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离心跑台运动促进大鼠腓肠肌适应性肥大

戴志强¹, 柯余^2,3, 赵艳^2,3, 阳颖^2,3, 吴慧雯^2,3, 尚画雨⁴, 夏志^2,3,*

¹南昌大学体育学院，南昌 330031；²温州大学体育与健康学院，温州 325035；³温州市生物健康材料与化学重点实验室，温州 325035；⁴成都体育学院运动医学与健康学院，成都 610041

摘要

本研究旨在探讨离心跑台运动对大鼠骨骼肌适应性肥大的影响及其机制。选取3月龄Sprague Dawley (SD)大鼠32只，据体重随机分为四组：2周安静对照组(2C)、2周下坡跑运动组(2E)、4周安静对照组(4C)和4周下坡跑运动组(4E)。运动组大鼠下坡跑方案为：坡度−16°，跑速16 m/min，训练时间90 min，每周训练5 d。末次训练24 h后让4组大鼠均进行一次力竭跑台运动，休息48 h后处死所有大鼠，取腓肠肌待测。用HE染色测量肌纤维横截面积与直径，用透射电镜观察肌纤维超微结构变化，用嘌呤霉素表面标记翻译法测定蛋白质合成率，用免疫荧光双标法检测溶酶体关联膜蛋白2 (lysosomalassociatedmembrane protein 2, Lamp2)-亮氨酰-tRNA合成酶(leucyl-tRNA synthetase, LARS)、Lamp2-哺乳动物雷帕霉素靶蛋白(mammalian target of rapamycin, mTOR)共定位情况，用免疫印迹法测定肌球蛋白重链(myosin heavy chain, MHC) IIb和LARS蛋白表达及mTOR、p70核糖体蛋白S6激酶(p70 ribosomal protein S6 kinase, p70S6K)和真核翻译起始因子4E结合蛋白1(eukaryotic translation initiation factor 4E binding protein 1, 4E-BP1)磷酸化水平。结果显示，与2C组大鼠相比，2E组大鼠腓肠肌湿重、腓肠肌湿重/体重比值、跑距、运动时间、运动前与运动后血乳酸水平、肌原纤维蛋白质含量、Lamp2-LARS和Lamp2-mTOR共定位水平和LARS蛋白表达显著提高；除了上述变化外，与4C组大鼠相比，4E组大鼠还表现出肌纤维横截面积、直径、蛋白质合成率、mTOR、p70S6K及4E-BP1磷酸化水平显著提高；与安静对照组相比，运动组大鼠腓肠肌表现出超微结构损伤，其中4E组更为明显。以上结果表明，离心跑台运动可能通过上调LARS表达促进mTOR转位至溶酶体膜而活化，并经mTOR-p70S6K-4E-BP1信号转导通路上调蛋白质合成速率，促进蛋白质沉积，从而诱发适应性骨骼肌肥大。尽管骨骼肌超微结构变化更为明显，但短期运动期限内相对较长的训练周期所产生的促腓肠肌蛋白质合成与适应性肥大效果更为显著。

关键词： 下坡跑; 骨骼肌; 蛋白质合成; 亮氨酰-tRNA合成酶; 哺乳动物雷帕霉素靶蛋白

Eccentric treadmill exercise promotes adaptive hypertrophy of gastrocnemius in rats

DAI Zhi-Qiang¹, KE Yu^2,3, ZHAO Yan^2,3, YANG Ying^2,3, WU Hui-Wen^2,3, SHANG Hua-Yu⁴, XIA Zhi^2,3,*

¹School of Physical Education, Nanchang University, Nanchang 330031, China；²College of Physical Education and Health, Wenzhou University, Wenzhou 325035, Chin；³Key Lab of Biohealth Materials and Chemistry of Wenzhou, Wenzhou 325035, China；⁴School of Sports Medicine and Health, Chengdu Sport University, Chengdu 610041, China

Abstract

The present study aimed to investigate the effects of eccentric treadmill exercise on adaptive hypertrophy of skeletal muscle in rats. Thirty-two 3-month-old Sprague Dawley (SD) rats were selected and randomly assigned to one of the four groups based on their body weights: 2-week quiet control group (2C), 2-week downhill running exercise group (2E), 4-week quiet control group (4C), and 4-week downhill running exercise group (4E). The downhill running protocol for rats in the exercise groups involved slope of −16°, running speed of 16 m/min, training duration of 90 min, and 5 training sessions per week. Twenty-four hours after the final session of training, all the four groups of rats underwent an exhaustion treadmill exercise. After resting for 48 h, all the rats were euthanized and their gastrocnemius muscles were harvested for analysis. HE staining was used to measure the cross-sectional area (CSA) and diameter of muscle fibers. Transmission electron microscope was used to observe the ultrastructural changes in muscle fibers. Purithromycin surface labeling translation method was used to measure protein synthesis rate. Immunofluorescence double labeling was used to detect the colocalization levels of lysosomal-associated membrane protein 2 (Lamp2)-leucyl-tRNA synthetase (LARS) and Lamp2-mammalian target of rapamycin (mTOR). Western blot was used to measure the protein expression levels of myosin heavy chain (MHC) IIb and LARS, as well as the phosphorylation levels of mTOR, p70 ribosomal protein S6 kinase (p70S6K), and eukaryotic translation initiation factor 4E binding protein 1 (4E-BP1). The results showed that, compared with the 2C group rats, the 2E group rats showed significant increases in wet weight of gastrocnemius muscle, wet weight/body weight ratio, running distance, running time, pre- and post-exercise blood lactate levels, myofibrillar protein content, colocalization levels of Lamp2- LARS and Lamp2-mTOR, and LARS protein expression. Besides these above changes, compared with the 4C group, the 4E group further exhibited significantly increased fiber CSA, fiber diameter, protein synthesis rate, and phosphorylation levels of mTOR, p70S6K, and 4E-BP1. Compared with the quiet control groups, the exercise groups exhibited ultrastructural damage of rat gastrocnemius muscle, which was more pronounced in the 4E group. These findings suggest that eccentric treadmill exercise may promote mTOR translocation to lysosomal membrane, activating mTOR signaling via up-regulating LARS expression. This, in turn, increases protein synthesis rate through the mTOR-p70S6K-4E-BP1 signaling pathway, promoting protein deposition and inducing adaptive skeletal muscle hypertrophy. Although the ultrastructural changes of skeletal muscle are more pronounced, the relatively long training cycles during short-term exercise periods have a more significant effect on promoting gastrocnemius muscle protein synthesis and adaptive hypertrophy.

Key words: downhill running; skeletal muscle; protein synthesis; leucyl-tRNA synthetase; mammalian target of Rapamycin

收稿日期：　　录用日期：

通讯作者：夏志　　E-mail:

DOI: 10.13294/j.aps.2025.0051

引用本文：

戴志强, 柯余, 赵艳, 阳颖, 吴慧雯, 尚画雨, 夏志. 离心跑台运动促进大鼠腓肠肌适应性肥大[J]. 生理学报 2025; 77 (3): 449-464.

DAI Zhi-Qiang, KE Yu, ZHAO Yan, YANG Ying, WU Hui-Wen, SHANG Hua-Yu, XIA Zhi. Eccentric treadmill exercise promotes adaptive hypertrophy of gastrocnemius in rats. Acta Physiol Sin 2025; 77 (3): 449-464 (in Chinese with English abstract).