Serum Paraoxonase-1 Activities and Their Relationship with Plasma oxHDL and oxLDL levels in dyslipidemic individuals with different lipid content

Dyslipidemia is one of the most important risk factors for atherosclerosis. Oxidized low-density lipoprotein (oxLDL) plays an important role in the pathogenesis of atherosclerosis. In contrast, high-density lipoprotein (HDL) has antiatherogenic properties due to its reverse cholesterol transport mechanism and the enzyme paraoxonase-1 (PON-1). PON-1 has paraoxonase, arylesterase and lactonase activities. In our study, we aimed to investigate the relationship between serum PON-1 levels and enzyme activities and serum oxLDL and serum oxidized high density lipoprotein (oxHDL) levels in dyslipidemic individuals with different lipid content. The study group consisted of 160 volunteers including normocholesterolemic normotriglyceridemic (n=40), normocholesterolemic hypertriglyceridemic (n=40), hypercholesterolemic normotriglyceridemic (n=40) and hypercholesterolemic hypertriglyceridemic (n=40). OxLDL, oxHDL and PON-1 levels were determined by enzyme-linked immunosorbent assay (ELISA). Enzyme activities were measured by spectrophotometric methods. In the whole study group (n=160), serum oxLDL levels were positively correlated with total cholesterol (r=0.523, p=0.0001), triglyceride (r=0.354, p=0.0001), low density lipoprotein (LDL-C) (r=0.399, p=0.0001) and oxHDL (r=0.235, p=0.003) levels. In hypercholesterolemic individuals, serum oxHDL levels were negatively correlated with specific paraoxonase enzyme activity (specific PON EA) (r=-0.460, p=0.0001), specific arylesterase enzyme activity (specific ARE EA) (r=-0.616, p=0.0001) and specific lactonase enzyme activity (specific LAC EA) (r=-0.538, p=0.0001). It was concluded that high-density lipoprotein cholesterol (HDL-C) concentrations and PON activities of hypertriglyceridemic individuals were more significantly affected than hypercholesterolemic individuals, not only the levels but also the structural proteins and enzymes of HDL-C were affected in dyslipidemic conditions and this may be related to increased serum oxLDL and serum oxHDL concentrations.