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Long-term treatment with glucagon-like peptide (GLP)-1 or its analog can improve insulin sensitivity. However, continuous administration is required due to its short half-life. We hypothesized that continuous production of therapeutic levels of GLP-1 in vivo by a gene therapy strategy may remit hyperglycemia and maintain prolonged normoglycemia. We produced a recombinant adenovirus expressing GLP-1 (rAd-GLP-1) under the cytomegalovirus promoter, intravenously injected it into diabetic ob/ob mice, and investigated the effect of this treatment on remission of diabetes, as well as the mechanisms involved. rAd-GLP-1-treated diabetic ob/ob mice became normoglycemic 4 days after treatment, remained normoglycemic over 60 days, and had reduced body weight gain. Glucose tolerance tests found that exogenous glucose was cleared normally, rAd-GLP-1-treated diabetic ob/ob mice showed improved β-cell function, evidenced by glucose-responsive insulin release, and increased insulin sensitivity, evidenced by improved insulin tolerance and increased insulin-stimulated glucose uptake in adipocytes, rAd-GLP-1 treatment increased basal levels of insulin receptor substrate (IRS)-1 in the liver and activation of IRS-1 and protein kinase C by insulin in liver and muscle; increased Akt activation was only observed in muscle, rAd-GLP-1 treatment reduced hepatic glucose production and hepatic expression of phosphoenolpyruvate carboxykinase, glucose-6-phosphatase, and fatty acid synthase in ob/ob mice. Taken together, these results show that a single administration of rAd-GLP-1 results in the long-term remission of diabetes in ob/ob mice by improving insulin sensitivity through restoration of insulin signaling and reducing hepatic gluconeogenesis., Glucagon-like peptide (GLP)-1 is produced through posttranslational processing of proglucagon and is secreted by intestinal L-cells in response to nutrient ingestion. Studies have shown that GLP-1 acts as a potent [...]

OBJECTIVE--Treatment of diabetic patients by pancreatic islet transplantation often requires the use of islets from two to four donors to produce insulin independence in a single recipient. Following isolation and transplantation, islets are susceptible to apoptosis, which limits their function and probably long-term islet graft survival. RESEARCH DESIGN AND METHODS--To address this issue, we examined the effect of the cell-permeable apoptosis inhibitor pentapeptide Val-Pro-Met-Leu-Lys, V5, on pancreatic islets in a mouse model. RESULTS--V5 treatment upregulated expression of anti-apoptotic proteins Bcl-2 and XIAP (X-linked inhibitor of apoptosis protein) by more than 3- and 11-fold and downregulated expression of apoptosis-inducing proteins Bax, Bad, and nuclear factor-κB-p65 by 10, 30, and nearly 50%, respectively. Treatment improved the recovered islet mass following collagenase digestion and isolation by 44% and in vitro glucose-responsive insulin secretion nearly fourfold. Following transplantation in streptozotocin-induced diabetic mice, 150 V5-treated islet equivalents functioned as well as 450 control untreated islet equivalents in normalizing blood glucose. CONCLUSIONS--These studies indicate that inhibition of apoptosis by V5 significantly improves islet function following isolation and improves islet graft function following transplantation. Use of this reagent in clinical islet transplantation could have a dramatic impact on the number of patients that might benefit from this therapy and could affect long-term graft survival., Pancreatic islet transplantation holds great promise as a treatment for type 1 diabetes. Insulin independence has been accomplished using a glucocorticoid-free immunosuppression regimen but often requires transplantation of islets from [...]

Type 1 diabetes results from the destruction of insulin-producing pancreatic β-cells by a β-cell-specific autoimmune process. Although converting other cell types into insulin-producing cells may compensate for the loss of the β-cell mass while evading β-cell-specific T-cell responses, proof-of-principle of this approach in large animal models is lacking. This investigation was initiated to determine whether an insulin-producing human hepatocyte line can control diabetes when transplanted into totally pancreatectomized diabetic pigs. We established a reversibly immortalized human hepatocyte line, YOCK-13, by transferring a human telomerase reverse transcriptase cDNA and a drug-inducible Cre recombinase cassette, followed by cDNA for a modified insulin under the control of the L-type pyruvate kinase (L-PK) promoter. YOCK-13 cells produced small amounts of modified insulin and no detectable endogenous L-PK at low glucose concentrations, whereas they produced large amounts of both modified insulin and L-PK in response to high glucose concentrations. Xenotransplantation of YOCK-13 cells via the portal vein into immunosuppressed, totally pancreatectomized pigs decreased hyperglycemia and prolonged survival without adverse effects such as portal thrombosis, liver necrosis, pulmonary embolism, and tumor development. We suggest that this reversibly immortalized, insulin-secreting human hepatocyte line may overcome the shortage of donor pancreata for islet transplantation into patients with type 1 diabetes., Despite intensive management, type 1 diabetes is still associated with a high incidence of complications and considerable subsequent mortality (1). Although much progress has been achieved in the field of [...]

GAD is a pancreatic β-cell autoantigen in humans and nonobese diabetic (NOD) mice. Modulation of GAD expression in pancreatic β-cells has been suggested to be associated with the development of autoimmune diabetes. Hormonal changes through environmental stimuli are considered to influence the expression of the disease. We determined whether steroid hormones would modulate the expression of GAD in pancreatic β-cells. We treated NOD mouse beta-cells (MIN6N8a cells) with various steroids, including testosterone, estradiol, progesterone, and cortisol, and examined the expression of GAD67 mRNA. We found that only cortisol enhanced the expression of GAD67, whereas the other steroid hormones had no effect. When we treated MIN6N8a cells with a synthetic glucocorticoid, dexamethasone, we found that GAD67 mRNA expression was stimulated in a dose- and time-dependent manner. Cells treated with 100 nmol/l dexamethasone for 6 h showed a 10-fold increase in the expression of GAD67 mRNA and an increase in GAD67 protein. The upregulation of GAD67 expression in β-cells by dexamethasone was found to be due to the transcriptional activation of the GAD67 promoter. We then examined whether dexamethasone would influence the development of diabetes in NOD mice. Injection of dexamethasone into neonatal NOD mice resulted in a significant increase in the expression of GAD67 mRNA in pancreatic β-cells and the development of insulitis and diabetes. We conclude that glucocorticoid hormones can modulate GAD expression by the transcriptional activation of the GAD promoter and may influence the development of autoimmune diabetes in NOD mice., GAD is an enzyme that catalyzes the formation of the inhibitory neurotransmitter γ-aminobutyric acid (GABA) from glutamic acid. The two isoforms of GAD, GAD65 and GAD67, are encoded by two [...]

The molecular mechanism by which some, but not all, variants of encephalomyocarditis (EMC) virus selectively infect pancreatic Β-cells in mice and induce IDDM has been an enigma for more than [...]

Autoimmunity to glutamic acid decarboxylase (GAD) was shown to be present in the early stage of insulitis in non-obese diabetic (NOD) mice, and the induction of tolerance to GAD before [...]

Proinflammatory cytokines and free radicals such as nitric oxide (NO) are known to play a role in the development of diabetes in spontaneously diabetic animal models. NO is produced by [...]

Insulin-dependent diabetes mellitus (IDDM) is believed to be an autoimmune disease resulting from T cell-mediated [Beta] cell destruction. It was previously shown that macrophages are one of the first infiltrates [...]

It was previously shown that transforming growth factor (FGF[Beta]) TGF[Beta] secreted from a [CD4.sup.+] suppressor T cell clone can prevent cell mediated autoimmune diabetes in nonobese diabetic (NOD) mice. However, [...]

The Structural Capsid Protein, VP2, of Kilham Rat Virus Controls the Development of Diabetes in DR-BB Rats by a Skewed Th1 Immune Response. Kilham rat virus (KRV) has been shown [...]