PW AND GLP-1 CONTRIBUTE TO FEEDBACK INHIBITION FROM THE CANINE ILEUM AND COLON

To explore mechanisms whereby unabsorbed nutrients in the ileum inhibi t the upper gut (''ileal brake''), we perfused the canine ileum or col on and monitored phase 3 in the duodenum. Easting motility was recorde d when the ileum or colon was perfused with 154 mM NaCl, a mixed isoto nic nutrient solution (Ensure), or individual nutrients (maltose, case in hydrolysates, or sodium oleate). Blood samples were collected befor e and during the perfusions. The ileum was also perfused with 154 mM N aCl while peptide YY (PYY) was infused by vein. In both sets of experi ments, plasma levels of PYY, neurotensin, and glucagon-like peptide-1 (GLP-1) were measured. Ileal or colonic perfusion of Ensure delayed ph ase 3 [migrating motor complexes (MMC)] in the duodenum, inhibited ile al motility, and increased plasma levels of PYY and GLP-1. Ileal casei n and oleate and colonic casein also delayed the duodenal MMC. The MMC cycle length and plasma levels of PW were closely correlated. Intrave nous PYY prolonged the MMC cycle; an intravenous dose of 100 pmol . kg (-1). h(-1) of PW mimicked the effects of ileal Ensure. These results support the hypothesis that PYY, and possibly GLP-1, participate in th e ileal brake. This negative feedback loop also affects the distal sma ll bowel. The proximal colon also triggers the feedback inhibition of gut motility (colonic brake).