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The idea that Alzheimer's disease, the most common form of dementia, could be caused by an infectious disease is controversial, but it is gaining credibility. Last year, for example, two major articles published an article linking Alzheimer's disease to common forms of the herpes virus, although it is still unclear how these viruses can affect the genes of a herpes virus. nobody to cause the disease.
Yesterday (23 January), researchers published a book (paywall) suggesting that another common infection could exacerbate the progression of Alzheimer's disease. Researchers led by a San Francisco-based start-up pharmaceutical company Cortexyme team have found evidence that the same bacterium that causes chronic gum infections can contribute to plaque and tau formation that characterize the disease. Alzheimer. This work could pave the way for new treatments targeting this bacterium to save neurons.
Porphyromonas gingivalis is a bacterium that can cause periodontitis or gum disease. Previous estimates suggest that about half of American adults (paywall) have this bacterial infection, although only about 10% have serious cases that can lead to tooth decay. People with periodontitis are also more likely to have Alzheimer's disease, although it is unclear if this is because people with dementia have more difficulty maintaining oral hygiene. or if there is a more causative explanation.
P. gingivalis do not always stay confined to the mouth. It was found to reach the brain where it could cause problems. (Scientists suspect it is carried by white blood cells or nerves leading to the brain.) A small study has revealed the presence of bacteria in the brains of people who have died of Alzheimer's disease. At the end of last year, scientists discovered that P. gingivalis Infections in mice have led their brains to degenerate in a manner similar to what happens in humans with Alzheimer's.
This latest study is the first to show how P. gingivalis can work in the brain to exacerbate Alzheimer's disease. The researchers examined the brains of about 50 people who died of Alzheimer's disease. More than 90% of them had evidence of some of the proteins released by P. gingivalis, called gingipains. The researchers also examined 50 brains of people who died without dementia and found Gingipains a little more than half the time. However, people who died of Alzheimer's disease tended to have higher protein levels. More gingipans were correlated with more tau tangle, characteristic of Alzheimer's disease.
The team also infected mice with P. gingivalis to see if that could reach their brains. Indeed, they have been able to detect in humans neuronal lesions similar to Alzheimer's disease.
Interestingly, they were able to reverse some of this early damage by giving the mice a dose of a protein that binds to certain gingipains, effectively neutralizing them and preventing them from harming the neurons.
This work does not definitively show that P. gingivalis causes Alzheimer's disease, but it could accelerate the damage caused by the disease in people already at higher risk of contracting the disease, such as those with poor nutrition or certain genetic characteristics. (Although it is always a good idea to avoid periodontitis with good brushing habits.) The development of drugs targeting gingipaine could be a future treatment for people who developed Alzheimer's disease at an early stage . In a small clinical trial, Corexyme showed that one of the drugs in question could be tolerated by people with Alzheimer's disease, although important work is needed to demonstrate that it actually works. against the disease.
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