title: Daily rhythms of the expression of genes from the somatotropic axis: The influence on tilapia (Oreochromis niloticus) of feeding and growth hormone administration at different times.
abstract: The aim of this research was to investigate the presence of daily rhythms in the somatotropic axis of tilapia fed at two times (mid-light, ML or mid-dark, MD) and the influence of the time of day of growth hormone (GH) administration on the response of this axis. Two different GH injection times were tested: ZT 3 (3h after lights on) and ZT 15 (3h after lights off). In both experiments, the mRNA expression levels of hypothalamic pituitary adenylate cyclase-activating polypeptide (pacap), pituitary growth hormone (gh), liver insulin-like growth factors (igf1 and igf2a), and liver and muscle growth hormone receptors (ghr1 and ghr2) and IGF receptors (igf1ra and igf2r) were evaluated by means of qPCR. Daily rhythms were observed in the liver for ghr1, ghr2 and igf2r but only in fish fed at ML, with the acrophases located in the light phase (ZT 3:30, 3:31 and 7:38 h, respectively). In the muscle, ghr1 displayed a significant rhythm in both groups and ghr2 in ML fed fish (acrophases at ZT 5:29, 7:14 and 9:23h). The time of both GH administration and feeding influenced the response to GH injection: ML fed fish injected with GH at ZT 15 h showed a significant increase in liver igf1, igf2a and ghr2; and muscle ghr2 expression. This is the first report that describes the existence of daily rhythms in the somatotropic axis of tilapia and its time-dependent responses of GH administration. Our results should be considered when investigating the elements of the somatotropic axis in tilapia and GH administration.
authors.affiliation: Department of Animal Science, Federal University of Lavras, Minas Gerais, 37200-000, Brazil; Department of Physiology, Faculty of Biology, Regional Campus of International Excellence "Campus Mare Nostrum", University of Murcia, 30100, Murcia, Spain.
authors.forename: Leandro S
authors.initials: LS
authors.lastname: Costa
authors.affiliation: Department of Animal Science, Federal University of Lavras, Minas Gerais, 37200-000, Brazil.
authors.forename: Priscila V
authors.initials: PV
authors.lastname: Rosa
authors.affiliation: Agricultural Science, Biological and Environmental Center, University of Bahia, 44380-000, Cruz das Almas, Bahia, Brazil.
authors.forename: Rodrigo
authors.initials: R
authors.lastname: Fortes-Silva
authors.affiliation: Department of Physiology, Faculty of Biology, Regional Campus of International Excellence "Campus Mare Nostrum", University of Murcia, 30100, Murcia, Spain. Electronic address: javisan@um.es.
authors.forename: F Javier
authors.initials: FJ
authors.lastname: Sánchez-Vázquez
authors.affiliation: Department of Physiology, Faculty of Biology, Regional Campus of International Excellence "Campus Mare Nostrum", University of Murcia, 30100, Murcia, Spain.
authors.forename: Jose F
authors.initials: JF
authors.lastname: López-Olmeda
mesh_terms: D000818:Animals; D023681:Cichlids / Q000235:genetics* / Q000502:physiology; D003624:Darkness; D029941:Fish Proteins / Q000235:genetics*; D005786:Gene Expression Regulation / Q000187:drug effects; D013006:Growth Hormone / Q000008:administration & dosage*; D008099:Liver / Q000187:drug effects / Q000502:physiology; D018482:Muscle, Skeletal / Q000187:drug effects / Q000502:physiology; D051219:Pituitary Adenylate Cyclase-Activating Polypeptide / Q000235:genetics; D017451:Receptors, Somatomedin / Q000235:genetics; D011986:Receptors, Somatotropin / Q000235:genetics
chemical_list: D029941:Fish Proteins; D051219:Pituitary Adenylate Cyclase-Activating Polypeptide; D017451:Receptors, Somatomedin; D011986:Receptors, Somatotropin; D013006:Growth Hormone
keywords: GH chronopharmacology; Growth hormone; Growth hormone receptor; IGF receptor; Insulin-like growth factor; Pituitary adenylate cyclase-activating polypeptide; Teleost fish