Marta Marcinkowska

Oxidative modifications of lipoproteins play a crucial role in the initiation of atherosclerotic cardiovascular diseases (ASCVDs). Nowadays, the one effective strategy for the treatment of patients with hyperlipoproteinemia(a) is lipoprotein apheresis (LA), which has a pleiotropic effect on reducing the risk of ASCVDs. The significance of oxidative susceptibility of the LDL fraction in ASCVDs has been extensively studied. Whether LA alters the susceptibility of lipoprotein(a) to oxidative modifications remains an unresolved issue. In this study, we isolated lipoprotein fractions by ultracentrifugation in patients with hyperlipoproteinemia(a) undergoing apheresis (LA group) at three time points and patients who were qualified for LA but did not consent to the procedure (non-LA group). We performed copper-mediated oxidation of Lp(a) and LDL fractions and determined autotaxin activity. After apheresis, we observed a lower susceptibility to oxidation of the Lp(a) and LDL fractions as expressed by the extended value of oxidation lag time, decreased slope of the oxidation curve, and decreased final concentration of conjugated dienes. No significant differences were found between these parameters before and 7 days after LA. Additionally, both patients undergoing and not undergoing LA had a significant correlation between autotaxin activity and all parameters characterizing susceptibility to oxidation in the Lp(a) fraction. Our results demonstrate that the pleiotropic effect of apheresis may be related to the reduced oxidative susceptibility of Lp(a) and LDL particles, which may influence the reduction in ASCVD risk in patients undergoing apheresis. The results of the rebound effect 7 days after LA will contribute to a better definition of apheresis frequency guidelines.

Objectives: Low-density lipoprotein cholesterol (LDL-C) is the main laboratory parameter used for the management of cardiovascular disease. The aim of this study was to compare measured LDL-C with LDL-C as calculated by the Friedewald, Martin/Hopkins, Vujovic, and Sampson formulas with regard to triglyceride (TG), LDL-C and non-high-density lipoprotein cholesterol (non-HDL-C)/TG ratio. Methods: The 1,209 calculated LDL-C results were compared with LDL-C measured using ultracentrifugation-precipitation (first study) and direct (second study) methods. The Passing-Bablok regression was applied to compare the methods. The percentage difference between calculated and measured LDL-C (total error) and the number of results exceeding the total error goal of 12% were established. Results: There was good correlation between the measurement and calculation methods (r 0.962–0.985). The median total error ranged from −2.7%/+1.4% (first/second study) for Vujovic formula to −6.7%/−4.3% for Friedewald formula. The numbers of underestimated results exceeding the total error goal of 12% were 67 (Vujovic), 134 (Martin/Hopkins), 157 (Samspon), and 239 (Friedewald). Less than 7% of those results were obtained for samples with TG >4.5 mmol/L. From 57% (Martin/Hopkins) to 81% (Vujovic) of underestimated results were obtained for samples with a non-HDL-C/TG ratio of <2.4. Conclusions: The Martin/Hopkins, Vujovic and Sampson formulas appear to be more accurate than the Friedewald formula. To minimize the number of significantly underestimated LDL-C results, we propose the implementation of risk categories according to non-HDL-C/TG ratio and suggest that for samples with a non-HDL-C/TG ratio of <1.2, the LDL-C level should not be calculated but measured independently from TG level.