Pancreatic Islet Endocrine Cells Research Articles

Pancreatic islet cell plasticity: Pathogenic or therapeutically exploitable?

The development of pancreatic islet endocrine cells is a tightly regulated process leading to the generation of distinct cell types harbouring different hormones in response to small changes in environmental stimuli. Cell differentiation is driven by transcription factors that are also critical for the maintenance of the mature islet cell phenotype. Alteration of the insulin-secreting β-cell transcription factor set by prolonged metabolic stress, associated with the pathogenesis of diabetes, obesity or pregnancy, results in the loss of β-cell identity through de- or transdifferentiation. Importantly, the glucose-lowering effects of approved and experimental antidiabetic agents, including glucagon-like peptide-1 mimetics, novel peptides and small molecules, have been associated with preventing or reversing β-cell dedifferentiation or promoting the transdifferentiation of non-β-cells towards an insulin-positive β-cell-like phenotype. Therefore, we review the manifestations of islet cell plasticity in various experimental settings and discuss the physiological and therapeutic sides of this phenomenon, focusing on strategies for preventing β-cell loss or generating new β-cells in diabetes. A better understanding of the molecular mechanisms underpinning islet cell plasticity is a prerequisite for more targeted therapies to help prevent β-cell decline in diabetes.

A plasma membrane-associated glycolytic metabolon is functionally coupled to KATP channels in pancreatic α and β cells from humans and mice

The ATP-sensitive K+ (KATP) channel is a key regulator of hormone secretion from pancreatic islet endocrine cells. Using direct measurements of KATP channel activity in pancreatic β cells and the lesser-studied α cells, from both humans and mice, we provide evidence that a glycolytic metabolon locally controls KATP channels on the plasma membrane. The two ATP-consuming enzymes of upper glycolysis, glucokinase and phosphofructokinase, generate ADP that activates KATP. Substrate channeling of fructose 1,6-bisphosphate through the enzymes of lower glycolysis fuels pyruvate kinase, which directly consumes the ADP made by phosphofructokinase to raise ATP/ADP and close the channel. We further show the presence of a plasma membrane-associated NAD+/NADH cycle whereby lactate dehydrogenase is functionally coupled to glyceraldehyde-3-phosphate dehydrogenase. These studies provide direct electrophysiological evidence of a KATP-controlling glycolytic signaling complex and demonstrate its relevance to islet glucose sensing and excitability.

The GLI code controls HNF1A levels during foregut differentiation.

Differentiation of human induced pluripotent stem cells towards pancreatic islet endocrine cells is a complex process, involving the stepwise modulation of key developmental pathways, such as the Hedgehog signaling inhibition during early differentiation stages. In tandem with this active inhibition, key transcription factors for the islet endocrine cell fate, such as HNF1A, show specific changes in their expression patterns. Here we designed a pilot study aimed at investigating the potential interconnection between HH-signaling inhibition and the increase in the HNF1A expression during early regeneration, by inducing changes in the GLI code. This unveiled a link between the two, where GLI3-R mediated Hedgehog target genes inhibition is apparently required for HNF1A efficient expression.

Targeted Gene Silencing by Using GapmeRs in Differentiating Human-Induced Pluripotent Stem Cells (hiPSC) Toward Pancreatic Progenitors.

Induced pluripotent stem cells as a source for generating pancreatic islet endocrine cells represent a great research tool for deciphering the molecular mechanisms of lineage commitment, a layered multi-step process. Additionally, targeted gene silencing by using GapmeRs, short antisense oligonucleotides, proved instrumental in studying the role of different developmental genes. Here we describe our approach to induce mTOR silencing by using specific GapmeRs during the differentiation of induced pluripotent stem cells toward pancreatic progenitors. We will describe our current differentiation protocol, the transfection procedure, and the quality control steps required for a successful experiment.

The Ldb1 transcriptional co-regulator is required for establishment and maintenance of the pancreatic endocrine lineage.

Pancreatic islet cell development is regulated by transcription factors (TFs) that mediate embryonic progenitor differentiation toward mature endocrine cells. Prior studies from our lab and others showed that the islet-enriched TF, Islet-1 (Isl1), interacts with the broadly-expressed transcriptional co-regulator, Ldb1, to regulate islet cell maturation and postnhyperatal function (by embryonic day (E)18.5). However, Ldb1 is expressed in the developing pancreas prior to Isl1 expression, notably in multipotent progenitor cells (MPCs) marked by Pdx1 and endocrine progenitors (EPs) expressing Neurogenin-3 (Ngn3). MPCs give rise to the endocrine and exocrine pancreas, while Ngn3+ EPs specify pancreatic islet endocrine cells. We hypothesized that Ldb1 is required for progenitor identity in MPC and EP populations during development to impact islet appearance and function. To test this, we generated a whole-pancreas Ldb1 knockout, termed Ldb1ΔPanc , and observed severe developmental and postnatal pancreas defects including disorganized progenitor pools, a significant reduction of Ngn3-expressing EPs, Pdx1HI β-cells, and early hormone+ cells. Ldb1ΔPanc neonates presented with severe hyperglycemia, hypoinsulinemia, and drastically reduced hormone expression in islets, yet no change in total pancreas mass. This supports the endocrine-specific actions of Ldb1. Considering this, we also developed an endocrine-enriched model of Ldb1 loss, termed Ldb1ΔEndo . We observed similar dysglycemia in this model, as well as a loss of islet identity markers. Through in vitro and in vivo chromatin immunoprecipitation experiments, we found that Ldb1 occupies key Pdx1 and Ngn3 promoter domains. Our findings provide insight into novel regulation of endocrine cell differentiation that may be vital toward improving cell-based diabetes therapies.

Adult pancreatic islet endocrine cells emerge as fetal hormone-expressing cells.

SummaryThe precise developmental dynamics of the pancreatic islet endocrine cell types, and their interrelation, are unknown. Some authors claim the persistence of islet cell differentiation from precursor cells after birth (“neogenesis”). Here, using four conditional cell lineage tracing (“pulse-and-chase”) murine models, we describe the natural history of pancreatic islet cells, once they express a hormone gene, until late in life. Concerning the contribution of early-appearing embryonic hormone-expressing cells to the formation of islets, we report that adult islet cells emerge from embryonic hormone-expressing cells arising at different time points during development, without any evidence of postnatal neogenesis. We observe specific patterns of hormone gene activation and switching during islet morphogenesis, revealing that, within each cell type, cells have heterogeneous developmental trajectories. This likely applies to most maturating cells in the body, and explains the observed phenotypic variability within differentiated cell types. Such knowledge should help devising novel regenerative therapies.

H3K4 Trimethylation Is Required for Postnatal Pancreatic Endocrine Cell Functional Maturation.

During pancreas development, endocrine progenitors differentiate into the islet cell subtypes, which undergo further functional maturation in postnatal islet development. In islet β-cells, genes involved in glucose-stimulated insulin secretion are activated, and glucose exposure increases the insulin response as β-cells mature. We investigated the role of H3K4 trimethylation in endocrine cell differentiation and functional maturation by disrupting TrxG complex histone methyltransferase activity in mouse endocrine progenitors. In the embryo, genetic inactivation of TrxG component Dpy30 in NEUROG3+ cells did not affect the number of endocrine progenitors or endocrine cell differentiation. H3K4 trimethylation was progressively lost in postnatal islets, and the mice displayed elevated nonfasting and fasting glycemia as well as impaired glucose tolerance by postnatal day 24. Although postnatal endocrine cell proportions were equivalent to controls, islet RNA sequencing revealed a downregulation of genes involved in glucose-stimulated insulin secretion and an upregulation of immature β-cell genes. Comparison of histone modification enrichment profiles in NEUROG3+ endocrine progenitors and mature islets suggested that genes downregulated by loss of H3K4 trimethylation more frequently acquire active histone modifications during maturation. Taken together, these findings suggest that H3K4 trimethylation is required for the activation of genes involved in the functional maturation of pancreatic islet endocrine cells.

A Method for Encapsulation and Transplantation into Diabetic Mice of Human Induced Pluripotent Stem Cells (hiPSC)-Derived Pancreatic Progenitors.

Pancreatic islet endocrine cells generated from patient-derived induced pluripotent stem cells represent a great strategy for both disease modeling and regenerative medicine. Nevertheless, these cells inherently miss the effects of the intricate network of systemic signals characterizing the living organisms. Xenotransplantation of in vitro differentiating cells into murine hosts substantially compensates for this drawback.Here we describe our transplantation strategy of encapsulated differentiating pancreatic progenitors into diabetic immunosuppressed (NSG) overtly diabetic mice generated by the total ablation of insulin-producing cells following diphtheria toxin administration. We will detail the differentiation protocol employed, the alginate encapsulation procedure, and the xenotransplantation steps required for a successful and reproducible experiment.

Adult Pancreatic Islet Endocrine Cells Emerge as Fetal Hormone-Expressing Cells

Adult Pancreatic Islet Endocrine Cells Emerge as Fetal Hormone-Expressing Cells

Developmental programming: Prenatal testosterone excess disrupts pancreatic islet developmental trajectory in female sheep

Prenatal testosterone (T)- treated female sheep manifest juvenile insulin resistance, post-pubertal increase in insulin sensitivity and return to insulin resistance during adulthood. Since compensatory hyperinsulinemia is associated with insulin resistance, altered pancreatic islet ontogeny may contribute towards metabolic defects. To test this, pregnant sheep were treated with or without T propionate from days 30–90 of gestation and pancreas collected from female fetuses at gestational day 90 and female offspring at 21 months-of-age. Uterine (maternal) and umbilical (fetal) arterial blood insulin/glucose ratios were determined at gestational day 90. The morphological and functional changes in pancreatic islet were assessed through detection of 1) islet hormones (insulin, glucagon) and apoptotic beta cells at fetal day 90 and 2) islet hormones (insulin, glucagon and somatostatin), and pancreatic lipid and collagen accumulation in adults. At gestational day 90, T-treatment led to maternal but not fetal hyperinsulinemia, decrease in pancreatic/fetal weight ratio and alpha cells, and a trend for increase in beta cell apoptosis in fetal pancreas. Adult prenatal T-treated female sheep manifested 1) significant increase in beta cell size and a tendency for increase in insulin and somatostatin stained area and proportion of beta cells in the islet; and 2) significant increase in pancreatic islet collagen and a tendency towards increased lipid accumulation. Gestational T-treatment induced changes in pancreatic islet endocrine cells during both fetal and adult ages track the trajectory of hyperinsulinemic status with the increase in adult pancreatic collagen accumulation indicative of impending beta cell failure with chronic insulin resistance.

Features of Bcl2 and p53 proteins synthesis in pancreatic islets of normotensive and hypertensive rats with streptozotocin-induced diabetes

In our previous studies it was established that the remodeling of pancreatic islets with decreasing β-cell population density is formed in hypertensive SHR rats. The imbalance between the synthesis of proapoptotic and antiapoptotic factors may be one of the possible causes of disturbed formation of the endocrinocyte population in the pancreas. The aim of the research was to study the parameters of Bcl2 and p53 proteins synthesis in pancreatic islets in normotensive and hypertensive rats in the streptozotocin-induced diabetes mellitus development. Materials and methods . The study was performed on 30 normotensive male Wistar rats (systolic BP=105.0 ±1.1 mm Hg) and 25 hypertensive SHR rats (systolic BP=155.7 ±0.9 mm Hg) with fasting normoglycemia (4.73 ± 0.10 mmol/l). Bcl2 and p53 proteins were detected in histological pancreas sections by immunofluorescence method. The relative area of Bcl2- and p53-immunopositive material, concentration of proteins in endocrinocytes, their content in the islets and apoptosis index p53/Bcl2 were analyzed in pancreatic islands. Results. The area of relative immunofluorescence to the Bcl2 protein was 2 times less, and the protein content was 3 times lower in pancreatic islets of hypertensive rats (SHR) compared with normotensive Wistar rats. At the same time, no statistical differences in the area of the immunopositive material to the p53 protein and its content in the islets between the experimental groups were revealed. The development of streptozotocin-induced diabetes in Wistar rats was accompanied by approximately 2-fold decrease in the Bcl2 protein expression in pancreatic islets, a significant increase in the specific content of p53 protein and a 3.8-fold increase in the apoptosis index of p53/Bcl2. In pancreatic islets of SHR rats, diabetes mellitus development was accompanied by 2-fold increase in the specific content of the proapoptotic protein p53 without the reduction of the antiapoptotic protein Bcl2 synthesis. At the same time, the p53/Bcl2 apoptosis index in SHR rats remained statistically higher than in Wistar rats. Conclusions. Endocrine cells of pancreatic islets of SHR rats are characterized by the prevalence of proapoptotic protein p53 expression as compared with Wistar line normotensive rats. The development of streptozotocin diabetes in Wistar rats leads to a significant decrease in the number of endocrinocytes synthesizing the antiapoptotic protein Bcl2. At the same time, an increase in the synthesis of the proapoptotic protein p53 in endocrinocytes in diabetes is observed both in normotensive and in hypertensive rats.

2197-P: SEL1L-HRD1 Endoplasmic Reticulum-Associated Degradation Is Required for Maintaining Glucagon Production in Pancreatic Alpha Cells

Endoplasmic reticulum-associated degradation (ERAD) is a key component of cellular protein quality control, an essential process for pancreatic islet endocrine cells, which synthesize peptide prohormones in high quantities. Two highly conserved ER membrane proteins comprise the core ERAD machinery: HRD1, a ubiquitin ligase that retrotranslocates and ubiquitinates misfolded proteins for proteasomal degradation, and SEL1L, an adaptor protein that identifies ERAD target proteins and is required for HRD1 stability and function. Pancreatic alpha cells, intestinal L-cells, and certain neurons synthesize and differentially cleave proglucagon into tissue-specific hormones, including glucagon and glucagon-like peptide 1 (GLP-1). To investigate the role of ERAD in these cells, we targeted SEL1L deletion with the Cre-lox system, using mice expressing Cre recombinase under the proglucagon promoter. We found that Sel1LGcg mice showed normal growth and glucose homeostasis in vivo. Oral glucose tolerance was equally impaired by administration of the GLP-1 receptor antagonist exendin 9-39 in both Sel1LGcg and control mice, suggesting intact GLP-1 signaling in Sel1LGcg mice. Glucagon secretion in vivo was not significantly different following a 24 hour fast or insulin-induced hypoglycemia. Interestingly, pancreatic glucagon content was reduced by half in Sel1LGcg mice, despite unchanged pancreatic weight. By immunofluorescence, pancreatic islet morphology in Sel1LGcg mice was normal, though α-cells demonstrated increased expression of the ER chaperone BiP and ERAD-associated proteins OS9 and XTP3-B. By transmission electron microscopy, a large subset of α-cells showed significant ER dilation and fewer, smaller glucagon granules. Our data demonstrate that SEL1L-HRD1 ERAD is required for maintaining normal glucagon expression and ER morphology in pancreatic α-cells but does not entirely disrupt proglucagon signaling in vivo. Disclosure R.B. Reinert: None. N. Shrestha: None. Y. Ji: None. L. Qi: None. Funding National Institutes of Health (5T32DK007245)

Islet prohormone processing in health and disease.

Biosynthesis of peptide hormones by pancreatic islet endocrine cells is a tightly orchestrated process that is critical for metabolic homeostasis. Like neuroendocrine peptides, insulin and other islet hormones are first synthesized as larger precursor molecules that are processed to their mature secreted products through a series of proteolytic cleavages, mediated by the prohormone convertases Pc1/3 and Pc2, and carboxypeptidase E. Additional posttranslational modifications including C-terminal amidation of the β-cell peptide islet amyloid polypeptide (IAPP) by peptidyl-glycine α-amidating monooxygenase (Pam) may also occur. Genome-wide association studies (GWAS) have showed genetic linkage of these processing enzymes to obesity, β-cell dysfunction, and type 2 diabetes (T2D), pointing to their important roles in metabolism and blood glucose regulation. In both type 1 diabetes (T1D) and T2D, and in the face of metabolic or inflammatory stresses, islet prohormone processing may become impaired; indeed elevated proinsulin:insulin (PI:I) ratios are a hallmark of the β-cell dysfunction in T2D. Recent studies suggest that genetic or acquired defects in proIAPP processing may lead to the production and secretion of incompletely processed forms of proIAPP that could contribute to T2D pathogenesis, and additionally that impaired processing of both PI and proIAPP may be characteristic of β-cell dysfunction in T1D. In islet α-cells, the prohormone proglucagon is normally processed to bioactive glucagon by Pc2 but may express Pc1/3 under certain conditions leading to production of GLP-1(7-36NH2 ). A better understanding of how β-cell processing of PI and proIAPP, as well as α-cell processing of proglucagon, are impacted by genetic susceptibility and in the face of diabetogenic stresses, may lead to new therapeutic approaches for improving islet function in diabetes.

Humanised recombinant antibody fragments bind human pancreatic islet cells

We describe here the humanisation of two mouse monoclonal antibodies that bind to surface markers on human pancreatic islet endocrine cells. Monoclonal antibodies produced by the HIC1-2B4 and HIC0-4F9 mouse hybridomas bind distinct surface molecules expressed on endocrine cells and have been validated for a number of experimental methods including immunohistochemistry and live cell sorting by flow cytometry. Variable region framework and first constant region domain sequences were replaced with that from compatible human antibody sequences, and the resulting recombinant antigen-binding fragments were cloned and expressed in mouse myeloma cells. ELISA, fluorescent immunohistochemistry, and flow cytometry were used to assess the specificity of the humanised antibody fragments. Purification and binding analyses indicated that human islet endocrine cell binding was retained in the humanised antibody fragments. These humanised, recombinant antibody fragments have a lower risk of eliciting adverse responses from a patient's immune system and, therefore, have highly improved clinical potential. Thus, they may be used to image, target or carry cargo specifically to islet cells in human patients.

Alkaline pH induces IRR-mediated phosphorylation of IRS-1 and actin cytoskeleton remodeling in a pancreatic beta cell line

Secretion of mildly alkaline (pH 8.0–8.5) juice to intestines is one of the key functions of the pancreas. Recent reports indicate that the pancreatic duct system containing the alkaline juice may adjoin the endocrine cells of pancreatic islets. We have previously identified the insulin receptor-related receptor (IRR) that is expressed in islets as a sensor of mildly alkaline extracellular media. In this study, we show that those islet cells that are in contact with the excretory ducts are also IRR-expressing cells. We further analyzed the effects of alkaline media on pancreatic beta cell line MIN6. Activation of endogenous IRR but not of the insulin receptor was detected that could be inhibited with linsitinib. The IRR autophosphorylation correlated with pH-dependent linsitinib-sensitive activation of insulin receptor substrate 1 (IRS-1), the primary adaptor in the insulin signaling pathway. However, in contrast with insulin stimulation, no protein kinase B (Akt/PKB) phosphorylation was detected as a result of alkali treatment. We observed overexpression of several early response genes (EGR2, IER2, FOSB, EGR1 and NPAS4) upon alkali treatment of MIN6 cells but those were IRR-independent. The alkaline medium but not insulin also triggered actin cytoskeleton remodeling that was blocked by pre-incubation with linsitinib. We propose that the activation of IRR by alkali might be part of a local loop of signaling between the exocrine and endocrine parts of the pancreas where alkalinization of the juice facilitate insulin release that increases the volume of secreted juice to control its pH and bicabonate content.

Quantitative proteomics of rat and human pancreatic beta cells.

Data set description: This data set is composed by label-free alternate-scanning LC-MS/MS proteomics analysis human and Wistar rat pancreatic islet endocrine cells.The mass spectrometry data of the human and rat pancreatic beta cells and the resulting proteome search output from ProteinLynx GlobalSERVER (PLGS) have been deposited to the ProteomeXchange Consortium [1] via the PRIDE partner repository with the dataset identifiers PXD001539 (human) and PXD001816 (rat). From these mass spectrometry data, ‘relative molar amount units’ between cell types and across species were calculated.Biological relevance: These data provide a quantitative view on the unfractionated proteomes of human and rat beta and alpha cells. It is likely biased towards the proteins with higher molar abundance, relating to core functional pathways, but also includes several proteins with an islet-enriched expression. The quality of the cell preps is state-of-the-art, and the label-free quantitation is both precise and accurate, allowing detailed quantitative analysis.

Abnormal anxiety- and depression-like behaviors in mice lacking both central serotonergic neurons and pancreatic islet cells.

Dysfunction of central serotonin (5-HT) system has been proposed to be one of the underlying mechanisms for anxiety and depression, and the association of diabetes mellitus and psychiatric disorders has been noticed by the high prevalence of anxiety/depression in patients with diabetes mellitus. This promoted us to examine these behaviors in central 5-HT-deficient mice and those also suffering with diabetes mellitus. Mice lacking either 5-HT or central serotonergic neurons were generated by conditional deletion of Tph2 or Lmx1b respectively. Simultaneous depletion of both central serotonergic neurons and pancreatic islet cells was achieved by administration of diphtheria toxin (DT) in Pet1-Cre;Rosa26-DT receptor (DTR) mice. The central 5-HT-deficient mice showed reduced anxiety-like behaviors as they spent more time in and entered more often into the light box in the light/dark box test compared with controls; similar results were observed in the elevated plus maze test. However, they displayed no differences in the immobility time of the forced swimming and tail suspension tests suggesting normal depression-like behaviors in central 5-HT-deficient mice. As expected, DT-treated Pet1-Cre;Rosa26-DTR mice lacking both central serotonergic neurons and pancreatic islet endocrine cells exhibited several classic diabetic symptoms. Interestingly, they displayed increased anxiety-like behaviors but reduced immobility time in the forced swimming and tail suspension tests. Furthermore, the hippocampal neurogenesis was dramatically enhanced in these mice. These results suggest that the deficiency of central 5-HT may not be sufficient to induce anxiety/depression-like behaviors in mice, and the enhanced hippocampal neurogenesis may contribute to the altered depression-like behaviors in the 5-HT-deficient mice with diabetes. Our current investigation provides understanding the relationship between diabetes mellitus and psychiatric disorders.

CTCF-regulating endocrine function of pancreatic islet cells in transgenic mice.

Pancreatic islet endocrine cells play crucial roles in regulation of glucose homeostasis. The differentiation and function of islet cells are regulated by various transcription factors, including Pax6, a member of the homeobox gene family. Pax6 plays a key role in the control of gene expression and islet cell development in the pancreas. Recent studies from our lab demonstrate for the first time that Pax6 transcription is regulated by CCCTC binding factor (CTCF), a nuclear protein and transcription regulator. CTCF downregulates Pax6 transcription through interaction with a repressor element located in Pax6 gene P0 promoter region. To further investigate the effect of CTCF on regulating Pax6 function in pancreatic islet cells, we measured blood glucose, insulin, and glucagons levels in newly established transgenic mice overexpressing CTCF. When compared to wild type mice, CTCF transgenic mice demonstrate an increase in insulin level and decrease in glucagon level resulting in lower blood glucose levels (hypoglycemia). In insulin tolerance test, hypoglycemia occurs quickly in CTCF transgenic mice and takes a recovery time. In the mean time, glucagon levels in CTCF mutant mice were significantly lower compared to its wild type counterpart. Our results indicate that CTCF transgenic mice are disordered in glucose homeostasis and suggest that CTCF is involved in regulating endocrine function of pancreatic islet cells by suppression of Pax6 expression.

Immunolocalization of leptin and its receptor in the pancreas of the horse

The aim of the present study was to demonstrate the presence and the distribution of leptin and its receptor in the pancreas of horses of both sexes by immunohistochemical techniques. The presence and the distribution of leptin receptor were also investigated in the initial portion of the duodenum, near the duodenal ampulla. The immunohistochemical investigation demonstrates the immunolocalization of both leptin and its receptor in the endocrine cells of pancreatic islets, which led us to hypothesize that leptin may possibly exert an autocrine/paracrine action on the endocrine pancreas. Examination of the exocrine pancreas in the same treated sections showed the presence of leptin-positive cells in the wall of the interlobular ducts where, however, the receptor was not found. This observation led us to consider that some cells of the ducts may perform some minimal secretory activity, and that leptin produced by these ductal cells may reach the duodenum in the pancreatic juice. This hypothesis is enhanced by the presence of leptin-receptor in the duodenum of the same animals, where the epithelial cells of the mucosa showed intense immunolocalization in the brush border. Consequently it is possible that the ductular leptin may play a regulatory role on the functionality of the enterocytes.

Regeneration of Pancreatic Non-β Endocrine Cells in Adult Mice following a Single Diabetes-Inducing Dose of Streptozotocin

The non-β endocrine cells in pancreatic islets play an essential counterpart and regulatory role to the insulin-producing β-cells in the regulation of blood-glucose homeostasis. While significant progress has been made towards the understanding of β-cell regeneration in adults, very little is known about the regeneration of the non-β endocrine cells such as glucagon-producing α-cells and somatostatin producing δ-cells. Previous studies have noted the increase of α-cell composition in diabetes patients and in animal models. It is thus our hypothesis that non-β-cells such as α-cells and δ-cells in adults can regenerate, and that the regeneration accelerates in diabetic conditions. To test this hypothesis, we examined islet cell composition in a streptozotocin (STZ)-induced diabetes mouse model in detail. Our data showed the number of α-cells in each islet increased following STZ-mediated β-cell destruction, peaked at Day 6, which was about 3 times that of normal islets. In addition, we found δ-cell numbers doubled by Day 6 following STZ treatment. These data suggest α- and δ-cell regeneration occurred rapidly following a single diabetes-inducing dose of STZ in mice. Using in vivo BrdU labeling techniques, we demonstrated α- and δ-cell regeneration involved cell proliferation. Co-staining of the islets with the proliferating cell marker Ki67 showed α- and δ-cells could replicate, suggesting self-duplication played a role in their regeneration. Furthermore, Pdx1+/Insulin− cells were detected following STZ treatment, indicating the involvement of endocrine progenitor cells in the regeneration of these non-β cells. This is further confirmed by the detection of Pdx1+/glucagon+ cells and Pdx1+/somatostatin+ cells following STZ treatment. Taken together, our study demonstrated adult α- and δ-cells could regenerate, and both self-duplication and regeneration from endocrine precursor cells were involved in their regeneration.