Scientists discover gut microbiome differences in children with autism

Scientists have discovered distinct gut bacteria in children with autism, offering clues to potential treatments. However, they emphasize the need for more personalized and cautious probiotic approaches.

Study: Unraveling the relative abundance of psychobiotic bacteria in children with Autism Spectrum Disorder. Image Credit: Kateryna Kon / Shutterstock

In a recent study published in the journal Scientific Reports, researchers investigated links between changes in gut microbiota and gastrointestinal symptoms in Egyptian children with Autism Spectrum Disorder (ASD).

Their findings uncovered differences in gut microbes between typically developing (TD) children and those with ASD and some associations between certain species and physical, behavioral, and health outcomes. However, the study also emphasized that further research is needed to understand these associations and their potential clinical applications fully.

Background

Researchers estimate that in Egypt, 5.4 children in 1,000 have ASD. ASD, which can begin in early childhood and is a lifelong condition, involves repetitive behaviors and challenges in social communication.

ASD is the result of complex environmental and genetic factors. One environmental factor that has been linked to ASD is gut dysbiosis or imbalances in gut bacteria, suggesting that there is a strong gut-brain connection.

Beneficial bacteria such as Lactobacillus and Bifidobacterium are probiotics whose live strains are consumed and can produce substances that affect the brain and improve mental health.

They are known as psychobiotics and have anti-anxiety and antidepressant effects and may reduce ASD symptoms by restoring healthy gut bacteria and enhancing the production of a brain chemical low in people with ASD.

Psychobiotics such as Lactobacillus plantarum, Lactobacillus reuteri, and Bifidobacterium longum have shown promise for improving mood (specifically, reducing despair) and social behavior, reducing disruptive behaviors, hyperactivity, anxiety, and inflammation while regulating key brain pathways related to ASD.

These bacteria may also strengthen abilities related to memory and learning. Findings from animal studies support these hypotheses, as Bifidobacterium longum has been shown to reduce stress and enhance brain function in mice.

However, it is important to note that the current study found no statistically significant correlation between the abundance of these bacteria and the severity of autism in children, cautioning that the relationship between gut microbes and ASD symptoms is complex and still not fully understood.

Probiotic therapy is seen as a potential supplement to improve ASD symptoms, particularly gastrointestinal issues, as it does not involve any health risks or side effects, but the selection of probiotics is often made without sufficient scientific backing or personalized investigation. Further research is needed to identify which strains are most effective in alleviating symptoms and improve outcomes for ASD children.

About the study

In this study, researchers aimed to identify and compare the levels of psychobiotic bacteria species in the gut microbiomes of children showing TD and those with ASD, assessing correlations between these bacteria and the severity of symptoms. The study emphasized that understanding these correlations is important for optimizing probiotic treatments in the future, but also noted that the findings should be approached cautiously.

The sample included 87 children with ASD, excluding those with certain medical conditions or who consumed probiotics or antibiotics in the three months preceding the study. The comparison group comprised 36 TD children who were unrelated to the children with ASD. Parents provided consent for their children to participate in the study.

Researchers assessed the severity of autism experienced by the children, along with autistic behavior, sensory impairment, and gastrointestinal symptoms. Researchers collected stool samples and extracted genetic material to analyze the gut microbiome to determine the abundance of psychobiotic bacteria.

To analyze the data, the researchers compared psychobiotic bacteria between ASD and TD children and examined relationships between ASD symptoms and bacteria levels.

Findings

The average age in the ASD group was 6.97, and two-thirds of the children were male, while the TD children were 5.79 years old on average, and 55.6% of them were female. There were no significant differences between girls and boys in the ASD group in terms of psychobiotic bacteria, but girls in the TD group had lower levels of Bifidobacterium than boys.

Of the children in the ASD group, about 76% had mild to moderate ASD, while the others had severe ASD. Nearly 84% of them experienced sensory impairment, predominantly under-responsiveness or seeking sensation, and approximately 89% had at least one gastrointestinal symptom, most commonly unusual stool smell or flatulence.

Children with ASD had significantly lower levels of Lactobacillus reuteri and Lactobacillus plantarum than TD children. However, no significant differences were found for overall Bifidobacterium levels. Bifidobacterium and Lactobacillus were positively correlated with health, physical behavior, and sociability and negatively correlated with sensory and cognitive awareness and under-responsiveness.

It is critical to note that while these correlations were observed, the study found no conclusive evidence that these bacterial levels directly influence the severity of ASD symptoms. Therefore, the therapeutic potential of psychobiotic treatments remains speculative.

Conclusions

The results of this study suggest that different species may have different associations with ASD, finding that some species are lower in ASD children than TD children, as well as links between some microbes and the severity of symptoms.

Though previous studies have reported improvements in symptoms after probiotic use, this analysis did not find significant differences in gastrointestinal symptoms based on bacteria levels. This suggests that the role of gut bacteria in managing ASD-related symptoms is still unclear.

Changes in gut bacteria in ASD children, particularly psychobiotics (bacteria affecting behavior), might influence ASD severity. However, the study cautions that further investigation is needed to confirm these findings, especially given that no statistically significant correlations were found between bacterial levels and autism severity. It is critical to consider individual gut microbiome profiles before using probiotics in ASD treatment, as probiotics may affect each person differently.

Moreover, the study highlights the need for personalized approaches in selecting probiotics rather than relying on general formulations, as different bacterial strains may have distinct effects on behavior and health outcomes.

Further research in this field should include a larger group of participants and expand the number of bacterial species considered.

Journal reference:

• Unraveling the relative abundance of psychobiotic bacteria in children with Autism Spectrum Disorder. Darwesh, M.K., Bakr, W., Omar, T.E.I., El-Kholy, M.A., Azzam, N.F. Scientific Reports (2024). DOI: 10.1038/s41598-024-72962-3,

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