Evidence for alterations in circulating low-molecular-weight antioxidants and increased lipid peroxidation in smokers on hemodialysis

Background/Aim: Cardiovascular disease is the major cause of mortality in d ialysis patients, accounting for about 40% of deaths in most large registri es. Oxidative stress has been strongly implicated in the pathogenesis of th ese events. As end-stage renal disease is a state of elevated free radical activity, the aim of the present study was to investigate the negative impa ct of smoking in 57 male hemodialysis patients. Methods: The patients, who were 20-85 yea rs of age (mean age 51.0 +/- 14 years), had been on hemodial ysis for at least 6 months before participating in this study. Fasting bloo d sampling for serum lipid, albumin, urate and lipophilic antioxidants such as tocopherols, carotenes, ascorbate and lipid peroxides was performed. Re sults: The plasma malondialdehyde (MDA) concentration was significantly hig her in hemodialysis patients who smoked compared to hemodialysis patients w ho were nonsmokers (1.92 +/- 0.52 vs. 1.59 +/- 0.42 nmol/ml, p = 0.006). No association was found between levels of MDA in smokers and parameters such as body mass index, serum cholesterol, serum triglycerides and smoking ind ex. There were no significant differences in the plasma levels of uric acid , alpha -tocopherol, gamma -tocopherol, delta -tocopherol, alpha -carotene, beta -carotene and retinol between the two groups. A significantly lower l evel of plasma ascorbate was observed in hemodialysis patients who smoked c ompared to the nonsmoking hemodialysis patients or healthy controls (4.59 /- 4.0 vs. 9.57 +/- 4.0 and 10.16 +/- 4.6 mug/ml, p < 0.05). Moreover, in s mokers, the plasma levels of ascorbate were negatively correlated with the levels of plasma MDA (r = -0.43, p < 0.001) of each patient. Partial correl ation analysis of the plasma levels of the measured antioxidants and the sm oking index revealed a negative correlation between the plasma levels of li pid-normalized lycopene and the smoking index (r = -0.53, p < 0.05). Conclu sion: Our data suggest that cigarette smoking further increases plasma-circ ulating products of lipid peroxidation, which are already increased in nons moking hemodialysis patients as compared to matched healthy controls. The l ower plasma levels of ascorbate in hemodialysis patients who smoke suggest that these patients may be more susceptible to oxidative tissue damage caus ed by smoking. Copyright (C) 2001 S. Karger AG, Basel.