A simple blood test may identify people who have an increased risk ofdying from cardiovascular disease, researchers report in Circulation:Journal of the American Heart Association.
The test measures gamma-glutamyl transferase (GGT) -- an enzymeproduced primarily by the liver and catalyzes glutathione, the mainantioxidant in the body. The enzyme is elevated in some forms of liverdisease, so physicians use GGT levels to detect liver damage andalcohol abuse.
In analyzing data from a long-term study involving more than 160,000Austrian adults, the researchers found that the higher a person's bloodlevel of GGT, the greater the risk of cardiovascular death. The levelsare given in units per liter (U/l) of blood. Normal low is less than 9U/l for women and less than 14 U/l for men. A moderately high value forGGT is 18 U/I for women and 28 U/I for men. High levels (twofoldelevated) are more than 36 U/I for women and 56 U/I for men.
"People with high GGT had more than a 1.5-fold risk of dying fromcardiovascular diseases in comparison to people with normal low levelsof GGT," said senior author Hanno Ulmer, Ph.D. "For people under 60years of age, this risk is even higher, amounting to more thantwo-fold."Over the past decade, some small studies have suggested a link betweenhigh GGT and cardiovascular disease," said Ulmer, associate professorof medical statistics at the Innsbruck Medical University in Austria.
Several years ago, Italian researchers reported that elevated GGT couldindicate early atherosclerosis. Ulmer and his colleagues investigatedthe researchers' findings. They examined medical data collected from1985-2001 from 163,944 (98.4 percent) of the then-enrolled volunteersin the Vorarlberg Health Monitoring and Promotion Program. This is anongoing study in Austria's westernmost province that examines riskfactors for chronic diseases.
The participants included 74,830 men and 89,114 women, age 19 or olderwhen they entered the study, and had been followed for an average of 11to 12 years.
After controlling for known cardiovascular risk factors, the team foundthat GGT was an independent predictor of fatal heart disease or stroke.
Among the study's other key findings:
- At enrollment, 21.9 percent of men and 15.6 percent of the women had elevated GGT.
- Of the 6,990 deaths that occurred among the volunteers, 43.3 percent resulted from heart disease or a stroke.
- Among all men, the risk of cardiovascular death was 28 percent higher for those with moderately high GGT, compared to men with normal levels of the enzyme, and rose to 64 percent for those with highly elevated GGT. In women, the increase in risk ranged from 35 percent to 51 percent.
- In men, elevated GGT had a statistically significant association with death caused by chronic coronary heart disease, congestive heart failure, ischemic stroke (caused by a blocked artery in the brain), and hemorrhagic stroke (caused by a ruptured blood vessel in the brain). Researchers found no significant correlation with acute heart attacks caused by a blocked artery, sub-acute coronary heart disease, or other cardiovascular disease.
- Women with elevated GGT had an increased risk of death from all cardiovascular diseases. However, the association with hemorrhagic and ischemic strokes was not statistically significant.
- GGT proved a strong predictor of cardiovascular death, third behind smoking and hypertension but ahead of high levels of blood sugar, cholesterol and triglycerides.
Ulmer cited two mechanisms that might explain why GGT can indicatecardiovascular disease. The first, originally proposed by the Italianresearchers, is that high GGT shows the presence of atherosclerosis.The second is that it's related to the ill effects of heavy drinking onblood vessels.
"Beyond its role as an indicator of liver function, GGT is very likelyto predict cardiovascular disease," Ulmer said. "Since GGT iscorrelated with established risk factors, the known ways of preventingthe disease might also be effective in lowering GGT levels."Because the study participants were overwhelmingly white Austrians, theteam could not say whether their findings hold true for other racialand ethnic groups.
"Both epidemiologic and experimental studies should be performed toconfirm these findings," Ulmer said. "GGT should be included as a majorparameter in future cardiovascular intervention studies."
In an accompanying editorial, Michele Emdin, M.D., of thecardiovascular medicine department at the National Research Council inPisa, Italy, wrote that elevated GGT might help identify people with"the most risky combination for the vulnerable plaque, and the bestmedical strategies for the stabilization of lesions, rather thanpercutaneous or surgical."
Co-authors are Elfriede Ruttmann, M.D.; Larry J. Brant, Ph.D.; HansConcin, M.D.; Gunter Diem, M.D.; and Kilian Rapp, M.D. Co-authors ofthe editorial are Alfonso Pompella, M.D., Ph.D., and Aldo Paolicchi,M.D., Ph.D.
Statements and conclusions of study authors that are published in theAmerican Heart Association scientific journals are solely those of thestudy authors and do not necessarily reflect association policy orposition. The American Heart Association makes no representation orwarranty as to their accuracy or reliability.
Cite This Page: