The gut microbiome is the aggregate genome of the microbiota living in the gastrointestinal tract, implicated in numerous host systemic functions, behaviors, and diseases.
Past studies have shown probiotics, ingestible microbes that interact with the microbiota to benefit health, comprised of Lactobacillus strains impact the reduction of anxiety and the improvement of memory in mice. These results suggest a link between the gut microbiome and host behavior via the gut-brain pathway, however, this axis remains unmapped in terms of neurology.
Probiotics for improved memory
Now, a study from researchers at two U.S. Department of Energy national laboratories traces the molecular connections between genetics, the gut microbiome, and memory in a mouse model bred to resemble the diversity of the human population. The team states one day it may be possible to use probiotics to improve memory in people with learning disabilities and neurodegenerative disorders. The opensource study is published in the journal Microbiome.
Previous studies show probiotics provide several health benefits via their production of chemical messengers capable of influencing parts of the body, including the brain. Many studies have indicated a link between specific metabolites produced by Lactobacilli and the host’s memory via the gut-brain axis.
However, the interaction between the host’s genetics, environment, quality of life, and gut microbiome greatly hinder the investigation into the role of the microbiota on memory in genomically varied human populations.
A solution to this problem could be what is known as a “Collaborative Cross” (CC), a population-based mouse model system with genetic and phenotypic diversity mimicking the human population. The current study establishes the existence of the link between host genetics, microbes in the gut, and memory using the CC mouse cohort, verified with microbiome and genomic analyses.
The microbiome and memory
The current study bred twenty-nine different strains of mice mimicking the genetic diversity of a human population to determine how genetics influence memory. Each genomic variation of mouse performed the same memory assessment and underwent genetic screening to correlate strain aberrations with different test results.
Results identified two sets of genes associated with memory, one of which was a set of previously unknown genes implicated in the influence of cognition, with the other set of genes already recorded.
The lab then analyzed the gut microbiome of each strain of mouse to link the microbiota to the neurogenetic-based memory results. Results show four families of microbes are associated with improved memory, the most common of which is a species of Lactobacillus, known as L. reuteri. To verify these findings L. reuteri was fed to mice lacking a gut microbiota before memory tests were run on them.
The group states a significant improvement was observed in the mice fed microbes as opposed to the germ-free mice who were not given probiotics. They go on to add this suggests genomic variation controls the performance of memory, as well as the differences in the composition of the gut microbiome and health across different strains of species.
The team surmises they provide new evidence of connections between the gut, genetics, and the brain in regards to memory. For the future, the researchers state further work is needed to show if Lactobacillus can improve memory in humans.
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