scholarly journals Effect of endurance training and branched-chain amino acids on the signaling for muscle protein synthesis in CKD model rats fed a low-protein diet

2017 ◽  
Vol 313 (3) ◽  
pp. F805-F814 ◽  
Author(s):  
Takuya Yoshida ◽  
Sachika Kakizawa ◽  
Yuri Totsuka ◽  
Miho Sugimoto ◽  
Shinji Miura ◽  
...  
Keyword(s):  
Amino Acids ◽  
Renal Function ◽  
Protein Synthesis ◽  
Sham Group ◽  
Treadmill Exercise ◽  
Muscle Protein ◽  
Muscle Protein Synthesis ◽  
Branched Chain Amino Acids ◽  
Low Protein ◽  
Branched Chain

A low-protein diet (LPD) protects against the progression of renal injury in patients with chronic kidney disease (CKD). However, LPD may accelerate muscle wasting in these patients. Both exercise and branched-chain amino acids (BCAA) are known to increase muscle protein synthesis by activating the mammalian target of rapamycin (mTOR) pathway. The aim of this study was to investigate whether endurance exercise and BCAA play a role for increasing muscle protein synthesis in LPD-fed CKD (5/6 nephrectomized) rats. Both CKD and sham rats were pair-fed on LPD or LPD fortified with a BCAA diet (BD), and approximately one-half of the animals in each group was subjected to treadmill exercise (15 m/min, 1 h/day, 5 days/wk). After 7 wk, renal function was measured, and soleus muscles were collected to evaluate muscle protein synthesis. Renal function did not differ between LPD- and BD-fed CKD rats, and the treadmill exercise did not accelerate renal damage in either group. The treadmill exercise slightly increased the phosphorylation of p70s6 kinase, a marker of mTOR activity, in the soleus muscle of LPD-fed CKD rats compared with the sham group. Furthermore, BCAA supplementation of the LPD-fed, exercise-trained CKD rats restored the phosphorylation of p70s6 kinase to the same level observed in the sham group; however, the corresponding induced increase in muscle protein synthesis and muscle mass was marginal. These results indicate that the combination of treadmill exercise and BCAA stimulates cell signaling to promote muscle protein synthesis; however, the implications of this effect for muscle growth remain to be clarified.

scholarly journals Amino acid infusion increases the sensitivity of muscle protein synthesis in vivo to insulin. Effect of branched-chain amino acids

1988 ◽  
Vol 254 (2) ◽  
pp. 579-584 ◽  
Author(s):  
P J Garlick ◽  
I Grant
Keyword(s):  
Amino Acids ◽  
Protein Synthesis ◽  
Amino Acid ◽  
Muscle Protein ◽  
Muscle Protein Synthesis ◽  
Branched Chain Amino Acids ◽  
Acid Infusion ◽  
Amino Acid Infusion ◽  
Branched Chain

Rates of muscle protein synthesis were measured in vivo in tissues of post-absorptive young rats that were given intravenous infusions of various combinations of insulin and amino acids. In the absence of amino acid infusion, there was a steady rise in muscle protein synthesis with plasma insulin concentration up to 158 mu units/ml, but when a complete amino acids mixtures was included maximal rates were obtained at 20 mu units/ml. The effect of the complete mixture could be reproduced by a mixture of essential amino acids or of branched-chain amino acids, but not by a non-essential mixture, alanine, methionine or glutamine. It is concluded that amino acids, particularly the branched-chain ones, increase the sensitivity of muscle protein synthesis to insulin.

scholarly journals Insulin does not stimulate muscle protein synthesis during increased plasma branched-chain amino acids alone but still decreases whole body proteolysis in humans

2016 ◽  
Vol 311 (4) ◽  
pp. E671-E677 ◽  
Author(s):  
Sarah Everman ◽  
Christian Meyer ◽  
Lee Tran ◽  
Nyssa Hoffman ◽  
Chad C. Carroll ◽  
...  
Keyword(s):  
Amino Acids ◽  
Protein Synthesis ◽  
Insulin Infusion ◽  
Muscle Protein ◽  
Muscle Protein Synthesis ◽  
Essential Amino Acids ◽  
Branched Chain Amino Acids ◽  
Whole Body ◽  
Synthesis Rate ◽  
Branched Chain

Insulin stimulates muscle protein synthesis when the levels of total amino acids, or at least the essential amino acids, are at or above their postabsorptive concentrations. Among the essential amino acids, branched-chain amino acids (BCAA) have the primary role in stimulating muscle protein synthesis and are commonly sought alone to stimulate muscle protein synthesis in humans. Fourteen healthy young subjects were studied before and after insulin infusion to examine whether insulin stimulates muscle protein synthesis in relation to the availability of BCAA alone. One half of the subjects were studied in the presence of postabsorptive BCAA concentrations (control) and the other half in the presence of increased plasma BCAA (BCAA). Compared with that prior to the initiation of the insulin infusion, fractional synthesis rate of muscle protein (%/h) did not change ( P > 0.05) during insulin in either the control (0.04 ± 0.01 vs 0.05 ± 0.01) or the BCAA (0.05 ± 0.02 vs. 0.05 ± 0.01) experiments. Insulin decreased ( P < 0.01) whole body phenylalanine rate of appearance (μmol·kg−1·min−1), indicating suppression of muscle proteolysis, in both the control (1.02 ± 0.04 vs 0.76 ± 0.04) and the BCAA (0.89 ± 0.07 vs 0.61 ± 0.03) experiments, but the change was not different between the two experiments ( P > 0.05). In conclusion, insulin does not stimulate muscle protein synthesis in the presence of increased circulating levels of plasma BCAA alone. Insulin's suppressive effect on proteolysis is observed independently of the levels of circulating plasma BCAA.

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