Codonopsis pilosula inulin-type fructan CPA ameliorates diarrhea-predominant irritable bowel syndrome via regulation of ER stress-induced autophagy and modulation of gut microbiota.

Diarrhea-predominant irritable bowel syndrome (IBS-D) is characterized by diarrhea, abdominal pain, and recurrent symptoms, posing significant clinical challenges. This study utilized the GSE36701 dataset from the Gene Expression Omnibus (GEO) and applied weighted gene co-expression network analysis (WGCNA) to identify IBS-D-associated genes, with a specific focus on endoplasmic reticulum (ER) stress. Codonopsis pilosula, a traditional Chinese medicinal herb, and its active inulin-type fructan monomer CPA, exhibit potential gastrointestinal protective effects. This study evaluated the therapeutic effects of CPA both in vivo, using an IBS-D model induced by senna leaf combined with chronic unpredictable stimuli, and in vitro, using a lipopolysaccharide (LPS)-induced IBS-D model in NCM460 cells. Hematoxylin-Eosin Staining (H&E), Alcian Blue-Periodic Acid-Schiff Staining (AB-PAS), immunohistochemistry (IHC), Immunofluorescence (IF), Elisa, qRT-PCR and Western blots were used to detect relative indices in this research. Our results indicated that CPA treatment improved IBS-D symptoms, including increased body weight, reduced abdominal withdrawal reflex, and normalized stool consistency. Histological analysis revealed improved colonic crypt and gland morphology, reduced inflammatory cell infiltration, and increased goblet cell numbers. CPA also upregulated tight junction protein expression, anti-inflammatory cytokines, and neuroeffector neuropeptide Y (NP-Y) levels. In addition, CPA downregulated ER-stress and autophagy markers, including p-eIF2α/eIF2α, ATF4, Bip, CHOP, Beclin-1, Atg5, P62, and LC3B. Additionally, CPA influenced gut microbiota composition, increasing microbial diversity and restoring microbial balance in IBS-D rats. Linear discriminant analysis Effect Size (LEfSe) identified CPA-responsive taxa, further supporting CPA's role in promoting a balanced and diverse gut microbiome. These experimental results suggested that CPA alleviates IBS-D by modulating the gut microbiota, regulating autophagy through the ER stress signaling pathway, and reinforcing colonic barrier integrity. This study highlights CPA as a promising therapeutic candidate for IBS-D.