Muscle metabolism.

PURPOSE OF REVIEW: To review the recent findings on metabolic derangements leading to loss of muscle mass and function. RECENT FINDINGS: Several recent studies investigated methods to assess muscle mass and function and its clinical relevance. These are also included. A few studies confirm that a low muscle mass is related to a worse outcome but also a compromised muscle function at discharge is related to long-term survival. A low quality of muscle assessed by the density of muscle from a computed tomography scan is related to mortality. For the metabolic derangements, a compromised handling of calcium is present in muscle of animal models and might be causing a decreased muscle function in patients. Transcriptomics analyses of muscle post-ICU indicated an upregulation of regenerative pathways, but still muscle mass is not recovering in most patients. This could be due to an impairment regenerative capacity due to satellite cells dysfunction. SUMMARY: Muscle mass and function are related to outcome. New finding show that not only muscle mass but also muscle quality is important, that a compromised handling of calcium might be involved in muscle weakness and that regaining muscle could be compromised due to a defective regenerative capacity of satellite cells.