Your gut microbiome can influence your social skills

            Have you ever heard the saying that your gut is your body’s second brain? This reference usually refers to the idea of the gut-brain-axis, a bi-directional signaling system between the central nervous system (CNS) and the enteric nervous system (ENS). Recent studies pertaining to the gut-brain-axis have centralized around the notion of the gut microbiome and the significance it may hold to an individual’s overall health. This bi-directional signaling system between the brain and the gastrointestinal tract is important for maintaining homeostasis and regulating hormonal and immunological levels in the body. Further evidence has suggested that this axis is significant because the interconnections between both systems may postulate an alternation with behavior. Interestingly, recent evidence demonstrates that the gut may have an overall function in mood, behavior, and diseases. It is suggestive that if disruption occurs within the gut-brain-axis, dysbiosis can present itself as mood disorders via dysbiosis of the microbiota. Notably, the lack or disturbance of microbial colonization of bacteria within the gut leads to both altered and turnover of neurotransmitters in the CNS and ENS. Previous studies have demonstrated the vagus nerve is significantly involved with communication occurring from brain to gut and vice versa.

Current research has expanded on the idea of the interconnections between behavior and the microbiome. Studies have mostly focused on animal behavior as it pertains to the microbiome. This is because most animals have a very diverse community of bacteria that can affect their physiology, metabolism, and susceptibility to disease. Scientists have focused on the notion that the microbiome can affect social behavior because microbes create chemical cues that animals use in social communication. The chemical signal is via an animal’s odor producing bacteria in their scent glands which is then used for communication. Experimental studies centralized on the gut microbiome specify that antibiotics or changes made to our diet can as well lead to changes in cognitive behavior, including gene expression levels in the brain.

In a more recent study, it has become suggested that zebra fish contain gut microbes that can be essential to the brain’s social development. Although the research is primarily focused on fish, scientists have indicated that there may be molecular and neurological evidence that suggest it could also occur in humans. This recent publication, researchers found that zebra fish that grew up without a diverse gut microbiome were far less social than other fish colonized colons and the structures of their brains as well reflected the difference. It has been known that there is a link between neurodevelopmental disorders and gastrointestinal disorders. Kara Margolis, a pediatric gastroenterologist at NYU’s Langone Health, elucidated, “Not only does the brain have an impact on the gut, but the gut can also profoundly affect the brain.” Zebra fish are known to be naturally social, after they turn two weeks old, they usually begin to socialize in groups ranging from four to twelve. Researchers experimented with “germ-free” zebra fish that lacked a gut microbiome when they were within the embryo stage. After they hatched, some of the fish were inoculated with healthy bacteria. The remaining fish weren’t inoculated until a week later therefore, forcing these group of fish to begin development with “a blank slate.”

Results concluded that the fish who were inoculated at birth began to socialize at 15 days, however the germ-free fish didn’t socialize at all. Upon examining the fishes’ brains, researchers discovered that forebrain neurons in fish who started life without a healthy mix of microbiome, demonstrated to have more interconnections. They also has fewer microglia. Microglia is essential for the clean-up of debris in the brain. It was hypothesized that having a healthy gut microbiome enables microglia to flourish in the brain. During development, it is important that microglia play its role because the branching of neurons otherwise become tangled and overgrown. It remains unclear how exactly these gut microbes send signals to the developing brain. A couple of possible explanations could relate to immune cells, the blood brain barrier, or the vagus nerve. The mechanisms pertaining to the gut microbiome is yet to be understood and is open for discovery. By understanding the mechanisms the interconnections of the gut microbiome as it pertains to the gut-brain-axis would allow us to gain a better understanding of gastrointestinal diseases and disorders, in addition to take preventive measures towards neurodevelopmental disorders and strengthen therapeutic measures.

1.      Archie, Elizabeth A., and Jenny Tung. "Social behavior and the microbiome." Current opinion in behavioral sciences 6 (2015): 28-34.

2.     Cryan, J. F., and S. M. O’Mahony. “The Microbiome-Gut-Brain Axis: from Bowel to Behavior.” Neurogastroenterology & Motility, vol. 23, no. 3, 2011, pp. 187–192., doi:10.1111/j.1365-2982.2010.01664.x. 

3.     Carabotti, Marilia et al. “The gut-brain axis: interactions between enteric microbiota, central and enteric nervous systems.” Annals of gastroenterology vol. 28,2 (2015): 203-209. 

4.   Thompson, Joanna, and substantive Quanta Magazine moderates comments to facilitate an informed. “The Gut Microbiome Helps Social Skills Develop in the Brain.” Quanta Magazine, 15 Nov. 2022, https://www.quantamagazine.org/the-gut-microbiome-helps-social-skills-develop-in-the-brain-20221115/.