Objective: Glucagon-like peptide-1 (GLP-1) and gastrin promote pancreatic beta-cell function, survival, and growth. Here, we investigated whether GLP-1 and gastrin can restore the beta-cell mass and reverse hyperglycemia in NOD mice with autoimmune diabetes.
Research design and methods: Acutely diabetic NOD mice were treated with GLP-1 and gastrin, separately or together, twice daily for 3 weeks. Blood glucose was measured weekly and for a further 5 weeks after treatments, after which pancreatic insulin content and beta-cell mass, proliferation, neogenesis, and apoptosis were measured. Insulin autoantibodies were measured, and adoptive transfer of diabetes and syngeneic islet transplant studies were done to evaluate the effects of GLP-1 and gastrin treatment on autoimmunity.
Results: Combination therapy with GLP-1 and gastrin, but not with GLP-1 or gastrin alone, restored normoglycemia in diabetic NOD mice. The GLP-1 and gastrin combination increased pancreatic insulin content, beta-cell mass, and insulin-positive cells in pancreatic ducts, and beta-cell apoptosis was decreased. Insulin autoantibodies were reduced in GLP-1- and gastrin-treated NOD mice, and splenocytes from these mice delayed adoptive transfer of diabetes in NOD-scid mice. Syngeneic islet grafts in GLP-1 -and gastrin-treated NOD mice were infiltrated by leukocytes with a shift in cytokine expression from interferon-gamma to transforming growth factor-beta1, and beta-cells were protected from apoptosis.
Conclusions: Combination therapy with GLP-1 and gastrin restores normoglycemia in diabetic NOD mice by increasing the pancreatic beta-cell mass and downregulating the autoimmune response.