title: Leptin extends the anorectic effects of chronic PYY(3-36) administration in ad libitum-fed rats.
abstract: Acute administration of peptide YY(3-36) [PYY(3-36)] results in a reduction in food intake in several different vertebrates. However, long-term continuous administration of PYY(3-36) causes only a transient reduction in food intake, thus potentially limiting its therapeutic efficacy. We hypothesized that a fall in leptin levels associated with reduced food intake could contribute to the transient anorectic effects of continuous PYY(3-36) infusion and thus that leptin replacement might prolong the anorectic effects of PYY(3-36). Seven-day administration of 100 microg x kg body wt(-1) x day(-1) PYY(3-36) using osmotic minipumps caused a significant reduction in food intake of ad libitum-fed rats, but only for the first 2 days postimplantation. Circulating levels of leptin were reduced 1 day following continuous infusion of PYY(3-36), and combined leptin infusion at a dose of leptin that had no anorectic effects on its own (100 microg x kg body wt(-1) x day(-1)) prolonged the anorectic actions of PYY(3-36) in ad libitum-fed rats for up to 6 days postimplantation and yielded reduced weight gain compared with either peptide alone. The inhibitory effects of 100 microg x kg body wt(-1) x day(-1) PYY(3-36) on food intake were absent in rats refed after a 24-h fast and substantially reduced at a dose of 1,000 microg x kg body wt(-1) x day(-1) PYY(3-36). Leptin replacement was unable to recover the anorectic effects of PYY(3-36) in fasted rats. Our results suggest that an acute fall in leptin levels is not solely responsible for limiting duration of action of chronic PYY(3-36) infusion, yet chronic coadministration of a subanorectic dose of leptin can extend the anorectic effects of PYY(3-36).
authors.affiliation: Laboratory of Molecular and Cellular Medicine, Departments of Cellular and Physiological Sciences and Surgery, Life Sciences Institute, University of British Columbia, Vancouver, Canada.
authors.forename: Suraj
authors.initials: S
authors.lastname: Unniappan
authors.forename: Timothy J
authors.initials: TJ
authors.lastname: Kieffer
mesh_terms: D020341:Absorbable Implants; D000818:Animals; D000855:Anorexia / Q000139:chemically induced*; D001067:Appetite Depressants / Q000008:administration & dosage / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D004334:Drug Administration Schedule; D004357:Drug Synergism; D020738:Leptin / Q000008:administration & dosage / Q000097:blood / Q000494:pharmacology*; D008297:Male; D010446:Peptide Fragments; D019894:Peptide YY / Q000008:administration & dosage / Q000494:pharmacology*; D051381:Rats; D011916:Rats, Inbred F344; D013997:Time Factors
chemical_list: D001067:Appetite Depressants; D020738:Leptin; D010446:Peptide Fragments; D019894:Peptide YY; C061785:peptide YY (3-36)