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Engineering    2017, Vol. 3 Issue (5) : 760 -765
Research |
Leucine Supplementation in a Chronically Protein-Restricted Diet Enhances Muscle Weight and Postprandial Protein Synthesis of Skeletal Muscle by Promoting the mTOR Pathway in Adult Rats
Bo Zhang1,2,Licui Chu1,2,Hong Liu1,2,Chunyuan Xie1,2,Shiyan Qiao1,2,Xiangfang Zeng1,2()
1. Beijing Advanced Innovation Center for Food Nutrition and Human Health, College of Animal Science and Technology, China Agricultural University, Beijing 100193, China
2. State Key Laboratory of Animal Nutrition, China Agricultural University, Beijing 100193, China

Low protein intake causes a decrease in protein deposition in most animal tissues. The purpose of this study was to investigate whether leucine supplementation would increase the synthesis rate of protein and muscle weight in adult rats, which chronically consume only 58.8% of their protein requirements. Thirty-six male Sprague-Dawley rats were assigned to one of three dietary treatments including a 20% casein diet (CON), a 10% casein+ 0.44% alanine diet (R), and a 10% casein+ 0.87% leucine diet (RL). After a 10 d dietary treatment, plasma amino acid levels were measured after feeding, the gastrocnemius muscles and soleus muscles were harvested and weighed, and the fractional synthesis rate (FSR) and mammalian target of rapamycin (mTOR) signaling proteins in skeletal muscle were measured. Regarding the plasma amino acid level, the RL group had the highest concentration of leucine (P<0.05) and the lowest concentration of isoleucine (P<0.05) among the three groups, and the CON group had a lower concentration of valine (P<0.05) than the R and RL groups. Compared with the R and RL groups, the CON group diet significantly increased (P<0.05) feed intake, protein synthesis rate, and the phosphorylation of eukaryotic initiation factor 4E binding protein 1 (4E-BP1), and decreased the weight of abdominal adipose. Compared with the R group, the RL group significantly increased in gastrocnemius muscle weight, protein synthesis rate, and phosphorylation of both ribosomal protein S6 kinase 1 (S6K1) and 4E-BP1. In conclusion, when protein is chronically restricted in adult rat diets, leucine supplementation moderately improves body weight gain and increases muscle protein synthesis through mTOR activation.

Keywords Low-protein diet      Leucine      Growth performance      Muscle weight      Protein synthesis      Adult rats     
Corresponding Authors: Xiangfang Zeng   
Just Accepted Date: 05 May 2017   Online First Date: 01 August 2017    Issue Date: 08 November 2017
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Bo Zhang
Licui Chu
Hong Liu
Chunyuan Xie
Shiyan Qiao
Xiangfang Zeng
Cite this article:   
Bo Zhang,Licui Chu,Hong Liu, et al. Leucine Supplementation in a Chronically Protein-Restricted Diet Enhances Muscle Weight and Postprandial Protein Synthesis of Skeletal Muscle by Promoting the mTOR Pathway in Adult Rats[J]. Engineering, 2017, 3(5): 760 -765 .
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