Physiological interindividual variability in endogenous estradiol concentration does not influence adipose tissue and hepatic lipid kinetics in women

Objective: Increased triglyceride (TG) and apolipoprotein B-100 (apoB-100) concentrations in plasma are important risk factors for cardiovascular disease in women. Administration of some estrogen preparations raises plasma TG and apoB-100 concentrations by increasing hepatic very low-density lipoprotein (VLDL) TG and apoB-100 secretion rates. However, the influence of physiological variation in endogenous estradiol on VLDL-TG and VLDL-apoB-100 metabolism and on free fatty acid (FFA) release into plasma (the major source of fatty acids for VLDL-TG production) is not known. Design and methods: We measured basal VLDL-TG, VLDL-apoB-100, and plasma FFA kinetics by using stable isotopically labeled tracers in 36 eumenorrheic, premenopausal women (age: 33 ± 2 years, BMI: 31 ± 1 kg/m²; mean ± s .e .m .) during the follicular phase of the menstrual cycle; participants were divided into two groups based on low (n = 18) or high (n = 18) plasma estradiol concentrations (defined as below or above the median value of 140 pmol/L in the whole group). Results: Mean plasma estradiol concentration was >3-fold higher in the high-estradiol than in the low-estradiol group (299 ± 37 and 96 ± 7 pmol/L, P < 0.001); there was no difference in plasma progesterone concentrations between the two groups (P = 0.976). There were no significant differences in plasma FFA concentration, FFA rate of appearance in plasma, VLDL-TG and VLDL-apoB-100 concentrations, hepatic VLDL-TG and VLDL-apoB-100 secretion rates, VLDL-TG and VLDL-apoB-100 plasma clearance rates, and mean residence times (all P ≥ 0.45). No significant associations were found between plasma estradiol concentration and FFA, VLDL-TG, and VLDL-apoB-100 concentrations and kinetics (all P > 0.19). Conclusions: Plasma estradiol concentration is not an important correlate of basal plasma FFA, VLDL-TG, and VLDLapoB-100 kinetics in premenopausal women.