Periodontal disease, a common but preventable gum infection, may facilitate the onset of Alzheimer’s disease, according to a new study by the University of Illinois at Chicago.
“Other studies have demonstrated a close association between periodontitis and cognitive impairment, but this is the first study to show that exposure to the periodontal bacteria results in the formation of senile plaques that accelerate the development of neuropathology found in Alzheimer’s patients,” said Dr. Keiko Watanabe, professor of periodontics at the UIC College of Dentistry and corresponding author on the study, in a statement.
Researchers used mice to study the impact of periodontal bacteria on brain health by establishing chronic periodontitis, characterized by soft tissue damage and bone loss in the oral cavity. After 22 weeks of repeated oral application of the bacteria, researchers studied their brain tissue and compared the health of that tissue to a control group of mice.
Mice that had been chronically exposed to the bacteria had significantly higher amounts of accumulated amyloid beta – a senile plaque found in the tissue of Alzheimer’s patients – as well as more brain inflammation and fewer intact neurons due to degeneration.
“We did not expect that the periodontal pathogen would have this much influence on the brain, or that the effects would so thoroughly resemble Alzheimer’s disease,” Watanabe said.
DNA from the periodontal bacteria was also found in the brain tissue of mice in the study group and a bacterial protein was observed outside their neurons. “Our data not only demonstrate the movement of bacteria from the mouth to the brain, but also that chronic infection leads to neural effects similar to Alzheimer’s,” Watanabe said.
While most studies use mice that have been genetically altered to more strongly express genes associated with senile plaque and enable Alzheimer’s disease, the current study did not. “Using a wild-type mouse model added strength to our study because these mice were not primed to develop the disease, and use of this model gives additional weight to our findings that periodontal bacteria may kick-start the development of the Alzheimer’s,” Watanabe said.
Understanding the causes and risk factors for Alzheimer’s disease is critical for the development of treatments, researchers say, especially for sporadic or late-onset disease, which accounts for more than 95 percent of cases.
“Oral hygiene is an important predictor of disease, including diseases that happen outside the mouth,” Watanbe said. “People can do so much for their personal health by taking oral health seriously.”
The study was published earlier this month in the journal PLOS ONE.
Additional co-authors on the paper are UIC researchers Paulina Zuchowska, Stefan Green, Peter Toth, Michael Ragozzino, Khuong Le and Haider Aljewari, and the University of Melbourne researchers Neil O’Brein-Simpson and Eric Reynolds.