Background: Endothelial dysfunction is common in cardiac transplant recipients and predicts the development of transplant coronary artery disease. Hyperhomocysteinemia is associated with endothelial dysfunction in the general population, is common in transplant recipients, and has been associated with transplant coronary artery disease. Thus therapy that decreases homocysteine concentrations might also improve endothelial function and decrease the risk of transplant coronary artery disease. Folate and pyridoxine are important cofactors in distinct aspects of homocysteine metabolism. The purpose of this study was to determine whether folate or pyridoxine supplementation improves endothelial function in cardiac transplant recipients.
Methods and results: This was a double-blind, randomized, placebo-controlled trial. We assigned 31 transplant recipients to either pyridoxine (n = 11:100 mg/day), folate (n = 12:5 mg/day), or placebo (n = 8) for 10 weeks. Fasting and post-methionine-load (methionine 100 mg/kg orally) homocysteine concentrations were determined. Brachial artery flow-mediated dilatation was used as a measure of endothelial function. At follow-up, we noted no significant changes in homocysteine concentrations in any of the groups. However, pyridoxine supplementation was associated with a significant improvement in endothelial function (2.8 +/- 6.7 to 6.9 +/- 6.3, p = 0.05). No significant changes were seen in patients treated with folate or placebo.
Conclusions: Pyridoxine, but not folate supplementation, significantly improves endothelial function in cardiac transplant recipients.