FMT from IBS-D rats impairs intestinal barrier function, linked to Ruminococcus and benzoic acid
Background
The etiology of diarrhea-predominant irritable bowel syndrome (IBS-D) is complex, but gut microbiota dysbiosis is increasingly recognized as a key contributor. Patients experience chronic abdominal pain and altered bowel habits, often accompanied by visceral hypersensitivity and impaired intestinal barrier function. Current treatments often address symptoms rather than underlying mechanisms. This study aimed to clarify the causal role of gut microbiota in IBS-D progression and identify specific microbial and metabolic drivers, addressing a critical gap in understanding disease pathogenesis.
Study Design
Researchers established a rat model of IBS-D characterized by visceral hypersensitivity and diarrhea. To investigate the microbiota's role, recipient rats were pretreated with broad-spectrum antibiotics before undergoing fecal microbiota transplantation (FMT) from the IBS-D model rats. The resulting model-microbiota recipient (MR) group was then assessed for IBS-D-like symptoms including abdominal pain, diarrhea, and depression-like behaviors. Key endpoints included serum diamine oxidase (DAO) concentrations, intestinal tight junction protein levels, serum TNF-α concentrations, intestinal TNF-α and IL-10 mRNA expression, gut microbiota composition via sequencing, and metabolomic analysis.
Results
Both the IBS-D model rats and the FMT recipient (MR) group developed prominent IBS-D-like symptoms, including abdominal pain, diarrhea, and depression-like behaviors. Both groups exhibited elevated serum diamine oxidase (DAO) concentrations and reduced intestinal tight junction protein levels, indicating impaired intestinal barrier integrity. Furthermore, serum TNF-α concentrations were increased, while intestinal TNF-α mRNA expression was upregulated and IL-10 mRNA expression was downregulated, signifying low-grade inflammation. Microbiota analysis revealed an elevated abundance of Ruminococcaceae in both IBS-D and MR groups. Metabolomic analysis showed enrichment in the phenylalanine, tyrosine, and tryptophan biosynthesis pathway, with benzoic acid being particularly prominent. > Pearson correlation analysis demonstrated a strong positive correlation between the Ruminococcus abundance and benzoic acid levels, suggesting a direct mechanistic link.
Key Findings
- FMT from IBS-D rats successfully transferred IBS-D-like symptoms, including abdominal pain, diarrhea, and depression-like behaviors, to recipient rats.
- Both IBS-D and FMT recipient groups showed impaired intestinal barrier function, evidenced by elevated serum
DAOand reduced tight junction proteins. - Low-grade intestinal inflammation was observed, with increased serum
TNF-αand altered intestinalTNF-α/IL-10mRNA expression. - Elevated
Ruminococcaceaeabundance was a common feature in both IBS-D and FMT recipient groups. - Metabolomic analysis revealed increased benzoic acid levels, strongly correlating with
Ruminococcusabundance.
Why It Matters
This study robustly demonstrates that gut microbiota dysbiosis is a causal factor in IBS-D pathophysiology, capable of transferring disease characteristics to healthy recipients via FMT. The identification of specific microbial taxa like Ruminococcaceae and metabolites such as benzoic acid provides novel, actionable insights. This could pave the way for developing targeted diagnostic biomarkers for IBS-D or precision therapeutic strategies, moving beyond broad-spectrum interventions. Future protocols might involve specific dietary interventions, prebiotics, or probiotics designed to modulate Ruminococcus abundance or benzoic acid levels, offering more personalized and effective treatments for IBS-D patients.
ibs-d
gut-microbiota
dysbiosis
fmt
ruminococcus
benzoic-acid