In vivo and in vitro degradation of peptide YY3–36 to inactive peptide YY3–34 in humans

Peptide YY (PYY) is a 36-amino-acid peptide released from enteroendocrine cells upon food intake. The NH 2 terminally truncated metabolite, PYY 3–36 , exerts anorexic effects and has received considerable attention as a possible antiobesity drug target. The kinetics and degradation products of PYY metabolism are not well described. A related peptide, neuropeptide Y, may be degraded from the COOH terminus, and in vivo studies in pigs revealed significant COOH-terminal degradation of PYY. We therefore investigated PYY metabolism in vitro after incubation in human blood and plasma and in vivo after infusion of PYY 1–36 and PYY 3–36 in eight young, healthy men. A metabolite, corresponding to PYY 3–34 , was formed after incubation in plasma and blood and during the infusion of PYY. PYY 3–34 exhibited no agonistic or antagonistic effects on the Y2 receptor. PYY 1–36 infused with and without coadministration of sitagliptin was eliminated with half-lives of 10.1 ± 0.5 and 9.4 ± 0.8 min (means ± SE) and metabolic clearance rates of 15.7 ± 1.5 and 14.1 ± 1.1 ml·kg −1 ·min −1 after infusion, whereas PYY 3–36 was eliminated with a significantly longer half-life of 14.9 ± 1.3 min and a metabolic clearance rate of 9.4 ± 0.6 ml·kg −1 ·min −1 . We conclude that, upon intravenous infusion in healthy men, PYY is inactivated by cleavage of the two COOH-terminal amino acids. In healthy men, PYY 3–36 has a longer half-life than PYY 1–36 .