Cholesterol byproduct blocks estrogen help

DALLAS, Sept. 18 (UPI) -- A byproduct of cholesterol metabolism interferes with the beneficial effects estrogen has on the cardiovascular system, a U.S. study found.

Researchers at the University of Texas Southwestern Medical Center in Dallas found that in rodents, a molecule called 27-hydroxycholesterol, or 27HC, binds to the same receptors in the blood vessels of the heart to which estrogen binds.

Senior author Dr. David Mangelsdorf said the findings may explain why hormone replacement therapy fails to protect some postmenopausal women from heart disease.

The study, published in the October issue of the journal Nature Medicine, found that when estrogen levels dropped relative to the amount of 27HC circulating in the blood, 27HC reacted and bound to the estrogen receptors in the cardiovascular system and blocked their protective function, primarily by inhibiting the production of nitric oxide.

Reduced levels of nitric oxide in blood vessels has been linked with high cholesterol and diabetes, the study said.