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Protein That Helps May Also Harm in High Amounts

Oct. 2, 2000 — We all know that smoking, high cholesterol levels, and obesity are bad for our heart. But what about — fibrinogen? Although most of us have never heard of it, a high level of the protein fibrinogen in the blood is rapidly coming to light as the latest enemy to good cardiovascular health.

In a study that appears in this week’s issue of Circulation: Journal of the American Heart Association, Boston researchers have found that high levels of this nasty protein in our blood not only put us at risk for developing heart disease, but may be the underlying reason standard risk factors such as smoking, obesity, and high cholesterol cause heart attacks.

“After you ? account [for] the standard risk factors [for heart disease,] which have already been identified,” lead author Ralph B. D’Agostino tells WebMD, “there’s a desire to know what else is a risk factor that may be important [in determining risk], and are we going to get some benefit from identifying these [newer] risk factors.” D’Agostino is a professor in the department of mathematics, statistics, and public health at Boston University.

Fibrinogen is a protein, synthesized by the liver, that is necessary for normal blood clotting. A number of previous studies have suggested that high levels of fibrinogen increases blood clotting and increases risk for having heart disease and strokes. People with diabetes or those who are obese or physically inactive also tend to have higher levels of fibrinogen. Smoking has also been found to raise fibrinogen levels, which drop back down to normal when smoking is stopped.

In this study, researchers looked at participants of the Framingham Offspring Study, an evaluation of risk factors for heart disease that has been ongoing since 1948, to see if those people with heart disease had higher fibrinogen levels than the rest of the population.

The researchers evaluated the fibrinogen levels of over 2,600 study participants; 267 of them had cardiovascular disease. They first looked at the relationship between fibrinogen and the well-known heart disease risk factors, including total and HDL (good) cholesterol, diabetes, age, and cigarette smoking. Second, they wanted to determine if people with diagnosed heart disease had higher levels of fibrinogen.

In the study, fibrinogen levels were higher among those people with cardiovascular disease. High fibrinogen levels were also found to be associated with traditional heart disease risk factors. In fact, elevated fibrinogen levels may be the common pathway by which the other risk factors cause cardiac disease.

Although this study does have some valuable information, Richard Karas, MD, says the fact that fibrinogen may be a risk factor in heart disease is nothing new. “These results just help confirm what other studies have already shown,” he says. Karas, who reviewed the study for WebMD, is co-director of the Molecular Cardiology Research Center and director of preventive cardiology at the New England Medical Center, in Boston.

“The main point to reiterate,” says D’Agostino, “is that [this new study] opens up the possibility for new intervention trials [for lowering fibrinogen] that will hopefully reduce cardiovascular disease. [Measuring fibrinogen] ? is also important as a diagnostic tool. If a person has symptoms and the fibrinogen is also high, then it’s an indication that they may be in more serious trouble.”

Screening for fibrinogen is also less invasive and less expensive than many other tests that doctors perform to determine if a person is at risk for heart disease, he adds, and it may be something that proactive heart patients may wish to ask their doctors about.

Karas tells WebMD, “[Because] we don’t have a particular [drug] ? that just targets fibrinogen ? we have no idea if just lowering fibrinogen in and of itself would help. So it may be just an [indicator for] assessing a person’s risk.”

Robert S. Rosenson, MD, director of the Preventive Cardiology Center at Rush-Presbyterian-St. Luke’s Medical Center in Chicago, agrees. “That’s why we can’t really say it’s a risk factor [for developing heart disease] as they did, because we don’t have any clinical trials which say that altering fibrinogen reduces cardiovascular events. That’s what’s missing in making fibrinogen in the same category of risk, as say, LDL cholesterol,” commonly called the “bad” cholesterol.

But D’Agostino emphasizes that, although there are not a lot of interventions available right now to lower fibrinogen levels, doctors and patients need to be aware of what probably does work. “There isn’t a drug you can pull right off the shelf,” he says, “but a person can make behavioral and lifestyle changes such as quitting smoking, losing weight, becoming more physically active, and lowering cholesterol, that lower fibrinogen.”

Posted by: Dr.Health

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