Adaptive β-cell replication occurs in response to increased metabolic demand during insulin resistance. The intracellular mediators of this compensatory response are poorly defined and their identification could provide significant targets for β-cell regeneration therapies. Here we show that glucose and insulin in vitro and insulin resistance in vivo activate protein kinase C ζ (PKCζ) in pancreatic islets and β-cells. PKCζ is required for glucose- and glucokinase activator-induced proliferation of rodent and human β-cells in vitro. Furthermore, either kinase-dead PKCζ expression (KD-PKCζ) or disruption of PKCζ in mouse β-cells blocks compensatory β-cell replication when acute hyperglycemia/hyperinsulinemia is induced. Importantly, KD-PKCζ inhibits insulin resistance-mediated mammalian target of rapamycin (mTOR) activation and cyclin-D2 upregulation independent of Akt activation. In summary, PKCζ activation is key for early compensatory β-cell replication in insulin resistance by regulating the downstream signals mTOR and cyclin-D2. This suggests that alterations in PKCζ expression or activity might contribute to inadequate β-cell mass expansion and β-cell failure leading to type 2 diabetes.

Discovery of common pathways that mediate both pancreatic β-cell function and end-organ function offers the opportunity to develop therapies that modulate glucose homeostasis and separately slow the development of diabetes complications. Here, we investigated the in vitro and in vivo effects of pharmacological agonism of the prostaglandin I2 (IP) receptor in pancreatic β-cells and in glomerular podocytes. The IP receptor agonist MRE-269 increased intracellular 3',5'-cyclic adenosine monophosphate (cAMP), augmented glucose-stimulated insulin secretion (GSIS), and increased viability in MIN6 β-cells. Its prodrug form, selexipag, augmented GSIS and preserved islet β-cell mass in diabetic mice. Determining that this preservation of β-cell function is mediated through cAMP/protein kinase A (PKA)/nephrin-dependent pathways, we found that PKA inhibition, nephrin knockdown, or targeted mutation of phosphorylated nephrin tyrosine residues 1176 and 1193 abrogated the actions of MRE-269 in MIN6 cells. Because nephrin is important to glomerular permselectivity, we next set out to determine whether IP receptor agonism similarly affects nephrin phosphorylation in podocytes. Expression of the IP receptor in podocytes was confirmed in cultured cells by immunoblotting and quantitative real-time PCR and in mouse kidneys by immunogold electron microscopy, and its agonism 1) increased cAMP, 2) activated PKA, 3) phosphorylated nephrin, and 4) attenuated albumin transcytosis. Finally, treatment of diabetic endothelial nitric oxide synthase knockout mice with selexipag augmented renal nephrin phosphorylation and attenuated albuminuria development independently of glucose change. Collectively, these observations describe a pharmacological strategy that posttranslationally modifies nephrin and the effects of this strategy in the pancreas and in the kidney.

Insulin resistance in mice typically does not manifest as diabetes due to multiple compensatory mechanisms. Here, we present a novel digenic model of type 2 diabetes in mice heterozygous for a null allele of the insulin receptor and an N-ethyl-N-nitrosourea-induced alternative splice mutation in the regulatory protein phosphatase 2A (PP2A) subunit PPP2R2A. Inheritance of either allele independently results in insulin resistance but not overt diabetes. Doubly heterozygous mice exhibit progressive hyperglycemia, hyperinsulinemia, and impaired glucose tolerance from 12 weeks of age without significant increase in body weight. Alternative splicing of Ppp2r2a decreased PPP2R2A protein levels. This reduction in PPP2R2A containing PP2A phosphatase holoenzyme was associated with decreased serine/threonine protein kinase AKT protein levels. Ultimately, reduced insulin-stimulated phosphorylated AKT levels were observed, a result that was confirmed in Hepa1-6, C2C12, and differentiated 3T3-L1 cells knocked down using Ppp2r2a small interfering RNAs. Altered AKT signaling and expression of gluconeogenic genes in the fed state contributed to an insulin resistance and hyperglycemia phenotype. This model demonstrates how genetic changes with individually small phenotypic effects interact to cause diabetes and how differences in expression of hypomorphic alleles of PPP2R2A and potentially other regulatory proteins have deleterious effects and may therefore be relevant in determining diabetes risk.

Adipose tissue (AT) macrophages (ATMs) contribute to obesity-induced inflammation and metabolic dysfunction, but also play critical roles in maintaining tissue homeostasis. ATMs catabolize lipid in a lysosomal-dependent manner required for the maintenance of AT; deficiency in lysosomal acid lipase (Lipa), the enzyme required for lysosome lipid catabolism, leads to AT atrophy and severe hepatic steatosis, phenotypes rescued by macrophage-specific expression of Lipa Autophagy delivers cellular products, including lipid droplets, to lysosomes. Given that obesity increases autophagy in AT and contributes to lipid catabolism in other cells, it was proposed that autophagy delivers lipid to lysosomes in ATMs and is required for AT homeostasis. We found that obesity does increase autophagy in ATMs. However, genetic or pharmacological inhibition of autophagy does not alter the lipid balance of ATMs in vitro or in vivo. In contrast to the deficiency of lysosomal lipid hydrolysis, the ablation of autophagy in macrophages does not lead to AT atrophy or alter metabolic phenotypes in lean or obese animals. Although the lysosomal catabolism of lipid is necessary for normal ATM function and AT homeostasis, delivery of lipid to lysosomes is not autophagy dependent and strongly suggests the existence of another lipid delivery pathway critical to lysosome triglyceride hydrolysis in ATMs.

The risk of type 2 diabetes (T2D) is increased by abnormalities in sleep quantity and quality, circadian alignment, and melatonin regulation. A common genetic variant in a receptor for the circadian-regulated hormone melatonin (MTNR1B) is associated with increased fasting blood glucose and risk of T2D, but whether sleep or circadian disruption mediates this risk is unknown. We aimed to test if MTNR1B diabetes risk variant rs10830963 associates with measures of sleep or circadian physiology in intensive in-laboratory protocols (n = 58-96) or cross-sectional studies with sleep quantity and quality and timing measures from self-report (n = 4,307-10,332), actigraphy (n = 1,513), or polysomnography (n = 3,021). In the in-laboratory studies, we found a significant association with a substantially longer duration of elevated melatonin levels (41 min) and delayed circadian phase of dim-light melatonin offset (1.37 h), partially mediated through delayed offset of melatonin synthesis. Furthermore, increased T2D risk in MTNR1B risk allele carriers was more pronounced in early risers versus late risers as determined by 7 days of actigraphy. Our results provide the surprising insight that the MTNR1B risk allele influences dynamics of melatonin secretion, generating a novel hypothesis that the MTNR1B risk allele may extend the duration of endogenous melatonin production later into the morning and that early waking may magnify the diabetes risk conferred by the risk allele.

The objectives of this study were 1) to describe maternal glucose and lipid kinetics and 2) to examine the relationships with infant birth weight in obese women with pregestational type 2 diabetes during late pregnancy. Using stable isotope tracer methodology and mass spectrometry, maternal glucose and lipid kinetic rates during the basal condition were compared in three groups: lean women without diabetes (Lean, n = 25), obese women without diabetes (OB, n = 26), and obese women with pregestational type 2 diabetes (OB+DM, n = 28; total n = 79). Glucose and lipid kinetics during hyperinsulinemia were also measured in a subset of participants (n = 56). Relationships between maternal glucose and lipid kinetics during both conditions and infant birth weight were examined. Maternal endogenous glucose production (EGP) rate was higher in OB+DM than OB and Lean during hyperinsulinemia. Maternal insulin value at 50% palmitate Ra suppression (IC50) for palmitate suppression with insulinemia was higher in OB+DM than OB and Lean. Maternal EGP per unit insulin and plasma free fatty acid concentration during hyperinsulinemia most strongly predicted infant birth weight. Our findings suggest maternal fatty acid and glucose kinetics are altered during late pregnancy and might suggest a mechanism for higher birth weight in obese women with pregestational diabetes.

Encoding acyl-CoA thioesterase-7 (Acot7) is one of ∼60 genes expressed ubiquitously across tissues but relatively silenced, or disallowed, in pancreatic β-cells. The capacity of ACOT7 to hydrolyze long-chain acyl-CoA esters suggests potential roles in β-oxidation, lipid biosynthesis, signal transduction, or insulin exocytosis. We explored the physiological relevance of β-cell-specific Acot7 silencing by re-expressing ACOT7 in these cells. ACOT7 overexpression in clonal MIN6 and INS1(832/13) β-cells impaired insulin secretion in response to glucose plus fatty acids. Furthermore, in a panel of transgenic mouse lines, we demonstrate that overexpression of mitochondrial ACOT7 selectively in the adult β-cell reduces glucose tolerance dose dependently and impairs glucose-stimulated insulin secretion. By contrast, depolarization-induced secretion was unaffected, arguing against a direct action on the exocytotic machinery. Acyl-CoA levels, ATP/ADP increases, membrane depolarization, and Ca(2+) fluxes were all markedly reduced in transgenic mouse islets, whereas glucose-induced oxygen consumption was unchanged. Although glucose-induced increases in ATP/ADP ratio were similarly lowered after ACOT7 overexpression in INS1(832/13) cells, changes in mitochondrial membrane potential were unaffected, consistent with an action of Acot7 to increase cellular ATP consumption. Because Acot7 mRNA levels are increased in human islets in type 2 diabetes, inhibition of the enzyme might provide a novel therapeutic strategy.

Multiple differentially methylated sites and regions associated with adiposity have now been identified in large-scale cross-sectional studies. We tested for replication of associations between previously identified CpG sites at HIF3A and adiposity in ∼1,000 mother-offspring pairs from the Avon Longitudinal Study of Parents and Children (ALSPAC). Availability of methylation and adiposity measures at multiple time points, as well as genetic data, allowed us to assess the temporal associations between adiposity and methylation and to make inferences regarding causality and directionality. Overall, our results were discordant with those expected if HIF3A methylation has a causal effect on BMI and provided more evidence for causality in the reverse direction (i.e., an effect of BMI on HIF3A methylation). These results are based on robust evidence from longitudinal analyses and were also partially supported by Mendelian randomization analysis, although this latter analysis was underpowered to detect a causal effect of BMI on HIF3A methylation. Our results also highlight an apparent long-lasting intergenerational influence of maternal BMI on offspring methylation at this locus, which may confound associations between own adiposity and HIF3A methylation. Further work is required to replicate and uncover the mechanisms underlying the direct and intergenerational effect of adiposity on DNA methylation.

Pharmacologically induced glycosuria elicits adaptive responses in glucose homeostasis and hormone release. In type 2 diabetes (T2D), along with decrements in plasma glucose and insulin levels and increments in glucagon release, sodium-glucose cotransporter 2 (SGLT2) inhibitors induce stimulation of endogenous glucose production (EGP) and a suppression of tissue glucose disposal (TGD). We measured fasting and postmeal glucose fluxes in 25 subjects without diabetes using a double glucose tracer technique; in these subjects and in 66 previously reported patients with T2D, we also estimated lipolysis (from [(2)H5]glycerol turnover rate and circulating free fatty acids, glycerol, and triglycerides), lipid oxidation (LOx; by indirect calorimetry), and ketogenesis (from circulating β-hydroxybutyrate concentrations). In both groups, empagliflozin administration raised EGP, lowered TGD, and stimulated lipolysis, LOx, and ketogenesis. The pattern of glycosuria-induced changes was similar in subjects without diabetes and in those with T2D but quantitatively smaller in the former. With chronic (4 weeks) versus acute (first dose) drug administration, glucose flux responses were attenuated, whereas lipid responses were enhanced; in patients with T2D, fasting β-hydroxybutyrate levels rose from 246 ± 288 to 561 ± 596 µmol/L (P < 0.01). We conclude that by shunting substantial amounts of carbohydrate into urine, SGLT2-mediated glycosuria results in a progressive shift in fuel utilization toward fatty substrates. The associated hormonal milieu (lower insulin-to-glucagon ratio) favors glucose release and ketogenesis.

Identifying novel biomarkers of type 2 diabetes risk may improve prediction and prevention among individuals at high risk of the disease and elucidate new biological pathways relevant to diabetes development. We performed plasma metabolite profiling in the Diabetes Prevention Program (DPP), a completed trial that randomized high-risk individuals to lifestyle, metformin, or placebo interventions. Previously reported markers, branched-chain and aromatic amino acids and glutamine/glutamate, were associated with incident diabetes (P < 0.05 for all), but these associations were attenuated upon adjustment for clinical and biochemical measures. By contrast, baseline levels of betaine, also known as glycine betaine (hazard ratio 0.84 per SD log metabolite level, P = 0.02), and three other metabolites were associated with incident diabetes even after adjustment. Moreover, betaine was increased by the lifestyle intervention, which was the most effective approach to preventing diabetes, and increases in betaine at 2 years were also associated with lower diabetes incidence (P = 0.01). Our findings indicate betaine is a marker of diabetes risk among high-risk individuals both at baseline and during preventive interventions and they complement animal models demonstrating a direct role for betaine in modulating metabolic health.

Hepatic steatosis is common in obesity and insulin resistance and results from a net retention of lipids in the liver. A key mechanism to prevent steatosis is to increase secretion of triglycerides (TG) packaged as VLDLs. Insulin controls nutrient partitioning via signaling through its cognate receptor in peripheral target organs such as liver, muscle, and adipose tissue and via signaling in the central nervous system (CNS) to orchestrate organ cross talk. While hepatic insulin signaling is known to suppress VLDL production from the liver, it is unknown whether brain insulin signaling independently regulates hepatic VLDL secretion. Here, we show that in conscious, unrestrained male Sprague Dawley rats the infusion of insulin into the third ventricle acutely increased hepatic TG secretion. Chronic infusion of insulin into the CNS via osmotic minipumps reduced the hepatic lipid content as assessed by noninvasive (1)H-MRS and lipid profiling independent of changes in hepatic de novo lipogenesis and food intake. In mice that lack the insulin receptor in the brain, hepatic TG secretion was reduced compared with wild-type littermate controls. These studies identify brain insulin as an important permissive factor in hepatic VLDL secretion that protects against hepatic steatosis.

Rapamycin extends life span in mice, yet paradoxically causes lipid dysregulation and glucose intolerance through mechanisms that remain incompletely understood. Whole-body energy balance can be influenced by beige/brite adipocytes, which are inducible by cold and other stimuli via β-adrenergic signaling in white adipose depots. Induction of beige adipocytes is considered a promising strategy to combat obesity because of their ability to metabolize glucose and lipids, dissipating the resulting energy as heat through uncoupling protein 1. Here, we report that rapamycin blocks the ability of β-adrenergic signaling to induce beige adipocytes and expression of thermogenic genes in white adipose depots. Rapamycin enhanced transcriptional negative feedback on the β3-adrenergic receptor. However, thermogenic gene expression remained impaired even when the receptor was bypassed with a cell-permeable cAMP analog, revealing the existence of a second inhibitory mechanism. Accordingly, rapamycin-treated mice are cold intolerant, failing to maintain body temperature and weight when shifted to 4°C. Adipocyte-specific deletion of the mTORC1 subunit Raptor recapitulated the block in β-adrenergic signaling. Our findings demonstrate a positive role for mTORC1 in the recruitment of beige adipocytes and suggest that inhibition of β-adrenergic signaling by rapamycin may contribute to its physiological effects.

Type 1 diabetes (T1D) results from a T cell-mediated destruction of pancreatic β-cells following the infiltration of leukocytes (including CD8(+), CD4(+), and CD20(+) cells) into and around pancreatic islets (insulitis). Recently, we reported that two distinct patterns of insulitis occur in patients with recent-onset T1D from the U.K. and that these differ principally in the proportion of infiltrating CD20(+) B cells (designated CD20Hi and CD20Lo, respectively). We have now extended this analysis to include patients from the Network for Pancreatic Organ Donors with Diabetes (U.S.) and Diabetes Virus Detection (DiViD) study (Norway) cohorts and confirm that the two profiles of insulitis occur more widely. Moreover, we show that patients can be directly stratified according to their insulitic profile and that those receiving a diagnosis before the age of 7 years always display the CD20Hi profile. By contrast, individuals who received a diagnosis beyond the age of 13 years are uniformly defined as CD20Lo. This implies that the two forms of insulitis are differentially aggressive and that patients with a CD20Hi profile lose their β-cells at a more rapid rate. In support of this, we also find that the proportion of residual insulin-containing islets (ICIs) increases in parallel with age at the onset of T1D. Importantly, those receiving a diagnosis in, or beyond, their teenage years retain ∼40% ICIs at diagnosis, implying that a functional deficit rather than an absolute β-cell loss may be causal for disease onset in these patients. We conclude that appropriate patient stratification will be critical for correct interpretation of the outcomes of intervention therapies targeted to islet-infiltrating immune cells in T1D.

Identifying markers of human insulin resistance may permit development of new approaches for treatment and prevention of type 2 diabetes. To this end, we analyzed the fasting plasma metabolome in metabolically characterized human volunteers across a spectrum of insulin resistance. We demonstrate that plasma betaine levels are reduced in insulin-resistant humans and correlate closely with insulin sensitivity. Moreover, betaine administration to mice with diet-induced obesity prevents the development of impaired glucose homeostasis, reduces hepatic lipid accumulation, increases white adipose oxidative capacity, and enhances whole-body energy expenditure. In parallel with these beneficial metabolic effects, betaine supplementation robustly increased hepatic and circulating fibroblast growth factor (Fgf)21 levels. Betaine administration failed to improve glucose homeostasis and liver fat content in Fgf21(-/-) mice, demonstrating that Fgf21 is necessary for betaine's beneficial effects. Together, these data indicate that dietary betaine increases Fgf21 levels to improve metabolic health in mice and suggest that betaine supplementation merits further investigation as a supplement for treatment or prevention of type 2 diabetes in humans.

Epidemiologic studies suggest that hepatocellular carcinoma (HCC) has a strong relationship with diabetes. However, the underlying molecular mechanisms still remain unclear. Here, we demonstrated that high glucose (HG), one of the main characteristics of diabetes, was capable of accelerating tumorigenesis in HCC cells. Advanced glycosylation end product-specific receptor (AGER) was identified as a stimulator during this process. Mechanistically, AGER activated a hexosamine biosynthetic pathway, leading to enhanced O-GlcNAcylation of target proteins. Notably, AGER was capable of increasing activity and stability of proto-oncoprotein c-Jun via O-GlcNAcylation of this protein at Ser73. Interestingly, c-Jun can conversely enhance AGER transcription. Thereby, a positive autoregulatory feedback loop that stimulates diabetic HCC was established. Finally, we found that AG490, an inhibitor of Janus kinase, has the ability to impair AGER expression and its functions in HCC cells. In conclusion, AGER and its functions to stimulate O-GlcNAcylation are important during liver tumorigenesis, when high blood glucose levels are inadequately controlled.

The lymphatic system is crucial for efficient immune surveillance and for the maintenance of a physiological pressure in the interstitial space. Even so, almost no information is available concerning the lymph drainage of the islets of Langerhans in the human pancreas. Immunohistochemical staining allowed us to distinguish lymphatic capillaries from blood capillaries. Almost no lymphatic capillaries were found within the islets in pancreatic biopsy specimens from subjects without diabetes or from subjects with type 1 or type 2 diabetes. Lymphatic capillaries were, however, found at the islet-exocrine interface, frequently located along blood capillaries and other fibrotic structures within or close to the islet capsule. Lymphatic capillaries were regularly found in the exocrine pancreas, with small lymphatic vessels located close to and around acini. Larger collecting lymphatic vessels were located in fibrotic septa between the exocrine lobules and adjacent to the ductal system of the pancreas. In summary, we report a pronounced deficiency of lymphatic capillaries in human islets, a finding with implications for immune surveillance and the regulation of interstitial fluid transport in the endocrine pancreas as well as for the pathophysiology of both type 1 and type 2 diabetes.

A common genetic variation in TCF7L2 is associated with type 2 diabetes. However, the mechanism by which this occurs remains elusive. In addition to affecting insulin secretion, genetic variation at the TCF7L2 locus may alter insulin action or directly modify hepatic glucose metabolism. We sought to determine whether the diabetes-associated variant in this locus (the T allele of rs7903146) increases fasting endogenous glucose production (EGP), and impairs insulin-induced suppression of EGP and insulin-stimulated glucose disappearance. To address this, we studied individuals who were either homozygous for the diabetes-associated allele (TT) at rs7903146 or were homozygous for the protective allele (CC). Subjects were matched for other anthropometric characteristics and were studied using a euglycemic clamp. EGP and glucose uptake were measured using the tracer dilution technique, and the relative contribution of gluconeogenesis to EGP was quantitated using deuterated water corrected for transaldolase exchange. We report that the diabetes-associated variation in TCF7L2 did not associate with fasting EGP, insulin-induced suppression of EGP, and insulin-induced stimulation of glucose uptake. There was no association with the contribution of gluconeogenesis and glycogenolysis to EGP. These data indicate that genetic variation at TCF7L2 does not predispose an individual to type 2 diabetes by altering either hepatic or extrahepatic insulin action.

Current evidence on exercise-mediated AMPK regulation in skeletal muscle of patients with type 2 diabetes (T2D) is inconclusive. This may relate to inadequate segregation of trimeric complexes in the investigation of AMPK activity. We examined the regulation of AMPK and downstream targets ACC-β, TBC1D1, and TBC1D4 in muscle biopsy specimens obtained from 13 overweight/obese patients with T2D and 14 weight-matched male control subjects before, immediately after, and 3 h after exercise. Exercise increased AMPK α2β2γ3 activity and phosphorylation of ACCβ Ser(221), TBC1D1 Ser(237)/Thr(596), and TBC1D4 Ser(704) Conversely, exercise decreased AMPK α1β2γ1 activity and TBC1D4 Ser(318)/Thr(642) phosphorylation. Interestingly, compared with preexercise, 3 h into exercise recovery, AMPK α2β2γ1 and α1β2γ1 activity were increased concomitant with increased TBC1D4 Ser(318)/Ser(341)/Ser(704) phosphorylation. No differences in these responses were observed between patients with T2D and control subjects. Subjects were also studied by euglycemic-hyperinsulinemic clamps performed at rest and 3 h after exercise. We found no evidence for insulin to regulate AMPK activity. Thus, AMPK signaling is not compromised in muscle of patients with T2D during exercise and insulin stimulation. Our results reveal a hitherto unrecognized activation of specific AMPK complexes in exercise recovery. We hypothesize that the differential regulation of AMPK complexes plays an important role for muscle metabolism and adaptations to exercise.

Proinsulin folding within the endoplasmic reticulum (ER) remains incompletely understood, but it is clear that in mutant INS gene-induced diabetes of youth (MIDY), progression of the (three) native disulfide bonds of proinsulin becomes derailed, causing insulin deficiency, β-cell ER stress, and onset of diabetes. Herein, we have undertaken a molecular dissection of proinsulin disulfide bond formation, using bioengineered proinsulins that can form only two (or even only one) of the native proinsulin disulfide bonds. In the absence of preexisting proinsulin disulfide pairing, Cys(B19)-Cys(A20) (a major determinant of ER stress response activation and proinsulin stability) preferentially initiates B-A chain disulfide bond formation, whereas Cys(B7)-Cys(A7) can initiate only under oxidizing conditions beyond that existing within the ER of β-cells. Interestingly, formation of these two "interchain" disulfide bonds demonstrates cooperativity, and together, they are sufficient to confer intracellular transport competence to proinsulin. The three most common proinsulin disulfide mispairings in the ER appear to involve Cys(A11)-Cys(A20), Cys(A7)-Cys(A20), and Cys(B19)-Cys(A11), each disrupting the critical Cys(B19)-Cys(A20) pairing. MIDY mutations inhibit Cys(B19)-Cys(A20) formation, but treatment to force oxidation of this disulfide bond improves folding and results in a small but detectable increase of proinsulin export. These data suggest possible therapeutic avenues to ameliorate ER stress and diabetes.

Endothelial dysfunction plays a crucial role in the development of diabetic vasculopathy. Our initial quantitative PCR results showed an increased miR-200c expression in arteries from diabetic mice and patients with diabetes. However, whether miR-200c is involved in diabetic endothelial dysfunction is unknown. Overexpression of miR-200c impaired endothelium-dependent relaxations (EDRs) in nondiabetic mouse aortas, whereas suppression of miR-200c by anti-miR-200c enhanced EDRs in diabetic db/db mice. miR-200c suppressed ZEB1 expression, and ZEB1 overexpression ameliorated endothelial dysfunction induced by miR-200c or associated with diabetes. More importantly, overexpression of anti-miR-200c or ZEB1 in vivo attenuated miR-200c expression and improved EDRs in db/db mice. Mechanistic study with the use of COX-2(-/-) mice revealed that COX-2 mediated miR-200c-induced endothelial dysfunction and that miR-200c upregulated COX-2 expression in endothelial cells through suppression of ZEB1 and increased production of prostaglandin E2, which also reduced EDR. This study demonstrates for the first time to our knowledge that miR-200c is a new mediator of diabetic endothelial dysfunction and inhibition of miR-200c rescues EDRs in diabetic mice. These new findings suggest the potential usefulness of miR-200c as the target for drug intervention against diabetic vascular complications.