Study of oxidative stress biomarkers in chronic obstructive pulmonary disease and their correlation with disease severity in north Indian population cohort

Abstract

Background: Oxidant-antioxidant imbalance forms a prime component in pathogenesis of chronic obstructive pulmonary disease (COPD). Studies of oxidative stress markers in South Asians were sparse.

Methods: One hundred and eighty COPD patients and eighty healthy nonsmokers were enrolled in the study. Serum malondialdehyde (MDA) and iron levels were estimated for oxidative stress. Three antioxidant markers evaluated-catalase, superoxide dismutase (SOD), and serum copper. Patients on antioxidant therapy and with sepsis and chronic illness were excluded from the study.

Results: The mean age of COPD patients was 59.29 ± 10.3 years. Serum levels of MDA and iron were significantly higher in COPD patients compared to controls (5.21 ± 1.9 vs. 0.71 ± 0.29 nmol MDA/ml, P = 0.0001 and 69.85 ± 85.49 vs. 79.32 ± 24.39 μg/dl, P = 0.0001, respectively). Mean level of all antioxidant enzymes catalase, SOD, and copper were significantly diminished in cases when compared to control population (P = 0.001). Levels of MDA and iron were found to be significantly elevated in higher Global Initiative for Chronic Obstructive Lung Disease (GOLD) classes (III, IV) when compared to lower GOLD Classes (I, II). The levels of serum antioxidants were significantly depleted in higher GOLD grades too. COPD patients who were male and smoked had significantly higher levels of oxidants and depleted antioxidant levels compared to female and nonsmoking compatriots. Serum MDA levels negatively correlated with forced expiratory volume 1 s and forced vital capacity (r = -0.19 and r = -0.21, P ≤ 0.01). The presence of a cough significantly correlated with higher levels of MDA and iron (P = 0.001). The levels of MDA negatively correlated with SOD and catalase levels.

Conclusion: Oxidative markers (MDA and iron) are higher whereas antioxidants (catalase, copper, and SOD) are significantly reduced in patients of COPD. Serum MDA levels correlate with lung functions and disease severity.

Figure 1

Distribution of biomarkers among chronic obstructive pulmonary disease patients (cases) and controls, (a) superoxide dismutase levels (in U/ml) were significantly decreased in cases (P = 0.0001), (b) serum malondialdehyde levels (in nmol MDA/ml) were significantly higher in cases (P = 0.0001), (c) serum catalase levels (U/ml) were significantly diminished in cases (P = 0.0001), (d) serum iron levels (μ gm/dl, blue bars) were significantly higher (P = 0.0001) in cases and serum copper levels (μ gm/dl, red bars) were significantly lower in cases (P = 0.002)

Figure 2

Scatter diagram showing negative linear correlation of malonidialdehyde with catalase (a) and superoxide dismutase (b), respectively