Sialic acid content of LDL and lipoprotein metabolism in combined hyperlipidemia and primary moderate hypercholesterolemia.

Low density lipoprotein (LDL) with low sialic acid content has been shown to cause intracellular lipid accumulation and therefore is suggested to be atherogenic. We investigated the sialic acid content of total LDL and its subfractions, and their relations to lipoprotein kinetics in 22 subjects with primary moderate hypercholesterolemia (IIa) and in 21 subjects with combined hyperlipidemia (IIb) matched for age, sex, BMI and the frequency of coronary artery disease. Sialic acid to protein ratio decreased gradually from VLDL and IDL to light and dense LDL and HDL, but was high in very dense LDL probably due to presence of Lp(a). Sialic acid to apo B ratio was significantly lower in dense and very dense subfractions of IIb than IIa. The sialic acid/apo B ratios of dense and very dense LDL subfractions were interrelated and were negatively associated with their cholesterol and triglyceride concentrations, and with the transport rate (TR) for dense LDL apo B. The only metabolic variable differing between the groups was the TR for dense LDL apo B, which was significantly higher in IIb vs. IIa. In addition, the TR for dense LDL apo B was positively associated with the esterification percentage of LDL cholesterol. In conclusion, low sialic acid content in dense and very dense LDL subfractions was associated with enhanced TR for LDL apo B and type IIb dyslipidemia.