Role of Circulating Peptide YY in the Inhibition of Gastric Acid Secretion by Dietary Fat in Humans

Intestinal fat inhibits gastric acid secretion and induces release of peptide YY (PYY) into the circulation. The aim of this study was to further establish the role of circulating PYY in the inhibition of gastric acid secretion by intraduodenal fat. Plasma PYY concentrations and gastrin-stimulated gastric acid output were measured in response to intravenous infusion of PYY in eight healthy men. The results were compared with those obtained after intraduodenal administration of dietary fat. Plasma PYY concentrations increased by 8.1 +/- 1.8 pmol/l (P < 0.005) in response to the lower and by 13.5 +/- 2.5 pmol/l (P < 0.005) in response to the higher PYY dose. These increments were comparable to those observed after intraduodenal fat (10.3 +/- 2.4 pmol/l). Intraduodenal fat significantly inhibited (P < 0.005 versus control) gastrin-stimulated gastric acid secretion by 74% +/- 6%, but neither the lower (3% +/- 7%; NS) nor the higher PYY dose (1% +/- 10%; NS) induced any change in gastric acid output. PYY was biologically active, as reflected by a significant delay (P = 0.04) of orocaecal transit time. Release of PYY into the circulation is not responsible for inhibition of gastrin-stimulated gastric acid secretion by dietary fat.