Lixia Bu1, Xiaohong Cao1, Zilong Zhang2, Huiwen Wu3, Renwei Guo4, Mingfeng Ma5. 1. Department of Geratology, Fenyang Hospital of Shanxi Province, Fenyang, Shanxi 032200, PR China. 2. Department of Cardiology, Emergency General Hospital, Beijing 100028, PR China. 3. Science and Technology Center, Fenyang College of Shanxi Medical University, Shanxi 032200, PR China. 4. Department of Cardiology, Fenyang Hospital of Shanxi Province, Fenyang, Shanxi 032200, PR China. Electronic address: grw_0303@163.com. 5. Department of Cardiology, Fenyang Hospital of Shanxi Province, Fenyang, Shanxi 032200, PR China. Electronic address: mamingfeng106@sina.com.
Abstract
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.
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.
Authors: Erika Aparecida Silveira; Lorena Pereira de Souza Rosa; Danilo Pires de Resende; Ana Paula Dos Santos Rodrigues; Adeliane Castro da Costa; Andréa Toledo de Oliveira Rezende; Matias Noll; Cesar de Oliveira; Ana Paula Junqueira-Kipnis Journal: Front Endocrinol (Lausanne) Date: 2022-05-02 Impact factor: 6.055