骨骼肌线粒体对细胞能量需求的快速应答:mfn1/2与fis1基因在急性运动中的动态表达

目的:本研究探讨在细胞能量需求急剧变化的条件下,骨骼肌线粒体能量代谢与线粒体融合基因mfn1/2和分裂基因fis1表达的动态变化,并分析这两者之间的关系。方法:以SD大鼠一次递增负荷跑台运动为实验模型,测定骨骼肌线粒体ROS生成速率和态3、态4呼吸速率,ATP合成酶活性和膜电位水平,并观察运动中及其恢复期骨骼肌线粒体mfn1/2和fis1 mRNA表达变化。结果:(1)150分钟运动过程中mfn1 mRNA表达逐渐降低,其中E45、E90、E120和E150组分别较安静组下降了21、42、707、7%(均P<0.01),PE-3h、PE-6h、PE-12h和PE-24h组则分别较安静组增加至144、152、134和135%(P<0.01);mfn2 mRNA表达呈相似表现,在运动中至运动后6小时较安静时分别下降了36、73、96、64、57和59%(均P<0.01),PE-12h和PE-24h组则增加至148和154%(均P<0.01);对应以上时间点,fis1 mRNA表达在运动中各时间点较安静时显著增加,并在运动后3小时达到峰值,分别增加至264、213、252、406和450%(均P<0.01),随后逐渐下降,但仍高于安静值(P<0.01)。(2)在运动中及运动后各时间点,ROS生成速率均较安静组显著增高,其中E45、E90和E120组ROS生成速率持续增高,E150、PE-3h、PE-6h、PE-12h和PE-24h组较E120组明显下降;整个过程中线粒体能化态膜电位无显著变化。E45组ATP合成酶活性与安静组比较明显增加,但PE-3h组显著降低,其余各组无明显变化;除E150组线粒体态3呼吸速率较安静组显著降低外,其它各组无明显差异。结论:(1)急性运动中骨骼肌mfn 1/2 mRNA表达显著减少,fis1 mRNA表达明显增加;运动后骨骼肌mfn1/2 mRNA水平逐渐明显增加,fis1 mRNA转录逐渐减少。(2)线粒体能量代谢耦联效率能够对机体的能量需求作出快速应答反应,线粒体分裂与融合基因的动态表达是线粒体对细胞能量需求急剧增加的快速应答反应的一个组成部分。

Mitochondrial Response to Rapid Variations of Energy Demand in Skeletal Muscle:Dynamic Expression of mfn1/2 and fis1 Genes during a Bout of Acute Exercise

Objective The purpose of this study was to investigate the dynamic change in expression of mfn1/2 and fis1 genes and mitochondrial energy metabolism under the condition of rapid increase in cellular energy demand,and to analysis the relations of the genes expression to the energy metabolism.Methods Sprague-Dawley rats underwent an incremental treadmill running,and they were divided into 9 groups(8 rats in each group):resting group(R),exercise groups running for 45(E45),90(E90),120(E120),and 150min(E150),and post-exercise groups 3 hours after exercise(PE-3h),6 hours after exercise(PE-6h),12 hours after exercise(PE-12h) and 24 hours after exercise(PE-24h).They were sacrificed at rest or immediately after each time course.The soleus and gastrocnemius muscle were harvested for analysis of mfn1/2 and fis1 mRNA expressions,ROS generation rate,state 3 and state 4 rates,transmembrane potential,and ATP synthase activity in isolated mitochondria.Results(1) In the course of 150-minute exercise and post exercise,as compared with that in group R: muscular mfn1 mRNA expression gradually decreased 21%,42%,70% and 77% respectively in groups E45 to E150(P<0.01),and increased to 144%,152%,134% and 135% respectively in groups E45 to PE-6h(P<0.01);mfn2 mRNA expression decreased 36%,73%,96%,64%,57% and 59% respectively in groups E45 to PE-6h(P<0.01),and increased to 148% and 154% respectively in group PE-12h and group PE-24h(P<0.01);muscular fis1 mRNA expression gradually increased to 264%,213%,252%,406% and 450% respectively in groups E45 to PE-3h(P<0.01) with insignificantly further decline.(2) In the course of 150-minute exercise and post exercise,as compared with that in group R,mitochondrial ROS generation rates significantly increased;there was no remarkable change in mitochondrial inner transmembrane potential in groups E45 to PE-24h;ATP synthase activity significantly increased in group E45(P<0.05) and significantly reduced in group PE-3h(P<0.05);the state 3 rates significantly reduced in group E150(P<0.05) without remarkable change in the other group.Conclusion There is a rapid response of the coupling efficiency of mitochondrial energy metabolism to the cellular energy demand,reflecting the interaction between the mitochondrial respiratory function and the mitochondrial morphology.