Reports investigating the association between the genetic polymorphism of glutathione S-transferase T1 (GSTT1) and the risk of rheumatoid arthritis (RA) have revealed conflicting results. To clarify the effect of GSTT1 polymorphism on the risk of developing RA, we carried out a meta-analysis using published data.
Electronic searches were conducted to select studies. Reports were included if they were observational studies investigating the link between GSTT1 genotype and the risk of RA. The principal outcome measure was the odds ratio (OR) with 95% confidence interval (CI) for the risk of RA with GSTT1 null genotype.
We identified 7 eligible studies including 2652 cases and 4117 controls. The combined results showed that there was not a statistically significant link between GSTT1 null genotype and RA. However, we observed an increased risk in heavy smokers (cigarette consumption >10 pack-years) with GSTT1 null polymorphism compared with never or light smokers (cigarette consumption ≤10 pack-years) with GSTT1 present. Moreover, compared to GSTT1 positive polymorphism with seronegative results, there was an increased risk in GSTT1 null polymorphism with seropositive results.
The results from this meta-analysis suggested that GSTT1 null genotype is not association with an increased susceptibility to RA. However, GSTT1 null polymorphism may increase the risk of RA in relation to heavy smokers or seropositive results. Whether GSTT1 polymorphism may act in synergy with other genes or environmental factors remains to be studied more in depth.