Muscle Protein Anabolic Resistance to Essential Amino Acids Does Not Occur in Healthy Older Adults Before or After Resistance Exercise Training
Muscle Protein Anabolic Resistance to Essential Amino Acids Does Not Occur in Healthy Older Adults Before or After Resistance Exercise Training
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DOI：
10.1093/jn/nxy064
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发表时间：
2018-06-01
影响因子：
4.2
通讯作者：
Rasmussen, Blake B.
中科院分区：
文献类型：
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作者：
Moro, Tatiana;Brightwell, Camille R.;Rasmussen, Blake B.
背景：老年人对肌肉蛋白质合成代谢的收缩和进食反应可能是迟钝的。急性运动可通过激活雷帕霉素复合体1的机械靶信号来提高氨基酸刺激肌肉蛋白质合成(MPS)的能力，但运动训练是否可提高肌肉对氨基酸可用性的敏感性尚不清楚。目的：本研究的目的是确定肌肉蛋白质合成是否对必需氨基酸(EaaS)具有抵抗力，以及抵抗性运动训练(RET)是否提高健康老年人肌肉对必需氨基酸(EAA)的敏感性。19名健康老年人[平均+/-SD年龄：71+/-4岁体重指数(kg/m(2))：28+/-3]进行12wk的全身递增RET训练(60~75%1次重复)。在训练前后测量身体成分、力量和代谢健康。我们还对训练前和训练后的肌肉活检进行了稳定同位素输注实验，以测量基础状态和6.8g EAA摄入后的MPS和氨基酸感觉标志物。结果：RET使健康老年人的肌肉力量增加了16%，瘦体重增加了2%，肌肉横截面积增加了27%(P<；0.05)。在训练前后摄入EAA(P<；0.05)后，MPS和mTORC1信号(即蛋白激酶B、4E结合蛋白1、70 kDa S6蛋白激酶和核糖体蛋白S6的磷酸化状态)增加。RET使基础MPS增加36%(P<；0.05)；但RET不影响MPS和mTORC1信号对EAA摄入的反应。结论：RET增加了健康老年人的强度和基础MPS，促进了肥厚。在这些受试者中，小剂量的EaaS刺激肌肉mTORC1信号和MPS，而这种对EaaS的反应在RET后没有改善。我们的数据表明，对氨基酸的合成代谢抵抗在健康的老年人中可能不是问题。
Background: The muscle protein anabolic response to contraction and feeding may be blunted in older adults. Acute bouts of exercise can improve the ability of amino acids to stimulate muscle protein synthesis (MPS) by activating mechanistic target of rapamycin complex 1 (mTORC1) signaling, but it is not known whether exercise training may improve muscle sensitivity to amino acid availability.Objective: The aim of this study was to determine if muscle protein anabolism is resistant to essential amino acids (EAAs) and whether resistance exercise training (RET) improves muscle sensitivity to EAA in healthy older adults.Methods: In a longitudinal study, 19 healthy older adults [mean +/- SD age: 71 +/- 4 y body mass index (kg/m(2)): 28 +/- 3] were trained for 12 wk with a whole-body program of progressive RET (60-75% 1-repetition maximum). Body composition, strength, and metabolic health were measured pre- and posttraining. We also performed stable isotope infusion experiments with muscle biopsies pre-and posttraining to measure MPS and markers of amino acid sensing in the basal state and in response to 6.8 g of EAA ingestion.Results: RET increased muscle strength by 16%, lean mass by 2%, and muscle cross-sectional area by 27% in healthy older adults (P < 0.05). MPS and mTORC1 signaling (i.e., phosphorylation status of protein kinase B, 4E binding protein 1, 70-kDa S6 protein kinase, and ribosomal protein S6) increased after EAA ingestion (P < 0.05) pre-and posttraining. RET increased basal MPS by 36% (P < 0.05); however, RET did not affect the response of MPS and mTORC1 signaling to EAA ingestion.Conclusions: RET increases strength and basal MPS, promoting hypertrophy in healthy older adults. In these subjects, a small dose of EAAs stimulates muscle mTORC1 signaling and MPS, and this response to EAAs does not improve after RET. Our data indicate that anabolic resistance to amino acids may not be a problem in healthy older adults.