Si-Si-Gu-Ben granules alleviate diarrhea-predominant irritable bowel syndrome by modulating gut microbiota and suppressing the TLR4/NF-κB pathway: A combined clinical and animal study.

ETHNOPHARMACOLOGICAL RELEVANCE: Si-Si-Gu-Ben (SSGB), a traditional Chinese medicinal formula derived from the theory of "warming the spleen and kidney to arrest diarrhea," is frequently prescribed for diarrhea-predominant irritable bowel syndrome (IBS-D) in clinical practice, yet its pharmacological mechanisms remain insufficiently elucidated. This study aimed to evaluate the therapeutic effects of SSGB on IBS-D and to clarify its regulatory effects on gut microbiota and the TLR4/NF-κB signaling pathway. AIM OF THE STUDY: This study aimed to evaluate the therapeutic effects of SSGB on IBS-D in both animal models and human patients, and to clarify its regulatory effects on gut microbiota and the TLR4/NF-κB signaling pathway. METHODS: An IBS-D rat model was established and treated with SSGB. Additionally, an open-label clinical case series was conducted to evaluate the effects of SSGB on gut microbiota and short-chain fatty acids (SCFAs) in IBS-D patients. Stool consistency, food intake, and visceral sensitivity were assessed to evaluate IBS-D-like symptoms. Network pharmacology was used to identify putative molecular targets and signaling pathways of SSGB, and colonic expression of TLR4/NF-κB pathway components and pro-inflammatory cytokines was subsequently measured for experimental validation. RESULTS: SSGB significantly improved IBS-D-like symptoms in rats, including diarrhea, reduced food intake and visceral hypersensitivity, in a dose-dependent manner. In IBS-D patients, SSGB treatment partially restored gut microbiota homeostasis, increasing beneficial genera, and SSGB intervention was associated with the regulation of valeric acid metabolism. It partially restored gut microbiota homeostasis by increasing beneficial genera (e.g., Lactobacillus) and decreasing pathogenic genera (e.g., Escherichia-Shigella), normalized SCFA profiles, and its beneficial effects were markedly attenuated in microbiota-depleted rats. SSGB inhibited activation of the TLR4/NF-κB pathway and reduced IL-1β, IL-6, and TNF-α levels in serum. CONCLUSION: SSGB ameliorates IBS-D by modulating gut microbiota and suppressing TLR4/NF-κB signaling pathway. These findings provide a pharmacological basis for its traditional use and support its potential as an evidence-based therapeutic option for IBS-D in clinical practice.