Kaempferol attenuates nonalcoholic steatohepatitis by regulating serum and liver bile acid metabolism

Objective: Changes in bile acids (BAs) are increasingly recognized as potential targets for non-alcoholic steatohepatitis (NASH). Kaempferol has been proved to be anti-inflammatory and reduce the disorder of lipid metabolism. In order to analyze the BA profile in NASH mice and determine the predictive biomarkers of kaempferol treatment, serum-targeted metabolomics and liver tissue RNA sequencing (RNA-seq) were carried out. Design: Six normal control mice (NC group), eight HFD-fed mice (HFD group), and eight kaempferol-treated HFD-fed mice (HFD + KP group) were included in the present study. Ultra-performance liquid chromatography coupled to a tandem mass spectrometry system (UPLC-MS/MS) was used to quantify serum and liver BAs, and RNA-seq was used to quantify liver differentially expressed genes related to BA metabolism. Results: The serum levels of CA, βMCA, UDCA, and 12-DHCA, as well as ωMCA in both the serum and liver, were significantly decreased in the HFD group compared with those in the NC group, and kaempferol can increase the serum levels of βMCA, UDCA, and ωMCA and the liver level of 12-DHCA. The serum levels of TDCA, THDCA, TUDCA, TDCA/CA, and TDCA/DCA were significantly increased in the HFD group compared with those of the NC group, and kaempferol can decrease them. Furthermore, NASH mice had a higher liver level of total CA%, total CDCA%, primary BAs/secondary BAs, 12α-OH BAs/non-12α-OH Bas, and conjugated BAs/unconjugated BAs, and all decreased after kaempferol treatment. According to the RNA-seq results, we found that compared with the NC group, the mRNA expression of cholesterol-7α-hydroxylase (CYP7A1) in the HFD group was significantly increased, and the mRNA expression of sterol 12α‐hydroxylase (CYP8B1) and multidrug resistance-related protein 3 (MRP3) was significantly decreased, while kaempferol significantly promoted the mRNA expression of mitochondrial sterol 27-hydroxylase (CYP27A1) and Na + -taurocholate cotransporting polypeptide (NTCP). Conclusion: βMCA, CA, UDCA, 12-DHCA, ωMCA, CDCA, TωMCA, TDCA, THDCA, TCDCA, and TUDCA in the serum, as well as 6,7-diketoLCA, 12-DHCA, and ωMCA in the liver, may be potential biomarkers for kaempferol to improve NASH. HFD-induced NASH may be associated with the increase of CYP7A1 and the decrease of CYP8B1, leading to increased BA synthesis, and the decrease of MRP3 leading to decreased BA synthesis, and kaempferol may alleviate NASH by increasing CYP27A1 and NTCP to enhance BA transport.