• Yehui Duan, Liming Zeng, Fengna Li, Wenlong Wang, Yinghui Li, Qiuping Guo, Yujiao Ji, Bi'e Tan, and Yulong Yin.
• Key Laboratory of Agro-ecological Processes in Subtropical Region, Institute of Subtropical Agriculture, Chinese Academy of Sciences, National Engineering Laboratory for Pollution Control and Waste Utilization in Livestock and Poultry Production; Hunan Provincial Engineering Research Center for Healthy Livestock and Poultry Production, Changsha, China; Scientific Observing and Experimental Station of Animal Nutrition and Feed Science in South-Central, Ministry of Agriculture, Changsha, China; University of Chinese Academy of Sciences, Beijing, China.
• Nutrition. 2017 Apr 1; 36: 8-16.

ObjectivesBranched-chain amino acids (BCAAs), including leucine (Leu), isoleucine (Ile), and valine (Val), are key regulators of protein synthesis in muscle. The aim of this study was to investigate the effect of different BCAA ratios (Leu:Ile:Val) on the proliferation, differentiation, and expression levels of the regulators related to protein metabolism of C2 C12 myocytes.MethodsStudies were conducted in C2C12 myocytes exposed to different BCAA ratios (Leu: Ile: Val = 0, 1:0.25:0.25, 1:1:1).ResultsThe ratio of 1:0.25:0.25 increased cell viability and promoted cell cycle progression from G0/G1 phase to S phase, which was an indicator of proliferation enhancement (P < 0.05). Moreover, this optimal ratio (1:0.25:0.25) promoted the differentiation of myocytes into myotubes by upregulating myogenin and interleukin-15 gene expression, and differently regulated the expression of L-type amino acid transporter 1 and 4 and system ASC amino acid transporters 2. Furthermore, the ratio stimulated mTOR expression at the mRNA and phosphorylated protein levels, as well as ribosomal protein S6 kinase and regulatory-associated protein of mTOR (raptor). In contrast, the optimal ratio decreased the amount of ubiquitin ligase muscle-specific RING finger 1 and muscle atrophy F-box during proliferation and differentiation (P < 0.05). No change was observed in the expression of key genes related to energy metabolism except for uncoupling protein 3 (P > 0.05).ConclusionsThe results suggested that appropriate BCAA ratios could enhance proliferation and differentiation of the C2 C12 myocytes, also mediate the key regulators related to protein metabolism including the mTORC1 pathway. A proper utilization of balanced BCAA ratio in food would be beneficial to human and animal nutrition.Copyright © 2016 Elsevier Inc. All rights reserved.

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