Plasma α-tocopherol and coronary endothelium-dependent vasodilator function

Abstract

Background - In the presence of atherosclerosis, the coronary endothelial vasomotor response to acetylcholine is frequently abnormal but is variable between patients. We tested the hypothesis that the plasma concentration of α-tocopherol is associated with the preservation of nitric oxide-mediated endothelium-dependent vasomotion. Methods and Results - We studied 15 men and 6 women (mean age 61 ± 10 years) at coronary angiography who were not taking vitamin supplements. Coronary endothelium-dependent and - independent vasomotion was assessed by intracoronary infusions of acetylcholine and nitroglycerin. The vasomotor responses were compared with the plasma concentration of α-tocopherol and the plasma α-tocopherol concentration relative to total lipid (total cholesterol plus triglycerides). The mean plasma α-tocopherol was 25.6±6.1 μmol/L, total cholesterol 193±27 mg/dL, triglycerides 115±66 mg/dL, and α-tocopherol to total lipid 4.2±0.9 μmol · L-1 · (mmol/L)-1. The mean vasomotor response to acetylcholine was -1% (range -33% to 28%) and to nitroglycerin 22% (range 0% to 54%). Plasma α-tocopherol was significantly correlated with the acetylcholine response (r=0.49, P<0.05) but not the nitroglycerin response (r=0.13, P>0.05). The acetylcholine response remained significant after adjustment for other potential sources of oxidant stress (total cholesterol, diabetes mellitus, smoking, angina class) (P<0.01). The relative concentration of α-tocopherol to total lipid was not related to endothelial function (r=0.24, P=0.3, n=20). Conclusions - α-Tocopherol may preserve endothelial vasomotor function in patients with coronary atherosclerosis. This effect may be related primarily to the action of α-tocopherol in the vascular wall. Further studies that assess the impact of α-tocopherol supplementation as therapy of endothelial dysfunction are justified.