One common gut microbe is seen to singlehandedly reverse autism-like behaviors in mice – strengthening the potential of a healthy gut microflora in dodging neurological conditions.

A quick reminder: the number of bacteria present in our gut outnumbers the cells in our body. The role of good bacterial balance goes beyond digestion and, as a mounting body of research suggests, includes significantly altering cognitive function and behavior patterns.

Now, researchers from Baylor College of Medicine demonstrated that adding a single specific bacterial species into gut of mice could reverse some of the detected autism-related behavioral deficits.

Past research use drugs or electrical brain stimulation to help modify autistic behavior. This new study is deemed a new approach.

"Whether it would be effective in humans, we don't know yet, but it is an extremely exciting way of affecting the brain from the gut,” said senior study author and neuroscientist Mauro Costa Mattioli.

Autism and Gut Health

The study was inspired by human studies showing evidence of maternal obesity during pregnancy as a risk factor for the development of autism and other neurodevelopmental issues in the offspring. Furthermore, a notable segment of individuals with autism spectrum disorders (ASD) disclose gastrointestinal issues.

Investigating these links, the team fed 60 female mice a high-fat diet, roughly the equivalent of consuming fast food multiple times in a day. The mouse offspring stayed with their moms for 3 weeks before being weaned onto a regular diet.

A month after, their offspring demonstrated ASD-resembling behaviors, including spending less time with their peers and not initiating interaction.

Altering the Microbiome, Then Behavior

Using 16S ribosomal RNA gene sequencing, the researchers determined the bacterial makeup of the guts of (1) offspring of mice fed a normal diet and (2) offspring of mice fed a high-fat diet. They discovered a distinction in the glut flora populations of the two groups.

Were these gut bacterial changes the root of the social behavioral issues? Because mice consume each other’s feces, the team housed the subjects together so the microbiome is spread among everyone.

When the autistic, 3-week-old offspring were paired with normal mice, their microbiome returned to normal in 4 weeks, while many of their behavior patterns were also restored to normal.

As the link between behavioral changes and gut bacteria had been established, it was time to pinpoint the involved bacterial species: Lactobacillus reuteri, seen to be decreased nine-fold in the animals born to mice fed a high-fat diet.

Bacterial Wonders

The researchers cultured an L. reuteri strain isolated originally from human breast milk, introducing it into the high-fat-diet offspring group’s water. The treatment made up of this sole bacterial strain was considered enough to rescue social behavior, the authors noted.

Interestingly, L. reuteri also appeared to enhance the release of the “bonding hormone” oxytocin, known to be a crucial factor in social behavior and implicated in human autism cases.

The results are deemed important in finding natural and minimally invasive therapies for autism, for which there is an uphill climb ahead for scientists.

The findings were detailed last June 16 in the journal Cell.

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