Early detection of Alzheimer’s dementia: gut microbiome could be key

New study shows changes in gut bacteria precede onset of Alzheimer’s symptoms

Ways to detect early signs of Alzheimer’s dementia are being intensively researched around the world. People are looking for reliable methods to diagnose the disease before the brain is severely damaged so that appropriate therapies can be initiated in time.

The scientific community is mostly focused on early detection strategies involving biomarkers in the blood or cerebrospinal fluid, including elevated levels of proteins such as amyloid beta and tau. Research is also underway to determine how imaging techniques, such as PET scans and MRI, can help detect early signs of AD. Recent studies are also beginning to explore the potential of the gut microbiome for early detection.

Study results point to changes in gut bacterial flora

Even in the initial stages of Alzheimer’s disease, long before cognitive impairments become apparent, study results from Washington University School of Medicine in St. Louis indicate noticeable changes in the bacterial flora of the gut. The results suggest that the study of gut bacteria could play a key role in the early detection of Alzheimer’s disease, according to the scientists:in. The study, titled “The nature of the gut microbiome as a potential indicator of preclinical Alzheimer’s disease,” has now been published in the journal Science Translational Medicine.

“When cognitive symptoms emerge in individuals, we often detect significant, usually irreversible, changes. But if we were able to make a diagnosis very early in the course of the disease, this would be the ideal time to begin effective therapy,” Beau Ances, MD, PhD, and co-author of the study, said in a press release.

“Of all things, the simplicity and accessibility of the gut microbiome make it a suitable screening tool,” Ances adds. “We can imagine that one day people might be able to give a stool sample to determine their risk for Alzheimer’s. Compared to brain scans or lumbar punctures, this would be a much less invasive and more accessible method for a broad population, especially underrepresented groups.”

Microorganisms may indicate dysregulation in Alzheimer’s

Our digestive tract is home to billions of bacteria and other microorganisms collectively known as the gut microbiome. These microscopic inhabitants of our digestive systems play an indispensable role in maintaining our health. New research suggests that they may exhibit dysregulation in Alzheimer’s and other neurodegenerative diseases.

The human gut is home to an incredible number of bacteria and other microorganisms that we refer to as the gut microbiome. These microscopic housemates of the digestive tract are essential for health maintenance. Recent research suggests that dysregulation of these microorganisms may occur in Alzheimer’s and other neurodegenerative diseases.

Amyloid accumulation also detected in healthy people

In the brain, Alzheimer’s disease is characterized by the formation of toxic deposits of the protein amyloid beta. However, it is interesting to note that these amyloid-beta accumulations can also be detected in some people who do not have symptoms of Alzheimer’s disease.

The researchers suggest that this asymptomatic accumulation of amyloid-beta represents an early, preclinical stage of Alzheimer’s disease. At this stage, the disease-causing biological processes have begun but have not progressed far enough to cause detectable symptoms.

“In the future, people could give a stool sample to determine if they are at increased risk of developing Alzheimer’s.”

Although changes in the gut microbiome have been reported in people with symptomatic Alzheimer’s disease compared with healthy individuals, it is still uncertain whether these changes also occur in preclinical stages of the disease. To address this issue, researchers compared data from stool samples of people with preclinical Alzheimer’s disease to those without Alzheimer’s.

The study included 164 participants, aged 68 to 94, who showed no irregularities on cognitive tests. Through data from brain scans and cerebrospinal fluid analyses, it was found that 49 of the participants (29.9 percent) had accumulation of amyloid beta and tau – another protein that forms toxic clumps in Alzheimer’s. The remaining 115 people (70.1 percent) showed no signs of such protein deposits and were considered healthy. These formed the control group.

The group of patients with preclinical Alzheimer’s disease tended to be older and had a lower body weight than the control group. In addition, fewer participants in this group were black or suffered from diabetes. Nevertheless, dietary habits, which can have a significant impact on the composition of the gut microbiome, were largely similar in the two groups. Using statistical models to account for demographic differences, the researchers compared the composition of the participants’ gut microbiome.

Higher concentrations of several bacterial species in preclinical Alzheimer’s dementia

The analysis revealed statistically significant differences in gut microbiome profiles between individuals with and without preclinical Alzheimer’s disease. Several bacterial species-including Dorea formicigenerans, Oscillibacter sp. 57_20, Faecalibacterium prausnitzii, Coprococcus catus, and Anaerostipes hadrus-had significantly higher concentrations in the group with preclinical Alzheimer’s disease.

“Our data suggest that the human gut microbiome may undergo early changes in Alzheimer’s disease, even before cognitive impairments become apparent,” the study authors said.

Further statistical analysis showed that accuracy in identifying individuals with preclinical Alzheimer’s disease was improved when gut microbiome data were included in the models. This compared with models that relied solely on demographic and clinical factors.

Among patients:with preclinical Alzheimer’s disease, those who had greater dysregulation of their gut microbiome tended to have higher levels of amyloid beta and tau.

“Linking gut characteristics to the unmistakable molecular features of early Alzheimer’s disease processes underscores their potential value as additional predictive markers of early disease progression,” the researchers emphasize.

However, the scientists point out a limitation of their study: The gut microbiome can change over time, while stool samples in their study were collected only once. Therefore, they emphasize the need for future studies that analyze the gut microbiome at different time points.

The fact that not everyone with preclinical AD actually develops symptomatic symptoms later in life also emphasizes the need for further long-term studies, the research team said.

Amended microbiome: cause or consequence of the disease?

The scientists:also emphasized that although the data suggest that the gut microbiome is dysregulated in the early stages of Alzheimer’s disease, it is not yet clear whether this finding is a cause or a consequence of the disease.

“We’re not yet sure whether the gut affects the brain or vice versa, but either way, this link is valuable to explore,” says Gautam Dantas, PhD and co-author of the study at Washington University.

Opening new doors for future treatment strategies

If the gut is shown to affect the brain in a way that contributes to the development of Alzheimer’s, it could open new doors for treatment strategies.

“All of these considerations are hypothetical at this point, but if a causal link is confirmed, we could consider whether promoting ‘good’ bacteria or eliminating ‘bad’ bacteria could slow or even stop progression toward symptomatic Alzheimer’s disease,” Dantas adds.