Journal of Lipid Research, Vol. 23, 201-204, January 1982
Copyright © 1982 by Lipid Research, Inc.

Rapid method for determining cholesteryl ester transitions of apoB-containing lipoproteins

D. A. Waugh and D. M. Small

Biophysics Institute, Boston University School of Medicine, Boston, MA 02118

A wide variety of cholesteryl ester-rich apoB-containing lipoproteins undergo an order-disorder transition in the cholesteryl ester core at approximately normal body temperature. The transition occurs over several °C with the mid-point being as high as 57°C in some cholesterol-fed animals. The transition mid-point of normal human low density lipoprotein (LDL) appears to vary from as low as 26°C to about body temperature. However, to screen a large population of patients at risk for atheroscerlotic cardiovascular disease (ACD), a rapid method for determining the transition temperature of LDL is needed. Since apoB-containing lipoproteins (VLDL and LDL) are readily precipitated from plasma by dextran sulfate and magnesium sulfate, we have studied the thermal properties of this precipitate using differential scanning calorimetry (DSC). The VLDL-LDL precipitate undergoes a reversible thermal transition similar in transition temperature and enthalpy to the cholesteryl ester transition of isolated pure LDL. The transition is seen with the precipitate from VLDL-free plasma, but no transition is seen when VLDL and LDL have been removed. Cholesteryl ester-rich apoB containing lipoproteins were isolated from a variety of sources (man, cholesterol-fed monkeys, and rabbits) and their transition temperatures compared with the apoB-containing lipoprotein precipitates from the same source. The mid-point of individual transitions varied over a wide range (17-57°C) and the correlation between the pure lipoprotein and the plasma precipitate was strong (r = 0.98, P < 0.001. Thus, DSC of the plasma apoB precipitate may be used as a rapid method of determining the cholesteryl ester transition of LDL and other apoB-containing lipoproteins.—Waugh, D. A., and D. M. Small. Rapid method for determining cholesteryl ester transitions of apoB-containing lipoproteins.

Supplementary key words differential scanning calorimetry • VLDL • LDL • dextran sulfate-Mg²⁺ precipitation of apoB-containing lipoproteins • lipid transition • cholesteryl esters • lipoprotein transitions

Submitted on June 3, 1981
Revised on September 4, 1981

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