The University Record, January 25, 1999

U-M researchers explore link between periodontal disease and heart disease

By Nancy Ross-Flanigan
News and Information Services

Reports over the past five years have suggested a link between periodontal (gum) disease and cardiovascular disease. But so far, no clear cause-and-effect relationship has been found. In a session on “The Link Between Systemic Conditions and Diseases and Oral Health” at the annual meeting of the American Association for the Advancement of Science last week, dentistry Prof. Walter Loesche suggested several possibilities.

Because evidence of the link has come to light only recently, few studies have looked directly at the mechanisms by which periodontal disease might contribute to cardiovascular disease. But by reviewing the literature on both types of disease, Loesche has found intriguing connections that suggest possible mechanisms:

• Blood vessels damaged by periodontal bacteria or their products. One possibility is that bacteria from the mouth—or products released by these bacteria—travel through the bloodstream to other parts of the body, where they damage the linings of blood vessels. In his own research, Loesche has found that patients with coronary artery disease have elevated levels of certain periodontal bacteria. These bacteria contain lipopolysaccharides, toxins that can cause illness when released into the body.

Other lines of research suggest that lipopolysaccharides may damage the cells that line blood vessels, as measured by the release of a substance called von Willebrand factor. Researchers have found that levels of von Willebrand factor are elevated in people with periodontal disease. This observation suggests that lipopolysaccharides produced by periodontal bacteria might travel through the bloodstream to blood vessel walls, where they cause damage.

A similar relationship appears to exist with a group of proteins called acute phase response proteins. Levels of these proteins increase in the bloodstream in response to chronic infection, injuries, and other physical trauma. Researchers at Harvard University have found that one of these proteins, C-reactive protein, is a good predictor of second heart attacks in cardiovascular patients. Increasingly, other studies show that patients with periodontal disease have increased levels of C-reactive protein, and that the levels drop when the periodontal disease is treated.

Researchers also have started looking for evidence of oral bacteria in blood vessel linings. Using DNA probes, researchers at the State University of New York, Buffalo, have found DNA from three and possibly four types of periodontal bacteria in the vessel walls. U-M researchers also are finding the DNA of periodontal bacteria in atheromas, fatty deposits on blood vessel linings that are a hallmark of cardiovascular disease.

• Inflammatory responses involving cytokines. When gum tissue becomes inflamed, white blood cells in the tissue respond by producing cytokines, small, protein-like signaling molecules. If the cyto-kines leak into the bloodstream, they too might alter blood vessel linings in ways that make it easier for a type of white blood cell, called a monocyte, to attach to and penetrate vessel walls, Loesche says. This is the first step in the process by which fatty deposits accumulate on blood vessel walls.

• Smoking. Smoking is a risk factor for both heart disease and periodontal disease, and it could serve as a link between the two, Loesche speculates. By increasing the disease-causing bacteria in the mouth, smoking may increase the odds that these bacteria or their products will get into the bloodstream. Smoking also makes blood vessel linings stickier, which might make it easier for bacteria and bacterial products to attach to vessel walls and cause damage.

Much more research is needed before researchers will know exactly how periodontal disease and cardiovascular disease are related. But what’s exciting, Loesche says, is that periodontal disease is both preventable and treatable. That could mean that preventing stroke and heart attack will someday be as simple as practicing good oral hygiene and treating gum infections promptly.