New evidence has emerged exploring the relationship between gut microbiome, autism spectrum disorder (ASD), and probiotic treatment. This research was presented at the Gut Microbiota for Health World Summit in Barcelona, Spain.

Elaine Y. Hsiao, PhD, from the California Institute of Technology, and colleagues sought to examine the relationship between microbial composition, gut conditions, and ASD and potential therapeutic connections. In the study, pregnant mice were injected with artificially created virus-like DNA to activate the immune system and induce ASD in the offspring. The offspring exhibited behavioral patterns consistent with ASD including spending less time in the middle of open space compared to healthy mice, being more easily startled by sounds, being less sociable, producing fewer vocalizations, and clinging to stereotypic actions. The ASD mice had altered gut microbiota composition and the permeability of their intestines (“leaky gut”) was greater compared to healthy mice.

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The serum of the ASD mice contained 46 times the normal amount of 4-ethylphenyl sulfate (4-EPS), a metabolite of gut bacteria that is chemically similar to p-cresol, a gut microbial metabolite that has been found at high concentrations in the urine of children with ASD. After 4-EPS was administered to healthy mice, this group began to exhibit some of the same behavioral symptoms as the ASD mice; this may indicate that leaked 4-EPS and similar molecules may travel in the bloodstream in high concentrations and reach the brain to influence behavior. Probiotic treatment with commensal microbe B. fragilis that is present in healthy human intestines for the ASD mice returned the intestinal permeability and 4-EPS levels to normal.

While Dr. Hsiao emphasizes that these results are currently restricted only to mice, the researchers hope that these findings could help to develop new treatment approaches for humans by which a bacterium can improve ASD-related gastrointestinal deficits and ASD-associated behavioral abnormalities.

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