Oral bacterium new suspect for developing alzheimer’s disease

A mouth bacterium that causes gum inflammation may play a role in the development of Alzheimer’s disease.This was concluded by researchers in Science Advances journal this week. The research was based on a series of experiments on humans and mice. They also present a potential drug that fights the bacterium.

​Alzheimer’s disease is a form of dementia that affects more than 150 thousand people in the Netherlands alone. Patients are increasingly having problems with their memory, but also with language and routine actions such as making coffee. On average, Alzheimer’s patients die within eight years after being diagnosed.

The scientists, led by the Jan Potempa Pole of the University of Cracow, found DNA of the oral bacterium, P. gingivali, in the brains of Alzheimer’s disease patients. This bacterium is one of the main causes of periodontitis, a serious gum inflammation that can lead, among other things, to losing teeth. Periodontitis is relatively common in the elderly.

The researchers also saw more gingipain in the brain in deceased Alzheimer’s patients than in people without the disease. Gingipain is an enzyme that produces the gingivalis bacterium and causes inflammation.

The researchers reason that these inflammations possibly lead to alzheimer’s disease, because in a follow-up experiment in mice they saw that gingipain caused an increase of the protein beta-amyloid in the brain.

In Alzheimer’s disease this beta-amyloid accumulates in so-called plaques between brain cells. As a result, these cells are no longer able to communicate well with each other, resulting in dementia. When and why such amyloid accumulation occurs has been largely unclear so far. Now it appears that P. gingivalis may be co-responsible for this.

Oral health

It’s a wonderful study,’ says Wim Crielaard, professor of molecular biology at the Amsterdam Academic Centre for Dentistry (ACTA) and not involved in the research. The idea that oral health and Alzheimer’s may have something to do with each other has been around for five years,’ he says on the phone. ‘These results fit in well with that.’ He does, however, emphasize that many more bacterium play a role in periodontitis, and possibly also in Alzheimer’s disease. ‘This is at most part of the story.’ University lecturer in molecular neurodegeneration Wiep Scheper also wants to watch out for hasty conclusions. ‘I’m not yet convinced that this bacterium causes Alzheimer’s disease,’ says the researcher at the Amsterdam UMC in a telephone response. ‘More research is really needed. In the experiments with patients’ body material, for example, there is mainly circumstantial evidence’.

Mice

In addition, she points out that the researchers saw amyloid accumulations in their mouse experiments, but no plaque formation. ‘That is necessary to make the story conclusive.’ To this end they would have been better off testing another type of mouse, according to Scheper, namely one with an adapted, human amyloid gene. ‘Mouse amyloid is different from human amyloid, and does not accumulate in plaques anyway.’

However, she is enthusiastic about a possible drug that inhibits gingipain. In their publication, the scientists showed its effectiveness in lab experiments. ‘Convincing’, says Scheper. But in contrast to the researchers – who let it be known that they will be investigating whether Alzheimer’s disease patients will benefit from it this calendar year – Scheper sees a role for this substance in combating serious gum inflammation. ‘For the time being, the link with this is a lot clearer than with Alzheimer’s disease.’

ACTA professor Crielaard finds this an interesting idea, although according to him the need for a P. gingivalis combatant is not so high. ‘In general, gums can be kept perfectly healthy now, especially with treatments by an oral hygienist.’