Microbiome and Metabolome Features of Patients with Diarrhea-type Irritable Bowel Syndrome

Background: Patients with diarrhea-type irritable bowel syndrome (IBS-D) often have symptoms of anxiety and depression. Several studies suggest that IBS-D patients may suffer from structural disturbances in the gut microbiota associated with psychi-atric symptoms such as anxiety and depression. In this investigation, we employed 16S rRNA gene sequencing and non-targeted metabolomics analysis to delve into the distinct microorganisms and metabolites associated with the physical and psychological symptoms experienced by individuals with IBS-D. This endeavor offers valuable insights into the potential for targeted intestinal therapy in IBS-D patients. Methods: 42 IBS-D patients and 20 healthy controls received a firm diagnosis of the condition between June 2020 and February 2022. 16S-rRNA gene amplicon sequencing on the Illumine platform and liquid chromatography tandem-mass spectrometry (LC-MS) were performed to detect and analyze the feces of the healthy control group and IBS-D group to obtain differential microorganisms and metabolites. Results: In patients with IBS-D, there was a notable reduction in the abundance and diversity of their intestinal microbiota compared to the healthy control group. Additionally, the ratio of Firmicutes to Bacteroides in IBS-D patients was lower than that observed in the healthy control group. Furthermore, significant distinctions were observed in the fecal metabolites of IBS-D patients compared to those of the healthy control group. The metabolism of alanine, aspartic acid, glutamate, and bile secretions were disturbed. Based on clinical and psychological symptom analysis, as well as analysis of the microbiome and metabolome features, it was found that Blautia, Intestinibacter, and Romboutsia were positively correlated with the severity of irritable bowel syndrome (IBS), as well as levels of anxiety and depression. The intestinal microbiota metabolite 2-Dodecenal was closely related to the presence of IBS-D. The 3-hydroxy-aminobenzoic acid, one of the fecal metabolites involved in tryptophan metabolism, in IBS-D patients complicated with anxious-depressive states was significantly reduced. Conclusion: This study has unveiled substantial disparities in fecal microbiota and metabolomic profiles between individuals afflicted with IBS-D and comorbid anxious-depressive conditions and their healthy counterparts. These findings provide valuable insights for prospective therapeutic interventions targeting the gut in this context.