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The Integrated Physiology of the Exocrine and Endocrine Compartments in Pancreatic Diseases workshop was a 1.5-day scientific conference at the National Institutes of Health (Bethesda, MD) that engaged clinical and basic science investigators interested in diseases of the pancreas. This report provides a summary of the proceedings from the workshop. The goals of the workshop were to forge connections and identify gaps in knowledge that could guide future research directions. Presentations were segregated into six major theme areas, including 1) pancreas anatomy and physiology, 2) diabetes in the setting of exocrine disease, 3) metabolic influences on the exocrine pancreas, 4) genetic drivers of pancreatic diseases, 5) tools for integrated pancreatic analysis, and 6) implications of exocrine–endocrine cross talk. For each theme, multiple presentations were followed by panel discussions on specific topics relevant to each area of research; these are summarized here. Significantly, the discussions resulted in the identification of research gaps and opportunities for the field to address. In general, it was concluded that as a pancreas research community, we must more thoughtfully integrate our current knowledge of normal physiology as well as the disease mechanisms that underlie endocrine and exocrine disorders so that there is a better understanding of the interplay between these compartments. [ABSTRACT FROM AUTHOR]

Indoleamine 2,3 dioxygenase-1 (IDO1) is a powerful immunoregulatory enzyme that is deficient in patients with type 1 diabetes (T1D). In this study, we present the first systematic evaluation of IDO1 expression and localization in human pancreatic tissue. Although IDO1 was constitutively expressed in β-cells from donors without diabetes, less IDO1 was expressed in insulin-containing islets from double autoantibody-positive donors and patients with recent-onset T1D, although it was virtually absent in insulin-deficient islets from donors with T1D. Scatter plot analysis suggested that IDO1 decay occurred in individuals with multiple autoantibodies, prior to β-cell demise. IDO1 impairment might therefore contribute to β-cell demise and could potentially emerge as a promising therapeutic target. [ABSTRACT FROM AUTHOR]

Microvascular and metabolic physiology are tightly linked. This Perspective reviews evidence that 1) the relationship between hyperglycemia and microvascular dysfunction (MVD) is bidirectional and constitutes a vicious cycle; 2) MVD in diabetes affects many, if not all, organs, which may play a role in diabetes-associated comorbidities such as depression and cognitive impairment; and 3) MVD precedes, and contributes to, hyperglycemia in type 2 diabetes (T2D) through impairment of insulin-mediated glucose disposal and, possibly, insulin secretion. Obesity and adverse early-life exposures are important drivers of MVD. MVD can be improved through weight loss (in obesity) and through exercise. Pharmacological interventions to improve MVD are an active area of investigation. [ABSTRACT FROM AUTHOR]

We investigated ethnicity-specific exonic variants of type 2 diabetes (T2D) and its related clinical phenotypes in an East Asian population. We performed whole-exome sequencing in 917 T2D case and control subjects, and the findings were validated by exome array genotyping in 3,026 participants. In silico replication was conducted for seven nonsynonymous variants in an additional 13,122 participants. Single-variant and gene-based association tests for T2D were analyzed. A total of 728,838 variants were identified by whole-exome sequencing. Among nonsynonymous variants, PAX4 Arg192His increased risk of T2D and GLP1R Arg131Gln decreased risk of T2D in genome-wide significance (odds ratio [OR] 1.48, P = 4.47 × 10-16 and OR 0.84, P = 3.55 × 10-8, respectively). Another variant at PAX4 192 codon Arg192Ser was nominally associated with T2D (OR 1.62, P = 5.18 × 10-4). In T2D patients, PAX4 Arg192His was associated with earlier age at diagnosis, and GLP1R Arg131Gln was associated with decreased risk of cardiovascular disease. In control subjects without diabetes, the PAX4 Arg192His was associated with higher fasting glucose and GLP1R Arg131Gln was associated with lower fasting glucose and HbA1c level. Gene-based analysis revealed that SLC30A8 was most significantly associated with decreased risk of T2D (P = 1.0 × 10-4). In summary, we have identified nonsynonymous variants associated with risk of T2D and related phenotypes in Koreans. [ABSTRACT FROM AUTHOR]

Gluconeogenesis is drastically increased in patients with type 2 diabetes and accounts for increased fasting plasma glucose concentrations. Circulating levels of prostaglandin (PG) F2α are also markedly elevated in diabetes; however, whether and how PGF2α regulates hepatic glucose metabolism remain unknown. Here, we demonstrated that PGF2α receptor (F-prostanoid receptor [FP]) was upregulated in the livers of mice upon fasting- and diabetic stress. Hepatic deletion of the FP receptor suppressed fasting-induced hepatic gluconeogenesis, whereas FP overexpression enhanced hepatic gluconeogenesis in mice. FP activation promoted the expression of gluconeogenic enzymes (PEPCK and glucose-6-phosphatase) in hepatocytes in a FOXO1-dependent manner. Additionally, FP coupled with Gq in hepatocytes to elicit Ca2+ release, which activated Ca2+/calmodulin-activated protein kinase IIγ (CaMKIIγ) to increase FOXO1 phosphorylation and subsequently accelerate its nuclear translocation. Blockage of p38 disrupted CaMKIIγ-induced FOXO1 nuclear translocation and abrogated FP-mediated hepatic gluconeogenesis in mice. Moreover, knockdown of hepatic FP receptor improved insulin sensitivity and glucose homeostasis in ob/ob mice. FP-mediated hepatic gluconeogenesis via the CaMKIIγ/p38/FOXO1 signaling pathway, indicating that the FP receptor might be a promising therapeutic target for type 2 diabetes. [ABSTRACT FROM AUTHOR]

There is wide variation in the age at diagnosis of diabetes in individuals with maturity-onset diabetes of the young (MODY) due to a mutation in the HNF1A gene. We hypothesized that common variants at the HNF1A locus (rs1169288 [I27L], rs1800574 [A98V]), which are associated with type 2 diabetes susceptibility, may modify age at diabetes diagnosis in individuals with HNF1A-MODY. Meta-analysis of two independent cohorts, comprising 781 individuals with HNF1A-MODY, found no significant associations between genotype and age at diagnosis. However after stratifying according to type of mutation (protein-truncating variant [PTV] or missense), we found each 27L allele to be associated with a 1.6-year decrease (95% CI -2.6, -0.7) in age at diagnosis, specifically in the subset (n = 444) of individuals with a PTV. The effect size was similar and significant across the two independent cohorts of individuals with HNF1A-MODY. We report a robust genetic modifier of HNF1A-MODY age at diagnosis that further illustrates the strong effect of genetic variation within HNF1A upon diabetes phenotype. [ABSTRACT FROM AUTHOR]

Previous studies by us and others have indicated that renal epidermal growth factor receptors (EGFR) are activated in models of diabetic nephropathy (DN) and that inhibition of EGFR activity protects against progressive DN in type 1 diabetes. In this study we examined whether inhibition of EGFR activation would affect the development of DN in a mouse model of accelerated type 2 diabetes (BKS db/db with endothelial nitric oxide knockout [eNOS-/-db/db]). eNOS-/-db/db mice received vehicle or erlotinib, an inhibitor of EGFR tyrosine kinase activity, beginning at 8 weeks of age and were sacrificed at 20 weeks of age. In addition, genetic models inhibiting EGFR activity (waved 2) and transforming growth factor-α (waved 1) were studied in this model of DN in type 2 diabetes. Compared with vehicle-treated mice, erlotinib-treated animals had less albuminuria and glomerulosclerosis, less podocyte loss, and smaller amounts of renal profibrotic and fibrotic components. Erlotinib treatment decreased renal oxidative stress, macrophage and T-lymphocyte infiltration, and the production of proinflammatory cytokines. Erlotinib treatment also preserved pancreas function, and these mice had higher blood insulin levels at 20 weeks, decreased basal blood glucose levels, increased glucose tolerance and insulin sensitivity, and increased blood levels of adiponectin compared with vehicle-treated mice. Similar to the aforementioned results, both waved 1 and waved 2 diabetic mice also had attenuated DN, preserved pancreas function, and decreased basal blood glucose levels. In this mouse model of accelerated DN, inhibition of EGFR signaling led to increased longevity. [ABSTRACT FROM AUTHOR]

We investigated how human proislet peptide (HIP) regulates differentiation of human fetus-derived pancreatic progenitor cells (HFPPCs) and explored the potential link between HIP signaling and the menin pathway, which is key to regulating pancreatic islet differentiation. The data show that HIP promoted expression of proislet transcription factors (TFs), including PDX-1, MAFA, and NKX6.1, as well as other maturation markers of b-cells, such as insulin, GLUT2, KIR6.2, SUR1, and VDCC. Moreover, HIP increased insulin content and promoted the ability of HFPPCs to normalize blood glucose in diabetic mice. HIP inhibited the TF FOXO1 by increasing AKT-mediated phosphorylation. HIP-induced repression of FOXO1 suppressed menin expression, leading to reducing menin binding to the promoter of the three key proislet TFs, decreasing recruitment of H3K9 methyltransferase SUV39H1, and thus reducing repressive H3K9me3 at the promoter. These coordinated actions lead to increased expression of the proislet TFs, resulting in induction of HFPPC differentiation. Consistently, constitutive activation of FOXO1 blocks HIP-induced transcription of these TFs. Together, these studies unravel the crucial role of theHIP/AKT/FOXO/menin axis in epigenetically controlling expression of proislet TFs, regulating the differentiation of HFPPCs, and normalizing blood glucose in diabetic mice. [ABSTRACT FROM AUTHOR]

Very recently one of the largest type 1 diabetes prevention trials using daily administration of oral insulin or placebo was completed. After 9 years of study enrollment and follow-up, the randomized controlled trial failed to delay the onset of clinical type 1 diabetes, which was the primary end point. The unfortunate outcome follows the previous large-scale trial, the Diabetes Prevention Trial-Type 1 (DPT-1), which again failed to delay diabetes onset with oral insulin or low-dose subcutaneous insulin injections in a randomized controlled trial with relatives at risk for type 1 diabetes. These sobering results raise the important question, "Where does the type 1 diabetes prevention field move next?" In this Perspective, we advocate for a paradigm shift in which smaller mechanistic trials are conducted to define immune mechanisms and potentially identify treatment responders. The stage is set for these interventions in individuals at risk for type 1 diabetes as Type 1 Diabetes TrialNet has identified thousands of relatives with islet autoantibodies and general population screening for type 1 diabetes risk is under way. Mechanistic trials will allow for better trial design and patient selection based upon molecular markers prior to large randomized controlled trials, moving toward a personalized medicine approach for the prevention of type 1 diabetes. [ABSTRACT FROM AUTHOR]

The Edwin Bierman Award Lecture is presented in honor of the memory of Edwin L. Bierman, MD, an exemplary scientist, mentor, and leader in the field of diabetes, obesity, hyperlipidemia, and atherosclerosis. The award and lecture recognizes a leading scientist in the field of macrovascular complications and contributing risk factors in diabetes. Clay F. Semenkovich, MD, the Irene E. and Michael M. Karl Professor and Chief of the Division of Endocrinology, Metabolism and Lipid Research at Washington University School of Medicine in St. Louis, St. Louis, MO, received the prestigious award at the American Diabetes Association's 76th Scientific Sessions, 10-14 June 2016, in New Orleans, LA. He presented the Edwin Bierman Award Lecture, "We Know More Than We Can Tell About Diabetes and Vascular Disease," on Sunday, 12 June 2016.Diabetes is a disorder of abnormal lipid metabolism, a notion strongly supported by the work of Edwin Bierman, for whom this eponymous lecture is named. This abnormal lipid environment continues to be associated with devastating vascular complications in diabetes despite current therapies, suggesting that our understanding of the pathophysiology of blood vessel disease in diabetes is limited. In this review, potential new insights into the nature of diabetic vasculopathy will be discussed. Recent observations suggest that while the concept of distinct macrovascular and microvascular complications of diabetes has been useful, vascular diseases in diabetes may be more interrelated than previously appreciated. Moreover, the intermediary metabolic pathway of de novo lipogenesis, which synthesizes lipids from simple precursors, is robustly sensitive to insulin and may contribute to these complications. De novo lipogenesis requires fatty acid synthase, and recent studies of this enzyme suggest that endogenously produced lipids are channeled to specific intracellular sites to affect physiology. These findings raise the possibility that novel approaches to treating diabetes and its complications could be based on altering the intracellular lipid milieu. [ABSTRACT FROM AUTHOR]

The article presents insights on the role of the brain in glucose homeostasis and diabetes. Topics discussed include the evidence of the brain's capacity to influence biologically defended level of circulating glucose through rapid and highly coordinated adjustments of both insulin sensitivity and insulin secretion, the possible influence of brain dysfunction on the pathogenesis of type 2 diabetes, and the implications of the concepts for the future of diabetes treatment.

A mechanistic cause for Mauriac syndrome, a syndrome of growth failure and delayed puberty associated with massive liver enlargement from glycogen deposition in children with poorly controlled type 1 diabetes, is unknown. We discovered a mutation in the catalytic subunit of liver glycogen phosphorylase kinase in a patient with Mauriac syndrome whose liver extended into his pelvis. Glycogen phosphorylase kinase activates glycogen phosphorylase, the enzyme that catalyzes the first step in glycogen breakdown. We show that the mutant subunit acts in a dominant manner to completely inhibit glycogen phosphorylase kinase enzyme activity and that this interferes with glycogenolysis causing increased levels of glycogen in human liver cells. It is known that even normal blood glucose levels physiologically inhibit glycogen phosphorylase to diminish glucose release from the liver when glycogenolysis is not needed. The patient's mother possessed the same mutant glycogen phosphorylase kinase subunit, but did not have diabetes or hepatomegaly. His father had childhood type 1 diabetes in poor glycemic control, but lacked the mutation and had neither hepatomegaly nor growth failure. This case proves that the effect of a mutant enzyme of glycogen metabolism can combine with hyperglycemia to directly hyperinhibit glycogen phosphorylase, in turn blocking glycogenolysis causing the massive liver in Mauriac disease. [ABSTRACT FROM AUTHOR]

Transcription factor expression fluctuates during β-cell ontogeny, and disruptions in this pattern can affect the development or function of those cells. Here we uncovered that murine endocrine pancreatic progenitors express high levels of the homeodomain transcription factor Prox1, whereas both immature and mature β-cells scarcely express this protein. We also investigated if sustained Prox1 expression is incompatible with β-cell development or maintenance using transgenic mouse approaches. We discovered that Prox1 upregulation in mature β-cells has no functional consequences; in contrast, Prox1 overexpression in immature β-cells promotes acute fasting hyperglycemia. Using a combination of immunostaining and quantitative and comparative gene expression analyses, we determined that Prox1 upregulation reduces proliferation, impairs maturation, and enables apoptosis in postnatal β-cells. Also, we uncovered substantial deficiency in β-cells that overexpress Prox1 of the key regulator of β-cell maturation MafA, several MafA downstream targets required for glucose-stimulated insulin secretion, and genes encoding important components of FGF signaling. Moreover, knocking down PROX1 in human EndoC-βH1 β-cells caused increased expression of many of these same gene products. These and other results in our study indicate that reducing the expression of Prox1 is beneficial for the expansion and maturation of postnatal β-cells. [ABSTRACT FROM AUTHOR]

The aim of this study was to determine the effects of single and repeated episodes of clamped hypoglycemia on fibrinolytic balance, pro-inflammatory biomarkers, pro-atherothrombotic mechanisms and endothelial function. Twenty healthy individuals (12M/8F) were studied during separate 2 day randomized protocols. Day 1 consisted of either two 2hr hyperinsulinemic (812±50 pmol/L) euglycemic (5±0.1 mmol/L) or hypoglycemic (2.9±0.1 mmol/L) clamps. Day 2 consisted of a single 2 hr hypoglycemic clamp. Two D Doppler ultrasound was used to determine brachial arterial endothelial function. PAI-1, VCAM-1, ICAM-1, E-selectin, P-selectin, TAT (thrombin/anti-thrombin complex), TNF-α and IL-6 responses were increased (p<0.05) during single or repeated hypoglycemia as compared to euglycemia. Endogenous and exogenous NO mediated vasodilation were both impaired by repeated hypoglycemia. Neuroendocrine and autonomic nervous system (ANS) responses were also blunted by repeated hypoglycemia (p<0.05). In summary, acute moderate hypoglycemia impairs fibrinolytic balance, increases pro-inflammatory responses, platelet activation and coagulation biomarkers and reduces NO mediated endothelial function in healthy individuals. Repeated episodes of hypoglycemia further impair vascular function by additionally reducing exogenously NO mediated endothelial function and increasing coagulation biomarkers. We conclude that despite reduced neuroendocrine and ANS responses, antecedent hypoglycemia results in greater endothelial dysfunction and an increased pro-atherothrombotic state as compared to a single acute episode of hypoglycemia. [ABSTRACT FROM AUTHOR]

Diabetic foot ulcer (DFU) caused by impaired wound healing is a common vascular complication of diabetes. The current study revealed that plasma levels of pigment epithelium--derived factor (PEDF) were elevated in type 2 diabetic patients with DFU and in db/db mice. To test whether elevated PEDF levels contribute to skin wound-healing delay in diabetes, endogenous PEDF was neutralized with an anti-PEDF antibody in db/db mice. Our results showed that neutralization of PEDF accelerated wound healing, increased angiogenesis in the wound skin, and improved the functions and numbers of endothelial progenitor cells (EPCs) in the diabetic mice. Further, PEDF-deficient mice showed higher baseline blood flow in the skin, higher density of cutaneous microvessels, increased skin thickness, improved numbers and functions of circulating EPCs, and accelerated wound healing compared with wild-type mice. Overexpression of PEDF suppressed the Wnt signaling pathway in the wound skin. Lithium chloride--induced Wnt signaling activation downstream of the PEDF interaction site attenuated the inhibitory effect of PEDF on EPCs and rescued the wound-healing deficiency in diabetic mice. Taken together, these results suggest that elevated circulating PEDF levels contribute to impaired wound healing in the process of angiogenesis and vasculogenesis through the inhibition of Wnt/β-catenin signaling. [ABSTRACT FROM AUTHOR]

Type 1 diabetes (T1D) is characterized by the destruction of the insulin-producing β-cells of pancreatic islets. Genetic and environmental factors both contribute to T1D development. Viral infection with enteroviruses is a suspected trigger for T1D, but a causal role remains unproven and controversial. Studies in animals are problematic because of species-specific differences in host cell susceptibility and immune responses to candidate viral pathogens such as coxsackievirus B (CVB). In order to resolve the controversial role of viruses in human T1D, we developed a viral infection model in immunodeficient mice bearing human islet grafts. Hyperglycemia was induced in mice by specific ablation of native β-cells. Human islets, which are naturally susceptible to CVB infection, were transplanted to restore normoglycemia. Transplanted mice were infected with CVB4 and monitored for hyperglycemia. Forty-seven percent of CVB4-infected mice developed hyperglycemia. Human islet grafts from infected mice contained viral RNA, expressed viral protein, and had reduced insulin levels compared with grafts from uninfected mice. Human-specific gene expression profiles in grafts from infected mice revealed the induction of multiple interferon-stimulated genes. Thus, human islets can become severely dysfunctional with diminished insulin production after CVB infection of β-cells, resulting in diabetes. [ABSTRACT FROM AUTHOR]

Endogenous pancreatic multipotent progenitors (PMPs) are ideal candidates for regenerative approaches to compensate for β-cell loss since their β-cell--producing capacities as well as strategic location would eliminate unnecessary invasive manipulations. However, little is known about the status and potentials of PMPs under diabetic conditions. Here we show that β-cell metabolic stress and hyperglycemia enhance the proliferation capacities of adult PMP cells and bias their production of progeny toward β-cells in mouse and human. These effects are dynamic and correlate with functional β-cell regeneration when conditions allow. [ABSTRACT FROM AUTHOR]

Hypoplastic coronary artery disease is a congenital coronary artery malformation associated with a high risk of sudden cardiac death. However, the etiology and pathogenesis of hypoplastic coronary artery disease remain undefined. Pregestational diabetes increases reactive oxygen species (ROS) levels and the risk of congenital heart defects. We show that pregestational diabetes in mice induced by streptozotocin significantly increased 4-hydroxynonenal production and decreased coronary artery volume in fetal hearts. Pregestational diabetes also impaired epicardial epithelialto- mesenchymal transition (EMT) as shown by analyses of the epicardium, epicardial-derived cells, and fate mapping. Additionally, the expression of hypoxia-inducible factor 1a (Hif-1a), Snail1, Slug, basic fibroblast growth factor (bFgf), and retinaldehyde dehydrogenase (Aldh1a2) was decreased and E-cadherin expression was increased in the hearts of fetuses of diabetic mothers. Of note, these abnormalities were all rescued by treatment with N-acetylcysteine (NAC) in diabetic females during gestation. Ex vivo analysis showed that high glucose levels inhibited epicardial EMT, which was reversed by NAC treatment. We conclude that pregestational diabetes in mice can cause coronary artery malformation through ROS signaling. This study may provide a rationale for further clinical studies to investigate whether pregestational diabetes could cause hypoplastic coronary artery disease in humans. [ABSTRACT FROM AUTHOR]

The dipeptidyl peptidase-4 inhibitor sitagliptin, an antidiabetic agent, which lowers blood glucose levels, also reduces postprandial lipid excursion after a mixed meal. The underlying mechanism of this effect, however, is not clear. This study examined the production and clearance of triglyceride-rich lipoprotein particles from the liver and intestine in healthy volunteers in response to a single oral dose of sitagliptin. Using stable isotope tracer techniques and with control of pancreatic hormone levels, the kinetics of lipoprotein particles of intestinal and hepatic origin were measured. Compared with placebo, sitagliptin decreased intestinal lipoprotein concentration by inhibiting particle production, independent of changes in pancreatic hormones, and circulating levels of glucose and free fatty acids. Fractional clearance of particles of both intestinal and hepatic origin, and production of particles of hepatic origin, were not affected. This pleiotropic effect of sitagliptin may explain the reduction in postprandial lipemia seen in clinical trials of this agent and may provide metabolic benefits beyond lowering of glucose levels. [ABSTRACT FROM AUTHOR]

Wolfram syndrome is an autosomal recessive disorder caused by mutations in WFS1 and is characterized by insulin-dependent diabetes mellitus, optic atrophy, and deafness. To investigate the cause of β-cell failure, we used induced pluripotent stem cells to create insulin-producing cells from individuals with Wolfram syndrome. WFS1-deficient β-cells showed increased levels of endoplasmic reticulum (ER) stress molecules and decreased insulin content. Upon exposure to experimental ER stress, Wolfram β-cells showed impaired insulin processing and failed to increase insulin secretion in response to glucose and other secretagogues. Importantly, 4-phenyl butyric acid, a chemical protein folding and trafficking chaperone, restored normal insulin synthesis and the ability to upregulate insulin secretion. These studies show that ER stress plays a central role in β-cell failure in Wolfram syndrome and indicate that chemical chaperones might have therapeutic relevance under conditions of ER stress in Wolfram syndrome and other forms of diabetes. [ABSTRACT FROM AUTHOR]

Telomere length (TL) has been implicated in the pathogenesis of age-related disorders. However, there are no prospective studies directly investigating the role of TL and relevant genes in diabetes development. In the multiethnic Women's Health Initiative, we identified 1,675 incident diabetes case participants in 6 years of follow-up and 2,382 control participants matched by age, ethnicity, clinical center, time of blood draw, and follow-up duration. Leukocyte TL at baseline was measured using quantitative PCR, and Mendelian randomization analysis was conducted to test whether TL is causally associated with diabetes risk. After adjustment for matching and known diabetes risk factors, odds ratios per 1-kilobase increment were 1.00 (95% CI 0.90-1.11) in whites, 0.95 (0.85-1.06) in blacks, 0.96 (0.79-1.17) in Hispanics, and 0.88 (0.70-1.10) in Asians. Of the 80 single nucleotide polymorphisms (SNPs) in nine genes involved in telomere regulation, 14 SNPs were predictive of TL, but none were significantly associated with diabetes risk. Using ethnicity-specific SNPs as randomization instruments, we observed no statistically significant association between TL and diabetes risk (P = 0.52). Although leukocyte TL was weakly associated with diabetes risk, this association was not independent of known risk factors. These prospective findings indicate limited clinical utility of TL in diabetes risk stratification among postmenopausal women. [ABSTRACT FROM AUTHOR]

Environmental factors such as diets rich in saturated fats contribute to dysfunction and death of pancreatic β-cells in diabetes. Endoplasmic reticulum (ER) stress is elicited in β-cells by saturated fatty acids. Here we show that palmitate-induced β-cell apoptosis is mediated by the intrinsic mitochondrial pathway. By microarray analysis, we identified a palmitate-triggered ER stress gene expression signature and the induction of the BH3-only proteins death protein 5 (DP5) and p53-upregulated modulator of apoptosis (PUMA). Knockdown of either protein reduced cytochrome c release, caspase- 3 activation, and apoptosis in rat and human β-cells. DP5 induction depends on inositol-requiring enzyme 1 (IRE1)--dependent c-Jun NH2-terminal kinase and PKR--like ER kinase (PERK)-- induced activating transcription factor (ATF3) binding to its promoter. PUMA expression is also PERK/ATF3-dependent, through tribbles 3 (TRB3)--regulated AKT inhibition and FoxO3a activation. DP5-/- mice are protected from high fat diet--induced loss of glucose tolerance and have twofold greater pancreatic β-cell mass. This study elucidates the crosstalk between lipotoxic ER stress and the mitochondrial pathway of apoptosis that causes β-cell death in diabetes. [ABSTRACT FROM AUTHOR]

Evaluation of the existence of a diurnal pattern of glucose tolerance after mixed meals is important to inform a closed-loop system of treatment for insulin requiring diabetes. We studied 20 healthy volunteers with normal fasting glucose (4.8 ± 0.1 mmol/L) and HbA1c (5.2 ± 0.0%) to determine such a pattern in nondiabetic individuals. Identical mixed meals were ingested during breakfast, lunch, or dinner at 0700, 1300, and 1900 h in randomized Latin square order on 3 consecutive days. Physical activity was the same on all days. Postprandial glucose turnover was measured using the triple tracer technique. Postprandial glucose excursion was significantly lower (P < 0.01) at breakfast than lunch and dinner. β-Cell responsivity to glucose and disposition index was higher (P < 0.01) at breakfast than lunch and dinner. Hepatic insulin extraction was lower (P < 0.01) at breakfast than dinner. Although meal glucose appearance did not differ between meals, suppression of endogenous glucose production tended to be lower (P < 0.01) and insulin sensitivity tended to be higher (P < 0.01) at breakfast than at lunch or dinner. Our results suggest a diurnal pattern to glucose tolerance in healthy humans, and if present in type 1 diabetes, it will need to be incorporated into artificial pancreas systems. [ABSTRACT FROM AUTHOR]

The article presents abstracts on acute and chronic complications of hypoglycemia including prediction of severe inpatient hypoglycemia using blood glucose trends, hypoglycemia alert dogs for Type 1 diabetes, and the extent of exercise reducing sympathoadrenal and symptomatic response to subsequent hypoglycemia in humans.

Inflammation plays an important role in diabetes-induced retinal vascular leakage. The purpose of this study is to examine the role of endoplasmic reticulum (ER) stress and the signaling pathway of ER stress--induced activating transcription factor 4 (ATF4) in the regulation of Müller cell--derived inflammatory mediators in diabetic retinopathy. In diabetic animals, elevated ER stress markers, ATF4, and vascular endothelial growth factor (VEGF) expression were partially localized to Müller cells in the retina. In cultured Müller cells, high glucose induced a time-dependent increase of ER stress, ATF4 expression, and inflammatory factor production. Inducing ER stress or overexpressing ATF4 resulted in elevated intracellular adhesion molecule 1 and VEGF proteins in Müller cells. In contrast, alleviation of ER stress or blockade of ATF4 activity attenuated inflammatory gene expression induced by high glucose or hypoxia. Furthermore, we found that ATF4 regulated the c-Jun NH2-terminal kinase pathway resulting in VEGF upregulation. ATF4 was also required for ER stress--induced and hypoxia-inducible factor-1a activation. Finally, we showed that administration of chemical chaperone 4-phenylbutyrate or genetic inhibition of ATF4 successfully attenuated retinal VEGF expression and reduced vascular leakage in mice with STZ-induced diabetes. Taken together, our data indicate that ER stress and ATF4 play a critical role in retinal inflammatory signaling and Müller cell--derived inflammatory cytokine production in diabetes. [ABSTRACT FROM AUTHOR]

Insulin resistance (IR), the hallmark of type 2 diabetes, may be under epigenetic control. This study examines the association between global DNA methylation and IR using 84 monozygotic twin pairs. IR was estimated using homeostasis model assessment (HOMA). Global DNA methylation of Alu repeats in peripheral blood leukocytes was quantified by bisulfite pyrosequencing. The association between global DNA methylation and IR was examined using generalized estimating equation (GEE) and within--twin pair analyses, adjusting for potential confounders. Results show that methylation levels at all four CpG sites were individually associated with IR by GEE (all false discovery rate--adjusted P values #0.026). A 10% increase in mean Alu methylation was associated with an increase of 4.55 units (95% CI 2.38-6.73) in HOMA. Intrapair difference in IR was significantly associated with intrapair difference in global methylation level. A 10% increase in the difference in mean Alu methylation was associated with an increase of 4.54 units (0.34-8.71; P = 0.036) in the difference in HOMA. Confirmation of the results by intrapair analyses suggests that genetic factors do not confound the association between global DNA methylation and IR. Exclusion of twins taking diabetes medication (n = 17) did not change our results. [ABSTRACT FROM AUTHOR]

Knowledge regarding the genetic risk loci for gestational diabetes mellitus (GDM) is still limited. In this study, we performed a two-stage genome-wide association analysis in Korean women. In the stage 1 genome scan, 468 women with GDM and 1,242 nondiabetic control women were compared using 2.19 million genotyped or imputed markers. We selected 11 loci for further genotyping in stage 2 samples of 931 case and 783 control subjects. The joint effect of stage 1 plus stage 2 studies was analyzed by meta-analysis. We also investigated the effect of known type 2 diabetes variants in GDM. Two loci known to be associated with type 2 diabetes had a genome-wide significant association with GDM in the joint analysis. rs7754840, a variant in CDKAL1, had the strongest association with GDM (odds ratio 1.518; P = 6.65 x 10-16). A variant near MTNR1B, rs10830962, was also significantly associated with the risk of GDM (1.454; P = 2.49 x 10-13). We found that there is an excess of association between known type 2 diabetes variants and GDM above what is expected under the null hypothesis. In conclusion, we have confirmed that genetic variants in CDKAL1 and near MTNR1B are strongly associated with GDM in Korean women. There seems to be a shared genetic basis between GDM and type 2 diabetes. [ABSTRACT FROM AUTHOR]

More than one-half of the ~50 human chemokines have been associated with or implicated in the pathogenesis of type 1 diabetes, yet their actual expression patterns in the islet environment of type 1 diabetic patients remain, at present, poorly defined. Here, we have integrated a human islet culture system, murine models of virus-induced and spontaneous type 1 diabetes, and the histopathological examination of pancreata from diabetic organ donors with the goal of providing a foundation for the informed selection of potential therapeutic targets within the chemokine/ receptor family. Chemokine (C-C motif) ligand (CCL) 5 (CCL5), CCL8, CCL22, chemokine (C-X-C motif) ligand (CXCL) 9 (CXCL9), CXCL10, and chemokine (C-X3-C motif) ligand (CX3CL) 1 (CX3CL1) were the major chemokines transcribed (in an inducible nitric oxide synthase--dependent but not nuclear factor-κB--dependent fashion) and translated by human islet cells in response to in vitro inflammatory stimuli. CXCL10 was identified as the dominant chemokine expressed in vivo in the islet environment of prediabetic animals and type 1 diabetic patients, whereas CCL5, CCL8, CXCL9, and CX3CL1 proteins were present at lower levels in the islets of both species. Of importance, additional expression of the same chemokines in human acinar tissues emphasizes an underappreciated involvement of the exocrine pancreas in the natural course of type 1 diabetes that will require consideration for additional type 1 diabetes pathogenesis and immune intervention studies. [ABSTRACT FROM AUTHOR]

Interest in how the gut microbiome can influence the metabolic state of the host has recently heightened. One postulated link is bacterial fermentation of "indigestible" prebiotics to short-chain fatty acids (SCFAs), which in turn modulate the release of gut hormones controlling insulin release and appetite. We show here that SCFAs trigger secretion of the incretin hormone glucagon-like peptide (GLP)-1 from mixed colonic cultures in vitro. Quantitative PCR revealed enriched expression of the SCFA receptors ffar2 (grp43) and ffar3 (gpr41) in GLP-1--secreting L cells, and consistent with the reported coupling of GPR43 to Gq signaling pathways, SCFAs raised cytosolic Ca2+ in L cells in primary culture. Mice lacking ffar2 or ffar3 exhibited reduced SCFA-triggered GLP-1 secretion in vitro and in vivo and a parallel impairment of glucose tolerance. These results highlight SCFAs and their receptors as potential targets for the treatment of diabetes. [ABSTRACT FROM AUTHOR]

OBJECTIVE—Congenital hyperinsulinemic hypoglycemia is a group of genetic disorders of insulin secretion most commonly associated with inactivating mutations of the β-cell ATP-sensitive K+ channel (KATP channel) genes ABCC8 (SUR1) and KCNJ11 (Kir6.2). Recessive mutations of these genes cause hyperinsulinism that is unresponsive to treatment with diazoxide, a channel agonist. Dominant KATP mutations have been associated with diazoxide-responsive disease. We hypothesized that some medically uncontrollable cases with only one KATP mutation might have dominant, diazoxide-unresponsive disease. RESEARCH DESIGN AND METHODS—Mutations of the KATP genes were identified by sequencing genomic DNA. Effects of mutations on KATP channel function in vitro were studied by expression in COSm6 cells. RESULTS—In 15 families with diazoxide-unresponsive diffuse hyperinsulism, we found 17 patients with a monoallelic missense mutation of SUR1. Nine probands had de novo mutations, two had an affected sibling or parent, and four had an asymptomatic carrier parent. Of the 13 different mutations, 12 were novel. Expression of mutations revealed normal trafficking of channels but severely impaired responses to diazoxide or MgADP. Responses were significantly lower compared with nine SUR1 mutations associated with dominant, diazoxide-responsive hyperinsulinism. CONCLUSIONS—These results demonstrate that some dominant mutations of SUR1 can cause diazoxide-unresponsive hyperinsulinism. In vitro expression studies may be helpful in distinguishing such mutations from dominant mutations of SUR1 associated with diazoxide-responsive disease. [ABSTRACT FROM AUTHOR]

OBJECTIVE--Diabetes is an independent risk factor for stroke. However, the underlying mechanism of how diabetes confers that this risk is not fully understood. We hypothesize that secretion of neurotrophic factors by the cerebral endothelium, such as brain-derived neurotrophic factor (BDNF), is suppressed in diabetes. Consequently, such accrued neuroprotective deficits make neurons more vulnerable to in jury. RESEARCH DESIGN AND METHODS--We examined BDNF protein levels in a streptozotocin-induced rat model of diabetes by Western blotting and immunohistochemistry. Levels of total and secreted BDNF protein were quantified in human brain microvascular endothelial cells after exposure to advanced glycation end product (AGE)-BSA by enzyme-linked immunosorbent assay and immunocytochemistry. In media transfer experiments, the neuroprotective efficacy of conditioned media from normal healthy endothelial cells was compared with AGE-treated endothelial cells in an in vitro hypoxic injury model. RESULTS--Cerebrovascular BDNF protein was reduced in the cortical endothelium in 6-month diabetic rats. Immunohistochemical analysis of 6-week diabetic brain sections showed that the reduction of BDNF occurs early after induction of diabetes. Treatment of brain microvascular endothelial cells with AGE caused a similar reduction in BDNF protein and secretion in an extracellular signal-related kinase-dependent manner. In media transfer experiments, conditioned media from AGE-treated endothelial cells were less neuroprotective against hypoxic injury because of a decrease in secreted BDNF. CONCLUSIONS--Taken together, our findings suggest that a progressive depletion of microvascular neuroprotection in diabetes elevates the risk of neuronal injury for a variety of central nervous system diseases, including stroke and neurodegeneration. [ABSTRACT FROM AUTHOR]

OBJECTIYE--Metreleptin has been efficacious in improving metabolic control in patients with lipodystrophy, but its efficacy has not been tested in obese patients with type 2 diabetes. RESEARCH DESIGN AND METHODS--We studied the role of leptin in regulating the endocrine adaptation to long-term caloric deprivation and weight loss in obese diabetic subjects over 16 weeks in the context of a double-blinded, placebo-controlled, randomized trial. We then performed detailed interventional and mechanistic signaling studies in humans in vivo, ex vivo, and in vitro. RESULTS--In obese patients with diabetes, metreleptin administration for 16 weeks did not alter body weight or circulating inflammatory markers but reduced HbA1c. marginally (8.01 ± 0.93-7.96 1.12, P = 0.03). Total leptin, leptin-binding protein, and antileptin antibody levels increased, limiting free leptin availability and resulting in circulating free leptin levels of ~50 ng/mL. Consistent with clinical observations, all metreleptin signaling pathways studied in human adipose tissue and peripheral blood mononuclear cells were saturable at ~50 ng/mL, with no major differences in timing or magnitude of leptin-activated STAT3 phosphorylation in tissues from male versus female or obese versus lean humans in vivo, ex vivo, or in vitro. We also observed for the first time that endoplasmic reticulum (ER) stress in human primary adipocytes inhibits leptin signaling. CONCLUSIONS--In obese patients with diabetes, metreleptin administration did not alter body weight or circulating inflammatory markers but reduced HbA1c marginally. ER stress and the saturable nature of leptin signaling pathways play a key role in the development of leptin tolerance in obese patients with diabetes. [ABSTRACT FROM AUTHOR]

To determine whether insulin reverses gestational diabetes mellitus (GDM)-reduced expression and activity of human equilibrative nucleoside transporters 1 (hENT1) in human umbilical vein endothelium cells (HUVECs). RESEARCH DESIGN AND METHODS--Primary cultured HUVECs from full-term normal (n = 44) and diet-treated GDM (n = 44) pregnancies were used. Insulin effect was assayed on hENT1 expression (protein, mRNA, SLC29A1 promoter activity) and activity (initial rates of adenosine transport) as well as endothelial nitric oxide (NO) synthase activity (serine1177 phosphorylation, L-citrulline formation). Adenosine concentration in culture medium and umbilical vein blood (high-performance liquid chromatography) as well as insulin receptor A and B expression (quantitative PCR) were determined. Reactivity of umbilical vein rings to adenosine and insulin was assayed by wire myography. Experiments were in the absence or presence of L-NG-nitro-L-arginine methyl ester (L-NAME; NO synthase inhibitor) or ZM-241385 (an A2A-adenosine receptor antagonist). RESULTS--Umbilical vein blood adenosine concentration was higher, and the adenosine- and insulin-induced NO/endothelium-dependent umbilical rein relaxation was lower in GDM. Cells from GDM exhibited increased insulin receptor A isoform expression in addition to the reported NO-dependent inhibition of hENT1-adenosine transport and SLC29A1 reporter repression, and increased extracellular concentration of adenosine and NO synthase activity. Insulin reversed ail these parameters to values in normal pregnancies, an effect blocked by ZM-241385 and L-NAME. CONCLUSIONS--GDM and normal pregnancy HUVEC phenotypes are differentially responsive to insulin, a phenomenon where insulin acts as protecting factor for endothelial dysfunction characteristic of this syndrome. Abnormal adenosine plasma levels, and potentially A2A-adenosine receptors and insulin receptor A, will play crucial roles in this phenomenon in GDM. [ABSTRACT FROM AUTHOR]

OBJECTIVE--Nominally resistant mouse strains such as C57BL/6 (B6) harbor latent type 1 diabetes susceptibility genes uncovered in outcross to disease-susceptible NOD mice. However, identification of possible recessively acting B6-derived susceptibility genes is limited because very few F2 progeny derived from outcrossing this strain with NOD develop spontaneous autoimmune diabetes. Thus, we assessed whether a transgenic T-cell receptor (TCR) disease transfer model allowed the mapping of recessively acting B6 genetic loci that in the proper context contribute to diabetes. RESEARCH DESIGN AND METIIODS--CD8 T-cells transgenically expressing the diabetogenic AI4 TCR were transferred into 91 (NODxB6.H2g7)F1xB6.H2g7 first-backcross (BC1) females. A genome-wide scan was performed for loci affecting clinical diabetes and insulitis severity. RESULTS--A major locus on chromosome 11 in tight linkage with the marker D11Mit48 (logarithm of odds score = 13.2) strongly determined whether BC1 progeny were susceptible to AI4 T-cell-mediated diabetes. Mice homozygous versus heterozygous for B6 markers of this chromosome 11 genetic locus were, respectively, highly susceptible or resistant to AI4-induced insulitis and diabetes. The genetic effect is manifest by host CD4 T-cells. Microarray analyses of mRNA transcript expression identified a limited number of candidate genes. CONCLUSIONS--The distal region of chromosome 11 in B6 mice harbors a previously unrecognized recessively acting gene (s) that can promote autoreactive diabetogenic CD8 T-cell responses. Future identification of this gene(s) may further aid the screening of heterogeneous humans at future risk for diabetes, and might also provide a target for possible disease interventions. [ABSTRACT FROM AUTHOR]

OBJECTIVE--The objective of this study was to test if the proportion of new-onset diabetic subjects with the HLA-DR3/ 4-DQB1*0302 genotype is decreasing over time. RESEARCH DESIGN AND METHODS--We analyzed HLA class II genotype frequencies over time in two large populations with type 1 diabetes diagnosed at ≤18 years of age. There were 4,075 subjects from the Type 1 Diabetes Genetics Consortium (T1DGC) and 1,675 subjects from the Barbara Davis Center (BDC). RESULTS--Both T1DGC and BDC cohorts showed a decrease of the highest-risk HLA-DR3/4-DQB1*0302 genotype over time. This decrease was greatest over time in T1DGC subjects with age of onset ≤5 years (P = 0.004) and onset between ages 6 and 10 years (P = 0.002). The overall percent of HLA-DR3/4-DQB1*0302 was greater in the T1DGC population compared with the BDC population. There was an increased percent over time of other HLA genotypes without HLA-DR3 or -DR4 in TIDGC new onsets (P = 0.003), and the trend was similar in BDC subjects (P = 0.08). Analyzing time trend, there appears to be a large stepwise decrease in percent DR3/4 in the 1980s in T1DGC subjects with onset age <5 years (P = 0.0001). CONCLUSIONS--The change in frequency of multiple different genotypes and a possible stepwise decrease in percent DR3/4 suggest a change in genetic risk factors and environmental determinants of type 1 diabetes. Larger studies are needed to confirm the changing pattern of genetic risk because a stepwise change may have direct bearing on defining critical environmental determinants of type 1 diabetes. [ABSTRACT FROM AUTHOR]

OBJECTIVE--Interactions between genetic and environmental factors lead to immune dysregulation causing type 1 diabetes and other autoimmune disorders. Recently, many common genetic variants have been associated with type 1 diabetes risk, but each has modest individual effects. Familial clustering of type 1 diabetes has not been explained fully and could arise from many factors, including undetected genetic variation and gene interactions. RESEARCH DESIGN AND METHODS--To address this issue, the Type 1 Diabetes Genetics Consortium recruited 3,892 families, including 4,422 affected sib-pairs. After genotyping 6,090 markers, linkage analyses of these families were performed, using a novel method and taking into account factors such as genotype at known susceptibility loci. RESULTS--Evidence for linkage was robust at the HLA and INS loci, with logarithm of odds (LOD) scores of 398.6 and 5.5, respectively. There was suggestive support for five other loci. Stratification by other risk factors (including HLA and age at diagnosis) identified one convincing region on chromosome 6q14 showing linkage in male subjects (corrected LOD = 4.49; replication P = 0.0002), a locus on chromosome 19q in HLA identical siblings (replication P = 0.006), and four other suggestive loci. CONCLUSIONS--This is the largest linkage study reported for any disease. Our data indicate there are no major type 1 diabetes subtypes definable by linkage analyses; susceptibility is caused by actions of HLA and an apparently random selection from a large number of modest-effect loci; and apart from HLA and INS, there is no important susceptibility factor discoverable by linkage methods. [ABSTRACT FROM AUTHOR]

The article describes the primary defects in hypoglycemia counterregulation present in individuals with type 1 diabetes. It also provides an overview of the current state of research into the mechanisms underlying the detection of hypoglycemia, with focus on research into animal models which are a valuable tool for dissecting the molecular mechanisms involved in glucose sensing. The article also offers a clinical review of hypoglycemia to provide a discussion on the clinical trials in human subjects.

OBJECTIVE--Although intensive glycemic control achieved with insulin therapy increases the incidence of both moderate and severe hypoglycemia, clinical reports of cognitive impairment due to severe hypoglycemia have been highly variable. It was hypothesized that recurrent moderate hypoglycemia preconditions the brain and protects against damage caused by severe hypoglycemia. RESEARCH DESIGN AND METHODS--Nine-week-old male Sprague-Dawley rats were subjected to either 3 consecutive days of recurrent moderate (25-40 mg/dl) hypoglycemia (RH) or saline injections. On the fourth day, rats were subjected to a hyperinsulinemic (0.2 units ⋅ kg-1 ⋅ min-1) severe hypoglycemic (∼11 mg/dl) clamp for 60 or 90 min. Neuronal damage was subsequently assessed by hematoxylin-eosin and Fluoro-Jade B staining. The functional significance of severe hypoglycemia-induced brain damage was evaluated by motor and cognitive testing. RESULTS--Severe hypoglycemia induced brain damage and striking deficits in spatial learning and memory. Rats subjected to recurrent moderate hypoglycemia had 62-74% less brain cell death and were protected from most of these cognitive disturbances. CONCLUSIONS--Antecedent recurrent moderate hypoglycemia preconditioned the brain and markedly limited both the extent of severe hypoglycemia-induced neuronal damage and associated cognitive impairment. In conclusion, changes brought about by recurrent moderate hypoglycemia can be viewed, paradoxically, as providing a beneficial adaptive response in that there is mitigation against severe hypoglycemia-induced brain damage and cognitive dysfunction. Diabetes 59:1055-1062, 2010 [ABSTRACT FROM AUTHOR]

OBJECTIVE--The potassium voltage-gated channel, KQT-like subfamily, member 1 (KCNQ1) has been found through a genome-wide association study to be a strong candidate for conferring susceptibility to type 2 diabetes in East Asian and European populations. Our objective was to describe the association between polymorphisms at the KCNQ1 locus with insulin resistance, β-cell function, and other type 2 diabetes-related traits in a sample of Chinese, Malays, and Asian Indians living in Singapore. RESEARCH DESIGN AND METHODS--We examined the associations between four previously reported KCNQ1 single-nucleotide polymorphisms (SNPs) with type 2 diabetes-related traits in 3,734 participants from the population-based 1998 Singapore National Health Survey cohort (2,520 Chinese, 693 Malay, and 521 Asian Indians). Insulin resistance was calculated from fasting insulin and glucose using the homeostasis model assessment method, whereas pancreatic β-cell function was assessed using the corrected insulin response at 120 min (CIR[sub 120]). RESULTS--SNPs rs2237897, rs2237892, and rs2283228 were significantly associated with type 2 diabetes (odds ratio [OR] 1.48, P = 3 X 10-4; OR 1.38, P = 0.002; OR 1.31, P = 0.012, respectively). Within the Chinese population, the risk alleles for rs2237897, rs2237892, and rs2283228 were significantly associated with higher fasting glucose levels (P = 0.014, 0.011, and 0.034, respectively) and reduced CIR[sub 120] (P = 0.007, 0.013, and 0.014, respectively). A similar trend was observed among the Malay and Asian Indian minority groups, although this did not reach statistical significance because of limited sample sizes. CONCLUSIONS--The increased risk for type 2 diabetes associated with KCNQ1 is likely to be caused by a reduction in insulin secretion. Further studies will be useful to replicate these findings and to fully delineate the role of KCNQ1 and its related pathways in disease pathogenesis. Diabetes 58:1445-1449, 2009 [ABSTRACT FROM AUTHOR]

OBJECTIVE--Obesity is associated with endocrine abnormalities that predict the progression of insulin resistance to type 2 diabetes. Because skeletal muscle has been shown to secrete proteins that could be used as biomarkers, we characterized the secreted protein profile of muscle cells derived from extremely obese (BMI 48.8 ± 14.8 kg/ms²; homeostasis model assessment [HOMA] 3.6 ± 1.0) relative to lean healthy subjects (BMI 25.7 ± 3.2 kg/ms²; HOMA 0.8 ± 0.2). RESEARCH DESIGN AND METHODS--We hypothesized that skeletal muscle would secrete proteins that predict the severity of obesity. To test this hypothesis, we used a "bottom-up" experimental design using stable isotope labeling by amino acids in culture (SILAC) and liquid chromatography/mass spectometry/ mass spectometry (LC-MS/MS) to both identify and quantify proteins secreted from cultured myotubes derived from extremely obese compared with healthy nonobese women. RESULTS--Using SILAC, we discovered a 2.9-fold increase in the secretion of myostatin from extremely obese human myotubes. The increased secretion and biological activity of myostatin were validated by immunoblot (3.16 ± 0.18, P < 0.01) and a myoblast proliferation assay using conditioned growth medium. Myostatin was subsequently shown to increase in skeletal muscle (23%, P < 0.05) and plasma (35%, P < 0.05) and to correlate (re = 0.6, P < 0.05) with the severity of insulin resistance. CONCLUSIONS--Myostatin is a potent antianabolic regulator of muscle mass that may also play a role in energy metabolism. These findings show that increased expression of myostatin in skeletal muscle with obesity and insulin resistance results in elevated circulating myostatin. This may contribute to systemic metabolic deterioration of skeletal muscle with the progression of insulin resistance to type 2 diabetes. Diabetes 58:30-38, 2009 [ABSTRACT FROM AUTHOR]

The article presents abstracts of medical studies including "Effect of Screening for Type 2 Diabetes on Population Mortality: A Randomised Trial," by Justin B. Echouffo, "Long-Term Impact of Lifestyle Interventions to Prevent Diabetes: 20-Year Follow-Up of Da Qing Diabetes Prevention Study," by Peter H. Bennett et al, and "Antidiabetic Therapies and Cancer Mortality in Type 2 Diabetes: Assessing Time-Varying Exposure," by Samantha L. Bowker et al.

OBJECTIVE--The ATP-binding cassette transporter A1 (ABCA1) R230C variant is associated with low HDL cholesterol levels, obesity, and the metabolic syndrome in Mexican-Mestizos. Because a pivotal role for ABCA1 in pancreatic β-cell function was recently observed in the mouse model, we assessed the association of this variant with type 2 diabetes in this population. RESEARCH DESIGN AND METHODS--The initial group included 446 unrelated Mexican individuals: 244 with type 2 diabetes aged 20-69 years (121 with onset ≤45 years), and 202 nondiabetic control subjects aged >50 years. An independent study group included 242 type 2 diabetic case subjects and 225 control subjects with similar characteristics. RESULTS--R230C/C230C genotypes were significantly more frequent in type 2 diabetic individuals (24.6%) than in control subjects (11.4%) in the initial study group (OR 2.501; P = 0.001). After stratifying by age at diagnosis, the association was significant only in the early-onset group (age at diagnosis ≤45 years) (OR 3.776, P = 3.3 x 10[sup -6]). Both associations remained significant after adjusting for admixture (P = 0.0008 and P = 8.1 x 10[sup -6], respectively). Similar trends were observed in the independent study group, and the combined analysis of both populations showed a highly significant association of the R230C variant with type 2 diabetes, particularly with that of early onset (P = 7.6 x 10[sup -6] and 9.4 x 10[sup -8], respectively). CONCLUSIONS--The R230C ABCA1 variant is associated with type 2 diabetes, particularly of early onset, in the Mexican-Mestizo population. Diabetes 57:509-513, 2008 [ABSTRACT FROM AUTHOR]

OBJECTIVE--The clinical expression of maturity-onset diabetes of the young (MODY)-3 is highly variable. This may be due to environmental and/or genetic factors, including molecular characteristics of the hepatocyte nuclear factor 1-α (HNF1A) gene mutation. RESEARCH DESIGN AND METHODS--We analyzed the mutations identified in 356 unrelated MODY3 patients, including 118 novel mutations, and searched for correlations between the genotype and age at diagnosis of diabetes. RESULTS--Missense mutations prevailed in the dimerization and DNA-binding domains (74%), while truncating mutations were predominant in the transactivation domain (62%). The majority (83%) of the mutations were located in exons 1- 6, thus affecting the three HNF1A isoforms. Age at diagnosis of diabetes was lower in patients with truncating mutations than in those with missense mutations (18 vs. 22 years, P = 0.005). Missense mutations affecting the dimerization/DNA-binding domains were associated with a lower age at diagnosis than those affecting the transactivation domain (20 vs. 30 years, P = 10-4). Patients with missense mutations affecting the three isoforms were younger at diagnosis than those with missense mutations involving one or two isoforms (P = 0.03). CONCLUSIONS--These data show that part of the variability of the clinical expression in MODY3 patients may be explained by the type and the location of HNF1A mutations. These findings should be considered in studies for the search of additional modifier genetic factors. Diabetes 57:503-508, 2008 [ABSTRACT FROM AUTHOR]

OBJECTIVE--Type 1 diabetes is an autoimmune disease characterized by a local inflammatory reaction in and around islets followed by selective destruction of insulin-secreting β-cells. We tested the hypothesis that chemokines affect different mechanisms responsible for the development of diabetes in NOD mice. RESEARCH DESIGN AND METHODS--We examined chemokine expression in islets of NOD mice and tested their functional relevance to development of diabetes using transgenic mice expressing the mouse herpesvirus 68-encoded chemokine decoy receptor M3 (NOD-M3 mice) in insulin-secreting β-cells. RESULTS--Multiple chemokines were expressed in pancreatic islets of NOD mice before development of diabetes. Islet-specific expression of the pan-chemokine inhibitor M3 dramatically reduced leukocyte infiltration and islet destruction and completely blocked development of diabetes in NOD-M3 mice. M3 blocked diabetes by inhibiting the priming of diabetogenic cells in the pancreatic lymph nodes and their recruitment into the islets. This effect was specific to the pancreatic islets because M3 expression did not affect other ongoing autoimmune processes. CONCLUSIONS--These results demonstrate that chemokines mediate afferent and efferent immunity in type 1 diabetes and suggest that broad chemokine blockade may represent a viable strategy to prevent insulitis and islet destruction. Diabetes 57: 387-394, 2008 [ABSTRACT FROM AUTHOR]

OBJECTIVE--To examine in vivo in a rodent model the potential role of AMP-activated protein kinase (AMPK) within the ventromedial hypothalamus (VMH) in glucose sensing during hypoglycemia. RESEARCH DESIGN AND METHODS--Using gene silencing technology to selectively downregulate AMPK in the VMH, a key hypothalamic glucose-sensing region, we demonstrate a key role for AMPK in the detection of hypoglycemia. In vivo hyperinsulinemic-hypoglycemic (50 mg dl[sup -1]) clamp studies were performed in awake, chronically catheterized Sprague-Dawley rats that had been microinjected bilaterally to the VMH with an adeno-associated viral (AAV) vector expressing a short hairpin RNA for AMPKα. RESULTS--In comparison with control studies, VMH AMPK downregulation resulted in suppressed glucagon (∼60%) and epinephrine (∼40%) responses to acute hypoglycemia. Rats with VMH AMPK downregulation also required more exogenous glucose to maintain the hypoglycemia plateau and showed significant reductions in endogenous glucose production and whole-body glucose uptake. CONCLUSIONS--We conclude that AMPK in the VMH plays a key role in the detection of acute hypoglycemia and initiation of the glucose counterregulatory response. Diabetes 57:444-450, 2008 [ABSTRACT FROM AUTHOR]

OBJECTIVE--Apoptotic destruction of insulin-producing pancreatic β-cells is involved in the etiology of both type 1 and type 2 diabetes. AMP-activated protein kinase (AMPK) is a sensor of cellular energy charge whose sustained activation has recently been implicated in pancreatic β-cell apoptosis and in islet cell death posttransplantation. Here, we examine the importance of β-cell AMPK in cytokine-induced apoptosis and in the cytotoxic action of CD8[sup +] T-cells. RESEARCH DESIGN AND METHODS--Clonal MIN6 β-cells or CD1 mouse pancreatic islets were infected with recombinant adenoviruses encoding enhanced green fluorescent protein (eGFP/null), constitutively active AMPK (AMPK-CA), or dominant-negative AMPK (AMPK-DN) and exposed or not to tumor necrosis factor-α, interleukin-lβ, and interferon-γ. Apoptosis was detected by monitoring the cleavage of caspase-3 and DNA fragmentation. The cytotoxic effect of CD8[sup +] purified T-cells was examined against pancreatic islets from NOD mice infected with either null or the AMPK-DN-expressing adenoviruses. RESULTS--Exposure to cytokines, or expression of AMPK-CA, induced apoptosis in clonal MIN6 β-cells and CD1 mouse pancreatic islets. By contrast, overexpression of AMPK-DN protected against the proapoptotic effect of these agents, in part by preventing decreases in cellular ATP, and lowered the cytotoxic effect of CD8[sup +] T-cells toward NOD mouse islets. CONCLUSIONS--Inhibition of AMPK activity enhances islet survival in the face of assault by either cytokines or T-cells. AMPK may therefore represent an interesting therapeutic target to suppress immune-mediated β-cell destruction and may increase the efficacy of islet allografts in type 1 diabetes. Diabetes 57:415-423, 2008 [ABSTRACT FROM AUTHOR]

OBJECTIVE--Vaspin was identified as an adipokine with insulin-sensitizing effects, which is predominantly secreted from visceral adipose tissue in a rat model of type 2 diabetes. We have recently shown that vaspin mRNA expression in adipose tissue is related to parameters of obesity and glucose metabolism. However, the regulation of vaspin serum concentrations in human obesity and type 2 diabetes is unknown. RESEARCH DESIGN AND METHODS--For the measurement of vaspin serum concentrations, we developed an enzyme-linked immunosorbent assay (ELISA). Using this ELISA, we assessed circulating vaspin in a cross-sectional study of 187 subjects with a wide range of obesity, body fat distribution, insulin sensitivity, and glucose tolerance and in 60 individuals with normal glucose tolerance (NGT), impaired glucose tolerance (IGT), or type 2 diabetes before and after a 4-week physical training program. RESULTS--Vaspin serum concentrations were significantly higher in female compared with male subjects. There was no difference in circulating vaspin between individuals with NGT and type 2 diabetes. In the normal glucose-tolerant group, circulating vaspin significantly correlated with BMI and insulin sensitivity. Moreover, physical training for 4 weeks resulted in significantly increased circulating vaspin levels. CONCLUSIONS--We found a sexual dimorphism in circulating vaspin. Elevated vaspin serum concentrations are associated with obesity and impaired insulin sensitivity, whereas type 2 diabetes seems to abrogate the correlation between increased circulating vaspin, higher body weight, and decreased insulin sensitivity. Low circulating vaspin correlates with a high fitness level, whereas physical training in untrained individuals causes increased vaspin serum concentrations. Diabetes 57:372-377, 2008 [ABSTRACT FROM AUTHOR]

Long before reaching diagnostic cutoff levels for type 2 diabetes, fasting glucose can be a powerful risk marker for this disease. We conducted a genome-wide search for fasting glucose as a quantitative trait in 412 young European sib-pairs including obese children, with adjustment for sex, age, and BMI. We identified more quantitative trait loci specific to fasting glucose and more significant than would be found by simple chance estimated by permutation tests. The strongest linkage was on chromosome 2q (logarithm of odds [LOD] = 3.00) in a region previously linked to type 2 diabetes as a disease. We also found linkage signals of fasting glucose with 7q (LOD = 2.03), 8q (1.28), 17p (2.12), 17q (1.4), and 11p (1.33). These findings suggest that the quantitative genetics of fasting glucose could contribute to the search for type 2 diabetes genes. Diabetes 56:1742-1745, 2007 [ABSTRACT FROM AUTHOR]

OBJECTIVE--Microalbuminuria in diabetic patients is a predictor for diabetic nephropathy and cardiovascular disease. The aim of this study is to investigate the clinical impact of reducing microalbuminuria in type 2 diabetic patients in an observational follow-up study. RESEARCH DESIGN AND METHODS--We enrolled 216 type 2 diabetic patients with microalbuminuria during an initial 2-year evaluation period and observed them for the next 8 years. Remission and a 50% reduction of microalbuminuria were defined as a shift to normoalbuminuria and a reduction <50% from the initial level of microalbuminuria. The association between reducing microalbuminuria and first occurrence of a renal or cardiovascular event and annual decline rate of estimated glomerular filtration rate (eGFR) was evaluated. RESULTS--Twelve events occurred in 93 patients who attained a 50% reduction of microalbuminuria during the follow-up versus 35 events in 123 patients without a 50% reduction. The cumulative incidence rate of events was significantly lower in patients with a 50% reduction. A pooled logistic regression analysis revealed that the adjusted risk for events in subjects after a 50% reduction was 0.41 (95% CI 0.15-0.96). In addition, the annual decline rate of eGFR in patients with a 50% reduction was significantly slower than in those without such a reduction. The same results were also found in the analysis regarding whether remission occurred. CONCLUSIONS--The present study provides clinical evidence implying that a reduction of microalbuminuria in type 2 diabetic patients is an integrated indicator for renal and cardiovascular risk reduction. Diabetes 56:1727-1730, 2007 [ABSTRACT FROM AUTHOR]

OBJECTIVE--The biobreeding diabetes-prone (BBDP) rat spontaneously develops type 1 diabetes. Two of the genetic factors contributing to this syndrome are the major histocompatibility complex (Iddm1) and a Gimap5 mutation (Iddm2) responsible for a T-lymphopenia. Susceptibility to experimentally induced type 1 diabetes is widespread among nonlymphopenic (wild-type Iddm2) rat strains provided they share the BBDP Iddm1 allele. The question follows as to whether spontaneous and experimentally induced type 1 diabetes share susceptibility loci besides Iddm1. Our objectives were to map a novel, serendipitously discovered Iddm locus, confirm its effects by developing congenic sublines, and assess its differential contribution to spontaneous and experimentally induced type 1 diabetes. RESEARCH DESIGN AND METHODS--An unexpected reduction in spontaneous type I diabetes incidence (86 to 31%, P < 0.0001) was observed in a BBDP line congenic for a Wistar Furth--derived allotypic marker, RT7 (chromosome 13). Genome-wide analysis revealed that, besides the RT7 locus, a Wistar Furth chromosome 8 fragment had also been introduced. The contribution of these intervals to diabetes resistance was assessed through linkage analysis using 134 F2 (BBDP x double congenic line) animals and a panel of congenic sublines. One of these sublines, resistant to spontaneous type 1 diabetes, was tested for susceptibility to experimentally induced type 1 diabetes. RESULTS--Both linkage analysis and congenic sublines mapped a novel locus (Iddm24) to the telomeric 10.34 Mb of chromosome 8, influencing cumulative incidence and age of onset of spontaneous type 1 diabetes but not insulitis nor experimentally induced type 1 diabetes. CONCLUSIONS--This study has identified a type 1 diabetes susceptibility locus that appears to act after the development of insulitis and that regulates spontaneous type 1 diabetes exclusively. Diabetes 56:1731-1736, 2007 [ABSTRACT FROM AUTHOR]