Effects of resistance exercise on SPARC expression in skeletal muscle of aging mice

Abstract

Backgrounds: Sarcopenia is age-related loss of muscle mass and the consequent loss of muscle strength and quality is closely related to mobility and functional impairment as it increases the prevalence of lifestyle-related diseases such as diabetes and cardiovascular disease. SPARC is a novel myokine which inhibits adipogenesis but promotes myogenesis and it has been suggested as a therapeutic target to overcome sarcopenia. However, there is no study that shows how the exercise effects on SPARC expression during the aging process. Therefore, the purpose of this study is to describe the effect of 12 weeks resistance exercise on SPARC expression in skeletal muscle of aging mice. Methods: Nineteen-month-old male wild-type C57BL/6 mice were randomized Old-CON, sedentary aging mice group (n=6)

Old-REX, resistance exercise aging mice group (n=7). Old-REX mice performed 12 weeks of resistance ladder climbing exercise after taking non-weight bearing adaptation period for one week. The body composition was scanned by using DEXA and SPARC expression in each muscle such as soleus (SOL), extensor digitorum longus (EDL), tibialis anterior (TA), and gastrocnemius (GAS) muscles were detected using ELISA. Moreover, muscle strength, endurance capacity and mobility were measured after the last resistance exercise. Results: SPARC protein levels in EDL, TA and GAS muscles were significantly increased in Old-REX mice compare to Old-CON mice, while there was no difference between groups in circulating SPARC level was found. The lean body mass in Old-REX mice was significantly increased without a change in body weight. Additionally, a significant increase in soleus muscle wet weight was observed. The mobility was significantly improved in Old-REX group and grip strength AUC was also increased. Conclusion: 12 weeks of resistance exercise increased the expression of SPARC in aging skeletal muscle. This is the first study that shows descriptive SPARC expression in various skeletal muscle of aging mice. In addition, resistance exercise increased muscle mass, but also improved physical functions. These observations suggest that decreased SPARC expression in aging skeletal muscle and declined muscle mass could be improved through resistance exercise and SPARC might be a potent contributor to overcome sarcopenia.