Institute of Experimental Genetics, Helmholtz Zentrum Muenchen, German Research Center for Environmental Health, Neuherberg, Germany;
Am J Physiol Cell Physiol. 2013 Oct 15;305(8):C877-86. doi: 10.1152/ajpcell.00043.2013. Epub 2013 Aug 7.
Muscle contraction during exercise is a major stimulus for the release of peptides and proteins (myokines) that are supposed to take part in the beneficial adaptation to exercise. We hypothesize that application of an in vitro exercise stimulus as electric pulse stimulation (EPS) to human myotubes enables the investigation of the molecular response to exercise in a clearly defined model. We applied EPS for 24 h to primary human myotubes and studied the whole genome-wide transcriptional response as well as the release of candidate myokines. We observed 183 differentially regulated transcripts with fold changes >1.3. The transcriptional response resembles several properties of the in vivo situation in the skeletal muscle after endurance exercise, namely significant enrichment of pathways associated with interleukin and chemokine signaling, lipid metabolism, and antioxidant defense. Multiplex immunoassays verified the translation of the transcriptional response of several cytokines into high-secretion levels (IL-6, IL-8, CXCL1, LIF, CSF3, IL-1B, and TNF) and the increased secretion of further myokines such as angiopoietin-like 4. Notably, EPS did not induce the release of creatine kinase. Inhibitor studies and immunoblotting revealed the participation of ERK1/2-, JNK-, and NF-κB-dependent pathways in the upregulation of myokines. To conclude, our data highlight the importance of skeletal muscle cells as endocrine cells. This in vitro exercise model is not only suitable to identify exercise-regulated myokines, but it might be applied to primary human myotubes obtained from different muscle biopsy donors to study the molecular mechanisms of the individual response to exercise.
运动过程中的肌肉收缩是释放肽和蛋白质（肌因子）的主要刺激因素，这些物质被认为参与了运动的有益适应。我们假设，应用体外运动刺激，如电脉冲刺激（EPS），对人类肌管进行刺激，能够在一个明确界定的模型中研究运动对分子的反应。我们对原代人肌管进行了 24 小时的 EPS 处理，研究了全基因组转录反应以及候选肌因子的释放。我们观察到 183 个差异调节转录本，其倍数变化>1.3。转录反应类似于耐力运动后骨骼肌中体内情况的几个特性，即与白细胞介素和趋化因子信号、脂质代谢和抗氧化防御相关的途径明显富集。多重免疫测定法验证了几种细胞因子的转录反应转化为高分泌水平（IL-6、IL-8、CXCL1、LIF、CSF3、IL-1B 和 TNF），以及进一步的肌因子如血管生成素样 4 的分泌增加。值得注意的是，EPS 并未诱导肌酸激酶的释放。抑制剂研究和免疫印迹揭示了 ERK1/2、JNK 和 NF-κB 依赖性途径在肌因子上调中的参与。总之，我们的数据强调了骨骼肌细胞作为内分泌细胞的重要性。这种体外运动模型不仅适合于鉴定运动调节的肌因子，而且可以应用于从不同肌肉活检供体获得的原代人肌管，以研究个体对运动反应的分子机制。
