PI3K阻断剂对大鼠运动骨骼肌Akt/mTOR信号的影响

Effects of Blocking PI3K and Exercise on Akt/mTOR Pathway of Skeletal Muscle in Rats

目的:通过阻断PI3K信号,以深入探讨Akt/mTOR通路在抗阻运动中骨骼肌蛋白合成的作用。方法:8周龄雄性SD大鼠在适应性训练后分为4组:安静组(S)、阻断剂组(SL)、运动组(E)、运动+阻断剂组(EL),每组6只。运动方式为跑台运动(坡度为10%,跑速20 m/min,60 min),每天1次,共7 d。腹腔注射外源性LY294002(剂量为5.5 mg/kg)。用Western Blotting法检测腓肠肌MHC、Akt和mTOR蛋白表达、Akt(Ser473)和mTOR(Ser2448)磷酸化表达。结果:在一周后,LY294002明显抑制MHC,运动有促进的趋势,并减弱LY294002对MHC的抑制效应。LY294002显著抑制Akt和mTOR蛋白表达、Akt(Ser473)和mTOR(Ser2448)的磷酸化表达,而运动明显增强mTOR、Akt(Ser473)和mTOR(Ser2448)表达。结论:1)阻断PI3K信号可使运动骨骼肌Akt/mTOR通路受到明显抑制,而同时骨骼肌MHC明显降低,明显抑制肌肉蛋白合成。2)运动明显促进该通路的表达,并减弱PI3K阻断剂对该通路的抑制效应。3)PI3K阻断剂对通路是整体性的抑制,而运动在对该通路的影响有所侧重。

Objective： The purpose of this study was to examine the effect of Akt/mTOR pathway on muscle protein synthesis in resistance exercise model through blocking PI3K.Methods： Adult male Sprague-Dawley rats（8 weeks old） were randomly divided into 4 groups after adaptive training： sedentary（S）,LY294002 group（SL）,exercise group（E） and LY294002 plus exercise group（EL）.The following treadmill training was applied： 20m/min at 10% slope,60 min;once per day,7 days. Either 8% ethanol or LY294002（5.5mg/kg,diluted with 8% ethanol） was using intraperitoneal injection.Total protein content of gastrocnemius muscle was determined by Bradford.The MHC,total-Akt and mTOR,phosphorylation of Akt（Ser473） and mammalian target of rapamycin（mTOR）（Ser2448） of gastrocnemius muscle were determined by Western blotting.Results： After 1 week,MHC was significantly inhibited by LY294002.Exercise had a tendency to increase MHC,and it attenuated the inhibitory effect of LY294002 on MHC.total-Akt（P0.01） and mTOR（P0.01）,Akt（Ser473）（P0.01） and mTOR（Ser2448）（P0.01） phosphorylation were significantly inhibited by LY294002,but total-mTOR（P0.05）and Akt（Ser473）（P0.01） and mTOR（Ser2448）（P0.05） phosphorylation were significantly elevated by exercise.Conclusions： These results suggest that： 1） The MHC and Akt/mTOR pathway of skeletal muscle were inhibited significantly by blocking on PI3K.Blocking PI3K could effectively inhibit the muscle protein synthesis.2） The Akt/mTOR pathway of skeletal muscle was significantly elevated by exercise.Exercise attenuated the negative effect of blocking PI3K in vivo.3） The negative effect of blocking PI3K on Akt/mTOR pathway was global,while the effect of exercise was particular emphasis on partial elements.