Folate Transport in Retina and Consequences on Retinal Structure and Function of Hyperhomocysteinemia

Folate is a water-soluble vitamin that is essential for the synthesis of DNA, RNA, and some amino acids. It is required for the proper function of every cell, including those of the retina. This chapter summarizes reported studies of the transport mechanisms by which retinal cells take up folate, including folate receptor α, reduced folate carrier, and proton-coupled folate transporter. It is well known that when folate is deficient, homocysteine levels increase. Genetic mutations can also trigger hyperhomocysteinemia. The second portion of the chapter focuses on the consequences on retina structure and function under conditions of hyperhomocysteinemia. It describes studies in several models in which defects in enzymes associated with the remethylation and transsulfuration pathway are associated with varying degrees of retinal neuropathy and vasculopathy.