Extrinsic neural contribution to ileal peptide YY (PYY) release

Abstract

Peptide YY (PYY) release into the ileal lumen is stimulated by cholecystokinin (CCK) and glucose ingestion. Previous data have implicated vagal activity in the mediation of PYY release into both the systemic circulation and the ileal lumen. The present study was designed to evaluate extrinsic neural involvement in CCK and glucose-stimulated circulating and ileal intraluminal PYY release. Distal ileal Thiry-Vella loops (TVL) of 25 cm were created in seven mongrel dogs. On separate days fasted dogs were given continuous infusions of CCK at 500 ng/kg/hr during the first hour of the study or an oral glucose (1.5 g/kg) tolerance test (OGTT) was performed. Peripheral blood samples and ileal effusates were collected before tests and following either CCK or glucose stimulation for 120 min at 20-min intervals. Ileal PYY recoveries were measured by the instillation and collection of 20 cc of normal saline from the TVL for each 20-min period. The dogs were again tested after surgical denervation of the TVL. OGTT resulted in a significant rise of PYY recovery from the TVL ( P < 0.05), while not affecting circulating PYY. Intravenous CCK resulted in significant increases in both plasma and ileal PYY concentrations ( P < 0.05). Denervation of the TVL decreased PYY recovery from the TVL after both CCK and OGTT, whereas this procedure did not affect circulating PYY levels or basal luminal levels. These data demonstrate the inhibition of CCK- and glucose-stimulated ileal PYY recovery from denervated ileal loops. The extrinsic neural pathways are involved in the mediation of glucose- and CCK-stimulated mechanisms for ileal PYY release.