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.

Dietary polyunsaturated fatty acids, and tissue oxidative stress: the effect of d,l-Ó-tocopherol

The effects of feeding young and aged rats with high doses of polyunsaturated fatty acids from marine oil on the susceptibility of erythrocyte membranes to the induction of oxidative stress, on the level of reduced glutathione of different tissues, and on the antioxidant capacity of blood plasma were studied. The protective effect of the supplementation of the oil with d,l-alpha-tocopherol was also assayed. d,l-alpha-Tocopherol supplementation protects erythrocyte membranes from young rats against the induction of oxidative stress, being unable to protect the membranes from the aged ones. The tripeptide glutathione shows a different behavior depending on the tissue. Blood glutathione is not affected by fish oil ingestion and by the d,l- alpha-tocopherol supplementation either in the young or in the aged animals. Liver glutathione is reduced by fish oil feeding in the aged animals only. Brain glutathione is not affected by the fish oil feeding. The supplementation with d,l-alpha-tocopherol restores the hepatic levels of glutathione and increases the brain level of the tripeptide over the controls, this effect being observed for young and the aged rats. The antioxidant capacity of blood plasma in response to the fish oil feeding increases in the young rats only. This capacity is not affected by the suplementation with d,l-alpha-tocopherol. These metabolic changes are ascribed to possible adaptative responses from the animals to the potential risk of oxidative stress induced by fish oil ingestion. We suggest that metabolic risks may be associated with the consumption of high doses of polyunsaturated fatty acids.

Estudios sobre el mecanismo bioquímico de acción del flavonoide silyvina: relación con sus propiedades terapéuticas / Studies on the biochemical mechanism of action of the flavonoid silyvin: relationship with its therapeutic properties

Este estudio presenta en forma sucinta los aspectos más relevantes de nuestro trabajo de investigación con el flavonoide silyvina. Su mecanismo de acción como citoprotector se relacionaría con una acción a tres niveles: como antioxidante, evitando la lipoperoxidación celular inducida por xenobióticos; aumentando la concentración intracelular de glutatión, permitiendo mejorar la función protectora y de desintoxicación de este tripéptido, y regulando la permeabilidad de las membranas celulares en forma relativamente específica a la entrada o salida de metabolitos. Se discuten las proyecciones terapéuticas del flavonoide, así como su efecto protector específico en la toxicidad hepática de la fenilhidrazina, el etanol y el acetaminofeno