Proliferative retinopathy (n = 146) was associated with higher levels of MMP-2 [0.71 (0.45; 0.96)], MMP-3 [0.49 (0.28; 0.70)], MMP-10 [0.39 (0.11; 0.66)] and TIMP-1 [0.54 (0.28; 0.81)] after adjustment for age, sex, duration of diabetes and HbA1c (Additional file 3: Table S3, Model 1). This evidence concerns the gene MMP3 and diabetes mellitus.