Abstract: BACKGROUND: Previous studies have revealed that massage can regulate the balance of blood glucose, delay the loss of skeletal muscle mass, and promote the conversion of muscle fiber types. Skeletal muscle is also an important organ to maintain blood glucose balance and stability, but its specific association and mechanism are still unclear.
OBJECTIVE: To investigate the effects of massage on the changes of skeletal muscle structure and function and the conversion of skeletal muscle fiber types in type 2 diabetic rats.
METHODS: Animal models of type II diabetics mellitus were established in 24 Wistar rats by high-fat feeding combined with low-dose streptozotocin intraperitoneal injection. Eighteen rat models were randomly divided into three groups (n=6 per group): model group, metformin group and massage group. In the model group, no treatment was given; in the metformin group, metformin hydrochloride was given by gavage, once a day, 6 times per session, with an 1-day interval between sessions, for 8 sessions in total; in the massage group, massage treatment was given by small animal massager at Fenglong, Zusanli, Sanyinjiao and Blood Sea points, once a day, 6 times per session, with an 1-day interval between sessions, for 8 sessions in total. Another six healthy rats were set as blank group and received no treatment. Blood glucose and serum insulin levels, grip strength, swimming exhaustion time and skeletal muscle wet mass were measured after treatment. Western blot and qPCR were used to detect the protein and mRNA expression of myogenic determinant and myostatin in gastrocnemius muscle. ATPase staining was used to observe the changes of skeletal muscle fiber types.
RESULTS AND CONCLUSION: Compared with the model group, fasting blood glucose and serum insulin levels after treatment were significantly reduced in the metformin group and massage group (P < 0.01). Compared with the model group, grip strength, swimming exhaustion time and skeletal muscle wet mass were increased in the massage group (P < 0.01), but there were no significant changes in the metformin group (P > 0.05). Compared with the blank group, there was a significant increase in type II muscle fibers in the model group. Compared with the model group, the number of type I muscle fibers was increased in the massage group. Compared with the blank group, the protein and mRNA expression of myogenic determinant in the gastrocnemius muscle was decreased 
(P < 0.01), while that of myostatin in the gastrocnemius muscle was increased in the model group (P < 0.01). Compared with the model group, the protein and mRNA expression of myogenic determinant in the gastrocnemius muscle was increased (P < 0.01), while that of myostatin in the gastrocnemius muscle was decreased in the model group (P < 0.01). To conclude, massage can reduce blood glucose and improve skeletal muscle dysfunction in type 2 diabetic rats. The mechanism may be through promoting the conversion of skeletal muscle type II fibers to type I fibers, promoting the expression of myogenic determinant and inhibiting the expression of myostatin in skeletal muscle, thereby promoting the myoblastic differentiation of muscle satellite cells.

Key words: massage, diabetic sarcopenia, skeletal muscle function, muscle fiber type, sarcopenia