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Cianflone K, Paglialunga S. Regulation of fatty acid transport and storage: influence of acylation-stimulating protein. SCANDINAVIAN JOURNAL OF FOOD & NUTRITION 2016. [DOI: 10.1080/17482970601069185] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
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Abstract
Obesity and its major comorbidities, including type 2 diabetes mellitus, nonalcoholic fatty liver disease (NAFLD), obesity cardiomyopathy, and certain cancers, have caused life expectancy in the United States to decline in recent years. Obesity is the increased accumulation of triglycerides (TG), which are synthesized from glycerol and long-chain fatty acids (LCFA) throughout the body. LCFA enter adipocytes, hepatocytes, and cardiomyocytes via specific, facilitated transport processes. Metabolism of increased cellular TG content in obesity may lead to comorbidities such as NAFLD and cardiomyopathy. Better understanding of LCFA transport processes may lead to successful treatment of obesity and NAFLD.
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Affiliation(s)
- Paul D Berk
- Division of Digestive and Liver Diseases, Department of Medicine, Columbia College of Physicians and Surgeons, Columbia University Medical Center, 650 West 168 Street, New York, NY 10032, USA; Division of Preventive Medicine, Department of Medicine, Columbia College of Physicians and Surgeons, Columbia University Medical Center, William Black Building, 650 West 168 Street, Room 1006, Box 57A, New York, NY 10032, USA.
| | - Elizabeth C Verna
- Division of Digestive and Liver Diseases, Department of Medicine, Columbia College of Physicians and Surgeons, Columbia University Medical Center, 650 West 168 Street, New York, NY 10032, USA
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Abstract
Dietary fat is well recognised as an important macronutrient that has major effects on growth, development and health of all animals including humans. The amount and type of fat in the diet impacts on many aspects of metabolism including lipoprotein pathways, lipid synthesis and oxidation, adipocyte differentiation and cholesterol metabolism. It has become increasingly apparent that many of these effects may be due to direct modulation of expression of key genes through the interaction of fatty acids with certain transcription factors. Peroxisome proliferator-activated receptors (PPARs), the liver X receptors (LXRs), hepatic nuclear factor 4 (HNF-4) and sterol regulatory binding proteins (SREBPs) represent four such factors. This review focuses on emerging evidence that the activity of these transcription factors are regulated by fatty acids and the interactions between them may be responsible for many of the effects of fatty acids on metabolism and the development of chronic disease.
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Bazan NG, Molina MF, Gordon WC. Docosahexaenoic acid signalolipidomics in nutrition: significance in aging, neuroinflammation, macular degeneration, Alzheimer's, and other neurodegenerative diseases. Annu Rev Nutr 2011; 31:321-51. [PMID: 21756134 DOI: 10.1146/annurev.nutr.012809.104635] [Citation(s) in RCA: 303] [Impact Index Per Article: 23.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
Essential polyunsaturated fatty acids (PUFAs) are critical nutritional lipids that must be obtained from the diet to sustain homeostasis. Omega-3 and -6 PUFAs are key components of biomembranes and play important roles in cell integrity, development, maintenance, and function. The essential omega-3 fatty acid family member docosahexaenoic acid (DHA) is avidly retained and uniquely concentrated in the nervous system, particularly in photoreceptors and synaptic membranes. DHA plays a key role in vision, neuroprotection, successful aging, memory, and other functions. In addition, DHA displays anti-inflammatory and inflammatory resolving properties in contrast to the proinflammatory actions of several members of the omega-6 PUFAs family. This review discusses DHA signalolipidomics, comprising the cellular/tissue organization of DHA uptake, its distribution among cellular compartments, the organization and function of membrane domains rich in DHA-containing phospholipids, and the cellular and molecular events revealed by the uncovering of signaling pathways regulated by DHA and docosanoids, the DHA-derived bioactive lipids, which include neuroprotectin D1 (NPD1), a novel DHA-derived stereoselective mediator. NPD1 synthesis agonists include neurotrophins and oxidative stress; NPD1 elicits potent anti-inflammatory actions and prohomeostatic bioactivity, is anti-angiogenic, promotes corneal nerve regeneration, and induces cell survival. In the context of DHA signalolipidomics, this review highlights aging and the evolving studies on the significance of DHA in Alzheimer's disease, macular degeneration, Parkinson's disease, and other brain disorders. DHA signalolipidomics in the nervous system offers emerging targets for pharmaceutical intervention and clinical translation.
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Affiliation(s)
- Nicolas G Bazan
- Neuroscience Center of Excellence and Department of Ophthalmology, School of Medicine, Louisiana State University Health Sciences Center, New Orleans, LA 70112, USA.
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Bordoni A, Di Nunzio M, Danesi F, Biagi PL. Polyunsaturated fatty acids: From diet to binding to ppars and other nuclear receptors. GENES AND NUTRITION 2011; 1:95-106. [PMID: 18850203 DOI: 10.1007/bf02829951] [Citation(s) in RCA: 62] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/07/2006] [Accepted: 06/21/2006] [Indexed: 01/01/2023]
Abstract
Dietary polyunsaturated fatty acids (PUFAs) function not only by altering membrane lipid composition, cellular metabolism, signal transduction, but possess also effects on gene expression by regulating the activity/abundance of different nuclear transcription factors: peroxisome proliferator activated receptors, retinoid X receptors, liver X receptors, hepatic nuclear factors-4a, and sterol regulatory binding proteins 1 and 2. PUFAs regulate the expression of genes in various tissues, including the liver, heart, adipose tissue, and brain, playing a major role in carbohydrate, fatty acid, triglyceride, and cholesterol metabolism. Before binding to transcription factors, PUFAs must be absorbed in the intestine and delivered to cells, and then they must enter the cell and the nucleus. PUFA concentration within the cell depends on many different factors, and regulate their possibility to act as transcription modulators. The aim of this review is to summarize recent knowledge about PUFAs destiny from dietto nuclear factors binding, examining the different variables which can modulate their interaction with nuclear factors themselves and therefore their effect on gene expression.
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Affiliation(s)
- A Bordoni
- Centro Ricerche sulla Nutrizione - Department of Biochemistry "G. Moruzzi", University of Bologna Via Irnerio, 48-40126, Bologna, Italy,
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Acyl-CoA synthetases: fatty acid uptake and metabolic channeling. Mol Cell Biochem 2008; 326:23-8. [DOI: 10.1007/s11010-008-0003-3] [Citation(s) in RCA: 64] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2008] [Accepted: 05/30/2008] [Indexed: 12/18/2022]
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Shu G, Jiang QY, Zhu XT, Zhang HX, Gao P, Zhang YL, Wang XQ. Identification of porcine fatty acid translocase: high-level transcript in intramuscular fat. J Anim Physiol Anim Nutr (Berl) 2008; 92:562-8. [DOI: 10.1111/j.1439-0396.2007.00749.x] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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Lee EG, Kim SH, Bae YA, Chung JY, Suh M, Na BK, Kim TS, Kang I, Ma L, Kong Y. A hydrophobic ligand-binding protein of the Taenia solium metacestode mediates uptake of the host lipid: implication for the maintenance of parasitic cellular homeostasis. Proteomics 2008; 7:4016-30. [PMID: 17960733 DOI: 10.1002/pmic.200700332] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
Parasitic organisms are incapable of de novo fatty acid synthesis due to a down-regulated expression of enzymes involved in the oxygen-dependent pathway. We investigated the uptake of host lipids by a 150-kDa hydrophobic ligand-binding protein (HLBP) of Taenia solium metacestode, an agent causative of neurocysticercosis. The protein was found to be a hetero-oligomeric complex consisting of multiple subunits (M(r) 7, 10, and 15 kDa within pH 8.0-9.7), which may originate from four unique genes of 7- and 10-kDa gene families with 2-3 polymorphic alleles/paralogs. The 15-kDa protein represented glycosylated forms of the 10-kDa. With high binding affinity to lipid analogs, these subunits evidenced high-level sequence identity with other cestode HLBPs and form a novel clade associated with excretory-secretory type HLBP. In vitro experiments with viable worms suggested that the excreted 150-kDa protein might bind to lipids, and participate in the translocation of host lipids across the syncytial membrane. This process was substantially inhibited by the specific anti-150 kDa antibodies. The protein was localized in the parasite syncytium and in the lipid droplets within host granuloma wall, where significant lipase activity was expressed. HLBP-mediated uptake of the host lipid may be critical for the parasite survival and thus could be targeted by chemotherapeutics and/or vaccine.
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Affiliation(s)
- Eung-Goo Lee
- Department of Molecular Parasitology, Sungkyunkwan University School of Medicine, Suwon, Korea
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Florent-Béchard S, Malaplate-Armand C, Koziel V, Kriem B, Olivier JL, Pillot T, Oster T. Towards a nutritional approach for prevention of Alzheimer's disease: Biochemical and cellular aspects. J Neurol Sci 2007; 262:27-36. [PMID: 17681547 DOI: 10.1016/j.jns.2007.06.046] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Alzheimer's disease (AD) is a major public health concern in all countries. Although the precise cause of AD is still unknown, a growing body of evidence supports the notion that soluble amyloid beta-peptide (Abeta) may be the proximate cause of synaptic injuries and neuronal death early in the disease. AD patients display lower levels of docosahexaenoic acid (DHA, C22:6 ; n-3) in plasma and brain tissues as compared to age-matched controls. Furthermore, epidemiological studies suggest that high DHA intake might have protective properties against neurodegenerative diseases. These observations are supported by in vivo studies showing that DHA-rich diets limits the synaptic loss and cognitive defects induced by Abeta peptide. Although the molecular basis of these neuroprotective effects remains unknown, several mechanisms have been proposed such as (i) regulation of the expression of potentially protective genes, (ii) activation of anti-inflammatory pathways, (iii) modulation of functional properties of the synaptic membranes along with changes in their physicochemical and structural features.
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Affiliation(s)
- Sabrina Florent-Béchard
- Lipidomix (JE 2482), ENSAIA-INPL, University of Nancy, 15, rue du Bois de la Champelle 54505, Vandoeuvre-lès-Nancy, France
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Gonzales AM, Orlando RA. Role of adipocyte-derived lipoprotein lipase in adipocyte hypertrophy. Nutr Metab (Lond) 2007; 4:22. [PMID: 17971230 PMCID: PMC2174487 DOI: 10.1186/1743-7075-4-22] [Citation(s) in RCA: 80] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2007] [Accepted: 10/30/2007] [Indexed: 12/14/2022] Open
Abstract
Background A major portion of available fatty acids for adipocyte uptake is derived from lipoprotein lipase (LPL)-mediated hydrolysis of circulating lipoprotein particles. In vivo studies aimed at identifying the precise role of adipocyte-derived LPL in fat storage function of adipose tissue have been unable to provide conclusive evidence due to compensatory mechanisms that activate endogenous fatty acid synthesis. To address this gap in knowledge, we have measured the effect of reducing adipocyte LPL expression on intracellular lipid accumulation using a well-established cultured model of adipocyte differentiation. Methods siRNA specific for mouse LPL was transfected into 3T3-L1 adipocytes. Expression of LPL was measured by quantitative real-time PCR and cell surface-associated LPL enzymatic activity was measured by colorimetric detection following substrate (p-nitrophenyl butyrate) hydrolysis. Apolipoprotein CII and CIII expression ratios were also measured by qRT-PCR. Intracellular lipid accumulation was quantified by Nile Red staining. Results During differentiation of 3T3-L1 pre-adipocytes, LPL mRNA expression increases 6-fold resulting in a 2-fold increase in cell surface-associated LPL enzymatic activity. Parallel to this increase in LPL expression, we found that intracellular lipids increased ~10-fold demonstrating a direct correlation between adipocyte-derived LPL expression and lipid storage. We next reduced LPL expression in adipocytes using siRNA transfections to directly quantify the contributions of adipocyte-derived LPL to lipid storage, This treatment reduced LPL mRNA expression and cell surface-associated LPL enzymatic activity to ~50% of non-treated controls while intracellular lipid levels were reduced by 80%. Exogenous addition of purified LPL (to restore extracellular lipolytic activity) or palmitate (as a source of free fatty acids) to siRNA-treated cells restored intracellular lipid levels to those measured for non-treated controls. We also found that adipocytes express apolipoprotein CII and CIII and, in addition, the apoCII/apoCIII ratio remains largely unchanged in cells with reduced LPL expression. Conclusion We provide evidence that adipocyte-derived LPL is required for efficient fatty acid uptake and storage, and that adipocytes express their own source of apoCII and apoCIII for regulating extracellular LPL activity. These findings demonstrate that adipocytes are capable of producing the necessary enzymatic components and co-factors for efficient lipid storage independent of vascular sources.
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Affiliation(s)
- Amanda M Gonzales
- Department of Biochemistry and Molecular Biology, University of New Mexico, School of Medicine, MSC08 4670, 1 University of New Mexico, Albuquerque, New Mexico, 87131, USA.
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Affiliation(s)
- Hee-Yong Kim
- Laboratory of Molecular Signaling, Division of Intramural Clinical and Biological Research, National Institute on Alcohol Abuse and Alcoholism, Bethesda, Maryland 20892-9410, USA.
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Finn PF, Dice JF. Proteolytic and lipolytic responses to starvation. Nutrition 2006; 22:830-44. [PMID: 16815497 DOI: 10.1016/j.nut.2006.04.008] [Citation(s) in RCA: 223] [Impact Index Per Article: 12.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2005] [Revised: 03/30/2006] [Accepted: 04/12/2006] [Indexed: 01/20/2023]
Abstract
Mammals survive starvation by activating proteolysis and lipolysis in many different tissues. These responses are triggered, at least in part, by changing hormonal and neural statuses during starvation. Pathways of proteolysis that are activated during starvation are surprisingly diverse, depending on tissue type and duration of starvation. The ubiquitin-proteasome system is primarily responsible for increased skeletal muscle protein breakdown during starvation. However, in most other tissues, lysosomal pathways of proteolysis are stimulated during fasting. Short-term starvation activates macroautophagy, whereas long-term starvation activates chaperone-mediated autophagy. Lipolysis also increases in response to starvation, and the breakdown of triacylglycerols provides free fatty acids to be used as an energy source by skeletal muscle and other tissues. In addition, glycerol released from triacylglycerols can be converted to glucose by hepatic gluconeogenesis. During long-term starvation, oxidation of free fatty acids by the liver leads to the production of ketone bodies that can be used for energy by skeletal muscle and brain. Tissues that cannot use ketone bodies for energy respond to these small molecules by activating chaperone-mediated autophagy. This is one form of interaction between proteolytic and lipolytic responses to starvation.
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Affiliation(s)
- Patrick F Finn
- Department of Molecular and Cellular Physiology, Tufts University School of Medicine, Boston, Massachusetts, USA
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Milger K, Herrmann T, Becker C, Gotthardt D, Zickwolf J, Ehehalt R, Watkins PA, Stremmel W, Füllekrug J. Cellular uptake of fatty acids driven by the ER-localized acyl-CoA synthetase FATP4. J Cell Sci 2006; 119:4678-88. [PMID: 17062637 DOI: 10.1242/jcs.03280] [Citation(s) in RCA: 166] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023] Open
Abstract
Long-chain fatty acids are important metabolites for the generation of energy and the biosynthesis of lipids. The molecular mechanism of their cellular uptake has remained controversial. The fatty acid transport protein (FATP) family has been named according to its proposed function in mediating this process at the plasma membrane. Here, we show that FATP4 is in fact localized to the endoplasmic reticulum and not the plasma membrane as reported previously. Quantitative analysis confirms the positive correlation between expression of FATP4 and uptake of fatty acids. However, this is dependent on the enzymatic activity of FATP4, catalyzing the esterification of fatty acids with CoA. Monitoring fatty acid uptake at the single-cell level demonstrates that the ER localization of FATP4 is sufficient to drive transport of fatty acids. Expression of a mitochondrial acyl-CoA synthetase also enhances fatty acid uptake, suggesting a general relevance for this mechanism. Our results imply that cellular uptake of fatty acids can be regulated by intracellular acyl-CoA synthetases. We propose that the enzyme FATP4 drives fatty acid uptake indirectly by esterification. It is not a transporter protein involved in fatty acid translocation at the plasma membrane.
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Affiliation(s)
- Katrin Milger
- Department of Gastroenterology, Im Neuenheimer Feld 345, University of Heidelberg, 69120 Heidelberg, Germany
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Abstract
Apart from being an important macronutrient, dietary fat has recently gained much prominence for its role in regulating gene expression. Polyunsaturated fatty acids (PUFAs) affect gene expression through various mechanisms including, but not limited to, changes in membrane composition, intracellular calcium levels, and eicosanoid production. Furthermore, PUFAs and their various metabolites can act at the level of the nucleus, in conjunction with nuclear receptors and transcription factors, to affect the transcription of a variety of genes. Several of these transcription mediators have been identified and include the nuclear receptors peroxisome proliferator-activated receptor (PPAR), hepatocyte nuclear factor (HNF)-4alpha, and liver X receptor (LXR) and the transcription factors sterol-regulatory element binding protein (SREBP) and nuclear factor-kappaB (NFkappaB). Their interaction with PUFAs has been shown to be critical to the regulation of several key genes of lipid metabolism. Working out the mechanisms by which these interactions and consequent effects occur is proving to be complicated but is invaluable to our understanding of the role that dietary fat can play in disease management and prevention.
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Affiliation(s)
- Harini Sampath
- Department of Nutritional Sciences, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA
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Abstract
PURPOSE OF REVIEW Fatty acid and triacylglycerol metabolism in adipose tissue may be involved in the generation of risk factors for cardiovascular disease and type 2 diabetes. Pharmaceutical companies are targeting adipocyte metabolism in their search for drugs for treating, or reducing the risk of, these conditions. We review new developments in adipose tissue fatty acid metabolism and how that might relate to cardiovascular disease. RECENT FINDINGS Fatty acid release from human adipose tissue is oscillatory, with a period of about 12 min. Remarkably, oscillatory fatty acid release is also seen in isolated adipocytes. Further evidence has emerged that not all adipose depots are equal, and that lower-body adipose tissue may exert protective effects against cardiovascular disease. There have been a number of developments in the area of fatty acid handling by adipocytes. Fatty acid binding proteins are clearly important in regulating fatty acid metabolism, with striking protection against atherosclerosis in mice deficient in both the binding proteins expressed in adipocytes. The demonstration that adipocytes lacking hormone-sensitive lipase still display lipolysis has led to the identification of novel lipases that may play crucial roles in adipose tissue fatty acid metabolism. Further evidence has accrued of the interaction between hormone-sensitive lipase and perilipin, the protein that coats the adipocyte lipid droplet. SUMMARY Recent developments in our understanding of adipose tissue fatty acid metabolism open up the possibility of new pharmaceutical targets. However, interference with adipose tissue fatty acid metabolism is not to be undertaken lightly and needs a clear understanding of the normal role of adipocyte lipolysis.
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Affiliation(s)
- Keith N Frayn
- Oxford Centre for Diabetes, Endocrinology and Metabolism, University of Oxford, UK.
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Bojesen IN, Hansen HS. Membrane transport of anandamide through resealed human red blood cell membranes. J Lipid Res 2005; 46:1652-9. [PMID: 15930521 DOI: 10.1194/jlr.m400498-jlr200] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
The use of resealed red blood cell membranes (ghosts) allows the study of the transport of a compound in a nonmetabolizing system with a biological membrane. Transmembrane movements of anandamide (N-arachidonoylethanolamine, arachidonoylethanolamide) have been studied by exchange efflux experiments at 0 degrees C and pH 7.3 with albumin-free and albumin-filled human red blood cell ghosts. The efflux kinetics is biexponential and is analyzed in terms of compartment models. The distribution of anandamide on the membrane inner to outer leaflet pools is determined to be 0.275 +/- 0.023, and the rate constant of unidirectional flux from inside to outside is 0.361 +/- 0.023 s(-1). The rate constant of unidirectional flux from the membrane to BSA in the medium ([BSA]o) increases with the square root of [BSA]o in accordance with the theory of an unstirred layer around ghosts. Anandamide passed through the red blood cell membrane very rapidly, within seconds. At a molar ratio of anandamide to BSA of <1, membrane binding of anandamide increases with increasing temperatures between 0 degrees C and 37 degrees C, and the equilibrium dissociation constants are in the nanomolar range. The nature of membrane binding and the mechanism of membrane translocation are discussed.
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Affiliation(s)
- Inge N Bojesen
- Department of Medical Biochemistry and Genetics, Laboratory B, University of Copenhagen, The Panum Institute, DK-2200 Copenhagen N, Denmark.
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Abstract
PURPOSE OF REVIEW Disturbed fatty acid metabolism and homeostasis is associated with insulin resistance. The aim of this review, therefore, is to summarize recent developments relating to the relevance and importance of the fatty acid transport proteins (FATPs) in the aetiology of insulin resistance. In particular, the potential differences between the six members of the FATP family will be considered. RECENT FINDINGS FATP1 knockout mice failed to develop insulin resistance associated with lipid infusion or a high-fat diet, as wild-type mice did. FATP1-mediated fatty acid uptake may cause intramuscular lipid accumulation leading to insulin resistance in muscle if the fatty acids are not oxidized. While mouse models demonstrated an absolute requirement for FATP4 for survival, they provided no direct evidence for a role of FATP4 in insulin resistance. However, expression of FATP4 in human adipose tissue was increased in obesity (independent of genetic factors). While other members of the FATP family have important roles in fatty acid metabolism, they have not been clearly linked to insulin resistance. FATP-mediated fatty acid uptake may be driven by intrinsic acyl-CoA synthase activity. SUMMARY Any role in the development of insulin resistance is likely to be different for each member of the FATP family. So far, both FATP1 and FATP4 have been associated with parameters related to insulin resistance. Whether increased FATP-mediated fatty acid uptake is beneficial or detrimental may be dependent on the tissue in question and on the subsequent fate of the fatty acids. These issues remain to be resolved.
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Affiliation(s)
- Rachel M Fisher
- Atherosclerosis Research Unit, King Gustaf V Research Institute, Karolinska Institutet, Karolinska University Hospital, Stockholm, Sweden.
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Wilsie LC, Chanchani S, Navaratna D, Orlando RA. Cell surface heparan sulfate proteoglycans contribute to intracellular lipid accumulation in adipocytes. Lipids Health Dis 2005; 4:2. [PMID: 15636641 PMCID: PMC545935 DOI: 10.1186/1476-511x-4-2] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2004] [Accepted: 01/06/2005] [Indexed: 01/01/2023] Open
Abstract
BACKGROUND Transport of fatty acids within the cytosol of adipocytes and their subsequent assimilation into lipid droplets has been thoroughly investigated; however, the mechanism by which fatty acids are transported across the plasma membrane from the extracellular environment remains unclear. Since triacylglycerol-rich lipoproteins represent an abundant source of fatty acids for adipocyte utilization, we have investigated the expression levels of cell surface lipoprotein receptors and their functional contributions toward intracellular lipid accumulation; these include very low density lipoprotein receptor (VLDL-R), low density lipoprotein receptor-related protein (LRP), and heparan sulfate proteoglycans (HSPG). RESULTS We found that expression of these three lipoprotein receptors increased 5-fold, 2-fold, and 2.5-fold, respectively, during adipocyte differentiation. The major proteoglycans expressed by mature adipocytes are of high molecular weight (>500 kD) and contain both heparan and chondroitin sulfate moieties. Using ligand binding antagonists, we observed that HSPG, rather than VLDL-R or LRP, play a primary role in the uptake of DiI-labeled apoE-VLDL by mature adipocytes. In addition, inhibitors of HSPG maturation resulted in a significant reduction (>85%) in intracellular lipid accumulation. CONCLUSIONS These results suggest that cell surface HSPG is required for fatty acid transport across the plasma membrane of adipocytes.
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Affiliation(s)
- Larissa C Wilsie
- Department of Biochemistry and Molecular Biology, University of New Mexico, Health Sciences Center, 915 Camino de Salud, Albuquerque, New Mexico, 87131, USA
| | - Shree Chanchani
- Department of Biochemistry and Molecular Biology, University of New Mexico, Health Sciences Center, 915 Camino de Salud, Albuquerque, New Mexico, 87131, USA
| | - Deepti Navaratna
- Department of Biochemistry and Molecular Biology, University of New Mexico, Health Sciences Center, 915 Camino de Salud, Albuquerque, New Mexico, 87131, USA
| | - Robert A Orlando
- Department of Biochemistry and Molecular Biology, University of New Mexico, Health Sciences Center, 915 Camino de Salud, Albuquerque, New Mexico, 87131, USA
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