Skip to main content
  • American Heart Association
  • Science Volunteer
  • Warning Signs
  • Advanced Search
  • Donate

  • Home
  • About this Journal
    • Editorial Board
    • Meet the Editors
    • ATVB Journal History
    • General Statistics
  • All Issues
  • Subjects
    • All Subjects
    • Arrhythmia and Electrophysiology
    • Basic, Translational, and Clinical Research
    • Critical Care and Resuscitation
    • Epidemiology, Lifestyle, and Prevention
    • Genetics
    • Heart Failure and Cardiac Disease
    • Hypertension
    • Imaging and Diagnostic Testing
    • Intervention, Surgery, Transplantation
    • Quality and Outcomes
    • Stroke
    • Vascular Disease
  • Browse Features
    • Cover Art Award
    • ATVB Early Career Award
    • ATVB in Focus
    • Recent Brief Reviews of ATVB
    • Lecture Series
    • Collections
    • Recent Highlights of ATVB
    • Commentaries
    • Browse Abstracts
    • Insight into ATVB Authors
  • Resources
    • Instructions for Authors
    • Online Submission/Peer Review Site
    • Council on ATVB
    • Permissions and Rights Q&A
    • AHA Guidelines and Statements
    • Customer Service and Ordering Information
    • Author Reprints
    • International Users
    • AHA Newsroom
  • AHA Journals
    • AHA Journals Home
    • Arteriosclerosis, Thrombosis, and Vascular Biology (ATVB)
    • Circulation
    • → Circ: Arrhythmia and Electrophysiology
    • → Circ: Genomic and Precision Medicine
    • → Circ: Cardiovascular Imaging
    • → Circ: Cardiovascular Interventions
    • → Circ: Cardiovascular Quality & Outcomes
    • → Circ: Heart Failure
    • Circulation Research
    • Hypertension
    • Stroke
    • Journal of the American Heart Association
  • Facebook
  • LinkedIn
  • Twitter

  • My alerts
  • Sign In
  • Join

  • Advanced search

Header Publisher Menu

  • American Heart Association
  • Science Volunteer
  • Warning Signs
  • Advanced Search
  • Donate

Arteriosclerosis, Thrombosis, and Vascular Biology

  • My alerts
  • Sign In
  • Join

  • Facebook
  • LinkedIn
  • Twitter
  • Home
  • About this Journal
    • Editorial Board
    • Meet the Editors
    • ATVB Journal History
    • General Statistics
  • All Issues
  • Subjects
    • All Subjects
    • Arrhythmia and Electrophysiology
    • Basic, Translational, and Clinical Research
    • Critical Care and Resuscitation
    • Epidemiology, Lifestyle, and Prevention
    • Genetics
    • Heart Failure and Cardiac Disease
    • Hypertension
    • Imaging and Diagnostic Testing
    • Intervention, Surgery, Transplantation
    • Quality and Outcomes
    • Stroke
    • Vascular Disease
  • Browse Features
    • Cover Art Award
    • ATVB Early Career Award
    • ATVB in Focus
    • Recent Brief Reviews of ATVB
    • Lecture Series
    • Collections
    • Recent Highlights of ATVB
    • Commentaries
    • Browse Abstracts
    • Insight into ATVB Authors
  • Resources
    • Instructions for Authors
    • Online Submission/Peer Review Site
    • Council on ATVB
    • Permissions and Rights Q&A
    • AHA Guidelines and Statements
    • Customer Service and Ordering Information
    • Author Reprints
    • International Users
    • AHA Newsroom
  • AHA Journals
    • AHA Journals Home
    • Arteriosclerosis, Thrombosis, and Vascular Biology (ATVB)
    • Circulation
    • → Circ: Arrhythmia and Electrophysiology
    • → Circ: Genomic and Precision Medicine
    • → Circ: Cardiovascular Imaging
    • → Circ: Cardiovascular Interventions
    • → Circ: Cardiovascular Quality & Outcomes
    • → Circ: Heart Failure
    • Circulation Research
    • Hypertension
    • Stroke
    • Journal of the American Heart Association
ATVB in Focus: HDL Structure, Function, Therapeutics, and Imaging

Reverse Cholesterol Transport Revisited

Contribution of Biliary Versus Intestinal Cholesterol Excretion

Gemma Brufau, Albert K. Groen, Folkert Kuipers
Download PDF
https://doi.org/10.1161/ATVBAHA.108.181206
Arteriosclerosis, Thrombosis, and Vascular Biology. 2011;31:1726-1733
Originally published July 20, 2011
Gemma Brufau
  • Find this author on Google Scholar
  • Find this author on PubMed
  • Search for this author on this site
Albert K. Groen
  • Find this author on Google Scholar
  • Find this author on PubMed
  • Search for this author on this site
Folkert Kuipers
  • Find this author on Google Scholar
  • Find this author on PubMed
  • Search for this author on this site
  • Article
  • Figures & Tables
  • Info & Metrics
  • eLetters

Jump to

  • Article
    • Abstract
    • HDL
    • RCT: Involvement of HDL
    • The Intestine and RCT
    • In Vivo RCT Measurement
    • Conclusions and Perspectives
    • Sources of Funding
    • Disclosures
    • Acknowledgments
    • References
  • Figures & Tables
  • Info & Metrics
  • eLetters
Loading

Abstract

Reverse cholesterol transport (RCT) is usually defined as high-density lipoprotein-mediated transport of excess cholesterol from peripheral tissues, including cholesterol-laden macrophages in vessel walls, to the liver. From the liver, cholesterol can then be removed from the body via secretion into the bile for eventual disposal via the feces. According to this paradigm, high plasma high-density lipoprotein levels accelerate RCT and hence are atheroprotective. New insights in individual steps of the RCT pathway, in part derived from innovative mouse models, indicate that the classical concept of RCT may require modification.

  • ABC transporter
  • atherosclerosis
  • genetically altered mice
  • lipoproteins
  • macrophages

Lipid accumulation in macrophages, leading to formation of foam cells, is a critical initial event in atherosclerosis development. The major lipid species stored in foam cells is cholesterol, either in its free form or esterified to a fatty acid. An imbalance of cholesterol uptake, synthesis, and export by macrophages underlies the development of foam cells.1 Currently, the main strategies to interfere with cholesterol accumulation in macrophages are still focused on reduction of the amount of “substrate,” ie, the concentration of atherogenic lipoproteins in plasma. Inhibition of cholesterol synthesis by statins, leading to lowering of low-density lipoprotein (LDL) cholesterol in plasma, is a successful approach to limit cholesterol uptake by the macrophages and progression of plaque formation. However, intensive statin treatment reduces the incidence of cardiovascular events only by ≈25%.2 It is generally assumed that in most of the remaining 75% of cases, atherosclerosis is already too far advanced to allow successful prevention of cardiovascular incidents. Consequently, the pathways involved in export of excess cholesterol from foam cells and its removal from the body are currently under intense investigation to provide novel targets for antiatherosclerotic therapies. The net result of these pathways is usually referred to as reverse cholesterol transport (RCT), a term coined by Glomset more than 4 decades ago.3

This article accompanies the ATVB in Focus: HDL Structure, Function, Therapeutics, and Imaging series that was published in the February 2010 issue.

In the literature, RCT is usually defined as the process by which excess cholesterol from cells in peripheral tissues and organs, including macrophages in vessel walls, is transported to the liver for removal from the body through excretion as neutral sterols or bile acids via the bile into the feces.3 High-density lipoprotein (HDL) is generally believed to protect against atherosclerosis by acting as the specific cholesterol carrier in the RCT pathway by delivering its cholesterol cargo to the liver. The term centripetal cholesterol flux has been introduced to describe bulk cholesterol transfer from periphery to the liver,4–6 with the inherent assumption that the magnitude of this flux by some means determines hepatobiliary removal of cholesterol. From a functional point of view, it would be instrumental to define relevant RCT as the flux of excess cholesterol from the peripheral tissues (including macrophages) into feces independent of its route. Methods have been developed to quantify the macrophage to feces flux of cholesterol, but these have been applied only in rodents.7,8

Recently, several studies have provided evidence for alternative routes for removal of (excess) cholesterol that does not involve HDL or the hepatobiliary route.9–16 Here, we review the most relevant new findings that may constitute a basis for a new definition of RCT.

HDL

HDL is generally considered to represent the primary mediator of RCT. However, HDL by no means refers to a homogenous class of lipoproteins. Up to 10 subpopulations of HDL can be classified depending on 5 physicochemical properties: (1) shape (discoidal or spherical), (2) density (HDL2 being the less dense and HDL3 the most dense), (3) size (the diameter may range from 7.6 to 10.6 nm), (4) protein composition (HDL containing both apolipoprotein [apo] A-I and apoA-II or only apoA-I), and (5) surface charge.17 Probably, the number of HDL subspecies present in vivo is even larger because proteomic analyses have indicated that human HDL can contain up to ≈100 different proteins.18–21 For many of these proteins the number of molecules present in plasma is smaller than the number of HDL particles, implying that not all particles have the same protein cargo. In addition, the space for proteins on an HDL particle is limited because of its relatively small size.

In apoA-I-synthesizing organs, such as the liver and the intestine,22 discoidal HDL (also known as pre-β HDL) is produced23 and subsequently lipidated with free cholesterol and phospholipids from peripheral cells (including macrophages) to form larger, more mature HDL2 particles. ApoA-I is also associated with small and large chylomicrons produced in the intestine,24 from which it can be transferred to HDL.25,26

ApoA-I is able to activate lecithin:cholesterol acyltransferase (LCAT), which in turn esterifies free cholesterol molecules present at discoidal HDL. This process will result in the transition from discoidal HDL to mature spherical HDL2 (for review, see Dobiasova and Frohlich27). Several attempts have been made to elucidate the role of LCAT in RCT, because this enzyme plays a crucial role in determining plasma HDL levels (for review, see Calabresi and Franceschini28). Glomset was the first to point to LCAT activity as first and potentially rate-limiting step in RCT. According to this author, LCAT activity maintains a gradient of free cholesterol between cell membranes and extracellular acceptors, such as HDL.3 However, recent data indicate that LCAT is not required for the flux of cholesterol from the macrophages to the liver.29–31

Nascent HDL particles interact with the ATP-binding cassette transporter A1 (ABCA1), a membrane-associated protein that is ubiquitously expressed in peripheral tissues and macrophages, as well as in liver and intestine.23 The importance of ABCA1 in HDL formation is evident from the phenotype of patients with Tangier disease, an autosomal recessive disorder characterized by 2 nonfunctional ABCA1 alleles and extremely low levels of HDL.32–34 In vitro experiments on cultured cells have provided evidence that in addition to ABCA1, ABCG1 may be involved in the HDL lipidation process.8 The cellular cholesterol and phospholipid transfer mediated by this transporter is donated to more mature HDL rather than to pre-β HDL.35 It should be noted that in vivo evidence for a dominant role of this transporter is lacking: Abcg1 knockout mice show no evident (plasma) lipid phenotype when kept on chow diet.36 However, Abca1/Abcg1 double knockout mice do show a very severe phenotype with massive lipid accumulation in several tissues including lung and liver.37 Apparently, in the absence of Abcg1, Abca1 compensates for the lack of efflux capacity in most organs. A very recent article demonstrates that these transporters have functions beyond control of lipid efflux from cells38: their concerted action appears to be pivotal for control of hematopoietic stem cell proliferation.

Cholesterol delivery to the liver, as well as to other (cholesterol-requiring) organs, can be mediated through various pathways. In this respect, it is important to distinguish between the flux of free cholesterol and that of cholesterol ester. In all classes of lipoproteins, cholesterol is predominantly carried in its esterified form. This is probably the reason why most published studies primarily address transport of cholesterol ester into target organs. However, some important early studies have shown that the flux of free cholesterol is at least 1 order of magnitude larger than the flux of esterified cholesterol and that the mechanism by which transport proteins mediate these fluxes may be quite different.30,39 In rodents, in which HDL is the prominent lipoprotein class, the main route for both free cholesterol and cholesterol ester uptake by the liver is assumed to involve selective uptake on direct interaction between HDL and the scavenger receptor BI (SR-BI/SCARB1).40 However, holoparticle uptake has also been described: an interesting novel route is mediated by a complex of different proteins, including F1F0-ATPase and the nucleotide receptor purinergic receptor P2Y, G-protein coupled 13.41–43 The relative contribution of the different pathways to total cholesterol uptake has never been determined.42 The routing of HDL cholesterol uptake is even more complex in animal species that express cholesterol ester transfer protein. Cholesteryl ester transfer protein mediates transfer of cholesteryl esters from HDL to LDL and very-low-density lipoprotein. Hepatic uptake of HDL-derived cholesterol is in this case also mediated by the LDL receptor. In 2004, Schwartz et al30 reported on the basis of isotope exchange studies that basically all hepatic cholesterol ester uptake follows the LDL receptor route in humans. Unfortunately, this result has never been confirmed, and it should be stressed that this assumption only holds for cholesterol ester uptake, which, also according to Schwartz et al,30 is one-tenth that of free cholesterol transport. Recently, direct evidence for a role of SR-BI in human HDL metabolism has been obtained in a study with subjects carrying the Pro297Ser mutation in SR-BI.44 These subjects, heterozygous for the mutation in SR-BI, showed a 50% increase in plasma HDL. Experiments in mice in which SR-BI with this mutation was expressed on a SR-BI-null background showed dysfunctional uptake of HDL.45 Hence, even a heterozygous mutation in SR-BI apparently causes a clear phenotype in humans, suggesting that this protein is much more important than has been assumed thus far.

RCT: Involvement of HDL

Although the role of HDL in RCT is generally considered to explain the antiatherogenic properties of this lipoprotein, there is in fact very little evidence that this lipoprotein actually regulates the rate of RCT in vivo. Most of the initial supportive evidence for the existence of the classical RCT pathway was derived from in vitro studies initiated by a landmark study by Fielding and Fielding demonstrating uptake of HDL cholesterol by cells.46 However, there is increasing evidence that the antiatherogenic properties of HDL do not depend on the total amount of this lipoprotein in blood but rather on the presence of specific HDL subpopulations.47

Recent studies have confirmed the contributions of macrophage ABCA1 and ABCG1 to the RCT pathway in mice, using an ex vivo macrophage labeling procedure.48–50 Adorni et al attempted to quantify the contribution of the different transporters to total cellular cholesterol efflux.51 Using knockdown approaches or specific inhibitors, the activity of ABCA1, ABCG1, and SR-BI was selectively abrogated in cultured macrophages. About 30% of total cholesterol efflux could not be accounted for by either of the transporters and was considered to be due to aqueous diffusion of cholesterol. The underlying molecular mechanism of ABCA1- and ABCG1-mediated lipid efflux is a matter of controversy that has been the subject of a number of recent reviews8,52 and will therefore not be covered here. A series of intriguing results was recently published by Cuchel et al.53 These authors infused apo-AI phospholipid complexes (also denoted as reconstituted HDL [rHDL]) into wild-type, Abca1-, Abcg1- and Sr-bI-deficient mice. Large amounts of free cholesterol were mobilized by rHDL in all genotypes except the Sr-bI−/− mice, suggesting that this protein plays an important role in a specific type of cholesterol efflux into plasma; it is tempting to speculate that this cholesterol may originate from the liver.

In addition to apoA-I and HDL, many other apolipoproteins are also able to mediate cholesterol efflux in vitro.54 Thus, apoE-containing very-low-density lipoprotein and LDL are also able to pick up cholesterol from cells and could hence theoretically contribute to RCT. The question whether the plasma HDL concentration correlates with the rate of RCT, defined as the flux of peripheral cholesterol into feces, independently of its route, has been addressed in a number of recent studies. Importantly, in several animal models of (partial) HDL deficiency, no (positive) correlation could be found.4–6,29,55–57 Modulation of apoA-I, LCAT, and SR-BI activity in mice resulted in marked changes in HDL cholesterol levels without any effect on biliary cholesterol secretion or fecal sterol excretion.57 In line with this, the complete absence of HDL in Abca1−/− mice also did not affect biliary or fecal cholesterol excretion.55,56 Infusion of reconstituted rHDL into HDL-deficient apoA-I−/− mice did not increase fecal sterol excretion.57 LCAT heterozygous mice display a severe plasma HDL reduction whereas macrophage to feces RCT is fully preserved,29 Elegant studies by Dietschy's group have demonstrated that the concentration of circulating HDL plays no role in the mass transport of cholesterol from the peripheral organs to the liver in mouse models.4–6

Data on the relationships between HDL levels and fecal sterol excretion in humans are scarce and ambiguous. Miettinen et al showed, surprisingly, a negative correlation between plasma HDL cholesterol levels and fecal neutral sterol excretion in a large study comprising 63 male normolipidemic subjects.58 Furthermore, doubling HDL cholesterol levels through cholesteryl ester transfer protein inhibition by torcetrapib had no effect on fecal sterol excretion in 16 individuals.59 Similarly, 2 very small studies, one with only 2 patients with low HDL cholesterol due to LCAT deficiency and one with 2 patients with familial combined hyperlipidemia, failed to show a difference in neutral sterol excretion compared with controls.60,61 In contrast, in 12 patients with familial hypoalphalipoproteinemia, plasma HDL cholesterol levels did correlate with fecal sterol excretion,62 and 2 intervention studies showed a clear increase in fecal sterol excretion after infusion of pro-apoA-I or rHDL in 4 and 16 individuals, respectively63,64 Altogether, a relationship between plasma HDL cholesterol concentrations and fecal sterol excretion in humans and animal models is by no means evident. However, in these studies, only the plasma concentrations of HDL cholesterol were determined, whereas the functionality of the HDL particles present may be more relevant with respect to RCT.

Changes in HDL protein and lipid composition have been associated with loss of HDL functionality.65 For instance, HDL isolated from transgenic mice overexpressing apoA-II or phospholipid transfer protein (which transfers phospholipids between HDL and very-low-density lipoprotein) show reduced functionality in cholesterol efflux assays.66,67 Treatment of HDL with 15-lipoxygenase (an enzyme involved in formation of lipid peroxides) also reduced HDL cholesterol acceptor activity.68,69 In addition, changes in HDL due to infection, inflammation, or diabetes may also result in loss of its functionality, or, adversely, it has been reported that HDL may even become proinflammatory.70–73 For example, impaired cholesterol efflux toward HDL isolated from patients with acute sepsis or from mice injected with lipopolysaccharide has been reported.70

The Intestine and RCT

A general problem with the interpretation of available data, for instance those generated by Dietschy's group4–6,74 is caused by the hepatobiliary paradigm, which states that all centripetal cholesterol flux originating from the periphery by definition enters the liver. We and others have recently falsified this paradigm in a series of studies (Table). These studies demonstrate the presence of a nonbiliary route for fecal sterols and imply the presence of a pathway for plasma cholesterol via enterocytes into the intestinal lumen. In principle, cholesterol present in the intestinal lumen can originate from enterocytes either as a component of shed cells or on secretion of locally synthesized cholesterol. Alternatively, plasma-derived cholesterol can be transported directly through the intestinal wall by a pathway called transintestinal cholesterol excretion (TICE), which has not yet been fully defined in molecular terms (for review, see75) (Figure). It has been estimated that the contribution of cell shedding adds, at most, ≈20% of fecal neutral sterols in mice.9,10,76 Furthermore, the contribution of intestine-derived de novo synthesized cholesterol to fecal neutral sterols is small in mice.10 Therefore, it is likely that most of the cholesterol excreted as neutral sterols originates from nonabsorbed dietary cholesterol, biliary cholesterol, or TICE. Recent work, outlined below, has demonstrated that TICE is a quantitatively important process.

View this table:
  • View inline
  • View popup
Table.

Studies in Which Biliary Cholesterol Does Not Account for Fecal Cholesterol Excretion

Figure.
  • Download figure
  • Open in new tab
  • Download powerpoint
Figure.

Schematic cartoon representing the main pathways of cholesterol excretion. TICE indicates transintestinal cholesterol excretion.

Although most of the studies have been carried out in mouse models, there is evidence for the existence of TICE in humans as well. As early as the late 1960s, Simmonds et al77 unintentionally quantified part of TICE in humans by perfusing the upper jejunum with a solution of bile salts, triglycerides, and radiolabeled cholesterol. This study estimated that ≈44% of total fecal sterol output must originate from endogenous (ie, nonhepatobiliary) sources. In addition, patients with biliary obstruction still excrete substantial amounts of neutral sterol into feces.78,79 It seems almost obvious that during evolution, efficient bypass pathways for cholesterol to leave the body have developed, in particular when considering the substantial (net) centripetal cholesterol flux. This flux has been estimated to amount to up to ≈15 mg/kg per day in humans, which is almost equal to the published values for fecal sterol output.80 In rodents, the relative magnitude of these fluxes is ≈5-fold higher than in humans, and the existence of alternative pathways for whole body cholesterol export has now been firmly established.80 As early as the 1920s, Sperry reported that bile diversion in mice does not decrease fecal neutral excretion, suggesting an additional pathway of cholesterol excretion.81 Kruit et al reported that in Mdr2−/− mice that completely lack biliary cholesterol secretion, fecal sterol output did not differ from that of wild-type controls.11 Moreover, on challenging these mice with the LXR agonist T091317, a 2-fold increase in fecal cholesterol excretion was obtained without any induction in biliary cholesterol secretion.11 In line with these results, a 3-fold induction in fecal neutral sterol excretion was found in wild-type mice treated with a LXR agonist, whereas biliary cholesterol was increased less than 2-fold.10 According to these authors, the flux of cholesterol excreted via TICE accounted for ≈33% of the fecal sterol excretion in untreated C57Bl/6J mice, whereas biliary cholesterol accounted for ≈25%. Treatment with a LXR agonist increased the contribution of TICE to up to ≈63%, whereas biliary cholesterol contributed ≈15% under these conditions, Peroxisome proliferator–activated receptor-δ agonists have also been identified as modulators of TICE.82 Vrins et al. reported that TICE almost doubled in mice receiving a diet enriched with the PPARδ agonist GW610742.82 Brown et al14 reported that in liver-specific ACAT2-deficient mice, the fecal neutral sterol excretion was increased whereas the biliary cholesterol secretion remained unchanged. In elegant experiments, these authors demonstrated the presence of TICE in the ACAT2 knockdown model and localized the process to the proximal part of the small intestine. Although the methodology used by Brown et al14 directly localized the activity of TICE to the proximal part of the small intestine, this method does not allow for quantitation of TICE. To accomplish this, van der Velde et al9 developed an intestinal perfusion method applicable to mice. More recently, van der Veen et al developed an in vivo method to estimate TICE.10 Using 3 different stable isotopes, these authors were able to quantify all major cholesterol fluxes toward feces in mice. Grosso modo, the results obtained with this methodology were similar to those of van der Velde et al.9 However, there was also an important difference. Using their intestinal perfusion methodology, van der Velde et al were unable to demonstrate a role for the dimeric cholesterol transporter Abcg5/Abcg8 in mice. Abcg8−/− mice showed, in fact, an unaltered rate of TICE compared with wild-type controls. In contrast, van der Veen et al found a reduction of TICE in mice deficient for this transporter using their in vivo approach.10 At present it is not clear whether and why the Abcg5/Abcg8 heterodimer loses its activity in the intestinal perfusion setup. Collectively, at least for mice, there is now overwhelming evidence for the existence of alternative pathways, in addition to the hepatobiliary route, to remove cholesterol from the body. However, limited data are available on the source of cholesterol excreted via TICE and the lipoprotein(s) involved in delivering cholesterol to this pathway.

Apart from Abcg5/Abcg8, no other enzymes/transporters have so far been identified that participate in the process. To identify potential candidates involved in TICE, expression of genes encoding proteins involved in cholesterol trafficking has been studied in the intestines of mice that exhibit an increased TICE flux. Based on gene expression analyses, no involvement of Npc1l1, Mttp, Lrp, Ldlr, Vldlr, Abca1, or Abcg1 in this pathway could be established.9,12,82

In Vivo RCT Measurement

Several methodologies have been developed to “measure” RCT in vivo. Considering the fact that the actual amount of cholesterol derived from macrophages can theoretically constitute only a minor percentage of fecal sterol excretion, the need for a macrophage-specific RCT measurement is evident. Probably the most extensively used method is the one developed by Rader and colleagues.7,83 In this method, macrophage cell lines or primary macrophages isolated from donor mice are labeled with [3H]cholesterol by ex vivo loading with radiolabeled acetyl LDL. Subsequently, these macrophages are injected into the peritoneal cavity of acceptor mice, and the appearance of cholesterol radioactivity is followed over time in plasma, liver, bile, and feces.7 This method has been successfully applied in a number of studies, including those aimed at estimating the contribution of Abca1, Abcg1, and Sr-b1 to macrophage RCT.53,84

Although this assay clearly demonstrates a flow of labeled cholesterol from injected macrophages to the plasma compartment and ultimately into feces, one wonders to what extent this flux mirrors the actual efflux of cholesterol from macrophages/foam cells localized in atherosclerotic plaques. This certainly holds true for the original protocol in which the J774 “macrophage” cell line was used.49 Clearly, the functionality of these cells differs from that of primary macrophages. Fortunately, this complication is increasingly being recognized, leading to more and more use of primary murine macrophages. Interestingly, to the best of our knowledge, the outcome of this assay has never been compared with that of an experiment in which cholesterol was injected directly into the peritoneal cavity, for instance encapsulated in triglyceride-rich particles. A limitation of the assay is the fact that macrophage RCT is calculated on the basis of the radioactivity (ie, counts) measured in plasma, bile, and feces, without correction for the specific activity of cholesterol in these compartments. When mouse models are compared with identical amounts of cholesterol in the different compartments, this obviously does not interfere with interpretation of the results. However, when plasma levels of cholesterol, for instance, are widely different, comparison is by nature at best qualitative. Therefore, results obtained with this method can easily under- or overestimate the actual rate of RCT. Taking these limitations into account, the ability to follow the fate of macrophage-derived cholesterol has evidently produced very interesting results. A case in point is the recent study of Temel et al.85 This work investigated whether macrophage-derived cholesterol could be excreted via TICE. Mice with acute biliary diversion were injected intraperitoneally with cholesterol-loaded macrophages, and the released radiolabeled cholesterol appeared in the intestinal lumen at unaltered rates compared with sham-operated control mice. Clearly, this result does not prove that mice dispose of their macrophage-derived cholesterol predominantly via TICE. It does demonstrate, however, the redundancy of the hepatobiliary pathway for cholesterol excretion in mice.

Several other attempts have been made to measure RCT in vivo. As mentioned, Dietschy's group developed a method to quantify the rate of centripetal cholesterol flux by adding up the rates of cholesterol synthesis and LDL cholesterol uptake in the extrahepatic tissues.4–6,74 However, a limitation of this method is that it inherently implies that the entire centripetal cholesterol flux originating from the periphery by definition enters the liver. Stein et al developed a method to measure quantitatively the removal of a localized and defined radiolabeled cholesterol deposit in rodents.86 These authors injected cationized LDL, labeled with trace amounts of [3H]free cholesterol into the rectus femoris muscle of mice and rats. According to these authors, this model system may simulate conditions occurring in the arterial wall during atherosclerosis because this modified lipoprotein adheres to the extracellular matrix, inducing the influx of mononuclear cells. However, whether this is actually the case has not yet been proven. Hellerstein and colleagues developed, from the early 1990s onwards, several kinetic models to quantify fluxes of biologically active molecules in vivo to predict their flow through complex pathways. These authors have been successful in measuring cholesterol synthesis and turnover and lipogenesis, among others (for review see87,88). A model able to predict the flux of cholesterol from the peripheral tissues to the feces has as yet been published only in abstract form.89,90

Conclusions and Perspectives

Glomset3 proposed the RCT concept more than 4 decades ago. Because it provided a very plausible explanation for a route via which cholesterol might leave the body, this concept became a generally accepted paradigm. Until recently, the validity of the paradigm had never been rigorously tested. However, we now know that transport via HDL and removal through the hepatobiliary secretion is certainly not the only pathway for excretion of “excess” cholesterol. Mice and humans without measurable HDL still excrete neutral sterols, and abrogation of biliary cholesterol secretion, at least in mice, does not influence the rate of fecal sterol excretion. We conclude that in addition to the HDL-mediated hepatobiliary pathway, there are alternative routes for cholesterol excretion. The distribution of the total flux across the different pathways has as yet been determined only in mouse models and may in fact vary under different conditions in mice and humans. However, we have shown that the direct TICE pathway is an important route for excretion of cholesterol, at least in mice. This pathway is amenable to upregulation by both dietary and pharmacological means, making it a very attractive target for development of novel therapeutical modalities to enhance body cholesterol turnover and thereby reduce cardiovascular risk.

Sources of Funding

This work was supported by grants from Top Institute Pharma (Grant T2-110) and the Netherlands Heart Foundation (Grant 2008B100).

Disclosures

None.

Acknowledgments

The authors apologize to the many investigators whose original contributions have not been cited because of space limitations.

  • © 2011 American Heart Association, Inc.

References

  1. 1.↵
    1. Libby P,
    2. Ridker PM,
    3. Hansson GK
    . Inflammation in atherosclerosis: from pathophysiology to practice. J Am Coll Cardiol. 2009;54:2129–2138.
    OpenUrlCrossRefPubMed
  2. 2.↵
    1. Paciaroni M,
    2. Bogousslavsky J
    . Statins and stroke prevention. Expert Rev Cardiovasc Ther. 2009;7:1231–1243.
    OpenUrlCrossRefPubMed
  3. 3.↵
    1. Glomset JA
    . The plasma lecithins:cholesterol acyltransferase reaction. J Lipid Res. 1968;9:155–167.
    OpenUrlAbstract
  4. 4.↵
    1. Xie C,
    2. Turley SD,
    3. Dietschy JM
    . ABCA1 plays no role in the centripetal movement of cholesterol from peripheral tissues to the liver and intestine in the mouse. J Lipid Res. 2009;50:1316–1329.
    OpenUrlAbstract/FREE Full Text
  5. 5.↵
    1. Osono Y,
    2. Woollett LA,
    3. Marotti KR,
    4. Melchior GW,
    5. Dietschy JM
    . Centripetal cholesterol flux from extrahepatic organs to the liver is independent of the concentration of high density lipoprotein-cholesterol in plasma. Proc Natl Acad Sci U S A. 1996;93:4114–4119.
    OpenUrlAbstract/FREE Full Text
  6. 6.↵
    1. Jolley CD,
    2. Woollett LA,
    3. Turley SD,
    4. Dietschy JM
    . Centripetal cholesterol flux to the liver is dictated by events in the peripheral organs and not by the plasma high density lipoprotein or apolipoprotein A-I concentration. J Lipid Res. 1998;39:2143–2149.
    OpenUrlAbstract/FREE Full Text
  7. 7.↵
    1. Cuchel M,
    2. Rader DJ
    . Macrophage reverse cholesterol transport: key to the regression of atherosclerosis? Circulation. 2006;113:2548–2555.
    OpenUrlFREE Full Text
  8. 8.↵
    1. Tall AR,
    2. Yvan-Charvet L,
    3. Terasaka N,
    4. Pagler T,
    5. Wang N
    . HDL, ABC transporters, and cholesterol efflux: implications for the treatment of atherosclerosis. Cell Metab. 2008;7:365–375.
    OpenUrlCrossRefPubMed
  9. 9.↵
    1. van der Velde AE,
    2. Vrins CL,
    3. van den Oever K,
    4. Kunne C,
    5. Oude Elferink RP,
    6. Kuipers F,
    7. Groen AK
    . Direct intestinal cholesterol secretion contributes significantly to total fecal neutral sterol excretion in mice. Gastroenterology. 2007;133:967–975.
    OpenUrlCrossRefPubMed
  10. 10.↵
    1. van der Veen JN,
    2. van Dijk TH,
    3. Vrins CL,
    4. van Meer H,
    5. Havinga R,
    6. Bijsterveld K,
    7. Tietge UJ,
    8. Groen AK,
    9. Kuipers F
    . Activation of the liver X receptor stimulates trans-intestinal excretion of plasma cholesterol. J Biol Chem. 2009;284:19211–19219.
    OpenUrlAbstract/FREE Full Text
  11. 11.↵
    1. Kruit JK,
    2. Plosch T,
    3. Havinga R,
    4. Boverhof R,
    5. Groot PH,
    6. Groen AK,
    7. Kuipers F
    . Increased fecal neutral sterol loss upon liver X receptor activation is independent of biliary sterol secretion in mice. Gastroenterology. 2005;128:147–156.
    OpenUrlCrossRefPubMed
  12. 12.↵
    1. van der Velde AE,
    2. Vrins CL,
    3. van den Oever K,
    4. Seemann I,
    5. Oude Elferink RP,
    6. van Eck M,
    7. Kuipers F,
    8. Groen AK
    . Regulation of direct transintestinal cholesterol excretion in mice. Am J Physiol Gastrointest Liver Physiol. 2008;295:G203–G208.
    OpenUrlAbstract/FREE Full Text
  13. 13.↵
    1. Schwarz M,
    2. Russell DW,
    3. Dietschy JM,
    4. Turley SD
    . Marked reduction in bile acid synthesis in cholesterol 7α-hydroxylase-deficient mice does not lead to diminished tissue cholesterol turnover or to hypercholesterolemia. J Lipid Res. 1998;39:1833–1843.
    OpenUrlAbstract/FREE Full Text
  14. 14.↵
    1. Brown JM,
    2. Bell TA III.,
    3. Alger HM,
    4. Sawyer JK,
    5. Smith TL,
    6. Kelley K,
    7. Shah R,
    8. Wilson MD,
    9. Davis MA,
    10. Lee RG,
    11. Graham MJ,
    12. Crooke RM,
    13. Rudel LL
    . Targeted depletion of hepatic ACAT2-driven cholesterol esterification reveals a non-biliary route for fecal neutral sterol loss. J Biol Chem. 2008;283:10522–10534.
    OpenUrlAbstract/FREE Full Text
  15. 15.↵
    1. Bell TA III.,
    2. Kelley K,
    3. Wilson MD,
    4. Sawyer JK,
    5. Rudel LL
    . Dietary fat-induced alterations in atherosclerosis are abolished by ACAT2-deficiency in ApoB100 only, LDLr−/− mice. Arterioscler Thromb Vasc Biol. 2007;27:1396–1402.
    OpenUrlAbstract/FREE Full Text
  16. 16.↵
    1. Temel RE,
    2. Tang W,
    3. Ma Y,
    4. Rudel LL,
    5. Willingham MC,
    6. Ioannou YA,
    7. Davies JP,
    8. Nilsson LM,
    9. Yu L
    . Hepatic Niemann-Pick C1-like 1 regulates biliary cholesterol concentration and is a target of ezetimibe. J Clin Invest. 2007;117:1968–1978.
    OpenUrlCrossRefPubMed
  17. 17.↵
    1. Rye KA,
    2. Bursill CA,
    3. Lambert G,
    4. Tabet F,
    5. Barter PJ
    . The metabolism and anti-atherogenic properties of HDL. J Lipid Res. 2009;50:S195–S200.
    OpenUrlAbstract/FREE Full Text
  18. 18.↵
    1. Karlsson H,
    2. Leanderson P,
    3. Tagesson C,
    4. Lindahl M
    . Lipoproteomics II: mapping of proteins in high-density lipoprotein using two-dimensional gel electrophoresis and mass spectrometry. Proteomics. 2005;5:1431–1445.
    OpenUrlCrossRefPubMed
  19. 19.↵
    1. Heller M,
    2. Stalder D,
    3. Schlappritzi E,
    4. Hayn G,
    5. Matter U,
    6. Haeberli A
    . Mass spectrometry-based analytical tools for the molecular protein characterization of human plasma lipoproteins. Proteomics. 2005;5:2619–2630.
    OpenUrlCrossRefPubMed
  20. 20.↵
    1. Rezaee F,
    2. Casetta B,
    3. Levels JH,
    4. Speijer D,
    5. Meijers JC
    . Proteomic analysis of high-density lipoprotein. Proteomics. 2006;6:721–730.
    OpenUrlCrossRefPubMed
  21. 21.↵
    1. Vaisar T,
    2. Pennathur S,
    3. Green PS,
    4. Gharib SA,
    5. Hoofnagle AN,
    6. Cheung MC,
    7. Byun J,
    8. Vuletic S,
    9. Kassim S,
    10. Singh P,
    11. Chea H,
    12. Knopp RH,
    13. Brunzell J,
    14. Geary R,
    15. Chait A,
    16. Zhao XQ,
    17. Elkon K,
    18. Marcovina S,
    19. Ridker P,
    20. Oram JF,
    21. Heinecke JW
    . Shotgun proteomics implicates protease inhibition and complement activation in the antiinflammatory properties of HDL. J Clin Invest. 2007;117:746–756.
    OpenUrlCrossRefPubMed
  22. 22.↵
    1. Wu AL,
    2. Windmueller HG
    . Relative contributions by liver and intestine to individual plasma apolipoproteins in the rat. J Biol Chem. 1979;254:7316–7322.
    OpenUrlFREE Full Text
  23. 23.↵
    1. Brunham LR,
    2. Kruit JK,
    3. Iqbal J,
    4. Fievet C,
    5. Timmins JM,
    6. Pape TD,
    7. Coburn BA,
    8. Bissada N,
    9. Staels B,
    10. Groen AK,
    11. Hussain MM,
    12. Parks JS,
    13. Kuipers F,
    14. Hayden MR
    . Intestinal ABCA1 directly contributes to HDL biogenesis in vivo. J Clin Invest. 2006;116:1052–1062.
    OpenUrlCrossRefPubMed
  24. 24.↵
    1. Wu AL,
    2. Windmueller HG
    . Identification of circulating apolipoproteins synthesized by rat small intestine in vivo. J Biol Chem. 1978;253:2525–2528.
    OpenUrlAbstract/FREE Full Text
  25. 25.↵
    1. Jeffery F,
    2. Redgrave TG
    . Chylomicron catabolism differs between Hooded and albino laboratory rats. J Lipid Res. 1982;23:154–160.
    OpenUrlAbstract
  26. 26.↵
    1. Redgrave TG,
    2. Small DM
    . Quantitation of the transfer of surface phospholipid of chylomicrons to the high density lipoprotein fraction during the catabolism of chylomicrons in the rat. J Clin Invest. 1979;64:162–171.
    OpenUrlCrossRefPubMed
  27. 27.↵
    1. Dobiasova M,
    2. Frohlich JJ
    . Advances in understanding of the role of lecithin cholesterol acyltransferase (LCAT) in cholesterol transport. Clin Chim Acta. 1999;286:257–271.
    OpenUrlCrossRefPubMed
  28. 28.↵
    1. Calabresi L,
    2. Franceschini G
    . Lecithin:cholesterol acyltransferase, high-density lipoproteins, and atheroprotection in humans. Trends Cardiovasc Med. 2010;20:50–53.
    OpenUrlCrossRefPubMed
  29. 29.↵
    1. Tanigawa H,
    2. Billheimer JT,
    3. Tohyama J,
    4. Fuki IV,
    5. Ng DS,
    6. Rothblat GH,
    7. Rader DJ
    . Lecithin:cholesterol acyltransferase expression has minimal effects on macrophage reverse cholesterol transport in vivo. Circulation. 2009;120:160–169.
    OpenUrlAbstract/FREE Full Text
  30. 30.↵
    1. Schwartz CC,
    2. Van den Broek JM,
    3. Cooper PS
    . Lipoprotein cholesteryl ester production, transfer, and output in vivo in humans. J Lipid Res. 2004;45:1594–1607.
    OpenUrlAbstract/FREE Full Text
  31. 31.↵
    1. Schwartz CC,
    2. Vlahcevic ZR,
    3. Berman M,
    4. Meadows JG,
    5. Nisman RM,
    6. Swell L
    . Central role of high density lipoprotein in plasma free cholesterol metabolism. J Clin Invest. 1982;70:105–116.
    OpenUrlCrossRefPubMed
  32. 32.↵
    1. Bodzioch M,
    2. Orso E,
    3. Klucken J,
    4. Langmann T,
    5. Bottcher A,
    6. Diederich W,
    7. Drobnik W,
    8. Barlage S,
    9. Buchler C,
    10. Porsch-Ozcurumez M,
    11. Kaminski WE,
    12. Hahmann HW,
    13. Oette K,
    14. Rothe G,
    15. Aslanidis C,
    16. Lackner KJ,
    17. Schmitz G
    . The gene encoding ATP-binding cassette transporter 1 is mutated in Tangier disease. Nat Genet. 1999;22:347–351.
    OpenUrlCrossRefPubMed
  33. 33.↵
    1. Rust S,
    2. Rosier M,
    3. Funke H,
    4. Real J,
    5. Amoura Z,
    6. Piette JC,
    7. Deleuze JF,
    8. Brewer HB,
    9. Duverger N,
    10. Denefle P,
    11. Assmann G
    . Tangier disease is caused by mutations in the gene encoding ATP-binding cassette transporter 1. Nat Genet. 1999;22:352–355.
    OpenUrlCrossRefPubMed
  34. 34.↵
    1. Marcil M,
    2. Brooks-Wilson A,
    3. Clee SM,
    4. Roomp K,
    5. Zhang LH,
    6. Yu L,
    7. Collins JA,
    8. van DM,
    9. Molhuizen HO,
    10. Loubster O,
    11. Ouellette BF,
    12. Sensen CW,
    13. Fichter K,
    14. Mott S,
    15. Denis M,
    16. Boucher B,
    17. Pimstone S,
    18. Genest J Jr.,
    19. Kastelein JJ,
    20. Hayden MR
    . Mutations in the ABC1 gene in familial HDL deficiency with defective cholesterol efflux. Lancet. 1999;354:1341–1346.
    OpenUrlCrossRefPubMed
  35. 35.↵
    1. Wang N,
    2. Lan D,
    3. Chen W,
    4. Matsuura F,
    5. Tall AR
    . ATP-binding cassette transporters G1 and G4 mediate cellular cholesterol efflux to high-density lipoproteins. Proc Natl Acad Sci U S A. 2004;101:9774–9779.
    OpenUrlAbstract/FREE Full Text
  36. 36.↵
    1. Wiersma H,
    2. Nijstad N,
    3. de Boer JF,
    4. Out R,
    5. Hogewerf W,
    6. van Berkel TJ,
    7. Kuipers F,
    8. Tietge UJ
    . Lack of Abcg1 results in decreased plasma HDL cholesterol levels and increased biliary cholesterol secretion in mice fed a high cholesterol diet. Atherosclerosis. 2009;206:141–147.
    OpenUrlCrossRefPubMed
  37. 37.↵
    1. Out R,
    2. Jessup W,
    3. Le GW,
    4. Hoekstra M,
    5. Gelissen IC,
    6. Zhao Y,
    7. Kritharides L,
    8. Chimini G,
    9. Kuiper J,
    10. Chapman MJ,
    11. Huby T,
    12. van Berkel TJ,
    13. van EM
    . Coexistence of foam cells and hypocholesterolemia in mice lacking the ABC transporters A1 and G1. Circ Res. 2008;102:113–120.
    OpenUrlAbstract/FREE Full Text
  38. 38.↵
    1. Yvan-Charvet L,
    2. Pagler T,
    3. Gautier EL,
    4. Avagyan S,
    5. Siry RL,
    6. Han S,
    7. Welch CL,
    8. Wang N,
    9. Randolph GJ,
    10. Snoeck HW,
    11. Tall AR
    . ATP-binding cassette transporters and HDL suppress hematopoietic stem cell proliferation. Science. 2010;328:1689–1693.
    OpenUrlAbstract/FREE Full Text
  39. 39.↵
    1. Schwartz CC,
    2. VandenBroek JM,
    3. Cooper PS
    . Modeling cholesterol in humans: update and dealing with the problem of exchange in vivo using the blood cell-lipoprotein paradigm. Adv Exp Med Biol. 2003;537:207–219.
    OpenUrlCrossRefPubMed
  40. 40.↵
    1. Kozarsky KF,
    2. Donahee MH,
    3. Rigotti A,
    4. Iqbal SN,
    5. Edelman ER,
    6. Krieger M
    . Overexpression of the HDL receptor SR-BI alters plasma HDL and bile cholesterol levels. Nature. 1997;387:414–417.
    OpenUrlCrossRefPubMed
  41. 41.↵
    1. Martinez LO,
    2. Jacquet S,
    3. Esteve JP,
    4. Rolland C,
    5. Cabezon E,
    6. Champagne E,
    7. Pineau T,
    8. Georgeaud V,
    9. Walker JE,
    10. Terce F,
    11. Collet X,
    12. Perret B,
    13. Barbaras R
    . Ectopic β-chain of ATP synthase is an apolipoprotein A-I receptor in hepatic HDL endocytosis. Nature. 2003;421:75–79.
    OpenUrlCrossRefPubMed
  42. 42.↵
    1. Fabre AC,
    2. Malaval C,
    3. Ben AA,
    4. Verdier C,
    5. Pons V,
    6. Serhan N,
    7. Lichtenstein L,
    8. Combes G,
    9. Huby T,
    10. Briand F,
    11. Collet X,
    12. Nijstad N,
    13. Tietge UJ,
    14. Robaye B,
    15. Perret B,
    16. Boeynaems JM,
    17. Martinez LO
    . P2Y13 receptor is critical for reverse cholesterol transport. Hepatology. 2010;52:1477–1483.
    OpenUrlCrossRefPubMed
  43. 43.↵
    1. Jacquet S,
    2. Malaval C,
    3. Martinez LO,
    4. Sak K,
    5. Rolland C,
    6. Perez C,
    7. Nauze M,
    8. Champagne E,
    9. Terce F,
    10. Gachet C,
    11. Perret B,
    12. Collet X,
    13. Boeynaems JM,
    14. Barbaras R
    . The nucleotide receptor P2Y13 is a key regulator of hepatic high-density lipoprotein (HDL) endocytosis. Cell Mol Life Sci. 2005;62:2508–2515.
    OpenUrlCrossRefPubMed
  44. 44.↵
    1. Vergeer M,
    2. Hovingh K,
    3. Vissers MN,
    4. Kastelein JJ,
    5. Kuivenhoven JA
    . Heterozygosity for a mutation in the extracellular domain of SR-BI is associated with high HDL cholesterol levels in a family of Caucasian descent. Circulation. 2006;114:II.
    OpenUrl
  45. 45.↵
    1. Vergeer M,
    2. Korporaal SJ,
    3. Franssen R,
    4. Meurs I,
    5. Out R,
    6. Hovingh GK,
    7. Hoekstra M,
    8. Sierts JA,
    9. Linga-Thie GM,
    10. Motazacker MM,
    11. Holleboom AG,
    12. van Berkel TJ,
    13. Kastelein JJ,
    14. van EM,
    15. Kuivenhoven JA
    . Genetic variant of the scavenger receptor BI in humans. N Engl J Med. 2011;364:136–145.
    OpenUrlCrossRefPubMed
  46. 46.↵
    1. Fielding CJ,
    2. Fielding PE
    . Cholesterol transport between cells and body fluids: role of plasma lipoproteins and the plasma cholesterol esterification system. Med Clin North Am. 1982;66:363–373.
    OpenUrlPubMed
  47. 47.↵
    1. Asztalos BF,
    2. Collins D,
    3. Cupples LA,
    4. Demissie S,
    5. Horvath KV,
    6. Bloomfield HE,
    7. Robins SJ,
    8. Schaefer EJ
    . Value of high-density lipoprotein (HDL) subpopulations in predicting recurrent cardiovascular events in the Veterans Affairs HDL Intervention Trial. Arterioscler Thromb Vasc Biol. 2005;25:2185–2191.
    OpenUrlAbstract/FREE Full Text
  48. 48.↵
    1. Wang MD,
    2. Franklin V,
    3. Marcel YL
    . In vivo reverse cholesterol transport from macrophages lacking ABCA1 expression is impaired. Arterioscler Thromb Vasc Biol. 2007;27:1837–1842.
    OpenUrlAbstract/FREE Full Text
  49. 49.↵
    1. Wang X,
    2. Collins HL,
    3. Ranalletta M,
    4. Fuki IV,
    5. Billheimer JT,
    6. Rothblat GH,
    7. Tall AR,
    8. Rader DJ
    . Macrophage ABCA1 and ABCG1, but not SR-BI, promote macrophage reverse cholesterol transport in vivo. J Clin Invest. 2007;117:2216–2224.
    OpenUrlCrossRefPubMed
  50. 50.↵
    1. Baldan A,
    2. Pei L,
    3. Lee R,
    4. Tarr P,
    5. Tangirala RK,
    6. Weinstein MM,
    7. Frank J,
    8. Li AC,
    9. Tontonoz P,
    10. Edwards PA
    . Impaired development of atherosclerosis in hyperlipidemic Ldlr−/− and ApoE−/− mice transplanted with Abcg1−/− bone marrow. Arterioscler Thromb Vasc Biol. 2006;26:2301–2307.
    OpenUrlAbstract/FREE Full Text
  51. 51.↵
    1. Adorni MP,
    2. Zimetti F,
    3. Billheimer JT,
    4. Wang N,
    5. Rader DJ,
    6. Phillips MC,
    7. Rothblat GH
    . The roles of different pathways in the release of cholesterol from macrophages. J Lipid Res. 2007;48:2453–2462.
    OpenUrlAbstract/FREE Full Text
  52. 52.↵
    1. Yvan-Charvet L,
    2. Wang N,
    3. Tall AR
    . Role of HDL, ABCA1, and ABCG1 transporters in cholesterol efflux and immune responses. Arterioscler Thromb Vasc Biol. 2010;30:139–143.
    OpenUrlAbstract/FREE Full Text
  53. 53.↵
    1. Cuchel M,
    2. Lund-Katz S,
    3. de lL-M,
    4. Millar JS,
    5. Chang D,
    6. Fuki I,
    7. Rothblat GH,
    8. Phillips MC,
    9. Rader DJ
    . Pathways by which reconstituted high-density lipoprotein mobilizes free cholesterol from whole body and from macrophages. Arterioscler Thromb Vasc Biol. 2010;30:526–532.
    OpenUrlAbstract/FREE Full Text
  54. 54.↵
    1. Movva R,
    2. Rader DJ
    . Laboratory assessment of HDL heterogeneity and function. Clin Chem. 2008;54:788–800.
    OpenUrlAbstract/FREE Full Text
  55. 55.↵
    1. Groen AK,
    2. Bloks VW,
    3. Bandsma RH,
    4. Ottenhoff R,
    5. Chimini G,
    6. Kuipers F
    . Hepatobiliary cholesterol transport is not impaired in Abca1-null mice lacking HDL. J Clin Invest. 2001;108:843–850.
    OpenUrlCrossRefPubMed
  56. 56.↵
    1. Drobnik W,
    2. Lindenthal B,
    3. Lieser B,
    4. Ritter M,
    5. Christiansen WT,
    6. Liebisch G,
    7. Giesa U,
    8. Igel M,
    9. Borsukova H,
    10. Buchler C,
    11. Fung-Leung WP,
    12. Von Bergmann K,
    13. Schmitz G
    . ATP-binding cassette transporter A1 (ABCA1) affects total body sterol metabolism. Gastroenterology. 2001;120:1203–1211.
    OpenUrlCrossRefPubMed
  57. 57.↵
    1. Alam K,
    2. Meidell RS,
    3. Spady DK
    . Effect of up-regulating individual steps in the reverse cholesterol transport pathway on reverse cholesterol transport in normolipidemic mice. J Biol Chem. 2001;276:15641–15649.
    OpenUrlAbstract/FREE Full Text
  58. 58.↵
    1. Miettinen TA,
    2. Kesaniemi YA
    . Cholesterol absorption: regulation of cholesterol synthesis and elimination and within-population variations of serum cholesterol levels. Am J Clin Nutr. 1989;49:629–635.
    OpenUrlAbstract/FREE Full Text
  59. 59.↵
    1. Brousseau ME,
    2. Diffenderfer MR,
    3. Millar JS,
    4. Nartsupha C,
    5. Asztalos BF,
    6. Welty FK,
    7. Wolfe ML,
    8. Rudling M,
    9. Bjorkhem I,
    10. Angelin B,
    11. Mancuso JP,
    12. Digenio AG,
    13. Rader DJ,
    14. Schaefer EJ
    . Effects of cholesteryl ester transfer protein inhibition on high-density lipoprotein subspecies, apolipoprotein A-I metabolism, and fecal sterol excretion. Arterioscler Thromb Vasc Biol. 2005;25:1057–1064.
    OpenUrlAbstract/FREE Full Text
  60. 60.↵
    1. Beher WT,
    2. Gabbard A,
    3. Norum RA,
    4. Stradnieks S
    . Effect of blood high density lipoprotein cholesterol concentration on fecal steroid excretion in humans. Life Sci. 1983;32:2933–2937.
    OpenUrlCrossRefPubMed
  61. 61.↵
    1. Gylling H,
    2. Miettinen TA
    . Non-cholesterol sterols, absorption and synthesis of cholesterol and apolipoprotein A-I kinetics in a Finnish lecithin-cholesterol acyltransferase deficient family. Atherosclerosis. 1992;95:25–33.
    OpenUrlCrossRefPubMed
  62. 62.↵
    1. Harchaoui KE,
    2. Franssen R,
    3. Hovingh GK,
    4. Bisoendial RJ,
    5. Stellaard F,
    6. Kuipers F,
    7. Kastelein JJ,
    8. Kuivenhoven JA,
    9. Stroes ES,
    10. Groen AK
    . Reduced fecal sterol excretion in subjects with familial hypoalphalipoproteinemia. Atherosclerosis. 2009;207:614–616.
    OpenUrlCrossRefPubMed
  63. 63.↵
    1. Eriksson M,
    2. Carlson LA,
    3. Miettinen TA,
    4. Angelin B
    . Stimulation of fecal steroid excretion after infusion of recombinant proapolipoprotein A-I. Potential reverse cholesterol transport in humans. Circulation. 1999;100:594–598.
    OpenUrlAbstract/FREE Full Text
  64. 64.↵
    1. Nanjee MN,
    2. Cooke CJ,
    3. Garvin R,
    4. Semeria F,
    5. Lewis G,
    6. Olszewski WL,
    7. Miller NE
    . Intravenous apoA-I/lecithin discs increase pre-β-HDL concentration in tissue fluid and stimulate reverse cholesterol transport in humans. J Lipid Res. 2001;42:1586–1593.
    OpenUrlAbstract/FREE Full Text
  65. 65.↵
    1. Smith JD
    . Dysfunctional HDL as a diagnostic and therapeutic target. Arterioscler Thromb Vasc Biol. 2010;30:151–155.
    OpenUrlAbstract/FREE Full Text
  66. 66.↵
    1. Castellani LW,
    2. Navab M,
    3. Van Lenten BJ,
    4. Hedrick CC,
    5. Hama SY,
    6. Goto AM,
    7. Fogelman AM,
    8. Lusis AJ
    . Overexpression of apolipoprotein AII in transgenic mice converts high density lipoproteins to proinflammatory particles. J Clin Invest. 1997;100:464–474.
    OpenUrlCrossRefPubMed
  67. 67.↵
    1. Moerland M,
    2. Samyn H,
    3. van GT,
    4. Jauhiainen M,
    5. Metso J,
    6. van HR,
    7. Grosveld F,
    8. van TA,
    9. de CR
    . Atherogenic, enlarged, and dysfunctional HDL in human PLTP/apoA-I double transgenic mice. J Lipid Res. 2007;48:2622–2631.
    OpenUrlAbstract/FREE Full Text
  68. 68.↵
    1. Pirillo A,
    2. Uboldi P,
    3. Bolego C,
    4. Kuhn H,
    5. Catapano AL
    . The 15-lipoxygenase-modified high density lipoproteins 3 fail to inhibit the TNF-α-induced inflammatory response in human endothelial cells. J Immunol. 2008;181:2821–2830.
    OpenUrlAbstract/FREE Full Text
  69. 69.↵
    1. Pirillo A,
    2. Uboldi P,
    3. Kuhn H,
    4. Catapano AL
    . 15-Lipoxygenase-mediated modification of high-density lipoproteins impairs SR-BI- and ABCA1-dependent cholesterol efflux from macrophages. Biochim Biophys Acta. 2006;1761:292–300.
    OpenUrlPubMed
  70. 70.↵
    1. Annema W,
    2. Nijstad N,
    3. Tolle M,
    4. de Boer JF,
    5. Buijs RV,
    6. Heeringa P,
    7. van der GM,
    8. Tietge UJ
    . Myeloperoxidase and serum amyloid A contribute to impaired in vivo reverse cholesterol transport during the acute phase response, but not group IIA secretory phospholipase A2. J Lipid Res. 2010;51:743–754.
    OpenUrlAbstract/FREE Full Text
  71. 71.↵
    1. Van Lenten BJ,
    2. Wagner AC,
    3. Nayak DP,
    4. Hama S,
    5. Navab M,
    6. Fogelman AM
    . High-density lipoprotein loses its anti-inflammatory properties during acute influenza a infection. Circulation. 2001;103:2283–2288.
    OpenUrlAbstract/FREE Full Text
  72. 72.↵
    1. Van Lenten BJ,
    2. Hama SY,
    3. de Beer FC,
    4. Stafforini DM,
    5. McIntyre TM,
    6. Prescott SM,
    7. La Du BN,
    8. Fogelman AM,
    9. Navab M
    . Anti-inflammatory HDL becomes pro-inflammatory during the acute phase response. Loss of protective effect of HDL against LDL oxidation in aortic wall cell cocultures. J Clin Invest. 1995;96:2758–2767.
    OpenUrlCrossRefPubMed
  73. 73.↵
    1. Kontush A,
    2. Chapman MJ
    . Why is HDL functionally deficient in type 2 diabetes? Curr Diab Rep. 2008;8:51–59.
    OpenUrlCrossRefPubMed
  74. 74.↵
    1. Xie C,
    2. Turley SD,
    3. Dietschy JM
    . Centripetal cholesterol flow from the extrahepatic organs through the liver is normal in mice with mutated Niemann-Pick type C protein (NPC1). J Lipid Res. 2000;41:1278–1289.
    OpenUrlAbstract/FREE Full Text
  75. 75.↵
    1. van der Velde AE,
    2. Brufau G,
    3. Groen AK
    . Transintestinal cholesterol efflux. Curr Opin Lipidol. 2010;21:167–171.
    OpenUrlCrossRefPubMed
  76. 76.↵
    1. Ferezou J,
    2. Coste T,
    3. Chevallier F
    . Origins of neutral sterols in human feces studied by stable isotope labeling (D and 13C). Existence of an external secretion of cholesterol. Digestion. 1981;21:232–243.
    OpenUrlPubMed
  77. 77.↵
    1. Simmonds WJ,
    2. Hofmann AF,
    3. Theodor E
    . Absorption of cholesterol from a micellar solution: intestinal perfusion studies in man. J Clin Invest. 1967;46:874–890.
    OpenUrlPubMed
  78. 78.↵
    1. Stanley MM,
    2. Pineda EP,
    3. Cheng SH
    . Serum cholesterol esters and intestinal cholesterol secretion and absorption in obstructive jaundice due to cancer. N Engl J Med. 1959;261:368–373.
    OpenUrlCrossRefPubMed
  79. 79.↵
    1. Cheng SH,
    2. Stanley MM
    . Secretion of cholesterol by intestinal mucosa in patients with complete common bile duct obstruction. Proc Soc Exp Biol Med. 1959;101:223–225.
    OpenUrlAbstract/FREE Full Text
  80. 80.↵
    1. Dietschy JM,
    2. Turley SD
    . Control of cholesterol turnover in the mouse. J Biol Chem. 2002;277:3801–3804.
    OpenUrlFREE Full Text
  81. 81.↵
    1. Sperry WM
    . Lipid Excretion IV. A study of the relationship of the bile to the fecal lipids with special reference to certain problems of sterol metabolism. J Biol Chem. 1927;71:351–378.
    OpenUrlFREE Full Text
  82. 82.↵
    1. Vrins CL,
    2. van der Velde AE,
    3. van den Oever K,
    4. Levels JH,
    5. Huet S,
    6. Oude Elferink RP,
    7. Kuipers F,
    8. Groen AK
    . Peroxisome proliferator-activated receptor δ activation leads to increased transintestinal cholesterol efflux. J Lipid Res. 2009;50:2046–2054.
    OpenUrlAbstract/FREE Full Text
  83. 83.↵
    1. deGoma EM,
    2. deGoma RL,
    3. Rader DJ
    . Beyond high-density lipoprotein cholesterol levels evaluating high-density lipoprotein function as influenced by novel therapeutic approaches. J Am Coll Cardiol. 2008;51:2199–2211.
    OpenUrlCrossRefPubMed
  84. 84.↵
    1. Wang MD,
    2. Kiss RS,
    3. Franklin V,
    4. McBride HM,
    5. Whitman SC,
    6. Marcel YL
    . Different cellular traffic of LDL-cholesterol and acetylated LDL-cholesterol leads to distinct reverse cholesterol transport pathways. J Lipid Res. 2007;48:633–645.
    OpenUrlAbstract/FREE Full Text
  85. 85.↵
    1. Temel RE,
    2. Sawyer JK,
    3. Yu L,
    4. Lord C,
    5. Degirolamo C,
    6. McDaniel A,
    7. Marshall S,
    8. Wang N,
    9. Shah R,
    10. Rudel LL,
    11. Brown JM
    . Biliary sterol secretion is not required for macrophage reverse cholesterol transport. Cell Metab. 2010;12:96–102.
    OpenUrlCrossRefPubMed
  86. 86.↵
    1. Stein O,
    2. Dabach Y,
    3. Hollander G,
    4. Ben-Naim M,
    5. Halperin G,
    6. Okon E,
    7. Stein Y
    . Cholesterol efflux in vivo from a depot of cationized LDL injected into a thigh muscle of small rodents. Atherosclerosis. 1997;133:15–22.
    OpenUrlCrossRefPubMed
  87. 87.↵
    1. Hellerstein MK
    . New stable isotope-mass spectrometric techniques for measuring fluxes through intact metabolic pathways in mammalian systems: introduction of moving pictures into functional genomics and biochemical phenotyping. Metab Eng. 2004;6:85–100.
    OpenUrlCrossRefPubMed
  88. 88.↵
    1. Hellerstein MK,
    2. Murphy E
    . Stable isotope-mass spectrometric measurements of molecular fluxes in vivo: emerging applications in drug development. Curr Opin Mol Ther. 2004;6:249–264.
    OpenUrlPubMed
  89. 89.↵
    1. Voogt J,
    2. Turner S,
    3. Luchoomun J,
    4. Hellerstein M
    . Measurement of reverse cholesterol transport (RCT) flux rates in humans: recent advances. Arterioscler Thromb Vasc Biol. 2009;29:E33.
    OpenUrlCrossRef
  90. 90.↵
    1. Voogt J,
    2. Killion S,
    3. Awada M,
    4. Murphy L,
    5. Hellerstein M,
    6. Turner S
    . Measurement of cholesterol efflux and global reverse cholesterol transport rates in vivo with stable isotopes. Arteriosclerosis Thrombosis and Vascular Biology. 2007;27:E124.
    OpenUrl
  91. 91.↵
    1. Tang W,
    2. Ma Y,
    3. Jia L,
    4. Ioannou YA,
    5. Davies JP,
    6. Yu L
    . Genetic inactivation of NPC1L1 protects against sitosterolemia in mice lacking ABCG5/ABCG8. J Lipid Res. 2009;50:293–300.
    OpenUrlAbstract/FREE Full Text
  92. 92.↵
    1. Yu L,
    2. York J,
    3. von Bergmann K,
    4. Lutjohann D,
    5. Cohen JC,
    6. Hobbs HH
    . Stimulation of cholesterol excretion by the liver X receptor agonist requires ATP-binding cassette transporters G5 and G8. J Biol Chem. 2003;278:15565–15570.
    OpenUrlAbstract/FREE Full Text
  93. 93.↵
    1. Plosch T,
    2. Bloks VW,
    3. Terasawa Y,
    4. Berdy S,
    5. Siegler K,
    6. Van Der SF,
    7. Kema IP,
    8. Groen AK,
    9. Shan B,
    10. Kuipers F,
    11. Schwarz M
    . Sitosterolemia in ABC-transporter G5-deficient mice is aggravated on activation of the liver-X receptor. Gastroenterology. 2004;126:290–300.
    OpenUrlCrossRefPubMed
  94. 94.↵
    1. Bandsma RH,
    2. Stellaard F,
    3. Vonk RJ,
    4. Nagel GT,
    5. Neese RA,
    6. Hellerstein MK,
    7. Kuipers F
    . Contribution of newly synthesized cholesterol to rat plasma and bile determined by mass isotopomer distribution analysis: bile-salt flux promotes secretion of newly synthesized cholesterol into bile. Biochem J. 1998;329:699–703.
    OpenUrlAbstract/FREE Full Text
View Abstract
Back to top
Previous ArticleNext Article

This Issue

Arteriosclerosis, Thrombosis, and Vascular Biology
August 2011, Volume 31, Issue 8
  • Table of Contents
Previous ArticleNext Article

Jump to

  • Article
    • Abstract
    • HDL
    • RCT: Involvement of HDL
    • The Intestine and RCT
    • In Vivo RCT Measurement
    • Conclusions and Perspectives
    • Sources of Funding
    • Disclosures
    • Acknowledgments
    • References
  • Figures & Tables
  • Info & Metrics
  • eLetters

Article Tools

  • Print
  • Citation Tools
    Reverse Cholesterol Transport Revisited
    Gemma Brufau, Albert K. Groen and Folkert Kuipers
    Arteriosclerosis, Thrombosis, and Vascular Biology. 2011;31:1726-1733, originally published July 20, 2011
    https://doi.org/10.1161/ATVBAHA.108.181206

    Citation Manager Formats

    • BibTeX
    • Bookends
    • EasyBib
    • EndNote (tagged)
    • EndNote 8 (xml)
    • Medlars
    • Mendeley
    • Papers
    • RefWorks Tagged
    • Ref Manager
    • RIS
    • Zotero
  •  Download Powerpoint
  • Article Alerts
    Log in to Email Alerts with your email address.
  • Save to my folders

Share this Article

  • Email

    Thank you for your interest in spreading the word on Arteriosclerosis, Thrombosis, and Vascular Biology.

    NOTE: We only request your email address so that the person you are recommending the page to knows that you wanted them to see it, and that it is not junk mail. We do not capture any email address.

    Enter multiple addresses on separate lines or separate them with commas.
    Reverse Cholesterol Transport Revisited
    (Your Name) has sent you a message from Arteriosclerosis, Thrombosis, and Vascular Biology
    (Your Name) thought you would like to see the Arteriosclerosis, Thrombosis, and Vascular Biology web site.
  • Share on Social Media
    Reverse Cholesterol Transport Revisited
    Gemma Brufau, Albert K. Groen and Folkert Kuipers
    Arteriosclerosis, Thrombosis, and Vascular Biology. 2011;31:1726-1733, originally published July 20, 2011
    https://doi.org/10.1161/ATVBAHA.108.181206
    del.icio.us logo Digg logo Reddit logo Twitter logo CiteULike logo Facebook logo Google logo Mendeley logo

Related Articles

Cited By...

Arteriosclerosis, Thrombosis, and Vascular Biology

  • About ATVB
  • Instructions for Authors
  • AHA CME
  • Meeting Abstracts
  • Permissions
  • Email Alerts
  • Open Access Information
  • AHA Journals RSS
  • AHA Newsroom

Contact the Editorial Office:
email: atvb@atvb.org

Information for:
  • Advertisers
  • Subscribers
  • Subscriber Help
  • Institutions / Librarians
  • Institutional Subscriptions FAQ
  • International Users
American Heart Association Learn and Live
National Center
7272 Greenville Ave.
Dallas, TX 75231

Customer Service

  • 1-800-AHA-USA-1
  • 1-800-242-8721
  • Local Info
  • Contact Us

About Us

Our mission is to build healthier lives, free of cardiovascular diseases and stroke. That single purpose drives all we do. The need for our work is beyond question. Find Out More about the American Heart Association

  • Careers
  • SHOP
  • Latest Heart and Stroke News
  • AHA/ASA Media Newsroom

Our Sites

  • American Heart Association
  • American Stroke Association
  • For Professionals
  • More Sites

Take Action

  • Advocate
  • Donate
  • Planned Giving
  • Volunteer

Online Communities

  • AFib Support
  • Garden Community
  • Patient Support Network
  • Professional Online Network

Follow Us:

  • Follow Circulation on Twitter
  • Visit Circulation on Facebook
  • Follow Circulation on Google Plus
  • Follow Circulation on Instagram
  • Follow Circulation on Pinterest
  • Follow Circulation on YouTube
  • Rss Feeds
  • Privacy Policy
  • Copyright
  • Ethics Policy
  • Conflict of Interest Policy
  • Linking Policy
  • Diversity
  • Careers

©2018 American Heart Association, Inc. All rights reserved. Unauthorized use prohibited. The American Heart Association is a qualified 501(c)(3) tax-exempt organization.
*Red Dress™ DHHS, Go Red™ AHA; National Wear Red Day ® is a registered trademark.

  • PUTTING PATIENTS FIRST National Health Council Standards of Excellence Certification Program
  • BBB Accredited Charity
  • Comodo Secured