Moderate aerobic exercise does not protect female mice from muscle wasting in a collagen-induced arthritis model

Abstract

Background Many rheumatoid arthritis (RA) patients undergo loss of muscle mass, which is a feature that leads to increased morbidity and mortality. Although the causative mechanisms of muscle wasting in RA are not fully understood, it has been suggested that physical exercise may be useful in reverting this condition. In this study, we aimed to evaluate the effect of moderate aerobic exercise upon skeletal muscle of mice subjected to collagen-induced arthritis (CIA). Methods CIA mice were subjected to aerobic exercise in a treadmill 5 days per week over 4 weeks. Sedentary CIA mice were used as control. Clinical severity of the joints and paw oedema were assessed daily; spontaneous exploratory locomotion and body weight were evaluated weekly. Tibialis anterior muscles were analyzed for weight and myofibers cross-sectional areas; gastrocnemius were used for total proteins measurement and western blot analysis of myogenin and Pax-7 expressions. Results Arthritis score (p = 0,08), paw oedema (p = 0,06), tibialis weight (p = 0,66), gastrocnemius weight (p = 0,20) and tibialis cross-sectional areas (p = 0,71) were not significantly different between groups, suggesting that exercise was not able to decrease muscle wasting. Distances coursed in spontaneous locomotion was not different between groups (p=0,36), most likely because there was not muscle mass improvements. Quantifications of myogenic transcription factors myogenin (p = 0,71) and Pax-7 (p = 0,27) were also of no statistical difference between groups. Conclusions In this model of CIA, moderate aerobic exercise did not cause increase damage to joints, but was not able to protect female mice from muscle wasting. Further studies are needed to evaluate influences of androgens upon muscle growth in CIA mice.