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γ-Aminobutyric acid (GABA) has been shown to inhibit apoptosis of rodent β-cells in vitro. In this study, we show that activation of [GABA.sub.A] receptors ([GABA.sub.A]-RS) or [GABA.sub.B]-RS significantly inhibits oxidative stress-related β-cell apoptosis and preserves pancreatic β-cells in streptozotocin-rendered hyperglycemic mice. Moreover, treatment with GABA, or a [GABA.sub.A]-R- or [GABA.sub.B]-R-specific agonist, inhibited human β-cell apoptosis following islet transplantation into NOD/scid mice. Accordingly, activation of [GABA.sub.A]-RS and/or [GABA.sub.B]-Rs may be a useful adjunct therapy for human islet transplantation. GABA-R agonists also promoted β-cell replication in hyperglycemic mice. While a number of agents can promote rodent β-cell replication, most fail to provide similar activities with human β-cells. In this study, we show that GABA administration promotes β-cell replication and functional recovery in human islets following implantation into NOD/scid mice. Human β-cell replication was induced by both [GABA.sub.A]-R and [GABA.sub.B]-R activation. Hence, GABA regulates both the survival and replication of human [3-cells. These actions, together with the anti-inflammatory properties of GABA, suggest that modulation of peripheral GABA-Rs may represent a promising new therapeutic strategy for improving [3-cell survival following human islet transplantation and increasing [3-cells in patients with diabetes. Diabetes 62:3760-3765, 2013, A central focus of research in the type 1 diabetes (T1D) field is to develop ways to safely improve [3-cell survival and function and promote their replication. The addition of [...]

OBJECTIVE--β-Cells that express an imaging reporter have provided powerful tools for studying β-cells development, islet transplantation, and β-Cells autoimmunity. To further expedite diabetes research, we generated transgenic C57BL/6 'MIP-TF' mice that have a mouse insulin promoter (MIP) driving the expression of a trifusion (TF) protein of three imaging reporters (luciferase/ enhanced green fluorescent protein/HSVl-sr39 thymidine kinase) in their β-cells. This should enable the noninvasive imaging of β-cells by charge-coupled device (CCD) and micro-positron emission tomography (PET), as well as the identification of β-cells at the cellular level by fluorescent microscopy. RESEARCH DESIGN AND METHODS--MIP-TF mouse β-Cells were multimodality imaged in models of type 1 and type 2 diabetes. RESULTS--MIP-TF mouse β-cells were readily identified in pancreatic tissue sections using fluorescent microscopy. We show that MIP-TF β-cells can be noninvasively imaged using microPET. There was a correlation between CCD and microPET signals from the pancreas region of individual mice. After low-dose streptozotocin administration to induce type 1 diabetes, we observed aprogressive reduction in bioluminescence from the pancreas region before the appearance of hyperglycemia. Although there have been reports of hyperglycemia inducing proinsulin expression in extrapancreatic tissues, we did not observe bioluminescent signals from extrapancreatic tissues of diabetic MIP-TF mice. Because MIP-TF mouse β-cells express a viral thymidine kinase, ganciclovir treatment induced hyperglycemia, providing a new experimental model of type 1 diabetes. Mice fed a high-fat diet to model early type 2 diabetes displayed a progressive increase in their pancreatic bioluminescent signals, which were positively correlated with area under the curve-intraperitoneal glucose tolerance test (AUC-IPGTT). CONCLUSIONS--MIP-TF mice provide a new tool for monitoring β-cells from the single cell level to noninvasive assessments of β-cells in models of type 1 diabetes and type 2 diabetes. Diabetes 60:1383-1392, 2011, The expression of imaging reporter genes in β-cells has provided powerful tools for studying β-cell development, embryonic and adult stem cell differentiation into β-cells, transdifferentiation, and islet transplantation (1-13). Bioluminescent [...]

OBJECTIVE--To study how tolerance to GAD65 affects the development of autoimmunity to other β-cell autoantigens (β-CAAs) in GAD654ransgenic (GAD-tg) NOD mice. RESEARCH DESIGN AND METHODS--We used ELISPOT to characterize the frequency and functional phenotype of T-cell responses to GAD65 and other β-CAAs at different ages in GAD-tg mice and their NOD mouse littermates. RESULTS--In young GAD-tg mice, Th1 responses to GAD65's dominant determinants were 13-18% of those in young NOD mice. This coincided with a great reduction in Th1 responses to other β-CAAs. Evidently, GAD65-reactive T-cells are important for activating and/or expanding early autoreactivities in NOD mice. As GAD-tg mice aged, their T-cell responses to GAD65 remained low, but they developed supernormal splenic and pancreatic lymph node T-cell autoimmunity to other β-CAAs. Apparently, the elimination/impairment of many GAD65-reactive T-cells allowed other β-CAA-reactive T-cells to eventually expand to a greater extent, perhaps by reducing competition for antigen-presenting cells, or homeostatic proliferation in the target tissue, which may explain the GAD-tg mouse's usual disease incidence. CONCLUSIONS--Transgenically induced reduction of GAD65 autoreactivity curtailed the development of early T-cell responses to other β-CAAs. However, later in life, β-CAA-reactive T-cells expanded to supernormal levels. These data suggest that early p-cell autoreactivities are mutually dependent for support to activate and expand, while later in the disease process, autoantigen-specific T-cell pools can expand autonomously. These findings have implications for understanding type 1 diabetes immunopathogenesis and for designing antigen-based immunotherapeutics., The role of T-cell autoreactivity to the 65-kDa form of GAD (GAD65) in the etiology of type 1 diabetes in nonobese diabetic (NOD) mice has been much debated, in large [...]

Antigen-based therapies (ABTs) seek to prevent or inhibit autoimmune diseases by inducing regulatory T-cell responses (active tolerance) or anergizing/deleting pathogenic T-cells (passive tolerance). The theoretical appeal of this therapeutic approach [...]

Reactive oxygen species, such as superoxide, and nitrogen oxides, such as peroxynitrite, are thought to contribute to β-cell destruction during the disease process that leads to type 1 diabetes. EUK-8 is a member of a new class of synthetic salen-manganese compounds with low toxicity that possess catalytic superoxide dismutase, peroxidase, and catalase activity that can inactivate superoxide and nitrogen oxides (e.g., peroxynitrite and nitrogen dioxide). We observed that EUK-8 administration inhibited the adoptive transfer of type 1 diabetes to NOD mice. In addition, administration of EUK-8 to NOD mice with established autoimmunity completely prevented the development of type 1 diabetes for up to 1 year in age, even though the treatment was discontinued after 35 weeks of age. EUK-8 treatment also prolonged the survival of islet allografts in newly diabetic NOD mice. Thus, reactive oxygen and nitrogen species contribute to the pathoetiology of both spontaneous type 1 diabetes and allograft rejection. In cultures of NIT-1 cells, EUK-8 inhibited cytotoxicity caused by superoxide as well as nitric oxide. Collectively, our findings implicate a greater role for nitrogen oxides (other than peroxynitrite) in β-cell damage. Antioxidants designed to prevent the formation of both cytotoxic reactive oxygen and nitrogen species may effectively protect β-cells from spontaneous autoimmunity and alloresponses., The pathology of type 1 diabetes is characterized by the infiltration of the pancreatic islets by T-and B-cells and macrophages. These cells mediate β-cell destruction by the production of proinflammatory [...]