Effects of intravenous glucagon-like peptide-1 on gastric emptying and intragastric distribution in healthy subjects: relationships with postprandial glycemic and insulinemic responses.

CONTEXT: The inhibitory action of glucagon-like peptide-1 (GLP-1) on gastric emptying (GE) is likely to be important in mediating its effects on postprandial glycemia, appetite, and gastrointestinal symptoms.
OBJECTIVE: The objective of the study was to evaluate the effects of "low" and "high" doses of iv GLP-1 on GE, intragastric meal distribution, glycemia, insulinemia, and appetite.
DESIGN: Ten healthy males were studied on 3 d. GE of a solid (ground beef)/liquid (glucose) meal, blood glucose, plasma insulin, glucagon and glucose-dependent insulinotropic peptide, appetite perceptions, and gastrointestinal symptoms were evaluated during iv infusion of: 1) GLP-1 at 0.3 pmol x kg(-1) x min(-1) (GLP-1 0.3); 2) GLP-1 at 0.9 pmol x kg(-1) x min(-1) (GLP-1 0.9); and 3) 0.9% saline.
RESULTS: GLP-1 0.3 and 0.9 slowed GE of solid (intragastric retention at t = 100 min; saline: 28 +/- 5%; GLP-1 0.3: 53 +/- 6%; GLP-1 0.9: 58 +/- 7%; P < 0.001) and liquid (time for 50% of the liquid to empty, saline: 28 +/- 2 min; GLP-1 0.3: 42 +/- 7 min; GLP-1 0.9: 50 +/- 9 min; P < 0.001). Both doses of GLP-1 induced gastroparesis in about half the cohort and increased meal retention in the distal stomach (P < 0.05). GLP-1 attenuated the rises in glucose, insulin, and glucose-dependent insulinotropic peptide (P < 0.05). There was an inverse relationship between blood glucose at t = 15 min and the time for 50% of the liquid to empty (r = -0.70, P < 0.001).
CONCLUSIONS: In healthy subjects exogenous GLP-1 increases meal retention in the distal stomach and, even when administered in a "low" dose, frequently induces "gastroparesis," and the effects of GLP-1 on postprandial glycemia are predictable on the basis of its effect on GE, supporting the concept that GE is a major target mechanism for the clinical use of incretin mimetics.