The microbiome of people with Alzheimer's disease may mediate disease risk.
Alzheimer’s disease, the most common cause of dementia, has been the subject of a large body of research in recent decades. However, the number of effective therapies for the disease is small, demonstrating the need for additional research into the mechanisms of dementia. Findings from a group of scientists researching the gut microbiota suggest the microbiota-gut-brain axis may contribute to Alzheimer’s pathology.
The microbiota-gut-brain axis is a recently developed way to understand the relationship between the behavior of microbes in the gut and behaviors generated by the brain. This bidirectional highway of information delivers commands from the brain to the gut using nervous and endocrine signals and sends information from bacteria in the gut to the brain using nervous, circulatory, and immune pathways. Previous research has identified alterations in the composition and function of the gut microbiota in people with neurodegenerative diseases such as Parkinson’s disease and amyotrophic lateral sclerosis; however, the relationship between the microbiota and brain in people with Alzheimer’s disease requires additional research.
The authors recruited 43 participants who had Alzheimer’s disease and 43 healthy participants who were matched with age and sex. Participants completed questionnaires about their mental health and cognitive function and provided a stool sample, which the researchers used to sequence the bacterial DNA in each participants' gut microbiome. Finally, the researchers selected twelve participants to receive a positron emission tomography (PET) scan to measure amyloid-beta deposition in the brain, which is the clinically standard way to diagnose Alzheimer’s disease.
Enjoying this research? Get deeper insights like this delivered every other week.
Every other week our Premium Members receive deep dives like this alongside Rhonda's commentary and 8+ other hand-picked papers.
The microbiome of participants with Alzheimer’s disease differed from those without Alzheimer’s disease at the phylum, order, and family levels (i.e., scientific categories used to organize microbes into groups using their genes), with higher levels of phyla Bacteroidetes and lower levels of the phyla Actinobacteria and Verrucomicrobia and family Ruminococcaceae. Altered levels of these bacteria may be related to diet, as previous research has shown that some members of the Ruminococcaceae produce harmful compounds from bile acids released by the liver in response to dietary fat. Also, Akkermansia muciniphila, a member of the Verrucomicrobia has been shown to produce beneficial products from dietary fibers, but may increase inflammation and attack the gut barrier in diseases such as ulcerative colitis.
In this cross-sectional study, the authors found important differences between the microbiomes of participants with and without Alzheimer’s disease. The authors did not measure microbial metabolites in this study; however, the authors suggest these compounds are a key mechanisms of these associations.
[Learn more about the gut microbiota and disease from expert, Dr. Eran Elinav, in this interview.](https://www.foundmyfitness.com/episodes/eran-elinav)