Abstract
The hormonal factors implicated as transmitters of signals from the gut to pancreatic β-cells are referred to as incretins. Gastric inhibitory polypeptide (GIP) and glucagon-like peptide-1 (GLP-1) are incretins. In addition to the insulinotropic effects, we have shown, using the GIP receptor and GLP-1 receptor-deficient mice, that GIP and GLP-1 have direct actions on adipocytes and the kidney, respectively. Because GIP receptors and GLP-1 receptors are differentially expressed in a tissue-specific manner, GIP and GLP-1 have specific physiological activities, and further comprehensive characterization of the extrapancreatic actions of GIP and GLP-1 is anticipated, as dipeptidyl peptidase IV inhibitors activate both GIP and GLP-1 signaling.