Glutathione Peroxidase in Stable Chronic Obstructive Pulmonary Disease: A Systematic Review and Meta-analysis

Abstract

Chronic obstructive pulmonary disease (COPD) is a progressive disease that is characterized by a state of persistent inflammation and oxidative stress. The presence of oxidative stress in COPD is the result of an imbalance between pro-oxidant and antioxidant mechanisms. The aim of this review was to investigate a possible association between glutathione peroxidase (GPx), a key component of antioxidant defense mechanisms, and COPD. A systematic search for relevant studies was conducted in the electronic databases PubMed, Web of Science, Scopus, and Google Scholar, from inception to June 2021. Standardized mean differences (SMDs) were used to express the differences in GPx concentrations between COPD patients and non-COPD subjects. Twenty-four studies were identified. In 15 studies assessing whole blood/erythrocytes (GPx isoform 1), the pooled results showed that GPx concentrations were significantly lower in patients with COPD (SMD = -1.91, 95% CI -2.55 to -1.28, p < 0.001; moderate certainty of evidence). By contrast, in 10 studies assessing serum/plasma (GPx isoform 3), the pooled results showed that GPx concentrations were not significantly different between the two groups (very low certainty of evidence). The concentration of GPx-1, but not GPx-3, is significantly lower in COPD patients, suggesting an impairment of antioxidant defense mechanisms in this group.

Keywords: antioxidant defense systems; chronic obstructive pulmonary disease; glutathione peroxidase; oxidative stress.

Figure 1

Flow chart of study selection.

Figure 2

Forest plot of studies examining blood/erythrocytes GPx values of COPD and non-COPD.

Figure 3

Sensitivity analysis of the association between blood/erythrocytes GPx and COPD disease. For each study, the displayed effect size (hollow circles) corresponds to an overall effect size computed from a meta-analysis excluding that study.

Figure 4

Funnel plot of the 15 retrieved studies evaluating the association between blood/erythrocytes GPx concentration and COPD disease.

Figure 5

Funnel plot of studies investigating the association between blood/erythrocytes GPx concentration and COPD disease after trimming and filling. Dummy studies and genuine studies are represented by enclosed circles and free circles, respectively.

Figure 6

Forest plot of studies examining erythrocyte GPx concentrations of COPD patients in stage I-II vs stage III-IV.

Figure 7

Forest plot of studies examining the serum/plasma GPx values of COPD and non-COPD.

Figure 8

Sensitivity analysis of the association between serum/plasma GPx and COPD disease. For each study, the displayed effect size (hollow circles) corresponds to an overall effect size computed from a meta-analysis which excluded that study.