Project description:b'Type-2 diabetes (T2D) is a complex metabolic disorder that affects hundreds of millions of people world-wide and is a growing public health concern. Despite recent advances in T2D research, the etiology of this disease and the mechanisms underlying the metabolic defects remain poorly understood. While obesity is thought to be the main cause for the rising prevalence of T2D, obesity alone cannot explain differences in the trends of T2D among different geographical regions and populations. Growing evidence suggests that environmental exposures to toxic and diabetogenic substances must play important roles. Inorganic arsenic (iAs) is a naturally occurring toxic metalloid. Hundreds of millions of people worldwide are exposed to unsafe levels of iAs in drinking water and food. iAs is a potent carcinogen, but iAs exposure has also been linked to increase risk of T2D. While the link between iAs exposure and T2D is well-established, the mechanisms underlying the diabetogenic effects of iAs exposure remain unclear. Results of our previously published and ongoing studies suggest that pancreatic islets are a primary target for iAs and its metabolites and that impaired insulin secretion by islets is the mechanism by which iAs exposure leads to diabetes. The proposed project will use metabolomics to identify metabolic pathways in -cells that are targeted by iAs and its metabolites, monomethyl-As (MAs) and dimethyl-As (DMAs). The metabolomics data combined with results of our ongoing mechanistic studies will provide a comprehensive picture of the metabolic dysfunction leading to the development of diabetes in individuals exposed to iAs and of the molecular mechanisms that underlie this dysfunction. Identifying the affected pathways and mechanisms will ultimately help to improve strategies for prevention and/or treatment of T2D associated with chronic exposure to iAs.'
Project description:Pancreatic islet transplantation is proposed as a cure for type 1 diabetes mellitus (T1D). Despite its success in optimal regulation of glucose levels, limitations in longevity of islet grafts still require innovative solutions. Inflammatory stress post-transplantation and loss of extracellular matrix attribute to the limited β-cell survival. Pancreatic stellate cells (PSCs), identified as pancreatic-specific stromal cells, have the potential to play a crucial role in preserving islet survival. Our study aimed to determine the effects of PSCs co-cultured with human CM β-cells and human islets under inflammatory stress induced by a cytokine cocktail of IFN-γ, TNF-α and IL-1β. Transwell culture inserts were utilized to assess the paracrine impact of PSCs on β-cells, alongside co-cultures enabling direct interaction between PSCs and human islets. We found that co-culturing PSCs with human CM β-cells and human cadaveric islets had rescuing effects on cytokine-induced stress. Effects were different under normoglycemic and hyperglycemic conditions. PSCs were associated with upregulation of β-cell mitochondrial activity and suppression of inflammatory gene expression. The rescuing effects exist both in indirect and direct co-culture methods. Furthermore, we tested whether PSCs have rescuing effects on human islets in conventional alginate-based microcapsules and in composite microcapsules composed of alginate-pectin collagen type IV, laminin sequence RGD, Nec-1, and amino acid. PSCs partially prevented cytokine-induced stress in both systems, but beneficial effects were stronger in composite capsules. Our findings show novel effects of PSCs on islet health. Islets and PSCs coculturing or co-transplantation might mitigate the inflammation stress and improve islet transplantation outcomes.
Project description:microRNAs (miRNAs) play an important role in pancreatic development and adult ?-cell physiology. Our hypothesis is based on the assumption that each islet cell type has a specific pattern of miRNA expression. We sought to determine the profile of miRNA expression in ?-and ?-cells, the main components of pancreatic islets, because this analysis may lead to a better understanding of islet gene regulatory pathways. Highly enriched (>98%) subsets of human ?-and ?-cells were obtained by flow cytometric sorting after intracellular staining with c-peptide and glucagon antibody. The method of sorting based on intracellular staining is possible because miRNAs are stable after fixation. MiRNA expression levels were determined by quantitative high throughput PCR-based miRNA array platform screening. Most of the miRNAs were preferentially expressed in ?-cells. From the total of 667 miRNAs screened, the Significant Analysis of Microarray identified 141 miRNAs, of which only 7 were expressed more in ?-cells (?-miRNAs) and 134 were expressed more in ?-cells (?-miRNAs). Bioinformatic analysis identified potential targets of ?-miRNAs analyzing the Beta Cell Gene Atlas, described in the T1Dbase, the web platform, supporting the type 1 diabetes (T1D) community. cMaf, a transcription factor regulating glucagon expression expressed selectively in ?-cells (TF?) is targeted by ?-miRNAs; miR-200c, miR-125b and miR-182. Min6 cells treated with inhibitors of these miRNAs show an increased expression of cMaf RNA. Conversely, over expression of miR-200c, miR-125b or miR-182 in the mouse alpha cell line ?TC6 decreases the level of cMAF mRNA and protein. MiR-200c also inhibits the expression of Zfpm2, a TF? that inhibits the PI3K signaling pathway, at both RNA and protein levels.In conclusion, we identified miRNAs differentially expressed in pancreatic ?- and ?-cells and their potential transcription factor targets that could add new insights into different aspects of islet biology and pathophysiology.
Project description:In this study, we achieved integrated transcriptomic and proteomic profiles of GK islets in a time-course fashion at different stages of T2D. Subsequent bioinformatics analysis revealed the chronological order of T2D-related molecular events during the deterioration of pancreatic islets. Our large quantitative dataset provide a valuable resource to obtain a comprehensive picture of the mechanisms responsible for islet dysfunction and to identify potential interventions to prevent beta-cell failure in human T2D.
Project description:Postnatal maintenance or regeneration of pancreatic beta cells is considered to occur exclusively via the replication of existing beta cells, but clinically meaningful restoration of human beta cell mass by proliferation has never been achieved. We discovered a population of immature beta cells that is present throughout life and forms from non-beta precursors at a specialized micro-environment or "neogenic niche" at the islet periphery. These cells express insulin, but lack other key beta cell markers, and are transcriptionally immature, incapable of sensing glucose, and unable to support calcium influx. They constitute an intermediate stage in the transdifferentiation of alpha cells to cells that are functionally indistinguishable from conventional beta cells. We thus identified a lifelong source of new beta cells at a specialized site within healthy islets. By comparing co-existing immature and mature beta cells within healthy islets, we stand to learn how to mature insulin-expressing cells into functional beta cells.
Project description:This study evaluated the clinical use of serum metabolomics to discriminate malignant cancers including pancreatic cancer (PC) from malignant diseases, such as biliary tract cancer (BTC), intraductal papillary mucinous carcinoma (IPMC), and various benign pancreaticobiliary diseases. Capillary electrophoresismass spectrometry was used to analyze charged metabolites. We repeatedly analyzed serum samples (n = 41) of different storage durations to identify metabolites showing high quantitative reproducibility, and subsequently analyzed all samples (n = 140). Overall, 189 metabolites were quantified and 66 metabolites had a 20% coefficient of variation and, of these, 24 metabolites showed significant differences among control, benign, and malignant groups (p < 0.05; Steel-Dwass test). Four multiple logistic regression models (MLR) were developed and one MLR model clearly discriminated all disease patients from healthy controls with an area under receiver operating characteristic curve (AUC) of 0.970 (95% confidential interval (CI), 0.946-0.994, p < 0.0001). Another model to discriminate PC from BTC and IPMC yielded AUC = 0.831 (95% CI, 0.650-1.01, p = 0.0020) with higher accuracy compared with tumor markers including carcinoembryonic antigen (CEA), carbohydrate antigen 19-9 (CA19-9), pancreatic cancer-associated antigen (DUPAN2) and s-pancreas-1 antigen (SPAN1). Changes in metabolomic profiles might be used to screen for malignant cancers as well as to differentiate between PC and other malignant diseases.
Project description:BackgroundNew sources of insulin-secreting cells are strongly in demand for treatment of diabetes. Induced pluripotent stem cells (iPSCs) have the potential to generate insulin-producing cells (iβ). However, the gene expression profile and secretory function of iβ still need to be validated in comparison with native β cells.MethodsTwo clones of human iPSCs, reprogrammed from adult fibroblasts through integration-free Sendai virus, were differentiated into iβ and compared with donor pancreatic islets and EndoC-βH1, an immortalized human β cell line.ResultsBoth clones of iPSCs differentiated into insulin+ cells with high efficiency (up to 20%). iβ were negative for pluripotency markers (Oct4, Sox2, Ssea4) and positive for Pdx1, Nkx6.1, Chromogranin A, PC1/3, insulin, glucagon and somatostatin. iβ basally secreted C-peptide, glucagon and ghrelin and released insulin in response either to increasing concentration of glucose or a depolarizing stimulus. The comparison revealed that iβ are remarkably similar to donor derived islets in terms of gene and protein expression profile and similar level of heterogeneity. The ability of iβ to respond to glucose instead was more related to that of EndoC-βH1.DiscussionWe demonstrated that insulin-producing cells generated from iPSCs recapitulate fundamental gene expression profiles and secretory function of native human β cells.