title: VGF changes during the estrous cycle: a novel endocrine role for TLQP peptides?
abstract: Although the VGF derived peptide TLQP-21 stimulates gonadotropin-releasing hormone (GnRH) and gonadotropin secretion, available data on VGF peptides and reproduction are limited. We used antibodies specific for the two ends of the VGF precursor, and for two VGF derived peptides namely TLQP and PGH, to be used in immunohistochemistry and enzyme-linked immunosorbent assay complemented with gel chromatography. In cycling female rats, VGF C-/N-terminus and PGH peptide antibodies selectively labelled neurones containing either GnRH, or kisspeptin (VGF N-terminus only), pituitary gonadotrophs and lactotrophs, or oocytes (PGH peptides only). Conversely, TLQP peptides were restricted to somatostatin neurones, gonadotrophs, and ovarian granulosa, interstitial and theca cells. TLQP levels were highest, especially in plasma and ovary, with several molecular forms shown in chromatography including one compatible with TLQP-21. Among the cycle phases, TLQP levels were higher during metestrus-diestrus in median eminence and pituitary, while increased in the ovary and decreased in plasma during proestrus. VGF N- and C-terminus peptides also showed modulations over the estrous cycle, in median eminence, pituitary and plasma, while PGH peptides did not. In ovariectomised rats, plasmatic TLQP peptide levels showed distinct reduction suggestive of a major origin from the ovary, while the estrogen-progesterone treatment modulated VGF C-terminus and TLQP peptides in the hypothalamus-pituitary complex. In in vitro hypothalamus, TLQP-21 stimulated release of growth hormone releasing hormone but not of somatostatin. In conclusion, various VGF peptides may regulate the hypothalamus-pituitary complex via specific neuroendocrine mechanisms while TLQP peptides may act at further, multiple levels via endocrine mechanisms involving the ovary.
authors.affiliation: Department of Biomedical Sciences, University of Cagliari, Monserrato (Cagliari), Italy.
authors.forename: Barbara
authors.initials: B
authors.lastname: Noli
authors.affiliation: Department of Biomedical Sciences, University of Cagliari, Monserrato (Cagliari), Italy.
authors.forename: Carla
authors.initials: C
authors.lastname: Brancia
authors.affiliation: Department of Biomedical Sciences, University of Cagliari, Monserrato (Cagliari), Italy.
authors.forename: Filomena
authors.initials: F
authors.lastname: D'Amato
authors.affiliation: Department of Biomedical Sciences, University of Cagliari, Monserrato (Cagliari), Italy.
authors.forename: Gian-Luca
authors.initials: GL
authors.lastname: Ferri
authors.affiliation: Department of Biomedical Sciences, University of Cagliari, Monserrato (Cagliari), Italy.
authors.forename: Cristina
authors.initials: C
authors.lastname: Cocco
mesh_terms: D000818:Animals; D004958:Estradiol / Q000494:pharmacology; D030762:Estrous Cycle / Q000187:drug effects / Q000378:metabolism*; D005260:Female; D007031:Hypothalamus / Q000378:metabolism; D009479:Neuropeptides / Q000737:chemistry / Q000378:metabolism*; D010052:Ovariectomy; D010053:Ovary / Q000378:metabolism; D010446:Peptide Fragments / Q000378:metabolism; D010902:Pituitary Gland / Q000378:metabolism; D011374:Progesterone / Q000494:pharmacology; D021381:Protein Transport; D051381:Rats
chemical_list: D009479:Neuropeptides; D010446:Peptide Fragments; C522412:TLQP-21 peptide; C062040:Vgf protein, rat; D011374:Progesterone; D004958:Estradiol