Insulin-secreting Beta Cells Research Articles

Exenatide improves antioxidant capacity and reduces the expression of LDL receptors and PCSK9 in human insulin-secreting 1.1E7 cell line subjected to hyperglycemia and oxidative stress

Abstract Introduction GLP-1 receptor agonists (e.g., exenatide) are novel drugs used in the treatment of diabetes. These drugs, working with other mechanisms of action, improve glycemic control by increasing secretion of insulin and improving survival of pancreatic islet beta cells. Alterations in the oxidative stress level or the expression of proteins associated with cholesterol uptake might be responsible for those findings. Currently, there are few in vitro studies on the impact of exenatide antioxidant capacity in human islet beta cell lines and none that assess the influence of exenatide on LDL receptors and PCSK9 under hyperglycemia and oxidative stress. Therefore, we evaluated the impact of exenatide on antioxidant capacity, insulin secretion, and proteins involved in cholesterol metabolism. Materials and Method An in vitro culture of insulin-secreting cells 1.1E7 was subjected to hyperglycemia and oxidative stress. Assessment was made of the expression of enzymes associated with oxidative stress (NADPH oxidase, catalase, glutathione peroxidase, superoxide dismutase, iNOS) and cholesterol uptake (LDL receptors, PCSK9). Additionally, insulin and nitrite levels in culture media were quantified. Results We showed that exenatide improves expression of catalase and reduces the amount of nitrite in cell cultures in a protein kinase A–dependent manner. Those results were accompanied by a drop in the expression of LDL receptors and PCSK9. Insulin secretion was modestly increased in the culture condition. Conclusions Our findings show potential protective mechanisms exerted by exenatide in human insulin-secreting pancreatic beta cell line (1.1E7), which may be exerted through increased antioxidant capacity and reduced accumulation of cholesterol.

Differentiation of Human Pluripotent Stem Cells into Pancreatic Beta-cell Precursors in a 2D Culture System.

Human pluripotent stem cells (hPSCs) are an excellent tool for studying early pancreatic development and investigating the genetic contributors to diabetes. hPSC-derived insulin-secreting cells can be generated for cell therapy and disease modeling,however,with limited efficiency and functional properties. hPSC-derived pancreatic progenitors that are precursors to beta cells and other endocrine cells, when co-express the two transcription factors PDX1 and NKX6.1, specify the progenitors to functional, insulin-secreting beta cells both in vitro and in vivo. hPSC-derived pancreatic progenitors are currently used for cell therapy in type 1 diabetes patients as part of clinical trials. However, current procedures do not generate a high proportion of NKX6.1 and pancreatic progenitors, leading to co-generation of non-functional endocrine cells and few glucose-responsive, insulin-secreting cells. This work thus developed an enhanced protocol for generating hPSC-derived pancreatic progenitors that maximize the co-expression of PDX1 and NKX6.1 in a 2D monolayer. The factors such as cell density, availability of fresh matrix, and dissociation of hPSC-derived endodermal cells are modulated that augmented PDX1 and NKX6.1 levels in the generated pancreatic progenitors and minimized commitment to alternate hepatic lineage. The study highlights that manipulating the cell's physical environment during in vitro differentiation can impact lineage specification and gene expression. Therefore, the current optimized protocol facilitates the scalable generation of PDX1 and NKX6.1 co-expressing progenitors for cell therapy and disease modeling.

Transcription factor 7-like 2 (TCF7L2): a culprit gene in Type 2 Diabetes Mellitus

The genetics of Type 2 diabetes a complex metabolic disorder, characterized by decreased insulin secretion and insulin resistance resulting in impaired blood glucose homeostasis remains enigma for geneticists. In 2006 an important step while finding genetic causes of diabetes type 2 was identification of transcription factor 7-like 2 (TCF7L2) gene an important marker in predisposition of type 2 diabetes in almost all ethnic population. Recent genetic research identifies numerous novel type 2 diabetes susceptible genes among these genes TCF7L2 is considered as gang head and emerged as the most promising types 2 diabetes causing gene. Risk variants in TCF7L2 effects pancreatic beta cell development and insulin secretion by influencing Wnt Signaling pathway. Genetic variants in TCF7L2 confer risk for type 2 diabetes by altering expression of transcription factor (which has key role in blood glucose regulation) in pancreas. The purpose of this paper is to evaluate type 2 diabetes susceptible gene the TCF7L2 and to present a comprehensive review of studies carried out worldwide in different ethnic population on association of TCF7L2 polymorphism with type 2 diabetes.

Prolactin-Induced Adaptation in Glucose Homeostasis in Mouse Pregnancy Is Mediated by the Pancreas and Not in the Forebrain.

Adaptive changes in glucose homeostasis during pregnancy require proliferation of insulin-secreting beta-cells in the pancreas, together with increased sensitivity for glucose-stimulated insulin secretion. Increased concentrations of maternal prolactin/placental lactogen contribute to these changes, but the site of action remains uncertain. Use of Cre-lox technology has generated pancreas-specific prolactin receptor (Prlr) knockouts that demonstrate the development of a gestational diabetic like state. However, many Cre-lines for the pancreas also express Cre in the hypothalamus and prolactin could act centrally to modulate glucose homeostasis. The aim of the current study was to examine the relative contribution of prolactin action in the pancreas and brain to these pregnancy-induced adaptations in glucose regulation. Deletion of prolactin receptor (Prlr) from the pancreas using Pdx-cre or Rip-cre led to impaired glucose tolerance and increased non-fasting blood glucose levels during pregnancy. Prlrl ox/lox /Pdx-Cre mice also had impaired glucose-stimulated insulin secretion and attenuated pregnancy-induced increase in beta-cell fraction. Varying degrees of Prlr recombination in the hypothalamus with these Cre lines left open the possibility that central actions of prolactin could contribute to the pregnancy-induced changes in glucose homeostasis. Targeted deletion of Prlr specifically from the forebrain, including areas of expression induced by Pdx-Cre and Rip-cre, had no effect on pregnancy-induced adaptations in glucose homeostasis. These data emphasize the pancreas as the direct target of prolactin/placental lactogen action in driving adaptive changes in glucose homeostasis during pregnancy.

Autofagia en las células beta pancreáticas

Autophagy is a crucial mechanism for the functioning and survival of pancreatic beta cells. Its dysregulation has been associated with obesity, insulin resistance, and glucose intolerance. Furthermore, decreased autophagy in insulin-secret ing beta cells has been reported to contribute to the devel opment of type 2 diabetes mellitus (T2DM), which constitutes about 95% of all diabetes cases and is a chronic metabolic disease that it currently affects millions of people around the world. In different models of rodents, whether diabetic or obese, it has been observed that treatment with autophagy enhancers lowers glucose levels, increases insulin sensitivity, and protects beta cells from apoptosis. As stated above, it has recently been proposed to carry out an early intervention in patients with T2DM, using drugs that promote autophagy, which could help preserve the mass of beta cells and prevent the progression of the disease. This review provides an over view of the importance of the physiological process of auto phagy and its imminent role in the development of T2DM. Keywords: Pancreatic beta cells; autophagy; cell death; diabetes mellitus type 2

Prenatal androgen excess impairs beta-cell function by decreased sirtuin 3 expression.

Prenatal androgen exposure induces metabolic disorders in female offspring. However, the long-term effect of maternal testosterone excess on glucose metabolism, especially on pancreatic beta-cell function, is rarely investigated. Our current study mainly focused on the effects of prenatal testosterone exposure on glucose metabolism and pancreatic beta- cell function in aged female offspring. By using maternal mice and their female offspring as animal models, we found that prenatal androgen treatment induced obesity and glucose intolerance in aged offspring. These influences were accompanied by decreased fasting serum insulin concentration, elevated serum triglyceride, and testosterone concentrations. Glucose stimulated insulin secretion in pancreatic beta cells of aged female offspring was also affected by prenatal testosterone exposure. We further confirmed that increased serum testosterone contributed to downregulation of sirtuin 3 expression, activated oxidative stress, and impaired pancreatic beta-cell function in aged female offspring. Moreover, over-expression of sirtuin 3 in islets isolated from female offspring treated with prenatal testosterone normalized the oxidative stress level, restored cyclic AMP, and ATP generation, which finally improved glucose-stimulated insulin secretion in beta cells. Taken together, these results demonstrated that prenatal testosterone exposure caused a metabolic disturbance in aged female offspring via suppression of sirtuin 3 expression and activation of oxidative stress in pancreatic beta cells.

RNA editing of 5-HT2C R impairs insulin secretion of pancreatic beta cells via altered store-operated calcium entry.

Recent studies emphasize the importance of 5-HT2C receptor (5-HT2C R) signaling in the regulation of energy homeostasis. The 5-HT2C R is the only G-protein-coupled receptor known to undergo post-transcriptional adenosine to inosine (A-to-I) editing by adenosine deaminase acting on RNA (ADAR). 5-HT2C R has emerged as an important role in the modulation of pancreatic β cell functions. This study investigated mechanisms behind the effects of palmitic acid (PA) on insulin secretion in different overexpressed 5-HT2C R edited isoforms in pancreatic MIN6 β cells. Results showed that the expressions of 5HT2C R and ADAR2 were upregulated in the pancreatic islets of mice fed with high-fat diet (HFD) compared to control mice. PA treatment significantly induced the expressions of 5-HT2C R and ADAR2 in pancreatic MIN6 β cells. PA treatment significantly induced the editing of 5-HT2C R in pancreatic MIN6 β cells. There was no significant difference in cell viability between naïve cells and three overexpressed 5-HT2C R edited isoforms in pancreatic MIN6 β cells. Overexpressed 5-HT2C R edited isoforms showed reduced glucose-stimulated insulin secretion (GSIS) compared with green fluorescent protein (GFP) expressed cells. Moreover, 5-HT2C R edited isoforms displayed reduced endoplasmic reticulum (ER) calcium release and store-operated calcium entry (SOCE) activation, probably through inhibition of stromal interaction molecule 1 trafficking under PA treatment. Altogether, our results show that PA-mediated editing of 5-HT2C R modulates GSIS through alteration of ER calcium release and SOCE activation in pancreatic MIN6 β cells.

Oxidized LDL Downregulates ABCA1 Expression via MEK/ERK/LXR Pathway in INS-1 Cells.

Impaired insulin secretion is one of the main causes of type 2 diabetes. Cholesterol accumulation-induced lipotoxicity contributes to impaired insulin secretion in pancreatic beta cells. However, the detailed mechanism in this process remains unclear. In this study, we proved that oxidized low-density lipoprotein (OxLDL) reduced insulin content, decreased PDX-1 expression, and impaired glucose-stimulated insulin secretion (GSIS) in INS-1 cells, which were rescued by addition of high-density lipoprotein (HDL). OxLDL receptors and cholesterol content were increased by OxLDL. Consistently, OxLDL suppressed cholesterol transporter ABCA1 expression and transcription in a dose-dependent and time-dependent manner. Inhibition of MEK by its specific inhibitor, PD98059, altered the effect of OxLDL on ABCA1 transcription and activation of ERK. Next, chromatin immunoprecipitation assay demonstrated that liver X receptor (LXR) could directly bind to ABCA1 promoter and this binding was inhibited by OxLDL. Furthermore, OxLDL decreased the nuclear LXR expression, which was prevented by HDL. LXR-enhanced ABCA1 transcription was suppressed by OxLDL, and the effect was cancelled by mutation of the LXR-binding sites. In summary, our study shows that OxLDL down-regulates ABCA1 expression by MEK/ERK/LXR pathway, leading to cholesterol accumulation in INS-1 cells, which may result in impaired insulin synthesis and GSIS.

Фактор транскрипции 7 (TCF7L2): фактор риска развития сахарного диабета 2 типа

The genetics of Type 2 diabetes a complex metabolic disorder, characterized by decreased insulin secretion and insulin resistance resulting in impaired blood glucose homeostasis remains enigma for geneticists. In 2006 an important step while finding genetic causes of diabetes type 2 was identification of transcription factor 7-like 2 (TCF7L2) gene an important marker in predisposition of type 2 diabetes in almost all ethnic population. Recent genetic research identifies numerous novel type 2 diabetes susceptible genes among these genes TCF7L2 is considered as gang head and emerged as the most promising types 2 diabetes causing gene. Risk variants in TCF7L2 effects pancreatic beta cell development and insulin secretion by influencing Wnt Signaling pathway. Genetic variants in TCF7L2 confer risk for type 2 diabetes by altering expression of transcription factor (which has key role in blood glucose regulation) in pancreas. The purpose of this paper is to evaluate type 2 diabetes susceptible gene the TCF7L2 and to present a comprehensive review of studies carried out worldwide in different ethnic population on association of TCF7L2 polymorphism with type 2 diabetes.

Extensive NEUROG3 occupancy in the human pancreatic endocrine gene regulatory network

ObjectiveMice lacking the bHLH transcription factor (TF) Neurog3 do not form pancreatic islet cells, including insulin-secreting beta cells, the absence of which leads to diabetes. In humans, homozygous mutations of NEUROG3 manifest with neonatal or childhood diabetes. Despite this critical role in islet cell development, the precise function of and downstream genetic programs regulated directly by NEUROG3 remain elusive. Therefore, we mapped genome-wide NEUROG3 occupancy in human induced pluripotent stem cell (hiPSC)–derived endocrine progenitors and determined NEUROG3 dependency of associated genes to uncover direct targets. MethodsWe generated a novel hiPSC line (NEUROG3-HA-P2A-Venus) where NEUROG3 is HA-tagged and fused to a self-cleaving fluorescent VENUS reporter. We used the CUT&RUN technique to map NEUROG3 occupancy and epigenetic marks in pancreatic endocrine progenitors (PEP) that were differentiated from this hiPSC line. We integrated NEUROG3 occupancy data with chromatin status and gene expression in PEPs as well as their NEUROG3-dependence. In addition, we investigated whether NEUROG3 binds type 2 diabetes mellitus (T2DM)–associated variants at the PEP stage. ResultsCUT&RUN revealed a total of 863 NEUROG3 binding sites assigned to 1263 unique genes. NEUROG3 occupancy was found at promoters as well as at distant cis-regulatory elements that frequently overlapped within PEP active enhancers. De novo motif analyses defined a NEUROG3 consensus binding motif and suggested potential co-regulation of NEUROG3 target genes by FOXA or RFX transcription factors. We found that 22% of the genes downregulated in NEUROG3−/− PEPs, and 10% of genes enriched in NEUROG3-Venus positive endocrine cells were bound by NEUROG3 and thus likely to be directly regulated. NEUROG3 binds to 138 transcription factor genes, some with important roles in islet cell development or function, such as NEUROD1, PAX4, NKX2-2, SOX4, MLXIPL, LMX1B, RFX3, and NEUROG3 itself, and many others with unknown islet function. Unexpectedly, we uncovered that NEUROG3 targets genes critical for insulin secretion in beta cells (e.g., GCK, ABCC8/KCNJ11, CACNA1A, CHGA, SCG2, SLC30A8, and PCSK1). Thus, analysis of NEUROG3 occupancy suggests that the transient expression of NEUROG3 not only promotes islet destiny in uncommitted pancreatic progenitors, but could also initiate endocrine programs essential for beta cell function. Lastly, we identified eight T2DM risk SNPs within NEUROG3-bound regions. ConclusionMapping NEUROG3 genome occupancy in PEPs uncovered unexpectedly broad, direct control of the endocrine genes, raising novel hypotheses on how this master regulator controls islet and beta cell differentiation.

In vitro effect of DDE exposure on the regulation of B-TC-6 pancreatic beta cell insulin secretion: a potential role in beta cell dysfunction and type 2 diabetes mellitus

Organochlorine compounds (OC) include synthetic insecticides previously used throughout the world before being banned for their adverse effects and environmental persistence; DDT (dichlorodiphenyltrichloroethane) was one of the most widely used. Epidemiological evidence suggests that higher levels of some OC, including metabolites of DDT, such as dichlorodiphenyldichloroethylene (DDE), are associated with type 2 diabetes mellitus (T2D). DDE exposure may affect pancreatic cellular functions associated with glucose control and possibly cause beta cell dysfunction. The in vitro effect of DDE exposure on pancreatic beta cell insulin secretion was investigated using Beta-Tumor Cell-6 (B-TC-6) murine pancreatic beta cells. DDE exposure significantly increased insulin secretion suggesting a role for DDE in altering insulin synthesis and secretion. Reactive oxygen species (ROS) levels were not significantly increased indicating that oxidative stress is not responsible for the DDE-induced insulin secretion. Pancreatic and duodenal homeobox factor-1 (PDX-1) levels were not significantly increased suggesting that DDE exposure does not alter insulin transcription, but prohormone convertase (PC) levels were increased suggesting a role for DDE in altering insulin translation. Based on these in vitro results, DDE may play a role in beta cell dysfunction by affecting mechanisms that regulate insulin secretion but it is not likely to be the major mechanism behind the DDE/T2D epidemiological association.

Mast Cells and the Pancreas in Human Type 1 and Type 2 Diabetes

Mast cells are highly differentiated, widely distributed cells of the innate immune system, that are currently considered as key regulators of both innate and adaptive immunity. Mast cells play a key role in health and survival mechanisms, especially as sentinel cells that can stimulate protective immune responses. On the other hand, it has been shown that mast cells are involved in the pathogenesis of several diseases, and recently a possible pathogenetic role of mast cells in diabetes has been proposed. In this review we summarize the evidence on the increased presence of mast cells in the pancreas of subjects with type 1 diabetes, which is due to the autoimmune destruction of insulin secreting beta cells, and discuss the differences with type 2 diabetes, the other major form of diabetes. In addition, we describe some of the pathophysiological mechanisms through which mast cells might exert their actions, which could be targeted to potentially protect the beta cells in autoimmune diabetes.

Placenta derived Mesenchymal Stem Cells transplantation in Type 1 diabetes: preliminary report of phase 1 clinical trial.

Type 1 Diabetes Mellitus (T1DM) is an auto immune reaction against insulin secreting beta cells. Exogenous insulin administration is the only standard treatment for T1DM. However, despite tight glycemic control many patients will develop chronic life-threatening complications. Recently, stem cell transplantation has been suggested as a novel treatment for eliminating the beta cell damage and promoting their regeneration by modulating auto-immunity. To our knowledge; this is the first preliminary report of placenta derived MSCs (PLMSCs) transplantation in juvenile T1DM. An Open label non-randomized phase 1 clinical trial was designed to evaluate the safety of PLMSCs transplantation in new onset juvenile T1DM (IRCT20171021036903N2). PLMSCs were manufactured in our clean room facility using a Xeno-free/GMP compliant protocol. The first series of patients (n = 4) received one dose of1 × 106 PLMSCs/kg intravenously. Diabetic clinical and laboratory parameters and side effects were evaluated weekly for the first month, monthly for 6 months, and then every 3 month till 1 year. Serious adverse events were not seen during 1 year follow-up. Partial remission and hypoglycemic attacks were happened one month after transplantation in two patients. ZnT8-Ab decreased till month 3 and then increased again in all patients. Anti Gad-Ab decreased till month 3 of follow up then increased. This preliminary report of our phase I clinical trial demonstrated the short term safety of PLMSCs transplantation in juvenile T1DM. To prove the long term safety and probable efficacy of this treatment more investigations are needed. Iranian Registry of Clinical Trials: IRCT20171021036903N2.

CARD9 mediates glucose-stimulated insulin secretion in pancreatic beta cells

Caspase recruitment domain containing protein 9 (CARD9) plays key regulatory role(s) in innate and adaptive immune responses. Recent evidence implicates CARD9 in the onset of metabolic diseases including insulin resistance. However, potential contributory roles of CARD9 in glucose-stimulated insulin secretion (GSIS) remain unknown. Herein, we report that CARD9 is expressed in human islets, rat islets, mouse islets and clonal INS-1 832/13 cells. Subcellularly, CARD9 is predominantly cytosolic (~75%) in INS-1 832/13 cells. siRNA-mediated depletion of CARD9 expression significantly (~50%) suppressed GSIS in INS-1 832/13 cells. Interestingly, glucose-induced activation of Rac1, a small G-protein, which is a requisite for GSIS to occur, is unaffected in CARD9-si transfected cells, suggesting that CARD9-mediates GSIS in a Rac1-independent fashion. Furthermore, insulin secretion promoted by KCl or mastoparan (a global G protein activator), remained resistant to CARD9 depletion in INS-1 832/13 cells. In addition, pharmacological inhibition (BRD5529) of interaction between CARD9 and TRIM62, its ubiquitin ligase, exerted no significant effects on GSIS. Lastly, depletion of CARD9 prevented glucose-induced p38, not ERK1/2 phosphorylation in beta cells. Based on these observations, we propose that CARD9 might regulate GSIS via a Rac1-independent and p38-dependent signaling module.

M1 macrophage-derived exosomes impair beta cell insulin secretion via miR-212-5p by targeting SIRT2 and inhibiting Akt/GSK-3β/β-catenin pathway in mice.

Macrophage levels are elevated in pancreatic islets, and the resulting inflammatory response is a major contributor to beta cell failure during obesity and type 2 diabetes mellitus. Previous studies by us and others have reported that exosomes released by macrophages play important roles in mediating cell-to-cell communication, and represent a class of inflammatory factors involved in the inflammatory process associated with type 2 diabetes mellitus. However, to date, no reports have demonstrated the effect of macrophage-derived exosomes on beta cells, and little is known regarding their underlying mechanisms in beta cell injury. Thus, we aimed to study the impact of macrophage-derived exosomes on islet beta cell injury in vitro and in vivo. The phenotypic profiles of islet-resident macrophages were analysed in C57BL/6J mice fed a high-fat diet (HFD). Exosomes were collected from the medium of cultured bone marrow-derived macrophages (BMDMs) and from isolated islet-resident macrophages of HFD-fed mice (HFD-Exos). The role of exosomes secreted by inflammatory M1 phenotype BMDMs (M1-Exos) and HFD-Exos on beta cell function was assessed. An miRNA microarray and quantitative real-time PCR (qPCR) were conducted to test the level of M1-Exos-derived miR-212-5p in beta cells. Then, miR-212-5p was overexpressed or inhibited in M1-Exos or beta cells to determine its molecular and functional impact. M1-polarised macrophages were enriched in the islets of obese mice. M1 macrophages and islet-resident macrophages of HFD-fed mice impaired beta cell insulin secretion in an exosome-dependent manner. miR-212-5p was notably upregulated in M1-Exos and HFD-Exos. Enhancing the expression of miR-212-5p impaired beta cell insulin secretion. Blocking miR-212-5p elicited a significant improvement in M1-Exos-mediated beta cell insulin secretion during injury. Mechanistically, M1-Exos mediated an intercellular transfer of the miR-212-5p, targeting the sirtuin 2 gene and regulating the Akt/GSK-3β/β-catenin pathway in recipient beta cells to restrict insulin secretion. A novel exosome-modulated mechanism was delineated for macrophage-beta cell crosstalk that drove beta cell dysfunction and should be explored for its therapeutic utility.

1242-P: Defining the Nkx6.1 Interactome in Beta Cells Reveals a Novel Interaction with Pdx1

The beta cell transcription factor Nkx6.1 plays a critical role in pancreatic progenitor cell differentiation, mature beta cell proliferation and insulin secretion. The pathways regulated by Nkx6.1 that results in these phenotypes are still being defined. Given that transcription factors generally function in complexes, we sought to determine proteins that interact with Nkx6.1 and may be harnessed to expand functional beta cell mass. INS-1 832/13 beta cells were transduced with AdCMV-Nkx6.1-BioID, AdCMV-GFP-BioID or left untreated. Biotinylated proteins were isolated and the Nkx6.1 interactome was defined using liquid chromatography-tandem mass spectrometry (LC-MS/MS). We defined 176 biotinylated proteins in cells transduced with AdCMV-Nkx6.1-BioID that were not observed with AdCMV-GFP-BioID or naturally biotinylated proteins from untreated lysates (P≤0.05, n=9). These 176 proteins are enriched in terms of nucleotide binding (P=3.6E-5), ribosomal proteins (P=9.1E-4), and transcription factors (P=4.3E-4). Among the enriched transcription factors, we validated that Pdx1, Mef2d and Nr2c2 were biotinylated in response to transduction with AdCMV-Nkx6.1 using biotin-targeted immunoprecipitation and western blot. To examine if these transcription factors are likely to interact with Nkx6.1 on the genome, we analyzed the frequency of proximal binding sites for Nkx6.1 and our candidate genes. Nr2c2 and Pdx1 binding sites in close proximity to Nkx6.1 binding sites were statistically overrepresented in the genome (P≤0.01). Given the role of Pdx1 on functional beta cell mass, we further characterized the interaction of endogenous Nkx6.1 and Pdx1 by co-immunoprecipitation (Co-IP). Our data demonstrates a significant Pdx1 binding by Nkx6.1 Co-IP, as compared to Co-IP with the IgG control (P=0.015, n=3). These data define potential Nkx6.1 binding partners in INS-1 832/13 cells, as well as a novel interaction between two essential beta cell transcription factors, Nkx6.1 and Pdx1. Disclosure C. C. Littlefield: None. N. C. Jensen: None. J. T. Hill: None. J. C. Price: None. J. S. Tessem: None. Funding Thomas J. Beatson, Jr. Foundation (2019-003)

1244-P: The Protein Phosphatase PPm1k Regulates Ribosomal Protein S6 Phosphorylation in Beta Cells

Phosphorylation of ribosomal protein S6 (RPS6) on ser235/236 and ser240/244 in the pancreatic beta cell increases cell size and insulin content and influences systemic glucose homeostasis. Our phosphoproteomic analysis identified the protein phosphatase, PPm1K, as a novel regulator of RPS6 phosphorylation. We find that beta cells account for most PPm1K expression within pancreatic islets and that exposure of INS1 832/13 beta cells to increasing concentrations of glucose results in suppression of PPm1K mRNA expression. siRNA mediated knockdown of PPm1K in INS1 832/13 cells, to levels achieved by glucose, increased insulin content and secretion in basal and glucose stimulated conditions that was accompanied by robust phosphorylation of RPS6 on ser235/236 and ser240/244. PPm1K knockdown did not increase phosphorylation of p70 S6 Kinase (S6K) or the mammalian target of rapamycin (mTOR) upstream of RPS6 suggesting that PPm1K regulates RPS6 phosphorylation in an mTOR-S6K independent manner. Accordingly, treatment with the mTORC1 inhibitor, Rapamycin, lowered S6K and RPS6 phosphorylation but did not override the effect of PPm1K knockdown to increase RPS6 phosphorylation compared to control siRNA treated cells. Lowering phosphorylation of PPm1K’s classical target, ser293 of the branched-chain keto acid dehydrogenase (BCKDH) with the small molecule, BT2, also did not impact the effect of PPm1K knockdown to increase RPS6 phosphorylation. Thus PPm1K exerts its effects on RPS6 phosphorylation in a BCKDH and mTOR/S6K independent manner. The effects of siRNA-mediated PPm1K knockdown on RPS6 phosphorylation were accompanied by a 1.5 fold increase in protein translation and the induction of an unfolded protein response as determined by an increase in XBP-1 splicing, and BiP expression. Together our data identify a new role for the phosphatase PPm1K as a glucose sensitive modulator of RPS6 phosphorylation and protein translation that impacts beta cell insulin content and secretion. Disclosure Y. Deleye: None. J. Herring: None. K. H. Hess: None. B. Leininger: None. R. W. Mcgarrah: None. J. S. Tessem: None. P. J. White: None. Funding American Diabetes Association/Pathway to Stop Diabetes (1-16-INI-17 to P.J.W.)

Diabetes in chronic pancreatitis: risk factors and natural history.

The purpose of this review is to delineate risk factors for the development of diabetes in patients with chronic pancreatitis. The natural history including progression to diabetes and complications that develop once diabetes occurs in chronic pancreatitis is also reviewed. Studies have found that predictors of diabetes in chronic pancreatitis include both risk factors for type 2 diabetes (e.g., obesity, genetic variants) as well as pancreas-specific factors (e.g., pancreatic calcification, exocrine insufficiency). Rates of diabetes in chronic pancreatitis are strongly related to the duration of chronic pancreatitis, reflecting progressive dysfunction and damage to the insulin-secreting beta cells. Patients with diabetes and chronic pancreatitis experience an excess burden of complications, including higher all-cause and cancer-related mortality. The high incidence and significant impact of diabetes on the morbidity and mortality of patients with chronic pancreatitis highlights the urgent need for clinically applicable models to predict diabetes in those with chronic pancreatitis, allowing efforts for targeted interventions to prevent diabetes. Research being carried out in the Consortium for the Study of Chronic Pancreatitis, Diabetes, and Pancreatic Cancer holds promise to fulfill these goals.

338-OR: Reversal of Insulin Resistance by Resveratrol and Hesperetin Combination in Overweight and Obese Subjects Correlates with Decrease in Expression of Thioredoxin Interacting Protein

Trans-Resveratrol and hesperetin combination (tRES-HESP) in randomized, double-blind, placebo-controlled crossover study in overweight and obese subjects corrected insulin resistance; healthy aging through functional food study (HATFF, Clinicaltrials.gov identifier NCT02095873). tRES-HESP is an optimized supplement for induction of expression of glyoxalase 1 (Glo1) via activation of transcription factor Nrf2. Increased Glo1 expression decreases reactive metabolite, methylglyoxal (MG), contributing to insulin resistance through glycation-linked unfolded protein formation and activation of the unfolded protein response (UPR). Herein, we report further analysis of study variables and follow-up reverse translational studies. With tRES-HESP treatment, plasma MG correlated negatively with peripheral blood mononuclear cell (PBMC) quinone reductase activity - a marker of Nrf2 activation (r = - 0.68, P<0.01). For change from baseline of PBMC gene expression with tRES-HESP treatment (assessed by the Nanostring method), change in area-under-the-curve plasma glucose (ΔAUGg) during oral glucose tolerance tests correlated negatively with change in Glo1 expression (r = - 0.56, P<0.05) and correlated positively with change in expression of thioredoxin interacting protein (TXNIP) (r = 0.59, P<0.05). In reverse translational studies, we found tRES-HESP decreased TXNIP expression by 39 ± 1% (P<0.001) in human hepatocyte-like HepG2 cells and 14 ± 3% in BJ fibroblasts in vitro (P<0.01). tRES-HESP may decrease TXNIP expression by decreasing the MG-driven UPR and by direct Nrf2-driven down regulation. TXNIP is a mediator of insulin resistance in liver and skeletal muscle and impaired pancreatic beta-cell insulin secretion. tRES-HESP is suitable for further evaluation for prevention and treatment of type 2 diabetes where decreased TXNIP may contribute to the therapeutic response. Disclosure M. Xue: None. M. Weickert: None. N. Rabbani: None. P. Thornalley: None. Funding Qatar Foundation; Qatar University

Expanding the spectrum of endocrinopathies identified in Schaaf-Yang syndrome - A case report and review of the literature

Schaaf-Yang syndrome is a genetic disorder caused by mutations in the paternal allele of the MAGEL2 gene. Developmental delay, feeding difficulties, joint contractures and a high prevalence of autism spectrum disorders are characteristic of the syndrome. Endocrine abnormalities include mostly various pituitary hormonal deficiencies, presenting as hypoglycemia in 48% of reported cases. Persistent hyperinsulinism was only described in two siblings and responded to diazoxide treatment. We describe a unique case of an infant with Schaaf-Yang syndrome that presented with persistent hyperinsulinism unresponsive to diazoxide. Furthermore, we conducted a literature review of the endocrine abnormalities described in MAGEL2 related disorders. The case presented expands the clinical phenotype of Schaaf-Yang syndrome and emphasizes the importance of endocrine follow-up in these patients. Further investigation into the role of MAGEL2 in the regulation of pancreatic beta-cell insulin secretion, will improve our understanding of the abnormalities in glucose regulation in this syndrome.