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Frost B, Martin CR, Calkins KL. Dilemmas in the delivery of intravenous lipid emulsions and approach to hypertriglyceridemia in very preterm and low birth weight infants. J Perinatol 2023; 43:1189-1193. [PMID: 37031340 DOI: 10.1038/s41372-023-01637-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/16/2022] [Revised: 02/10/2023] [Accepted: 02/22/2023] [Indexed: 04/10/2023]
Abstract
Intravenous lipid emulsions (ILEs) are an essential component of parenteral nutrition for very preterm and very low birth weight infants (VLBWs). This article offers a perspective on advancements and controversies on ILE use in this population. ILEs prescribed after birth at a dose of 1.5-2 g/kg/day and advanced to 3 g/kg/day enhance growth. Growth appears to be similar for infants who receive an ILE composed of 100% soybean oil or a multi-oil ILE with 15% fish oil. 100% fish oil is the preferred ILE for the management of parenteral nutrition associated cholestasis and intestinal failure associated liver disease. Research is warranted to help determine how we can optimize ILEs to improve neurodevelopment and prematurity complications. Last, we lack a universal definition of hypertriglyceridemia (HTG) and consensus on triglyceride surveillance and HTG management. Investigation is required to determine the health impact of specific triglyceride ranges in very preterm infants and VLBWs.
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Affiliation(s)
- Brandy Frost
- Department of Pediatrics, Division of Neonatology, NorthShore University HealthSystem, Pritzker School of Medicine, University of Chicago, Evanston, IL, USA
| | - Camilia R Martin
- Department of Pediatrics, Division of Neonatology, Weill Cornell Medicine, New York, NY, USA
| | - Kara L Calkins
- Department of Pediatrics, Division of Neonatology & Developmental Biology, Neonatal Research Center of the UCLA Children's Discovery and Innovation Institute, David Geffen School of Medicine UCLA, Los Angeles, CA, USA.
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2
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Lipoprotein size is a main determinant for the rate of hydrolysis by exogenous lipoprotein lipase in human plasma. J Lipid Res 2021; 63:100144. [PMID: 34710432 PMCID: PMC8953621 DOI: 10.1016/j.jlr.2021.100144] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2021] [Revised: 10/19/2021] [Accepted: 10/20/2021] [Indexed: 12/19/2022] Open
Abstract
Lipoprotein lipase (LPL) is a key player in plasma triglyceride metabolism. Consequently, LPL is regulated by several proteins during synthesis, folding, secretion, and transport to its site of action at the luminal side of capillaries, as well as during the catalytic reaction. Some proteins are well known, while others have been identified but are still not fully understood. We set out to study the effects of the natural variations in the plasma levels of all known LPL regulators on the activity of purified LPL added to samples of fasted plasma taken from 117 individuals. The enzymatic activity was measured at 25° C using isothermal titration calorimetry. This method allows quantification of the ability of an added fixed amount of exogenous LPL to hydrolyze triglyceride-rich lipoproteins in plasma samples by measuring the heat produced. Our results indicate that, under the conditions used, the normal variation in the endogenous levels of apolipoprotein C1, C2 and C3, or the levels of angiopoietin-like proteins 3, 4, and 8 in the fasted plasma samples had no significant effect on the recorded activity of the added LPL. Instead, the key determinant for the LPL activity was a lipid signature strongly correlated to the average size of the VLDL particles. The signature involved several lipoprotein and plasma lipid parameters, but also apolipoprotein A5 levels. While the measurements cannot fully represent the action of LPL when attached to the capillary wall, our study provides knowledge on the interindividual variation of LPL lipolysis rates in human plasma.
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3
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Taskinen MR, Björnson E, Matikainen N, Söderlund S, Pietiläinen KH, Ainola M, Hakkarainen A, Lundbom N, Fuchs J, Thorsell A, Andersson L, Adiels M, Packard CJ, Borén J. Effects of liraglutide on the metabolism of triglyceride-rich lipoproteins in type 2 diabetes. Diabetes Obes Metab 2021; 23:1191-1201. [PMID: 33502078 DOI: 10.1111/dom.14328] [Citation(s) in RCA: 20] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/21/2020] [Revised: 01/08/2021] [Accepted: 01/23/2021] [Indexed: 01/07/2023]
Abstract
AIM To elucidate the impact of liraglutide on the kinetics of apolipoprotein (apo)B48- and apoB100-containing triglyceride-rich lipoproteins in subjects with type 2 diabetes (T2D) after a single fat-rich meal. MATERIALS AND METHODS Subjects with T2D were included in a study to investigate postprandial apoB48 and apoB100 metabolism before and after 16 weeks on l.8 mg/day liraglutide (n = 14) or placebo (n = 4). Stable isotope tracer and compartmental modelling techniques were used to determine the impact of liraglutide on chylomicron and very low-density lipoprotein (VLDL) production and clearance after a single fat-rich meal. RESULTS Liraglutide reduced apoB48 synthesis in chylomicrons by 60% (p < .0001) and increased the triglyceride/apoB48 ratio (i.e. the size) of chylomicrons (p < .001). Direct clearance of chylomicrons, a quantitatively significant pathway pretreatment, decreased by 90% on liraglutide (p < .001). Liraglutide also reduced VLDL1 -triglyceride secretion (p = .017) in parallel with reduced liver fat. Chylomicron-apoB48 production and particle size were related to insulin sensitivity (p = .015 and p < .001, respectively), but these associations were perturbed by liraglutide. CONCLUSIONS In a physiologically relevant setting that mirrored regular feeding in subjects with T2D, liraglutide promoted potentially beneficial changes on postprandial apoB48 metabolism. Using our data in an integrated metabolic model, we describe how the action of liraglutide in T2D on chylomicron and VLDL kinetics could lead to decreased generation of remnant lipoproteins.
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Affiliation(s)
- Marja-Riitta Taskinen
- Research Program for Clinical and Molecular Metabolism, Faculty of Medicine, University of Helsinki, Helsinki, Finland
| | - Elias Björnson
- Department of Molecular and Clinical Medicine, University of Gothenburg, Gothenburg, Sweden
| | - Niina Matikainen
- Research Program for Clinical and Molecular Metabolism, Faculty of Medicine, University of Helsinki, Helsinki, Finland
- Endocrinology, Abdominal Center, Helsinki University Hospital, Helsinki, Finland
| | - Sanni Söderlund
- Research Program for Clinical and Molecular Metabolism, Faculty of Medicine, University of Helsinki, Helsinki, Finland
- Endocrinology, Abdominal Center, Helsinki University Hospital, Helsinki, Finland
| | - Kirsi H Pietiläinen
- Research Program for Clinical and Molecular Metabolism, Faculty of Medicine, University of Helsinki, Helsinki, Finland
- Endocrinology, Abdominal Center, Helsinki University Hospital, Helsinki, Finland
| | - Mari Ainola
- Research Program for Clinical and Molecular Metabolism, Faculty of Medicine, University of Helsinki, Helsinki, Finland
| | - Antti Hakkarainen
- HUS Medical Imaging Center, Radiology, Helsinki University Hospital, University of Helsinki, Finland
- Department of Neuroscience and Biomedical Engineering, Aalto University School of Science, Espoo, Finland
| | - Nina Lundbom
- HUS Medical Imaging Center, Radiology, Helsinki University Hospital, University of Helsinki, Finland
| | - Johannes Fuchs
- Proteomics Core Facility at Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden
| | - Annika Thorsell
- Proteomics Core Facility at Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden
| | - Linda Andersson
- Department of Molecular and Clinical Medicine, University of Gothenburg, Gothenburg, Sweden
| | - Martin Adiels
- Department of Molecular and Clinical Medicine, University of Gothenburg, Gothenburg, Sweden
| | - Chris J Packard
- Institute of Cardiovascular and Medical Sciences, University of Glasgow, Glasgow, UK
| | - Jan Borén
- Department of Molecular and Clinical Medicine, University of Gothenburg, Gothenburg, Sweden
- Wallenberg Laboratory/Cardiology, Sahlgrenska University Hospital, Gothenburg, Sweden
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4
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Lightbourne M, Wolska A, Abel BS, Rother KI, Walter M, Kushchayeva Y, Auh S, Shamburek RD, Remaley AT, Muniyappa R, Brown RJ. Apolipoprotein CIII and Angiopoietin-like Protein 8 are Elevated in Lipodystrophy and Decrease after Metreleptin. J Endocr Soc 2020; 5:bvaa191. [PMID: 33442570 DOI: 10.1210/jendso/bvaa191] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/24/2020] [Indexed: 02/08/2023] Open
Abstract
Context Lipodystrophy syndromes cause hypertriglyceridemia that improves with leptin treatment using metreleptin. Mechanisms causing hypertriglyceridemia and improvements after metreleptin are incompletely understood. Objective Determine relationship of circulating lipoprotein lipase (LPL) modulators with hypertriglyceridemia in healthy controls and in patients with lipodystrophy before and after metreleptin. Methods Cross-sectional comparison of patients with lipodystrophy (generalized lipodystrophy n = 3; partial lipodystrophy n = 11) vs age/sex-matched healthy controls (n = 28), and longitudinal analyses in patients before and after 2 weeks and 6 months of metreleptin. The study was carried out at the National Institutes of Health, Bethesda, Maryland. Outcomes were LPL stimulators apolipoprotein (apo) C-II and apoA-V and inhibitors apoC-III and angiopoietin-like proteins (ANGPTLs) 3, 4, and 8; ex vivo activation of LPL by plasma. Results Patients with lipodystrophy were hypertriglyceridemic and had higher levels of all LPL stimulators and inhibitors vs controls except for ANGPTL4, with >300-fold higher ANGPTL8, 4-fold higher apoC-III, 3.5-fold higher apoC-II, 1.9-fold higher apoA-V, 1.6-fold higher ANGPTL3 (P < .05 for all). At baseline, all LPL modulators except ANGPLT4 positively correlated with triglycerides. Metreleptin decreased apoC-II and apoC-III after 2 weeks and 6 months, and decreased ANGPTL8 after 6 months (P < 0.05 for all). Plasma from patients with lipodystrophy caused higher ex vivo LPL activation vs hypertriglyceridemic control plasma (P < .0001), which did not change after metreleptin. Conclusion Elevations in LPL inhibitors apoC-III and ANGPTL8 may contribute to hypertriglyceridemia in lipodystrophy, and may mediate reductions in circulating and hepatic triglycerides after metreleptin. These therefore are strong candidates for therapies to lower triglycerides in these patients.
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Affiliation(s)
- Marissa Lightbourne
- Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD, USA
| | - Anna Wolska
- Lipoprotein Metabolism Laboratory, Translational Vascular Medicine Branch, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD, USA
| | - Brent S Abel
- National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD, USA
| | - Kristina I Rother
- National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD, USA
| | - Mary Walter
- National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD, USA
| | - Yevgeniya Kushchayeva
- National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD, USA
| | - Sungyoung Auh
- National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD, USA
| | - Robert D Shamburek
- Cardiovascular Branch, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD, USA
| | - Alan T Remaley
- Lipoprotein Metabolism Laboratory, Translational Vascular Medicine Branch, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD, USA
| | - Ranganath Muniyappa
- National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD, USA
| | - Rebecca J Brown
- National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD, USA
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Alterations in plasma triglycerides lipolysis in patients with history of multifactorial chylomicronemia. Atherosclerosis 2017; 265:22-28. [DOI: 10.1016/j.atherosclerosis.2017.07.030] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/23/2017] [Revised: 07/18/2017] [Accepted: 07/27/2017] [Indexed: 11/19/2022]
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6
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Aspichueta P, Pérez-Agote B, Pérez S, Ochoa B, Fresnedo O. Impaired response of VLDL lipid and apoB secretion to endotoxin in the fasted rat liver. ACTA ACUST UNITED AC 2016. [DOI: 10.1177/09680519060120030501] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Bacterial infection elicits hypertriglyceridemia attributed to increased hepatic production of very low-density lipoprotein (VLDL) particles and decreased peripheral metabolism. The mechanisms underlying VLDL overproduction in sepsis are as yet unclear, but seem to be fed/fasted state-dependent. To learn more about this, we investigated hepatocytes isolated from fasted rats, made endotoxic by 1 mg/kg lipopolysaccharide (LPS) injection, for their ability to secrete the VLDL protein and lipid components. The results were then related to lipogenesis markers and expression of genes critical to VLDL biogenesis. Endotoxic rats showed increased levels of serum VLDL-apoB (10-fold), -triglyceride (2-fold), and -cholesterol (2-fold), whereby circulating VLDL were lipid-poor particles. Similarly, VLDL-apoB secretion by isolated endotoxic hepatocytes was ~85% above control, whereas marginal changes in the output of VLDL-lipid classes occurred. This was accompanied by a substantial rise in apoB and a moderate rise in MTP mRNA levels, but with basal de novo formation and efficiency of secretion of triglycerides, cholesterol and cholesteryl esters. These results indicate that during periods of food restriction, endotoxin does not enhance lipid provision to accomplish normal lipidation of overproduced apoB molecules, though this does occur to a sufficient extent to pass the proteasome checkpoint and secretion of lipid-poor, type 2 VLDL takes place.
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Affiliation(s)
- Patricia Aspichueta
- Department of Physiology, University of the Basque Country Medical School, Bilbao, Spain
| | - Begoña Pérez-Agote
- Department of Physiology, University of the Basque Country Medical School, Bilbao, Spain
| | - Silvia Pérez
- Department of Physiology, University of the Basque Country Medical School, Bilbao, Spain
| | - Begoña Ochoa
- Department of Physiology, University of the Basque Country Medical School, Bilbao, Spain,
| | - Olatz Fresnedo
- Department of Physiology, University of the Basque Country Medical School, Bilbao, Spain
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7
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Prescription Omega-3s. J Cardiovasc Nurs 2011; 26:290-7. [DOI: 10.1097/jcn.0b013e3182017c36] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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8
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A Model of NEFA Dynamics with Focus on the Postprandial State. Ann Biomed Eng 2009; 37:1897-909. [DOI: 10.1007/s10439-009-9738-6] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2006] [Accepted: 06/04/2009] [Indexed: 11/29/2022]
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9
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van Schalkwijk DB, de Graaf AA, van Ommen B, van Bochove K, Rensen PCN, Havekes LM, van de Pas NCA, Hoefsloot HCJ, van der Greef J, Freidig AP. Improved cholesterol phenotype analysis by a model relating lipoprotein life cycle processes to particle size. J Lipid Res 2009; 50:2398-411. [PMID: 19515990 DOI: 10.1194/jlr.m800354-jlr200] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
Increased plasma cholesterol is a known risk factor for cardiovascular disease. Lipoprotein particles transport both cholesterol and triglycerides through the blood. It is thought that the size distribution of these particles codetermines cardiovascular disease risk. New types of measurements can determine the concentration of many lipoprotein size-classes but exactly how each small class relates to disease risk is difficult to clear up. Because relating physiological process status to disease risk seems promising, we propose investigating how lipoprotein production, lipolysis, and uptake processes depend on particle size. To do this, we introduced a novel model framework (Particle Profiler) and evaluated its feasibility. The framework was tested using existing stable isotope flux data. The model framework implementation we present here reproduced the flux data and derived lipoprotein size pattern changes that corresponded to measured changes. It also sensitively indicated changes in lipoprotein metabolism between patient groups that are biologically plausible. Finally, the model was able to reproduce the cholesterol and triglyceride phenotype of known genetic diseases like familial hypercholesterolemia and familial hyperchylomicronemia. In the future, Particle Profiler can be applied for analyzing detailed lipoprotein size profile data and deriving rates of various lipolysis and uptake processes if an independent production estimate is given.
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10
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Capillary isotachophoresis study of lipoprotein network sensitive to apolipoprotein E phenotype. 1. ApoE distribution between lipoproteins. Mol Cell Biochem 2009; 325:41-51. [DOI: 10.1007/s11010-008-0018-9] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2008] [Accepted: 12/30/2008] [Indexed: 10/21/2022]
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Abstract
While the precise definition of hypertriglyceridaemia remains contentious, the condition is becoming more common in western populations as the prevalence of obesity and diabetes mellitus rise. Although there is strong epidemiological evidence that hypertriglyceridaemia is an independent risk factor for cardiovascular disease, it is has been difficult to demonstrate this by drug intervention studies, as drugs that reduce triglycerides also raise high density lipoprotein cholesterol. Precise target values have also been difficult to agree, although several of the new guidelines for coronary risk management now include triglycerides. The causes of hypertriglyceridaemia are numerous. The more severe forms have a genetic basis, and may lead to an increased risk of pancreatitis. Several types of hypertriglyceridaemia are familial and are associated with increased cardiovascular risk. Secondary causes of hypertriglyceridaemia are also numerous and it is important to exclude these before starting treatment with specific triglyceride-lowering agents. Lifestyle management is also very effective and includes weight reduction, restricted alcohol and fat intake and exercise.
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12
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Abstract
The neonate receiving parenteral nutrition (PN) therapy requires a physiologically appropriate solution in quantity and quality given according to a timely, cost-effective strategy. Maintaining tissue integrity, metabolism, and growth in a neonate is challenging. To support infant growth and influence subsequent development requires critical timing for nutrition assessment and intervention. Providing amino acids to neonates has been shown to improve nitrogen balance, glucose metabolism, and amino acid profiles. In contrast, supplying the lipid emulsions (currently available in the United States) to provide essential fatty acids is not the optimal composition to help attenuate inflammation. Recent investigations with an omega-3 fish oil IV emulsion are promising, but there is need for further research and development. Complications from PN, however, remain problematic and include infection, hepatic dysfunction, and cholestasis. These complications in the neonate can affect morbidity and mortality, thus emphasizing the preference to provide early enteral feedings, as well as medication therapy to improve liver health and outcome. Potential strategies aimed at enhancing PN therapy in the neonate are highlighted in this review, and a summary of guidelines for practical management is included.
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Affiliation(s)
- Christina J Valentine
- Neonatal Nutrition Team, Section of Neonatology, Pharmacy Department, Columbus Children's Hospital, Ohio State University, Columbus, OH 43205, USA.
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13
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Fritz G, Wagner EM, Lindner H, Hofmann W, Zechner R, Glatter O. Dependence of lipoprotein-lipase-catalyzed triacylglycerol hydrolysis on droplet size of synthetic monodisperse emulsions measured with static light scattering. J Colloid Interface Sci 2004; 275:642-8. [PMID: 15178298 DOI: 10.1016/j.jcis.2004.02.085] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2003] [Accepted: 02/27/2004] [Indexed: 10/26/2022]
Abstract
Well-defined triolein emulsions of low polydispersity were prepared by shearing a crude emulsion in a modified Couette cell, resulting in radii in the range of 300 to 900 nm. These emulsions were used as synthetic substrates for lipoprotein lipase, a key enzyme for the hydrolysis of serum triacylglycerols. The change in radius with time was studied with on-line static light scattering at 37 degrees C. An optimum radius of about 750 nm was found for this reaction.
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Affiliation(s)
- Gerhard Fritz
- Institut für Chemie, Karl-Franzens Universität Graz, Heinrichstrasse 28, A-8010 Graz, Austria.
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14
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Rashid S, Watanabe T, Sakaue T, Lewis GF. Mechanisms of HDL lowering in insulin resistant, hypertriglyceridemic states: the combined effect of HDL triglyceride enrichment and elevated hepatic lipase activity. Clin Biochem 2003; 36:421-9. [PMID: 12951168 DOI: 10.1016/s0009-9120(03)00078-x] [Citation(s) in RCA: 178] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Hypertriglyceridemia, low plasma concentrations of high density lipoproteins (HDL) and qualitative changes in low density lipoproteins (LDL) comprise the typical dyslipidemia of insulin resistant states and type 2 diabetes. Although isolated low plasma HDL-cholesterol (HDL-c) and apolipoprotein A-I (apo A-I, the major apolipoprotein component of HDL) can occur in the absence of hypertriglyceridemia or any other features of insulin resistance, the majority of cases in which HDL-c is low are closely linked with other clinical features of insulin resistance and hypertriglyceridemia. We and others have postulated that triglyceride enrichment of HDL particles secondary to enhanced CETP-mediated exchange of triglycerides and cholesteryl ester between HDL and triglyceride-rich lipoproteins, combined with the lipolytic action of hepatic lipase (HL), are driving forces in the reduction of plasma HDL-c and apoA-I plasma concentrations. The present review focuses on these metabolic alterations in insulin resistant states and their important contributions to the reduction of HDL-c and HDL-apoA-I plasma concentrations.
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Affiliation(s)
- Shirya Rashid
- Department of Medicine, Division of Endocrinology, University of Toronto, Toronto, Ontario, Canada
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15
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Sato K, Takahashi Y, Takahashi T, Katoh N, Akiba Y. Identification of factors regulating lipoprotein lipase catalyzed hydrolysis in rats with the aid of monoacid-rich lipoprotein preparations(1). J Nutr Biochem 2002; 13:528. [PMID: 12231423 DOI: 10.1016/s0955-2863(02)00194-8] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
To identify the substrate specificity and regulatory factors in lipoprotein lipase (LPL) catalyzed hydrolysis of triacylglycerol-rich lipoprotein, monoacid-rich lipoproteins were used to study the kinetic parameters of LPL. Feeding growing rats with diets rich in palmitic acid (16:0), oleic acid (18:1) or linoleic acid (18:2) for 10 days increased the corresponding acid content in the triacylglycerols of the lipoproteins. Force-feeding the monoacid-rich triacylglycerols, particularly 16:0 or 18:1, increased the respective fatty acid content in both chylomicrons and VLDLs. Major apolipoproteins and lipid compositions were essentially similar among all lipoproteins differing in monoacid species, except for apo A-IV. The Vmax of LPL for 16:0-rich chylomicrons and VLDLs were higher than for 18:1- or 18:2-rich lipoproteins. Order parameter (S), an indicator of the surface fluidity of lipoproteins, decreased with the chain length and unsaturation of monoacid in similar manner as the Vmax. The Vmax of LPL increased linearly (P < 0.05) with an increase in either the palmitic acid content of the lipoprotein triacylglycerols or order parameter (S) of the lipoproteins. The order parameter (S) and Vmax of LPL were higher in 16:0 triacylglycerol emulsions with apo B than with 18:1 or 18:2 triacylglycerols. The apo A-IV in triacylglycerol emulsions stimulated Vmax of LPLs in the presence of apo B and apo C-II. The binding of apo A-IV to 16:0 triacylglycerol emulsions was higher than to other triacylglycerol emulsions. These findings suggest that lipoprotein catalysis by LPL is modulated by the 16:0 level in the lipoprotein triacylglycerol, which affects the surface fluidity and apo A-IV content of lipoproteins.
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Affiliation(s)
- Kan Sato
- Animal Nutrition, Division of Life Science, Graduate School of Agricultural Science, Tohoku University, 981-8555, Sendai-shi, Japan
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16
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Huang Y, Ji ZS, Brecht WJ, Rall SC, Taylor JM, Mahley RW. Overexpression of apolipoprotein E3 in transgenic rabbits causes combined hyperlipidemia by stimulating hepatic VLDL production and impairing VLDL lipolysis. Arterioscler Thromb Vasc Biol 1999; 19:2952-9. [PMID: 10591675 DOI: 10.1161/01.atv.19.12.2952] [Citation(s) in RCA: 66] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
The differential effects of overexpression of human apolipoprotein (apo) E3 on plasma cholesterol and triglyceride metabolism were investigated in transgenic rabbits expressing low (<10 mg/dL), medium (10 to 20 mg/dL), or high (>20 mg/dL) levels of apoE3. Cholesterol levels increased progressively with increasing levels of apoE3, whereas triglyceride levels were not significantly affected at apoE3 levels up to 20 mg/dL but were markedly increased at levels of apoE3 >20 mg/dL. The medium expressers had marked hypercholesterolemia (up to 3- to 4-fold over nontransgenics), characterized by an increase in low density lipoprotein (LDL) cholesterol, while the low expressers had only slightly increased plasma cholesterol levels. The medium expressers displayed an 18-fold increase in LDL but also had a 2-fold increase in hepatic very low density lipoprotein (VLDL) triglyceride production, an 8-fold increase in VLDL apoB, and a moderate decrease in the ability of the VLDL to be lipolyzed. However, plasma clearance of VLDL was increased, likely because of the increased apoE3 content. The increase in LDL appears to be due to an enhanced competition of VLDL for LDL receptor binding and uptake, resulting in the accumulation of LDL. The combined hyperlipidemia of the apoE3 high expressers (>20 mg/dL) was characterized by a 19-fold increase in LDL cholesterol but also a 4-fold increase in hepatic VLDL triglyceride production associated with a marked elevation of plasma VLDL triglycerides, cholesterol, and apoB100 (4-, 9-, and 25-fold over nontransgenics, respectively). The VLDL from the high expressers was much more enriched in apoE3 and markedly depleted in apoC-II, which contributed to a >60% inhibition of VLDL lipolysis. The combined effects of stimulated VLDL production and impaired VLDL lipolysis accounted for the increases in plasma triglyceride and VLDL concentrations in the apoE3 high expressers. The hyperlipidemic apoE3 rabbits have phenotypes similar to those of familial combined hyperlipidemia, in which VLDL overproduction is a major biochemical feature. Overall, elevated expression of apoE3 appears to determine plasma lipid levels by stimulating hepatic VLDL production, enhancing VLDL clearance, and inhibiting VLDL lipolysis. Thus, the differential expression of apoE may, within a rather narrow range of concentrations, play a critical role in modulating plasma cholesterol and triglyceride levels and may represent an important determinant of specific types of hyperlipoproteinemia.
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Affiliation(s)
- Y Huang
- Gladstone Institute of Cardiovascular Disease, San Francisco, CA 94141-9100, USA
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17
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Xiang SQ, Cianflone K, Kalant D, Sniderman AD. Differential binding of triglyceride-rich lipoproteins to lipoprotein lipase. J Lipid Res 1999. [DOI: 10.1016/s0022-2275(20)33411-8] [Citation(s) in RCA: 67] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
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18
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Huang Y, Liu XQ, Rall SC, Taylor JM, von Eckardstein A, Assmann G, Mahley RW. Overexpression and accumulation of apolipoprotein E as a cause of hypertriglyceridemia. J Biol Chem 1998; 273:26388-93. [PMID: 9756870 DOI: 10.1074/jbc.273.41.26388] [Citation(s) in RCA: 159] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023] Open
Abstract
The molecular mechanisms of hypertriglyceridemia (HTG), a common lipid metabolic disorder in humans, often of genetic origin, are not well understood. In studying the effect of apolipoprotein (apo) E on the metabolism of triglyceride-rich lipoproteins, we found that expressing high plasma levels of human apoE3 in transgenic mice lacking endogenous mouse apoE caused HTG. These transgenic animals had 3-fold higher plasma triglyceride levels, higher very low density lipoproteins (VLDL), and lower high density lipoproteins than did nontransgenics. Removing one or both low density lipoprotein receptor alleles in the apoE3-overexpressing mice caused severe HTG (8-11-fold over nontransgenics) and increased VLDL and decreased low and high density lipoproteins, and apoE3-enriched VLDL were markedly depleted in apoC-II. At least two mechanisms could explain HTG associated with apoE3 overexpression: stimulated VLDL triglyceride production and impaired VLDL lipolysis. The apoE3 mice with HTG had a 50% increase in hepatic VLDL triglyceride production. Furthermore, overexpression of apoE (E2, E3, or E4) in cultured hepatocytes (McA-RH7777 cells) correlated positively with secretion of VLDL into the medium. However, apoE3 overexpression-associated HTG was only partially explained by VLDL overproduction, as lipoprotein lipase-mediated VLDL lipolysis was also decreased 20-86% depending on apoE3 levels, most likely by displacing or masking apoC-II on the particles. In human subjects, HTG correlated positively with increased VLDL triglyceride and plasma and VLDL apoE levels. However, plasma and VLDL apoE correlated negatively with VLDL apoC-II levels and lipoprotein lipase-mediated VLDL lipolysis. Thus, optimal expression of apoE is crucial for normal metabolism of triglyceride-rich lipoproteins, and overexpression and/or accumulation of apoE may contribute to HTG by stimulating VLDL triglyceride production and by impairing VLDL lipolysis. The apoE3-overexpressing mice will be useful for studying the pathophysiology of this disorder.
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Affiliation(s)
- Y Huang
- Gladstone Institute of Cardiovascular Disease, and Pathology, University of California, San Francisco, California 94141-9100, USA
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19
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Zsigmond E, Fuke Y, Li L, Kobayashi K, Chan L. Resistance of chylomicron and VLDL remnants to post-heparin lipolysis in ApoE-deficient mice: the role of apoE in lipoprotein lipase-mediated lipolysis in vivo and in vitro. J Lipid Res 1998. [DOI: 10.1016/s0022-2275(20)32173-8] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022] Open
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Huang Y, Liu XQ, Rall SC, Mahley RW. Apolipoprotein E2 reduces the low density lipoprotein level in transgenic mice by impairing lipoprotein lipase-mediated lipolysis of triglyceride-rich lipoproteins. J Biol Chem 1998; 273:17483-90. [PMID: 9651338 DOI: 10.1074/jbc.273.28.17483] [Citation(s) in RCA: 65] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Apolipoprotein (apo) E2 is often associated with low levels of low density lipoprotein (LDL) cholesterol and high levels of plasma triglycerides in humans. Mice expressing apoE2 also have low LDL levels. To evaluate the possible role of the LDL receptor in the cholesterol-lowering effect of apoE2, we bred transgenic mice expressing low levels of apoE2 with LDL receptor-null mice (hE2(+/0), LDLR-/-). Even in the absence of the LDL receptor, plasma total and LDL cholesterol levels decreased progressively with increasing levels of plasma apoE2. At plasma apoE2 levels >20 mg/dl, LDL cholesterol was approximately 45% lower than in LDLR-/- mice. Thus, the LDL cholesterol-lowering effect of apoE2 is independent of the LDL receptor. In contrast, plasma triglyceride levels increased (mostly in very low density lipoproteins (VLDL) and intermediate density lipoproteins (IDL)) progressively as apoE2 levels increased. At plasma apoE2 levels >20 mg/dl, triglycerides were approximately 150% higher than in LDLR-/- mice. Furthermore, in apoE-null mice (hE2(+/0), mE-/-), apoE2 levels also correlated positively with plasma triglyceride levels, suggesting impaired lipolysis in both hE2(+/0),LDLR-/- and hE2(+/0),mE-/- mice. Incubating VLDL or IDL from the hE2(+/0),LDLR-/- or the hE2(+/0),mE-/- mice with mouse postheparin plasma inhibited lipoprotein lipase-mediated lipolysis of apoE2-containing VLDL and IDL by approximately 80 and approximately 70%, respectively, versus normal VLDL and IDL. This observation was confirmed by studies with triglyceride-rich emulsion particles, apoE2, and purified lipoprotein lipase. Furthermore, apoE2-containing VLDL had much less apoC-II than normal VLDL. Adding apoC-II to the incubation partially corrected the apoE2-impaired lipolysis in apoE2-containing VLDL or IDL and corrected it completely in apoE2-containing emulsion particles. Thus, apoE2 lowers LDL cholesterol by impairing lipoprotein lipase-mediated lipolysis of triglyceride-rich lipoproteins (mostly by displacing or masking apoC-II). Furthermore, the effects of apoE2 on both plasma cholesterol and triglyceride levels are dose dependent and act via different mechanisms. The increase in plasma cholesterol caused by apoE2 is due mostly to impaired clearance, whereas the increase in plasma triglycerides is caused mainly by apoE2-impaired lipolysis of triglyceride-rich lipoproteins.
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Affiliation(s)
- Y Huang
- Gladstone Institute of Cardiovascular Disease, University of California, San Francisco, California 94141-9100, USA
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21
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Mero N, Van Tol A, Scheek L, Van Gent T, Labeur C, Rosseneu M, Taskinen MR. Decreased postprandial high density lipoprotein cholesterol and apolipoproteins A-I and E in normolipidemic smoking men: relations with lipid transfer proteins and LCAT activities. J Lipid Res 1998. [DOI: 10.1016/s0022-2275(20)32531-1] [Citation(s) in RCA: 40] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
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22
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Preferential clearance of apoB-48-containing lipoproteins after heparin-induced lipolysis is modulated by lipoprotein lipase activity. J Lipid Res 1998. [DOI: 10.1016/s0022-2275(20)33894-3] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
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23
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Huang Y, Schwendner SW, Rall SC, Sanan DA, Mahley RW. Apolipoprotein E2 transgenic rabbits. Modulation of the type III hyperlipoproteinemic phenotype by estrogen and occurrence of spontaneous atherosclerosis. J Biol Chem 1997; 272:22685-94. [PMID: 9312550 DOI: 10.1074/jbc.272.36.22685] [Citation(s) in RCA: 46] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
Transgenic rabbits were produced that expressed high plasma levels (30-70 mg/dl) of human apolipoprotein (apo) E2(Cys-158), an apoE variant associated with the human genetic disorder type III hyperlipoproteinemia (HLP). Male transgenic rabbits fed normal chow had up to 8-fold (289 +/- 148 mg/dl) and 15-fold (697 +/- 452 mg/dl) increases in plasma total cholesterol and triglycerides, respectively, compared with nontransgenic males. Female transgenic rabbits had only a modest hyperlipidemia (total cholesterol, 140 +/- 46 mg/dl; total triglycerides, 174 +/- 66 mg/dl). Both sexes displayed the hallmarks fo type III HLP: beta-migrating very low density lipoproteins (beta-VLDL) (intestinal and hepatic remnant lipoproteins) and significantly increased VLDL and intermediate density lipoproteins. Apolipoprotein E2-containing VLDL particles were cleared from teh circulation more slowly and were more resistant to lipoprotein lipase-mediated lipolysis than normal VLDL. Only females had increased high density lipoproteins (HDL) (40%), which were shifted from typical small HDL to larger HDL1. Plasma apoE2 was predominantly associated with beta-VLDL in males and with HDL in females. To ascertain reasons for the phenotypic gender difference, we treated male transgenic rabbits with 17alpha-ethinyl estradiol. Estrogen treatment for 10 days dramatically decreased total cholesterol (73%) and triglycerides (89%) and converted beta-VLDL to pre-beta-migrating VLDL. Concomitantly, lipoprotein lipase and hepatic lipase activities increased by 90%, low density lipoprotein receptor activity was stimulated significantly, apoE2 was redistributed to HDL, and HDL were converted to HDL1. Conversely, ovariectomy in female transgenic rabbits significantly increased total cholesterol (75%), triglycerides (117%), and beta-VLDL, while decreasing lipoprotein lipase and hepatic lipase activities by 35% and redistributing apoE2 to the beta-VLDL. Thus, estrogen status appears to be responsible for much of the gender difference of the lipoprotein phenotype, mainly by modulating both lipase and low density lipoprotein receptor activities. Furthermore, transgenic rabbits fed normal chow for 11 months developed fatty streaks, and some had more advanced atherosclerotic lesions, especially around the aortic arch and proximal abdominal aorta. The lesions were more extensive in males, roughly correlating with the magnitude of the hyperlipidemia. Therefore, high plasma levels of human apoE2 in transgenic rabbits result in a type III HLP phenotype, in which males have both more severe hyperlipidemia and more extensive atherosclerosis than females.
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Affiliation(s)
- Y Huang
- Gladstone Institute of Cardiovascular Disease, Cardiovascular Research Institute, University of California, San Francisco, California 94141-9100, USA
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24
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MacPhee CE, Chan RY, Sawyer WH, Stafford WF, Howlett GJ. Interaction of lipoprotein lipase with homogeneous lipid emulsions. J Lipid Res 1997. [DOI: 10.1016/s0022-2275(20)37183-2] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023] Open
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25
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Bravo E, Flora L, Cantafora A, De Luca V, Tripodi M, Avella M, Mayes PA, Botham KM. Comparison of the uptake and processing of cholesterol from chylomicrons of different fatty acid composition in rats fed high-fat and low-fat diets. EUROPEAN JOURNAL OF BIOCHEMISTRY 1997; 246:92-102. [PMID: 9210470 DOI: 10.1111/j.1432-1033.1997.t01-2-00092.x] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
The fate of [3H]cholesterol carried in chylomicrons prepared from rats given a meal of palm oil (rich in long-chain saturated fatty acids), olive oil (rich in monounsaturated fatty acids) or corn oil (rich in n-6 polyunsaturated fatty acids) was investigated in vivo in rats fed a low-fat diet or a diet supplemented with the corresponding oil (to provide 40% of the calories) for 21 days. In the low-fat-fed groups, radioactivity was removed from the blood and secreted into bile over 180 min more rapidly when the chylomicrons were derived from corn oil as compared to palm or olive oil. After feeding the corresponding high-fat diets, however, both parameters were decreased in rats fed palm and corn oil, but not olive oil. As a result of these changes, the rates of removal of radioactivity from the blood and secretion into bile were similar in animals given the olive oil and corn oil diets, and higher than those in rats fed the palm oil diet. All the high-fat diets tended to increase the proportion of the radioactivity in the plasma found in the 1.006-1.050-g/ml fraction (low-density lipoprotein) and decrease that in the 1.050-1.25-g/ml (high-density lipoprotein) fraction in comparison to the respective low-fat diet groups, but the transfer of radioactivity to the plasma high-density lipoprotein fraction was particularly slow in palm-oil-fed rats. These findings indicate that diets high in saturated or n-6 polyunsaturated fat retard the metabolism of chylomicron cholesterol in comparison to diets low in fat, while those high in monounsaturated fat do not have this effect. As a consequence of this, the rate of removal of cholesterol of dietary origin from the body is slower in animals fed saturated as compared to monounsaturated or n-6 polyunsaturated fat. Thus, differential metabolism of chylomicron cholesterol clearly plays an important role in the hyper- and hypo-cholesterolaemic effects of these dietary fats.
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MESH Headings
- Animals
- Bile/metabolism
- Blotting, Northern
- Cholesterol/blood
- Cholesterol/metabolism
- Cholesterol Esters/blood
- Chylomicrons/administration & dosage
- Chylomicrons/metabolism
- Diet, Fat-Restricted
- Dietary Fats/administration & dosage
- Dietary Fats, Unsaturated/administration & dosage
- Fatty Acids, Omega-6
- Fatty Acids, Unsaturated/administration & dosage
- Lipase/genetics
- Lipase/metabolism
- Lipoproteins, HDL/blood
- Lipoproteins, HDL/metabolism
- Lipoproteins, LDL/blood
- Lipoproteins, LDL/metabolism
- Liver/enzymology
- Male
- Phosphatidylcholine-Sterol O-Acyltransferase/genetics
- Phosphatidylcholine-Sterol O-Acyltransferase/metabolism
- Plant Oils/administration & dosage
- RNA, Messenger/metabolism
- Rats
- Rats, Wistar
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Affiliation(s)
- E Bravo
- Instituto Superiore di Sanita, Laboratory of Metabolism and Pathological Biochemistry, Rome, Italy
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Choi SY, Pang L, Kern PA, Kayden HJ, Curtiss LK, Vanni-Reyes TM, Goldberg IJ. Dissociation of LPL and LDL: effects of lipoproteins and anti-apoB antibodies. J Lipid Res 1997. [DOI: 10.1016/s0022-2275(20)37277-1] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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28
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Rensen PC, van Berkel TJ. Apolipoprotein E effectively inhibits lipoprotein lipase-mediated lipolysis of chylomicron-like triglyceride-rich lipid emulsions in vitro and in vivo. J Biol Chem 1996; 271:14791-9. [PMID: 8662966 DOI: 10.1074/jbc.271.25.14791] [Citation(s) in RCA: 120] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023] Open
Abstract
Apolipoprotein E (apoE) is an important determinant for the liver uptake of triglyceride-rich lipoproteins and emulsions by the remnant receptor. In the current study, we assessed an additional role of apoE as modulator of the metabolism of triglyceride-rich lipoproteins in vitro and in vivo. Glycerol tri[3H]oleate [14C]cholesteryl oleate double-labeled triglyceride-rich emulsions were injected into fasted rats. The serum half-life of glycerol tri[3H]oleate was 3-fold faster (5.4 min) than that of [14C]cholesteryl oleate (16.7 min), confirming lipoprotein lipase (LPL)-mediated processing. To establish a specific effect of apoE on emulsion lipolysis rather than liver uptake, rats were functionally hepatectomized, and hypo(apo)lipoproteinemia was induced by 17alpha-ethinyl estradiol treatment. An apoE concentration-dependent inhibition of emulsion-triglyceride hydrolysis was observed, reaching a 14.8-fold increased half-life of glycerol tri[3H]oleate as compared with that in the absence of exogenous apoE. The mechanism and specificity of the effect of apoE on emulsion lipolysis by purified LPL was assessed in vitro. Addition of apoE to glycerol tri[3H]oleate-labeled emulsions led to a concentration-dependent inhibition of [3H]oleate release (9.5% residual LPL activity at 60 microg/ml apoE), while apoA-I was ineffective. The inhibitory effect of apoE was not abolished by reductive methylation of lysine residues, whereas selective modification of arginine residues by 1,2-cyclohexadione completely cancelled the inhibitory effect of apoE. It is concluded that apoE can specifically inhibit the LPL-mediated hydrolysis of emulsion triglycerides both in vitro and in vivo, and that arginine residues in apoE are essential for this effect. We suggest that in addition to its role in receptor recognition, apoE also modulates the LPL-mediated processing of triglyceride-rich lipoproteins.
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Affiliation(s)
- P C Rensen
- Division of Biopharmaceutics, Leiden-Amsterdam Center for Drug Research, University of Leiden, Sylvius Laboratories, 2300 RA Leiden, The Netherlands
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29
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Bravo E, Cantafora A, Marinelli T, Avella M, Mayes PA, Botham KM. Differential effects of chylomicron remnants derived from corn oil or palm oil on bile acid synthesis and very low density lipoprotein secretion in cultured rat hepatocytes. Life Sci 1996; 59:331-7. [PMID: 8761005 DOI: 10.1016/0024-3205(96)00302-5] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
The effects of chylomicron remnants derived from corn oil (rich in n-6 polyunsaturated fatty acids) and palm oil (rich in long chain saturated fatty acids) on bile acid synthesis and very low density lipoprotein secretion in cultured rat hepatocytes were studied. Incubation of the cells with corn oil remnants led to increased bile acid production, while the secretion of lipid in very low density lipoprotein remained unchanged. In contrast, addition of palm oil remnants to the medium did not affect bile acid synthesis, but resulted in the secretion of cholesterol-rich very low density lipoprotein. These findings show that chylomicron remnants of different fatty acid composition have differential effects on cholesterol metabolism in liver cells, and provide part of the explanation for the hyper- and hypocholesterolaemic effects of saturated and polyunsaturated fatty acids.
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Affiliation(s)
- E Bravo
- Istituto Superiore di Sanita, Laboratory of Metabolism and Pathological Biochemistry, Rome, Italy
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30
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Goldberg IJ. Lipoprotein lipase and lipolysis: central roles in lipoprotein metabolism and atherogenesis. J Lipid Res 1996. [DOI: 10.1016/s0022-2275(20)37569-6] [Citation(s) in RCA: 323] [Impact Index Per Article: 11.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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31
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Ng DS, Vezina C, Wolever TS, Kuksis A, Hegele RA, Connelly PW. Apolipoprotein A-I deficiency. Biochemical and metabolic characteristics. Arterioscler Thromb Vasc Biol 1995; 15:2157-64. [PMID: 7489237 DOI: 10.1161/01.atv.15.12.2157] [Citation(s) in RCA: 25] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
Familial HDL deficiencies are associated with variable susceptibility to premature coronary heart disease, but the mechanism underlying this association remains poorly understood. Three homozygotes with isolated complete apo A-I deficiency caused by an autosomal codominant apo A-I Q[-2]X mutation and one heterozygote developed coronary heart disease before age 40 years. We characterized the effects of this mutation on lipoprotein metabolism. LDL FC, phospholipid, and apo B were all significantly higher in homozygotes than in heterozygotes. The HDLs of the heterozygotes were apo A-I poor relative to apo A-II. Lecithin-cholesterol acyltransferase activity was 59% lower in homozygotes than in normal subjects or heterozygotes. Cholesteryl ester transfer activity was increased in a homozygote compared with a normolipidemic control subject. Postprandial lipid metabolism was studied in one homozygote and one heterozygote. Post-prandial TG response in the homozygote was significantly exaggerated, while residual plasma HDL level remained unaffected. The homozygote also had delayed clearance of retinyl ester, a marker of chylomicron remnant metabolism. Thus, homozygosity and heterozygosity for apo A-I Q[-2]X are associated with qualitative, as well as quantitative, disturbances in plasma HDLs, LDLs, lipid-modifying enzyme activities, and postprandial retinyl ester metabolism. The observed elevation of atherogenic lipoproteins and reduction in antiatherogenic lipoproteins in the affected members of the apo A-I Q[-2]X kindred are consistent with the primary deficiency in apo A-I having pleiotropic effects that markedly enhance susceptibility for coronary heart disease.
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Affiliation(s)
- D S Ng
- Department of Medicine, St Michael's Hospital, University of Toronto, Ontario, Canada
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32
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Fan J, McCormick SP, Krauss RM, Taylor S, Quan R, Taylor JM, Young SG. Overexpression of human apolipoprotein B-100 in transgenic rabbits results in increased levels of LDL and decreased levels of HDL. Arterioscler Thromb Vasc Biol 1995; 15:1889-99. [PMID: 7583569 DOI: 10.1161/01.atv.15.11.1889] [Citation(s) in RCA: 51] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
In this study, and 80-kb human genomic DNA fragment spanning the human apoB gene was used to generate transgenic New Zealand White rabbits that expressed human apoB-100. The concentration of human apoB in the plasma of the transgenic rabbits ranged between 5 and 100 mg/dL. The transgenic rabbits had nearly threefold elevations in the plasma levels of triglycerides and cholesterol compared with nontransgenic controls. Nearly all the cholesterol and human apoB in the plasma was in the LDL fraction. Pronounced triglyceride enrichment of the LDL fraction was a striking feature of human apoB overexpression in the transgenic rabbits, in which the LDL fraction contained more than 75% of the plasma triglycerides. The triglyceride-enriched LDL particles were smaller and more dense than the native rabbit LDL and contained markedly increased amounts of apoE and apoC-III. In the nontransgenic control animals most of the triglycerides were in the VLDL, and most of the apoE and apoC-III were in the VLDL and HDL fractions. In addition to increased LDL levels, overexpression of human apoB in rabbits resulted in lower plasma levels of HDL cholesterol and apoA-I. In our prior studies on transgenic mice expressing human apoB, we documented triglyceride-rich LDL and reduced levels of HDL cholesterol. These prior findings in mice, together with the present findings in transgenic rabbits, suggest that triglyceride-rich LDL and lowered levels of HDL cholesterol may be hallmark features of apoB overexpression.
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Affiliation(s)
- J Fan
- Gladstone Institute of Cardiovascular Disease, San Francisco, CA 94141, USA
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33
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Coleman T, Seip RL, Gimble JM, Lee D, Maeda N, Semenkovich CF. COOH-terminal disruption of lipoprotein lipase in mice is lethal in homozygotes, but heterozygotes have elevated triglycerides and impaired enzyme activity. J Biol Chem 1995; 270:12518-25. [PMID: 7759497 DOI: 10.1074/jbc.270.21.12518] [Citation(s) in RCA: 91] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023] Open
Abstract
The role of the enzyme lipoprotein lipase (LPL) in atherosclerosis is uncertain. To generate an animal model of LPL deficiency, we targeted the LPL gene in embryonic stem cells with a vector designed to disrupt the COOH terminus of the protein and used these cells to generate LPL-deficient mice. Germ line transmission of the disrupted LPL allele was achieved with two chimeric males, and offspring from each of these animals were phenotypically identical. Pups homozygous (-/-) for LPL deficiency died within 48 h of birth with extreme elevations of serum triglycerides (13,327 mg/dl) associated with essentially absent LPL enzyme activity in heart and carcass. Newborn heterozygous (+/-) LPL-deficient pups had lower LPL enzyme activity and higher triglycerides (370 versus 121 mg/dl) than wild type (+/+) littermates. Adult heterozygotes had higher triglycerides than wild type mice with ad libitum feeding (236 mg/dl for +/- versus 88 mg/dl for +/+) and after fasting for 4 h (98 mg/dl for +/- versus 51 for +/+) or 12 h (109 mg/dl for +/- versus 56 mg/dl for +/+). Triglycerides were present as very low density lipoprotein particles and chylomicrons, but high density lipoprotein cholesterol levels were not decreased in +/- animals. Plasma heparin-releasable LPL activity was 43% lower in +/- versus +/+ adult animals. LPL activity, mRNA, and protein were lower in the tissues of +/- versus +/+ mice. Homozygous LPL deficiency caused by disruption of the COOH terminus of the enzyme is lethal in mice. Heterozygous LPL deficiency caused by this mutation is associated with mild to moderate hypertriglyceridemia without affecting static HDL cholesterol levels. Heterozygous LPL-deficient mice could be useful for determining if hypertriglyceridemia, independently or in combination with other discrete defects, influences atherosclerosis.
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Affiliation(s)
- T Coleman
- Department of Medicine, Washington University School of Medicine, St. Louis, Missouri 63110, USA
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34
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Choi SY, Sivaram P, Walker DE, Curtiss LK, Gretch DG, Sturley SL, Attie AD, Deckelbaum RJ, Goldberg IJ. Lipoprotein lipase association with lipoproteins involves protein-protein interaction with apolipoprotein B. J Biol Chem 1995; 270:8081-6. [PMID: 7713910 DOI: 10.1074/jbc.270.14.8081] [Citation(s) in RCA: 49] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
Lipoprotein lipase (LPL) hydrolyzes chylomicron and very low density lipoprotein (VLDL) triglycerides and potentiates the cellular uptake of lipoproteins. These LPL-lipoprotein associations could involve only protein-lipid interaction, or they could be modulated by apolipoproteins (apo). ApoB is the major protein component of chylomicrons, VLDL, and low density lipoprotein (LDL). ApoB100, a large glycoprotein with a molecular mass of 550 kDa, is composed of several functional domains. A carboxyl-terminal region of the protein is the ligand for the LDL receptor. There are several hydrophobic domains that are believed to be important in lipid binding. The relatively hydrophilic amino-terminal region of apoB, however, has no known function. Using solid phase assays we quantified LPL-lipoprotein complex formation. On a molar basis, severalfold greater amounts of LPL bound to LDL and VLDL than to high density lipoprotein at all the concentrations of LPL tested (0.9-55 nM). To assess the roles of LDL protein versus lipid, we performed competition and ligand blotting experiments. LDL and an amino-terminal fragment of apoB competed better for 125I-LPL binding to LDL than did lipid emulsion particles. Delipidation of LDL-coated plates did not alter LPL binding. On ligand blots, LPL bound to amino-terminal fragments of apoB generated by thrombin digestion but not to apoA1, apoE, or carboxyl-terminal fragments of apoB. Further evidence for LPL interaction with the amino-terminal region of apoB was obtained using anti-apoB monoclonal antibodies. Antibodies directed against the amino-terminal regions of apoB blocked LPL interaction with LDL, whereas those against the carboxyl-terminal region of apoB did not inhibit LPL interaction with LDL. Thus, we conclude that a specific interaction between LPL and the amino-terminal region of apoB may facilitate LPL association with circulating lipoproteins.
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Affiliation(s)
- S Y Choi
- Department of Medicine, Columbia University College of Physicians and Surgeons, New York, New York 10032, USA
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