title: Peptide YY (PYY)3-36 modulates thyrotropin secretion in rats.
abstract: Peptide YY (PYY)3-36 is a gut-derived hormone, with a proposed role in central mediation of postprandial satiety signals, as well as in long-term energy balance. In addition, recently, the ability of the hormone to regulate gonadotropin secretion, acting at pituitary and at hypothalamus has been reported. Here, we examined PYY3-36 effects on thyrotropin (TSH) secretion, both in vitro and in vivo. PYY3-36-incubated rat pituitary glands showed a dose-dependent decrease in TSH release, with 44 and 62% reduction at 10(-8) and 10(-6) M (P < 0.05 and P < 0.001 respectively), and no alteration in TSH response to thyrotropin-releasing hormone. In vivo, PYY3-36 i.p. single injection in the doses of 3 or 30 cg/kg body weight, administered to rats fed ad libitum, was not able to change serum TSH after 15 or 30 min. However, in fasted rats, PYY3-36 at both doses elicited a significant rise (approximately twofold increase, P < 0.05) in serum TSH observed 15 min after the hormone injection. PYY3-36 treatment did not modify significantly serum T4, T3, or leptin. Therefore, in the present paper, we have demonstrated that the gut hormone PYY3-36 acts directly on the pituitary gland to inhibit TSH release, and in the fasting situation, in vivo, when serum PYY3-36 is reduced, the activity of thyroid axis is reduced as well. In such a situation, systemically injected PYY3-36 was able to acutely activate the thyrotrope axis, suggesting a new role for PYY3-36 as a regulator of the hypothalamic-pituitary-thyroid axis.
authors.affiliation: Laboratório de Endocrinologia Molecular, Instituto de Biofísica Carlos Chagas Filho, Universidade Federal do Rio de Janeiro, Rio de Janeiro 21949-900, Brazil.
authors.forename: K J
authors.initials: KJ
authors.lastname: Oliveira
authors.forename: G S M
authors.initials: GS
authors.lastname: Paula
authors.forename: R H
authors.initials: RH
authors.lastname: Costa-e-Sousa
authors.forename: L L
authors.initials: LL
authors.lastname: Souza
authors.forename: D C
authors.initials: DC
authors.lastname: Moraes
authors.forename: F H
authors.initials: FH
authors.lastname: Curty
authors.forename: C C
authors.initials: CC
authors.lastname: Pazos-Moura
mesh_terms: D000818:Animals; D002478:Cells, Cultured; D003864:Depression, Chemical; D004305:Dose-Response Relationship, Drug; D005215:Fasting / Q000378:metabolism*; D020738:Leptin / Q000097:blood; D008297:Male; D019894:Peptide YY / Q000494:pharmacology*; D010903:Pituitary Gland, Anterior / Q000187:drug effects / Q000378:metabolism*; D051381:Rats; D017208:Rats, Wistar; D013972:Thyrotropin / Q000032:analysis / Q000097:blood / Q000378:metabolism*; D013973:Thyrotropin-Releasing Hormone / Q000378:metabolism / Q000494:pharmacology; D013974:Thyroxine / Q000097:blood; D014284:Triiodothyronine / Q000097:blood
chemical_list: D020738:Leptin; D014284:Triiodothyronine; D019894:Peptide YY; D013973:Thyrotropin-Releasing Hormone; D013972:Thyrotropin; D013974:Thyroxine