Insulinotropic actions of intravenous glucagon-like peptide-1 (GLP-1) [7-36 amide] in the fasting state in healthy subjects.

GLP-1 (7-36 amide) stimulates insulin and suppresses glucagon secretion in normal subjects and may, in pharmacological doses, normalize hyperglycaemia in type 2 diabetic patients. It is not known whether such pharmacological doses can actually lower blood glucose to hypoglycaemic levels. Therefore, in seven normal fasting subjects, GLP-1 (7-36 amide) was infused intravenously at 0.3, 0.9 and 2.7 pmol/kg per min for 30 min each. The plasma concentration of GLP-1 (7-36 amide) increased dose-dependently, but insulin secretion (insulin, C-peptide) was stimulated only marginally. Glucagon was slightly suppressed, and plasma glucose was reduced, but not into the hypoglycaemia range. In conclusion, when plasma glucose concentrations are in the normal fasting range, GLP-1 (7-36 amide) is not able to stimulate insulin secretion to a degree that causes hypoglycaemia. This should limit the risk of hypoglycaemic responses when GLP-1 (7-36 amide) is administered in pharmacological doses to reduce hyperglycaemia in type 2 diabetic patients.