Reduced ribosomal protein s6 phosphorylation after progressive resistance exercise in growing adolescent rats.
Reduced ribosomal protein s6 phosphorylation after progressive resistance exercise in growing adolescent rats.
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DOI：
10.1519/jsc.0b013e318231abc9
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发表时间：
2012-06
影响因子：
3.2
通讯作者：
Mantilla CB
中科院分区：
文献类型：
--
作者：
Hellyer NJ;Nokleby JJ;Thicke BM;Zhan WZ;Sieck GC;Mantilla CB
本研究的目的是调查中等强度的渐进阻力运动（PRE）在成长中的青春期大鼠和其对肌肉肥大（定义为增加纤维横截面积）的影响。我们假设，与年龄匹配的久坐对照组（SED）相比，在青春期动物中，中等强度的PRE会增加：1）纤维横截面积（CSA）; 2）肌球蛋白重链（MyHC）含量; 3）参与翻译调节的细胞信号分子的表达和磷酸化。在PRE组中，训练三周龄雄性大鼠攀爬垂直梯子作为PRE训练模式，使得到10周时，PRE组中的所有动物都进展到每次攀爬额外携带80%的体重。与我们的假设一致，我们观察到，10周的中度PRE在青春期动物足以增加CSA的肌纤维和增加的MyHC含量。与SED动物相比，PRE组中平均肌纤维CSA增加大于10%，总MyHC含量增加35%（p<0.05）。与此同时，我们研究了在成人动物模型中先前确定的肥大调节因子的关键信号分子的表达和磷酸化的持续变化。与我们的假设相反，翻译调节因子mTOR和Akt的表达和磷酸化在PRE组中没有增加。此外，我们观察到磷酸化与非磷酸化核糖体蛋白S6（rpS 6）的比率在PRE动物中降低了6倍以上（p<0.05），而总rpS 6蛋白水平在PRE和久坐动物之间没有变化（p>0.05）。我们的结论是，中等强度的PRE是足以诱导肌肉肥大的青春期动物，而与肌肉肥大相关的信号转导机制可能会有所不同的成长中的青少年和成年人。
The purpose of the present study was to investigate moderate intensity progressive resistance exercise (PRE) in growing adolescent rats and its effect on muscle hypertrophy (defined as an increase in fiber cross-sectional area). We hypothesized that in adolescent animals moderate intensity PRE would increase: 1) fiber cross-sectional area (CSA); 2) myosin heavy chain (MyHC) content; and 3) expression and phosphorylation of cell signaling molecules involved in translational regulation, compared to age-matched sedentary controls (SED). In the PRE group, three-week old male rats were trained to climb a vertical ladder as a mode of PRE training such that by 10 weeks, all animals in the PRE group had progressed to carry an additional 80% of body weight per climb. In agreement with our hypotheses, we observed that 10 weeks of moderate PRE in adolescent animals was sufficient to increase CSA of muscle fibers and increase MyHC content. Average muscle fiber CSA increased by greater than 10% and total MyHC content increased by 35% (p<0.05) in the PRE group compared to SED animals. Concurrently, we investigated sustained changes in the expression and phosphorylation of key signaling molecules that are previously identified regulators of hypertrophy in adult animal models. Contrary to our hypotheses, expression and phosphorylation of the translational regulators mTOR and Akt were not increased in the PRE group. In addition, we observed that the ratio of phosphorylated-to-unphosphorylated ribosomal protein S6 (rpS6) was reduced over six-fold in PRE animals (p<0.05) and total rpS6 protein levels were unchanged between PRE and sedentary animals (p>0.05). We conclude that moderate intensity PRE is sufficient to induce muscle hypertrophy in adolescent animals while the signaling mechanisms associated with muscle hypertrophy may differ between growing adolescents and adults.