Folate protects against oxidative modification of human LDL.

Elevated plasma total homocysteine is considered to be a graded risk factor for cardiovascular disease. Folate, through its homocysteine-lowering potential, may therefore be protective. Folate, however, may have protective effects independent of homocysteine-lowering. We have measured the effects of folate on Cu-catalysed oxidative damage to the unsaturated lipids in human LDL. Experiments were carried out in the presence of citrate, and followed increases in absorption at 234 nm, which measures the amount of conjugated diene produced. There is a lag time during which endogenous antioxidants are oxidised, followed by rapid oxidation of lipid. Addition of 0-6 microm - 5-methyltetrahydrofolate produced a dose-dependent increase in the lag time, suggesting that folate may have a direct anti-oxidant role in vivo, which is independent of any indirect effects through lowering of homocysteine levels.