Suppression of glucose production by GLP-1 independent of islet hormones: a novel extrapancreatic effect.

Glucagon-like peptide-1 (GLP-1) is an intestinal hormone that stimulates insulin secretion and decreases glucagon release. It has been hypothesized that GLP-1 also reduces glycemia independent of its effect on islet hormones. Based on preliminary evidence that GLP-1 has independent actions on endogenous glucose production, we undertook a series of experiments that were optimized to address this question.

Differential effects of acute and extended infusions of glucagon-like peptide-1 on first- and second-phase insulin secretion in diabetic and nondiabetic humans.

Objective: The purpose of this study was to determine whether an extended infusion of the incretin hormone glucagon-like peptide 1 (GLP-1) has a greater effect to promote insulin secretion in type 2 diabetic subjects than acute administration of the peptide.

Research Design And Methods: Nine diabetic subjects and nine nondiabetic volunteers of similar age and weight were studied in identical protocols. First-phase insulin release (FPIR; the incremental insulin response in the first 10 min after the intravenous glucose bolus) and second-phase insulin release (SPIR; the incremental insulin response from 10-60 min after intravenous glucose) were measured during three separate intravenous glucose tolerance tests (IVGTTs): 1).