NATURALLY-OCCURRING MODIFIED LOW-DENSITY LIPOPROTEINS ARE SIMILAR IF NOT IDENTICAL - MORE ELECTRONEGATIVE AND DESIALYLATED LIPOPROTEIN SUBFRACTIONS

Previous studies demonstrated that more electronegative low density li poprotein (LDL) isolated from human blood by ion exchange chromatograp hy has a chemical composition and physical properties similar to desia lylated LDL obtained by lectin chromatography (Avogaro er al., 1988; O rekhov et nl., 1989). In this study, sialic acid content and percentag e of desialylated LDL in the electronegative LDL (LDL(-)) subfraction have been investigated. The sialic acid content of the LDL(-) was 2- t o 6-fold lower than that of native LDL and close to that of desialylat ed LDL. In the native LDL subfraction, 83% of lipoprotein particles di d not bind to the Ricinus communis agglutinin, indicating lack of term inal galactose, presumably appearing as a result of desialylation of L DL carbohydrate chains. By contrast, a major proportion of human LDL(- ) (81%) was bound to the lectin. It was also found that the desialylat ed LDL subfraction consists of 88% LDL(-). Native LDL did nor affect t he contents of free and esterified cholesterol in intimal cells cultur ed from grossly normal human aorta, while LDL(-) and desialylated LDL induced a 1.5- to 3-fold increase in the intracellular content of chol esteryl esters. Thus, LDL(-) is desialylated LDL which induces lipid a ccumulation in intimal cells. Our findings suggest that the LDL(-) par ticle is similar if not identical to the desialylated LDL particle. (C ) 1995 Academic Press, Inc.