Role of the estrogen and progestin in hormonal replacement therapy on apolipoprotein A-I kinetics in postmenopausal women.
OBJECTIVE
Plasma high-density lipoprotein (HDL) cholesterol levels are inversely correlated with the risk of developing coronary heart disease. Hormonal replacement therapy (HRT) affects plasma HDL cholesterol levels, with estrogen increasing HDL cholesterol levels and progestins blunting this effect. This study was designed to assess the mechanism responsible for these effects.


METHODS
HDL apolipoprotein A-I (apoA-I) kinetics were studied in 8 healthy postmenopausal women participating in a double-blind, randomized, crossover study comprising 3 phases: placebo, conjugated equine estrogen (CEE) (0.625 mg/d), and CEE plus medroxyprogesterone acetate (MPA) (2.5 mg/d). Compared with placebo, treatment with CEE resulted in an increase in apoA-I pool size (+20%, P<0.01) because of a significant increase in apoA-I production rate (+47%, P<0.05) and no significant changes in apoA-I fractional catabolic rate. Compared with the CEE alone phase, treatment with the CEE plus MPA resulted in an 8% (P<0.02) reduction in apoA-I pool size and a significant reduction in apoA-I production rate (-13%, P<0.04), without changes in apoA-I fractional catabolic rate.


CONCLUSIONS
Postmenopausal estrogen replacement increases apoA-I levels and production rate. When progestin is added to estrogen, it opposes these effects by reducing the production of apoA-I.
Lamon-Fava
Stefania
S
Lipid Metabolism Laboratory, Jean Mayer USDA Human Nutrition Research, Center on Aging, Tufts University, Boston, MA 02111, USA. stefania.lamon-fava@tufts.edu
Postfai
Borbala
B
Diffenderfer
Margaret
M
DeLuca
Carl
C
O'Connor
John
J
Welty
Francine K
FK
Dolnikowski
Gregory G
GG
Barrett
P Hugh R
PH
Schaefer
Ernst J
EJ
D016632:Apolipoprotein A-I / Q000097:blood*; D008076:Cholesterol, HDL / Q000097:blood; D008078:Cholesterol, LDL / Q000097:blood; D003327:Coronary Disease / Q000097:blood / Q000517:prevention & control*; D018592:Cross-Over Studies; D004347:Drug Interactions; D004359:Drug Therapy, Combination; D015914:Estrogen Replacement Therapy; D004966:Estrogens, Conjugated (USP) / Q000627:therapeutic use*; D005260:Female; D006801:Humans; D007700:Kinetics; D017258:Medroxyprogesterone Acetate / Q000627:therapeutic use*; D008875:Middle Aged; D017698:Postmenopause
D016632:Apolipoprotein A-I; D008076:Cholesterol, HDL; D008078:Cholesterol, LDL; D004966:Estrogens, Conjugated (USP); D017258:Medroxyprogesterone Acetate