The brains of people who die with Alzheimer’s contain different proportions of some bacteria than do the brains of people without the disease, according to a study published in the journal Frontiers in Aging Neuroscience.
The study used donations to a brain bank to compare the brains of eight people with Alzheimer’s to the brains of six people without signs of Alzheimer’s.
Bacterial Changes in Brains with Alzheimer’s
Previous research has found the brains of people with Alzheimer’s often show signs of inflammation. Inflammation is linked to a wide range of health problems and might cause neural degeneration in those with Alzheimer’s.
Researchers do not know what causes neuroinflammation. It is possible that several factors are at play. Genetic risk factors for the disease might alter the brain’s inflammatory response. Infections can also cause inflammation, suggesting bacteria might play a role in Alzheimer’s.
Researchers sought a full analysis of the bacterial content of the donated brains. Using a technique called next generation sequencing (NGS), which detects specific bacterial genes, they sequenced millions of DNA molecules and produced a comprehensive overview of each brain’s bacterial contents.
Link Between Infections and Alzheimer’s
Other research supports the conclusion that infections may play a role in Alzheimer’s-related neuroinflammation. A study of mice found the amyloid plaques characteristic of Alzheimer’s and the biofilm produced by some gut bacteria may elicit an identical immune response. This offers another explanation for the chronic inflammation seen in most Alzheimer’s brains.
A 2016 editorial published in the Journal of Alzheimer’s Disease calls for more investigation into potential infectious causes of Alzheimer’s. The editorial points to more than 100 studies finding a link between the herpes virus HSV1 and Alzheimer’s.
Several studies suggest people with Alzheimer’s may also be more likely to have fungal infections.
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- Alzheimer’s-causing amyloid and bacteria trigger same immune response. (n.d.). Retrieved from http://www.ucdmc.ucdavis.edu/welcome/features/20090909_Alzheimers/
- Bacteria found in Alzheimer’s brains. (2017, July 17). Retrieved from https://www.eurekalert.org/pub_releases/2017-07/f-bfi071717.php
- Emery, D. C., Shoemark, D. K., Batstone, T. E., Waterfall, C. M., Coghill, J. A., Cerajewska, T. L., . . . Allen, S. J. (2017). 16S rRNA next generation sequencing analysis shows bacteria in Alzheimer’s post-mortem brain. Frontiers in Aging Neuroscience, 9. doi:10.3389/fnagi.2017.00195
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