Skeletal muscle is an endocrine organ secreting exercise-induced factors (exerkines), which play a pivotal role in inter-organ crosstalk. Using mass spectrometry (MS)-based proteomics, we characterized the secretome and identified thymosin beta-4 (TMSB4X) as the most upregulated secreted protein in the media of contracting C2C12 myotubes. TMSB4X was also acutely increased in plasma of exercising humans irrespective of the insulin resistance condition or exercise mode. Treatment of mice with TMSB4X did not ameliorate the metabolic disruptions associated with diet induced-obesity, nor did it enhance muscle regeneration in vivo. However, TMSB4X increased osteoblast proliferation and neurite outgrowth, consistent with its WADA-classification as a prohibited growth factor. Therefore, we report TMSB4X as a human exerkine with a potential role in cellular crosstalk.

中文翻译：

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发现胸腺素 Beta-4 作为人类运动因子和生长因子


骨骼肌是分泌运动诱发因子（运动因子）的内分泌器官，在器官间串扰中发挥着关键作用。使用基于质谱 (MS) 的蛋白质组学，我们对分泌组进行了表征，并确定胸腺素 beta-4 (TMSB4X) 是收缩 C2C12 肌管培养基中上调最多的分泌蛋白。无论胰岛素抵抗状况或运动模式如何，运动人群血浆中的 TMSB4X 也会急剧增加。用 TMSB4X 治疗小鼠并没有改善与饮食引起的肥胖相关的代谢紊乱，也没有增强体内肌肉再生。然而，TMSB4X 增加了成骨细胞增殖和神经突生长，这与 WADA 将其列为禁用生长因子的情况一致。因此，我们将 TMSB4X 报告为一种人类运动因子，在细胞串扰中具有潜在作用。