Hyperhomocysteinemia and oxidative stress in hemodialysis: effects of supplementation with folic acid

Abstract

This study was undertaken to evaluate two different doses of folic acid and their effects on the control of hyperhomocysteinemia, and on pro-oxidant and antioxidant changes in a group of 32 hemodialysis (HD) patients. Blood samples were collected in a group of patients at three different times: before (basal; B), after the first (S1), and after the second (S2) three-month supplementation periods, and compared to samples from a group of healthy individuals. Analysis of vitamins (C, E, folate, and B12), oxidant parameters (lipid and protein oxidation), and homocysteine were performed. Hyperhomocysteinemia of different degrees was observed in all patients on HD (45.30 +/- 24.89 microM). Oxidative stress was also detected, with lipoperoxidation and protein oxidation being associated with lower concentrations of antioxidant substances (vitamins E and C). The first folate dose (2.5 mg after each dialysis session) reduced by half the initial concentrations of homocysteine (44.92 +/- 22.05 to 20.56 +/- 6.79 microM; p < 0.05) but did not normalize its values. The second dose (15 mg) did not show an additional effect, but it was at this time that lipoperoxidation was significantly reduced, although the protein oxidation showed no change. It was concluded that the first dose of folic acid was efficient in reducing homocysteine concentrations, without normalization of values. The participation of hyperhomocysteinemia in oxidative stress appeared to be partial, but in combination with dialysis treatment, may contribute to the induction of an oxidative environment in this group. The possible antioxidant action of folate must also be considered in this case, acting directly against lipoperoxidation or through hyperhomocysteinemia control. Routine supplementations of folic acid and other antioxidant vitamins should be considered in hemodialysis in order to reduce homocysteine levels to lower values, that although not normal, may be more beneficial in minimizing the cardiovascular risk in this group.