Changes in apolipoprotein E-containing high-density lipoprotein (HDL) have little impact on HDL-cholesterol measurements using homogeneous assays in normolipidemic and dyslipidemic subjects

Abstract Background High-density lipoprotein-cholesterol (HDL-C) is generally measured using several homogeneous assays. We aimed to clarify whether apolipoprotein E-containing HDL (apoE-HDL) subfractions are altered during storage, and if so, whether such changes affect the HDL-C concentration measured using homogeneous assays. Methods We stored serum from normolipidemic (n = 32) and dyslipidemic (n = 17) subjects at 4 °C for up to 7 days. ApoE-HDL subfractions were analyzed using native 2-dimensional gel (native 2D-gel) electrophoresis. HDL-C concentrations were determined using 2 precipitation and 4 homogeneous assays. Results Native 2D-gel electrophoresis revealed variously sized apoE-HDL subfractions. After 4 h incubation at 37 °C, subfractions of smaller particles were converted into larger particles by lecithin:cholesterol acyltransferase (LCAT) activity. After 7 days storage at 4 °C, the smaller subfractions were decreased in the normolipidemic group, accompanying increases in larger subfractions, whereas changes in the respective subfractions varied among individuals in the dyslipidemic group. HDL-C concentrations were significantly lower after storage at 4 °C in all assays, except that using Sekisui Medical's reagent. Therefore, changes in HDL-C concentration and apoE-HDL subfractions were independent of each other. Conclusion ApoE-HDL subfractions change during storage, but these changes are not linked to those in HDL-C concentration measured using homogeneous assays.