Figure - available from: Oxidative Medicine and Cellular Longevity
This content is subject to copyright. Terms and conditions apply.
Diabetes induced photoreceptor cell degeneration in vivo. (a, b) Retinal function in diabetic mice was measured by ERG. (c) Retinal morphology in diabetic mice was observed by HE staining. The thicknesses of the total retina (d), ONL (e), INL (f), and RGC (g) were measured in diabetic mice. (h, i) The expression of rhodopsin and opsin was measured in diabetic mice. (j, l) The expression of AGEs and p-AMPK as measured in diabetic mice. The data are presented as the mean±SD (n=5 in each group). ∗p<0.05, ∗∗p<0.01, ∗∗∗p<0.001.
Source publication
Diabetic retinopathy (DR) is a kind of severe retinal neurodegeneration. The advanced glycation end products (AGEs) affect autophagy, and mitochondrial function is involved in DR. Adenosine-activated protein kinase (AMPK) is an important metabolic sensor that can regulate energy homeostasis in cells. However, the effect of AMPK in DR is still not f...
Citations
... Moreover, increasing evidence indicates that retinal neurodegeneration and microangiopathy participate in the pathogenesis of DR together [10]. Additionally, in our previous research, we found that decreasing 661 w cell apoptosis under high glucose conditions, which helps maintain photoreceptor cell structure, function stability, and micro-environment hemostasis, can delay DR in vitro [11]. Therefore, targeting photoreceptor cells for neurodegeneration prevention is a promising method for delaying DR at an early clinical stage in the future. ...
... The normal control group was intraperitoneally injected with an equal volume of sodium citrate buffer. As the random blood glucose was more than 16.7 mmol/L, the model is considered to have been successfully constructed [11]. The entire experimental protocol was approved by the Institutional Animal Care and Use Commi ee of the Dalian Medical University Laboratory Animal Center (L20120021 and AEE22090). ...
Diabetic retinopathy (DR) is a very serious diabetes complication. Changes in the O-linked N-acetylglucosamine (O-GlcNAc) modification are associated with many diseases. However, its role in DR is not fully understood. In this research, we explored the effect of O-GlcNAc modification regulation by activating AMP-activated protein kinase (AMPK) in DR, providing some evidence for clinical DR treatment in the future. Bioinformatics was used to make predictions from the database, which were validated using the serum samples of diabetic patients. As an in vivo model, diabetic mice were induced using streptozotocin (STZ) injection with/without an AMPK agonist (metformin) or an AMPK inhibitor (compound C) treatment. Electroretinogram (ERG) and H&E staining were used to evaluate the retinal functional and morphological changes. In vitro, 661 w cells were exposed to high-glucose conditions, with or without metformin treatment. Apoptosis was evaluated using TUNEL staining. The protein expression was detected using Western blot and immunofluorescence staining. The angiogenesis ability was detected using a tube formation assay. The levels of O-GlcNAc transferase (OGT) and O-GlcNAcase (OGA) in the serum changed in the DR patients in the clinic. In the diabetic mice, the ERG wave amplitude and retinal thickness decreased. In vitro, the apoptotic cell percentage and Bax expression were increased, and Bcl2 expression was decreased in the 661 w cells under high-glucose conditions. The O-GlcNAc modification was increased in DR. In addition, the expression of GFAT/TXNIP O-GlcNAc was also increased in the 661 w cells after the high-glucose treatment. Additionally, the Co-immunoprecipitation(CO-IP) results show that TXNIP interacted with the O-GlcNAc modification. However, AMPK activation ameliorated this effect. We also found that silencing the AMPKα1 subunit reversed this process. In addition, the conditioned medium of the 661 w cells may have affected the tube formation in vitro. Taken together, O-GlcNAc modification was increased in DR with photoreceptor cell degeneration and neovascularization; however, it was reversed after activating AMPK. The underlying mechanism is linked to the GFAT/TXNIP-O-GlcNAc modification signaling axis. Therefore, the AMPKα1 subunit plays a vital role in the process.
... Further, metformin also prevents retinal cell death in diabetic mouse models. Metformin has also been shown to increase AMPK activity and prevent photoreceptor and retinal endothelial cell degeneration in mice [69]. Furthermore, metformin has been shown to prevent diabetes-associated histopathological ocular deteriorations in various ocular tissues such as cornea, sclera, iris, retina, and ciliary body by preventing oxidative stress, inflammatory response, and neovascularization in a STZ-induced diabetic rat model [70]. ...
Metformin, a widely used first-line anti-diabetic therapy for the treatment of type-2 diabetes, has been shown to lower hyperglycemia levels in the blood by enhancing insulin actions. For several decades this drug has been used globally to successfully control hyperglycemia. Lactic acidosis has been shown to be a major adverse effect of metformin in some type-2 diabetic patients, but several studies suggest that it is a typically well-tolerated and safe drug in most patients. Further, recent studies also indicate its potential to reduce the symptoms associated with various inflammatory complications and infectious diseases including coronavirus disease 2019 (COVID-19). These studies suggest that besides diabetes, metformin could be used as an adjuvant drug to control inflammatory and infectious diseases. In this article, we discuss the current understanding of the role of the anti-diabetic drug metformin in the prevention of various inflammatory complications and infectious diseases in both diabetics and non-diabetics.
... Thus, the downregulation of these proteins may suggest a decrease in energy metabolism in the R28 cells exposed to glutamate and H 2 O 2 . Furthermore, a decline in energy metabolism has been shown to be involved in neurodegenerative diseases such as Alzheimer's and Parkinson's diseases [89], as well as retinal diseases, such as DR [90], AMD [91] and glaucoma [92]. ...
Glaucoma is a heterogeneous group of optic neuropathies characterized by a progressive degeneration of the retinal ganglion cells (RGCs), leading to irreversible vision loss. Nowadays, the traditional therapeutic approach to glaucoma consists of lowering the intraocular pressure (IOP), which does not address the neurodegenerative features of the disease. Besides animal models of glaucoma, there is a considerable need for in vitro experimental models to propose new therapeutic strategies for this ocular disease. In this study, we elucidated the pathological mechanisms leading to neuroretinal R28 cell death after exposure to glutamate and hydrogen peroxide (H2O2) in order to develop new therapeutic approaches for oxidative stress-induced retinal diseases, including glaucoma. We were able to show that glutamate and H2O2 can induce a decrease in R28 cell viability in a concentration-dependent manner. A cell viability of about 42% was found after exposure to 3 mM of glutamate and about 56% after exposure to 100 µM of H2O2 (n = 4). Label-free quantitative mass spectrometry analysis revealed differential alterations of 193 and 311 proteins in R28 cells exposed to 3 mM of glutamate and 100 µM of H2O2, respectively (FDR < 1%; p < 0.05). Bioinformatics analysis indicated that the protein changes were associated with the dysregulation of signaling pathways, which was similar to those observed in glaucoma. Thus, the proteomic alteration induced by glutamate was associated with the inhibition of the PI3K/AKT signaling pathway. On the other hand, H2O2-induced toxicity in R28 cells was linked to the activation of apoptosis signaling and the inhibition of the mTOR and ERK/MAPK signaling pathways. Furthermore, the data show a similarity in the inhibition of the EIF2 and AMPK signaling pathways and the activation of the sumoylation and WNT/β-catenin signaling pathways in both groups. Our findings suggest that the exposure of R28 cells to glutamate and H2O2 could induce glaucoma-like neurodegenerative features and potentially provide a suitable tool for the development of new therapeutic strategies for retinal diseases.
... Although the mechanism of phagosome formation is well understood, the constituent lipids and membrane modeling proteins involved in determining the shape and size of phagosomes have been at the center of controversy for decades (Tooze, 2013;Carlsson and Simonsen, 2015). It is now widely accepted that phagosomes originate near or on the ER, where several organelles including the mitochondria, Golgi complex, plasma membrane, and endosomes provide membranes for phagosome formation (Graef et al., 2013;Shibutani and Yoshimori, 2014;Sanchez-Wandelmer et al., 2015;Li J. et al., 2021). It has also been found that the ER exit site works synergy Atg9 in the autophagy-related gene (Atg) family to promote the assembly of autophagy mechanism, and may provide membranes for phagophore nucleation, maturation, and growth (Graef et al., 2013;Tooze, 2013;Sanchez-Wandelmer et al., 2015). ...
... Xiao et al. discovered that after administering the mTOR inhibitor rpapamycin to streptozotocin (STZ)-induced DM mice, there was a significant increase in LC3 expression in podocytes, upregulation of autophagy activity, and reduction in kidney injury (Xiao et al., 2014). Metformin, an AMPK agonist, restores autophagic activity in podocytes, protecting against DM injury (Song A. et al., 2021). Similarly, according to Xu et al., SIRT1/FOXO1 pathways influenced by metformin enhance autophagy, mitigating diabetic kidney injury (Xu J. et al., 2020). ...
... At the same time, the expression of caspase-3 was further increased, indicating that the activation of autophagy would lead to apoptosis . In addition, studies have also shown that activation of AMPK can reduce the expression of apoptosisrelated proteins Bax, increase Bcl-2, and decrease LC3 expression, and restore autophagy and mitochondrial function to delay DRinduced photoreceptor cell degeneration (Song S. et al., 2021). ...
As the quality of life improves, the incidence of diabetes mellitus and its microvascular complications (DMC) continues to increase, posing a threat to people’s health and wellbeing. Given the limitations of existing treatment, there is an urgent need for novel approaches to prevent and treat DMC. Autophagy, a pivotal mechanism governing metabolic regulation in organisms, facilitates the removal of dysfunctional proteins and organelles, thereby sustaining cellular homeostasis and energy generation. Anomalous states in pancreatic β-cells, podocytes, Müller cells, cardiomyocytes, and Schwann cells in DMC are closely linked to autophagic dysregulation. Natural products have the property of being multi-targeted and can affect autophagy and hence DMC progression in terms of nutrient perception, oxidative stress, endoplasmic reticulum stress, inflammation, and apoptosis. This review consolidates recent advancements in understanding DMC pathogenesis via autophagy and proposes novel perspectives on treating DMC by either stimulating or inhibiting autophagy using natural products.
... Previous studies have indicated that photoreceptor degeneration is a critical event in the development and progression of DR. Multiple modes of cell death, including apoptosis [14] and autophagy [15], have been demonstrated to play an important role in diabetes-induced photoreceptor degeneration. Notably, although therapies targeting the apoptotic and autophagic pathways have displayed significant advantages in protecting the photoreceptors in DR [14,15], photoreceptor cell loss is still sustained, probably because of the participation of other death pathways. ...
... Multiple modes of cell death, including apoptosis [14] and autophagy [15], have been demonstrated to play an important role in diabetes-induced photoreceptor degeneration. Notably, although therapies targeting the apoptotic and autophagic pathways have displayed significant advantages in protecting the photoreceptors in DR [14,15], photoreceptor cell loss is still sustained, probably because of the participation of other death pathways. Ferroptosis, a form of iron-dependent regulated cell death triggered by excessive lipid peroxidation [6], is involved in diverse pathophysiological states and has been indicated to play a critical role in the pathogenesis of various diabetic complications, such as diabetic nephropathy [16], diabetic cardiomyopathy [17], and diabetic osteoporosis [18]. ...
Diabetic retinopathy (DR) is a leading cause of vision impairment in the working-age population worldwide. Various modes of photoreceptor cell death contribute to the development of DR, including apoptosis and autophagy. However, whether ferroptosis is involved in the pathogenesis of photoreceptor degeneration in DR is still unclear. High-glucose (HG)-stimulated 661W cells and diabetic mice models were used for in vitro and in vivo experiments, respectively. The levels of intracellular iron, glutathione (GSH), reactive oxygen species (ROS), lipid peroxidation (MDA), and ferroptosis-related proteins (GPX4, SLC7A11, ACSL4, FTH1, and NCOA4) were quantified to indicate ferroptosis. The effect of ferroptosis inhibition was also assessed. Our data showed the levels of iron, ROS, and MDA were enhanced and GSH concentration was reduced in HG-induced 661W cells and diabetic retinas. The expression of GPX4 and SLC7A11 was downregulated, while the expression of ACSL4, FTH1, and NCOA4 was upregulated in the 661W cells cultured under HG conditions and in the photoreceptor cells in diabetic mice. Furthermore, the administration of the ferroptosis inhibitor ferrostatin-1 (Fer-1) obviously alleviated ferroptosis-related changes in HG-cultured 661W cells and in retinal photoreceptor cells in diabetic mice. Taken together, our findings suggest that ferroptosis is involved in photoreceptor degeneration in the development of the early stages of DR.
... It has been demonstrated that diabetes-induced inflammation strongly correlates with a reduced AMPK pathway, the downregulation of which leads to diminished SIRT1 activation [40]. AMPK stimulation is known to prevent photoreceptor cell degeneration in T1D mice [41]. Therefore, an increase in AMPK activity may indicate a reduced inflammatory response and diminished photoreceptor functional loss. ...
Previously, the RXR agonist UAB126 demonstrated therapeutic potential to treat obese mice by controlling blood glucose levels (BGL) and altering the expression of genes associated with lipid metabolism and inflammatory response. The purpose of the study was to assess the effects of UAB126 on the progression of diabetic retinopathy (DR) in rodent models of type 1 diabetes (T1D), streptozotocin-induced, and type 2 diabetes (T2D), in db/db mice. UAB126 treatment was delivered either by oral gavage for 6 weeks or by topical application of eye drops for 2 weeks. At the end of the treatment, the retinal function of diabetic mice was assessed by electroretinography (ERG), and their retinal tissue was harvested for protein and gene expression analyses. Bone-marrow cells were isolated and differentiated into bone marrow-derived macrophages (BMDMs). The glycolysis stress test and the 2-DG glucose uptake analysis were performed. Our results demonstrated that in the UAB126-treated diabetic BMDMs, the ECAR rate and the 2-DG uptake were improved as compared to untreated diabetic BMDMs. In UAB126-treated diabetic mice, hyperglycemia was reduced and associated with the preservation of ERG amplitudes and enhanced AMPK activity. Retinas from diabetic mice treated with topical UAB126 demonstrated an increase in Rxr and Ppar and the expression of genes associated with lipid metabolism. Altogether, our data indicate that RXR activation is beneficial to preclinical models of DR.
... 9 For example, in the physiological state or at the early stage of some diseases, autophagy helps to clear senescent and damaged cells or organelles, while when autophagy is too strong, it has a pathogenic effect on cells, tissues, and organs. 10 Recently, many researches demonstrated that activating autophagy might be a promising therapeutic strategy in DR. 11,12 Adenosine monophosphate-activated protein kinase (AMPK) participates in the regulation of energy metabolism, plays a protective role in many diseases including DR. 13 Sirtuin 1 (SIRT1), one of the sirtuins family members, is a nicotinamide adenine dinucleotide (NAD +)-dependent histone deacetylase. SIRT1 is activated by the increase of intracellular adenosine monophosphate and NAD + levels. ...
Background
Diabetes retinopathy (DR) is a chronic, progressive, and potentially harmful retinal disease associated with persistent hyperglycemia. Autophagy is a lysosome-dependent degradation pathway that widely exists in eukaryotic cells, which has recently been demonstrated to participate in the DR development. Stachydrine (STA) is a water-soluble alkaloid extracted from Leonurus heterophyllus. This study aimed to explore the effects of STA on the autophagy in DR progression in vivo and in vitro.
Methods
High glucose-treated human retinal microvascular endothelial cells (HRMECs) and STA-treated rats were used to establish DR model. The reactive oxygen species (ROS) and inflammatory factor levels (TNF-α, IL-1β, and IL-6) were determined using corresponding kits. Additionally, the cell growth was analyzed using CCK-8 and EdU assays. Besides, LC3BII, p62, p-AMPKα, AMPKα, and SIRT1 protein levels were measured using Western blot. The LC3BII and SIRT1 expressions were also determined using immunofluorescence.
Results
The results showed that STZ decreased the ROS and inflammatory factor levels in the HG-treated HRMECs. Besides, after STA treatment, the beclin-1, LC3BII, p-AMPKα, and SIRT1 levels were increased, and p62 was decreased in the HG-treated HRMECs and the retinal tissue of STZ-treated rats.
Conclusion
In conclusion, this study demonstrated that STA effectively relieved the inflammation and promoted the autophagy in DR progression in vivo and in vitro through activating the AMPK/SIRT1 signaling pathway.
... 38 AMPK stimulation is known to prevent photoreceptor cell degeneration in T1D mice. 39 Therefore, an increase in AMPK activity may indicate the reduced inflammatory response and diminished photoreceptor functional loss. This data correlate with the observed reduction in the decline of A-wave scotopic amplitudes in UAB126-treated diabetic mice vs. untreated ones. ...
Previously, the RXR agonist UAB126 demonstrated therapeutic potential to treat obese mice by controlling blood glucose levels (BGL) and altering the expression of genes associated with lipid metabolism and inflammatory response. The purpose of the study was to assess UAB126 effect in progression of diabetic retinopathy (DR) in rodent models of Type1 diabetes (T1D), streptozotocin-induced, and Type2 diabetes (T2D), the db/db mice. UAB126 treatment was delivered either by oral gavage for 6 weeks or by topical application of eye drops for 2 weeks. At the end of the treatment, the retinal function of diabetic mice was assessed by electroretinography (ERG), and their retinal tissue was harvested for protein and gene expression analyses. Bone-marrow cells were isolated and differentiated into bone marrow-derived macrophages (BMDMs). The glycolysis stress test and the 2-DG glucose uptake analysis were performed. Our results demonstrated that in the UAB126-treated diabetic BMDMs, the ECAR rate and the 2-DG uptake were improved as compared to untreated diabetic BMDMs. In UAB126-treated diabetic mice, hyperglycemia was reduced and associated with the preservation of ERG amplitudes and enhanced AMPK activity. Retinas from diabetic mice treated with topical UAB126 demonstrated an increase in Rxr and Ppar, and expression of genes associated with lipid metabolism. Altogether, our data indicate that RXR activation is beneficial to preclinical models of DR.
... The control group was intraperitoneally injected with an equal volume of sodium citrate buffer. The onset of diabetes was defined as any blood glucose level higher than 16.7 mmol/L in blood collected from each mouse's tail [16]. Mice were randomly divided into three groups (n = 5-7 per group): nondiabetic control (control group), diabetic control (T1D group), and diabetic with butyrate supplementation (T1D + NaB group). ...
Background
Diabetic retinopathy (DR) development is associated with disturbances in the gut microbiota and related metabolites. Butyric acid is one of the short-chain fatty acids (SCFAs), which has been found to possess a potential antidiabetic effect. However, whether butyrate has a role in DR remains elusive. This study aimed to investigate the effect and mechanism of sodium butyrate supplementation on DR.
Methods
C57BL/6J mice were divided into three groups: Control group, diabetic group, and diabetic with butyrate supplementation group. Type 1 diabetic mouse model was induced by streptozotocin. Sodium butyrate was administered by gavage to the experimental group daily for 12 weeks. Optic coherence tomography, hematoxylin–eosin, and immunostaining of whole-mount retina were used to value the changes in retinal structure. Electroretinography was performed to assess the retinal visual function. The tight junction proteins in intestinal tissue were evaluated using immunohistochemistry. 16S rRNA sequencing and LC–MS/MS were performed to determine the alteration and correlation of the gut microbiota and systemic SCFAs.
Results
Butyrate decreased blood glucose, food, and water consumption. Meanwhile, it alleviated retinal thinning and activated microglial cells but improved electroretinography visual function. Additionally, butyrate effectively enhanced the expression of ZO-1 and Occludin proteins in the small intestine. Crucially, only butyric acid, 4-methylvaleric acid, and caproic acid were significantly decreased in the plasma of diabetic mice and improved after butyrate supplementation. The deeper correlation analysis revealed nine genera strongly positively or negatively correlated with the above three SCFAs. Of note, all three positively correlated genera, including norank_f_Muribaculaceae, Ileibacterium, and Dubosiella, were significantly decreased in the diabetic mice with or without butyrate treatment. Interestingly, among the six negatively correlated genera, Escherichia-Shigella and Enterococcus were increased, while Lactobacillus, Bifidobacterium, Lachnospiraceae_NK4A136_group, and unclassified_f_Lachnospiraceae were decreased after butyrate supplementation.
Conclusion
Together, these findings demonstrate the microbiota regulating and diabetic therapeutic effects of butyrate, which can be used as a potential food supplement alternative to DR medicine.
... AMPK also can activate numerous targets coordinating changes in the production of energy. Upregulation of AMPK prevented various eye diseases, including DR, AMD, cataracts, and optic neuritis [92]. It has been reported that AMPK stimulation delays the photoreceptor degeneration induced by diabetes, with the regulation of the autophagy-related proteins LC3 and p62 expression. ...
... It has been reported that AMPK stimulation delays the photoreceptor degeneration induced by diabetes, with the regulation of the autophagy-related proteins LC3 and p62 expression. This process improves mitochondrion-related gene expression, membrane potential, and morphological abnormalities [92]. ...
Retinopathy is one of the leading causes of irreversible blindness and vision loss worldwide. Imbalanced nutrients play important roles in the pathogenesis and pathophysiology of retinal diseases. Branched-Chain Amino Acids (BCAAs), as essential amino acids, perform a variety of biological functions, including protein synthesis, glucose metabolism, lipid metabolism, inflammation, and oxidative stress in metabolic tissues of diabetes and aging-related diseases. Recently, it has been shown that BCAAs are highly related to neuroprotection, oxidative stress, inflammatory and glutamate toxicity in the retina of retinopathy. Therefore, this review summarizes the alterations of BCAA levels in retinopathy, especially diabetic retinopathy and aging-related macular disease, and the genetics, functions, and mechanisms of BCAAs in the retina as well as other metabolic tissues for reference. All of these efforts aim to provide fundamental knowledge of BCAAs for further discoveries and research on retina health based on the sensing and signaling of essential amino acids.
