ENPP2 and proliferative diabetic retinopathy: The purpose of this study was to test the hypothesis that increased intraocular autotaxin (ATX) levels contribute to the progression of diabetic retinopathy (DR), we investigated ATX levels in the vitreous of patients with type 2 diabetes with proliferative diabetic retinopathy (PDR) and assessed the effect of an ATX peptide vaccine (VA) in a db/db mouse model of type 2 diabetes.