Intestinal FXR controls transintestinal cholesterol excretion in mice

ABSTRACT Background & aims: The role of the intestine in the maintenance of cholesterol homeostasis is increasingly recognized. Fecal excretion of cholesterol is the last step in the atheroprotective reverse cholesterol transport (RCT) pathway, to which both biliary and transintestinal cholesterol excretion (TICE) contribute. The mechanisms controlling the flux of cholesterol through the TICE pathway are,however, poorly understood. In the current study we aimed to identify treatment modalities that stimulate TICE and to uncover underlying driving mechanisms. Methods: TICE was assessed in a panel of knock-out and transgenic mice as well as in mice treated with the FXR agonist PX20606 either or not combined with the cholesterol absorption inhibitor ezetimibe. Results: We show that TICE is regulated by intestinal farnesoid X receptor (FXR) via its target fibroblast growth factor 15/19 (FGF15/19) and that the pathway can be stimulated to such an extent that mice excrete ~60% of their total cholesterol content each day. Both PX20606 and FGF19 increased the muricholate/cholate ratio in bile, inducing a more hydrophilic bile salt pool. The altered bile salt pool robustly stimulated secretion of cholesterol into the intestinal lumen via the sterol exporting heterodimer ATP binding cassette subfamily G member 5/8 (ABCG5/G8). Of note, we demonstrate that the increase in TICE induced by PX20206 is independent of changes in cholesterol absorption. Conclusions: Hydrophilicity of the bile salt pool, controlled by FXR and FGF15/19, is an important determinant of cholesterol removal via TICE. Translation of these results to humans may offer new treatment modalities for prevention of cardiovascular disease. 4 WT mice on chow and 4 WT mice on chow supplemented with FXR agonist PX20606 (PX) compound 10mg/kg/day for 2 weeks. Liver and intestine (s1=proximal, s3=distal) were collected from all 8 mice.