Vascular Effects of Sitagliptin in Diabetes Mellitus

Glucagon-like peptide 1 (GLP-1) is a 30-amino acid gut hormone secreted in a nutrient-dependent manner that stimulates insulin secretion and inhibits glucagon secretion and gastric emptying, thereby reducing postprandial glycemia.1,2 GLP-1 is derived from posttranslational proteolysis of preproglucagon, and its peptide sequence is identical in mouse, rat, and human.2,3 After secretion from enteroendocrine L cells, GLP-1(7-36) amide is rapidly degraded by dipeptidyl peptidase-4 (DPP-4) to its N-terminally truncated metabolite GLP-1(9-36), which does not interact with the known GLP-1 receptor.4,5 The diverse actions of GLP-1 include the proliferation, differentiation, and protection from apoptosis of pancreatic β cells and the induction of satiety. GLP-1 also improves memory and learning, stimulates afferent sensory nerves, and has neuroprotective functions.1,6 Furthermore, GLP-1 receptor agonists have been reported to have cardiac and vascular actions in rodents and humans that include effects on contractility, blood pressure, cardiac output,7-10 and cardioprotection.11-14