2023-06-18 08:06:45
The microbiota is a central element of our health, it changes with age but also because of diseases. So much so that scientists believe that changes in the intestinal microbiota could predict Alzheimer’s disease.
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Between the appearance of the first amyloid plaque and the first symptoms of Alzheimer’s, an average of ten years elapses during which a patient suffers from a pre-clinical form of the disease. Scientists are seeking to identify biological markers that will be able to predict the evolution of symptoms until the diagnosis of Alzheimer’s diseaseAlzheimer’s disease is confirmed (all pre-clinical forms of Alzheimer’s progress towards the typical symptoms of the disease).
At Washington University in St. Louis, in the United States, a group of researchers believe that an imbalance in the intestinal microbiota could constitute a reliable biomarker of pre-clinical Alzheimer’s. Indeed, they observed significant differences in the microbiotamicrobiota healthy volunteers and volunteers at the pre-clinical stage. Their work has appeared in Science Translational Medecine.
The intestinal microbiota, the first indicator of Alzheimer’s disease
The gut microbiota is a complex community of microorganismsmicroorganisms which have no less than one hundred trillion bacteria. To simplify the study of the imbalance, which is also called dysabiosis, which can affect this fragile community, the scientists use the ratio between the bacteria belonging to the group of FirmicutesFirmicutes and those belonging to the Bacteroides group. This ratio changes according to age or the presence of pathologypathologyfor example, the microbiota of a healthy adult of normal build contains five times more Firmicutes than Bacteroides, that of an elderly person five times more and that of an obese person one hundred times more.
In this study, the scientists did not observe any significant differences in the Firmicutes/Bacteroides ratio between healthy volunteers and volunteers with a pre-clinical stage of Alzheimer’s. On the other hand, some speciesspecies bacteria are present only in sick patients, like the genus Alistipes, Barnesiellaor Odoribacter. The presence of these bacteria is also correlated with that of amyloid plaques and aggregates of tau proteintau protein observed in the brainbrain thanks to a PET-scan, but not with other markers of neurodegeneration.
Obviously, these results remain to be confirmed because they were obtained on only 49 patients with pre-clinical Alzheimer’s. If the composition of the adult microbiota is stable, taking certain medications or aging can modify it. At present, these observations cannot therefore be generalized to the entire population.
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