title: Role of the estrogen and progestin in hormonal replacement therapy on apolipoprotein A-I kinetics in postmenopausal women.
abstract: 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.
authors.affiliation: Lipid Metabolism Laboratory, Jean Mayer USDA Human Nutrition Research, Center on Aging, Tufts University, Boston, MA 02111, USA. stefania.lamon-fava@tufts.edu
authors.forename: Stefania
authors.initials: S
authors.lastname: Lamon-Fava
authors.forename: Borbala
authors.initials: B
authors.lastname: Postfai
authors.forename: Margaret
authors.initials: M
authors.lastname: Diffenderfer
authors.forename: Carl
authors.initials: C
authors.lastname: DeLuca
authors.forename: John
authors.initials: J
authors.lastname: O'Connor
authors.forename: Francine K
authors.initials: FK
authors.lastname: Welty
authors.forename: Gregory G
authors.initials: GG
authors.lastname: Dolnikowski
authors.forename: P Hugh R
authors.initials: PH
authors.lastname: Barrett
authors.forename: Ernst J
authors.initials: EJ
authors.lastname: Schaefer
mesh_terms: 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
chemical_list: D016632:Apolipoprotein A-I; D008076:Cholesterol, HDL; D008078:Cholesterol, LDL; D004966:Estrogens, Conjugated (USP); D017258:Medroxyprogesterone Acetate