Oxidative and Antioxidative Stress Linked Biomarkers in Ankylosing Spondylitis: A Systematic Review and Meta-analysis

Abstract

Objective. Ankylosing spondylitis (AS) is a chronic inflammatory disease that affects the axial skeleton, leading to joint disability. Our study aims at investigating the change of oxidative and antioxidative stress linked biomarkers in AS. Methods. This systematic review and meta-analysis was performed following the Preferred Reporting Items of Systematic Reviews and Meta-Analyses (PRISMA) statement. PubMed, Web of Science, and Cochrane Library databases till May 2020 were searched. Only articles published in English were included. Two reviewers screened relevant studies, extracted data, and assessed the quality of included studies using the Newcastle-Ottawa scale independently. Either random or fixed effect model was adopted base on the heterogeneity testing by $I^2$ statistic. Standardized mean difference (SMD) and 95% confidence intervals (CI) of oxidative and antioxidative markers were calculated. $p$ value <0.05 was considered statistically significant. Results. A total of 22 studies including 931 AS patients and 917 healthy controls met the selection criteria. Significantly increased levels of all oxidative stress markers except myeloperoxidase, and significantly decreased levels of total antioxidant status ( $\text{SMD}=-1.19$ , 95% CI -2.35 to -0.03, $p=0.044$ ) and paraoxonase 1( $\text{SMD}=-1.01$ , 95% CI -1.78 to -0.24, $p=0.010$ ) in serum were observed in AS patients when compared with healthy controls. However, there were no significant differences of all oxidative and anti-oxidative stress biomarkers in erythrocytes. Additionally, the levels of malondialdehyde ( $\text{SMD}=0.51$ , 95% CI 0.21 to 0.81, $p=0.001$ ) and advanced oxidation protein products ( $\text{SMD}=0.95$ , 95% CI 0.58 to 1.31, $p<0.001$ ) in serum were significantly higher in active patients when compared with inactive AS patients. Conclusion. This meta-analysis demonstrated an overall increase of oxidative markers and decrease of antioxidative markers in AS, suggesting that oxidative stress may play an important role in the pathogenesis of AS.