有氧训练联合补充亮氨酸对增龄小鼠骨骼肌蛋白质代谢的影响

摘要

Objective: To investigate the effect and mechanism of aerobic training in combination with leucine supplementation on muscle protein synthesis and protein degradation. Methods: Thirteen-month-old male CD-1? mice were randomly divided into sedentary control, aerobic training control, dietary leucine supplementation, and aerobic training in combination with leucine supplementation. Leucine was supplemented with 5% dosage. Mice in training group received 45 min swimming training with 3% body weight workload for 8 weeks (6 days/wk). Protein content were measured with Bradford kit. The expression and phosphorylation rate of protein were determined by using Western blotting. The concentration of serum inflammatory cytokines were measured with ELISA kit. The profile of free amino acids in muscle was detected with an amino acids analyzer. The activity of chymotrypsin-like enzyme was determined by using fluorescence method. Results: Both aerobic training and 5% leucine supplementation did not change the body weight, and food intake. Myofibrillar, sarcoplasmic and total protein content, the phosphorylation rate of mTORSer2448, 4E-BP1Thr37/46, p70S6KThr389 and the expression of MHCⅡ were significantly elevated, while the expression of Ubiquitin, Atrogin-1 and MuRF-1, and the concentration of pro-inflammatory cytokines in serum were decreased obviously. Besides, leucine supplementation induced a significant decrease of chymotrypsin-like enzyme activity, and increases of leucine, isoleucine and valine in skeletal muscle. The combination of aerobic training and leucine supplementation leaded more significant effects when in comparison with training or leucine supplementation alone. Conclusion: Moderate aerobic training in combination with 5% leucine supplementation promotes post-prandial protein synthesis in skeletal muscle of pre-senescent mice, and inhibits protein degradation, which may be correlated with elevated functional expression of mTOR-p70S6K/4E-BP1 pathway and decreased activity of ubiquitin-proteasome system.%目的:探讨有氧训练联合补充亮氨酸对增龄小鼠骨骼肌蛋白质合成与降解代谢的影响及机制.方法:将32只13月龄雄性CD-1?小鼠随机纳入安静对照组(Sed组)、运动对照组(Tra组)、补充亮氨酸组(Leus组)和补充亮氨酸+训练组(Leu T组),其中,亮氨酸以5%剂量进行补充,训练方案为以自体重3%的负荷进行45 min游泳,每周训练6 天,共计8 周.采用Bradford法进行蛋白定量,Western blotting法检测蛋白表达与磷酸化率,酶联免疫吸附测定血清炎性细胞因子含量,氨基酸分析仪检测骨骼肌氨基酸谱,荧光法检测类糜蛋白酶活性.结果:有氧训练与补充5%剂量亮氨酸未显著影响小鼠体重与采食量.但蛋白总量、肌原纤维与肌浆蛋白浓度、mTORSer2448、4E-BP1Thr37/46与p70S6KThr389磷酸化率及MHC Ⅱ蛋白表达显著升高, Ubiquitin、Atrogin-1与MuRF-1蛋白表达以及血清促炎因子则均显著下降.此外,单纯补充亮氨酸导致了类糜蛋白酶活性的显著下降,以及骨骼肌亮氨酸、异亮氨酸和缬氨酸含量的增加,有氧训练未产生类似影响.较单纯有氧训练与补充亮氨酸而言,联合干预可产生更为显著的效果.结论:中等强度有氧训练联合补充5%亮氨酸可促进增龄小鼠在餐后状态的骨骼肌蛋白质合成,抑制降解,具有防治Sarcopenia的重要潜力,其机制可能与其对mTOR-p70S6K/4E-BP1途径功能表达的上调以及对泛素-蛋白酶体系统活性的下调有关.