A recently published article in Nature explored the link between gut health and autism.
In the past 20 years, rates of autism have increased among children in North America, but the exact causes for the disorder are unknown. Researchers have long believed that autism is caused by a combination of genetic and environmental factors, but new research has shown there may also be a link to gut health.
Microorganisms such as Clostridia spp., and Bacteroidetes are found in higher concentrations in the guts of children with autism, compared to those without. A major by-product of digestion by these microorganisms is propionic acid, an acid commonly used as a preservative in processed foods. Propionic acid occurs naturally in the body, and at normal levels circulates in the blood to help regulate various internal processes, but when in excess it can have adverse effects such as developmental delays. It is hypothesized that excess propionic acid in a mother’s gut, possibly due to overconsumption of processed foods, may be passed to the fetus’ blood and affect their neural development. Therefore in order to understand how gut health and autism are linked, researchers analyzed the growth patterns of in-vitro neural stem cells treated with propionic acid.
Researchers treated neural stem cells with either propionic acid, butyric acid (another common by-product of microbe digestion found in the guts of children with autism), or a control substance. Typically, neural stem cells grow into neuroepithelial progenitor cells which then change into either glial cells or neural cells. Glial cells not only protect neurons, but they supply necessary nutrients to them as well. They then incubated the cells and measured the sizes of the neural stem cell clusters that formed, as well as gene expression and protein levels in the neural cells.
Propionic acid stimulates glial cell production
Propionic acid was found to increase the generation of glial cells and the amount of glial fibrillary acid protein, which supports neural activity and protects neurons and reduces the production of neurons. Treatment of neural stem cells with propionic acid also resulted in high levels of inflammatory compounds, compared to the butyric acid group and the control group.
Although glial cells are beneficial, their overproduction can become detrimental. This change in neural make-up can disrupt normal neural pathways and prevent proper communication within the brain, resulting in some of the symptoms observed in children with autism. As a mother’s gut microbiome influences a fetus’ health, research analyzing the relationship between processed food consumption and propionic acid production in the mother and neural development in her fetus should be explored.
Monica Naatey-Ahumah, BSc
Reference: Abdelli, L.S., Samsam, A., & Naser, S.A. (2019). Propionic Acid Induces Gliosis and Neuro-infammation through Modulation of PTEN/AKT Pathway in Autism Spectrum Disorder. Scientific Reports, 9. https://doi.org/10.1038/s41598-019-45348-z
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