Association of aberrant brain network dynamics with gut microbial composition uncovers disrupted brain-gut-microbiome interactions in irritable bowel syndrome: Preliminary findings Original paper

What was studied?

This study explored the association between brain network dynamics and gut microbial composition in patients with Irritable Bowel Syndrome (IBS), highlighting disrupted brain–gut–microbiome (BGM) interactions as a contributing factor to IBS pathophysiology. The research integrated neuroimaging data, specifically resting-state functional magnetic resonance imaging (rs-fMRI), with gut microbiota profiling through 16S rRNA gene sequencing. Dynamic functional connectivity (DFC) analysis was employed to identify temporal changes in brain networks, while microbial diversity and community composition were assessed in fecal samples. This dual analysis aimed to bridge the gap between neural dysfunction and microbial imbalances in IBS patients.

Who was studied?

The study included 33 IBS patients (23 with diarrhea-predominant IBS, 4 with constipation-predominant IBS, and 6 with mixed IBS) and 32 healthy controls, all right-handed and matched for age and gender. Participants were recruited from Lanzhou University Second Hospital, and all met the Rome IV criteria for IBS. Neuroimaging and fecal sampling were performed to analyze both brain network dynamics and gut microbial composition. Exclusion criteria included the use of probiotics or antibiotics within one month of the study, as well as a history of neurological, psychiatric, or significant gastrointestinal disorders.

What were the most important findings?

The study identified significant alterations in both brain network dynamics and gut microbial diversity in IBS patients. In the DFC analysis, four distinct connectivity states were identified, with IBS patients exhibiting prolonged fraction and mean dwell times in State 4—a state associated with weak brain connectivity linked to self-focused thinking and emotional dysregulation. Furthermore, reduced transitions from State 3 to State 1 were noted, indicating impaired cognitive flexibility, a hallmark of IBS symptomatology. Temporal variability of functional connectivity was also disrupted, particularly within the cognitive control network (CCN) and the sensorimotor network (SMN), implicating these brain regions in IBS-related cognitive and sensory processing abnormalities.

In parallel, gut microbiome analysis revealed decreased alpha diversity and altered beta diversity in IBS patients. Notably, IBS patients showed higher abundances of Anaerostipes, Streptococcus, and Ruminococcus, along with elevated levels of Erysipelotrichaceae. These microbial shifts were associated with symptom severity, depression, and anxiety scores. Correlation analysis demonstrated that specific microbial abundances corresponded to changes in brain network connectivity, suggesting a mechanistic link between gut dysbiosis and brain dysfunction in IBS.

What are the greatest implications of this study?

The findings underscore the critical role of brain-gut-microbiome interactions in IBS pathophysiology, highlighting dynamic brain network disruptions alongside distinct microbial imbalances. Prolonged dwell time in weakly connected brain states and altered microbiota composition suggest that IBS symptomatology is driven by both central neural dysregulation and peripheral microbial alterations. These insights open avenues for targeted therapies aimed at modulating both brain connectivity and gut microbiota to alleviate IBS symptoms. The study also establishes a foundational framework for future investigations into BGM axis interventions as a therapeutic strategy for IBS.