Blunted nocturnal fall in blood pressure and oxidative stress in men and women with essential hypertension

Abstract

Low-density lipoprotein oxidation and antioxidant vitamins E and C were investigated in dipper (nocturnal blood pressure fall > 10%) and nondipper (nocturnal blood pressure fall < 10%) hypertensives. We studied 40 dippers and 28 nondippers balanced for gender, age, and body mass index. Blood samples were drawn for lipid profile determination, assessment of thiobarbituric acid-reactive substances, and fluorescent products of lipid peroxidation in native low-density lipoprotein, evaluation of susceptibility to low-density lipoprotein oxidation in vitro (lag phase and propagation rate), and determination of low-density lipoprotein vitamin E and plasma vitamins E and C contents. Compared with dippers, nondippers had significantly higher thiobarbituric acid-reactive substances and fluorescent products of lipid peroxidation (0.63 ± 0.1 v 0.77 ± 0.08 nmol malondialdehyde/mg low-density lipoprotein protein, and 14.5 ± 6 v 17.9 ± 4 units of relative fluorescence/mg low-density lipoprotein protein, respectively, both P < .05), shorter lag phase (56 ± 13 v 49 ± 9 min, P < .05), and lower plasma vitamin C content (42 ± 9 v 35 ± 10 μmol/L, P < .05). When gender was taken into account, differences were not significant between dipper and nondipper men, whereas, compared with dipper women, nondipper women showed significantly higher thiobarbituric acid-reactive substances and fluorescent products of lipid peroxidation (0.56 ± 0.1 v 0.77 ± 0.07 nmol malondialdehyde/mg low-density lipoprotein protein, and 12.5 ± 4 v 17.5 ± 4.6 units of relative fluorescence/mg low-density lipoprotein protein, respectively, both P < .05), shorter lag phase (62.5 ± 11 v 49 ± 9.5 min, P < .05), and lower plasma vitamin C content (44.9 ± 10 v 34.7 ± 10.8 μmol/L, P < .05). Given the role of low-density lipoprotein oxidation in the pathogenesis of atherosclerosis and that of vitamin C in protecting against it, our data suggest that nondippers, especially among women, show higher atherogenic risk than dippers.