Nitrosative and Oxidative Stress, Reduced Antioxidant Capacity, and Fiber Type Switch in Iron-Deficient COPD Patients: Analysis of Muscle and Systemic Compartments

This cross-sectional cohort study enrolled 20 iron-deficient and 20 non-iron-deficient severe COPD patients to compare oxidative/nitrosative stress markers, antioxidant capacity, and muscle fiber phenotype across systemic (blood) and muscle (vastus lateralis biopsy) compartments. Iron-deficient COPD patients showed significantly greater lipofuscin and 3-nitrotyrosine levels in both muscle and blood compared to non-iron-deficient patients. Mitochondrial superoxide dismutase (SOD) and Trolox equivalent antioxidant capacity (TEAC) were significantly reduced in iron-deficient patients across both compartments. The proportion of fast-twitch muscle fibers was nearly 80% in iron-deficient patients, representing a significantly more pronounced slow-to-fast fiber switch compared to non-iron-deficient COPD patients. No differences in quadriceps muscle function were observed between groups. A significant positive correlation was found between mitochondrial SOD and slow-twitch fiber proportions. Study limitations include its descriptive cross-sectional design, which precludes causal inference and longitudinal assessment of whether iron treatment reverses observed changes.