Oct. 4 (UPI) -- Exposure to periodontal bacteria may initiate Alzheimer's disease in humans based upon inflammation and degeneration of brain neurons in mice, according to a study.
Researchers at the University of Illinois at Chicago studied the effects of periodontal disease, a common but preventable gum infection, with Alzheimer's, which currently has no treatment or cure. The findings were published Wednesday in PLOS One.
"This was a big surprise," corresponding author Dr. Keiko Watanabe, a professor of periodontics at the UIC College of Dentistry, said in a press release. "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 noted other studies found 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."
In the study, researchers established chronic periodontitis, which is characterized by soft tissue damage and bone loss in the oral cavity, in 10 mice. Another 10 mice served as the control group.
After 22 weeks of repeated oral application of the bacteria, the researchers studied the brain tissue of the mice and compared brain health.
Mice chronically exposed to the bacteria had significantly higher amounts of accumulated amyloid beta as well as more brain inflammation and fewer intact neurons because of degeneration.
Amyloid beta protein and RNA analyses also displayed greater expression of genes associated with inflammation and degeneration in the study group. In addition, DNA from the periodontal bacteria was also found in the brain tissue of mice and a bacterial protein was observed inside their neurons in the study group.
"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.
She said using the wild-type mice makes a difference compared with transgenic mice, which are genetically altered to more strongly express genes associated with the senile plaque and enable Alzheimer's development.
"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.
The researchers hope these study results can lead to treatments.
In the meantime, better oral hygiene can reduce risk.
"Oral hygiene is an important predictor of disease, including diseases that happen outside the mouth," she said. "People can do so much for their personal health by taking oral health seriously."