有氧运动对高脂膳食诱导的胰岛素抵抗小鼠骨骼肌细胞胰岛素受体底物1及其丝氨酸磷酸化活性的影响

摘要

目的:探讨有氧运动对高脂膳食诱导胰岛素抵抗(insulin resistance,IR)小鼠骨骼肌细胞胰岛素受体底物1(insulin receptor substrates-1,IRS1)及其丝氨酸磷酸化活性的影响,以及结节性硬化复合物蛋白2(tuberous sclerosis complex-2,TSC2)在此过程中的可能作用.方法:选取4周龄C57BL/6/b鼠,经10周高脂膳食,诱导小鼠产生IR.将40只IR小鼠随机分为安静对照组(HC)和有氧运动组(HE),每组20只.HC组继续高脂饮食,HE组在高脂饮食的同时进行5天/周、1小时/天、75%VO2max强度的有氧跑台运动;6周后,小鼠禁食16小时,进行空腹血清胰岛素(FINS)检测和口服葡萄糖耐量试验(oral glucose tolerance test,OGTT);随后迅速分离小鼠骨骼肌,液氮速冻后,-80℃保存备用.采用逆转录PCR、Western blot、免疫荧光组化染色等方法检测骨骼肌TSC2、IRS1、pIRS1-Ser307、pIRS1-Ser636/639的表达,并比较结果的组间差异.结果:与HC组小鼠相比,HE组小鼠FINS水平降低25.5%(P<0.05),葡萄糖耐受能力明显提高;HE组小鼠骨骼肌TSC2基因表达较HC组增加21.45%(P<0.05),HE组TSC2蛋白表达比HC组增加24.42%(P<0.05);组间IRS1基因和蛋白表达均无显著性差异(P>0.05):但HE组pIRS1-Ser307和pIRS1-Ser636/639蛋白表达与HC组相比分别降低15.36%和19.80%(P<0.05).结论:有氧运动明显降低了小鼠空腹血清胰岛素水平,提高了其葡萄糖耐受能力.有氧运动可能通过增强骨骼肌细胞TSC2表达,抑制IRS1-Ser307和IRS1-Ser636/639的磷酸化活性,从而增强胰岛素信号通路敏感性;6周、75%VO2max的有氧运动对IRS1基因和蛋白表达无显著影响.%Objective To study the effects of aerobic exercise on the insulin receptor substrates-1 (IRS 1 ) and its serine phosphorylation activity in mice with high fat diet induced-insulin resistance (IR) and to explore the possible role of tuberous sclerosis complex-2 (TSC2) during this process.Methods 4-week old C57BL/6 mice were fed with high fat diet for 10 weeks to induce IR. The IR mice were randomly divided into control group (HC, n=20) and exercise group (HE, n=20) . All mice were continually fed with high fat diet for another 6 weeks. At the same time, the HE mice were acclimatized to the motorized treadmill running, 60 min per day at the intensity of 75％VO2max, five days per week, for a total of 6 weeks. The mice were fasted for 16 hours before the assay of fasting serum insulin level (FINS) and oral glucose tolerance test (OGTT) . A square piece of skeletal muscle from each mouse was surgically removed and rapidly frozen. The expression of TSC2, IRS 1, pIRS 1-Ser307 and pIRS1-Ser636/639 in skeletal muscle were determined by RT-PCR, Western blot, and immunofiuorescence. Results As compared with HC, the FINS was 25.33％ lower (P ＜ 0.05) and the glucose tolerance was improved in HE group. Comparing with HC group, the expression of TSC2 mRNA and protein in HE group were respectively increased by 21.45％ and 24.42％ (P ＜ 0.05 ) . There were not significant differences between two groups in the expression of IRS 1 mRNA and protein (P ＞ 0.05 ) . And comparing with HC group, the expression of pIRS 1-Ser307 and pIRS 1-Ser636/639 proteins significantly decreased by 15.36％ (P ＜ 0.05 ) and 19.80％ (P ＜ 0.05 ) respectively in HE group. Conclusions Aerobic exercise can decline the FINS and improve the glucose tolerance, probably through ameliorating IR by enhancing the expression of TSC2 and attenuating the activity of IRS 1-Ser307 and IRS 1-Ser636/639 phosphorylation. However, the IRS 1 mRNA and protein is not responsive to 6-week exercise at the intensity of 75％ VO2 max.