MMP9 and chronic obstructive pulmonary disease: In patients with chronic obstructive pulmonary disease (COPD), CLA supplementation at a dose of 3.2 g/day for 6 weeks (c9, t11, and c12, t10 isomers in a 50/50 ratio) demonstrated a reduction in serum oxidative stress-related factors, including MDA and matrix metalloproteinase-9 (MMP-9), compared to the placebo group [27], The study suggested that these antioxidant effects were likely a result of the anti-inflammatory properties of CLA, which partly occur through the stimulation of peroxisome proliferator-activated receptors [27].