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 gluc
ose-dependent insulin secretion. Recently, GLP-1 has also been reporte
d to potentiate insulin action. We attempted to investigate the effect
of GLP-1 on in vivo insulin sensitivity, using rat euglycemic hyperin
sulinemic glucose clamp. Although the maximum effect of insulin on glu
cose uptake was the same both with and without infusion of GLP-1, the
dose-response curve of glucose uptake with GLP-1 infusion was signific
antly shifted to the left, when compared to that of the insulin alone
infusion group. However, the dose-response curves of suppression of he
patic glucose output during clamp with and without GLP-1 infusion were
the same. In conclusion, GLP-1 enhanced insulin-stimulated glucose up
take by peripheral tissue, but did not influence the insulin-mediated
suppression of hepatic glucose output.