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Otaibi AA, Mubarak SA, Qarni AA, Hawwari A, Bakillah A, Iqbal J. ATP-Binding Cassette Protein ABCC10 Deficiency Prevents Diet-Induced Obesity but Not Atherosclerosis in Mice. Int J Mol Sci 2022; 23:ijms232213813. [PMID: 36430292 PMCID: PMC9694421 DOI: 10.3390/ijms232213813] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2022] [Revised: 09/20/2022] [Accepted: 09/20/2022] [Indexed: 11/11/2022] Open
Abstract
Excess plasma lipid levels are a risk factor for various cardiometabolic disorders. Studies have shown that improving dyslipidemia lowers the progression of these disorders. In this study, we investigated the role of ATP-binding cassette transporter C10 (ABCC10) in regulating lipid metabolism. Our data indicate that deletion of the Abcc10 gene in male mice results in lower plasma and intestinal triglycerides by around 38% and 36%, respectively. Furthermore, deletion of ABCC10 ameliorates diet-induced obesity in mice and leads to a better response during insulin and glucose tolerance tests. Unexpectedly, ABCC10 deficiency does not affect triglyceride levels or atherosclerosis in ApoE-deficient mice. In addition, our studies demonstrate low oleate uptake by enterocytes (~25-30%) and less absorption (~37%) of triglycerides in the small intestine of ABCC10 knockout mice. Deletion of the Abcc10 gene also alters several lipid metabolism genes in the intestine, suggesting that ABCC10 regulates dietary fat absorption, which may contribute to diet-induced obesity in mice.
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2
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Peng H, Chiu TY, Liang YJ, Lee CJ, Liu CS, Suen CS, Yen JJY, Chen HT, Hwang MJ, Hussain MM, Yang HC, Yang-Yen HF. PRAP1 is a novel lipid-binding protein that promotes lipid absorption by facilitating MTTP-mediated lipid transport. J Biol Chem 2021; 296:100052. [PMID: 33168624 PMCID: PMC7949078 DOI: 10.1074/jbc.ra120.015002] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2020] [Revised: 10/30/2020] [Accepted: 11/09/2020] [Indexed: 01/10/2023] Open
Abstract
Microsomal triglyceride transfer protein (MTTP) is an endoplasmic reticulum resident protein that is essential for the assembly and secretion of triglyceride (TG)-rich, apoB-containing lipoproteins. Although the function and structure of mammalian MTTP have been extensively studied, how exactly MTTP transfers lipids to lipid acceptors and whether there are other biomolecules involved in MTTP-mediated lipid transport remain elusive. Here we identify a role in this process for the poorly characterized protein PRAP1. We report that PRAP1 and MTTP are partially colocalized in the endoplasmic reticulum. We observe that PRAP1 directly binds to TG and facilitates MTTP-mediated lipid transfer. A single amino acid mutation at position 85 (E85V) impairs PRAP1's ability to form a ternary complex with TG and MTTP, as well as impairs its ability to facilitate MTTP-mediated apoB-containing lipoprotein assembly and secretion, suggesting that the ternary complex formation is required for PRAP1 to facilitate MTTP-mediated lipid transport. PRAP1 is detectable in chylomicron/VLDL-rich plasma fractions, suggesting that MTTP recognizes PRAP1-bound TG as a cargo and transfers TG along with PRAP1 to lipid acceptors. Both PRAP1-deficient and E85V knock-in mutant mice fed a chow diet manifested an increase in the length of their small intestines, likely to compensate for challenges in absorbing lipid. Interestingly, both genetically modified mice gained significantly less body weight and fat mass when on high-fat diets compared with littermate controls and were prevented from hepatosteatosis. Together, this study provides evidence that PRAP1 plays an important role in MTTP-mediated lipid transport and lipid absorption.
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Affiliation(s)
- Hubert Peng
- Institute of Molecular Biology, Academia Sinica, Taipei, Taiwan
| | - Tzu-Yuan Chiu
- Institute of Molecular Biology, Academia Sinica, Taipei, Taiwan
| | - Yu-Jen Liang
- Institute of Statistical Science, Academia Sinica, Taipei, Taiwan
| | - Chia-Jen Lee
- Institute of Molecular Biology, Academia Sinica, Taipei, Taiwan
| | - Chih-Syuan Liu
- Institute of Molecular Biology, Academia Sinica, Taipei, Taiwan
| | - Ching-Shu Suen
- Institute of Biomedical Sciences, Academia Sinica, Taipei, Taiwan
| | - Jeffrey J-Y Yen
- Institute of Biomedical Sciences, Academia Sinica, Taipei, Taiwan
| | - Hung-Ta Chen
- Institute of Molecular Biology, Academia Sinica, Taipei, Taiwan
| | - Ming-Jing Hwang
- Institute of Biomedical Sciences, Academia Sinica, Taipei, Taiwan
| | - M Mahmood Hussain
- Foundations of Medicine, NYU Long Island School of Medicine, Mineola, New York, USA
| | - Hsin-Chou Yang
- Institute of Statistical Science, Academia Sinica, Taipei, Taiwan
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3
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Badi SA, Motahhary A, Bahramali G, Masoumi M, Khalili SFS, Ebrahimzadeh N, Nouri P, Rahimi A, Masotti A, Moshiri A, Siadat SD. The regulation of Niemann-Pick C1-Like 1 (NPC1L1) gene expression in opposite direction by Bacteroides spp. and related outer membrane vesicles in Caco-2 cell line. J Diabetes Metab Disord 2020; 19:415-422. [PMID: 32550192 DOI: 10.1007/s40200-020-00522-3] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/09/2019] [Accepted: 03/24/2020] [Indexed: 11/28/2022]
Abstract
Purpose The intestine has substantial role in cholesterol homeostasis due to the presence of various cholesterol transporters and gut microbiota. Bacteroides spp. are important members of gut microbiota that employ outer membrane vesicles (OMVs) to interact with host. In this regard, we evaluated the effect of Bacteroides fragilis, Bacteroides thetaiotaomicron and related OMVs on the gene expression of important cholesterol transporters, Niemann-Pick C1-Like 1 (NPC1L1), ATP-binding cassette (ABCA1), and liver X receptors (LXRs) in Caco-2 cells. Methods OMVs were isolated from overnight brain heart infusion (BHI) broth of bacterial standard strains using deoxycholate and assessed by Scanning electron microscopy (SEM). The relative change in genes expression was assessed by Quantitative reverse transcription PCR (RT-qPCR) based on SYBR Green and 2-∆∆ct method in Caco-2 cells that were treated with bacteria and OMVs. Data were statistically analyzed with GraphPad Prism software. Finally, pathway enrichment based on the studied genes was performed using Cytoscape plugin ClueGO. Results B. fragilis (P value = 0.002) and B. thetaiotaomicron (P value = 0.001) significantly reduced NPC1L1 gene expression in Caco-2 cells. Interestingly, NPC1L1 transcripts were significantly increased by both OMVs(P value = 0.04) (P value = 0.01). Also, LXRβ was significantly down regulated by B. thetaiotaomicron (P value = 0.02). ClueGO analysis on the studied genes demonstrated several functional groups which involve in lipid and cholesterol metabolism. Conclusion The opposite effect of B. fragilis, B. thetaiotaomicron and related OMVs on the NPC1L1 gene expression was observed in Caco-2 cells. Interestingly, these effects partially were in line with the alternation of LXRs expression. However, based on pathway enrichment analysis, further molecular investigations are required to elaborate in details the specific association between Bacteroides spp. and OMVs with regulation of cholesterol signaling pathways including cholesterol transport, lipid storage, lipid homeostasis and cholesterol homeostasis.
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Affiliation(s)
- Sara Ahmadi Badi
- Microbiology Research Center, Pasteur Institute of Iran, Tehran, Iran
| | - Atiyyeh Motahhary
- Microbiology Research Center, Pasteur Institute of Iran, Tehran, Iran
| | - Golnaz Bahramali
- Department of Hepatitis and AIDS, Pasteur Institute of Iran, Tehran, Iran
| | - Morteza Masoumi
- Mycobacteriology and Pulmonary Research Department, Pasteur Institute of Iran, Tehran, Iran
| | | | - Nayereh Ebrahimzadeh
- Mycobacteriology and Pulmonary Research Department, Pasteur Institute of Iran, Tehran, Iran
| | - Pegah Nouri
- Microbiology Research Center, Pasteur Institute of Iran, Tehran, Iran
| | - Ayoub Rahimi
- Mycobacteriology and Pulmonary Research Department, Pasteur Institute of Iran, Tehran, Iran
| | - Andrea Masotti
- Bambino Gesù Children's Hospital-IRCCS, Research Laboratories, Rome, Italy
| | - Arfa Moshiri
- Cancer Department, Gastroenterology and Liver Diseases Research Center, Research Institute for Gastroenterology and Liver Diseases, Shahid Beheshti University of Medical Sciences, Tehran, Iran.,Laboratory of Experimental Therapies in Oncology, IRCCS Istituto Giannina Gaslini, Genoa, Italy
| | - Seyed Davar Siadat
- Microbiology Research Center, Pasteur Institute of Iran, Tehran, Iran.,Mycobacteriology and Pulmonary Research Department, Pasteur Institute of Iran, Tehran, Iran.,Endocrinologyand Metabolism Research Center, Endocrinology and Metabolism Clinical Sciences Institute, Tehran University of Medical Sciences, Tehran, Iran
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4
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Meyer S, Thiel V, Joergensen RG, Sundrum A. Relationships between feeding and microbial faeces indices in dairy cows at different milk yield levels. PLoS One 2019; 14:e0221266. [PMID: 31430322 PMCID: PMC6701754 DOI: 10.1371/journal.pone.0221266] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2018] [Accepted: 08/04/2019] [Indexed: 11/25/2022] Open
Abstract
A study was carried out to gain quantitative information on the diet-dependent faecal microbial biomass of dairy cows, especially on the biomass fractions of fungi, Gram-positive (G+) and Gram-negative (G-) bacteria. Groups of high-yield, low-yield and non-lactating cows were investigated at four different farms. A mean faecal microbial biomass C (MBC) concentration of 33.5 mg g-1 DM was obtained by the chloroform fumigation extraction method. This is similar to a mean microbial C concentration of 31.8 mg g-1 DM, which is the sum of bacterial C and fungal C, estimated by cell-wall derived muramic acid (MurN) and fungal glucosamine (GlcN), respectively. However, the response of these two approaches to the feeding regime was contradictory, due to feeding effects on the conversion values. The higher neutral detergent fibre (NDF) and acid detergent fibre (ADF) concentrations in the non-lactating group led to higher (P < 0.05) concentrations of cellulose and lignin in their faeces in comparison with the lactating cows. This change in faecal chemical composition in the non-lactating group was accompanied by usually higher ratios of G+/G- phospholipid fatty acids (PLFA), ergosterol/MBC and fungal C/bacterial C. Although bacteria dominate the faecal microbial biomass, fungi contribute a considerable mean percentage of roughly 20% to the faecal microbiome, according to PLFA and amino sugar data, which requires more attention in the future. Near-infra red spectroscopic estimates of organic N and C fractions of cow faeces were able to model microbial biomarkers successfully, which might be useful in the future to predict its N2O emission potential and fertilizer value.
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Affiliation(s)
- Stephanie Meyer
- Animal Nutrition and Animal Health, University of Kassel, Witzenhausen, Germany
- Soil Biology and Plant Nutrition, University of Kassel, Witzenhausen, Germany
| | - Volker Thiel
- Geobiology Group, Geoscience Centre, University of Göttingen, Germany
| | | | - Albert Sundrum
- Animal Nutrition and Animal Health, University of Kassel, Witzenhausen, Germany
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5
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Lütjohann D, Stellaard F, Mulder MT, Sijbrands EJG, Weingärtner O. The emerging concept of "individualized cholesterol-lowering therapy": A change in paradigm. Pharmacol Ther 2019; 199:111-116. [PMID: 30877023 DOI: 10.1016/j.pharmthera.2019.03.004] [Citation(s) in RCA: 28] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2018] [Accepted: 03/06/2019] [Indexed: 12/17/2022]
Abstract
High LDL-cholesterol concentrations constitute a risk for atherosclerotic cardiovascular disease. By consensus, cholesterol-lowering therapy is initiated with a statin that reduces endogenous cholesterol synthesis, upregulates hepatic LDL receptor activity, increases LDL clearance and lowers LDL-cholesterol concentrations in the bloodstream. The efficacy of statin treatment is dose dependent and achieves a risk reduction of up to 50%. However, a substantial body of evidence suggests that a quarter of statin-treated patients do not respond adequately as a result of low endogenous cholesterol synthesis. In humans fractional cholesterol absorption varies from 20% to 80%. High cholesterol absorbers, which are characterized by a low-to-normal cholesterol synthesis, exhibit poor responsiveness to statin treatment. On the other hand, the cholesterol absorption inhibitor ezetimibe effectively reduces serum cholesterol levels in these patients. On this background, we suggest to "get personal" and individualize cholesterol-lowering therapies, according to the individual's status of cholesterol synthesis and absorption.
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Affiliation(s)
- Dieter Lütjohann
- Institute of Clinical Chemistry and Clinical Pharmacology, University Hospital Bonn, Bonn, Germany
| | - Frans Stellaard
- Institute of Clinical Chemistry and Clinical Pharmacology, University Hospital Bonn, Bonn, Germany
| | - Monique T Mulder
- Department of Internal Medicine, Section of Pharmacology Vascular and Metabolic Diseases, Cardiovascular Research School COEUR, Erasmus Medical Center, Rotterdam, The Netherlands
| | - Eric J G Sijbrands
- Department of Internal Medicine, Section of Pharmacology Vascular and Metabolic Diseases, Cardiovascular Research School COEUR, Erasmus Medical Center, Rotterdam, The Netherlands
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6
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Pan X, Schwartz GJ, Hussain MM. Oleoylethanolamide differentially regulates glycerolipid synthesis and lipoprotein secretion in intestine and liver. J Lipid Res 2018; 59:2349-2359. [PMID: 30369486 DOI: 10.1194/jlr.m089250] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2018] [Revised: 10/26/2018] [Indexed: 01/13/2023] Open
Abstract
Dietary fat absorption takes place in the intestine, and the liver mobilizes endogenous fat to other tissues by synthesizing lipoproteins that require apoB and microsomal triglyceride transfer protein (MTP). Dietary fat triggers the synthesis of oleoylethanolamide (OEA), a regulatory fatty acid that signals satiety to reduce food intake mainly by enhancing neural PPARα activity, in enterocytes. We explored OEA's roles in the assembly of lipoproteins in WT and Ppara -/- mouse enterocytes and hepatocytes, Caco-2 cells, and human liver-derived cells. In differentiated Caco-2 cells, OEA increased synthesis and secretion of triacylglycerols, apoB secretion in chylomicrons, and MTP expression in a dose-dependent manner. OEA also increased MTP activity and triacylglycerol secretion in WT and knockout primary enterocytes. In contrast to its intestinal cell effects, OEA reduced synthesis and secretion of triacylglycerols, apoB secretion, and MTP expression and activity in human hepatoma Huh-7 and HepG2 cells. Also, OEA reduced MTP expression and triacylglycerol secretion in WT, but not knockout, primary hepatocytes. These studies indicate differential effects of OEA on lipid synthesis and lipoprotein assembly: in enterocytes, OEA augments glycerolipid synthesis and lipoprotein assembly independent of PPARα. Conversely, in hepatocytes, OEA reduces MTP expression, glycerolipid synthesis, and lipoprotein secretion through PPARα-dependent mechanisms.
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Affiliation(s)
- Xiaoyue Pan
- Department of Cell Biology, State University of New York Downstate Medical Center, Brooklyn, NY .,Diabetes and Obesity Research Center, New York University Winthrop Hospital, Mineola, NY
| | - Gary J Schwartz
- Departments of Medicine and Neuroscience, Albert Einstein College of Medicine, Bronx, NY
| | - M Mahmood Hussain
- Department of Cell Biology, State University of New York Downstate Medical Center, Brooklyn, NY .,Diabetes and Obesity Research Center, New York University Winthrop Hospital, Mineola, NY.,Veterans Affairs New York Harbor Healthcare System, Brooklyn, NY
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7
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Iqbal J, Walsh MT, Hammad SM, Cuchel M, Rader DJ, Hussain MM. ATP binding cassette family A protein 1 determines hexosylceramide and sphingomyelin levels in human and mouse plasma. J Lipid Res 2018; 59:2084-2097. [PMID: 30279221 DOI: 10.1194/jlr.m087502] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2018] [Revised: 09/19/2018] [Indexed: 12/31/2022] Open
Abstract
Sphingolipids, including ceramide, SM, and hexosylceramide (HxCer), are carried in the plasma by lipoproteins. They are possible markers of metabolic diseases, but little is known about their control. We previously showed that microsomal triglyceride transfer protein (MTP) is critical to determine plasma ceramide and SM, but not HxCer, levels. In human plasma and mouse models, we examined possible HxCer-modulating pathways, including the role of ABCA1 in determining sphingolipid plasma concentrations. Compared with control samples, plasma from patients with Tangier disease (deficient in ABCA1) had significantly lower HxCer (-69%) and SM (-40%) levels. Similarly, mice deficient in hepatic and intestinal ABCA1 had significantly reduced HxCer (-79%) and SM (-85%) levels. Tissue-specific ablation studies revealed that hepatic ABCA1 determines plasma HxCer and SM levels; that ablation of MTP and ABCA1 in the liver and intestine reduces plasma HxCer, SM, and ceramide levels; and that hepatic and intestinal MTP contribute to plasma ceramide levels, whereas only hepatic MTP modulates plasma SM levels. These results identify the contribution of ABCA1 to plasma SM and HxCer levels and suggest that MTP and ABCA1 are critical determinants of plasma sphingolipid levels.
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Affiliation(s)
- Jahangir Iqbal
- Department of Cell Biology, SUNY Downstate Medical Center, Brooklyn, NY.,King Abdullah International Medical Research Center, King Saud Bin Abdulaziz University for Health Sciences, Eastern Region, Ministry of National Guard Health Affairs, Al Ahsa, Saudi Arabia
| | - Meghan T Walsh
- Department of Cell Biology, SUNY Downstate Medical Center, Brooklyn, NY
| | - Samar M Hammad
- Department of Regenerative Medicine and Cell Biology, Medical University of South Carolina, Charleston, SC
| | - Marina Cuchel
- Institute for Translational Medicine and Therapeutics, Cardiovascular Institute, University of Pennsylvania, Philadelphia, PA
| | - Daniel J Rader
- Institute for Translational Medicine and Therapeutics, Cardiovascular Institute, University of Pennsylvania, Philadelphia, PA
| | - M Mahmood Hussain
- Department of Cell Biology, SUNY Downstate Medical Center, Brooklyn, NY .,Diabetes and Obesity Research Center, New York University Winthrop Hospital, Mineola, NY.,Department of Veterans Affairs New York Harbor Healthcare System, Brooklyn, NY
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8
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de Boer JF, Kuipers F, Groen AK. Cholesterol Transport Revisited: A New Turbo Mechanism to Drive Cholesterol Excretion. Trends Endocrinol Metab 2018; 29:123-133. [PMID: 29276134 DOI: 10.1016/j.tem.2017.11.006] [Citation(s) in RCA: 43] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/21/2017] [Revised: 11/26/2017] [Accepted: 11/29/2017] [Indexed: 12/31/2022]
Abstract
A fine-tuned balance between cholesterol uptake and excretion by the body is pivotal to maintain health and to remain free from the deleterious consequences of cholesterol accumulation such as cardiovascular disease. The pathways involved in intracellular and extracellular cholesterol transport are a subject of intense investigation and are being unraveled in increasing detail. In addition, insight into the complex interactions between cholesterol and bile acid metabolism has increased considerably in the last couple of years. This review provides an overview of the mechanisms involved in cholesterol uptake and excretion, with a particular emphasis on the most recent progress in this field. Special attention is given to the transintestinal cholesterol excretion (TICE) pathway, which was recently demonstrated to have a remarkably high transport capacity and to be sensitive to pharmacological modulation.
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Affiliation(s)
- Jan Freark de Boer
- Department of Pediatrics, University of Groningen, University Medical Center Groningen, Groningen, The Netherlands; Department of Laboratory Medicine, University of Groningen, University Medical Center Groningen, Groningen, The Netherlands.
| | - Folkert Kuipers
- Department of Pediatrics, University of Groningen, University Medical Center Groningen, Groningen, The Netherlands; Department of Laboratory Medicine, University of Groningen, University Medical Center Groningen, Groningen, The Netherlands
| | - Albert K Groen
- Department of Pediatrics, University of Groningen, University Medical Center Groningen, Groningen, The Netherlands; Department of Laboratory Medicine, University of Groningen, University Medical Center Groningen, Groningen, The Netherlands; Department of Vascular Medicine, University of Amsterdam Academic Medical Center, Amsterdam, The Netherlands
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9
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Wang O, McAllister TA, Plastow G, Stanford K, Selinger B, Guan LL. Host mechanisms involved in cattle Escherichia coli O157 shedding: a fundamental understanding for reducing foodborne pathogen in food animal production. Sci Rep 2017; 7:7630. [PMID: 28794460 PMCID: PMC5550497 DOI: 10.1038/s41598-017-06737-4] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2016] [Accepted: 06/16/2017] [Indexed: 11/09/2022] Open
Abstract
The host mechanisms involved in Escherichia coli O157 super-shedding in cattle is largely unknown. In this study, the comparison of transcriptomes of intestinal tissues between super-shedders (SS) and cattle negative for E. coli O157 (NS) was performed, aiming to identify genes that are potentially associated with super-shedding. In total, 16,846 ± 639 (cecum) to 18,137 ± 696 (distal jejunum) were expressed throughout the intestine, with the expressed genes associated with immune functions more pronounced in the small intestine. In total, 351 differentially expressed (DE) genes were identified throughout the intestine between SS and NS, with 101 being up-regulated and 250 down-regulated in SS. Functional analysis revealed DE genes were involved in increased T-cell responses and cholesterol absorption in the distal jejunum and descending colon, and decreased B-cell maturation in the distal jejunum of SS. RNA-Seq based SNP discovery revealed that the mutations in seven DE genes involved in leukocyte activation and cholesterol transportation were associated with E. coli O157 shedding. Our findings suggest that T-cell responses and cholesterol metabolism in the intestinal tract may be associated with super-shedding phenomenon, and the SNPs in the DE genes are possibly associated with the observed gene expression difference between SS and NS.
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Affiliation(s)
- Ou Wang
- Department of Agricultural, Food and Nutritional Science, University of Alberta, Edmonton, AB, T6G 2P5, Canada
| | - Tim A McAllister
- Agriculture and Agri-Food Canada, Lethbridge Research Centre, Lethbridge, AB, T1J 4B1, Canada
| | - Graham Plastow
- Department of Agricultural, Food and Nutritional Science, University of Alberta, Edmonton, AB, T6G 2P5, Canada
| | - Kim Stanford
- Alberta Agriculture and Forestry, Lethbridge, AB, T1J 4V6, Canada
| | - Brent Selinger
- Department of Biological Sciences, University of Lethbridge, Lethbridge, AB, T1K 3M4, Canada
| | - Le Luo Guan
- Department of Agricultural, Food and Nutritional Science, University of Alberta, Edmonton, AB, T6G 2P5, Canada.
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10
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Poulcharidis D, Belfor K, Kros A, van Kasteren SI. A flow cytometry assay to quantify intercellular exchange of membrane components. Chem Sci 2017; 8:5585-5590. [PMID: 28970937 PMCID: PMC5618768 DOI: 10.1039/c7sc00260b] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2017] [Accepted: 05/20/2017] [Indexed: 12/12/2022] Open
Abstract
Membrane-compound exchange is vital for cell-to-cell communication, yet quantification of this process is difficult. Here we present a method using flow cytometry in combination with bioorthogonal and fluorescent labelling techniques to quantify the amount of exchange of cholesterol and sialylated compounds between cells. We demonstrate that direct cell-cell contact is the likely mechanism of sterol-exchange and show that by manipulating the contact time between cells using complementary coiled-coil peptides results in an enhanced exchange rate of membrane components between cells.
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Affiliation(s)
- Dimitrios Poulcharidis
- Division of Bio-organic Synthesis , Leiden Institute of Chemistry , Gorlaeus Laboratories , Leiden University , Leiden , The Netherlands .
- Division of Supramolecular and Biomaterials Chemistry , Leiden Institute of Chemistry , Leiden University , Einsteinweg 55 , 2333 CC Leiden , The Netherlands .
| | - Kimberley Belfor
- Division of Bio-organic Synthesis , Leiden Institute of Chemistry , Gorlaeus Laboratories , Leiden University , Leiden , The Netherlands .
| | - Alexander Kros
- Division of Supramolecular and Biomaterials Chemistry , Leiden Institute of Chemistry , Leiden University , Einsteinweg 55 , 2333 CC Leiden , The Netherlands .
| | - Sander I van Kasteren
- Division of Bio-organic Synthesis , Leiden Institute of Chemistry , Gorlaeus Laboratories , Leiden University , Leiden , The Netherlands .
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11
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Summers JA, Harper AR, Feasley CL, Van-Der-Wel H, Byrum JN, Hermann M, West CM. Identification of Apolipoprotein A-I as a Retinoic Acid-binding Protein in the Eye. J Biol Chem 2016; 291:18991-9005. [PMID: 27402828 DOI: 10.1074/jbc.m116.725523] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2016] [Indexed: 12/31/2022] Open
Abstract
All-trans-retinoic acid may be an important molecular signal in the postnatal control of eye size. The goal of this study was to identify retinoic acid-binding proteins secreted by the choroid and sclera during visually guided ocular growth. Following photoaffinity labeling with all-trans-[11,12-(3)H]retinoic acid, the most abundant labeled protein detected in the conditioned medium of choroid or sclera had an apparent Mr of 27,000 Da. Following purification and mass spectrometry, the Mr 27,000 band was identified as apolipoprotein A-I. Affinity capture of the radioactive Mr 27,000 band by anti-chick apolipoprotein A-I antibodies confirmed its identity as apolipoprotein A-I. Photoaffinity labeling and fluorescence quenching experiments demonstrated that binding of retinoic acid to apolipoprotein A-I is 1) concentration-dependent, 2) selective for all-trans-retinoic acid, and 3) requires the presence of apolipoprotein A-I-associated lipids for retinoid binding. Expression of apolipoprotein A-I mRNA and protein synthesis were markedly up-regulated in choroids of chick eyes during the recovery from induced myopia, and apolipoprotein A-I mRNA was significantly increased in choroids following retinoic acid treatment. Together, these data suggest that apolipoprotein A-I may participate in a regulatory feedback mechanism with retinoic acid to control the action of retinoic acid on ocular targets during postnatal ocular growth.
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Affiliation(s)
| | | | - Christa L Feasley
- Biochemistry and Molecular Biology, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma 73104, Thermo Fisher Scientific, West Palm Beach, Florida 33407
| | - Hanke Van-Der-Wel
- Biochemistry and Molecular Biology, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma 73104, Department of Biochemistry and Molecular Biology, University of Georgia, Athens, Georgia, 30602, and
| | - Jennifer N Byrum
- Biochemistry and Molecular Biology, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma 73104
| | - Marcela Hermann
- Department of Medical Biochemistry, Medical University of Vienna, Max F. Perutz Laboratories, Dr. Bohr Gasse 9/2, 1030 Vienna, Austria
| | - Christopher M West
- Biochemistry and Molecular Biology, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma 73104, Department of Biochemistry and Molecular Biology, University of Georgia, Athens, Georgia, 30602, and
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12
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TTC39B deficiency stabilizes LXR reducing both atherosclerosis and steatohepatitis. Nature 2016; 535:303-7. [PMID: 27383786 PMCID: PMC4947007 DOI: 10.1038/nature18628] [Citation(s) in RCA: 61] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2013] [Accepted: 06/02/2016] [Indexed: 01/07/2023]
Abstract
Cellular mechanisms that mediate steato-hepatitis, an increasingly prevalent condition in the Western world for which no therapies are available1, are poorly understood. Despite the fact its synthetic agonists induce fatty liver, the Liver X receptor (LXR) transcription factor remains a target of interest because of its anti-atherogenic, cholesterol removal and anti-inflammatory activities. We discovered that tetratricopeptide repeat (TPR) domain protein 39B (Ttc39b, C9orf52) (T39), a high density lipoprotein (HDL) gene discovered in human genome wide association studies (GWAS)2, promotes the ubiquitination and degradation of LXR. Chow-fed T39-/- mice displayed increased HDL cholesterol levels associated with increased enterocyte ATP binding cassette transporter A1 (Abca1) expression and increased LXR protein without change in LXR mRNA. When challenged with a high fat/high cholesterol/bile salt (HF/HC/BS) diet, T39-/- mice or mice with hepatocyte-specific T39 deficiency showed increased hepatic LXR protein and target gene expression, and unexpectedly protection from steato-hepatitis and death. Western Type Diet (WTD)-fed Low density lipoprotein receptor (Ldlr)-/-T39-/- mice showed decreased fatty liver, increased HDL, decreased LDL and reduced atherosclerosis. In addition to increasing hepatic Abcg5/8 expression and limiting dietary cholesterol absorption, T39 deficiency inhibited hepatic sterol regulatory element binding protein 1 (SREBP-1, ADD1) processing. This was explained by an increase in microsomal phospholipids containing polyunsaturated fatty acids (PUFA), linked to an LXRα-dependent increase in expression of enzymes mediating PC biosynthesis and incorporation of PUFA into phospholipids. The preservation of endogenous LXR protein activates a beneficial profile of gene expression that promotes cholesterol removal and inhibits lipogenesis. T39 inhibition could be an effective strategy for reducing both steato-hepatitis and atherosclerosis.
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13
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Sachdev V, Leopold C, Bauer R, Patankar JV, Iqbal J, Obrowsky S, Boverhof R, Doktorova M, Scheicher B, Goeritzer M, Kolb D, Turnbull AV, Zimmer A, Hoefler G, Hussain MM, Groen AK, Kratky D. Novel role of a triglyceride-synthesizing enzyme: DGAT1 at the crossroad between triglyceride and cholesterol metabolism. Biochim Biophys Acta Mol Cell Biol Lipids 2016; 1861:1132-1141. [PMID: 27344248 PMCID: PMC4948681 DOI: 10.1016/j.bbalip.2016.06.014] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2016] [Revised: 06/13/2016] [Accepted: 06/22/2016] [Indexed: 12/13/2022]
Abstract
Acyl-CoA:diacylglycerol acyltransferase 1 (DGAT1) is a key enzyme in triacylglycerol (TG) biosynthesis. Here we show that genetic deficiency and pharmacological inhibition of DGAT1 in mice alters cholesterol metabolism. Cholesterol absorption, as assessed by acute cholesterol uptake, was significantly decreased in the small intestine and liver upon DGAT1 deficiency/inhibition. Ablation of DGAT1 in the intestine (I-DGAT1−/−) alone is sufficient to cause these effects. Consequences of I-DGAT1 deficiency phenocopy findings in whole-body DGAT1−/− and DGAT1 inhibitor-treated mice. We show that deficiency/inhibition of DGAT1 affects cholesterol metabolism via reduced chylomicron size and increased trans-intestinal cholesterol excretion. These effects are independent of cholesterol uptake at the apical surface of enterocytes but mediated through altered dietary fatty acid metabolism. Our findings provide insight into a novel role of DGAT1 and identify a pathway by which intestinal DGAT1 deficiency affects whole-body cholesterol homeostasis in mice. Targeting intestinal DGAT1 may represent a novel approach for treating hypercholesterolemia.
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Affiliation(s)
- Vinay Sachdev
- Institute of Molecular Biology and Biochemistry, Medical University of Graz, 8010 Graz, Austria
| | - Christina Leopold
- Institute of Molecular Biology and Biochemistry, Medical University of Graz, 8010 Graz, Austria
| | - Raimund Bauer
- Institute of Molecular Biology and Biochemistry, Medical University of Graz, 8010 Graz, Austria; Center of Experimental Medicine, University Medical Center Hamburg-Eppendorf, 20246 Hamburg, Germany
| | - Jay V Patankar
- Institute of Molecular Biology and Biochemistry, Medical University of Graz, 8010 Graz, Austria; Centre for Molecular Medicine and Therapeutics, University of British Columbia, Vancouver, BC V5Z 4H4, Canada
| | - Jahangir Iqbal
- Department of Cell Biology, SUNY Downstate Medical Center, 11203 New York, United States
| | - Sascha Obrowsky
- Institute of Molecular Biology and Biochemistry, Medical University of Graz, 8010 Graz, Austria
| | - Renze Boverhof
- Departments of Pediatrics, Center for Liver, Digestive, and Metabolic Diseases, University of Groningen, University Medical Center Groningen, 9713 Groningen, The Netherlands
| | - Marcela Doktorova
- Departments of Pediatrics, Center for Liver, Digestive, and Metabolic Diseases, University of Groningen, University Medical Center Groningen, 9713 Groningen, The Netherlands
| | - Bernhard Scheicher
- Institute of Pharmaceutical Sciences, University of Graz, 8010 Graz, Austria
| | - Madeleine Goeritzer
- Institute of Molecular Biology and Biochemistry, Medical University of Graz, 8010 Graz, Austria
| | - Dagmar Kolb
- Institute of Cell Biology, Histology, and Embryology, Medical University of Graz, 8010 Graz, Austria
| | | | - Andreas Zimmer
- Institute of Pharmaceutical Sciences, University of Graz, 8010 Graz, Austria
| | - Gerald Hoefler
- Institute of Pathology, Medical University of Graz, 8010 Graz, Austria
| | - M Mahmood Hussain
- Department of Cell Biology, SUNY Downstate Medical Center, 11203 New York, United States
| | - Albert K Groen
- Departments of Pediatrics, Center for Liver, Digestive, and Metabolic Diseases, University of Groningen, University Medical Center Groningen, 9713 Groningen, The Netherlands
| | - Dagmar Kratky
- Institute of Molecular Biology and Biochemistry, Medical University of Graz, 8010 Graz, Austria.
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14
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Si Y, Zhang Y, Chen X, Zhai L, Zhou G, Yu A, Cao H, Shucun Q. Phospholipid transfer protein deficiency in mice impairs macrophage reverse cholesterol transport in vivo. Exp Biol Med (Maywood) 2016; 241:1466-72. [PMID: 27037277 DOI: 10.1177/1535370216641218] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2015] [Accepted: 02/16/2016] [Indexed: 12/16/2022] Open
Abstract
Phospholipid transfer protein is expressed in various cell types and secreted into plasma, where it transfers phospholipids between lipoproteins and modulates the composition of high-density lipoprotein particles. Phospholipid transfer protein deficiency in vivo can lower high-density lipoprotein cholesterol level significantly and impact the biological quality of high-density lipoprotein. Considering high-density lipoprotein was a critical determinant for reverse cholesterol transport, we investigated the role of systemic phospholipid transfer protein deficiency in macrophage reverse cholesterol transport in vivo After the littermate phospholipid transfer protein KO and WT mice were fed high-fat diet for one month, they were injected intraperitoneally with (3)H-cholesterol-labeled and acLDL-loaded macrophages. Then the appearance of (3)H-tracer in plasma, liver, bile, intestinal wall, and feces over 48 h was determined. Plasma lipid analysis indicated phospholipid transfer protein deficiency lowered total cholesterol, high-density lipoprotein-C and apolipoprotein A1 levels significantly but increased triglyceride level in mice. The isotope tracing experiment showed (3)H-cholesterol of plasma was decreased by 68% for male and 62% for female, and (3)H-tracer of bile was decreased by 37% for male and 21% for female in phospholipid transfer protein KO mice compared with WT mice. However, there was no difference in liver, and (3)H-tracer of intestinal wall was increased by 43% for male and 27% for female. Finally, (3)H-tracer of fecal excretion in phospholipid transfer protein KO mice was reduced significantly by 36% for male and 43% for female during 0-24 h period, but there was no significant difference during 24-48 h period. Meanwhile, Western Blot analysis showed the expressions of reverse cholesterol transport -related protein liver X receptor α (LXRα), ATP binding cassette transporter A1, and cholesterol 7α-hydroxylase A1 were upregulated in liver of phospholipid transfer protein KO mice compared with WT mice. These data reveal that systemic phospholipid transfer protein deficiency in mice impairs macrophage-specific reverse cholesterol transport in vivo.
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Affiliation(s)
- Yanhong Si
- Key Laboratory of Atherosclerosis in Universities of Shandong and Institute of Atherosclerosis, Taishan Medical University, Taian 271000, China
| | - Ying Zhang
- Key Laboratory of Atherosclerosis in Universities of Shandong and Institute of Atherosclerosis, Taishan Medical University, Taian 271000, China
| | - Xiaofeng Chen
- Key Laboratory of Atherosclerosis in Universities of Shandong and Institute of Atherosclerosis, Taishan Medical University, Taian 271000, China
| | - Lei Zhai
- Key Laboratory of Atherosclerosis in Universities of Shandong and Institute of Atherosclerosis, Taishan Medical University, Taian 271000, China
| | - Guanghai Zhou
- Key Laboratory of Atherosclerosis in Universities of Shandong and Institute of Atherosclerosis, Taishan Medical University, Taian 271000, China
| | - Ailing Yu
- Taian Center Hospital, Taian 271000, China
| | - Haijun Cao
- Taian Center Hospital, Taian 271000, China
| | - Qin Shucun
- Key Laboratory of Atherosclerosis in Universities of Shandong and Institute of Atherosclerosis, Taishan Medical University, Taian 271000, China
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15
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Khatun I, Clark RW, Vera NB, Kou K, Erion DM, Coskran T, Bobrowski WF, Okerberg C, Goodwin B. Characterization of a Novel Intestinal Glycerol-3-phosphate Acyltransferase Pathway and Its Role in Lipid Homeostasis. J Biol Chem 2015; 291:2602-15. [PMID: 26644473 DOI: 10.1074/jbc.m115.683359] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2015] [Indexed: 01/01/2023] Open
Abstract
Dietary triglycerides (TG) are absorbed by the enterocytes of the small intestine after luminal hydrolysis into monacylglycerol and fatty acids. Before secretion on chylomicrons, these lipids are reesterified into TG, primarily through the monoacylglycerol pathway. However, targeted deletion of the primary murine monoacylglycerol acyltransferase does not quantitatively affect lipid absorption, suggesting the existence of alternative pathways. Therefore, we investigated the role of the glycerol 3-phosphate pathway in dietary lipid absorption. The expression of glycerol-3-phosphate acyltransferase (GPAT3) was examined throughout the small intestine. To evaluate the role for GPAT3 in lipid absorption, mice harboring a disrupted GPAT3 gene (Gpat3(-/-)) were subjected to an oral lipid challenge and fed a Western-type diet to characterize the role in lipid and cholesterol homeostasis. Additional mechanistic studies were performed in primary enterocytes. GPAT3 was abundantly expressed in the apical surface of enterocytes in the small intestine. After an oral lipid bolus, Gpat3(-/-) mice exhibited attenuated plasma TG excursion and accumulated lipid in the enterocytes. Electron microscopy studies revealed a lack of lipids in the lamina propria and intercellular space in Gpat3(-/-) mice. Gpat3(-/-) enterocytes displayed a compensatory increase in the synthesis of phospholipid and cholesteryl ester. When fed a Western-type diet, hepatic TG and cholesteryl ester accumulation was significantly higher in Gpat3(-/-) mice compared with the wild-type mice accompanied by elevated levels of alanine aminotransferase, a marker of liver injury. Dysregulation of bile acid metabolism was also evident in Gpat3-null mice. These studies identify GPAT3 as a novel enzyme involved in intestinal lipid metabolism.
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Affiliation(s)
- Irani Khatun
- From the Cardiovascular and Metabolic Diseases Research Unit, Pfizer Worldwide Research and Development, Cambridge, Massachusetts 02139 and
| | - Ronald W Clark
- From the Cardiovascular and Metabolic Diseases Research Unit, Pfizer Worldwide Research and Development, Cambridge, Massachusetts 02139 and
| | - Nicholas B Vera
- From the Cardiovascular and Metabolic Diseases Research Unit, Pfizer Worldwide Research and Development, Cambridge, Massachusetts 02139 and
| | - Kou Kou
- From the Cardiovascular and Metabolic Diseases Research Unit, Pfizer Worldwide Research and Development, Cambridge, Massachusetts 02139 and
| | - Derek M Erion
- From the Cardiovascular and Metabolic Diseases Research Unit, Pfizer Worldwide Research and Development, Cambridge, Massachusetts 02139 and
| | - Timothy Coskran
- Drug Safety Research and Development, Pfizer Worldwide Research and Development, Groton, Connecticut 06340
| | - Walter F Bobrowski
- Drug Safety Research and Development, Pfizer Worldwide Research and Development, Groton, Connecticut 06340
| | - Carlin Okerberg
- Drug Safety Research and Development, Pfizer Worldwide Research and Development, Groton, Connecticut 06340
| | - Bryan Goodwin
- From the Cardiovascular and Metabolic Diseases Research Unit, Pfizer Worldwide Research and Development, Cambridge, Massachusetts 02139 and
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16
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Iqbal J, Walsh MT, Hammad SM, Cuchel M, Tarugi P, Hegele RA, Davidson NO, Rader DJ, Klein RL, Hussain MM. Microsomal Triglyceride Transfer Protein Transfers and Determines Plasma Concentrations of Ceramide and Sphingomyelin but Not Glycosylceramide. J Biol Chem 2015; 290:25863-75. [PMID: 26350457 DOI: 10.1074/jbc.m115.659110] [Citation(s) in RCA: 65] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2015] [Indexed: 11/06/2022] Open
Abstract
Sphingolipids, a large family of bioactive lipids, are implicated in stress responses, differentiation, proliferation, apoptosis, and other physiological processes. Aberrant plasma levels of sphingolipids contribute to metabolic disease, atherosclerosis, and insulin resistance. They are fairly evenly distributed in high density and apoB-containing lipoproteins (B-lps). Mechanisms involved in the transport of sphingolipids to the plasma are unknown. Here, we investigated the role of microsomal triglyceride transfer protein (MTP), required for B-lp assembly and secretion, in sphingolipid transport to the plasma. Abetalipoproteinemia patients with deleterious mutations in MTP and absence of B-lps had significantly lower plasma ceramide and sphingomyelin but normal hexosylceramide, lactosylceramide, and different sphingosines compared with unaffected controls. Furthermore, similar differential effects on plasma sphingolipids were seen in liver- and intestine-specific MTP knock-out (L,I-Mttp(-/-)) mice, suggesting that MTP specifically plays a role in the regulation of plasma ceramide and sphingomyelin. We hypothesized that MTP deficiency may affect either their synthesis or secretion. MTP deficiency had no effect on ceramide and sphingomyelin synthesis but reduced secretion from primary hepatocytes and hepatoma cells. Therefore, MTP is involved in ceramide and sphingomyelin secretion but not in their synthesis. We also found that MTP transferred these lipids between vesicles in vitro. Therefore, we propose that MTP might regulate plasma ceramide and sphingomyelin levels by transferring these lipids to B-lps in the liver and intestine and facilitating their secretion.
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Affiliation(s)
| | | | - Samar M Hammad
- the Department of Regenerative Medicine and Cell Biology, Medical University of South Carolina, Charleston, South Carolina 29425
| | - Marina Cuchel
- the Institute for Translational Medicine and Therapeutics, Cardiovascular Institute, University of Pennsylvania, Philadelphia, Pennsylvania 19104
| | - Patrizia Tarugi
- the Department of Life Sciences, University of Modena and Reggio Emilia, 41121 Modena, Italy
| | - Robert A Hegele
- the Blackburn Cardiovascular Genetics Laboratory, The Robarts Research Institute, London, Ontario N6A 5B7, Canada
| | - Nicholas O Davidson
- the Department of Medicine, Washington University School of Medicine, St. Louis, Missouri 63110
| | - Daniel J Rader
- the Institute for Translational Medicine and Therapeutics, Cardiovascular Institute, University of Pennsylvania, Philadelphia, Pennsylvania 19104
| | - Richard L Klein
- the Department of Medicine, Division of Endocrinology, Metabolism, and Medical Genetics, Medical University of South Carolina, Charleston, South Carolina 29425, the Research Service, Ralph H. Johnson Department of Veterans Affairs Medical Center, Charleston, South Carolina 29401, and
| | - M Mahmood Hussain
- From the Departments of Cell Biology and Pediatrics, State University of New York Downstate Medical Center, Brooklyn, New York 11203, the Department of Veterans Affairs New York Harbor Healthcare System, Brooklyn, New York 11209
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17
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High-density lipoprotein-mediated transcellular cholesterol transport in mouse aortic endothelial cells. Biochem Biophys Res Commun 2015; 465:256-61. [PMID: 26255968 DOI: 10.1016/j.bbrc.2015.08.011] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2015] [Accepted: 08/03/2015] [Indexed: 01/26/2023]
Abstract
Accumulation of unesterified cholesterol-rich lipid vesicles in the subendothelial space contributes to atherogenesis. Transport of cholesterol from the subendothelial intima back to the circulating blood inhibits atherosclerosis development; however, the mechanism for this process has not been fully defined. Using cultured mouse aortic endothelial cells (MAECs), we observed that unesterified cholesterol can be transported across the endothelial cell monolayer from the basolateral to the apical compartment. Administration of high-density lipoprotein (HDL) or apolipoprotein AI (apoAI) to the apical compartment enhanced transendothelial cholesterol transport in a concentration-dependent manner. Knockdown of ATP-binding cassette transporter G1 (ABCG1) or scavenger receptor class B type I (SR-B1), or inhibition of SR-B1 diminished HDL-induced transendothelial cholesterol transport; while knockdown of ABCA1 reduced apoAI-mediated cholesterol transport. HDL enhanced phosphorylation of phosphatidylinositol 3-kinase (PI3K) and Akt in MAECs. However, inhibition of PI3K or Akt did not reduce HDL-induced transendothelial cholesterol transport. These results suggest that HDL enhances transendothelial cholesterol transport by activation of a mechanism involving ABCA1, ABCG1 and SR-B1 but not involving PI3K and Akt.
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18
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Rosenblat M, Volkova N, Aviram M. Selective oxidative stress and cholesterol metabolism in lipid-metabolizing cell classes: Distinct regulatory roles for pro-oxidants and antioxidants. Biofactors 2015; 41:273-88. [PMID: 26228307 DOI: 10.1002/biof.1223] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/14/2015] [Accepted: 06/21/2015] [Indexed: 12/13/2022]
Abstract
Atherogenesis is associated with macrophage cholesterol and oxidized lipids accumulation and foam cell formation. However, two other major lipid-metabolizing cell classes, namely intestinal and liver cells, are also associated with atherogenesis. This study demonstrates that manipulations of cellular oxidative stress (by fatty acids, glucose, low-density lipoprotein, angiotensin II, polyphenolic antioxidants, or the glutathione/paraoxonase 1 systems) have some similar, but also some different effects on cholesterol metabolism in macrophages (J774A.1) versus intestinal cells (HT-29) versus liver cells (HuH7). Cellular oxidative stress was ≈3.5-folds higher in both intestinal and liver cells versus macrophages. In intestinal cells or liver cells versus macrophages, the cholesterol biosynthesis rate was increased by 9- or 15-fold, respectively. In both macrophages and intestinal cells C-18:1 and C-18:2 but not C-18:0, fatty acids significantly increased oxidative stress, whereas in liver cells oxidative stress was significantly decreased by all three fatty acids. In liver cells, trans C-18:1 versus cis C-18:1, unlike intestinal cells or macrophages, significantly increased cellular oxidative stress and cellular cholesterol biosynthesis rate. Pomegranate juice (PJ), red wine, or their phenolics gallic acids or quercetin significantly reduced cellular oxidation mostly in macrophages. Recombinant PON1 significantly decreased macrophage (but not the other cells) oxidative stress by ≈30%. We conclude that cellular atherogenesis research should look at atherogenicity, not only in macrophages but also in intestinal and liver cells, to advance our understanding of the complicated mechanisms behind atherogenesis. © 2015 BioFactors, 41(4):273-288, 2015.
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Affiliation(s)
- Mira Rosenblat
- The Lipid Research Laboratory, Technion Rappaport Faculty of Medicine, Haifa, Israel
| | - Nina Volkova
- The Lipid Research Laboratory, Technion Rappaport Faculty of Medicine, Haifa, Israel
| | - Michael Aviram
- The Lipid Research Laboratory, Technion Rappaport Faculty of Medicine, Haifa, Israel
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19
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Gaibelet G, Allart S, Tercé F, Azalbert V, Bertrand-Michel J, Hamdi S, Collet X, Orlowski S. Specific cellular incorporation of a pyrene-labelled cholesterol: lipoprotein-mediated delivery toward ordered intracellular membranes. PLoS One 2015; 10:e0121563. [PMID: 25875769 PMCID: PMC4398402 DOI: 10.1371/journal.pone.0121563] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2014] [Accepted: 01/25/2015] [Indexed: 11/18/2022] Open
Abstract
In the aim of testing tools for tracing cell trafficking of exogenous cholesterol, two fluorescent derivatives of cholesterol, 22-nitrobenzoxadiazole-cholesterol (NBD-Chol) and 21-methylpyrenyl-cholesterol (Pyr-met-Chol), with distinctive chemico-physical characteristics, have been compared for their cell incorporation properties, using two cell models differently handling cholesterol, with two incorporation routes. In the Caco-2 cell model, the cholesterol probes were delivered in bile salt micelles, as a model of intestinal absorption. The two probes displayed contrasting behaviors for cell uptake characteristics, cell staining, and efflux kinetics. In particular, Pyr-met-Chol cell incorporation involved SR-BI, while that of NBD-Chol appeared purely passive. In the PC-3 cell model, which overexpresses lipoprotein receptors, the cholesterol probes were delivered via the serum components, as a model of systemic delivery. We showed that Pyr-met-Chol-labelled purified LDL or HDL were able to specifically deliver Pyr-met-Chol to the PC-3 cells, while NBD-Chol incorporation was independent of lipoproteins. Observations by fluorescence microscopy evidenced that, while NBD-Chol readily stained the cytosolic lipid droplets, Pyr-met-Chol labelling led to the intense staining of intracellular structures of membranous nature, in agreement with the absence of detectable esterification of Pyr-met-Chol. A 48 h incubation of PC-3 cells with either Pyr-met-Chol-labelled LDL or HDL gave same staining patterns, mainly colocalizing with Lamp1, caveolin-1 and CD63. These data indicated convergent trafficking downwards their respective receptors, LDL-R and SR-BI, toward the cholesterol-rich internal membrane compartments, late endosomes and multivesicular bodies. Interestingly, Pyr-met-Chol staining of these structures exhibited a high excimer fluorescence emission, revealing their ordered membrane environment, and indicating that Pyr-met-Chol behaves as a fair cholesterol tracer regarding its preferential incorporation into cholesterol-rich domains. We conclude that, while NBD-Chol is a valuable marker of cholesterol esterification, Pyr-met-Chol is a reliable new lipoprotein fluorescent marker which allows to probe specific intracellular trafficking of cholesterol-rich membranes.
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Affiliation(s)
- Gérald Gaibelet
- INSERM U563/1048, CHU Purpan, 31024, Toulouse, cedex 3, France
- CEA, SB2SM and UMR8221/UMR9198 CNRS, I2BC, IBiTec-Saclay, 91191, Gif-sur-Yvette, cedex, France
- Université Toulouse III, UMR 1048, F-31000, Toulouse, France
| | - Sophie Allart
- Université Toulouse III, UMR 1048, F-31000, Toulouse, France
- Plateau technique d’Imagerie Cellulaire, INSERM U1043, F-31300, Toulouse, France
| | - François Tercé
- Université Toulouse III, UMR 1048, F-31000, Toulouse, France
- INSERM U1048, F-31400, Toulouse, France
| | - Vincent Azalbert
- Université Toulouse III, UMR 1048, F-31000, Toulouse, France
- INSERM U1048, F-31400, Toulouse, France
| | - Justine Bertrand-Michel
- Université Toulouse III, UMR 1048, F-31000, Toulouse, France
- INSERM U1048, Lipidomic Platform Metatoul, F-31400, Toulouse, France
| | - Safouane Hamdi
- INSERM U563/1048, CHU Purpan, 31024, Toulouse, cedex 3, France
| | - Xavier Collet
- Université Toulouse III, UMR 1048, F-31000, Toulouse, France
- INSERM U1048, F-31400, Toulouse, France
| | - Stéphane Orlowski
- INSERM U563/1048, CHU Purpan, 31024, Toulouse, cedex 3, France
- CEA, SB2SM and UMR8221/UMR9198 CNRS, I2BC, IBiTec-Saclay, 91191, Gif-sur-Yvette, cedex, France
- * E-mail:
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20
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Abstract
Plasma levels of triacylglycerols and diacylglycerols, the lipoproteins that transport them, and proteins involved in their absorption from the intestinal lumen fluctuate in a circadian manner. These changes are likely controlled by clock genes expressed in the intestine that are probably synchronized by neuronal and humoral signals from the suprachiasmatic nuclei, which constitute a master clock entrained by light signals from the eyes and from the environment, e.g., food availability. Acute changes in circadian rhythms--e.g., due to nonsynchronous work schedules or a transcontinental flight--may trigger intestinal discomfort. Chronic disruptions in circadian control mechanisms may predispose the individual to irritable bowel syndrome, gastroesophageal reflux disease, and peptic ulcer disease. A more detailed understanding of the molecular mechanisms underlying temporal changes in intestinal activity might allow us to identify novel targets for developing therapeutic approaches to these disorders.
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Affiliation(s)
- M Mahmood Hussain
- Departments of Cell Biology and Pediatrics, SUNY Downstate Medical Center, Brooklyn, New York 11203, and Virginia New York Harbor Healthcare System, Brooklyn, New York 11209;
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21
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Gnocchi D, Pedrelli M, Hurt-Camejo E, Parini P. Lipids around the Clock: Focus on Circadian Rhythms and Lipid Metabolism. BIOLOGY 2015; 4:104-32. [PMID: 25665169 PMCID: PMC4381220 DOI: 10.3390/biology4010104] [Citation(s) in RCA: 54] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/10/2014] [Accepted: 01/28/2015] [Indexed: 12/24/2022]
Abstract
Disorders of lipid and lipoprotein metabolism and transport are responsible for the development of a large spectrum of pathologies, ranging from cardiovascular diseases, to metabolic syndrome, even to tumour development. Recently, a deeper knowledge of the molecular mechanisms that control our biological clock and circadian rhythms has been achieved. From these studies it has clearly emerged how the molecular clock tightly regulates every aspect of our lives, including our metabolism. This review analyses the organisation and functioning of the circadian clock and its relevance in the regulation of physiological processes. We also describe metabolism and transport of lipids and lipoproteins as an essential aspect for our health, and we will focus on how the circadian clock and lipid metabolism are greatly interconnected. Finally, we discuss how a deeper knowledge of this relationship might be useful to improve the recent spread of metabolic diseases.
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Affiliation(s)
- Davide Gnocchi
- Division of Clinical Chemistry, Department of Laboratory Medicine, Karolinska Institutet at Karolinska University Hospital Huddinge, Stockholm, 14186, Sweden.
| | - Matteo Pedrelli
- Division of Clinical Chemistry, Department of Laboratory Medicine, Karolinska Institutet at Karolinska University Hospital Huddinge, Stockholm, 14186, Sweden.
- Strategy and Externalization, CVMD iMED, AstraZeneca, R&D, Mölndal, SE-431 83, Sweden.
| | - Eva Hurt-Camejo
- Strategy and Externalization, CVMD iMED, AstraZeneca, R&D, Mölndal, SE-431 83, Sweden.
| | - Paolo Parini
- Division of Clinical Chemistry, Department of Laboratory Medicine, Karolinska Institutet at Karolinska University Hospital Huddinge, Stockholm, 14186, Sweden.
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22
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Abstract
Among all the metabolites present in the plasma, lipids, mainly triacylglycerol and diacylglycerol, show extensive circadian rhythms. These lipids are transported in the plasma as part of lipoproteins. Lipoproteins are synthesized primarily in the liver and intestine and their production exhibits circadian rhythmicity. Studies have shown that various proteins involved in lipid absorption and lipoprotein biosynthesis show circadian expression. Further, intestinal epithelial cells express circadian clock genes and these genes might control circadian expression of different proteins involved in intestinal lipid absorption. Intestinal circadian clock genes are synchronized by signals emanating from the suprachiasmatic nuclei that constitute a master clock and from signals coming from other environmental factors, such as food availability. Disruptions in central clock, as happens due to disruptions in the sleep/wake cycle, affect intestinal function. Similarly, irregularities in temporal food intake affect intestinal function. These changes predispose individuals to various metabolic disorders, such as metabolic syndrome, obesity, diabetes, and atherosclerosis. Here, we summarize how circadian rhythms regulate microsomal triglyceride transfer protein, apoAIV, and nocturnin to affect diurnal regulation of lipid absorption.
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Affiliation(s)
- M Mahmood Hussain
- Departments of Cell Biology and Pediatrics, State University of New York Downstate Medical Center, Brooklyn, NY 11203; and Veterans Affairs New York Harbor Healthcare System, Brooklyn, NY 11209
| | - Xiaoyue Pan
- Departments of Cell Biology and Pediatrics, State University of New York Downstate Medical Center, Brooklyn, NY 11203; and Veterans Affairs New York Harbor Healthcare System, Brooklyn, NY 11209
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23
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Iqbal J, Boutjdir M, Rudel LL, Hussain MM. Intestine-specific MTP and global ACAT2 deficiency lowers acute cholesterol absorption with chylomicrons and HDLs. J Lipid Res 2014; 55:2261-75. [PMID: 25030663 DOI: 10.1194/jlr.m047951] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Intestinal cholesterol absorption involves the chylomicron and HDL pathways and is dependent on microsomal triglyceride transfer protein (MTP) and ABCA1, respectively. Chylomicrons transport free and esterified cholesterol, whereas HDLs transport free cholesterol. ACAT2 esterifies cholesterol for secretion with chylomicrons. We hypothesized that free cholesterol accumulated during ACAT2 deficiency may be secreted with HDLs when chylomicron assembly is blocked. To test this, we studied cholesterol absorption in mice deficient in intestinal MTP, global ACAT2, and both intestinal MTP and global ACAT2. Intestinal MTP ablation significantly increased intestinal triglyceride and cholesterol levels and reduced their transport with chylomicrons. In contrast, global ACAT2 deficiency had no effect on triglyceride absorption but significantly reduced cholesterol absorption with chylomicrons and increased cellular free cholesterol. Their combined deficiency reduced cholesterol secretion with both chylomicrons and HDLs. Thus, contrary to our hypothesis, free cholesterol accumulated in the absence of MTP and ACAT2 is unavailable for secretion with HDLs. Global ACAT2 deficiency causes mild hypertriglyceridemia and reduces hepatosteatosis in mice fed high cholesterol diets by increasing hepatic lipoprotein production by unknown mechanisms. We show that this phenotype is preserved in the absence of intestinal MTP in global ACAT2-deficient mice fed a Western diet. Further, we observed increases in hepatic MTP activity in these mice. Thus, ACAT2 deficiency might increase MTP expression to avoid hepatosteatosis in cholesterol-fed animals. Therefore, ACAT2 inhibition might avert hepatosteatosis associated with high cholesterol diets by increasing hepatic MTP expression and lipoprotein production.
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Affiliation(s)
- Jahangir Iqbal
- Departments of Cell Biology and Pediatrics, SUNY Downstate Medical Center, Brooklyn, NY 11203 Veterans Affairs New York Harbor Healthcare System, Brooklyn, NY 11209
| | - Mohamed Boutjdir
- Departments of Cell Biology and Pediatrics, SUNY Downstate Medical Center, Brooklyn, NY 11203 Veterans Affairs New York Harbor Healthcare System, Brooklyn, NY 11209
| | - Lawrence L Rudel
- Departments of Pathology and Biochemistry, Wake Forest University School of Medicine, Winston-Salem, NC 27104
| | - M Mahmood Hussain
- Departments of Cell Biology and Pediatrics, SUNY Downstate Medical Center, Brooklyn, NY 11203 Veterans Affairs New York Harbor Healthcare System, Brooklyn, NY 11209
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24
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Abstract
PURPOSE OF REVIEW To summarize the evidence for the presence of two lipid absorption pathways and their regulation. RECENT FINDINGS Lipid absorption involves hydrolysis of dietary fat in the lumen of the intestine, followed by the uptake of hydrolyzed products by enterocytes. Lipids are resynthesized in the endoplasmic reticulum and are either secreted with chylomicrons and HDLs or stored as cytoplasmic lipid droplets. Lipids in the droplets are hydrolyzed and are secreted at a later time. Secretion of lipids by the chylomicron and HDL pathways are dependent on microsomal triglyceride transfer protein (MTP) and ATP-binding cassette family A protein 1, respectively, and are regulated independently. Gene-ablation studies showed that MTP function and chylomicron assembly is essential for the absorption of triglycerides. Ablation of MTP abolishes triglyceride absorption and results in massive triglyceride accumulation in enterocytes. Although the majority of phospholipid, cholesterol, and vitamin E are absorbed through the chylomicron pathway, a significant amount of these lipids are also absorbed via the HDL pathway. Chylomicron assembly and secretion is increased by the enhanced availability of fatty acids, whereas the HDL pathway is upregulated by liver X receptor agonists. SUMMARY Triglycerides are exclusively transported with chylomicrons and this process is critically dependent on MTP. In addition to chylomicrons, absorption of phospholipids, free cholesterol, retinol, and vitamin E also involves HDLs. These two pathways are complementary and are regulated independently. They may be targeted to lower lipid absorption in order to control hyperlipidemia, obesity, metabolic syndrome, steatosis, insulin resistance, atherosclerosis, and other disorders.
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Affiliation(s)
- M Mahmood Hussain
- aDepartment of Cell Biology bDepartment of Pediatrics, SUNY Downstate Medical Center cVA New York Harbor Healthcare System, Brooklyn, New York, USA
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Hu YW, Hu YR, Zhao JY, Li SF, Ma X, Wu SG, Lu JB, Qiu YR, Sha YH, Wang YC, Gao JJ, Zheng L, Wang Q. An agomir of miR-144-3p accelerates plaque formation through impairing reverse cholesterol transport and promoting pro-inflammatory cytokine production. PLoS One 2014; 9:e94997. [PMID: 24733347 PMCID: PMC3986368 DOI: 10.1371/journal.pone.0094997] [Citation(s) in RCA: 81] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2014] [Accepted: 03/20/2014] [Indexed: 12/13/2022] Open
Abstract
Aims ATP-binding cassette transporter A1 (ABCA1) mediates the efflux of cholesterol and phospholipids to lipid-poor apolipoproteins, which then form nascent HDL, a key step in the mechanism of reverse cholesterol transport (RCT). While a series of microRNAs (miRNAs) have been identified as potent post-transcriptional regulators of lipid metabolism, their effects on ABCA1 function and associated mechanisms remain unclear. Methods and Results ABCA1 was identified as a potential target of miR-144-3p, based on the results of bioinformatic analysis and the luciferase reporter assay, and downregulated after transfection of cells with miR-144-3p mimics, as observed with real-time PCR and western blot. Moreover, miR-144-3p mimics (agomir) enhanced the expression of inflammatory factors, including IL-1β, IL-6 and TNF-α, in vivo and in vitro, inhibited cholesterol efflux in THP-1 macrophage-derived foam cells, decreased HDL-C circulation and impaired RCT in vivo, resulting in accelerated pathological progression of atherosclerosis in apoE−/− mice. Clinical studies additionally revealed a positive correlation of circulating miR-144-3p with serum CK, CK-MB, LDH and AST in subjects with AMI. Conclusions Our findings clearly indicate that miR-144-3p is essential for the regulation of cholesterol homeostasis and inflammatory reactions, supporting its utility as a potential therapeutic target of atherosclerosis and a promising diagnostic biomarker of AMI.
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Affiliation(s)
- Yan-Wei Hu
- Laboratory Medicine Center, Nanfang Hospital, Southern Medical University, Guangzhou, Guangdong, China
| | - Ya-Rong Hu
- Laboratory Medicine Center, Nanfang Hospital, Southern Medical University, Guangzhou, Guangdong, China
| | - Jia-Yi Zhao
- Laboratory Medicine Center, Nanfang Hospital, Southern Medical University, Guangzhou, Guangdong, China
| | - Shu-Fen Li
- Laboratory Medicine Center, Nanfang Hospital, Southern Medical University, Guangzhou, Guangdong, China
| | - Xin Ma
- Department of Anesthesiology, Nanfang Hospital, Southern Medical University, Guangzhou, Guangdong, China
| | - Shao-Guo Wu
- Laboratory Medicine Center, Nanfang Hospital, Southern Medical University, Guangzhou, Guangdong, China
| | - Jing-Bo Lu
- Department of Vascular Surgery, Nanfang Hospital, Southern Medical University, Guangzhou, Guangdong, China
| | - Yu-Rong Qiu
- Laboratory Medicine Center, Nanfang Hospital, Southern Medical University, Guangzhou, Guangdong, China
| | - Yan-Hua Sha
- Laboratory Medicine Center, Nanfang Hospital, Southern Medical University, Guangzhou, Guangdong, China
| | - Yan-Chao Wang
- Laboratory Medicine Center, Nanfang Hospital, Southern Medical University, Guangzhou, Guangdong, China
| | - Ji-Juan Gao
- Laboratory Medicine Center, Nanfang Hospital, Southern Medical University, Guangzhou, Guangdong, China
| | - Lei Zheng
- Laboratory Medicine Center, Nanfang Hospital, Southern Medical University, Guangzhou, Guangdong, China
- * E-mail: (QW); (LZ)
| | - Qian Wang
- Laboratory Medicine Center, Nanfang Hospital, Southern Medical University, Guangzhou, Guangdong, China
- * E-mail: (QW); (LZ)
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Zhou L, Yang H, Okoro EU, Guo Z. Up-regulation of cholesterol absorption is a mechanism for cholecystokinin-induced hypercholesterolemia. J Biol Chem 2014; 289:12989-99. [PMID: 24692543 DOI: 10.1074/jbc.m113.534388] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
Excessive absorption of intestinal cholesterol is a risk factor for atherosclerosis. This report examines the effect of cholecystokinin (CCK) on plasma cholesterol level and intestinal cholesterol absorption using the in vivo models of C57BL/6 wild-type and low density lipoprotein receptor knock-out (LDLR(-/-)) mice. These data were supported by in vitro studies involving mouse primary intestinal epithelial cells and human Caco-2 cells; both express CCK receptor 1 and 2 (CCK1R and CCK2R). We found that intravenous injection of [Thr(28),Nle(31)]CCK increased plasma cholesterol levels and intestinal cholesterol absorption in both wild-type and LDLR(-/-) mice. Treatment of mouse primary intestinal epithelial cells with [Thr(28),Nle(31)]CCK increased cholesterol absorption, whereas selective inhibition of CCK1R and CCK2R with antagonists attenuated CCK-induced cholesterol absorption. In Caco-2 cells, CCK enhanced CCK1R/CCK2R heterodimerization. Knockdown of both CCK1R and CCK2 or either one of them diminished CCK-induced cholesterol absorption to the same extent. CCK also increased cell surface-associated NPC1L1 (Niemann-Pick C1-like 1) transporters but did not alter their total protein expression. Inhibition or knockdown of NPC1L1 attenuated CCK-induced cholesterol absorption. CCK enhanced phosphatidylinositide 3-kinase (PI3K) and Akt phosphorylation and augmented the interaction between NPC1L1 and Rab11a (Rab-GTPase-11a), whereas knockdown of CCK receptors or inhibition of G protein βγ dimer (Gβγ) diminished CCK-induced PI3K and Akt phosphorylation. Inhibition of PI3K and Akt or knockdown of PI3K diminished CCK-induced NPC1L1-Rab11a interaction and cholesterol absorption. Knockdown of Rab11a suppressed CCK-induced NPC1L1 translocation and cholesterol absorption. These data imply that CCK enhances cholesterol absorption by activation of a pathway involving CCK1R/CCK2R, Gβγ, PI3K, Akt, Rab11a, and NPC1L.
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Affiliation(s)
- LiChun Zhou
- From the Department of Physiology, Meharry Medical College, Nashville, Tennessee 37208
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Yamaguchi S, Zhang B, Tomonaga T, Seino U, Kanagawa A, Segawa M, Nagasaka H, Suzuki A, Miida T, Yamada S, Sasaguri Y, Doi T, Saku K, Okazaki M, Tochino Y, Hirano KI. Selective evaluation of high density lipoprotein from mouse small intestine by an in situ perfusion technique. J Lipid Res 2014; 55:905-18. [PMID: 24569139 DOI: 10.1194/jlr.m047761] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The small intestine (SI) is the second-greatest source of HDL in mice. However, the selective evaluation of SI-derived HDL (SI-HDL) has been difficult because even the origin of HDL obtained in vivo from the intestinal lymph duct of anesthetized rodents is doubtful. To shed light on this question, we have developed a novel in situ perfusion technique using surgically isolated mouse SI, with which the possible filtration of plasma HDL into the SI lymph duct can be prevented. With the developed method, we studied the characteristics of and mechanism for the production and regulation of SI-HDL. Nascent HDL particles were detected in SI lymph perfusates in WT mice, but not in ABCA1 KO mice. SI-HDL had a high protein content and was smaller than plasma HDL. SI-HDL was rich in TG and apo AIV compared with HDL in liver perfusates. SI-HDL was increased by high-fat diets and reduced in apo E KO mice. In conclusion, with our in situ perfusion model that enables the selective evaluation of SI-HDL, we demonstrated that ABCA1 plays an important role in intestinal HDL production, and SI-HDL is small, dense, rich in apo AIV, and regulated by nutritional and genetic factors.
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Affiliation(s)
- Satoshi Yamaguchi
- Laboratory of Cardiovascular Disease, Novel, Non-invasive and Nutritional Therapeutics (CNT), Graduate School of Medicine, Osaka University, Osaka, Japan
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Nicod N, Parker RS. Vitamin E secretion by Caco-2 monolayers to APOA1, but not to HDL, is vitamer selective. J Nutr 2013; 143:1565-72. [PMID: 23946344 PMCID: PMC3771812 DOI: 10.3945/jn.113.176834] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
The aim of this study was to characterize the pathways of basolateral secretion of common dietary tocopherols from polarized Caco-2 monolayers, a model of intestinal absorption. Given differences in structure and physical properties, we hypothesized that secretion may differ between different forms of vitamin E, thus potentially contribute to the selectivity seen in vivo. Monolayers were incubated apically and simultaneously with 10 μmol/L α-, γ-, and δ-tocopherol (1:1:1) in lipid micelles. Treatment with the microsomal triglyceride transfer protein inhibitor BMS201038 revealed that the triglyceride-rich particle secretory pathway (apolipoprotein B-dependent pathway) accounted for ~ 80% of total tocopherol secretion, without selectivity among the three forms of vitamin E. Apolipoprotein B-independent secretion of tocopherols (and cholesterol) was greatly enhanced by the liver X receptor agonist T0901317. T0901317 induced ATP-binding cassette transporter A1 (ABCA1) protein expression and basolateral secretion of tocopherols to apolipoprotein A1. ABCA1-dependent secretion demonstrated vitamer selectivity such that efficiency of secretion of α- and γ-tocopherols exceeded that of δ-tocopherol. Basal addition of HDL stimulated vitamin E secretion but without selectivity among the three forms, whereas LDL had no effect. Basal addition of scavenger receptor class B member I (SR-BI) blocking antibody, which inhibits the interaction between SR-BI and HDL, increased basal accumulation of all tocopherols, demonstrating a role for SR-BI in cellular re-uptake of secreted vitamin E. These findings demonstrated that vitamin E and cholesterol utilize common pathways of secretion and that secretion via the ABCA1 pathway favors certain forms of vitamin E.
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Iqbal J, Parks JS, Hussain MM. Lipid absorption defects in intestine-specific microsomal triglyceride transfer protein and ATP-binding cassette transporter A1-deficient mice. J Biol Chem 2013; 288:30432-30444. [PMID: 24019513 DOI: 10.1074/jbc.m113.501247] [Citation(s) in RCA: 50] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
We have previously described apolipoprotein B (apoB)-dependent and -independent cholesterol absorption pathways and the role of microsomal triglyceride transfer protein (MTP) and ATP-binding cassette transporter A1 (ABCA1) in these pathways. To assess the contribution of these pathways to cholesterol absorption and to determine whether there are other pathways, we generated mice that lack MTP and ABCA1, individually and in combination, in the intestine. Intestinal deletions of Mttp and Abca1 decreased plasma cholesterol concentrations by 45 and 24%, respectively, whereas their combined deletion reduced it by 59%. Acute cholesterol absorption was reduced by 28% in the absence of ABCA1, and it was reduced by 92-95% when MTP was deleted in the intestine alone or together with ABCA1. MTP deficiency significantly reduced triglyceride absorption, although ABCA1 deficiency had no effect. ABCA1 deficiency did not affect cellular lipids, but Mttp deficiency significantly increased intestinal levels of triglycerides and free fatty acids. Accumulation of intestinal free fatty acids, but not triglycerides, in Mttp-deficient intestines was prevented when mice were also deficient in intestinal ABCA1. Combined deficiency of these genes increased intestinal fatty acid oxidation as a consequence of increased expression of peroxisome proliferator-activated receptor-γ (PPARγ) and carnitine palmitoyltransferase 1α (CPT1α). These studies show that intestinal MTP and ABCA1 are critical for lipid absorption and are the main determinants of plasma and intestinal lipid levels. Reducing their activities might lower plasma lipid concentrations.
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Affiliation(s)
- Jahangir Iqbal
- From the Departments of Cell Biology and Pediatrics, State University of New York Downstate Medical Center, Brooklyn, New York 11203 and
| | - John S Parks
- the Department of Pathology, Section on Lipid Sciences and Biochemistry, Wake Forest School of Medicine, Winston-Salem, North Carolina 25157
| | - M Mahmood Hussain
- From the Departments of Cell Biology and Pediatrics, State University of New York Downstate Medical Center, Brooklyn, New York 11203 and.
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Abstract
BACKGROUND Clock is a key transcription factor that positively controls circadian regulation. However, its role in plasma cholesterol homeostasis and atherosclerosis has not been studied. METHODS AND RESULTS We show for the first time that dominant-negative Clock mutant protein (Clock(Δ19/Δ19)) enhances plasma cholesterol and atherosclerosis in 3 different mouse models. Detailed analyses revealed that Clk(Δ19/Δ19)Apoe(-/-) mice display hypercholesterolemia resulting from the accumulation of apolipoprotein B48-containing cholesteryl ester-rich lipoproteins. Physiological studies showed that enhanced cholesterol absorption by the intestine contributes to hypercholesterolemia. Molecular studies indicated that the expression of Niemann Pick C1 Like 1, Acyl-CoA:Cholesterol acyltransferase 1, and microsomal triglyceride transfer protein in the intestines of Clk(Δ19/Δ19)Apoe(-/-) mice was high and that enterocytes assembled and secreted more chylomicrons. Furthermore, we identified macrophage dysfunction as another potential cause of increased atherosclerosis in Clk(Δ19/Δ19)Apoe(-/-) mice. Macrophages from Clk(Δ19/Δ19)Apoe(-/-) mice expressed higher levels of scavenger receptors and took up more modified lipoproteins compared with Apoe(-/-) mice, but they expressed low levels of ATP binding casette protein family A member 1 and were defective in cholesterol efflux. Molecular studies revealed that Clock regulates ATP binding casette protein family A member 1 expression in macrophages by modulating upstream transcription factor 2 expression. CONCLUSIONS Clock(Δ19/Δ19) protein enhances atherosclerosis by increasing intestinal cholesterol absorption, augmenting uptake of modified lipoproteins by macrophages, and reducing cholesterol efflux from macrophages. These studies establish that circadian Clock activity is crucial in maintaining low plasma cholesterol levels and in reducing atherogenesis in mice.
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Affiliation(s)
- Xiaoyue Pan
- Departments of Cell Biology and Pediatrics, SUNY Downstate Medical Center, Brooklyn, NY
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Soh J, Iqbal J, Queiroz J, Fernandez-Hernando C, Hussain MM. MicroRNA-30c reduces hyperlipidemia and atherosclerosis in mice by decreasing lipid synthesis and lipoprotein secretion. Nat Med 2013; 19:892-900. [PMID: 23749231 PMCID: PMC4121125 DOI: 10.1038/nm.3200] [Citation(s) in RCA: 225] [Impact Index Per Article: 20.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2012] [Accepted: 04/16/2013] [Indexed: 02/07/2023]
Abstract
Hyperlipidemia is a risk factor for various cardiovascular and metabolic disorders. Overproduction of lipoproteins, a process critically dependent on microsomal triglyceride transfer protein (MTP), can contribute to hyperlipidemia. We show that microRNA-30c (miR-30c) interacts with the 3′-untranslated region of the MTP mRNA and induces degradation leading to reductions in its activity and media apolipoprotein B. Further, miR-30c reduces hyperlipidemia and atherosclerosis in Western diet fed mice by decreasing lipid synthesis and secretion of triglyceride-rich apoB-containing lipoproteins. Therefore, miR-30c coordinately reduces lipid biosynthesis and lipoprotein secretion to control hepatic and plasma lipids and might be useful in treating hyperlipidemias and associated disorders.
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Affiliation(s)
- James Soh
- School of Graduate Studies, Molecular and Cell Biology Program, State University of New York Downstate Medical Center, Brooklyn, New York, USA
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Pan X, Munshi MK, Iqbal J, Queiroz J, Sirwi AA, Shah S, Younus A, Hussain MM. Circadian regulation of intestinal lipid absorption by apolipoprotein AIV involves forkhead transcription factors A2 and O1 and microsomal triglyceride transfer protein. J Biol Chem 2013; 288:20464-76. [PMID: 23729668 DOI: 10.1074/jbc.m113.473454] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
We have shown previously that Clock, microsomal triglyceride transfer protein (MTP), and nocturnin are involved in the circadian regulation of intestinal lipid absorption. Here, we clarified the role of apolipoprotein AIV (apoAIV) in the diurnal regulation of plasma lipids and intestinal lipid absorption in mice. Plasma triglyceride in apoAIV(-/-) mice showed diurnal variations similar to apoAIV(+/+) mice; however, the increases in plasma triglyceride at night were significantly lower in these mice. ApoAIV(-/-) mice absorbed fewer lipids at night and showed blunted response to daytime feeding. To explain reasons for these lower responses, we measured MTP expression; intestinal MTP was low at night, and its induction after food entrainment was less in apoAIV(-/-) mice. Conversely, apoAIV overexpression increased MTP mRNA in hepatoma cells, indicating transcriptional regulation. Mechanistic studies revealed that sequences between -204/-775 bp in the MTP promoter respond to apoAIV and that apoAIV enhances expression of FoxA2 and FoxO1 transcription factors and their binding to the identified cis elements in the MTP promoter at night. Knockdown of FoxA2 and FoxO1 abolished apoAIV-mediated MTP induction. Similarly, knockdown of apoAIV in differentiated Caco-2 cells reduced MTP, FoxA2, and FoxO1 mRNA levels, cellular MTP activity, and media apoB. Moreover, FoxA2 and FoxO1 expression showed diurnal variations, and their expression was significantly lower in apoAIV(-/-) mice. These data indicate that apoAIV modulates diurnal changes in lipid absorption by regulating forkhead transcription factors and MTP and that inhibition of apoAIV expression might reduce plasma lipids.
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Affiliation(s)
- Xiaoyue Pan
- Department of Cell Biology, SUNY Downstate Medical Center, Brooklyn, New York 11203, USA.
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Williams HD, Trevaskis NL, Charman SA, Shanker RM, Charman WN, Pouton CW, Porter CJH. Strategies to address low drug solubility in discovery and development. Pharmacol Rev 2013; 65:315-499. [PMID: 23383426 DOI: 10.1124/pr.112.005660] [Citation(s) in RCA: 985] [Impact Index Per Article: 89.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
Drugs with low water solubility are predisposed to low and variable oral bioavailability and, therefore, to variability in clinical response. Despite significant efforts to "design in" acceptable developability properties (including aqueous solubility) during lead optimization, approximately 40% of currently marketed compounds and most current drug development candidates remain poorly water-soluble. The fact that so many drug candidates of this type are advanced into development and clinical assessment is testament to an increasingly sophisticated understanding of the approaches that can be taken to promote apparent solubility in the gastrointestinal tract and to support drug exposure after oral administration. Here we provide a detailed commentary on the major challenges to the progression of a poorly water-soluble lead or development candidate and review the approaches and strategies that can be taken to facilitate compound progression. In particular, we address the fundamental principles that underpin the use of strategies, including pH adjustment and salt-form selection, polymorphs, cocrystals, cosolvents, surfactants, cyclodextrins, particle size reduction, amorphous solid dispersions, and lipid-based formulations. In each case, the theoretical basis for utility is described along with a detailed review of recent advances in the field. The article provides an integrated and contemporary discussion of current approaches to solubility and dissolution enhancement but has been deliberately structured as a series of stand-alone sections to allow also directed access to a specific technology (e.g., solid dispersions, lipid-based formulations, or salt forms) where required.
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Affiliation(s)
- Hywel D Williams
- Drug Delivery, Disposition and Dynamics, Monash Institute of Pharmaceutical Sciences, Monash University, Parkville, Victoria, Australia
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Vanmierlo T, Husche C, Schött HF, Pettersson H, Lütjohann D. Plant sterol oxidation products--analogs to cholesterol oxidation products from plant origin? Biochimie 2012; 95:464-72. [PMID: 23009926 DOI: 10.1016/j.biochi.2012.09.021] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2012] [Accepted: 09/15/2012] [Indexed: 12/27/2022]
Abstract
Cholesterol and plant sterols are lipids which are abundantly present in a western type diet of animal and plant origin, respectively. The daily intake averages 300 mg/day each. Over the past decades, a steadily increasing consumption of plant sterol enriched dairy products (2-3 g/day) took place to lower circulating LDL cholesterol concentrations. Like all unsaturated components, plant sterols can be attacked by reactive oxygen species resulting in plant sterol oxidation products (POPs). The most widespread methods for POP determination are high-performance liquid chromatography and gas-liquid chromatography. Yet, based on the low plasma POP concentrations in normophytosterolemic subjects (POPs: ∼0.3-4.5 ng/mL), a reliable quantification yielding an appropriate limit of detection remains a challenge. While the more abundantly present cholesterol oxidation products (COPs) have elaborately been studied, research on the metabolism and biological effects of POPs is only emerging. In relation to atherogenity, biological effects including modulation of cholesterol homeostasis, membrane functioning, and inflammation are attributed to POPs. Although mostly supra-physiological concentrations are applied in in vitro assays, anti-tumor activity, cytotoxicity and estrogen-competition have been attributed to specific POPs. However, it is not obvious, if and how POPs may exert in vivo adverse or beneficial health effects similar to those attributed to COPs. In the field of nutritional science, standardized methods for the determination of POPs are required to perform relevant biological studies and to assess their presence in complex foods or biological tissues and fluids. The aim of this review is to provide an overview and evaluation of the published methods and an update on the biological effects attributed to POPs.
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Affiliation(s)
- T Vanmierlo
- Institute for Clinical Chemistry and Clinical Pharmacology, University Clinics Bonn, Sigmund-Freud-Strasse 25, Bonn, Germany
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Brauner R, Johannes C, Ploessl F, Bracher F, Lorenz RL. Phytosterols reduce cholesterol absorption by inhibition of 27-hydroxycholesterol generation, liver X receptor α activation, and expression of the basolateral sterol exporter ATP-binding cassette A1 in Caco-2 enterocytes. J Nutr 2012; 142:981-9. [PMID: 22535758 DOI: 10.3945/jn.111.157198] [Citation(s) in RCA: 53] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Phytosterol-enriched foods are increasingly marketed to lower cholesterol levels and atherosclerosis in the general population. Phytosterols reduce cholesterol absorption, but the molecular mechanism is controversial. We therefore investigated the phytosterol effects on cholesterol metabolism in human enterocyte, hepatocyte, and macrophage models relevant for sterol absorption, reverse transport, and excretion. Isomolar sitosterol (50 μmol/L) was less effectively taken up by enterocytes than cholesterol but suppressed apical cholesterol uptake by 50% (P < 0.01) and basolateral secretion by two-thirds (P < 0.01) whether added in micelles or ethanol or complexed to cyclodextrin. In contrast, enterocytes handled nanomolar (3)H-sitosterol similarly to cholesterol. Enterocytes selectively oxidized all sterols to 27-hydroxy- and 27-carboxy-sterols. Conversion rates were much lower for sitosterol (0.05 ± 0.02 nmol/mg protein) and campesterol (0.48 ± 0.10) compared with cholesterol (3.73 ± 0.60) (P < 0.001). 27-Hydroxycholesterol (27OH-C) activated liver-X-receptor alpha (LXRα) (P < 0.01) and stimulated ATP-binding cassette transporter (ABC) A1 expression (P < 0.001) and basolateral systemic cholesterol secretion from enterocytes (P < 0.05). In co-incubations, phytosterols inhibited 27OH-C generation by sterol 27-hydroxylase (P < 0.001) and reduced LXRα-mediated ABCA1 expression (P < 0.01) and basolateral systemic cholesterol secretion. In contrast, ABCG8 transcription and apical sterol resecretion was unchanged by LXRα activation in human enterocytes. Exogenous LXRα agonists reverted sterol selectivity and phytosterol cholesterol interaction. Due to constitutive apical expression of ABCG5/G8 and LXRα-enhanced basolateral expression of ABCA1 in enterocytes, interference of phytosterols with the generation of the dominating LXRα-agonist 27OH-C blocks the self-priming component of cholesterol absorption. This local LXRα antagonism of dietary phytosterols contributes to sterol selectivity and reduces fractional cholesterol absorption and preloading of nascent HDL with dietary cholesterol.
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Xie Y, Kennedy S, Sidhu R, Luo J, Ory DS, Davidson NO. Liver X receptor agonist modulation of cholesterol efflux in mice with intestine-specific deletion of microsomal triglyceride transfer protein. Arterioscler Thromb Vasc Biol 2012; 32:1624-31. [PMID: 22580900 DOI: 10.1161/atvbaha.112.246066] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
OBJECTIVE Previous work demonstrated that intestinal cholesterol absorption and regulated expression of intestinal Niemann-Pick C1-like 1 and ATP-binding cassette protein A1 are required for liver X receptor (LXR) agonist-mediated increases in high-density lipoprotein biogenesis. We re-examined those conclusions in mice with intestine-specific deletion of the microsomal triglyceride transfer protein (MTTP-IKO), where chylomicron formation is eliminated. METHODS AND RESULTS MTTP-IKO mice demonstrated sustained ≈90% reduction in cholesterol absorption and >80% reduction in Niemann-Pick C1-like 1 expression, yet LXR agonist treatment increased serum high-density lipoprotein and upregulated intestinal ATP-binding cassette protein A1 expression. Hepatic lipogenesis and triglyceride content increased with LXR agonist treatment in both genotypes. Biliary cholesterol secretion was increased in MTTP-IKO mice without further increase upon LXR agonist administration. LXR agonist treatment caused a paradoxical increase in cholesterol absorption in MTTP-IKO mice and decreased fecal neutral sterol excretion, but to levels that still exceeded fecal neutral sterol excretion in LXR agonist-treated control mice. Finally, MTTP-IKO mice demonstrated indistinguishable patterns of increased cholesterol turnover and efflux after intravenous radiolabeled cholesterol administration, with or without LXR agonist treatment. CONCLUSIONS Both intestinal and hepatic cholesterol efflux pathways are basally upregulated in MTTP-IKO mice. Moreover, LXR-dependent pathways modulate intestinal cholesterol absorption, transport, efflux, and high-density lipoprotein production independent of chylomicron assembly and secretion.
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Affiliation(s)
- Yan Xie
- Department of Medicine, Washington University School of Medicine, St Louis, MO 63110, USA
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Iqbal J, Queiroz J, Li Y, Jiang XC, Ron D, Hussain MM. Increased intestinal lipid absorption caused by Ire1β deficiency contributes to hyperlipidemia and atherosclerosis in apolipoprotein E-deficient mice. Circ Res 2012; 110:1575-84. [PMID: 22556338 DOI: 10.1161/circresaha.112.264283] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
RATIONALE High fasting serum lipid levels are significant risk factors for atherosclerosis. However, the contributions of postprandial excursions in serum lipoproteins to atherogenesis are less well-characterized. OBJECTIVE This study aims to delineate whether changes in intestinal lipid absorption associated with loss of inositol-requiring enzyme 1β (Ire1β) would affect the development of hyperlipidemia and atherosclerosis in Apoe(-/-) mice. METHODS AND RESULTS We used Ire1β-deficient mice to assess the contribution of intestinal lipid absorption to atherosclerosis. Here, we show that Ire1b(-/-)/Apoe(-/-) mice contain higher levels of intestinal microsomal triglyceride transfer protein, absorb more lipids, exhibit hyperlipidemia, and have higher levels of atherosclerotic plaques compared with Apoe(-/-) mice when fed chow and western diets. CONCLUSIONS These studies indicate that Ire1β regulates intestinal lipid absorption and that increased intestinal lipoprotein production contributes to atherosclerosis.
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Affiliation(s)
- Jahangir Iqbal
- Department of Cell Biology, Box 5, SUNY Downstate Medical Center, 450 Clarkson Ave, Brooklyn, NY 11203, USA.
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Borel P. Genetic variations involved in interindividual variability in carotenoid status. Mol Nutr Food Res 2012; 56:228-40. [DOI: 10.1002/mnfr.201100322] [Citation(s) in RCA: 117] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2011] [Revised: 06/23/2011] [Accepted: 07/22/2011] [Indexed: 11/08/2022]
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Respective contributions of intestinal Niemann-Pick C1-like 1 and scavenger receptor class B type I to cholesterol and tocopherol uptake: in vivo v. in vitro studies. Br J Nutr 2011; 107:1296-304. [PMID: 21929836 DOI: 10.1017/s0007114511004405] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
The intestinal absorption of cholesterol and lipid micronutrients such as vitamin E has been shown to share some common pathways. The present study aims to further compare the uptake of cholesterol ([3H]cholesterol v. 22-(N-(7-nitrobenz-2-oxa-1,3-diazol-4-yl)amino)-23,24-bisnor-5-cholen-3-ol (NBD-cholesterol)) and tocopherol in Caco-2 TC-7 cells and in mouse intestine, with special focus on the respective roles of scavenger receptor class B type I (SR-BI) and Niemann-Pick C1-like 1 (NPC1L1). Conversely to NBD-cholesterol, the uptakes of [3H]cholesterol and tocopherol by Caco-2 cells were impaired by both block lipid transport-1 and ezetimibe, which inhibit SR-BI and NPC1L1, respectively. These inhibitions occurred only when cholesterol or tocopherol was delivered to cells included in micelles that contained biliary acid and at least oleic acid as a lipid. In vivo, after 2 h of digestion in mice, the uptake of the two cholesterol analogues and of tocopherol all showed distinct patterns along the duodenum-jejunum axis. [3H]Cholesterol uptake, which correlated closely to NPC1L1 mRNA expression in wild-type (wt) mice, was strongly inhibited by ezetimibe. Intestinal SR-BI overexpression did not change NPC1L1 expression and led to a significant increase in [3H]cholesterol uptake in the distal jejunum. Conversely, neither ezetimibe treatment nor SR-BI overexpression had an effect on NBD-cholesterol uptake. However, in contrast with SR-BI mRNA expression, tocopherol absorption increased strongly up to the distal jejunum in wt mice where it was specifically inhibited by ezetimibe, and was increased in the proximal intestine of intestinal SR-BI-overexpressing mice. Thus, cholesterol and tocopherol uptakes share common pathways in cell culture models, but display different in vivo absorption patterns associated with distinct contributions of SR-BI and NPC1L1.
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Pons V, Rolland C, Nauze M, Danjoux M, Gaibelet G, Durandy A, Sassolas A, Lévy E, Tercé F, Collet X, Mas E. A severe form of abetalipoproteinemia caused by new splicing mutations of microsomal triglyceride transfer protein (MTTP). Hum Mutat 2011; 32:751-9. [DOI: 10.1002/humu.21494] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2010] [Accepted: 02/17/2011] [Indexed: 11/09/2022]
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Warnakula S, Hsieh J, Adeli K, Hussain MM, Tso P, Proctor SD. New insights into how the intestine can regulate lipid homeostasis and impact vascular disease: frontiers for new pharmaceutical therapies to lower cardiovascular disease risk. Can J Cardiol 2011; 27:183-91. [PMID: 21459267 DOI: 10.1016/j.cjca.2010.12.020] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2010] [Accepted: 06/07/2010] [Indexed: 01/27/2023] Open
Abstract
In recent years, evidence has emerged that the intestine is a significant regulator of systemic cholesterol homeostasis and can contribute to raised plasma cholesterol concentration. In this review we provide a context for the role the intestine may have in cardiovascular disease during conditions of chronic disease (insulin resistance, obesity). In particular, we highlight the physiological role of the intestine in lipid absorption, identify novel elements in enterocyte molecular biology, review the concept that chylomicrons and their remnants contribute to atherogenesis during chronic disease, and address new principles of chylomicron overproduction during conditions of insulin resistance including the associated hormonal control of the intestine during these conditions. Finally, we raise the issue of a growing need for novel lipid-lowering pharmaceutical therapies that target intestinal lipid metabolism.
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Boudry G, David ES, Douard V, Monteiro IM, Le Huërou-Luron I, Ferraris RP. Role of intestinal transporters in neonatal nutrition: carbohydrates, proteins, lipids, minerals, and vitamins. J Pediatr Gastroenterol Nutr 2010; 51:380-401. [PMID: 20808244 DOI: 10.1097/mpg.0b013e3181eb5ad6] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
To support rapid growth and a high metabolic rate, infants require enormous amounts of nutrients. The small intestine must have the complete array of transporters that absorb the nutrients released from digested food. Failure of intestinal transporters to function properly often presents symptoms as "failure to thrive" because nutrients are not absorbed and as diarrhea because unabsorbed nutrients upset luminal osmolality or become substrates of intestinal bacteria. We enumerate the nutrients that constitute human milk and various infant milk formulas, explain their importance in neonatal nutrition, then describe for each nutrient the transporter(s) that absorbs it from the intestinal lumen into the enterocyte cytosol and from the cytosol to the portal blood. More than 100 membrane and cytosolic transporters are now thought to facilitate absorption of minerals and vitamins as well as products of digestion of the macronutrients carbohydrates, proteins, and lipids. We highlight research areas that should yield information needed to better understand the important role of these transporters during normal development.
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Affiliation(s)
- Gaëlle Boudry
- Institut National de Recherche Agronomique, UMR1079 Système d'Elevage, Nutrition, Animale et Humaine, St-Gilles, France
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Yamamoto T, Yamaguchi H, Miki H, Shimada M, Nakada Y, Ogino M, Asano K, Aoki K, Tamura N, Masago M, Kato K. Coenzyme A: diacylglycerol acyltransferase 1 inhibitor ameliorates obesity, liver steatosis, and lipid metabolism abnormality in KKAy mice fed high-fat or high-carbohydrate diets. Eur J Pharmacol 2010; 640:243-9. [PMID: 20478303 DOI: 10.1016/j.ejphar.2010.04.050] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2009] [Revised: 03/17/2010] [Accepted: 04/23/2010] [Indexed: 10/19/2022]
Abstract
Coenzyme A (CoA):diacylglycerol acyltransferase 1 (DGAT1) is 1 of the 2 known DGAT enzymes that catalyze the final and only committed step in triacylglycerol synthesis; this enzyme is considered to be a potential therapeutic target in metabolic disorders such as obesity and its related lipid abnormalities. Compound-Z, a novel specific small-molecule DGAT1 inhibitor, significantly reduced adipose tissue weight and tended to hepatic lipid accumulation in genetically obese KKAy mice. These actions were shown to almost the same extent in both a high-fat feeding condition in which triacylglycerols are synthesized mainly via exogenous fatty acid and a low-fat, high-carbohydrate feeding condition in which triacylglycerols are synthesized mainly via de novo fatty acid synthesis. This inhibitor also significantly reduced plasma and/or hepatic cholesterol levels in KKAy mice in a high-fat feeding condition. This cholesterol-lowering effect was suggested to be due to mainly decreases in cholesterol absorption from the small intestine. These results suggest that Compound-Z is a promising and attractive agent not only for the treatment of obesity but also hepatic steatosis and circulating lipid abnormalities that are the leading causes of atherosclerosis.
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Affiliation(s)
- Toshihiro Yamamoto
- Pharmacology Research Laboratories, Pharmaceutical Research Division, Takeda Pharmaceutical Company Limited, Osaka, Japan.
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Curcio CA, Johnson M, Huang JD, Rudolf M. Aging, age-related macular degeneration, and the response-to-retention of apolipoprotein B-containing lipoproteins. Prog Retin Eye Res 2009; 28:393-422. [PMID: 19698799 PMCID: PMC4319375 DOI: 10.1016/j.preteyeres.2009.08.001] [Citation(s) in RCA: 189] [Impact Index Per Article: 12.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Abstract
The largest risk factor for age-related macular degeneration (ARMD) is advanced age. A prominent age-related change in the human retina is the accumulation of histochemically detectable neutral lipid in normal Bruch's membrane (BrM) throughout adulthood. This change has the potential to have a major impact on physiology of the retinal pigment epithelium (RPE). It occurs in the same compartment as drusen and basal linear deposit, the pathognomonic extracellular, lipid-containing lesions of ARMD. Here we present evidence from light microscopic histochemistry, ultrastructure, lipid profiling of tissues and isolated lipoproteins, and gene expression analysis that this deposition can be accounted for by esterified cholesterol-rich, apolipoprotein B-containing lipoprotein particles constitutively produced by the RPE. This work collectively allows ARMD lesion formation and its aftermath to be conceptualized as a response to the retention of a sub-endothelial apolipoprotein B lipoprotein, similar to a widely accepted model of atherosclerotic coronary artery disease (CAD) (Tabas et al., 2007). This approach provides a wide knowledge base and sophisticated clinical armamentarium that can be readily exploited for the development of new model systems and the future benefit of ARMD patients.
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Affiliation(s)
- Christine A Curcio
- Department of Ophthalmology, University of Alabama School of Medicine, Birmingham, AL 35294-0009, USA.
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Curcio CA, Johnson M, Huang JD, Rudolf M. Apolipoprotein B-containing lipoproteins in retinal aging and age-related macular degeneration. J Lipid Res 2009; 51:451-67. [PMID: 19797256 DOI: 10.1194/jlr.r002238] [Citation(s) in RCA: 139] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023] Open
Abstract
The largest risk factor for age-related macular degeneration (ARMD) is advanced age. With aging, there is a striking accumulation of neutral lipids in Bruch's membrane (BrM) of normal eye that continues through adulthood. This accumulation has the potential to significantly impact the physiology of the retinal pigment epithelium (RPE). It also ultimately leads to the creation of a lipid wall at the same locations where drusen and basal linear deposit, the pathognomonic extracellular, lipid-containing lesions of ARMD, subsequently form. Here, we summarize evidence obtained from light microscopy, ultrastructural studies, lipid histochemistry, assay of isolated lipoproteins, and gene expression analysis. These studies suggest that lipid deposition in BrM is at least partially due to accumulation of esterified cholesterol-rich, apolipoprotein B-containing lipoprotein particles produced by the RPE. Furthermore, we suggest that the formation of ARMD lesions and their aftermath may be a pathological response to the retention of a sub-endothelial apolipoprotein B lipoprotein, similar to a widely accepted model of atherosclerotic coronary artery disease (Tabas, I., K. J. Williams, and J. Borén. 2007. Subendothelial lipoprotein retention as the initiating process in atherosclerosis: update and therapeutic implications. Circulation. 116:1832-1844). This view provides a conceptual basis for the development of novel treatments that may benefit ARMD patients in the future.
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Affiliation(s)
- Christine A Curcio
- Department of Ophthalmology, University of Alabama School of Medicine, Birmingham, AL, USA.
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Pan X, Hussain MM. Clock is important for food and circadian regulation of macronutrient absorption in mice. J Lipid Res 2009; 50:1800-13. [PMID: 19387090 PMCID: PMC2724783 DOI: 10.1194/jlr.m900085-jlr200] [Citation(s) in RCA: 149] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2009] [Revised: 04/17/2009] [Indexed: 11/20/2022] Open
Abstract
Clock genes respond to external stimuli and exhibit circadian rhythms. This study investigated the expression of clock genes in the small intestine and their contribution in the regulation of nutrient absorption by enterocytes. We examined expression of clock genes and macronutrient transport proteins in the small intestines of wild-type and Clock mutant (Clk(mt/mt)) mice with free or limited access to food. In addition, we studied absorption of macronutrients in these mice. Intestinal clock genes show circadian expression and respond to food entrainment in wild-type mice. Dominant negative Clock in Clk(mt/mt) mice disrupts circadian expression and food entrainment of clock genes. The absorption of lipids and monosaccharides was high in Clk(mt/mt) mice whereas peptide absorption was reduced. Molecular studies revealed that Clock regulates several transport proteins involved in nutrient absorption. Clock plays an important role in light and food entrainment of intestinal functions by regulating nutrient transport proteins. Disruptions in intestinal circadian activity may contribute to hyperlipidemia and hyperglycemia.
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Affiliation(s)
- Xiaoyue Pan
- Departments of Anatomy and Cell Biology, and Pediatrics, State University of New York Downstate Medical Center, 450 Clarkson Avenue, Brooklyn, NY 11203, USA
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Ratcliffe DR, Iqbal J, Hussain MM, Cramer EB. Fibrillar collagen type I stimulation of apolipoprotein B secretion in Caco-2 cells is mediated by beta1 integrin. Biochim Biophys Acta Mol Cell Biol Lipids 2009; 1791:1144-54. [PMID: 19646550 DOI: 10.1016/j.bbalip.2009.07.005] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2009] [Revised: 06/29/2009] [Accepted: 07/21/2009] [Indexed: 11/19/2022]
Abstract
Caco-2 cells spontaneously differentiate into enterocyte-like cells and secrete apolipoprotein B (apoB) lipoproteins. We evaluated the effect of different extracellular matrix proteins on lipoprotein secretion by these cells. Caco-2 cells grown on human amnion connective tissue (HACT) secreted twice as much apoB as control cells on Transwells, but secreted similar amounts of apoA1. Cells cultured on fibrillar collagen type I secreted increased amounts of apoB similar to the cells cultured on HACT, but cells cultured on non-fibrillar collagen type I, type IV collagen or laminin-1 did not. The increased secretion was nullified by a function inhibiting anti-integrin beta1 monoclonal antibody. Therefore, interactions between type I collagen and beta1 integrins augment apoB secretion by Caco-2 cells. Cells on HACT formed a more uniform columnar epithelium with lipid droplets polarized to the basolateral membrane. We also studied the effect of extracellular matrix proteins on transepithelial resistance (TER) of differentiated Caco-2 cells. TER in cells cultured on HACT was similar to that on Transwells, but cells on laminin-1 and collagen IV exhibited higher TER. Thus, various extracellular matrix proteins regulate apoB secretion and TER differently. This new observation that extracellular matrix proteins can enhance apoB secretion in Caco-2 cells could be useful to explore the modulation of lipid transport by these proteins.
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Affiliation(s)
- Don R Ratcliffe
- Department of Anatomy, State University of New York Downstate Medical Center, Brooklyn, NY 11203, USA
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Abstract
Our knowledge of the uptake and transport of dietary fat and fat-soluble vitamins has advanced considerably. Researchers have identified several new mechanisms by which lipids are taken up by enterocytes and packaged as chylomicrons for export into the lymphatic system or clarified the actions of mechanisms previously known to participate in these processes. Fatty acids are taken up by enterocytes involving protein-mediated as well as protein-independent processes. Net cholesterol uptake depends on the competing activities of NPC1L1, ABCG5, and ABCG8 present in the apical membrane. We have considerably more detailed information about the uptake of products of lipid hydrolysis, the active transport systems by which they reach the endoplasmic reticulum, the mechanisms by which they are resynthesized into neutral lipids and utilized within the endoplasmic reticulum to form lipoproteins, and the mechanisms by which lipoproteins are secreted from the basolateral side of the enterocyte. apoB and MTP are known to be central to the efficient assembly and secretion of lipoproteins. In recent studies, investigators found that cholesterol, phospholipids, and vitamin E can also be secreted from enterocytes as components of high-density apoB-free/apoAI-containing lipoproteins. Several of these advances will probably be investigated further for their potential as targets for the development of drugs that can suppress cholesterol absorption, thereby reducing the risk of hypercholesterolemia and cardiovascular disease.
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Affiliation(s)
- Jahangir Iqbal
- Dept. of Anatomy, 450 Clarkson Ave., State University of New York Downstate Medical Center, Brooklyn, NY 11203, USA.
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Nguyen DV, Drover VA, Knopfel M, Dhanasekaran P, Hauser H, Phillips MC. Influence of class B scavenger receptors on cholesterol flux across the brush border membrane and intestinal absorption. J Lipid Res 2009; 50:2235-44. [PMID: 19454765 DOI: 10.1194/jlr.m900036-jlr200] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
To learn more about how the step of cholesterol uptake into the brush border membrane (BBM) of enterocytes influences overall cholesterol absorption, we measured cholesterol absorption 4 and 24 h after administration of an intragastric bolus of radioactive cholesterol in mice with scavenger receptor class B, type 1 (SR-BI) and/or cluster determinant 36 (CD36) deleted. The cholesterol absorption efficiency is unaltered by deletion of either one or both of the receptors. In vitro determinations of the cholesterol uptake specific activity of the BBM from the mice reveal that the scavenger receptors facilitate cholesterol uptake into the proximal BBM. It follows that cholesterol uptake into the BBM is not normally rate-limiting for the cholesterol absorption process in vivo; a subsequent step, such as NPC1L1-mediated transfer from the BBM into the interior of the enterocyte, is rate-limiting. The absorption of dietary cholesterol after 4 h in mice lacking SR-BI and/or CD36 and fed a high-fat/high-cholesterol diet is delayed to more distal regions of the small intestine. This effect probably arises because ATP binding cassette half transporters G5 and G8-mediated back flux of cholesterol from the BBM to the lumen of the small intestine limits absorption and causes the local cholesterol uptake facilitated by SR-BI and CD36 to become rate-limiting under this dietary condition.
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Affiliation(s)
- David V Nguyen
- Gastroenterology, Hepatology, and Nutrition Division, Children's Hospital of Philadelphia and University of Pennsylvania School of Medicine, Philadelphia, PA 19104-4318, USA
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Petruzzelli M, Groen AK, van Erpecum KJ, Vrins C, van der Velde AE, Portincasa P, Palasciano G, van Berge Henegouwen GP, Lo Sasso G, Morgano A, Moschetta A. Micellar lipid composition profoundly affects LXR-dependent cholesterol transport across CaCo2 cells. FEBS Lett 2009; 583:1274-80. [PMID: 19303409 DOI: 10.1016/j.febslet.2009.03.021] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2008] [Revised: 02/12/2009] [Accepted: 03/11/2009] [Indexed: 11/15/2022]
Abstract
Intraluminal phospholipids affect micellar solubilization and absorption of cholesterol. We here study cholesterol transport from taurocholate-phospholipid-cholesterol micelles to CaCo2 cells, and associated effects on ABC-A1 mediated cholesterol efflux. Micellar incorporation of egg-yolk-phosphatidylcholine markedly increased apical retention of the sterol with decreased expression of ABC-A1, an effect that is prevented by synthetic liver X receptor (LXR) or retinoid X receptor (RXR) agonists. On the other hand, incorporation of lyso-phosphatidylcholine (LysoPC) increased ABC-A1-HDL-dependent basolateral cholesterol efflux, an effect that is abated when LXR is silenced. Thus, the modulation of cholesterol metabolism via intraluminal phospholipids is related to the activity of the oxysterol nuclear receptor LXR.
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Affiliation(s)
- Michele Petruzzelli
- Department of Experimental Hepatology, Academic Medical Center, Amsterdam, The Netherlands
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