Suetta Charlotte, Clemmensen Christoffer, Andersen Jesper L, Magnusson S Peter, Schjerling Peter, Kjaer Michael
Institute of Sports Medicine, Bispebjerg Hospital, University of Copenhagen, Denmark.
Growth Horm IGF Res. 2010 Apr;20(2):134-40. doi: 10.1016/j.ghir.2009.11.005. Epub 2009 Dec 23.
Hypertrophy of developing skeletal muscle involves stimulation by insulin-like growth factor-I (IGF-I), however, the role of IGF-I in adult muscle is less clarified. In the present study, the mRNA splice variants of IGF-I (IGF-IEa and MGF) and the changes in muscle fiber cross sectional area after 12 weeks of training were studied in elderly post-operative patients. About 28 subjects, 14 men and 14 women (age 69, range 60-86 years) were randomized to unilateral resistance training (RT: 3/week), electrical stimulation (ES: 1h/day) or functional exercises (FE: 1h/day). The non-operated-side served as a within subject control. Muscle biopsies were obtained from the vastus lateralis of both limbs at +2d post-operative (baseline), at 5 weeks and 12 weeks post-surgery to analyze for changes in type 1 and type 2 muscle fiber area. Changes in expression levels of IGF-I mRNA isoforms were determined using real-time RT-PCR, normalized to the ribosomal protein large protein 0 (RPLP0) mRNA and presented relative to the control-side. At baseline there was no difference between the three groups in muscle fiber area or resting levels of IGF-IEa and MGF. RT resulted in a significant increase in muscle fiber area of type 1 (+17%, p<0.05) and type 2 (+36%, p<0.05) parallel to an increase in the expression of IGF-IEa and MGF, in contrast to ES and FE. The present study demonstrates that resistance training initiated in the acute post-operative phase is highly effective in increasing mean fiber area and in addition induces marked increases in the expression of IGF-I splice variants, supporting the idea that IGF-I is involved in regulating muscle hypertrophy.
发育中的骨骼肌肥大涉及胰岛素样生长因子-I（IGF-I）的刺激作用，然而，IGF-I在成年肌肉中的作用尚不清楚。在本研究中，对老年术后患者进行了12周训练后，研究了IGF-I的mRNA剪接变体（IGF-IEa和MGF）以及肌纤维横截面积的变化。约28名受试者，14名男性和14名女性（年龄69岁，范围60 - 86岁）被随机分为单侧阻力训练组（RT：每周3次）、电刺激组（ES：每天1小时）或功能锻炼组（FE：每天1小时）。未手术侧作为受试者自身对照。在术后第2天（基线）、术后5周和12周从双侧股外侧肌获取肌肉活检样本，以分析1型和2型肌纤维面积的变化。使用实时RT-PCR测定IGF-I mRNA亚型表达水平的变化，以核糖体蛋白大蛋白0（RPLP0）mRNA进行标准化，并相对于对照侧进行呈现。在基线时，三组在肌纤维面积或IGF-IEa和MGF的静息水平方面没有差异。与ES和FE相反，RT导致1型肌纤维面积显著增加（+17%，p<0.05）和2型肌纤维面积显著增加（+36%，p<0.05），同时IGF-IEa和MGF的表达也增加。本研究表明，在术后急性期开始的阻力训练在增加平均纤维面积方面非常有效，此外还能显著诱导IGF-I剪接变体的表达增加，支持了IGF-I参与调节肌肉肥大的观点。
