Do chemicals produced by gut bacteria affect children with autism? This week, researchers presented findings from a small study that suggests this possibility. They did so at the annual meeting of the American Society for Microbiology, in Boston.
"Most gut bacteria are beneficial, aiding food digestion, producing vitamins, and protecting against harmful bacteria,” says Dae-Wook Kang of the Biodesign Institute of Arizona State University, an author on the new study. “If left unchecked, however, harmful bacteria can excrete dangerous metabolites or disturb a balance in metabolites that can affect the gut and the rest of the body, including the brain."
Previous research has suggested that some – perhaps many – children with autism have abnormal communities of digestive bacteria in their intestines. And some of these studies have associated specific types of gut bacteria with more-severe autism symptoms.
“Many processes in the GI and nervous systems may be interconnected,” comments developmental pediatrician Paul Wang, Autism Speaks head of medical research. “This is why Autism Speaks has become a pioneer in funding research into autism’s gut-brain connection. (Dr. Wang and Autism Speaks were not involved in the Arizona State study.)
Read more about Autism Speaks gut-brain research initiative here.
In their new research, Kang and his team compared the bacterial waste products in stool samples from 23 children with autism. They compared these to samples from 21 typically developing children.
Overall, they found that children with autism had significantly different concentrations of seven of the fifty chemical compounds they detected.
"Most of the seven metabolites could play a role in the brain as neurotransmitters or controlling neurotransmitter biosynthesis," Kang says. "We suspect that gut microbes may alter levels of neurotransmitter-related metabolites, affecting gut-to-brain communication and/or altering brain function."
For example, the researchers found that the samples from children with autism differed in the overall ratio of two chemicals linked to autism’s brain chemistry: glutamine and glutamate. These two chemicals are needed to form gamma-aminobutyric acid (GABA), an inhibitory neurotransmitter. Previous research has implicated brain imbalances of glutamate and GABA transmission with autism.
The Arizona State researchers also confirmed earlier research suggesting that children with autism tend to have abnormal and less-diverse communities of gut bacteria.
"Correlations between gut bacteria and neurotransmitter-related metabolites are stepping stones for a better understanding of the crosstalk between gut bacteria and autism,” Kang says. “[This] may provide potential targets for diagnosis or treatment."
In comments with reporters at the conference, Kang said his team would like to conduct a clinical study using fecal transplants from healthy donors. The aim would be to see if the treatment would reduce autism symptoms by “normalizing” an individual’s community of gut bacteria.
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