Folate and retinal vascular diseases

Folate, a pteroylglutamic acid derivative, participates in fundamental cellular metabolism. Homocysteine, an amino acid, serves as an intermediate of the methionine cycle and can be converted back to methionine. Hyperhomocysteinemia is a recognized risk factor for atherosclerotic and cardiovascular diseases. In recent decades, elevated plasma homocysteine levels and low folate status have been observed in many patients with retinal vascular diseases, such as retinal vascular occlusions, diabetic retinopathy, and age-related degeneration. Homocysteine-induced toxicity toward vascular endothelial cells might participate in the formation of retinal vascular diseases. Folate is an important dietary determinant of homocysteine. Folate deficiency is the most common cause of hyperhomocysteinemia. Folate supplementation can eliminate excess homocysteine in plasma. In in vitro experiments, folic acid had a protective effect on vascular endothelial cells against high glucose. Many studies have explored the relationship between folate and various retinal vascular diseases. This review summarizes the most important findings that lead to the conclusion that folic acid supplementation might be a protective treatment in patients with retinal vascular diseases with high homocysteine or glucose status. More research is still needed to validate the effect of folate and its supplementation in retinal vascular diseases.