Laboratory of Muscle & Translational Therapeutics, Department of Exercise Science, Division of Applied Physiology, University of South Carolina, Columbia, SC 29208, USA.
Am J Sports Med. 2011 Oct;39(10):2233-41. doi: 10.1177/0363546511414857. Epub 2011 Jul 22.
Animal models of skeletal muscle damage and repair demonstrate that therapeutic ultrasound (TUS) enhances muscle force recovery after damage, increases satellite cell proliferation, and decreases insulin-like growth factor (IGF)-1 splice variant (mechano growth factor) gene expression. However, these effects have not been verified in humans.
This study was undertaken to examine the 3 known splice variants of the IGF-1 gene in human skeletal muscle after damage and TUS treatment.
Controlled laboratory study.
Sixteen healthy men (18-29 years of age), physically active, were randomized to either a control (CON) or experimental group (EXP). The EXP group underwent 200 lengthening contractions (muscle damage) of the quadriceps of both legs, 48 hours before TUS. Both groups received TUS, delivered for 10 minutes on a standardized area of the vastus lateralis of only 1 leg (1.0 MHz, 1.5 W/cm(2)). Bilateral muscle biopsy samples were taken from all participants, 6 hours after TUS. Total RNA was extracted, and quantitative real-time polymerase chain reaction conducted for each IGF-1 splice variant.
Muscle damage was confirmed by a decrease in the isometric peak torque and increase in creatine kinase activity levels 48 hours after damage (P < .01). After muscle damage, gene expression of total IGF-1 and 2 IGF-1 splice variants increased. Therapeutic ultrasound induced significant increase in IGF-1Eb gene expression in undamaged muscle (1.4 ± 0.2-fold, P < 0.01). In damaged skeletal muscle, no significant change in gene expression attributable to TUS was determined.
Insulin-like growth factor-1 splice variants are differentially regulated in human skeletal muscle in response to exercise-induced muscle damage and TUS treatment. A single treatment of TUS in damaged muscle induces no change in the gene expression of the 3 IGF-1 splice variants in humans. In contrast, in undamaged skeletal muscle, TUS significantly increased IGF-1Eb splice variant gene expression.
These findings suggest that TUS may have additional therapeutic uses beyond its current common practice but may not be effective for muscle injury treatment in a young, healthy population.
骨骼肌肉损伤和修复的动物模型表明，治疗性超声（TUS）可增强损伤后肌肉力量的恢复，增加卫星细胞的增殖，并降低胰岛素样生长因子（IGF）-1 剪接变异体（机械生长因子）的基因表达。然而，这些影响尚未在人类中得到验证。
本研究旨在研究 TUS 治疗后人类骨骼肌中 IGF-1 基因的 3 种已知剪接变体。
对照实验室研究。
16 名健康男性（18-29 岁），身体活跃，随机分为对照组（CON）或实验组（EXP）。EXP 组先在双侧股四头肌进行 200 次牵伸收缩（肌肉损伤），48 小时前进行 TUS。两组均接受 10 分钟的 TUS，仅在 1 条腿的股外侧肌标准区域（1.0 MHz，1.5 W/cm²）进行。在 TUS 后 6 小时，所有参与者均从双侧肌肉活检样本中提取总 RNA，并进行定量实时聚合酶链反应以检测每个 IGF-1 剪接变体。
肌肉损伤 48 小时后通过等长峰值扭矩的降低和肌酸激酶活性水平的升高得到证实（P <.01）。肌肉损伤后，总 IGF-1 和 2 种 IGF-1 剪接变体的基因表达增加。TUS 可显著增加未损伤肌肉中 IGF-1Eb 基因的表达（1.4±0.2 倍，P <.01）。在损伤的骨骼肌中，未发现 TUS 引起的基因表达有明显变化。
IGF-1 剪接变体在人类骨骼肌中对运动引起的肌肉损伤和 TUS 治疗的反应不同。TUS 单次治疗在损伤肌肉中不会引起 3 种 IGF-1 剪接变体的基因表达发生变化。相反，在未损伤的骨骼肌中，TUS 可显著增加 IGF-1Eb 剪接变体基因的表达。
这些发现表明，TUS 除了目前的常规应用之外，可能还有其他治疗用途，但对年轻健康人群的肌肉损伤治疗可能无效。
