Proteomic analysis of muscle tissue from rainbow trout (Oncorhynchus mykiss) fed dietary β-glucan.

The aim of this study was to examine the changes in muscle proteome of the rainbow trout fed dietary β-glucan. The experimental diets contained 0 (control), 0.1% and 0.2% β-1,3/1,6 yeast glucan. First, feeding larvae were fed to apparent satiation nine times per day with their respective diets over two months. The percentage of body weight gain and feed efficiency of fish fed 0.2% diet was significantly higher than those of fish fed the control and 0.1% diets. Fish fed the control and 0.2% diets were subjected to proteomic analysis. Proteins of the muscle tissue were analyzed using two-dimensional electrophoresis and mass spectrometry. Spots that were found to differ significantly in abundance between control and β-glucan fed fish were selected for identification. Out of 8 protein spots showing differential expression, 7 spots were successfully identified. Two protein spots that were found to be increased in abundance in the β-glucan treated rainbow trout corresponded to tropomyosin alpha-1 chain (spot 1) and slow myotomal muscle tropomyosin (spot 2). The five spots that were down-regulated with dietary β-glucan supplementation were identified as different forms of myosin: myosin light polypeptide 3-2 (spot 3), myosin light chain 1 (spots 4 and 5), fast myosin light chain 2 (spot 6) and myosin heavy chain (spot 7). The altered expression of structural proteins in fish fed β-glucan may be related to higher growth rate in rainbow trout. These findings provide basic information to understand possible mechanisms of dietary β-glucan contribution to better growth in rainbow trout.