Homocysteine-lowering treatment with folic acid plus vitamin B6 lowers urinary albumin excretion but not plasma markers of endothelial function or C-reactive protein: further analysis of secondary end-points of a randomized clinical trial

Background Hyperhomocysteinaemia is an independent risk factor for atherosclerosis and is thought to induce its effects through causing endothelial dysfunction. We studied the effect of homocysteine-lowering treatment with folic acid plus vitamin B-6 on urinary and plasma markers of endothelial function, and on plasma C-reactive protein, a marker of chronic inflammation. Design We performed a placebo-controlled 2-year trial among 158 healthy siblings of patients with premature atherosclerotic disease to determine the effect of daily folic acid (5 mg) plus vitamin B-6 (250 mg) treatment as compared with placebo medication (n = 80) on markers of endothelial function (urinary albumin-to-creatinine ratio and plasma concentrations of soluble E-selectin, soluble vascular cell adhesion molecule-1, von Willebrand factor, tissue-type plasminogen activator and plasminogen activator inhibitor-1) and inflammation (C-reactive protein). Outcome variables were assessed at baseline and after 1 and 2 years of treatment. Results Fasting homocysteine concentrations (mumol L-1 ) at baseline and after treatment were 14.7 +/- 8.2 and 7.4 +/- 1.9 in the vitamin and 14.7 +/- 8.8 and 12.0 +/- 5.4 for the placebo group, respectively. Vitamin treatment was associated with a decreased urinary albumin-to-creatinine ratio at follow up [regression coefficient (beta) -0.20 mg mmol(-1) (CI: -0.43-0.03); P = 0.09]. After adjustment for age, sex, baseline concentrations of postmethionine total homocysteine plus the baseline albumin-to-creatinine ratio, the beta was -0.23 mg mmol(-1) (CI: -0.43 to -0.02; P = 0.03), which amounts to a decrease of approximately 20%. There was no apparent effect of vitamin treatment on the other markers. Conclusions Homocysteine-lowering vitamin treatment in healthy siblings of patients with premature atherosclerotic disease is associated with a decreased urinary albumin-to-creatinine ratio, but not with other markers of endothelial dysfunction, or in plasma C-reactive protein. The clinical significance of these findings remains to be determined.