HDAC4 and chronic obstructive pulmonary disease: miR-1, miR-133, and −206 were downregulated in the diaphragms of mild, moderate and severe COPD patients, with miR-206 being more downregulated, whilst histone deacetylase 4 (HDAC4) and myocyte enhancer factor 2 (MEF2) protein levels were increased, muscle fibre type and cross-sectional area size does not differ between patients with mild COPD and healthy sedentary controls, whilst an increase in the proportion of diaphragm fibre type I was found in moderate and severe COPD patients with no difference in their cross-sectional area.