1
|
Ghelani H, Razmovski-Naumovski V, Chang D, Nammi S. Chronic treatment of curcumin improves hepatic lipid metabolism and alleviates the renal damage in adenine-induced chronic kidney disease in Sprague-Dawley rats. BMC Nephrol 2019; 20:431. [PMID: 31752737 PMCID: PMC6873446 DOI: 10.1186/s12882-019-1621-6] [Citation(s) in RCA: 21] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2018] [Accepted: 11/08/2019] [Indexed: 12/17/2022] Open
Abstract
Background Chronic kidney disease (CKD), including nephrotic syndrome, is a major cause of cardiovascular morbidity and mortality. The literature indicates that CKD is associated with profound lipid disorders due to the dysregulation of lipoprotein metabolism which progresses kidney disease. The objective of this study is to evaluate the protective effects of curcumin on dyslipidaemia associated with adenine-induced chronic kidney disease in rats. Methods Male SD rats (n = 29) were divided into 5 groups for 24 days: normal control (n = 5, normal diet), CKD control (n = 6, 0.75% w/w adenine-supplemented diet), CUR 50 (n = 6, 50 mg/kg/day curcumin + 0.75% w/w adenine-supplemented diet), CUR 100 (n = 6, 100 mg/kg/day curcumin + 0.75% w/w adenine-supplemented diet), and CUR 150 (n = 6, 150 mg/kg/day curcumin + 0.75% w/w adenine-supplemented diet). The serum and tissue lipid profile, as well as the kidney function test, were measured using commercial diagnostic kits. Results The marked rise in total cholesterol, low-density lipoprotein (LDL) cholesterol, very low-density lipoprotein (VLDL) cholesterol, triglycerides and free fatty acids in serum, as well as hepatic cholesterol, triglyceride and free fatty acids of CKD control rats were significantly protected by curcumin co-treatment (at the dose of 50, 100 and 150 mg/kg). Furthermore, curcumin significantly increased the serum high-density lipoprotein (HDL) cholesterol compared to the CKD control rats but did not attenuate the CKD-induced weight retardation. Mathematical computational analysis revealed that curcumin significantly reduced indicators for the risk of atherosclerotic lesions (atherogenic index) and coronary atherogenesis (coronary risk index). In addition, curcumin improved kidney function as shown by the reduction in proteinuria and improvement in creatinine clearance. Conclusion The results provide new scientific evidence for the use of curcumin in CKD-associated dyslipidaemia and substantiates the traditional use of curcumin in preventing kidney damage.
Collapse
Affiliation(s)
- Hardik Ghelani
- School of Science and Health, Western Sydney University, Sydney, NSW, 2751, Australia.,NICM Health Research Institute, Western Sydney University, Sydney, NSW, 2751, Australia
| | - Valentina Razmovski-Naumovski
- School of Science and Health, Western Sydney University, Sydney, NSW, 2751, Australia.,NICM Health Research Institute, Western Sydney University, Sydney, NSW, 2751, Australia.,South Western Sydney Clinical School School of Medicine, University of New South Wales, Sydney, NSW, 2052, Australia
| | - Dennis Chang
- School of Science and Health, Western Sydney University, Sydney, NSW, 2751, Australia.,NICM Health Research Institute, Western Sydney University, Sydney, NSW, 2751, Australia
| | - Srinivas Nammi
- School of Science and Health, Western Sydney University, Sydney, NSW, 2751, Australia. .,NICM Health Research Institute, Western Sydney University, Sydney, NSW, 2751, Australia.
| |
Collapse
|
2
|
The Reelin Receptors Apolipoprotein E receptor 2 (ApoER2) and VLDL Receptor. Int J Mol Sci 2018; 19:ijms19103090. [PMID: 30304853 PMCID: PMC6213145 DOI: 10.3390/ijms19103090] [Citation(s) in RCA: 48] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2018] [Revised: 10/03/2018] [Accepted: 10/03/2018] [Indexed: 01/28/2023] Open
Abstract
Apolipoprotein E receptor 2 (ApoER2) and VLDL receptor belong to the low density lipoprotein receptor family and bind apolipoprotein E. These receptors interact with the clathrin machinery to mediate endocytosis of macromolecules but also interact with other adapter proteins to perform as signal transduction receptors. The best characterized signaling pathway in which ApoER2 and VLDL receptor (VLDLR) are involved is the Reelin pathway. This pathway plays a pivotal role in the development of laminated structures of the brain and in synaptic plasticity of the adult brain. Since Reelin and apolipoprotein E, are ligands of ApoER2 and VLDLR, these receptors are of interest with respect to Alzheimer’s disease. We will focus this review on the complex structure of ApoER2 and VLDLR and a recently characterized ligand, namely clusterin.
Collapse
|
3
|
Pietzner M, Engelmann B, Kacprowski T, Golchert J, Dirk AL, Hammer E, Iwen KA, Nauck M, Wallaschofski H, Führer D, Münte TF, Friedrich N, Völker U, Homuth G, Brabant G. Plasma proteome and metabolome characterization of an experimental human thyrotoxicosis model. BMC Med 2017; 15:6. [PMID: 28065164 PMCID: PMC5220622 DOI: 10.1186/s12916-016-0770-8] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/10/2016] [Accepted: 12/15/2016] [Indexed: 12/20/2022] Open
Abstract
BACKGROUND Determinations of thyrotropin (TSH) and free thyroxine (FT4) represent the gold standard in evaluation of thyroid function. To screen for novel peripheral biomarkers of thyroid function and to characterize FT4-associated physiological signatures in human plasma we used an untargeted OMICS approach in a thyrotoxicosis model. METHODS A sample of 16 healthy young men were treated with levothyroxine for 8 weeks and plasma was sampled before the intake was started as well as at two points during treatment and after its completion, respectively. Mass spectrometry-derived metabolite and protein levels were related to FT4 serum concentrations using mixed-effect linear regression models in a robust setting. To compile a molecular signature discriminating between thyrotoxicosis and euthyroidism, a random forest was trained and validated in a two-stage cross-validation procedure. RESULTS Despite the absence of obvious clinical symptoms, mass spectrometry analyses detected 65 metabolites and 63 proteins exhibiting significant associations with serum FT4. A subset of 15 molecules allowed a robust and good prediction of thyroid hormone function (AUC = 0.86) without prior information on TSH or FT4. Main FT4-associated signatures indicated increased resting energy expenditure, augmented defense against systemic oxidative stress, decreased lipoprotein particle levels, and increased levels of complement system proteins and coagulation factors. Further association findings question the reliability of kidney function assessment under hyperthyroid conditions and suggest a link between hyperthyroidism and cardiovascular diseases via increased dimethylarginine levels. CONCLUSION Our results emphasize the power of untargeted OMICs approaches to detect novel pathways of thyroid hormone action. Furthermore, beyond TSH and FT4, we demonstrated the potential of such analyses to identify new molecular signatures for diagnosis and treatment of thyroid disorders. This study was registered at the German Clinical Trials Register (DRKS) [DRKS00011275] on the 16th of November 2016.
Collapse
Affiliation(s)
- Maik Pietzner
- Institute of Clinical Chemistry and Laboratory Medicine, University Medicine Greifswald, Ferdinand-Sauerbruch-Straße, 17475 Greifswald, Germany
- DZHK (German Centre for Cardiovascular Research), partner site Greifswald, Greifswald, Germany
| | - Beatrice Engelmann
- Department of Functional Genomics, Interfaculty Institute for Genetics and Functional Genomics, University Medicine and Ernst-Moritz-Arndt University Greifswald, Friedrich-Ludwig-Jahn-Straße 15a, D-17475 Greifswald, Germany
| | - Tim Kacprowski
- DZHK (German Centre for Cardiovascular Research), partner site Greifswald, Greifswald, Germany
- Department of Functional Genomics, Interfaculty Institute for Genetics and Functional Genomics, University Medicine and Ernst-Moritz-Arndt University Greifswald, Friedrich-Ludwig-Jahn-Straße 15a, D-17475 Greifswald, Germany
| | - Janine Golchert
- Department of Functional Genomics, Interfaculty Institute for Genetics and Functional Genomics, University Medicine and Ernst-Moritz-Arndt University Greifswald, Friedrich-Ludwig-Jahn-Straße 15a, D-17475 Greifswald, Germany
| | - Anna-Luise Dirk
- Medical Clinic I, University of Lübeck, Experimental and Clinical Endocrinology, Ratzeburger Allee 160, Zentralklinikum (Haus 40), 23538 Lübeck, Germany
| | - Elke Hammer
- DZHK (German Centre for Cardiovascular Research), partner site Greifswald, Greifswald, Germany
- Department of Functional Genomics, Interfaculty Institute for Genetics and Functional Genomics, University Medicine and Ernst-Moritz-Arndt University Greifswald, Friedrich-Ludwig-Jahn-Straße 15a, D-17475 Greifswald, Germany
| | - K. Alexander Iwen
- Medical Clinic I, University of Lübeck, Experimental and Clinical Endocrinology, Ratzeburger Allee 160, Zentralklinikum (Haus 40), 23538 Lübeck, Germany
| | - Matthias Nauck
- Institute of Clinical Chemistry and Laboratory Medicine, University Medicine Greifswald, Ferdinand-Sauerbruch-Straße, 17475 Greifswald, Germany
- DZHK (German Centre for Cardiovascular Research), partner site Greifswald, Greifswald, Germany
| | - Henri Wallaschofski
- Institute of Clinical Chemistry and Laboratory Medicine, University Medicine Greifswald, Ferdinand-Sauerbruch-Straße, 17475 Greifswald, Germany
- Private Practice Endocrinology, Krämpferstraße 6, 99094 Erfurt, Germany
| | - Dagmar Führer
- Department of Endocrinology and Metabolism, University Hospital Essen, University Duisburg-Essen, Hufelandstraße 55, 45122 Essen, Germany
| | - Thomas F. Münte
- Department of Neurology, University of Lübeck, Ratzeburger Allee 169, 23538 Lübeck, Germany
| | - Nele Friedrich
- Institute of Clinical Chemistry and Laboratory Medicine, University Medicine Greifswald, Ferdinand-Sauerbruch-Straße, 17475 Greifswald, Germany
- DZHK (German Centre for Cardiovascular Research), partner site Greifswald, Greifswald, Germany
- Research Centre for Prevention and Health, Glostrup University Hospital, Nordre Ringvej 57, 2600 Glostrup, Denmark
| | - Uwe Völker
- DZHK (German Centre for Cardiovascular Research), partner site Greifswald, Greifswald, Germany
- Department of Functional Genomics, Interfaculty Institute for Genetics and Functional Genomics, University Medicine and Ernst-Moritz-Arndt University Greifswald, Friedrich-Ludwig-Jahn-Straße 15a, D-17475 Greifswald, Germany
- ZIK-FunGene (Zentrum für Innovationskompetenz - Funktionelle Genomforschung), Greifswald, Germany
| | - Georg Homuth
- Department of Functional Genomics, Interfaculty Institute for Genetics and Functional Genomics, University Medicine and Ernst-Moritz-Arndt University Greifswald, Friedrich-Ludwig-Jahn-Straße 15a, D-17475 Greifswald, Germany
- ZIK-FunGene (Zentrum für Innovationskompetenz - Funktionelle Genomforschung), Greifswald, Germany
| | - Georg Brabant
- Medical Clinic I, University of Lübeck, Experimental and Clinical Endocrinology, Ratzeburger Allee 160, Zentralklinikum (Haus 40), 23538 Lübeck, Germany
| |
Collapse
|
4
|
Evans RD, Hauton D. The role of triacylglycerol in cardiac energy provision. Biochim Biophys Acta Mol Cell Biol Lipids 2016; 1861:1481-91. [DOI: 10.1016/j.bbalip.2016.03.010] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2016] [Revised: 03/08/2016] [Accepted: 03/09/2016] [Indexed: 02/07/2023]
|
5
|
Vaziri ND. Disorders of lipid metabolism in nephrotic syndrome: mechanisms and consequences. Kidney Int 2016; 90:41-52. [PMID: 27165836 DOI: 10.1016/j.kint.2016.02.026] [Citation(s) in RCA: 137] [Impact Index Per Article: 17.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2015] [Revised: 02/02/2016] [Accepted: 02/11/2016] [Indexed: 12/17/2022]
Abstract
Nephrotic syndrome results in hyperlipidemia and profound alterations in lipid and lipoprotein metabolism. Serum cholesterol, triglycerides, apolipoprotein B (apoB)-containing lipoproteins (very low-density lipoprotein [VLDL], immediate-density lipoprotein [IDL], and low-density lipoprotein [LDL]), lipoprotein(a) (Lp[a]), and the total cholesterol/high-density lipoprotein (HDL) cholesterol ratio are increased in nephrotic syndrome. This is accompanied by significant changes in the composition of various lipoproteins including their cholesterol-to-triglyceride, free cholesterol-to-cholesterol ester, and phospholipid-to-protein ratios. These abnormalities are mediated by changes in the expression and activities of the key proteins involved in the biosynthesis, transport, remodeling, and catabolism of lipids and lipoproteins including apoproteins A, B, C, and E; 3-hydroxy-3-methylglutaryl-coenzyme A reductase; fatty acid synthase; LDL receptor; lecithin cholesteryl ester acyltransferase; acyl coenzyme A cholesterol acyltransferase; HDL docking receptor (scavenger receptor class B, type 1 [SR-B1]); HDL endocytic receptor; lipoprotein lipase; and hepatic lipase, among others. The disorders of lipid and lipoprotein metabolism in nephrotic syndrome contribute to the development and progression of cardiovascular and kidney disease. In addition, by limiting delivery of lipid fuel to the muscles for generation of energy and to the adipose tissues for storage of energy, changes in lipid metabolism contribute to the reduction of body mass and impaired exercise capacity. This article provides an overview of the mechanisms, consequences, and treatment of lipid disorders in nephrotic syndrome.
Collapse
Affiliation(s)
- Nosratola D Vaziri
- Division of Nephrology and Hypertension, Departments of Medicine, Physiology, and Biophysics, University of California, Irvine, Irvine, California.
| |
Collapse
|
6
|
Endothelial Expression of Scavenger Receptor Class B, Type I Protects against Development of Atherosclerosis in Mice. BIOMED RESEARCH INTERNATIONAL 2015; 2015:607120. [PMID: 26504816 PMCID: PMC4609362 DOI: 10.1155/2015/607120] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/30/2015] [Revised: 07/10/2015] [Accepted: 07/24/2015] [Indexed: 11/23/2022]
Abstract
The role of scavenger receptor class B, type I (SR-BI) in endothelial cells (EC) was examined in several novel transgenic mouse models expressing SR-BI in endothelium of mice with normal C57Bl6/N, apoE-KO, or Scarb1-KO backgrounds. Mice were also created expressing SR-BI exclusively in endothelium and liver. Endothelial expression of the Tie2-Scarb1 transgene had no significant effect on plasma lipoprotein levels in mice on a normal chow diet but on an atherogenic diet, significantly decreased plasma cholesterol levels, increased plasma HDL cholesterol (HDL-C) levels, and protected mice against atherosclerosis. In 8-month-old apoE-KO mice fed a normal chow diet, the Tie2-Scarb1 transgene decreased aortic lesions by 24%. Mice expressing SR-BI only in EC and liver had a 1.5 ± 0.1-fold increase in plasma cholesterol compared to mice synthesizing SR-BI only in liver. This elevation was due mostly to increased HDL-C. In EC culture studies, SR-BI was found to be present in both basolateral and apical membranes but greater cellular uptake of cholesterol from HDL was found in the basolateral compartment. In summary, enhanced expression of SR-BI in EC resulted in a less atherogenic lipoprotein profile and decreased atherosclerosis, suggesting a possible role for endothelial SR-BI in the flux of cholesterol across EC.
Collapse
|
7
|
Rinninger F, Heine M, Singaraja R, Hayden M, Brundert M, Ramakrishnan R, Heeren J. High density lipoprotein metabolism in low density lipoprotein receptor-deficient mice. J Lipid Res 2014; 55:1914-24. [PMID: 24954421 DOI: 10.1194/jlr.m048819] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The LDL receptor (LDLR) and scavenger receptor class B type I (SR-BI) play physiological roles in LDL and HDL metabolism in vivo. In this study, we explored HDL metabolism in LDLR-deficient mice in comparison with WT littermates. Murine HDL was radiolabeled in the protein ((125)I) and in the cholesteryl ester (CE) moiety ([(3)H]). The metabolism of (125)I-/[(3)H]HDL was investigated in plasma and in tissues of mice and in murine hepatocytes. In WT mice, liver and adrenals selectively take up HDL-associated CE ([(3)H]). In contrast, in LDLR(-/-) mice, selective HDL CE uptake is significantly reduced in liver and adrenals. In hepatocytes isolated from LDLR(-/-) mice, selective HDL CE uptake is substantially diminished compared with WT liver cells. Hepatic and adrenal protein expression of lipoprotein receptors SR-BI, cluster of differentiation 36 (CD36), and LDL receptor-related protein 1 (LRP1) was analyzed by immunoblots. The respective protein levels were identical both in hepatic and adrenal membranes prepared from WT or from LDLR(-/-) mice. In summary, an LDLR deficiency substantially decreases selective HDL CE uptake by liver and adrenals. This decrease is independent from regulation of receptor proteins like SR-BI, CD36, and LRP1. Thus, LDLR expression has a substantial impact on both HDL and LDL metabolism in mice.
Collapse
Affiliation(s)
- Franz Rinninger
- Department of Medicine, University Hospital Hamburg Eppendorf, 20246 Hamburg, Germany
| | - Markus Heine
- Department of Biochemistry and Molecular Cell Biology, University Hospital Hamburg Eppendorf, 20246 Hamburg, Germany
| | - Roshni Singaraja
- Translational Laboratories in Genetic Medicine, Agency for Science, Technology and Research National University of Singapore, Singapore 117609 Department of Medicine, National University of Singapore, Singapore 117609
| | - Michael Hayden
- Centre for Molecular Medicine and Therapeutics and Child and Family Research Institute, University of British Columbia, Vancouver, British Columbia V5Z 4H4, Canada
| | - May Brundert
- Department of Medicine, University Hospital Hamburg Eppendorf, 20246 Hamburg, Germany
| | - Rajasekhar Ramakrishnan
- Department of Pediatrics, College of Physicians and Surgeons of Columbia University, New York, NY 10032
| | - Joerg Heeren
- Department of Biochemistry and Molecular Cell Biology, University Hospital Hamburg Eppendorf, 20246 Hamburg, Germany
| |
Collapse
|
8
|
Mizuta H, Luo W, Ito Y, Mushirobira Y, Todo T, Hara A, Reading BJ, Sullivan CV, Hiramatsu N. Ovarian expression and localization of a vitellogenin receptor with eight ligand binding repeats in the cutthroat trout (Oncorhynchus clarki). Comp Biochem Physiol B Biochem Mol Biol 2013; 166:81-90. [PMID: 23872140 DOI: 10.1016/j.cbpb.2013.07.005] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2013] [Revised: 07/12/2013] [Accepted: 07/12/2013] [Indexed: 10/26/2022]
Abstract
A cDNA encoding a vitellogenin receptor with 8 ligand binding repeats (vtgr) was cloned from ovaries of the cutthroat trout, Oncorhynchus clarki. In situ hybridization and quantitative PCR analyses revealed that the main site of vtgr mRNA expression was the oocytes. Expression was strongly detected in perinucleous stage oocytes, gradually decreased as oocytes grew, and became hardly detectable in vitellogenic oocytes. A rabbit antibody (a-Vtgr) was raised against a recombinant Vtgr protein in order to immunologically detect and localize Vtgr within the ovarian follicles. Western blotting using a-Vtgr detected a bold band with an apparent mass of ~95-105kDa in an ovarian preparation that also bound Sakhalin taimen, Hucho perryi, vitellogenin in ligand blots. Immunohistochemistry using a-Vtgr revealed that the Vtgr was uniformly distributed throughout the ooplasm of perinucleolus stage oocytes, subsequently translocated to the periphery of lipid droplet stage oocytes, and became localized to the oolemma during vitellogenesis. We provide the first characterization of Vtgr at both the transcriptional and the translational levels in the cutthroat trout, and our results suggest that this receptor is involved in uptake of Vtg by oocytes of this species.
Collapse
Affiliation(s)
- Hiroko Mizuta
- Division of Marine Life Science, Graduate School of Fisheries Sciences, Hokkaido University, 3-1-1 Minato, Hakodate, Hokkaido, 041-8611, Japan
| | | | | | | | | | | | | | | | | |
Collapse
|
9
|
Iwata K, Izumo N, Matsuzaki H, Manabe T, Ishibashi Y, Ichitani Y, Yamada K, Thanseem I, Anitha A, Vasu MM, Shimmura C, Wakuda T, Kameno Y, Takahashi T, Iwata Y, Suzuki K, Nakamura K, Mori N. Vldlr overexpression causes hyperactivity in rats. Mol Autism 2012; 3:11. [PMID: 23110844 PMCID: PMC3533969 DOI: 10.1186/2040-2392-3-11] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2012] [Accepted: 09/26/2012] [Indexed: 01/05/2023] Open
Abstract
UNLABELLED BACKGROUND Reelin regulates neuronal positioning in cortical brain structures and neuronal migration via binding to the lipoprotein receptors Vldlr and Lrp8. Reeler mutant mice display severe brain morphological defects and behavioral abnormalities. Several reports have implicated reelin signaling in the etiology of neurodevelopmental and psychiatric disorders, including autism, schizophrenia, bipolar disorder, and depression. Moreover, it has been reported that VLDLR mRNA levels are increased in the post-mortem brain of autistic patients. METHODS We generated transgenic (Tg) rats overexpressing Vldlr, and examined their histological and behavioral features. RESULTS Spontaneous locomotor activity was significantly increased in Tg rats, without detectable changes in brain histology. Additionally, Tg rats tended to show performance deficits in the radial maze task, suggesting that their spatial working memory was slightly impaired. Thus, Vldlr levels may be involved in determining locomotor activity and memory function. CONCLUSIONS Unlike reeler mice, patients with neurodevelopmental or psychiatric disorders do not show striking neuroanatomical aberrations. Therefore, it is notable, from a clinical point of view, that we observed behavioral phenotypes in Vldlr-Tg rats in the absence of neuroanatomical abnormalities.
Collapse
Affiliation(s)
- Keiko Iwata
- Research Center for Child Mental Development, Hamamatsu University School of Medicine, Hamamatsu, Japan
| | - Nobuo Izumo
- Department of Clinical Pharmacology, Yokohama College of Pharmacy, Yokohama, Japan
| | - Hideo Matsuzaki
- Research Center for Child Mental Development, Hamamatsu University School of Medicine, Hamamatsu, Japan
| | - Takayuki Manabe
- Division of Gene Expression Mechanism, Institute for Comprehensive Medical Science, Fujita Health University, Toyoake, Japan
| | - Yukiko Ishibashi
- Department of Synthetic Organic Chemistry, Yokohama College of Pharmacy, Yokohama, Japan
| | - Yukio Ichitani
- Institute of Psychology and Behavioral Neuroscience, University of Tsukuba, Tsukuba, Japan
| | - Kazuo Yamada
- Institute of Psychology and Behavioral Neuroscience, University of Tsukuba, Tsukuba, Japan
| | - Ismail Thanseem
- Department of Psychiatry, Hamamatsu University School of Medicine, Hamamatsu, Japan
| | - Ayyappan Anitha
- Research Center for Child Mental Development, Hamamatsu University School of Medicine, Hamamatsu, Japan
| | - Mahesh Mundalil Vasu
- Department of Psychiatry, Hamamatsu University School of Medicine, Hamamatsu, Japan
| | - Chie Shimmura
- Department of Psychiatry, Hamamatsu University School of Medicine, Hamamatsu, Japan
| | - Tomoyasu Wakuda
- Department of Psychiatry, Hamamatsu University School of Medicine, Hamamatsu, Japan
| | - Yosuke Kameno
- Department of Psychiatry, Hamamatsu University School of Medicine, Hamamatsu, Japan
| | - Taro Takahashi
- Research Center for Child Mental Development, Hamamatsu University School of Medicine, Hamamatsu, Japan
| | - Yasuhide Iwata
- Department of Psychiatry, Hamamatsu University School of Medicine, Hamamatsu, Japan
| | - Katsuaki Suzuki
- Research Center for Child Mental Development, Hamamatsu University School of Medicine, Hamamatsu, Japan
| | - Kazuhiko Nakamura
- Department of Psychiatry, Hamamatsu University School of Medicine, Hamamatsu, Japan
| | - Norio Mori
- Department of Psychiatry, Hamamatsu University School of Medicine, Hamamatsu, Japan
| |
Collapse
|
10
|
Grasselli E, Voci A, Demori I, Canesi L, De Matteis R, Goglia F, Lanni A, Gallo G, Vergani L. 3,5-Diiodo-L-thyronine modulates the expression of genes of lipid metabolism in a rat model of fatty liver. J Endocrinol 2012; 212:149-58. [PMID: 22107956 DOI: 10.1530/joe-11-0288] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Recent reports demonstrated that 3,5-diiodo-l-thyronine (T(2)) was able to prevent lipid accumulation in the liver of rats fed a high-fat diet (HFD). In this study, we investigated how the rat liver responds to HFD and T(2) treatment by assessing the transcription profiles of some genes involved in the pathways of lipid metabolism: oxidation, storage and secretion. The mRNA levels of the peroxisome proliferator-activated receptors (PPARα, PPARγ and PPARδ), and of their target enzymes acyl-CoA oxidase and stearoyl-CoA desaturase were evaluated by real-time RT-PCR. Moreover, the expression of the adipose triglyceride lipase involved in lipid mobilisation, of the main PAT proteins acting in lipid droplet (LD) turnover, and of apoprotein B (apo B), the major protein component of very low-density lipoproteins (VLDLs) were analysed. Overall, our data demonstrated that T(2) administration to HFD rats counteracts most of the hepatic transcriptional changes that occurred in response to the excess exogenous fat. In particular, our results suggest that T(2) may prevent the pathways leading to lipid storage in LDs, promote the processes of lipid mobilisation from LDs and secretion as VLDL, in addition to the stimulation of pathways of lipid oxidation. In conclusion, our findings might give an insight into the mechanisms underlying the anti-steatotic ability of T(2) and help to define the potential therapeutic role of T(2) for preventing or treating liver steatosis.
Collapse
|
11
|
Wang C, Li SJ, Yu WH, Xin QW, Li C, Feng YP, Peng XL, Gong YZ. Cloning and expression profiling of the VLDLR gene associated with egg performance in duck (Anas platyrhynchos). Genet Sel Evol 2011; 43:29. [PMID: 21819592 PMCID: PMC3162882 DOI: 10.1186/1297-9686-43-29] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2010] [Accepted: 08/05/2011] [Indexed: 11/15/2022] Open
Abstract
Background The very low density lipoprotein receptor gene (VLDLR), a member of the low density lipoprotein receptor (LDLR) gene family, plays a crucial role in the synthesis of yolk protein precursors in oviparous species. Differential splicing of this gene has been reported in human, rabbit and rat. In chicken, studies showed that the VLDLR protein on the oocyte surface mediates the uptake of yolk protein precursors into growing oocytes. However, information on the VLDLR gene in duck is still scarce. Methods Full-length duck VLDLR cDNA was obtained by comparative cloning and rapid amplification of cDNA ends (RACE). Tissue expression patterns were analysed by semi-quantitative reverse-transcription polymerase chain reaction (RT-PCR). Association between the different genotypes and egg performance traits was investigated with the general linear model (GLM) procedure of the SAS® software package. Results In duck, two VLDLR transcripts were identified, one transcript (variant-a) containing an O-linked sugar domain and the other (variant-b) not containing this sugar domain. These transcripts share ~70 to 90% identity with their counterparts in other species. A phylogenetic tree based on amino acid sequences showed that duck VLDLR proteins were closely related with those of chicken and zebra finch. The two duck VLDLR transcripts are differentially expressed i.e. VLDLR-a is mainly expressed in muscle tissue and VLDLR-b in reproductive organs. We have localized the duck VLDLR gene on chromosome Z. An association analysis using two completely linked SNP sites (T/C at position 2025 bp of the ORF and G/A in intron 13) and records from two generations demonstrated that the duck VLDLR gene was significantly associated with egg production (P < 0.01), age of first egg (P < 0.01) and body weight of first egg (P < 0.05). Conclusions Duck and chicken VLDLR genes probably perform similar function in the development of growing oocytes and deposition of yolk lipoprotein. Therefore, VLDLR could be a candidate gene for duck egg performance and be used as a genetic marker to improve egg performance in ducks.
Collapse
Affiliation(s)
- Cui Wang
- Key Laboratory of Agricultural Animal Genetics, Breeding, and Reproduction of Ministry of Education, Huazhong Agricultural University, Wuhan, Hubei 430070, PR China
| | | | | | | | | | | | | | | |
Collapse
|
12
|
Yuan G, Liu Y, Sun T, Xu Y, Zhang J, Yang Y, Zhang M, Cianflone K, Wang DW. The Therapeutic Role of Very Low-Density Lipoprotein Receptor Gene in Hyperlipidemia in Type 2 Diabetic Rats. Hum Gene Ther 2011; 22:302-12. [PMID: 21087152 DOI: 10.1089/hum.2010.038] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Affiliation(s)
- Gang Yuan
- Department of Internal Medicine, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan 430030, People's Republic of China
| | - Yongjian Liu
- Department of Internal Medicine, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan 430030, People's Republic of China
- Department of Endocrinology, Puai Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan 430030, People's Republic of China
| | - Tingting Sun
- Department of Internal Medicine, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan 430030, People's Republic of China
| | - Yongping Xu
- Department of Internal Medicine, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan 430030, People's Republic of China
| | - Jianhuan Zhang
- Department of Internal Medicine, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan 430030, People's Republic of China
| | - Yan Yang
- Department of Internal Medicine, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan 430030, People's Republic of China
| | - Muxun Zhang
- Department of Internal Medicine, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan 430030, People's Republic of China
| | - Katherine Cianflone
- Centre de Recherche, Institut Universitaire de Cardiologie et de Pneumologie de Québec, Université Laval, Quebec, QC, Canada
| | - Dao Wen Wang
- Department of Internal Medicine, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan 430030, People's Republic of China
| |
Collapse
|
13
|
Brundert M, Heeren J, Merkel M, Carambia A, Herkel J, Groitl P, Dobner T, Ramakrishnan R, Moore KJ, Rinninger F. Scavenger receptor CD36 mediates uptake of high density lipoproteins in mice and by cultured cells. J Lipid Res 2011; 52:745-58. [PMID: 21217164 DOI: 10.1194/jlr.m011981] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The mechanisms of HDL-mediated cholesterol transport from peripheral tissues to the liver are incompletely defined. Here the function of scavenger receptor cluster of differentiation 36 (CD36) for HDL uptake by the liver was investigated. CD36 knockout (KO) mice, which were the model, have a 37% increase (P = 0.008) of plasma HDL cholesterol compared with wild-type (WT) littermates. To explore the mechanism of this increase, HDL metabolism was investigated with HDL radiolabeled in the apolipoprotein (¹²⁵I) and cholesteryl ester (CE, [³H]) moiety. Liver uptake of [³H] and ¹²⁵I from HDL decreased in CD36 KO mice and the difference, i. e. hepatic selective CE uptake ([³H]¹²⁵I), declined (-33%, P = 0.0003) in CD36 KO compared with WT mice. Hepatic HDL holo-particle uptake (¹²⁵I) decreased (-29%, P = 0.0038) in CD36 KO mice. In vitro, uptake of ¹²⁵I-/[³H]HDL by primary liver cells from WT or CD36 KO mice revealed a diminished HDL uptake in CD36-deficient hepatocytes. Adenovirus-mediated expression of CD36 in cells induced an increase in selective CE uptake from HDL and a stimulation of holo-particle internalization. In conclusion, CD36 plays a role in HDL uptake in mice and by cultured cells. A physiologic function of CD36 in HDL metabolism in vivo is suggested.
Collapse
Affiliation(s)
- May Brundert
- University Hospital Hamburg Eppendorf Hamburg, Germany
| | | | | | | | | | | | | | | | | | | |
Collapse
|
14
|
Effect of insulin on the differential expression of VLDL receptor isoforms of SGC7901 cell and its biological implication. ACTA ACUST UNITED AC 2010; 30:551-5. [DOI: 10.1007/s11596-010-0541-2] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2010] [Indexed: 11/26/2022]
|
15
|
Sakai K, Tiebel O, Ljungberg MC, Sullivan M, Lee HJ, Terashima T, Li R, Kobayashi K, Lu HC, Chan L, Oka K. A neuronal VLDLR variant lacking the third complement-type repeat exhibits high capacity binding of apoE containing lipoproteins. Brain Res 2009; 1276:11-21. [PMID: 19393635 DOI: 10.1016/j.brainres.2009.04.030] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2009] [Revised: 03/30/2009] [Accepted: 04/12/2009] [Indexed: 12/31/2022]
Abstract
Very-low-density lipoprotein receptor (VLDLR) is a multi ligand apolipoprotein E (apoE) receptor and is involved in brain development through Reelin signaling. Different forms of VLDLR can be generated by alternative splicing. VLDLR-I contains all exons. VLDLR-II lacks an O-linked sugar domain encoded by exon 16, while VLDLR-III lacks the third complement-type repeat in the ligand binding domain encoded by exon 4. We quantitatively compared lipoprotein binding to human VLDLR variants and analyzed their mRNA expression in both human cerebellum and mouse brain. VLDLR-III exhibited the highest capacity in binding to apoE enriched beta-VLDL in vitro and was more effective in removing apoE containing lipoproteins from the circulation than other variants in vivo. In human cerebellum, the major species was VLDLR-II, while the second most abundant species was a newly identified VLDLR-IV which lacks both exon 4 and 16. VLDLR-I was present at low levels. In adult mice, exon 4 skipping varied between 30 and 47% in different brain regions, while exon 16 skipping ranged by 51-76%. Significantly higher levels of VLDLR proteins were found in mouse cerebellum and cerebral cortex than other regions. The deletions of exon 4 and exon 16 frequently occurred in primary neurons, indicating that newly identified variant VLDLR-IV is abundant in neurons. In contrast, VLDLR mRNA lacking exon 4 was not detectable in primary astrocytes. Such cell type-specific splicing patterns were found in both mouse cerebellum and cerebral cortex. These results suggest that a VLDLR variant lacking the third complement-type repeat is generated by neuron-specific alternative splicing. Such differential splicing may result in different lipid uptake in neurons and astrocytes.
Collapse
Affiliation(s)
- Keiko Sakai
- Department of Neurology, Baylor College of Medicine, Houston, TX 77030, USA
| | | | | | | | | | | | | | | | | | | | | |
Collapse
|
16
|
Prawitt J, Niemeier A, Kassem M, Beisiegel U, Heeren J. Characterization of lipid metabolism in insulin-sensitive adipocytes differentiated from immortalized human mesenchymal stem cells. Exp Cell Res 2007; 314:814-24. [PMID: 18068701 DOI: 10.1016/j.yexcr.2007.11.011] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2007] [Revised: 11/01/2007] [Accepted: 11/14/2007] [Indexed: 11/28/2022]
Abstract
There is a great demand for cell models to study human adipocyte function. Here we describe the adipogenic differentiation of a telomerase-immortalized human mesenchymal stem cell line (hMSC-Tert) that maintains numerous features of terminally differentiated adipocytes even after prolonged withdrawal of the peroxisome proliferator activated receptor gamma (PPARgamma) agonist rosiglitazone. Differentiated hMSC-Tert developed the characteristic monolocular phenotype of mature adipocytes. The expression of adipocyte specific markers was highly increased during differentiation. Most importantly, the presence of the PPARgamma agonist rosiglitazone was not required for the stable expression of lipoprotein lipase, adipocyte fatty acid binding protein and perilipin on mRNA and protein levels. Adiponectin expression was post-transcriptionally down-regulated in the absence of rosiglitazone. Insulin sensitivity as measured by insulin-induced phosphorylation of Akt and S6 ribosomal protein was also independent of rosiglitazone. In addition to commonly used adipogenic markers, we investigated further PPARgamma-stimulated proteins with a role in lipid metabolism. We observed an increase of lipoprotein receptor (VLDLR, LRP1) and apolipoprotein E expression during differentiation. Despite this increased expression, the receptor-mediated endocytosis of lipoproteins was decreased in differentiated adipocytes, suggesting that these proteins may have an additional function in adipose tissue beyond lipoprotein uptake.
Collapse
Affiliation(s)
- Janne Prawitt
- Department of Biochemistry and Molecular Biology II: Molecular Cell Biology, University Medical Center Hamburg-Eppendorf, Hamburg, Germany
| | | | | | | | | |
Collapse
|
17
|
Chen Y, Hu Y, Lu K, Flannery JG, Ma JX. Very Low Density Lipoprotein Receptor, a Negative Regulator of the wnt Signaling Pathway and Choroidal Neovascularization. J Biol Chem 2007; 282:34420-8. [PMID: 17890782 DOI: 10.1074/jbc.m611289200] [Citation(s) in RCA: 86] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023] Open
Abstract
Choroidal neovascularization (CNV) in age-related macular degeneration is a leading cause of blindness. Very low density lipoprotein receptor gene knock-out (Vldlr(-/-)) mice have been shown to develop subretinal neovascularization (NV) with an unknown mechanism. The present study showed that in Vldlr(-/-) mice, NV initiated in the choroid and progressed to penetrate the retinal pigment epithelium layer, proliferating in the subretinal space. This phenotype recapitulated what is seen in wet age-related macular degeneration, suggesting that this is a CNV model. The CNV correlated with overexpression of vascular endothelial growth factor in Vldlr(-/-) eyecups and was blocked by a neutralizing antibody against vascular endothelial growth factor receptor-2. The wnt co-receptor LRP5/6 expression was significantly up-regulated in Vldlr(-/-) eyecups compared with that in wild-type mice. Significantly, Vldlr(-/-) mice showed impaired phosphorylation of downstream effectors of the wnt signaling pathway, glycogen synthase kinase-3beta (GSK-3beta), and beta-catenin, concomitant with increased levels of free GSK-3beta and beta-catenin, suggesting an increased activity of the wnt pathway. Down-regulation of VLDLR by small interference RNA resulted in up-regulation of LRP5/6 expression and activation of beta-catenin in cultured endothelial cells. Furthermore, Dickkopf-1, a specific inhibitor of the wnt pathway, effectively decreased vascular endothelial growth factor and beta-catenin levels in the retinal pigment epithelium of Vldlr(-/-) mice and in cells transfected with the VLDLR small interference RNA. These results suggest that VLDLR functions as a negative regulator of CNV, and this function is mediated through the wnt pathway.
Collapse
Affiliation(s)
- Ying Chen
- Department of Cell Biology, University of Oklahoma Health Sciences Center, 941 Stanton L. Young Boulevard, Oklahoma City, OK 73104, USA
| | | | | | | | | |
Collapse
|
18
|
Zhang X, Moor AN, Merkler KA, Liu Q, McLean MP. Regulation of alternative splicing of liver scavenger receptor class B gene by estrogen and the involved regulatory splicing factors. Endocrinology 2007; 148:5295-304. [PMID: 17673517 DOI: 10.1210/en.2007-0376] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
The scavenger receptor class B isoforms (SR-B) type I and type II mediate the selective uptake of high-density lipoprotein cholesterol and promote reverse cholesterol transport, an important atherosclerosis protection mechanism, in the liver. Previously it was shown that the hepatic expression of SR-BI and SR-BII is regulated by estrogen. In the present study, we demonstrate that estrogen differentially regulates expression of the glycosylated and nonglycosylated forms of SR-BI and SR-BII in rat liver and hepatic cells. We report that estrogen mainly induces the down-regulation of glycosylated SR-BI and the up-regulation of nonglycosylated SR-BII. To study how estrogen regulates expression of the SR-B isoforms, we constructed a SR-B minigene containing minimal genomic sequences and were able to demonstrate that estrogen directly regulates the pre-mRNA alternative splicing of the exogenously expressed SR-B minigene in hepatic cells. Furthermore, we showed that the overexpression of splicing factors alternative splicing factor/splicing factor 2, Transformer (Tra)-2alpha, and Tra2beta changes the splicing pattern of SR-B dramatically, whereas other splicing factors, such as heterogeneous nuclear ribonucleoprotein-G, SC-35, and arginine/serine-rich p40, had no effect. We also demonstrate that estrogen regulates Tra2beta expression levels in liver cells. These studies suggest that estrogen may regulate SR-B isoform expression at both the RNA splicing and posttranslational modification levels and that, for alternative splicing regulation, estrogen may function by regulating the expression of the splicing factors alternative splicing factor/splicing factor 2, Tra2alpha, and especially Tra2beta.
Collapse
Affiliation(s)
- Xiaohui Zhang
- Department of Obstetrics and Gynecology, University of South Florida College of Medicine, Tampa, FL 33612, USA
| | | | | | | | | |
Collapse
|
19
|
Iwasaki T, Takahashi S, Takahashi M, Zenimaru Y, Kujiraoka T, Ishihara M, Nagano M, Suzuki J, Miyamori I, Naiki H, Sakai J, Fujino T, Miller NE, Yamamoto TT, Hattori H. Deficiency of the very low-density lipoprotein (VLDL) receptors in streptozotocin-induced diabetic rats: insulin dependency of the VLDL receptor. Endocrinology 2005; 146:3286-94. [PMID: 15878964 DOI: 10.1210/en.2005-0043] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Hyperlipidemia is a common feature of diabetes and is related to cardiovascular disease. The very low-density lipoprotein receptor (VLDL-R) is a member of the low-density lipoprotein receptor (LDL-R) family. It binds and internalizes triglyceride-rich lipoproteins with high specificity. We examined the etiology of hyperlipidemia in the insulin-deficient state. VLDL-R expression in heart and skeletal muscle were measured in rats with streptozotocin (STZ)-induced diabetes. STZ rats showed severe hyperlipidemia on d 21 and 28, with a dramatic decline in VLDL-R protein in skeletal muscle (>90%), heart (approximately 50%) and a loss of adipose tissues itself on d 28. The reduction of VLDL-R protein in skeletal muscle could not be explained simply by a decrease at the transcriptional level, because a dissociation between VLDL-R protein and mRNA expression was observed. The expression of LDL-R and LDL-R-related protein in liver showed no consistent changes. Furthermore, no effect on VLDL-triglyceride production in liver was observed in STZ rats. A decrease in postheparin plasma lipoprotein lipase activity started on d 7 and continued to d 28 at the 50% level even though severe hyperlipidemia was detected only on d 21 and 28. In rat myoblast cells, serum deprivation for 24 h induced a reduction in VLDL-R proteins. Insulin (10(-6) m), but not IGF-I (10 ng/ml), restored the decreased VLDL-R proteins by serum deprivation. These results suggest that the combination of VLDL-R deficiency and reduced plasma lipoprotein lipase activity may be responsible for severe hyperlipidemia in insulin-deficient diabetes.
Collapse
Affiliation(s)
- Tadao Iwasaki
- Department of Advanced Medical Technology and Development, BML, Inc, Kawagoe, Japan
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
20
|
Sato T, Liang K, Vaziri ND. Protein restriction and AST-120 improve lipoprotein lipase and VLDL receptor in focal glomerulosclerosis. Kidney Int 2004; 64:1780-6. [PMID: 14531811 DOI: 10.1046/j.1523-1755.2003.00281.x] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
BACKGROUND Imai rats exhibit spontaneous focal glomerulosclerosis (FGS) with progressive proteinuria and hyperlipidemia leading to renal insufficiency by age 34 weeks. Recently, we reported marked down-regulations of skeletal muscle and adipose tissue lipoprotein lipase (LPL) and very low-density lipoprotein (VLDL) receptor in male Imai rats at 32 weeks of age. Dietary protein restriction and oral adsorbent AST-120 (AST) have been shown to slow progression of renal disease and attenuate hyperlipidemia in the Imai rats. This study tested the hypothesis that amelioration of proteinuria by protein restriction or use of oral adsorbent AST-120 beginning at 10 weeks of age may improve renal disease and LPL and VLDL receptor deficiencies in Imai rats. METHODS Ten-week-old male Imai rats were randomly assigned to those fed either a regular diet, low protein diet (LPD), or regular diet containing the adsorbent preparation, AST-120. Ten-week-old male Sprague-Dawley rats served as controls. The animals were observed for 24 weeks. Six rats were included in each group. All diets were prepared in powder form. RESULTS The untreated 34-week-old Imai rats showed severe proteinuria, hypoalbuminemia, 50% reduction in creatinine clearance, hypercholesterolemia, hypertriglyceridemia, and elevated plasma VLDL concentration. This was associated with significant reductions in plasma post-heparin LPL activity, hepatic lipase activity, as well as adipose tissue and skeletal muscle immunodetectable LPL and VLDL receptor proteins. Protein restriction mitigated the decline in creatinine clearance, ameliorated proteinuria, hypoalbuminemia, hypertension, and hypercholesterolemia, lowered plasma VLDL, and improved plasma postheparin LPL activity, hepatic lipase activity, LPL, and VLDL receptor proteins in skeletal muscle and adipose tissue. Similar improvements were observed in all parameters with AST administration. CONCLUSION Moderate protein restriction and use of oral adsorbent can slow progression of renal disease and, thereby, ameliorate LPL, hepatic lipase, and VLDL receptor deficiencies and the associated hyperlipidemia in rats with spontaneous FGS.
Collapse
Affiliation(s)
- Tadashi Sato
- Department of Pediatrics, Saga Medical School, Saga-City, Japan
| | | | | |
Collapse
|
21
|
Al-Tonsi AA, Abdel-Gayoum AA, Saad M. The secondary dyslipidemia and deranged serum phosphate concentration in thyroid disorders. Exp Mol Pathol 2004; 76:182-7. [PMID: 15010297 DOI: 10.1016/j.yexmp.2003.10.006] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2003] [Indexed: 12/18/2022]
Abstract
Hyperlipidemia is a secondary disorder associated with many metabolic disorders including hypothyroidism. The occurrence of dyslipidemia in subclinical hypothyroidism is controversial. Hyperphosphatemia may accompany the dyslipidemia in some metabolic disorders. Both hyperlipidemia and hyperphosphatemia are considered to be risk factors for the coronary heart diseases. In the present study, we investigated the occurrence of dyslipidemia and altered serum phosphate concentrations in patients with thyroid disorders. The results indicated a significantly elevated serum cholesterol and triglyceride concentrations in the hypothyroid patients. The dyslipidemia was accompanied with significantly elevated serum phosphate level. On the other hand, no significant difference was evident in the serum lipid or phosphate concentrations of subclinical hypothyroid patients compared to euthyroid subjects. A significantly reduced serum phosphate level was shown in hyperthyroid patients with unaltered serum lipid levels. Significant correlations were evident between TSH and T(4) levels as independent parameters and the serum concentrations of triglyceride, cholesterol and phosphate. The results indicate in hypothyroidism that a secondary hyperphosphatemia may aggravate myocardial and arterial abnormalities induced by the secondary hyperlipidemia, which may need correction.
Collapse
Affiliation(s)
- A A Al-Tonsi
- Department of Biochemistry, Banha Faculty of Medicine, Zagazig University, Egypt
| | | | | |
Collapse
|
22
|
Hiramatsu N, Chapman RW, Lindzey JK, Haynes MR, Sullivan CV. Molecular characterization and expression of vitellogenin receptor from white perch (Morone americana). Biol Reprod 2004; 70:1720-30. [PMID: 14766733 DOI: 10.1095/biolreprod.103.023655] [Citation(s) in RCA: 61] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/01/2022] Open
Abstract
A full-length (4021 base pair [bp]) cDNA encoding a polypeptide (844 amino acids) with a predicted mass of 93 kDa and other characteristic structural features of a vertebrate vitellogenin receptor (VgR) was isolated from a white perch (Morone americana) ovarian cDNA library. Northern blotting performed using a specific digoxygenin-labeled VgR cDNA probe revealed a distinct approximately 4.1 kilobase (kb) hybridization signal in an mRNA preparation obtained from previtellogenic perch ovaries. The deduced amino acid sequence of the perch VgR was 89% and 82% identical, respectively, to that of the tilapia and rainbow trout. Because it possessed an eight-repeat ligand-binding domain (LR8) but lacked an O-linked sugar domain (-), the perch VgR was identified as a non-O-linked form of VgR (LR8-). Unlike the case in other vertebrates investigated, including tilapia and trout, no species of mRNA encoding an O-linked form of VgR (LR8+) could be detected when perch ovarian or liver mRNA reverse transcripts or cDNA libraries were screened by PCR using primer sets flanking the putative O-linked sugar domain. These novel findings call into question the assumptions that an LR8+ splice variant of the VgR always is dominantly present in somatic tissues and exists at lower levels in ovarian tissues to sequester lipoproteins distinct from Vg. A SYBR-green-based real-time reverse transcription-polymerase chain reaction assay was developed and used to quantitatively measure VgR expression in gonadal and somatic tissues, for the first time in any vertebrate. The main site of perch VgR mRNA expression was the ovary and the highest level of VgR mRNA expression was in ovaries whose largest follicles contained previtellogenic oocytes. Expression of VgR mRNA decreased with oocyte growth during vitellogenesis and was very limited in ovulated eggs. These quantitative results verify the concept that growing oocytes must extensively recycle LR8- forms of the VgR.
Collapse
Affiliation(s)
- Naoshi Hiramatsu
- Department of Zoology, College of Agriculture and Life Sciences, North Carolina State University, Raleigh,North Carolina 27695-7617, USA
| | | | | | | | | |
Collapse
|
23
|
Ritsch A, Tancevski I, Schgoer W, Pfeifhofer C, Gander R, Eller P, Foeger B, Stanzl U, Patsch JR. Molecular characterization of rabbit scavenger receptor class B types I and II: portal to central vein gradient of expression in the liver. J Lipid Res 2004; 45:214-22. [PMID: 14595001 DOI: 10.1194/jlr.m300353-jlr200] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
To further elucidate the role of scavenger receptor class B type I (SR-BI) in reverse cholesterol transport and in atherogenesis, we performed studies in the rabbit, an animal model displaying a lipoprotein profile similar to that of human, expressing cholesteryl ester transfer protein in plasma and having been demonstrated to be susceptible to atherosclerosis. In this report, we describe for the first time the isolation and characterization of rabbit cDNA fragments encoding SR-BI and scavenger receptor class B type II (SR-BII). Development of an isoform-specific Taqman Real Time PCR system and generation of isoform-specific polyclonal antibodies allowed us to measure SR-BI and SR-BII expression in various rabbit organs on mRNA and protein levels, respectively. We found the highest expression of SR-BI in adrenal gland, liver, and proximal intestine; lesser expression was found in appendix and spleen. Immunohistochemical staining of frozen sections showed SR-BI expression in the cortex but not in the medulla of adrenal gland. An increasing portal to central vein gradient of expression was found within the hepatic lobule. As shown in this report, identification and characterization of SR-BI expression in the rabbit affords a powerful tool to elucidate the role of SR-BI in cholesterol homeostasis and atherogenesis in human.
Collapse
Affiliation(s)
- A Ritsch
- Department of Medicine, University of Innsbruck, Innsbruck, Austria.
| | | | | | | | | | | | | | | | | |
Collapse
|
24
|
Feingold K, Kim MS, Shigenaga J, Moser A, Grunfeld C. Altered expression of nuclear hormone receptors and coactivators in mouse heart during the acute-phase response. Am J Physiol Endocrinol Metab 2004; 286:E201-7. [PMID: 14701665 DOI: 10.1152/ajpendo.00205.2003] [Citation(s) in RCA: 107] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Severe sepsis results in the decreased uptake and oxidation of fatty acids in the heart and cardiac failure. Some of the key proteins required for fatty acid uptake and oxidation in the heart have been shown to be downregulated after endotoxin (LPS) administration. The nuclear hormone receptors, peroxisome proliferator-activated receptor (PPAR) and thyroid receptor (TR), which heterodimerize with the retinoid X receptor (RXR), are important regulators of fatty acid metabolism and decrease in the liver after LPS administration. In the present study, we demonstrate that LPS treatment produces a rapid and marked decrease in the mRNA levels of all three RXR isoforms, PPARalpha and PPARdelta, and TRalpha and TRbeta in the heart. Moreover, LPS administration also decreased the expression of the coactivators CREB-binding protein (CBP)/p300, steroid receptor coactivator (SRC)-1, SRC-3, TR-associated protein (TRAP)220, and PPARgamma coactivator (PGC)-1, all of which are required for the transcriptional activity of RXR-PPAR and RXR-TR. In addition, the mRNA levels of the target genes malic enzyme, Spot 14, sarcoplasmic reticulum Ca2+-ATPase, or SERCA2, the VLDL receptor, fatty acyl-CoA synthetase, fatty acid transporter/CD36, carnitine palmitoyltransferase Ibeta, and lipoprotein lipase decrease in the heart after LPS treatment. The decrease in expression of RXRalpha, -beta, and -gamma, PPARalpha and -delta, and TRalpha and -beta, and of the coactivators CBP/p300, SRC-1, SRC-3, TRAP220, and PGC-1 and the genes they regulate, induced by LPS in the heart, could account for the decreased expression of key proteins required for fatty acid oxidation and thereby play an important role in cardiac contractility. These alterations could contribute to the myocardial dysfunction that occurs during sepsis.
Collapse
Affiliation(s)
- Kenneth Feingold
- Metabolism Section, Department of Medicine, University of California San Francisco, Medical Service, Department of Veterans Affairs Medical Center, San Francisco, California 94121, USA.
| | | | | | | | | |
Collapse
|
25
|
Takahashi S, Sakai J, Fujino T, Hattori H, Zenimaru Y, Suzuki J, Miyamori I, Yamamoto TT. The Very Low-density Lipoprotein (VLDL) Receptor: Characterization and Functions as a Peripheral Lipoprotein Receptor. J Atheroscler Thromb 2004; 11:200-8. [PMID: 15356379 DOI: 10.5551/jat.11.200] [Citation(s) in RCA: 116] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
The very low-density lipoprotein (VLDL) receptor is a member of the low-density lipoprotein (LDL) receptor family. In vitro and in vivo studies have shown that VLDL receptor binds triglyceride (TG)-rich lipoproteins but not LDL, and functions as a peripheral remnant lipoprotein receptor. VLDL receptor is expressed abundantly in fatty acid-active tissues (heart, skeletal muscle and fat), the brain and macrophages. It is likely that VLDL receptor functions in concert with lipoprotein lipase (LPL), which hydrolyses TG in VLDL and chylomicron. In contrast to the LDL receptor, VLDL receptor binds apolipoprotein (apo) E2/2 VLDL particles as well as apoE3/3 VLDL, and the expression is not down-regulated by intracellular lipoproteins. Recently, various functions of the VLDL receptor have been reported in lipoprotein metabolism, metabolic syndrome/atherosclerosis, cardiac fatty acid metabolism, neuronal migration and angiogenesis/tumor growth. Gene therapy of VLDL receptor into the liver showed a benefit effect for lipoprotein metabolism in both LDL receptor knockout and apoE mutant mice. Beyond its function as a peripheral lipoprotein receptor, possibilities of its physiological function have been extended to include signal transduction, angiogenesis and tumor growth.
Collapse
Affiliation(s)
- Sadao Takahashi
- The Third Department of Internal Medicine, University of Fukui, 23-3, Matsuokacho, Fukui, 910-1193, Japan.
| | | | | | | | | | | | | | | |
Collapse
|
26
|
Moreno M, Molina H, Amigo L, Zanlungo S, Arrese M, Rigotti A, Miquel JF. Hepatic overexpression of caveolins increases bile salt secretion in mice. Hepatology 2003; 38:1477-88. [PMID: 14647059 DOI: 10.1016/j.hep.2003.09.011] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
Caveolins are cholesterol-binding proteins involved in the regulation of several intracellular processes, including cholesterol transport. Because hepatocytes express caveolin-1 and caveolin-2, these proteins might modulate hepatic lipid metabolism and biliary lipid secretion. Our aim was to investigate the potential physiologic role of caveolins in hepatic cholesterol and bile salt (BS) metabolism and transport using adenoviral gene transfer. C57BL/6 mice were infected with recombinant human caveolin-1 and caveolin-2 adenoviruses. Mice infected with adenovirus lacking the transgene were used as controls. Hepatic caveolin expression was evaluated by immunochemical methods. Reverse-transcription polymerase chain reaction (RT-PCR) and immunoblotting were used to assess messenger RNA (mRNA) levels and protein mass of BS transporters (sodium taurocholate cotransporting polypeptide [Ntcp] and bile salt export pump [Bsep]). Serum, liver, biliary, and fecal biochemical determinations and BS maximal secretory rate (SRm) were performed by standard methods. Ad.Cav-1- and Ad.Cav-2-infected mice exhibited a 10- and 7-fold increase in hepatic caveolin-1 and caveolin-2 protein expression, respectively. Caveolin-1-overexpressing mice had a significant increase in plasma high-density lipoprotein (HDL) cholesterol and hepatic free cholesterol content, whereas total plasma cholesterol and triglyceride levels remained unchanged. Hepatic caveolin-1 and/or caveolin-2 overexpression significantly increased bile flow and secretion of all biliary lipids. Caveolin-1-overexpressing mice showed a 2.5-fold increase in taurocholate (TC) SRm, indicating increased canalicular BS transport capacity. BS pool size and fecal BS excretion remained within the normal range in mice with Cav-1 overexpression. No changes were seen in the protein mass of BS transporters Ntcp and Bsep. In conclusion, our findings indicate that caveolins may play an important role in regulating hepatic BS and cholesterol metabolism.
Collapse
Affiliation(s)
- Mauricio Moreno
- Departamento de Gastroenterología, Pontificia Universidad Católica de Chile, Santiago, Chile
| | | | | | | | | | | | | |
Collapse
|
27
|
|
28
|
Mardones P, Pilon A, Bouly M, Duran D, Nishimoto T, Arai H, Kozarsky KF, Altayo M, Miquel JF, Luc G, Clavey V, Staels B, Rigotti A. Fibrates down-regulate hepatic scavenger receptor class B type I protein expression in mice. J Biol Chem 2003; 278:7884-90. [PMID: 12511553 DOI: 10.1074/jbc.m211627200] [Citation(s) in RCA: 106] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Fibrates are normolipidemic drugs used in atherogenic dyslipidemia because of their ability to raise high density lipoprotein (HDL) and decrease triglyceride levels. They exert multiple effects on lipid metabolism by activating the peroxisome proliferator-activated receptor-alpha (PPAR-alpha), which controls the transcriptional regulation of genes involved in hepatic fatty acid, cholesterol, and lipoprotein metabolism. The hepatic expression of the scavenger receptor class B type I (SR-BI) plays a critical role in lipoprotein metabolism, mainly due to its ability to mediate selective cholesterol uptake. Because fibrates and PPAR-alpha agonists up-regulate SR-BI expression in human and murine macrophages, we tested whether fibrates raised a similar regulatory response on hepatic SR-BI expression in mice. Surprisingly, fibrate treatment suppressed SR-BI protein expression in the liver without changing steady state SR-BI mRNA levels. Decreased hepatic SR-BI protein expression correlated with enlarged HDL particle size. This effect was concomitant with down-regulation of CLAMP, a putative SR-BI-stabilizing protein found in the hepatic plasma membrane, which was also not associated to changes in CLAMP mRNA levels. The post-transcriptional regulatory effect of fibrates over hepatic SR-BI protein levels was dependent on PPAR-alpha expression, because it was absent in PPAR-alpha-deficient mice. Restoring hepatic SR-BI expression in fibrate-treated mice by recombinant adenoviral gene transfer abolished fibrate-mediated HDL particle size enlargement. This study describes a novel effect of fibrates on hepatic SR-BI expression providing an alternative mechanism by which this drug family modulates HDL metabolism in vivo.
Collapse
Affiliation(s)
- Pablo Mardones
- Departamento de Gastroenterologia, Facultad de Medicina, Pontificia Universidad Católica, Marcoleta 367, Santiago, Chile
| | | | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
29
|
Rao RM, Jo Y, Leers-Sucheta S, Bose HS, Miller WL, Azhar S, Stocco DM. Differential regulation of steroid hormone biosynthesis in R2C and MA-10 Leydig tumor cells: role of SR-B1-mediated selective cholesteryl ester transport. Biol Reprod 2003; 68:114-21. [PMID: 12493702 DOI: 10.1095/biolreprod.102.007518] [Citation(s) in RCA: 52] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/01/2022] Open
Abstract
The rat R2C Leydig tumor cell line is constitutively steroidogenic in nature, while the mouse MA-10 Leydig tumor cell line synthesizes large amounts of steroids only in response to hormonal stimulation. Earlier studies showed abundant cAMP-independent steroid production and constitutive expression of steroidogenic acute regulatory (StAR) protein in R2C cells. The objective of the current study was to identify possible genetic alterations in the R2C cell line responsible for rendering it a constitutively steroidogenic cell line, especially those that might have altered its cholesterol homeostatic mechanisms. Measurement of the levels of cholesterol esters and free cholesterol, precursors for steroidogenesis, indicated that R2C mitochondria were fourfold enriched in free cholesterol content compared with MA-10 mitochondria. In addition to the previously demonstrated increased expression of StAR protein, we show that R2C cells possess marginally enhanced protein kinase A activity, exhibit higher capacity to take up extracellular cholesterol esters, and express much higher levels of scavenger receptor-type B class 1 (SR-B1) and hormone sensitive lipase (HSL). These observations suggest that the high level of steroid biosynthesis in R2C cells is a result of the constitutive expression of the components involved in the uptake of cholesterol esters (SR-B1), their conversion to free cholesterol (HSL), and its mobilization to the inner mitochondrial membrane (StAR).
Collapse
Affiliation(s)
- Rekha M Rao
- Department of Cell Biology and Biochemistry, Texas Tech University Health Sciences Center, Lubbock, Texas 79430, USA
| | | | | | | | | | | | | |
Collapse
|
30
|
Amigo L, Mendoza H, Castro J, Quiñones V, Miquel JF, Zanlungo S. Relevance of Niemann-Pick type C1 protein expression in controlling plasma cholesterol and biliary lipid secretion in mice. Hepatology 2002; 36:819-28. [PMID: 12297829 DOI: 10.1053/jhep.2002.35617] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/07/2022]
Abstract
Receptor-mediated endocytosis is one of the major mechanisms for uptake of lipoprotein cholesterol in the liver. Because Niemann-Pick C1 (NPC1) protein is a key component in the intracellular distribution of cholesterol obtained from lipoproteins by the endocytic pathway, it may play a critical role in controlling plasma lipoprotein cholesterol and its biliary secretion. A murine model of Niemann-Pick type C disease (NPC), the NPC1-deficient [NPC1 (-/-)] mouse, was used to evaluate the relevance of hepatic NPC1 expression in regulating plasma lipoprotein cholesterol profile and biliary lipid secretion under chow and high-cholesterol diets. Total plasma cholesterol concentrations were increased in NPC1 (-/-) mice compared with wild-type mice when both mouse strains were fed chow or high-cholesterol diets. The increased plasma cholesterol levels found in NPC1 (-/-) mice were mostly due to elevated cholesterol content in larger and more heterogeneous HDL particles. On the chow diet, biliary lipid secretion was not impaired by NPC1 deficiency. Furthermore, chow-fed NPC1 (-/-) mice showed a small, but significant, increase in biliary cholesterol secretion. On the high-cholesterol diet, wild-type mice increased biliary cholesterol output, whereas NPC1 (-/-) mice did not. Finally, hepatic NPC1 overexpression by adenovirus-mediated gene transfer increased biliary cholesterol secretion by 100% to 150% in both wild-type mice and cholesterol-fed NPC1 (-/-) mice. In conclusion, hepatic NPC1 expression is an important factor for regulating plasma HDL cholesterol levels and biliary cholesterol secretion in mice.
Collapse
Affiliation(s)
- Ludwig Amigo
- Departamento de Gastroenterología, Facultad de Medicina, Pontificia Universidad Católica, Santiago, Chile
| | | | | | | | | | | |
Collapse
|
31
|
Correlating Changes in Follicular VLDL Binding and Follicular Aromatase Activity in the Ovulation Cycle of the Laying Hen. J Poult Sci 2002. [DOI: 10.2141/jpsa.39.100] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
|
32
|
Nakamura Y, Yamamoto M, Kumamaru E. Significance of the variant and full-length forms of the very low density lipoprotein receptor in brain. Brain Res 2001; 922:209-15. [PMID: 11743951 DOI: 10.1016/s0006-8993(01)03170-5] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
The very low density lipoprotein receptor (VLDLR) is a newly described receptor which binds to apolipoprotein E (apoE) specifically. The authors designed a synthetic peptide of 17 amino acids representing the N-terminus of the putative first ligand binding domain of human VLDLR, this being a unique domain for VLDLR. When the synthetic peptide was used as the antigen, two different monoclonal antibodies were obtained (anti-VLDLR1 and anti-VLDLR2). Expressional cloning revealed that anti-VLDLR1 recognized the variant form of VLDLR which lacks 84 bp of O-linked sugar domain and anti-VLDLR2 recognized the full length form of VLDLR. The variant VLDLR was expressed in neuroblasts as well as matrix cells and Cajal-Retzius cells in the early stages of the developing human brain; later its expression was sequentially found in glioblasts, astrocytes, oligodendrocytes and finally in myelin. The expression of a full length form of VLDLR was detected in senile plaques and some neurons and satellite glia in aged and Alzheimer brains. This suggests that the variant VLDLR is important for the developing human brain and the full length VLDLR has modified functions in aged and Alzheimer brains.
Collapse
MESH Headings
- Adult
- Aged
- Aged, 80 and over
- Alzheimer Disease/metabolism
- Alzheimer Disease/pathology
- Alzheimer Disease/physiopathology
- Animals
- Antibodies, Monoclonal
- Antibody Specificity/genetics
- Apolipoproteins E/metabolism
- Base Sequence/genetics
- Blotting, Northern
- Brain/cytology
- Brain/embryology
- Brain/metabolism
- Epitopes/immunology
- Female
- Fetus
- Gene Expression Regulation, Developmental/genetics
- Humans
- Immunohistochemistry
- Infant
- Infant, Newborn
- Mice
- Mice, Inbred BALB C
- Middle Aged
- Molecular Sequence Data
- Neuroglia/cytology
- Neuroglia/metabolism
- Neurons/cytology
- Neurons/metabolism
- Plaque, Amyloid/metabolism
- Plaque, Amyloid/pathology
- RNA, Messenger/metabolism
- Receptors, LDL/genetics
- Receptors, LDL/immunology
- Receptors, LDL/metabolism
- Reverse Transcriptase Polymerase Chain Reaction
Collapse
Affiliation(s)
- Y Nakamura
- Department of Pathology, St. Mary's Hospital, Tsubukuhon-machi 422, Kurume 830-8543, Japan.
| | | | | |
Collapse
|
33
|
Bhuiyan MM, Sato M, Murao K, Imachi H, Namihira H, Ishida T, Takahara J, Miyauchi A. Differential expression of menin in various adrenal tumors. The role of menin in adrenal tumors. Cancer 2001; 92:1393-401. [PMID: 11745215 DOI: 10.1002/1097-0142(20010915)92:6<1393::aid-cncr1462>3.0.co;2-4] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
BACKGROUND Adrenocortical tumors occur as sporadic tumors, as part of the multiple endocrine neoplasia type 1 (MEN1) syndrome, or as part of other hereditary disorders. MEN1 is a tumor suppressor gene located on chromosome 11q13 that encodes a 610-amino acid protein called menin, and plays an important role in the development of MEN1 syndrome. Recent reports indicate that heterozygous germline mutations of this gene are responsible for the disease onset of MEN1. METHODS To investigate the role of menin in sporadic adrenocortical tumors, the authors examined a series of adrenocortical adenoma cases and a single case of carcinoma and adrenomedulary tumors with the corresponding adjacent tumor tissues using reverse transcriptase-polymerase chain reaction (RT-PCR) for menin mRNA and Western blot analysis for menin protein. Both RNA and protein from these tumors were applied to RT-PCR and Western blot analysis, respectively, although they are not truly quantitative. Primers for RT-PCR were designed to amplify the sequence between exons 2 and 3 of the MEN1 gene. A specific antibody against menin was generated in guinea pigs immunized with the recombinant peptide from the amino acid residues 443-535 of menin made by using glutathione-S-transferase gene fusion. RESULTS Based on the results of RT-PCR and Western blot analysis, both MEN1 mRNA and menin protein appeared to be highly expressed in Cushing syndrome resulting from adrenocortical adenomas and carcinoma. However, their expression was found to be greatly decreased in primary aldosteronism compared with their expression in Cushing syndrome. Although weak expression of MEN1 mRNA also was detected in pheochromocytoma on RT-PCR, menin expression was not detected in any case of pheochromocytoma by Western blot analysis, possibly due to the lower sensitivity of this assay compared with RT-PCR. Neither MEN1 mRNA nor menin protein was detected in any of the corresponding adjacent tumor tissues examined. CONCLUSIONS The findings of the current study indicate that menin expression appears to be up-regulated in Cushing syndrome, suggesting that adrenocortical proliferation might be one of the primary lesions in the MEN1 syndrome in which menin might play a significant role in some specific cellular functions.
Collapse
Affiliation(s)
- M M Bhuiyan
- First Department of Internal Medicine, Kagawa Medical University, Kagawa, Japan
| | | | | | | | | | | | | | | |
Collapse
|
34
|
Tacken PJ, Hofker MH, Havekes LM, van Dijk KW. Living up to a name: the role of the VLDL receptor in lipid metabolism. Curr Opin Lipidol 2001; 12:275-9. [PMID: 11353330 DOI: 10.1097/00041433-200106000-00006] [Citation(s) in RCA: 61] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
The VLDL receptor (VLDLR) is a member of the LDL receptor family. The VLDLR was hypothesized to mediate fatty acid entry into peripheral tissues, on the basis of its expression in tissues that are active in fatty acid metabolism and its capacity to bind apolipoprotein-E-rich VLDL in vitro. This hypothesis initially proved difficult to confirm, because VLDLR-knockout mice were reported to display normal plasma lipid levels. Moreover, studies in VLDLR-knockout mice that were also deficient in a second LDL receptor family member, the apolipoprotein E receptor 2, indicated a role for the VLDLR in neuronal migration during brain development. However, in accordance with what the term VLDLR suggests, recent studies using VLDLR-deficient and transgenic mice have provided compelling evidence that the VLDLR does indeed play a role in VLDL-triglyceride metabolism, and that it is important for triglyceride storage in the adipocyte.
Collapse
Affiliation(s)
- P J Tacken
- Department of Human and Clinical Genetics, Leiden University Medical Center, Leiden, The Netherlands
| | | | | | | |
Collapse
|
35
|
Garcia CK, Wilund K, Arca M, Zuliani G, Fellin R, Maioli M, Calandra S, Bertolini S, Cossu F, Grishin N, Barnes R, Cohen JC, Hobbs HH. Autosomal recessive hypercholesterolemia caused by mutations in a putative LDL receptor adaptor protein. Science 2001; 292:1394-8. [PMID: 11326085 DOI: 10.1126/science.1060458] [Citation(s) in RCA: 405] [Impact Index Per Article: 17.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
Atherogenic low density lipoproteins are cleared from the circulation by hepatic low density lipoprotein receptors (LDLR). Two inherited forms of hypercholesterolemia result from loss of LDLR activity: autosomal dominant familial hypercholesterolemia (FH), caused by mutations in the LDLR gene, and autosomal recessive hypercholesterolemia (ARH), of unknown etiology. Here we map the ARH locus to an approximately 1-centimorgan interval on chromosome 1p35 and identify six mutations in a gene encoding a putative adaptor protein (ARH). ARH contains a phosphotyrosine binding (PTB) domain, which in other proteins binds NPXY motifs in the cytoplasmic tails of cell-surface receptors, including the LDLR. ARH appears to have a tissue-specific role in LDLR function, as it is required in liver but not in fibroblasts.
Collapse
Affiliation(s)
- C K Garcia
- McDermott Center for Human Growth and Development and Department of Internal Medicine, University of Texas Southwestern Medical Center at Dallas, 5323 Harry Hines Boulevard, Dallas, TX 75390, USA
| | | | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
36
|
Affiliation(s)
- J Herz
- Department of Molecular Genetics, University of Texas Southwestern Medical Center, 5323 Harry Hines Boulevard, Dallas, TX 75390, USA.
| |
Collapse
|
37
|
Hepatic cholesterol and bile acid metabolism and intestinal cholesterol absorption in scavenger receptor class B type I-deficient mice. J Lipid Res 2001. [DOI: 10.1016/s0022-2275(20)31676-x] [Citation(s) in RCA: 230] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
|
38
|
Sakthivel R, Zhang JC, Strickland DK, Gåfvels M, McCrae KR. Regulation of the ligand binding activity of the human very low density lipoprotein receptor by protein kinase C-dependent phosphorylation. J Biol Chem 2001; 276:555-62. [PMID: 11010963 DOI: 10.1074/jbc.m003953200] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The very low density lipoprotein receptor (VLDL-R) binds and internalizes several ligands, including very low density lipoprotein (VLDL), urokinase-type plasminogen activator:plasminogen activator inhibitor type 1 complexes, lipoprotein lipase, and the 39-kDa receptor-associated protein that copurifies with the low density lipoprotein receptor-related protein/alpha(2)-macroglobulin receptor. Although several agonists regulate VLDL-R mRNA and/or protein expression, post-transcriptional regulation of receptor activity has not been described. Here, we report that the ligand binding activity of the VLDL-R in THP-1 monocytic cells, endothelial cells, smooth muscle cells, and VLDL-R-transfected HEK 293 cells is diminished after treatment with phorbol 12-myristate 13-acetate. This response was blocked by inhibitors of protein kinase C (PK-C), including a specific inhibitor of the PK-C beta II isoform, and was associated with phosphorylation of serine residues in the cytoplasmic domain of the receptor. Culture of endothelial cells in the presence of high glucose concentrations, which stimulate diacylglycerol synthesis and PK-C beta II activation, also induced a PK-C-dependent loss of VLDL-R ligand binding activity. Taken together, these studies demonstrate that the ligand binding activity of the VLDL-R is regulated by PK-C-dependent phosphorylation and that hyperglycemia may diminish VLDL-R activity.
Collapse
Affiliation(s)
- R Sakthivel
- Department of Medicine, Case Western Reserve University School of Medicine, Cleveland, Ohio 44106, USA
| | | | | | | | | |
Collapse
|
39
|
Zanlungo S, Amigo L, Mendoza H, Miquel JF, Vío C, Glick JM, Rodríguez A, Kozarsky K, Quiñones V, Rigotti A, Nervi F. Sterol carrier protein 2 gene transfer changes lipid metabolism and enterohepatic sterol circulation in mice. Gastroenterology 2000; 119:1708-19. [PMID: 11113092 DOI: 10.1053/gast.2000.20198] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
Abstract
BACKGROUND & AIMS Sterol carrier protein 2 (SCP-2) enhances sterol cycling and facilitates cholesterol translocation between intracellular organelles and plasma membrane in cultured cells, including hepatocytes. We examined the role of SCP-2 in hepatic cholesterol and lipid trafficking through the sinusoidal and canalicular secretory pathways of the liver in vivo. METHODS Recombinant adenovirus-mediated SCP-2 gene transfer was used to obtain hepatic overexpression of SCP-2 in C57BL/6 mice. RESULTS SCP-2 overexpression in the mouse liver resulted in an 8-fold increase of SCP-2 protein levels and determined various effects on lipid metabolism. It decreased high-density lipoprotein cholesterol and increased low-density lipoprotein (LDL) cholesterol concentrations. The expressions of hepatic LDL receptor, apolipoprotein (apo) A-I, apoB, and apoE were decreased. SCP-2 overexpression also increased hepatic cholesterol concentration, associated with decreased cholesterol neosynthesis. Increased biliary cholesterol and bile acid secretion, bile acid pool size, and intestinal cholesterol absorption were also observed. CONCLUSIONS These results indicate that modulation of SCP-2 expression in the liver determines important modifications on lipoprotein metabolism, hepatic cholesterol synthesis and storage, biliary lipid secretion, bile acid metabolism, and intestinal cholesterol absorption.
Collapse
Affiliation(s)
- S Zanlungo
- Departamento de Gastroenterología, Facultad de Medicina, Pontificia Universidad Católica, Santiago, Chile
| | | | | | | | | | | | | | | | | | | | | |
Collapse
|
40
|
Berge KE, Tian H, Graf GA, Yu L, Grishin NV, Schultz J, Kwiterovich P, Shan B, Barnes R, Hobbs HH. Accumulation of dietary cholesterol in sitosterolemia caused by mutations in adjacent ABC transporters. Science 2000; 290:1771-5. [PMID: 11099417 DOI: 10.1126/science.290.5497.1771] [Citation(s) in RCA: 1131] [Impact Index Per Article: 47.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Abstract
In healthy individuals, acute changes in cholesterol intake produce modest changes in plasma cholesterol levels. A striking exception occurs in sitosterolemia, an autosomal recessive disorder characterized by increased intestinal absorption and decreased biliary excretion of dietary sterols, hypercholesterolemia, and premature coronary atherosclerosis. We identified seven different mutations in two adjacent, oppositely oriented genes that encode new members of the adenosine triphosphate (ATP)-binding cassette (ABC) transporter family (six mutations in ABCG8 and one in ABCG5) in nine patients with sitosterolemia. The two genes are expressed at highest levels in liver and intestine and, in mice, cholesterol feeding up-regulates expressions of both genes. These data suggest that ABCG5 and ABCG8 normally cooperate to limit intestinal absorption and to promote biliary excretion of sterols, and that mutated forms of these transporters predispose to sterol accumulation and atherosclerosis.
Collapse
MESH Headings
- ATP Binding Cassette Transporter, Subfamily G, Member 5
- ATP-Binding Cassette Transporters/chemistry
- ATP-Binding Cassette Transporters/genetics
- ATP-Binding Cassette Transporters/metabolism
- Amino Acid Sequence
- Animals
- Bile/metabolism
- Cholesterol/blood
- Cholesterol, Dietary/administration & dosage
- Cholesterol, Dietary/metabolism
- Chromosome Mapping
- Chromosomes, Human, Pair 2
- Codon
- DNA-Binding Proteins
- Expressed Sequence Tags
- Gene Expression Regulation
- Humans
- Intestinal Absorption
- Intestinal Mucosa/metabolism
- Lipid Metabolism, Inborn Errors/genetics
- Lipid Metabolism, Inborn Errors/metabolism
- Lipoproteins/chemistry
- Lipoproteins/genetics
- Lipoproteins/metabolism
- Liver/metabolism
- Liver X Receptors
- Mice
- Mice, Inbred C57BL
- Molecular Sequence Data
- Mutation
- Orphan Nuclear Receptors
- RNA, Messenger/genetics
- RNA, Messenger/metabolism
- Receptors, Cytoplasmic and Nuclear/metabolism
- Sitosterols/blood
- Sitosterols/metabolism
Collapse
Affiliation(s)
- K E Berge
- Department of Molecular Genetics and McDermott Center for Human Growth and Development and Howard Hughes Medical Institute, University of Texas Southwestern Medical Center at Dallas, 5323 Harry Hines Boulevard, Dallas, TX 75390-9046, USA
| | | | | | | | | | | | | | | | | | | |
Collapse
|
41
|
Bhuiyan MM, Sato M, Murao K, Imachi H, Namihira H, Takahara J. Expression of menin in parathyroid tumors. J Clin Endocrinol Metab 2000; 85:2615-9. [PMID: 10902816 DOI: 10.1210/jcem.85.7.6688] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
The multiple endocrine neoplasia type 1 (MEN1) gene seems to be a tumor suppressor that encodes a 610-amino acid protein termed menin and that plays an important role in the development of MEN1 syndrome. Recent reports indicate that heterozygous germline mutations of this gene are responsible for the disease onset of MEN1. In this study we examined the expression of menin in parathyroid tumors from primary hyperparathyroidism (PHP), secondary hyperparathyroidism (SHP), and MEN1 and thyroid tumors including Basedow's disease, thyroid cancer, and adrenocortical tumors. Both ribonucleic acid and protein from these tumors were applied to RT-PCR and Western blotting, respectively. Primers for RT-PCR were designed to amplify the sequence between exons 2 and 3 of the MEN1 gene. Specific antibody against menin was generated in guinea pigs immunized with the recombinant peptide from amino acid residues 443-535 of menin made by using glutathione-S-transferase (GST) gene fusion. Menin messenger ribonucleic acid was strongly expressed on RT-PCR analysis in the parathyroid tumors from both PHP and SHP. Western blotting revealed a specific band of approximately 67 kDa in parathyroid tumors from PHP and SHP, with a much weaker such band detected in thyroid tumors. Menin expression was down-regulated in MEN1 samples, including nonsense mutation and deletion mutant. These findings suggest that menin is predominantly synthesized and stored in parathyroid tumors resulting from PHP and SHP.
Collapse
Affiliation(s)
- M M Bhuiyan
- First Department of Internal Medicine, Kagawa Medical University, Japan
| | | | | | | | | | | |
Collapse
|
42
|
Nakamura Y, Yamamoto M, Kumamaru E. Very low-density lipoprotein receptor in fetal intestine and gastric adenocarcinoma cells. Arch Pathol Lab Med 2000; 124:119-22. [PMID: 10629142 DOI: 10.5858/2000-124-0119-vldlri] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
BACKGROUND A very low-density lipoprotein receptor (VLDLR) was recently identified. This receptor reportedly binds specifically to very low-density lipoproteins; however, its distribution and functions in vivo have yet to be elucidated. We investigated the expression and regulation of VLDLR in fetal and carcinoma cells. OBJECTIVE The expression of VLDLR was examined by immunohistochemistry and reverse-transcriptase polymerase chain reaction using several specimens, including a fetus of 12 to 15 weeks' gestation, various tumors, AGS cells, and INT407 cells. RESULTS Immunoreactive VLDLR was abundantly present in human fetal intestinal epithelial and gastric adenocarcinoma cells. This receptor was also noted in the intestinal cell line, INT407, and gastric cancer cell line, AGS. In addition, the VLDLR that was expressed in INT407 cells, AGS cells, and gastric adenocarcinoma tissue was present mainly in a variant form lacking the O-linked sugar domain. CONCLUSIONS These data suggest that an important function of VLDLR may be the mediation of cell growth in developing tissues, such as fetal intestinal and cancer cells. The INT407 and AGS cell lines appear to be useful for examining the regulation of VLDLR expression.
Collapse
Affiliation(s)
- Y Nakamura
- Department of Pathology, St Mary's Hospital, Tsubukuhon-machi, Kurume, Japan.
| | | | | |
Collapse
|
43
|
Savonen R, Obermoeller LM, Trausch-Azar JS, Schwartz AL, Bu G. The carboxyl-terminal domain of receptor-associated protein facilitates proper folding and trafficking of the very low density lipoprotein receptor by interaction with the three amino-terminal ligand-binding repeats of the receptor. J Biol Chem 1999; 274:25877-82. [PMID: 10464330 DOI: 10.1074/jbc.274.36.25877] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The 39-kDa receptor-associated protein (RAP) is a specialized antagonist that inhibits all known ligand interactions with receptors that belong to the low density lipoprotein (LDL) receptor gene family. Recent studies have demonstrated a role for RAP as a molecular chaperone for the LDL receptor-related protein during receptor folding and trafficking within the early secretory pathway. In the present study, we investigated a potential role for RAP as a chaperone for the very low density lipoprotein (VLDL) receptor, another member of the LDL receptor gene family. Using intracellular cross-linking techniques, we found that RAP is associated with newly synthesized VLDL receptor. In the absence of RAP co-expression, newly synthesized VLDL receptor exhibited slower trafficking along the early secretory pathway, most likely due to misfolding of the receptor. The role of RAP in the folding of the VLDL receptor was further studied using an anchor-free, soluble VLDL receptor. Metabolic pulse-chase labeling experiments showed that while only 3% of the soluble VLDL receptor was folded and secreted in the absence of RAP co-expression, over 50% of the soluble receptor was secreted in the presence of RAP co-expression. The functions of RAP in VLDL receptor folding and trafficking were mediated by its carboxyl-terminal repeat but not by the amino-terminal and central repeats. Using truncated VLDL receptor constructs, we identified the RAP-binding site within the first three ligand-binding repeats of the VLDL receptor. Thus, our present study demonstrates that RAP serves as a folding and trafficking chaperone for the VLDL receptor via interactions of its carboxyl-terminal repeat with the three amino-terminal ligand-binding repeats of the VLDL receptor.
Collapse
Affiliation(s)
- R Savonen
- Departments of Pediatrics, Washington University School of Medicine, St. Louis, Missouri 63110, USA
| | | | | | | | | |
Collapse
|
44
|
Fechner H, Haack A, Wang H, Wang X, Eizema K, Pauschinger M, Schoemaker R, Veghel R, Houtsmuller A, Schultheiss HP, Lamers J, Poller W. Expression of coxsackie adenovirus receptor and alphav-integrin does not correlate with adenovector targeting in vivo indicating anatomical vector barriers. Gene Ther 1999; 6:1520-35. [PMID: 10490761 DOI: 10.1038/sj.gt.3301030] [Citation(s) in RCA: 243] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
Recombinant adenoviral vectors are broadly applied in gene therapy protocols. However, adenovector-mediated gene transfer has limitations in vivo. One of these is the low gene transfer rate into organs other than the liver after systemic intravenous vector injection. Local direct injection into the target organ has been used as one possible solution, but increases necessary equipment and methodology and is traumatic to the target. Wild-type adenovirus infection as well as adenovector-mediated gene transfer depends on virus interaction with the Coxsackie adenovirus receptor (CAR) mediating virus attachment to the cell surface, and on interaction with alphavbeta3 and alphavbeta5 integrins mediating virus entry into the cell. In order to assess the receptor-associated potential of different tissues to act as adenovector targets, we have therefore determined CAR and alphav-integrin expression in multiple organs from different species. In addition, we have newly determined several human, rat, pig and dog CAR-mRNA sequences. Sequence comparison and structural analyses of known and of newly determined sequences suggests a potential adenovirus binding site between amino acids 29 and 128 of the CAR. With respect to the virus receptor expression patterns we found that CAR-mRNA expression was extremely variable between different tissues, with the highest levels in the liver, whereas alphav-integrin expression was far more homogenous among different organs. Both CAR and alphav-integrin showed similar expression patterns among different species. There was no correlation, however, between the adenovector expression patterns after intravenous, intracardiac and aortic root injection, respectively, and the virus receptor patterns. In summary, many organs carry both receptors required to make them potential adenovector targets. In sharp contrast, their actual targeting clearly indicates that adenovirus receptor expression is necessary but not sufficient for vector transfer after systemic injection. The apparently very important role of anatomical barriers, in particular the endothelium, requires close attention when developing non-traumatic, organ-specific gene therapy protocols.
Collapse
Affiliation(s)
- H Fechner
- Department of Cardiology and Pneumology, University Hospital Benjamin Franklin, Freie Universität, Berlin, Germany
| | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
45
|
Zerbinatti CV, Dyer CA. Apolipoprotein E peptide stimulation of rat ovarian theca cell androgen synthesis is mediated by members of the low density lipoprotein receptor superfamily. Biol Reprod 1999; 61:665-72. [PMID: 10456843 DOI: 10.1095/biolreprod61.3.665] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/01/2022] Open
Abstract
Ovarian androgen production is rate limiting for follicular maturation and can induce follicular atresia. Thus, it is important to define the actions of the intraovarian agents, such as apolipoprotein (apo) E, that modulate theca cell androgen production. Theca cell androgen production is stimulated at low concentrations and inhibited at higher concentrations of native apo E. The apo E peptide, acetyl-Y(LRKLRKRLLRDADDL)(2)C or acetyl-Y(141-155)(2)C, has low density lipoprotein (LDL) receptor and LDL receptor-related protein-binding activity, and it mimics the activity of native apo E in the theca-interstitial cell system. To define the role of members of the LDL receptor superfamily in the apo E peptide-mediated responses, we found that receptor-associated protein prevented the stimulation without altering the inhibition of androstenedione production. The apo E peptide (129-162), which has no LDL receptor-binding activity, did not stimulate androstenedione production. The apo E peptide acetyl-Y(141-155)(2)C did not stimulate androstenedione production when cell surface heparan sulfate proteoglycans were degraded with heparinase. The apo E peptide acetyl-Y(141-155)(2)C bound to heparin, a property of LDL receptor ligands, and in this complex the peptide had no effect on androstenedione production. These observations support the conclusion that apo E-mediated stimulation, but not inhibition, of ovarian theca cell androstenedione production was mediated by members of the LDL receptor superfamily.
Collapse
Affiliation(s)
- C V Zerbinatti
- Department of Biological Sciences, Northern Arizona University, Flagstaff, Arizona 86011, USA.
| | | |
Collapse
|
46
|
Buechler C, Ritter M, Quoc CD, Agildere A, Schmitz G. Lipopolysaccharide inhibits the expression of the scavenger receptor Cla-1 in human monocytes and macrophages. Biochem Biophys Res Commun 1999; 262:251-4. [PMID: 10448100 DOI: 10.1006/bbrc.1999.1193] [Citation(s) in RCA: 56] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Human Cla-1 is the likely homologue of the murine scavenger receptor class B type I (SR-BI). SR-BI mediates selective transfer of cholesterol to high-density lipoprotein (HDL) and the efflux of endogenously synthesized and plasma membrane sterols to HDL. HDL protects against atherosclerosis but also reduces endotoxic activity by complexation and neutralization of LPS. We found that Cla-1 is upregulated during phagocytic as well as dendritic differentiation of monocytes, indicating a function of this receptor for cholesterol homeostasis in phagocytes and antigen-presenting cells. Cla-1 expression is suppressed by the proinflammatory stimuli lipopolysaccharide, interferon-gamma, and tumor necrosis factor alpha in monocytes and macrophages. Downregulation of Cla-1 mRNA by LPS is likely due to a modification and subsequent destabilization of the mRNA. We propose that suppression of Cla-1 expression may help to stabilize the lipoprotein status in the blood compartment important for host defense.
Collapse
Affiliation(s)
- C Buechler
- Klinikum der Universität Regensburg, Regensburg, D-93042, Germany
| | | | | | | | | |
Collapse
|
47
|
Abstract
The low-density lipoprotein (LDL) receptor (LDL-R) family consists of cell-surface receptors that recognize extracellular ligands and internalize them for degradation by lysosomes. The LDL-R is the prototype of this family, which also contains very-low-density lipoprotein receptors (VLDL-R), apolipoprotein E receptor 2, LRP, and megalin. The family members contain four major structural modules: the cysteine-rich complement-type repeats, epidermal growth factor precursor-like repeats, a transmembrane domain, and a cytoplasmic domain. Each structural module serves distinct and important functions. These receptors bind several structurally dissimilar ligands. It is proposed that instead of a primary sequence, positive electrostatic potential in different ligands constitutes a receptor binding domain. This family of receptors plays crucial roles in various physiologic functions. LDL-R plays an important role in cholesterol homeostasis. Mutations cause familial hypercholesterolemia and premature coronary artery disease. LDL-R-related protein plays an important role in the clearance of plasma-activated alpha 2-macroglobulin and apolipoprotein E-enriched lipoproteins. It is essential for fetal development and has been associated with Alzheimer's disease. Megalin is the major receptor in absorptive epithelial cells of the proximal tubules and an antigenic determinant for Heymann nephritis in rats. Mutations in a chicken homolog of VLDL-R cause female sterility and premature atherosclerosis. This receptor is not expressed in liver tissue; however, transgenic expression of VLDL-R in liver corrects hypercholesterolemia in experiment animals, which suggests that it can be a candidate for gene therapy for various hyperlipidemias. The functional importance of individual receptors may lie in their differential tissue expression. The regulation of expression of these receptors occurs at the transcriptional level. Expression of the LDL-R is regulated by intracellular sterol levels involving novel membrane-bound transcription factors. Other members of the family are not regulated by sterols. All the members are, however, regulated by hormones and growth factors, but the mechanisms of regulation by hormones have not been elucidated. Studies of these receptors have provided important insights into receptor structure-function and mechanisms of ligand removal and catabolism. It is anticipated that increased knowledge about the LDL-R family members will open new avenues for the treatment of many disorders.
Collapse
Affiliation(s)
- M M Hussain
- Department of Biochemistry, MCP Hahnemann University, Philadelphia, Pennsylvania 19129, USA.
| | | | | |
Collapse
|
48
|
Tiebel O, Oka K, Robinson K, Sullivan M, Martinez J, Nakamuta M, Ishimura-Oka K, Chan L. Mouse very low-density lipoprotein receptor (VLDLR): gene structure, tissue-specific expression and dietary and developmental regulation. Atherosclerosis 1999; 145:239-51. [PMID: 10488949 DOI: 10.1016/s0021-9150(99)00068-4] [Citation(s) in RCA: 55] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
The very low density lipoprotein receptor (VLDLR) is a multifunctional apolipoprotein (apo) E receptor that shares a common structural feature as well as some ligand specificity to apo E with members of the low density lipoprotein receptor gene family. We have isolated and characterized the mouse VLDLR gene. The mouse VLDLR gene contains 19 exons spanning approximately 50 kb. The exon-intron organization of the gene is completely conserved between mouse and human. Since the 5'-flanking region of the mouse VLDLR gene contains two copies of a sterol regulatory element-1 like sequence (SRE-1), we next studied regulation of the VLDLR mRNA expression in heart, skeletal muscle and adipose tissue in C57BL/6, LDLR-/-, apo E-/- and LDLR-/-apo E-/- mice fed normal chow or atherogenic diet. The VLDLR mRNA expression was down-regulated 3-fold by feeding atherogenic diet in heart and skeletal muscle only in LDLR-/- mice. In contrast, VLDLR mRNA expression was up-regulated by atherogenic diet in adipose tissue in all animal models except double knockout mice. These results suggest that SRE-1 may be functional and VLDLR plays a role in cholesterol homeostasis in heart and skeletal muscle when LDLR is absent and that apo E is required for this modulation. Developmental regulation of the VLDLR mRNA expression was also tissue-specific. VLDLR mRNA expression in heart displayed significant up and down regulation during development. Maximal level was detected on post-natal day 3. However, the VLDLR mRNA levels in skeletal muscle remained relatively constant except a slight dip on post-natal day 7. In kidney and brain, VLDLR mRNA also peaked on post-natal day 3 but remained relatively constant thereafter. In liver, VLDLR mRNA expression was very low; it was barely detectable at day 19 of gestation and was decreased further thereafter. In adipose tissue, the VLDLR mRNA level showed an increase on post-natal day 13, went down again during weaning and then continued to increase afterwards. This developmental pattern as well as dietary regulation in adipose tissue supports the notion that VLDLR plays a role in lipid accumulation in this tissue. Although the primary role of VLDLR in heart, muscle and adipose tissue is likely in lipid metabolism, developmental pattern of this receptor in other tissues suggests that VLDLR has functions that are unrelated to lipid metabolism.
Collapse
MESH Headings
- Adipose Tissue/growth & development
- Adipose Tissue/metabolism
- Animals
- Base Sequence
- Blotting, Northern
- Diet, Atherogenic
- Down-Regulation
- Female
- Gene Expression Regulation, Developmental
- Heart/growth & development
- Lipoproteins, VLDL/biosynthesis
- Lipoproteins, VLDL/genetics
- Mice
- Mice, Inbred C57BL
- Mice, Knockout
- Molecular Sequence Data
- Muscle Development
- Muscle, Skeletal/growth & development
- Muscle, Skeletal/metabolism
- Myocardium/metabolism
- Polymerase Chain Reaction
- Pregnancy
- RNA Probes/chemistry
- RNA, Messenger/biosynthesis
- RNA, Messenger/genetics
- Receptors, LDL/biosynthesis
- Receptors, LDL/genetics
Collapse
Affiliation(s)
- O Tiebel
- Department of Cell Biology and Medicine, Baylor College of Medicine, Houston, TX 77030, USA
| | | | | | | | | | | | | | | |
Collapse
|
49
|
Magrané J, Casaroli-Marano RP, Reina M, Gåfvels M, Vilaró S. The role of O-linked sugars in determining the very low density lipoprotein receptor stability or release from the cell. FEBS Lett 1999; 451:56-62. [PMID: 10356983 DOI: 10.1016/s0014-5793(99)00494-9] [Citation(s) in RCA: 54] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
Abstract
The very low density lipoprotein receptor is a member of the low density lipoprotein receptor supergene family for which two isoforms have been reported, one lacking and the other containing an O-linked sugar domain. In order to gain insight into their functionality, transient and stable transformants separately overexpressing previously cloned bovine variants were analyzed. We report evidence that the variant lacking the O-linked sugar domain presented a rapid cleavage from the cell and that a large amino-terminal very low density lipoprotein receptor fragment was released into the culture medium. As only minor proteolysis was involved in the other very low density lipoprotein receptor variant, the clustered O-linked sugar domain may be responsible for blocking the access to the protease-sensitive site(s). To test this hypothesis, a mutant Chinese hamster ovary cell line, ldlD, with a reversible defect in the protein O-glycosylation, was used. The instability of the O-linked sugar-deficient very low density lipoprotein receptor on the cell surface was comparable to that induced by the proteolysis of the variant lacking the O-linked sugar domain. Moreover, our data suggest that the O-linked sugar domain may also protect the very low density lipoprotein receptor against unspecific proteolysis. Taken together, these results indicate that the presence of the O-linked sugar domain may be required for the stable expression of the very low density lipoprotein receptor on the cell surface and its absence may be required for release of the receptor to the extracellular space. The exclusive expression of the variant lacking the O-linked sugar domain in the bovine aortic endothelium opens new perspectives in the physiological significance of the very low density lipoprotein receptor.
Collapse
Affiliation(s)
- J Magrané
- Department of Cellular Biology, Faculty of Biology, University of Barcelona, Spain.
| | | | | | | | | |
Collapse
|
50
|
Perazzolo LM, Coward K, Davail B, Normand E, Tyler CR, Pakdel F, Schneider WJ, Le Menn F. Expression and localization of messenger ribonucleic acid for the vitellogenin receptor in ovarian follicles throughout oogenesis in the rainbow trout, Oncorhynchus mykiss. Biol Reprod 1999; 60:1057-68. [PMID: 10208965 DOI: 10.1095/biolreprod60.5.1057] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/01/2022] Open
Abstract
The expression and localization of vitellogenin (VTG) receptor (VTGR) mRNA were identified throughout ovarian development in the rainbow trout, Oncorhynchus mykiss. Northern blot confirmed the presence of a transcript (approximately 3.9 kilobases [kb]) that was specific to the ovary. The expression of VTGR mRNA varied throughout ovarian development and was highest in previtellogenic ovaries and in ovaries at the onset of vitellogenesis containing ovarian follicles (OF) from 35 to 600 microm in diameter. In situ hybridization using 35S riboprobes showed that the transcription of the VTGR gene was initiated in OF measuring 45-50 microm in diameter, with transcripts being exclusively localized in the ooplasm. A dramatic increase in mRNA synthesis occurred during previtellogenic growth (OF from 50 to 200 microm); this was followed by a gradual decrease during the vitellogenic growth phase. VTGR mRNA was not detected in OF greater than 1000 microm in diameter (oocytes actively sequestering VTG). Immunocytolocalization of yolk proteins derived from VTG demonstrated that oocytes started to sequester VTG when they were around 300 microm in diameter, shortly after the time of maximal density of VTGR mRNA in the ooplasm. The timing of transcription of the VTGR gene, predominantly during previtellogenesis, suggests that the VTGR is recycled to the oocyte surface during the vitellogenic growth phase.
Collapse
Affiliation(s)
- L M Perazzolo
- Laboratoire de Biologie de la Reproduction des Poissons, Unité Associée INRA, Université Bordeaux I, 33405 Talence, France
| | | | | | | | | | | | | | | |
Collapse
|