transcription factors thus far recorded, which parallels the transition from the fetal to the adult hepatic phenotype.
Expression of the phosphoenolpyruvate carboxykinase (PEPCK) gene is repressed during fetal liver development and activated at birth. It has been shown that the PEPCK gene is a retinoid-responsive gene, but whether it is regulated by vitamin A in the fetus has not been established. In this study, we found that PEPCK mRNA can be detected in the murine fetal liver as early as gestational d 17. In addition, expression and cAMP induction of the PEPCK gene during late gestation and at birth require vitamin A sufficiency in the fetus and neonate. The PEPCK promoter contains several regulatory elements that bind a diverse array of transcription factors and nuclear coregulators, although it is largely unknown which of these factors are expressed early in liver development. Expression of some of these nuclear factors in livers of fetal mice was investigated by immunohistochemistry (IHC). Fetuses were from dams that were fed from the beginning of gestation diets that were adequate or devoid of vitamin A. Hepatocyte nuclear factor 4alpha (HNF4alpha) was expressed at the earliest stage of liver development on d 11, whereas retinoid X receptor alpha (RXRalpha) and nuclear coactivator CREB-binding protein (CBP) were expressed from d 16 onward. Although expressions of RXRalpha and CBP in livers of vitamin A-sufficient and vitamin A-depleted fetal mice did not differ, the level of HNF4alpha was consistently lower in the latter. Our findings strongly suggest that vitamin A is required during liver development for staged expression of the PEPCK gene and that HNF4alpha may be involved in mediating vitamin A regulation of the PEPCK gene at these critical periods.
The transcriptional regulatory networks that specify and maintain human tissue diversity are largely uncharted. To gain insight into this circuitry, we used chromatin immunoprecipitation combined with promoter microarrays to identify systematically the genes occupied by the transcriptional regulators HNF1alpha, HNF4alpha, and HNF6, together with RNA polymerase II, in human liver and pancreatic islets. We identified tissue-specific regulatory circuits formed by HNF1alpha, HNF4alpha, and HNF6 with other transcription factors, revealing how these factors function as master regulators of hepatocyte and islet transcription. Our results suggest how misregulation of HNF4alpha can contribute to type 2 diabetes.
Regulation of hepatic fasting response by PPARgamma coactivator-1alpha (PGC-1): requirement for hepatocyte nuclear factor 4alpha in gluconeo-genesis
- Rhee J Y Inoue
- Yoon
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Rhee J, Inoue Y, Yoon JC et al (2003) Regulation of hepatic fasting response by PPARgamma coactivator-1alpha (PGC-1): requirement for hepatocyte nuclear factor 4alpha in gluconeo-genesis. Proc Natl Acad Sci USA 100:4012–4017
Hepatocyte nuclear factor 4a. In: McCabe ERB (ed) Nuclear receptors and genetic disease
- F M Sladek
- S D Seidel
- FM Sladek