The separation of plasma lipoproteins using gel electrofocusing and polyacrylamide gradient gel electrophoresis

Elucidation of lipoprotein particles structure by proteomic analysis

Lipoproteins are responsible for lipid packaging and transport through the bloodstream, and for their delivery to target tissues. Their participation in process, such as inflammation and innate immunity has also been suggested recently. Lipoprotein particles have very complex biochemical structures, which result from intricate processes involving coordinated mechanisms of protein and lipid synthesis, intracellular assembling and trafficking, and intra- and extracellular metabolism. Alterations in these mechanisms cause several negative effects on human health. The ability of current proteomic approaches to dissect the dynamic nature of complex particles revealing protein composition and post-translational modifications is shedding further light on lipoprotein structures and functions. This review summarizes lipoprotein classification, biogenesis and metabolism as well as discussing how the results of 20 proteomics-based reports integrate our knowledge on both their biochemical composition and their effects on target cells, thus contributing to reveal the possible functions.

Historical milestones in measurement of HDL-cholesterol: Impact on clinical and laboratory practice

High-density lipoprotein cholesterol (HDL-C) comprises a family of particles with differing physicochemical characteristics. Continuing progress in improving HDL-C analysis has originated from two separate fields-one clinical, reflecting increased attention to HDL-C in estimating risk for coronary heart disease (CHD), and the other analytical, reflecting increased emphasis on finding more reliable and cost-effective HDL-C assays. Epidemiologic and prospective studies established the inverse association of HDL-C with CHD risk, a relationship that is consistent with protective mechanisms demonstrated in basic research and animal studies. Atheroprotective and less atheroprotective HDL subpopulations have been described. Guidelines on primary and secondary CHD prevention, which increased the workload in clinical laboratories, have led to a revolution in HDL-C assay technology. Many analytical techniques including ultracentrifugation, electrophoresis, chromatography, and polyanion precipitation methods have been developed to separate and quantify HDL-C and HDL subclasses. More recently developed homogeneous assays enable direct measurement of HDL-C on an automated analyzer, without the need for manual pretreatment to separate non-HDL. Although homogeneous assays show improved accuracy and precision in normal serum, discrepant results exist in samples with atypical lipoprotein characteristics. Hypertriglyceridemia and monoclonal paraproteins are important interfering factors. A novel approach is nuclear magnetic resonance spectroscopy that allows rapid and reliable analysis of lipoprotein subclasses, which may improve the identification of individuals at increased CHD risk. Apolipoprotein A-I, the major protein of HDL, has been proposed as an alternative cardioprotective marker avoiding the analytical limitations of HDL-C.