New research adds more strength to the potential link between gut bacteria and autism.
In a small study, researchers from Arizona State University found evidence that gut bacteria may differ between children with and without autism.
Specifically, the researchers found that the fecal concentrations of certain metabolites -- which are chemicals produced by bacteria -- differ between children with autism and children without the condition. Researchers examined 56 different metabolites in the children's feces, and identified seven with differing concentrations.
"Most of the seven metabolites could play a role in the brain, working as neurotransmitters or controlling neurotransmitter biosynthesis," study researcher Dae-Wook Kang, of the university's Biodesign Institute, said in a statement. "We suspect that gut microbes may alter levels of neurotransmitter-related metabolites affecting gut-to-brain communication and/or altering brain function."
The study was presented at a meeting of the American Society for Microbiology; because the findings have yet to be published in a peer-reviewed journal, they should be regarded as preliminary. However, NBC News reported that the researchers are now seeking approval to conduct research on whether fecal transplants could affect autism symptoms.
The study included 21 children without autism and 23 with autism, NBC News reported.
Homovanillate was one of the metabolites that was present at lower levels in children with autism; it's what's produced when the neurotransmitter dopamine is broken down. N,N-dimethylglycine was another metabolite found at lower levels in children with autism; it's been used before to decrease autism symptoms. Meanwhile, the ratio of glutamine to glutamate was higher among children with autism, researchers found. According to a release on the findings:
Glutamine and glutamate are further metabolized to gamma-aminobutyric acid (GABA), an inhibitory neurotransmitter. An imbalance between glutamate and GABA transmission has been associated with ASD-like behaviors such as hyper-excitation.
This isn't the first time there have been signs of gut bacteria differences between children with and without autism. Arizona State University researchers had a study published last year in the journal PLOS One showing that children with autism seemed to have lower levels of three gut bacteria -- Prevotella, Coprococcus and Veillonellaceae -- compared with children without autism, Medscape reported. Meanwhile, New Scientist reported in 2010 on a study from Imperial College London scientists, who found that a urine chemical signature -- indicative of gut bacteria differences -- is present in children with autism.