Isolation of Plasma Lipoproteins as a Source of Extracellular RNA

Plasma lipoproteins are essential vehicles of lipid distribution for cellular energy and structural requirements as well as for excretion of lipid excess. Imbalances in lipoprotein metabolism are known to contribute to metabolic diseases ranging from vascular inflammation and atherosclerosis to obesity and diabetes. The lipid and protein cargo carried by lipoprotein subclasses have long been the focus of studies exploring the contribution of plasma lipoproteins in health and in metabolic disorders. More recent studies have revealed the presence of noncoding RNA as a new form of cargo carried by plasma lipoproteins. Lipoprotein-associated microRNAs have been identified to distribute differentially among plasma lipoprotein subclasses and contribute to cellular signaling. These findings highlight plasma lipoprotein-associated RNA as a potential source of biological signaling and warrant a renewed interest in the study of plasma lipoprotein biology. This chapter describes principles and methods based on density ultracentrifugation and size exclusion chromatography for the isolation of plasma lipoproteins as a source of extracellular RNA.