Chronic inflammation is a major cause of muscle loss.
“Both chronic and extreme inflammation are associated with disruptions of anabolic signals initiating muscle growth. Chronic inflammation has been implicated as part of the cause of the muscle loss that occurs with aging.[39][57] Increased protein levels of myostatin have been described in patients with diseases characterized by chronic low-grade inflammation.[58] Increased levels of TNF-α can suppress the AKT/mTOR pathway, a crucial pathway for regulating skeletal muscle hypertrophy,[59] thereby increasing muscle catabolism.[60][61][62] Cytokines may antagonize the anabolic effects of Insulin-like growth factor 1 (IGF-1).[63][64] In the case of sepsis, an extreme whole body inflammatory state, the synthesis of both myofibrillar and sarcoplasmic proteins are inhibited, with the inhibition taking place preferentially in fast-twitch muscle fibers.[65][63] Sepsis is also able to prevent leucine from stimulating muscle protein synthesis.[44] In animal models, when inflammation is created, mTOR loses its ability to be stimulated by muscle growth.[66]”