Synthetic Farnesoid X Receptor Agonists Induce High-Density Lipoprotein-Mediated Transhepatic Cholesterol Efflux in Mice and Monkeys and Prevent Atherosclerosis in Cholesteryl Ester Transfer Protein Transgenic Low-Density Lipoprotein Receptor (−/−) Mice

Abstract

Farnesoid X receptor (FXR), a bile acid-activated nuclear hormone receptor, plays an important role in the regulation of cholesterol and more specifically high-density lipoprotein (HDL) homeostasis. Activation of FXR is reported to lead to both proand anti-atherosclerotic effects. In the present study we analyzed the impact of different FXR agonists on cholesterol homeostasis, plasma lipoprotein profiles, and transhepatic cholesterol efflux in C57BL/6J mice and cynomolgus monkeys and atherosclerosis development in cholesteryl ester transfer protein transgenic (CETPtg) low-density lipoprotein receptor (LDLR) (Ϫ/Ϫ) mice. In C57BL/6J mice on a high-fat diet the synthetic FXR agonists isopropyl 3-(3,benzoic acid (PX20606) demonstrated potent plasma cholesterollowering activity that affected all lipoprotein species, whereas 3-[2-ethenyl]benzoic acid (GW4064) and 6-ethyl chenodeoxycholic acid (6-ECDCA) showed only limited effects. In FXR wild-type mice, but not FXR(Ϫ/Ϫ) mice, the more efficacious FXR agonists increased fecal cholesterol excretion and reduced intestinal cholesterol (re)uptake. In CETPtg-LDLR(Ϫ/Ϫ) mice PX20606 potently lowered total cholesterol and, despite the observed HDL cholesterol (HDLc) reduction, caused a highly significant decrease in atherosclerotic plaque size. In normolipidemic cynomolgus monkeys PX20606 and 6-ECDCA both reduced total cholesterol, and PX20606 specifically lowered HDL 2c but not HDL 3c or apolipoprotein A1. That pharmacological FXR activation specifically affects this cholesterol-rich HDL 2 subclass is a new and highly interesting finding and sheds new light on FXR-dependent HDLc lowering, which has been perceived as a major limitation for the clinical development of FXR agonists.

Intestinal Farnesoid X Receptor Controls Transintestinal Cholesterol Excretion in Mice

“…C57BL/6J mice were treated with the FXR agonist PX20606 (PX) for two weeks. In line with data obtained in hyperlipidemic mice and monkeys 22 , the compound was well-tolerated and had no effect on body weight or food intake (data not shown). PX treatment decreased plasma cholesterol and triglycerides ( Figure 1A,B) but increased hepatic levels of these lipids ( Figure S1A,B).…”

“…21 PX was shown previously to potently decrease plasma cholesterol levels and progression of atherosclerosis in cholesteryl ester transfer protein (CETP)-transgenic/low-density lipoprotein (LDL)-receptor knock-out mice. 22 At first sight, our results indicate that mobilization of cholesterol, driven by increased TICE, may explain the cholesterol-lowering effect in plasma. Indeed, plasma cholesterol was also reduced in PX-treated wildtype mice in our study ( Figure 1A).…”

“…When stated, mice received 10 mg/kg/day PX20606 (PX) (Phenex Pharmaceuticals, AG, Heidelberg, Germany) 21,22 , 0.005% (w/w) ezetimibe (Ezetrol; Pharmacy UMCG, Groningen, The Netherlands), or both compounds mixed into their diet. Additionally, ABCG8 KO mice were injected with 1 x 10 11 particles/mouse of an Abcg8-encoding adenovirus (AdABCG8) or control virus (AdNull) and experiments were performed between day 3 and day 5 after administration.…”

“…22 To disentangle the effects of hepatic and intestinal FXR, we performed experiments in intestine-specific FXR (iFXR) KO mice. Interestingly, the PX-induced changes in cholesterol fluxes were almost completely abrogated in these mice; only marginal inductions of FNS excretion ( Figure 3A) and TICE ( Figure 3B …”

Farnesoid X receptor activation increases cholesteryl ester transfer protein expression in humans and transgenic mice

“…CETP expression on cholesterol-enriched Western-type diets ( 45 ) to exert antiatherogenic effects, in a large part via decreasing levels of proatherogenic apoB-containing lipoproteins. These metabolic effects are likely mediated by decreased intestinal cholesterol absorption in response However, in Ldlr-defi cient mice with transgenic CETP expression, as well as in cynomolgous monkeys, FXR activation consistently resulted in a strong decrease in plasma HDL-C levels ( 45 ), similar to our results in the E3L.CETP model.…”