The actions of exogenous leucine on mTOR signalling and amino acid transporters in human myotubes.
The actions of exogenous leucine on mTOR signalling and amino acid transporters in human myotubes.
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DOI：
10.1186/1472-6793-11-10
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发表时间：
2011-06-25
期刊：
影响因子：
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通讯作者：
Cameron-Smith D
中科院分区：
文献类型：
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作者：
Gran P;Cameron-Smith D
支链氨基酸(BCAA)亮氨酸被认为是骨骼肌合成代谢的关键调节因子。合成代谢信号的激活通过哺乳动物的雷帕霉素靶标(MTOR)通过一种未知的机制发生。A系统和L溶质载体通过质膜运输必需氨基酸；然而，目前尚不清楚是否有外源亮氨酸供应来调节它们的基因表达。本研究的目的是利用原代培养的人骨骼肌细胞，研究急性和慢性亮氨酸刺激对合成代谢信号和特定氨基酸转运体的影响。分别用亮氨酸、胰岛素或与亮氨酸、胰岛素共同作用30min、3h、2 4h后，检测mTOR信号通路的激活情况，以及可能的营养感受器人类空泡蛋白分选34(HVps34)和部分氨基酸转运体的基因表达。MTOR和p70S6K的磷酸化在亮氨酸暴露后一过性增加，与胰岛素无关。HVps34蛋白表达也显著增加。然而，编码氨基酸转运蛋白的基因受胰岛素而不是亮氨酸的差异调控。MTOR信号是由人肌管内的亮氨酸瞬时激活的，不依赖于胰岛素刺激。虽然这发生在氨基酸转运蛋白基因表达没有变化的情况下，但hVps34的蛋白表达增加。
The branched-chain amino acid (BCAA) leucine has been identified to be a key regulator of skeletal muscle anabolism. Activation of anabolic signalling occurs via the mammalian target of rapamycin (mTOR) through an undefined mechanism. System A and L solute carriers transport essential amino acids across plasma membranes; however it remains unknown whether an exogenous supply of leucine regulates their gene expression. The aim of the present study was to investigate the effects of acute and chronic leucine stimulation of anabolic signalling and specific amino acid transporters, using cultured primary human skeletal muscle cells. Human myotubes were treated with leucine, insulin or co-treated with leucine and insulin for 30 min, 3 h or 24 h. Activation of mTOR signalling kinases were examined, together with putative nutrient sensor human vacuolar protein sorting 34 (hVps34) and gene expression of selected amino acid transporters. Phosphorylation of mTOR and p70S6K was transiently increased following leucine exposure, independently to insulin. hVps34 protein expression was also significantly increased. However, genes encoding amino acid transporters were differentially regulated by insulin and not leucine. mTOR signalling is transiently activated by leucine within human myotubes independently of insulin stimulation. While this occurred in the absence of changes in gene expression of amino acid transporters, protein expression of hVps34 increased.