Atrial fibrillation occurs when the heart beats irregularly, leading to a higher risk of stroke and other cardiovascular complications. Atrial fibrosis, which involves thickening and scarring of the heart’s atrial tissue, plays a key role in the development and persistence of AF. The researchers note that recent studies suggest a link between gum disease and atrial fibrillation (AF), but the exact reasons remain unclear. Porphyromonas gingivalis, a harmful bacteria responsible for gum infections, is known to be highly infectious.
Against the above background, Mutsumi Miyauchi, Oral and Maxillofacial Pathobiology, Graduate School of Biomedical and Health Sciences, Hiroshima University, 1-2-3 Kasumi, Minami-ku, Hiroshima, Japan, and colleagues focused on P. gingivalis and explored its connection to gum disease, its movement to the heart, and its role in atrial fibrosis and atrial fibrillation.
For this purpose, the researchers conducted an experiment using P. gingivalis–infected mice by injecting the bacteria into their molar pulp. They used immunohistochemistry to track the bacteria’s location and a specialized DNA test to detect P. gingivalis in the left atrium. AF inducibility was assessed through intracardiac stimulation. Additionally, left atrial tissue samples were collected from 68 AF patients, who underwent a periodontal examination before surgery. Researchers measured periodontal disease severity using quantitative indices and analyzed bacterial presence in heart tissue through a polymerase chain reaction test. Atrial fibrosis was evaluated using Azan-Mallory staining.
The study led to the following findings:
- Immunohistochemistry and DNA analysis confirmed that P. gingivalis traveled from dental granulomas to the left atrium through the circulatory system in infected mice.
- P. gingivalis–infected mice showed increased atrial fibrosis (21.9% vs. 16.3%) and higher AF inducibility (30.0% vs. 5.0%) compared to control mice.
- Increased GAL3 (galectin 3) and transforming growth factor-beta 1 levels were detected in the left atrium of infected mice.
- Immunohistochemistry confirmed the presence of P. gingivalis in human atrial tissue.
- The bacterial load of P. gingivalis in human atrial tissue was positively correlated with periodontal epithelial surface area, periodontal inflamed surface area, and the extent of atrial fibrosis.
Preclinical research suggests that P. gingivalis, a bacteria linked to gum disease, may travel to the left atrium, contributing to atrial fibrosis and worsening atrial fibrillation. The severity of periodontitis correlates with higher bacterial presence in the heart, indicating a possible causal link.
"Managing gum disease may help reduce AF risk by preventing bacterial translocation. Additionally, targeting P. gingivalis could offer a new therapeutic approach for AF treatment beyond conventional risk factor management," the authors concluded.
Reference: https://doi.org/10.1161/CIRCULATIONAHA.124.071310
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