Effect of glucagon-like peptide 1 (7-37) on in vivo insulin sensitivity in rats

Glucagon-like peptide 1 (GLP-1) (7-37) has been known as an 'incretin' which is released from the gut after glucose load and stimulates glucose-dependent insulin secretion. Recently, GLP-1 has also been reported to potentiate insulin action. We attempted to investigate the effect of GLP-1 on in vivo insulin sensitivity, using rat euglycemic hyperinsulinemic glucose clamp. Although the maximum effect of insulin on glucose uptake was the same both with and without infusion of GLP-1, the dose-response curve of glucose uptake with GLP-1 infusion was significantly shifted to the left, when compared to that of the insulin alone infusion group. However, the dose-response curves of suppression of hepatic glucose output during clamp with and without GLP-1 infusion were the same. In conclusion, GLP-1 enhanced insulin-stimulated glucose uptake by peripheral tissue, but did not influence the insulin-mediated suppression of hepatic glucose output.