title: Insulin-like growth factor-I and genetic effects on indexes of protein degradation in response to feed deprivation in rainbow trout (Oncorhynchus mykiss).
abstract: This study determined the effect of genetic variation, feed deprivation, and insulin-like growth factor-I (IGF-I) on weight loss, plasma IGF-I and growth hormone, and indexes of protein degradation in eight full-sibling families of rainbow trout. After 2 wk of feed deprivation, fish treated with IGF-I lost 16% less (P < 0.05) wet weight than untreated fish. Feed deprivation increased growth hormone (P < 0.05) and decreased IGF-I (P < 0.05), but hormone levels were not altered by IGF-I. Plasma 3-methylhistidine concentrations were not affected by IGF-I but were decreased after 2 wk (P < 0.05) and increased after 4 wk (P < 0.05) of feed deprivation. In white muscle, transcript abundance of genes in the ubiquitin-proteasome, lysosomal, and calpain- and caspase-dependent pathways were affected by feed deprivation (P < 0.05). IGF-I prevented the feed deprivation-induced upregulation of MAFbx (F-box) and cathepsin transcripts and reduced abundance of proteasomal mRNAs (P < 0.05), suggesting that reduction of protein degradation via these pathways may be partially responsible for the IGF-I-induced reduction of weight loss. Family variations in gene expression, IGF-I concentrations, and weight loss during fasting suggest genetic variation in the fasting response, with considerable impact on regulation of proteolytic pathways. These data indicate that nutrient availability, IGF-I, and genetic variation affect weight loss, in part through alterations of proteolytic pathways in rainbow trout, and that regulation of genes within these pathways is coordinated in a way that supports a similar physiological response.
authors.affiliation: Agricultural Research Service-US Department of Agriculture, National Center for Cool and Cold Water Aquaculture, Kearneysville, West Virginia 25430, USA. beth.cleveland@ars.usda.gov
authors.forename: Beth M
authors.initials: BM
authors.lastname: Cleveland
authors.forename: Gregory M
authors.initials: GM
authors.lastname: Weber
authors.forename: Kenneth P
authors.initials: KP
authors.lastname: Blemings
authors.forename: Jeffrey T
authors.initials: JT
authors.lastname: Silverstein
mesh_terms: D000818:Animals; D002403:Cathepsins / Q000378:metabolism; D044783:F-Box Proteins / Q000378:metabolism; D005508:Food Deprivation / Q000502:physiology*; D013006:Growth Hormone / Q000097:blood; D007334:Insulin-Like Growth Factor I / Q000378:metabolism / Q000494:pharmacology*; D009124:Muscle Proteins / Q000187:drug effects* / Q000378:metabolism*; D018482:Muscle, Skeletal / Q000378:metabolism; D017686:Oncorhynchus mykiss / Q000235:genetics* / Q000502:physiology*; D012333:RNA, Messenger / Q000378:metabolism; D015431:Weight Loss / Q000187:drug effects / Q000502:physiology
chemical_list: D044783:F-Box Proteins; D009124:Muscle Proteins; D012333:RNA, Messenger; D007334:Insulin-Like Growth Factor I; D013006:Growth Hormone; D002403:Cathepsins