Endurance training attenuates catabolic signals induced by TNF-α in muscle of mice

Purpose To determine whether endurance training attenuates the negative effects induced by an acute injection of tumor necrosis factor-α (TNF-α) in skeletal muscle of mice. Methods Trained (6 wk of endurance training at 60% of maximal velocity) and untrained mice were injected with TNF-α or vehicle and killed 6 h after. Tibialis anterior muscles were analyzed using Western blot and qRT-PCR for markers of inflammation and protein synthesis/degradation. Results Independently of training, TNF-α increased the mRNA of cytokines and downregulated signals linked to protein synthesis. The phosphorylation of IKKα/β and IκBα induced by TNF-α was blunted in trained mice, suggesting altered NF-κB activation. This was associated with lower induction of several markers of protein degradation (FoxO1, MURF1, MAFbx, myostatin, Gabarapl1, and LC3BII/LC3BI ratio). Conclusions Endurance training protects skeletal muscle against the activation of protein degradation signaling pathways induced by TNF-α.