Published Online
on August 4, 2003

A more recent version of this article appeared on August 19, 2003

This Article Full Text (PDF) All Versions of this Article: 108/7/808    most recent 01.CIR.0000084552.54277.64v1 Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Request Permissions Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Wakatsuki, A. Articles by Fukaya, T. Search for Related Content PubMed PubMed Citation Articles by Wakatsuki, A. Articles by Fukaya, T. Pubmed/NCBI databases Compound via MeSH Substance via MeSH Hazardous Substances DB ESTRADIOL ESTROGENIC SUBSTANCES, CONJUGATED ESTRONE Related Collections Lipid and lipoprotein metabolism

Submitted on April 8, 2003
Revised on May 28, 2003
Accepted on May 28, 2003

Effect of Lower Dose of Oral Conjugated Equine Estrogen on Size and Oxidative Susceptibility of Low-Density Lipoprotein Particles in Postmenopausal Women

Akihiko Wakatsuki MD^*, Yuji Okatani MD, Nobuo Ikenoue MD, Koichi Shinohara MD, Kazushi Watanabe MD, and Takao Fukaya MD

From the Department of Obstetrics and Gynecology, Kochi Medical School, Kochi, Japan.

Background--Estrogen replacement therapy (ERT) has an antioxidant effect that opposes the oxidation of LDL. Oral ERT-induced increases in plasma triglyceride, however, are associated with decreased LDL size, which may counteract this antioxidant effect. Because lower doses of oral estrogen do not affect plasma triglyceride concentrations, LDL size might not change, and the antioxidant effect of estrogen might be preserved. We investigated whether a lower dose of oral estrogen could eliminate the adverse effects of high-dose oral ERT on the size and oxidative susceptibility of LDL in postmenopausal women.

Methods and Results--Postmenopausal women received no treatment or were treated with oral conjugated equine estrogen (CEE) 0.625 or 0.3125 mg/d for 3 months. CEE at a dose of 0.625 mg/d significantly increased plasma triglyceride concentrations and decreased LDL diameter, but the concentrations of LDL-derived thiobarbituric acid reactive substances (TBARS) and lag time for conjugated diene formation did not change. In contrast, 0.3125 mg of CEE did not affect plasma triglyceride concentrations or LDL diameter and significantly decreased LDL-derived TBARS concentrations and significantly prolonged LDL lag time. Estrogen-induced changes in LDL diameter correlated negatively with changes in plasma triglyceride (r=-0.44, P<0.01) and LDL-derived TBARS (r=-0.57, P<0.001) but positively with changes in LDL lag time (r=0.42, P<0.01).

Conclusions--Because oral CEE at a dose of 0.3125 mg/d does not elevate plasma triglyceride, resulting in unchanged size of LDL particles that are resistant to oxidation, the antioxidant effect of estrogen can be preserved.

Key words: lipoproteins • hormones • women

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