2023-06-16 07:45:13
Intestinal microorganisms in presymptomatic Alzheimer’s differ from those of healthy people.
More and more studies highlight the associations between what is known as the gut-brain axis and there are also more relationships on the influence of the microbiome on different systems of the organism.
The neurological field is one of those that have been incorporated into the influence of bacteria in pathologies, especially neurodegenerative ones. In many cases, scientists are looking for interrelationships that may offer potential causes of the disease process, as well as preventive or therapeutic approaches.
One of the latest contributions, published by Science Translational Medicine, shows that people who are in the earliest stage of Alzheimer’s disease -a period in which brain changes have begun but cognitive symptoms have not yet manifested -, harbor a variety of bacteria in their gut microbiome different from those of people who do not have this neurodegenerative disease, according to a study by researchers at the University of Washington School of Sciences, United States.
Gautam Dantas, professor of Genomic Medicine at the aforementioned university and co-author of the work, considers that these observations “open up the possibility of analyzing the intestinal bacterial community to identify people with a higher risk of developing dementia. This would also allow the design of potential preventive treatments: microbiome modifiers capable of preventing cognitive deterioration.”
Microbiome Modifiers
Dantas also points out that it is still unknown which system pivots the influence. “We don’t know if the gut is influencing the brain or if the brain is influencing the gut. In any case, the knowledge of this association is very valuable”.
The researcher suggests that it could be that changes in the gut microbiome are just a readout of pathological variations in the brain. Another alternative is that the gut microbiome is contributing to Alzheimer’s disease, in which case “altering or modifying the gut microbiome with probiotics or fecal transplants could help change the course of neurodegeneration.”
The paper explains that the idea to study the connection between the gut microbiome and Alzheimer’s arose at a youth soccer game, where Dantas and neurologists from the same university, Beau M. Ance and Daniel J. Brennan, chatted while their children played.
The scientific community knows that the gut microbiomes of people with symptomatic Alzheimer’s differ from the microbiomes of healthy people of the same age. But, the University of Washington professors noted that “no one had yet examined the gut microbiomes of people in the critical presymptomatic phase.”
According to Ances, co-author of the study, “by the time people have cognitive symptoms, there are already significant changes that are often irreversible. But if it were possible to make an early diagnosis, that would be the optimal time to intervene therapeutically effectively.”
During the early stage of Alzheimer’s disease, which can last for two decades or more, affected individuals accumulate clusters of beta amyloid and tau proteins in their brains, but show no signs of neurodegeneration or cognitive decline.
Dantas, Ances and Aura L. Ferreiro, first signatory of the work, and member of the Laboratory of the aforementioned university, evaluated the participants who volunteered for studies at the Charles F. and Joanne Knight Alzheimer’s Disease Research Center at the University of Washington. All participants were cognitively normal. As part of this study, participants provided stool, blood, and cerebrospinal fluid samples; as well as daily monitoring of food consumed. Imaging tests such as PET and MRI brain scans were also performed.
To distinguish participants who were already in the early stages of Alzheimer’s disease from those who were healthy, the researchers looked for signs of amyloid beta and tau buildup through brain scans and cerebrospinal fluid. Of the 164 participants, about a third (49 people) had signs of early Alzheimer’s.
The various analyzes revealed that healthy people, versus those with preclinical Alzheimer’s disease, have markedly different gut bacteria, referring to the species of bacteria present and the biological processes those bacteria are involved in, despite eating basically the same diet.
“These differences were correlated with amyloid and tau levels, which rise before cognitive symptoms appear, but did not correlate with neurodegeneration, which becomes apparent when cognitive abilities begin to decline. These differences could potentially be used to detect early Alzheimer’s,” says Ferreiro. “The good thing about using the gut microbiome as a screening tool is its simplicity and ease,” Ances adds.
Does it cause the result?
The same researchers have launched a five-year follow-up study designed to determine whether differences in the gut microbiome are a cause or a result of the brain changes seen in early Alzheimer’s disease.
According to Dantas, if there is a causal link, it is most likely inflammatory. “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 whole body’s immune system.”
These claims currently sit in the realm of speculation, but “if a causal link turns out to exist, we might start to think about whether promoting ‘good’ bacteria or eliminating ‘bad’ bacteria would slow or even stop the development of symptomatic symptoms of the disease.” Alzheimer’s.” Rachel Serrano
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