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Liu Y, Mihna D, Izem L, Morton RE. Both full length-cholesteryl ester transfer protein and exon 9-deleted cholesteryl ester transfer protein promote triacylglycerol storage in cultured hepatocytes. Lipids 2022; 57:69-79. [PMID: 34866179 PMCID: PMC9060302 DOI: 10.1002/lipd.12330] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2021] [Revised: 11/22/2021] [Accepted: 11/23/2021] [Indexed: 01/03/2023]
Abstract
We previously reported that overexpression of full-length cholesteryl ester transfer protein (FL-CETP), but not its exon 9-deleted variant (∆E9-CETP), in an adipose cell line reduces their triacylglycerol (TAG) content. This provided mechanistic insight into several in vivo studies where FL-CETP levels are inversely correlated with adiposity. However, increased FL-CETP is also associated with elevated hepatic lipids, suggesting that the effect of CETP on cellular lipid metabolism may be tissue-specific. Here, we directly investigated the role of FL-CETP and ∆E9-CETP in hepatic lipid metabolism. FL- or ∆E9-CETP was overexpressed in HepG2-C3A by adenovirus transduction. Overexpression of either FL or ∆E9-CETP in hepatocytes increased cellular TAG mass by 25% but reduced TAG secretion. This cellular TAG was contained in larger and more numerous lipid droplets. Analysis of TAG synthetic and catabolic pathways showed that this elevated TAG content was due to increased incorporation of fatty acid into TAG (24%), and higher de novo synthesis of fatty acid (50%) and TAG from acetate (40%). siRNA knockdown of CETP had the opposite effect on TAG synthesis and lipogenesis, and decreased cellular TAG. This novel increase in cellular TAG by FL-CETP overexpression was reproduced in Caco-2 intestinal epithelial cells. We conclude that, unlike that seen in adipocyte cells, overexpression of either CETP isoform in lipoprotein-secreting cells promotes the accumulation of TAG. These data suggest that the in vivo correlation between CETP levels and hepatic steatosis can be explained, in part, by a direct effect of CETP on hepatocyte cellular metabolism.
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Affiliation(s)
- Yan Liu
- Department of Cardiovascular and Metabolic Sciences, Lerner Research Institute, Cleveland Clinic Foundation, Cleveland, Ohio, USA
| | - Daniel Mihna
- Department of Cardiovascular and Metabolic Sciences, Lerner Research Institute, Cleveland Clinic Foundation, Cleveland, Ohio, USA
| | - Lahoucine Izem
- Department of Cardiovascular and Metabolic Sciences, Lerner Research Institute, Cleveland Clinic Foundation, Cleveland, Ohio, USA
| | - Richard E Morton
- Department of Cardiovascular and Metabolic Sciences, Lerner Research Institute, Cleveland Clinic Foundation, Cleveland, Ohio, USA
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Raposo HF, Forsythe P, Chausse B, Castelli JZ, Moraes-Vieira PM, Nunes VS, Oliveira HCF. Novel role of cholesteryl ester transfer protein (CETP): attenuation of adiposity by enhancing lipolysis and brown adipose tissue activity. Metabolism 2021; 114:154429. [PMID: 33166579 DOI: 10.1016/j.metabol.2020.154429] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/29/2020] [Revised: 10/13/2020] [Accepted: 11/04/2020] [Indexed: 01/07/2023]
Abstract
OBJECTIVE The systemic function of CETP has been well characterized. CETP plasma activity reduces HDL cholesterol and thus increases the risk of atherosclerosis. Here, we investigated whether CETP expression modulate adiposity. METHODS Body adiposity and energy metabolism related assays and gene/protein expression were compared in CETP transgenic and non-transgenic mice and in hamsters treated with CETP neutralizing antibody. RESULTS We found that transgenic mice expressing human CETP present less white adipose tissue mass and lower leptinemia than nontransgenic (NTg) littermates. No differences were found in physical activity, food intake, fat fecal excretion, lipogenesis or exogenous lipid accumulation in adipose depots. Nonetheless, adipose lipolysis rates and whole-body energy expenditure were elevated in CETP mice. In accordance, lipolysis-related gene expression and protein content were increased in visceral and brown adipose tissue (BAT). In addition, we verified increased BAT temperature and oxygen consumption. These results were confirmed in two other animal models: 1) hamsters treated with CETP neutralizing antibody and 2) an independent line of transgenic mice expressing simian CETP. CONCLUSIONS These findings reveal a novel anti-adipogenic role for CETP.
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Affiliation(s)
- Helena F Raposo
- Department of Structural and Functional Biology, Institute of Biology, State University of Campinas, Campinas, SP, Brazil; Obesity and Comorbidities Research Center, Institute of Biology, State University of Campinas, Campinas, SP, Brazil
| | - Patricia Forsythe
- Department of Structural and Functional Biology, Institute of Biology, State University of Campinas, Campinas, SP, Brazil
| | - Bruno Chausse
- Obesity and Comorbidities Research Center, Institute of Biology, State University of Campinas, Campinas, SP, Brazil
| | - Júlia Z Castelli
- Department of Structural and Functional Biology, Institute of Biology, State University of Campinas, Campinas, SP, Brazil; Obesity and Comorbidities Research Center, Institute of Biology, State University of Campinas, Campinas, SP, Brazil
| | - Pedro M Moraes-Vieira
- Obesity and Comorbidities Research Center, Institute of Biology, State University of Campinas, Campinas, SP, Brazil; Laboratory of Immunometabolism, Department of Genetics, Evolution, Microbiology and Immunology, Institute of Biology, State University of Campinas, Campinas, SP, Brazil; Experimental Medicine Research Cluster (EMRC), State University of Campinas, SP, Brazil
| | - Valéria S Nunes
- Laboratorio de Lipides (LIM10), Hospital das Clínicas HCFMUSP, Faculdade de Medicina, Universidade de Sao Paulo, Sao Paulo, SP, Brazil
| | - Helena C F Oliveira
- Department of Structural and Functional Biology, Institute of Biology, State University of Campinas, Campinas, SP, Brazil; Obesity and Comorbidities Research Center, Institute of Biology, State University of Campinas, Campinas, SP, Brazil.
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Ueland T, Roland MCP, Michelsen AE, Godang K, Aukrust P, Henriksen T, Bollerslev J, Lekva T. Elevated Cholesteryl Ester Transfer Protein Activity Early in Pregnancy Predicts Prediabetes 5 Years Later. J Clin Endocrinol Metab 2020; 105:5608982. [PMID: 31665383 DOI: 10.1210/clinem/dgz119] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/23/2019] [Accepted: 10/08/2019] [Indexed: 11/19/2022]
Abstract
CONTEXT Cholesteryl ester transfer protein (CETP) regulates high-density lipoprotein (HDL) cholesterol levels and interaction between glucose, and HDL metabolism is central in the development of diabetes. OBJECTIVE We hypothesized that CETP levels would be regulated in diabetic pregnancies. We tested the hypothesis by evaluating CETP activity measured multiple times during pregnancy and at 5 years' follow-up in a prospective cohort (STORK) and investigated its association with gestational diabetes mellitus (GDM) during pregnancy or development of prediabetes 5 years after pregnancy. We also evaluated the strongest correlation of CETP activity among measures of adipocity and glucose metabolism, lipoproteins, adipokines, and monocyte/macrophage activation markers. DESIGN A population-based longitudinal cohort study was conducted from 2001 to 2013. SETTING The study setting was Oslo University Hospital. PATIENTS OR OTHER PARTICIPANTS A total of 300 women during pregnancy and at 5 years postpartum participated in this study. MAIN OUTCOME MEASURES CETP activity was measured at 14 to 16, 22 to 24, 30 to 32, and 36 to 38 weeks' gestation, and at 5 years' follow-up. RESULTS We found higher CETP activity in pregnancy in women developing prediabetes but no association with GDM. CETP activity decreased throughout pregnancy and remained low at follow-up. High CETP activity was associated with sCD14 levels, in particular in women who developed prediabetes. These data show that enhanced CETP activity during pregnancy is associated with systemic indices of monocyte/macrophage activation, in particular in women who develop prediabetes later in life. CONCLUSIONS CETP activity during pregnancy identifies women at risk for later diabetes development.
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Affiliation(s)
- Thor Ueland
- Research Institute of Internal Medicine, Oslo University Hospital, Rikshospitalet, Oslo, Norway
- Faculty of Medicine; University of Oslo, Oslo, Norway
- K.G. Jebsen Thrombosis Research and Expertise Center, University of Tromsø, Tromsø, Norway
| | - Marie Cecilie Paasche Roland
- National Advisory Unit for Women's Health; Oslo University Hospital, Rikshospitalet, Oslo, Norway
- Department of Obstetrics, Oslo University Hospital, Rikshospitalet, Oslo, Norway
| | - Annika E Michelsen
- Research Institute of Internal Medicine, Oslo University Hospital, Rikshospitalet, Oslo, Norway
- Faculty of Medicine; University of Oslo, Oslo, Norway
| | - Kristin Godang
- Section of Specialized Endocrinology, Department of Endocrinology, Oslo University Hospital, Rikshospitalet, Oslo, Norway
| | - Pål Aukrust
- Research Institute of Internal Medicine, Oslo University Hospital, Rikshospitalet, Oslo, Norway
- Faculty of Medicine; University of Oslo, Oslo, Norway
- K.G. Jebsen Thrombosis Research and Expertise Center, University of Tromsø, Tromsø, Norway
- Section of Clinical Immunology and Infectious Diseases, Oslo University Hospital, Rikshospitalet, Oslo, Norway
- K.G. Jebsen Inflammatory Research Center, University of Oslo, Oslo, Norway
| | - Tore Henriksen
- Faculty of Medicine; University of Oslo, Oslo, Norway
- Department of Obstetrics, Oslo University Hospital, Rikshospitalet, Oslo, Norway
| | - Jens Bollerslev
- Faculty of Medicine; University of Oslo, Oslo, Norway
- Section of Specialized Endocrinology, Department of Endocrinology, Oslo University Hospital, Rikshospitalet, Oslo, Norway
| | - Tove Lekva
- Research Institute of Internal Medicine, Oslo University Hospital, Rikshospitalet, Oslo, Norway
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Izem L, Liu Y, Morton RE. Exon 9-deleted CETP inhibits full length-CETP synthesis and promotes cellular triglyceride storage. J Lipid Res 2020; 61:422-431. [PMID: 31988147 DOI: 10.1194/jlr.ra120000583] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2020] [Revised: 01/27/2020] [Indexed: 11/20/2022] Open
Abstract
Cholesteryl ester transfer protein (CETP) exists as full-length (FL) and exon 9 (E9)-deleted isoforms. The function of E9-deleted CETP is poorly understood. Here, we investigated the role of E9-deleted CETP in regulating the secretion of FL-CETP by cells and explored its possible role in intracellular lipid metabolism. CETP overexpression in cells that naturally express CETP confirmed that E9-deleted CETP is not secreted, and showed that cellular FL- and E9-deleted CETP form an isolatable complex. Coexpression of CETP isoforms lowered cellular levels of both proteins and impaired FL-CETP secretion. These effects were due to reduced synthesis of both isoforms; however, the predominate consequence of FL- and E9-deleted CETP coexpression is impaired FL-CETP synthesis. We reported previously that reducing both CETP isoforms or overexpressing FL-CETP impairs cellular triglyceride (TG) storage. To investigate this further, E9-deleted CETP was expressed in SW872 cells that naturally synthesize CETP and in mouse 3T3-L1 cells that do not. E9-deleted CETP overexpression stimulated SW872 triglyceride synthesis and increased stored TG 2-fold. Expression of E9-deleted CETP in mouse 3T3-L1 cells produced a similar lipid phenotype. In vitro, FL-CETP promotes the transfer of TG from ER-enriched membranes to lipid droplets. E9-deleted CETP also promoted this transfer, although less effectively, and it inhibited the transfer driven by FL-CETP. We conclude that FL- and E9-deleted CETP isoforms interact to mutually decrease their intracellular levels and impair FL-CETP secretion by reducing CETP biosynthesis. E9-deleted CETP, like FL-CETP, alters cellular TG metabolism and storage but in a contrary manner.
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Affiliation(s)
- Lahoucine Izem
- Department of Cardiovascular and Metabolic Sciences, Lerner Research Institute, Cleveland Clinic Foundation, Cleveland, OH 44195
| | - Yan Liu
- Department of Cardiovascular and Metabolic Sciences, Lerner Research Institute, Cleveland Clinic Foundation, Cleveland, OH 44195
| | - Richard E Morton
- Department of Cardiovascular and Metabolic Sciences, Lerner Research Institute, Cleveland Clinic Foundation, Cleveland, OH 44195
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Oliveira HCF, Raposo HF. Cholesteryl Ester Transfer Protein and Lipid Metabolism and Cardiovascular Diseases. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2020; 1276:15-25. [PMID: 32705591 DOI: 10.1007/978-981-15-6082-8_2] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
In this chapter, we present the major advances in CETP research since the detection, isolation, and characterization of its activity in the plasma of humans and several species. Since CETP is a major modulator of HDL plasma levels, the clinical importance of CETP activity was recognized very early. We describe the participation of CETP in reverse cholesterol transport, conflicting results in animal and human genetic studies, possible new functions of CETP, and the results of the main clinical trials on CETP inhibition. Despite major setbacks in clinical trials, the hypothesis that CETP inhibitors are anti-atherogenic in humans is still being tested.
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Affiliation(s)
- Helena C F Oliveira
- Department of Structural and Functional Biology, Biology Institute, State University of Campinas, Campinas, SP, Brazil.
| | - Helena F Raposo
- Department of Structural and Functional Biology, Biology Institute, State University of Campinas, Campinas, SP, Brazil
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Johns DG, Wang S, Rosa R, Hubert J, Xu S, Chen Y, Bateman T, Blaustein RO. Impact of drug distribution into adipose on tissue function: The cholesteryl ester transfer protein (CETP) inhibitor anacetrapib as a test case. Pharmacol Res Perspect 2019; 7:e00543. [PMID: 31832204 PMCID: PMC6857080 DOI: 10.1002/prp2.543] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2019] [Revised: 10/11/2019] [Accepted: 10/15/2019] [Indexed: 12/28/2022] Open
Abstract
Anacetrapib is an inhibitor of cholesteryl ester transfer protein (CETP) previously under development as a lipid-modifying agent that reduces LDL-cholesterol and increases HDL-cholesterol in hypercholesterolemic patients. Anacetrapib demonstrates a long terminal half-life and accumulates in adipose tissue, which contributes to a long residence time of anacetrapib. Given our previous report that anacetrapib distributes into the lipid droplet of adipose tissue, we sought to understand whether anacetrapib affected adipose function, using a diet-induced obese (DIO) mouse model. Following 20 weeks of treatment with anacetrapib (100 mg/kg/day), levels of the drug increased to approximately 0.6 mmol/L in white adipose tissue. This level of anacetrapib was not associated with any impairment in adipose functionality as evidenced by a lack of any reduction in biomarkers of adipose functionality (plasma adiponectin, leptin, insulin; adipose adiponectin, leptin mRNA). In DIO wild-type (WT) mice treated with anacetrapib for 2 weeks and then subjected to 30% food restriction during washout to induce weight loss (18%) and fat mass loss (7%), levels of anacetrapib in adipose and plasma were not different between food restricted and ad lib-fed mice. These data indicate that despite deposition and long-term residence of ~0.6 mmol/L levels of anacetrapib in adipose tissue, adipose tissue function appears to be unaffected in mice. In addition, these data also indicate that even with severe caloric restriction and acute loss of fat mass, anacetrapib does not appear to be mobilized from the fat depot, thereby solidifying the role of adipose as a long-term storage site of anacetrapib.
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Affiliation(s)
- Douglas G. Johns
- Department of Translational PharmacologyMerck & Co., Inc.KenilworthNJUSA
| | - Sheng‐Ping Wang
- Department of Cardiometabolic Diseases/AtherosclerosisMerck & Co., Inc.KenilworthNJUSA
| | - Raymond Rosa
- Department of Cardiometabolic Diseases/AtherosclerosisMerck & Co., Inc.KenilworthNJUSA
| | - James Hubert
- Department of Cardiometabolic Diseases/AtherosclerosisMerck & Co., Inc.KenilworthNJUSA
| | - Suoyu Xu
- Department of Pharmacokinetics, Pharmacodynamics and Drug MetabolismMerck & Co., Inc.KenilworthNJUSA
| | - Ying Chen
- Department of Cardiometabolic Diseases/AtherosclerosisMerck & Co., Inc.KenilworthNJUSA
| | - Thomas Bateman
- Department of Pharmacokinetics, Pharmacodynamics and Drug MetabolismMerck & Co., Inc.KenilworthNJUSA
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Chen D, Huang X, Zhou H, Luo H, Wang P, Chang Y, He X, Ni S, Shen Q, Cao G, Sun H, Wen X, Liu J. Discovery of pentacyclic triterpene 3β-ester derivatives as a new class of cholesterol ester transfer protein inhibitors. Eur J Med Chem 2017; 139:201-213. [DOI: 10.1016/j.ejmech.2017.08.012] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2017] [Revised: 07/08/2017] [Accepted: 08/03/2017] [Indexed: 01/06/2023]
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8
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Guo W, Gong Y, Fu Z, Fu J, Sun Y, Ju X, Chang Y, Wang W, Zhu X, Gao B, Liu X, Yang T, Zhou H. The effect of cholesteryl ester transfer protein on pancreatic beta cell dysfunction in mice. Nutr Metab (Lond) 2016; 13:21. [PMID: 26973702 PMCID: PMC4788865 DOI: 10.1186/s12986-016-0082-1] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2015] [Accepted: 03/06/2016] [Indexed: 12/25/2022] Open
Abstract
BACKGROUND Cholesterol accumulation causes pancreatic beta cell lipotoxicity and dysfunction. Cholesteryl ester transfer protein (CETP) plays an important role in blood lipid homeostasis. However, its role in tissue lipid metabolism remains unclear. We hypothesized that plasma CETP impact cholesterol homeostasis in the beta cells, thus damaging their functions. METHODS The adipose tissue-specific CETP expression transgenic (aP2-CETPTg) mice, characterized by high CETP levels in the circulation, were used in this study. Pancreatic islet cholesterol and beta cell function were assessed in mice. We further measured mRNA levels of the genes involved in beta cell proliferation and differentiation, inflammation and cholesterol metabolism. TUNEL assay was applied to investigate beta cell apoptosis in islets. RESULTS The aP2-CETPTg mice exhibited glucose intolerance, lower plasma insulin concentrations but increased insulin sensitivity compared with wild type mice. In addition, glucose-stimulated insulin secretion from isolated pancreatic islets significantly decreased, and free cholesterol significantly increased. Moreover, the number and size of islets from aP2-CETPTg mice were significantly decreased. Genes involved in beta cell proliferation, such as Pdx1 and BETA2, were down-regulated; genes involved in inflammation and ER stress, such as IL-1β, CHOP, and Xbp1 were up-regulated, in line with an increase of beta cell apoptosis. CONCLUSIONS Plasma CETP causes free cholesterol accumulation in islets which could contribute to beta cell dysfunction. Thus, CETP inhibition could be a novel protective strategy for dyslipidemia related to diabetes and obese.
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Affiliation(s)
- Wen Guo
- Department of Endocrinology, the First Affiliated Hospital of Nanjing Medical University, 300 Guangzhou Road, Nanjing, 210029 China
| | - Yingyun Gong
- Department of Endocrinology, the First Affiliated Hospital of Nanjing Medical University, 300 Guangzhou Road, Nanjing, 210029 China
| | - Zhenzhen Fu
- Department of Endocrinology, the First Affiliated Hospital of Nanjing Medical University, 300 Guangzhou Road, Nanjing, 210029 China
| | - Jinxiang Fu
- Department of Endocrinology, the First Affiliated Hospital of Nanjing Medical University, 300 Guangzhou Road, Nanjing, 210029 China
| | - Yan Sun
- Department of Endocrinology, the First Affiliated Hospital of Nanjing Medical University, 300 Guangzhou Road, Nanjing, 210029 China
| | - Xianxia Ju
- Department of Endocrinology, the First Affiliated Hospital of Nanjing Medical University, 300 Guangzhou Road, Nanjing, 210029 China
| | - Yina Chang
- Department of Endocrinology, the First Affiliated Hospital of Nanjing Medical University, 300 Guangzhou Road, Nanjing, 210029 China
| | - Wen Wang
- Department of Endocrinology, the First Affiliated Hospital of Nanjing Medical University, 300 Guangzhou Road, Nanjing, 210029 China
| | - Xiaohui Zhu
- Department of Endocrinology, the First Affiliated Hospital of Nanjing Medical University, 300 Guangzhou Road, Nanjing, 210029 China
| | - Beibei Gao
- Department of Endocrinology, the First Affiliated Hospital of Nanjing Medical University, 300 Guangzhou Road, Nanjing, 210029 China
| | - Xiaoyun Liu
- Department of Endocrinology, the First Affiliated Hospital of Nanjing Medical University, 300 Guangzhou Road, Nanjing, 210029 China
| | - Tao Yang
- Department of Endocrinology, the First Affiliated Hospital of Nanjing Medical University, 300 Guangzhou Road, Nanjing, 210029 China
| | - Hongwen Zhou
- Department of Endocrinology, the First Affiliated Hospital of Nanjing Medical University, 300 Guangzhou Road, Nanjing, 210029 China
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Greene DJ, Izem L, Morton RE. Defective triglyceride biosynthesis in CETP-deficient SW872 cells. J Lipid Res 2015. [PMID: 26203075 DOI: 10.1194/jlr.m056481] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
We previously reported that reducing the expression of cholesteryl ester transfer protein (CETP) disrupts cholesterol homeostasis in SW872 cells and causes an ∼50% reduction in TG. The causes of this reduced TG content, investigated here, could not be attributed to changes in the differentiation status of CETP-deficient cells, nor was there evidence of endoplasmic reticulum (ER) stress. In short-term studies, the total flux of oleate through the TG biosynthetic pathway was not altered in CETP-deficient cells, although mRNA levels of some pathway enzymes were different. However, the conversion of diglyceride (DG) to TG was impaired. In longer-term studies, newly synthesized TG was not effectively transported to lipid droplets, yet this lipid did not accumulate in the ER, apparently due to elevated lipase activity in this organelle. DG, shown to be a novel CETP substrate, was also inefficiently transferred to lipid droplets. This may reduce TG synthesis on droplets by resident diacylglycerol acyltransferase. Overall, these data suggest that the decreased TG content of CETP-deficient cells arises from the reduced conversion of DG to TG in the ER and/or on the lipid droplet surface, and enhanced TG degradation in the ER due to its ineffective transport from this organelle.
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Affiliation(s)
- Diane J Greene
- Department of Cellular and Molecular Medicine, Lerner Research Institute, Cleveland Clinic Foundation, Cleveland, OH 44195
| | - Lahoucine Izem
- Department of Cellular and Molecular Medicine, Lerner Research Institute, Cleveland Clinic Foundation, Cleveland, OH 44195
| | - Richard E Morton
- Department of Cellular and Molecular Medicine, Lerner Research Institute, Cleveland Clinic Foundation, Cleveland, OH 44195
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10
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Murphy AJ, Yvan-Charvet L. Adipose modulation of ABCG1 uncovers an intimate link between sphingomyelin and triglyceride storage. Diabetes 2015; 64:689-92. [PMID: 25713191 DOI: 10.2337/db14-1553] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Affiliation(s)
- Andrew J Murphy
- Baker IDI Heart and Diabetes Institute, Melbourne, Australia
| | - Laurent Yvan-Charvet
- Institut National de la Santé et de la Recherche Médicale U1065, Centre Mediterranéen de Médecine Moléculaire, Nice, France
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Izem L, Greene DJ, Bialkowska K, Morton RE. Overexpression of full-length cholesteryl ester transfer protein in SW872 cells reduces lipid accumulation. J Lipid Res 2015; 56:515-525. [PMID: 25593327 DOI: 10.1194/jlr.m053678] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
Abstract
Cells produce two cholesteryl ester transfer protein (CETP) isoforms, full-length and a shorter variant produced by alternative splicing. Blocking synthesis of both isoforms disrupts lipid metabolism and storage. To further define the role of CETP in cellular lipid metabolism, we stably overexpressed full-length CETP in SW872 cells. These CETP(+) cells had several-fold higher intracellular CETP and accumulated 50% less TG due to a 26% decrease in TG synthesis and 2.5-fold higher TG turnover rate. Reduced TG synthesis was due to decreased fatty acid uptake and impaired conversion of diglyceride to TG even though diacylglycerol acyltransferase activity was normal. Sterol-regulatory element binding protein 1 mRNA levels were normal, and although PPARγ expression was reduced, the expression of several of its target genes including adipocyte triglyceride lipase, FASN, and APOE was normal. CETP(+) cells contained smaller lipid droplets, consistent with their higher levels of perilipin protein family (PLIN) 3 compared with PLIN1 and PLIN2. Intracellular CETP was mostly associated with the endoplasmic reticulum, although CETP near lipid droplets poorly colocalized with this membrane. A small pool of CETP resided in the cytoplasm, and a subfraction coisolated with lipid droplets. These data show that overexpression of full-length CETP disrupts lipid homeostasis resulting in the formation of smaller, more metabolically active lipid droplets.
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Affiliation(s)
- Lahoucine Izem
- Department of Cellular and Molecular Medicine, Lerner Research Institute, Cleveland Clinic Foundation, Cleveland, OH 44195
| | - Diane J Greene
- Department of Cellular and Molecular Medicine, Lerner Research Institute, Cleveland Clinic Foundation, Cleveland, OH 44195
| | - Katarzyna Bialkowska
- Department of Molecular Cardiology, Lerner Research Institute, Cleveland Clinic Foundation, Cleveland, OH 44195
| | - Richard E Morton
- Department of Cellular and Molecular Medicine, Lerner Research Institute, Cleveland Clinic Foundation, Cleveland, OH 44195.
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McEneny J, Blair S, Woodside JV, Murray L, Boreham C, Young IS. High-density lipoprotein subfractions display proatherogenic properties in overweight and obese children. Pediatr Res 2013; 74:279-83. [PMID: 23884162 DOI: 10.1038/pr.2013.93] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/10/2012] [Accepted: 12/29/2012] [Indexed: 11/09/2022]
Abstract
BACKGROUND In adults, obesity-driven inflammation can lead to increased cardiovascular disease (CVD). However, information regarding childhood obesity and its inflammatory sequelae is less well defined. Serum amyloid-A (SAA) is an inflammatory molecule that rapidly associates with high-density lipoproteins (HDLs) and renders them dysfunctional. Therefore, SAA may be a useful biomarker to identify increased CVD potential in overweight and obese children. METHODS Young Hearts 2000 is a cross-sectional cohort study in which 92 children who were obese were matched for age and sex with 92 overweight and 92 lean children. HDL(2) and HDL(3) (HDL(2&3)) were isolated from plasma by a three-step rapid-ultracentrifugation procedure. SAA was measured in serum and HDL(2&3) by an enzyme-linked immunosorbent assay procedure, and the activities of cholesterol ester transfer protein (CETP) and lecithin cholesteryl acyltransferase (LCAT) were measured by fluorimetric assays. RESULTS Trends across the groups indicated that SAA increased in serum and HDL(2&3) as BMI increased, as did HDL(2)-CETP and HDL(2)-LCAT activities. CONCLUSION These results have provided evidence that overweight and obese children are exposed to an inflammatory milieu that impacts the antiatherogenic properties of HDL and that could increase CVD risk. This supports the concept that it is important to target childhood obesity to help minimize future cardiovascular events.
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Affiliation(s)
- Jane McEneny
- Centre for Public Health, Nutrition and Metabolism Group, Queen's University Belfast, Belfast, UK.
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van de Woestijne AP, Monajemi H, Kalkhoven E, Visseren FLJ. Adipose tissue dysfunction and hypertriglyceridemia: mechanisms and management. Obes Rev 2011; 12:829-40. [PMID: 21749607 DOI: 10.1111/j.1467-789x.2011.00900.x] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Elevated plasma triglyceride levels, as often seen in obese subjects, are independently associated with an increased risk of cardiovascular diseases. By secreting adipokines (such as adiponectin and leptin) and other proteins (such as lipoprotein lipase and cholesteryl ester transferase protein), adipose tissue affects triglyceride metabolism. In obesity, adipocyte hypertrophy leads to many changes in adipocyte function and production of anti- and pro-inflammatory cytokines. Furthermore, free fatty acids are released into the circulation contributing to insulin resistance. Adipose tissue dysfunction will eventually lead to abnormalities in lipid metabolism, such as hypertriglyceridemia (due to increased hepatic very-low-density lipoprotein production and decreased triglyceride hydrolysis), small dense low-density lipoprotein particles, remnant lipoproteins and low high-density lipoprotein cholesterol levels, all associated with a higher risk for the development of cardiovascular diseases. The clinical implications of elevated plasma triglycerides are still a matter of debate. Understanding the pathophysiology of adipose tissue dysfunction in obesity, which is becoming a pandemic condition, is essential for designing appropriate therapeutic interventions. Lifestyle changes are important to improve adipose tissue function in obese patients. Pharmacological interventions to improve adipose tissue function need further evaluation. Although statins are not very potent in reducing plasma triglycerides, they remain the mainstay of therapy for cardiovascular risk reduction in high-risk patients.
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Affiliation(s)
- A P van de Woestijne
- Department of Vascular Medicine, University Medical Center, Utrecht, the Netherlands Department of Metabolic and Endocrine Diseases, University Medical Center, Utrecht, the Netherlands
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Ju X, Cui Q, Zhang M, Wang W, Jiang J, Chang Y, Wang K, Yang T, Zhou H. Human cholesteryl ester transfer protein enhances insulin-mediated glucose uptake in adipocytes. Life Sci 2011; 89:479-84. [PMID: 21816162 DOI: 10.1016/j.lfs.2011.07.014] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2011] [Revised: 07/08/2011] [Accepted: 07/16/2011] [Indexed: 10/17/2022]
Abstract
AIMS Adipose tissue plays an important role in the pathogenesis of insulin resistance, obesity, and Type-2 diabetes. Human adipocytes express abundant cholesteryl ester transfer protein (CETP). However, the function and role of CETP in regulating lipoprotein metabolism are mostly unknown. In this study, we examined whether CETP affected the insulin-mediated responses in adipocytes. MAIN METHODS Because mouse 3T3-L1 preadipocytes do not express CETP, we established a stable cell line expressing human CETP by transfecting the cells with pcDNA3.1/human CETP. We used a standard approach to differentiate the cells into mature adipocytes, and we examined the cholesterol balance and insulin responses. KEY FINDINGS The human CETP stable cell line expressed stable levels of CETP without affecting the expression of either peroxisome proliferator-activated receptor-gamma (PPARγ) or glucose transporter-4 (GLUT4) throughout cell differentiation. CETP expression significantly increased the level of both total and free cholesterol in the mature adipocytes. Upon insulin stimulation, CETP expressing cells had significantly higher protein kinase B (Akt) phosphorylation and 2-(3)H-deoxyglucose uptake, as compared with 3T3-L1 cells and cells transfected with control vector. SIGNIFICANCE Human CETP expression increased cellular cholesterol levels and enhanced insulin-stimulated Akt phosphorylation and glucose uptake in adipocytes. Thus, CETP may modulate glucose metabolism and insulin action in addition to its effects on lipoprotein metabolism.
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Affiliation(s)
- Xianxia Ju
- Department of Endocrinology, The First Affiliated Hospital, Nanjing Medical University, Nanjing, PR China
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15
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Povel CM, Boer JMA, Imholz S, Dollé MET, Feskens EJM. Genetic variants in lipid metabolism are independently associated with multiple features of the metabolic syndrome. Lipids Health Dis 2011; 10:118. [PMID: 21767357 PMCID: PMC3156750 DOI: 10.1186/1476-511x-10-118] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2011] [Accepted: 07/18/2011] [Indexed: 12/05/2022] Open
Abstract
Background Our objective was to find single nucleotide polymorphisms (SNPs), within transcriptional pathways of glucose and lipid metabolism, which are related to multiple features of the metabolic syndrome (MetS). Methods 373 SNPs were measured in 3575 subjects of the Doetinchem cohort. Prevalence of MetS features, i.e. hyperglycemia, abdominal obesity, decreased HDL-cholesterol levels and hypertension, were measured twice in 6 years. Associations between the SNPs and the individual MetS features were analyzed by log-linear models. For SNPs related to multiple MetS features (P < 0.01), we investigated whether these associations were independent of each other. Results Two SNPs, CETP Ile405Val and APOE Cys112Arg, were associated with both the prevalence of low HDL-cholesterol level (Ile405Val P = < .0001; Cys112Arg P = 0.001) and with the prevalence of abdominal obesity (Ile405Val P = 0.007; Cys112Arg P = 0.007). For both SNPs, the association with HDL-cholesterol was partly independent of the association with abdominal obesity and vice versa. Conclusion Two SNPs, mainly known for their role in lipid metabolism, were associated with two MetS features i.e., low HDL-cholesterol concentration, as well as, independent of this association, abdominal obesity. These SNPs may help to explain why low HDL-cholesterol levels and abdominal obesity frequently co-occur.
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Affiliation(s)
- Cécile M Povel
- Centre for Nutrition and Health, National Institute for Public Health and the Environment, Bilthoven, the Netherlands.
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16
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Zachariah JP, Pencina MJ, Lyass A, Kaur G, D'Agostino RB, Ordovas JM, Vasan RS. Circulating plasma cholesteryl ester transfer protein activity and blood pressure tracking in the community. J Hypertens 2011; 29:863-8. [PMID: 21430561 PMCID: PMC3204923 DOI: 10.1097/hjh.0b013e3283450223] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
OBJECTIVE Clinical trials using cholesteryl ester transfer protein (CETP) inhibitors to raise high-density lipoprotein cholesterol (HDL-C) concentrations reported an 'off-target' blood pressure (BP) raising effect. We evaluated the relations of baseline plasma CETP activity and longitudinal BP change. METHODS AND RESULTS One thousand, three hundred and seven Framingham Study participants free of cardiovascular disease attending consecutive examinations 4 years apart (mean age 48 years) had baseline plasma CETP activity related to change in BP over the 4-year interval, adjusting for standard risk factors. Systolic BP increased [median +2 mmHg, 95% confidence interval (CI) -16,+23 mmHg], whereas diastolic BP decreased (median -3 mmHg, 95% CI -15,+11 mmHg). Plasma CETP activity was not related to change in diastolic BP, but was inversely related to change in systolic BP that was borderline significant (P=0.09). On multivariable analyses, plasma CETP activity was inversely related to change in pulse pressure (PP; beta per SD increment= -0.71 mmHg, P=0.005). When dichotomized at the median, plasma CETP activity above the median was associated with a 1 mmHg lower PP on follow-up (P=0.045). CONCLUSION Decreasing plasma CETP activity was modestly related to increasing PP on follow-up in our community-based sample, suggesting that inhibition of intrinsic CETP activity itself is likely associated with minimal changes in BP.
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Oliveira HCF, de Faria EC. Cholesteryl ester transfer protein: The controversial relation to atherosclerosis and emerging new biological roles. IUBMB Life 2011; 63:248-57. [DOI: 10.1002/iub.448] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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18
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Liu H, Wu G, Zhou B, Chen B. Structure and function of cholesteryl ester transfer protein in the tree shrew. Lipids 2011; 46:607-16. [PMID: 21455733 DOI: 10.1007/s11745-011-3552-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2010] [Accepted: 03/15/2011] [Indexed: 11/26/2022]
Abstract
Cholesteryl ester transfer protein (CETP) plays an important role in reverse cholesterol transport (RCT). To study on the structure and function of CETP in the tree shrew, a kind of animal resistant to atherosclerosis, we completed the cloning of the full-length tree-shrew CETP cDNA sequence based on the reported partial sequence. The full-length cDNA of tree shrew CETP was 1,704 bp and the deduced protein of the cDNA showed a sequence identity of 81, 80 and 74%, respectively, with the human, monkey and rabbit CETP. The level of CETP mRNA in the liver was much more abundant than that in the other tissues. A mutant protein with a substitution of Asn at position 110 by Gln was found to possess an impaired secretion property compared with the wild-type tree shrew CETP. The mutant proteins, respectively, with a substitution of Pro at position 344 by Ser and a substitution of Gln at position 452 by Arg displayed similar secretion ability, but a decreased cholesteryl ester transfer capability compared with the wild type (48 and 26% lower, respectively). These findings demonstrate that liver is the main tissue synthesizing CETP in the tree shrew. Asn at position 110 plays an important role in the secretion of tree shrew CETP. The residues at position 344 and 452 play essential roles in cholesteryl ester transferring process.
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Affiliation(s)
- Huirong Liu
- College of Life Sciences, Inner Mongolia Agricultural University, Hohhot 010018, China.
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19
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Abstract
Schizophrenia is one of the most severe psychiatric disorders affecting 1% of the world population. There is yet no empirical method to validate the diagnosis of the disease. The identification of an underlying molecular alteration could lead to an improved disease understanding and may yield an objective panel of biomarkers to aid in the diagnosis of this devastating disease. Presented is the largest reported liquid chromatography-mass spectrometry-based proteomic profiling study investigating serum samples taken from first-onset drug-naive patients compared with samples collected from healthy volunteers. The results of this large-scale study are presented along with enzyme-linked immunosorbent assay-based validation data.
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20
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Yu BL, Zhao SP, Hu JR. Cholesterol imbalance in adipocytes: a possible mechanism of adipocytes dysfunction in obesity. Obes Rev 2010; 11:560-7. [PMID: 20025694 DOI: 10.1111/j.1467-789x.2009.00699.x] [Citation(s) in RCA: 61] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Abstract
Studies of the past decade have increased our understanding of the role of adipose tissue dysfunction in obesity and obesity-related insulin resistance and type 2 diabetes. Although adipose tissue is the body's largest pool of free cholesterol, adipocytes have limited activity in cholesterol synthetic pathway. Thus, the majority of adipocyte cholesterol originates from circulating lipoproteins. To maintain cholesterol homeostasis, adipocytes have developed multiple pathways for cholesterol efflux. Several transcriptional factors, such as sterol regulatory element-binding proteins and liver X receptors may be responsible for the regulation of cholesterol homeostasis in adipocytes. Most notably, because altering cholesterol balance profoundly modifies adipocyte metabolism in a way resembling that seen in hypertrophied adipocytes, cholesterol imbalance is recognized as a characteristic for enlarged adipocytes per se in the obese state. In addition, plasma membrane cholesterol normalization by chromium picolinate can fully restore insulin-stimulated glucose transport, further supporting the role of the adipocyte cholesterol imbalance in obesity and insulin resistance.
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Affiliation(s)
- B-L Yu
- Department of Cardiology, The Second Xiangya Hospital of Central South University, Changsha, Hunan, China
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21
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Bouchard L, Rabasa-Lhoret R, Faraj M, Lavoie ME, Mill J, Pérusse L, Vohl MC. Differential epigenomic and transcriptomic responses in subcutaneous adipose tissue between low and high responders to caloric restriction. Am J Clin Nutr 2010; 91:309-20. [PMID: 19939982 DOI: 10.3945/ajcn.2009.28085] [Citation(s) in RCA: 171] [Impact Index Per Article: 12.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023] Open
Abstract
BACKGROUND Caloric restriction is recommended for the treatment of obesity, but it is generally characterized by large interindividual variability in responses. The factors affecting the magnitude of weight loss remain poorly understood. Epigenetic factors (ie, heritable but reversible changes to genomic function that regulate gene expression independently of DNA sequence) may explain some of the interindividual variability seen in weight-loss responses. OBJECTIVE The objective was to determine whether epigenetics and gene expression changes may play a role in weight-loss responsiveness. DESIGN Overweight/obese postmenopausal women were recruited for a standard 6-mo caloric restriction intervention. Abdominal subcutaneous adipose tissue biopsy samples were collected before (n = 14) and after (n = 14) intervention, and the epigenomic and transcriptomic profiles of the high and low responders to dieting, on the basis of changes in percentage body fat, were compared by using microarray analysis. RESULTS Significant DNA methylation differences at 35 loci were found between the high and low responders before dieting, with 3 regions showing differential methylation after intervention. Some of these regions contained genes known to be involved in weight control and insulin secretion, whereas others were localized in known imprinted genomic regions. Differences in gene expression profiles were observed only after dieting, with 644 genes being differentially expressed between the 2 groups. These included genes likely to be involved in metabolic pathways related to angiogenesis and cerebellar long-term depression. CONCLUSIONS These data show that both DNA methylation and gene expression are responsive to caloric restriction and provide new insights about the molecular pathways involved in body weight loss as well as methylation regulation during adulthood.
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Affiliation(s)
- Luigi Bouchard
- Nutraceuticals and Functional Foods Institute, Université Laval, Laval, Canada
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22
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Quintão ECR, Cazita PM. Lipid transfer proteins: past, present and perspectives. Atherosclerosis 2009; 209:1-9. [PMID: 19733354 DOI: 10.1016/j.atherosclerosis.2009.08.002] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/26/2009] [Revised: 07/02/2009] [Accepted: 08/03/2009] [Indexed: 11/15/2022]
Abstract
Lipid transfer proteins (PLTP and CETP) play roles in atherogenesis by modifying the arterial intima cholesterol content via altering the concentration and function of plasma lipoproteins and influencing inflammation. In this regard, endotoxins impair the reverse cholesterol transport (RCT) system in an endotoxemic rodent model, supporting a pro-inflammatory role of HDL reported in chronic diseases where atherosclerosis is premature. High PLTP activity related to atherosclerosis in some clinical studies, but the mechanisms involved could not be ascertained. In experimental animals the relation of elevated plasma PLTP concentration with atherosclerosis was confounded by HDL-C lowering and by unfavorable effects on several inflammatory markers. Coincidently, PLTP also increases in human experimental endotoxemia and in clinical sepsis. Human population investigations seem to favor low CETP as atheroprotective; this is supported by animal models where overexpression of huCETP is atherogenic, most likely due to increased concentration of apoB-lipoprotein-cholesterol. Thus, in spite of CETP facilitating the HDL-C-mediated RCT, the reduction of apoB-LP-cholesterol concentration is the probable antiatherogenic mechanism of CETP inhibition. On the other hand, experimental huCETP expression protects mice from the harmful effects of a bacterial polysaccharide infusion and the mortality rate of severely ill patients correlates with reduction of the plasma CETP concentration. Thus, the roles played by PLTP and CETP on atherosclerosis and acute inflammation seem contradictory. Therefore, the biological roles of PLTP and CETP must be carefully monitored when investigating drugs that inhibit their activity in the prevention of atherosclerosis.
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Affiliation(s)
- Eder C R Quintão
- Lipids Lab, LIM 10, Faculty of Medical Sciences, University of São Paulo, SP, Brazil.
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Kolovou GD, Anagnostopoulou KK, Mikhailidis DP. The link between human and transgenic animal studies involving postprandial hypertriglyceridemia and CETP gene polymorphisms. Open Cardiovasc Med J 2009; 3:48-50. [PMID: 19557147 PMCID: PMC2701274 DOI: 10.2174/1874192400903010048] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2009] [Revised: 05/18/2009] [Accepted: 05/20/2009] [Indexed: 11/22/2022] Open
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Cholesteryl ester transfer protein (CETP) increases postprandial triglyceridaemia and delays triacylglycerol plasma clearance in transgenic mice. Biochem J 2009; 419:629-34. [PMID: 19191759 DOI: 10.1042/bj20081299] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
The CETP (cholesteryl ester transfer protein) is a plasma protein synthesized in several tissues, mainly in the liver; CETP reduces plasma HDL (high-density lipoprotein) cholesterol and increases the risk of atherosclerosis. The effect of CETP levels on postprandial intravascular metabolism of TAGs (triacylglycerols) is an often-overlooked aspect of the relationship between CETP and lipoprotein metabolism. Here, we tested the hypothesis that CETP delays the plasma clearance of TAG-rich lipoprotein by comparing human CETP expressing Tg (transgenic) and non-Tg mice. After an oral fat load, the postprandial triglyceridaemia curve was markedly increased in CETP-Tg compared with non-Tg mice (280+/-30 versus 190+/-20 mg/dl per 6 h respectively, P<0.02). No differences in intestinal fat absorption and VLDL (very-low-density lipoprotein) secretion rates were observed. Kinetic studies of double-labelled chylomicron-like EMs (emulsions) showed that both [(3)H]triolein and [(14)C]cholesteryl oleate FCRs (fractional clearance rates) were significantly reduced ( approximately 20%) in CETP-Tg mice. Furthermore, TAG from lipid EM pre-incubated with CETP-Tg plasma had plasma clearance and liver uptake significantly lower than the non-Tg plasma-treated lipid EM. In addition, reductions in post-heparin plasma LPL (lipoprotein lipase) activity (50%) and adipose tissue mRNA abundance (39%) were verified in CETP-Tg mice. Therefore we conclude that CETP expression in Tg mice delays plasma clearance and liver uptake of TAG-rich lipoproteins by two mechanisms: (i) transferring TAG to HDLs and increasing CE content of the remnant particles and (ii) by diminishing LPL expression. These findings show that the level of CETP expression can influence the responsiveness to dietary fat and may lead to fat intolerance.
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Goulas A, Kosmidou M, Hatzitolios AI, Molyva D, Fidani L, Giannopoulos S, Mirtsou V. Glutathione S-Transferase Null and Cholesteryl Ester Transfer Protein TaqI B Polymorphisms and Lipid Response to Atorvastatin in Greek Dyslipidaemic Patients. Basic Clin Pharmacol Toxicol 2008; 102:559-62. [DOI: 10.1111/j.1742-7843.2008.00220.x] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
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26
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Nantermet P, Harada SI, Liu Y, Cheng S, Johnson C, Yu Y, Kimme D, Holder D, Hodor P, Phillips R, Ray WJ. Gene expression analyses in cynomolgus monkeys provides mechanistic insight into high-density lipoprotein-cholesterol reduction by androgens in primates. Endocrinology 2008; 149:1551-61. [PMID: 18187556 DOI: 10.1210/en.2007-1151] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Androgens increase muscle mass, decrease fat mass, and reduce high-density lipoprotein cholesterol (HDL), but the relationship between body composition, lipoprotein metabolism, and androgens has not been explained. Here we treated ovariectomized cynomolgus monkeys with 5alpha-dihydrotestosterone (DHT) or vehicle for 14 d and measured lipoprotein and triglycerides. Nuclear magnetic resonance analysis revealed that DHT dose-dependently reduced the cholesterol content of large HDL particles and decreased mean HDL particle size (P < 0.01) and also tended to lower low-density lipoprotein cholesterol without altering other lipoprotein particles. Liver and visceral fat biopsies taken before and after DHT treatment for 1 or 14 d were analyzed by genome-wide microarrays. In liver, DHT did not alter the expression of most genes involved in cholesterol synthesis or uptake but rapidly increased small heterodimer partner (SHP) RNA, along with concomitant repression of CYP7A1, a target of SHP transcriptional repression and the rate-limiting enzyme in bile acid synthesis. DHT regulation of SHP and CYP7A1 also occurs in rats, indicating a conserved mechanism. In adipose tissue, pathway analyses suggested coordinate regulation of adipogenesis, tissue remodeling, and lipid homeostasis. Genes encoding IGF-I and beta-catenin were induced, as were extracellular matrix, cell adhesion, and cytoskeletal components, whereas there was consistent down-regulation of genes involved in triacylglycerol metabolism. Interestingly, cholesterol ester transfer protein RNA was induced rapidly in monkey adipose tissue, whereas its inhibitor apolipoprotein CI was repressed. These data provide insight into the androgenic regulation of lipoprotein homeostasis and suggest that changes in adipose lipoprotein metabolism could contribute to HDL cholesterol reduction.
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Affiliation(s)
- Pascale Nantermet
- Department of Alzheimer's Disease Research, Merck Research Laboratories, West Point, PA 19486, USA
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Lee-Rueckert M, Vikstedt R, Metso J, Jauhiainen M, Kovanen PT. Association of cholesteryl ester transfer protein with HDL particles reduces its proteolytic inactivation by mast cell chymase. J Lipid Res 2008; 49:358-68. [DOI: 10.1194/jlr.m700392-jlr200] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
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28
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Jiang XC. Generation of adipose tissue-specific transgenic mouse models. Methods Mol Biol 2008; 456:55-64. [PMID: 18516552 DOI: 10.1007/978-1-59745-245-8_4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
Adipose tissue plays a critical role in energy homeostasis, not only in storing triglycerides, but also in responding to nutrient, neural, and hormonal signals, and secreting adipokines that control feeding, thermogenesis, immunity, and neuroendocrine function. It is conceivable that adipose tissue-specific gene expression would influence the aforementioned functions. A feasible approach to prepare adipose tissue-specific transgenic mouse models is necessary for such studies. Here, we report the preparation of adipose tissue-specific cholesteryl ester transfer protein transgenic mice. The general principle might apply to the establishment of other adipose tissue-specific transgenic mice models.
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Affiliation(s)
- Xian-Cheng Jiang
- Department of Anatomy and Cell Biology, SUNY Downstate Medical Center, Brooklyn, NY, USA
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Dallinga-Thie GM, Dullaart RPF, van Tol A. Concerted actions of cholesteryl ester transfer protein and phospholipid transfer protein in type 2 diabetes: effects of apolipoproteins. Curr Opin Lipidol 2007; 18:251-7. [PMID: 17495597 DOI: 10.1097/mol.0b013e3280e12685] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
PURPOSE OF REVIEW Type 2 diabetes frequently coincides with dyslipidemia, characterized by elevated plasma triglycerides, low high-density lipoprotein cholesterol levels and the presence of small dense low-density lipoprotein particles. Plasma lipid transfer proteins play an essential role in lipoprotein metabolism. It is thus vital to understand their pathophysiology and determine which factors influence their functioning in type 2 diabetes. RECENT FINDINGS Cholesteryl ester transfer protein-mediated transfer is increased in diabetic patients and contributes to low plasma high-density lipoprotein cholesterol levels. Apolipoproteins A-I, A-II and E are components of the donor lipoprotein particles that participate in the transfer of cholesteryl esters from high-density lipoprotein to apolipoprotein B-containing lipoproteins. Current evidence for functional roles of apolipoproteins C-I, F and A-IV as modulators of cholesteryl ester transfer is discussed. Phospholipid transfer protein activity is increased in diabetic patients and may contribute to hepatic very low-density lipoprotein synthesis and secretion and vitamin E transfer. Apolipoprotein E could stimulate the phospholipid transfer protein-mediated transfer of surface fragments of triglyceride-rich lipoproteins to high-density lipoprotein, and promote high-density lipoprotein remodelling. SUMMARY Both phospholipid and cholesteryl ester transfer proteins are important in very low and high-density lipoprotein metabolism and display concerted actions in patients with type 2 diabetes.
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Affiliation(s)
- Geesje M Dallinga-Thie
- Department of Vascular Medicine, Erasmus University Medical Center, Rotterdam, The Netherlands.
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Izem L, Morton RE. Possible role for intracellular cholesteryl ester transfer protein in adipocyte lipid metabolism and storage. J Biol Chem 2007; 282:21856-65. [PMID: 17522050 DOI: 10.1074/jbc.m701075200] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Cholesteryl ester transfer protein (CETP) transfers cholesteryl ester (CE) and triglyceride (TG) between lipoproteins in plasma. However, short term suppression of CETP biosynthesis in cells alters cellular cholesterol homeostasis, demonstrating an intracellular role for CETP as well. The consequences of chronic CETP deficiency in lipid-storing cells normally expressing CETP have not been reported. Here, SW872 adipocytes stably expressing antisense CETP cDNA and synthesizing 20% of normal CETP were created. CETP-deficient cells had 4-fold more CE but an approximately 3-fold decrease in cholesterol biosynthesis. This phenotype of cholesterol overload is consistent with the observed 45% reduction in low density lipoprotein receptor and 2.5-fold increase in ABCA1 levels. However, cholesterol mass in CETP-deficient adipocytes was actually reduced. Strikingly, CETP-deficient adipocytes stored <50% of normal TG, principally reflecting reduced synthesis. The hydrolysis of cellular CE and TG in CETP-deficient cells was reduced by >50%, although hydrolase/lipase activity was increased 3-fold. Notably, the incorporation of recently synthesized CE and TG into lipid storage droplets in CETP-deficient cells was just 40% of control, suggesting that these lipids are inefficiently transported to droplets where the hydrolase/lipase resides. The capacity of cellular CETP to transport CE and TG into storage droplets was directly demonstrated in vitro. Overall, chronic CETP deficiency disrupts lipid homeostasis and compromises the TG storage function of adipocytes. Inefficient CETP-mediated translocation of CE and TG from the endoplasmic reticulum to their site of storage may partially explain these defects. These studies in adipocytic cells strongly support a novel role for CETP in intracellular lipid transport and storage.
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Affiliation(s)
- Lahoucine Izem
- Department of Cell Biology, Lerner Research Institute, Cleveland Clinic Foundation, Cleveland, OH 44195, USA
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Salerno AG, Silva TR, Amaral MEC, Alberici LC, Bonfleur ML, Patrício PR, Francesconi EPMS, Grassi-Kassisse DM, Vercesi AE, Boschero AC, Oliveira HCF. Overexpression of apolipoprotein CIII increases and CETP reverses diet-induced obesity in transgenic mice. Int J Obes (Lond) 2007; 31:1586-95. [PMID: 17471296 DOI: 10.1038/sj.ijo.0803646] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
OBJECTIVE We recently described that hypertriglyceridemic apolipoprotein (apo) CIII transgenic mice show increased whole body metabolic rate. In this study, we used these apo CIII-expressing mice, combined or not with the expression of the natural promoter-driven CETP gene, to test the hypothesis that both proteins modulate diet-induced obesity. MEASUREMENTS AND RESULTS Mice expressing apo CIII, CIII/CETP, CETP and nontransgenic (NonTg) mice were maintained on a high-fat diet (14% fat by weight) during 20 weeks after weaning. At the end of this period, all groups exhibited the expected lipemic phenotype. Fasting glucose levels were neither affected by the high-fat diet nor by the distinct genotypes. However, apo CIII mice showed significantly higher glycemia ( approximately 35%) and lower insulin levels ( approximately 45%) in the fed state, compared with the NonTg mice. The apo CIII mice presented significantly increased body weight, lipid content of the carcass ( approximately 25%), visceral adipose tissue mass (about twofold) and adipocyte size ( approximately 25%) compared with the CETP and NonTg mice. The CETP expression in the apo CIII background normalized the subcutaneous adipose depot and visceral adipocyte size to the levels of NonTg mice. Plasma leptin levels were lower in CETP groups (25-50%) and higher in the apo CIII mice. Similar core body temperature in all groups and similar liver mitochondrial resting respiration rates in CIII and NonTg mice indicate no differences in basal energy expenditure rates among these mice fed a high-fat diet. CONCLUSION The elevation of plasma apo CIII levels aggravates diet-induced obesity and the expression of physiological levels of circulating CETP reverses this adipogenic effect, indicating a novel role for CETP in modulating adiposity.
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Affiliation(s)
- A G Salerno
- Departamento de Fisiologia e Biofísica, Instituto de Biologia, Universidade Estadual de Campinas, 13086-970 Campinas, SP, Brazil
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Dullaart RPF, de Vries R, Dallinga-Thie GM, van Tol A, Sluiter WJ. Plasma cholesteryl ester transfer protein mass and phospholipid transfer protein activity are associated with leptin in type 2 diabetes mellitus. Biochim Biophys Acta Mol Cell Biol Lipids 2007; 1771:113-8. [PMID: 17185032 DOI: 10.1016/j.bbalip.2006.11.003] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2006] [Revised: 11/02/2006] [Accepted: 11/10/2006] [Indexed: 10/23/2022]
Abstract
Adipose tissue contributes to plasma levels of lipid transfer proteins and is also the major source of plasma adipokines. We hypothesized that plasma cholesteryl ester transfer protein (CETP) mass, phospholipid transfer protein (PLTP) activity and cholesteryl ester transfer (CET, a measure of CETP action) are determined by adipokine levels. In this study, relationships of plasma CETP mass, PLTP activity and CET with leptin, resistin and adiponectin were analyzed in type 2 diabetic patients and control subjects. Plasma PLTP activity (P<0.001), CET (P<0.001), leptin (P=0.003), resistin (P<0.001), high sensitive C-reactive protein (P=0.005), and insulin resistance (HOMA(ir)) (P<0.001) were higher, whereas HDL cholesterol (P<0.001) and plasma adiponectin (P<0.001) were lower in 83 type 2 diabetic patients (32 females) than in 83 sex-matched control subjects. Multiple linear regression analysis demonstrated that in diabetic patients plasma leptin levels were related to plasma CETP mass (P=0.018) and PLTP activity (P<0.001), but not to the other adipokines measured. Plasma CET was inversely correlated with adiponectin in univariate analysis, but this association disappeared in multivariate models that included plasma lipids and CETP. In conclusion, both plasma CETP mass and PLTP activity are associated with plasma leptin in type 2 diabetes. The elevated CET in these patients is not independently related to any of the measured plasma adipokines.
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Affiliation(s)
- R P F Dullaart
- Department of Endocrinology, University of Groningen and University Medical Center Groningen, Groningen, The Netherlands
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