Dl-Methionine supplementation in a low-fishmeal diet affects the TOR/S6K pathway by stimulating ASCT2 amino acid transporter and insulin-like growth factor-I in the dorsal muscle of juvenile cobia (Rachycentron canadum). Issue 7 (14th October 2019)

• Record Type: Journal Article
• Authors: He, Yuanfa; Chi, Shuyan; Tan, Beiping; Dong, Xiaohui; Yang, Qihui; Liu, Hongyu; Zhang, Shuang; Han, Fenglu; Liu, Di
• Is Part Of: British journal of nutrition. Volume 122:Issue 7(2019)
• Page Start: 734
• Page End: 744
• Publication Date: 2019-10-14
• Subjects: Rachycentron canadum, -- Methionine, -- Serum hormones, -- Amino acid transporters, -- TOR/S6K pathway; Nutrition -- Periodicals; 572.4
• DOI: 10.1017/S0007114519001648
• Languages: English
• ISSNs: 0007-1145

Abstract

Abstract: An 8-week feeding experiment was conducted to investigate the effects ofdl -methionine (Met) supplementation in a low-fishmeal diet on growth, key gene expressions of amino acid transporters and target of rapamycin (TOR) pathway in juvenile cobia, Rachycentron canadum . Seven isonitrogenous and isolipidic diets were formulated, containing 0·72, 0·90, 1·00, 1·24, 1·41, 1·63 and 1·86 % Met. Weight gain and specific growth rates increased gradually with Met levels of up to 1·24 % and then decreased gradually. In dorsal muscle, mRNA levels of ASCT2 in the 1·00 % Met group were significantly up-regulated compared with 0·72, 1·63, and 1·86 %. The insulin-like growth factor-I (IGF-I) mRNA levels in the dorsal muscle of fish fed 1·00 and 1·24 % Met were higher than those in fish fed other Met levels. In addition, fish fed 1·24 % Met showed the highest mRNA levels of TOR and phosphorylation of TOR on Ser 2448 . The phosphorylation of ribosomal p70-S6 kinase (S6K) on Ser 371 in the dorsal muscle of fish fed 1·86 % Met was higher than those in the 0·72 % group. In conclusion, straight broken-line analysis of weight gain rate against dietary Met level indicates that the optimal Met requirement for juvenile cobia is 1·24 % (of DM, or 2·71 % dietary protein). Met supplementation in a low-fishmeal diet increased cobia growth via a mechanism that can partly be attributed to Met's ability to affect the TOR/S6K signalling pathway by enhancing ASCT2 and IGF-I transcription in cobia dorsal muscle.