Association of plasma homocysteine and macular edema in type 2 diabetes mellitus

PURPOSE. The aim of this study was to assess the association of macular edema (ME) with plasma homocysteine, vitamin B6, vitamin B12, and folic acid levels in patients with Type 2 diabetes. METHODS. Sixty-five diabetic subjects with no retinopathy and nonproliferative diabetic retinopathy (NPDR) (no DR, without ME, with ME: 16, 25, 24, respectively), 28 with proliferative diabetic retinopathy (PDR) (with and without ME: 14, 14, respectively), and 19 healthy subjects as control were recruited in this cross-sectional study. Plasma homocysteine, vitamin B12, vitamin B6, and folate levels were determined after 8-hour of fasting for all subjects. The levels of serum homocysteine and vitamin B6 were measured using high performance liquid chromatography (HPLC) with fluorescence detection, and the levels of serum vitamin B12 and folic acid were measured by electrochemiluminescence immunoassay. RESULTS. When diabetic groups with ME were compared with diabetic groups without ME for homocysteine, vitamin B12, vitamin B6, and folic acid, the only significant difference was detected in homocysteine levels (p= 0.001). There was no significant difference between NPDR with ME group compared with NPDR without ME group and no DR group for plasma homocysteine, vitamin B12, vitamin B6, and folic acid (p= 0.200, p= 0.660; p= 0.999, p= 0.678; p= 1.0, p= 0.248; p= 1.0, p= 0.982, respectively). On the other hand, when PDR with ME group was compared with PDR without ME group, there was only significant difference in homocysteine levels (p= 0.023). CONCLUSIONS. Mild to moderate elevation of homocysteine may explain the role of vascular dysregulation and endothelial dysfunction in patients with DR. The present study suggests hyperhomocysteinemia may be one of the crucial risk factors for development of ME.