What is already known about this topic
Several studies have suggested a connection between gut bacteria and autism spectrum disorder (ASD). Gastrointestinal problems are common in people with ASD, and fecal transplants from neurotypical individuals to people with ASD appear to improve behavioral and psychological traits of autism in children.
What this research adds
By comparing gut microbes between 40 neurotypical children and 39 children with ASD, researchers found differences in gut bacterial populations as well as in metabolic pathways.
The team identified enzyme deficiencies in children with ASD that prevent them from breaking down environmental toxins. The microbiota alterations and the inability of ridding the body of harmful compounds from the environment could contribute to mitochondrial dysfunction, which is known to alter the brain and other tissues.
The findings could help to develop therapeutics that restore microbial detoxification in people with ASD.
Recent studies have suggested an intriguing connection between gut bacteria and autism. Now, researchers have found that individuals with autism are unable to break down some environmental toxins, which could allow the toxins to enter the bloodstream and injure brain cells.
The findings, published in Science Advances, suggest that gut microbes that would normally rid the body of harmful substances from the environment fail to function properly in children with autism.
Scientists have known that people with autism spectrum disorder (ASD) experience gastrointestinal problems, and fecal transplants from neurotypical individuals to people with ASD appear to improve behavioral and psychological traits of autism in children. But the exact mechanisms that link gut bacteria and ASD remain unclear.
To better understand microbial changes specific to ASD, Yu Kang at the Beijing Institute of Genomics, Juan Wang at Peking University and their colleagues analyzed stool samples from 39 children between the ages of three and eight with ASD. Then, they compared them to samples from 40 children of the same age without the condition.
By comparing the two groups of children, the researchers identified substantial differences in their gut bacterial populations.
The analysis of stool samples identified a total of 209 bacterial species. Of these, 18 showed significant differences between children with ASD and neurotypical kids. In particular, Veillonella parvula and Lactobacillus rhamnosus tended to be common in children with ASD, whereas Bifidobacterium longum and Prevotella copri were more widesprwad in controls.
The team also observed deficiencies in five metabolic pathways, including a pathway linked to detoxification processes. Because these processes are typically triggered by enzymes produced by gut bacteria, the researchers hypothesize that the microbiota alterations and the inability of ridding the body of harmful compounds from the environment could contribute to mitochondrial dysfunction, which is known to alter the brain and other tissues.
Indeed, the researchers found that the levels aconitic acid, suberic acid, 2-hydroxyhippuric acid, and fumaric acid — which indicate mitochondrial damage — were disrupted in children with ASD.
“Our finding of impaired microbial detoxification helps explain why ASD children are so vulnerable to environmental toxins and suggests that impairment in microbial detoxification might be involved in the pathogenesis of ASD,” the researchers say.
The findings could help to develop therapeutics that restore microbial detoxification in people with ASD, they say.