title: The anorexic hormone Peptide YY3-36 is rapidly metabolized to inactive Peptide YY3-34 in vivo.
abstract: Peptide YY (PYY) is a 36 amino acid peptide hormone released from enteroendocrine cells. An N-terminally degraded metabolite, PYY3-36, has anorexigenic effects, which makes the PYY system a target for obesity treatment. However, little is known about the kinetics and degradation products of PYY. A related peptide, Neuropeptide Y (NPY), may be degraded from the C-terminus. We therefore investigated PYY degradation after in vitro incubations in porcine plasma and blood and in vivo by infusing PYY3-36 into multicatheterized pigs (n = 7) (2 pmol/kg/min). Plasma samples were analyzed by region-specific radioimmunoassays (RIA) and HPLC analysis. A metabolite, corresponding to PYY3-34 was formed after incubation in plasma and blood and during the infusion study. When taking the C-terminal degradation into account, the half-life (T½) of PYY in blood and plasma amounted to 3.4 ± 0.2 and 6.2 ± 0.2 h, respectively. After PYY3-36 infusion in pigs, the peptide was degraded with a T½ of 3.6 ± 0.5 min. Significant extraction (20.5 ± 8.0%) compatible with glomerular filtration was observed across the kidneys and significant C-terminal degradation (26.5 ± 4.8%) was observed across the liver. Net balances across the hind limb, splanchnic bed, and lungs were not significantly different from zero. PYY3-34 was unable to activate the Y2 receptor in a transfected cell line. In conclusion, PYY3-36 is extensively degraded to PYY3-34 in the pig, a degradation that renders the peptide inactive on the Y2 receptor. Currently used assays are unlikely to be able to detect this degradation and therefore measure falsely elevated levels of PYY3-36, leading to underestimation of its physiological effects.
authors.affiliation: NNF Center for Basic Metabolic Research and Department of Biomedical Sciences, Faculty of Health Sciences, University of Copenhagen, Copenhagen, Denmark.
authors.forename: Signe
authors.initials: S
authors.lastname: Toräng
authors.affiliation: NNF Center for Basic Metabolic Research and Department of Biomedical Sciences, Faculty of Health Sciences, University of Copenhagen, Copenhagen, Denmark.
authors.forename: Simon
authors.initials: S
authors.lastname: Veedfald
authors.affiliation: Department of Neuroscience and Pharmacology, Faculty of Health Sciences, University of Copenhagen, Copenhagen, Denmark.
authors.forename: Mette Marie
authors.initials: MM
authors.lastname: Rosenkilde
authors.affiliation: NNF Center for Basic Metabolic Research and Department of Biomedical Sciences, Faculty of Health Sciences, University of Copenhagen, Copenhagen, Denmark.
authors.forename: Bolette
authors.initials: B
authors.lastname: Hartmann
authors.affiliation: NNF Center for Basic Metabolic Research and Department of Biomedical Sciences, Faculty of Health Sciences, University of Copenhagen, Copenhagen, Denmark jjholst@sund.ku.dk.
authors.forename: Jens Juul
authors.initials: JJ
authors.lastname: Holst
keywords: Degradation; Peptide YY; kinetics