Application of electrophoretic techniques to the diagnosis of disorders of lipoprotein metabolism. Examples at the levels of lipoproteins and apolipoproteins Review Article

Disorders of lipoprotein metabolism are strongly related to the development of chronic degenerative diseases of the cardiovascular and of the central nervous system. The analysis of lipoproteins and apolipoproteins is essential to the assessment of cardiovascular risk and to the monitoring of individuals on treatment. We provide an overview of electrophoretic methods serving the analysis of lipoproteins in body fluids, placing particular emphasis on those techniques that have contributed to the classification of lipoprotein disorders and to the elucidation of the structure and function of lipoproteins. Electrophoresis in agarose separates the major classes of lipoproteins in the plasma. During recent years, considerable progress has been made in the quantification of electrophoretically separated lipoproteins using enzymatic staining of cholesterol and triglycerides. Evidence is now accumulating that the distinction of subclasses of low density lipoproteins and high density lipoproteins is clinically significant as well, and electrophoresis-based methods have become available to examine lipoprotein microheterogeneity. One- and two-dimensional immunoelectrophoresis has been used to characterize and to quantify lipoproteins and apolipoproteins. Apolipoprotein isoforms have been separated according to size and isoelectric point or a combination of both under denaturing conditions. In the clinical laboratory, these techniques have mainly been applied to the analysis of the apolipoprotein (a) size polymorphism and to the determination of the apolipoprotein E phenotype. Although immunoelectrophoretic approaches to the quantification of apolipoproteins will widely be replaced by automated methods like enzyme immunoassays, nephelometry and turbidimetry, we expect that electrophoresis will continue to make significant contributions to our understanding of disorders of the lipoprotein metabolism and thus provide new and more precise tools to identify individuals at an augmented risk of cardiovascular and other chronic diseases.