Changes in bacteria in the gut can influence autism-like behaviors in a mouse model, say researchers at California Institute Technology.
Sarkis K. Mazmanian, a professor of biology, said to study this gut--microbiota--brain interaction, the researchers used a mouse model of autism previously developed at Caltech in the laboratory of Paul H. Patterson, the Anne P. and Benjamin F. Biaggini Professor of Biological Sciences.
"Traditional research has studied autism as a genetic disorder and a disorder of the brain, but our work shows that gut bacteria may contribute to ASD-like symptoms in ways that were previously unappreciated," Mazmanian said in a statement. "Gut physiology appears to have effects on what are currently presumed to be brain functions."
The research has been getting a great deal of media attention. As is usually the case with autism research "breakthroughs," much of the coverage overlooks important caveats.
“This is a real limitation in the conclusions from this study, as, in many ways, social interaction deficits are at the core of the phenotype of autism,” says Ted Abel, professor of biology at the University of Pennsylvania, who was not involved in the research. He suggests that other mechanisms may underlie the social behavior in these mice.
The researchers emphasize that the results are in mice and that they may model only one type of autism. “We need to be very cautious here. We are looking at an initial report in one mouse model,” says Mazmanian. “At best, they represent a subset of the autism population.”
Researchers also shouldn’t underestimate the challenges of trying to change the microbiome in people, says [Yale Professor David] Littman. Finding a gut molecule that is elevated in people with autism and pinning down bacteria that reverse its production would be “a tremendous advance,” he says. “It’s very difficult to target the microbiome without knowing what’s going on.”
The researchers do, however, have promising preliminary results with mice that carry mutations seen in people with autism. They are now treating mice with commercially available probiotics and are planning a clinical trial with B. fragilis in people with autism. These are only the early first steps, notes Patterson. “I don’t want people rushing out trying to buy B. fragilis,” he says.