Effects of folic acid before and after vitamin B12 on plasma homocysteine concentrations in hemodialysis patients with known MTHFR genotypes.

Background: Treatment with folic acid and vitamin B12 appears to be effective in lowering total plasma homocysteine (tHcy) concentrations, but whether vitamin B12 alone lowers tHcy in patients with normal vitamin B12 status is unknown. The aims of the present study were to explore the effect of individual supplementation with folic acid or vitamin B12 on tHcy concentrations in hemodialysis (HD) patients and to compare changes in tHcy concentrations with MTHFR genotype.

Methods: We recruited 200 HD patients (119 men) from the "Umberto I" Hospital (Frosinone, Italy) and the Dialysis Unit of University Hospital "Tor Vergata". These patients were randomized blindly into 2 groups of 100 each. Unfortunately, during the study, 36 patients in the first group and 16 in the second group died. The first group was treated initially with vitamin B12 for 2 months and with folic acid for a following 2 months. The second group was treated initially with folic acid and then with vitamin B12. Samples were drawn before administration of either, after the first and second periods, and again 2 months after treatment.

Results: The concentrations of tHcy decreased in both groups after the consecutive vitamin therapies, and the decrease was genotype-dependent. The decrease was greater for the T/T genotype (P <0.05) and was more significant when the treatment was started with folic acid (P <0.01).

Conclusion: The alternating vitamin treatment demonstrated for the first time the importance of folate therapy and the secondary contribution of vitamin B12 in lowering tHcy in HD patients.