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Goupille C, Ouldamer L, Pinault M, Guimares C, Arbion F, Jourdan ML, Frank PG. Identification of a Positive Association between Mammary Adipose Cholesterol Content and Indicators of Breast Cancer Aggressiveness in a French Population. J Nutr 2021; 151:1119-1127. [PMID: 33831951 DOI: 10.1093/jn/nxaa432] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2020] [Revised: 08/26/2020] [Accepted: 12/10/2020] [Indexed: 11/13/2022] Open
Abstract
BACKGROUND Several studies have recently highlighted important roles for adipose tissue in cancer. However, few have examined adipose tissue cholesterol, and no study has been performed in breast adipose tissue associated with breast tumors. OBJECTIVES The present work was designed to determine if breast adipose tissue cholesterol from the tumor-surrounding area is associated with breast cancer aggressiveness. METHODS Between 2009 and 2011, 215 breast adipose tissue samples were collected at the Tours University Hospital (France) during surgery of women (aged 28-89 y) with invasive breast cancer. Associations of free cholesterol (FC), esterified cholesterol (EC), and total cholesterol (TC) amounts with clinical variables (age, BMI, and treated or untreated hypercholesterolemia) and tumor aggressiveness parameters [phenotype, grade, presence of inflammatory breast cancer (IBC), and multifocality] were tested using Student's t test and after ANOVA. RESULTS The predominant form of cholesterol in adipose tissue was FC, and 50% of patients had no detectable EC. The adipose tissue FC content (μg/mg total lipid) was 18% greater in patients >70 y old than in those 40-49 y old (P < 0.05) and the TC content tended to be 12% greater in untreated hypercholesterolemic patients than in normocholesterolemic patients (P = 0.06). Breast adipose cholesterol concentrations were increased in tissues obtained from patients with human-epidermal-growth-factor-receptor-2 (HER2) phenotype (+13% FC; P < 0.05 compared with luminal A), IBC (+15% FC; P = 0.06 compared with noninflammatory tumors), as well as with multifocal triple-negative tumors (+34% FC, P < 0.05; +30% TC, P < 0.05, compared with unifocal triple-negative tumors). Among patients with triple-negative tumors, hypercholesterolemia was significantly more common (P < 0.05) in patients with multifocal tumors (64%) than in patients with unifocal tumors (25%). CONCLUSIONS This study is the first of this magnitude that analyzes cholesterol concentrations in adipose tissue from female breast cancer patients. An increase in breast adipose tissue cholesterol content may contribute to breast cancer aggressiveness (HER2 phenotype, multifocality of triple-negative tumors, and IBC).
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Affiliation(s)
- Caroline Goupille
- CHRU de Tours, Hôpital Bretonneau, Service de Gynécologie, Tours, France.,Laboratoire "Nutrition, Growth and Cancer", Université de Tours, INSERM UMR1069, Tours, France
| | - Lobna Ouldamer
- CHRU de Tours, Hôpital Bretonneau, Service de Gynécologie, Tours, France.,Laboratoire "Nutrition, Growth and Cancer", Université de Tours, INSERM UMR1069, Tours, France
| | - Michelle Pinault
- Laboratoire "Nutrition, Growth and Cancer", Université de Tours, INSERM UMR1069, Tours, France
| | - Cyrille Guimares
- Laboratoire "Nutrition, Growth and Cancer", Université de Tours, INSERM UMR1069, Tours, France
| | - Flavie Arbion
- CHRU de Tours, Hôpital Bretonneau, Service de Pathologie, Tours, France
| | - Marie L Jourdan
- CHRU de Tours, Hôpital Bretonneau, Service de Gynécologie, Tours, France.,Laboratoire "Nutrition, Growth and Cancer", Université de Tours, INSERM UMR1069, Tours, France
| | - Philippe G Frank
- Laboratoire "Nutrition, Growth and Cancer", Université de Tours, INSERM UMR1069, Tours, France.,French Network for Nutrition and Cancer Research (NACRe network), France.,SGS France Life Services, Saint Benoît, France
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Abstract
PURPOSE OF REVIEW Adipose tissue is a critical endocrine and immunological organ that regulates systemic energy homeostasis. During the pathogenesis of obesity, adipocyte hypertrophy is accompanied by adipose tissue inflammation, impeding insulin sensitivity and endocrine function of adipose tissue and other tissues. Adipocyte cholesterol accumulates in proportion to triglyceride as adipocytes undergo hypertrophy. Recent studies suggest that dietary cholesterol contributes to increased adipocyte cholesterol. However, how dietary cholesterol accumulates in adipocytes and its metabolic consequences are poorly understood. This review summarizes recent advances in knowledge of adipocyte cholesterol balance and highlights the emerging role of dietary cholesterol in adipose tissue cholesterol balance, inflammation, and systemic energy metabolism. RECENT FINDINGS Perturbation of cholesterol balance in adipocytes alters intracellular cholesterol distribution and modulates adipocyte insulin and proinflammatory signaling. Adipocyte cholesterol levels are maintained by a balance between dietary cholesterol uptake from triglyceride-enriched lipoproteins and cellular cholesterol efflux to HDL. Recent animal studies established a critical role for dietary cholesterol in promoting adipose tissue inflammation, thereby worsening obesity-mediated metabolic complications. SUMMARY Recent studies identified high dietary cholesterol as a potentiator of adipose tissue inflammation and dysfunction. Reducing excessive dietary cholesterol intake is suggested as a simple, but novel, way to attenuate obesity-associated metabolic diseases.
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Affiliation(s)
- Soonkyu Chung
- Department of Nutrition and Health Sciences, University of Nebraska, Lincoln, NE 68516
| | - John S. Parks
- Department of Internal Medicine/Molecular Medicine, Wake Forest School of Medicine, Winston-Salem, NC 27157
- Department of Biochemistry, Wake Forest School of Medicine, Winston-Salem, NC 27157
- Corresponding author: John S. Parks; Department of Internal Medicine/Section on Molecular Medicine, Wake Forest School of Medicine, Medical Center Blvd, Winston-Salem, NC 27157 phone: 336-716-2145 fax: 336-716-6279
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Li H, Li H, Guo H, Liu F. Cholesterol suppresses adipocytic differentiation of mouse adipose-derived stromal cells via PPARγ2 signaling. Steroids 2013; 78:454-61. [PMID: 23454216 DOI: 10.1016/j.steroids.2013.02.009] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/10/2012] [Revised: 01/24/2013] [Accepted: 02/04/2013] [Indexed: 12/14/2022]
Abstract
The effects of cholesterol on cell proliferation and adipocytic differentiation have been evaluated for the first time in mouse adipose-derived stromal cells (mASCs). Cholesterol loading by using cholesterol:methyl- β-cyclodextrin (Chol:MβCD) complexes promoted cellular levels of free cholesterol (FC) and cholesteryl ester (CE), induced high cell proliferation of mASCs dose-dependently. Compared with control cells, cholesterol-treated mASCs showed an impaired differentiation process in both dose- and time-dependent manners, based on reduced oil red O-stained lipid droplets, SREBP-1, PPARγ2 and aP2 expression levels. The involvement of SREBP-1-mediated PPARγ2 in the effects of cholesterol on mASC adipogenesis was elucidated. These results point to cholesterol as a modulator of adipogenesis, which separate cholesterol itself from other components of modified lipoproteins.
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Affiliation(s)
- Haifang Li
- College of Life Sciences, Shandong Agricultural University, Tai'an 271018, China.
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4
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Fruchart JC. Lipoprotein Heterogeneity and its Effect on Apolipoprotein Assays. Scandinavian Journal of Clinical and Laboratory Investigation 2011. [DOI: 10.1080/00365519009091086] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
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5
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Erol A. The role of fat tissue in the cholesterol lowering and the pleiotropic effects of statins – statins activate the generation of metabolically more capable adipocytes. Med Hypotheses 2005; 64:69-73. [PMID: 15533614 DOI: 10.1016/j.mehy.2004.06.014] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2004] [Accepted: 06/02/2004] [Indexed: 11/26/2022]
Abstract
Statins have very important influences on adipocyte physiology, particularly via their effects on sterol regulatory element binding proteins (SREBPs), which are extremely important transcription factors for the regulation of adipocyte physiology. SREBP-1c activation in fat cell by the cytosolic cholesterol deprivation through HMG-reductase inhibition is responsible for most of the beneficial effects of statins. Glucose and lipid excess, and oxidative overload coming with energy dense nutrition, which might be deleterious, can be removed from the circulation by adipo-lipogenetic enhancement through the activated SREBP-1c. SREBP-1c causes formation of new small and competent adipocytes, which are insulin and leptin sensitive. Thus, adipocytes gain the ability of fat storing, and much more importantly, fat-burning machines. Statins already have a large and growing number of indications in the treatment of atherovascular diseases. General mechanism for the action of statins is their inhibitory effects on 3-hydroxy 3-methyl glutaryl CoA reductase, which is the rate-limiting enzyme in cholesterol biosynthesis, particularly in the liver. Recently, the beneficial effects of statins beyond their cholesterol lowering, which are called pleiotropic effects, have been the focus of great attention. Certain characteristics of the statin molecule itself have been proposed to explain these effects. Adipocytes are in the very heart of metabolic regulations. Therefore, the important elements of the pleiotropic effects of statins occur through executive improvements on impaired adipocyte functions by the activation of SREBP-1c.
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Affiliation(s)
- Adnan Erol
- Internal Medicine, Silivri City Hospital, Ali Cetinkaya Cad, 34930 Silivri, Istanbul, Turkey.
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6
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Prattes S, Hörl G, Hammer A, Blaschitz A, Graier WF, Sattler W, Zechner R, Steyrer E. Intracellular distribution and mobilization of unesterified cholesterol in adipocytes: triglyceride droplets are surrounded by cholesterol-rich ER-like surface layer structures. J Cell Sci 2000; 113 ( Pt 17):2977-89. [PMID: 10934037 DOI: 10.1242/jcs.113.17.2977] [Citation(s) in RCA: 117] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
In addition to their central role in triglyceride storage, fat cells are a primary depot of unesterified cholesterol (FC) in the body. In comparison, peripheral cells contain very little FC. This difference in adipocytes versus peripheral tissues is inconsistent with the current theory of cholesterol homeostasis. Attempting to resolve this discrepancy, we examined intracellular storage sites of FC in murine 3T3-F442A adipocytes. Using the cholesterol-binding antibiotic, filipin, in combination with high resolution fluorescence microscopy, intense fluorescent staining characteristically decorated the periphery of triglyceride droplets (TGD) as well as the plasma membrane (PM) of fat cells. Filipin-staining was not visible inside the lipid droplets. Purification of TGD by subcellular fractionation demonstrated that the rise in total FC content of adipocytes upon differentiation was attributable to an increase in TGD-FC, which contributed up to one third of the total cellular FC. The protein component of purified TGD from cultured adipocytes as well as from murine adipocytes obtained from fresh tissues contained the lumenal endoplasmic reticulum (ER) immunoglobulin binding protein (BiP) and the integral ER membrane protein calnexin. Efflux experiments using the extracellular FC acceptors (β)-cyclodextrin or apolipoprotein A-I demonstrated that TGD-associated FC was releasable from TGD. Whereas FC efflux from adipocytes was unaffected in the presence of brefeldin A or monensin, the secretion of a control protein, lipoprotein lipase, was effectively reduced. In summary, our findings identify the TGD surface layer as primary intracellular storage site for FC within adipocytes. We suggest that the structural role of ER-resident proteins in this adipocyte TGD envelope has been previously neglected. Our findings support the suggestion that an ER-like structure, albeit of modified lipid composition, constitutes the lipid droplets' surface layer. Finally, the efflux process of FC from adipocytes upon extracellular stimulation with (beta)-cyclodextrin provides evidence for an energy-dependent intracellular trafficking route between the TGD-FC pool and the PM-FC sites which is distinct from the secretory pathway of proteins.
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Affiliation(s)
- S Prattes
- Department of Medical Biochemistry and Medical Molecular Biology, University of Graz, Austria
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7
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Swami S, Sztalryd C, Kraemer FB. Effects of streptozotocin-induced diabetes on low density lipoprotein receptor expression in rat adipose tissue. J Lipid Res 1996. [DOI: 10.1016/s0022-2275(20)37611-2] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
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8
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Low density lipoprotein receptors in rat adipose cells: subcellular localization and regulation by insulin. J Lipid Res 1994. [DOI: 10.1016/s0022-2275(20)39771-6] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
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9
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Dehouck B, Dehouck MP, Fruchart JC, Cecchelli R. Upregulation of the low density lipoprotein receptor at the blood-brain barrier: intercommunications between brain capillary endothelial cells and astrocytes. J Cell Biol 1994; 126:465-73. [PMID: 8034745 PMCID: PMC2200038 DOI: 10.1083/jcb.126.2.465] [Citation(s) in RCA: 177] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023] Open
Abstract
In contrast to the endothelial cells in large vessels where LDL receptors are downregulated, brain capillary endothelial cells in vivo express an LDL receptor. Using a cell culture model of the blood-brain barrier consisting of a coculture of brain capillary endothelial cells and astrocytes, we observed that the capacity of endothelial cells to bind LDL is enhanced threefold when cocultured with astrocytes. We next investigated the ability of astrocytes to modulate endothelial cell LDL receptor expression. We have shown that the lipid requirement of astrocytes increases the expression of endothelial cell LDL receptors. Experiments with dialysis membranes of different pore size showed that this effect is mediated by a soluble factor(s) with relative molecular mass somewhere between 3,500 and 14,000. Substituting astrocytes with smooth muscle cells or brain endothelium with endothelium from the aorta or the adrenal cortex did not enhance the luminal LDL receptor expression on endothelial cells, demonstrating the specificity of the interactions. This factor(s) is exclusively secreted by astrocytes cocultured with brain capillary endothelial cells, but it also upregulates the LDL receptor on other cell types. This study confirms the notion that the final fine tuning of cell differentiation is under local control.
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Affiliation(s)
- B Dehouck
- Institut National de la Santé et de la Recherche Médicale U325 Service d'Etude et de Recherche sur les Lipoprotéines et l'Atherosclérose, Institut Pasteur, Lille, France
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10
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Luchoomun J, Theret N, Clavey V, Duchateau P, Rosseneu M, Brasseur R, Denefle P, Fruchart JC, Castro GR. Structural domain of apolipoprotein A-I involved in its interaction with cells. BIOCHIMICA ET BIOPHYSICA ACTA 1994; 1212:319-26. [PMID: 7515279 DOI: 10.1016/0005-2760(94)90206-2] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
Apolipoprotein A-I (apo A-I) is the major protein constituent of high-density lipoprotein (HDL), the lipoprotein fraction which mediates the reverse cholesterol transport. This apolipoprotein plays an important role in the binding of HDL to cells and participates in the efflux of cellular cholesterol. We have recently compared six different genetic variants of apo A-I and found that the apo A-I (Pro 165-->Arg) mutant is defective in promoting cellular cholesterol efflux from murine adipocytes and peritoneal macrophages and we have proposed that this region of apo A-I may be involved in their interaction with cells. To confirm this hypothesis, four monoclonal antibodies (mAbs) specific for apo A-I were used to study the inhibition of the interaction of palmitoyloleoylphosphatidylcholine (POPC): apoA-I complexes with HeLa cells and adipocytes. Among these antibodies, the apo A-I epitope recognized by the A44 mAb lies in the COOH terminal region (amino acid residues 149-186) including the proposed region. The antibodies A05, and A03 react with residues 25-82, 135-140, respectively and the A11 mAb corresponds to a discontinuous epitope at residues 99-105 and 126-132. Our results show clearly that the A44 and A05 mAbs reduce both the binding to HeLa cells and the cholesterol efflux from adipocytes. The inhibition of POPC: apoA-I complexes binding to both cell types is more strictly observed with the Fab fragments of monoclonal antibodies A44 and A05. Partial cotitration curves of these mAbs in a solid phase assay (RIA), indicated partial competition between these two antibodies. We propose a structural model for the POPC: apoA-I complexes where the N-terminal domain of one apo A-I molecule is in close spatial relationship with the C-terminal domain of the adjacent apo A-I molecule. We therefore suggest that the domain around amino acid 165 of apo A-I and which is recognized by mAb A44 (149-186) forms or contains some specific regions which mediate selectively the interaction with the binding site of cells and is involved in the efflux of cellular cholesterol.
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Affiliation(s)
- J Luchoomun
- Service d'Etude et de Recherche sur les Lipoprotéines et l'Athérosclérose, INSERM U325, Institut Pasteur, Lille, France
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11
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Kraemer FB, Laane C, Park B, Sztalryd C. Low-density lipoprotein receptors in rat adipocytes: regulation with fasting. THE AMERICAN JOURNAL OF PHYSIOLOGY 1994; 266:E26-32. [PMID: 8304441 DOI: 10.1152/ajpendo.1994.266.1.e26] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
Adipose tissue metabolism is exquisitely sensitive to caloric intake. With increasing adiposity more triglyceride and cholesterol are stored within increasingly large adipocytes, whereas less triglyceride and cholesterol are stored as the size of the fat cell decreases. A portion of the uptake of cholesterol by adipocytes is mediated by low-density lipoprotein (LDL) receptors. The present studies addressed whether LDL receptors are differentially regulated in adipose tissue and the liver during fasting in the rat. Two days of fasting caused a reduction in body weight with an approximately 40% decrease in the epididymal fat depot and fat cell size. No changes in serum cholesterol were noted, but serum triglycerides fell approximately 55% with fasting. LDL receptors detected by immunoblotting decreased progressively with fasting to levels that were 95% below controls in adipocytes isolated from epididymal fat pads by 2-3 days. In contrast, hepatic LDL receptor expression was unaltered by fasting. After 2 days of fasting, the rate of synthesis of LDL receptors in isolated adipose cells was decreased approximately 35%, whereas levels of LDL receptor mRNA were diminished approximately 55%. It is concluded that the expression of LDL receptors in rat adipocytes is markedly downregulated during fasting through transcriptional and posttranscriptional mechanisms. Furthermore, LDL receptor expression is differentially regulated in adipose tissue and liver during fasting in the rat.
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Affiliation(s)
- F B Kraemer
- Veterans Affairs Medical Center, Palo Alto 94304
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12
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Duverger N, Rader D, Duchateau P, Fruchart JC, Castro G, Brewer HB. Biochemical characterization of the three major subclasses of lipoprotein A-I preparatively isolated from human plasma. Biochemistry 1993; 32:12372-9. [PMID: 8241125 DOI: 10.1021/bi00097a014] [Citation(s) in RCA: 47] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
Apolipoprotein (apo) A-I is the major protein constituent of plasma high-density lipoproteins (HDL). HDL consist of two major classes of apoA-I-containing lipoproteins: LpA-I and LpA-I:A-II. LpA-I includes heterogeneous lipoprotein particles that differ in size and hydrated density. LpA-I was isolated by immunoaffinity chromatography from the fasting plasma of 24 normal human subjects and separated by gel filtration chromatography. Three major subclasses of LpA-I were eluted: large (Lg-LpA-I), medium (Md-LpA-I), and small LpA-I (Sm-LpA-I). By nondenaturing gradient PAGE, Lg-LpA-I, Md-LpA-I, and Sm-LpA-I had mean Strokes diameters of 10.8 +/- 0.5, 8.9 +/- 0.5, and 7.5 +/- 0.3 nm, respectively. The lipid/protein ratios were 1.25 +/- 0.12 for Lg-LpA-I, 0.75 +/- 0.10 for Md-LpA-I, and 0.38 +/- 0.08 for Sm-LpA-I. Lg-LpA-I was relatively lipid and cholesteryl ester rich compared with Md-LpA-I and Sm-LpA-I. Sm-LpA-I contained phospholipids as the major lipid component. ApoA-I was the major apolipoprotein in all LpA-I subfractions, whereas apoE was present only in Lg-LpA-I and apoA-IV was associated with both Md-LpA-I and Sm-LpA-I. All three LpA-I subclasses exhibited predominantly alpha mobility on agarose electrophoresis. Lg-LpA-I migrated as a diffuse band in the fast alpha position, whereas Md-LpA-I and Sm-LpA-I migrated to the slow alpha position.(ABSTRACT TRUNCATED AT 250 WORDS)
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Affiliation(s)
- N Duverger
- Molecular Disease Branch, National Heart, Lung and Blood Institute, National Institutes of Health, Bethesda, Maryland 20892
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13
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Oikawa S, Mendez AJ, Oram JF, Bierman EL, Cheung MC. Effects of high-density lipoprotein particles containing apo A-I, with or without apo A-II, on intracellular cholesterol efflux. BIOCHIMICA ET BIOPHYSICA ACTA 1993; 1165:327-34. [PMID: 8418891 DOI: 10.1016/0005-2760(93)90144-x] [Citation(s) in RCA: 52] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
Previous reports have shown a differential effect of high-density lipoprotein (HDL) particles which contain apolipoprotein (apo) A-I without apo A-II (Lp A-I) and particles containing both apo A-I and apo A-II (Lp A-I/A-II) on cholesterol efflux from the mouse adipocyte cell line Ob1771, with Lp A-I and Lp A-I/A-II being active and inactive cholesterol efflux promotors, respectively. The present study was conducted to examine the roles of these two populations of apo-specific HDL particles on reverse cholesterol transport from cholesterol-loaded human skin fibroblasts and bovine aortic endothelial cells. The ability of HDL particles to remove intracellular cholesterol was tested by measuring depletion of the substrate pool for acylCoA:cholesterol acyltransferase (ACAT) and efflux of newly synthesized cholesterol, while removal of plasma membrane cholesterol was assessed by measuring efflux of [3H]cholesterol from prelabeled cells. Lp A-I and Lp A-I/A-II isolated from HDL2, HDL3 or plasma by immunoaffinity techniques each decreased esterification of cholesterol by both fibroblasts and endothelial cells. A mixture of Lp A-I and Lp A-I/A-II isolated from HDL3 decreased cholesterol esterification by fibroblasts in an additive manner, thus demonstrating that Lp A-I/A-II did not inhibit Lp A-I-mediated cholesterol efflux. Both Lp A-I and Lp A-I/A-II promoted efflux of sterol newly synthesized by fibroblasts, and no significant differences were observed between the apo-specific particles. Apo-specific particles were also similarly effective at preventing the accumulation of LDL-derived cholesterol in cholesterol-depleted fibroblasts. Efflux of [3H]cholesterol from plasma membranes was stimulated to similar extents by Lp A-I and Lp A-I/A-II isolated from either HDL2, HDL3 or plasma. Thus, the apo-specific HDL particles Lp A-I and Lp A-I/A-II are both effective promoters of cholesterol efflux from fibroblasts and aortic endothelial cells.
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Affiliation(s)
- S Oikawa
- Department of Medicine, University of Washington, Seattle
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14
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Vadiveloo PK, Fidge NH. The role of apoproteins AI and AII in binding of high-density lipoprotein3 to membranes derived from bovine aortic endothelial cells. Biochem J 1992; 284 ( Pt 1):145-51. [PMID: 1599393 PMCID: PMC1132709 DOI: 10.1042/bj2840145] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Although binding of high-density lipoproteins (HDL) to a variety of cells in culture has been widely reported, the mechanism of this binding has yet to be fully elucidated. The aim of the current studies was to explore the roles of apoproteins (apo) AI and AII in HDL3 binding to membranes derived from bovine aortic endothelial cells. Binding studies showed that HDL3 (which contains both apo AI and apo AII) and AII-HDL3 (which contain only apo AII) bound to membranes with similar affinity (44 +/- 6 and 41 +/- 9 micrograms/ml respectively) and capacity (673 +/- 97 and 969 +/- 101 ng bound/mg of membrane protein respectively). In contrast with these results, HDL3 [AI w/o AII] (which contain apo AI, but not apo AII) bound to the membranes with a significantly higher capacity (2228 +/- 206 ng bound/mg of membrane protein) and lower affinity (65 +/- 3 micrograms/ml) as compared with HDL3 or AII-HDL3. Therefore, although both apo AI and apo AII appear capable of facilitating HDL3 binding, the mechanisms involved probably differ. A model which fits the data postulates that a common receptor exists which binds both apo AI and apo AII, and that a particle containing AII can occupy up to four receptors (partly owing to each AII molecule containing two binding domains), whereas an HDL3 [AI w/o AII] particle can occupy only one.
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Affiliation(s)
- P K Vadiveloo
- Baker Medical Research Institute, Prahran, Victoria, Australia
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15
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Barkia A, Puchois P, Ghalim N, Torpier G, Barbaras R, Ailhaud G, Fruchart JC. Differential role of apolipoprotein AI-containing particles in cholesterol efflux from adipose cells. Atherosclerosis 1991; 87:135-46. [PMID: 1906713 DOI: 10.1016/0021-9150(91)90016-v] [Citation(s) in RCA: 66] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Cholesterol efflux was studied in cultured Ob1771 adipose cells after preloading with LDL cholesterol. Exposure to particles containing apo AII (LpAI) and particles containing apo AI and apo AII (LpAI:AII) isolated from native human plasma, and from HDL2 or HDL3, showed that only LpAI were able to promote cholesterol efflux, despite the fact that both kinds of particles were able to bind to receptor sites within the same range of concentrations (apparent Kd values between 10 and 25 micrograms/ml). During this long-term exposure, LpAI:AII demonstrated a concentration-dependent inhibition (10-60 micrograms/ml) of LpAI-mediated cholesterol efflux from adipose cells under conditions where LpAI:AII did not deliver cholesterol to the cells and where no net change in the distribution of apo AI between LpAI and LpAI:AII was observed. The antagonizing and modulating role of LpAI:AII in preventing cholesterol efflux mediated by LpAI appears not to be related to the lipid composition and cholesterol content of the particles but, rather, appears dependent upon the presence of apo AI in LpAI particles and apo AII in LpAI:AII particles. The actual concentrations of these particles in the interstitial fluid bathing peripheral cells might be critical for the in vivo occurrence of cholesterol efflux.
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Affiliation(s)
- A Barkia
- Institut Pasteur, SERLIA & INSERM U-325, Lille, France
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16
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Theret N, Delbart C, Aguie G, Fruchart JC, Vassaux G, Ailhaud G. Cholesterol efflux from adipose cells is coupled to diacylglycerol production and protein kinase C activation. Biochem Biophys Res Commun 1990; 173:1361-8. [PMID: 2268337 DOI: 10.1016/s0006-291x(05)80938-6] [Citation(s) in RCA: 59] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Apolipoprotein A-I (apo A-I)*/DMPC complexes have been previously shown to promote cholesterol efflux from cholesterol-preloaded adipose cells whereas apo A-II/DMPC complexes, which bind to the same cell surface binding sites, were ineffective. Addition of apo A-I/DMPC complexes led to a rapid and transient formation of diacylglycerol. However, in contrast to PGF2 alpha (Doglio et al., Proc. Natl. Acad. Sci. USA, 1989, 86, 1148), no accumulation of inositol phosphates was observed. Apo A-II/DMPC complexes had no effect on diacylglycerol formation. Stimulation by apo A-I/DMPC complexes or native HDL3 of cells prelabelled with (2-palmitoyl 9,10[3H])phosphatidylcholine induced also the formation of labelled diacylglycerol whereas apo A-II/DMPC complexes and HDL3 treated with tetranitromethane showed no effect. Direct activation of protein kinase C(s) by PMA promoted cholesterol efflux providing that DMPC liposomes were present as cholesterol acceptor. It is proposed that lipoprotein particles have two separate effects, i.e. a ligand-induced effect leading to cholesterol translocation from intracellular stores to the cell surface and a bilayer-induced effect allowing cholesterol efflux from the cell surface to the acceptor.
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Affiliation(s)
- N Theret
- SERLIA, U325 INSERM, Institut Pasteur, Lille, France
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Barbaras R, Puchois P, Pradines-Figuères A, Steinmetz A, Clavey V, Ghalim N, Fruchart JC, Ailhaud G. Binding of apolipoproteins A to adipose cells: role of receptor sites in cholesterol efflux and purification of binding protein(s). ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 1990; 285:85-92. [PMID: 1650121 DOI: 10.1007/978-1-4684-5904-3_11] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Affiliation(s)
- R Barbaras
- Centre de Biochimie, Parc Valrose, Nice, France
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Gurusinghe A, de Niese M, Renaud JF, Austin L. The binding of lipoproteins to human muscle cells: binding and uptake of LDL, HDL, and alpha-tocopherol. Muscle Nerve 1988; 11:1231-9. [PMID: 3237238 DOI: 10.1002/mus.880111207] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
The specific binding of low-density lipoprotein (LDL) to cells and its subsequent uptake into these cells is well documented, but little is known of the LDL binding and uptake by skeletal muscle. Lipoproteins are the major transporters of tocopherols, deficiencies of which have been associated with a number of muscle diseases of animals. Their possible implication in human muscle diseases prompted our investigation of LDL and high-density lipoprotein (HDL) binding and uptake into human muscle cells in culture. Cultured human muscle cells were used at both the myoblast and myotube stage. They were incubated with LDL or HDL which were labelled by protein iodination or with (3H) alpha-tocopherol and receptor binding and cell uptake characteristics established. LDL binds to both myoblasts and myotubes, but the binding affinity increases significantly with the more highly differentiated cells. This binding appears to be specific to LDL receptors. The LDL is taken into the muscle cell and protein is degraded, as with other types of cells. HDL also binds to muscle cells, but there is no evidence of internalization. alpha-Tocopherol is transferred to muscle cells from both LDL and HDL, but the transfer is not dependent on lipoprotein internalization. HDL is effective as a means of transport of alpha-tocopherol to muscle cells, but LDL appears to be about one order more effective.
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Affiliation(s)
- A Gurusinghe
- Department of Biochemistry, Monash University, Clayton, Australia
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Barbaras R, Puchois P, Grimaldi P, Barkia A, Fruchart JC, Ailhaud G. HDL receptor and reverse cholesterol transport in adipose cells. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 1988; 243:271-7. [PMID: 2851928 DOI: 10.1007/978-1-4613-0733-4_34] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Affiliation(s)
- R Barbaras
- Centre de Biochimie (CNRS), Parc Valrose, Nice, France
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Barbaras R, Puchois P, Grimaldi P, Barkia A, Fruchart JC, Ailhaud G. Relationship in adipose cells between the presence of receptor sites for high density lipoproteins and the promotion of reverse cholesterol transport. Biochem Biophys Res Commun 1987; 149:545-54. [PMID: 2827645 DOI: 10.1016/0006-291x(87)90402-5] [Citation(s) in RCA: 48] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
The role of a high-affinity receptor site for high-density lipoproteins (HDL) has been investigated in parental Ob1771 adipose cells and their transformed counterparts after transfer of the complete early region of polyoma virus (Ob17PY cells). Binding of ApoAI, ApoAII and HDL3 occurs in Ob1771 cells and derived membranes, whereas no binding is observed in Ob17PY cells and derived membranes. After thymidine block, growth-arrested Ob17PY cells become able to bind ApoAI, ApoAII and HDL3; this recovery is prevented in actinomycin D- or cycloheximide-treated cells. In contrast to ApoAI, ApoAII or HDL3 binding, both growing and growth-arrested Ob17PY cells do show receptor activities for low density lipoproteins and transferrin, respectively, which are similar in affinity and maximal capacity. Following cholesterol accumulation which takes place in the presence of LDL cholesterol, subsequent exposure to HDL3 or ApoAI promotes cholesterol efflux from Ob1771 cells and growth-arrested Ob17PY cells but not from growing Ob17PY cells. These results show that the presence of a high-affinity receptor site for HDL in intact adipose cells is required for the promotion of reverse cholesterol transport.
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Affiliation(s)
- R Barbaras
- Centre de Biochimie du CNRS, Faculté des Sciences, Nice, France
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Barbaras R, Grimaldi P, Negrel R, Ailhaud G. Characterization of high-density lipoprotein binding and cholesterol efflux in cultured mouse adipose cells. BIOCHIMICA ET BIOPHYSICA ACTA 1986; 888:143-56. [PMID: 3017445 DOI: 10.1016/0167-4889(86)90015-7] [Citation(s) in RCA: 60] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
Binding of high-density lipoproteins to cultured mouse Ob1771 adipose cells was studied, using labeled human HDL3, mouse HDL and apolipoprotein AI- or AII-containing liposomes. In each case, saturation curves were obtained, yielding linear Scatchard plots. The Kd values were found to be respectively 18, 42, 30 and 3.4 micrograms/ml, whereas the maximal binding capacities were found to be 160, 100, 90 and 21 ng/mg of cell protein. Apoprotein AI not inserted into liposomes did not bind. The binding of 125I-HDL3 was competitively inhibited by apolipoprotein AI-containing liposomes greater than mouse HDL greater than HDL3. The binding of 125I-labeled apolipoprotein AI- and 125I-labeled apolipoprotein AII-containing liposomes was competitively inhibited by HDL3, apolipoprotein AI- and apolipoprotein AII-containing liposomes. Dimyristoylphosphatidylcholine liposomes containing or not cholesterol did not interfere with the binding of labeled HDL3 or apolipoprotein-containing liposomes. Binding studies on crude membranes of Ob1771 adipose cells revealed the presence of intracellular binding sites for LDL and HDL3. Thus, adipose cells have specific binding sites for apolipoprotein E-free HDL and apolipoprotein AI (or AII) is the ligand for these binding sites. Long-term exposure of adipose cells to LDL cholesterol as a function of LDL concentration led to an accumulation of cellular unesterified cholesterol. This process was saturable and reversible as a function of time and concentration by exposure to HDL3 or apolipoprotein AI-containing liposomes, whereas apolipoprotein AII-containing liposomes did not promote any cholesterol efflux. Since long-term exposure of adipose cells to LDL and HDL3 did not affect the number of apolipoprotein B,E receptors and apolipoprotein E-free binding sites, respectively, it appears that adipose cells do not show efficient cholesterol homeostasis and thus could accumulate or mobilize unesterified cholesterol.
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Czerucka D, Grimaldi P, Ailhaud G. Transformation of Ob17 cells promotes proliferation and differentiation of Ob17 preadipocytes via distinct extracellular intermediates. Biochem Biophys Res Commun 1986; 137:378-87. [PMID: 3013189 DOI: 10.1016/0006-291x(86)91221-0] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
Conditioned serum-free medium of Ob17 cells transformed by the middle-T-only gene of polyoma virus (Ob17MT cells) is able to support growth and adipose conversion of the parental Ob17 cells. Conditioned media from 3T3-F442A cells (untransformed preadipocyte clonal line) and MTT4 cells (middle-T-transformed non-preadipocyte clonal line) are inactive. The serum-free conditioned medium of Ob17MT cells is also active on growth and adipose conversion of 3T3-F442A cells. The morphological differentiation of Ob17 cells is accompanied by the expression of early (lipoprotein lipase, LPL) and late (glycerol-3-phosphate dehydrogenase, GPDH) biochemical markers of adipose conversion. Bio-Gel P-60 chromatography and SDS-PAGE have allowed characterization of a mitogenic fraction of apparent MW approximately equal to 28 Kd distinct from an adipogenic fraction of apparent MW less than 10 Kd. This adipogenic fraction is only required for the acquisition of the GPDH activity and is therefore active on terminal differentiation.
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Nano JL, Barbaras R, Négrel R, Rampal P. Regulation of cholesterol synthesis and binding of lipoproteins in cultured rat intestinal epithelial cells. BIOCHIMICA ET BIOPHYSICA ACTA 1986; 876:72-9. [PMID: 3633199 DOI: 10.1016/0005-2760(86)90319-x] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
The regulation of cholesterol synthesis has been studied using a rat epithelial intestinal cell line (IRD 98) as a cellular model. As observed in other cell types, mevinolin increases the levels of 3-hydroxy-3-methylglutaryl coenzyme A reductase (EC 1.1.1.34) and concomitantly reduces the incorporation of [14C]acetate into cholesterol. Free cholesterol is able to suppress reductase activity. In contrast, when cells are shifted from standard culture medium to lipoprotein-deficient medium, an increase in hydroxymethylglutaryl-CoA reductase specific activity (2-5-fold) is observed. The possible regulatory roles of the different classes of human lipoproteins were thus compared. The effects of a long-term exposure to LDL and HDL vary according to cell density. In actively growing cells, VLDL and LDL cause a decrease in the level of hydroxymethylglutaryl-CoA reductase, whereas HDL do not have a significant effect. In contrast, in subconfluent preresting cells, HDL provoke large decreases in hydroxymethylglutaryl-CoA reductase activity as compared to VLDL and LDL. While LDL binding is constant, the maximal binding capacity of HDL in subconfluent cells is seven times that of actively growing cells. Altogether, these results suggest an important role for HDL in the regulation of intestinal cholesterol synthesis.
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