Analyzing the composition of the gut microbiota could help identify people at higher risk of developing Alzheimer’s, since once the brain changes associated with this neurodegenerative disease have begun, but before cognitive symptoms begin to manifest, the variety of bacteria present in the gut is different from that of healthy people, a team of researchers at the Washington University School of Medicine in St. Louis has discovered.
“We don’t yet know if the gut is influencing the brain or the brain is influencing the gut, but in any case it is useful to know this association,” said co-author Gautam Dantas, Conan Professor of Laboratory and Genomic Medicine. “It could be that changes in the gut microbiome are just a readout for pathological changes in the brain. The other alternative is that the gut microbiome is contributing to Alzheimer’s disease (AD), in which case altering the gut microbiome with probiotics or fecal transplants could help change the course of the disease.”
The results of the new research have been published in Science Translational Medicine and could allow early detection of Alzheimer’s through analysis of the intestinal bacterial community and contribute to the development of therapies capable of altering the intestinal microbiome to prevent cognitive decline.
Promote ‘good’ bacteria or eliminate ‘bad’ bacteria to prevent Alzheimer’s
Although it was already known that the gut microbiomes of patients with Alzheimer’s symptoms were different from those of healthy people of the same age, the gut microbiomes of people who already have accumulations of beta amyloid and tau proteins have not been examined until now. their brains –characteristics of this pathology–, but that still did not show signs of neurodegeneration or cognitive deterioration.
“Someday, people will be able to provide a stool sample and find out if they are at increased risk of developing Alzheimer’s disease.”
“By the time people have cognitive symptoms, there are significant changes that are often irreversible,” said Beau M. Ances, MD, Daniel J. Brennan Professor of Neurology and co-author. “But if you can diagnose someone very early in the disease process, that would be the optimal time to effectively intervene with a therapy.”
Dantas, Ances, and first author Aura L. Ferreiro, evaluated 164 volunteers, who were cognitively normal, and underwent brain scans (PET and MRI) that revealed that about a third of them (49) had early preclinical AD biomarkers. . Participants also provided stool, blood, and cerebrospinal fluid samples and kept a food diary.
Although the volunteers ate basically the same diet, an analysis revealed that healthy people and people with preclinical Alzheimer’s disease had markedly different gut bacteria, both with respect to the species of bacteria present and the biological processes in which those bacteria are involved. These differences correlated with amyloid and tau levels, which rise before cognitive symptoms appear, but did not correlate with neurodegeneration, which becomes evident when cognitive abilities begin to decline. These differences could potentially be used to detect early Alzheimer’s disease, the researchers have said.
“The beauty of using the gut microbiome as a screening tool is its simplicity and ease,” Ances said. “Someday, people will be able to provide a stool sample and find out if they are at increased risk of developing Alzheimer’s disease. It would be much easier, less invasive and more accessible for a large part of the population, especially underrepresented groups, compared to brain scans or spinal taps.”
Researchers have launched a five-year follow-up study designed to determine whether differences in the gut microbiome are a cause or a consequence of the brain changes seen in the early stages of Alzheimer’s. “If there is a causal link, the link is most likely inflammatory,” Dantas said. “Bacteria are these amazing chemical factories, and some of their metabolites affect inflammation in the gut or even make their way into the bloodstream, where they can influence the immune system throughout the body. This is all speculative at this point, but if a causal link turns out, we can start to think about whether promoting the ‘good’ bacteria or eliminating the ‘bad’ bacteria might slow or even stop the development of symptomatic Alzheimer’s.”
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