Pancreatic Islet Β-cells Research Articles

Deconstructing the integrated oscillator model for pancreatic [formula omitted]-cells

Electrical bursting oscillations in the β-cells of pancreatic islets have been a focus of investigation for more than fifty years. This has been aided by mathematical models, which are descendants of the pioneering Chay–Keizer model. This article describes the key biophysical and mathematical elements of this model, and then describes the path forward from there to the Integrated Oscillator Model (IOM). It is both a history and a deconstruction of the IOM that describes the various elements that have been added to the model over time, and the motivation for adding them. Finally, the article is a celebration of the 40th anniversary of the publication of the Chay–Keizer model.

Identification of quality markers for Cyanotis arachnoidea and analysis of its physiological mechanism based on chemical pattern recognition, network pharmacology, and experimental validation.

Cyanotis arachnoidea C. B. Clarke is a traditional Chinese medicinal herb that has a limited clinical use in the treatment of diabetes mellitus (DM) in minority areas of Guizhou in China. However, few prior reports are available on the quality control of Cyanotis arachnoidea, and its quality markers and hypoglycemic mechanism are still unclear. The purpose of this study is to explore the quality markers (Q-markers) of Cyanotis arachnoidea and predict its hypoglycemic mechanism. In this study, ultra-high-performance liquid chromatography (UHPLC) fingerprint combined with chemical pattern recognition were performed, and four differential components were screened out as quality markers, including 20-Hydroxyecdysone, 3-O-acetyl-20-hydroxyecdysone, Ajugasterone C, and 2-O-acetyl-20-hydroxyecdysone. Network pharmacology analysis revealed 107 therapeutic target genes of Cyanotis arachnoidea in DM treatment, and the key targets were Akt1, TNF, IL-6, MAPK3, and JUN. The hypoglycemic mode of action of Cyanotis arachnoidea may be mediated by tumor necrosis factor (TNF) signaling, cancer, insulin resistance, and JAK-STAT pathways. Molecular docking analysis disclosed that the foregoing quality markers effectively bound their key target genes. An in vitro experiment conducted on pancreatic islet β-cells indicated that the forenamed active components of Cyanotis arachnoidea had hypoglycemic efficacy by promoting PI3K/Akt and inhibiting MAPK signaling. UHPLC also accurately quantified the quality markers. The identification and analysis of quality markers for Cyanotis arachnoidea is expected to provide references for the establishment of a quality control evaluation system and clarify the material basis and hypoglycemic mechanisms of this traditional Chinese medicine (TCM).

Analysis of an antioxidative defence system of hydrogen peroxide-treated pancreatic islet-derived 1.1B4 cells and siRNA targeting NR4A3-treated cells by microarray

ABSTRACTPancreatic islet β-cells weaken under oxidative stress. In this study, human pancreatic islet-derived 1.1B4 cells were exposed to H2O2 and analysed using a human microarray, which revealed that heme oxygenase 1 (HMOX1), glutamate-cysteine ligase, early growth response 1, nuclear receptor subfamily 4 group A member 3 (NR4A3) and jun B proto-oncogene were upregulated, whereas superoxide dismutase 1 and catalase were not. Expression of NR4A3 rapidly increased after H2O2 addition, and the 1.1B4 cells treated with siRNA targeting NR4A3 became sensitive to H2O2; further, HMOX1 expression was strongly inhibited, suggesting that NR4A3 is an oxidative stress-responsive transcription factor that functions through HMOX1 expression in pancreatic islet β-cells. Expression of cyclin E1 and cyclin-dependent kinase 1 was also inhibited by siRNAs targeting NR4A3.

Genetic ablation of synaptotagmin-9 alters tomosyn-1 function to increase insulin secretion from pancreatic β-cells improving glucose clearance.

Stimulus-coupled insulin secretion from the pancreatic islet β-cells involves the fusion of insulin granules to the plasma membrane (PM) via SNARE complex formation-a cellular process key for maintaining whole-body glucose homeostasis. Less is known about the role of endogenous inhibitors of SNARE complexes in insulin secretion. We show that an insulin granule protein synaptotagmin-9 (Syt9) deletion in mice increased glucose clearance and plasma insulin levels without affecting insulin action compared to the control mice. Upon glucose stimulation, increased biphasic and static insulin secretion were observed from ex vivo islets due to Syt9 loss. Syt9 colocalizes and binds with tomosyn-1 and the PM syntaxin-1A (Stx1A); Stx1A is required for forming SNARE complexes. Syt9 knockdown reduced tomosyn-1 protein abundance via proteasomal degradation and binding of tomosyn-1 to Stx1A. Furthermore, Stx1A-SNARE complex formation was increased, implicating Syt9-tomosyn-1-Stx1A complex is inhibitory in insulin secretion. Rescuing tomosyn-1 blocked the Syt9-knockdown-mediated increases in insulin secretion. This shows that the inhibitory effects of Syt9 on insulin secretion are mediated by tomosyn-1. We report a molecular mechanism by which β-cells modulate their secretory capacity rendering insulin granules nonfusogenic by forming the Syt9-tomosyn-1-Stx1A complex. Altogether, Syt9 loss in β-cells decreases tomosyn-1 protein abundance, increasing the formation of Stx1A-SNARE complexes, insulin secretion, and glucose clearance. These outcomes differ from the previously published work that identified Syt9 has either a positive or no effect of Syt9 on insulin secretion. Future work using β-cell-specific deletion of Syt9 mice is key for establishing the role of Syt9 in insulin secretion.

Oral nano-formulation improves pancreatic islets dysfunction via lymphatic transport for antidiabetic treatment.

Type 2 diabetes mellitus (T2DM) therapy is facing the challenges of long-term medication and gradual destruction of pancreatic islet β-cells. Therefore, it is timely to develop oral prolonged action formulations to improve compliance, while restoring β-cells survival and function. Herein, we designed a simple nanoparticle with enhanced oral absorption and pancreas accumulation property, which combined apical sodium-dependent bile acid transporter-mediated intestinal uptake and lymphatic transportation. In this system, taurocholic acid (TCA) modified poly(lactic-co-glycolic acid) (PLGA) was employed to achieve pancreas location, hydroxychloroquine (HCQ) was loaded to execute therapeutic efficacy, and 1,2-dilauroyl-sn-glycero-3-phosphocholine (DLPC) was introduced as stabilizer together with synergist (PLGA-TCA/DLPC/HCQ). Invitro and invivo results have proven that PLGA-TCA/DLPC/HCQ reversed the pancreatic islets damage and dysfunction, thus impeding hyperglycemia progression and restoring systemic glucose homeostasis via only once administration every day. In terms of mechanism PLGA-TCA/DLPC/HCQ ameliorated oxidative stress, remodeled the inflammatory pancreas microenvironment, and activated PI3K/AKT signaling pathway without obvious toxicity. This strategy not only provides an oral delivery platform for increasing absorption and pancreas targetability but also opens a new avenue for thorough T2DM treatment.

The role of GLUT2 in glucose metabolism in multiple organs and tissues.

The glucose transporter family has an important role in the initial stage of glucose metabolism; Glucose transporters 2 (GLUTs, encoded by the solute carrier family 2, SLC2A genes) is the major glucose transporter in β-cells of pancreatic islets and hepatocytes but is also expressed in the small intestine, kidneys, and central nervous system; GLUT2 has a relatively low affinity to glucose. Under physiological conditions, GLUT2 transports glucose into cells and allows the glucose concentration to reach balance on the bilateral sides of the cellular membrane; Variation of GLUT2 is associated with various endocrine and metabolic disorders; In this study, we discussed the role of GLUT2 in participating in glucose metabolism and regulation in multiple organs and tissues and its effects on maintaining glucose homeostasis.

88-OR: Targeted Drug Delivery to Human ß-Cells Using Novel Nanocapsule Delivery Vehicle for T1D Treatment

In type 1 diabetes (T1D), autoreactive immune cells destroy insulin secreting β-cells in pancreatic islets. Islet transplantation shows promise in restoring glucose homeostasis without exogenous insulin; however, long-term graft survival remains a critical barrier to the success of this treatment. Therapies aimed to protect or proliferate endogenous β-cells have off target affects and require targeted delivery to improve efficacy. We have developed a nanocapsule (NC) delivery system to specifically target and deliver cargo to human β-cells. We hypothesize NCs will selectively be taken up by human β-cells and deliver therapeutic cargo. NCs were synthesized with a water in oil emulsion evaporation technique. NCs were coated via ionic interactions with ectonucleoside triphosphate diphosphohydrolase 3 (ENTPD3) antibody, a human β-cell specific marker or Exendin-4 conjugated to hyaluronic acid (HA-Ex4). NC size, size distribution, charge, stability, and drug release profiles were determined. NCs loaded with pentamidine (PTM) or Cy5 were cultured for 24-168h with human iPSC-derived β-cells (sBC) or injected into the tail vein of NOD-SCID mice. Confocal microscopy confirmed delivery of cargo to β-cells and pancreatic islets, viability, and cytotoxicity. NCs were 271 ± 7nm in size with excellent size homogeneity (polydispersity index 0.06 ± 0.03, n=3). NCs displayed a sustained release of cargo for >45 days (n=5). In vitro, we observed no cytotoxicity of NCs up to 168h (n=3) and a significant increase in β-cell death with PTM loaded ENTPD3 coated NCs compared to controls at 24 (p<0.001, n=4) and 72h (p<0.01, n=4). sBCs treated with PTM loaded ENTPD3 coated NCs had more insulin+ dead cells (88 ± 4%) than controls (p<0.01, n=4). ENTPD3 or HA-Ex4 NCs were internalized into sBCs in vitro and pancreatic islets in vivo respectively. Our data shows long term stability and in vivo targeting of NCs to β-cells and supports use of our NCs for targeted delivery of therapeutics to human β-cells to treat T1D. Disclosure J.Collins: None. K.Holcomb: None. A.Ocampo: None. A.Shilleh: None. H.A.Russ: Advisory Panel; Sigilon Therapeutics, Inc., Consultant; Prellis, Minutia, Eli Lilly and Company. N.L.Farnsworth: None. Funding JDRF (1-INO-2022-1231-S-B); National Institutes of Health (P30-DK116073)

1779-P: Lipotoxicity-Induced Beta-Cell Small Extracellular Vesicles Promote Beta-Cell Functional Failure through Activation of the TGFß/Smad3 Pathway

Lipotoxicity is a pathological process that occurs in several metabolic disorders including obesity-driven Type 2 diabetes (T2D). Chronically elevated circulating free fatty acids have been shown to exert detrimental effects on pancreatic islet β-cells through reduced glucose-stimulated insulin secretion (GSIS), alterations in β-cell transcriptional identity, and apoptosis. β-cell-derived small extracellular vesicles (sEV) have been shown to contribute to β-cell failure in T2D, however their role in lipotoxicity-mediated β-cell failure has yet to be elucidated. We hypothesize that lipotoxicity-induced β-cell functional failure is mediated in part by aberrant release of altered β-cell-derived sEV. To test this, MIN6 β-cells were exposed to free fatty acid, palmitate (PAL) (0.5 mM, 24h) and EV were isolated using differential ultracentrifugation to yield PAL EV (vs. control (CTL) EV). β-cell functional assessment using GSIS on mouse islets exposed to PAL EV (48h) resulted in significant suppression of GSIS (~80% decrease in stimulation index). RNA-Seq was conducted on islets exposed to PAL EV (vs. untreated (UT)). De novo motif analysis from this data identified enriched transcription factor binding motifs associated with several SMAD genes in TGFβ signaling. Gene Set Enrichment Analysis revealed significant enrichment of genes associated with TGFβ receptor binding suggesting its potential role in lipotoxic β-cell EV-mediated β-cell failure. To confirm, analysis of p-Smad3 expression was conducted by immunofluorescence staining on mouse islets exposed to PAL EV (48h; vs. UT). The results showed an ~60-fold increase in β-cell p-Smad3 expression (p<.05). Moreover, mouse islets were treated with a TGFβ receptor inhibitor in the presence of PAL EV (48h; vs. UT). GSIS results showed a significant improvement in β-cell function (p<.05) suggesting the role of the TGFβ/Smad3 pathway in lipotoxic β-cell sEV induced β-cell failure. Disclosure A.Roy: None. A.Hoff: None. T.K.Her: None. K.Sankaran rajagopalan: None. D.D.Maltais: None. A.Matveyenko: None. N.Javeed: None. Funding National Institute of Diabetes and Digestive and Kidney Diseases (DK129208-01); JDRF (2-SRA-2022-1272-S-B)

1488-P: Reduced iPLA2b Expression in T-Lymphocytes Decreases Proinflammatory Eicosanoid Production and Cytokine Secretion Delaying Type 1 Diabetes Development in NOD Mice

Type 1 diabetes (T1D) is characterized by the destruction of insulin-producing pancreatic islet β-cells, but the causes of this process remain unclear. We find that Ca2+-independent phospholipase A2β (iPLA2β), which hydrolyzes membrane phospholipids at the sn-2 substituent to yield iPLA2β-derived lipids (iDLs), is induced under a diabetic milieu and mitigation of iPLA2β activity attenuates β-cell death. Several iDLs are pro-inflammatory and have been studied in different diseases but are not understood in diabetes. We investigated the role of immune-cell iDLs by utilizing T-cell adoptive transfer. Isolated CD4+/8+ T-cells from splenocytes prepared from donor female NOD and NOD. iPLA2β+/− (HET) mice, were transferred i.p. to NOD.scid recipient mice. We observed T1D onset for all T-cell recipient groups between 10-12 weeks of age. However, reduction of iPLA2β in CD4/8 T-cells delayed 50% incidence by 10 weeks in NOD4/HET8-recipient mice and HET4/NOD8 T-cell recipients compared to “matched” T-cell recipients. Furthermore, reduced insulitis and increased β-cell preservation was detected in HET4/NOD8-recipients compared to NOD4/8 recipients. The immune cell composition between our genotypes revealed no difference suggesting iDL signaling contributes to the observed incidence. Lipidomic analyses revealed a decrease in pro-inflammatory eicosanoids (PGs, DHETs and HETEs) in nondiabetic recipient mice, compared to diabetic counterparts. In addition, by targeting select eicosanoid signaling (PGE2 and DHET) utilizing chemical inhibitors (i.e., Grapiprant (EP4 receptor antagonist) and EC5026 (soluble epoxide hydrolase inhibitor)), we observed decreased IFN-γ production by Th1 helper cells in HET donors compared to NOD. These findings suggest that iPLA2β in T-cells is a critical contributor to the production of pro-inflammatory iDLs and could be a potential target in reducing T1D development. Disclosure T. White: None. S. Ramanadham: None. T.P. DiLorenzo: None. C.E. Chalfant: None. Funding National Institute of Diabetes and Digestive and Kidney Diseases (R01DK069455); National Institute of Allergy and Infectious Diseases (R21AI146743, R21AI169214); JDRF (2-SRA-2022-1210-S-B); University of Alabama at Birmingham (5T32GM8111-34)

295-LB: Pancreatic Peroxisomes Are Required for Physiological Regulation of Insulin Secretion and Maintenance of Normal Glucose Tolerance in Male Mice

The regulation of glucose-stimulated insulin secretion (GSIS) is central to maintenance of glucose disposal. The role of lipid storage and lipid oxidation to regulate pancreatic islet β-cell insulin secretion is not completely understood. Peroxisomes are enriched in insulin-producing β-cells, but their contribution to β-cell function and maturity is lacking. Therefore, we generated a novel model of peroxisomal dysfunction to test the hypothesis that peroxisomal lipid metabolism is required to prevent a hyperlipidemic environment that interferes with β-cell function and maturity. Pex5 plays a critical role in importing the majority of peroxisomal proteins into the peroxisomal matrix; thus, deletion of the Pex5 gene creates a cellular environment with reductions in function of this organelle. In this study, we bred Pex5 mice on a C57BL/6J background containing ‘floxed’ alleles to Pdx1-cre mice to generate offspring with a pancreas-wide deficiency in Pex5 expression and abundance. Glucose tolerance was impaired by 12 weeks in male mice (n=20; AUC p<0.05). Surprisingly, GSIS was elevated in Pex5Pdx1-/- mice compared to littermate controls both in vivo (n=15; AUC p<0.05) and ex vivo in isolated islets as measured by perifusion analysis (n=12; AUC p<0.01). We further found that a subset of β-cells from Pex5Pdx1-/- mice expressed the de-differentiation marker Aldh1a3, while a subset of β-cells showed reductions in MafA and Nkx6.1 staining compared to controls. Perilipin-1 staining showed increased presence of lipid droplets in pancreatic tissue of Pex5Pdx1-/- mice versus controls. Thus, pancreatic deletion of peroxisomal function results in increased lipid storage in pancreatic tissue that is correlated with exaggerated insulin secretion. Collectively, these data are in support of a model whereby peroxisomal function supports β-cell insulin secretion and maintenance of the fully differentiated state. Disclosure S. Burke: None. S. Ghosh: None. D. Burk: None. R. Noland: None. J. Collier: None.

Decellularized bladder as scaffold to support proliferation and functionality of insulin-secreting pancreatic cells.

Loss in the number or function of insulin-producing β-cells in pancreatic islets has been associated with diabetes mellitus. Although islet transplantation can be an alternative treatment, complications such as apoptosis, ischaemia and loss of viability have been reported. The use of decellularized organs as scaffolds in tissue engineering is of interest owing to the unique ultrastructure and composition of the extracellular matrix (ECM) believed to act on tissue regeneration. In this study, a cell culture system has been designed to study the effect of decellularized porcine bladder pieces on INS-1 cells, a cell line secreting insulin in response to glucose stimulation. Porcine bladders were decellularized using two techniques: a detergent-containing and a detergent-free methods. The resulting ECMs were characterized for the removal of both cells and dsDNA. INS-1 cells were not viable on ECM produced using detergent (i.e., sodium dodecyl sulfate). INS-1 cells were visualized following 7 days of culture on detergent-free decellularized bladders using a cell viability and metabolism assay (MTT) and cell proliferation quantified (CyQUANT™ NF Cell Proliferation Assay). Further, glucose-stimulated insulin secretion and immunostaining confirmed that cells were functional in response to glucose stimulation, as well as they expressed insulin and interacted with the detergent-free produced ECM, respectively.

Membrane protease prostasin promotes insulin secretion by regulating the epidermal growth factor receptor pathway

Prostasin (PRSS8) is a serine protease that metabolizes and moderates the effect of specific substrates. Epidermal growth factor receptor (EGFR), which modulates insulin secretion and pancreatic β-cell proliferation, is regulated via proteolytic shedding by PRSS8. We first detected PRSS8 expression in β-cells of pancreatic islets of mice. To better understand the molecular processes involved in PRSS8-associated insulin secretion, pancreatic β-cell-specific PRSS8 knockout (βKO) and PRSS8-overexpressing (βTG) male mice were generated. We found that glucose intolerance and reduction in glucose-stimulated insulin secretion developed in βKO mice compared with the control subjects. A higher response to glucose was noted in islets retrieved from βTG mice. Erlotinib, a specific blocker of EGFR, blocks EGF- and glucose-stimulated secretion of insulin among MIN6 cells, and glucose improves EGF release from β-cells. After silencing PRSS8 in MIN6 cells, glucose-stimulated insulin secretion decreased, and EGFR signaling was impaired. Conversely, overexpression of PRSS8 in MIN6 cells induced higher concentrations of both basal and glucose-stimulated insulin secretion and increased phospho-EGFR concentrations. Furthermore, short-term exposure to glucose improved the concentration of endogenous PRSS8 in MIN6 cells through inhibition of intracellular degradation. These findings suggest that PRSS8 is involved in glucose-dependent physiological regulation of insulin secretion via the EGF–EGFR signaling pathway in pancreatic β-cells.

The therapeutic mechanism of Yuye decoctionon type 2 diabetes mellitusbasedon network pharmacology and experimental verification.

Yuye decoction (YYD) has been widely used as a folk Chinese herbal formula in clinical treatment of type 2 diabetes mellitus(T2DM) for many years. However, its mechanism is still unclear. The aim of this study was to explore the potential mechanism of YYD against T2DM initially by UHPLC-MS/MS combining with network pharmacology, molecular docking techniques and experimental validation. The main ingredients in the water extract of YYD were initially identified using UHPLC-MS/MS analysis. Combined with network pharmacology and molecular docking techniques, the YYD key compounds-core targets-key signaling pathways network was constructed and the binding activity of key components to core targets was validated. The T2DM rat model was induced by Streptozotocin combined with high glucose and high fat diets. The apoptosis cell model of mouse islet β-cell of Min6 was induced by high-glucose and palmitic acid. Histopathological and immunofluorescence satining were used to evaluate pancreatic islet β-cell function and apoptosis in rats. Min6 cell viability and apoptosis ratio were evaluated by CCK-8 and TUNEL staining. The predicted targets and pathways were validated by experiments in vitro and in vivo. The 56 compounds from YYD were identified by UHPLC-MS/MS. The potential targets of the above compounds were predicted by online compound target database, among of which 362 targets were associated with T2DM. Protein-protein interaction analysis identified the main targets such as SRC, MAPK1, PIK3R1, AKT1, HRAS and HSP90AA1, which were considered as the therapeutic targets of YYD on against T2DM. Functional enrichment analysis revealed that PI3K/AKT, FoxO and apoptosis signaling pathways were significantly enriched. Molecular docking results showed that compounds of monolinolein, neomangiferin, mangiferin, pelargonidin-3-O-glucoside and acacetin from YYD had high binding activities to PIK3R1, AKT1, Sirt1 and FoxO1. Therefore, PI3K/AKT1, Sirt1/FoxO1 and apoptotic signaling pathways were considered as predicted targets for experimental validation study. Animal experiments showed that YYD reduced blood glucose levels, improved pancreatic dysfunction and pancreatic islet β-cells apoptosis in T2DM rats which contributed to the activation of AKT1 and FoxO1 and their related signaling molecules. These results were confirmed in Min6 cell model induced by high-glucose and palmitic acid. In summary, this study systematically visualized the possible therapeutic effects and mechanisms of YYD on T2DM through the network pharmacology approach and experimental study. The results indicated that YYD could prevent pancreatic islet dysfunction and reverse islet of β-cells apoptosis possibly via PI3K/AKT1, Sirt1/FoxO1 signaling pathways.

Discovery of orally effective and safe GPR40 agonists by incorporating a chiral, rigid and polar sulfoxide into β-position to the carboxylic acid.

GPR40 is primarily expressed in pancreatic islet β-cells, and its activation by endogenous ligands of medium to long-chain free fatty acids or synthetic agonists is clinically proved to improve glycemic control by stimulating glucose-dependent insulin secretion. However, most of the reported agonists are highly lipophilic, which might cause lipotoxicity and the off-target effects in CNS. Particularly, the withdrawal of TAK-875 from clinical trials phase III due to liver toxicity concern threw doubt over the long-term safety of targeting GPR40. Improving the efficacy and the selectivity, thus enlarging the therapeutic window would provide an alternative to develop safe GPR40-targeted therapeutics. Herein, by employing an innovative "three-in-one" pharmacophore drug design strategy, the optimal structural features for GPR40 agonist was integrated into one functional group of sulfoxide, which was incorporated into the β-position of the propanoic acid core pharmacophore. As a result, the conformational constraint, polarity as well as chirality endowed by the sulfoxide significantly enhanced the efficacy, selectivity and ADMET properties of the novel (S)- 2-(phenylsulfinyl)acetic acid-based GPR40 agonists. The lead compounds (S)-4a and (S)-4s exhibited robust plasma glucose-lowering effects and insulinotropic action during an oral glucose tolerance test in C57/BL6 mice, excellent pharmacokinetic profile and little hepatobiliary transporter inhibition, marginal cell toxicities against human primary hepatocyte at 100μM.

Identification of Heterophilic Epitopes of H1N1 Influenza Virus Hemagglutinin

Our previous studies found that the H1-50 monoclonal antibody (mAb) of influenza A virus hemagglutinin (HA) cross-reacted with pancreatic tissue and islet β-cells, and further studies showed that H1-50 mAb binds to prohibitin (PHB) protein of islet β-cells. These suggest that there are heterophilic epitopes between influenza virus HA and pancreatic tissue, which may be involved in the pathogenesis of type 1 diabetes. To further investigate these heterophilic epitopes, we screened binding epitopes of H1-50 mAb using a phage 12-peptide library. DNA sequencing and comparative analysis were performed on specific positive phage clones, and the sequence of 12-peptide binding to H1-50 mAb was obtained. The binding epitopes of H1-50 mAb in influenza virus HA were determined by sequence analysis and experimental verification, and their distribution within the three-dimensional structure was assessed by PyMOL. The results showed that H1-50 mAb specifically binds to polypeptides (306-SLPFQNIHPITIGK-319) of influenza A virus HA, located in the stem of the HA protein. However, there is no specific binding sequence between H1-50 mAb and the PHB protein of islet β-cells in the primary structure, and we speculate that the binding of H1-50 mAb to islet β-cells may depend on the spatial conformation. The identification of the heterophilic epitopes of H1N1 influenza virus hemagglutinin provides a new perspective on type 1 diabetes that may be caused by influenza virus infection, which may contribute to the prevention and control of influenza.

Small molecule glucagon release inhibitors with activity in human islets.

Type 1 diabetes (T1D) accounts for an estimated 5% of all diabetes in the United States, afflicting over 1.25 million individuals. Maintaining long-term blood glucose control is the major goal for individuals with T1D. In T1D, insulin-secreting pancreatic islet β-cells are destroyed by the immune system, but glucagon-secreting islet α-cells survive. These remaining α-cells no longer respond properly to fluctuating blood glucose concentrations. Dysregulated α-cell function contributes to hyper- and hypoglycemia which can lead to macrovascular and microvascular complications. To this end, we sought to discover small molecules that suppress α-cell function for their potential as preclinical candidate compounds. Prior high-throughput screening identified a set of glucagon-suppressing compounds using a rodent α-cell line model, but these compounds were not validated in human systems. Here, we dissociated and replated primary human islet cells and exposed them to 24 h treatment with this set of candidate glucagon-suppressing compounds. Glucagon accumulation in the medium was measured and we determined that compounds SW049164 and SW088799 exhibited significant activity. Candidate compounds were also counter-screened in our InsGLuc-MIN6 β-cell insulin secretion reporter assay. SW049164 and SW088799 had minimal impact on insulin release after a 24 h exposure. To further validate these hits, we treated intact human islets with a selection of the top candidates for 24 h. SW049164 and SW088799 significantly inhibited glucagon release into the medium without significantly altering whole islet glucagon or insulin content. In concentration-response curves SW088799 exhibited significant inhibition of glucagon release with an IC50 of 1.26 µM. Given the set of tested candidates were all top hits from the primary screen in rodent α-cells, this suggests some conservation of mechanism of action between human and rodents, at least for SW088799. Future structure-activity relationship studies of SW088799 may aid in elucidating its protein target(s) or enable its use as a tool compound to suppress α-cell activity in vitro.

Comparative effects of xylitol and erythritol on modulating blood glucose; inducing insulin secretion; reducing dyslipidemia and redox imbalance in a type 2 diabetes rat model

Xylitol and erythritol have been reported in numerous previous and recent studies as potential antidiabetic sweeteners, however, it is not certain which one is most effective in this regard. In the present study, the effects of xylitol and erythritol were comparatively investigated on blood glucose, insulin level, dyslipidemia, pancreatic islet morphology and β-cell function, and redox imbalance in a type 2 diabetes (T2D) model of rats. Seven-week-old male Sprague-Dawley rats were randomly divided into 8 groups: Normal Control (NC), Diabetic Control (DC), Diabetic Xylitol 5 % (DX5), Diabetic Xylitol 10 % (DX10), Diabetic Xylitol 20 % (DX20), Diabetic Erythritol 5 % (DE5), Diabetic Erythritol 10 % (DE10), and Diabetic Erythritol 20 % (DE20). T2D was induced in the diabetic groups initially by feeding 10 % fructose solution to induce insulin resistance followed by an intraperitoneal injection of streptozotocin (40 mg/kg body weight) dissolved in citrate buffer (pH 4.5) to induce partial pancreatic β-cells dysfunctions. The animals in NC group were fed with normal drinking water and injected with citrate buffer only. After the confirmation of diabetes, the xylitol and erythritol with above-mentioned concentrations were supplied to the respective animal groups when the animals in NC and DC groups were supplied with normal drinking water. After 8 weeks intervention period, the body weight, fluid and water intake, blood glucose, serum alanine aminotransferase, aspartate aminotransferase, CK-MB and creatinine were significantly decreased, while the serum insulin level, serum lipids, glucose tolerance ability, pancreatic islet morphology and β-cell function, pancreatic and serum redox imbalance were improved in the most xylitol and erythritol fed groups compared to the DC group, when effects were better for xylitol compared to erythritol. The data of this study suggest that xylitol has better antioxidant and antidiabetic effects compared to erythritol. Therefore, xylitol can be used as a preferrable dietary anti-diabetic sweetener or supplement over erythritol for the management of diabetes and its associated complications.

Synchronized proinsulin trafficking reveals delayed Golgi export accompanies β-cell secretory dysfunction in rodent models of hyperglycemia

The pancreatic islet β-cell’s preference for release of newly synthesized insulin requires careful coordination of insulin exocytosis with sufficient insulin granule production to ensure that insulin stores exceed peripheral demands for glucose homeostasis. Thus, the cellular mechanisms regulating insulin granule production are critical to maintaining β-cell function. In this report, we utilized the synchronous protein trafficking system, RUSH, in primary β-cells to evaluate proinsulin transit through the secretory pathway leading to insulin granule formation. We demonstrate that the trafficking, processing, and secretion of the proinsulin RUSH reporter, proCpepRUSH, are consistent with current models of insulin maturation and release. Using both a rodent dietary and genetic model of hyperglycemia and β-cell dysfunction, we show that proinsulin trafficking is impeded at the Golgi and coincides with the decreased appearance of nascent insulin granules at the plasma membrane. Ultrastructural analysis of β-cells from diabetic leptin receptor deficient mice revealed gross morphological changes in Golgi structure, including shortened and swollen cisternae, and partial Golgi vesiculation, which are consistent with defects in secretory protein export. Collectively, this work highlights the utility of the proCpepRUSH reporter in studying proinsulin trafficking dynamics and suggests that altered Golgi export function contributes to β-cell secretory defects in the pathogenesis of Type 2 diabetes.

Human Hematopoietic Stem/Progenitor Cells in Type One Diabetes Mellitus Treatment: Is There an Ideal Candidate?

Type 1 diabetes mellitus (T1DM) is a highly prevalent autoimmune disease causing the destruction of pancreatic islet β-cells. The resulting insulin production deficiency leads to a lifelong need for insulin re-placement therapy, systemic complications, and reduced life quality and expectancy. Cell therapy has been extensively attempted to restore insulin independence (IID), and autologous nonmyeloablative hematopoietic stem cell transplantation (AHST) has appeared to give the most promising results, but with a highly variable quote of patients achieving IID across the studies. We performed a comprehensive review of the trials involving stem cells, and in particular AHST, for the treatment of T1DM. We then pooled the patients enrolled in the different trials and looked for the patient characteristics that could be associated with the achievement of IID. We found a significantly higher probability of achieving IID in older patients (OR 1.17, 95%CI 1.06-1.33, p = 0.002) and a significantly lower probability in patients with a history of ketoacidosis (OR 0.23, 95%CI 0.06-0.78, p = 0.023). This suggests that there could be a population of patients more likely to benefit from AHST, but further data would be required to depict the profile of the ideal candidate.

Revisiting the role of glucagon in health, diabetes mellitus and other metabolic diseases.

Insulin and glucagon exert opposing effects on glucose metabolism and, consequently, pancreatic islet β-cells and α-cells are considered functional antagonists. The intra-islet hypothesis has previously dominated the understanding of glucagon secretion, stating that insulin acts to inhibit the release of glucagon. By contrast, glucagon is a potent stimulator of insulin secretion and has been used to test β-cell function. Over the past decade, α-cells have received increasing attention due to their ability to stimulate insulin secretion from neighbouring β-cells, and α-cell-β-cell crosstalk has proven central for glucose homeostasis in vivo. Glucagon is not only the counter-regulatory hormone to insulin in glucose metabolism but also glucagon secretion is more susceptible to changes in the plasma concentration of certain amino acids than to changes in plasma concentrations of glucose. Thus, the actions of glucagon also include a central role in amino acid turnover and hepatic fat oxidation. This Review provides insights into glucagon secretion, with a focus on the local paracrine actions on glucagon and the importance of α-cell-β-cell crosstalk. We focus on dysregulated glucagon secretion in obesity, non-alcoholic fatty liver disease and type 2 diabetes mellitus. Lastly, the future potential of targeting hyperglucagonaemia and applying dual and triple receptor agonists with glucagon receptor-activating properties in combination with incretin hormone receptor agonism is discussed.