368Evaluation of myostatin as a possible regulator of the skeletal muscle-cortical bone interaction in adults

Background Bone mass was recently reported to be related to skeletal muscle mass in humans, and a decrease in cortical bone is a risk factor for osteoporosis. Since circulating myostatin is a factor that primarily controls muscle metabolism, this study examined the role of myostatin in blood in bone mass-skeletal muscle mass interactions. Methods The subjects were 375 middle-aged community residents with no history of osteoporosis or sarcopenia who participated in a health check-up. The subjects were divided into those with low cortical bone thickness (LCT) or low cancellous bone density (LBD) and those with normal values (NCT/NBD). Bone metabolism markers (BAP, TRACP-5b, etc.), skeletal muscle mass, serum myostatin levels, and lifestyle, were then compared between the groups. Results The percentage of diabetic participants and blood HbA1c, TRACP-5b, and myostatin levels were significantly higher, and the frequency of physical activity, skeletal muscle mass, grip strength, and leg strength were significantly lower in the LCT group than in the NCT group. The odds ratio of high myostatin in the LCT group compared with the NCT group was significant (2.26) even after adjusting for related factors. Significant differences were observed in the same items between the LBD and NBD groups as between the LCT and NCT groups, with no significant differences in skeletal muscle mass and serum myostatin levels. The serum myostatin level was significantly negatively correlated with cortical bone thickness and skeletal muscle mass. Conclusions Myostatin may regulate bone-skeletal muscle interactions and serve as a surrogate marker of cortical bone metabolism. Key messages The interaction between bone and skeletal muscle is reported to be important for preserving the activity of bone and muscle metabolism. Herein, we report for the first time that myostatin may regulate bone-skeletal muscle interactions and serve as a surrogate marker of cortical bone metabolism in adults.