A recent study conducted by Professor Omry Koren and graduate student Atara Uzan-Yuzari at the Azrieli Faculty of Medicine at Bar-Ilan University identified a strong link between the gut microbiome and aggressive behavior in mice. Published in the journal Brain, Behavior, and Immunity, the research demonstrates how alterations in the microbiome, particularly resulting from early-life antibiotic exposure, can contribute to heightened aggression.
The study expands upon prior research that observed a connection between antibiotic exposure and increased aggression in fruit flies. By employing a mouse model, the researchers have advanced this investigation, exploring behavioral, biochemical, and neurological modifications resulting from changes in the microbiome.
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The team also transplanted a microbiome derived from infants who had received antibiotics shortly after birth into mice, observing notable increases in aggression compared to those receiving a microbiome from infants not exposed to antibiotics.
“Our findings are revolutionary,” said Prof. Koren. “They suggest that a disrupted microbiome during critical developmental periods can lead to persistent aggressive behaviors later in life.”
To assess aggression, the research team employed the resident-intruder paradigm, where a foreign mouse is introduced into the home cage of a resident mouse. The results indicated a clear link between reduced diversity in gut bacteria—caused by antibiotic treatment—and increased aggression. Additionally, significant changes in metabolites and gene expression related to aggression were observed in the brains of the mice.
The study is particularly noteworthy for its use of “humanized” mice, which have been implanted with human intestinal bacteria. This approach enhances the relevance of the findings to human health and behavior, providing insights into how early-life antibiotic exposure can shape future social behaviors.
The research also explores the biochemical mechanisms underlying these behavioral changes, measuring neurotransmitter levels such as serotonin and tryptophan in the brains of the mice. The team identified key patterns of gene expression in several brain regions, highlighting the septum as a crucial area in regulating aggression.
The results of this study indicate that the gut-brain axis is instrumental in the development of aggression, especially when the microbiome is disrupted during critical developmental stages, like infancy. This research suggests new possibilities for understanding how early-life interventions might impact long-term behavioral outcomes and for creating strategies to mitigate these effects and enhance social behavior.
