Scientists have identified a species of gut bacteria linked to behavioural deficits that may reverse symptoms of autism spectrum disorders.

The absence of the species of gut bacteria causes social deficits in mice, researchers at Baylor College of Medicine found.

By adding this bacteria species back to the guts of affected mice, the researchers were able to reverse some of their behavioural deficits, which are reminiscent of symptoms of autism spectrum disorders (ASDs) in humans.

“Other research groups are trying to use drugs or electrical brain stimulation as a way to reverse some of the behavioural symptoms associated with neurodevelopmental disorders - but here we have, perhaps, a new approach,” said Mauro Costa-Mattioli, a neuroscientist at Baylor College of Medicine in the US.

Previous studies in humans have found that maternal obesity during pregnancy ups children’s risk of developing neurodevelopmental disorders, including ASDs. Some people with ASD also report recurring gastrointestinal problems.

With emerging research showing how diet can change the gut microbiome and how gut microbes can influence the brain, researchers suspected there could be a connection.

They fed about 60 female mice a high-fat diet that was the rough equivalent of consistently eating fast food multiple times a day. They bred the mice daily.

The offspring stayed with their mother for three weeks and then were weaned onto a normal diet.

After a month, these offspring showed behavioural deficits, such as spending less time in contact with their peers and not initiating interactions.

“First we wanted to see if there was a difference in the microbiome between the offspring of mouse mothers fed a normal diet versus those of mothers fed a high-fat diet,” said Shelly Buffington, a postdoctoral fellow in Costa-Mattioli’s lab.

“We found a clear difference in the microbiota of the two maternal diet groups,” said Buffington.

Researchers then tested whether the specific differences in the microbiome were causative factors underlying the social impairments in offspring of mothers fed a high-fat diet.

Since the mice eat each other’s excrement, the researchers housed the animals together so that they would acquire microbiota from their cagemates.

When socially impaired three-week-old mice born to mothers on a high-fat diet were paired with normal mice, a full restoration of the gut microbiome and a concurrent improvement in behaviour was observed within four weeks.

The researchers concluded that one or more beneficial bacterial species might be important for normal social behaviour.

The researchers believe that their work, which uses a human bacteria species to promote oxytocin levels and improve social behavioural deficits in deficient mice, could be explored as a probiotic intervention for the treatment of neurodevelopmental disorders in humans. The study was published in the journal Cell.

by The Statesman