A new study has identified distinct patterns in the gut bacteria of children and adolescents with autism spectrum disorder, attention-deficit/hyperactivity disorder, and anorexia nervosa. Published in the journal Neuroscience, the research also reveals altered levels of hormones that regulate appetite, suggesting a complex interplay between gut microbes, eating behaviors, and brain health in these conditions.
The human digestive tract is home to a bustling community of trillions of microorganisms, collectively known as the gut microbiota. This internal ecosystem communicates with the brain through a complex network of signals, often called the gut-brain axis. Researchers are increasingly recognizing that an imbalance in this microbial community, sometimes referred to as dysbiosis, may be associated with a range of health conditions, including those affecting the brain.
Neurodevelopmental disorders like autism spectrum disorder (ASD) and attention-deficit/hyperactivity disorder (ADHD), along with the psychiatric disorder anorexia nervosa (AN), are frequently accompanied by gastrointestinal issues and atypical eating patterns.
A team of researchers from Comenius University in Bratislava, Slovakia, sought to better understand the potential connections between gut health and these conditions. Their work aimed to compare the gut microbiota across these three distinct disorders and explore links to appetite-regulating hormones and other biological markers.
The research team, led by Marcela Soltysova and Aleksandra Tomova, recruited 117 children and adolescents for the study. This group included 30 boys with ASD, 14 children with ADHD, and 21 adolescent girls with AN. Their biological data were compared against a group of 52 healthy children who were matched for age and sex to serve as a baseline for comparison.
To conduct their investigation, the scientists collected stool and blood samples from all participants. From the stool samples, they analyzed the composition of the gut microbiota using genetic sequencing techniques. They also measured the levels of calprotectin and zonulin, two proteins that can indicate inflammation or increased permeability in the gut.
From the blood samples, they measured the levels of several hormones involved in hunger and satiety, including leptin, ghrelin, and peptide YY (PYY), as well as certain proteins associated with nerve cell growth and health.
The analysis revealed several commonalities among the patient groups when compared to healthy controls. All three patient groups, those with ASD, ADHD, and AN, showed a higher ratio of two major groups of bacteria, known as Bacteroidetes to Firmicutes. This ratio is often considered an indicator of the overall balance of the gut ecosystem. Patients across the three disorders also tended to have lower levels of beneficial bacteria such as Bifidobacterium and Faecalibacterium.
Beyond these shared characteristics, each condition was associated with a unique microbial signature. Children with ASD and ADHD both had lower overall bacterial richness, meaning a less diverse community of microbes in their guts. The ASD group had higher levels of Bacteroidetes and Escherichia-Shigella bacteria and lower levels of Actinobacteriota and Ruminococcus.
Similarly, the ADHD group showed an increase in Escherichia-Shigella and a group called Desulfovibriota, along with a decrease in Firmicutes. The adolescents with AN also had lower levels of Firmicutes but showed elevated levels of several other bacterial groups, including Proteobacteria, Cyanobacteria, and Verrucomicrobiota.
When the researchers examined the appetite-regulating hormones, they found notable differences. Children with ADHD had significantly lower levels of PYY, a hormone that helps signal fullness after a meal. The changes were more pronounced in the group with AN, where participants had lower levels of leptin, ghrelin, and PYY compared to their healthy counterparts. The researchers did not find significant differences in markers of intestinal inflammation or in the levels of nerve-growth factors among the groups.
The study provides a snapshot of the gut environment in these conditions, and its conclusions are accompanied by certain limitations. The authors note that the sample size was relatively small, a challenge that was intensified by the data collection period occurring during the COVID-19 pandemic. A smaller participant pool means the findings should be viewed as preliminary and require confirmation in larger, more diverse groups of patients.
Additionally, the gut microbiota can be influenced by many external factors, including diet, physical activity, and medication use, which were not the focus of this particular investigation. Future research could aim to control for these variables to gain a clearer picture of the specific role microbes play.
The study, “Gut microbiota in children and adolescents with autism, ADHD and anorexia nervosa, and its link to the levels of satiety hormones,” was authored by Marcela Soltysova, Aleksandra Tomova, Martina Paulinyova, Silvia Lakatosova, Jana Trebaticka, and Daniela Ostatnikova.
