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Earlier this month, researchers at Baylor College published a study revealing that the absence of a specific series of gut bacteria causes social deficits in mice.  Through adding this bacteria species back to the guts of affected mice, the researchers were able to reverse some of their behavioral deficits, which are reminiscent of autism spectrum disorders (ASDs) among humans.  While other research groups have been trying to use drugs or electrical brain stimulation to reverse some of the behavioral symptoms associated with neurodevelopmental disorders, the researchers say their paper is offering a unique approach.  

The paper was inspired by human epidemiological studies, which have found that maternal obesity during pregnancy could increase the risk of their children developing neurodevelopmental disorders.  In addition, some people with ASDs have reported recurring gastrointestinal problems, hinting at a possible connection between the two.  With emerging research exploring the relationship between food and the brain, the researchers decided to look into this connection further.  The researchers fed around 60 female mice a high-fat diet, then bred them and waited for them to bear offspring.  These offspring stayed with their mother for three weeks, then were weaned onto a normal diet; after a month, these started to show behavioral deficits.

At first, the researchers wanted to see if there was a difference in the microbiome between the offspring of mouse mothers fed a normal diet versus those fed a high-fat one.  The researchers therefore used 16S ribosomal RNA gene sequencing so they could determine the bacterial composition of their gut.  They discovered a clear difference in the microbiota of these different groups.  They next tested if these specific differences were underlying the social impairments in the offspring of mothers fed a high-fat diet.  Since mice eat each others’ excrement, the researchers housed animals together so they would acquire their cagemates’ microbiota.  When the socially impaired mice were paired with normal mice, the researchers noticed a full restoration of the gut microbiome, as well as an improvement in behavior, hinting that some bacterial species were important for normal social behavior.  

To find out which specific bacterial species could be affecting the social behavior of mice, the researchers cultured a strain of Lactobacillus reuteri – a bacteria that was reduced dramatically among socially impaired mice – from human breast milk, then introduced it into the diet of the mice.  Treatment with this single bacterial strain was able to change the social behavior of the mice whose mothers were fed a high-fat diet.  The researchers also found that this bacteria promoted the production of the “bonding hormone” oxytocin, which is known to play a crucial role in social behavior.  

The researchers believe that their work could be used to treat neurodevelopmental disorders in humans as well.  A unique approach to ASDs, it will be interesting to see where it goes.  If you’d like to learn more, you can click here!