α-Tocopherol is important to inhibit low-density lipoprotein oxidation in smokers

Smoking is recognized as an independent risk factor for atherosclerosis. This study was designed to study the effect of smoking on plasma and low-density lipoprotein (LDL) antioxidant concentrations and LDL oxidation susceptibility. A total of 89 subjects, consisting of 27 smokers and 62 nonsmokers, were recruited. Biochemical values and plasma ascorbic acid, α-tocopherol, and LDL α-tocopherol levels were assessed. LDL lag time, oxidation rate, and correlation between LDL α-tocopherol and LDL oxidation rate were determined. No differences were demonstrated for ascorbic acid and α-tocopherol concentrations in plasma between smokers and nonsmokers; however, LDL α-tocopherol was significantly higher for nonsmokers (P = 0.012). Furthermore, the lag time for LDL oxidation was significantly longer for nonsmokers (P = 0.019), whereas the LDL oxidation rate was significantly greater for smokers (P = 0.018). Additionally, a highly significant negative correlation was demonstrated for LDL α-tocopherol concentration and LDL oxidation rate in smokers (r = -0.440, P = 0.026), but not in nonsmokers. The results of this study suggest that LDL α-tocopherol is more susceptible to oxidative stress caused by smoking than ascorbic acid and α-tocopherol in plasma. For smokers, the presence of α-tocopherol in LDL effectively protects LDL from oxidation.