MFF and chronic obstructive pulmonary disease: The phosphorylation levels of DRP1 and the protein levels of DRP1 and MFF exhibited an elevation while the protein levels of MFN2 and OPA1 showed a reduction in COPD patients compared to non-smokers (p < 0.05, p < 0.01, p < 0.001, p < 0.001 and p < 0.001 respectively, Fig. 2E–I).