Variation of MuRF1 (A), atrogin-1 (C), FoxO1 (E), FoxO3 (G) and myostatin (H) RNA expression levels in COPD myotubes after ascorbic acid treatment. Variations of MuRF1 (B), atrogin-1 (D) and FoxO1 (F) protein expression relative to tubulin expression in COPD myotubes after ascorbic acid treatment, and the representative Western blots showing their expression levels as well as tubulin expression in cultured COPD myotubes derived from 12 COPD patients (1–12). (n.s.) indicates statistically non-significant. (*), (**) and (***) indicate statistical significance at P≤0.05, P<0.01 and P<0.001, respectively. The medians are indicated. Statistical analysis showing correlations between the variations in the RNA expression of MuRF1 and: (I) the variations in myotube diameter, and (J) the variations in the RNA expression of FoxO1, after ascorbic acid treatment.