Exercise-induced modulation of the unfolded protein response: a therapeutic avenue for muscle wasting disorders.

Muscle wasting, prevalent in various pathological conditions including cancer, cardiac dysfunction, and neurodegeneration, is typified by sustained protein depletion in muscle and a compromised ability of the tissue to repair and regenerate effectively. Triggered by disruptions in protein folding in the endoplasmic reticulum (ER), the unfolded protein response (UPR) represents a key regulatory system that sustains intracellular proteostasis under conditions of stress. While the UPR is crucial for cellular survival, prolonged activation or dysfunction of the pathway can contribute to muscle atrophy and the progression of muscle wasting diseases. Recent evidence suggests that exercise, through its impact on cellular stress responses, can modulate the UPR in muscle cells, promoting a protective response that enhances protein folding capacity, reduces ER stress, and stimulates muscle regeneration. This review explores how exercise influences the UPR in muscle cells, focusing on the activation of key UPR sensors, including IRE1, PERK, and ATF6, and their downstream effects on protein quality control, autophagy, and muscle fiber maintenance. We also examine the role of exercise in promoting adaptive responses in muscle cells, including increased mitochondrial function, autophagy, and the activation of stress resistance pathways, all of which can counteract muscle wasting. The review also emphasizes exercise as an effective strategy to influence ER stress pathways and attenuate muscle atrophy associated with pathological conditions, offering critical insights into the molecular benefits of physical activity for muscle preservation.