ARS | Publication request: Effects of maturation, diet, and estradiol on indices of protein degradation in rainbow trout (Oncorhychus mykiss)

Submitted to: Aquaculture America Conference
Publication Type: Abstract Only
Publication Acceptance Date: January 15, 2012
Publication Date: February 29, 2012
Citation: Cleveland, B.M., Kenney, P., Manor, M.L., Weber, G.M. 2012. Effects of maturation, diet, and estradiol on indices of protein degradation in rainbow trout (Oncorhychus mykiss). Aquaculture America Conference. 12.

Technical Abstract: Sexual maturation in salmonids requires mobilization of proteins from muscle tissue as evidenced by increased expression of proteolytic genes and decreased muscle protein content. However, it is unknown how ration level affects this proteolytic response. Female diploid rainbow trout (Oncorhynchus mykiss) approaching ovulation were fed for twelve weeks at 0.25% and 0.50% tank weight, and to apparent satiation. Triploid trout, which exhibit little ovarian growth, were included at the 0.50% ration level. Reduced feed intake and maturation decreased fillet weight and fillet protein and lipid content. During mid-vitellogenesis, proteolytic gene expression was higher in diploids compared to triploids and the majority of the differentially expressed transcripts were cathepsin and autophagy-related genes. These differences increased with maturation and expanded to include multiple components of the proteasome, ubiquitin ligases, calpastatins, and caspase 9. These results suggest that maturation-related signals increase protein degradation and that higher levels of feed intake are unable to alleviate these effects. However, higher levels of feed intake prevent a net loss of muscle protein, suggesting that dietary nutrients are able to replace endogenous nutrients mobilized from skeletal muscle in support of gonad growth. The maturation-related signal contributing to increases in protein degradation in skeletal muscle may be estradiol, which decreased rates of protein synthesis and increased rates of protein degradation and proteolytic gene expression in primary myocyte cultures. Estradiol injection also increased proteolytic gene expression in muscle tissue of rainbow trout.