ARS | Publication request: Effect of feed deprivation and insulin-like growth hormone on indices of protein degradation in rainbow trout (Oncorhynchus mykiss)

Submitted to: Aquaculture America Conference
Publication Type: Abstract Only
Publication Acceptance Date: February 15, 2009
Publication Date: February 15, 2009
Citation: Cleveland, B.M., Blemings, K.P., Silverstein, J., Weber, G.M. 2009. Effect of feed deprivation and insulin-like growth hormone on indices of protein degradation in rainbow trout (Oncorhynchus mykiss). Aquaculture America Conference.

Technical Abstract: Insulin-like growth factor-I (IGF-I) is a hormone that promotes growth by both increasing protein synthesis and decreasing protein degradation. This study utilizes a comparative slaughter approach to determine the effect of feed deprivation and IGF-I treatment on weight loss and indices of protein degradation. Knowing how proteolytic pathways are affected by nutrient deprivation and IGF-I will contribute to the understanding of the impact and regulation these pathways have on protein turnover. Two yearling fish from each of eight families of rainbow trout were stocked into 35 30-gallon tanks. Seven tanks were harvested on day 1 and fish in 14 tanks were implanted with an osmotic pump containing either recombinant human IGF-I (25 ug/kg/d) or saline. All fish that received impants and an additional 7 tanks of fish were harvested after 14 days of feed deprivation. The final 7 tanks were harvested after 28 days of feed deprivation. For each tank one fish from each family was kept whole for proximate analysis while liver and white muscle samples were snap frozen for gene expression analysis and blood was collected for 3-methylhistine detection. Fish treated with IGF-I lost less weight (P<0.05) than untreated fish after 14 days of feed deprivation, however, dry weight and fat loss were not significantly affected by IGF-I treatment. A reduction in the mRNA abundance of genes in the proteosome and cathepsin pathways was observed in IGF-I treated fish (P<0.05), indicating that the IGF-I mediated reduction in weight loss during starvation may involve regulation of these two pathways. Genes in all proteolytic pathways were affected by the duration of feed deprivation (P<0.05). These data indicate that nutrient availability and IGF-I can differentially regulate specific proteolytic pathways in rainbow trout.