Objective: The gut hormone glucagon-like peptide 1 (GLP-1) has insulinotropic and anorectic effects during intravenous infusion and has been proposed as a new treatment for type 2 diabetes and obesity. The effect of a single subcutaneous injection is brief because of rapid degradation. We therefore sought to evaluate the effect of infusion of GLP-1 for 48 h in patients with type 2 diabetes.
Research design and methods: We infused GLP-1 (2.4 pmol.kg-1.min-1) or saline subcutaneously for 48 h in randomized order in six patients with type 2 diabetes to evaluate the effect on appetite during fixed energy intake and on plasma glucose, insulin, glucagon, postprandial lipidemia, blood pressure, heart rate, and basal metabolic rate.
Results: The infusion resulted in elevations of the plasma concentrations of intact GLP-1 similar to those observed after intravenous infusion of 1.2 pmol.kg-1.min-1, previously shown to lower blood glucose effectively in type 2 diabetic patients. Fasting plasma glucose (day 2) decreased from 14.1 +/- 0.9 (saline) to 12.2 +/- 0.7 mmol/l (GLP-1), P = 0.009, and 24-h mean plasma glucose decreased from 15.4 +/- 1.0 to 13.0 +/- 1.0 mmol/l, P = 0.0009. Fasting and total area under the curve for insulin and C-peptide levels were significantly higher during the GLP-1 administration, whereas glucagon levels were unchanged. Neither triglycerides nor free fatty acids were affected. GLP-1 administration decreased hunger and prospective food intake and increased satiety, whereas fullness was unaffected. No side effects during GLP-1 infusion were recorded except for a brief cutaneous reaction. Basal metabolic rate and heart rate did not change significantly during GLP-1 administration. Both systolic and diastolic blood pressure tended to be lower during the GLP-1 infusion.
Conclusions: We conclude that 48-h continuous subcutaneous infusion of GLP-1 in type 2 diabetic patients 1) lowers fasting as well as meal-related plasma glucose, 2) reduces appetite, 3) has no gastrointestinal side effects, and 4) has no negative effect on blood pressure.