Cell-Surface ZnT8 Antibody Prevents and Reverses Autoimmune Diabetes in Mice.

Type 1 diabetes (T1D) is an autoimmune disease in which pathogenic lymphocytes target autoantigens expressed in pancreatic islets, leading to the destruction of insulin-producing ß-cells. Zinc transporter 8 (ZnT8) is a major autoantigen abundantly present on the ß-cell surface. This unique molecular target offers the potential to shield ß-cells against autoimmune attacks in T1D. Our previous work showed that a monoclonal antibody (mAb43) against cell-surface ZnT8 could home in on pancreatic islets and prevent autoantibodies from recognizing ß-cells. This study demonstrates that mAb43 binds to exocytotic sites on the ß-cell surface, masking the antigenic exposure of ZnT8 and insulin after glucose-stimulated insulin secretion. In vivo administration of mAb43 to NOD mice selectively increased the proportion of regulatory T cells in the islet, resulting in complete and sustained protection against T1D onset as well as reversal of new-onset diabetes. The mAb43-induced self-tolerance was reversible after treatment cessation, and no adverse effects were exhibited during long-term monitoring. Our findings suggest that mAb43 masking of the antigenic exposure of ß-cells suppresses the immunological cascade from B-cell antigen presentation to T cell-mediated ß-cell destruction, providing a novel islet-targeted and antigen-specific immunotherapy to prevent and reverse clinical T1D.

Hydrogel Alginate Considerations for Improved 3D Matrix Stability and Cell Graft Viability and Function in Studying Type 1 Diabetes In Vitro.

Biomedical devices such as islet-encapsulating systems are used for treatment of type 1 diabetes (T1D). Despite recent strides in preventing biomaterial fibrosis, challenges remain for biomaterial scaffolds due to limitations on cells contained within. The study demonstrates that proliferation and function of insulinoma (INS-1) cells as well as pancreatic rat islets may be improved in alginate hydrogels with optimized gel%, crosslinking, and stiffness. Quantitative polymerase chain reaction (qPCR)-based graft phenotyping of encapsulated INS-1 cells and pancreatic islets identified a hydrogel stiffness range between 600 and 1000 Pa that improved insulin Ins and Pdx1 gene expression as well as glucose-sensitive insulin-secretion. Barium chloride (BaCl2 ) crosslinking time is also optimized due to toxicity of extended exposure. Despite possible benefits to cell viability, calcium chloride (CaCl2 )-crosslinked hydrogels exhibited a sharp storage modulus loss in vitro. Despite improved stability, BaCl2 -crosslinked hydrogels also exhibited stiffness losses over the same timeframe. It is believed that this is due to ion exchange with other species in culture media, as hydrogels incubated in dIH2 O exhibited significantly improved stability. To maintain cell viability and function while increasing 3D matrix stability, a range of useful media:dIH2 O dilution ratios for use are identified. Such findings have importance to carry out characterization and optimization of cell microphysiological systems with high fidelity in vitro.

Cell-Surface Autoantibody Targets Zinc Transporter-8 (ZnT8) for In Vivo ß-Cell Imaging and Islet-Specific Therapies.

Type 1 diabetes (T1D) is a disease in which autoimmune attacks are directed at the insulin-producing ß-cell in the pancreatic islet. Autoantigens on the ß-cell surface membrane are specific markers for molecular recognition and targets for engagement by autoreactive B lymphocytes, which produce islet cell surface autoantibody (ICSA) upon activation. We report the cloning of an ICSA (mAb43) that recognizes a major T1D autoantigen, ZnT8, with a subnanomolar binding affinity and conformation specificity. We demonstrate that cell-surface binding of mAb43 protects the extracellular epitope of ZnT8 against immunolabeling by serum ICSA from a patient with T1D. Furthermore, mAb43 exhibits in vitro and ex vivo specificity for islet cells, mirroring the exquisite specificity of islet autoimmunity in T1D. Systemic administration of mAb43 yields a pancreas-specific biodistribution in mice and islet homing of an mAb43-linked imaging payload through the pancreatic vasculature, thereby validating the in vivo specificity of mAb43. Identifying ZnT8 as a major antigenic target of ICSA allows for research into the molecular recognition and engagement of autoreactive B cells in the chronic phase of T1D progression. The in vivo islet specificity of mAb43 could be further exploited to develop in vivo imaging and islet-specific immunotherapies.

Mitochondrial ATP6 and ND3 genes are associated with type 2 diabetic peripheral neuropathy.

BACKGROUND AND AIMS: The association of mitochondrial NADH dehydrogenase gene mutations with type 2 diabetes in the Karaikudi population was previously reported. This is a case report that demonstrated rare mutations are responsible for maternally inherited peripheral neuropathy of diabetes. METHODS: We describe a 70-year-old male and his family (n = 25) with type 2 diabetic peripheral neuropathy having four rare mutations, 8597T > C, 8699T > C, 8966T > C, 10188A > G, and 9 bp deletion in various regions of the mitochondrial genes. Mutations were identified through direct sequencing of DNA isolated from the blood of the selected individuals. Blood samples were also analyzed for glucose, hemoglobin A1c, triglyceride, total cholesterol, oxidative stress markers, antioxidant status, cytochrome-C-oxidase and mitochondrial DNA content using appropriate methods. RESULTS: Oxidative stress markers were found elevated while the antioxidant status, mitochondrial DNA content and the activity of cytochrome C-oxidase was reduced significantly. Analysis of mtDNA showed the presence of several mutations in various regions of mitochondrial genome. However, 8597T > C, 8699T > C, 8966T > C, 10188A > G, and 9 bp deletion were observed in the patient's family including his siblings. CONCLUSION: This study shows that the mutations observed in the patient and his family is maternally inherited and suspected to be pathogenic in developing T2D associated peripheral neuropathy.