Social fear is actually determined by microorganisms in the body. Scientists have now realized that "the mechanism is hard to find, intestinal flora"

Zhan Shi comes from Aofei Temple
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Is social phobia determined by the microbes in the body? ? ?

Recently, a series of studies from the University of Oregon point to this claim.

More specifically, the researchers found that the diverse gut microbiota help shape brain systems related to social skills during the early critical stages of animal brain development.

Conversely, animals lacking a gut microbiome were less social than their microbiota-implanted counterparts.

This conclusion has attracted a lot of attention so far.

The technology media QuantaMagazine reported on the discovery, and the related post on Reddit also received over 500 likes.

Some netizens said that yogurt is about to be bought. ( Isn’t it a bit late to drink now? )

Some netizens also shared their observations that autism is often accompanied by gastrointestinal problems, and the two may be related.

So, what exactly did scientists observe?

Kill the "little transparent" intestinal flora

The research subject of this experiment is quite interesting. It is a type of zebrafish that reproduces rapidly and is naturally social. Social characteristics such as aggregation, kin recognition, and aggression appear at 12-16 days of embryonic development.

In addition, most of the body of this fish is transparent before it becomes an adult, which allows scientists to observe the internal development of these "little transparent" fish without having to perform dissection.

△ Source: wikicommons

The research team first sterilized a portion of the embryos and then performed sterilization treatment to remove their own microbiota. Then, after 7 days of development, they were inoculated with normal microbiota and observed their social behavior.

Simultaneously, a control group ( CVZ ) was cultured so that they were implanted with the gut microbiome and allowed to grow naturally from day zero.

The results showed that the frequency of social behaviors in zebrafish that were aseptic and implanted with microorganisms ( XGF group, the same below ) was significantly reduced compared to the control group with normal growth of microorganisms .

Moreover, compared with fish of the same age, the trajectory of the fish swimming with the school ( the cyan XGF group in the figure below ) is more likely to deviate and become uncertain.

At the same time, the researchers also stimulated their vision and observed their reactions and swimming speeds. No obvious differences were found, indicating that the relevant microbiota did not affect their sensory and motor abilities.

To further explore why, they observed neuron development in the brains of zebrafish re-implanted with microbiota through a microscope and found obvious structural differences .

Earlier research has shown that normal social behavior in animals is related to a neuron called vTely321. In this experiment, the researchers found that vTely321 neurons were significantly reduced in embryonic development after sterile treatment.

In addition, compared with the control group, the synapses of sterile-treated zebrafish vTely321 showed deeper "arborization" characteristics. And this process continues into late childhood development.

The details are as shown in the figure below. The upper part is the naturally grown control group, and the lower part is the XGF group that was treated aseptically and then implanted with microorganisms:

The above phenomena lead researchers to believe that various types of microbiota in the intestine can influence the differentiation and growth of vTely321 neurons with biological social abilities.

Furthermore, researchers speculate that the intestinal microbiota is related to microglia in the organism.

Because this type of cells is mainly responsible for "building" the overly complex arms of neurons and inhibiting arborization during the critical period of rapid development of the embryonic brain.

Through observation, they found that indeed after sterile treatment ( GF group ), the number of microglia in the fish brain was less than that in the control group:

From this, the researchers confirmed that the intestinal microbiota will affect the function of microglial organelles in biological development.

It is worth mentioning that the phenomenon of intestinal microbiota affecting the social ability of zebrafish is not a special case .

In another experiment from the same laboratory at the University of Oregon, scientists found that zebrafish vTely321 neurons and mouse social-related neuron clusters had a high degree of overlap in gene expression and function.

In the figure below, the first column shows the expression of vTely321 neurons in zebrafish during embryonic development, and the second and third columns show the expression of two CGN neurons in mice. The scientists observed using markers and found a high degree of similarity:

However, scientists also remind that the neural pathways of different organisms are different. In the future, they will continue to study how intestinal microbiota affects brain principles, especially in humans.

In addition, they hope to find ways to intervene to reverse brain development problems caused by the microbiome.

team introduction

Finally, let’s get to know the team behind the above research, they are from the University of Oregon Neuroscience Institute.

The scientists who led the series of studies included Judith S. Eisen and Philip Washbourne.

Philip Washbourne and his team focus on studying the impact of genetic molecules and cells on animal social behavior.

Judith S. Eisen's team focuses on the nervous system of vertebrates, including: how neurodiversity arises, neural circuit connections, and the relationship between microorganisms and the host in neural development.

Reference links:
[1] https://www.quantamagazine.org/the-gut-microbiome-helps-social-skills-develop-in-the-brain-20221115/
[2] https://journals.plos.org /plosbiology/article?id=10.1371/journal.pbio.3001838#sec001
[3] https://bmcgenomics.biomedcentral.com/articles/10.1186/s12864-022-08879-w
[4] https://ion.uoregon .edu/