Chronic kidney disease (CKD), a chronic catabolic condition, is characterized by muscle wasting and a decreased muscle endurance. Many insights have made into the molecular mechanisms of muscle atrophy in CKD. A persistent imbalance between protein synthesis and degradation causes a loss of muscle mass. A decrease in insulin/IGF-1-Akt-mTOR signaling and an increased ubiquitin-proteasome system (UPS) have emerged as inducers of muscle loss. During muscle wasting, abnormal levels of reactive oxygen species (ROS) and inflammatory cytokines are detected in skeletal muscle. These increased ROS and inflammatory cytokine levels induce the expression of myostatin. The binding of myostatin to its receptor ActRIIB stimulates the expression of Foxo-dependent atrogenes. An impaired mitochondrial function also contributes to reduced muscle endurance. Increased glucocorticoid, angiotensin II, parathyroid hormone, and protein-bound uremic toxin levels that are observed in CKD all have a negative effect on muscle mass and endurance. The loss of skeletal muscle mass during the progression of CKD further contributes to the development of renal failure. Some potential therapeutic approaches based on the molecular mechanisms of muscle wasting in CKD are currently in the testing stages using animal models and clinical settings.
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