30.01.2019 change 30.01.2019

Bacteria in our gums may be linked to Alzheimer`s disease

Photo: Fotolia Photo: Fotolia

Bacteria that attack human gums have been detected in the brains of people who died from Alzheimer`s disease, according to a study, in which Polish scientists also participated. The journal Science Advances informed about the results.

In recent years, there have been papers suggesting that Alzheimer`s disease could be infectious. But so far the exact mechanism of infection has not been discovered.

An international team of scientists, including Polish researchers, found Porphyromonas gingivalis in the brains of deceased Alzheimer`s patients. The bacteria may cause chronic gingivitis and is associated with rheumatoid arthritis and atherosclerosis.

P. gingivalis DNA was detected both in the brains of the deceased who suffered from Alzheimer`s and in the cerebrospinal fluid of living patients with suspicion of this disease. Perhaps testing cerebrospinal fluid for the presence of this bacterium could facilitate early detection of the disease.

During experiments on mice, oral administration of the pathogen resulted in colonization of rodent brains by bacteria and increased production of amyloid beta - a sticky protein characteristic of Alzheimer`s disease. The results of the study suggest that amyloid beta may have an antibacterial effect and is not the cause of dementia, but a symptom of infection.

In 96 percent of the samples taken from the brains of people suffering from Alzheimer`s, the team also identified toxic enzymes known as gingipains, secreted by Porphyromonas gingivalis. Their presence was associated with two different indicators of Alzheimer`s disease: abnormal tau protein and ubiquitin.

What`s more, the team detected toxic gingipains in the brains of the deceased, who had never been diagnosed with Alzheimer`s. This is important because P. gingivalis had already been linked to Alzheimer`s disease, but it was not clear whether it was gum disease that caused dementia, or rather dementia promoted deterioration of oral hygiene. The detection of low levels of gingipains also in people not diagnosed with Alzheimer`s suggests that the disease could develop if they lived longer.

With the co-operation of the pharmaceutical company Cortexyme, scientists developed the potential drug COR388, which is currently in the clinical human trials phase. The drug inhibits the action of gingipains. During tests on mice, it reduced the number of P. gingivalis bacteria in the brain, while lowering the production of beta amyloid, alleviating the inflammatory process and protecting the neurons in the brain section responsible for memorizing - the hippocampus. It is possible that the drug would also work in the case of periodontal disease.

An issue that still requires clarification is whether other gingipain-producing bacterial species could cause brain disease. That includes, for example, Porphyromonas gulae, found in the saliva of pets, including dogs. Recent studies indicate that dogs can pass this bacteria on to their owners.

The research authors include biochemist and microbiologist Prof. Jan Potempa from the Jagiellonian University and the University of Louisville in the U.S. The team consisting of 26 people also included: Karina Adamowicz, Dr. Małgorzata Benedyk, Agata Marczyk, Dr. Piotr Mydel.

More information here.

PAP - Science in Poland, Paweł Wernicki

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