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Originally published In Press as doi:10.1194/jlr.M400400-JLR200 on December 16, 2004

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Journal of Lipid Research, Vol. 46, 526-534, March 2005
Copyright © 2005 by American Society for Biochemistry and Molecular Biology

Reduced cholesterol absorption upon PPAR{delta} activation coincides with decreased intestinal expression of NPC1L1

Jelske N. van der Veen1,2,*, Janine K. Kruit2,*, Rick Havinga*, Julius F. W. Baller*, Giovanna Chimini{dagger}, Sophie Lestavel§, Bart Staels§, Pieter H. E. Groot**, Albert K. Groen{dagger}{dagger} and Folkert Kuipers*

* Department of Pediatrics, Center for Liver, Digestive, and Metabolic Diseases, University Hospital Groningen, Groningen, The Netherlands
{dagger} Centre de Immunology, Marseille, France
§ Unité de Recherche 545, Institut National de la Santé et de la Recherche Médicale, Departement d'Atherosclerose, Institut Pasteur de Lille, Lille, France
** Atherosclerosis Department, GlaxoSmithKline Pharmaceuticals, Stevenage, United Kingdom
{dagger}{dagger} Department of Experimental Hepatology, Academic Medical Center, Amsterdam, The Netherlands

Published, JLR Papers in Press, December 16, 2004. DOI 10.1194/jlr.M400400-JLR200

2 J. N. van der Veen and J. K. Kruit contributed equally to this work. Back

1 To whom correspondence should be addressed. e-mail: j.n.van.der.veen{at}med.rug.nl


   ABSTRACT
TOP
 ABSTRACT
INTRODUCTION
 EXPERIMENTAL PROCEDURES
 RESULTS
 DISCUSSION
 REFERENCES
 
Peroxisome proliferator-activated receptors (PPARs) control the transcription of genes involved in lipid metabolism. Activation of PPAR{delta} may have antiatherogenic effects through the increase of plasma HDL, theoretically promoting reverse cholesterol transport from peripheral tissues toward the liver for removal via bile and feces. Effects of PPAR{delta} activation by GW610742 were evaluated in wild-type and Abca1-deficient (Abca1–/–) mice that lack HDL. Treatment with GW610742 resulted in an ~50% increase of plasma HDL-cholesterol in wild-type mice, whereas plasma cholesterol levels remained extremely low in Abca1–/– mice. Yet, biliary cholesterol secretion rates were similar in untreated wild-type and Abca1–/– mice and unaltered upon treatment. Unexpectedly, PPAR{delta} activation led to enhanced fecal neutral sterol loss in both groups without any changes in intestinal Abca1, Abcg5, Abcg8, and 3-hydroxy-3-methylglutaryl-coenzyme A reductase expression. Moreover, GW610742 treatment resulted in a 43% reduction of fractional cholesterol absorption in wild-type mice, coinciding with a significantly reduced expression of the cholesterol absorption protein Niemann-Pick C1-like 1 (Npc1l1) in the intestine. PPAR{delta} activation is associated with increased plasma HDL and reduced intestinal cholesterol absorption efficiency that may be related to decreased intestinal Npc1l1 expression.

Thus, PPAR{delta} is a promising target for drugs aimed to treat or prevent atherosclerosis.

Abbreviations: Abca1–/–, Abca1-deficient; FPLC, fast-protein liquid chromatography; Hmgr, 3-hydroxy-3-methylglutaryl-coenzyme A reductase; Mdr2, multidrug resistance P-glycoprotein 2; NPC1L1, Niemann-Pick C1-like 1; Pdk4, pyruvate dehydrogenase kinase isoenzyme 4; PPAR, peroxisome proliferator-activated receptor; RCT, reverse cholesterol transport; Sr-b1, scavenger receptor B1

Supplementary key words Niemann-Pick C1-like 1 • peroxisome proliferator-activated receptor {delta} • nuclear receptors • high density lipoprotein-cholesterol


   INTRODUCTION
TOP
 ABSTRACT
 INTRODUCTION
EXPERIMENTAL PROCEDURES
 RESULTS
 DISCUSSION
 REFERENCES
 
Plasma levels of HDL-cholesterol are inversely related to the development of atherosclerosis (1). This protective effect has been attributed to a role of HDL in reverse cholesterol transport (RCT), defined as the flux of excess cholesterol from peripheral cells to nascent HDL particles followed by transport to the liver. The liver is able to secrete cholesterol into bile, either as free cholesterol or after conversion into bile salts, for removal via the feces. Stimulation of HDL-mediated cholesterol efflux is considered an attractive approach to diminish the development of atherosclerosis.

ABCA1 is considered to be essential in RCT (2). ABCA1 is ubiquitously expressed and probably involved in the formation of preß-HDL particles and the efflux of cholesterol from peripheral tissues toward HDL (3). HDL is considered a major source for bile-destined cholesterol (4). However, we recently demonstrated that, despite the absence of HDL, hepatobiliary cholesterol flux and fecal sterol excretion are not affected in Abca1-deficient (Abca1–/–) mice (5, 6). The ABCG5/ABCG8 heterodimer was recently shown to be of crucial importance for hepatobiliary cholesterol secretion and for transport of cholesterol from enterocytes back into the intestinal lumen, thereby promoting net cholesterol removal from the body (7, 8).

Several genes involved in the control of cholesterol metabolism are transcriptionally regulated by nuclear receptors. Peroxisome proliferator-activated receptors (PPARs) constitute a subgroup of the nuclear receptor superfamily, designated PPAR{alpha} (NR1C1), PPAR{delta}/ß (NR1C2), and PPAR{gamma} (NR1C3), all of which serve functions in lipid homeostasis and energy metabolism (9). PPAR{delta} is ubiquitously expressed and activated by long-chain fatty acids and prostacyclins. Recent work suggests that activation of PPAR{delta} may induce RCT and hence have antiatherogenic effects (10). Whether or not PPAR{delta} activation, like PPAR{alpha} activation (11, 12), is associated with altered bile formation and fecal sterol loss is not known.

This study shows that PPAR{delta} activation in mice increased plasma HDL concentrations and accelerated fecal cholesterol removal from the body without changing hepatobiliary sterol excretion. Moreover, intestinal cholesterol absorption efficiency was reduced upon PPAR{delta} activation, which coincided with the downregulation of intestinal gene expression of the very recently identified cholesterol absorption protein Niemann-Pick C1-like 1 (NPC1L1) (13).


   EXPERIMENTAL PROCEDURES
TOP
 ABSTRACT
 INTRODUCTION
 EXPERIMENTAL PROCEDURES
RESULTS
 DISCUSSION
 REFERENCES
 
Animals
Female Abca1–/– mice with a DBA/1 background and age-matched DBA/1 wild-type mice were purchased from IFFA Credo (Saint-Germain-sur-l'Arbesle, France). Separate groups of wild-type DBA/1 mice were obtained from Harlan (Horst, The Netherlands). All experimental procedures were in accordance with local guidelines for the use of experimental animals.

PPAR{delta} agonist
GW610742 (GlaxoSmithKline Pharmaceuticals, Stevenage, UK) (Fig. 1) is a high-affinity ligand for PPAR{delta}. The specificity of GW610742, as evaluated by ligand binding studies, revealed EC50 values of 28 nM for murine PPAR{delta} versus 8,900 nM and >10,000 nM for murine PPAR{alpha} and PPAR{gamma}, respectively. For human PPAR{delta}, PPAR{alpha}, and PPAR{gamma}, the EC50 values are 1, 1,200, and 4,100 nM, respectively (14) (L. Patel, personal communication). The specificity of GW1516 has been described previously (10, 14).



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  		Fig. 1. Chemical structure of the peroxisome proliferator-activated receptor {delta} (PPAR{delta})-specific agonist GW610742.

 
Experimental methods
Abca1–/– and DBA/1 wild-type mice (n = 6 per group) were fed GW610742 mixed through chow at a level of 0.017% (w/w) for 8 days. With an average daily food intake of 3 g, this provided an approximate intake of 20 mg/kg/day, leading to an average plasma concentration of 1 µM (L. Patel, personal communication). Control mice received standard chow without GW610742. From day 7–8, feces was collected from individual mice. Mice were then anesthetized by intraperitoneal injection of ketamine (1 ml/kg) and diazepam (10 mg/kg). Bile was collected for 30 min after cannulating the gallbladder, and a blood sample was taken by cardiac puncture. Livers and small intestines were excised. Parts of both liver and intestine were snap-frozen in liquid nitrogen and stored at –80°C for RNA isolation and biochemical analysis. Samples for microscopic evaluation were frozen in isopentane and stored at –80°C or fixed in paraformaldehyde.

Analytical methods
Livers were homogenized and hepatic and biliary lipids were extracted (15). Hepatic, biliary, and plasma concentrations of cholesterol, triglycerides, and phospholipids were determined as previously described (6). Fecal neutral sterols and fatty acids were analyzed by gas chromatography. Bile salts in feces and in bile were measured enzymatically. Pooled plasma samples were used for lipoprotein separation by fast-protein liquid chromatography (FPLC).

RNA isolation and measurement of mRNA levels by real-time PCR (Taqman)
RNA isolation, cDNA synthesis, and real-time quantitative PCR were performed as described by Plösch et al. (6). Primer and probe sequences for Abca1, Abcg5, Abcg8, Acat2, 3-hydroxy-3-methylglutaryl-coenzyme A reductase (Hmgr), liver X receptor {alpha}, multidrug resistance P-glycoprotein 2 (Mdr2), and scavenger receptor B1 (Sr-b1) (6) as well as for ß-actin (11) have been published. Furthermore, the following primers/probes were used. For Ppar{delta}, sense, 5'-AGA TGG TGG CAG AGC TAT GAC C-3'; antisense, 5'-TCT CCT CCT GTG GCT GTT CC-3'; and probe, 5'-CCC ACT TGG CGT GGC GCC T-3' (accession number, NM_013141). For pyruvate dehydrogenase kinase isoenzyme 4 (Pdk4), sense, 5'-GCA TTT CTA CTC GGA TGC TCA TG-3'; antisense, 5'-CCA ATG TGG CTT GGG TTT CC-3'; and probe, 5'-CAG CAC ATC CTC ATA TTC AGT GAC TCA AAG AC-3' (accession number, NM_013743). For Npc1l1, sense, 5'-GAG AGC CAA AGA TGC TAC TAT CTT CA-3'; antisense, 5'-CCC GGG AAG TTG GTC ATG-3'; and probe, 5'-ACT CCA GCA AAC ACC GCA CTG CC-3' (accession number, AY437866). For 36b4, sense, 5'-GCT TCA TTG TGG GAG CAG ACA-3'; antisense, 5'-CAT GGT GTT CTT GCC CAT CAG-3'; and probe, 5'-TCC AAG CAG ATG CAG CAG ATC CGC-3' (accession number, NM_007475).

Isolation of peritoneal macrophages
DBA/1 wild-type mice were treated with the GW610742-containing diet for 8 days. Thioglycollate-elicited peritoneal macrophages of treated and untreated DBA/1 wild-type mice were harvested as described by Herijgers et al. (16). Cells were washed, and RNA isolation, cDNA synthesis, and real-time PCR were performed as described.

Plasma dual-isotope ratio method
Cholesterol absorption was measured using the plasma dual-isotope ratio method (17). DBA/1 wild-type mice (n = 5 per group) received a diet with or without 0.017% (w/w) GW610742. After 6 days, mice received an intravenous injection of 1.1 µCi of [3H]cholesterol dissolved in intralipid and an oral dose of 1.0 µCi of [14C]cholesterol dissolved in medium-chain triglyceride oil. At 24, 48, and 72 h after administration, blood samples were taken by retro-orbital puncture and feces was collected. At day 10, mice were anesthetized and bile was collected for 30 min. 14C and 3H activity in plasma, bile, and feces was measured by liquid scintillation counting. Blood samples obtained 72 h after administration were used for the calculation of cholesterol absorption.

In vitro activation of PPARs in Caco-2 cells
Cell culture reagents were obtained from Eurobio (Les Ulis, France), and microporous polyethylene membrane inserts (23.1 mm, 3 µm pore size) were obtained from Becton Dickinson (Le Pont de Claix, France). Caco-2 cells were routinely grown in plastic flasks (ATGC Biotechnologie, Marne la Vallée, France) under a humidified atmosphere containing 10% CO2 at 37°C in Dulbecco's modified essential medium containing 25 mM glucose and Glutamax, supplemented with penicillin-streptomycin (100 IU/ml and 100 g/ml, respectively), 1% nonessential amino acids, and 20% heat-inactivated fetal calf serum.

To establish the intestinal barrier model for the assay, Caco-2 cells (between passages 40 and 45) were plated at a density of 0.25 x 106 cells per insert and grown in the complete medium. Confluence was routinely reached 8 days after seeding. Cells were then cultured in asymmetric conditions, with medium containing fetal calf serum in the lower compartment and serum-free medium in the upper compartment. Media were changed every day. Three weeks later, cells were activated with ligands for PPAR{alpha} (Wy14643 at 50 µM), PPAR{gamma} (rosiglitazone at 100 nM), or PPAR{delta} (GW1516 at 100 nM) for 24 h in the upper compartment. After incubation, cell layers were briefly rinsed twice with ice-cold PBS (10 mM phosphate buffer, pH 7.5, 2.7 mM KCl, and 150 mM NaCl) and total cellular RNA was extracted using RNA-Plus (Q-BIOgene, Illkirch, France). For quantitative PCR, total RNA were reverse transcribed using random hexameric primers and Superscript reverse transcriptase (Life Technologies). cDNAs were quantified by real-time PCR on a MX 4000 apparatus (Stratagene) using specific primers for NPC1L1 (sense, 5'-GGG GCA TCA GTT ACA ATG CT-3'; antisense, 5'-AAA CAC CGC ACT TCC CAT AG-3'). PCR amplification was performed in a volume of 25 µl containing 100 nmol/l of each primer, 4 mmol/l MgCl2, the Brilliant Quantitative PCR Core Reagent Kit mix as recommended by the manufacturer (Stratagene), and 0.33x SYBR Green (Sigma-Aldrich, Saint Quentin Fallavier, France). The conditions were 95°C for 10 min followed by 40 cycles of 30 s at 95°C, 30 s at 55°C, and 30 s at 72°C. NPC1L1 mRNA levels were subsequently normalized to 28S mRNA (sense, 5'-AAA CTC TGG TGG AGG TCC GT-3'; antisense, 5'-CTT ACC AAA AGT GGC CCA CTA-3'). The activated condition was then normalized to the control condition set at 100%. Each experiment was performed in triplicate.

Immunohistochemistry
Histology of livers and small intestines was examined after hematoxylin/eosin staining on paraformaldehyde-fixed sections. Neutral lipids were stained by oil red O on frozen sections, and peroxisome proliferation was determined by catalase staining. Intestinal cell proliferation was examined after Ki67 staining on paraformaldehyde-fixed sections, using a Ki67 polyclonal antibody (1:500; Novo Castra, Newcastle, UK).

Statistics
Statistical analyses were performed using SPSS version 10.0 for Windows (SPSS, Inc., Chicago, IL). Treated and untreated groups were compared by Student's t-test. P < 0.05 was considered statistically significant.


   RESULTS
TOP
 ABSTRACT
 INTRODUCTION
 EXPERIMENTAL PROCEDURES
 RESULTS
DISCUSSION
 REFERENCES
 
Animal characteristics
Table 1 shows that body weights of DBA/1 wild-type and Abca1–/– mice were similar and not influenced by treatment with GW610742. Liver weights of untreated wild-type and Abca1–/– mice did not differ, but treatment with the PPAR{delta} agonist resulted in slightly increased liver weights in both strains. This was probably related to peroxisome proliferation, as revealed by enhanced catalase staining in liver sections of treated animals (data not shown). Treatment with GW610742 did not induce liver injury, as indicated by unaffected plasma lactate dehydrogenase (LDH) and aspartate aminotransferase (ALAT) levels.


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  		TABLE 1. Animal characteristics and plasma and hepatic lipid concentrations in untreated and GW610742-treated DBA/1 wild-type and Abca1–/– mice

 
PPAR{delta} activation increases plasma HDL and induces Abca1 expression in macrophages but has no effect on hepatobiliary cholesterol excretion
In accordance with previous reports (5, 18), plasma cholesterol levels were ~75% lower in Abca1–/– mice than in wild-type mice (Table 1). Treatment with GW610742 increased total plasma cholesterol by ~30% in wild-type mice, whereas cholesterol levels in Abca1–/– mice remained extremely low. FPLC analysis (Fig. 2) confirmed the complete lack of HDL-cholesterol in Abca1–/– mice and revealed an ~50% increase in HDL-cholesterol levels in wild-type mice upon PPAR{delta} activation.



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  		Fig. 2. Fast-protein liquid chromatography (FPLC) separation of plasma lipoproteins of untreated and GW610742-treated DBA/1 wild-type and Abca1-deficient (Abca1–/–) mice. DBA/1 wild-type mice (open symbols) and Abca1–/– mice (closed symbols) were treated with solvent (circles) or with GW610742 (squares) for 8 days (n = 6 per group). Plasma from all individual mice per group was pooled and subjected to gel filtration using Superose 6 columns. Cholesterol content in each fraction was measured.

 
Expression levels of both Abca1 and Sr-b1 in thioglycollate-elicited peritoneal macrophages of wild-type mice were ~3-fold upregulated upon PPAR{delta} activation (Fig. 3) , demonstrating that GW610742 did induce systemic effects.



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  		Fig. 3. Gene expression in the peritoneal macrophages of untreated (open bars) and GW610742-treated (closed bars) DBA/1 wild-type mice, measured by real-time PCR. Data are presented as means of three assays performed in duplicate ± SD. Expression values are normalized to 36b4, and expression in untreated mice was set to 1.00 (n = 3 per group). * Significant differences by Student's t-test (P < 0.05).

 
Hepatic concentrations of cholesterol, phospholipids, and triglycerides (Table 1) were similar in wild-type and Abca1–/– mice and were not affected by PPAR{delta} activation in wild-type mice, whereas hepatic triglycerides were slightly increased upon treatment in Abca1–/– mice.

Biliary secretion rates of bile salts, cholesterol, and phospholipids were similar in untreated Abca1–/– mice compared with wild-type mice (Table 2), in accordance with published data (5). Treatment with GW610742 did not significantly affect biliary secretion rates in wild-type or Abca1–/– mice. This is in accordance with the absence of any effect on the hepatic expression of several genes involved in cholesterol metabolism and transport (Fig. 4 , left panels). Only hepatic Abcb4 (Mdr2) expression was slightly but significantly induced upon treatment, but this did not affect biliary phospholipid secretion. As a positive control, expression of the PPAR{delta} target gene Pdk4 (19) was measured. Hepatic expression of this gene was ~6-fold upregulated upon PPAR{delta} activation in both strains of mice.


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  		TABLE 2. Bile flow and biliary secretion rates in untreated and GW610742-treated DBA/1 wild-type and Abca1–/– mice

 


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  		Fig. 4. Gene expression in the livers and intestines of untreated (open bars) and GW610742-treated (closed bars) DBA/1 wild-type and Abca1–/– mice, measured by real-time PCR. Data are presented as means of six assays performed in duplicate ± SD. Expression values are normalized to ß-actin, and expression in untreated wild-type mice was set to 1.00. *,# Significant differences by Student's t-test (P < 0.05 and P < 0.01, respectively). Hmgr, 3-hydroxy-3-methylglutaryl-coenzyme A reductase; Mdr2, multidrug resistance P-glycoprotein 2; Pdk4, pyruvate dehydrogenase kinase isoenzyme 4.

 
Fecal excretion of neutral sterols is induced upon PPAR{delta} activation
Fecal excretion of acidic sterols (bile salts) was similar in all groups (Fig. 5A) . However, fecal excretion of neutral sterols, 80% of which comprised cholesterol, was 2- to 3-fold increased upon PPAR{delta} activation in wild-type and Abca1–/– mice (Fig. 5B). Because hepatobiliary efflux of cholesterol was not induced upon treatment, increased sterol excretion might be directly mediated by intestinal adaptations. Figure 4 (right panels) shows that intestinal expression levels of Abca1, Abcg5, and Abcg8 were not affected upon treatment with GW610742. Expression of Acat2, which is responsible for the esterification of cholesterol in enterocytes and crucial for cholesterol absorption, and of Hmgr, the rate-limiting enzyme in cholesterol synthesis, were also unaffected.



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  		Fig. 5. Fecal loss of acidic sterols (A) and neutral sterols (B) in untreated and GW610742-treated DBA/1 wild-type and Abca1–/– mice. Feces of untreated (open bars) and treated (closed bars) wild-type and Abca1–/– mice were collected during the last 24 h of the experiment. *,# Significant differences by Student's t-test (P < 0.005 and P < 0.001, respectively). Values represent means ± SD.

 
To investigate whether increased intestinal cell proliferation may have contributed to the increased fecal cholesterol excretion through accelerated cell shedding, Ki67 staining was performed on intestinal sections. This, however, did not show any sign of accelerated proliferation upon PPAR{delta} activation (data not shown).

PPAR{delta} activation decreases cholesterol absorption, accelerates fecal excretion of plasma-derived cholesterol, and reduces intestinal Npc1l1 expression
Figure 6 shows that PPAR{delta} activation led to a 43% reduction of cholesterol absorption efficiency in DBA/1 wild-type mice, despite the unaffected expression levels of Abcg5 and Abcg8. Recently, NPC1L1 was identified as a critical component of the intestinal cholesterol absorption machinery (13). Therefore, we measured mRNA levels of Npc1l1 along the length of the small intestine of untreated and treated mice. Expression of the gene was decreased by 35% in the jejunum upon PPAR{delta} activation and was also lower in ileal sections of treated animals (Fig. 7) . A similar decrease in intestinal Npc1l1 expression (i.e., –40%) was observed in Abca1–/– mice upon treatment with GW610742.



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  		Fig. 6. Cholesterol absorption in untreated (open bars) and GW610742-treated (closed bars) DBA/1 wild-type mice. Cholesterol absorption in treated and untreated mice was measured using the plasma dual-isotope method (n = 5 per group). After 6 days of treatment, mice received an intravenous injection of [3H]cholesterol and an oral dose of [14C]cholesterol. Plasma samples obtained 72 h after administration were used for the calculation of fractional cholesterol absorption. Values represent means ± SD. * Significant differences by Student's t-test (P < 0.005).

 


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  		Fig. 7. Expression of Niemann-Pick C1-like 1 (Npc1l1) along the length of the small intestine of untreated (open bars) and GW610742-treated (closed bars) DBA/1 wild-type mice, measured by real-time PCR. Data are presented as means of six assays performed in duplicate ± SD. Expression values are normalized to ß-actin, and expression in duodenum of untreated mice was set to 1.00. * Significant differences by Student's t-test (P < 0.05).

 
Reduced cholesterol absorption is also apparent from Fig. 8A , showing markedly increased fecal recovery of orally administered [14C]cholesterol in GW610742-treated mice. Figure 8B shows that fecal excretion of intravenously injected [3H]cholesterol was higher upon treatment with GW610742, which is likely attributable in part to less efficient reabsorption of biliary [3H]cholesterol. However, the 2.5-fold increase in fecal [3H]cholesterol loss is larger then expected on the basis of a 40% reduction in cholesterol absorption efficiency. These data suggest that cholesterol may partly be excreted directly from plasma into the intestinal lumen (20). Conversion of labeled cholesterol into bile salts was not affected by PPAR{delta} activation, as shown in Fig. 8C. Fecal excretion of 14C-labeled bile salts (Fig. 8D) was somewhat lower in the treated mice, probably because of the lower efficiency of cholesterol absorption in these animals.



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  		Fig. 8. Fecal loss of intravenously and orally administered radiolabeled cholesterol in untreated and GW610742-treated DBA/1 wild-type mice. A and B show fecal loss of 14C-labeled and 3H-labeled neutral sterols, respectively, in treated (closed symbols) and untreated (open symbols) mice. C and D show fecal loss of 14C-labeled and 3H-labeled bile salts, respectively. Values are presented as percentages of administered dose ± SD (n = 5 per group). *,# Significant differences by Student's t-test (P < 0.01 and P < 0.05, respectively).

 
Total fat absorption was not affected by treatment with the PPAR{delta} agonist, as indicated by similar fecal fat excretion rates in both groups (data not shown).

Repression of Npc1l1 expression is specific for PPAR{delta} agonist in Caco2 cells
To assess the specificity of the observed effects on Npc1l1 expression, we evaluated the consequences of PPAR{alpha}, PPAR{gamma}, and PPAR{delta} activation by specific agonists in polarized Caco2 cells. Figure 9 shows that both the PPAR{alpha} agonist Wy14643 and the PPAR{gamma} agonist rosiglitazone had no effect on Npc1l1 expression, whereas the PPAR{delta} agonist GW1516 exhibited a clear (–33%) reduction in Npc1l1 expression. This demonstrates that the reduced expression of Npc1l1 is specific for PPAR{delta} activation.



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  		Fig. 9. Expression of Npc1l1 in polarized Caco2 cells treated with PPAR{alpha}, PPAR{gamma}, or PPAR{delta} agonists, as measured by real-time PCR. Data are presented as means of three assays ± SD. Expression values are normalized to 28S, and expression in control cells was set to 1.00. * Significant differences by one-tailed Mann-Whitney U test (P < 0.05).

 

   DISCUSSION
TOP
 ABSTRACT
 INTRODUCTION
 EXPERIMENTAL PROCEDURES
 RESULTS
 DISCUSSION
REFERENCES
 
This study shows that activation of PPAR{delta} results in increased plasma HDL levels in DBA/1 wild-type mice. Although increased HDL levels might theoretically deliver more cholesterol to the liver for excretion into bile, hepatobiliary excretion of cholesterol and bile salts was not affected upon PPAR{delta} activation in wild-type mice. In fact, excretion rates were highly similar in wild-type and Abca1–/– mice, confirming that HDL is not an essential source of biliary cholesterol in mice (5, 6). In spite of the unaltered biliary excretion rates, fecal loss of neutral sterols was doubled in both strains after treatment with GW610742, which could not be ascribed to either increased intestinal cholesterol synthesis or accelerated intestinal cell proliferation. PPAR{delta} activation reduced cholesterol absorption efficiency in wild-type mice without any change in intestinal Abca1, Abcg5, or Abcg8 expression but did not affect total fat absorption. Reduction of cholesterol absorption without changes in Abcg5 and Abcg8 expression has also been reported upon treatment of mice with the cholesterol absorption-reducing drug ezetimibe (21): intestinal expression of the recently described potential target of ezetimibe, Npc1l1 (13), appeared to be decreased upon PPAR{delta} activation.

Analogous to the situation described in obese and hyperlipidemic rhesus monkeys (10), PPAR{delta} activation beneficially altered plasma lipid profiles in wild-type mice by increasing HDL-cholesterol concentrations. This increase in HDL-cholesterol levels was not observed in Abca1–/– mice, supporting the essential role of ABCA1 in HDL formation. The question of by which mechanism PPAR{delta} activation increases HDL-cholesterol concentrations remains to be answered. Induced expression of Abca1 as well as Sr-b1 in peritoneal macrophages isolated from GW610742-treated wild-type mice suggests that induction of these efflux mediators may contribute. However, bone marrow transplantation studies (22) indicate that the contribution of macrophage-derived cholesterol to plasma HDL levels is limited in mice: plasma HDL-cholesterol levels probably reflect ABCA1-mediated efflux events in all peripheral organs and tissues. ABCA1-mediated cholesterol efflux appeared to be a major source of plasma HDL-cholesterol in mice (23). Yet, we did not observe the induction of hepatic Abca1 expression. The reason for the discrepancy in PPAR{delta}-mediated effects on Abca1 expression between macrophages and liver remains to be established.

HDL-cholesterol is considered a preferential source of biliary cholesterol (4). However, despite the marked differences in plasma HDL-cholesterol levels, no differences in biliary cholesterol excretion were observed between untreated wild-type and Abca1–/– mice or between treated and untreated wild-type mice. These observations are consistent with earlier work (5, 6) indicating that delivery of HDL-cholesterol to the liver is not rate controlling for biliary cholesterol secretion in mice.

Surprisingly, fecal excretion of neutral sterols was 2- to 3-fold increased upon PPAR{delta} activation in both wild-type and Abca1–/– mice, in spite of the fact that biliary cholesterol excretion was not induced. This could theoretically be attributable to a higher intestinal cholesterol synthesis. This parameter has not been measured directly, but intestinal expression of Hmgr was not affected upon PPAR{delta} activation, which strongly suggests unaltered intestinal cholesterol synthesis. Most cholesterol is synthesized in the peripheral tissues in mice (24), and peripheral synthesis may have been enhanced upon PPAR{delta} activation to maintain total body cholesterol balance. It is also highly unlikely that accelerated intestinal cell turnover was the cause of enhanced fecal sterol loss: Ki67 staining of intestinal sections revealed no differences between GW610742-treated and untreated mice.

Cholesterol absorption efficiency was clearly reduced upon PPAR{delta} activation in wild-type mice. Because the amounts of bile salts and phospholipids excreted into the intestinal lumen, important for efficient cholesterol absorption (25, 26), as well as Acat2 expression were unaffected, these factors can be excluded as the cause of the reduced cholesterol absorption. Surprisingly, reduced cholesterol absorption was not associated with any change in the intestinal expression of Abcg5 and Abcg8. Our data suggest that PPAR{delta} may reduce cholesterol absorption by interference with cellular uptake (i.e., by a mechanism that is related to the mode of action of the cholesterol absorption inhibitor ezetimibe) (21). Very recently, Altmann et al. (13) proposed NPC1L1 to be critical for intestinal cholesterol absorption and to represent a target of ezetimibe. Our results show that PPAR{delta} activation clearly reduced intestinal expression of Npc1l1, predominantly in the jejunal part of the small intestine, where most of the cholesterol absorption takes place. Our in vitro results show that this reduced expression of Npc1l1 is highly specific for PPAR{delta} activation. There was no effect of selective PPAR{alpha} and PPAR{gamma} agonists on Npc1l1 expression in Caco-2 cells, but there was a clear suppression by the PPAR{delta} agonist, indicating that human Npc1l1 is also responsive to PPAR{delta} activation.

No data are available yet on the factors involved in Npc1l1 transcription regulation: whether PPAR{delta} controls intestinal Npc1l1 expression by direct or indirect means remains to be established. Because the amount of NPC1L1 protein is clearly reduced in enterocytes of heterozygous Npc1l1+/– mice (13), it is likely that the ~40% reduction in jejunal Npc1l1 mRNA levels was associated with reduced amounts of the protein. Upon oral administration of [14C]cholesterol, absorption in chow-fed Npc1l1+/– mice into plasma and liver appeared to be reduced by ~40% compared with wild-type mice, although this difference failed to reach statistical significance (27). A significant reduction in fractional cholesterol absorption in heterozygote mice compared with wild-type controls was noted after feeding a diet containing 0.1% sodium cholate (13).

It has been proposed that PPAR{delta} might induce antiatherogenic actions (10). Our data support this notion, because PPAR{delta} activation resulted in increased HDL-cholesterol levels. However, potential antiatherogenic effects would not be expected to be achieved by induction of the "classical" pathway of RCT, because fecal cholesterol loss was enhanced without stimulation of hepatobiliary cholesterol excretion. Activation of PPAR{delta} may stimulate direct excretion of plasma-derived cholesterol via the intestine, a mechanism that has been described by Kruit et al. (20), as suggested by the unexpectedly rapid fecal excretion of intravenously administered 3H-labeled neutral sterols in GW610742-treated mice (Fig. 8B). In addition, enhanced fecal neutral sterol loss as a consequence of impaired intestinal cholesterol absorption upon PPAR{delta} activation, which in effect increases RCT, can be considered a beneficial action. Indeed, studies have shown a 20% reduction of LDL levels in hypercholesterolemic humans (28) and prevention of atherosclerosis development in Apolipoprotein E–/– mice (29) upon inhibition of cholesterol absorption by ezetimibe. Our results suggest that reduction of cholesterol absorption upon treatment with GW610742 is, at least in part, mediated by reduced intestinal expression of Npc1l1, a proposed target of ezetimibe. Interestingly, ezetimibe was also shown to increase plasma HDL-cholesterol in mice and humans by an unidentified mechanism of action. Thus, PPAR{delta} is a promising target for the development of novel drugs aimed at preventing atherosclerosis.


   ACKNOWLEDGMENTS
 
The authors thank Renze Boverhof and Vincent W. Bloks for excellent technical assistance. Dr. Lisa Patel (GlaxoSmithKline Pharmaceuticals) is thanked for stimulating discussions and support. This work was supported by Grant 912-02-063 from the Netherlands Organization for Scientific Research.

Manuscript received October 12, 2004 and in revised form November 23, 2004.


   REFERENCES
TOP
 ABSTRACT
 INTRODUCTION
 EXPERIMENTAL PROCEDURES
 RESULTS
 DISCUSSION
 REFERENCES
 
  1. Castelli, W. P., R. J. Garrison, P. W. Wilson, R. D. Abbott, S. Kalousdian, and W. B. Kannel. 1986. Incidence of coronary heart disease and lipoprotein cholesterol levels. The Framingham Study. J. Am. Med. Assoc. 256: 2835–2838.[Abstract/Free Full Text]

  2. Brooks-Wilson, A., M. Marcil, S. M. Clee, L. H. Zhang, K. Roomp, M. van Dam, L. Yu, C. Brewer, J. A. Collins, H. O. Molhuizen, O. Loubser, B. F. Ouelette, K. Fichter, K. J. Ashbourne-Excoffon, C. W. Sensen, S. Scherer, S. Mott, M. Denis, D. Martindale, J. Frohlich, K. Morgan, B. Koop, S. Pimstone, J. J. Kastelein, and M. R. Hayden. 1999. Mutations in ABC1 in Tangier disease and familial high-density lipoprotein deficiency. Nat. Genet. 22: 336–345.[CrossRef][Medline]

  3. Tall, A. R., P. Costet, and N. Wang. 2002. Regulation and mechanisms of macrophage cholesterol efflux. J. Clin. Invest. 110: 899–904.[CrossRef][Medline]

  4. Schwartz, C. C., L. G. Halloran, Z. R. Vlahcevic, D. H. Gregory, and L. Swell. 1978. Preferential utilization of free cholesterol from high-density lipoproteins for biliary cholesterol secretion in man. Science. 200: 62–64.[Abstract/Free Full Text]

  5. Groen, A. K., V. W. Bloks, R. H. Bandsma, R. Ottenhoff, G. Chimini, and F. Kuipers. 2001. Hepatobiliary cholesterol transport is not impaired in Abca1-null mice lacking HDL. J. Clin. Invest. 108: 843–850.[CrossRef][Medline]

  6. Plösch, T., T. Kok, V. W. Bloks, M. J. Smit, R. Havinga, G. Chimini, A. K. Groen, and F. Kuipers. 2002. Increased hepatobiliary and fecal cholesterol excretion upon activation of the liver X receptor is independent of ABCA1. J. Biol. Chem. 277: 33870–33877.[Abstract/Free Full Text]

  7. Kosters, A., R. J. Frijters, F. G. Schaap, E. Vink, T. Plösch, R. Ottenhoff, M. Jirsa, I. M. De Cuyper, F. Kuipers, and A. K. Groen. 2003. Relation between hepatic expression of ATP-binding cassette transporters G5 and G8 and biliary cholesterol secretion in mice. J. Hepatol. 38: 710–716.[CrossRef][Medline]

  8. Yu, L., J. Li-Hawkins, R. E. Hammer, K. E. Berge, J. D. Horton, J. C. Cohen, and H. H. Hobbs. 2002. Overexpression of ABCG5 and ABCG8 promotes biliary cholesterol secretion and reduces fractional absorption of dietary cholesterol. J. Clin. Invest. 110: 671–680.[CrossRef][Medline]

  9. Duval, C., G. Chinetti, F. Trottein, J. C. Fruchart, and B. Staels. 2002. The role of PPARs in atherosclerosis. Trends Mol. Med. 8: 422–430.[CrossRef][Medline]

  10. Oliver, W. R., Jr., J. L. Shenk, M. R. Snaith, C. S. Russell, K. D. Plunket, N. L. Bodkin, M. C. Lewis, D. A. Winegar, M. L. Sznaidman, M. H. Lambert, H. E. Xu, D. D. Sternbach, S. A. Kliewer, B. C. Hansen, and T. M. Willson. 2001. A selective peroxisome proliferator-activated receptor delta agonist promotes reverse cholesterol transport. Proc. Natl. Acad. Sci. USA. 98: 5306–5311.[Abstract/Free Full Text]

  11. Kok, T., V. W. Bloks, H. Wolters, R. Havinga, P. L. Jansen, B. Staels, and F. Kuipers. 2003. Peroxisome proliferator-activated receptor alpha (PPARalpha)-mediated regulation of multidrug resistance 2 (Mdr2) expression and function in mice. Biochem. J. 369: 539–547.[CrossRef][Medline]

  12. Post, S. M., H. Duez, P. P. Gervois, B. Staels, F. Kuipers, and H. M. Princen. 2001. Fibrates suppress bile acid synthesis via peroxisome proliferator-activated receptor-alpha-mediated downregulation of cholesterol 7alpha-hydroxylase and sterol 27-hydroxylase expression. Arterioscler. Thromb. Vasc. Biol. 21: 1840–1845.[Abstract/Free Full Text]

  13. Altmann, S. W., H. R. Davis, Jr., L. J. Zhu, X. Yao, L. M. Hoos, G. Tetzloff, S. P. Iyer, M. Maguire, A. Golovko, M. Zeng, L. Wang, N. Murgolo, and M. P. Graziano. 2004. Niemann-Pick C1 Like 1 protein is critical for intestinal cholesterol absorption. Science. 303: 1201–1204.[Abstract/Free Full Text]

  14. Sznaidman, M. L., C. D. Haffner, P. R. Maloney, A. Fivush, E. Chao, D. Goreham, M. L. Sierra, C. LeGrumelec, H. E. Xu, V. G. Montana, M. H. Lambert, T. M. Willson, W. R. Oliver, and D. D. Sternbach. 2003. Novel selective small molecule agonists for peroxisome proliferator-activated receptor delta (PPARdelta)—synthesis and biological activity. Bioorg. Med. Chem. Lett. 13: 1517–1521.[CrossRef][Medline]

  15. Bligh, E. G., and W. J. Dyer. 1959. Rapid method of total lipid extraction and purification. Can. J. Biochem. Biophys. 37: 911–917.

  16. Herijgers, N., M. Van Eck, P. H. Groot, P. M. Hoogerbrugge, and T. J. Van Berkel. 2000. Low density lipoprotein receptor of macrophages facilitates atherosclerotic lesion formation in C57Bl/6 mice. Arterioscler. Thromb. Vasc. Biol. 20: 1961–1967.[Abstract/Free Full Text]

  17. Turley, S. D., M. W. Herndon, and J. M. Dietschy. 1994. Reevaluation and application of the dual-isotope plasma ratio method for the measurement of intestinal cholesterol absorption in the hamster. J. Lipid Res. 35: 328–339.[Abstract]

  18. McNeish, J., R. J. Aiello, D. Guyot, T. Turi, C. Gabel, C. Aldinger, K. L. Hoppe, M. L. Roach, L. J. Royer, J. de Wet, C. Broccardo, G. Chimini, and O. L. Francone. 2000. High density lipoprotein deficiency and foam cell accumulation in mice with targeted disruption of ATP-binding cassette transporter-1. Proc. Natl. Acad. Sci. USA. 97: 4245–4250.[Abstract/Free Full Text]

  19. Muoio, D. M., P. S. MacLean, D. B. Lang, S. Li, J. A. Houmard, J. M. Way, D. A. Winegar, J. C. Corton, G. L. Dohm, and W. E. Kraus. 2002. Fatty acid homeostasis and induction of lipid regulatory genes in skeletal muscles of peroxisome proliferator-activated receptor (PPAR) alpha knock-out mice. Evidence for compensatory regulation by PPAR delta. J. Biol. Chem. 277: 26089–26097.[Abstract/Free Full Text]

  20. Kruit, J. K., T. Plösch, R. Havinga, R. Boverhof, P. H. E. Groot, A. K. Groen, and F. Kuipers. 2004. Increased fecal neutral sterol loss upon liver X receptor activation is independent of biliary sterol secretion in mice. Gastroenterology. 128: 147–156.[CrossRef]

  21. Repa, J. J., J. M. Dietschy, and S. D. Turley. 2002. Inhibition of cholesterol absorption by SCH 58053 in the mouse is not mediated via changes in the expression of mRNA for ABCA1, ABCG5, or ABCG8 in the enterocyte. J. Lipid Res. 43: 1864–1874.[Abstract/Free Full Text]

  22. Haghpassand, M., P. A. Bourassa, O. L. Francone, and R. J. Aiello. 2001. Monocyte/macrophage expression of ABCA1 has minimal contribution to plasma HDL levels. J. Clin. Invest. 108: 1315–1320.[CrossRef][Medline]

  23. Basso, F., L. Freeman, C. L. Knapper, A. Remaley, J. Stonik, E. B. Neufeld, T. Tansey, M. J. Amar, J. Fruchart-Najib, N. Duverger, S. Santamarina-Fojo, and H. B. Brewer, Jr. 2003. Role of the hepatic ABCA1 transporter in modulating intrahepatic cholesterol and plasma HDL cholesterol concentrations. J. Lipid Res. 44: 296–302.[Abstract/Free Full Text]

  24. Dietschy, J. M., and S. D. Turley. 2002. Control of cholesterol turnover in the mouse. J. Biol. Chem. 277: 3801–3804.[Free Full Text]

  25. Schwarz, M., D. W. Russell, J. M. Dietschy, and S. D. Turley. 2001. Alternate pathways of bile acid synthesis in the cholesterol 7alpha-hydroxylase knockout mouse are not upregulated by either cholesterol or cholestyramine feeding. J. Lipid Res. 42: 1594–1603.[Abstract/Free Full Text]

  26. Voshol, P. J., R. Havinga, H. Wolters, R. Ottenhoff, H. M. Princen, R. P. Oude Elferink, A. K. Groen, and F. Kuipers. 1998. Reduced plasma cholesterol and increased fecal sterol loss in multidrug resistance gene 2 P-glycoprotein-deficient mice. Gastroenterology. 114: 1024–1034.[CrossRef][Medline]

  27. Davis, H. R., Jr., L. J. Zhu, L. M. Hoos, G. Tetzloff, M. Maguire, J. Liu, X. Yao, S. P. Iyer, M. H. Lam, E. G. Lund, P. A. Detmers, M. P. Graziano, and S. W. Altmann. 2004. Niemann-Pick C1 Like 1 (NPC1L1) is the intestinal phytosterol and cholesterol transporter and a key modulator of whole-body cholesterol homeostasis. J. Biol. Chem. 279: 33586–33592.[Abstract/Free Full Text]

  28. Bays, H. E., P. B. Moore, M. A. Drehobl, S. Rosenblatt, P. D. Toth, C. A. Dujovne, R. H. Knopp, L. J. Lipka, A. P. LeBeaut, B. Yang, L. E. Mellars, C. Cuffie-Jackson, and E. P. Veltri. 2001. Effectiveness and tolerability of ezetimibe in patients with primary hypercholesterolemia: pooled analysis of two phase II studies. Clin. Ther. 23: 1209–1230.[CrossRef][Medline]

  29. Davis, H. R., Jr., D. S. Compton, L. Hoos, and G. Tetzloff. 2001. Ezetimibe, a potent cholesterol absorption inhibitor, inhibits the development of atherosclerosis in ApoE knockout mice. Arterioscler. Thromb. Vasc. Biol. 21: 2032–2038.[Abstract/Free Full Text]


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