Human Pancreatic Beta Cells Research Articles

2164-P: Paired Box 6 Modulates Pancreatic Beta-Cell Insulin Secretion through Regulation of Munc18-1/2 Expression: Involvement of CREB Signaling

The Paired box 6 (PAX6) transcription factor is crucial for normal pancreatic islet development and function. Heterozygous mutations of PAX6 are associated with impaired insulin secretion and early-onset diabetes mellitus in human. Previous studies demonstrated that PAX6 plays critical roles in insulin biosynthesis, glucose-sensing and glucose-induced ATP synthesis (the proximal signaling of insulin secretion). Yet the molecular mechanism of PAX6 in controlling beta-cell insulin secretion, especially the involvement of distal signaling, remains ambiguous. This study investigated the regulatory role of PAX6 in exocytotic proteins, the core components of distal signaling of insulin secretion, by using human pancreatic beta-cell line EndoC-bH1. The correlation between PAX6 and type 2 diabetes mellitus (T2DM)-associated beta-cell dysfunction was also assessed. Loss-of-function and gain-of-function studies showed that PAX6 positively regulated the expression of exocytotic proteins Munc18-1 and Munc18-2 in beta-cells by modulating the activity of cAMP response element-binding protein (CREB). The PAX6/CREB/Munc18-1/2 axis in turn controlled glucose-stimulated insulin secretion. On the other hand, EndoC-bH1 cells under diabetic condition displayed diminished PAX6 expression, blunted CREB phosphorylation and Munc18-1/2 down-regulation which were rescued by PAX6 overexpression. We conclude that PAX6 regulates distal signaling of insulin secretion through CREB/Munc18-1/2 axis; while maintenance of normal PAX6 expression or activity in human beta-cells may serve as a promising strategy in preserving beta-cell function and delaying the onset of T2DM. Disclosure W. So: None. W. Han: None. Funding National Medical Research Council of Australia

The Effect of Wnt Pathway Modulators on Human iPSC-Derived Pancreatic Beta Cell Maturation.

Current published protocols for targeted differentiation of human stem cells toward pancreatic β-cells fail to deliver sufficiently mature cells with functional properties comparable to human islet β-cells. We aimed to assess whether Wnt-modulation could promote the final protocol stages of β-cell maturation, building our hypothesis on our previous findings of Wnt activation in immature hiPSC-derived stage 7 (S7) cells compared to adult human islets and with recent data reporting a link between Wnt/PCP and in vitro β-cell maturation. In this study, we stimulated canonical and non-canonical Wnt signaling in hiPSC-derived S7 cells using syntetic proteins including WNT3A, WNT4, WNT5A and WNT5B, and we inhibited endogenous Wnt signaling with the Tankyrase inhibitor G007-LK (TKi). Whereas neither canonical nor non-canonical Wnt stimulation alone was able to mature hiPSC-derived S7 cells, WNT-inhibition with TKi increased the fraction of monohormonal cells and global proteomics of TKi-treated S7 cells showed a proteomic signature more similar to adult human islets, suggesting that inhibition of endogenous Wnt contributes toward final β-cell maturation.

Studies of cell surface and soluble HLA class I expression in pancreatic beta cells exposed to interferons or Poly I:C

HLA class I (HLA-I) molecules play a crucial role in cell-mediated immunity by presenting peptide antigens to cytotoxic CD8+T cells. A pathological hallmark of Type 1 diabetes (T1D) is the hyperexpression of HLA-I in pancreatic islets that contain residual insulin producing beta cells. The expression of HLA-I can be induced following exposure to interferons (IFN). Previous studies have implicated enteroviruses (EV) as major players in triggering an autoimmune response against beta cells and it seems likely that the hyperexpression of HLA-I contributes to the recognition and targeting of beta cells by CD8+T cells. Whilst HLA-I molecules are expressed on the surface of nucleated cells, there is increasing evidence that HLA-I can also be found in a soluble form in the plasma, including in patients with viral infections. Intriguingly, soluble HLA-I (sHLA-I) levels are significantly elevated in the serum of patients with autoimmune diseases such as systemic lupus erythematosus, rheumatoid arthritis and T1D, yet the function of sHLA-I is still unclear. In this project, we are investigating the impact of interferons and poly I:C, a viral dsRNA mimetic, on the expression of surface and soluble HLA-I in the human pancreatic beta cell line EndoC-βH1, the human pancreatic ductal cell line PANC1 and in HeLa cells. We show that surface HLA-I is upregulated in response to these stimuli in each of the cell lines, with greatest magnitude in EndoC-βH1. We also show for the first time that release of sHLA-I is significantly increased in response to IFNγ in EndoC-βH1 cell line.

Modulation of Autophagy Influences the Function and Survival of Human Pancreatic Beta Cells Under Endoplasmic Reticulum Stress Conditions and in Type 2 Diabetes.

Autophagy is the major mechanism involved in degradation and recycling of intracellular components, and its alterations have been proposed to cause beta cell dysfunction. In this study, we explored the effects of autophagy modulation in human islets under conditions associated to endoplasmic reticulum (ER) stress. Human pancreatic islets were isolated by enzymatic digestion and density gradient purification from pancreatic samples of non-diabetic (ND; n = 17; age 65 ± 21 years; gender: 5 M/12 F; BMI 23.4 ± 3.3 kg/m2) and T2D (n = 9; age 76 ± 6 years; 4 M/5 F; gender: BMI 25.4 ± 3.7 kg/m2) organ donors. Nine ND organ donors were treated for hypertension and 1 for both hypertension and hypercholesterolemia. T2D organ donors were treated with metformin (1), oral hypoglycemic agents (2), diet + oral hypoglycemic agents (3), insulin (3) or insulin plus metformin (3) as for antidiabetic therapy and, of these, 3 were treated also for hypertension and 6 for both hypertension and hypercholesterolemia. Two days after isolation, they were cultured for 1–5 days with 10 ng/ml rapamycin (autophagy inducer), 5 mM 3-methyladenine or 1.0 nM concanamycin-A (autophagy blockers), either in the presence or not of metabolic (0.5 mM palmitate) or chemical (0.1 ng/ml brefeldin A) ER stressors. In ND islets palmitate exposure induced a 4 to 5-fold increase of beta cell apoptosis, which was significantly prevented by rapamycin and exacerbated by 3-MA. Similar results were observed with brefeldin treatment. Glucose-stimulated insulin secretion from ND islets was reduced by palmitate (−40 to 50%) and brefeldin (−60 to 70%), and rapamycin counteracted palmitate, but not brefeldin, cytotoxic actions. Both palmitate and brefeldin induced PERK, CHOP and BiP gene expression, which was partially, but significantly prevented by rapamycin. With T2D islets, rapamycin alone reduced the amount of p62, an autophagy receptor that accumulates in cells when macroautophagy is inhibited. Compared to untreated T2D cells, rapamycin-exposed diabetic islets showed improved insulin secretion, reduced proportion of beta cells showing signs of apoptosis and better preserved insulin granules, mitochondria and ER ultrastructure; this was associated with significant reduction of PERK, CHOP and BiP gene expression. This study emphasizes the importance of autophagy modulation in human beta cell function and survival, particularly in situations of ER stress. Tuning autophagy could be a tool for beta cell protection.

Towards a Model of the Human Pancreatic Beta Cell

Towards a Model of the Human Pancreatic Beta Cell

The Distinct Effects of Palmitic and Oleic Acid on Pancreatic Beta Cell Function: The Elucidation of Associated Mechanisms and Effector Molecules.

In this study, we aimed to identify the mechanisms underlying the different effects of palmitic acid and oleic acid on human pancreatic beta cell function. To address this problem, the oxidative stress, endoplasmic reticulum stress, inflammation, apoptosis and their mediator molecules have been investigated in the insulin releasing beta cells exposed to palmitic and/or oleic acid. Herein, we have demonstrated that in cultured 1.1B4 beta cells oleic acid promotes neutral lipid accumulation and insulin secretion, whereas palmitic acid is poorly incorporated into triglyceride and it does not stimulate insulin secretion from human pancreatic islets at physiologically glucose concentrations. In addition, palmitic acid caused: (1) oxidative stress through a mechanism involving increases in ROS production and MMP-2 protein expression/gelatinolytic activity associated with down-regulation of SOD2 protein; (2) endoplasmic reticulum stress by up-regulation of chaperone BiP protein and unfolded protein response (UPR) transcription factors (eIF2α, ATF6, XBP1u proteins) and by PTP-1B down-regulation in both mRNA and protein levels; (3) inflammation through enhanced synthesis of proinflammatory cytokines (IL6, IL8 proteins); and (4) apoptosis by enforced proteic expression of CHOP multifunctional transcription factor. Oleic acid alone had opposite effects due to its different capacity of controlling these metabolic pathways, in particular by reduction of the ROS levels and MMP-2 activity, down-regulation of BiP, eIF2α, ATF6, XBP1u, CHOP, IL6, IL8 and by SOD2 and PTP-1B overexpression. The supplementation of saturated palmitic acid with the monounsaturated oleic acid reversed the negative effects of palmitic acid alone regulating insulin secretion from pancreatic beta cells through ROS, MMP-2, ATF6, XBP1u, IL8 reduction and SOD2, PTP-1B activation. Our findings have shown the protective action of oleic acid against palmitic acid on beta cell lipotoxicity through promotion of triglyceride accumulation and insulin secretion and regulation of some effector molecules involved in oxidative stress, endoplasmic reticulum stress, inflammation and apoptosis.

Safety in numbers: Identifying multiple targets for beta cell proliferation.

Combined inhibition of DYRK1A and TGF-β pathways synergistically enhances proliferation and differentiation of human pancreatic beta cells.

Human anti‐NKp46 antibody for studies of NKp46‐dependent NK cell function and its applications for type 1 diabetes and cancer research

Natural killer (NK) cells are innate lymphocytes that efficiently eliminate cancerous and infected cells. NKp46 is an important NK activating receptor shown to participate in recognition and activation of NK cells against pathogens, tumor cells, virally infected cells, and self-cells in autoimmune conditions, including type I and II diabetes. However, some of the NKp46 ligands are unknown and therefore investigating human NKp46 activity and its critical role in NK cell biology is problematic. We developed a unique anti-human NKp46 monocloncal antibody, denoted hNKp46.02 (02). The 02 mAb can induce receptor internalization and degradation. By binding to a unique epitope on a particular domain of NKp46, 02 lead NKp46 to lysosomal degradation. This downregulation therefore enables the investigation of all NKp46 activities. Indeed, using the 02 mAb we determined NK cell targets which are critically dependent on NKp46 activity, including certain tumor cells lines and human pancreatic beta cells. Most importantly, we showed that a toxin-conjugated 02 inhibits the growth of NKp46-positive cells; thus, exemplifying the potential of 02 in becoming an immunotherapeutic drug to treat NKp46-dependent diseases, such as, type I diabetes and NK and T cell related malignancies.

DEXI, a candidate gene for type 1 diabetes, modulates rat and human pancreatic beta cell inflammation via regulation of the type I IFN/STAT signalling pathway.

The initial stages of type 1 diabetes are characterised by an aberrant islet inflammation that is in part regulated by the interaction between type 1 diabetes susceptibility genes and environmental factors. Chromosome 16p13 is associated with type 1 diabetes and CLEC16A is thought to be the aetiological gene in the region. Recent gene expression analysis has, however, indicated that SNPs in CLEC16A modulate the expression of a neighbouring gene with unknown function named DEXI, encoding dexamethasone-induced protein (DEXI). We therefore evaluated the role of DEXI in beta cell responses to 'danger signals' and determined the mechanisms involved. Functional studies based on silencing or overexpression of DEXI were performed in rat and human pancreatic beta cells. Beta cell inflammation and apoptosis, driven by a synthetic viral double-stranded RNA, were evaluated by real-time PCR, western blotting and luciferase assays. DEXI-silenced beta cells exposed to a synthetic double-stranded RNA (polyinosinic:polycytidylic acid [PIC], a by-product of viral replication) showed reduced activation of signal transducer and activator of transcription (STAT) 1 and lower production of proinflammatory chemokines that was preceded by a reduction in IFNβ levels. Exposure to PIC increased chromatin-bound DEXI and IFNβ promoter activity. This effect on IFNβ promoter was inhibited in DEXI-silenced beta cells, suggesting that DEXI is implicated in the regulation of IFNβ transcription. In a mirror image of knockdown experiments, DEXI overexpression led to increased levels of STAT1 and proinflammatory chemokines. These observations support DEXI as the aetiological gene in the type 1 diabetes-associated 16p13 genomic region, and provide the first indication of a link between this candidate gene and the regulation of local antiviral immune responses in beta cells. Moreover, our results provide initial information on the function of DEXI.

Unexpected subcellular distribution of a specific isoform of the Coxsackie and adenovirus receptor, CAR-SIV, in human pancreatic beta cells

Aims/hypothesisThe Coxsackie and adenovirus receptor (CAR) is a transmembrane cell-adhesion protein that serves as an entry receptor for enteroviruses and may be essential for their ability to infect cells. Since enteroviral infection of beta cells has been implicated as a factor that could contribute to the development of type 1 diabetes, it is often assumed that CAR is displayed on the surface of human beta cells. However, CAR exists as multiple isoforms and it is not known whether all isoforms subserve similar physiological functions. In the present study, we have determined the profile of CAR isoforms present in human beta cells and monitored the subcellular localisation of the principal isoform within the cells.MethodsFormalin-fixed, paraffin-embedded pancreatic sections from non-diabetic individuals and those with type 1 diabetes were studied. Immunohistochemistry, confocal immunofluorescence, electron microscopy and western blotting with isoform-specific antisera were employed to examine the expression and cellular localisation of the five known CAR isoforms. Isoform-specific qRT-PCR and RNA sequencing (RNAseq) were performed on RNA extracted from isolated human islets.ResultsAn isoform of CAR with a terminal SIV motif and a unique PDZ-binding domain was expressed at high levels in human beta cells at the protein level. A second isoform, CAR-TVV, was also present. Both forms were readily detected by qRT-PCR and RNAseq analysis in isolated human islets. Immunocytochemical studies indicated that CAR-SIV was the principal isoform in islets and was localised mainly within the cytoplasm of beta cells, rather than at the plasma membrane. Within the cells it displayed a punctate pattern of immunolabelling, consistent with its retention within a specific membrane-bound compartment. Co-immunofluorescence analysis revealed significant co-localisation of CAR-SIV with zinc transporter protein 8 (ZnT8), prohormone convertase 1/3 (PC1/3) and insulin, but not proinsulin. This suggests that CAR-SIV may be resident mainly in the membranes of insulin secretory granules. Immunogold labelling and electron microscopic analysis confirmed that CAR-SIV was localised to dense-core (insulin) secretory granules in human islets, whereas no immunolabelling of the protein was detected on the secretory granules of adjacent exocrine cells. Importantly, CAR-SIV was also found to co-localise with protein interacting with C-kinase 1 (PICK1), a protein recently demonstrated to play a role in insulin granule maturation and trafficking.Conclusions/interpretationThe SIV isoform of CAR is abundant in human beta cells and is localised mainly to insulin secretory granules, implying that it may be involved in granule trafficking and maturation. We propose that this subcellular localisation of CAR-SIV contributes to the unique sensitivity of human beta cells to enteroviral infection.

LDL receptor (LDLR) expression and LDL uptake in human pancreatic beta cells are regulated by statins and PCSK9 - Consequence for glucose-stimulated insulin secretion (GSIS)

Aim: Statins increase the risk of type-2-diabetes in predisposed individuals. It is not known whether PCSK9 inhibitors may also increase this risk. A massive upregulation of LDLR in beta cells could prove lipotoxic and alter GSIS. We aimed to assess the regulation of LDLR expression and function as well as the effects of LDL uptake on GSIS in beta cells.

MANF protects human pancreatic beta cells against stress-induced cell death

Aims/hypothesisThere is a great need to identify factors that could protect pancreatic beta cells against apoptosis or stimulate their replication and thus prevent or reverse the development of diabetes. One potential candidate is mesencephalic astrocyte-derived neurotrophic factor (MANF), an endoplasmic reticulum (ER) stress inducible protein. Manf knockout mice used as a model of diabetes develop the condition because of increased apoptosis and reduced proliferation of beta cells, apparently related to ER stress. Given this novel association between MANF and beta cell death, we studied the potential of MANF to protect human beta cells against experimentally induced ER stress.MethodsPrimary human islets were challenged with proinflammatory cytokines, with or without MANF. Cell viability was analysed and global transcriptomic analysis performed. Results were further validated using the human beta cell line EndoC-βH1.ResultsThere was increased expression and secretion of MANF in human beta cells in response to cytokines. Addition of recombinant human MANF reduced cytokine-induced cell death by 38% in human islets (p < 0.05). MANF knockdown in EndoC-βH1 cells led to increased ER stress after cytokine challenge. Mechanistic studies showed that the protective effect of MANF was associated with repression of the NF-κB signalling pathway and amelioration of ER stress. MANF also increased the proliferation of primary human beta cells twofold when TGF-β signalling was inhibited (p < 0.01).Conclusions/interpretationOur studies show that exogenous MANF protein can provide protection to human beta cells against death induced by inflammatory stress. The antiapoptotic and mitogenic properties of MANF make it a potential therapeutic agent for beta cell protection.

The Investigation of Antidiabetic Effects of Leontice leontopetalum Extract on Human Pancreatic β Cell Lines (1.1B4) Treated with Streptozotocin

One of the alternative therapeutic methods is herbal medicine. Leontice leontopetalum belongs to Berberidaceae family. The aim of study was investigated the extract of LL on human pancreatic beta cell-treated with STZ. Materials and methods: The human pancreatic beta cell (1.1B4) line was used the current study. LL‘s extracts (1, 10, 100, and 1000 ug/ml) were supplemented in media for twenty-four hours and/or after STZ treatment (10 and 20 mM). Cells survivals (MTT), cells proliferation were shown by using xCelligence. Insulin content and releasing were measured at 1.1, 8.4 and 16.7 mM glucose concentrations. Results: The result of MTT was shown that cell survival was decreased, based on dose-dependent. When looked at xCelligence results, cell proliferation in STZ groups and the lowest and highest concentrations of LL were attenuated in a dose-dependent manner. Also, cotreatments of LL and STZ were decreased as well. The result of insulin-releasing on glucose induction was shown that STZ concentration gave rise to reduce insulin content at low and high glucose levels. Also, co-treatment of LL and STZ attenuated insulin content based on dose. Conclusion: It was considered that LL treatment led to increased insulin realizing, resulting from decreasing insulin content in diabetic beta cells, but decrease cell survival.

Metabolic activation-driven mitochondrial hyperpolarization predicts insulin secretion in human pancreatic beta-cells

Mitochondrial metabolism plays a central role in insulin secretion in pancreatic beta-cells. Generation of protonmotive force and ATP synthesis from glucose-originated pyruvate are critical steps in the canonical pathway of glucose-stimulated insulin secretion. Mitochondrial metabolism is intertwined with pathways that are thought to amplify insulin secretion with mechanisms distinct from the canonical pathway, and the relative importance of these two pathways is controversial. Here I show that glucose-induced mitochondrial membrane potential (MMP) hyperpolarization is necessary for, and predicts, the rate of insulin secretion in primary cultured human beta-cells. When glucose concentration is elevated, increased metabolism results in a substantial MMP hyperpolarization, as well as in increased rates of ATP synthesis and turnover marked by faster cell respiration. Using modular kinetic analysis I explored what properties of cellular energy metabolism enable a large glucose-induced change in MMP in human beta-cells. I found that an ATP-dependent pathway activates glucose or substrate oxidation, acting as a positive feedback in energy metabolism. This activation mechanism is essential for concomitant fast respiration and high MMP, and for a high magnitude glucose-induced MMP hyperpolarization and therefore for insulin secretion.

Functional Beta Cell Mass from Device-Encapsulated hESC-Derived Pancreatic Endoderm Achieving Metabolic Control.

SummaryHuman stem cells represent a potential source for implants that replace the depleted functional beta cell mass (FBM) in diabetes patients. Human embryonic stem cell-derived pancreatic endoderm (hES-PE) can generate implants with glucose-responsive beta cells capable of reducing hyperglycemia in mice. This study with device-encapsulated hES-PE (4 × 106 cells/mouse) determines the biologic characteristics at which implants establish metabolic control during a 50-week follow-up. A metabolically adequate FBM was achieved by (1) formation of a sufficient beta cell number (>0.3 × 106/mouse) at >50% endocrine purity and (2) their maturation to a functional state comparable with human pancreatic beta cells, as judged by their secretory responses during perifusion, their content in typical secretory vesicles, and their nuclear NKX6.1-PDX1-MAFA co-expression. Assessment of FBM in implants and its correlation with in vivo metabolic markers will guide clinical translation of stem cell-derived grafts in diabetes.

The Glycolytic Pathway is the Predominate Path for Glucose Utilization in Human Pancreatic Beta Cells (1.1B4)

The oxidative metabolism of energy substrates has a paramount role in the stimulus secretion pathway of insulin. However, the role of glycolytic pathway in pancreatic beta cells is not very well understood. To address this, we have investigated and compared the functional effects of two mitochondrial substrates (glucose and α-ketoisocaproate) between the human (1.1B4) and murine (MIN6) pancreatic beta cell lines. MTS assay was conducted as an indicator of the metabolic activity of both cell lines. Polarographic detection of (ΔO2) and lactate were used to measure the oxygen consumption rate and anaerobic glycolysis respectively. The mitochondrial redox state was monitored via RH123 distribution and NAD(P)H autofluorescence. The metabolic assays showed glucose stimulated MTS reduction in MIN6 cells in a time and concentration dependent manner and nor in 1.1B4. Both sub strates failed to affect OCR, NADPH and increased lactate production in 1.1B4 cells. However, they stimulated OCR, increased NADPH, increased lactate output but was less extent and hyperpolarized the mitochondria in MIN6 cells. The above results showed that 1.1B4 cells are mainly depending on the glycolytic pathway different from MIN6 cells which rely on mitochondrial respiration. In conclusion, 1.1B4 cell line represents a new model to study the bioenergetics profile because it depends on the anaerobic glycolysis rather than aerobic respiration of the other models such as MIN6 and islets.

Modeling human pancreatic beta cell dedifferentiation

ObjectiveDedifferentiation could explain reduced functional pancreatic β-cell mass in type 2 diabetes (T2D). MethodsHere we model human β-cell dedifferentiation using growth factor stimulation in the human β-cell line, EndoC-βH1, and human pancreatic islets. ResultsFibroblast growth factor 2 (FGF2) treatment reduced expression of β-cell markers, (INS, MAFB, SLC2A2, SLC30A8, and GCK) and activated ectopic expression of MYC, HES1, SOX9, and NEUROG3. FGF2-induced dedifferentiation was time- and dose-dependent and reversible upon wash-out. Furthermore, FGF2 treatment induced expression of TNFRSF11B, a decoy receptor for RANKL and protected β-cells against RANKL signaling. Finally, analyses of transcriptomic data revealed increased FGF2 expression in ductal, endothelial, and stellate cells in pancreas from T2D patients, whereas FGFR1, SOX,9 and HES1 expression increased in islets from T2D patients. ConclusionsWe thus developed an FGF2-induced model of human β-cell dedifferentiation, identified new markers of dedifferentiation, and found evidence for increased pancreatic FGF2, FGFR1, and β-cell dedifferentiation in T2D.

DPP-4 is expressed in human pancreatic beta cells and its direct inhibition improves beta cell function and survival in type 2 diabetes.

It has been reported that the incretin system, including regulated GLP-1 secretion and locally expressed DPP-4, is present in pancreatic islets. In this study we comprehensively evaluated the expression and role of DPP-4 in isletalpha and beta cells from non-diabetic (ND) and type 2 diabetic (T2D) individuals, including the effects of its inhibition on beta cell function and survival. Isolated islets were prepared from 25 ND and 18 T2D organ donors; studies were also performed with the human insulin-producing EndoC-βH1 cells. Morphological (including confocal microscopy), ultrastructural (electron microscopy, EM), functional (glucose-stimulated insulin secretion), survival (EM and nuclear dyes) and molecular (RNAseq, qPCR and western blot) studies were performed under several different experimental conditions. DPP-4 co-localized with glucagon and was also expressed in human islet insulin-containing cells. Furthermore, DPP-4 was expressed in EndoC-βH1 cells. The proportions of DPP-4 positive alpha and beta cells and DPP-4 gene expression were significantly lower in T2D islets. A DPP-4 inhibitor protected ND human beta cells and EndoC-βH1 cells against cytokine-induced toxicity, which was at least in part independent from GLP1 and associated with reduced NFKB1 expression. Finally, DPP-4 inhibition augmented glucose-stimulated insulin secretion, reduced apoptosis and improved ultrastructure in T2D beta cells. These results demonstrate the presence of DPP-4 in human isletalpha and beta cells, with reduced expression in T2D islets, and show that DPP-4 inhibition has beneficial effects on human ND and T2D beta cells. This suggests that DPP-4, besides playing a role in incretin effects, directly affects beta cell function and survival.

IFN-α induces a preferential long-lasting expression of MHC class I in human pancreatic beta cells.

IFN-α, a cytokine expressed in human islets from individuals affected by type 1 diabetes, plays a key role in the pathogenesis of diabetes by upregulating inflammation, endoplasmic reticulum (ER) stress and MHC class I overexpression, three hallmarks of islet histology in early type 1 diabetes. We tested whether expression of these mediators of beta cell loss is reversible upon IFN-α withdrawal or IFN-α pathway inhibition. IFN-α-induced MHC class I overexpression, ER stress and inflammation were evaluated by flow cytometry, immunofluorescence and real-time PCR in human EndoC-βH1 cells or human islets exposed to IFN-α with or without the presence of Janus kinase (JAK) inhibitors. Protein expression was evaluated by western blot. IFN-α-induced expression of inflammatory and ER stress markers returned to baseline after 24-48h following cytokine removal. In contrast, MHC class I overexpression at the cell surface persisted for at least 7days. Treatment with JAK inhibitors, when added with IFN-α, prevented MHC class I overexpression, but when added 24h after IFN-α exposure these inhibitors failed to accelerate MHC class I return to baseline. IFN-α mediates a long-lasting and preferential MHC class I overexpression in human beta cells, which is not affected by the subsequent addition of JAK inhibitors. These observations suggest that IFN-α-stimulated long-lasting MHC class I expression may amplify beta cell antigen presentation during the early phase of type 1 diabetes and that IFN-α inhibitors might need to be used at very early stages of the disease to be effective.

Cell-Based Methods to Identify Inducers of Human Pancreatic Beta-Cell Proliferation.

Diabetes is the result of the insufficiency or dysfunction of pancreatic beta cells alone or in combination with insulin resistance. The replacement or regeneration of beta cells can effectively reverse diabetes in humans and rodents. Therefore, the identification of novel small molecules that promote pancreatic beta-cell proliferation is an attractive approach for diabetic therapy. While numerous hormones, small molecules, and growth factors are able to drive rodent beta cells to replicate, only a few small molecules have demonstrated the ability to stimulate human beta-cell proliferation. Hence, there is an urgent need for therapeutic agents that induce regeneration and expansion of adult human beta cells. Here, we describe a detailed protocol for coating chamber slides, culturing primary islets, performing islet cell disassociation, seeding cells on chamber slides, treating islet cells with compounds or infecting them with adenovirus, immunostaining of proliferation markers and imaging, and data analysis.