OPTN and chronic obstructive pulmonary disease: We tested these hypotheses by assessing differences in skeletal muscle expression of molecular markers of mitochondrial breakdown (i.e. BNIP3, BNIP3L, FUNDC1, PINK1, PARK2), general autophagy (i.e. LC3B, GABRARAPL1, SQSTM1, OPTN, CALCOCO2), and mitochondrial dynamics (i.e. DNM1L, FIS1, OPA1, MFN1) between COPD patients and controls, and studied if the mitochondrial breakdown markers correlated with markers for mitochondrial content (i.e. NDUFB8, SDHB, UQCR2, MT-COI, ATP5A, mtDNA/gDNA ratio).