Objective: To determine the acute effects of exogenous glucagon-like peptide-1 on gastric emptying, glucose absorption, glycemia, plasma insulin, and glucagon in critically ill patients.
Design: Randomized, double-blind, crossover study.
Setting: Intensive care unit.
Subjects: Twenty-five mechanically ventilated patients, without known diabetes, studied on consecutive days.
Interventions: Intravenous glucagon-like peptide-1 (1.2 pmol/kg/min) or placebo was infused between -30 and 330 mins. At 0 min, 100 mL liquid nutrient (1 kcal/mL) including 100 microg of 13C-octanoic acid and 3 grams of 3-O-methyl-glucose was administered.
Measurements and main results: Blood glucose, serum 3-O-methyl-glucose (as an index of glucose absorption), insulin and glucagon concentrations, as well as exhaled 13CO2 were measured. The gastric emptying coefficient was calculated to quantify gastric emptying. Data are presented as mean (sd). There was a nonsignificant trend for glucagon-like peptide-1 to slow gastric emptying (gastric emptying coefficient) (glucagon-like peptide-1, 2.45 [0.93] vs. placebo, 2.75 [0.83]; p = .09). In 11 of the 25 patients, gastric emptying was delayed during placebo infusion and glucagon-like peptide-1 had no detectable effect on gastric emptying in this group (1.92 [0.82] vs. 1.90 [0.68]; p = .96). In contrast, in patients who had normal gastric emptying during placebo, glucagon-like peptide-1 slowed gastric emptying substantially (2.86 [0.58] vs. 3.41 [0.37]; p = .006). Glucagon-like peptide-1 markedly reduced the rate of glucose absorption (3-O-methyl-glucose area under the curve(0-330), 37  vs. 76  mmol/L/min; p < .001), decreased preprandial glucagon (at 0 min change in glucagon, -15  vs. -3  pmol/L; p < .001), increased the insulin/glucose ratio throughout the infusion (area under the curve(-30-330), 1374  vs. 1172  mU/mmol/min; p = .041), and attenuated the glycemic response to the meal (glucose area under the curve(0-330), 2071  vs. 2419  mmol/L/min; p = .001).
Conclusions: Exogenous glucagon-like peptide-1 lowers postprandial glycemia in the critically ill. This may occur, at least in part, by slowing gastric emptying when the latter is normal but not when it is delayed.