Effects of dietary glutamate supplementation on flesh quality, antioxidant defense and gene expression related to lipid metabolism and myogenic regulation in Jian carp (Cyprinus carpio var. Jian)

The present study was conducted to investigate the effects of dietary glutamate (Glu) supplementation on flesh quality, antioxidant defense and gene expression related to lipid metabolism and myogenic regulation. A total of 600 Jian carp Cyprinus carpio var. Jian with the similar size (mean initial weight 126.40 +/- 0.21 g) were randomly assigned to five dietary treatment groups for feeding 63 days: a basal diet, basal diet supplemented with 4, 8, 16, and 32 g kg(-1) Glu. With Glu supplement, the relative shear force, hydroxyproline content, and pH value have been significantly increased, and cooking loss and lactate content have been significantly decreased in muscle. Muscle protein, lipid, and the total essential amino acid concentration were significantly improved by Glu. Meanwhile, dietary Glu supplementation also modified muscle fatty acid profiles. Additionally, Glu supplementation significantly enhanced GSH content and the activities and gene expression of CuZnSOD, GPx, GST, and GR in muscle. The enhanced antioxidant enzymes activities were modulated by Nrf2. The expression level of genes involved in myogenic regulation (MyoD, Myf5, myogenin, and Mrf4) and TOR were significantly elevated by dietary Glu supplementation. Moreover, dietary Glu supplementation increased FAS mRNA level and decreased LPL mRNA level. In conclusion, these results suggest that Glu is a potential role to improve muscle flesh quality and the underlying mechanism may be partly due to regulate lipid metabolism, myogenic regulatory factors, and antioxidative capacity induced by Glu.