Fisetin ameliorates atherosclerosis through activating FXR-mediated hepatic cholesterol metabolism and transintestinal cholesterol excretion

Cholesterol homeostasis dysregulation is a primary risk factor for atherosclerosis (AS) development. Fisetin, a flavonoid compound, has shown promise in regulating cholesterol homeostasis by enhancing transintestinal cholesterol excretion (TICE). This study aimed to investigate the regulatory effects and underlying mechanisms of fisetin in AS. In this study, ApoE^-/- mice fed a high-fat diet (HFD) were employed to investigate the effects of fisetin on the prevention of AS. Various methods, including biochemical analyses, histopathological staining, lipid deposition assessment, untargeted lipidomics analysis and RNA sequencing, were employed to explore the underlying mechanisms. The results showed that treatment with fisetin notably reduced lipid deposition in the aortic root of HFD-treated ApoE^-/- mice and attenuated hepatic lipid deposition and histopathological changes. This was accompanied by decreased serum levels of total cholesterol, triglyceride and LDL cholesterol. Fisetin also effectively mitigated HFD-induced oxidative stress and inflammation in mice. Hepatic lipidomics revealed significant alterations in lipid content and composition following fisetin treatment, including reductions in lipids associated with AS risk, such as cholesteryl ester (ChE), phosphatidylcholines (PC), phosphatidylethanolamine (PE), lysophosphatidylcholine (LPC), cardiolipin (CL), phosphatidylinositol (PI), and TG. Additionally, phosphatidylserine (PS) levels were increased. RNA sequencing of livers revealed that fisetin affected genes related to cholesterol metabolism and bile acid biosynthesis, including cytochrome P450 (Cyp) family and Nr1h4 (Fxr). Molecular docking analysis suggested FXR may be a potential target of fisetin. In the liver, cholesterol can be either converted into bile acids or pumped out to bile ducts by ATP-binding cassette (ABC) transporters G5 (ABCG5) and G8 (ABCG8) for elimination. Fisetin treatment notably modulated the hepatic proteins related to cholesterol metabolism (HMGCR, PCSK9, LDLR, FXR, CYP27A1, CYP7A1, CYP8B1 and BSEP) and cholesterol excretion (ABCG5, ABCG8), maintaining cholesterol homeostasis. Additionally, fisetin increased the excretion of fecal neutral sterols, including cholesterol, dihydrocholesterol, and coprosterone. It also increased the expression of FXR, ABCG5, ABCG8, and LDLR, while decreasing NPC1L1 and PCSK9 levels in the jejunum, thereby stimulating the TICE pathway. These findings provide compelling evidence that fisetin reduces cholesterol levels and alleviates AS by stimulating FXR-mediated hepatic cholesterol metabolism and the TICE pathway. The findings suggest that fisetin-regulated cholesterol metabolism may represent a promising therapeutic strategy for the treatment of AS.