Small-molecule targeting MuRF1 enhances functional exercise capacity in rats: an exploratory study

Maintenance of skeletal muscle function is essential for functional independence, quality of life and healthspan. Muscle RING-finger protein-1 (MuRF1) negatively regulates muscle function and mass through ubiquitination and degradation of muscle proteins. Accordingly, genetic and pharmacological inhibition of MuRF1 attenuates muscle wasting and weakness under catabolic stress. To explore the potential of MuRF1 inhibitors (e.g., MyoMed-205) to improve muscle health, we investigated here the long-term effects of MyoMed-205 on functional capacity and muscle physiology in rats under basal conditions. Wistar rats were randomized to control or MyoMed-205 groups and were followed for 4 or 8 weeks. Body weight, food and water intake, and exercise capacity were monitored weekly. At each endpoint, the soleus muscle was collected for histological analyses. MyoMed-205-treated rats showed normal basic survival-related behaviors and body growth. After 8 weeks, MyoMed-205-treated animals exhibited enhanced exercise capacity (speed (m/min): +45%, p = 0.01; endurance (min): +47%, p = 0.03; and distance covered (m): +87%, p = 0.04) compared with baseline performance. Conversely, no differences were found in soleus fiber type distribution, cross-sectional area, or lipid and collagen content. Our findings indicate that MyoMed-205 enhances functional exercise capacity independently of changes in soleus muscle structure in rats under basal conditions.