Researchers from the University of Geneva in Switzerland have confirmed the link between an imbalance of gut bacteria and the development of amyloid-beta plaques in human brains, a widely used biomarker for Alzheimer's disease.
Previous research has already found that people with neurodegenerative disorders tend to have different gut microbiota composition to those without. Given a previously-found association between an inflammatory phenomenon in the blood, certain intestinal bacteria, and Alzheimer's disease, the researchers wanted to test whether inflammation in the blood could mediate between the microbiota and the brain.
To test out their hypothesis, they studied 89 people aged been 68 and 85. While some had Alzheimer's disease or another neurodegenerative disease resulting in similar memory problems, others did not.
Using PET imaging, the researchers were able to measure amyloid deposition in their brains. They also analyzed their blood for the presence of various markers for inflammation and proteins produced by intestinal bacteria, including lipopolysaccharides and short-chain fatty acids.
In the end, the researchers found that high levels of lipopolysaccharides and certain short-chain fatty acids (acetate and valerate) were linked to larger amyloid deposits in the brain. They also found that high levels of butyrate, another short-chain fatty acid, were associated with fewer amyloid plaques.
As such, the researchers say that their findings provide clear evidence of a link between certain proteins in the gut microbiota and the build up of amyloid plaques through a blood inflammatory issue. The researchers now aim to identify the specific bacteria behind this phenomenon.
Afterward, they hope to develop their findings into a viable treatment for neurodegenerative diseases. However, they say that neuroprotective effects are likely to only be felt at the very early stages of the disease and, as such, be considered more of a preventative strategy than a cure.