To gain more insight into the mechanism of hypertrophy of myofibers observed in the tongue muscle of DMD rats, we investigated the amount and phosphorylation of molecules that act in the downstream of PI3K-Akt-mTOR pathway as well as the number of nuclei per myofiber in 6-month-old tongue muscle. The gene discussed is MTOR; the disease is Duchenne muscular dystrophy.