Oxidative stress in white coat hypertension; role of paraoxonase.

Oxidative stress in sustained hypertension was shown with several biochemical parameters. Oxidized low-density lipoprotein (oxLDL) plays an important role during the atherosclerosis process and paraoxonase (PON1) can significantly inhibit lipid peroxidation. Serum PON1 activity, oxLDL and malondialdehyde (MDA) concentrations and their relationship with serum lipid parameters and systolic and diastolic blood pressures (SBP and DBP) were determined in subjects with white coat hypertension (WCH), sustained hypertension (HT) and normotension (NT). The study group consisted of a total of 86 subjects, 30 with WCH (14 male, 16 female subjects), 30 with HT (13 male, 17 female subjects) and 26 with NT (12 male, 14 female subjects). Both white coat hypertensive and hypertensive subjects had significantly higher levels of MDA than normotensives (P<0.026 and P<0.001, respectively). The oxLDL level of the HT group was significantly higher than the NT group (P<0.023). The WCH group had an oxLDL level similar to both hypertensive and normotensive groups. HT and WCH groups had significantly lower PON1 levels than the normotensive group (P<0.001). oxLDL correlated with MDA positively (P=0.008), and PON1 negatively (P=0.008). A negative correlation between MDA and PON1 (P=0.014) was detected. MDA correlated positively with both SBP and DBP (P=0.001), while PON1 correlated with both of them negatively (P=0.01 and P=0.008, respectively). OxLDL correlated with diastolic blood pressure positively (P=0.008). Our data demonstrate that oxidative stress increase in WCH is associated with a decrease in PON1 activity. The reduction in PON1 activity may be one of the factors leading to an increase in oxidative status in WCH.