Researchers link gut microbiota and Alzheimer's disease

There may be a correlation in humans between an imbalance in the gut microbiota and the development of amyloid plaques in the brain, which are characteristic of Alzheimer's disease, according to a new study published in the Journal of Alzheimer's Disease.

Proteins produced by certain intestinal bacteria, identified in the blood of patients, could modify the interaction between the immune and the nervous systems and trigger the disease. These results make it possible to envisage new preventive strategies based on the modulation of the microbiota of people at risk, the researchers said.

To determine whether inflammation mediators and bacterial metabolites constitute a link between the gut microbiota and amyloid pathology in Alzheimer's disease, researchers studied a cohort of 89 people between 65 and 85 years old. Some suffered from Alzheimer's disease or other neurodegenerative diseases causing similar memory problems, while others did not have any memory problems, according to the study.

Using PET imaging, the researchers measured amyloid deposition and then quantified the presence in their blood of various inflammation markers and proteins produced by intestinal bacteria, such as lipopolysaccharides and short-chain fatty acids.

The researchers found that certain bacterial products of the intestinal microbiota are correlated with the quantity of amyloid plaques in the brain. High blood levels of lipopolysaccharides and certain short-chain fatty acids were associated with both large amyloid deposits in the brain. Conversely, high levels of another short-chain fatty acid, butyrate, were associated with less amyloid pathology, the researchers said.

The study provides evidence of an association between certain proteins of the gut microbiota and cerebral amyloidosis through a blood inflammatory phenomenon. The researchers said they will now work to identify specific bacteria, or a group of bacteria, involved in this phenomenon.