Estrogen and stroke risk

There are eighteen this month announced the National Institutes of Health (NIH) to investigate an innovative study on women and cardiovascular disease to provide financial support. As the Women's Health Initiative (WHI) knowledge who wrote the study, more than 161,000 women. In 2004, the Government had two arms of the study of estrogen ended after investigators found, they represent a low risk but with an incidence of stroke among postmenopausal women, hormone. The results caught many in the scientific community by surprise, as estrogen has been shown to protect the brain after a stroke animal model. Stroke, also known as stroke is the third leading cause of death in America. It usually occurs when blood flow is blocked to the brain, usually due to a blocked artery. When you encounter a stroke can cause brain damage can be adopted, particularly in the area of the hippocampus is well known that the location of memory, loss of memory and learning. Despite taking the possible link between estrogen and stroke, many women continue hormone to manage their menopausal symptoms.

Does replacement therapy with estrogen must occur before menopause to protect the brain?

Researchers at the Medical College of Georgia (MCG), has together with collaborators coal in Northern China Medical University, Tangshan, China, and the University of Texas Health Science Center at San Antonio, the agreement between hormones and the risk and has taken advanced scientific understanding. Their new study, by techniques derived from animals (1) estrogen clearly protects the hippocampus after a stroke, making certain aspects of stroke associated with brain damage, (2) that the hippocampus is brain after a stroke are hypersensitive, if it was not enough estrogen for an extended absence (and this is the first study to observe the changes taking place), (3), long periods of low estrogen insensitive to the 'hippocampus is protective against estrogen, when the tissue of the uterus to retain their sensitivity to estrogen, and (4) estrogen inhibits the activation of a key enzyme significantly membranes - NADPH oxidase, reactive molecules produced by free radicals leading to brain damage - after a stroke.

The study supports the theory that there may be a "critical period" for the beneficial protective effects of estrogen on the brain - for example, that replacement therapy of estrogen may need to start before or at menopause when estrogen to protect the brain. Further studies should confirm the results.

The study was conducted by Darrell W. Brann, Quan-Guang Zhang Dong Han Limor Raz and the Institute for Molecular Medicine and Genetics, Medical College of Georgia, Augusta, Ratna Vadlamudi, University of Texas Health Science Center at San Antonio and Ruimin Fang and Wang Yang, Center search for molecular biology, North China Coal Medical University, Tangshan. Dr. Brann presents an overview of the results of the team of the American Physiological Society (APS) Conference Sex and Gender in the summer. The findings of the study were selected and the 4th November 2009 online edition of the Journal of Neuroscience published () http://www.jneurosci.org/. The article is entitled "Estrogen attenuates ischemic oxidative damage during an ERα inhibition of activation of NADPH oxidase."

Methodology and Results

E2 or 17β-estradiol is a specific form of estrogen. We do not know how to use it to protect the brain in general or to the hippocampus in particular. Rats whose ovaries were removed were used for the study and received either a placebo or 17β-estradiol by the ovaries in an attempt to mimic the progression of loss of estrogen during menopause have been removed.

The animals were randomly assigned to one of four treatment groups. Group 1 have known that the sham surgery and no history of stroke or estrogen (fictional). Group 2 was induced by a stroke and received) an immediate false (placebo. Group 3 animals were treated with 17β-estradiol in ovariectomized, then a week after a stroke was induced. Group 4 rats received either placebo or estrogen ten weeks after ovariectomy, and a week later, a stroke was induced.

Samples were taken from rats and examined. Statistical analysis was performed. Subsequently, the researchers found:

* The fact that there was no attack in group 1, there was little or no production of free radicals in the brain.
* In group 2, there was a strong induction of superoxide free radicals by the enzyme NADPH oxidase in the hippocampus occurs after a stroke.
* In group 3 was found strongly estrogen-block NADPH oxidase-induced superoxide production, and it protects the brain and reduce oxidative damage.
* In group 4 animals, which was estrogen over a long period comparable to the situation that made post-menopausal women, was the protective effect of estrogen on the brain is completely lost. This is no longer blocking the activation of NADPH oxidase and superoxide production, and are no longer protected the brain.
* In the long-term estrogen-deprived animals, it was found that there is a significant loss in the hippocampus of one of the estrogen receptor, leading to loss of sensitivity to estrogen.
* In addition, another region of the hippocampus is the region CA3, which is usually resistant to damage and stroke, are hypersensitive to damage caused by stroke in animals that were deprived of estrogen over a long period weather.

Thus, the study showed that experienced a long period of estrogen deficiency to a loss of sensitivity and protective effects of estrogen in the hippocampus, and parts of the hippocampus, which are generally resistant to damage stroke to lose if this resistance to estrogen for a longer disadvantaged.

Conclusions

According to Dr Tan, "Every study has potential limitations, including ours. Our investigations have been conducted on animals and it is unclear whether the results are applicable to humans. Further research is needed to resolve this problem. "However, this Brann," The study supports the idea that there is a "critical period" for the positive effect of estrogen on the brain and allows better understand the mechanisms behind this critical period. " He added: "It suggests that human studies should investigate the replacement of estrogen before or during menopause on the possible positive effects on the brain to concentrate."