Objectives: The incretin hormone glucagon-like peptide-1 (GLP-1) retards gastric emptying and decreases caloric intake. It is unclear whether increased GLP-1 concentrations achieved by inhibition of the inactivating enzyme dipeptidyl peptidase-4 (DPP-4) alter gastric volumes and satiation in people with type 2 diabetes.
Methods: In a double-blind, placebo-controlled crossover design, 14 subjects with type 2 diabetes received vildagliptin (50 mg bid) or placebo for 10 days in random order separated by a 2-week washout. On day 7, fasting and postmeal gastric volumes were measured by a (99m)Tc single-photon emission computed tomography (SPECT) method. On day 8, a liquid Ensure meal was consumed at 30 ml/min, and maximum tolerated volume (MTV) and symptoms 30 min later were measured using a visual analogue scale (VAS) to assess effects on satiation. On day 10, subjects ingested water until maximum satiation was achieved. The volume ingested was recorded and symptoms similarly measured using a VAS.
Results: Vildagliptin raised plasma GLP-1 concentrations. However, fasting (248 +/- 21 vs. 247 +/- 19 ml, P = 0.98) and fed (746 +/- 28 vs. 772 +/- 26 ml, P = 0.54) gastric volumes did not differ when subjects received vildagliptin or placebo. Treatment with vildagliptin did not alter the MTV of Ensure (1657 +/- 308 vs. 1389 +/- 197 ml, P = 0.15) or water compared to placebo (1371 +/- 141 vs. 1172 +/- 156 ml, P = 0.23). Vildagliptin was associated with decreased peptide YY (PYY) concentrations 60 min after initiation of the meal (166 +/- 27 vs. 229 +/- 34 pmol/l, P = 0.01).
Conclusions: Vildagliptin does not alter satiation or gastric volume in people with type 2 diabetes despite elevated GLP-1 concentrations. Compensatory changes in enteroendocrine secretion could account for the lack of gastrointestinal symptoms.