Dysfunction In Metabolic Disorders Research Articles

ROLE OF H2S AS A PREDICTOR OF CARDIOVASCULAR DISEASE IN METABOLIC SYNDROME

Objective: One of the possible protective factors that can protect target vascular cells (endothelial, smooth muscle cells) from damage during the development of metabolic syndrome (MetS) is hydrogen sulfide (H2S). Design and method: A study was carried out in male Wistar rats weighing 250–320 g, 140 days old at the end of research. The rats from the control group were fed standard rat chow. The rats from the experimental group had a high-fat high-carbohydrate (HFHC) diet. Biochemical parameters of rat blood were determined. The concentration of H2S in the blood serum and adipose tissue of rats was determined by the photometric method at 670 nm. The expression of the H2S synthesis enzyme CSE was studied in aortic tissue samples using Western blot. Results: It was found that HFHC diet led to an increase in body weight, obesity, hyperglycemia, insulin resistance, dyslipidemia, and leptinemia in the experimental group rats. It was found that the concentration of H2S significantly decreased in the blood serum and adipose tissue of rats with MetS. The rate of production of H2S in adipose tissue of rats with MetS also decreased. In the aortic tissue of rats with MetS, there was a decrease in the amount of protein of the CSE. Conclusions: Changes in the activity of the H2S/CSE system in MetS may be additional evidence of the development of vascular dysfunction in metabolic disorders.

Isolation of Murine Adipose-Derived Stromal/Stem Cells for Adipogenic and Osteogenic Differentiation or Flow Cytometry-Based Analysis.

Murine models of obesity or reduced adiposity are a valuable resource for understanding the role of adipocyte dysfunction in metabolic disorders. Adipose tissue stromal vascular cells or primary adipocytes derived from murine adipose tissue and grown in culture are essential tools for studying the mechanisms underlying adipocyte development and function. Herein, we describe methods for the isolation, expansion, and long-term storage of murine adipose-derived stromal/stem cells, along with protocols for inducing adipogenesis to white or beige adipocytes in this cell population and osteogenic differentiation. Isolation of the adipose stromal vascular fraction cells for flow cytometric analysis is also described.

Mitochondrial dysfunction in metabolic disorders induced by per- and polyfluoroalkyl substance mixtures in zebrafish larvae

Several per- and polyfluoroalkyl substances (PFAS) have been linked to metabolic disorders in organisms. However, few studies have considered their combined effects, which would be more representative of PFAS occurring in the environment. In this study, zebrafish embryos were exposed to a mixture of 18 PFAS at three environmentally relevant concentrations for 5 days to assess their bioconcentration and metabolic consequences. The burdens of ∑PFAS in zebrafish larvae were 0.12, 1.58, and 9.63 mg/kg in the 0.5, 5, and 50 μg/L treatment groups, respectively. Exposure to the PFAS mixture accelerated hatching and larval heart rates, increased energy expenditure, and reduced ATP levels and glucose contents due to decreased feed intake and glucose uptake. Metabolomic analysis revealed that exposure to the PFAS mixture enhanced glycolysis but inhibited phospholipid synthesis, and significantly increased the expression of lipid metabolism related genes (srebf1, acox, and pparα), which indicated enhanced β-oxidation. The significant changes in mitochondrial membrane potential, mitochondrial content, and the transcription of genes involved in the mitochondrial respiratory chain (mfn2, ndufs1, atp5fa1, and mt-nd1) and mitochondrial DNA replication and transcription (18rs-rrn, and polg1) suggested that exposure to the PFAS mixture could cause mitochondrial dysfunction and further disrupt glucose and lipid metabolic pathways, ultimately causing metabolic disorders in zebrafish larvae. These findings demonstrate the importance of assessing the metabolic effects of PFAS mixtures on early development in wildlife and humans.

The Functional Effects of Visfatin on Human Left Internal Mammary Artery.

Visfatin may play a role in vascular dysfunction in metabolic disorders. Apart from its insulin-mimetic actions, it has divergent actions in the cardiovascular system with discordant results in the literature. Thus, we aimed to study the effects of visfatin on vascular responses of the human left internal mammary artery. Sections of redundant human left internal mammary artery were cut into 3-mm wide rings and hung in 20-mL organ baths containing physiologic salt solution and attached to an isometric force transducer connected to a computer-based data acquisition system. Removing endothelium caused an increase in pD2 values for visfatin-induced relaxation responses (10 -12 -10 -7 M) (9.06 ± 0.21 and 11.08 ± 0.92, respectively). Nicotinamide phosphoribosyltransferase inhibitor FK866 (10 µM) reversed the visfatin-induced relaxations (10 -12 -10 -7 M) ( P = 0.024). Incubations with nitric oxide synthase inhibitor nitro- l -arginine methylester and guanylate cyclase inhibitor 1H-[1,2,4] oxadiazolo [4,3-a] quinoxalin-1-one (ODQ) caused significant reductions in relaxation responses of visfatin ( P = 0.011 and 0.008, respectively). Visfatin incubations decreased relaxation responses to acetylcholine but not to sodium nitroprusside. Incubations with visfatin did not change contractile responses to angiotensin II, endothelin-1, noradrenalin, and phenylephrine. In this study, visfatin caused endothelium-dependent relaxations mediated by nitric oxide-cyclic guanosine monophosphate pathway and nicotinamide phosphoribosyltransferase activity. Furthermore, visfatin-induced decreases in relaxation responses were also related to endothelium-derived nitric oxide.

3,4',5-Trimethoxy-trans-stilbene Alleviates Endothelial Dysfunction in Diabetic and Obese Mice via Activation of the AMPK/SIRT1/eNOS Pathway.

3,4′,5-trimethoxy-trans-stilbene (TMS) is a methoxylated derivative of resveratrol. Previous studies showed the vaso-protective effects of resveratrol; nevertheless, research on this derivative is scarce. The current study aimed to explore whether TMS can alleviate endothelial dysfunction in diabetic and obese mice, along with the underlying mechanisms. Thoracic aortas isolated from male C57BL/6J mice and primary cultures of rat aortic endothelial cells were treated with high glucose with or without TMS. High glucose exposure impaired acetylcholine-induced endothelium-dependent relaxations, down-regulated NO bioavailability and the AMP-activated protein kinase (AMPK)/Sirtuin 1 (SIRT1)/endothelial nitric oxide synthase (eNOS) pathway, increased endoplasmic reticulum (ER) stress and oxidative stress, which were reversed by TMS treatment. Moreover, the protective effects of TMS were abolished by Compound C (AMPK inhibitor), and EX527 (SIRT1 inhibitor). The mice were fed with high-fat diet (60% kcal% fat) for 14 weeks to establish a diabetic and obese model, and were orally administered TMS (10 mg/kg/day) in the last 4 weeks. Chronic TMS treatment alleviated endothelial dysfunction via enhancing the AMPK/SIRT1/eNOS pathway and attenuated oxidative stress and ER stress in aortas of diet-induced obese mice. In summary, our study reveals the potent vaso-protective effect of TMS and its therapeutic potential against endothelial dysfunction in metabolic disorders.

Phytochemicals: Targeting Mitophagy to Treat Metabolic Disorders.

Metabolic disorders include metabolic syndrome, obesity, type 2 diabetes mellitus, non-alcoholic fatty liver disease and cardiovascular diseases. Due to unhealthy lifestyles such as high-calorie diet, sedentary and physical inactivity, the prevalence of metabolic disorders poses a huge challenge to global human health, which is the leading cause of global human death. Mitochondrion is the major site of adenosine triphosphate synthesis, fatty acid β−oxidation and ROS production. Accumulating evidence suggests that mitochondrial dysfunction-related oxidative stress and inflammation is involved in the development of metabolic disorders. Mitophagy, a catabolic process, selectively degrades damaged or superfluous mitochondria to reverse mitochondrial dysfunction and preserve mitochondrial function. It is considered to be one of the major mechanisms responsible for mitochondrial quality control. Growing evidence shows that mitophagy can prevent and treat metabolic disorders through suppressing mitochondrial dysfunction-induced oxidative stress and inflammation. In the past decade, in order to expand the range of pharmaceutical options, more and more phytochemicals have been proven to have therapeutic effects on metabolic disorders. Many of these phytochemicals have been proved to activate mitophagy to ameliorate metabolic disorders. Given the ongoing epidemic of metabolic disorders, it is of great significance to explore the contribution and underlying mechanisms of mitophagy in metabolic disorders, and to understand the effects and molecular mechanisms of phytochemicals on the treatment of metabolic disorders. Here, we investigate the mechanism of mitochondrial dysfunction in metabolic disorders and discuss the potential of targeting mitophagy with phytochemicals for the treatment of metabolic disorders, with a view to providing a direction for finding phytochemicals that target mitophagy to prevent or treat metabolic disorders.

Exploring the Mediators that Promote Carotid Body Dysfunction in Type 2 Diabetes and Obesity Related Syndromes.

Carotid bodies (CBs) are peripheral chemoreceptors that sense changes in blood O2, CO2, and pH levels. Apart from ventilatory control, these organs are deeply involved in the homeostatic regulation of carbohydrates and lipid metabolism and inflammation. It has been described that CB dysfunction is involved in the genesis of metabolic diseases and that CB overactivation is present in animal models of metabolic disease and in prediabetes patients. Additionally, resection of the CB-sensitive nerve, the carotid sinus nerve (CSN), or CB ablation in animals prevents and reverses diet-induced insulin resistance and glucose intolerance as well as sympathoadrenal overactivity, meaning that the beneficial effects of decreasing CB activity on glucose homeostasis are modulated by target-related efferent sympathetic nerves, through a reflex initiated in the CBs. In agreement with our pre-clinical data, hyperbaric oxygen therapy, which reduces CB activity, improves glucose homeostasis in type 2 diabetes patients. Insulin, leptin, and pro-inflammatory cytokines activate the CB. In this manuscript, we review in a concise manner the putative pathways linking CB chemoreceptor deregulation with the pathogenesis of metabolic diseases and discuss and present new data that highlight the roles of hyperinsulinemia, hyperleptinemia, and chronic inflammation as major factors contributing to CB dysfunction in metabolic disorders.

Metabolic control of B cell immune responses.

Humoral immunity critically depends on appropriate B cell responses. B cell activation, proliferation, differentiation and antibody secretion are processes carefully orchestrated by a complex network of intracellular signaling pathways and transcription factors. In order to meet the energetic and biosynthetic demands of protein synthesis and cell division, signal transduction pathways reshape the metabolic profile of activated B cells. However, the relationship between signaling and metabolism is by no means unidirectional. Emerging evidence suggests that shifts in available fuel sources and intracellular metabolite concentrations profoundly impact cell fate decisions. The reciprocal regulation of cell signaling and metabolism could potentially be exploited to curb immune dysfunction in metabolic disorders or to antagonize autoimmunity and B cell malignancies.

Quercetin improves endothelial insulin sensitivity in obese mice by inhibiting Drp1 phosphorylation at serine 616 and mitochondrial fragmentation.

Studies have shown that endothelial insulin resistance induced by oxidative stress contributes to vascular dysfunction in metabolic disorders. Quercetin, a natural antioxidant, has been recently shown to exert protective effects on endothelial function. However, the effects of quercetin on endothelial insulin resistance and its underlying mechanism are unclear. Here, we found that chronic oral treatment of obese mice with quercetin increased vascular endothelial insulin sensitivity, accompanied by alleviated mitochondrial fragmentation as revealed by confocal imaging. In addition, western blot analysis showed that quercetin treatment suppressed the levels of dynamin-related protein 1 (Drp1) and phosphorylation at serine 616 in endothelial cells of obese mice. Mechanistically, quercetin specifically suppressed Drp1 phosphorylation at serine 616, whereas it showed little effects on the Drp1 level and its phosphorylation at serine 637 in cultured endothelial cells under oxidative stress. Furthermore, our results also showed that quercetin suppressed Drp1 phosphorylation at serine 616 by inhibiting PKCδ as revealed by western blot analysis. Knockdown of PKCδ with siRNA alleviated the protective effects of quercetin on endothelial-mitochondrial dynamics and insulin sensitivity. These results suggest that chronic oral treatment with quercetin exerts endothelial protective effects through inhibition of PKCδ and the resultant mitochondrial fragmentation.

The Role of Osteoprotegerin and Its Ligands in Vascular Function.

The superfamily of tumor necrosis factor (TNF) receptors includes osteoprotegerin (OPG) and its ligands, which are receptor activators of nuclear factor kappa-B ligand (RANKL) and TNF-related apoptosis-inducing ligand (TRAIL). The OPG/RANKL/RANK system plays an active role in pathological angiogenesis and inflammation as well as cell survival. It has been demonstrated that there is crosstalk between endothelial cells and osteoblasts during osteogenesis, thus establishing a connection between angiogenesis and osteogenesis. This OPG/RANKL/RANK/TRAIL system acts on specific cell surface receptors, which are then able to transmit their signals to other intracellular components and modify gene expression. Cytokine production and activation of their receptors induce mechanisms to recruit monocytes and neutrophils as well as endothelial cells. Data support the role of an increased OPG/RANKL ratio as a possible marker of progression of endothelial dysfunction in metabolic disorders in relationship with inflammatory marker levels. We review the role of the OPG/RANKL/RANK triad in vascular function as well as molecular mechanisms related to the etiology of vascular diseases. The potential therapeutic strategies may be very promising in the future.

Isolation of Murine Adipose-Derived Stromal/Stem Cells for Adipogenic Differentiation or Flow Cytometry-Based Analysis.

Murine models of obesity or reduced adiposity are a valuable resource for understanding the role of adipocyte dysfunction in metabolic disorders. Adipose tissue stromal vascular cells or primary adipocytes derived from murine adipose tissue and grown in culture are essential tools for studying the mechanisms underlying adipocyte development and function. Herein, we describe methods for the isolation, expansion, and long-term storage of murine adipose-derived stromal/stem cells along with protocols for inducing adipogenesis in this cell population or isolating the adipose stromal vascular fraction cells for flow cytometric analysis.

Calpain inhibition decreases inflammatory protein expression in vessel walls in a model of chronic myocardial ischemia

Emerging data suggest a link between calpain activation and the enhanced inflammatory response of the cardiovascular system. We hypothesize that calpain activation associates with altered inflammatory protein expression in correlation with the proinflammatory profile of the myocardium. Our pig hypercholesterolemic model with chronic myocardial ischemia was treated with calpain inhibitors to establish their potential to improve cardiac function. Yorkshire swine, fed a high cholesterol diet for 4weeks then underwent placement of an ameroid constrictor on the left circumflex artery. Two weeks later, animals received either no drug (high-cholesterol control group, n=8), a low dose of calpain inhibitors (0.12mg/kg, n=9), or a high dose of calpain inhibitors (0.25mg/kg; n=8). The high-cholesterol diet and calpain inhibitors were continued for 5weeks, after which the pig was euthanized. The left ventricular myocardial tissue (ischemic and nonischemic) was harvested and analyzed for inflammatory protein expression. Data were statistically analyzed via the Kruskal-Wallis and Dunn post hoc test. Calpain inhibitor treatment coincides with increased expression of IKB-α and decreased expression of macrophages, NFkB, IL-1, and tumor necrosis factor (TNF)-α in the ischemic myocardial tissue as compared with the control group. An NFkB array revealed decreased expression of IRF5, JNK1/2, JNK2, CD18, NFkB p65, c-Rel, Sharpin, TNF R1, TNF R2, and DR5 in the ischemic myocardium of the group treated with a high dose of calpain inhibitors compared with the control. Calpain activation in metabolic syndrome is a potential contributor to cardiac dysfunction in metabolic disorders with ischemic background. We suggest that calpain inhibition downregulates NFkB signaling in the vessel walls, which might be useful for improving myocardial blood flow in ischemic conditions.

Caloric Restriction as a Strategy to Improve Vascular Dysfunction in Metabolic Disorders.

Caloric restriction (CR) has proved to be the most effective and reproducible dietary intervention to increase healthy lifespan and aging. A reduction in cardiovascular disease (CVD) risk in obese subjects can be already achieved by a moderate and sustainable weight loss. Since pharmacological approaches for body weight reduction have, at present, a poor long-term efficacy, CR is of great interest in the prevention and/or reduction of CVD associated with obesity. Other dietary strategies changing specific macronutrients, such as altering carbohydrates, protein content or diet glycemic index have been also shown to decrease the progression of CVD in obese patients. In this review, we will focus on the positive effects and possible mechanisms of action of these strategies on vascular dysfunction.

Alzheimer‐associated Aβ oligomers impact the central nervous system to induce peripheral metabolic deregulation

Alzheimer's disease (AD) is associated with peripheral metabolic disorders. Clinical/epidemiological data indicate increased risk of diabetes in AD patients. Here, we show that intracerebroventricular infusion of AD-associated Aβ oligomers (AβOs) in mice triggered peripheral glucose intolerance, a phenomenon further verified in two transgenic mouse models of AD. Systemically injected AβOs failed to induce glucose intolerance, suggesting AβOs target brain regions involved in peripheral metabolic control. Accordingly, we show that AβOs affected hypothalamic neurons in culture, inducing eukaryotic translation initiation factor 2α phosphorylation (eIF2α-P). AβOs further induced eIF2α-P and activated pro-inflammatory IKKβ/NF-κB signaling in the hypothalamus of mice and macaques. AβOs failed to trigger peripheral glucose intolerance in tumor necrosis factor-α (TNF-α) receptor 1 knockout mice. Pharmacological inhibition of brain inflammation and endoplasmic reticulum stress prevented glucose intolerance in mice, indicating that AβOs act via a central route to affect peripheral glucose homeostasis. While the hypothalamus has been largely ignored in the AD field, our findings indicate that AβOs affect this brain region and reveal novel shared molecular mechanisms between hypothalamic dysfunction in metabolic disorders and AD.

Alzheimer-associated Ab oligomers impact the central nervous system to induce peripheral metabolic deregulation

Alzheimer’s disease (AD) is associated with peripheral metabolic disorders. Clinical/epidemiological data indicate increased risk of diabetes in AD patients. Here, we show that intracerebroventricular infusion of AD-associated Ab oligomers (AbOs) in mice triggered peripheral glucose intolerance, a phenomenon further verified in two transgenic mouse models of AD. Systemically injected AbOs failed to induce glucose intolerance, suggesting AbOs target brain regions involved in peripheral metabolic control. Accordingly, we show that AbOs affected hypothalamic neurons in culture, inducing eukaryotic translation initiation factor 2a phosphorylation (eIF2a-P). AbOs further induced eIF2a-P and activated proinflammatory IKKb/NF-jB signaling in the hypothalamus of mice and macaques. AbOs failed to trigger peripheral glucose intolerance in tumor necrosis factor-a (TNF-a) receptor 1 knockout mice. Pharmacological inhibition of brain inflammation and endoplasmic reticulum stress prevented glucose intolerance in mice, indicating that AbOs act via a central route to affect peripheral glucose homeostasis. While the hypothalamus has been largely ignored in the AD field, our findings indicate that AbOs affect this brain region and reveal novel shared molecular mechanisms between hypothalamic dysfunction in metabolic disorders and AD.

Mitochondria and Metabolic Homeostasis

Mitochondrial function is fundamental to metabolic homeostasis. In addition to converting the nutrient flux into the energy molecule ATP, the mitochondria generate intermediates for biosynthesis and reactive oxygen species (ROS) that serve as a secondary messenger to mediate signal transduction and metabolism. Alterations of mitochondrial function, dynamics, and biogenesis have been observed in various metabolic disorders, including aging, cancer, diabetes, and obesity. However, the mechanisms responsible for mitochondrial changes and the pathways leading to metabolic disorders remain to be defined. In the last few years, tremendous efforts have been devoted to addressing these complex questions and led to a significant progress. In a timely manner, the Forum on Mitochondria and Metabolic Homeostasis intends to document the latest findings in both the original research article and review articles, with the focus on addressing three major complex issues: (1) mitochondria and mitochondrial oxidants in aging-the oxidant theory (including mitochondrial ROS) being revisited by a hyperfunction hypothesis and a novel role of SMRT in mitochondrion-mediated aging process being discussed; (2) impaired mitochondrial capacity (e.g., fatty acid oxidation and oxidative phosphorylation [OXPHOS] for ATP synthesis) and plasticity (e.g., the response to endocrine and metabolic challenges, and to calorie restriction) in diabetes and obesity; (3) mitochondrial energy adaption in cancer progression-a new view being provided for H(+)-ATP synthase in regulating cell cycle and proliferation by mediating mitochondrial OXPHOS, oxidant production, and cell death signaling. It is anticipated that this timely Forum will advance our understanding of mitochondrial dysfunction in metabolic disorders.

Mechanism of superoxide and hydrogen peroxide generation by human electron-transfer flavoprotein and pathological variants

Reactive oxygen species production by mitochondrial enzymes plays a fundamental role both in cellular signaling and in the progression of dysfunctional states. However, sources of reactive oxygen species and the mechanisms by which enzymes produce these reactive species still remain elusive. We characterized the generation of reactive oxygen species by purified human electron-transfer flavoprotein (ETF), a mitochondrial enzyme that has a central role in the metabolism of lipids, amino acids, and choline. The results showed that ETF produces significant amounts of both superoxide and hydrogen peroxide in the presence of its partner enzyme medium-chain acyl-CoA dehydrogenase (MCAD). ETF-mediated production of reactive oxygen species is partially inhibited at high MCAD/ETF ratios, whereas it is enhanced at high ionic strength. Determination of the reduction potentials of ETF showed that thermodynamic properties of the FAD cofactor are changed upon formation of a complex between ETF and MCAD, supporting the notion that protein:protein interactions modulate the reactivity of the protein with dioxygen. Two pathogenic ETF variants were also studied to determine which factors modulate the reactivity toward molecular oxygen and promote reactive oxygen species production. The results obtained show that destabilized conformations and defective protein:protein interactions increase the ability of ETF to generate reactive oxygen species. A possible role for these processes in mitochondrial dysfunction in metabolic disorders of fatty acid β-oxidation is discussed.

Inhibition of Insulin Signaling in Endothelial Cells by Protein Kinase C-induced Phosphorylation of p85 Subunit of Phosphatidylinositol 3-Kinase (PI3K)

The regulation of endothelial function by insulin is consistently abnormal in insulin-resistant states and diabetes. Protein kinase C (PKC) activation has been reported to inhibit insulin signaling selectively in endothelial cells via the insulin receptor substrate/PI3K/Akt pathway to reduce the activation of endothelial nitric-oxide synthase (eNOS). In this study, it was observed that PKC activation differentially inhibited insulin receptor substrate 1/2 (IRS1/2) signaling of insulin's activation of PI3K/eNOS by decreasing only tyrosine phosphorylation of IRS2. In addition, PKC activation, by general activator and specifically by angiotensin II, increased the phosphorylation of p85/PI3K, which decreases its association with IRS1 and activation. Thr-86 of p85/PI3K was identified to be phosphorylated by PKC activation and confirmed to affect IRS1-mediated activation of Akt/eNOS by insulin and VEGF using a deletion mutant of the Thr-86 region of p85/PI3K. Thus, PKC and angiotensin-induced phosphorylation of Thr-86 of p85/PI3K may partially inhibit the activation of PI3K/eNOS by multiple cytokines and contribute to endothelial dysfunction in metabolic disorders.

MiR-486-5p Induces Replicative Senescence of Human Adipose Tissue-Derived Mesenchymal Stem Cells and Its Expression Is Controlled by High Glucose

The reduction of adult stem cell self-renewal can be an important mechanism of aging. MicroRNAs have been reported to be involved in aging processes. Through a microarray approach, we have identified miR-486-5p, the expression of which is progressively expressed in human adipose tissue-derived mesenchymal stem cells (hAT-MSCs) with aging. Overexpression of miR-486-5p induces a premature senescence-like phenotype and inhibits proliferation of hAT-MSCs and inhibits adipogenic and osteogenic differentiation, whereas inhibition of miR-486-5p has the opposite effects. miR-486-5p regulates the expression of silent information regulator 1 (SIRT1), a major regulator of longevity and metabolic disorders. Decrease of SIRT1 deacetylase activity in hAT-MSCs is correlated with their passage number. miR-486-5p inhibits SIRT1 expression through a miR-486-5p binding site within the 3'-untranslated region of SIRT1. Overexpression of miR-486-5p inhibits SIRT1 deacetylase activity in hAT-MSCs, and transfection of miR-486-5p inhibitor shows the opposite effect. Downregulation of SIRT1 in hAT-MSCs induces senescence and inhibits cell proliferation. Exposure to high glucose increases miR-486-5p expression and inhibits SIRT1 expression in hAT-MSCs. Our data pinpoint miR-486-5p as an endogenous inhibitor of SIRT1 that promotes hAT-MSCs senescence and is potentially applicable to therapeutic manipulation of hAT-MSCs dysfunction in metabolic disorders.

MicroRNA 217 Modulates Endothelial Cell Senescence via Silent Information Regulator 1

Aging is a major risk factor for the development of atherosclerosis and coronary artery disease. Through a microarray approach, we have identified a microRNA (miR-217) that is progressively expressed in endothelial cells with aging. miR-217 regulates the expression of silent information regulator 1 (SirT1), a major regulator of longevity and metabolic disorders that is progressively reduced in multiple tissues during aging. miR-217 inhibits SirT1 expression through a miR-217-binding site within the 3'-UTR of SirT1. In young human umbilical vein endothelial cells, human aortic endothelial cells, and human coronary artery endothelial cells, miR-217 induces a premature senescence-like phenotype and leads to an impairment in angiogenesis via inhibition of SirT1 and modulation of FoxO1 (forkhead box O1) and endothelial nitric oxide synthase acetylation. Conversely, inhibition of miR-217 in old endothelial cells ultimately reduces senescence and increases angiogenic activity via an increase in SirT1. miR-217 is expressed in human atherosclerotic lesions and is negatively correlated with SirT1 expression and with FoxO1 acetylation status. Our data pinpoint miR-217 as an endogenous inhibitor of SirT1, which promotes endothelial senescence and is potentially amenable to therapeutic manipulation for prevention of endothelial dysfunction in metabolic disorders.