The Role of Probiotics in the Use of Treatment for Autism Spectrum Disorder to Correct Intestinal Permeability and Behavior Abnormalities

Truce Pham

Introduction: Autism Spectrum Disorder (ASD) is a severe neurodevelopmental disorder that affects an individual’s communication and interaction skills with an incidence of 1 in 59 in 20141,2. Because many causative factors have been attributed to ASD and none being a leading cause, there is no agreed upon treatment3. Instead, research has focused on gastrointestinal disturbances, a common comorbidity of ASD that affects 12% of ASD children4. The gut-brain axis is an extensive two-way communication pathway and is attributed to the connection between ASD and gastrointestinal disturbances5. Studies show dysbiosis in the microbiome of ASD patients compared to controls3,5. Elevated levels of the anaerobe Clostridium in ASD contributes to an increase in propionic acid, a neurotoxin that travels to the brain at elevated levels6,7. Studies also demonstrated that an increase in propionic acid and decreases in tryptophan and serotonin lead to decreased intestinal mobility7,8. Researchers looked at how correcting the microbiome in the gut through probiotic treatment would affect behavior and intestinal symptoms5. Methods: Offspring of maternal immune activated (MIA) mice were used as an accepted model of autism. Pregnant mice were injected with a viral mimic poly(I:C) and pregnant controls were injected with saline. The MIA offspring were treated with oral Bacteroides fragilis to determine if there were corrections of ASD-related behavioral abnormalities and GI changes. Intestinal permeability was measured using a FITC-assay. Anxiety-like behaviors were determined through time spent in open-field exploration and communication was measured through ultrasonic vocalizations. Sociability was measured by interactions with familiar and unfamiliar mice. Statistical analysis was done using a two-tailed, unpaired Student t test. Results: B. fragilis restored epithelial barrier integrity compared to controls through decreased intensity of the FITC dextran solution in serum samples5. Mice improved their communication with longer ultrasonic vocalizations and decreased anxiety-like behaviors by spending more time in the open-field. However, mice did not show differences in sociability. Results were not just limited to B. fragilis but were relieved by other commensal bacteria as well. Conclusions: In ASD, the microbiomes of patients lead to symptoms associated with behavior and GI disturbances. B. fragilis treatment corrects most ASD behavior symptoms like communication and anxiety. Increased intestinal integrity can lead to protective effects by decreasing toxins produced in the gut from reaching the brain. Probiotic supplements are cheap and cost-effective and can be used as treatment.


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