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目的:采用注射外源性IGF-I和一周跑台运动,观察对大鼠骨骼肌mTOR信号通路的影响,深入探讨IGF-I对运动骨骼肌适应性肥大的机理。方法:8周龄雄性SD大鼠在适应性训练后分为四组:安静组(S)、安静IGF-I组(SI)、运动组(E)、运动+IGF-I组(EI)。运动方式为跑台运动(20m/min,10%,60min/d),每天一次,共7天。外源性IGF-I为小腿后侧肌肉隆起处的皮下注射。用Western Blotting法检测腓肠肌MHC、PI3K、AKt、mTOR、p70S6K蛋白和Akt(Ser473)、mTOR(Ser2448)和p70S6K(Thr389)的磷酸化表达。结果:在一周后,外源性IGF-I显著促进骨骼肌MHC的表达,骨骼肌PI3K、Akt、mTOR蛋白和Akt(Ser473)、mTOR(Ser2448)和p70S6K(Thr389)的磷酸化表达显著增强。运动显著促进mTOR蛋白和Akt(Ser473)、mTOR(Ser2448)和p70S6K(Thr389)磷酸化的表达。对运动的反应,上述信号的磷酸化表达高于蛋白表达。结论:1)一周外源性IGF-I注射明显促进运动骨骼肌mTOR通路的活性;而1周跑台运动与IGF-I具有协同增强效应。2)在运动和注射外源性IGF-I的刺激下,mTOR通路各信号分子的磷酸化表达比蛋白表达更为敏感。建议今后对信号的研究以检测信号分子的磷酸化表达为主。
OBJECTIVE: To observe the effect of exogenous IGF-I and treadmill exercise on the mTOR signal transduction pathway in rat skeletal muscle in order to investigate the mechanism of adaptive hypertrophy induced by IGF-I on skeletal muscle. Methods: Eight-week-old male Sprague-Dawley rats were randomly divided into four groups: sedentary group (S), quiescent IGF-I group (SI), exercise group (E) and exercise + IGF-I group (EI). Exercise for treadmill exercise (20m / min, 10%, 60min / d), once daily, a total of 7 days. Exogenous IGF-I is injected subcutaneously at the muscular uplift of the calf. The phosphorylation of gastrocnemius MHC, PI3K, AKt, mTOR, p70S6K and Akt (Ser473), mTOR (Ser2448) and p70S6K (Thr389) were detected by Western Blotting. Results: After a week, exogenous IGF-I significantly enhanced the expression of MHC in skeletal muscle. The phosphorylation of PI3K, Akt, mTOR protein and Akt (Ser473), mTOR (Ser2448) and p70S6K (Thr389) were significantly increased. Exercise significantly promoted phosphorylation of both mTOR protein and Akt (Ser473), mTOR (Ser2448) and p70S6K (Thr389). In response to exercise, phosphorylation of these signals is higher than protein expression. Conclusion: 1) Weekly exogenous IGF-I injection significantly promoted the activity of mTOR pathway in exercise-induced skeletal muscle, while 1-week treadmill exercise had synergistic enhancement effect with IGF-I. 2) Phosphorylation of various signaling molecules in the mTOR pathway is more sensitive than protein expression, stimulated by exercise and exogenous IGF-I injection. It is suggested that in the future, the research of signal should be based on the detection of phosphorylation of signal molecules.