GLP-1 inhibits gastric emptying of water but does not influence plasma vasopressin, sodium, or osmolality

Background: Glucagon-like peptide-1 (GLP-1) has been shown to inhibit gastr ic emptying of a caloric load but the effect on a non-caloric load is unkno wn. Methods: Seven healthy men were studied after an over-night fast. Thirt y min before the intake of 330 ml radioactively labeled water either GLD-I (0.75 pmol/kg/min) or saline was administered intravenously and continued f or 75 min. Scintigraphic gastric emptying was performed for 45 min and plas ma samples were obtained for analysis of vasopressin, sodium, osmolality, G LP-1, insulin, and glucose. In addition, electric field stimulation of huma n gastric muscle strips was done. Results: The median (range) percent water retained in the stomach, 45 min after intake of water, was 96% (68%-98%) a nd 12% (2%-42%) (P = 0.02) during infusion of GLP-1 and saline, respectivel y. Additionally, GLP-1 did not affect basal tune or contractile response of gastric muscle strips to electric field stimulation or acetylcholine (ACh) . There was no change in plasma concentrations of vasopressin, sodium, or p lasma osmolality during GLP-1 compared to saline infusion. Conclusion: GLP- 1 has a profound inhibitory effect on the gastric emptying of water in man, but no short-term effect on water homeostasis. No effect was seen on contr actility of gastric muscle strips suggesting an indirect action on gastric emptying.