Flavonoids from Whole-Grain Oat Alleviated High-Fat Diet-Induced Hyperlipidemia via Regulating Bile Acid Metabolism and Gut Microbiota in Mice

A high-fat diet (HFD) causes hyperlipidemia, which worsens disturbances in bile acid (BA) metabolism and gut microbiota. This study aimed to investigate the regulation of flavonoids from whole-grain oat (FO) on BA metabolism and gut microbiota in HFD-induced hyperlipidemic mice. The experiment results showed that FO improved serum lipid profiles and decreased body weight and lipid deposition in HFD-fed mice. Through real-time qualitative polymerase chain reaction (RT-qPCR) and Western blot assays, by up-regulating the expression of PPARα, CPT-1, CYP7A1, FXR, TGR5, NTCP, and BSTP, and down-regulating those of SREBP-1c, FAS, and ASBT, FO suppressed lipogenesis, promoted lipolysis and BA synthesis, and efflux to faeces via the FXR pathway. 16s rRNA sequencing revealed that FO significantly increased Akkermansia and significantly decreased Lachnoclostridium, Blautia, Colidextribacter, and Desulfovibrio. Spearman's correlation analysis showed that these bacteria were strongly correlated with hyperlipidemia-related parameters. Therefore, our results indicated that FO possessed an antihyperlipidemic effect via regulating the gut–liver axis, i.e., BA metabolism and gut microbiota.