Paraoxonase (PON1) activity in patients with subclinical thoracic aortic atherosclerosis

High density lipoprotein (HDL), a powerful antioxidant, protects low density lipoprotein (LDL) particles against oxidative stress. By limiting LDL oxidation, HDL plays an important role in preventing atherosclerosis (AS). The antioxidant effect of HDL is mostly associated with the paraoxonase (PON1) activity. It has been known that increased aortic intima-media thickness (IMT) is an earlier marker AS than carotid IMT. We aimed to investigate the association between thoracic aortic IMT and serum PON1 activity. We studied 133 patients (mean age: 46.3 ± 8 years) who underwent transesophageal echocardiography (TEE) for various indications. The measurements of thoracic aortic IMT by TEE are classified into four grades (1, 2, 3 and 4). Serum PON1 activity was measured spectrophotometrically. Oxidative and anti-oxidative status was evaluated by measuring serum lipid hydroperoxide (LOOH), total anti-oxidant status (TAS). Serum PON1 activity was progressively decreasing from grade 1 IMT to grade 4 IMT (p < 0.001). However, serum LOOH was significantly lower and TAS was significantly higher in patients with grade 1 when compared with other grades. In multiple linear regression analysis, IMT was independently correlated with PON1 activity (β = -0.495, p < 0.001), TAS level (β = -196, p < 0.009), age (β = 0.145, p = 0.029) and LDL cholesterol level (β = 0.169, p = 0.009). Decreased PON1 activity was independently associated with the extent of thoracic AS. PON1 activity may play a role in pathogenesis of thoracic AS besides age, TAS and LDL cholesterol levels.