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December 7, 2009
Marker of oxidative stress predicts heart disease outcome

By Quinn Eastman

Judging from the number of juices and teas advertised as containing antioxidants, consumers are aware of the dangers of oxidative stress. But what is the best way to measure it - and fight it?

Doctors at Emory have identified a substance in the blood that may be useful in predicting an individual's risk for heart disease. The substance is cystine, an oxidized form of the amino acid cysteine and an indirect measure of oxidative stress.

Cardiology fellow Riyaz Patel, part of a team led by Arshed Quyyumi, presented the team’s results Nov. 16 at the American Heart Association Scientific Sessions meeting in Orlando.

In a study of more than 1,200 people undergoing cardiac imaging at Emory because of suspected heart disease, people with high levels of cystine in the blood were twice as likely to have a heart attack or die over the next few years. There were 105 deaths and 56 heart attacks in all patient groups.

When considered independently of variables such as the presence of diabetes, high levels of cystine still predicted future trouble, Patel says.

"Cystine could be a valuable marker of cardiovascular risk, but it also has a direct harmful effect on cells, so reducing it may be a valuable treatment strategy," he says. "What's exciting is there are already known ways to intervene and drive down cystine levels in patients."

For example, a previous study has shown that supplementing the diet with zinc can lower cystine levels, he says.

Clinical biomarker expert Dean Jones – also at Emory -- has shown that when white blood cells are exposed to high levels of cystine, they display signs of inflammation and become stickier. That makes them more likely to adhere to blood vessels in the heart, an event that contributes to the development of heart disease.

Several studies have shown that levels of oxidized cysteine in the blood tend to rise as people age. Smoking and alcohol consumption are also linked with higher levels of oxidized cysteine.

The team's future plans include comparing cystine to other markers that may predict heart disease and understanding the relationships between them.