The Effect of Exogenous Glucose-Dependent Insulinotropic Polypeptide in Combination With Glucagon-Like Peptide-1 on Glycemia in the Critically Ill

OBJECTIVE Glucose-dependent insulinotropic polypeptide (GIP) and glucagon-like peptide-1 (GLP-1) have additive insulinotropic effects when coadministered in health. We aimed to determine whether GIP confers additional glucose-lowering to that of GLP-1 in the critically ill. RESEARCH DESIGN AND METHODS Twenty mechanically ventilated critically ill patients without known diabetes were studied in a prospective, randomized, double-blind, crossover fashion on 2 consecutive days. Between T 0 and T 420 minutes, GLP-1 (1.2 pmol/kg · min −1 ) was infused intravenously with either GIP (2 pmol/kg · min −1 ) or 0.9% saline. Between T 60 and T 420 minutes, nutrient liquid was infused into the small intestine at 1.5 kcal/min. RESULTS Adding GIP did not alter blood glucose or insulin responses to small intestinal nutrient. GIP increased glucagon concentrations slightly before nutrient delivery ( P = 0.03), but not thereafter. CONCLUSIONS The addition of GIP to GLP-1 does not result in additional glucose-lowering or insulinotropic effects in critically ill patients with acute-onset hyperglycemia.