Gut microbes may shape human intelligence and continue to influence our brains

A study published in Proceedings of the National Academy of Sciences found that transplanting gut microbes from different primates into mice changed gene expression in the mice's brains, affecting energy use and genes linked to synapses. The results come from animal models and researchers say testing for similar effects in humans is the next step.

Researchers report that gut microbes from different primate species can change gene activity in mouse brains. The study, published in Proceedings of the National Academy of Sciences, involved transplanting gut microbes from humans, squirrel monkeys and macaques into mice. After eight weeks, mouse brain gene expression shifted in ways that reflected the animals that supplied the microbes. Many of the affected genes related to how much energy the brain uses and to synapse formation. The authors say the results offer clues about brain evolution and raise questions about whether similar influences occur in people. Key findings: - The PNAS study transplanted gut microbes from humans, squirrel monkeys (larger-brained) and macaques (smaller-brained) into mice and observed brain gene changes after eight weeks. - Mice that received microbes from larger-brained primates showed gene expression linked to higher brain energy use and to genes associated with synapse production. - Mice given macaque-associated microbes showed brain gene patterns more like macaques, while mice given human-associated microbes showed patterns more like humans. - Researchers outline three main pathways for microbial influence on the brain: direct interaction with the gut nervous system, effects via the immune system, and microbial production of neurotransmitters such as serotonin and dopamine. - The authors note that each primate species has a characteristic microbial profile, and they emphasize that current findings come from animal models, so human relevance is undetermined at this time. - Commenting on broader implications, one researcher described the findings as adding to evidence that age-related microbiome changes may relate to cognitive decline. Summary: The study suggests gut microbes can modulate brain gene activity and provides a possible link to questions about brain evolution and brain-related conditions. Determining whether comparable microbial influences occur in humans is the next key step, and researchers plan further work on behavior and other physiological effects.