The role the microbiome plays in human health has long been studied, but recent studies have been elucidating that it may play a bigger role than originally thought.
Links between the gut and the brain have been established, named the “gut-brain axis”, referring to the physical and chemical connections between the gut and the brain – suggesting improving the gut microbiome may improve brain health. A new study has traced the molecular connections between the gut microbiome, genetics and memory in mouse models.
The study indicates that the microbiome might partner with genetics to affect memory in mice. Antoine Snijders, co-author of the study, states that the challenge is that “a mouse’s unique genetic makeup and environmental conditions also impact its memory and microbiome.” To know if a microbial molecule influenced memory, they needed to understand the interaction between the microbiome and genetics.
More than 100 papers have been published in the last five years on links between common probiotics and memory. The researchers of the study bread 29 strains of mice to mimic the diversity of the human population, including mice of different sizes, colours, and disposition. Then each strain of mice was given a memory test and compared with GWAS. Two sets of genes were found to be associated with memory. The researchers then analysed the gut microbiome of each strain and identified four families of microbes that were associated with improved memory – the most common of which was Lactobacillus Reuteri. Mice without any gut microbes were then fed L. reuteri and saw a significant improvement to memory relative to germ-free mice who were not fed any microbes.
The link between Lactobacillus and memory has been reported previously but this study found it independently, in an unbiased genetic screen, suggesting that genetic variation largely controls memory as well as gut composition. The study concluded by analysing the stool, blood and brain tissue of the germ-free mice that were fed the lactobacillus and found that lactate was a common molecular by-product produced by the bacteria. To identify whether the lactate played a role, the team fed lactate to mice that were previously identified to have poor memory and noted an improvement.
More work is needed to show whether Lactobacillus can improve memory in humans, but the research strengthens the idea that diet, genetics and the gut microbiota all influence memory.