Gut Bacteria Linked to Autism, Find Scientists Who Transplanted Feces From Children With Autism in to Mice

Gut bacteria have been linked to autism-like symptoms in mice, according to scientists who say their research brings us a step closer to understanding the cause of the condition.

Scientists performed fecal transplants on mice, where fecal samples of 16 children (11 of whom had autism) were put inside their digestive systems. The team then monitored the rodents' behavior.

When compared with mice didn't undergo the fecal transplant, the colonized mice showed symptoms comparable to autism, such as repetitive behavior and lower levels of social interaction.

The scientists also noticed the expression of genes associated with autism in the colonized mice was different. These animals also had lower levels of the metabolites 5-aminovaleric acid (5AV) and taurine. When scientists treated the mice with these metabolites, their symptoms of autism appeared to ease.

It is not known what causes autism, a condition the U.S. CDC describes as a developmental disability. Autism can change how a person communicates, interacts with others, behaves and learns.

First author of the study Sharon Gil, senior postdoctoral scholar at Caltech who received funding from the advoacy group Autism Speaks for the research, told Newsweek evidence has been building since the early 2000s suggesting microbes could be involved in the development of autism.

"While many of these studies have shown differences in gut bacteria between subjects and controls, and mouse models have shown that addressing some of these changes can affect mouse behavior, it was still unclear whether or not the gut microbiome in autism contributes to behavioral hallmarks of autism." That's partly because there are no known biomarkers of autism, and a behavioral assessment is the only way to be diagnosed with the condition, he said.

However, Gil stressed that as the work is in mice, future studies are needed to confirm whether the results relate to humans too. Also, problems may have arisen when the human microbes were transferred into the mice. Gil acknowledged 16 donors isn't many when it comes to producing results that can relate to a wide population.

"Maybe most important—we can't tell if changes in the microbiota are a cause of autism in people, though this work in mice suggests that differences in gut microbial communities may differentially contribute to behaviors."

Thomas Frazier, a science officer for Autism Speaks who did not work on the research told Newsweek: "The gut-brain connection is an important emerging research area. Earlier this year, an Autism Speaks-funded researcher linked changes in the gut microbiome and metabolome to specific GI [Gastrointestinal] symptoms in children with autism. This new study complements that work by connecting the gut microbiome to the behavioral side of autism."

"If a specific metabolite profile can be identified that improves ASD [Autism spectrum disorder] behavior, that would be a major advance—assuming it translates to humans.

He concluded: "The possibility that the microbiome is regulating behavior through metabolites is very exciting and a worthwhile hypothesis to pursue in future research."

This article was updated with additional information provided by Gil Sharon.