BNIP3介导骨骼肌线粒体自噬：不同强度运动的影响

文题释义：BNIP3：隶属于Bcl-2蛋白超家族，是一种线粒体促凋亡蛋白，可与腺病毒转录基因E1B编码的蛋白或Bcl-2蛋白结合。可起到促进细胞凋亡、引起线粒体去极化和自噬，在机体中发挥重要作用。线粒体自噬：线粒体是细胞的能量工厂，其功能还涉及细胞代谢、信号传导、分化、生长、凋亡和死亡等重要过程。线粒体自噬(mitophagy)是细胞清除损伤或衰老的线粒体，并循环利用其组成元素的过程；与衰老、神经退行性疾病和癌症等诸多生理病理过程密切相关。背景：不同强度运动对机体可产生不同的影响，运动后骨骼肌的变化也不明确，而运动中机体的生理变化机制更是目前研究的热点。目的：探讨不同强度运动对大鼠骨骼肌质量的影响以及BNIP3介导的骨骼肌线粒体自噬在维持骨骼肌质量中的作用。方法：实验方案经北京体育大学动物实验伦理委员会批准。8周龄雄性SD大鼠24只，随机分为对照组、中等强度运动组(5°，15 m/min，1 h，60%VO_2max)和大强度运动组(5°，35 m/min，20 min，85%VO_2max)，每组8只，每周运动6次。4周运动后取大鼠比目鱼肌和腓肠肌，称量湿质量，免疫荧光检测肌纤维横截面积，Western Blot检测比目鱼肌和腓肠肌BNIP3、p62和LC3蛋白的表达。结果与结论：①腓肠肌湿质量大强度运动组和中等强度运动组显著低于对照组(P < 0.01)；②比目鱼肌肌纤维横截面积大强度运动组显著小于对照组(P < 0.01)；腓肠肌肌纤维横截面积中等强度运动组和大强度运动组均显著大于对照组(P < 0.01)；③中等强度运动诱导线粒体自噬增加，表现为BNIP3、LC3-Ⅱ/LC3-Ⅰ值相较对照组表达增加(P < 0.05)，而p62较对照组表达下降(P < 0.05)；大强度运动组LC3-Ⅱ/LC3-Ⅰ、p62的表达量相较4周中等强度运动分别为上升和下降(P < 0.05)，但其BNIP3的表达量却下降(P < 0.05)；④结果表明，4周中等强度运动可促进骨骼肌通过BNIP3途径的线粒体自噬清除损伤线粒体，维持骨骼肌功能。4周大强度运动自噬水平更高，但可能对骨骼肌产生不利影响。ORCID: 0000-0003-3836-3002(于亮)中国组织工程研究杂志出版内容重点：组织构建；骨细胞；软骨细胞；细胞培养；成纤维细胞；血管内皮细胞；骨质疏松；组织工程

Effects of different intensities of exercises on BNIP3-mediated mitophagy in skeletal muscle

BACKGROUND:Different intensities of exercises make different effects on human body,and the changes of skeletal muscle after exercise remain unclear.Physical change of human body during exercise is a hotspot.OBJECTIVE:To investigate the effect of different intensities of exercises on the mass of rat skeletal muscle,and the role of BNIP3-mediated mitophagy in maintaining skeletal muscle mass.METHODS:The study was approved by the Laboratory Animal Ethical Committee of Beijing Sport University.Twenty-four healthy male Sprague-Dawley rats aged 8 weeks were randomly divided into three groups:control,moderate-intensity exercise(5°,15 m/min,1 hour,60%VO2max) and high-intensity exercise(5°,35 m/min,20 minutes,85% VO2max) groups(n=8/group),6 times weekly.The rat soleus and gastrocnemius were removed to measure the wet weights.The cross-sectional area of muscle fiber was detected by immunofluorescence.The protein expression levels of BNIP3,p62 and LC3 in the soleus and gastrocnemius were detected by western blot assay.RESULTS AND CONCLUSION:(1) The wet weight of gastrocnemius in the exercise groups was significantly lower than that in the control group(P <0.01).(2) The cross-sectional area of gastrocnemius fiber in the exercise groups was significantly less than that in the control group(P <0.01),and the cross-sectional area of soleus fiber in the exercise groups was significantly more than that in the control group(P <0.01).(3) The moderate-intensity exercise induced increased mitophagy,and the expression level of BNIP3 and LC3-Ⅱ/LC3-Ⅰ were up-regulated(P<0.05),while p62 was down-regulated(P<0.05) compared with the control group.The expression level of LC3-II/LC3-I in the high-intensity exercise group was higher(P<0.05),but the expression level of p62 was lower than that in the moderate-intensity exercise group and the expression of BNIP3 was decreased(P<0.05).(4) To conclude,4-week moderate-intensity exercise can promote the removal of damaged mitochondria and maintain skeletal muscle function by increasing BNIP3-regulated mitophagy in skeletal muscle.In high-intensity exercise,the level of autophagy is higher,but will cause harmful effect on skeletal muscle.