In a study published in Science Advances, researchers discovered that Porphyromonas gingivalis, a bacterium that causes chronic periodontitis (gum infection), colonizes the brains of Alzheimer's patients. The toxic substances produced by P. gingivalis -- called gingipains -- correlate with the levels of tau and ubiquitin in their brains. These proteins are linked to the development of Alzheimer's. The researchers found that inhibiting the activity of gingipains reduces tau and ubiquitin levels and protects brain neurons from damage caused by inflammation. (Related: Exercise found to reduce the severity of Alzheimer’s symptoms.)
The new study corroborates the idea first put forth by Alois Alzheimer in the early 20th century that infection contributes to the development of Alzheimer's. It also supports an earlier study by Ruth Itzhaki of the University of Manchester and Oxford University, which demonstrated the role of herpes simplex virus type 1 (HSV1) in the pathogenesis of the disease. Similarly, a 2018 study by researchers from the University of Illinois reported that inducing chronic gum disease in young and healthy mice leads to the development of pathological hallmarks of Alzheimer’s disease.
“Infectious agents have been implicated in the development and progression of Alzheimer's disease before, but the evidence of causation hasn't been convincing,” said Stephen Dominy, the present study’s lead author.
But despite the solid evidence they've presented in their study, Dominy and his team made it clear that the bacterium itself does not directly cause Alzheimer’s disease. Its presence only substantially raises the risk of developing the disease and contributes to its rapid progression.
The study also comes with some good news: The team was able to come up with a possible treatment for Alzheimer's disease in the form of small molecules that can inhibit gingipains. These inhibitors successfully reduced not only the P. gingivalis infection and neuroinflammation in the brains of experimental mice, but also the production of proteins associated with Alzheimer's.
The researchers noted that among the inhibitors they developed, COR388, a selective inhibitor of the gingipain Kgp, was the most effective and showed dose-dependent effects. They also found that COR388 can stop the production of toxic beta-amyloid peptides -- harmful strings of amino acids involved in Alzheimer's -- and preserve neurons in the hippocampus, the area of the brain largely responsible for memory-related processes.
According to an article by MedicalNewsToday, COR388 is already under trial, and researchers have reported that volunteers -- healthy or with Alzheimer's -- have responded well to treatments with the inhibitor.
But as with all things, prevention is better than cure. And the study is clear about what people need to do to lower their risk of developing Alzheimer's: maintain good oral hygiene.
“Brush your teeth and use floss,” said co-author Piotr Mydel, a researcher from the University of Bergen in Norway. Mydel stressed that those steps are very important, especially for people with gingivitis and a family history of Alzheimer's.
Other natural ways of preventing Alzheimer's disease include maintaining a healthy diet, getting constant mental stimulation, getting optimal amounts of sleep, managing your stress levels and engaging in social activities.