["The Journal of Physiology, EarlyView. ", "\nAbstract figure legend Effects of TUDCA treatment on skeletal muscle of ageing mice. Image generated with BioRender (2025, https://BioRender.com, accessed 30 May 2025).\n\n\n\n\n\n\n\n\n\nAbstract\nAgeing leads to changes in body composition, including increased adiposity and reduced skeletal muscle mass and force. The alterations in ageing skeletal muscle result from impaired proteostasis driven by factors such as chronic inflammation, hormonal changes and reduced nutrient absorption. Those age‐related changes in body composition and skeletal muscle compromise mobility and increase the risk of falls, fractures and metabolic disorders. Tauroursodeoxycholic acid (TUDCA), a bile acid with known benefits in chronic diseases, has been shown by our group to improve cognition and metabolic homeostasis in ageing and Alzheimer's disease mouse models. Interestingly, in previous studies, TUDCA treatment was also associated with increased skeletal muscle mass in ageing mice, leading us to hypothesize that TUDCA could target skeletal muscle to reduce age‐related muscle loss. To explore this, we treated 18‐month‐old C57BL/6 mice with TUDCA or vehicle for 20 days, using 3‐month‐old mice as a young control group. We demonstrate that TUDCA treatment decreases body weight while increasing skeletal muscle mass, restores muscle fibre size and preserves functional integrity. Additionally, TUDCA enhances skeletal muscle insulin sensitivity through increased AKT activation and reduces tissue inflammation. Such improvements collectively support the restoration of skeletal muscle proteostasis, as indicated by increased protein synthesis and phosphorylation of key anabolic signalling pathways, including ribosomal protein S6 kinase beta‐1 (P70S6K) and eukaryotic translation initiation factor 4E‐binding protein 1 (4EBP1). These findings contribute to a better understanding of TUDCA's actions on skeletal muscles of ageing mice and highlight its role as a promising strategy against age‐related muscle loss.\n\n\n\n\n\n\n\n\n\nKey points\n\nTauroursodeoxycholic acid (TUDCA) treatment attenuates skeletal muscle loss in ageing mice.\nTUDCA improves skeletal muscle insulin sensitivity and restores AKT signalling.\nTUDCA exerts an anti‐inflammatory effect in skeletal muscle of ageing mice.\nTUDCA emerges as a potential therapy for age‐related skeletal muscle loss.\n\n\n"]