The glutathione S-transferase M1 and P1 polymorphisms and rheumatoid arthritis: a meta-analysis

The aim of this study was to determine whether the Glutathione S-transferase M1 (GSTM1) and P1 (GSTP1) polymorphisms confer susceptibility to rheumatoid arthritis (RA). Meta-analysis was performed on the associations between the GSTM1 and GSTP1 null genotypes and RA, and on the association between smoking or seropositive status and the GSTM1 null genotype in RA patients. Twelve studies involving 3,990 RA patients and 2,815 controls were included in the meta-analysis. All 12 studies examined the GSTM1 polymorphism and three the GSTP1 polymorphism. Meta-analysis of GSTM1 null polymorphism in 2,291 RA and 2,713 control subjects revealed no association between RA and the GSTM1 null genotype (OR = 1.139, 95 % CI = 0.914-1.419, p = 0.246). Stratification by ethnicity indicated no association between the GSTM1 null genotype and RA in Asians or Europeans (OR = 1.245, 95 % CI = 0.729-2.124, p = 0.422; OR = 1.023, 95 % CI = 0.794-1.318, p = 0.863). Furthermore, there was no association between smoking and the GSTM1 null genotype (OR = 0.943, 95 % CI = 0.734-1.210, p = 0.642). In addition, no association was found between seropositive status including anti-CCP (anti-citrullinated antibody) and/or RF (rheumatoid factor) and the GSTM1 null genotype. Meta-analysis of 915 RA and 1,082 controls revealed no association between RA and the GSTP1 null genotype (OR = 0.965, 95 % CI = 0.802-1.161, p = 0.704). Furthermore, stratification by ethnicity indicated no association between the GSTP1 null genotype and RA in Europeans (OR = 0.794, 95 % CI = 0.594-1.061, p = 0.119). This meta-analysis suggests that the GSTM1 and GSTP1 polymorphisms are not associated with the risk of RA. However, due to the small number of studies included and our inability to perform subgroup analysis by environmental factors, further studies are required to explore the roles played by GSTM1 and GSTP1 polymorphisms in the pathogenesis of RA.