Glutathione S-transferase T1 and M1 null genotypes and Parkinson's disease risk: evidence from an updated meta-analysis.

Glutathione S-transferase T1 and M1 (GSTT1 and GSTM1) have been reported to be associated with Parkinson's disease (PD). However, the results of these previous studies were inconsistent. The reported studies were conducted from 1990 to 2014 by searching PubMed. The total Odds Ratio and 95 % Confidence Interval were calculated and analyzed by Review Manager 5.1 and STATA 12. We also did subgroup analysis of ethnicity, publication year and sample size of total cases. Sensitivity analysis and publication bias were also done to evaluate the credibility of the results. A total of 3753 PD patients and 5636 controls from 19 case-control studies were identified. Overall, no association was observed (OR 1.01, 95 % CI 0.99-1.21, P = 0.07) between GSTM1 null genotype and PD. There was significant association in Caucasians when subgroup analysis of ethnicity was performed, and the same conclusion was observed in European and UK. And it was also in publication year of 1995-1999 and in sample size of total cases of <90 and 91-181. However, there was no significant association between GSTT1 null genotype and PD risk in this meta-analysis. Publication bias was negligible and the overall results were stable by sensitivity analysis. A slight increase of PD risk was detected in the meta-analysis of GSTM1 null genotype in subgroup analysis of ethnicity, publication year and sample size of total cases. However, short of statistical significance was detected for GSTT1 null genotype.