Alpha-Cell Sensitivity to GLP-1 in Patients With Type 2 Diabetes

Background: Glucagon-like peptide-1 (GLP-1) possesses insulinotropic and glucagonostatic properties, and, therefore, GLP-based antidiabetic therapies have been developed. Even though the insulinotropic potency of GLP-1 has been shown to be reduced in patients with type 2 diabetes mellitus (T2DM), a small dose of GLP-1 is capable of normalizing the beta-cell responsiveness to glucose in these patients. The glucagonostatic potency of GLP-1 in patients with T2DM is not known, and, furthermore, the capability of GLP-1 to reestablish normal glucagon secretion in these patients remains to be elucidated. Objective: To investigate the alpha-cell sensitivity to GLP-1 in patients with T2DM and to establish if GLP-1 is able to reestablish normal glucagon secretion in such patients. Method: Ten patients with T2DM and ten healthy control subjects are clamped at their fasting blood glucose levels during GLP-1 infusions at increasing doses (0.25, 0.5, 1.0 and 2.0 pmol/kg/min) and placebo, respectively. Furthermore, the patients will be hospitalized overnight while receiving intravenous insulin and thereafter examined under normoglycaemic conditions. Blood are being drawn for analysis of plasma insulin, C-peptide, GLP-1 and glucagon. Expected results and conclusions: We expect that GLP-1 will inhibit glucagon secretion in a dose dependent manner, leading too an increase in glucose turn-over. The results will potentially elucidate the interaction between GLP-1 and glucagon secretion and thereby broaden our knowledge on the pathophysiology of T2DM. Furthermore, the present study will determine the therapeutic impact of GLP-1 on the alpha-cell deficiency characterizing patients with T2DM.