The accumulation of fat in the liver, or "fatty liver," resulting from accumulation of central body fat, and perhaps not alcohol consumption, may represent an important underlying mechanism for the association between liver enzymes and hypertension.
The study, conducted by researchers at the University at Buffalo, appears in the current issue (November 2005) of the journal Hypertension.
"Our findings extend previous work, and indicate that the association of the liver enzyme GGT with hypertension risk is strongly affected by variation in weight and, above all, body fat distribution," said lead author Saverio Stranges, Ph.D., assistant professor of social and preventive medicine in the UB School of Public Health and Health Professions.
"Specifically, we found that GGT was a significant predictor of hypertension only among overweight participants with increased central body fat.
"If we consider that fatty liver is the most common cause of liver injury in the United States, these findings may have both important clinical and public health implications," said Stranges.
Alcohol consumption initially was thought to be the link between liver enzymes and high blood pressure for several reasons: Alcoholism is a known risk factor for hypertension; the liver enzyme GGT is a marker for alcohol consumption, and GGT also has been associated with hypertension.
In addition, chronic liver disease, in which GGT levels can be increased, often is associated with heavy alcohol consumption or actual alcoholism.
However, this study showed that the accumulation of fat in the liver, or "fatty liver" (in this case non-alcoholic fatty liver) in study participants with increased central body fat may be the important underlying mechanism linking GGT and hypertension. The association was found in nondrinkers as well as drinkers.
The study involved 1,455 participants who took part in the Western New York Health Study. A number of measures were taken at baseline, including GGT, blood pressure, weight, abdominal height and size of waistline.
At the six-year follow-up, participants were divided into five groups according to their baseline GGT levels. The baseline measurements were repeated, and participants completed questionnaires concerning lifestyle and health habits, including alcohol use.
Fatty liver has no symptoms, but it can develop into the chronic conditions of hepatitis or cirrhosis.
Stranges said these findings suggest that fatty liver should be considered part of the metabolic syndrome, a cluster of conditions physicians use to help assess a patient's risk for cardiovascular disease.
Persons with any three of the conditions are considered at high risk. Conditions currently included in the metabolic syndrome are abdominal obesity, low HDL cholesterol, high blood sugar, high blood pressure and high triglycerides.
Stranges and colleagues are now studying the association between liver enzymes and diabetes.
Additional contributors to the research were Maurizio Trevisan, M.D., professor and dean of the School of Public Health and Professions, along with Joan M. Dorn, Ph.D., Jacek Dmochowski, Ph.D., and Richard Donahue, Ph.D., all of the UB Department of Social and Preventive Medicine.
The study was supported in part by a grant to Donahue from the National Institutes of Health.
The University at Buffalo is a premier research-intensive public university, the largest and most comprehensive campus in the State University of New York.
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