Further Aspects on the Characterization of High and Very Low Density Lipoproteins in Patients with Liver Disease

Various liver disorders are often associated with decreased concentrations of serum α‐ and pre‐ β‐lipoproteins. The decreased concentrations of high density lipoproteins (HDL) is primarily due to an impaired lipid binding capacity of apolipoprotein A (apo A), the major protein moiety of HDL. This results in an abnormally high protein/lipid ratio and in severe cases in a lack of neutral lipids in this density class. In contrast to normal α‐lipoproteins this fraction does not stain for lipids but shows two distinct and nonidentical precipitin bands on immunoelectrophoresis and immunodiffusion. The isolated very low density lipoproteins (VLDL) from patients with liver disorders revealed a regular particle size and a protein/lipid ratio close to normal but developed β‐mobility on electrophoresis. Analysis of the protein moieties of this fraction indicated a lack of apolipoprotein A. It is suggested that disturbed liver function leads to the synthesis of an altered apo A resulting (a) in α‐lipoproteins with dissociated apo A peptides and (b) in very low density lipoproteins devoid of apo A. Both findings may be explained by the impaired capacity of this apolipoprotein A to bind neutral lipids.