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Am J Physiol Regul Integr Comp Physiol. 2009 Nov;297(5):R1332-42. doi: 10.1152/ajpregu.00272.2009. Epub 2009 Sep 2.

Insulin-like growth factor-I and genetic effects on indexes of protein degradation in response to feed deprivation in rainbow trout (Oncorhynchus mykiss).

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1
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

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.

PMID:
19726716
DOI:
10.1152/ajpregu.00272.2009
[Indexed for MEDLINE]
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