GSTM1 and GSTT1 null genotype and diabetic retinopathy: a meta-analysis

Glutathione S-transferases (GSTs) have proved to be involved in the detoxifying several oxidants and may play an important role in diabetic retinopathy (DR). Previous studies on the association between glutathione S-transferase T1 (GSTT1) and GSTM1 polymorphism and DR risk reported inconclusive results. To clarify the possible association, we conducted a meta-analysis of eligible studies. We searched in the PubMed, Embase, and Wangfang Medicine databases for studies assessing the association between GSTM1 and GSTT1 null genotype and DR risk. Odds ratios (ORs) with 95% confidence intervals (CIs) were used to assess the strength of association between GSTM1 and GSTT1 null genotype and DR risk. Five studies with 3563 subjects were included in this meta-analysis. The null genotypes of GSTT1 and GSTM1 were associated with a significantly increased risk of DR (OR = 1.69; 95% CI, 1.33-2.16; OR = 1.59; 95% CI, 1.22-2.06), respectively. When stratified by the type of DM, a significantly elevated DR risk was observed in T2DM patients. In conclusion, this meta-analysis suggested that an increased risk of DR was associated with the null polymorphism of GSTT1 and GSTT1, respectively.