The primary author of the study, Lisa Aziz-Zadeh, serves as a professor at the Brain and Creativity Institute located within the USC Dornsife College of Letters, Arts and Sciences. (USC Photo/Stephen Gee)
Health
Researchers at USC uncover a connection between the gut and brain that may influence behavior in children with autism
An imbalance in the microbiome disrupts neurotransmitter synthesis and may present as social challenges and repetitive actions.
A recent USC investigation indicates that imbalances in the gut of children with autism could lead to disrupted metabolites in the digestive tract — ultimately affecting neurotransmitter synthesis and impacting behavioral symptoms.
The findings, published Monday in Nature Communications, contribute to a growing compilation of research linking the “gut-brain” axis to autism. This revelation suggests potential new therapeutic paths. It exemplifies how scientific inquiry at USC and other universities fosters innovation and leads to breakthroughs that enhance lives.
“We showed that metabolites from the gut affect the brain, which in turn influences behavior. Essentially, the brain serves as the intermediary between gut health and behaviors associated with autism,” stated lead author Lisa Aziz-Zadeh, a faculty member at the Brain and Creativity Institute at USC Dornsife College of Letters, Arts and Sciences. “Earlier studies have emphasized variations in gut microbiomes and neural structures in autism, but our work bridges the gap.”
The gut-brain link may not be as implausible as it appears. From an evolutionary viewpoint, the gut was likely the first “brain,” commented Aziz-Zadeh, who additionally is a faculty member at USC Dornsife’s Department of Psychology and the USC Mrs. T.H. Chan Division of Occupational Science and Occupational Therapy.
In fact, the majority of neurons from the gut transmit signals to the brain; there are more neurons in the gut than within the spinal cord. Approximately 90% of neural communications between the gut and brain travel from the gut to the brain, while merely 10% are directed the other way.
‘Gut instinct’
This ongoing dialogue elucidates why we refer to “gut instinct” or “sensing it in your gut.” Numerous emotions are processed through gut-related mechanisms, a concept known as interoception — the awareness of internal bodily sensations.
In the study, researchers gathered behavioral data, brain imaging data, and stool samples from 43 children with autism and 41 neurotypical children aged 8-17. From the stool samples, they examined metabolites engendered by gut bacteria that decompose food in the digestive tract.
Subsequently, the researchers correlated these metabolites with neural variations seen in children with autism and their behavioral traits. They particularly focused on the “tryptophan pathway” through which tryptophan, an amino acid present in numerous foods, is metabolized into several byproducts, including serotonin.
Serotonin plays a critical role in emotional processing, social interaction, learning, and other cerebral functions. Given that a significant portion of the body’s serotonin is produced within the gut microbiome, modifications in gut health can impact serotonin synthesis.
“We understand that individuals with autism present with brain differences — certain regions of their brain are either less or more active in comparison to typically developing children,” Aziz-Zadeh remarked. “We also realize they frequently face gastrointestinal difficulties such as constipation, abdominal discomfort, and other digestive issues. Furthermore, autism is linked with a variety of symptoms, including repetitive actions and social challenges.”
Sofronia Ringold, a doctoral candidate at the Brain and Creativity Institute who contributed to the study, expressed enthusiasm about the potential for interventions that might target the gut and influence neural function and behavior “while also ideally alleviating some of the most distressing symptoms for them.”
In addition to Aziz-Zadeh and Ringold, the study also includes contributions from Aditya Jayashankar, Emily Kilroy, Ravi Bhatt, and Christiana Butera from USC; as well as Jonathan Jacobs, Skylar Tanartkit, Swapna Joshi, Mirella Dapretto, Jennifer Labus, and Emeran Mayer from UCLA.
This study was funded by a grant from the Eunice Kennedy Shriver National Institute of Child Health and Human Development (R01HD079432) and an award from the Department of Defense’s Idea Development Award (AR170062).