Effect of vitamin E on endothelial vasodilator function in patients with hypercholesterolemia, chronic smoking or both

OBJECTIVES The purpose of this study was to test the hypothesis that long-t erm supplementation with Vitamin E improves endothelium-dependent relaxatio n in hypercholesterolemia patients and/or chronic smoking, two risk factors that have been shown to be associated with increased radical formation. BACKGROUND Experimental evidence suggests that oxidized low density lipopro tein (LDL) impairs endothelium-dependent relaxation, and vitamin E, a lipid -soluble antioxidant, reduces the oxidation of LDL. METHODS Thirteen subjects with hypercholesterolemia, 14 smokers and 15 hype rcholesterolemic smokers were enrolled in a double-blind, placebo-controlle d study. After baseline measurements of plasma autoantibodies against oxidi zed LDL and assessment of endothelium-dependent relaxation using intra-arte rial forearm infusions of acetylcholine, participants within each group wer e randomly assigned in a 1:2 fashion to receive either placebo or vitamin E for 4 months, when plasma levels of autoantibodies against oxidized LDL an d vascular function were reassessed. RESULTS Vitamin E significantly augmented endothelium-dependent relaxation in hypercholesterolemic smokers but not in patients with either hypercholes terolemia or chronic smoking. At baseline, hypercholesterolemic smokers had significantly higher autoantibody levels against oxidized LDL (compared wi th the other two groups), which were significantly reduced after 4 months o f vitamin E supplementation. There was a significant relationship between i mprovement in acetylcholine-induced vasodilation and the change in autoanti body titer against oxidized LDL (r = -0.59; p = 0.002). CONCLUSIONS Long-term vitamin E supplementation improves endothelium-depend ent relaxation in forearm resistance Vessels of hypercholesterolemic smoker s, which are characterized by increased levels of autoantibodies against ox idized LDL. These findings may suggest that the beneficial effect of vitami n E is confined to subjects with increased exposure to oxidized LDL. (C) 19 99 by the American College of Cardiology.