Estrogen and homocysteine.

Cardiovascular diseases are the major causes of illness and death in women. Premenopausal women are relatively protected from coronary artery disease and atherosclerosis as compared to postmenopausal women, and this protection is attributed to the effects of the female sex hormone (estrogen). The vasculature, like the reproductive tissues, bone, liver, and brain, is now recognized as an important site of estrogen's action. Although estrogen's beneficial effects on the cardiovascular system are well described in many studies, the molecular basis of estrogen protective mechanisms are still quite vague. Both genomic mechanisms, mediated primarily through estrogen receptor alpha (ER alpha) and estrogen receptor beta (ER beta), and non-genomic mechanisms, through nitric oxide (NO), of estrogen action are controversial and do not entirely explain the effects of estrogen on vascular preservation during conditions of oxidative stress. Until recently, the atheroprotective effects of estrogen were attributed principally to its effects on serum lipid concentrations and cholesterol levels. However, two recent reports that estrogen therapy has no effect on the progression of coronary atherosclerosis in women with established disease, despite the favorable changes in LDL and cholesterol levels, leads to questions about the lipid/cholesterol mechanism of estrogen-mediated effects on atherosclerosis. Alternatively, the high level of homocysteine, found to correlate with accelerated cardiovascular disease and identified as an independent risk factor for atherosclerosis, was recently described to be diminished by estrogen. Protection against disturbed sulfhydryl metabolism and higher homocysteine level could be the missing link in understanding how exactly estrogen affects vascular cells metabolism and responses to oxidative stress. This review focuses on estrogen/homocysteine interactions and their relevance to the cardiovascular system.