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Ghosh SS, Wang J, Ghosh S. Measurement of In Vivo VLDL and Chylomicron Secretion. Methods Mol Biol 2022; 2455:63-71. [PMID: 35212986 DOI: 10.1007/978-1-0716-2128-8_6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
Intestinal lipid absorption as well as secretion of absorbed lipids as chylomicrons by the enterocytes is a direct measure of the availability of dietary lipids. Measurement of this parameter is central to the understanding of the influence of diet on plasma lipids, specifically when modulation of intestinal lipid absorption by targeted interventions is being examined. In the post-prandial state, very low-density lipoprotein (VLDL) secreted from the liver represent the major source of plasma lipids and rate of VLDL secretion reports on hepatic lipid homeostasis. Here, we describe the methods to specifically measure secretion of chylomicron and VLDL in vivo. Tight regulation of dietary lipid absorption (chylomicron secretion) and hepatic secretion of VLDL underlies the development of dyslipidemia preceding hepatic lipid accumulation seen in non-alcoholic fatty liver disease (NAFLD) and subsequent progression to non-alcoholic steatohepatitis (NASH) underscoring the importance of measurement of lipoprotein secretion in vivo.
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Affiliation(s)
- Siddhartha S Ghosh
- Department of Internal Medicine, Virginia Commonwealth University Medical Center, Richmond, VA, USA
| | - Jing Wang
- Department of Internal Medicine, Virginia Commonwealth University Medical Center, Richmond, VA, USA
| | - Shobha Ghosh
- Department of Internal Medicine, Virginia Commonwealth University Medical Center, Richmond, VA, USA.
- Hunter Holmes McGuire VA Medical Center, Richmond, VA, USA.
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2
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Palmisano BT, Yu S, Neuman JC, Zhu L, Luu T, Stafford JM. Low-density lipoprotein receptor is required for cholesteryl ester transfer protein to regulate triglyceride metabolism in both male and female mice. Physiol Rep 2021; 9:e14732. [PMID: 33625789 PMCID: PMC7903989 DOI: 10.14814/phy2.14732] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2020] [Revised: 12/30/2020] [Accepted: 01/04/2021] [Indexed: 11/24/2022] Open
Abstract
Elevated triglycerides (TGs) and impaired TG clearance increase the risk of cardiovascular disease in both men and women, but molecular mechanisms remain poorly understood. Cholesteryl ester transfer protein (CETP) is a lipid shuttling protein known for its effects on high-density lipoprotein cholesterol. Although mice lack CETP, transgenic expression of CETP in mice alters TG metabolism in males and females by sex-specific mechanisms. A unifying mechanism explaining how CETP alters TG metabolism in both males and females remains unknown. Since low-density lipoprotein receptor (LDLR) regulates both TG clearance and very low density lipoprotein (VLDL) production, LDLR may be involved in CETP-mediated alterations in TG metabolism in both males and females. We hypothesize that LDLR is required for CETP to alter TG metabolism in both males and females. We used LDLR null mice with and without CETP to demonstrate that LDLR is required for CETP to raise plasma TGs and to impair TG clearance in males. We also demonstrate that LDLR is required for CETP to increase TG production and to increase the expression and activity of VLDL synthesis targets in response to estrogen. Additionally, we show that LDLR is required for CETP to enhance β-oxidation. These studies support that LDLR is required for CETP to regulate TG metabolism in both males and females.
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Affiliation(s)
- Brian T. Palmisano
- Tennessee Valley Health SystemVeterans AffairsNashvilleTNUSA
- Department of Molecular Physiology & BiophysicsVanderbilt University School of MedicineNashvilleTNUSA
- Division of Cardiovascular MedicineStanford University Medical CenterStanfordCAUSA
| | - Sophia Yu
- Department of MedicineDivision of Diabetes, Endocrinology and MetabolismVanderbilt University Medical CenterNashvilleTNUSA
| | - Joshua C. Neuman
- Department of Molecular Physiology & BiophysicsVanderbilt University School of MedicineNashvilleTNUSA
| | - Lin Zhu
- Department of MedicineDivision of Diabetes, Endocrinology and MetabolismVanderbilt University Medical CenterNashvilleTNUSA
| | - Thao Luu
- Tennessee Valley Health SystemVeterans AffairsNashvilleTNUSA
- Department of MedicineDivision of Diabetes, Endocrinology and MetabolismVanderbilt University Medical CenterNashvilleTNUSA
| | - John M. Stafford
- Tennessee Valley Health SystemVeterans AffairsNashvilleTNUSA
- Department of Molecular Physiology & BiophysicsVanderbilt University School of MedicineNashvilleTNUSA
- Department of MedicineDivision of Diabetes, Endocrinology and MetabolismVanderbilt University Medical CenterNashvilleTNUSA
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3
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He H, Wang J, Yannie PJ, Kakiyama G, Korzun WJ, Ghosh S. Sterol carrier protein-2 deficiency attenuates diet-induced dyslipidemia and atherosclerosis in mice. J Biol Chem 2018; 293:9223-9231. [PMID: 29700117 DOI: 10.1074/jbc.ra118.002290] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2018] [Revised: 04/25/2018] [Indexed: 01/05/2023] Open
Abstract
Intracellular cholesterol transport proteins move cholesterol to different subcellular compartments and thereby regulate its final metabolic fate. In hepatocytes, for example, delivery of high-density lipoprotein (HDL)-associated cholesterol for bile acid synthesis or secretion into bile facilitates cholesterol elimination from the body (anti-atherogenic effect), whereas delivery for esterification and subsequent incorporation into apolipoprotein B-containing atherogenic lipoproteins (e.g. very-low-density lipoprotein (VLDL)) enhances cholesterol secretion into the systemic circulation (pro-atherogenic effect). Intracellular cholesterol transport proteins such as sterol carrier protein-2 (SCP2) should, therefore, play a role in regulating these pro- or anti-atherosclerotic processes. Here, we sought to evaluate the effects of SCP2 deficiency on the development of diet-induced atherosclerosis. We generated LDLR-/- mice deficient in SCP2/SCPx (LS) and examined the effects of this deficiency on Western diet-induced atherosclerosis. SCP2/SCPx deficiency attenuated atherosclerosis in LS mice by >80% and significantly reduced plasma cholesterol and triglyceride levels. Investigation of the likely underlying mechanisms revealed a significant reduction in intestinal cholesterol absorption (given as an oral gavage) in SCP2/SCPx-deficient mice. Consistently, siRNA-mediated knockdown of SCP2 in intestinal cells significantly reduced cholesterol uptake. Furthermore, hepatic triglyceride/VLDL secretion from the liver or hepatocytes isolated from SCP2/SCPx-deficient mice was significantly reduced. These results indicate an important regulatory role for SCP2 deficiency in attenuating diet-induced atherosclerosis by limiting intestinal cholesterol absorption and decreasing hepatic triglyceride/VLDL secretion. These findings suggest targeted inhibition of SCP2 as a potential therapeutic strategy to reduce Western diet-induced dyslipidemia and atherosclerosis.
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Affiliation(s)
| | - Jing Wang
- From the Departments of Internal Medicine and
| | - Paul J Yannie
- the Hunter Homes McGuire Veterans Affairs Medical Center, Richmond, Virginia 23249
| | - Genta Kakiyama
- the Hunter Homes McGuire Veterans Affairs Medical Center, Richmond, Virginia 23249
| | - William J Korzun
- Clinical and Laboratory Sciences, Virginia Commonwealth University (VCU) Medical Center, Richmond, Virginia 23298 and
| | - Shobha Ghosh
- From the Departments of Internal Medicine and .,the Hunter Homes McGuire Veterans Affairs Medical Center, Richmond, Virginia 23249
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4
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Hetherington AM, Sawyez CG, Sutherland BG, Robson DL, Arya R, Kelly K, Jacobs RL, Borradaile NM. Treatment with didemnin B, an elongation factor 1A inhibitor, improves hepatic lipotoxicity in obese mice. Physiol Rep 2017; 4:4/17/e12963. [PMID: 27613825 PMCID: PMC5027364 DOI: 10.14814/phy2.12963] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2016] [Accepted: 08/18/2016] [Indexed: 12/12/2022] Open
Abstract
Eukaryotic elongation factor EEF1A1 is induced by oxidative and ER stress, and contributes to subsequent cell death in many cell types, including hepatocytes. We recently showed that blocking the protein synthesis activity of EEF1A1 with the peptide inhibitor, didemnin B, decreases saturated fatty acid overload-induced cell death in HepG2 cells. In light of this and other recent work suggesting that limiting protein synthesis may be beneficial in treating ER stress-related disease, we hypothesized that acute intervention with didemnin B would decrease hepatic ER stress and lipotoxicity in obese mice with nonalcoholic fatty liver disease (NAFLD). Hyperphagic male ob/ob mice were fed semipurified diet for 4 weeks, and during week 5 received i.p. injections of didemnin B or vehicle on days 1, 4, and 7. Interestingly, we observed that administration of this compound modestly decreased food intake without evidence of illness or distress, and thus included an additional control group matched for food consumption with didemnin B-treated animals. Treatment with didemnin B improved several characteristics of hepatic lipotoxicity to a greater extent than the effects of caloric restriction alone, including hepatic steatosis, and some hepatic markers of ER stress and inflammation (GRP78, Xbp1s, and Mcp1). Plasma lipid and lipoprotein profiles and histopathological measures of NAFLD, including lobular inflammation, and total NAFLD activity score were also improved by didemnin B. These data indicate that acute intervention with the EEF1A inhibitor, didemnin B, improves hepatic lipotoxicity in obese mice with NAFLD through mechanisms not entirely dependent on decreased food intake, suggesting a potential therapeutic strategy for this ER stress-related disease.
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Affiliation(s)
- Alexandra M Hetherington
- Department of Physiology and Pharmacology, Schulich School of Medicine and Dentistry Western University, London, Ontario, Canada
| | - Cynthia G Sawyez
- Department of Physiology and Pharmacology, Schulich School of Medicine and Dentistry Western University, London, Ontario, Canada Robarts Research Institute, Schulich School of Medicine and Dentistry Western University, London, Ontario, Canada Department of Medicine, Schulich School of Medicine and Dentistry Western University, London, Ontario, Canada
| | - Brian G Sutherland
- Robarts Research Institute, Schulich School of Medicine and Dentistry Western University, London, Ontario, Canada
| | - Debra L Robson
- Department of Physiology and Pharmacology, Schulich School of Medicine and Dentistry Western University, London, Ontario, Canada
| | - Rigya Arya
- Department of Physiology and Pharmacology, Schulich School of Medicine and Dentistry Western University, London, Ontario, Canada
| | - Karen Kelly
- Metabolic and Cardiovascular Diseases Laboratory, Department of Agricultural, Food and Nutritional Science, University of Alberta, Edmonton, Alberta, Canada
| | - René L Jacobs
- Metabolic and Cardiovascular Diseases Laboratory, Department of Agricultural, Food and Nutritional Science, University of Alberta, Edmonton, Alberta, Canada
| | - Nica M Borradaile
- Department of Physiology and Pharmacology, Schulich School of Medicine and Dentistry Western University, London, Ontario, Canada
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Fukuda N, Ito T, Ohwada K, Fujii J. Upregulation of fatty acid synthesis and the suppression of hepatic triglyceride lipase as a direct cause of hereditary postprandial hypertriglyceridemia in rabbits. J Clin Biochem Nutr 2013; 53:114-21. [PMID: 24062609 PMCID: PMC3774926 DOI: 10.3164/jcbn.13-21] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2013] [Accepted: 06/16/2013] [Indexed: 12/03/2022] Open
Abstract
Rabbits with hereditary postprandial hypertriglyceridemia exhibit central obesity and are regarded as a reliable model for metabolic syndrome. This study was performed to gain insight into the affected process of lipid metabolism and into the causative genes of the postprandial hypertriglyceridemia rabbits. Eleven genes that play key roles in lipid metabolism were selected, their mRNA levels were assessed by quantitative PCR, and their expressions were compared among postprandial hypertriglyceridemia rabbits using Japanese white rabbits as the control. Two genes appeared to be in causal connection with postprandial hypertriglyceridemia, and these were regarded as likely candidates for the pathogenesis. One was the fatty acid synthase gene, which had an expression constitutively higher in postprandial hypertriglyceridemia rabbits than in Japanese white rabbits during the fasting state and reached quite high levels after feeding. The other was the gene for hepatic triglyceride lipase with an expression that was approximately one order lower than that found in the Japanese white rabbits. The low plasma hepatic triglyceride lipase activities were consistent with the low levels of the transcript in the livers of the postprandial hypertriglyceridemia rabbits. Thus, elevated fatty acid synthesis and defected lipid hydrolysis together would cause the postprandial hypertriglyceridemia in postprandial hypertriglyceridemia rabbits.
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Affiliation(s)
- Naoki Fukuda
- Department of Biochemistry and Molecular Biology, Graduate School of Medical Science, Yamagata University, 2-2-2 Iidanishi, Yamagata 990-9585, Japan
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6
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Gu P, Jiang W, Chen M, Lu B, Shao J, Du H, Jiang S. Association of leptin receptor gene polymorphisms and essential hypertension in a Chinese population. J Endocrinol Invest 2012; 35:859-65. [PMID: 22293279 DOI: 10.3275/8238] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
BACKGROUND The leptin receptor (LEPR) is an important regulator of leptin activity and resistance. Several single nucleotide polymorphisms (SNP) of LEPR have been linked to diseases accompanying obesity and/or obesity-related diseases in different populations. However, the results from published studies remain inconsistent rather than conclusive. AIM To investigate whether LEPR SNP are associated with essential hypertension and related metabolic traits in Chinese subjects. MATERIALS AND METHODS A total of 544 Chinese patients with hypertension and 357 non-hypertensive subjects were screened. The genotypes of LEPR polymorphisms were determined by PCR-restriction fragment length polymorphism methods. Demographic and biochemical characteristics including waist circumference, waist-to-hip ratio, body mass index (BMI), lipids profiles, glucose metabolism, and leptin levels were obtained for analysis. RESULTS This case-control study showed associations between the frequencies of AA genotype and A allele of Gln223Arg and hypertension (p=0.029, p=0.002, respectively). Furthermore, the Gln223Arg polymorphism was significantly associated with plasma leptin levels (p<0.001), while no correlations between Lys109Arg SNP and hypertension were found. Multivariate logistic regression analysis evidenced that A allele carriers of Gln223Arg (AA+AG) showed higher risks of hypertension than GG carriers after adjustment of age and sex (adjusted odds ratio: 1.549, 95% confidence interval: 1.031- 2.036, p=0.035). BMI, fasting serum insulin, oral glucose tolernace test (OGTT)-2h glucose, serum leptin, as well as LDL-cholesterol (LDL-C) levels were also independent risk factors of hypertension in this population. In addition, significant associations were observed between the Gln223Arg and Lys109Arg SNP and serum total cholesterol, LDL-C, and fasting plasma glucose levels in hypertensive patients. Besides, A allele of Gln223Arg had raised diastolic blood pressure, compared with GG carriers (p=0.001). While variance of Lys109Arg was associated with waist-to-hip ratio, OGTT-2h glucose, and homeostasis model assessment of insulin resistance (p<0.05). CONCLUSIONS LEPR polymorphisms may be a marker for susceptibility to essential hypertension in Chinese subjects, and be involved in the development of several features including dyslipidemia and impaired glucose regulation in hypertension subjects.
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Affiliation(s)
- P Gu
- Department of Endocrinology, Nanjing General Hospital of Nanjing Command, Jiangsu Province, PR China
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7
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Murali G, Milne GL, Webb CD, Stewart AB, McMillan RP, Lyle BC, Hulver MW, Saraswathi V. Fish oil and indomethacin in combination potently reduce dyslipidemia and hepatic steatosis in LDLR(-/-) mice. J Lipid Res 2012; 53:2186-2197. [PMID: 22847176 DOI: 10.1194/jlr.m029843] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
Abstract
Fish oil (FO) is a potent anti-inflammatory and lipid-lowering agent. Because inflammation can modulate lipid metabolism and vice versa, we hypothesized that combining FO with cyclooxygenase inhibitors (COXIBs), well-known anti-inflammatory drugs, can enhance the anti-inflammatory and lipid-lowering effect of FO. LDLR(-/-) mice were fed a high-fat diet supplemented with 6% olive oil or FO for 12 wk in the presence or absence of indomethacin (Indo, 6 mg/l drinking water). FO reduced plasma total cholesterol by 30% but, in combination with Indo, exerted a greater decrease (44%). The reduction of liver cholesterol ester (CE) and triglycerides (TG) by FO (63% and 41%, respectively) was enhanced by Indo (80% in CE and 64% in TG). FO + Indo greatly increased the expression of genes modulating lipid metabolism and reduced the expression of inflammatory genes compared with control. The mRNA and/or protein expression of pregnane X receptor (PXR) and cytochrome P450 isoforms that alter inflammation and/or lipid metabolism are increased to a greater extent in mice that received FO + Indo. Moroever, the nuclear level of PXR is significantly increased in FO + Indo group. Combining FO with COXIBs may exert their beneficial effects on inflammation and lipid metabolism via PXR and cytochrome P450.
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Affiliation(s)
- Ganesan Murali
- Division of Diabetes, Endocrinology and Metabolism, University of Nebraska Medical Center and the VA Nebraska Western Iowa Health Care System, Omaha, NE
| | - Ginger L Milne
- Department of Clinical Pharmacology, Vanderbilt University Medical Center, Nashville, TN
| | - Corey D Webb
- Department of Molecular Physiology and Biophysics, Vanderbilt University Medical Center, Nashville, TN; and
| | - Ann B Stewart
- Department of Molecular Physiology and Biophysics, Vanderbilt University Medical Center, Nashville, TN; and
| | - Ryan P McMillan
- Department of Human Nutrition, Foods, and Exercise and The Virginia Tech Metabolic Phenotyping Core, Virginia Polytechnic Institute and State University, Blacksburg, VA
| | - Brandon C Lyle
- Department of Molecular Physiology and Biophysics, Vanderbilt University Medical Center, Nashville, TN; and
| | - Matthew W Hulver
- Department of Human Nutrition, Foods, and Exercise and The Virginia Tech Metabolic Phenotyping Core, Virginia Polytechnic Institute and State University, Blacksburg, VA
| | - Viswanathan Saraswathi
- Department of Molecular Physiology and Biophysics, Vanderbilt University Medical Center, Nashville, TN; and.
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8
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Bie J, Zhao B, Marqueen KE, Wang J, Szomju B, Ghosh S. Macrophage-specific transgenic expression of cholesteryl ester hydrolase attenuates hepatic lipid accumulation and also improves glucose tolerance in ob/ob mice. Am J Physiol Endocrinol Metab 2012; 302:E1283-91. [PMID: 22395110 PMCID: PMC3361987 DOI: 10.1152/ajpendo.00511.2011] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Cellular cholesterol homeostasis is increasingly being recognized as an important determinant of the inflammatory status of macrophages, and a decrease in cellular cholesterol levels polarizes macrophages toward an anti-inflammatory or M2 phenotype. Cholesteryl ester hydrolase (CEH) catalyzes the hydrolysis of stored intracellular cholesteryl esters (CE) and thereby enhances free cholesterol efflux and reduces cellular CE content. We have reported earlier reduced atherosclerosis as well as lesion necrosis and improved insulin sensitivity (due to decreased adipose tissue inflammation) in macrophage-specific CEH transgenic (CEHTg) mice in the LDLR(-/-) background. In the present study, we examined the effects of reduced intracellular accumulation of CE in CEHTg macrophages in an established diabetic mouse model, namely the leptin-deficient ob/ob mouse. Macrophage-specific transgenic expression of CEH improved glucose tolerance in ob/ob-CEHTg mice significantly compared with ob/ob nontransgenic littermates, but with no apparent change in macrophage infiltration into the adipose tissue. However, there was a significant decrease in hepatic lipid accumulation in ob/ob-CEHTg mice. Consistently, decreased [(14)C]acetate incorporation into total lipids and triglycerides was noted in precision-cut liver slices from ob/ob-CEHTg mice. In the primary hepatocyte-macrophage coculture system, macrophages from CEHTg mice significantly reduced the incorporation of [(14)C]acetate into triglycerides in hepatocytes, indicating a direct effect of macrophages on hepatocyte triglyceride biosynthesis. Kupffer cells isolated from ob/ob-CEHTg mice were polarized toward an anti-inflammatory M2 (Ly6C(lo)) phenotype. Taken together, these studies demonstrate that transgenic overexpression of CEH in macrophages polarizes hepatic macrophages (Kupffer cells) to an anti-inflammatory M2 phenotype that attenuates hepatic lipid synthesis and accumulation.
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Affiliation(s)
- Jinghua Bie
- Dept. of Internal Medicine, Div. of Pulmonary and Critical Care, VCU Medical Center, Richmond, VA 23298-0050, USA
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9
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The 223A>G polymorphism of the leptin receptor gene is associated with macroangiopathy in type 2 diabetes mellitus. Mol Biol Rep 2011; 39:4759-64. [DOI: 10.1007/s11033-011-1268-2] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2011] [Accepted: 09/14/2011] [Indexed: 12/22/2022]
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10
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Kennedy AJ, Ellacott KLJ, King VL, Hasty AH. Mouse models of the metabolic syndrome. Dis Model Mech 2010; 3:156-66. [PMID: 20212084 DOI: 10.1242/dmm.003467] [Citation(s) in RCA: 181] [Impact Index Per Article: 12.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
The metabolic syndrome (MetS) is characterized by obesity concomitant with other metabolic abnormalities such as hypertriglyceridemia, reduced high-density lipoprotein levels, elevated blood pressure and raised fasting glucose levels. The precise definition of MetS, the relationships of its metabolic features, and what initiates it, are debated. However, obesity is on the rise worldwide, and its association with these metabolic symptoms increases the risk for diabetes and cardiovascular disease (among many other diseases). Research needs to determine the mechanisms by which obesity and MetS increase the risk of disease. In light of this growing epidemic, it is imperative to develop animal models of MetS. These models will help determine the pathophysiological basis for MetS and how MetS increases the risk for other diseases. Among the various animal models available to study MetS, mice are the most commonly used for several reasons. First, there are several spontaneously occurring obese mouse strains that have been used for decades and that are very well characterized. Second, high-fat feeding studies require only months to induce MetS. Third, it is relatively easy to study the effects of single genes by developing transgenic or gene knockouts to determine the influence of a gene on MetS. For these reasons, this review will focus on the benefits and caveats of the most common mouse models of MetS. It is our hope that the reader will be able to use this review as a guide for the selection of mouse models for their own studies.
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Affiliation(s)
- Arion J Kennedy
- Department of Molecular Physiology, Vanderbilt University Medical Center, Nashville, TN 37232, USA
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11
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Sundaram M, Yao Z. Recent progress in understanding protein and lipid factors affecting hepatic VLDL assembly and secretion. Nutr Metab (Lond) 2010; 7:35. [PMID: 20423497 PMCID: PMC2873297 DOI: 10.1186/1743-7075-7-35] [Citation(s) in RCA: 118] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2009] [Accepted: 04/27/2010] [Indexed: 02/06/2023] Open
Abstract
Excess lipid induced metabolic disorders are one of the major existing challenges for the society. Among many different causes of lipid disorders, overproduction and compromised catabolism of triacylglycerol-rich very low density lipoproteins (VLDL) have become increasingly prevalent leading to hyperlipidemia worldwide. This review provides the latest understanding in different aspects of VLDL assembly process, including structure-function relationships within apoB, mutations in APOB causing hypobetalipoproteinemia, significance of modulating microsomal triglyceride-transfer protein activity in VLDL assembly, alterations of VLDL assembly by different fatty acid species, and hepatic proteins involved in vesicular trafficking, and cytosolic lipid droplet metabolism that contribute to VLDL assembly. The role of lipoprotein receptors and exchangeable apolipoproteins that promote or diminish VLDL assembly and secretion is discussed. New understanding on dysregulated insulin signaling as a consequence of excessive triacylglycerol-rich VLDL in the plasma is also presented. It is hoped that a comprehensive view of protein and lipid factors that contribute to molecular and cellular events associated with VLDL assembly and secretion will assist in the identification of pharmaceutical targets to reduce disease complications related to hyperlipidemia.
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Affiliation(s)
- Meenakshi Sundaram
- Department of Biochemistry, Microbiology and Immunology, Ottawa Institute of Systems Biology, University of Ottawa, 451 Smyth Road, Ottawa, Ontario K1H 8M5, Canada
| | - Zemin Yao
- Department of Biochemistry, Microbiology and Immunology, Ottawa Institute of Systems Biology, University of Ottawa, 451 Smyth Road, Ottawa, Ontario K1H 8M5, Canada
- Department of Pathology and Laboratory Medicine, University of Ottawa, 451 Smyth Road, Ottawa, Ontario K1H 8M5, Canada
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12
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Saraswathi V, Morrow JD, Hasty AH. Dietary fish oil exerts hypolipidemic effects in lean and insulin sensitizing effects in obese LDLR-/- mice. J Nutr 2009; 139:2380-6. [PMID: 19864403 PMCID: PMC2777481 DOI: 10.3945/jn.109.111567] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Obesity is often associated with dyslipidemia, insulin resistance, and hypertension. Together, these metabolic perturbations greatly increase the risk of developing cardiovascular disease and diabetes. Although fish oil is a well-established hypolipidemic agent, the mechanisms by which it mediates its lipid-lowering effects are not clear. In addition, it has not been established whether dietary fish oil has different effects in lean and obese mice. LDL receptor deficient (LDLR-/-) and leptin deficient mice on a LDLR-/- background (ob/ob;LDLR-/-) were fed a high fat diet (39% total fat) supplemented with 6% olive oil or fish oil for 6 wk. Fish oil supplementation resulted in lower concentrations of plasma total cholesterol (P < 0.01), triglycerides (P < 0.01), and free fatty acids (P < 0.001) in lean LDLR-/- mice, but not in ob/ob;LDLR-/- mice. In contrast, a fish oil diet did not modulate insulin sensitivity in lean LDLR-/- mice, but it improved insulin sensitivity in ob/ob;LDLR-/- mice (P < 0.05) compared with olive oil fed ob/ob;LDLR-/- mice. Interestingly, plasma adiponectin concentrations were significantly higher and hepatic steatosis was reduced in both mouse models upon fish oil feeding. Finally, fish oil fed LDLR-/- mice exhibited higher hepatic AMP activated protein kinase (AMPK) phosphorylation (P < 0.05), whereas AMPK phosphorylation was not elevated by fish oil feeding in ob/ob;LDLR-/- mice. Taken together, our data suggest that fish oil reduces hepatic steatosis in both lean and obese mice, has potent plasma lipid lowering effects in lean mice, and exerts insulin sensitizing effects in obese mice.
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Affiliation(s)
- Viswanathan Saraswathi
- Department of Molecular Physiology and Biophysics and Division of Clinical Pharmacology, Vanderbilt University Medical Center, Nashville, Tennessee 37232
| | - Jason D. Morrow
- Department of Molecular Physiology and Biophysics and Division of Clinical Pharmacology, Vanderbilt University Medical Center, Nashville, Tennessee 37232
| | - Alyssa H. Hasty
- Department of Molecular Physiology and Biophysics and Division of Clinical Pharmacology, Vanderbilt University Medical Center, Nashville, Tennessee 37232,To whom correspondence should be addressed.
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13
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Sun YM, Wang LF, Li J, Li ZQ, Pan W. The 223A>G polymorphism of the leptin receptor gene and lipid-lowering efficacy of simvastatin in Chinese patients with coronary heart disease. Eur J Clin Pharmacol 2008; 65:157-61. [DOI: 10.1007/s00228-008-0578-3] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2008] [Accepted: 09/29/2008] [Indexed: 12/01/2022]
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14
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Lloyd DJ, McCormick J, Helmering J, Kim KW, Wang M, Fordstrom P, Kaufman SA, Lindberg RA, Véniant MM. Generation and characterization of two novel mouse models exhibiting the phenotypes of the metabolic syndrome: Apob48-/-Lepob/ob mice devoid of ApoE or Ldlr. Am J Physiol Endocrinol Metab 2008; 294:E496-505. [PMID: 18160459 DOI: 10.1152/ajpendo.00509.2007] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
The metabolic syndrome is a group of disorders including obesity, insulin resistance, atherogenic dyslipidemia, hyperglycemia, and hypertension. To date, few animal models have been described to recapitulate the phenotypes of the syndrome. In this study, we generated and characterized two lines of triple-knockout mice that are deficient in either apolipoprotein E (Apoe(-/-)) or low-density lipoprotein receptor (Ldlr(-/-)) and express no leptin (Lep(ob/ob)) or apolipoprotein B-48 but exclusively apolipoprotein B-100 (Apob(100/100)). These two lines are referred to as Apoe triple-knockout-Apoe 3KO (Apoe(-/-)Apob(100/100)Lep(ob/ob)) and Ldlr triple-knockout-Ldlr 3KO (Ldlr(-/-)Apob(100/100)Lep(ob/ob)) mice. Both lines develop obesity, hyperinsulinemia, hyperlipidemia, hypertension, and atherosclerosis. However, only Apoe 3KO mice are hyperglycemic and glucose intolerant and are more obese than Ldlr 3KO mice. To evaluate the utility of these lines as pharmacological models, we treated both with leptin and found that leptin therapy ameliorated most metabolic derangements. Leptin was more effective in improving glucose tolerance in Ldlr 3KO than Apoe 3KO animals. The reduction of plasma cholesterol by leptin in Ldlr 3KO mice can be accounted for by its suppressive effect on food intake. However, in Apoe 3KO mice, leptin further reduced plasma cholesterol independently of its effect on food intake, and this improvement correlated with a smaller plaque lesion area. These effects suggest a direct role of leptin in modulating VLDL levels and, likewise, the lesion areas in VLDL-enriched animals. These two lines of mice represent new models with features of the metabolic syndrome and will be useful in testing therapies targeted for combating the human condition.
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Affiliation(s)
- David J Lloyd
- Department of Metabolic Disorders, Amgen Incorporated, Thousand Oaks, California 91320, USA
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Atkinson RD, Coenen KR, Plummer MR, Gruen ML, Hasty AH. Macrophage-derived apolipoprotein E ameliorates dyslipidemia and atherosclerosis in obese apolipoprotein E-deficient mice. Am J Physiol Endocrinol Metab 2008; 294:E284-90. [PMID: 18029445 DOI: 10.1152/ajpendo.00601.2007] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Previous studies have demonstrated that macrophage-derived apolipoprotein E (apoE) reduces atherosclerotic lesion formation in lean apoE-deficient ((-/-)) mice. apoE has also been demonstrated to play a role in adipocyte differentiation and lipid accumulation. Because the prevalence of obesity has grown to epidemic proportions, we sought to determine whether macrophage-derived apoE could impact atherosclerotic lesion formation or adipose tissue expansion and inflammation in obese apoE(-/-) mice. To this end, we transplanted obese leptin-deficient (ob/ob) apoE(-/-) mice with bone marrow from either ob/ob;apoE(-/-) or ob/ob;apoE(+/+) donors. There were no differences in body weight, total body adipose tissue, or visceral fat pad mass between recipient groups. The presence of macrophage-apoE had no impact on adipose tissue macrophage content or inflammatory cytokine expression. Recipients of apoE(+/+) marrow demonstrated 3.7-fold lower plasma cholesterol (P < 0.001) and 1.7-fold lower plasma triglyceride levels (P < 0.01) by 12 wk after transplantation even though apoE was present in plasma at concentrations <10% of wild-type levels. The reduced plasma lipids reflected a dramatic decrease in very low density lipoprotein and a mild increase in high-density lipoprotein levels. Atherosclerotic lesion area was >10-fold lower in recipients of ob/ob;apoE(+/+) marrow (P < 0.005). Similar results were seen in leptin receptor-deficient (db/db) apoE(-/-) mice. Finally, when bone marrow transplantation was performed in 4-mo-old ob/ob;apoE(-/-) and db/db;apoE(-/-) mice with preexisting lesions, recipients of apoE(+/+) marrow had a 2.8-fold lower lesion area than controls (P = 0.0002). These results demonstrate that macrophage-derived apoE does not impact adipose tissue expansion or inflammatory status; however, even very low levels of macrophage-derived apoE are capable of reducing plasma lipids and atherosclerotic lesion area in obese mice.
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Affiliation(s)
- Robin D Atkinson
- Department of Molecular Physiology and Biophysics, Vanderbilt University Medical Center, Nashville, TN 37232-0615, USA
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