New sight in arginine-improved flesh quality: Role of MRFs, cyclins, and WNT signaling in grass carp (Ctenopharyngodon idellus)

Abstract

In this study, we investigated the functional roles and mechanisms of arginine in improving the muscle quality of sub-adult grass carp. We divided 450 healthy fish (661.60 ± 1.00 g) into six groups and fed them separate diets with increasing levels of arginine (3.51, 7.01, 10.51, 14.01, 17.51, and 21.01 g/kg) for 63 days. The results showed that optimal dietary arginine levels promoted grass carp growth and improved muscle lipid content, shear force (hardness), pH, hydrolyzed amino acid contents, and the chemical score of essential amino acids (protein quality). Suitable dietary arginine levels also decreased the proportion of hypertrophic fibers and increased the proportion of hyperplastic fibers. Furthermore, appropriate arginine supplementation increased the expression levels of MyoD, MyoG, Myf5, MRF4, MyHC, cyclin D1, cyclin B, cyclin E, WNT1, WNT3a, and β-catenin and decreased the expression levels of MSTN and GSK3β. In conclusion, appropriate arginine levels in the diet (10.51–14.01 g/kg) may promote the growth and muscle quality of grass carp while increasing the proportion of hyperplasia fibers and decreasing the proportion of hypertrophic fibers probably by regulating the WNT/β-catenin pathway to increase the expression levels of MRFs and cyclins. This study offers novel insights into the regulatory role of arginine in muscle fiber growth, which can facilitate the improvement of grass carp muscle quality.