To investigate the correlation between Glutathione-S-transferase (GST) genes and diabetic retinopathy (DR) in patients with type 2 diabetes mellitus (DM).

In this case-control study, 131 patients who were diagnosed with DR, 105 diabetic patients who did not have DR, and 45 nondiabetic controls were examined from January 2013 to November 2015. To analyze deletion of the GSTT1 and GSTM1 genes, polymerase chain reactions of DNA in a buffy coat from peripheral blood were performed via electrophoresis.

There were no statistically significant differences in age, sex, or spherical equivalent between the 236 type 2 diabetic patients and the 45 normal controls ( p > 0.05). In both univariate and multivariate analyses, the duration of type 2 DR was longer ( p = 0.004, p = 0.013), and HbA1c was higher ( p = 0.004, p = 0.007) in the DR group than in the non-DR group. Presence of a GSTM1 deletion is associated with a lower frequency of DR ( p = 0.017, p = 0.012).

Deletion of the GSTT1 gene is not associated with an increased risk of DR, whereas GSTM1 deletion is associated with a lower risk of DR in patients with type 2 DM in the Korean population. Additional studies with larger sample sizes and different types of GST genes are needed to confirm this study.