mTOR复合物在有氧运动改善小鼠骨骼肌糖代谢过程中的作用

The Role of mTOR Complex in Aerobic Exercise Improving Skeletal Muscle Glucose Metabolism of Mice

目的:探讨运动及饮食对小鼠骨骼肌mTOR复合物及胰岛素信号通路蛋白活性的影响,分析高脂状态下运动在改善高脂饮食诱导的小鼠胰岛素抵抗过程中的作用机制,以便为运动改善机体代谢稳态提供新的理论依据。方法:随机将50只C57BL/6小鼠分为正常饮食组(C组,n=10)及高脂饮食组(n=40),分别给予正常及高脂饲料喂养6周,随后再根据口服糖耐量(OGTT)和空腹胰岛素检测结果取高脂饮食组中25只成模小鼠随机分为高脂安静组(H组,n=10)和高脂运动组(HE组,n=15)。H组和HE组继续喂以高脂饲料,同时HE组小鼠施以8周、强度为75%VO2max有氧跑台运动干预(12 m/min、60 min/天、5次/周)。8周后麻醉处死、取材,Western Blot检测小鼠比目鱼肌胰岛素信号通路相关蛋白表达,免疫共沉淀法分别检测比目鱼肌和腓肠肌Raptor-mTOR及Rictor-mTOR结合情况。结果:(1)在以氧化型肌纤维为主的比目鱼肌纤维,与C组相比,H组p Akt-T308(P<0.05),pIRS1-S307(P<0.001)位点的表达显著降低,而pS6K1-T389(P<0.05)显著增高,Raptor-mTOR结合量明显增加(P<0.05),而Rictor-mTOR结合量明显降低(P<0.05);与H组小鼠对比发现,HE组p Akt-S473(P<0.05)、pAkt-T308(P<0.05)、pAMPKα-T172(P<0.05)、pIRS1-S307(P<0.001)均显著增加,而p S6K1-T389表达、Raptor-mTOR结合量均显著降低(P<0.05),Rictor-mTOR结合量则显著增加(P<0.05)。(2)在小鼠腓肠肌纤维,与C组相比,H组Raptor-mTOR结合量显著增加(P<0.05),而Rictor-mTOR结合量虽有增加趋势,但无统计学显著意义(P>0.05);与H组对比,HE组Raptor-mTOR显著降低(P<0.05),Rictor-mTOR虽有降低趋势,但无显著意义(P>0.05)。结论:8周有氧跑台运动干预可有效逆转C57BL/6小鼠由高脂饮食诱导的代谢稳态失衡,其机制可能是通过抑制比目鱼肌纤维Akt/mTORC1信号,激活Akt/mTORC2信号通路实现的。

Objective To explore the effect of exercise and diet on the activity of mammalian target of rapa-mycin(mTOR) complex and proteins of the insulin signaling pathway in skeletal muscles of mice,and to ana-lyze how exercise improves the insulin resistance in high-fat mice induced by a high-fat diet,so as to providea new theoretical basis for improving the metabolic homeostasis in mice by exercises.Method Fifty C57BL/6mice were randomly divided into a control group(group C,n=10) and a high-fat diet group(n=40).After feed-ing the normal diet or high-fat diet for 6 weeks according to their group names implied,25 mice from thehigh-fat diet group were selected based on their oral glucose tolerance test and fasting insulin results,and thenrandomly divided into a sedentary group(groupH,n=10) and an exercise group(group HE,n=15).The HEgroup performed 8-week aerobic running,with the intensity of 75% VO2max(12 m/min),60 minutes per dayand 5 times per week.Both groups were weighed and recorded weekly.Western blotting was used to detect theexpression of insulin-related proteins in the soleus.Co-immunoprecipitation was employed to detect the bindingof Raptor-mTOR and Rictor-mTOR in the soleus muscle and gastrocnemius muscle respectively.Results In thesoleus muscle mainly composed of oxidized muscle fibers,compared with group C,the expression of pAkt-T308(P<0.05) and pIRS1-S307(P<0.001) as well as the Rictor-mTOR binding of group H decreased significantly,while the expression of pS6K1-T389(P<0.05) and the Raptor-mTOR binding increased significantly.Comparedwith groupH,a significant increase was found in the expression of pAkt-S473(P<0.05),pAkt-T308(P<0.05),pAMPKα-T172(P<0.05) and p IRS1-S307(P<0.001),as well as the Rictor-mTOR binding(P<0.05) of groupHE,while a significant decrease was observed in the p S6K1-T389 expression(P<0.05) and Raptor-mTOR bind-ing(P<0.05).In the gastrocnemius of mice,compared with group C,the Raptor-mTOR binding of groupH in-creased significantly(P<0.05),while the Rictor-mTOR binding increased,but not significantly(P>0.05).Com-pared with groupH,the Raptor-mTOR binding decreased significantly in groupHE,while the Rictor-mTORbinding decreased,but not significantly(P>0.05).Conclusion Eight weeks of aerobic exercises can effectively re-verse the metabolic disorder caused by a high-fat diet,which may be achieved by inhibiting Akt/mTORC1 andactivating Akt/mTORC2 signaling molecules in the oxidized myofibers of mice.