December 6, 2013
Possible Link Between Autistic Behavior, Gut Bacteria Discovered
redOrbit Staff & Wire Reports - Your Universe Online
Scientists have discovered a possible link between the symptoms of autism spectrum disorders (ASD) and changes occurring in the gut bacteria of mice, according to new research appearing in Thursday’s edition of the journal Cell.
While autism is a neurodevelopmental condition typically diagnosed when people demonstrate specific behaviors such as decreased social interaction and impaired communication skills, those who are diagnosed with these disorders also often suffer from abdominal cramps and other gastrointestinal issues, the researchers said.
Using the apparent link between the gut and brain issues in ASD patients as their guide, the study authors discovered that changes in gut bacteria could influence autism-like behaviors in mice. Furthermore, after the rodents were treated with bacteria from a healthy gut, many of their behavioral abnormalities (including anxiety-like behaviors) went away. Their findings suggest that probiotics could be used to treat at least some ASD symptoms.
“Several studies have shown that the microbiota can influence a variety of behaviors, from anxiety and pain to social and emotional behavior,” Elaine Hsiao of the California Institute of Technology (Caltech) explained in a statement. “Our work is the first to demonstrate that modulating the microbiota can influence autism-related behaviors in the context of a disease model.”
“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,” added Caltech biology professor Sarkis K. Mazmanian. “Gut physiology appears to have effects on what are currently presumed to be brain functions.”
Hsiao, Mazmanian and their colleagues studied the possible connection between gut bacteria and the brain by using a mouse model of autism, which simulated a severe viral infection known to increase the risk that a pregnant woman will give birth to an autistic child. They said that the “autistic” offspring of similarly infected pregnant mice also possessed abnormalities in their gastrointestinal systems.
Specifically, the GI tracts of these pseudo-autistic mice were “leaky,” meaning that material could pass through the intestinal wall and into the bloodstream, the researchers said. In order to determine whether or not the autism-like behaviors were influenced by the GI symptoms, the investigators treated the rodents with an experimental form of probiotic therapy involving Bacteroides fragilis.
The treatment helped fix the “leaky” gut, and after observing the treated mice, the study authors also found that their behavior had changed. For example, they were more likely to interact with other mice, tended to be less anxious, and were also less likely to engage in a repetitive digging behavior.
“The B. fragilis treatment alleviates GI problems in the mouse model and also improves some of the main behavioral symptoms. This suggests that GI problems could contribute to particular symptoms in neurodevelopmental disorders,” Hsiao said. The research team now hopes to test the probiotic treatment on the behavioral symptoms of human autism within the next two years.
“This probiotic treatment is postnatal, which means that the mother has already experienced the immune challenge, and, as a result, the growing fetuses have already started down a different developmental path,” added Patterson. “In this study, we can provide a treatment after the offspring have been born that can help improve certain behaviors. I think that's a powerful part of the story.”