Repeated bouts of resistance exercise in rats alter mechanistic target of rapamycin complex 1 activity and ribosomal capacity but not muscle protein synthesis
Repeated bouts of resistance exercise in rats alter mechanistic target of rapamycin complex 1 activity and ribosomal capacity but not muscle protein synthesis
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DOI：
10.1113/ep089699
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发表时间：
2021-07-14
影响因子：
2.7
通讯作者：
Ishii, Naokata
中科院分区：
文献类型：
--
作者：
Kotani, Takaya;Takegaki, Junya;Ishii, Naokata
新发现 这项研究的中心问题是什么？当反复进行抗阻运动 (RE) 后核糖体容量增加时，肌肉蛋白合成 (MPS) 是否会在运动后额外激活？主要发现及其重要性是什么？通过重复 RE 回合，核糖体含量增加的骨骼肌显示出 MPS 的充分激活，雷帕霉素复合物 1 信号传导的机械靶标较低。因此，重复的 RE 可能会改变翻译能力和效率，以优化 RE 后的翻译激活。抗阻运动 (RE) 激活核糖体生物发生并增加骨骼肌中的核糖体含量。然而，目前尚不清楚核糖体含量的增加是否会导致 RE 诱导的肌肉蛋白合成 (MPS) 激活增加。因此，本研究旨在利用大鼠 RE 模型研究运动后核糖体含量与 MPS 之间的关系。雄性 Sprague-Dawley 大鼠被分为三组（每组 n = 6）：久坐组（SED）和 RE 训练一组（1B）或三组（3B）。在异氟烷麻醉下通过经皮电刺激将 RE 刺激施加到右侧腓肠肌。 3B组每隔一天接受一次刺激。我们的结果显示，最后一轮 RE 后 6 小时，与 SED 组和 1B 组相比，3B 组的肌肉中单位肌肉重量的总 RNA 和 18S+28S rRNA 含量有所增加。运动后 6 小时，1B 组和 3B 组的 MPS（通过蛋白质中嘌呤霉素掺入量估算）均高于 SED 组；然而，1B 组和 3B 组之间没有观察到显着差异。在 1B 和 3B 组中，Thr-389 位点的磷酸化 p70S6K 增加，表明雷帕霉素复合物 1 (mTORC1) 活性的机制靶标。 3B组中p70S6K磷酸化水平低于1B组。最后，3B 组中每个核糖体的蛋白质合成（翻译效率的指标）低于 1B 组。因此，三轮 RE 改变了核糖体含量和 mTORC1 激活，但没有改变 RE 诱导的总体 MPS 激活程度。
New Findings What is the central question of this study? Is muscle protein synthesis (MPS) additionally activated following exercise when ribosomal capacity is increased after repeated bouts of resistance exercise (RE)? What is the main finding and its importance? Skeletal muscles with increased ribosome content through repeated RE bouts showed sufficient activation of MPS with lower mechanistic target of rapamycin complex 1 signalling. Thus, repeated bouts of RE possibly change the translational capacity and efficiency to optimize translation activation following RE. Resistance exercise (RE) activates ribosome biogenesis and increases ribosome content in skeletal muscles. However, it is unclear whether the increase in ribosome content subsequently causes an increase in RE-induced activation of muscle protein synthesis (MPS). Thus, this study aimed to investigate the relationship between ribosome content and MPS after exercise using a rat RE model. Male Sprague-Dawley rats were categorized into three groups (n = 6 for each group): sedentary (SED) and RE trained with one bout (1B) or three bouts (3B). The RE stimulus was applied to the right gastrocnemius muscle by transcutaneous electrical stimulation under isoflurane anaesthesia. The 3B group underwent stimulation every other day. Our results revealed that 6 h after the last bout of RE, muscles in the 3B group showed an increase in total RNA and 18S+28S rRNA content per muscle weight compared with the SED and 1B groups. In both the 1B and 3B groups, MPS, estimated by puromycin incorporation in proteins, was higher than that in the SED group 6 h after exercise; however, no significant difference was observed between the 1B and 3B groups. In the 1B and 3B groups, phosphorylated p70S6K at Thr-389 increased, indicating mechanistic target of rapamycin complex 1 (mTORC1) activity. p70S6K phosphorylation level was lower in the 3B group than in the 1B group. Finally, protein synthesis per ribosome (indicator of translation efficiency) was lower in the 3B group than in the 1B group. Thus, three bouts of RE changed the ribosome content and mTORC1 activation, but not the degree of RE-induced global MPS activation.