Peroxisome proliferator-activated receptor delta activation leads to increased transintestinal cholesterol efflux

Abstract

Peroxisome proliferator-activated receptor delta (PPARdelta) is involved in regulation of energy homeostasis. Activation of PPARdelta markedly increases fecal neutral sterol secretion, the last step in reverse cholesterol transport. This phenomenon can neither be explained by increased hepatobiliary cholesterol secretion, nor by reduced cholesterol absorption. To test the hypothesis that PPARdelta activation leads to stimulation of transintestinal cholesterol efflux (TICE), we quantified it by intestine perfusions in FVB mice treated with PPARdelta agonist GW610742. To exclude the effects on cholesterol absorption, mice were also treated with cholesterol absorption inhibitor ezetimibe or ezetimibe/GW610742. GW601742 treatment had little effect on plasma lipid levels but stimulated both fecal neutral sterol excretion ( approximately 200%) and TICE ( approximately 100%). GW610742 decreased intestinal Npc1l1 expression but had no effect on Abcg5/Abcg8. Interestingly, expression of Rab9 and LIMPII, encoding proteins involved in intracellular cholesterol trafficking, was increased upon PPARdelta activation. Although treatment with ezetimibe alone had no effect on TICE, it reduced the effect of GW610742 on TICE. These data show that activation of PPARdelta stimulates fecal cholesterol excretion in mice, primarily by the two-fold increase in TICE, indicating that this pathway provides an interesting target for the development of drugs aiming at the prevention of atherosclerosis.

Fig. 1.

Effect of GW610742 treatment on intestinal cholesterol efflux. FVB mice (n = 7 per group) received casein diet, a GW610742 diet (0.017% w/w), an ezetimibe diet (10 mg/kg/day), or an ezetimibe + GW610742 diet for 2 weeks. Proximal small intestinal perfusions were performed, using TC/PC (10:2 mM) as cholesterol acceptor. Values are expressed as means SD. * indicates a significant effect of GW610742 in comparison to control treated animals.

Fig. 2.

Plasma analysis of GW610742 treated mice. FVB mice (n = 7 per group) received casein diet, a GW610742 diet (20 mg/kg/day), an ezetimibe diet (10 mg/kg/day) or an ezetimibe + GW610742 diet for 2 weeks. Blood was collected and plasma was obtained by centrifugation. A: Total plasma cholesterol levels and (B) plasma triglyceride levels were measured. C: Lipoproteins were separated by HPGC combined with subsequent in-line total cholesterol determination. D: Fractions obtained by HPGC were subjected to Western blot. Via detection of ApoA1, ApoB, and ApoE, the apolipoprotein composition of the lipoprotein profiles was determined.

Fig. 3.

Intestinal gene expression analysis of GW610742 treated mice. FVB mice (n = 7 per group) received casein diet, a GW610742 diet (20 mg/kg/day), an ezetimibe diet (10 mg/kg/day) or an ezetimibe + GW610742 diet for 2 weeks. Proximal small intestinal perfusions were performed, using TC/PC (10:2 mM) as cholesterol acceptor. At the end of the 2 h perfusion period, intestines were collected cut into three equal segments. The middle segment was analyzed. As control genes cyclophilin, 36B4 and HPRT were used. Values are expressed as means SD. * indicates a significant effect of GW610742 in comparison to control treated animals.