Sirtuin (SIRT) 1 and SIRT6, class III HDACs that catalyze nicotinamide adenine dinucleotide (NAD)+-dependent deacetylation, are downregulated in the peripheral lungs of patients with COPD [146,147], and loss of SIRT1 correlates with tissue inhibitor of metalloproteinase (TIMP)-1 lysine acetylation and subsequent degradation of TIMP-1, the major anti-MMP protease, resulting in increased MMP-9 in human COPD lung tissue [148]. Here, MMP9 is linked to chronic obstructive pulmonary disease.