title: Responses of insulin-like growth factor (IGF)-I and two IGF-binding protein-1 subtypes to fasting and re-feeding, and their relationships with individual growth rates in yearling masu salmon (Oncorhynchus masou).
abstract: Two subtypes of insulin-like growth factor binding protein (IGFBP)-1 are present in salmon blood and they are both up-regulated under catabolic conditions such as stress. The present study examined effects of fasting and re-feeding on IGFBP-1a (28-kDa form) and IGFBP-1b (22-kDa form) both at mRNA and protein levels along with IGF-I and RNA/DNA ratio in yearling masu salmon. Fish were individually tagged and assigned to one of three treatments: Fed, Fasted or Re-fed. Circulating IGF-I levels significantly decreased after fasting for 5 weeks and were positively correlated with individual growth rates. Liver igf-1 mRNA levels were not affected by the treatment. Muscle RNA/DNA ratio did not respond to fasting nor showed correlations with growth rates. Circulating IGFBP-1a and IGFBP-1b increased during fasting and decreased after re-feeding. Both serum levels were inversely correlated with growth rates, while IGFBP-1b had consistent negative relationships with growth rates. Fasting/re-feeding also affected their mRNA levels in the liver. These results suggest that circulating IGF-I and IGFBP-1b could serve as positive and negative indices of growth, respectively, in masu salmon. Different sensitivities of IGBP-1a and IGFBP-1b may be useful to assess a broad range of catabolic conditions when they are combined.
authors.affiliation: Faculty of Fisheries Sciences, Hokkaido University, 3-1-1 Minato, Hakodate, Hokkaido 041-8611, Japan.
authors.forename: Kohei
authors.initials: K
authors.lastname: Kawaguchi
authors.forename: Nobuto
authors.initials: N
authors.lastname: Kaneko
authors.forename: Miki
authors.initials: M
authors.lastname: Fukuda
authors.forename: Yusuke
authors.initials: Y
authors.lastname: Nakano
authors.forename: Shizuo
authors.initials: S
authors.lastname: Kimura
authors.forename: Akihiko
authors.initials: A
authors.lastname: Hara
authors.forename: Munetaka
authors.initials: M
authors.lastname: Shimizu
mesh_terms: D000818:Animals; D015153:Blotting, Western; D004435:Eating; D005215:Fasting / Q000097:blood / Q000378:metabolism; D029941:Fish Proteins / Q000097:blood / Q000235:genetics* / Q000378:metabolism; D015200:Fluoroimmunoassay; D018507:Gene Expression Regulation, Developmental; D018970:Insulin-Like Growth Factor Binding Protein 1 / Q000097:blood / Q000235:genetics* / Q000378:metabolism; D007334:Insulin-Like Growth Factor I / Q000235:genetics* / Q000378:metabolism; D008099:Liver / Q000254:growth & development / Q000378:metabolism; D017683:Oncorhynchus / Q000235:genetics* / Q000254:growth & development / Q000378:metabolism; D020033:Protein Isoforms / Q000097:blood / Q000235:genetics / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013997:Time Factors
chemical_list: D029941:Fish Proteins; D018970:Insulin-Like Growth Factor Binding Protein 1; D020033:Protein Isoforms; D007334:Insulin-Like Growth Factor I