DEOXYCHOLATE IS AN IMPORTANT RELEASER OF PEPTIDE-YY AND ENTEROGLUCAGON FROM THE HUMAN COLON

Peptide YY (PYY) and enteroglucagon are hormonal peptides found in end ocrine cells of the distal intestinal mucosa. Although it is known tha t plasma concentrations of both peptides increase in response to feedi ng, the mechanism by which ingested food causes release of colonic hor mones is not understood. The release of PYY and enteroglucagon was mea sured in response to intraluminal stimuli in 176 patients having inves tigative colonoscopy. Introduction of air, saline (isotonic and hypert onic), glucose (isotonic and hypertonic), oleic acid (without bile sal ts), and casein hydrolysate all failed to release PYY but glucose caus ed a small but significant increase in enteroglycagon concentrations. In contrast with the lack of effect of nutrients, infusion of deoxycho lic acid produced a rapid and marked dose responsive increase in plasm a PYY concentrations when introduced into the sigmoid colon. PYY relea se was statistically significant at doses between 3.3 mM to 30 mM; for example 10 mM deoxycholate caused a sixfold increase in plasma PYY co ncentrations. Infusion of 10 mM deoxycholate into the transverse colon or caecum produced an increase of PYY that was similar to the respons es in the sigmoid colon. There was also a significant release of enter oglucagon in response to infusion of this bile salt into the sigmoid c olon at doses between 3-3 mM and 30 mM. The enteroglucagon response to 10 mM deoxycholate was similar in all three colonic regions. When ole ic acid was added to deoxycholate as an emulsion, the release of PYY a nd enteroglucagon was similar to that seen with the bile salt alone. T hese findings suggest that bile salts may play an important part in th e control of colonic endocrine function and may explain the increased circulating concentrations of colonic regulatory peptides that are see n in malabsorption states and after small bowel resection in humans.