The application of exercise-like electrical pulse simulation (EL-EPS) has become a widely used exercise mimetic in vitro. EL-EPS produces similar physiological responses as in vivo exercise, while less is known about the detailed metabolic effects. Routinely the C2C12 myotubes are cultured in high glucose medium (4.5 g/l), which may alter EL-EPS responses. In this study, we evaluate the metabolic effects of EL-EPS under the high and low glucose (1.0 g/l) conditions to understand how substrate availability affects the myotube response to EL-EPS.The C2C12 myotube, media and cell-free media metabolites were analyzed using untargeted nuclear magnetic resonance (NMR)-based metabolomics. Further, translational and metabolic changes and possible exerkine effects were analyzed. EL-EPS enhanced substrate utilization as well as production and secretion of lactate, acetate, 3-hydroxybutyrate and branched chain fatty acids (BCFAs). The increase in BCFAs correlated with branched chain amino acids (BCAAs) and BCFAs were strongly decreased when myotubes were cultured without BCAAs suggesting the action of acyl-CoA thioesterases on BCAA catabolites. Notably, not all EL-EPS responses were augmented by high glucose because EL-EPS increased phosphorylated c-Jun N-terminal kinase and interleukin-6 secretion independent of glucose availability. Administration of acetate and EL-EPS conditioned media on HepG2 hepatocytes had no adverse effects on lipolysis or triacylglycerol content.Our results demonstrate that unlike in cell-free media, the C2C12 myotube and media metabolites were affected by EL-EPS, particularly under high glucose condition suggesting that media composition should be considered in future EL-EPS studies. Further, acetate and BCFAs were identified as putative exerkines warranting more research.

中文翻译：

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更高的葡萄糖可用性增强了 C2C12 肌管对类似运动的电脉冲刺激的代谢反应

运动样电脉冲模拟（EL-EPS）的应用已成为一种广泛使用的体外运动模拟物。EL-EPS 产生与体内运动相似的生理反应，而对详细的代谢影响知之甚少。C2C12 肌管通常在高葡萄糖培养基 (4.5 g/l) 中培养，这可能会改变 EL-EPS 反应。在这项研究中，我们评估了 EL-EPS 在高糖和低糖 (1.0 g/l) 条件下的代谢作用，以了解底物可用性如何影响肌管对 EL-EPS 的反应。C2C12 肌管、培养基和无细胞培养基使用基于非靶向核磁共振 (NMR) 的代谢组学分析代谢物。此外，还分析了转化和代谢变化以及可能的运动效应。EL-EPS 增强了底物利用以及乳酸、乙酸、3-羟基丁酸和支链脂肪酸 (BCFA) 的产生和分泌。与支链氨基酸 (BCAAs) 相关的 BCFAs 的增加和 BCFAs 的增加在没有 BCAAs 的情况下培养肌管时显着降低，这表明酰基辅酶 A 硫酯酶对 BCAA 分解代谢物的作用。值得注意的是，并非所有 EL-EPS 反应都因高葡萄糖而增强，因为 EL-EPS 增加了磷酸化 c-Jun N-末端激酶和白细胞介素 6 的分泌，而与葡萄糖可用性无关。在 HepG2 肝细胞上施用醋酸盐和 EL-EPS 条件培养基对脂肪分解或三酰基甘油含量没有不利影响。我们的结果表明，与无细胞培养基不同，C2C12 肌管和培养基代谢物受到 EL-EPS 的影响，特别是在高葡萄糖条件下，表明在未来的 EL-EPS 研究中应考虑培养基成分。此外，醋酸盐和 BCFA 被确定为推定的运动因子，需要进行更多研究。