Integration of UPLC-MS/MS-based metabolomics and desorption electrospray ionization-mass spectrometry imaging reveals that Shouhui Tongbian Capsule alleviates slow transit constipation by regulating bile acid metabolism

Slow transit constipation (STC) is a common intestinal disorder. Some studies reported that Shouhui Tongbian Capsule (SHTB) can effectively mitigate STC symptoms. A detailed understanding of the changes in the endogenous metabolite profile of rats is crucial for a more accurate comprehension of the molecular pathological characteristics of SHTB in treating STC. In the present study, a method integrating metabolomics based on Ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) and Desorption electrospray ionization (DESI)-mass spectrometry imaging (MSI) was proposed to investigate serum, feces and colon tissue metabolic alterations of STC rats induced by diphenoxylate and the effect of SHTB treatment on metabolism. Then, Enzyme-linked immunosorbent assay (ELISA) and Western blot (WB) analysis for verifying the potential mechanism of SHTB in treating STC. As a result, we first indicated that SHTB significantly improved intestinal peristalsis and low fecal water content in STC rats. Furthermore, after treatment with SHTB, the thickness of muscle layers was increased, demonstrated SHTB's effectiveness in reducing intestinal injury in STC rats. Besides, bile acid (BA) metabolomics based on UPLC-MS/MS revealed significant increase in serum levels of Cholic acid (CA), Deoxycholic acid (DCA), Chenodeoxycholic acid (CDCA), Ursodeoxycholic acid (UDCA), and Glycolithocholic acid (GLCA), whereas the contents of CA and DCA in feces were significantly decreased in STC rats. Nonetheless, they returned to the control levels after the SHTB administration. ELISA results showed that SHTB significantly hindered the excessive reabsorption of BAs by inhibiting apical sodium-dependent bile acid transporter (ASBT), organic solute transporter alpha (OSTα) and organic solute transporter beta (OSTβ) in the ileum tissue of STC rats. Furthermore, the DESI-MSI analysis revealed that SHTB remarkably enhanced DCA in the colon tissue of STC rats. The WB results indicated that SHTB reinstated Takeda G-protein-coupled receptor 5 (TGR5) expression, a receptor for BAs and a key regulator of colonic motility. Consequently, DCA exerted its effects on TGR5, leading to the promotion of colonic motility. This study provided more comprehensive and detailed information about the BA metabolomics in the serum, feces and colon of STC rats. These findings highlighted the promising potential of metabolomics based on UPLC-MS/MS and DESI-MSI method for application in the study of STC diseases.