Exercise training accelerates UPS- and mTOR-mediated protein turnover of grass carp Ctenopharyngodon idella

Abstract

The present study is aimed to investigate the effects and mechanism of exercise training on the growth and protein turnover in grass carp Ctenopharyngodon idella. To this end, grass carp were respectively cultured at four water velocities (0 (control), 0.5, 1 and 1.5 body length s−1 (bl s−1)) for 10 weeks. The results showed that exercise training increased weight gain rate (WGR) and specific growth rate (SGR), and significantly decreased feed conversion ratio (FCR). The level of serum GH and the mRNA levels of GH/IGF-1 pathway-related genes (ghr and igf-1) of liver were significantly upregulated in C. idella after exercise training at 0.5 and 1 bl s−1. These indicated that at low and medium water velocities, exercise training was beneficial for fish growth. In addition, histochemical analysis of muscle showed that 0.5 bl s−1 exercise training significantly increased muscle fiber density of C. idella. The mRNA expression levels of UPS-related genes (ub, psmc1, psma2 and murf1) and mTOR-related genes (pi3k, mtor and s6k1) were significantly upregulated by 1 and 1.5 bl s−1 water velocity treatments. The levels of polyubiquitinated protein and 3-methylhistidine (3-MH) were significantly increased by the 1 bl s−1 exercise training treatment. These suggested that exercise training facilitated the protein turnover by motivating UPS and mTOR pathway. Taken together, our study demonstrated mechanism of exercise training increasing the growth rate and protein turnover in water velocity-dependent manner in C. idella, which will help to provide fundamental information for raceway-based and recirculating aquaculture system (RAS) aquaculture.