GSTM1 and diabetes mellitus: In recent years, many studies have assessed the associations between diabetes mellitus (DM), Type 2 diabetes mellitus (T2DM) and GSTT1 polymorphism; although no significant association was found [28], GST polymorphic genes (GSTM1-null and GSTT1-null) can be used as biological markers to determine the diabetic risk of individuals [4].