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THURSDAY, Aug. 26 (HealthDayNews) -- A protein playing an important role in controlling heartbeat might help explain the increased risk of potentially fatal congestive heart failure among type 2 diabetics, researchers say.

The finding might someday lead to preventive treatments that lower diabetics' risk for heart failure.

Studies have found elevated activity of the protein, G-alpha-i, in heart tissue from people with type 2 diabetes, according to a report in the Aug. 26 issue of the journal Diabetes. The study was led by Madan Kwatra, an associate professor of anesthesiology and pharmacology at Duke University Medical Center, in Durham, N.C.

"The normal function of G-alpha-i is to slow the heart rate," Kwatra said. "Its level of activity has been found to increase in congestive heart failure. We are adding the knowledge that there are elevated levels of activity in diabetics, who are highly susceptible to congestive heart failure."

In type 2 diabetes, the body gradually loses its ability to metabolize sugar.

Elevated levels of G-alpha-1 and the molecule that transmits its effects to cells were found in tissue samples from human atria, the upper chambers of the heart, from 51 people between the ages of 41 and 85 who had heart surgery. That molecule, cardiac muscarinic acetylcholine receptor, was much more common on heart cells from patients with diabetes than those without the condition, the researchers found.

Having more receptors means that G-alpha-i slows the heartbeat more than usual, which could lead to an abnormal expansion of the heart known as dilated cardiomyopathy. Dilated cardiomyopathy can, in turn, lead to congestive heart failure, Kwatra said.

That progression is just a theory now, he said, but studies to prove it are in the planning stages. A first study, expected to begin soon, will look for elevated activity of G-alpha-i and its receptor -- not in heart tissue, which is difficult to obtain -- but in white blood cells, which are more readily available.

If the expected increase is found in that first study, which will compare G-alpha-i activity in 20 people with type 2 diabetes and 20 without the condition, the next step would be expanded human studies to tell more about the role of the protein in congestive heart failure.

Beyond that lies the possibility of drug treatment to reduce the risk, Kwatra said. One widely used class of cardiovascular drugs, the beta-blockers, is known to reduce G-alpha-1 activity, he said. They now are prescribed for conditions that may accompany diabetes, such as heart failure and high blood pressure, but not for diabetes itself. Results of these upcoming studies could change that situation and could make diabetes a less dangerous disease, Kwatra said.

More information

Causes and treatment of congestive heart failure are explained by the American Heart Association.

(SOURCES: Madan Kwatra, Ph.D., associate professor of anesthesiology and pharmacology, Duke University Medical Center, Durham, N.C.; Aug. 26, 2004, Diabetes)

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