NEW YORK, Sep 17 (Reuters Health) -- Scientists have long known that estrogen, the female sex hormone, protects women from heart disease, but until now they were unsure exactly how it exerted such cardio-protective effects.
A new study in the September 17th issue of the journal Science shows that estrogen binds to and activates part of a "molecular gate" on the surface of blood vessel cells. When the gate opens, potassium, a mineral known to help control blood pressure, flows through and helps regulate the contraction and relaxation of artery walls. The ability of artery walls to respond to changes in blood flow is important to protect the blood supply to vital organs, such as the heart.
Estrogen has beneficial effects on the heart and the bones, but it is not without its risks -- namely an increased risk of breast cancer. The new findings, however, may one day pave the way toward new drugs that protect the heart without increasing breast cancer risk, notes chief researcher Miguel A. Valverde of the Universidad Pompeu Fabra in Barcelona, Spain.
"The idea will be to design a drug that may retain all the benefits of estrogens, preventing the discomfort of (menopausal hot flashes), osteoporosis, cardiovascular protection... but without ...increasing the risk of estrogen dependent cancers such as breast cancer," Valverde told Reuters Health. "It is impossible to foresee when such a drug will be available," he notes.
In laboratory studies, Valverde and colleagues found that a potassium ion, known as Maxi K+, is directly activated by estrodial, the major circulating estrogen in premenopausal women. "The Maxi-K channel can be used to design new drugs. These drugs theoretically should work both in women and men as the potassium channel receptor is present in both sexes," he says.
In a related editorial, Shel D. Silberberg of Ben Gurion University of the Negev in Beer Sheva, Israel, and Karl L. Magleby of the University if Miami School of Medicine in Florida, write that "when it comes to longevity, women have an advantage over men because they are less susceptible to cardiovascular disease, at least until the onset of menopause. This advantage is due largely to the beneficial effects of their estrogen hormones on blood vessels."
They explain that the contraction of smooth muscles decreases the diameter of blood vessels, and thus controls blood flow and blood pressure.
"New methods for treating cardiovascular disease are continually being sought. There is accumulating evidence that postmenopausal estrogen-replacement therapy decreases the risk of major coronary heart disease," the editorialists write. "However, the benefit of estrogen treatment decreases with long-term hormone use because of the increased risk of breast cancer."
Estrogen-like drugs that preserve the beneficial effects of estrogen on the heart without having harmful effects on the breast and other organs are needed. The new findings "may pave the way for the rational design of new drugs for the prevention of cardiovascular disease," Silberberg and Magleby conclude.
