101
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Lee J, Ridgway ND. Phosphatidylcholine synthesis regulates triglyceride storage and chylomicron secretion by Caco2 cells. J Lipid Res 2018; 59:1940-1950. [PMID: 30115754 DOI: 10.1194/jlr.m087635] [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: 06/19/2018] [Revised: 08/09/2018] [Indexed: 11/20/2022] Open
Abstract
Intracellular lipid droplets (LDs) supply fatty acids for energy, membrane biogenesis, and lipoprotein secretion. The surface monolayer of LDs is composed of phospholipids, primarily phosphatidylcholine (PC), that stabilize the neutral lipid core of triglyceride (TG). To determine the relationship between PC synthesis and TG storage and secretion in chylomicrons, we used a model of intestinal-derived human epithelial colorectal adenocarcinoma (Caco2) cells with knockout of PCYT1A, which encodes the rate-limiting enzyme CTP:phosphocholine cytidylyltransferase (CCT)α in the CDP-choline pathway, that were treated with the fatty acid oleate. CRISPR/Cas9 knockout of CCTα in Caco2 cells (Caco2-KO cells) reduced PC synthesis by 50%. Compared with Caco2 cells, Caco2-KO cells exposed to oleate had fewer and larger LDs and greater TG accumulation as a result. The addition of exogenous lysophosphatidylcholine to Caco2-KO cells reversed the LD morphology defect. Caco2-KO cells, differentiated into epithelial monolayers, accumulated intracellular TG and had deficient TG and chylomicron-associated apoB48 secretion; apoB100 secretion was unaffected by CCTα knockout or oleate. Metabolic-labeling and LD imaging of Caco2-KO cells indicated preferential shuttling of de novo synthesized TG into larger LDs rather than into chylomicrons. Thus, reduced de novo PC synthesis in Caco2 cells enhances TG storage in large LDs and inhibits apoB48 chylomicron secretion.
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Affiliation(s)
- Jonghwa Lee
- Atlantic Research Center, Departments of Pediatrics, and Biochemistry and Molecular Biology, Dalhousie University, Halifax, Nova Scotia, Canada
| | - Neale D Ridgway
- Atlantic Research Center, Departments of Pediatrics, and Biochemistry and Molecular Biology, Dalhousie University, Halifax, Nova Scotia, Canada
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102
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Chan JP, Wong BH, Chin CF, Galam DLA, Foo JC, Wong LC, Ghosh S, Wenk MR, Cazenave-Gassiot A, Silver DL. The lysolipid transporter Mfsd2a regulates lipogenesis in the developing brain. PLoS Biol 2018; 16:e2006443. [PMID: 30074985 PMCID: PMC6093704 DOI: 10.1371/journal.pbio.2006443] [Citation(s) in RCA: 69] [Impact Index Per Article: 11.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2018] [Revised: 08/15/2018] [Accepted: 07/11/2018] [Indexed: 01/12/2023] Open
Abstract
Brain development requires a massive increase in brain lipogenesis and accretion of the essential omega-3 fatty acid docosahexaenoic acid (DHA). Brain acquisition of DHA is primarily mediated by the transporter Major Facilitator Superfamily Domain containing 2a (Mfsd2a) expressed in the endothelium of the blood-brain barrier (BBB) and other abundant cell types within the brain. Mfsd2a transports DHA and other polyunsaturated fatty acids (PUFAs) esterified to lysophosphatidylcholine (LPC-DHA). However, the function of Mfsd2a and DHA in brain development is incompletely understood. Here, we demonstrate, using vascular endothelial-specific and inducible vascular endothelial-specific deletion of Mfsd2a in mice, that Mfsd2a is uniquely required postnatally at the BBB for normal brain growth and DHA accretion, with DHA deficiency preceding the onset of microcephaly. In Mfsd2a-deficient mouse models, a lipidomic signature was identified that is indicative of increased de novo lipogenesis of PUFAs. Gene expression profiling analysis of these DHA-deficient brains indicated that sterol regulatory-element binding protein (Srebp)-1 and Srebp-2 pathways were highly elevated. Mechanistically, LPC-DHA treatment of primary neural stem cells down-regulated Srebp processing and activation in a Mfsd2a-dependent fashion, resulting in profound effects on phospholipid membrane saturation. In addition, Srebp regulated the expression of Mfsd2a. These data identify LPC-DHA transported by Mfsd2a as a physiological regulator of membrane phospholipid saturation acting in a feedback loop on Srebp activity during brain development. The brain is the most lipid-rich organ in the body. Brain development involves a tremendous increase in the synthesis and accretion of fatty acids. De novo synthesis of fatty acids is mediated by Srebp transcription factors, whereas acquisition of essential fatty acids via uptake of plasma-derived lysophosphatidylcholine containing the essential omega-3 fatty acid docosahexaenoic acid (LPC-DHA) is mediated by the transporter Mfsd2a in the cells that line the blood vessels in the brain. The function of Mfsd2a and DHA in brain development is incompletely understood. Our study determined that Mfsd2a is required at the blood-brain barrier for brain development and accretion of DHA after birth in mice. Moreover, we determined that a major function of DHA in the brain is to negatively regulate Srebp activation, resulting in profound effects on membrane phospholipid composition. These findings reveal that LPC-DHA transported by Mfsd2a plays a physiological role in both brain growth and in maintaining plasma membrane phospholipid composition during brain development.
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Affiliation(s)
- Jia Pei Chan
- Signature Research Program in Cardiovascular and Metabolic Disorders, Duke-NUS Medical School, Singapore, Singapore
| | - Bernice H. Wong
- Signature Research Program in Cardiovascular and Metabolic Disorders, Duke-NUS Medical School, Singapore, Singapore
| | - Cheen Fei Chin
- Signature Research Program in Cardiovascular and Metabolic Disorders, Duke-NUS Medical School, Singapore, Singapore
| | - Dwight L. A. Galam
- Signature Research Program in Cardiovascular and Metabolic Disorders, Duke-NUS Medical School, Singapore, Singapore
| | - Juat Chin Foo
- Department of Biochemistry, National University of Singapore, Singapore, Singapore
| | - Loo Chin Wong
- Signature Research Program in Cardiovascular and Metabolic Disorders, Duke-NUS Medical School, Singapore, Singapore
| | - Sujoy Ghosh
- Centre for Computational Biology, Duke-NUS Medical School, Singapore, Singapore
| | - Markus R. Wenk
- Department of Biochemistry, National University of Singapore, Singapore, Singapore
| | | | - David L. Silver
- Signature Research Program in Cardiovascular and Metabolic Disorders, Duke-NUS Medical School, Singapore, Singapore
- * E-mail:
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103
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Abstract
Liver X receptors α and β (LXRα and LXRβ) are nuclear receptors with pivotal roles in the transcriptional control of lipid metabolism. Transcriptional activity of LXRs is induced in response to elevated cellular levels of cholesterol. LXRs bind to and regulate the expression of genes that encode proteins involved in cholesterol absorption, transport, efflux, excretion and conversion to bile acids. The coordinated, tissue-specific actions of the LXR pathway maintain systemic cholesterol homeostasis and regulate immune and inflammatory responses. LXRs also regulate fatty acid metabolism by controlling the lipogenic transcription factor sterol regulatory element-binding protein 1c and regulate genes that encode proteins involved in fatty acid elongation and desaturation. LXRs exert important effects on the metabolism of phospholipids, which, along with cholesterol, are major constituents of cellular membranes. LXR activation preferentially drives the incorporation of polyunsaturated fatty acids into phospholipids by inducing transcription of the remodelling enzyme lysophosphatidylcholine acyltransferase 3. The ability of the LXR pathway to couple cellular sterol levels with the saturation of fatty acids in membrane phospholipids has implications for several physiological processes, including lipoprotein production, dietary lipid absorption and intestinal stem cell proliferation. Understanding how LXRs regulate membrane composition and function might provide new therapeutic insight into diseases associated with dysregulated lipid metabolism, including atherosclerosis, diabetes mellitus and cancer.
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Affiliation(s)
- Bo Wang
- Department of Pathology and Laboratory Medicine, Molecular Biology Institute, David Geffen School of Medicine, University of California, Los Angeles, CA, USA
| | - Peter Tontonoz
- Department of Pathology and Laboratory Medicine, Molecular Biology Institute, David Geffen School of Medicine, University of California, Los Angeles, CA, USA.
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104
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Tran M, Liu Y, Huang W, Wang L. Nuclear receptors and liver disease: Summary of the 2017 basic research symposium. Hepatol Commun 2018; 2:765-777. [PMID: 30129636 PMCID: PMC6049066 DOI: 10.1002/hep4.1203] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/15/2018] [Revised: 05/03/2018] [Accepted: 05/10/2018] [Indexed: 12/11/2022] Open
Abstract
The nuclear receptor superfamily contains important transcriptional regulators that play pleiotropic roles in cell differentiation, development, proliferation, and metabolic processes to govern liver physiology and pathology. Many nuclear receptors are ligand-activated transcription factors that regulate the expression of their target genes by modulating transcriptional activities and epigenetic changes. Additionally, the protein complex associated with nuclear receptors consists of a multitude of coregulators, corepressors, and noncoding RNAs. Therefore, acquiring new information on nuclear receptors may provide invaluable insight into novel therapies and shed light on new interventions to reduce the burden and incidence of liver diseases. (Hepatology Communications 2018;2:765-777).
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Affiliation(s)
- Melanie Tran
- Department of Physiology and Neurobiology and Institute for Systems Genomics, University of Connecticut, Storrs, CT
| | - Yanjun Liu
- Department of Diabetes Complications and Metabolism, Diabetes and Metabolism Research Institute, Beckman Research Institute City of Hope National Medical Center Duarte CA
| | - Wendong Huang
- Department of Diabetes Complications and Metabolism, Diabetes and Metabolism Research Institute, Beckman Research Institute City of Hope National Medical Center Duarte CA
| | - Li Wang
- Department of Physiology and Neurobiology and Institute for Systems Genomics, University of Connecticut, Storrs, CT.,Veterans Affairs Connecticut Healthcare System West Haven CT.,Department of Internal Medicine, Section of Digestive Diseases Yale University New Haven CT
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105
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Thomas C, Jalil A, Magnani C, Ishibashi M, Queré R, Bourgeois T, Bergas V, Ménégaut L, Patoli D, Le Guern N, Labbé J, Gautier T, de Barros JPP, Lagrost L, Masson D. LPCAT3 deficiency in hematopoietic cells alters cholesterol and phospholipid homeostasis and promotes atherosclerosis. Atherosclerosis 2018; 275:409-418. [PMID: 29866392 DOI: 10.1016/j.atherosclerosis.2018.05.023] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/06/2018] [Revised: 05/04/2018] [Accepted: 05/16/2018] [Indexed: 12/29/2022]
Abstract
BACKGROUND AND AIMS LPCAT3 plays a major role in phospholipid metabolism in the liver and intestine. However, the impact of LPCAT3 on hematopoietic cell and macrophage functions has yet to be described. Our aim was to understand the functions of LPCAT3 in macrophages and to investigate whether LPCAT3 deficiency in hematopoietic cells may affect atherosclerosis development. METHODS Mice with constitutive Lpcat3 deficiency (Lpcat3-/-) were generated. We used fetal hematopoietic liver cells to generate WT and Lpcat3-/- macrophages in vitro and to perform hematopoietic cell transplantation in recipient Ldlr-/- mice. RESULTS Lpcat3-deficient macrophages displayed major reductions in the arachidonate content of phosphatidylcholines, phosphatidylethanolamines and, unexpectedly, plasmalogens. These changes were associated with altered cholesterol homeostasis, including an increase in the ratio of free to esterified cholesterol and a reduction in cholesterol efflux in Lpcat3-/- macrophages. This correlated with the inhibition of some LXR-regulated pathways, related to altered cellular availability of the arachidonic acid. Indeed, LPCAT3 deficiency was associated with decreased Abca1, Abcg1 and ApoE mRNA levels in fetal liver cells derived macrophages. In vivo, these changes translated into a significant increase in atherosclerotic lesions in Ldlr-/- mice with hematopoietic LPCAT3 deficiency. CONCLUSIONS This study identifies LPCAT3 as a key factor in the control of phospholipid homeostasis and arachidonate availability in myeloid cells and underlines a new role for LPCAT3 in plasmalogen metabolism. Moreover, our work strengthens the link between phospholipid and sterol metabolism in hematopoietic cells, with significant consequences on nuclear receptor-regulated pathways and atherosclerosis development.
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Affiliation(s)
- Charles Thomas
- Univ. Bourgogne Franche-Comté, LNC UMR1231, F-21000, Dijon, France; INSERM, LNC UMR 1231, F-21000, Dijon, France; FCS Bourgogne-Franche Comté, LipSTIC LabEx, F-21000, Dijon, France
| | - Antoine Jalil
- Univ. Bourgogne Franche-Comté, LNC UMR1231, F-21000, Dijon, France; INSERM, LNC UMR 1231, F-21000, Dijon, France; FCS Bourgogne-Franche Comté, LipSTIC LabEx, F-21000, Dijon, France
| | - Charlène Magnani
- Univ. Bourgogne Franche-Comté, LNC UMR1231, F-21000, Dijon, France; INSERM, LNC UMR 1231, F-21000, Dijon, France; FCS Bourgogne-Franche Comté, LipSTIC LabEx, F-21000, Dijon, France
| | - Minako Ishibashi
- Univ. Bourgogne Franche-Comté, LNC UMR1231, F-21000, Dijon, France; INSERM, LNC UMR 1231, F-21000, Dijon, France; FCS Bourgogne-Franche Comté, LipSTIC LabEx, F-21000, Dijon, France
| | - Ronan Queré
- Univ. Bourgogne Franche-Comté, LNC UMR1231, F-21000, Dijon, France; INSERM, LNC UMR 1231, F-21000, Dijon, France; FCS Bourgogne-Franche Comté, LipSTIC LabEx, F-21000, Dijon, France
| | - Thibaut Bourgeois
- Univ. Bourgogne Franche-Comté, LNC UMR1231, F-21000, Dijon, France; INSERM, LNC UMR 1231, F-21000, Dijon, France; FCS Bourgogne-Franche Comté, LipSTIC LabEx, F-21000, Dijon, France
| | - Victoria Bergas
- Lipidomic analytic plate-forme, UBFC, Batiment B3, Bvd Maréchal de Lattre de Tassigny, 21000, Dijon, France
| | - Louise Ménégaut
- Univ. Bourgogne Franche-Comté, LNC UMR1231, F-21000, Dijon, France; INSERM, LNC UMR 1231, F-21000, Dijon, France; FCS Bourgogne-Franche Comté, LipSTIC LabEx, F-21000, Dijon, France; CHU Dijon, laboratoire de Biochimie, F-21000, Dijon, France
| | - Danish Patoli
- Univ. Bourgogne Franche-Comté, LNC UMR1231, F-21000, Dijon, France; INSERM, LNC UMR 1231, F-21000, Dijon, France; FCS Bourgogne-Franche Comté, LipSTIC LabEx, F-21000, Dijon, France
| | - Naig Le Guern
- Univ. Bourgogne Franche-Comté, LNC UMR1231, F-21000, Dijon, France; INSERM, LNC UMR 1231, F-21000, Dijon, France; FCS Bourgogne-Franche Comté, LipSTIC LabEx, F-21000, Dijon, France
| | - Jérôme Labbé
- Univ. Bourgogne Franche-Comté, LNC UMR1231, F-21000, Dijon, France; INSERM, LNC UMR 1231, F-21000, Dijon, France; FCS Bourgogne-Franche Comté, LipSTIC LabEx, F-21000, Dijon, France
| | - Thomas Gautier
- Univ. Bourgogne Franche-Comté, LNC UMR1231, F-21000, Dijon, France; INSERM, LNC UMR 1231, F-21000, Dijon, France; FCS Bourgogne-Franche Comté, LipSTIC LabEx, F-21000, Dijon, France
| | - Jean Paul Pais de Barros
- Univ. Bourgogne Franche-Comté, LNC UMR1231, F-21000, Dijon, France; INSERM, LNC UMR 1231, F-21000, Dijon, France; FCS Bourgogne-Franche Comté, LipSTIC LabEx, F-21000, Dijon, France; Lipidomic analytic plate-forme, UBFC, Batiment B3, Bvd Maréchal de Lattre de Tassigny, 21000, Dijon, France
| | - Laurent Lagrost
- Univ. Bourgogne Franche-Comté, LNC UMR1231, F-21000, Dijon, France; INSERM, LNC UMR 1231, F-21000, Dijon, France; FCS Bourgogne-Franche Comté, LipSTIC LabEx, F-21000, Dijon, France; CHU Dijon, laboratoire de Biochimie, F-21000, Dijon, France
| | - David Masson
- Univ. Bourgogne Franche-Comté, LNC UMR1231, F-21000, Dijon, France; INSERM, LNC UMR 1231, F-21000, Dijon, France; FCS Bourgogne-Franche Comté, LipSTIC LabEx, F-21000, Dijon, France; CHU Dijon, laboratoire de Biochimie, F-21000, Dijon, France.
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106
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Lysophosphatidylcholine acyltransferase 3 deficiency impairs 3T3L1 cell adipogenesis through activating Wnt/β-catenin pathway. Biochim Biophys Acta Mol Cell Biol Lipids 2018; 1863:834-843. [PMID: 29673706 DOI: 10.1016/j.bbalip.2018.04.008] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2017] [Revised: 04/07/2018] [Accepted: 04/15/2018] [Indexed: 11/21/2022]
Abstract
Levels of polyunsaturated phosphatidylcholine (PC) influence plasma membrane structure and function. Phosphatidylcholine (PC) is synthesized de novo in the Kennedy pathway and then undergoes extensive deacylation/reacylation remodeling via Lands' cycle (non-Kennedy pathway). The reacylation is catalyzed by lysophosphatidylcholine acyltransferase (LPCAT), which adds a polyunsaturated fatty acid at the sn-2 position. Four LPCAT isoforms have been described to date, among which we found LPCAT3 to be the major isoform in adipose tissue, but its exact role in adipogenesis is unclear. In this study, we aimed to investigate whether LPCAT3 activity affects 3T3L1 cell adipogenic differentiation potential and its underline mechanism. Lentivirus-mediated LPCAT3 shRNA expression stably knocked down LPCAT3 in 3T3L1 preadipocytes and LPCAT3 deficiency dramatically reduced the levels of cellular polyunsaturated PCs. Importantly, we found that this deficiency activated the β-catenin dependent Wnt signaling pathway, which suppressed the expression of adipogenesis-related genes, thereby inhibiting 3T3L1 preadipocyte differentiation and lipid accumulation. Moreover, three different Wnt/β-catenin pathway inhibitors reversed the effect of LPCAP3 deficiency, suggesting that Wnt/β-catenin pathway activation is one of the causes for the observed phenotypes. To the best of our knowledge, we show here for the first time that PC remodeling is an important regulator of adipocyte differentiation.
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107
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Kalsbeek A, Veenstra J, Westra J, Disselkoen C, Koch K, McKenzie KA, O’Bott J, Vander Woude J, Fischer K, Shearer GC, Harris WS, Tintle NL. A genome-wide association study of red-blood cell fatty acids and ratios incorporating dietary covariates: Framingham Heart Study Offspring Cohort. PLoS One 2018; 13:e0194882. [PMID: 29652918 PMCID: PMC5898718 DOI: 10.1371/journal.pone.0194882] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2017] [Accepted: 03/12/2018] [Indexed: 02/07/2023] Open
Abstract
Recent analyses have suggested a strong heritable component to circulating fatty acid (FA) levels; however, only a limited number of genes have been identified which associate with FA levels. In order to expand upon a previous genome wide association study done on participants in the Framingham Heart Study Offspring Cohort and FA levels, we used data from 2,400 of these individuals for whom red blood cell FA profiles, dietary information and genotypes are available, and then conducted a genome-wide evaluation of potential genetic variants associated with 22 FAs and 15 FA ratios, after adjusting for relevant dietary covariates. Our analysis found nine previously identified loci associated with FA levels (FADS, ELOVL2, PCOLCE2, LPCAT3, AGPAT4, NTAN1/PDXDC1, PKD2L1, HBS1L/MYB and RAB3GAP1/MCM6), while identifying four novel loci. The latter include an association between variants in CALN1 (Chromosome 7) and eicosapentaenoic acid (EPA), DHRS4L2 (Chromosome 14) and a FA ratio measuring delta-9-desaturase activity, as well as two loci associated with less well understood proteins. Thus, the inclusion of dietary covariates had a modest impact, helping to uncover four additional loci. While genome-wide association studies continue to uncover additional genes associated with circulating FA levels, much of the heritable risk is yet to be explained, suggesting the potential role of rare genetic variation, epistasis and gene-environment interactions on FA levels as well. Further studies are needed to continue to understand the complex genetic picture of FA metabolism and synthesis.
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Affiliation(s)
- Anya Kalsbeek
- Department of Mathematics, Statistics and Computer Science, Dordt College, Sioux Center, Iowa, United States of America
| | - Jenna Veenstra
- Department of Mathematics, Statistics and Computer Science, Dordt College, Sioux Center, Iowa, United States of America
| | - Jason Westra
- Department of Mathematics, Statistics and Computer Science, Dordt College, Sioux Center, Iowa, United States of America
| | - Craig Disselkoen
- Department of Mathematics, Statistics and Computer Science, Dordt College, Sioux Center, Iowa, United States of America
| | - Kristin Koch
- Department of Statistics, Baylor University, Waco, TX, United States of America
| | - Katelyn A. McKenzie
- Department of Statistics, Duke University, Durham, NC, United States of America
| | - Jacob O’Bott
- Department of Mathematics and Statistics, University of Maryland- Baltimore County, Baltimore, MD, United States of America
| | - Jason Vander Woude
- Department of Mathematics, Statistics and Computer Science, Dordt College, Sioux Center, Iowa, United States of America
| | - Karen Fischer
- Department of Mathematics, Statistics and Computer Science, Dordt College, Sioux Center, Iowa, United States of America
| | - Greg C. Shearer
- Department of Nutritional Sciences, Penn State University, State College, PA, United States of America
| | | | - Nathan L. Tintle
- Department of Mathematics, Statistics and Computer Science, Dordt College, Sioux Center, Iowa, United States of America
- * E-mail:
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108
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Manni MM, Tiberti ML, Pagnotta S, Barelli H, Gautier R, Antonny B. Acyl chain asymmetry and polyunsaturation of brain phospholipids facilitate membrane vesiculation without leakage. eLife 2018. [PMID: 29543154 PMCID: PMC5903860 DOI: 10.7554/elife.34394] [Citation(s) in RCA: 94] [Impact Index Per Article: 15.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Phospholipid membranes form cellular barriers but need to be flexible enough to divide by fission. Phospholipids generally contain a saturated fatty acid (FA) at position sn1 whereas the sn2-FA is saturated, monounsaturated or polyunsaturated. Our understanding of the impact of phospholipid unsaturation on membrane flexibility and fission is fragmentary. Here, we provide a comprehensive view of the effects of the FA profile of phospholipids on membrane vesiculation by dynamin and endophilin. Coupled to simulations, this analysis indicates that: (i) phospholipids with two polyunsaturated FAs make membranes prone to vesiculation but highly permeable; (ii) asymmetric sn1-saturated-sn2-polyunsaturated phospholipids provide a tradeoff between efficient membrane vesiculation and low membrane permeability; (iii) When incorporated into phospholipids, docosahexaenoic acid (DHA; omega-3) makes membranes more deformable than arachidonic acid (omega-6). These results suggest an explanation for the abundance of sn1-saturated-sn2-DHA phospholipids in synaptic membranes and for the importance of the omega-6/omega-3 ratio on neuronal functions. Surrounding each living cell is a membrane that is mainly made of fat molecules called phospholipids. Similar membranes also surround many of the structures inside cells. It is important for life that these membranes are impermeable to many molecules; for example, they do not allow ions to cross them freely. The membranes also need to be flexible and allow cells to form different shapes. Flexible membranes also allow cells to move molecules around and to divide to produce new cells. Each phospholipid includes two long chains of atoms called fatty acids. There are many fatty acids but they are typically grouped into saturated and unsaturated based on their chemical structures. The omega-3 and omega-6 fats are both groups of unsaturated fatty acids that are found in brain cells. Many phospholipids in cell membranes contain one saturated and one unsaturated fatty acid but it is not clear why. By studying fat molecules in the laboratory and combining this with simulations, Manni et al. have now examined the effects of fatty acids on membranes. The investigation showed that phospholipids with both saturated and unsaturated fatty acids strike a balance between impermeable and flexible membranes. More unsaturated fatty acids make more flexible membranes but they are too permeable to be used in cells. The experiments also revealed that omega-3 unsaturated fats aid flexibility more than omega-6. This finding may help to explain why the relative amounts of omega-3 and -6 are so important in the membranes of brain cells. The connection between the fats we eat and the fatty acids in our cells is complex. Yet, findings like these serve to remind us that we need a balanced diet of different fats to keep all our cells healthy.
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Affiliation(s)
- Marco M Manni
- Institut de Pharmacologie Moléculaire et Cellulaire, Université Côte d'Azur et CNRS, Valbonne, France.,Instituto Biofisika (UPV/EHU, CSIC), Leioa, Spain
| | - Marion L Tiberti
- Institut de Pharmacologie Moléculaire et Cellulaire, Université Côte d'Azur et CNRS, Valbonne, France
| | - Sophie Pagnotta
- Centre Commun de Microscopie Appliquée, Université Côte d'Azur, Nice, France
| | - Hélène Barelli
- Institut de Pharmacologie Moléculaire et Cellulaire, Université Côte d'Azur et CNRS, Valbonne, France
| | - Romain Gautier
- Institut de Pharmacologie Moléculaire et Cellulaire, Université Côte d'Azur et CNRS, Valbonne, France
| | - Bruno Antonny
- Institut de Pharmacologie Moléculaire et Cellulaire, Université Côte d'Azur et CNRS, Valbonne, France
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109
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Miranda DA, Krause WC, Cazenave-Gassiot A, Suzawa M, Escusa H, Foo JC, Shihadih DS, Stahl A, Fitch M, Nyangau E, Hellerstein M, Wenk MR, Silver DL, Ingraham HA. LRH-1 regulates hepatic lipid homeostasis and maintains arachidonoyl phospholipid pools critical for phospholipid diversity. JCI Insight 2018. [PMID: 29515023 DOI: 10.1172/jci.insight.96151] [Citation(s) in RCA: 31] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
Excess lipid accumulation is an early signature of nonalcoholic fatty liver disease (NAFLD). Although liver receptor homolog 1 (LRH-1) (encoded by NR5A2) is suppressed in human NAFLD, evidence linking this phospholipid-bound nuclear receptor to hepatic lipid metabolism is lacking. Here, we report an essential role for LRH-1 in hepatic lipid storage and phospholipid composition based on an acute hepatic KO of LRH-1 in adult mice (LRH-1AAV8-Cre mice). Indeed, LRH-1-deficient hepatocytes exhibited large cytosolic lipid droplets and increased triglycerides (TGs). LRH-1-deficient mice fed high-fat diet displayed macrovesicular steatosis, liver injury, and glucose intolerance, all of which were reversed or improved by expressing wild-type human LRH-1. While hepatic lipid synthesis decreased and lipid export remained unchanged in mutants, elevated circulating free fatty acid helped explain the lipid imbalance in LRH-1AAV8-Cre mice. Lipidomic and genomic analyses revealed that loss of LRH-1 disrupts hepatic phospholipid composition, leading to lowered arachidonoyl (AA) phospholipids due to repression of Elovl5 and Fads2, two critical genes in AA biosynthesis. Our findings reveal a role for the phospholipid sensor LRH-1 in maintaining adequate pools of hepatic AA phospholipids, further supporting the idea that phospholipid diversity is an important contributor to healthy hepatic lipid storage.
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Affiliation(s)
- Diego A Miranda
- Department of Cellular and Molecular Pharmacology, UCSF, San Francisco, California, USA
| | - William C Krause
- Department of Cellular and Molecular Pharmacology, UCSF, San Francisco, California, USA
| | - Amaury Cazenave-Gassiot
- Department of Biochemistry, Yong Loo Lin School of Medicine and Singapore Lipidomics Incubator, Life Sciences Institute, National University of Singapore, Singapore
| | - Miyuki Suzawa
- Department of Cellular and Molecular Pharmacology, UCSF, San Francisco, California, USA
| | - Hazel Escusa
- Department of Cellular and Molecular Pharmacology, UCSF, San Francisco, California, USA
| | - Juat Chin Foo
- Department of Biochemistry, Yong Loo Lin School of Medicine and Singapore Lipidomics Incubator, Life Sciences Institute, National University of Singapore, Singapore
| | - Diyala S Shihadih
- Department of Nutritional Sciences and Toxicology, University of California Berkeley, Berkeley, California, USA
| | - Andreas Stahl
- Department of Nutritional Sciences and Toxicology, University of California Berkeley, Berkeley, California, USA
| | - Mark Fitch
- Department of Nutritional Sciences and Toxicology, University of California Berkeley, Berkeley, California, USA
| | - Edna Nyangau
- Department of Nutritional Sciences and Toxicology, University of California Berkeley, Berkeley, California, USA
| | - Marc Hellerstein
- Department of Nutritional Sciences and Toxicology, University of California Berkeley, Berkeley, California, USA
| | - Markus R Wenk
- Department of Biochemistry, Yong Loo Lin School of Medicine and Singapore Lipidomics Incubator, Life Sciences Institute, National University of Singapore, Singapore
| | - David L Silver
- Signature Research Program in Cardiovascular and Metabolic Diseases, Duke-National University of Singapore, Singapore
| | - Holly A Ingraham
- Department of Cellular and Molecular Pharmacology, UCSF, San Francisco, California, USA
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110
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Xiao C, Stahel P, Carreiro AL, Buhman KK, Lewis GF. Recent Advances in Triacylglycerol Mobilization by the Gut. Trends Endocrinol Metab 2018; 29:151-163. [PMID: 29306629 DOI: 10.1016/j.tem.2017.12.001] [Citation(s) in RCA: 43] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/16/2017] [Revised: 11/30/2017] [Accepted: 12/04/2017] [Indexed: 11/26/2022]
Abstract
Dietary lipid absorption and lipoprotein secretion by the gut are important in maintaining whole-body energy homeostasis and have significant implications for health and disease. The processing of dietary lipids, including storage within and subsequent mobilization and transport from enterocyte cytoplasmic lipid droplets or other intestinal lipid storage pools (including the secretary pathway, lamina propria and lymphatics) and secretion of chylomicrons, involves coordinated steps that are subject to various controls. This review summarizes recent advances in our understanding of the mechanisms that underlie lipid storage and mobilization by small intestinal enterocytes and the intestinal lymphatic vasculature. Therapeutic targeting of lipid processing by the gut may provide opportunities for the treatment and prevention of dyslipidemia, and for improving health status.
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Affiliation(s)
- Changting Xiao
- Departments of Medicine and Physiology, Division of Endocrinology and Metabolism, Banting and Best Diabetes Centre, University of Toronto, Toronto, ON, Canada
| | - Priska Stahel
- Departments of Medicine and Physiology, Division of Endocrinology and Metabolism, Banting and Best Diabetes Centre, University of Toronto, Toronto, ON, Canada
| | - Alicia L Carreiro
- Department of Nutrition Science, Purdue University, West Lafayette, IN 47907, USA
| | - Kimberly K Buhman
- Department of Nutrition Science, Purdue University, West Lafayette, IN 47907, USA
| | - Gary F Lewis
- Departments of Medicine and Physiology, Division of Endocrinology and Metabolism, Banting and Best Diabetes Centre, University of Toronto, Toronto, ON, Canada.
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111
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112
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Phospholipid Remodeling and Cholesterol Availability Regulate Intestinal Stemness and Tumorigenesis. Cell Stem Cell 2018; 22:206-220.e4. [PMID: 29395055 PMCID: PMC5807072 DOI: 10.1016/j.stem.2017.12.017] [Citation(s) in RCA: 183] [Impact Index Per Article: 30.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2017] [Revised: 10/31/2017] [Accepted: 12/20/2017] [Indexed: 02/02/2023]
Abstract
Adequate availability of cellular building blocks, including lipids, is a prerequisite for cellular proliferation, but excess dietary lipids are linked to increased cancer risk. Despite these connections, specific regulatory relationships between membrane composition, intestinal stem cell (ISC) proliferation, and tumorigenesis are unclear. We reveal an unexpected link between membrane phospholipid remodeling and cholesterol biosynthesis and demonstrate that cholesterol itself acts as a mitogen for ISCs. Inhibition of the phospholipid-remodeling enzyme Lpcat3 increases membrane saturation and stimulates cholesterol biosynthesis, thereby driving ISC proliferation. Pharmacologic inhibition of cholesterol synthesis normalizes crypt hyperproliferation in Lpcat3-deficient organoids and mice. Conversely, increasing cellular cholesterol content stimulates crypt organoid growth, and providing excess dietary cholesterol or driving endogenous cholesterol synthesis through SREBP-2 expression promotes ISC proliferation in vivo. Finally, disruption of Lpcat3-dependent phospholipid and cholesterol homeostasis dramatically enhances tumor formation in Apcmin mice. These findings identify a critical dietary-responsive phospholipid-cholesterol axis regulating ISC proliferation and tumorigenesis.
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113
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Tabe S, Hikiji H, Ariyoshi W, Hashidate-Yoshida T, Shindou H, Shimizu T, Okinaga T, Seta Y, Tominaga K, Nishihara T. Lysophosphatidylcholine acyltransferase 4 is involved in chondrogenic differentiation of ATDC5 cells. Sci Rep 2017; 7:16701. [PMID: 29196633 PMCID: PMC5711957 DOI: 10.1038/s41598-017-16902-4] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2016] [Accepted: 11/20/2017] [Indexed: 12/14/2022] Open
Abstract
Glycerophospholipids have important structural and functional roles in cells and are the main components of cellular membranes. Glycerophospholipids are formed via the de novo pathway (Kennedy pathway) and are subsequently matured in the remodeling pathway (Lands’ cycle). Lands’ cycle consists of two steps: deacylation of phospholipids by phospholipases A2 and reacylation of lysophospholipids by lysophospholipid acyltransferases (LPLATs). LPLATs play key roles in the maturation and maintenance of the fatty acid composition of biomembranes, and cell differentiation. We examined whether LPLATs are involved in chondrogenic differentiation of ATDC5 cells, which can differentiate into chondrocytes. Lysophosphatidylcholine acyltransferase 4 (LPCAT4) mRNA expression and LPCAT enzymatic activity towards 18:1-, 18:2-, 20:4-, and 22:6-CoA increased in the late stage of chondrogenic differentiation, when mineralization occurred. LPCAT4 knockdown decreased mRNA and protein levels of chondrogenic markers as well as Alcian blue staining intensity and alkaline phosphatase activity in ATDC5 cells. These results suggest that LPCAT4 plays important roles during the transition of chondrocytes into hypertrophic chondrocytes and/or a mineralized phenotype.
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Affiliation(s)
- Shirou Tabe
- Division of Infections and Molecular Biology, Department of Health Promotion, Kyushu Dental University, Kitakyushu, Fukuoka, 803-8580, Japan.,Division of Oral and Maxillofacial Surgery, Department of Science of Physical Functions, Kyushu Dental University, Kitakyushu, Fukuoka, 803-8580, Japan
| | - Hisako Hikiji
- School of Oral Health Sciences, Kyushu Dental University, Kitakyushu, Fukuoka, 803-8580, Japan.
| | - Wataru Ariyoshi
- Division of Infections and Molecular Biology, Department of Health Promotion, Kyushu Dental University, Kitakyushu, Fukuoka, 803-8580, Japan
| | - Tomomi Hashidate-Yoshida
- Department of Lipid Signaling, Research Institute, National Center for Global Health and Medicine, Shinjuku-ku, Tokyo, 162-8655, Japan
| | - Hideo Shindou
- Department of Lipid Signaling, Research Institute, National Center for Global Health and Medicine, Shinjuku-ku, Tokyo, 162-8655, Japan.,Agency for Medical Research and Development-Core Research for Evolutional Medical Science and Technology (AMED-CREST), AMED, Chiyoda-ku, Tokyo, 100-0004, Japan
| | - Takao Shimizu
- Department of Lipid Signaling, Research Institute, National Center for Global Health and Medicine, Shinjuku-ku, Tokyo, 162-8655, Japan.,Department of Lipidomics, Graduate School of Medicine, The University of Tokyo, Bunkyo-ku, Tokyo, 113-0033, Japan
| | - Toshinori Okinaga
- Division of Infections and Molecular Biology, Department of Health Promotion, Kyushu Dental University, Kitakyushu, Fukuoka, 803-8580, Japan
| | - Yuji Seta
- Division of Anatomy, Department of Health Improvement, Kyushu Dental University, Kitakyushu, Fukuoka, 803-8580, Japan
| | - Kazuhiro Tominaga
- Division of Oral and Maxillofacial Surgery, Department of Science of Physical Functions, Kyushu Dental University, Kitakyushu, Fukuoka, 803-8580, Japan
| | - Tatsuji Nishihara
- Division of Infections and Molecular Biology, Department of Health Promotion, Kyushu Dental University, Kitakyushu, Fukuoka, 803-8580, Japan
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114
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Modulating fat digestion through food structure design. Prog Lipid Res 2017; 68:109-118. [DOI: 10.1016/j.plipres.2017.10.001] [Citation(s) in RCA: 110] [Impact Index Per Article: 15.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2017] [Revised: 10/05/2017] [Accepted: 10/06/2017] [Indexed: 01/21/2023]
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115
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Hishikawa D, Valentine WJ, Iizuka-Hishikawa Y, Shindou H, Shimizu T. Metabolism and functions of docosahexaenoic acid-containing membrane glycerophospholipids. FEBS Lett 2017; 591:2730-2744. [PMID: 28833063 PMCID: PMC5639365 DOI: 10.1002/1873-3468.12825] [Citation(s) in RCA: 68] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2017] [Revised: 08/13/2017] [Accepted: 08/17/2017] [Indexed: 12/12/2022]
Abstract
Omega‐3 (ω‐3) fatty acids (FAs) such as docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA) are known to have important roles in human health and disease. Besides being utilized as fuel, ω‐3 FAs have specific functions based on their structural characteristics. These functions include serving as ligands for several receptors, precursors of lipid mediators, and components of membrane glycerophospholipids (GPLs). Since ω‐3 FAs (especially DHA) are highly flexible, the levels of DHA in GPLs may affect membrane biophysical properties such as fluidity, flexibility, and thickness. Here, we summarize some of the cellular mechanisms for incorporating DHA into membrane GPLs and propose biological effects and functions of DHA‐containing membranes of several cell and tissue types.
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Affiliation(s)
- Daisuke Hishikawa
- Department of Lipid Signaling, National Center for Global Health and Medicine, Shinjuku-ku, Tokyo, Japan
| | - William J Valentine
- Department of Lipid Signaling, National Center for Global Health and Medicine, Shinjuku-ku, Tokyo, Japan
| | - Yoshiko Iizuka-Hishikawa
- Department of Lipid Signaling, National Center for Global Health and Medicine, Shinjuku-ku, Tokyo, Japan
| | - Hideo Shindou
- Department of Lipid Signaling, National Center for Global Health and Medicine, Shinjuku-ku, Tokyo, Japan.,Department of Lipid Science, The University of Tokyo, Bunkyo-ku, Japan.,AMED, Chiyoda-ku, Tokyo, Japan
| | - Takao Shimizu
- Department of Lipid Signaling, National Center for Global Health and Medicine, Shinjuku-ku, Tokyo, Japan.,Department of Lipidomics Graduate School of Medicine, The University of Tokyo, Bunkyo-ku, Japan
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116
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Suárez-García S, Caimari A, Del Bas JM, Suárez M, Arola L. Serum lysophospholipid levels are altered in dyslipidemic hamsters. Sci Rep 2017; 7:10431. [PMID: 28874705 PMCID: PMC5585394 DOI: 10.1038/s41598-017-10651-0] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2017] [Accepted: 08/10/2017] [Indexed: 12/12/2022] Open
Abstract
Dyslipidemias are common disorders that predispose individuals to severe diseases. It is known that healthy living habits can prevent dyslipidemias if they are diagnosed properly. Therefore, biomarkers that assist in diagnosis are essential. The aim of this study was to identify biomarkers of dyslipidemia progression, which in turn disclose its etiology. These findings will pave the way for examinations of the regulatory mechanisms involved in dyslipidemias. Hamsters were fed either a normal-fat diet (NFD) or a high-fat diet. Some of the NFD-fed animals were further treated with the hyperlipidemic agent Poloxamer 407. Non-targeted metabolomics was used to investigate progressive changes in unknown serum metabolites. The hepatic expression of putative biomarker-related genes was also analyzed. The serum levels of lysophospholipids (Lyso-PLs) and their related enzymes lecithin-cholesterol acyltransferase (LCAT), secreted phospholipase A2 (sPLA2) and paraoxonase-1 were altered in dyslipidemic hamsters. Lysophosphatidylcholine levels were increased in diet-induced dyslipidemic groups, whereas lysophosphatidylethanolamine levels increased in response to the chemical treatment. The liver was significantly involved in regulating the levels of these molecules, based on the modified expression of endothelial lipase (Lipg), sPLA2 (Pla2g2a) and acyltransferases (Lcat and Lpcat3). We concluded that Lyso-PL evaluation could aid in the comprehensive diagnosis and management of lipid disorders.
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Affiliation(s)
- Susana Suárez-García
- Nutrigenomics Research Group, Department of Biochemistry and Biotechnology, Universitat Rovira i Virgili (URV), Tarragona, 43007, Spain
| | - Antoni Caimari
- Technological Unit of Nutrition and Health. EURECAT-Technological Center of Catalonia, Reus, 43204, Spain
| | - Josep Maria Del Bas
- Technological Unit of Nutrition and Health. EURECAT-Technological Center of Catalonia, Reus, 43204, Spain
| | - Manuel Suárez
- Nutrigenomics Research Group, Department of Biochemistry and Biotechnology, Universitat Rovira i Virgili (URV), Tarragona, 43007, Spain.
| | - Lluís Arola
- Nutrigenomics Research Group, Department of Biochemistry and Biotechnology, Universitat Rovira i Virgili (URV), Tarragona, 43007, Spain
- Technological Unit of Nutrition and Health. EURECAT-Technological Center of Catalonia, Reus, 43204, Spain
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117
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Rong X, Wang B, Palladino EN, de Aguiar Vallim TQ, Ford DA, Tontonoz P. ER phospholipid composition modulates lipogenesis during feeding and in obesity. J Clin Invest 2017; 127:3640-3651. [PMID: 28846071 DOI: 10.1172/jci93616] [Citation(s) in RCA: 64] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2017] [Accepted: 07/11/2017] [Indexed: 12/31/2022] Open
Abstract
Sterol regulatory element-binding protein 1c (SREBP-1c) is a central regulator of lipogenesis whose activity is controlled by proteolytic cleavage. The metabolic factors that affect its processing are incompletely understood. Here, we show that dynamic changes in the acyl chain composition of ER phospholipids affect SREBP-1c maturation in physiology and disease. The abundance of polyunsaturated phosphatidylcholine in liver ER is selectively increased in response to feeding and in the setting of obesity-linked insulin resistance. Exogenous delivery of polyunsaturated phosphatidylcholine to ER accelerated SREBP-1c processing through a mechanism that required an intact SREBP cleavage-activating protein (SCAP) pathway. Furthermore, induction of the phospholipid-remodeling enzyme LPCAT3 in response to liver X receptor (LXR) activation promoted SREBP-1c processing by driving the incorporation of polyunsaturated fatty acids into ER. Conversely, LPCAT3 deficiency increased membrane saturation, reduced nuclear SREBP-1c abundance, and blunted the lipogenic response to feeding, LXR agonist treatment, or obesity-linked insulin resistance. Desaturation of the ER membrane may serve as an auxiliary signal of the fed state that promotes lipid synthesis in response to nutrient availability.
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Affiliation(s)
- Xin Rong
- Department of Pathology and Laboratory Medicine, Department of Medicine, UCLA, Los Angeles, California, USA
| | - Bo Wang
- Department of Pathology and Laboratory Medicine, Department of Medicine, UCLA, Los Angeles, California, USA
| | - Elisa Nd Palladino
- Department of Biochemistry and Molecular Biology, and Center for Cardiovascular Research, Saint Louis University, St. Louis, Missouri, USA
| | | | - David A Ford
- Department of Biochemistry and Molecular Biology, and Center for Cardiovascular Research, Saint Louis University, St. Louis, Missouri, USA
| | - Peter Tontonoz
- Department of Pathology and Laboratory Medicine, Department of Medicine, UCLA, Los Angeles, California, USA.,Molecular Biology Institute, and.,Howard Hughes Medical Institute, UCLA, Los Angeles, California, USA
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118
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Kiamehr M, Viiri LE, Vihervaara T, Koistinen KM, Hilvo M, Ekroos K, Käkelä R, Aalto-Setälä K. Lipidomic profiling of patient-specific iPSC-derived hepatocyte-like cells. Dis Model Mech 2017; 10:1141-1153. [PMID: 28733363 PMCID: PMC5611970 DOI: 10.1242/dmm.030841] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2017] [Accepted: 07/10/2017] [Indexed: 12/18/2022] Open
Abstract
Hepatocyte-like cells (HLCs) differentiated from human induced pluripotent stem cells (iPSCs) offer an alternative model to primary human hepatocytes to study lipid aberrations. However, the detailed lipid profile of HLCs is yet unknown. In the current study, functional HLCs were differentiated from iPSCs generated from dermal fibroblasts of three individuals by a three-step protocol through the definitive endoderm (DE) stage. In parallel, detailed lipidomic analyses as well as gene expression profiling of a set of lipid-metabolism-related genes were performed during the entire differentiation process from iPSCs to HLCs. Additionally, fatty acid (FA) composition of the cell culture media at different stages was determined. Our results show that major alterations in the molecular species of lipids occurring during DE and early hepatic differentiation stages mainly mirror the quality and quantity of the FAs supplied in culture medium at each stage. Polyunsaturated phospholipids and sphingolipids with a very long FA were produced in the cells at a later stage of differentiation. This work uncovers the previously unknown lipid composition of iPSC-HLCs and its alterations during the differentiation in conjunction with the expression of key lipid-associated genes. Together with biochemical, functional and gene expression measurements, the lipidomic analyses allowed us to improve our understanding of the concerted influence of the exogenous metabolite supply and cellular biosynthesis essential for iPSC-HLC differentiation and function. Importantly, the study describes in detail a cell model that can be applied in exploring, for example, the lipid metabolism involved in the development of fatty liver disease or atherosclerosis.
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Affiliation(s)
- Mostafa Kiamehr
- Faculty of Medicine and Life Sciences, University of Tampere, Tampere, 33520, Finland
| | - Leena E Viiri
- Faculty of Medicine and Life Sciences, University of Tampere, Tampere, 33520, Finland
| | | | | | | | | | - Reijo Käkelä
- Department of Biosciences, University of Helsinki, Helsinki, 00014, Finland
| | - Katriina Aalto-Setälä
- Faculty of Medicine and Life Sciences, University of Tampere, Tampere, 33520, Finland.,Heart Hospital, Tampere University Hospital, Tampere, 33520, Finland
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119
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Schulman IG. Liver X receptors link lipid metabolism and inflammation. FEBS Lett 2017; 591:2978-2991. [PMID: 28555747 DOI: 10.1002/1873-3468.12702] [Citation(s) in RCA: 136] [Impact Index Per Article: 19.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2017] [Accepted: 05/23/2017] [Indexed: 12/14/2022]
Abstract
The response of immune cells to pathogens is often associated with changes in the flux through basic metabolic pathways. Indeed, in many cases changes in metabolism appear to be necessary for a robust immune response. The Liver X receptors (LXRs) are members of the nuclear hormone receptor superfamily that regulate gene networks controlling cholesterol and lipid metabolism. In immune cells, particularly in macrophages, LXRs also inhibit proinflammatory gene expression. This Review will highlight recent studies that connect LXR-dependent control of lipid metabolism to regulation of the immune response.
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Affiliation(s)
- Ira G Schulman
- Department of Pharmacology, University of Virginia School of Medicine, Charlottesville, VA, USA
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120
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Paalvast Y, de Boer JF, Groen AK. Developments in intestinal cholesterol transport and triglyceride absorption. Curr Opin Lipidol 2017; 28:248-254. [PMID: 28338522 DOI: 10.1097/mol.0000000000000415] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
PURPOSE OF REVIEW To discuss recent advances in research focused on intestinal lipid handling. RECENT FINDINGS An important strategy in reducing atherosclerosis and risk of cardiovascular events is to increase the rate of reverse cholesterol transport, including its final step; cholesterol excretion from the body. The rate of removal is determined by a complex interplay between the factors involved in regulation of intestinal cholesterol absorption. One of these factors is a process known as transintestinal cholesterol excretion. This pathway comprises transport of cholesterol directly from the blood, through the enterocyte, into the intestinal lumen. In humans, this pathway accounts for 35% of cholesterol excretion in the feces. Mechanistic studies in mice revealed that, activation of the bile acid receptor farnesoid X receptor increases cholesterol removal via the transintestinal cholesterol excretion pathway as well as decreases plasma cholesterol and triglyceride providing an interesting target for treatment of dyslipidemia in humans. The physical chemical properties of bile acids are under control of farnesoid X receptor and determine intestinal cholesterol and triglyceride solubilization as well as absorption, providing a direct link between these two important factors in the pathogenesis of cardiovascular disease. Besides bile acids, intestinal phospholipids are important for luminal lipid solubilization. Interestingly, phospholipid remodeling through LPCAT3 was shown to be pivotal for uptake of fatty acids by enterocytes, which may provide a mechanistic handle for therapeutic intervention. SUMMARY The importance of the intestine in control of cholesterol and triglyceride homeostasis is increasingly recognized. Recently, novel factors involved in regulation of cholesterol excretion and intestinal triglyceride and fatty acid uptake have been reported and are discussed in this short review.
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Affiliation(s)
- Yared Paalvast
- aDepartment of Pediatrics bDepartment of Laboratory Medicine, University of Groningen, University Medical Center Groningen cDepartment of Vascular Medicine, Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands
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121
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Gluchowski NL, Becuwe M, Walther TC, Farese RV. Lipid droplets and liver disease: from basic biology to clinical implications. Nat Rev Gastroenterol Hepatol 2017; 14:343-355. [PMID: 28428634 PMCID: PMC6319657 DOI: 10.1038/nrgastro.2017.32] [Citation(s) in RCA: 396] [Impact Index Per Article: 56.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Lipid droplets are dynamic organelles that store neutral lipids during times of energy excess and serve as an energy reservoir during deprivation. Many prevalent metabolic diseases, such as the metabolic syndrome or obesity, often result in abnormal lipid accumulation in lipid droplets in the liver, also called hepatic steatosis. Obesity-related steatosis, or NAFLD in particular, is a major public health concern worldwide and is frequently associated with insulin resistance and type 2 diabetes mellitus. Here, we review the latest insights into the biology of lipid droplets and their role in maintaining lipid homeostasis in the liver. We also offer a perspective of liver diseases that feature lipid accumulation in these lipid storage organelles, which include NAFLD and viral hepatitis. Although clinical applications of this knowledge are just beginning, we highlight new opportunities for identifying molecular targets for treating hepatic steatosis and steatohepatitis.
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Affiliation(s)
- Nina L. Gluchowski
- Department of Genetics and Complex Diseases, Harvard T. H. Chan School of Public Health, 655 Huntington Avenue, Boston, Massachusetts 02115, USA.,Boston Children’s Hospital Department of Gastroenterology, Hepatology and Nutrition, 300 Longwood Avenue Boston, Massachusetts 02115, USA
| | - Michel Becuwe
- Department of Genetics and Complex Diseases, Harvard T. H. Chan School of Public Health, 655 Huntington Avenue, Boston, Massachusetts 02115, USA
| | - Tobias C. Walther
- Department of Genetics and Complex Diseases, Harvard T. H. Chan School of Public Health, 655 Huntington Avenue, Boston, Massachusetts 02115, USA.,Department of Cell Biology, Harvard Medical School, 240 Longwood Avenue Boston, Massachusetts 02115, USA.,Department of Genetics, Harvard Medical School, 77 Avenue Louis Pasteur Boston, Massachusetts 02115, USA.,Howard Hughes Medical Institute, Department of Genetics and Complex Diseases, Harvard T. H. Chan School of Public Health, 655 Huntington Avenue, Boston, Massachusetts 02115, USA
| | - Robert V. Farese
- Department of Genetics and Complex Diseases, Harvard T. H. Chan School of Public Health, 655 Huntington Avenue, Boston, Massachusetts 02115, USA.,Department of Cell Biology, Harvard Medical School, 240 Longwood Avenue Boston, Massachusetts 02115, USA.,Department of Genetics, Harvard Medical School, 77 Avenue Louis Pasteur Boston, Massachusetts 02115, USA
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122
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Transient receptor potential canonical 5 channels plays an essential role in hepatic dyslipidemia associated with cholestasis. Sci Rep 2017; 7:2338. [PMID: 28539583 PMCID: PMC5443755 DOI: 10.1038/s41598-017-02439-z] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2017] [Accepted: 04/11/2017] [Indexed: 02/06/2023] Open
Abstract
Transient receptor potential canonical 5 (TRPC5), a calcium-permeable, non-selective cation channel is expressed in the periphery, but there is limited knowledge of its regulatory roles in vivo. Endogenous modulators of TRPC5 include a range of phospholipids that have an established role in liver disease, including lysophosphatidylcholine (LPC). Cholestasis is characterized by impairment of excretion of bile acids, leading to elevation of hepatic bile acids. We investigated the contribution of TRPC5 in a murine model of cholestasis. Wild-type (WT) and TRPC5 knock-out (KO) mice were fed a diet supplemented with 0.5% cholic acid (CA) for 21 days. CA-diet supplementation resulted in enlargement of the liver in WT mice, which was ameliorated in TRPC5 KO mice. Hepatic bile acid and lipid content was elevated in WT mice, with a reduction observed in TRPC5 KO mice. Consistently, liver enzymes were significantly increased in cholestatic WT mice and significantly blunted in TRPC5 KO mice. Localized dyslipidaemia, secondary to cholestasis, was investigated utilizing a selected lipid analysis. This revealed significant perturbations in the lipid profile following CA-diet feeding, with increased cholesterol, triglycerides and phospholipids, in WT, but not TRPC5 KO mice. Our results suggest that activation of TRPC5 contributes to the development of cholestasis and associated dyslipidemia. Modulation of TRPC5 activity may present as a novel therapeutic target for liver disease.
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123
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Depletion of TM6SF2 disturbs membrane lipid composition and dynamics in HuH7 hepatoma cells. Biochim Biophys Acta Mol Cell Biol Lipids 2017; 1862:676-685. [PMID: 28434889 DOI: 10.1016/j.bbalip.2017.04.004] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2016] [Revised: 04/13/2017] [Accepted: 04/15/2017] [Indexed: 01/02/2023]
Abstract
A polymorphism of TM6SF2 associates with hepatic lipid accumulation and reduction of triacylglycerol (TAG) secretion, but the function of the encoded protein has remained enigmatic. We studied the effect of stable TM6SF2 knock-down on the lipid content and composition, mitochondrial fatty acid oxidation and organelle structure of HuH7 hepatoma cells. Knock-down of TM6SF2 resulted in intracellular accumulation of TAGs, cholesterol esters, phosphatidylcholine (PC) and phosphatidylethanolamine. In all of these lipid classes, polyunsaturated lipid species were significantly reduced while saturated and monounsaturated species increased their proportions. The PCs encountered relative and absolute arachidonic acid (AA, 20:4n-6) depletion, and AA was also reduced in the total cellular fatty acid pool. Synthesis and turnover of the hepatocellular glycerolipids was enhanced. The TM6SF2 knock-down cells secreted lipoprotein-like particles with a smaller diameter than in the controls, and more lysosome/endosome structures appeared in the knock-down cells. The mitochondrial capacity for palmitate oxidation was significantly reduced. These observations provide novel clues to TM6SF2 function and raise altered mebrane lipid composition and dynamics among the mechanism(s) by which the protein deficiency disturbs hepatic TAG secretion.
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124
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van der Veen JN, Kennelly JP, Wan S, Vance JE, Vance DE, Jacobs RL. The critical role of phosphatidylcholine and phosphatidylethanolamine metabolism in health and disease. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2017; 1859:1558-1572. [PMID: 28411170 DOI: 10.1016/j.bbamem.2017.04.006] [Citation(s) in RCA: 921] [Impact Index Per Article: 131.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/16/2016] [Revised: 03/27/2017] [Accepted: 04/09/2017] [Indexed: 12/11/2022]
Abstract
Phosphatidylcholine (PC) and phosphatidylethanolamine (PE) are the most abundant phospholipids in all mammalian cell membranes. In the 1950s, Eugene Kennedy and co-workers performed groundbreaking research that established the general outline of many of the pathways of phospholipid biosynthesis. In recent years, the importance of phospholipid metabolism in regulating lipid, lipoprotein and whole-body energy metabolism has been demonstrated in numerous dietary studies and knockout animal models. The purpose of this review is to highlight the unappreciated impact of phospholipid metabolism on health and disease. Abnormally high, and abnormally low, cellular PC/PE molar ratios in various tissues can influence energy metabolism and have been linked to disease progression. For example, inhibition of hepatic PC synthesis impairs very low density lipoprotein secretion and changes in hepatic phospholipid composition have been linked to fatty liver disease and impaired liver regeneration after surgery. The relative abundance of PC and PE regulates the size and dynamics of lipid droplets. In mitochondria, changes in the PC/PE molar ratio affect energy production. We highlight data showing that changes in the PC and/or PE content of various tissues are implicated in metabolic disorders such as atherosclerosis, insulin resistance and obesity. This article is part of a Special Issue entitled: Membrane Lipid Therapy: Drugs Targeting Biomembranes edited by Pablo V. Escribá.
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Affiliation(s)
- Jelske N van der Veen
- Group on the Molecular and Cell Biology of Lipids, Canada; Department of Biochemistry, University of Alberta, Edmonton, AB T6G 2S2, Canada
| | - John P Kennelly
- Group on the Molecular and Cell Biology of Lipids, Canada; Department of Agricultural, Food and Nutritional Science, 4-002 Li Ka Shing Centre for Heath Research Innovations, University of Alberta, Edmonton, AB T6G 2E1, Canada
| | - Sereana Wan
- Group on the Molecular and Cell Biology of Lipids, Canada; Department of Biochemistry, University of Alberta, Edmonton, AB T6G 2S2, Canada
| | - Jean E Vance
- Group on the Molecular and Cell Biology of Lipids, Canada; Department of Medicine, University of Alberta, Edmonton, AB T6G 2S2, Canada
| | - Dennis E Vance
- Group on the Molecular and Cell Biology of Lipids, Canada; Department of Biochemistry, University of Alberta, Edmonton, AB T6G 2S2, Canada
| | - René L Jacobs
- Group on the Molecular and Cell Biology of Lipids, Canada; Department of Biochemistry, University of Alberta, Edmonton, AB T6G 2S2, Canada; Department of Agricultural, Food and Nutritional Science, 4-002 Li Ka Shing Centre for Heath Research Innovations, University of Alberta, Edmonton, AB T6G 2E1, Canada.
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125
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Saito K, Goda K, Kobayashi A, Yamada N, Maekawa K, Saito Y, Sugai S. Arachidonic acid-containing phosphatidylcholine characterized by consolidated plasma and liver lipidomics as an early onset marker for tamoxifen-induced hepatic phospholipidosis. J Appl Toxicol 2017; 37:943-953. [PMID: 28138993 DOI: 10.1002/jat.3442] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2016] [Revised: 12/16/2016] [Accepted: 12/26/2016] [Indexed: 01/27/2023]
Abstract
Lipid profiling has emerged as an effective approach to not only screen disease and drug toxicity biomarkers but also understand their underlying mechanisms of action. Tamoxifen, a widely used antiestrogenic agent for adjuvant therapy against estrogen-positive breast cancer, possesses side effects such as hepatic steatosis and phospholipidosis (PLD). In the present study, we administered tamoxifen to Sprague-Dawley rats and used lipidomics to reveal tamoxifen-induced alteration of the hepatic lipid profile and its association with the plasma lipid profile. Treatment with tamoxifen for 28 days caused hepatic PLD in rats. We compared the plasma and liver lipid profiles in treated vs. untreated rats using a multivariate analysis to determine differences between the two groups. In total, 25 plasma and 45 liver lipids were identified and altered in the tamoxifen-treated group. Of these lipids, arachidonic acid (AA)-containing phosphatidylcholines (PCs), such as PC (17:0/20:4) and PC (18:1/20:4), were commonly reduced in both plasma and liver. Conversely, tamoxifen increased other phosphoglycerolipids in the liver, such as phosphatidylethanolamine (18:1/18:1) and phosphatidylinositol (18:0/18:2). We also examined alteration of AA-containing PCs and some phosphoglycerolipids in the pre-PLD stage and found that these lipid alterations were initiated before pathological alteration in the liver. In addition, changes in plasma and liver levels of AA-containing PCs were linearly associated. Moreover, levels of free AA and mRNA levels of AA-synthesizing enzymes, such as fatty acid desaturase 1 and 2, were decreased by tamoxifen treatment. Therefore, our study demonstrated that AA-containing PCs might have potential utility as novel and predictive biomarkers for tamoxifen-induced PLD. Copyright © 2017 John Wiley & Sons, Ltd.
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Affiliation(s)
- Kosuke Saito
- Division of Medicinal Safety Science, National Institute of Health Sciences, Setagaya, Tokyo, 158-8501, Japan
| | - Keisuke Goda
- Toxicology Research Lab, Central Pharmaceutical Research Institute, Japan Tobacco Inc., Hadano, Kanagawa, 257-0024, Japan
| | - Akio Kobayashi
- Toxicology Research Lab, Central Pharmaceutical Research Institute, Japan Tobacco Inc., Hadano, Kanagawa, 257-0024, Japan
| | - Naohito Yamada
- Toxicology Research Lab, Central Pharmaceutical Research Institute, Japan Tobacco Inc., Hadano, Kanagawa, 257-0024, Japan
| | - Kyoko Maekawa
- Division of Medicinal Safety Science, National Institute of Health Sciences, Setagaya, Tokyo, 158-8501, Japan
| | - Yoshiro Saito
- Division of Medicinal Safety Science, National Institute of Health Sciences, Setagaya, Tokyo, 158-8501, Japan
| | - Shoichiro Sugai
- Toxicology Research Lab, Central Pharmaceutical Research Institute, Japan Tobacco Inc., Hadano, Kanagawa, 257-0024, Japan
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126
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Singh AB, Liu J. Identification of Hepatic Lysophosphatidylcholine Acyltransferase 3 as a Novel Target Gene Regulated by Peroxisome Proliferator-activated Receptor δ. J Biol Chem 2016; 292:884-897. [PMID: 27913621 DOI: 10.1074/jbc.m116.743575] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2016] [Revised: 11/29/2016] [Indexed: 12/31/2022] Open
Abstract
Peroxisome proliferator-activated receptor δ (PPARδ) regulates many genes involved in lipid metabolism. Hepatic lysophosphatidylcholine acyltransferase 3 (LPCAT3) has critical functions in triglycerides transport and endoplasmic reticulum stress response due to its unique ability to catalyze the incorporation of polyunsaturated fatty acids into phospholipids. Previous studies identified liver X receptor as the transcription factor controlling LPCAT3 expression in mouse liver tissue. Here we show that the hepatic LPCAT3 gene is transcriptionally regulated by PPARδ. Adenovirus-mediated knockdown of PPARδ in cultured hepatic cells and liver tissue reduced LPCAT3 mRNA levels, and exogenous overexpression of PPARδ increased LPCAT3 mRNA expression. Activation of PPARδ in HepG2, Huh7, and Hepa 1-6 cells with its specific agonists increased LPCAT3 mRNA levels in all three hepatic cell lines. Through conducting sequence analysis, LPCAT3 promoter assays, and direct DNA binding assays, we have mapped the functional PPAR-responsive element to a proximal region from -135 to -123 of the LPCAT3 promoter that plays an essential role in mediating PPARδ-induced transactivation of the LPCAT3 gene. Finally, we have provided in vivo evidence showing that activation of PPARδ by agonist L165041 in mice increased hepatic LPCAT3 mRNA abundance and LPCAT enzymatic activity, which is associated with increased incorporations of arachidonate into liver phosphatidylcholine and phosphatidylethanolamine. Furthermore, transient liver-specific knockdown of LPCAT3 in mice affected PPARδ-mediated activation of several hepatic genes involving in FA metabolism. Altogether, our new findings identify LPCAT3 as a direct PPARδ target gene and suggest a novel function of PPARδ in regulation of phospholipid metabolism through LPCAT3.
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Affiliation(s)
- Amar Bahadur Singh
- From the Department of Veterans Affairs Palo Alto Health Care System, Palo Alto, California 94304
| | - Jingwen Liu
- From the Department of Veterans Affairs Palo Alto Health Care System, Palo Alto, California 94304
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127
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Luukkonen PK, Zhou Y, Hyötyläinen T, Leivonen M, Arola J, Orho-Melander M, Orešič M, Yki-Järvinen H. The MBOAT7 variant rs641738 alters hepatic phosphatidylinositols and increases severity of non-alcoholic fatty liver disease in humans. J Hepatol 2016; 65:1263-1265. [PMID: 27520876 DOI: 10.1016/j.jhep.2016.07.045] [Citation(s) in RCA: 120] [Impact Index Per Article: 15.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/30/2016] [Revised: 07/22/2016] [Accepted: 07/26/2016] [Indexed: 02/07/2023]
Affiliation(s)
- Panu K Luukkonen
- Department of Medicine, University of Helsinki, Helsinki University Hospital, Helsinki, Finland; Minerva Foundation Institute for Medical Research, Helsinki, Finland.
| | - You Zhou
- Department of Medicine, University of Helsinki, Helsinki University Hospital, Helsinki, Finland; Systems Immunity University Research Institute and Division of Infection and Immunity, School of Medicine, Cardiff University, Cardiff, United Kingdom; Minerva Foundation Institute for Medical Research, Helsinki, Finland
| | | | - Marja Leivonen
- Department of Surgery, University of Helsinki, Helsinki University Hospital, Helsinki, Finland
| | - Johanna Arola
- Department of Pathology, University of Helsinki, Helsinki University Hospital, Helsinki, Finland
| | | | | | - Hannele Yki-Järvinen
- Department of Medicine, University of Helsinki, Helsinki University Hospital, Helsinki, Finland; Minerva Foundation Institute for Medical Research, Helsinki, Finland
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128
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Abstract
PURPOSE OF REVIEW Phospholipids are major constituents in the intestinal lumen after meal consumption. This article highlights current literature suggesting the contributory role of intestinal phospholipid metabolism toward cardiometabolic disease manifestation. RECENT FINDINGS Group 1b phospholipase A2 (PLA2g1b) catalyzes phospholipid hydrolysis in the intestinal lumen. The digestive product lysophospholipid, particularly lysophosphatidylcholine (LPC), has a direct role in mediating chylomicron assembly and secretion. The LPC in the digestive tract is further catabolized into lysophosphatidic acid and choline via autotaxin-mediated and autotaxin-independent mechanisms. The LPC and lysophosphatidic acid absorbed through the digestive tract and transported to the plasma directly promote systemic inflammation and cell dysfunction, leading to increased risk of cardiovascular disease and obesity/diabetes. The choline moiety generated in the digestive tract can also be used by gut bacteria to generate trimethylamine, which is subsequently transported to the liver and oxidized into trimethylamine-N-oxide that also enhances atherosclerosis and cardiovascular abnormalities. SUMMARY Products of phospholipid metabolism in the intestine through PLA2g1b and autotaxin-mediated pathways directly contribute to cardiometabolic diseases through multiple mechanisms. The implication of these studies is that therapeutic inhibition of PLA2g1b and autotaxin in the digestive tract may be a viable approach for cardiovascular and metabolic disease intervention.
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Affiliation(s)
- David Y Hui
- Department of Pathology, Metabolic Disease Research Center, University of Cincinnati College of Medicine, Cincinnati, Ohio, USA
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129
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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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Mancina RM, Dongiovanni P, Petta S, Pingitore P, Meroni M, Rametta R, Borén J, Montalcini T, Pujia A, Wiklund O, Hindy G, Spagnuolo R, Motta BM, Pipitone RM, Craxì A, Fargion S, Nobili V, Käkelä P, Kärjä V, Männistö V, Pihlajamäki J, Reilly DF, Castro-Perez J, Kozlitina J, Valenti L, Romeo S. The MBOAT7-TMC4 Variant rs641738 Increases Risk of Nonalcoholic Fatty Liver Disease in Individuals of European Descent. Gastroenterology 2016; 150:1219-1230.e6. [PMID: 26850495 PMCID: PMC4844071 DOI: 10.1053/j.gastro.2016.01.032] [Citation(s) in RCA: 458] [Impact Index Per Article: 57.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/12/2015] [Revised: 01/26/2016] [Accepted: 01/26/2016] [Indexed: 02/06/2023]
Abstract
BACKGROUND & AIMS Nonalcoholic fatty liver disease (NAFLD) is a leading cause of liver damage and is characterized by steatosis. Genetic factors increase risk for progressive NAFLD. A genome-wide association study showed that the rs641738 C>T variant in the locus that contains the membrane bound O-acyltransferase domain-containing 7 gene (MBOAT7, also called LPIAT1) and transmembrane channel-like 4 gene (TMC4) increased the risk for cirrhosis in alcohol abusers. We investigated whether the MBOAT7-TMC4 is a susceptibility locus for the development and progression of NAFLD. METHODS We genotyped rs641738 in DNA collected from 3854 participants from the Dallas Heart Study (a multi-ethnic population-based probability sample of Dallas County residents) and 1149 European individuals from the Liver Biopsy Cross-Sectional Cohort. Clinical and anthropometric data were collected, and biochemical and lipidomics were measured in plasma samples from participants. A total of 2736 participants from the Dallas Heart Study also underwent proton magnetic resonance spectroscopy to measure hepatic triglyceride content. In the Liver Biopsy Cross-Sectional Cohort, a total of 1149 individuals underwent liver biopsy to diagnose liver disease and disease severity. RESULTS The genotype rs641738 at the MBOAT7-TMC4 locus associated with increased hepatic fat content in the 2 cohorts, and with more severe liver damage and increased risk of fibrosis compared with subjects without the variant. MBOAT7, but not TMC4, was found to be highly expressed in the liver. The MBOAT7 rs641738 T allele was associated with lower protein expression in the liver and changes in plasma phosphatidylinositol species consistent with decreased MBOAT7 function. CONCLUSIONS We provide evidence for an association between the MBOAT7 rs641738 variant and the development and severity of NAFLD in individuals of European descent. This association seems to be mediated by changes in the hepatic phosphatidylinositol acyl-chain remodeling.
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Affiliation(s)
| | - Paola Dongiovanni
- Internal Medicine, Fondazione IRCCS Ca’ Granda Ospedale Policlinico Milano, Milan, Italy
| | - Salvatore Petta
- Department of Gastroenterology, Università di Palermo, Palermo, Italy
| | - Piero Pingitore
- Department of Molecular and Clinical Medicine, University of Gothenburg, Sweden
| | - Marica Meroni
- Department of Pathophysiology and Transplantation Università degli Studi di Milano, Milan, Italy
| | - Raffaela Rametta
- Department of Pathophysiology and Transplantation Università degli Studi di Milano, Milan, Italy
| | - Jan Borén
- Department of Molecular and Clinical Medicine, University of Gothenburg, Sweden
| | - Tiziana Montalcini
- Clinical Nutrition Unit, Department of Medical and Surgical Sciences, University Magna Graecia, Catanzaro, Italy
| | - Arturo Pujia
- Clinical Nutrition Unit, Department of Medical and Surgical Sciences, University Magna Graecia, Catanzaro, Italy
| | - Olov Wiklund
- Department of Molecular and Clinical Medicine, University of Gothenburg, Sweden,Cardiology Department, Sahlgrenska University Hospital, Gothenburg, Sweden
| | - George Hindy
- Diabetes and Cardiovascular Disease-Genetic Epidemiology, Lund, Sweden
| | - Rocco Spagnuolo
- Division of Gastroenterology, Fondazione Tommaso Campanella, University Magna Graecia of Catanzaro, Italy
| | | | - Rosaria Maria Pipitone
- Department of Pathophysiology and Transplantation Università degli Studi di Milano, Milan, Italy
| | - Antonio Craxì
- Department of Gastroenterology, Università di Palermo, Palermo, Italy
| | - Silvia Fargion
- Internal Medicine, Fondazione IRCCS Ca’ Granda Ospedale Policlinico Milano, Milan, Italy,Department of Pathophysiology and Transplantation Università degli Studi di Milano, Milan, Italy
| | | | - Pirjo Käkelä
- Department of Surgery, University of Eastern Finland and Kuopio University Hospital, Kuopio, Finland
| | - Vesa Kärjä
- Department of Pathology, University of Eastern Finland and Kuopio University Hospital, Kuopio, Finland
| | - Ville Männistö
- Department of Medicine, University of Eastern Finland and Kuopio University Hospital, Kuopio, Finland
| | - Jussi Pihlajamäki
- Clinical Nutrition and Obesity Center, Kuopio University Hospital, Kuopio, Finland,Department of Public Health and Clinical Nutrition, University of Eastern Finland, Kuopio, Finland
| | - Dermot F. Reilly
- Merck Research Laboratories, Genetics and Pharmacogenomics, Boston, Massachusetts, USA
| | - Jose Castro-Perez
- Merck Research Laboratories, Diabetes Department, Kenilworth, New Jersey, USA,Waters Corporation, Milford, Massachusetts, USA
| | - Julia Kozlitina
- McDermott Center for Human Growth and Development, University of Texas Southwestern Medical Center, Dallas, Texas.
| | - Luca Valenti
- Internal Medicine, Fondazione IRCCS Ca' Granda Ospedale Policlinico Milano, Milan, Italy; Department of Pathophysiology and Transplantationm Università degli Studi di Milano, Milan, Italy.
| | - Stefano Romeo
- Department of Molecular and Clinical Medicine, University of Gothenburg, Sweden; Clinical Nutrition Unit, Department of Medical and Surgical Sciences, University Magna Graecia, Catanzaro, Italy; Cardiology Department, Sahlgrenska University Hospital, Gothenburg, Sweden.
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131
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D'Aquila T, Hung YH, Carreiro A, Buhman KK. Recent discoveries on absorption of dietary fat: Presence, synthesis, and metabolism of cytoplasmic lipid droplets within enterocytes. Biochim Biophys Acta Mol Cell Biol Lipids 2016; 1861:730-47. [PMID: 27108063 DOI: 10.1016/j.bbalip.2016.04.012] [Citation(s) in RCA: 88] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2015] [Revised: 03/16/2016] [Accepted: 04/16/2016] [Indexed: 02/07/2023]
Abstract
Dietary fat provides essential nutrients, contributes to energy balance, and regulates blood lipid concentrations. These functions are important to health, but can also become dysregulated and contribute to diseases such as obesity, diabetes, cardiovascular disease, and cancer. Within enterocytes, the digestive products of dietary fat are re-synthesized into triacylglycerol, which is either secreted on chylomicrons or stored within cytoplasmic lipid droplets (CLDs). CLDs were originally thought to be inert stores of neutral lipids, but are now recognized as dynamic organelles that function in multiple cellular processes in addition to lipid metabolism. This review will highlight recent discoveries related to dietary fat absorption with an emphasis on the presence, synthesis, and metabolism of CLDs within this process.
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Affiliation(s)
- Theresa D'Aquila
- Department of Nutrition Science, Purdue University, West Lafayette, IN 47907, USA
| | - Yu-Han Hung
- Department of Nutrition Science, Purdue University, West Lafayette, IN 47907, USA
| | - Alicia Carreiro
- Department of Nutrition Science, Purdue University, West Lafayette, IN 47907, USA
| | - Kimberly K Buhman
- Department of Nutrition Science, Purdue University, West Lafayette, IN 47907, USA.
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132
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Barelli H, Antonny B. Lipid unsaturation and organelle dynamics. Curr Opin Cell Biol 2016; 41:25-32. [PMID: 27062546 DOI: 10.1016/j.ceb.2016.03.012] [Citation(s) in RCA: 75] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2016] [Revised: 03/16/2016] [Accepted: 03/23/2016] [Indexed: 12/13/2022]
Abstract
The number of double bonds (=unsaturation) in the acyl chains of phospholipids (PL) influences the physical properties of cellular membranes. Here, we discuss disparate molecular processes, including vesicle budding, ion channel opening, and lipoprotein formation, which are greatly facilitated by PL polyunsaturation in membranes. Experimental and computer-based approaches for the structure and dynamics of PL suggest a common cause for these effects: the ability of the polyunsaturated acyl chain of PL to extend or bent along the membrane normal according to various constraints, thereby enabling a third dimension of motion in a structure that is essentially a 2D fluid.
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Affiliation(s)
- Hélène Barelli
- Institut de Pharmacologie Moléculaire et Cellulaire, 660 route des lucioles, 06560 Valbonne, France.
| | - Bruno Antonny
- Institut de Pharmacologie Moléculaire et Cellulaire, 660 route des lucioles, 06560 Valbonne, France.
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133
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Smagris E, Gilyard S, BasuRay S, Cohen JC, Hobbs HH. Inactivation of Tm6sf2, a Gene Defective in Fatty Liver Disease, Impairs Lipidation but Not Secretion of Very Low Density Lipoproteins. J Biol Chem 2016; 291:10659-76. [PMID: 27013658 PMCID: PMC4865914 DOI: 10.1074/jbc.m116.719955] [Citation(s) in RCA: 138] [Impact Index Per Article: 17.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2016] [Indexed: 12/18/2022] Open
Abstract
A missense mutation (E167K) in TM6SF2 (transmembrane 6 superfamily member 2), a polytopic protein of unknown function, is associated with the full spectrum of fatty liver disease. To investigate the role of TM6SF2 in hepatic triglyceride (TG) metabolism, we inactivated the gene in mice. Chronic inactivation of Tm6sf2 in mice is associated with hepatic steatosis, hypocholesterolemia, and transaminitis, thus recapitulating the phenotype observed in humans. No dietary challenge was required to elicit the phenotype. Immunocytochemical and cell fractionation studies revealed that TM6SF2 was present in the endoplasmic reticulum and Golgi complex, whereas the excess neutral lipids in the Tm6sf2(-/-) mice were located in lipid droplets. Plasma VLDL-TG levels were reduced in the KO animals due to a 3-fold decrease in VLDL-TG secretion rate without any associated reduction in hepatic apoB secretion. Both VLDL particle size and plasma cholesterol levels were significantly reduced in KO mice. Despite levels of TM6SF2 protein being 10-fold higher in the small intestine than in the liver, dietary lipid absorption was only modestly reduced in the KO mice. Our data, taken together, reveal that TM6SF2 is required to mobilize neutral lipids for VLDL assembly but is not required for secretion of apoB-containing lipoproteins. Despite TM6SF2 being located in the endoplasmic reticulum and Golgi complex, the lipids that accumulate in its absence reside in lipid droplets.
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Affiliation(s)
- Eriks Smagris
- From the Departments of Molecular Genetics and Internal Medicine and
| | - Shenise Gilyard
- From the Departments of Molecular Genetics and Internal Medicine and
| | | | | | - Helen H Hobbs
- From the Departments of Molecular Genetics and Internal Medicine and the Howard Hughes Medical Institute, University of Texas Southwestern Medical Center, Dallas, Texas 75390
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134
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Chattopadhyay A, Navab M, Hough G, Grijalva V, Mukherjee P, Fogelman HR, Hwang LH, Faull KF, Lusis AJ, Reddy ST, Fogelman AM. Tg6F ameliorates the increase in oxidized phospholipids in the jejunum of mice fed unsaturated LysoPC or WD. J Lipid Res 2016; 57:832-47. [PMID: 26965826 DOI: 10.1194/jlr.m064352] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2015] [Indexed: 12/13/2022] Open
Abstract
Mouse chow supplemented with lysophosphatidylcholine with oleic acid at sn-1 and a hydroxyl group at sn-2 (LysoPC 18:1) increased LysoPC 18:1 in tissue of the jejunum of LDL receptor (LDLR)-null mice by 8.9 ± 1.7-fold compared with chow alone. Western diet (WD) contained dramatically less phosphatidylcholine 18:1 or LysoPC 18:1 compared with chow, but feeding WD increased LysoPC 18:1 in the jejunum by 7.5 ± 1.4-fold compared with chow. Feeding LysoPC 18:1 or feeding WD increased oxidized phospholipids in the jejunum by 5.2 ± 3.0-fold or 8.6 ± 2.2-fold, respectively, in LDLR-null mice (P < 0.0004), and 2.6 ± 1.5-fold or 2.4 ± 0.92-fold, respectively, in WT C57BL/6J mice (P < 0.0001). Adding 0.06% by weight of a concentrate of transgenic tomatoes expressing the 6F peptide (Tg6F) decreased LysoPC 18:1 in the jejunum of LDLR-null mice on both diets (P < 0.0001), and prevented the increase in oxidized phospholipids in the jejunum in LDLR-null and WT mice on both diets (P < 0.008). Tg6F decreased inflammatory cells in the villi of the jejunum, decreased dyslipidemia, and decreased systemic inflammation in LDLR-null and WT mice on both diets. We conclude that Tg6F reduces diet-induced inflammation by reducing the content of unsaturated LysoPC and oxidized phospholipids in the jejunum of mice.
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Affiliation(s)
- Arnab Chattopadhyay
- Departments of Medicine, David Geffen School of Medicine at University of California, Los Angeles, Los Angeles, CA 90095-1736
| | - Mohamad Navab
- Departments of Medicine, David Geffen School of Medicine at University of California, Los Angeles, Los Angeles, CA 90095-1736
| | - Greg Hough
- Departments of Medicine, David Geffen School of Medicine at University of California, Los Angeles, Los Angeles, CA 90095-1736
| | - Victor Grijalva
- Departments of Medicine, David Geffen School of Medicine at University of California, Los Angeles, Los Angeles, CA 90095-1736
| | - Pallavi Mukherjee
- Departments of Medicine, David Geffen School of Medicine at University of California, Los Angeles, Los Angeles, CA 90095-1736
| | - Hannah R Fogelman
- Departments of Medicine, David Geffen School of Medicine at University of California, Los Angeles, Los Angeles, CA 90095-1736
| | - Lin H Hwang
- Semel Institute for Neuroscience and Human Behavior, David Geffen School of Medicine at University of California, Los Angeles, Los Angeles, CA 90095-1736
| | - Kym F Faull
- Semel Institute for Neuroscience and Human Behavior, David Geffen School of Medicine at University of California, Los Angeles, Los Angeles, CA 90095-1736
| | - Aldons J Lusis
- Departments of Medicine, David Geffen School of Medicine at University of California, Los Angeles, Los Angeles, CA 90095-1736 Human Genetics, David Geffen School of Medicine at University of California, Los Angeles, Los Angeles, CA 90095-1736 Microbiology, Immunology, and Molecular Genetics, David Geffen School of Medicine at University of California, Los Angeles, Los Angeles, CA 90095-1736
| | - Srinivasa T Reddy
- Departments of Medicine, David Geffen School of Medicine at University of California, Los Angeles, Los Angeles, CA 90095-1736 Molecular and Medical Pharmacology, David Geffen School of Medicine at University of California, Los Angeles, Los Angeles, CA 90095-1736 Obstetrics and Gynecology, David Geffen School of Medicine at University of California, Los Angeles, Los Angeles, CA 90095-1736
| | - Alan M Fogelman
- Departments of Medicine, David Geffen School of Medicine at University of California, Los Angeles, Los Angeles, CA 90095-1736
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135
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Wang B, Rong X, Duerr MA, Hermanson DJ, Hedde PN, Wong JS, Vallim TQDA, Cravatt BF, Gratton E, Ford DA, Tontonoz P. Intestinal Phospholipid Remodeling Is Required for Dietary-Lipid Uptake and Survival on a High-Fat Diet. Cell Metab 2016; 23:492-504. [PMID: 26833026 PMCID: PMC4785086 DOI: 10.1016/j.cmet.2016.01.001] [Citation(s) in RCA: 94] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/25/2015] [Revised: 11/02/2015] [Accepted: 12/30/2015] [Indexed: 01/31/2023]
Abstract
Phospholipids are important determinants of membrane biophysical properties, but the impact of membrane acyl chain composition on dietary-lipid absorption is unknown. Here we demonstrate that the LXR-responsive phospholipid-remodeling enzyme Lpcat3 modulates intestinal fatty acid and cholesterol absorption and is required for survival on a high-fat diet. Mice lacking Lpcat3 in the intestine thrive on carbohydrate-based chow but lose body weight rapidly and become moribund on a triglyceride-rich diet. Lpcat3-dependent incorporation of polyunsaturated fatty acids into phospholipids is required for the efficient transport of dietary lipids into enterocytes. Furthermore, loss of Lpcat3 amplifies the production of gut hormones, including GLP-1 and oleoylethanolamide, in response to high-fat feeding, contributing to the paradoxical cessation of food intake in the setting of starvation. These results reveal that membrane phospholipid composition is a gating factor in passive lipid absorption and implicate LXR-Lpcat3 signaling in a gut-brain feedback loop that couples absorption to food intake.
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Affiliation(s)
- Bo Wang
- Department of Pathology and Laboratory Medicine, University of California, Los Angeles, Los Angeles, CA 90095, USA; Howard Hughes Medical Institute, University of California, Los Angeles, Los Angeles, CA 90095, USA
| | - Xin Rong
- Department of Pathology and Laboratory Medicine, University of California, Los Angeles, Los Angeles, CA 90095, USA; Howard Hughes Medical Institute, University of California, Los Angeles, Los Angeles, CA 90095, USA
| | - Mark A Duerr
- Department of Biochemistry and Molecular Biology, Center for Cardiovascular Research, Saint Louis University, St. Louis, MO 63104, USA
| | - Daniel J Hermanson
- Department of Chemical Physiology, The Skaggs Institute for Chemical Biology, The Scripps Research Institute, La Jolla, CA 92037, USA
| | - Per Niklas Hedde
- Laboratory of Fluorescence Dynamics, Biomedical Engineering Department, University of California, Irvine, Irvine, CA 92697, USA; Center for Complex Biological Systems, University of California, Irvine, Irvine, CA 92697, USA
| | - Jinny S Wong
- Electron Microscopy Core, Gladstone Institute of Cardiovascular Disease, San Francisco, CA 94158, USA
| | - Thomas Q de Aguiar Vallim
- Division of Cardiology, Department of Medicine, University of California, Los Angeles, Los Angeles, CA 90095, USA
| | - Benjamin F Cravatt
- Department of Chemical Physiology, The Skaggs Institute for Chemical Biology, The Scripps Research Institute, La Jolla, CA 92037, USA
| | - Enrico Gratton
- Laboratory of Fluorescence Dynamics, Biomedical Engineering Department, University of California, Irvine, Irvine, CA 92697, USA; Center for Complex Biological Systems, University of California, Irvine, Irvine, CA 92697, USA
| | - David A Ford
- Department of Biochemistry and Molecular Biology, Center for Cardiovascular Research, Saint Louis University, St. Louis, MO 63104, USA
| | - Peter Tontonoz
- Department of Pathology and Laboratory Medicine, University of California, Los Angeles, Los Angeles, CA 90095, USA; Howard Hughes Medical Institute, University of California, Los Angeles, Los Angeles, CA 90095, USA.
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136
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Kabir I, Li Z, Bui HH, Kuo MS, Gao G, Jiang XC. Small Intestine but Not Liver Lysophosphatidylcholine Acyltransferase 3 (Lpcat3) Deficiency Has a Dominant Effect on Plasma Lipid Metabolism. J Biol Chem 2016; 291:7651-60. [PMID: 26828064 DOI: 10.1074/jbc.m115.697011] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2015] [Indexed: 11/06/2022] Open
Abstract
Lysophosphatidylcholine acyltransferase 3 (Lpcat3) is involved in phosphatidylcholine remodeling in the small intestine and liver. We investigated lipid metabolism in inducible intestine-specific and liver-specificLpcat3gene knock-out mice. We producedLpcat3-Flox/villin-Cre-ER(T2)mice, which were treated with tamoxifen (at days 1, 3, 5, and 7), to deleteLpcat3specifically in the small intestine. At day 9 after the treatment, we found that Lpcat3 deficiency in enterocytes significantly reduced polyunsaturated phosphatidylcholines in the enterocyte plasma membrane and reduced Niemann-Pick C1-like 1 (NPC1L1), CD36, ATP-binding cassette transporter 1 (ABCA1), and ABCG8 levels on the membrane, thus significantly reducing lipid absorption, cholesterol secretion through apoB-dependent and apoB-independent pathways, and plasma triglyceride, cholesterol, and phospholipid levels, as well as body weight. Moreover, Lpcat3 deficiency does not cause significant lipid accumulation in the small intestine. We also utilized adenovirus-associated virus-Cre to depleteLpcat3in the liver. We found that liver deficiency only reduces plasma triglyceride levels but not other lipid levels. Furthermore, there is no significant lipid accumulation in the liver. Importantly, small intestine Lpcat3 deficiency has a much bigger effect on plasma lipid levels than that of liver deficiency. Thus, inhibition of small intestine Lpcat3 might constitute a novel approach for treating hyperlipidemia.
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Affiliation(s)
- Inamul Kabir
- From the Department of Cell Biology, State University of New York Downstate Medical Center, Brooklyn, New York 11203
| | - Zhiqiang Li
- From the Department of Cell Biology, State University of New York Downstate Medical Center, Brooklyn, New York 11203, the Molecular and Cellular Cardiology Program, Veterans Affairs New York Harbor Healthcare System, Brooklyn, New York 11209
| | - Hai H Bui
- the Lilly Research Laboratories, Eli Lilly & Co., Indianapolis, Indiana 46285, and
| | - Ming-Shang Kuo
- the Lilly Research Laboratories, Eli Lilly & Co., Indianapolis, Indiana 46285, and
| | - Guangping Gao
- the Horae Gene Therapy Center and Department of Microbiology and Physiological Systems, University of Massachusetts Medical School, Worcester, Massachusetts 01605
| | - Xian-Cheng Jiang
- From the Department of Cell Biology, State University of New York Downstate Medical Center, Brooklyn, New York 11203, the Molecular and Cellular Cardiology Program, Veterans Affairs New York Harbor Healthcare System, Brooklyn, New York 11209,
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137
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Renne MF, Bao X, De Smet CH, de Kroon AIPM. Lipid Acyl Chain Remodeling in Yeast. Lipid Insights 2016; 8:33-40. [PMID: 26819558 PMCID: PMC4720183 DOI: 10.4137/lpi.s31780] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2015] [Accepted: 11/21/2015] [Indexed: 11/05/2022] Open
Abstract
Membrane lipid homeostasis is maintained by de novo synthesis, intracellular transport, remodeling, and degradation of lipid molecules. Glycerophospholipids, the most abundant structural component of eukaryotic membranes, are subject to acyl chain remodeling, which is defined as the post-synthetic process in which one or both acyl chains are exchanged. Here, we review studies addressing acyl chain remodeling of membrane glycerophospholipids in Saccharomyces cerevisiae, a model organism that has been successfully used to investigate lipid synthesis and its regulation. Experimental evidence for the occurrence of phospholipid acyl chain exchange in cardiolipin, phosphatidylcholine, phosphatidylinositol, and phosphatidylethanolamine is summarized, including methods and tools that have been used for detecting remodeling. Progress in the identification of the enzymes involved is reported, and putative functions of acyl chain remodeling in yeast are discussed.
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Affiliation(s)
- Mike F Renne
- Membrane Biochemistry and Biophysics, Bijvoet Center for Biomolecular Research, Institute of Biomembranes, Utrecht University, Utrecht, the Netherlands
| | - Xue Bao
- Membrane Biochemistry and Biophysics, Bijvoet Center for Biomolecular Research, Institute of Biomembranes, Utrecht University, Utrecht, the Netherlands
| | - Cedric H De Smet
- Membrane Biochemistry and Biophysics, Bijvoet Center for Biomolecular Research, Institute of Biomembranes, Utrecht University, Utrecht, the Netherlands.; Present address: Division of Cell Biology, Biocenter, Innsbruck Medical University, Innsbruck, Austria
| | - Anton I P M de Kroon
- Membrane Biochemistry and Biophysics, Bijvoet Center for Biomolecular Research, Institute of Biomembranes, Utrecht University, Utrecht, the Netherlands
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138
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Rodríguez M, Márquez S, Montero O, Alonso S, Frade JG, Crespo MS, Fernández N. Pharmacological inhibition of eicosanoids and platelet-activating factor signaling impairs zymosan-induced release of IL-23 by dendritic cells. Biochem Pharmacol 2015; 102:78-96. [PMID: 26673542 DOI: 10.1016/j.bcp.2015.12.001] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2015] [Accepted: 12/02/2015] [Indexed: 12/13/2022]
Abstract
The engagement of the receptors for fungal patterns induces the expression of cytokines, the release of arachidonic acid, and the production of PGE2 in human dendritic cells (DC), but few data are available about other lipid mediators that may modulate DC function. The combined antagonism of leukotriene (LT) B4, cysteinyl-LT, and platelet-activating factor (PAF, 1-O-alkyl-2-acetyl-sn-glycero-3-phosphocholine) inhibited IL23A mRNA expression in response to the fungal surrogate zymosan and to a lower extent TNFA (tumor necrosis factor-α) and CSF2 (granulocyte macrophage colony-stimulating factor) mRNA. The combination of lipid mediators and the lipid extract of zymosan-conditioned medium increased the induction of IL23A by LPS (bacterial lipopolysaccharide), thus suggesting that unlike LPS, zymosan elicits the production of mediators at a concentration enough for optimal response. Zymosan induced the release of LTB4, LTE4, 12-hydroxyeicosatetraenoic acid (12-HETE), and PAF C16:0. DC showed a high expression and detectable Ser663 phosphorylation of 5-lipoxygenase in response to zymosan, and a high expression and activity of LPCAT1/2 (lysophosphatidylcholine acyltransferase 1 and 2), the enzymes that incorporate acetate from acetyl-CoA into choline-containing lysophospholipids to produce PAF. Pharmacological modulation of the arachidonic acid cascade and the PAF receptor inhibited the binding of P-71Thr-ATF2 (activating transcription factor 2) to the IL23A promoter, thus mirroring their effects on the expression of IL23A mRNA and IL-23 protein. These results indicate that LTB4, cysteinyl-LT, and PAF, acting through their cognate G protein-coupled receptors, contribute to the phosphorylation of ATF2 and play a central role in IL23A promoter trans-activation and the cytokine signature induced by fungal patterns.
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Affiliation(s)
- Mario Rodríguez
- Departamento de Bioquímica y Biología Molecular, Facultad de Medicina, Universidad de Valladolid, 47005 Valladolid, Spain
| | - Saioa Márquez
- Departamento de Bioquímica y Biología Molecular, Facultad de Medicina, Universidad de Valladolid, 47005 Valladolid, Spain
| | - Olimpio Montero
- Centro para el Desarrollo de la Biotecnología, CSIC, Parque Tecnológico de Boecillo, Valladolid, Spain
| | - Sara Alonso
- Instituto de Biología y Genética Molecular, CSIC, 47003 Valladolid, Spain
| | - Javier García Frade
- Servicio de Hematología, Hospital Universitario Rio-Hortega, 47012 Valladolid, Spain
| | | | - Nieves Fernández
- Departamento de Bioquímica y Biología Molecular, Facultad de Medicina, Universidad de Valladolid, 47005 Valladolid, Spain
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139
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Li Z, Jiang H, Ding T, Lou C, Bui HH, Kuo MS, Jiang XC. Deficiency in lysophosphatidylcholine acyltransferase 3 reduces plasma levels of lipids by reducing lipid absorption in mice. Gastroenterology 2015; 149:1519-29. [PMID: 26226572 PMCID: PMC4628552 DOI: 10.1053/j.gastro.2015.07.012] [Citation(s) in RCA: 55] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/09/2015] [Revised: 07/15/2015] [Accepted: 07/21/2015] [Indexed: 12/02/2022]
Abstract
BACKGROUND & AIMS Phosphatidylcholines (PCs) are structural and functional constituents of cell membranes. The activity of acyltransferase (lysophosphatidylcholine acyltransferase [LPCAT]) is required for addition of polyunsaturated fatty acids to the sn-2 position of PCs and is therefore required to maintain cell membrane structure and function. LPCAT3 is the most abundant isoform of LPCAT in the small intestine and liver, which are important sites of plasma lipoprotein metabolism. We investigated the effects of Lpcat3 disruption on lipid metabolism in mice. METHODS We disrupted the gene Lpcat3 in C57BL/6J mice to create LPCAT3 knockout (KO) mice. Livers and small intestinal tissues were collected from LPCAT3 KO and C57BL/6J parental strain (controls), and levels of LPCAT messenger RNAs and protein were measured. Levels of lipids and lipoproteins were measured in plasma samples. We isolated enterocytes from mice and measured levels of RNAs and proteins involved in lipid uptake by real-time polymerase chain reaction and immunoblot assays, respectively. We assessed lipid absorption and PC subspecies in the enterocyte plasma membrane using liquid chromatography with tandem mass spectometry. RESULTS LPCAT3 KO mice survived only 3 weeks after birth. Oil Red O staining showed that the control but not LPCAT3 KO mice accumulated lipids in the small intestine; levels of Niemann-Pick C1-like 1 (NPC1L1) and fatty acid transporter protein 4 (FATP4), which regulate lipid uptake, were greatly reduced in the small intestines of LPCAT3 KO mice. Oral administration of PC and olive oil allowed the LPCAT3 KO mice to survive with the same body weights as controls, but the KO mice had shorter and wider small-intestinal villi and longer and bigger small intestines. Plasma membranes of enterocytes from LPCAT3 KO mice also had significant reductions in the composition of polyunsaturated PCs and reduced levels of NPC1L1, CD36, and FATP4 proteins. These reductions were associated with reduced intestinal uptake of lipid by the small intestine and reduced plasma levels of cholesterol, phospholipid, and triglyceride. CONCLUSIONS LPCAT3 KO mice have longer and larger small intestines than control mice, with shorter wide villi, reduced lipid absorption, and lower levels NPC1L1, CD36, and FATP4 proteins. Inhibition of LPCAT3 in the small intestine could be developed as an approach to treat hyperlipidemia.
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Affiliation(s)
- Zhiqiang Li
- Department of Cell Biology, State University of New York, Downstate Medical Center, Brooklyn, New York; Molecular and Cellular Cardiology Program, VA New York Harbor Healthcare System, Brooklyn, New York
| | - Hui Jiang
- Department of Cell Biology, State University of New York, Downstate Medical Center, Brooklyn, New York
| | - Tingbo Ding
- Department of Cell Biology, State University of New York, Downstate Medical Center, Brooklyn, New York; School of Pharmacy, Fudan University, China
| | - Caixia Lou
- Department of Cell Biology, State University of New York, Downstate Medical Center, Brooklyn, New York; Guangdong Medical Laboratory Animal Center, Foshan, China
| | - Hai H Bui
- Lilly Research Laboratories, Eli Lilly & Company, Indianapolis, Indiana
| | - Ming-Shang Kuo
- Lilly Research Laboratories, Eli Lilly & Company, Indianapolis, Indiana
| | - Xian-Cheng Jiang
- Department of Cell Biology, State University of New York, Downstate Medical Center, Brooklyn, New York; Molecular and Cellular Cardiology Program, VA New York Harbor Healthcare System, Brooklyn, New York; School of Pharmacy, Fudan University, China.
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140
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Lee SD, Tontonoz P. Liver X receptors at the intersection of lipid metabolism and atherogenesis. Atherosclerosis 2015; 242:29-36. [PMID: 26164157 PMCID: PMC4546914 DOI: 10.1016/j.atherosclerosis.2015.06.042] [Citation(s) in RCA: 108] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/06/2015] [Revised: 06/19/2015] [Accepted: 06/22/2015] [Indexed: 12/14/2022]
Affiliation(s)
- Stephen D Lee
- Howard Hughes Medical Institute, Department of Pathology and Laboratory Medicine, University of California, Los Angeles, CA 90095, USA
| | - Peter Tontonoz
- Howard Hughes Medical Institute, Department of Pathology and Laboratory Medicine, University of California, Los Angeles, CA 90095, USA.
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141
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Ito A, Hong C, Rong X, Zhu X, Tarling EJ, Hedde PN, Gratton E, Parks J, Tontonoz P. LXRs link metabolism to inflammation through Abca1-dependent regulation of membrane composition and TLR signaling. eLife 2015; 4:e08009. [PMID: 26173179 PMCID: PMC4517437 DOI: 10.7554/elife.08009] [Citation(s) in RCA: 204] [Impact Index Per Article: 22.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2015] [Accepted: 07/13/2015] [Indexed: 01/22/2023] Open
Abstract
The liver X receptors (LXRs) are transcriptional regulators of lipid homeostasis that also have potent anti-inflammatory effects. The molecular basis for their anti-inflammatory effects is incompletely understood, but has been proposed to involve the indirect tethering of LXRs to inflammatory gene promoters. Here we demonstrate that the ability of LXRs to repress inflammatory gene expression in cells and mice derives primarily from their ability to regulate lipid metabolism through transcriptional activation and can occur in the absence of SUMOylation. Moreover, we identify the putative lipid transporter Abca1 as a critical mediator of LXR's anti-inflammatory effects. Activation of LXR inhibits signaling from TLRs 2, 4 and 9 to their downstream NF-κB and MAPK effectors through Abca1-dependent changes in membrane lipid organization that disrupt the recruitment of MyD88 and TRAF6. These data suggest that a common mechanism-direct transcriptional activation-underlies the dual biological functions of LXRs in metabolism and inflammation.
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Affiliation(s)
- Ayaka Ito
- Department of Pathology and Laboratory Medicine, Howard Hughes Medical Institute, University of California, Los Angeles, Los Angeles, United States
| | - Cynthia Hong
- Department of Pathology and Laboratory Medicine, Howard Hughes Medical Institute, University of California, Los Angeles, Los Angeles, United States
| | - Xin Rong
- Department of Pathology and Laboratory Medicine, Howard Hughes Medical Institute, University of California, Los Angeles, Los Angeles, United States
| | - Xuewei Zhu
- Department of Internal Medicine-Section on Molecular Medicine, Wake Forest School of Medicine, Winston-Salem, United States
| | - Elizabeth J Tarling
- Department of Medicine, University of California, Los Angeles, Los Angeles, United States
| | - Per Niklas Hedde
- Laboratory of Fluorescence Dynamics, Biomedical Engineering Department, Center for Complex Biological Systems, University of California, Irvine, Irvine, United States
| | - Enrico Gratton
- Laboratory of Fluorescence Dynamics, Biomedical Engineering Department, Center for Complex Biological Systems, University of California, Irvine, Irvine, United States
| | - John Parks
- Department of Internal Medicine-Section on Molecular Medicine, Wake Forest School of Medicine, Winston-Salem, United States
| | - Peter Tontonoz
- Howard Hughes Medical Institute, University of California, Los Angeles, Los Angeles, United States
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