FOR RELEASE:1:30 p.m. ET, WednesdayOctober 25, 2000
CONTACT:Maggie Francis (214) 706-1397
Carole Bullock (214) 706-1279[email protected]
Abstract P130
American Heart Association meeting report: High iron levels may speed atherosclerosis and increase risk of heart attack
WASHINGTON, Oct. 25 -- High levels of iron in the body can damage arteries, speeding the development of atherosclerosis and sharply increasing the risk of heart attack, according to a study reported today at the 54th Annual Fall Conference of the American Heart Association's Council for High Blood Pressure Research.
The researchers found that iron can damage the endothelium -- the inner lining of the blood vessels. The endothelium keeps blood flowing to the heart and brain by expanding and contracting arteries. High cholesterol levels, diabetes or high blood pressure can damage the endothelium so that it doesn't function well.
"A number of studies have demonstrated that elevated iron stores in the body are closely related to both heart attacks and atherosclerosis of the carotid arteries, the main arteries leading to the brain, which can cause strokes," says Hidehiro Matsuoka, M.D., Ph.D., chief of the Kurume Medical School's Division of Hypertension, who directed the research. The Japanese study is the first, however, to show that iron loading has adverse effects on the endothelium and that reducing iron concentrations in the blood improves endothelial function.
"Our study shows that we should recognize iron as a risk factor for atherosclerosis and understand the need to control our body iron levels to prevent cardiovascular disease," Matsuoka explains.
The researchers believe that iron is somehow interfering with the action of a chemical released by the endothelium, called nitric oxide, which plays a central role in the anti-atherosclerotic effects of the endothelium. Nitric oxide causes the blood vessels to relax in order to accommodate increased blood supply pumped by the heart during physical exercise, exertion or other activity.
One phase of the study focused on a cohort of 10 healthy volunteers, who were injected with high doses of iron. High-resolution ultrasound was used to examine the function of their artery walls. A second phase tracked the effects of lowering blood levels of iron with a chemical called deferoxamine in 10 cigarette smokers, all of whom were free of apparent cardiovascular disease.
The researchers found that iron loading in healthy volunteers increased levels of the chemical malondialdehyde, a marker of oxidation, and impaired endothelial function. However, iron removal in smokers significantly decreased levels of the chemical and restored normal endothelial function.
Too much iron can be particularly dangerous for smokers due to the effects of oxidation, which occurs when there are high levels of reactive oxygen molecules, or "free-radicals," in the blood. Free radicals are associated with the oxidation of the "bad" low-density lipoprotein (LDL) cholesterol, allowing it to enter and damage the artery walls.
"We wanted to examine the effect of iron removal in smokers because, among coronary risk factors, smoking is one of the strongest causes of oxidation," says Matsuoka. "Collectively, iron impairs endothelial function via oxidative stress on the blood vessels," he emphasizes.
"Many scientists attribute the significantly low risk of cardiovascular disease among pre-menopausal women to the protective effects of estrogen," says Matsuoka. "But the hypothesis has been raised that the iron depletion associated with menstruation also protects against heart disease."
Matsuoka points out that this hypothesis is supported by two large studies showing that people who donate blood also have a lower risk of heart attacks and strokes. These findings have led to several prospective studies to determine if there is any merit to this phenomenon.
"I don't think it's a good idea for people to take in more iron than is normally contained in a healthful diet," Matsuoka says, "but compared to the heavy intravenous doses of iron used in our study, oral iron supplements are relatively safe. Taken orally, excessive iron will be excreted, but long-term overload that increases the body's iron stores is strongly associated with cardiovascular events such as heart attack, chest pain or stroke."
Co-authors of the study include Kei Fukami, Shuji Iida, Akira Satoh, Seiya Okuda, and Tsutomu Imaizumi.
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NR00-1199 (HBP2000-Matsuoka)
Media advisory: Dr. Matsuoka can be reached by phone at 81-94-23-17562; by fax at 81-94-23-36509; or by e-mail at [email protected]. (Please do not publish telephone numbers or e-mail address.)
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