Ubiquitin D regulates IRE1 α/c-Jun N-terminal kinase (JNK) protein-dependent apoptosis in pancreatic beta cells

Pro-inflammatory cytokines contribute to pancreatic beta cell apoptosis in type 1 diabetes at least in part by inducing endoplasmic reticulum (ER) stress and the consequent unfolded protein response (UPR). It remains to be determined what causes the transition from "physiological" to "apoptotic" UPR, but accumulating evidence indicates that signaling by the ER transmembrane protein IRE1 alpha is critical for this transition. IRE1 alpha activation is regulated by both intra-ER and cytosolic cues. We evaluated the role for the presently discovered cytokine-induced and IRE1 alpha-interacting protein ubiquitin D (UBD) on the regulation of IRE1 alpha and its downstream targets. UBD was identified by use of a MAPPIT (mammalian protein-protein interaction trap)-based IRE1 alpha interactome screen followed by comparison against functional genomic analysis of human and rodent beta cells exposed to pro-inflammatory cytokines. Knockdown ofUBDin human and rodent beta cells and detailed signal transduction studies indicated that UBD modulates cytokine-induced UPR/IRE1 alpha activation and apoptosis. UBD expression is induced by the pro-inflammatory cytokines interleukin (IL)-1 beta and interferon (IFN)-gamma in rat and human pancreatic beta cells, and it is also up-regulated in beta cells of inflamed islets from non-obese diabetic mice. UBD interacts with IRE1 alpha in human and rodent beta cells, modulating IRE1 alpha-dependent activation of JNK and cytokine-induced apoptosis. Our data suggest that UBD provides a negative feedback on cytokine-induced activation of the IRE1 alpha/JNK pro-apoptotic pathway in cytokine-exposed beta cells

Autoimmunity against INS-IGF2 expressed in human pancreatic islets.

Insulin is a major autoantigen in islet autoimmunity and progression to type 1 diabetes. It has been suggested that the insulin B-chain may be critical to insulin autoimmunity in type 1 diabetes. INS-IGF2 consists of the preproinsulin signal peptide, the insulin B-chain and eight amino acids of the C-peptide in addition to 138 amino acids from the IGF2 gene. We aimed to determine 1) expression of INS-IGF2 in human pancreatic islets and 2) autoantibodies in newly diagnosed type 1 diabetes children and controls. INS-IGF2, expressed primarily in beta cells, showed higher levels of expression in islets from normal compared to donors with either type 2 diabetes (p=0.006) or high HbA1c levels (p<0.001). INS-IGF2 autoantibody levels were increased in newly diagnosed type 1 diabetes patients (n=304) compared to healthy controls (n=355; p<0.001). Displacement with cold insulin and INS-IGF2 revealed that more patients than controls had doubly reactive insulin-INS-IGF2 autoantibodies. These data suggest that INS-IGF2, which contains the preproinsulin signal peptide, the B-chain and eight amino acids of the C-peptide may be an autoantigen in type 1 diabetes. INS-IGF2 and insulin may share autoantibody binding sites, thus complicating the notion that insulin is the primary autoantigen in type 1 diabetes

A nanobody-based tracer targeting DPP6 for non-invasive imaging of human pancreatic endocrine cells

There are presently no reliable ways to quantify endocrine cell mass (ECM) in vivo, which prevents an accurate understanding of the progressive beta cell loss in diabetes or following islet transplantation. To address this unmet need, we coupled RNA sequencing of human pancreatic islets to a systems biology approach to identify new biomarkers of the endocrine pancreas. Dipeptidyl-Peptidase 6 (DPP6) was identified as a target whose mRNA expression is at least 25-fold higher in human pancreatic islets as compared to surrounding tissues and is not changed by proinflammatory cytokines. At the protein level, DPP6 localizes only in beta and alpha cells within the pancreas. We next generated a high-affinity camelid single-domain antibody (nanobody) targeting human DPP6. The nanobody was radiolabelled and in vivo SPECT/CT imaging and biodistribution studies were performed in immunodeficient mice that were either transplanted with DPP6-expressing Kelly neuroblastoma cells or insulin-producing human EndoC-βH1 cells. The human DPP6-expressing cells were clearly visualized in both models. In conclusion, we have identified a novel beta and alpha cell biomarker and developed a tracer for in vivo imaging of human insulin secreting cells. This provides a useful tool to non-invasively follow up intramuscularly implanted insulin secreting cells

Estrogen and Serotonin – old dogs, new tricks, Implications for pancreatic beta-cell function

Islet hormone secretion is tightly regulated by metabolic status as well as local and circulating factors. These factors can activate different receptors on the pancreatic islet cells, for instance G-protein coupled receptors (GPCRs). When activated, these receptors are able to fine-tune islet hormone secretion and regulate overall β-cell function. Estrogen and serotonin are circulating factors that bind to GPCRs. First, we studied the activation of GPER-1 in pancreatic islets using two agonists G-1 and Estrogen (E2). Both G-1 and E2 displayed a similar response in mouse and human islets even in the presence of estrogen receptor blockers, ICI 182, 720 and EM652. G-1 and E2 potentiated insulin secretion and inhibited glucagon and somatostatin secretion. G-1 induced cAMP generation, suggesting positive coupling to adenylate cyclase and a subsequent rise in insulin release. Furthermore both agonists protected pancreatic islets from cytokine-induced apoptosis via activation of anti-apoptotic signals, CREB, ERK1/2 and AKT and reduced phosphorylation of the pro-apoptotic signals SAPK/JNK and p38. Second, we studied serotonin (5-HT) receptors in human islets and INS (832/13) cells. We detected 15 different 5-HT receptors and the 5-HT producing enzymes, TPH1 and TPH2 as well as DDC. Cellular localization for 5-HT1A, 5-HT1D and 5-HT2A were observed in both β- and α-cells; while 5-HT2B was only present in β-cells. Agonists targeting these four receptors were able to either inhibit or stimulate insulin secretion from human islets and INS (832/13) cells. In addition, 5-HT was quantified using GC/MS in INS (832/13) cells, rat islets and detected in human α and β-cells with immunohistochemistry. Third, we investigated the peripheral role of a 5-HT2 receptor agonist, α-methyl serotonin maleate salt (AMS) in insulin resistance and β cell function. Long-term treatment with AMS in a high fat diet fed mouse model resulted in increased insulin sensitivity in vivo in high fat fed AMS treated mice. Moreover, insulin secretion from AMS treated control fed mice in vitro was decreased while plasma glucose levels were similar in vivo between AMS treated and untreated controls. In addition, AMS mediated protection from lipotoxicity in INS-1(832/13) cells. In conclusion, this thesis contributes to increased understanding of how estrogen and peripheral 5-HT mediate their effects on islet function and overall glucose homeostasis

GPR30 New Player in Type 2 Diabetes Mellitus.

<p> The gCube System - Task Execution Logger<br> --------------------------------------------------<br> <br> Task Execution Logger<br> <br> <br> This software is part of the gCube Framework (https://www.gcube-system.org/): an<br> open-source software toolkit used for building and operating Hybrid Data<br> Infrastructures enabling the dynamic deployment of Virtual Research Environments<br> by favouring the realisation of reuse oriented policies.<br> <br> The projects leading to this software have received funding from a series of <br> European Union programmes including: <br> * the Sixth Framework Programme for Research and Technological Development - <br> DILIGENT (grant no. 004260); <br> * the Seventh Framework Programme for research, technological development and <br> demonstration - D4Science (grant no. 212488), D4Science-II (grant no. <br> 239019),ENVRI (grant no. 283465), EUBrazilOpenBio (grant no. 288754), iMarine <br> (grant no. 283644); <br> * the H2020 research and innovation programme - BlueBRIDGE (grant no. 675680), <br> EGIEngage (grant no. 654142), ENVRIplus (grant no. 654182), Parthenos (grant <br> no. 654119), SoBigData (grant no. 654024);<br> <br> <br> Version<br> --------------------------------------------------<br> <br> 1.1.0-4.2.0-126127 (2016-12-16)<br> <br> Please see the file named "changelog.xml" in this directory for the release notes.<br> <br> <br> Authors<br> --------------------------------------------------<br> <br> * Panagiota Koltsida ([email protected]), University of Athens<br> <br> <br> Maintainers<br> -----------<br> <br> * Panagiota Koltsida ([email protected]), University of Athens<br> <br> <br> Download information<br> --------------------------------------------------<br> <br> Source code is available from SVN: <br> http://svn.research-infrastructures.eu/public/d4science/gcube/trunk/application-support-layer/TaskExecutionLogger<br> <br> Binaries can be downloaded from the gCube website: <br> https://www.gcube-system.org/<br> <br> <br> Installation<br> --------------------------------------------------<br> <br> Use the respective jar<br> <br> <br> Documentation <br> --------------------------------------------------<br> <br> Documentation is available on-line in the gCube Wiki:<br> https://wiki.gcube-system.org/gcube/index.php/ASL#ASL_Access_Logger_Library<br> <br> <br> Support <br> --------------------------------------------------<br> <br> Bugs and support requests can be reported in the gCube issue tracking tool:<br> https://support.d4science.org/projects/gcube/<br> <br> <br> Licensing<br> --------------------------------------------------<br> <br> This software is licensed under the terms you may find in the file named "LICENSE" in this directory.<br> </p

Activation of G protein-coupled receptor 30 modulates hormone secretion and counteracts cytokine-induced apoptosis in pancreatic islets of female mice.

The role of the newly discovered estrogen receptor GPR30 in islet physiology and pathophysiology is unclear. We examined GPR30 expression in relation to hormone secretion and possible anti-apoptotic effects in isolated mouse islets using the synthetic GPR30 ligand G-1. The mRNA and protein expression of GPR30 was analyzed by qPCR, Western blot and confocal microscopy. Hormone secretion and cAMP content were determined with RIA and apoptosis in islet cells with the Annexin-V method. GPR30 mRNA and protein expression was markedly higher in islets from females compared to male. This gender difference was not found for the genomic estrogen receptors ERalpha and ERbeta, the ERalpha expression being 10-fold higher than ERbeta in both genders. Confocal microscopy revealed abounden GPR30 expression in insulin, glucagon and somatostatin cells. Dose-response studies of G-1 vs 17beta-estradiol in isolated islets at 1 or 12mM glucose showed an almost identical pattern in that both compounds increased insulin and inhibited glucagon and somatostatin secretion. ICI-182,780 and EM-652, potent antagonists of the 17beta-estradiol receptors (ERalpha and ERbeta) did not influence the amplifying effect of G-1 or 17beta-estradiol on cAMP content or insulin secretion from isolated islets. Cytokine-induced (IL-1beta+TNFalpha+INFgamma) apoptosis in islets, cultured for 24h at 5mM glucose, was almost abolished by G-1 or 17beta-estradiol treatment. Addition of ICI-182,780 or EM-652 did not affect this beneficial effect of G-1 or 17beta-estradiol. Taken together, our findings show that GPR30 is expressed in most islet endocrine cells. The synthetic GPR30 ligand G-1 mimics the non-genomic effects of 17beta-estradiol on islet hormone secretion, cAMP content in islets and its anti-apoptotic effects. G-1 or analogs thereof might be new potential candidates in the therapeutic strategy for type 2 diabetes in women