Determination of relative protein degradation activity at different life stages in rainbow trout (Oncorhynchus mykiss) fed fishmeal or plant based diets.

Authors: Overturf, Kenneth - Ken; Gaylord, Thomas

Submitted to: Comparative Biochemistry and Physiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/22/2008
Publication Date: 1/15/2008
Citation: Overturf, K. & Gaylord, T. 2009. Determination of relative protein degradation activity at different life stages in rainbow trout (Oncorhynchus mykiss). Comparative Biochemistry and Physiology Part B 152:150-160

Interpretive Summary: Management of muscle turnover in regards to synthesis of new muscle and breakdown of existing muscle is what determines the rate of growth in the animal. Rainbow trout were reared on a diet formulated to supply the required protein from normal and sustainable plant sources and sampled 6 times over 3 months. Isolated samples from the fish reared on these diets were tested for changes in muscle turnover by evaluating the expression of genes related to muscle development and the expression of genes and activity of proteins involved in muscle degradation. Some significant differences were found for one gene involved in muscle development between the two diets. Degradation rates were also found to differ over time for the activity of several of the protein degradation factors.

Technical Abstract: Rainbow trout were reared on a diet formulated to supply the required protein from either fishmeal or protein meal sources. From liver and muscle tissue samples RNA and protein were isolated and analyzed for the expression of a number of muscle regulatory and protein degradation genes and enzymatic activity for proteins involved in degradation pathways for protein proteolysis. Only MyoD2 showed significant differences in expression between the two diets and no significant increases or decreases over the course of the experiment were determined for MyoD2 or the other muscle factors. For the degradation genes significant changes in expression were determined for calpain1 and calpastatinL. CalpastatinL also showed a significant increase in expression over the course of the experiment in the muscle of fish fed a fishmeal diet and significant decrease in expression in the liver of fish fed the fishmeal based diet. Differences in proteasome enzyme activity were found between diets in the liver and muscle of fish and for caspase-3 activity in muscle. These findings suggest that diets replacing fishmeal with plant material can have some effects on protein turnover in muscle and that some degradation pathways are differentially regulated during the growth of rainbow trout.