University Of Georgia Study Suggests Free Radicals Contribute To Higher Incidence Of Cardiovascular Disease In African Americans

November 11, 1997

ATHENS, Ga. -- A University of Georgia study released today at the American Heart Association's 70th Scientific Sessions, in Orlando, Fla., may help explain why African Americans have a higher incidence of cardiovascular disease than Caucasians.

The study of saphenous vein tissue (a vein in the leg) from heart bypass patients suggests that blood vessels from African Americans generate almost twice as many free radicals as blood vessels from Caucasian patients. This finding has important implications in understanding the disease process in African Americans. It also may suggest the beneficial use of antioxidants such as vitamins C and E in therapy.

"The body produces free radicals, which are highly reactive molecules that circulate in the bloodstream and can attack body tissues such as the blood vessels and damage them," said Randall Tackett, professor of clinical and administrative sciences at the University of Georgia College of Pharmacy and the study's lead researcher.

"Some free radicals, including one called superoxide, have been shown to interfere with the ability of blood vessels to vasodilate, or relax," Tackett said.

Constricted blood vessels reduce the flow of blood and raise blood pressure. When vessels in the heart are severely constricted or totally blocked, they can cause a heart attack.

"Free radicals also may play a role in the development of plaques such as occurs in atherosclerosis, or hardening of the arteries, by attacking the blood vessel walls, damaging them so they can't relax," Tackett said.

The body has several defenses against free radicals, including enzymes that scavenge free radicals such as superoxide, he said.

Tackett's study measured the generation of superoxide in saphenous vein segments of 18 African Americans and 26 Caucasians. His is the first study to measure free radical levels in blood vessels of African Americans. Other research has demonstrated that free radicals play a role in cardiovascular diseases, such as coronary artery disease, but no other studies have evaluated free radical production in African Americans.

Tackett's team also measured the levels of enzymes that scavenge free radicals to determine if these levels were different in African Americans. After finding the same enzyme levels in both African Americans and Caucasians, the researchers concluded that African Americans do not have an enhanced defense system to scavenge the increased production of free radicals.

The prevalence of hypertension, coronary artery disease and diabetes is higher in African Americans. African American males have been reported to have a 27 percent higher death rate from cardiovascular disease than Caucasian men do. Despite this higher incidence of cardiovascular disease in African Americans, the mechanisms responsible still are unknown.

Tackett's findings complement his team's research widely reported three years ago that racial differences exist in blood vessels. They showed that blood vessels from African Americans had a reduced ability to dilate because of a lack of nitric oxide, a substance produced by the cells that line the blood vessels. Since superoxide can inactivate nitric oxide, an increase in superoxide production could help explain the reduced vasodilation reported earlier by the research team.

To determine if the increased production of the free radical superoxide was involved in the decreased vasodilation observed in African Americans, Tackett's team evaluated the vasorelaxation of the vein segments in the presence of antioxidant compounds and observed an improved ability to vasodilate.

These studies may have important implications in the use of antioxidants to treat cardiovascular disease in African Americans.

In addition to Tackett, the research team includes Dr. Lionel Zumbro, University Hospital, Augusta, Ga., and Dr. Joe Rubin, Medical College of Georgia, Augusta, Ga., as well as UGA technician Cynthia Lane, UGA graduate student LiFan Zhao and UGA research apprentice Vija Fleming.

University of Helsinki

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