Effects of glutamine and its precursors on the growth performance and relevant protein synthesis pathway of mirror carp Cyprinus carpio
2017
Zhao, Zhigang | Song, Fangjie | Xu, Qiyou
This study aimed to investigate the effects of Gln and its precursors on Gln anabolism and ammonia excretion to determine the role of Gln in protein synthesis in Cyprinus carpio. The growth performance, glutamine synthetase (GS) activity, blood ammonia level, and gene expression of GS, rhesus glycoprotein (Rhag, Rhbg and Rhcg), TOR and 4E-BP1 of fish were measured. Seven diet treatments including glucose (control), glutamine (Gln), glusate (Glu), α-ketoglutarate (AKG), L-ornithine-α-ketoglutarate (OKG), L-arginine-α-ketoglutarate (AAKG), and α-ketoglutarate sodium (2Na-AKG) were conducted. All were substituted for glucose at 1.5% of the dry diet. The results showed the feed conversion ratios (FCRs) of the AKG group and AAKG group were significantly lower (P < 0.05) than that of the control group. The expression levels of the Rhbg gene in the gills of the AKG, AAKG and 2Na-AKG groups were significantly higher than that in the control group (P < 0.05). The expression levels of the TOR gene in the gut of the fish in the AKG group and the Glu group were significantly higher than that in the control group (P < 0.05). Therefore, the addition of AAKG in feed can significantly reduce the FCR of Cyprinus carpio and significantly improve the weight gain rate (WGR) and protein efficiency of the fish. Gln can reduce ammonia release in gills, and AKG can effectively promote the excretion of ammonia. The addition of Gln, Glu, AKG and AAKG in diets can effectively promote protein synthesis. The Gln, Glu, AKG and AAKG can significantly up-regulate GS gene expression in the gut; however, the expression level of the GS gene is not significantly correlated with GS activity.
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