A number of studies have suggested that people with gum disease may face an increased risk of heart disease. Now research in mice provides evidence that gum disease-causing bacteria conspire with fatty diets and genetic susceptibility to clog heart arteries.

The findings "pave the way" for a greater understanding of how chronic infection may contribute to the hardening and narrowing of arteries known as atherosclerosis.

In experiments with mice, the investigators found that animals inoculated with the gum disease pathogen Porphyromonas gingivalis generally developed larger artery-clogging plaques than non-inoculated animals did. This bacterium has been strongly associated with the common gum disease periodontitis.

Some, but not all, studies on the issue have linked gum disease with a higher risk of atherosclerosis. Several explanations have been proposed. One theory is that when gum disease bacteria get released into the bloodstream over time, this leads to a chronic inflammatory response that injures blood vessels and helps instigate or worsen artery plaques.

In their experiments, mice given weekly injections of the bacterium tended to develop atherosclerosis earlier and to a greater degree -- but only if they were fed a high-fat diet or had a genetic susceptibility. The genetically susceptible mice had a deficiency in the apolipoprotein E gene, which encodes a cholesterol-carrying protein that has been implicated in human heart disease.

Circulation 2002;105:861-867