Molecular and cellular mechanisms of skeletal muscle atrophy: an update

Skeletal muscle atrophy is defined as a decrease in muscle mass and occurs when protein degradation exceeds protein synthesis. Potential triggers of muscle wasting are long-term immobilization, malnutrition, severe burns, aging as well as various serious and often chronic diseases, such as chronic heart failure, obstructive lung disease, renal failure, AIDS, sepsis, immune disorders, cancer and dystrophies. Interestingly, a cooperation between several pathophysiological factors, including inappropriately adapted anabolic (e.g. growth hormone, insulin-like growth factor 1) and catabolic proteins (e.g. tumor necrosis factor alpha, myostatin), may tip the balance towards muscle-specific protein degradation through activation of the proteasomal and autophagic systems or the apoptotic pathway. Based on the current literature, we present an overview of the molecular and cellular mechanisms that contribute to muscle wasting. We also focus on the multi-facetted therapeutic approach that is currently employed to prevent the development of muscle wasting and to counteract its progression. This approach includes adequate nutritional support, implementation of exercise training and possible pharmacological compounds.