17 beta-estradiol affects in vivo the low density lipoprotein composition,particle size, and oxidizability

The aim of this study was to explore the possible modifications induced by 17 beta -estradiol (E-2) in vivo on low-density lipoprotein (LDL) lipid com position, particle size, and oxidizability. For this purpose, women were re cruited from an in vitro fertilization program, ranging their plasma E-2 le vels from less than 12 pg/ml to more than 2000 pg/ml at the end of the trea tment. The LDL lipid constituents were analyzed by thin layer chromatograph y and image analysis, and the LDL diameter was calculated from the lipid da ta. The results showed that high plasma E-2 levels were associated with sma ller LDL particles, with lower amounts of free and esterified cholesterol a nd an increased relative content of a-tocopherol. The hormonal treatment pr oduced a remodelation of the LDL acyl composition, rendering a lipoprotein enriched in saturated fatty acids, with a poorer polyunsaturated fatty acid content. These alterations in the physicochemical properties of LDL parall eled changes in the susceptibility of LDL to in vitro oxidation induced by both Cu2+ and the peroxyl radical generator, 2,2'-azobis (2-amidinopropane) , these changes being mainly reflected in a reduced maximum oxidation rate. The in vivo changes in the physicochemical properties of LDL induced by E- 2 could explain some of the antiatherogenic actions of estrogens. (C) 2001 Elsevier Science Inc.