AHR Deficiency Exacerbates Hepatic Cholesterol Accumulation via Inhibiting Bile Acid Synthesis in MAFLD Rats

Metabolic-dysfunction-associated fatty liver disease (MAFLD) is a chronic liver disease characterized by abnormal lipid metabolism. The aryl hydrocarbon receptor (AHR) is a ligand-dependent transcription factor involved in regulating multiple physiological processes. Recent studies have demonstrated that AHR exerts a multifaceted regulatory role in liver diseases by integrating metabolic and immune signaling pathways; however, the specific role of AHR in MAFLD is not clear. In our work, a rat model of MAFLD was established by feeding wild-type (WT) and AHR knockout (AHR^-/-) rats with a high-fat, high-fructose, and high-cholesterol diet (HFHFrHCD) for 10 weeks, and then the liver injury markers, lipid-related biochemical indices and liver histopathology were examined to elucidate the effect of AHR on MAFLD progression. We discovered that AHR deficiency can elevate plasma transaminase levels, increase hepatic triglyceride (TG) and total cholesterol (TC), and exacerbate insulin resistance (IR) under an overnutrition environment. Subsequently, liver transcriptome and RT-qPCR were performed to investigate the underlying mechanism, which revealed that the hepatic bile acid synthesis was inhibited because of lower Cytochrome P450 Family 7 Subfamily A Member 1 (CYP7A1) expression in the liver when AHR was knockout. Additionally, intestinal flora dysbiosis occurred in AHR^-/- rats fed with HFHFrHCD, which might also contribute to the hepatic cholesterol accumulation. Taken together, our results suggested that AHR might play an important role in regulating cholesterol metabolism by inhibiting bile acid synthesis and breaking the steady state of the gut microbiota during the MAFLD progression.