How to make insulin-producing pancreatic β cells for diabetes treatment

Around 400 million people worldwide suffer from diabetes mellitus.The major pathological event for Type 1 diabetes and advanced Type 2 diabetes is loss or impairment of insulin-secreting β cells of the pancreas.For the past 100 years,daily insulin injection has served as a life-saving treatment for these patients.However,insulin injection often cannot achieve full glucose control,and over time poor glucose control leads to severe complications and mortality.As an alternative treatment,islet transplantation has been demonstrated to effectively maintain glucose homeostasis in diabetic patients,but its wide application is limited by the scarcity of donated islets.Therefore,it is important to define new strategies to obtain functional human β cells for transplantation therapies.Here,we summarize recent progress towards the production of β cells in vitro from pluripotent stem cells or somatic cell types including a cells,pancreatic exocrine cells,gastrointestinal stem cells,fibroblasts and hepatocytes.We also discuss novel methods for optimizing β cell transplantation and maintenance in vivo.From our perspective,the future of βcell replacement therapy is very promising although it is still challenging to control differentiation of β cells in vitro and to protect these cells from autoimmune attack in Type 1 diabetic patients.Overall,tremendous progress has been made in understanding βcell differentiation and producing functional β cells with different methods.In the coming years,we believe more clinical trials will be launched to move these technologies towards treatments to benefit diabetic patients.     

Autoimmune Diabetes Is Suppressed by Treatment with Recombinant Human Tissue Kallikrein-1

The kallikrein-kinin system (KKS) comprises a cascade of proteolytic enzymes and biogenic peptides that regulate several physiological processes. Over-expression of tissue kallikrein-1 and modulation of the KKS shows beneficial effects on insulin sensitivity and other parameters relevant to type 2 diabetes mellitus. However, much less is known about the role of kallikreins, in particular tissue kallikrein-1, in type 1 diabetes mellitus (T1D). We report that chronic administration of recombinant human tissue kallikrein-1 protein (DM199) to non-obese diabetic mice delayed the onset of T1D, attenuated the degree of insulitis, and improved pancreatic beta cell mass in a dose- and treatment frequency-dependent manner. Suppression of the autoimmune reaction against pancreatic beta cells was evidenced by a reduction in the relative numbers of infiltrating cytotoxic lymphocytes and an increase in the relative numbers of regulatory T cells in the pancreas and pancreatic lymph nodes. These effects may be due in part to a DM199 treatment-dependent increase in active TGF-beta1. Treatment with DM199 also resulted in elevated C-peptide levels, elevated glucagon like peptide-1 levels and a reduction in dipeptidyl peptidase-4 activity. Overall, the data suggest that DM199 may have a beneficial effect on T1D by attenuating the autoimmune reaction and improving beta cell health.     

Two incretin hormones GLP-1 and GIP: comparison of their actions in insulin secretion and β cell preservation

Gastric inhibitory polypeptide (GIP) and glucagon-like peptide-1 (GLP-1) are the two primary incretin hormones secreted from the intestine upon ingestion of glucose or nutrients to stimulate insulin secretion from pancreatic β cells. GIP and GLP-1 exert their effects by binding to their specific receptors, the GIP receptor (GIPR) and the GLP-1 receptor (GLP-1R), which belong to the G-protein coupled receptor family. Receptor binding activates and increases the level of intracellular cAMP in pancreatic β cells, thereby stimulating insulin secretion glucose-dependently. In addition to their insulinotropic effects, GIP and GLP-1 have been shown to preserve pancreatic β cell mass by inhibiting apoptosis of β cells and enhancing their proliferation. Due to such characteristics, incretin hormones have been gaining mush attention as attractive targets for treatment of type 2 diabetes, and indeed incretin-based therapeutics have been rapidly disseminated worldwide. However, despites of plethora of rigorous studies, molecular mechanisms underlying how GIPR and GLP-1R activation leads to enhancement of glucose-dependent insulin secretion are still largely unknown. Here, we summarize the similarities and differences of these two incretin hormones in secretion and metabolism, their insulinotropic actions and their effects on pancreatic β cell preservation. We then try to discuss potential of GLP-1 and GIP in treatment of type 2 diabetes.     

Selective destruction of mouse islet beta cells by human T lymphocytes in a newly-established humanized type 1 diabetic model

Type 1 diabetes (T1D) is caused by a T cell-mediated autoimmune response that leads to the loss of insulin-producing β cells. The optimal preclinical testing of promising therapies would be aided by a humanized immune-mediated T1D model. We develop this model in NOD-scid IL2rγ^null mice. The selective destruction of pancreatic islet β cells was mediated by human T lymphocytes after an initial trigger was supplied by the injection of irradiated spleen mononuclear cells (SMC) from diabetic nonobese diabetic (NOD) mice. This resulted in severe insulitis, a marked loss of total β-cell mass, and other related phenotypes of T1D. The migration of human T cells to pancreatic islets was controlled by the β cell-produced highly conserved chemokine stromal cell-derived factor 1 (SDF-1) and its receptor C-X-C chemokine receptor (CXCR) 4, as demonstrated by in vivo blocking experiments using antibody to CXCR4. The specificity of humanized T cell-mediated immune responses against islet β cells was generated by the local inflammatory microenvironment in pancreatic islets including human CD4⁺ T cell infiltration and clonal expansion, and the mouse islet β-cell-derived CD1d-mediated human iNKT activation. The selective destruction of mouse islet β cells by a human T cell-mediated immune response in this humanized T1D model can mimic those observed in T1D patients. This model can provide a valuable tool for translational research into T1D.     

Protective effects of polyamine depletion in mouse models of type 1 diabetes: implications for therapy

The underlying pathophysiology of type 1 diabetes involves autoimmune-mediated islet inflammation, leading to dysfunction and death of insulin-secreting islet β cells. Recent studies have shown that polyamines, which are essential for mRNA translation, cellular replication, and the formation of the hypusine modification of eIF5A may play an important role in the progression of cellular inflammation. To test a role for polyamines in type 1 diabetes pathogenesis, we administered the ornithine decarboxylase inhibitor difluoromethylornithine to two mouse models—the low-dose streptozotocin model and the NOD model—to deplete intracellular polyamines, and administered streptozotocin to a third model, which was haploinsufficient for the gene encoding the hypusination enzyme deoxyhypusine synthase. Subsequent development of diabetes and/or glucose intolerance was monitored. In the low-dose streptozotocin mouse model, continuous difluoromethylornithine administration dose-dependently reduced the incidence of hyperglycemia and led to the preservation of β cell area, whereas in the NOD mouse model of autoimmune diabetes difluoromethylornithine reduced diabetes incidence by 50 %, preserved β cell area and insulin secretion, led to reductions in both islet inflammation and potentially diabetogenic Th17 cells in pancreatic lymph nodes. Difluoromethylornithine treatment reduced hypusinated eIF5A levels in both immune cells and islets. Animals haploinsufficient for the gene encoding deoxyhypusine synthase were partially protected from hyperglycemia induced by streptozotocin. Collectively, these studies suggest that interventions that interfere with polyamine biosynthesis and/or eIF5A hypusination may represent viable approaches in the treatment of diabetes.     

Advances in the cellular immunological pathogenesis of type 1 diabetes

Type 1 diabetes is an autoimmune disease caused by the immune‐mediated destruction of insulin‐producing pancreatic β cells. In recent years, the incidence of type 1 diabetes continues to increase. It is supposed that genetic, environmental and immune factors participate in the damage of pancreatic β cells. Both the immune regulation and the immune response are involved in the pathogenesis of type 1 diabetes, in which cellular immunity plays a significant role. For the infiltration of CD4⁺ and CD8⁺ T lymphocyte, B lymphocytes, natural killer cells, dendritic cells and other immune cells take part in the damage of pancreatic β cells, which ultimately lead to type 1 diabetes. This review outlines the cellular immunological mechanism of type 1 diabetes, with a particular emphasis to T lymphocyte and natural killer cells, and provides the effective immune therapy in T1D, which is approached at three stages. However, future studies will be directed at searching for an effective, safe and long‐lasting strategy to enhance the regulation of a diabetogenic immune system with limited toxicity and without global immunosuppression.     

microRNA deficiency in pancreatic islet cells exacerbates streptozotocin-induced murine autoimmune diabetes

Recent studies have demonstrated that gene expression is regulated not only by protein-coding genes, but also by non-protein-coding small RNA molecules, microRNAs (miRNAs). miRNAs have emerged as important regulators involved in many biological processes, including cell proliferation and differentiation, apoptosis and metabolism, and disease development. Here we report that specific miRNA deficiency in pancreatic islet cells exacerbates multiple low-dose streptozotocin-induced murine autoimmune type 1 diabetes, suggesting that miRNAs expressed in islet β cells regulate their susceptibility to immune-mediated β cell destruction.     

Investigating Maturity Onset Diabetes of the Young

Maturity Onset Diabetes of Young (MODY) is a monogenic and autosomal dominant form of diabetes mellitus with onset of the disease often before 25 years of age. It is due to dysfunction of pancreatic ß cells characterised by non-ketotic diabetes and absence of pancreatic auto-antibodies. It is frequently mistaken for type 1 or type 2 diabetes mellitus. Diagnosis of MODY is important as the GCK subtype has better prognosis and may not require any treatment. Subtypes HNF1A and HNF4A are sensitive to sulfonylureas, however diabetes complications are common if not treated early. Moreover, there is genetic implication for the patient and family. Rare MODY subtypes can be associated with pancreatic and renal anomalies as well as exocrine dysfunction of the pancreas. So far there are six widely accepted subtypes of MODY described but the list has grown to nine. Although the majority of diabetes mellitus in youth remains type 1 and the incidence of type 2 is rising, MODY should be considered in patients with non-ketotic diabetes at presentation, and in patients with a strong family history of diabetes mellitus without pancreatic auto-antibodies. Furthermore the diagnosis must be confirmed by molecular studies. With advancement in genomic technology, rapid screening for MODY mutations will become readily available in the future.     

Differential regulation of embryonic and adult β cell replication

Diabetes results from an inadequate functional β cell mass, either due to autoimmune destruction (Type 1 diabetes) or insulin resistance combined with β cell failure (Type 2 diabetes). Strategies to enhance β cell regeneration or increase cell proliferation could improve outcomes for patients with diabetes. Research conducted over the past several years has revealed that factors regulating embryonic β cell mass expansion differ from those regulating replication ofβ cells post-weaning. This article aims to compare and contrast factors known to control embryonic and postnatal β cell replication. In addition, we explore the possibility that connective tissue growth factor (CTGF) could increase adult β cell replication. We have already shown that CTGF is required for embryonicβ cell proliferation and is sufficient to induce replication of embryonic β cells. Here we examine whether adult β cell replication and expansion of β cell mass can be enhanced by increased CTGF expression in mature β cells.     

Immune modulation for prevention of type 1 diabetes mellitus

Prevention of type 1 diabetes mellitus requires early intervention in the autoimmune process directed against beta cells of the pancreatic islets of Langerhans. This autoimmune inflammatory process is thought to be caused by the effect of Th1 cells and their secreted cytokines (e.g. interferon) and to be suppressed by Th2-secreted anti-inflammatory cytokines (e.g. IL-4, IL-10). Various methods aimed specifically at halting or modulating this response have been attempted. An alternative method is the re-induction of tolerance towards the putative self antigen that causes the disease. Proposed antigens such as insulin, glutamic acid decarboxilase (GAD) and the heat shock protein 60 (Hsp60)-derived peptide 277 have been used successfully in murine diabetes models and in initial clinical trials in early diabetes patients. Here, we review the results of these trials.     

In Type 1 Diabetes a Subset of Anti-Coxsackievirus B4 Antibodies Recognize Autoantigens and Induce Apoptosis of Pancreatic Beta Cells

Type 1 diabetes is characterized by autoimmune destruction of pancreatic beta cells. The role played by autoantibodies directed against beta cells antigens in the pathogenesis of the disease is still unclear. Coxsackievirus B infection has been linked to the onset of type 1 diabetes; however its precise role has not been elucidated yet. To clarify these issues, we screened a random peptide library with sera obtained from 58 patients with recent onset type 1 diabetes, before insulin therapy. We identified an immunodominant peptide recognized by the majority of individual patients’sera, that shares homology with Coxsackievirus B4 VP1 protein and with beta-cell specific autoantigens such as phogrin, phosphofructokinase and voltage-gated L-type calcium channels known to regulate beta cell apoptosis. Antibodies against the peptide affinity-purified from patients’ sera, recognized the viral protein and autoantigens; moreover, such antibodies induced apoptosis of the beta cells upon binding the L-type calcium channels expressed on the beta cell surface, suggesting a calcium dependent mechanism. Our results provide evidence that in autoimmune diabetes a subset of anti-Coxsackievirus antibodies are able to induce apoptosis of pancreatic beta cells which is considered the most critical and final step in the development of autoimmune diabetes without which clinical manifestations do not occur.     

Caveolin-1 deficiency protects pancreatic β cells against palmitate-induced dysfunction and apoptosis

Lipotoxicity leads to insulin secretion deficiency, which is among the important causes for the onset of type 2 diabetes mellitus. Thus, the restoration of β-cell mass and preservation of its endocrine function are long-sought goals in diabetes research. Previous studies have suggested that the membrane protein caveolin-1 (Cav-1) is implicated in β-cell apoptosis and insulin secretion, however, the underlying mechanisms still remains unclear. Our objective is to explore whether Cav-1 depletion protects pancreatic β cells from lipotoxicity and what are the underlying mechanisms. In this study, we found that Cav-1 silencing significantly promoted β-cell proliferation, inhibited palmitate (PA)-induced pancreatic β-cell apoptosis and enhanced insulin production and secretion. These effects were associated with enhanced activities of Akt and ERK1/2, which in turn downregulated the expression of cell cycle inhibitors (FOXO1, GSK3β, P21, P27 and P53) and upregulated the expression of Cyclin D2 and Cyclin D3. Subsequent inhibition of PI3K/Akt and ERK/MAPK pathways abolished Cav-1 depletion induced β-cell mass protection. Furthermore, under PA induced endoplasmic reticulum (ER) stress, Cav-1 silencing significantly reduced eIF2α phosphorylation and the expression of ER stress-responsive markers BiP and CHOP, which are among the known sensitizers of lipotoxicity. Our findings suggest Cav-1 as potential target molecule in T2DM treatment via the preservation of lipotoxicity-induced β-cell mass reduction and the attenuation of insulin secretion dysfunction.     

MicroRNA-203a regulates pancreatic β cell proliferation and apoptosis by targeting IRS2

Molecular Biology Reports - The main pathogenesis of type 1 diabetes mellitus (T1DM) is autoimmune-mediated apoptosis of pancreatic islet β cells. We sought to characterize the function of...     

Secretin-stimulated amylase release into blood is impaired in type 1 diabetes mellitus.

BACKGROUND: Prior studies have provided data indicating the existence of close interaction between pancreatic endocrine and exocrine function, but few clinical studies have explored this relationship in depth. We compared pancreatic exocrine function non-endoscopically in individuals with type 1 diabetes mellitus, type 2 diabetes mellitus, and normal glucose tolerant controls, to assess the importance of local insulin production to pancreatic exocrine function. METHODS: The plasma amylase response to intravenous secretin challenge was measured in men with type 1 diabetes mellitus (n = 5), type 2 diabetes mellitus (n = 5), and normal controls (n = 3). Patients were characterized by their urinary excretion of c-peptide and albumin over 24 hours. Autonomic neuropathy was non-invasively assessed by measuring RR variation (with deep respiration on EKG). RESULTS: Post-secretin amylase responses were generally absent with low baseline levels in the patients with type 1 diabetes mellitus. Patients with type 2 diabetes mellitus and controls showed similar twofold increases over baseline after secretin administration. When normal glucose tolerant and type 2 diabetic patients were pooled and compared against type 1 diabetes mellitus, the differences were statistically significant (p < 0.03). Total amylase response correlated positively, but weakly, with 24 h urinary C-peptide excretion (r = 0.507; p < 0.112), but not with glycemic control, duration of diabetes, or indices of autonomic neuropathy. CONCLUSIONS: Patients with type 1 diabetes mellitus, but not type 2 diabetes mellitus, have reduced pancreatic exocrine function, supporting the concept of a local paracrine effect of insulin on pancreatic acinar cells. Further studies are needed to determine the clinical impact of this deficiency, and whether such patients with type 1 diabetes mellitus would benefit from therapy with pancreatic enzyme supplementation.     

The binary switch that controls the life and death decisions of ER stressed β cells

Diabetes mellitus is a group of common metabolic disorders defined by hyperglycemia. One of the most important factors contributing to hyperglycemia is dysfunction and death of β cells. Increasing experimental, clinical, and genetic evidence indicates that endoplasmic reticulum (ER) stress plays an important role in β cell dysfunction and death during the progression of type 1 and type 2 diabetes as well as genetic forms of diabetes such as Wolfram syndrome. The mechanisms of ER stress-mediated β cell dysfunction and death are complex and not homogenous. Here we review the recent key findings on the role of ER stress and the unfolded protein response (UPR) in β cells and the mechanisms of ER stress-mediated β cell dysfunction and death. Complete understanding of these mechanisms will lead to novel therapeutic modalities for diabetes.     

胰岛细胞抗体分型与胰岛细胞凋亡的实验研究

研究通过大量临床糖尿病病人胰岛细胞抗体（Islet Cell Antibody,ICA)检测,发现ICA阳性反应有两种完全不同的形态学表现;弥漫型ICA和边缘型ICA,经免疫组织化学双标技术鉴别。弥漫型ICA可同时有着染α细胞和β细胞,边缘型ICA则仅着染α细胞。这种只着染α细胞的ICA国内外尚未见有报道,为探讨其在糖尿病发病中所起的作用。选择1型糖尿病（1-DM）的弥漫型ICA和边缘型ICA各3例。另选正常3例作对照,用患血清分别以2、4、8小时三个时相与分离并贴壁生长的正常人胰岛细胞孵育后,进行原位细胞凋亡检测。结果发现,弥漫型ICA,边缘型ICA均可导致胰岛细胞产生凋亡,其中弥漫型ICA使β细胞及α细胞出现凋亡;边缘型ICA使α细胞产生凋亡,这一结果提示;糖尿病发病机制除与分泌胰岛素的β细胞有密切关系的经典途径之外,可能还与分泌胰高血糖素的α细胞存在某种关系。     

Diabetes mellitus-cell transplantation and gene therapy approaches

Diabetes mellitus affects millions of people in the United States and worldwide. It has become clear over the past decade that the chronic complications of diabetes result from lack of proper blood glucose concentration regulation, and particularly the toxic effects of chronic hyperglycemia on organs and tissues. Pancreas transplants can cure insulin-dependent diabetes mellitus (IDDM). Furthermore, recent advances in pancreatic islet isolation and immunosuppressive regimens have resulted in dramatic improvements in the survival and function of islet allografts. Therefore, islet replacement strategies are becoming increasingly attractive options for patients at risk for severe diabetic complications. A major limitation of these approaches is the small number of organs available for transplantation or islet isolation. Thus, an important next step in developing curative treatments for type I diabetes will be the generation of a replenishable source of glucose-responsive, insulin-secreting cells that can be used for beta cell replacement. This review focuses on approaches to developing robust and widely applicable beta-cell replacement strategies with an emphasis on manipulating beta-cell growth and differentiation by genetic engineering.     

mTORC2 Signaling: A Path for Pancreatic β Cell's Growth and Function

The mechanistic target of rapamycin (mTOR) signaling pathway is an evolutionary conserved pathway that senses signals from nutrients and growth factors to regulate cell growth, metabolism and survival. mTOR acts in two biochemically and functionally distinct complexes, mTOR complex 1 (mTORC1) and 2 (mTORC2), which differ in terms of regulatory mechanisms, substrate specificity and functional outputs. While mTORC1 signaling has been extensively studied in islet/β-cell biology, recent findings demonstrate a distinct role for mTORC2 in the regulation of pancreatic β-cell function and mass. mTORC2, a key component of the growth factor receptor signaling, is declined in β cells under diabetogenic conditions and in pancreatic islets from patients with type 2 diabetes. β cell-selective mTORC2 inactivation leads to glucose intolerance and acceleration of diabetes as a result of reduced β-cell mass, proliferation and impaired glucose-stimulated insulin secretion. Thereby, many mTORC2 targets, such as AKT, PKC, FOXO1, MST1 and cell cycle regulators, play an important role in β-cell survival and function. This indicates mTORC2 as important pathway for the maintenance of β-cell homeostasis, particularly to sustain proper β-cell compensatory response in the presence of nutrient overload and metabolic demand. This review summarizes recent emerging advances on the contribution of mTORC2 and its associated signaling on the regulation of glucose metabolism and functional β-cell mass under physiological and pathophysiological conditions in type 2 diabetes.