MSTN and chronic obstructive pulmonary disease: Nevertheless, although the RNA expression of atrogin-1, FoxO3 and myostatin were not modified in the treated myotubes (P = 0.616, P = 0.762 and P = 0.510, respectively; Fig 4B, 4E and 4F), the MuRF1 and FoxO1 RNA expression levels were significantly more elevated in the H2O2-treated COPD myotubes (P = 0.022 and P = 0.030, respectively; Fig 4A and 4C).