Effects of lipid composition on the association of plasma proteins with lipid emulsions

Lipid emulsions stabilized with phospholipids provide a means for experimental study of lipid-protein interactions at the emulsion surface. The triacylglycerol-rich plasma lipoproteins can be modeled by emulsions, to determine how associations with plasma proteins may regulate the metabolism of chylomicrons and very-low-density lipoproteins. In these experiments emulsions of methyl oleate, ethyl oleate, glyceryl trioleate, and erythrityl tetraoleate were prepared. In each case the emulsion was stabilized with egg yolk phosphatidylcholine, and cholesterol was present in amounts similar to nascent triacylglycerol-rich lipoproteins. When these four emulsions were incubated with plasma or with plasma subfractions the glyceryl trioleate and erythrityl tetraoleate emulsions bound the plasma apolipoproteins AI, AIV, CII, CIII, and E plus albumin, in patterns similar to lymph chylomicrons. In contrast the methyl oleate and ethyl oleate emulsions bound less proteins overall, and the pattern was different from lymph chylomicrons. Also in comparison with the glyceryl trioleate emulsion, the commercial emulsion Intralipid bound more albumin and less apolipoproteins. The glyceryl trioleate emulsion bound bovine serum albumin in larger amounts than human serum albumin. Emulsions with cores of erythrityl tetraoleate may be useful as experimental substitutes for triacylglycerols in lipoprotein model emulsions.