Autism is a complex set of neurodevelopmental differences affecting social skills, communication, and behavior. The prevalence of autism has been increasing worldwide and affects about 1 in 54 American children. The precise cause of autism is unknown but likely involves a wide range of environmental and genetic factors. Growing evidence suggests that autism is strongly associated with imbalances in the bacterial populations that reside in our gut. In particular, people with autism are often deficient in digestive proteins that alter the nutrients and growth of these bacteria.
Since there is such large diversity in the bacterial species present in the guts of different individuals, a group of researchers in Beijing recently developed a new strategy to study these gut bacteria in people with autism. They paired autism stool samples with control samples from individuals that would be expected to have similar bacterial populations due to age, location, and other environmental factors. In comparing the two groups, they found a number of bacterial species that were significantly stronger or weaker in people with autism. These species participate in a total of 96 metabolic pathways, which are the chemical reactions that convert food and other chemicals into energy or waste.
There was a clear trend that many of the pathways not present in people with autism involved the degradation of a wide range of toxins. These toxins, many of which are widely used in insecticides and food additives, were found to be correlated with a particular type of cellular damage known to be present in people with autism. As a result, the researchers believe that gut bacterial species may function as our body’s first defense against toxins that we ingest via our digestive tract. Without these bacteria, the toxins can enter our body’s circulation and accumulate in tissues, especially fatty tissue such as the brain, where they can contribute to altered neuron function and brain development.
This study thus demonstrates the differences in gut bacteria between autistic and non-autistic people, shedding some insight into why cognitive differences may exist between the two populations. More work is still needed to determine the reasons for bacterial detoxification deficiencies and to confirm if this is truly causative for altered brain function and development. Nevertheless, these findings suggest that it might be possible to create a therapy that helps the detoxification process or that prevents toxins from being ingested in the first place.
Dr. Juan Wang is a professor in the Department of Biomedical Informatics at Peking University in Beijing. Dr. Yu Kang is a professor in the Beijing Institute of Genomics at the Chinese Academy of Sciences in Beijing.
Managing Correspondent: Lauren Davancaze
Press Articles: “Evidence found of link between gut microbe deficiency and autism spectrum disorder,” Medical Press
Original Journal Article: “A quasi-paired cohort strategy reveals the impaired detoxifying function of microbes in the gut of autistic children,” Science Advances