Glutamine and myostatin expression in muscle

Key points • skeletal muscle mass depends on the balance between protein synthesis and degradation rates; • muscle wasting in pathological states is mainly associated with activation of protein breakdown above control levels; • myostatin is a negative regulator of skeletal muscle mass, acting on both myogenesis and protein turnover; • increased myostatin expression is a frequent finding in diseases characterized by the occurrence of muscle atrophy; • glutamine levels are generally decreased in acute and chronic illnesses, and glutamine supplementation to critically ill patients results in improved clinical conditions; • myotube atrophy induced by glucocorticoid or proinflammatory cytokine exposure can be reverted by glutamine treatment. Such an effect is associated with normalization of myostatin hyperexpression and signaling; • glutamine effectiveness in restoring normal myostatin pathway could depend on the inhibition of proinflammatory cascades as well as on the regulation of microRNA expression.