Serum paraoxonase 1 activity and oxidative markers of LDL in patients with cardiac syndrome X

Abstract

Objective — Myocardial ischaemia in cardiac syndrome X (CSX) is believed to be due to microvascular dysfunction. Increased oxidative stress is one of the suspected mechanisms of microvascular dysfunction. The aim of this study was to evaluate the oxidative status in patients with CSX, by determining serum paraoxonase-1 (PON1) activity in addition to LDL-oxidation markers.

Methods and results — This cross-sectional study consisted of patients with CSX (group I, n = 30), patients with coronary artery disease (group II, n = 31), and healthy controls (group III, n = 32). Lipid parameters, PON-1 activity, and LDL oxidation markers (conjugated-diene and thiobarbituric acid-reactive substance-TBARS) were measured. Endothelium-dependent vasodilatation was determined by brachial artery ultrasonography.There were no significant differences in serum LDL, apolipopro-tein-B, baseline LDL-diene, and LDL-TBARS levels between groups.There were no differences in both apolipoprotein-A1 and HDL levels between group I and group III. Apolipoprotein-A1 and HDL levels were significantly lower in group II than group I patients (P < 0.001). PON-1 activity was lowest in group II patients. Average PON-1 activity in group I was in between of group II and group III.The percent change of LDL-diene levels after stimulation was significantly higher in group II than in groups I and III (P = 0.005 and P = 0.02, respectively).The percent change of LDL-TBARS levels was lowest in group I (P = 0.03). There was a moderate correlation between endothelium-dependent vasodilatation and PON-1 activity in group I (r = 0.43, P = 0.04).

Conclusions — Enhanced oxidative stress might be one of the causes of impaired endothelial functions resulting in myocardial ischaemia and chest pain in patients with CSX.The relatively preserved HDL and apolipoprotein-A1 levels in patients with CSX might be a protective mechanism against progression of coronary microvascular dysfunction to atherosclerotic coronary artery disease.

Key Words:

• cardiac syndrome X
• paraoxonase
• LDL oxidation markers
• endothelium-dependent vasodilation