Wed. Mar 22nd, 2023
Probiotics on the brain: One gut microbe reverses autism-like symptoms in mice

When making a decision, it can be a safe bet to go with your gut. And according to a new study, putting your gut in charge all the time might not be a bad idea — it may actually help prevent neurodevelopmental disorders.

While microbial mind control may sound far-fetched, one common gut microbe can single-handedly reverse autism-like social behavior in mice, researchers report in the journal Cell. While the study is not yet applicable to human health, it highlights the power of connections that can develop between the gut and brain, known as the gut-brain axis.

If the findings hold up in more animal studies and human trials, it could mean that treatments as simple and no-nonsense as probiotic foods could alleviate some symptoms of neurodevelopmental disorders, including autism spectrum disorders, the authors conclude.

Researchers began the study by connecting the dots of human studies, starting with epidemiological data that found a higher risk of autism in children born to obese mothers. Maternal obesity is also associated with changes in the gut microbiome in offspring, according to studies in human and non-human primates. And finally, some individuals with autism also suffer from gastrointestinal problems related to imbalances in the gut microbes.

With all that and other data on the increasing importance of the gut-brain axis, the researchers hypothesized that a misaligned gut microbiome may play a role in the development of conditions such as autism.

To test the idea, researchers subjected female mice to an established obesity-inducing procedure in which the rodents were fed an extremely high-fat diet (60 percent kilocalories from fat). Then they allowed the obese females to mate and produce litters. Of those offspring, raised on a normal diet and of normal weight, many showed autism-like behaviors, including an aversion to interacting with their cage mates, anxiety, and repetitive behaviors (assessed in mice when they repeatedly buried marbles).

Researchers examined the mice’s microbiomes and found that they had less microbial diversity than control mice from normal-weight mothers. Notably, they had a drastic reduction in their quantity Lactobacillus reuteri, a bacteria known to increase oxytocin levels in mice. Oxytocin is a hormone involved in many things, including social behavior, anxiety, and autism.

Unsurprisingly, the mice with autism-like behavior had fewer neurons producing oxytocin. And during social interactions, they also showed weaker signals in the brain circuits involved in rewards.

When the mice from obese mothers were housed with mice from normal mothers, they became more social. This may be because they were better socialized, but the researchers suspected it could be because of a change in their microbiome. Mice eat each other’s poop and therefore share gut microbes.

Then the researchers gave the mice with autism-like behavior mixed drinking water L. reuteritheir social problems (but not their anxiety) disappeared and their oxytocin levels and reward circuit signals recovered.

The study needs to be repeated and a lot more human research would have to be done before a similar treatment could make it to clinics. Also, researchers still don’t know exactly how L. reuteri can alter oxytocin levels. Still, the study provides a proof of concept that probiotics can treat certain social disorders.

Cell2016. DOI: 10.1016/j.cell.2016.06.001 (About DOIs).

By akfire1

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