1
|
Whitacre BE, Howles P, Street S, Morris J, Swertfeger D, Davidson WS. Apolipoprotein E content of VLDL limits LPL-mediated triglyceride hydrolysis. J Lipid Res 2022; 63:100157. [PMID: 34863862 PMCID: PMC8953696 DOI: 10.1016/j.jlr.2021.100157] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2021] [Revised: 11/24/2021] [Accepted: 11/28/2021] [Indexed: 12/20/2022] Open
Abstract
High levels of circulating triglycerides (TGs), or hypertriglyceridemia, are key components of metabolic diseases, such as type 2 diabetes, metabolic syndrome, and CVD. As TGs are carried by lipoproteins in plasma, hypertriglyceridemia can result from overproduction or lack of clearance of TG-rich lipoproteins (TRLs) such as VLDLs. The primary driver of TRL clearance is TG hydrolysis mediated by LPL. LPL is regulated by numerous TRL protein components, including the cofactor apolipoprotein C-II, but it is not clear how their effects combine to impact TRL hydrolysis across individuals. Using a novel assay designed to mimic human plasma conditions in vitro, we tested the ability of VLDL from 15 normolipidemic donors to act as substrates for human LPL. We found a striking 10-fold difference in hydrolysis rates across individuals when the particles were compared on a protein or a TG basis. While VLDL TG contents moderately correlated with hydrolysis rate, we noticed substantial variations in non-apoB proteins within these particles by MS. The ability of LPL to hydrolyze VLDL TGs did not correlate with apolipoprotein C-II content, but it was strongly inversely correlated with apolipoprotein E (APOE) and, to a lesser extent, apolipoprotein A-II. Addition of exogenous APOE inhibited LPL lipolysis in a dose-dependent manner. The APOE3 and (particularly) APOE4 isoforms were effective at limiting LPL hydrolysis, whereas APOE2 was not. We conclude that APOE on VLDL modulates LPL activity and could be a relevant factor in the pathogenesis of metabolic disease.
Collapse
Affiliation(s)
- Brynne E Whitacre
- Department of Pathology and Laboratory Medicine, University of Cincinnati, Cincinnati, OH, USA
| | - Philip Howles
- Department of Pathology and Laboratory Medicine, University of Cincinnati, Cincinnati, OH, USA
| | - Scott Street
- Department of Pathology and Laboratory Medicine, University of Cincinnati, Cincinnati, OH, USA
| | - Jamie Morris
- Department of Pathology and Laboratory Medicine, University of Cincinnati, Cincinnati, OH, USA
| | - Debi Swertfeger
- Department of Pediatrics, Cincinnati Children's Hospital Medical Center, Cincinnati, OH, USA
| | - W Sean Davidson
- Department of Pathology and Laboratory Medicine, University of Cincinnati, Cincinnati, OH, USA.
| |
Collapse
|
2
|
Liu G, Lai P, Guo J, Wang Y, Xian X. Genetically-engineered hamster models: applications and perspective in dyslipidemia and atherosclerosis-related cardiovascular disease. MEDICAL REVIEW (BERLIN, GERMANY) 2021; 1:92-110. [PMID: 37724074 PMCID: PMC10388752 DOI: 10.1515/mr-2021-0004] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/17/2021] [Accepted: 08/03/2021] [Indexed: 09/20/2023]
Abstract
Cardiovascular disease is the leading cause of morbidity and mortality in both developed and developing countries, in which atherosclerosis triggered by dyslipidemia is the major pathological basis. Over the past 40 years, small rodent animals, such as mice, have been widely used for understanding of human atherosclerosis-related cardiovascular disease (ASCVD) with the advantages of low cost and ease of maintenance and manipulation. However, based on the concept of precision medicine and high demand of translational research, the applications of mouse models for human ASCVD study would be limited due to the natural differences in metabolic features between mice and humans even though they are still the most powerful tools in this research field, indicating that other species with biological similarity to humans need to be considered for studying ASCVD in future. With the development and breakthrough of novel gene editing technology, Syrian golden hamster, a small rodent animal replicating the metabolic characteristics of humans, has been genetically modified, suggesting that gene-targeted hamster models will provide new insights into the precision medicine and translational research of ASCVD. The purpose of this review was to summarize the genetically-modified hamster models with dyslipidemia to date, and their potential applications and perspective for ASCVD.
Collapse
Affiliation(s)
- George Liu
- Institute of Cardiovascular Sciences and Key Laboratory of Molecular Cardiovascular Sciences, Ministry of Education, School of Basic Medical Sciences, Peking University 38 Xueyuan Road, Beijing 100191, China
| | - Pingping Lai
- Institute of Cardiovascular Sciences and Key Laboratory of Molecular Cardiovascular Sciences, Ministry of Education, School of Basic Medical Sciences, Peking University 38 Xueyuan Road, Beijing 100191, China
| | - Jiabao Guo
- Institute of Cardiovascular Sciences and Key Laboratory of Molecular Cardiovascular Sciences, Ministry of Education, School of Basic Medical Sciences, Peking University 38 Xueyuan Road, Beijing 100191, China
| | - Yuhui Wang
- Institute of Cardiovascular Sciences and Key Laboratory of Molecular Cardiovascular Sciences, Ministry of Education, School of Basic Medical Sciences, Peking University 38 Xueyuan Road, Beijing 100191, China
| | - Xunde Xian
- Institute of Cardiovascular Sciences and Key Laboratory of Molecular Cardiovascular Sciences, Ministry of Education, School of Basic Medical Sciences, Peking University 38 Xueyuan Road, Beijing 100191, China
| |
Collapse
|
3
|
Gao M, Yang C, Wang X, Guo M, Yang L, Gao S, Zhang X, Ruan G, Li X, Tian W, Lu G, Dong X, Ma S, Li W, Wang Y, Zhu H, He J, Yang H, Liu G, Xian X. ApoC2 deficiency elicits severe hypertriglyceridemia and spontaneous atherosclerosis: A rodent model rescued from neonatal death. Metabolism 2020; 109:154296. [PMID: 32562799 DOI: 10.1016/j.metabol.2020.154296] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/13/2020] [Revised: 06/09/2020] [Accepted: 06/17/2020] [Indexed: 12/26/2022]
Abstract
RATIONALE ApoC2 is an important activator for lipoprotein lipase-mediated hydrolysis of triglyceride-rich plasma lipoproteins. ApoC2-deficient patients display severe hypertriglyceridemia (sHTG) and recurrent acute pancreatitis. However, due to embryonic lethality in ApoC2 deleted mouse extensive understanding of ApoC2 function is limited in mammalian species. OBJECTIVE We sought to generate an animal model with ApoC2 deficiency in a rodent with some human-like features and then study the precise effects of ApoC2 on lipid and glucose homeostasis. METHODS AND RESULTS Using CRISPR/Cas9, we deleted Apoc2 gene from golden Syrian hamster and the homozygous (-/-) pups can be born in matured term but exhibited neonatal lethality. By continuous iv administration of normal hamster serum the ApoC2-/- pups could survive till weaning and displayed severe HTG in adulthood on chow diet. A single iv injection of AAV-hApoC2 at birth can also rescue the neonatal death of ApoC2-/- pups. Adult ApoC2-/-hamsters exhibited a unique phenotype of sHTG with hypoglycemia, hypoinsulinemia and spontaneous atherosclerosis. The sHTG in ApoC2-/- adult hamsters could not be corrected by various lipid-lowering medications, but partially ameliorated by medium chain triglyceride diet and completely corrected by AAV-hApoC2. CONCLUSIONS Our study provides a novel ApoC2-deleted mammalian model with severe hypertriglyceridemia that was fully characterized and highlights a potential therapeutic approach for the treatment of ApoC2 deficient patients.
Collapse
Affiliation(s)
- Mingming Gao
- Institute of Cardiovascular Sciences and Key Laboratory of Molecular Cardiovascular Sciences, Ministry of Education, Peking University, Beijing, China; Laboratory of Lipid Metabolism, Institute of Basic Medicine, Hebei Medical University, Shijiazhuang, China
| | - Chun Yang
- Institute of Cardiovascular Sciences and Key Laboratory of Molecular Cardiovascular Sciences, Ministry of Education, Peking University, Beijing, China
| | - Xiaowei Wang
- Laboratory of Lipid Metabolism, Institute of Basic Medicine, Hebei Medical University, Shijiazhuang, China
| | - Mengmeng Guo
- Institute of Cardiovascular Sciences and Key Laboratory of Molecular Cardiovascular Sciences, Ministry of Education, Peking University, Beijing, China
| | - Liu Yang
- State Key Laboratory for Bioactive Substances and Functions of Natural Medicines, Beijing Key Laboratory of New Drug Mechanisms and Pharmacological Evaluation Study, Institute of Materia Medica, Chinese Academy of Medical Sciences and Peking Union Medical College, Xian Nong Tan Street 1, Xicheng District, Beijing 100050, China
| | - Shanshan Gao
- State Key Laboratory for Bioactive Substances and Functions of Natural Medicines, Beijing Key Laboratory of New Drug Mechanisms and Pharmacological Evaluation Study, Institute of Materia Medica, Chinese Academy of Medical Sciences and Peking Union Medical College, Xian Nong Tan Street 1, Xicheng District, Beijing 100050, China
| | - Xin Zhang
- Hebei Invivo Biotech Co, Shijiazhuang, China
| | - Guiyun Ruan
- Department of Cardiovascular Medicine, The Second Xiangya Hospital, Central South University, Changsha, China
| | - Xiangping Li
- Department of Cardiovascular Medicine, The Second Xiangya Hospital, Central South University, Changsha, China
| | - Wenhong Tian
- Beijing FivePlus Molecular Medicine Institute Co. Ltd., Beijing, China
| | - Guotao Lu
- Surgical Intensive Care Unit, Department of General Surgery, Jinling Hospital, Medical School of Nanjing University, Nanjing, China
| | - Xiaoyan Dong
- Beijing FivePlus Molecular Medicine Institute Co. Ltd., Beijing, China
| | - Sisi Ma
- Beijing FivePlus Molecular Medicine Institute Co. Ltd., Beijing, China
| | - Weiqin Li
- Surgical Intensive Care Unit, Department of General Surgery, Jinling Hospital, Medical School of Nanjing University, Nanjing, China
| | - Yuhui Wang
- Institute of Cardiovascular Sciences and Key Laboratory of Molecular Cardiovascular Sciences, Ministry of Education, Peking University, Beijing, China
| | - Haibo Zhu
- State Key Laboratory for Bioactive Substances and Functions of Natural Medicines, Beijing Key Laboratory of New Drug Mechanisms and Pharmacological Evaluation Study, Institute of Materia Medica, Chinese Academy of Medical Sciences and Peking Union Medical College, Xian Nong Tan Street 1, Xicheng District, Beijing 100050, China
| | - Jiuming He
- State Key Laboratory for Bioactive Substances and Functions of Natural Medicines, Beijing Key Laboratory of New Drug Mechanisms and Pharmacological Evaluation Study, Institute of Materia Medica, Chinese Academy of Medical Sciences and Peking Union Medical College, Xian Nong Tan Street 1, Xicheng District, Beijing 100050, China
| | - Hongyuan Yang
- School of Biotechnology and Biomolecular Sciences, University of New South Wales, Sydney, Australia
| | - George Liu
- Institute of Cardiovascular Sciences and Key Laboratory of Molecular Cardiovascular Sciences, Ministry of Education, Peking University, Beijing, China.
| | - Xunde Xian
- Institute of Cardiovascular Sciences and Key Laboratory of Molecular Cardiovascular Sciences, Ministry of Education, Peking University, Beijing, China.
| |
Collapse
|
4
|
Barros D, García-Río F. Obstructive sleep apnea and dyslipidemia: from animal models to clinical evidence. Sleep 2020; 42:5204276. [PMID: 30476296 DOI: 10.1093/sleep/zsy236] [Citation(s) in RCA: 60] [Impact Index Per Article: 15.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2018] [Revised: 10/02/2018] [Accepted: 11/22/2018] [Indexed: 01/11/2023] Open
Abstract
Lipid metabolism deregulation constitutes the pathogenic basis for the development of atherosclerosis and justifies a high incidence of cardiovascular-related morbidity and mortality. Some data suggest that dyslipidemia may be associated with sleep-disordered breathing, mainly obstructive sleep apnea (OSA), due to alterations in fundamental biochemical processes, such as intermittent hypoxia (IH). The aim of this systematic review was to identify and critically evaluate the current evidence supporting the existence of a possible relationship between OSA and alterations in lipid metabolism. Much evidence shows that, during the fasting state, OSA and IH increase lipid delivery from the adipose tissue to the liver through an up-regulation of the sterol regulatory element-binding protein-1 and stearoyl-CoA desaturase-1, increasing the synthesis of cholesterol esters and triglycerides. In the postprandial state, lipoprotein clearance is delayed due to lower lipoprotein lipase activity, probably secondary to IH-up-regulation of angiopoietin-like protein 4 and decreased activity of the peroxisome proliferator-activated receptor alpha. Moreover, oxidative stress can generate dysfunctional oxidized lipids and reduce the capacity of high-density lipoproteins (HDL) to prevent low-density lipoprotein (LDL) oxidation. In the clinical field, several observational studies and a meta-regression analysis support the existence of a link between OSA and dyslipidemia. Although there is evidence of improved lipid profile after apnea-hypopnea suppression with continuous positive airway pressure (CPAP), the majority of the data come from observational studies. In contrast, randomized controlled trials evaluating the effects of CPAP on lipid metabolism present inconclusive results and two meta-analyses provide contradictory evidence.
Collapse
Affiliation(s)
- David Barros
- Servicio de Neumología, Hospital Montecelo, Pontevedra, Spain
| | - Francisco García-Río
- Servicio de Neumología, Hospital Universitario La Paz-IdiPAZ, Madrid, Spain.,Centro de Investigación Biomédica en Red de Enfermedades Respiratorias (CIBERES), Madrid, Spain.,Facultad de Medicina, Universidad Autónoma de Madrid, Madrid, Spain
| |
Collapse
|
5
|
Barchuk M, Miksztowicz V, Zago V, Cevey A, López G, Goren N, Friedman S, Gelpi RJ, Morales C, Fernandez Tomé MDC, Schreier L, Berg G. Endothelial Lipase Is an Alternative Pathway for Fatty Acid Release from Lipoproteins: Evidence from a High Fat Diet Model of Obesity in Rats. Lipids 2018; 53:993-1003. [DOI: 10.1002/lipd.12107] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2018] [Revised: 10/19/2018] [Accepted: 10/26/2018] [Indexed: 11/06/2022]
Affiliation(s)
- Magalí Barchuk
- Departamento de Bioquímica Clínica. Laboratorio de Lípidos y Aterosclerosis, Facultad de Farmacia y Bioquímica; Universidad de Buenos Aires, Junin 956 (1113); Buenos Aires Argentina
- Instituto de Fisiopatología y Bioquímica Clínica (INFIBIOC), Facultad de Farmacia y Bioquímica; Universidad de Buenos Aires, Junin 956 (1113); Buenos Aires Argentina
| | - Verónica Miksztowicz
- Departamento de Bioquímica Clínica. Laboratorio de Lípidos y Aterosclerosis, Facultad de Farmacia y Bioquímica; Universidad de Buenos Aires, Junin 956 (1113); Buenos Aires Argentina
- Instituto de Fisiopatología y Bioquímica Clínica (INFIBIOC), Facultad de Farmacia y Bioquímica; Universidad de Buenos Aires, Junin 956 (1113); Buenos Aires Argentina
- CONICET. Facultad de Farmacia y Bioquímica; Universidad de Buenos Aires, Junin 956 (1113); Buenos Aires Argentina
| | - Valeria Zago
- Departamento de Bioquímica Clínica. Laboratorio de Lípidos y Aterosclerosis, Facultad de Farmacia y Bioquímica; Universidad de Buenos Aires, Junin 956 (1113); Buenos Aires Argentina
- Instituto de Fisiopatología y Bioquímica Clínica (INFIBIOC), Facultad de Farmacia y Bioquímica; Universidad de Buenos Aires, Junin 956 (1113); Buenos Aires Argentina
- CONICET. Facultad de Farmacia y Bioquímica; Universidad de Buenos Aires, Junin 956 (1113); Buenos Aires Argentina
| | - Agata Cevey
- CONICET. Instituto de Investigaciones Biomédicas en Retrovirus y SIDA (INBIRS). Facultad de Medicina; Universidad de Buenos Aires, Paraguay 2155 (1121); Buenos Aires Argentina
| | - Graciela López
- Departamento de Bioquímica Clínica. Laboratorio de Lípidos y Aterosclerosis, Facultad de Farmacia y Bioquímica; Universidad de Buenos Aires, Junin 956 (1113); Buenos Aires Argentina
- Instituto de Fisiopatología y Bioquímica Clínica (INFIBIOC), Facultad de Farmacia y Bioquímica; Universidad de Buenos Aires, Junin 956 (1113); Buenos Aires Argentina
| | - Nora Goren
- CONICET. Instituto de Investigaciones Biomédicas en Retrovirus y SIDA (INBIRS). Facultad de Medicina; Universidad de Buenos Aires, Paraguay 2155 (1121); Buenos Aires Argentina
| | - Silvia Friedman
- Facultad de Odontología. Cátedra de Bioquímica General y Bucal; Universidad de Buenos Aires, Marcelo T. de Alvear 2142 (1122); Buenos Aires Argentina
| | - Ricardo Jorge Gelpi
- Departamento de Patología, Facultad de Medicina. Instituto de Fisiopatología Cardiovascular; Universidad de Buenos Aires, Uriburu 950 (1121); Buenos Aires Argentina
| | - Celina Morales
- Departamento de Patología, Facultad de Medicina. Instituto de Fisiopatología Cardiovascular; Universidad de Buenos Aires, Uriburu 950 (1121); Buenos Aires Argentina
| | - María del Carmen Fernandez Tomé
- Facultad de Farmacia y Bioquímica. Cátedra de Biología Celular y Molecular. Instituto de Química y Fisicoquímica Biológicas (IQUIFIB). CONICET; Universidad de Buenos Aires, Junin 956 (1113); Buenos Aires Argentina
| | - Laura Schreier
- Departamento de Bioquímica Clínica. Laboratorio de Lípidos y Aterosclerosis, Facultad de Farmacia y Bioquímica; Universidad de Buenos Aires, Junin 956 (1113); Buenos Aires Argentina
- Instituto de Fisiopatología y Bioquímica Clínica (INFIBIOC), Facultad de Farmacia y Bioquímica; Universidad de Buenos Aires, Junin 956 (1113); Buenos Aires Argentina
| | - Gabriela Berg
- Departamento de Bioquímica Clínica. Laboratorio de Lípidos y Aterosclerosis, Facultad de Farmacia y Bioquímica; Universidad de Buenos Aires, Junin 956 (1113); Buenos Aires Argentina
- Instituto de Fisiopatología y Bioquímica Clínica (INFIBIOC), Facultad de Farmacia y Bioquímica; Universidad de Buenos Aires, Junin 956 (1113); Buenos Aires Argentina
- CONICET. Facultad de Farmacia y Bioquímica; Universidad de Buenos Aires, Junin 956 (1113); Buenos Aires Argentina
| |
Collapse
|
6
|
Intrinsic and extrinsic regulation of cardiac lipoprotein lipase following diabetes. Biochim Biophys Acta Mol Cell Biol Lipids 2014; 1851:163-71. [PMID: 25463481 DOI: 10.1016/j.bbalip.2014.11.007] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2014] [Revised: 11/10/2014] [Accepted: 11/12/2014] [Indexed: 02/07/2023]
Abstract
Cardiac lipoprotein lipase (LPL) is a pivotal enzyme controlling heart metabolism by providing the majority of fatty acids required by this organ. From activation in cardiomyocytes to secretion to the vascular lumen, cardiac LPL is regulated by multiple pathways, which are altered during diabetes. Hence, dimerization/activation of LPL is modified following diabetes, a process controlled by lipase maturation factor 1. The role of AMP-activated protein kinase, protein kinase D, and heparan sulfate proteoglycans, intrinsic factors that regulate the intracellular transport of LPL is also shifted, and is discussed. More recent studies have identified several exogenous factors released from endothelial cells (EC) and adipose tissue that are required for proper functioning of LPL. In response to hyperglycemia, both active and latent heparanase are released from EC to facilitate LPL secretion. Diabetes also increased the expression of glycosylphosphatidylinositol-anchored high density lipoprotein-binding protein 1 (GPIHBP1) in EC, which mediates the transport of LPL across EC. Angiopoietin-like protein 4 secreted from the adipose tissue has the potential to reduce coronary LPL activity. Knowledge of these intrinsic and extrinsic factors could be used develop therapeutic targets to normalize LPL function, and maintain cardiac energy homeostasis after diabetes.
Collapse
|
7
|
Kuivenhoven JA, Hegele RA. Mining the genome for lipid genes. Biochim Biophys Acta Mol Basis Dis 2014; 1842:1993-2009. [PMID: 24798233 DOI: 10.1016/j.bbadis.2014.04.028] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2014] [Revised: 04/22/2014] [Accepted: 04/27/2014] [Indexed: 12/12/2022]
Abstract
Mining of the genome for lipid genes has since the early 1970s helped to shape our understanding of how triglycerides are packaged (in chylomicrons), repackaged (in very low density lipoproteins; VLDL), and hydrolyzed, and also how remnant and low-density lipoproteins (LDL) are cleared from the circulation. Gene discoveries have also provided insights into high-density lipoprotein (HDL) biogenesis and remodeling. Interestingly, at least half of these key molecular genetic studies were initiated with the benefit of prior knowledge of relevant proteins. In addition, multiple important findings originated from studies in mouse, and from other types of non-genetic approaches. Although it appears by now that the main lipid pathways have been uncovered, and that only modulators or adaptor proteins such as those encoded by LDLRAP1, APOA5, ANGPLT3/4, and PCSK9 are currently being discovered, genome wide association studies (GWAS) in particular have implicated many new loci based on statistical analyses; these may prove to have equally large impacts on lipoprotein traits as gene products that are already known. On the other hand, since 2004 - and particularly since 2010 when massively parallel sequencing has become de rigeur - no major new insights into genes governing lipid metabolism have been reported. This is probably because the etiologies of true Mendelian lipid disorders with overt clinical complications have been largely resolved. In the meantime, it has become clear that proving the importance of new candidate genes is challenging. This could be due to very low frequencies of large impact variants in the population. It must further be emphasized that functional genetic studies, while necessary, are often difficult to accomplish, making it hazardous to upgrade a variant that is simply associated to being definitively causative. Also, it is clear that applying a monogenic approach to dissect complex lipid traits that are mostly of polygenic origin is the wrong way to proceed. The hope is that large-scale data acquisition combined with sophisticated computerized analyses will help to prioritize and select the most promising candidate genes for future research. We suggest that at this point in time, investment in sequence technology driven candidate gene discovery could be recalibrated by refocusing efforts on direct functional analysis of the genes that have already been discovered. This article is part of a Special Issue entitled: From Genome to Function.
Collapse
Affiliation(s)
- Jan Albert Kuivenhoven
- University of Groningen, University Medical Center Groningen, Department of Pediatrics, Section Molecular Genetics, Antonius Deusinglaan 1, 9713GZ Groningen, The Netherlands
| | - Robert A Hegele
- Blackburn Cardiovascular Genetics Laboratory, Robarts Research Institute, 4288A-1151 Richmond Street North, London, ON N6A 5B7, Canada
| |
Collapse
|
8
|
Donahoo WT, Stob NR, Ammon S, Levin N, Eckel RH. Leptin increases skeletal muscle lipoprotein lipase and postprandial lipid metabolism in mice. Metabolism 2011; 60:438-43. [PMID: 20494377 DOI: 10.1016/j.metabol.2010.03.016] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/05/2009] [Revised: 11/23/2009] [Accepted: 03/23/2010] [Indexed: 11/16/2022]
Abstract
The ability of leptin to preserve lean tissue during weight loss may be in part due to differences in nutrient partitioning. Because lipoprotein lipase (LPL) plays a key role in partitioning lipid nutrients, this study was conducted to test the hypothesis that leptin would modify the tissue-specific regulation of LPL and result in increased lipid oxidation and decreased storage. The effects of daily intraperitoneal leptin injections (2 mg/kg body weight) over 2 weeks on LPL activity and postprandial lipid metabolism were tested in both wild-type (WT), leptin-deficient ob/ob obese mice and mice pair fed to the leptin-treated mice. On the experimental day, mice were given food by gavage, blood was drawn periodically, and adipose tissue and skeletal muscle were harvested for measurements of LPL activity at 240 minutes. After 2 weeks of leptin administration, skeletal muscle LPL (SMLPL) activity was increased in leptin-treated compared with pair-fed (P = .012) and WT (P = .002) mice. There was no effect of leptin or pair feeding on postprandial adipose tissue LPL activity. In ob/ob mice, leptin treatment normalized the decrease in postprandial free fatty acid concentration (P = .066). Leptin had no effect on either the area under the triglyceride (TG) excursion or the integrated area under the TG excursion in WT mice. In ob/ob mice, however, the TG excursion was lower in the leptin-treated than the pair-fed mice by area under the TG excursion (P = .012) and was lower than in the WT mice by integrated area under the TG excursion (P = .027). As expected, 2 weeks of leptin treatment decreased body weight in both the WT and ob/ob mice (-2.6% and -10.4%, respectively). Leptin treatment increased SMLPL, an effect that may have contributed to the leptin-induced weight loss. The leptin-induced decreased postprandial TG excursion in ob/ob mice suggests that leptin acts to augment clearance of postprandial TG-rich lipoprotein lipid and that this increase may in part be secondary to the increased activity of SMLPL. The trend for decreased postprandial free fatty acid may indicate that leptin decreases adipose tissue lipid stores without increasing lipolysis.
Collapse
Affiliation(s)
- William T Donahoo
- Division of Endocrinology, Metabolism, and Diabetes, University of Colorado Denver, 12801 East 17th Avenue, Mail Stop 8106, Aurora, CO 80045, USA
| | | | | | | | | |
Collapse
|
9
|
Wang BF, Tian PY, Feng K, Wu FR, Lu YG, Yang Y. Role of insulin resistance in the pathogenesis of nonalcoholic fatty liver disease. Shijie Huaren Xiaohua Zazhi 2010; 18:3175-3180. [DOI: 10.11569/wcjd.v18.i30.3175] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
AIM: To investigate the role of insulin resistance (IR) in the pathogenesis of nonalcoholic fatty liver disease in rats.
METHODS: Spraque-Dawley rats were randomly divided into normal control group and model group. The model group was fed a high-fat cholesterol-rich diet for 8 wk to induce nonalcoholic fatty liver disease and insulin resistance. The model group was further divided randomly into two equal subgroups: model control subgroup and therapeutic subgroup. Physiological saline and rosiglitazone maleate were given to the model control subgroup and therapeutic subgroup for 4 wk, respectively. Hepatic histological changes were then observed. Fasting plasma glucose, fasting insulin, plasma ApoC II and ApoC III were determined to calculate insulin resistance index. The activity of lipoprotein lipase and hepatic lipase was measured, and the expression of ApoB-100 mRNA was detected.
RESULTS: Compared with the normal control group, the body mass, fasting plasma glucose, fasting insulin and insulin resistance index were significantly higher in the model control subgroup and therapeutic subgroup (fasting plasma glucose: 6.46 mmol/L ± 0.75 mmol/L, 6.61 mmol/L ± 0.45 mmol/L vs 5.48 mmol/L ± 0.47 mmol/L; fasting insulin: 78.82 mU/L ± 11.13 mU/L, 78.48 mU/L ± 12.94 mU/L vs 40.90 mU/L ± 7.76 mU/L; insulin resistance index: 22.48 ± 2.81, 22.98 ± 3.47 vs 9.85 ± 1.15; all P < 0.05). Histological analysis revealed that the rats of the model control subgroup and therapeutic subgroup met the diagnostic criteria for fatty liver. Compared with the model control subgroup, hepatic histological changes were milder in the therapeutic subgroup. Treatment with rosiglitazone maleate significantly lowered the fasting plasma glucose (6.01 mmol/L ± 0.56 mmol/L vs 6.43 mmol/L ± 0.47 mmol/L), fasting insulin (68.11 mU/L ± 10.52 mU/L vs 82.48 mU/L ± 15.20 mU/L), insulin resistance index (18.49 ± 2.44 vs 23.39 ± 3.16) and plasma ApoC III level, but increased plasma ApoC II level and the activity of lipoprotein lipase.
CONCLUSION: Improvement of insulin resistance in fatty liver rats can improve the activity of lipoprotein lipase and hepatic lipase by altering plasma ApoC II and ApoC III levels, promote the degradation of peripheral very low-density lipoprotein and triglycerides, up-regulate hepatic expression of ApoB-100 mRNA, facilitate the synthesis of very low-density lipoprotein in the liver and the transport of endogenous triglycerides, and lessen fatty infiltration of the liver.
Collapse
|
10
|
Drager LF, Jun JC, Polotsky VY. Metabolic consequences of intermittent hypoxia: relevance to obstructive sleep apnea. Best Pract Res Clin Endocrinol Metab 2010; 24:843-51. [PMID: 21112030 PMCID: PMC3011976 DOI: 10.1016/j.beem.2010.08.011] [Citation(s) in RCA: 160] [Impact Index Per Article: 11.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Obstructive sleep apnea (OSA) is recurrent obstruction of the upper airway leading to sleep fragmentation and intermittent hypoxia (IH) during sleep. There is growing evidence from animal models of OSA that IH is independently associated with metabolic dysfunction, including dyslipidemia and insulin resistance. The precise mechanisms by which IH induces metabolic disturbances are not fully understood. Over the last decade, several groups of investigators developed a rodent model of IH, which emulates the oxyhemoglobin profile in human OSA. In the mouse model, IH induces dyslipidemia, insulin resistance and pancreatic endocrine dysfunction, similar to those observed in human OSA. Recent reports provided new insights in possible mechanisms by which IH affects lipid and glucose metabolism. IH may induce dyslipidemia by up-regulating lipid biosynthesis in the liver, increasing adipose tissue lipolysis with subsequent free fatty acid flux to the liver, and inhibiting lipoprotein clearance. IH may affect glucose metabolism by inducing sympathetic activation, increasing systemic inflammation, increasing counter-regulatory hormones and fatty acids, and causing direct pancreatic beta-cell injury. IH models of OSA have improved our understanding of the metabolic impact of OSA, but further studies are needed before we can translate recent basic research findings to clinical practice.
Collapse
Affiliation(s)
- Luciano F Drager
- Division of Pulmonary and Critical Care Medicine, Johns Hopkins University School of Medicine, Johns Hopkins Asthma and Allergy Center, 5501 Hopkins Bayview Circle, Baltimore, MD 21224, USA
| | | | | |
Collapse
|
11
|
Abstract
Lipoprotein lipase (LPL) is a multifunctional enzyme produced by many tissues, including adipose tissue, cardiac and skeletal muscle, islets, and macrophages. LPL is the rate-limiting enzyme for the hydrolysis of the triglyceride (TG) core of circulating TG-rich lipoproteins, chylomicrons, and very low-density lipoproteins (VLDL). LPL-catalyzed reaction products, fatty acids, and monoacylglycerol are in part taken up by the tissues locally and processed differentially; e.g., they are stored as neutral lipids in adipose tissue, oxidized, or stored in skeletal and cardiac muscle or as cholesteryl ester and TG in macrophages. LPL is regulated at transcriptional, posttranscriptional, and posttranslational levels in a tissue-specific manner. Nutrient states and hormonal levels all have divergent effects on the regulation of LPL, and a variety of proteins that interact with LPL to regulate its tissue-specific activity have also been identified. To examine this divergent regulation further, transgenic and knockout murine models of tissue-specific LPL expression have been developed. Mice with overexpression of LPL in skeletal muscle accumulate TG in muscle, develop insulin resistance, are protected from excessive weight gain, and increase their metabolic rate in the cold. Mice with LPL deletion in skeletal muscle have reduced TG accumulation and increased insulin action on glucose transport in muscle. Ultimately, this leads to increased lipid partitioning to other tissues, insulin resistance, and obesity. Mice with LPL deletion in the heart develop hypertriglyceridemia and cardiac dysfunction. The fact that the heart depends increasingly on glucose implies that free fatty acids are not a sufficient fuel for optimal cardiac function. Overall, LPL is a fascinating enzyme that contributes in a pronounced way to normal lipoprotein metabolism, tissue-specific substrate delivery and utilization, and the many aspects of obesity and other metabolic disorders that relate to energy balance, insulin action, and body weight regulation.
Collapse
Affiliation(s)
- Hong Wang
- Division of Endocrinology, Metabolism and Diabetes, University of Colorado Denver Anschutz Medical Campus, Aurora, Colorado 80045, USA
| | | |
Collapse
|