Tiantian capsule alleviates low-fiber diet-induced constipation with improved 5-HT-associated gastrointestinal motility and gut microbiota remodeling.

BACKGROUND: Insufficient dietary fiber intake is closely associated with functional constipation. Although laxatives are widely used, their long-term or inappropriate use may cause adverse effects such as diarrhea and electrolyte imbalance. Tiantian Capsule (TTC) is a marketed health food product with reported laxative effects. However, its effects on low-fiber diet (LFD)-induced constipation and the associated biological changes remain incompletely understood. PURPOSE: This study aimed to evaluate the effects of TTC on LFD-induced constipation and to investigate its experimentally supported mechanisms. METHODS: An LFD-induced constipation rat model was established and evaluated using fecal parameters, gastrointestinal (GI) transit assessment, and intestinal histological staining. Colonic transcriptomic profiling was performed to identify potential biological processes associated with TTC intervention. Fecal microbiota profiling and enzyme-linked immunosorbent assay (ELISA) were further used to assess microbiota changes and motility-related GI hormones/neurotransmitters. RESULTS: TTC improved defecation function and restored intestinal histopathological changes in LFD-induced constipation. Colonic transcriptomic analysis suggested that TTC intervention was associated with changes in serotonergic signaling and intestinal immune-related pathways. Consistently, TTC improved GI transit, modulated serum 5-HT and other GI hormones/neurotransmitters levels, and restored fecal microbiota diversity and composition. CONCLUSION: This study suggests that TTC improves LFD-induced constipation-like phenotypes, accompanied by changes in 5-HT-associated GI motility regulation and fecal microbiota composition, warranting further exploration and development.