Disturbance of bile acids profile aggravates the diarrhea induced by capecitabine through inhibiting the Wnt/β-catenin pathway.

Introduction: Diarrhea is the primary dose-limiting side effect of capecitabine(Cap) hindering its clinical application, but the mechanism is unclear. Clarifying this mechanism may enhance the patient compliance and improve the treatment outcome.

Objectives: To assess if the endogenous metabolic profile could prodict the diarrhea induced by Cap and explore and validate underlying mechanisms.

Methods: Untargeted and targeted bile acids(BAs) metabolomics were performed to analyzed the metabolic profile of baseline samples from colorectal cancer(CRC) patients and the association with the diarrhea induced by Cap was assessed. The toxicity of BAs and Cap and its metabolites alone or their combinations to the human normal intestinal epithelial cell(HIEC) was assessed, and the key genes that mediated the BAs-enhanced toxicity of Cap were discovered by RNA-seq and then validated. A mouse model with high exposure levels of BAs was constructed and then treated with Cap to verify the Cap-induced diarrhea enhanced by BAs.

Results: The baseline endogenous metabolic profile showed obviously difference between diarrhea and non-diarrhea CRC patients, and the differential metabolites mainly enriched in BAs metabolism; the deoxycholic acid(DCA) and lithocholic acid(LCA) were selected to be the key BAs that enhanced the toxicity of Cap metabolite 5-FU to the HIEC cell; the DCA and LCA could inhibit the Wnt/β-catenin signaling pathway, which then suppressed the P-glycoprotein and increased the exposure level of 5-FU in the HIEC cell. The results of animal experiment verified that the excessive DCA and LCA could aggravate the Cap-induced diarrhea through inhibiting Wnt/β-catenin-P-glycoprotein pathway.

Conclusions: The disordered BAs metabolic profile showed close relationship with diarrhea induced by Cap, and excessive DCA and LCA were proved to be the key BAs, which could aggravate the Cap-induced diarrhea through inhibiting Wnt/β-catenin-P-glycoprotein pathway.