title: Nutritional status and growth hormone regulate insulin-like growth factor binding protein (igfbp) transcripts in Mozambique tilapia.
abstract: Growth in teleosts is controlled in large part by the activities of the growth hormone (Gh)/insulin-like growth factor (Igf) system. In this study, we initially identified igf-binding protein (bp)1b, -2b, -4, -5a and -6b transcripts in a tilapia EST library. In Mozambique tilapia (Oreochromis mossambicus), tissue expression profiling of igfbps revealed that igfbp1b and -2b had the highest levels of expression in liver while igfbp4, -5a and -6b were expressed at comparable levels in most other tissues. We compared changes in hepatic igfbp1b, -2b and -5a expression during catabolic conditions (28days of fasting) along with key components of the Gh/Igf system, including plasma Gh and Igf1 and hepatic gh receptor (ghr2), igf1 and igf2 expression. In parallel with elevated plasma Gh and decreased Igf1 levels, we found that hepatic igfbp1b increased substantially in fasted animals. We then tested whether systemic Gh could direct the expression of igfbps in liver. A single intraperitoneal injection of ovine Gh into hypophysectomized tilapia specifically stimulated liver igfbp2b expression along with plasma Igf1 and hepatic ghr2 levels. Our collective data suggest that hepatic endocrine signaling during fasting may involve post-translational regulation of plasma Igf1 via a shift towards the expression of igfbp1b. Thus, Igfbp1b may operate as a molecular switch to restrict Igf1 signaling in tilapia; furthermore, we provide new details regarding isoform-specific regulation of igfbp expression by Gh.
authors.affiliation: Hawaii Institute of Marine Biology, University of Hawaii, Kaneohe, HI 96744, USA; Department of Biology & Center for Neuroendocrine Studies, University of Massachusetts, Amherst, MA 01003, USA. Electronic address: breves@bio.umass.edu.
authors.forename: Jason P
authors.initials: JP
authors.lastname: Breves
authors.affiliation: Hawaii Institute of Marine Biology, University of Hawaii, Kaneohe, HI 96744, USA; Department of Biological Sciences, University of Arkansas, Fayetteville, AR 72701, USA.
authors.forename: Christian K
authors.initials: CK
authors.lastname: Tipsmark
authors.affiliation: Department of Biological Sciences, University of Arkansas, Fayetteville, AR 72701, USA.
authors.forename: Beth A
authors.initials: BA
authors.lastname: Stough
authors.affiliation: Hawaii Institute of Marine Biology, University of Hawaii, Kaneohe, HI 96744, USA.
authors.forename: Andre P
authors.initials: AP
authors.lastname: Seale
authors.affiliation: Department of Biological Sciences, University of Arkansas, Fayetteville, AR 72701, USA.
authors.forename: Brenda R
authors.initials: BR
authors.lastname: Flack
authors.affiliation: Hawaii Institute of Marine Biology, University of Hawaii, Kaneohe, HI 96744, USA; Department of Molecular Biosciences and Bioengineering, University of Hawaii at Manoa, Honolulu, HI 96822, USA.
authors.forename: Benjamin P
authors.initials: BP
authors.lastname: Moorman
authors.affiliation: Hawaii Institute of Marine Biology, University of Hawaii, Kaneohe, HI 96744, USA; Sea Grant College Program, University of Hawaii at Manoa, Honolulu, HI 96822, USA.
authors.forename: Darren T
authors.initials: DT
authors.lastname: Lerner
authors.affiliation: Hawaii Institute of Marine Biology, University of Hawaii, Kaneohe, HI 96744, USA.
authors.forename: E Gordon
authors.initials: EG
authors.lastname: Grau
mesh_terms: D000818:Animals; D005215:Fasting / Q000502:physiology; D013006:Growth Hormone / Q000494:pharmacology*; D007016:Hypophysectomy; D018969:Insulin-Like Growth Factor Binding Proteins / Q000235:genetics* / Q000378:metabolism; D007334:Insulin-Like Growth Factor I / Q000378:metabolism*; D008099:Liver / Q000378:metabolism*; D020033:Protein Isoforms; D012333:RNA, Messenger / Q000235:genetics; D011863:Radioimmunoassay; D060888:Real-Time Polymerase Chain Reaction; D020133:Reverse Transcriptase Polymerase Chain Reaction; D017210:Tilapia / Q000378:metabolism
chemical_list: D018969:Insulin-Like Growth Factor Binding Proteins; D020033:Protein Isoforms; D012333:RNA, Messenger; D007334:Insulin-Like Growth Factor I; D013006:Growth Hormone
keywords: Binding proteins; Fasting; Growth hormone; Insulin-like growth factor; Receptor; Tilapia