Abstract: Somatostatin is a paracrine modulator of insulin secretion and beta cell function with pleotropic effects on glucose homeostasis. The mechanism of somatostatin-mediated communication between delta and beta cells is not well-understood, which we address in this study via the ciliary somatostatin receptor 3 (SSTR3). Primary cilia are membrane organelles that act as signaling hubs in islets by virtue of their subcellular location and enrichment in signaling proteins such as G-protein coupled receptors (GPCRs). We show that SSTR3, a ciliary GPCR, mediates somatostatin suppression of insulin secretion in mouse islets. Quantitative analysis of calcium flux using a mouse model of genetically encoded beta cell-specific GCaMP6f calcium reporter shows that somatostatin signaling alters beta cell calcium flux after physiologic glucose stimulation, an effect that depends on endogenous SSTR3 expression and the presence of intact primary cilia on beta cells. Comparative in vitro studies using SSTR isoform antagonists demonstrate a role for SSTR3 in mediating somatostatin regulation of insulin secretion in mouse islets. Our findings support a model in which ciliary SSTR3 mediates a distinct pathway of delta-to-beta cell regulatory crosstalk and may serve as a target for paracrine modulation.

Abstract: ABSTRACT Pancreatic β-cell dysfunction is a key factor in the development of type 2 diabetes. Pancreatic β-cell senescence accelerates abnormal glucose metabolism, which decreases insulin secretion and cell regeneration ability, eventually leading to diabetes. A cholesterol oxidation product, 7-ketocholesterol (7-KC) can affect pancreatic β-cell function. However, its role in pancreatic β-cell senescence has not been reported. We investigated the role of 7-KC in pancreatic β-cell senescence and its underlying molecular mechanism in MIN6 cells. MIN6 cells were treated with 25 μmol/L 7-KC for 24 h and the proportion of senescent cells was detected based on senescence-associated β-galactosidase (SA-β-gal) activity. The cell cycle, DNA damage, and the senescence-associate secretory phenotype (SASP) and protein expression were detected by flow cytometry, immunofluorescence, and western blotting, respectively. 7-KC can significantly increase SA-β-gal activity, promoted G0/G1 arrest, DNA damage, and interleukin-1β expression in MIN6 cells and significantly inhibited insulin synthesis. Further studies indicated that 7-KC induced β-cell senescence by inhibiting the SIRT1/CDK4–Rb – E2F1 signaling pathway.

Abstract: ABSTRACT The pancreatic β cell synthesizes, packages, and secretes insulin in response to glucose-stimulation to maintain blood glucose homeostasis. Under diabetic conditions, a subset of β cells fail and lose expression of key transcription factors (TFs) required for insulin secretion. Among these TFs is Pancreatic and duodenal homeobox 1 (PDX1), which recruits a unique subset of transcriptional coregulators to modulate its activity. Here we describe a novel interacting partner of PDX1, the Staphylococcal Nuclease and Tudor domain-containing protein (SND1), which has been shown to facilitate protein-protein interactions and transcriptional control through diverse mechanisms in a variety of tissues. PDX1:SND1 interactions were confirmed in rodent β cell lines, mouse islets, and human islets. Utilizing CRISPR-Cas9 gene editing technology, we deleted Snd1 from the mouse β cell lines, which revealed numerous differentially expressed genes linked to insulin secretion and cell proliferation, including limited expression of Glp1r. We observed Snd1 deficient β cell lines had reduced cell expansion rates, GLP1R protein levels, and limited cAMP accumulation under stimulatory conditions, and further show that acute ablation of Snd1 impaired insulin secretion in rodent and human β cell lines. Lastly, we discovered that PDX1:SND1 interactions were profoundly reduced in human β cells from donors with type 2 diabetes (T2D). These observations suggest the PDX1:SND1 complex formation is critical for controlling a subset of genes important for β cell function and is targeted in diabetes pathogenesis.

Abstract: ABSTRACT The escalating worldwide occurrence of diabetes mellitus, recognized as a chronic metabolic ailment contributing to an amplified global disease burden, has stimulated researchers to explore its etiology. Consequently, the study employed a two-sample Mendelian randomization (MR) methodology to examine the causal connection between bacterial pneumonia and diabetes, drawing upon the existing observational study that identified a potential association between bacterial pneumonia and diabetes. Furthermore, MR investigations suggest a reciprocal causal relationship between bacterial pneumonia and gestational diabetes mellitus(GDM), and a plausible causal link between bacterial pneumonia and T1DM. Background Previous observational studies have established the high prevalence of bacterial pneumonia in diabetic patients, which in turn leads to increased mortality. However, the presence of a causal connection between bacterial pneumonia and diabetes remains unobserved. Methods We chose genome-wide significant (Ρ < 1 × 10−5 and Ρ < 1 × 10−6) and independent (r2 < 0.001) single-nucleotide polymorphisms (SNPs) as instrumental variables (IVs) to proceed a bidirectional two-sample MR study. The extracted SNPs explored the relationship between bacterial pneumonia and diabetes by Inverse variance weighted (IVW), MR-Egger, and weighted median methods. In addition, we conducted the Heterogeneity test, the Pleiotropy test, MR-presso and the Leave-one-out (LOO) sensitivity test to validate the reliability of results. Results In an MR study with bacterial pneumonia as an exposure factor, four different types of diabetes as outcome. It was observed that bacterial pneumonia increases the incidence of GDM (OR = 1.150 (1.027–1.274, P = 0.011) and T1DM (OR = 1.277 (1.024–1.531), P = 0.016). In the reverse MR analysis, it was observed that GDM (OR = 1.112 (1.023–1.201, P = 0.009) is associated with an elevated risk of bacterial pneumonia. However, no significant association was observed bacterial pneumonia with T1DM and other types of diabetes (P > 0.05). Conclusion This study utilizing MR methodology yields robust evidence supporting a bidirectional causal association between bacterial pneumonia and GDM. Furthermore, our findings suggest a plausible causal link between bacterial pneumonia and T1DM.

Abstract: ABSTRACT In recent years, the number of studies on islet and beta cell autophagy have substantially increased due to growing interest in the role of autophagy in maintaining cellular homeostasis in diabetes. In type 2 diabetes, human islet amyloid polypeptide (hIAPP) aggregates to form higher structure oligomers and fibrils that are toxic to beta cells and induce islet inflammation. The primary mechanism of oligomer and fibril clearance in beta cells is through the autophagic pathway, a process that is impaired in type 2 diabetes. Thus, toxic oligomeric and fibrillar forms of hIAPP accumulate in type 2 diabetic islets. Recently, Kim et al. characterized the ability of a small molecule autophagy enhancer, MSL-7, to clear hIAPP oligomers in mice expressing hIAPP. Herein, we outline the primary findings of the study, limitations, and future directions to further investigate the therapeutic potential of autophagy enhancers to treat diabetes.

Abstract: Of the β-cell signaling pathways altered by obesity and insulin resistance, some are adaptive while others contribute to β-cell failure. Two critical second messengers are Ca2+ and cAMP, which control the timing and amplitude of insulin secretion. Previous work has shown the importance of the cAMP-inhibitory Prostaglandin EP3 receptor (EP3) in mediating the β-cell dysfunction of type 2 diabetes (T2D). Here, we used three groups of C57BL/6J mice as a model of the progression from metabolic health to T2D: wildtype, normoglycemic LeptinOb (NGOB), and hyperglycemic LeptinOb (HGOB). Robust increases in β-cell cAMP and insulin secretion were observed in NGOB islets as compared to wildtype controls; an effect lost in HGOB islets, which exhibited reduced β-cell cAMP and insulin secretion despite increased glucose-dependent Ca2+ influx. An EP3 antagonist had no effect on β-cell cAMP or Ca2+ oscillations, demonstrating agonist-independent EP3 signaling. Finally, using sulprostone to hyperactivate EP3 signaling, we found EP3-dependent suppression of β-cell cAMP and Ca2+ duty cycle effectively reduces insulin secretion in HGOB islets, while having no impact insulin secretion on NGOB islets, despite similar and robust effects on cAMP levels and Ca2+ duty cycle. Finally, increased cAMP levels in NGOB islets are consistent with increased recruitment of the small G protein, Rap1GAP, to the plasma membrane, sequestering the EP3 effector, Gɑz, from inhibition of adenylyl cyclase. Taken together, these results suggest that rewiring of EP3 receptor-dependent cAMP signaling contributes to the progressive changes in β cell function observed in the LeptinOb model of diabetes.

Abstract: ABSTRACT Type 2 diabetes mellitus (T2D) affects 463 million individuals worldwide. β-cell dysfunction and relatively inadequate β-cell mass has been implicated in the pathogenesis of T2D. Primary human islets from T2D patients can reveal the islet dysfunction and the underlying mechanisms and thus have become valued resources for diabetes research. Our center (Human Islet Resource Center, China) has prepared a number of batches of human islets from T2D organ donors. The present study aims to characterize islet isolation processes, islet yields, and qualities of T2D pancreases by comparing with non-diabetic (ND) ones. Overall, 24 T2D and 80 ND pancreases were obtained with informed research consents. The digestion time, islet purity, yield, size distribution, islet morphology score, viability, and function in each islet preparation were analyzed. We found that at digestion stage, T2D pancreases need significantly longer digestion duration and have worse digestion rates and lower gross islet yields. At purification stage, T2D pancreases have poorer purity, purification rate, morphology score, and islet yields after purification. Functional evaluation by GSI assay showed that the human T2D islets have significantly lower glucose stimulated insulin secretion ability. In conclusion, the features of longer digestion duration, lower yields and quality, and impaired insulin secretion in T2D group are consistent with the pathological condition of this disease. Both islet yields and islet function evaluation results did not support human T2D islets as clinical transplantation resources. However, they could serve as good research models for T2D disease studies and promote the advancement of diabetes research.

Abstract: ABSTRACT Background Patients with chronic pancreatitis (CP) often have severe and intractable abdominal pain, leading to decreased quality of life (QOL), inability to work or attend school, and increased health care costs due to repeated emergency room visits and hospitalizations. Methods We evaluated the efficacy of total pancreatectomy and islet autotransplantation (TPIAT) in terms of pain control and QOL in CP patients treated at our center in Japan. To evaluate QOL, we used the Short-Form 36 Health Survey version 2 (SF-36v2® Standard, Japanese), European Organization for Research and Treatment of Cancer Quality of Life Questionnaire Core 30 (EORTC QLQ-C30), and Quality of Life Questionnaire-Pancreatic Modification (QLQ-PAN28). Results Between August 2016 and June 2019, we performed this procedure in 5 patients. All patients were followed up for 12 months and all transplanted islets were still functioning at the 1-year follow-up. The major adverse events were abdominal wall hemorrhage, intestinal obstruction, intra-abdominal abscess, and abdominal pain requiring hospitalization; no case had sequelae. No major complications were due to islet transplantation. Pain scores improved postoperatively in all patients. Three QOL item dimensions role-physical (p = 0.03125), general health perception (p = 0.03125) and vitality (p = 0.03125) in the SF-36 were significantly improved 12 months after TPIAT. Mean values of many other QOL items improved, though not significantly. Conclusion The QOL improvement after TPIAT for CP suggests its effectiveness in the Japanese population.

Abstract: ABSTRACT Targeting β-cell failure could prevent, delay or even partially reverse Type 2 diabetes. However, development of such drugs is limited as the molecular pathogenesis is complex and incompletely understood. Further, while β-cell failure can be modeled experimentally, only some of the molecular changes will be pathogenic. Therefore, we used a novel approach to identify molecular pathways that are not only changed in a diabetes-like state but also are reversible and can be targeted by drugs. INS1E cells were cultured in high glucose (HG, 20 mM) for 72 h or HG for an initial 24 h followed by drug addition (exendin-4, metformin and sodium salicylate) for the remaining 48 h. RNAseq (Illumina TruSeq), gene set enrichment analysis (GSEA) and pathway analysis (using Broad Institute, Reactome, KEGG and Biocarta platforms) were used to identify changes in molecular pathways. HG decreased function and increased apoptosis in INS1E cells with drugs partially reversing these effects. HG resulted in upregulation of 109 pathways while drug treatment downregulated 44 pathways with 21 pathways in common. Interestingly, while hyperglycemia extensively upregulated metabolic pathways, they were not altered with drug treatment, rather pathways involved in the cell cycle featured more heavily. GSEA for hyperglycemia identified many known pathways validating the applicability of our cell model to human disease. However, only a fraction of these pathways were downregulated with drug treatment, highlighting the importance of considering druggable pathways. Overall, this provides a powerful approach and resource for identifying appropriate targets for the development of β-cell drugs.

Abstract: ABSTRACT We previously developed a deep learning-based web service (IsletNet) for an automated counting of isolated pancreatic islets. The neural network training is limited by the absent consensus on the ground truth annotations. Here, we present a platform (IsletSwipe) for an exchange of graphical opinions among experts to facilitate the consensus formation. The platform consists of a web interface and a mobile application. In a small pilot study, we demonstrate the functionalities and the use case scenarios of the platform. Nine experts from three centers validated the drawing tools, tested precision and consistency of the expert contour drawing, and evaluated user experience. Eight experts from two centers proceeded to evaluate additional images to demonstrate the following two use case scenarios. The Validation scenario involves an automated selection of images and islets for the expert scrutiny. It is scalable (more experts, images, and islets may readily be added) and can be applied to independent validation of islet contours from various sources. The Inquiry scenario serves the ground truth generating expert in seeking assistance from peers to achieve consensus on challenging cases during the preparation for IsletNet training. This scenario is limited to a small number of manually selected images and islets. The experts gained an opportunity to influence IsletNet training and to compare other experts’ opinions with their own. The ground truth-generating expert obtained feedback for future IsletNet training. IsletSwipe is a suitable tool for the consensus finding. Experts from additional centers are welcome to participate.

Abstract: ABSTRACT Background: Intrauterine chronic hypoxia (ICH) can lead to pancreatic dysmetabolism in offspring. This study aimed to determine the changes in islet function of offspring through a rat ICH model and detect the factors affecting islet function. Methods: Twenty couples of healthy Sprague – Dawley adult rats were randomly mated, and the pregnant rats were randomly allocated to ICH and normal control (NC) groups. Pregnant rats in the ICH group were placed in a hypoxic chamber with 13% oxygen concentration for hypoxia treatment twice a day for 4 h until delivery at 21 days. NC group is inlet with normal air from beginning to end. After delivery, blood was taken from the heart of pregnant rats for blood gas analysis. The weight of the offspring rats was measured at 12 h after birth and 16 weeks after birth. At 16 weeks, the immunohistochemical results of β-cell total, islet area, insulin (INS), and glucose transporter 2 (GLUT2) proteins were obtained from the islets. The mRNA data of INS and pancreatic and duodenal homeobox 1 (PDX-1) genes were obtained from pancreas. Results: We found the β-cell total, islet area, and the positive cell area of INS and GLUT2 of offspring rats in ICH group were lower than those of NC group, while the levels of INS and PDX-1 genes were higher in ICH group than in NC group. Conclusions: ICH can lead to islet hypoplasia in adult male offspring rats. However, this is within the compensatory range.

Abstract: ABSTRACT Previous studies indicated that ductal cells can contribute to endocrine neogenesis in adult rodents after alpha cells convert into beta cells. This can occur through Pax4 mis-expression in alpha cells or through long-term administration of gamma-aminobutyric acid (GABA) to healthy mice. GABA has also been reported to increase the number of beta cells through direct effects on their proliferation, but only in specific genetic mouse backgrounds. To test whether GABA induces neogenesis of beta cells from ductal cells or affects pancreatic cell proliferation, we administered GABA or saline over 2 or 6 months to Sox9CreER;R26RYFP mice in which 60–80% of large or small ducts were efficiently lineage labeled. We did not observe any increases in islet neogenesis from ductal cells between 1 and 2 months of age in saline treated mice, nor between 2 and 6 months of saline treatment, supporting previous studies indicating that adult ductal cells do not give rise to new endocrine cells during homeostasis. Unlike previous reports, we did not observe an increase in beta cell neogenesis after 2 or 6 months of GABA administration. Nor did we observe a significant increase in the pancreatic islet area, the number of insulin and glucagon double positive cells, or cell proliferation in the pancreas. This indicates that the effect of long term GABA administration on the pancreas is minimal or highly context dependent.

Abstract: ABSTRACT The following review focuses on the scientific studies related to the role of endocannabinoid system (ECS) in pancreatic islet physiology and dysfunction. Different natural or synthetic agonists and antagonists have been suggested as an alternative treatment for diabetes, obesity and metabolic syndrome. Therapeutic use of Cannabis led to the discovery and characterization of the ECS, a signaling complex involved in regulation of various physiological processes, including food intake and metabolism. After the development of different agonists and antagonists, evidence have demonstrated the presence and activity of cannabinoid receptors in several organs and tissues, including pancreatic islets. Insulin and glucagon expression, stimulated secretion, and the development of diabetes and other metabolic disorders have been associated with the activity and modulation of ECS in pancreatic islets. However, according to the animal model and experimental design, either endogenous or pharmacological ligands of cannabinoid receptors have guided to contradictory and paradoxical results that suggest a complex physiological interaction. In consensus, ECS activity modulates insulin and glucagon secretions according to glucose in media; over-stimulation of cannabinoid receptors affects islets negatively, leading to glucose intolerance, meanwhile the treatment with antagonists in diabetic models and humans suggests an improvement in islets function.