This is a request or an NHLBI Clinical Investigator Development Award (K- 08) for Stefania Lamon-Fava, M.D., Ph.D., entitled """"""""Mechanism of increased plasma apo A-I levels by estrogens"""""""". The candidate's primary interest focuses on coronary heart disease risk factors, with particular emphasis on lipoprotein metabolism both at the clinical and the molecular biology level. Dr. Lamon-Fava wishes to further develop her skills in both clinical and laboratory research, focusing on the study of the relationship between hormones and lipoprotein metabolism. The research project designed to complement this training involves the study of sex hormone-induced changes in apolipoprotein metabolism. Numerous epidemiological studies have indicated that premenopausal women are at lower risk of coronary heart disease (CHD) than men of the same age. This relative protection is no longer evident a few years after menopause. However, prospective studies have shown that estrogen replacement therapy significantly reduces the risk of CDH in postmenopausal women. Estrogens affect several aspects of lipoprotein metabolism and the most important effects have been observed in high density lipoprotein (HDL) and low density lipoprotein cholesterol concentrations. The addition of progestins to the hormonal replacement therapy opposes the effects of estrogens on HDL and LDL lipoprotein levels. The study proposed here consists of two parts. In the first part, the kinetics of apo A-I in HDL particles differing in apolipoprotein composition (HDL containing only apo A-I and HDL containing apo A-I and apo A-II) will be determined in postmenopausal women undergoing a placebo- controlled, randomized, cross-over treatment with each of the following regimens: a) placebo, b) 0.625 mg/d conjugated estrogens, and c) 0.625 mg/d conjugated estrogens+2.5 mg/d medroxyprogesterone acetate. The kinetics of apo A-I will be determined by stable isotope techniques developed in the sponsor's laboratory. This approach will determine the effects of a low dose continuous estrogen therapy versus a low dose estrogen-progesterone combination on apo A-I metabolism. The second part of this study will focus on the molecular mechanisms involved in the increase in apo A-I levels by estrogens. The primary objective is to determine whether estrogens increase apo A-I production through a direct mechanism such as transcription activation via the interaction of an estrogen-responsive element in the DNA sequences flanking the apo A-I gene or the modulation of the transcription factor complex interacting with the specific apo A-I enhancer, or by post-transcriptional or post translational mechanisms such as stabilization of apo A-I mRNA or more efficient secretion of apo A-I by liver cells. This integrated combination of training and research will serve to foster the candidate's development into a clinical investigator interested in the relationship between hormones and cardiovascular risk in women. The laboratory where the research will be conducted (Lipid Metabolism Laboratory at the Human Nutrition Research Center on Aging, Tufts University, Boston, directed by Dr. Schaefer) is a recognized center for the study of a lipoprotein kinetics and for the molecular biology studies of apo A-I gene expression.
