Gum Disease Raises Alzheimer’s Risk

Alzheimer’s could be triggered by an infection, a new study finds. Bacteria found in periodontal disease has been linked to Alzheimer’s before, but now more definitive research has emerged.

The latest study was published in January of 2019 in the journal Science Advances and was led by an international team of researchers.

The researchers, coordinated by pharmaceutical startup Cortexyme, discovered that a pathogen called Porphyromonas gingivalis (Pg) seems to lead to Alzheimer’s disease. It’s also responsible for chronic periodontitis, or gum disease.

Gum Disease

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Gum disease is a major culprit behind bad breath and bleeding gums. The first symptom of periodontal disease is gum inflammation. If left untreated, the bacteria can cause teeth pockets and teeth loss. The disease affects 10–15% of adults across the world, according to the World Health Organization (WHO).

Periodontal disease has previously been linked to other chronic health problems like heart disease. Multiple studies have found that periodontitis occurs more frequently in patients who have systemic diseases like diabetes mellitus, AIDS, leukemia, and Down’s syndrome. Previous studies have also found that people with long-term gum disease are 70% more likely to get dementia.

The Pg bacteria that drives periodontitis is able to slip into the bloodstream from the mouth. From there, it travels to other areas of the body. In the case of Alzheimer’s disease, it spreads to the brain and slowly expands throughout it over the course of multiple years.

The Study

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In this study, mice who had an oral infection of Pg were found to have high levels of the pathogen in their brain, along with large amounts of amyloid beta plaques, which have long been linked to Alzheimer’s.

While in the brain, the Pg bacteria secreted toxic enzymes called gingipains. Gingipains are already linked to tau tangles as well as ubiquitin, a protein tag found in tau tangles and amyloid beta plaques that indicate when a protein is damaged and needs to be broken down.

The researchers also collected data on humans with Alzheimer’s. They found that the Pg bacteria was present in the brains of 51 out of 53 people with Alzheimer’s disease. On top of that, the gingipains were present in the brains of deceased people who had never been diagnosed with Alzheimer’s.

The big question is, does gum disease cause Alzheimer’s, or do Alzheimer’s and dementia lead to poor dental hygiene habits?

The study claims to have answered that question. “Our identification of gingipain antigens in the brains of individuals with AD and also with AD pathology but no diagnosis of dementia argues that brain infection with P. gingivalis is not a result of poor dental care following the onset of dementia or a consequence of late-stage disease, but is an early event that can explain the pathology found in middle-aged individuals before cognitive decline.”

Therapy & Clinical Trials

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Cortexyme experimented with small molecule therapies to see if they could block the Pg toxins. They found that one therapy in particular, COR388, was successful in doing this. It stopped amyloid beta production, reduced inflammation in the brain, and protected neurons in the hippocampus, which is responsible for regulating emotion and memory.

Cortexyme is set to being a larger Phase 2/3 clinical trial of COR388 in 2019.

Dr. David Reynolds, the Chief Scientific Officer from Alzheimer’s Research UK, is wary of the results thus far, stating: “Maintaining good dental health is an important part of a healthy lifestyle, and while we don’t yet fully know the extent to which it can affect our dementia risk, the presence of a single type of bacteria is extremely unlikely to be the only cause of the condition.”

While the researchers on the project don’t think they have a definitive cause of Alzheimer’s just yet, they are hopeful.

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