Testosterone Causes Decrease in the Content of Skeletal Muscle Myostatin

抄録

Myostatin, a potent negative regulator of skeletal muscle growth, plays an important role in the regulation of muscle size. However, the mechanisms by which muscle myostatin production is regulated have not been fully understood. We hypothesized that testosterone, a positive regulator of muscle growth, causes a reduction of muscular myostatin content. To test this, we measured the content of myostatin in skeletal muscle after injection of testosterone at varied doses. Male C57BL/6j mice (age, 11 wk; n=6 for each group) were subjected to subcutaneous injections of testosterone (0.3, 0.6, or 1.2mg/ day per 100g body weight) for 3 days. On the 4th day, the gastrocnemius/ plantaris complex (Gast/ Plant) and the soleus muscles were dissected and the content of myostatin protein was measured. Injection of testosterone tended to cause increases in body weight, Gast/ Plant and soleus muscle wet weight when compared to the control group. Myostatin content in the Gast/ Plant muscle decreased significantly after the injection at 1.2mg per 100g body weight when compared to both control and after the injection at 0.3mg per 100g body weight. In the soleus muscle, the myostatin content also decreased significantly after the injection at 0.3, 0.6 or 1.2mg per 100g body weight when compared to the control group. These results suggest that testosterone plays a part in the regulation of myostatin content in skeletal muscle.