AIMS Macrophages, as an important member of immune system, engulf and digest pathogens in innate immunity and help initiate adaptive immunity. However, macrophages also involve in occurrence and development of many diseases, such as obesity and type 2 diabetes. Here, we aimed to reveal how activated macrophages cause insulin resistance in skeletal muscle in vitro through simulating body environment. MAIN METHODS We established RAW264.7 macrophages and C2C12 myotubes co-incubation model in vitro using Transwell filter to simulate body environment and investigated effects of RAW264.7 cells on insulin-regulated glucose metabolism in C2C12 myotubes. Immunofluorescence, Immunoblot and glucose uptake tests were used to assess metabolic changes in C2C12 myotubes. ELISA test detected secretions of tumor necrosis factor α (TNF-α) and interleukin-6 (IL-6) from RAW264.7 cells. In addition, RNA interference and inhibitor treatment were used. KEY FINDINGS Activated RAW264.7 cells attenuated insulin response in C2C12 myotubes. Activated RAW264.7 cells secreted a lot of TNF-α and IL-6. We found that TNFα, but not IL-6, caused insulin resistance of skeletal muscle in a dose-dependent manner. The results further indicated that activation of TNF-α downstream proteins, inhibitor of nuclear factor κ-B kinase (IKK) and the jun-N-terminal kinase 1 (JNK1) led to phosphorylation of insulin receptor substrate 1 (IRS-1) at Ser residues and insulin resistance in C2C12 myotubes. SIGNIFICANCE Our research provided further and direct demonstration on activated macrophage-induced insulin resistance in skeletal muscle, suggesting TNF-α might become a therapeutic target to ameliorate and treat type 2 diabetes.

中文翻译：

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肿瘤坏死因子-α的分泌减少会减弱巨噬细胞诱导的骨骼肌胰岛素抵抗。

AIMS巨噬细胞作为免疫系统的重要成员，吞噬并消化先天免疫中的病原体，并有助于启动适应性免疫。然而，巨噬细胞也参与许多疾病的发生和发展，例如肥胖症和2型糖尿病。在这里，我们旨在通过模拟人体环境揭示活化的巨噬细胞如何在体外引起骨骼肌的胰岛素抵抗。主要方法我们使用Transwell过滤器在体外模拟人体环境，建立了RAW264.7巨噬细胞和C2C12肌管共孵育模型，并研究了RAW264.7细胞对胰岛素调节的C2C12肌管葡萄糖代谢的影响。免疫荧光，免疫印迹和葡萄糖摄取测试用于评估C2C12肌管中的代谢变化。ELISA法检测RAW264.7细胞中肿瘤坏死因子α（TNF-α）和白介素6（IL-6）的分泌。另外，使用了RNA干扰和抑制剂处理。主要发现激活的RAW264.7细胞减弱了C2C12肌管中的胰岛素反应。激活的RAW264.7细胞分泌大量TNF-α和IL-6。我们发现TNFα而非IL-6以剂量依赖性方式引起骨骼肌的胰岛素抵抗。结果进一步表明，TNF-α下游蛋白，核因子κB激酶抑制剂（IKK）和jun-N端激酶1（JNK1）的激活导致胰岛素受体底物1（IRS-1）的磷酸化。 C2C12肌管中的丝氨酸残基和胰岛素抵抗。意义我们的研究为活化巨噬细胞诱导的骨骼肌胰岛素抵抗提供了进一步直接的证明，