title: Effects of fasting on IGF-I, IGF-II, and IGF-binding protein mRNA concentrations in channel catfish (Ictalurus punctatus).
abstract: The effects of fasting on insulin-like growth factor (IGF)-I, IGF-II, and IGF-binding protein (IGFBPs) mRNA in channel catfish were examined. Fed control fish (Fed) were compared to fish that had been fasted for 30 d followed by 15 d of additional feeding (Restricted). Sequence alignment and similarity to orthologous proteins in other vertebrates provided structural evidence that the 3 catfish sequences identified in the present research were IGFBP-1, -2, and -3. Prolonged fasting (30 d) reduced body weight approximately 60% (P<0.001) and decreased IGF-I mRNA in the liver and muscle (P<0.01). Fifteen days of re-feeding restored concentrations of hepatic and muscle IGF-I mRNA. Liver IGF-II mRNA was not affected by fasting but was increased 2.2-fold after 15 d of re-feeding (P<0.05). Abundance of muscle IGF-II mRNA was similar between the fed control group and the restricted group throughout the experimental period. Fasting also increased liver IGFBP-1 mRNA (P<0.05) and decreased IGFBP-3 mRNA (P<0.01), whereas abundance of IGFBP-2 mRNA was not significantly affected. Interestingly, re-feeding for 15 d did not restore concentrations of IGFBP-1 and IGFBP-3 mRNA relative to fed control concentrations. The IGF results suggest that IGF-I and IGF-II are differently regulated by nutritional status and probably have a differential effect in promoting muscle growth during recovery from fasting. Similar to mammals, IGFBP-1 mRNA in catfish is increased during catabolism, whereas IGFBP-3 mRNA is decreased during inhibited somatic growth. The IGFBP results provide additional evidence of the conserved nature of the IGF-IGFBP-growth axis in catfish.
authors.affiliation: USDA/ARS Catfish Genetics Research Unit, Thad Cochran National Warmwater Aquaculture Center, Stoneville, MS 38776, USA. brian.peterson@ars.usda.gov
authors.forename: B C
authors.initials: BC
authors.lastname: Peterson
authors.forename: G C
authors.initials: GC
authors.lastname: Waldbieser
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D005215:Fasting / Q000502:physiology*; D005502:Food; D005786:Gene Expression Regulation / Q000502:physiology; D007059:Ictaluridae / Q000378:metabolism*; D018970:Insulin-Like Growth Factor Binding Protein 1 / Q000737:chemistry / Q000235:genetics; D018971:Insulin-Like Growth Factor Binding Protein 2 / Q000737:chemistry / Q000235:genetics; D018972:Insulin-Like Growth Factor Binding Protein 3 / Q000737:chemistry / Q000235:genetics; D018969:Insulin-Like Growth Factor Binding Proteins / Q000235:genetics*; D007334:Insulin-Like Growth Factor I / Q000235:genetics*; D007335:Insulin-Like Growth Factor II / Q000235:genetics*; D008099:Liver / Q000737:chemistry; D008969:Molecular Sequence Data; D009132:Muscles / Q000737:chemistry; D009752:Nutritional Status; D012333:RNA, Messenger / Q000032:analysis*
chemical_list: D018970:Insulin-Like Growth Factor Binding Protein 1; D018971:Insulin-Like Growth Factor Binding Protein 2; D018972:Insulin-Like Growth Factor Binding Protein 3; D018969:Insulin-Like Growth Factor Binding Proteins; D012333:RNA, Messenger; D007334:Insulin-Like Growth Factor I; D007335:Insulin-Like Growth Factor II