Pathophysiological mechanisms leading to muscle loss in chronic kidney disease

Loss of muscle proteins is a deleterious consequence of chronic kidney disease (CKD) that causes a decrease in muscle strength and function, and can lead to a reduction in quality of life and increased risk of morbidity and mortality. The effectiveness of current treatment strategies in preventing or reversing muscle protein losses is limited. The limitations largely stem from the systemic nature of diseases such as CKD, which stimulate skeletal muscle protein degradation pathways while simultaneously activating mechanisms that impair muscle protein synthesis and repair. Stimuli that initiate muscle protein loss include metabolic acidosis, insulin and IGF1 resistance, changes in hormones, cytokines, inflammatory processes and decreased appetite. A growing body of evidence suggests that signalling molecules secreted from muscle can enter the circulation and subsequently interact with recipient organs, including the kidneys, while conversely, pathological events in the kidney can adversely influence protein metabolism in skeletal muscle, demonstrating the existence of crosstalk between kidney and muscle. Together, these signals, whether direct or indirect, induce changes in the levels of regulatory and effector proteins via alterations in mRNAs, microRNAs and chromatin epigenetic responses. Advances in our understanding of the signals and processes that mediate muscle loss in CKD and other muscle wasting conditions will support the future development of therapeutic strategies to reduce muscle loss. Loss of muscle protein is a deleterious consequence of chronic kidney disease (CKD) that results in decreased muscle strength and function. This Review summarizes the cellular mechanisms that lead to reductions in muscle protein in patients with CKD and highlights commonalities with other catabolic conditions such as cancer and diabetes. Key points Loss of muscle mass in patients with chronic kidney disease (CKD) leads to frailty and is associated with reduced quality of life and increased risks of morbidity and mortality. In healthy individuals, muscle mass is maintained by a balance of processes — including protein synthesis, protein degradation, energy production and utilization — that support muscle growth and turnover. In patients with CKD and other wasting conditions, pathophysiological changes at the cellular and organ system levels disrupt muscle proteostasis and cellular bioenergetics processes, suppress muscle repair and protein synthesis pathways, and i