• March 3, 2024

Altered gut microbes may indicate Alzheimer’s disease 2023

Researchers at Washington University School of Medicine in St. Louis found that people in the early stages of Alzheimer’s disease, after brain changes but before cognitive symptoms, have a different gut bacteria than healthy people.

The findings, published June 14 in Science Translational Medicine, suggest examining the gut bacterial ecology to determine dementia risk and creating microbiome-altering preventative medicines.

“We don’t yet know whether the gut is influencing the brain or the brain is influencing the gut, but this association is valuable in either case,” said co-corresponding author Gautam Dantas, PhD, the Conan Professor of Laboratory and Genomic Medicine.

The gut microbiota may reflect brain pathology. Altering the gut microbiota with probiotics or feces may modify the course of Alzheimer’s disease if it’s contributing to it.

Intestinal microorganisms vary in early Alzheimer’s patients.

While watching their children play soccer, Dantas and Beau M. Ances, MD, PhD, the Daniel J. Brennan Professor of Neurology, discussed exploring the gut microbiota and Alzheimer’s disease. Ances treats Alzheimer’s patients; Dantas examines gut microbiomes.

Scientists previously knew that symptomatic Alzheimer’s patients’ gut microbiomes varied from healthy persons of the same age. Ances told Dantas that no one had studied pre-symptomatic gut microbiomes.

“By the time people have cognitive symptoms, there are significant changes that are often irreversible,” said Ances, another co-corresponding author. “But if you can diagnosis someone very early in the disease process, that would be the optimal time to effectively intervene with a therapy.”

Early Alzheimer’s disease, which can span two decades or more, causes brain aggregates of amyloid beta and tau but no neurodegeneration or cognitive impairment.

Dantas, Ances, and lead author Aura L. Ferreiro, PhD, then a graduate student in Dantas’ lab and now a postdoctoral researcher, examined Washington University’s Charles F. and Joanne Knight Alzheimer Disease Research Center volunteers. Everyone was intellectually normal. This study required feces, blood, and cerebrospinal fluid samples, diet diaries, and PET and MRI brain images.

Brain scans and cerebrospinal fluid were examined for amyloid beta and tau buildup to identify early-stage Alzheimer’s patients. 49% of 164 individuals had early Alzheimer’s.

“The gut microbiome is simple and easy to screen,” Ances added. One day, people may be able to offer a feces sample to determine their risk of Alzheimer’s disease. Compared to brain scans or spinal taps, it would be easier, less intrusive, and more accessible for a huge section of the population, especially underrepresented groups.

“If there is a causal link, we can start thinking about whether promoting ‘good’ bacteria or getting rid of ‘bad’ bacteria could slow down or even stop the development of symptomatic Alzheimer’s disease.”

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