Role of circulating peptide YY in the inhibition of gastric acid secretionby dietary fat in humans

Intestinal fat inhibits gastric acid secretion and induces release of pepti de YY (PYY) into the circulation. The aim of this study was to further esta blish the role of circulating PYY in the inhibition of gastric acid secreti on by intraduodenal far, Methods: Plasma PYY concentrations and gastrin-sti mulated gastric acid output were measured in response to intravenous infusi on of PYY in eight healthy men. The results were compared with those obtain ed after intraduodenal administration of dietary fat. Results: Plasma PYY c oncentrations increased by 8.1 +/- 1.8 pmol/l (P < 0.005) in response to th e: lower and by 13.5 +/- 2.5 pmol/l (P < 0.005) in response to the higher P YY dose. These increments were comparable to those observed after intraduod enal fat (10.3 +/- pmol/l). Intraduodenal fat significantly inhibited (P < 0.005 versus control) gastric in-stimulated secretion by 74% +/- 6%, but ne ither the lower (3% +/- 7%: NS) nor the higher PYY dose (1% +/- 10%; NS) in duced any change in gastric acid output. PYY was biologically active, as re flected by a significant delay (P = 0.04) of orocaecal transit time. Conclu sion: Release of PYY into the circulation is not responsible for inhibition of` gastrin-stimulated gastric acid secretion by dietary fat.