Screening of Lipoperoxides Performed in Low Density Lipoprotein Isolated by a Polyanion Precipitation Method. Its Relationship with Seric Triglyceride Levels

pp 499-506

Abstract

We describe a simple and sensitive methodology developed for detection of preformed lipid peroxides (LPO) in low-density lipoprotein (LDL). The iodometric assay of El-Saadani et al (J Lipid Res,1989; 30: 627-630) was adapted to the fraction containing LDL isolated by polyanion precipitation avoiding ultracentrifugation. This fraction also includes intermediate density lipoprotein. We performed the stratification of 53 individuals by their serum triglyceride levels (TG) and the highest quartile showed a highly significant elevation ofLDL-LPO compared with the lowest one (69.2±41.2vs 22.9 ± 10.0 nmol/mg Ldl-apoB, p < 0.001). LDL-LPO concentration also showed a strong correlation with TG (r = 0.73, p < 0.00001) and significant inverse correlations with high density lipoprotein cholesterol (HDL-C) and HDL 3-C subfraction (r = -0.37,p < 0.01 and r = -0.38, p = 0.01, respectively). The TG/HDL-C ratio, which is closely associated with insulin resistance, was strongly correlated with LDL-LPO (r = 0.83, p < 0.00001). Significant elevations of LPO were seen in phenotypic hyperlipoproteinemias (HLP) lib and IV (p <'0.01 and p < 0.02, respectively). When we expressed LPO in mol/mol of LDL-apo B, 2 and 2.5 fold higher values were found in types II b and IV HLP, respectively, com-pared with normolipidemic subjects. This finding suggests a more oxidative environment for apo Bin both phenotypes. No variations in LPO were found in type Ila HLP. This simple essay for in vivo detection of LDL-LPO, emphasizes the possible atherogenic effect of TG through their oxidativecapacity and suggests the integration of LPO to thecluster of associated risk factors: high TG, lowHDL-C and insulin resistance.