Efecto del 27- hidroxicolesterol en la acción antiplaquetaria de estradiol en mujeres postmenopáusicas / 27- Hydroxycholesterol reverses estradiol induced inhibition of platelet aggregation in postmenopausal women

Background: The decline of estrogen levels increases cardiovascular risk in women. Platelets express estrogen receptors and 17β-estradiol- (E2) can produce a protective effect on thrombus formation. The hydroxylation of cholesterol generates several sterols and 27-hydroxycholesterol (27HC) predominates in circulation. Aim: To evaluate the effect of 27HC as an endogenous antagonist of the anti-aggregating properties of E2 in platelets of postmenopausal women. Material and Methods: Platelet function of postmenopausal women was evaluated ex-vivo. Platelets pre-incubated with 27HC in the presence or absence of E2, were stimulated with collagen. Aggregation was evaluated using turbidimetry using a Chrono-log aggregometer. Results: Collagen-stimulated platelet aggregation was significantly inhibited by E2. The inhibitory effect of E2 on collagen-stimulated platelet aggregation was significantly reversed in the presence of 27HC. Conclusions: The suppressive effect of E2 on platelet aggregation is inhibited by 27HC, which could contribute to increase cardiovascular risk in postmenopausal women.

Isoflavonas de soya y salud humana: cáncer de mama y sincronización de la pubertad / Soy isoflavones and human health: breast cancer and puberty timing

Background: Accumulated exposure to high levels of estrogen is associated with an increased incidence of breast cancer. Thus, factors such as early puberty, late menopause and hormone replacement therapy are considered to be risk factors, whereas early childbirth, breastfeeding and puberty at a later age are known to consistently decrease the lifetime breast cancer risk. Epidemiological studies suggest that consumption of isoflavones correlates with a lower incidence of breast cancer. Data from human intervention studies show that the effects of isoflavones on early breast cancer markers differ between pre- and post-menopausal women. The reports from experimental animals (rats and mice) on mammary tumors are variable. These results taken together with heterogeneous outcomes of human interventions, have led to a controversy surrounding the intake of isoflavones to reduce breast cancer risk. This review summarizes recent studies and analyzes factors that could explain the variability of results. In mammary tissue, from the cellular endocrine viewpoint, we analyze the effect of isoflavones on the estrogen receptor and their capacity to act as agonists or antagonists. On the issue of puberty timing, we analyze the mechanisms by which girls, but not boys, with higher prepuberal isoflavone intakes appear to enter puberty at a later age.