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Della Guardia L, Luzi L, Codella R. Muscle-UCP3 in the regulation of energy metabolism. Mitochondrion 2024; 76:101872. [PMID: 38499130 DOI: 10.1016/j.mito.2024.101872] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2023] [Revised: 03/10/2024] [Accepted: 03/15/2024] [Indexed: 03/20/2024]
Abstract
Uncoupling protein-3 (UCP3) is a mitochondria-regulatory protein with potential energy- homeostatic functions. This study explores the role of UCP3 in the regulation of muscle- and energy metabolism. UCP3 is critical for tuning substrate utilization, favoring lipid oxidation, particularly in conditions of high-fat availability. While UCP3 is non-essential for lipid oxidation during energy excess, it proves vital during fasting, indicating an energy-homeostatic trait. Preliminary evidence indicates UCP3' promotion of glucose uptake and oxidation, at least in conditions of high glucose/low fat availability. However, the dynamics of how fats and glucose differentially influence UCP3 remain undefined. UCP3 exhibits inducible proton transport and uncoupling activity, operating in a dual manner: a resting state with no/low activity and an activated state in the presence of activators. Uncoupling may enhance thermogenesis in specific conditions and in the presence of activators such as fatty acids, thyroid hormones, and catecholamines. This energy-dissipative activity adapts to varying energy availability, balancing energy dissipation with fatty acid oxidation to optimize whole-body energy homeostasis: fasting triggers UCP3 upregulation, enhancing lipid utilization while suppressing uncoupling. Additionally, UCP3 upregulation induces glucose and lipid disposal from the bloodstream and decreases tri-/diglyceride storage in muscle. This process improves mitochondrial functionality and insulin signaling, leading to enhanced systemicgluco-metabolic balance and protection from metabolic conditions. Reviewed evidence suggests that UCP3 plays a crucial role in adapting the system to changing energy conditions. However, the precise role of UCP3 in regulating metabolism requires further elucidation.
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Affiliation(s)
- Lucio Della Guardia
- Department of Biomedical Sciences for Health, Università degli Studi di Milano, Milano, Italy
| | - Livio Luzi
- Department of Biomedical Sciences for Health, Università degli Studi di Milano, Milano, Italy; Department of Endocrinology, Nutrition and Metabolic Diseases, IRCCS MultiMedica, Milano, Italy
| | - Roberto Codella
- Department of Biomedical Sciences for Health, Università degli Studi di Milano, Milano, Italy; Department of Endocrinology, Nutrition and Metabolic Diseases, IRCCS MultiMedica, Milano, Italy.
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Hayashi M, Futawaka K, Matsushita M, Koyama R, Fun Y, Fukuda Y, Nushida A, Nezu S, Tagami T, Moriyama K. GH directly stimulates UCP3 expression. Growth Horm IGF Res 2018; 40:44-54. [PMID: 29398371 DOI: 10.1016/j.ghir.2018.01.002] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/23/2017] [Revised: 12/27/2017] [Accepted: 01/18/2018] [Indexed: 01/23/2023]
Abstract
OBJECTIVE We evaluated the direct action of GH signaling in energy homeostasis in myocytes. DESIGN We investigated the GH-induced expression of UCP3 in human embryonic kidney 293 cells, human H-EMC-SS chondrosarcoma cells, murine C2C12 skeletal muscle myoblasts, and rat L6 skeletal muscle cells, as well as its direct effect on the GHR/JAK/STAT5 pathway using a combination of a reporter assay, real-time quantitative polymerase chain reaction, and western blotting. RESULTS We demonstrated that the regulation of energy metabolism by GH involves UCP3 via activated STAT5, a signal transducer downstream of GH. UCP3 expression increased with STAT5 in a dose-dependent manner and was higher than that of UCP2. We confirmed the functional STAT5 binding site consensus sequences at -861 and -507 bp in the UCP3 promoter region. CONCLUSION The results suggest that GH stimulates UCP3 directly and that UCP2 and that UCP3 participate in the signal transduction pathway that functions downstream of the GHR/JAK/STAT.
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Affiliation(s)
- Misa Hayashi
- Medicine & Clinical Science, Faculty of Pharmaceutical Sciences, Mukogawa Women's University, Hyogo 663-8179, Japan
| | - Kumi Futawaka
- Medicine & Clinical Science, Faculty of Pharmaceutical Sciences, Mukogawa Women's University, Hyogo 663-8179, Japan
| | - Midori Matsushita
- Medicine & Clinical Science, Faculty of Pharmaceutical Sciences, Mukogawa Women's University, Hyogo 663-8179, Japan
| | - Rie Koyama
- Medicine & Clinical Science, Faculty of Pharmaceutical Sciences, Mukogawa Women's University, Hyogo 663-8179, Japan
| | - Yue Fun
- Medicine & Clinical Science, Faculty of Pharmaceutical Sciences, Mukogawa Women's University, Hyogo 663-8179, Japan
| | - Yuki Fukuda
- Medicine & Clinical Science, Faculty of Pharmaceutical Sciences, Mukogawa Women's University, Hyogo 663-8179, Japan
| | - Ayaka Nushida
- Medicine & Clinical Science, Faculty of Pharmaceutical Sciences, Mukogawa Women's University, Hyogo 663-8179, Japan
| | - Syoko Nezu
- Medicine & Clinical Science, Faculty of Pharmaceutical Sciences, Mukogawa Women's University, Hyogo 663-8179, Japan
| | - Tetsuya Tagami
- Clinical Research Institute for Endocrine and Metabolic Diseases, National Hospital Organization Kyoto Medical Center, Kyoto 612-8555, Japan
| | - Kenji Moriyama
- Medicine & Clinical Science, Faculty of Pharmaceutical Sciences, Mukogawa Women's University, Hyogo 663-8179, Japan; Clinical Research Institute for Endocrine and Metabolic Diseases, National Hospital Organization Kyoto Medical Center, Kyoto 612-8555, Japan.
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Li Y, Li R, Chen W, Chen G. Vitamin A status and its metabolism contribute to the regulation of hepatic genes during the cycle of fasting and refeeding in rats. J Nutr Biochem 2016; 30:33-43. [PMID: 27012619 DOI: 10.1016/j.jnutbio.2015.11.012] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2015] [Revised: 11/12/2015] [Accepted: 11/20/2015] [Indexed: 02/07/2023]
Abstract
Vitamin A (VA) status and its metabolism affect hepatic metabolic homeostasis. We investigated if VA status and metabolism contribute to energy metabolism and expression of hepatic genes in the cycle of fasting and refeeding. Zucker lean rats with VA sufficient (VAS) or VA deficient (VAD) status were respectively grouped as: ad libitum (VAS-AD or VAD-AD), 48-h fasted (VAS-Fasted or VAD-Fasted), 48-h fasted and refed a VAS diet (VAS-Refed-VAS or VAD-Refed-VAS), or refed a VAD diet (VAS-Refed-VAD or VAD-Refed-VAD) for 6 h. Respiratory exchange ratio (RER) of rats fed the VAS or VAD diet was monitored for 6 weeks. From week four, rats fed the VAS diet had higher RER than those fed the VAD diet. VAS-Refed rats had higher plasma levels of glucose, triglyceride, insulin and leptin than VAD-Refed rats. The mRNA and protein levels of hepatic genes for fuel metabolism in the fasting and refeeding cycle were determined using real-time polymerase chain reaction and immunoblot, respectively. The mRNA levels of glucokinase (Gck), sterol regulatory element-binding protein 1c (Srebp-1c), and fatty acid synthase (Fas) were lowered in VAS-Fasted and VAD-Fasted rats, and increased in VAS-Refed-VAS, VAS-Refed-VAD and VAD-Refed-VAS, but not VAD-Refed-VAD, rats. The ACL and FAS protein levels only dropped in VAS-Fasted rats and increased in VAS-Refed-VAS rats. The GK protein level decreased only in VAS-Fasted rats, and increased in VAS-Refed-VAS, VAS-Refed-VAD and VAD-Refed-VAS (but not VAD-Refed-VAD) rats. We conclude that VA status and its metabolism in the fasting and refeeding cycle contribute to the regulation of hepatic gene expression in rats.
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Affiliation(s)
- Yang Li
- Department of Nutrition, University of Tennessee at Knoxville, Knoxville, TN, USA
| | - Rui Li
- Department of Nutrition, University of Tennessee at Knoxville, Knoxville, TN, USA
| | - Wei Chen
- Department of Nutrition, University of Tennessee at Knoxville, Knoxville, TN, USA
| | - Guoxun Chen
- Department of Nutrition, University of Tennessee at Knoxville, Knoxville, TN, USA.
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Bianco AC, Anderson G, Forrest D, Galton VA, Gereben B, Kim BW, Kopp PA, Liao XH, Obregon MJ, Peeters RP, Refetoff S, Sharlin DS, Simonides WS, Weiss RE, Williams GR. American Thyroid Association Guide to investigating thyroid hormone economy and action in rodent and cell models. Thyroid 2014; 24:88-168. [PMID: 24001133 PMCID: PMC3887458 DOI: 10.1089/thy.2013.0109] [Citation(s) in RCA: 145] [Impact Index Per Article: 14.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
BACKGROUND An in-depth understanding of the fundamental principles that regulate thyroid hormone homeostasis is critical for the development of new diagnostic and treatment approaches for patients with thyroid disease. SUMMARY Important clinical practices in use today for the treatment of patients with hypothyroidism, hyperthyroidism, or thyroid cancer are the result of laboratory discoveries made by scientists investigating the most basic aspects of thyroid structure and molecular biology. In this document, a panel of experts commissioned by the American Thyroid Association makes a series of recommendations related to the study of thyroid hormone economy and action. These recommendations are intended to promote standardization of study design, which should in turn increase the comparability and reproducibility of experimental findings. CONCLUSIONS It is expected that adherence to these recommendations by investigators in the field will facilitate progress towards a better understanding of the thyroid gland and thyroid hormone dependent processes.
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Affiliation(s)
- Antonio C. Bianco
- Division of Endocrinology, Diabetes and Metabolism, University of Miami Miller School of Medicine, Miami, Florida
| | - Grant Anderson
- Department of Pharmacy Practice and Pharmaceutical Sciences, College of Pharmacy, University of Minnesota Duluth, Duluth, Minnesota
| | - Douglas Forrest
- Laboratory of Endocrinology and Receptor Biology, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland
| | - Valerie Anne Galton
- Department of Physiology and Neurobiology, Dartmouth Medical School, Lebanon, New Hampshire
| | - Balázs Gereben
- Department of Endocrine Neurobiology, Institute of Experimental Medicine, Hungarian Academy of Sciences, Budapest, Hungary
| | - Brian W. Kim
- Division of Endocrinology, Diabetes and Metabolism, University of Miami Miller School of Medicine, Miami, Florida
| | - Peter A. Kopp
- Division of Endocrinology, Metabolism, and Molecular Medicine, and Center for Genetic Medicine, Feinberg School of Medicine, Northwestern University, Chicago, Illinois
| | - Xiao Hui Liao
- Section of Adult and Pediatric Endocrinology, Diabetes, and Metabolism, The University of Chicago, Chicago, Illinois
| | - Maria Jesus Obregon
- Institute of Biomedical Investigation (IIB), Spanish National Research Council (CSIC) and Autonomous University of Madrid, Madrid, Spain
| | - Robin P. Peeters
- Division of Endocrinology, Department of Internal Medicine, Erasmus Medical Center, Rotterdam, The Netherlands
| | - Samuel Refetoff
- Section of Adult and Pediatric Endocrinology, Diabetes, and Metabolism, The University of Chicago, Chicago, Illinois
| | - David S. Sharlin
- Department of Biological Sciences, Minnesota State University, Mankato, Minnesota
| | - Warner S. Simonides
- Laboratory for Physiology, Institute for Cardiovascular Research, VU University Medical Center, Amsterdam, The Netherlands
| | - Roy E. Weiss
- Section of Adult and Pediatric Endocrinology, Diabetes, and Metabolism, The University of Chicago, Chicago, Illinois
| | - Graham R. Williams
- Department of Medicine, Imperial College London, Hammersmith Campus, London, United Kingdom
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Addition of adult serum improves endothelium-dependent relaxation of organ-cultured rat mesenteric artery via inhibiting mitochondrial reactive oxygen species. Vascul Pharmacol 2013; 58:105-11. [DOI: 10.1016/j.vph.2012.08.006] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2012] [Revised: 07/31/2012] [Accepted: 08/26/2012] [Indexed: 11/24/2022]
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Osuna M, Sonobe Y, Itakura E, Devnath S, Kato T, Kato Y, Inoue K. Differentiation capacity of native pituitary folliculostellate cells and brain astrocytes. J Endocrinol 2012; 213:231-7. [PMID: 22434586 DOI: 10.1530/joe-12-0043] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Pituitary folliculostellate (FS) cells are characterized by producing S100B protein, as do brain astrocytes. FS cells have some functions in the pituitary gland, i.e. scavenger functions, sustentacular cell activity through cytokines, and intercellular communication through gap junctions. However, the biological significances of FS cells, especially their differentiation capacities in the anterior pituitary gland, are still under discussion. To understand FS cells with new approaches, we generated a transgenic rat expressing GFP under S100b gene promoter, which regulates tissue-specific expression of S100b gene. Using the transgenic rat, we succeeded in inducing skeletal muscle cells from FS cells by culturing it in serum-free medium containing B-27 supplement, thyroid hormone (tri-iodothyronine), epidermal growth factor, and basic fibroblast growth factor. In this study, we also succeeded in inducing skeletal muscle cells from primary cultured astrocytes and astrocyte cell line, C6 cells. Hence, we concluded that pituitary FS cells have wide differentiation potential and have similar characteristics to astrocytes, which not only support cell activity but also support differentiation capacity.
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Affiliation(s)
- Marumi Osuna
- Graduate School of Science and Engineering, Saitama University, 255 Shimo-ohkubo, Sakura-ku, Saitama 338-8570, Japan
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Villarroya F, Iglesias R, Giralt M. PPARs in the Control of Uncoupling Proteins Gene Expression. PPAR Res 2011; 2007:74364. [PMID: 17389766 PMCID: PMC1779581 DOI: 10.1155/2007/74364] [Citation(s) in RCA: 146] [Impact Index Per Article: 11.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2006] [Revised: 10/18/2006] [Accepted: 10/18/2006] [Indexed: 11/17/2022] Open
Abstract
Uncoupling proteins (UCPs) are mitochondrial membrane transporters involved in the control of energy conversion in mitochondria. Experimental and genetic evidence relate dysfunctions of UCPs with metabolic syndrome and obesity. The PPAR subtypes mediate to a large extent the transcriptional regulation of the UCP genes, with a distinct relevance depending on the UCP gene and the tissue in which it is expressed. UCP1 gene is under the dual control of PPARγ and PPARα in relation to brown adipocyte differentiation and lipid oxidation, respectively. UCP3 gene is regulated by PPARα and PPARδ in the muscle, heart, and adipose tissues. UCP2 gene is also under the control of PPARs even in tissues in which it is the predominantly expressed UCP (eg, the pancreas and liver). This review summarizes the current understanding of the role of PPARs in UCPs gene expression in normal conditions and also in the context of type-2 diabetes or obesity.
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Affiliation(s)
- Francesc Villarroya
- Department of Biochemistry and Molecular Biology, University of Barcelona, Barcelona 585 08007, Spain
- *Francesc Villarroya:
| | - Roser Iglesias
- Department of Biochemistry and Molecular Biology, University of Barcelona, Barcelona 585 08007, Spain
| | - Marta Giralt
- Department of Biochemistry and Molecular Biology, University of Barcelona, Barcelona 585 08007, Spain
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O'Neal P, Alamdari N, Smith I, Poylin V, Menconi M, Hasselgren PO. Experimental hyperthyroidism in rats increases the expression of the ubiquitin ligases atrogin-1 and MuRF1 and stimulates multiple proteolytic pathways in skeletal muscle. J Cell Biochem 2010; 108:963-73. [PMID: 19777444 DOI: 10.1002/jcb.22329] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
Muscle wasting is commonly seen in patients with hyperthyroidism and is mainly caused by stimulated muscle proteolysis. Loss of muscle mass in several catabolic conditions is associated with increased expression of the muscle-specific ubiquitin ligases atrogin-1 and MuRF1 but it is not known if atrogin-1 and MuRF1 are upregulated in hyperthyroidism. In addition, it is not known if thyroid hormone increases the activity of proteolytic mechanisms other than the ubiquitin-proteasome pathway. We tested the hypotheses that experimental hyperthyroidism in rats, induced by daily intraperitoneal injections of 100 microg/100 g body weight of triiodothyronine (T3), upregulates the expression of atrogin-1 and MuRF1 in skeletal muscle and stimulates lysosomal, including cathepsin L, calpain-, and caspase-3-dependent protein breakdown in addition to proteasome-dependent protein breakdown. Treatment of rats with T3 for 3 days resulted in an approximately twofold increase in atrogin-1 and MuRF1 mRNA levels. The same treatment increased proteasome-, cathepsin L-, and calpain-dependent proteolytic rates by approximately 40% but did not influence caspase-3-dependent proteolysis. The expression of atrogin-1 and MuRF1 remained elevated during a more prolonged period (7 days) of T3 treatment. The results provide support for a role of the ubiquitin-proteasome pathway in muscle wasting during hyperthyroidism and suggest that other proteolytic pathways as well may be activated in the hyperthyroid state.
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Affiliation(s)
- Patrick O'Neal
- Department of Surgery, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, Massachusetts 02215, USA
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Girousse A, Tavernier G, Tiraby C, Lichtenstein L, Iacovoni JS, Mairal A, Villarroya F, Langin D. Transcription of the human uncoupling protein 3 gene is governed by a complex interplay between the promoter and intronic sequences. Diabetologia 2009; 52:1638-46. [PMID: 19468707 DOI: 10.1007/s00125-009-1385-9] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/23/2009] [Accepted: 04/17/2009] [Indexed: 11/24/2022]
Abstract
AIMS/HYPOTHESIS Uncoupling protein (UCP) 3 is an inner mitochondrial membrane transporter mainly produced in skeletal muscle in humans. UCP3 plays a role in fatty acid metabolism and energy homeostasis and modulates insulin sensitivity. In humans, UCP3 content is higher in fast-twitch glycolytic muscle than in slow-twitch oxidative muscle and is dysregulated in type 2 diabetes. Here, we studied the molecular mechanisms determining human UCP3 levels in skeletal muscle and their regulation by fasting in transgenic mice. METHODS We produced a series of transgenic lines with constructs bearing different putative regulatory regions of the human UCP3 gene, including promoter and intron sequences. UCP3 mRNA and reporter gene expression and activity were measured in different skeletal muscles and tissues. RESULTS The profile of expression and the response to fasting and thyroid hormone of human UCP3 mRNA in transgenic mice with 16 kb of the human UCP3 gene were similar to that of the endogenous human gene. Various parts of the UCP3 promoter did not confer expression in transgenic lines. Inclusion of intron 1 resulted in an expression profile in skeletal muscle that was identical to that of human UCP3 mRNA. Further dissection of intron 1 revealed that distinct regions were involved in skeletal muscle expression, distribution among fibre types and response to fasting. CONCLUSIONS/INTERPRETATION The control of human UCP3 transcription in skeletal muscle is not solely conferred by the promoter, but depends on several cis-acting elements in intron 1, suggesting a complex interplay between the promoter and intronic sequences.
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Affiliation(s)
- A Girousse
- Inserm U858, Institut de Médecine Moléculaire de Rangueil, Laboratoire de recherches sur les obésités, Equipe 4, 31432 Toulouse Cedex 4, France
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Perra A, Simbula G, Simbula M, Pibiri M, Kowalik MA, Sulas P, Cocco MT, Ledda-Columbano GM, Columbano A. Thyroid hormone (T3) and TRβ agonist GC‐1 inhibit/reverse nonalcoholic fatty liver in rats. FASEB J 2008; 22:2981-9. [DOI: 10.1096/fj.08-108464] [Citation(s) in RCA: 92] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Affiliation(s)
- Andrea Perra
- Department of Toxicology, Oncology and Molecular Pathology UnitUniversity of CagliariCagliariItaly
| | - Gabriella Simbula
- Department of Toxicology, Oncology and Molecular Pathology UnitUniversity of CagliariCagliariItaly
| | - Michela Simbula
- Department of Toxicology, Oncology and Molecular Pathology UnitUniversity of CagliariCagliariItaly
| | - Monica Pibiri
- Department of Toxicology, Oncology and Molecular Pathology UnitUniversity of CagliariCagliariItaly
| | - Marta A. Kowalik
- Department of Toxicology, Oncology and Molecular Pathology UnitUniversity of CagliariCagliariItaly
| | - Pia Sulas
- Department of Toxicology, Oncology and Molecular Pathology UnitUniversity of CagliariCagliariItaly
| | - Maria T. Cocco
- Department of Toxicology, Oncology and Molecular Pathology UnitUniversity of CagliariCagliariItaly
| | | | - Amedeo Columbano
- Department of Toxicology, Oncology and Molecular Pathology UnitUniversity of CagliariCagliariItaly
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Amengual J, Ribot J, Bonet ML, Palou A. Retinoic acid treatment increases lipid oxidation capacity in skeletal muscle of mice. Obesity (Silver Spring) 2008; 16:585-91. [PMID: 18239600 DOI: 10.1038/oby.2007.104] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
OBJECTIVE All-trans retinoic acid (ATRA), a carboxylic form of vitamin A, favors in mice a mobilization of body fat reserves that correlates with an increment of oxidative and thermogenic capacity in adipose tissues. The objective of this study has been to investigate the effect of ATRA treatment on skeletal muscle capacity for fatty-acid catabolism. METHODS AND PROCEDURES Tissue composition and gene expression related to lipid and oxidative metabolism were analyzed in skeletal muscle of mice acutely treated with ATRA or vehicle (olive oil). RESULTS ATRA treatment triggered a dose-dependent increase in the muscle mRNA expression levels of selected enzymes, transporters and transcription factors involved in fatty-acid oxidation, respiration, and thermogenesis namely: muscle-type carnitine palmitoyltransferase 1, acyl CoA oxidase 1, subunit II of cytochrome oxidase, uncoupling protein 3, peroxisome proliferator-activated receptor-gamma co-activator -1alpha and peroxisome proliferator-activated receptor-delta (PPARdelta). The treatment also resulted in the upregulation of the mRNA levels of acetyl-CoA carboxylase 2 (ACC2), a key regulatory enzyme for mitochondrial fatty-acid oxidation in muscle. Skeletal muscle protein levels of PPARdelta and retinoid X receptor gamma, a partner for many nuclear receptors involved in lipid metabolism, were increased after ATRA treatment. Muscle lipid content was decreased. DISCUSSION These results indicate that ATRA treatment increases the capacity of skeletal muscle for fatty-acid oxidation. Knowledge of nutrients or nutrient-derivatives capable of enhancing oxidative metabolism in muscle and other tissues can contribute to new avenues of prevention and treatment of obesity and related disorders.
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Affiliation(s)
- Jaume Amengual
- Laboratory of Molecular Biology, Nutrition and Biotechnology, Universitat de les Illes Balears, Palma de Mallorca, Spain
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12
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Kim D, Jitrapakdee S, Thompson M. Differential regulation of the promoter activity of the mouse UCP2 and UCP3 genes by MyoD and myogenin. BMB Rep 2008; 40:921-7. [PMID: 18047787 DOI: 10.5483/bmbrep.2007.40.6.921] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
UCP2 and UCP3 are members of the uncoupling protein family, which may play roles in energy homeostasis. In order to determine the regulation of the predominant expression of UCP3 in skeletal muscle, the effects of differentiation and myogenic regulatory factors on the promoter activities of the mouse UCP2 and UCP3 genes were studied. Reporter plasmids, containing approximately 3 kb of the 5'-upstream region of the mouse UCP2 and UCP3 genes, were transfected into C2C12 myoblasts, which were then induced to differentiate. Differentiation positively induced the reporter expression about 20-fold via the UCP3 promoter, but by only 2-fold via the UCP2 promoter. C2C12 myoblasts were cotransfected with expression vectors for myogenin and/or MyoD as well as reporter constructs. The simultaneous expression of myogenin and MyoD caused an additional 20-fold increase in the reporter expression via the UCP3 promoter, but only a weak effect via the UCP2 promoter. In L6 myoblasts, only MyoD activated the UCP3 promoter, but in 3T3-L1 cells neither factor activated the UCP3 promoter, indicating that additional cofactors are required, which are present only in C2C12 myoblasts. The expression of UCP2 and UCP3 is differentially regulated during muscle differentiation due to the different responsiveness of their promoter regions to myogenin and MyoD.
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Affiliation(s)
- Dongho Kim
- Department of Biochemistry, University of Otago, PO Box 56, Dunedin 9054, New Zealand.
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13
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Nabben M, Hoeks J. Mitochondrial uncoupling protein 3 and its role in cardiac- and skeletal muscle metabolism. Physiol Behav 2007; 94:259-69. [PMID: 18191161 DOI: 10.1016/j.physbeh.2007.11.039] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2007] [Revised: 11/22/2007] [Accepted: 11/23/2007] [Indexed: 11/20/2022]
Abstract
Uncoupling protein 3 (UCP3), is primarily expressed in skeletal muscle mitochondria and has been suggested to be involved in mediating energy expenditure via uncoupling, hereby dissipating the mitochondrial proton gradient necessary for adenosine triphosphate (ATP) synthesis. Although some studies support a role for UCP3 in energy metabolism, other studies pointed towards a function in fatty acid metabolism. Thus, the protein is up regulated or high when fatty acid supply to the mitochondria exceeds the capacity to oxidize fatty acids and down regulated or low when oxidative capacity is high or improved. Irrespective of the exact operating mechanism, UCP3 seems to protect mitochondria against lipid-induced oxidative stress, which makes this protein a potential player in the development of type 2 diabetes mellitus. Next to skeletal muscle, UCP3 is also expressed in cardiac muscle where its role is relatively unexplored. Interestingly, energy deficiency in cardiac muscle is associated to heart failure and UCP3 might contribute to this energy deficiency. It has been suggested that UCP3 decreases energy status via uncoupling of mitochondrial respiration, but the available data does not provide a unified answer. In fact, the results obtained regarding cardiac UCP3 are very similar as in skeletal muscle, implying that its physiological function can be extrapolated. Therefore, cardiac UCP3 can just as well serve to protect the heart against lipid-induced oxidative stress, similar to the function described for skeletal muscle UCP3. The present review will deal with the available literature on both skeletal muscle- and cardiac UCP3 to elucidate its physiological function in these tissues.
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Affiliation(s)
- Miranda Nabben
- Department of Human Biology, Nutrition and Toxicology Research Institute Maastricht (NUTRIM), Maastricht University, P.O. Box 616, 6200 MD, Maastricht, The Netherlands.
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14
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Cantó C, Pich S, Paz JC, Sanches R, Martínez V, Orpinell M, Palacín M, Zorzano A, Gumà A. Neuregulins increase mitochondrial oxidative capacity and insulin sensitivity in skeletal muscle cells. Diabetes 2007; 56:2185-93. [PMID: 17563068 DOI: 10.2337/db06-1726] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
OBJECTIVE Neuregulins are growth factors that are essential for myogenesis and regulate muscle metabolism. The addition of a recombinant neuregulin-1 isoform, heregulin-beta1(177-244) (Hrg), containing 3 nmol/l of the bioactive epidermal growth factor-like domain, to developing L6E9 myocytes has acute and chronic effects on glucose uptake and enhances myogenesis. Here, we studied the metabolic adaptation of myocytes to chronic treatments with Hrg. RESEARCH DESIGN AND METHODS L6E9 and C2C12 myocytes were chronically treated with low concentrations of Hrg (3 pmol/l) that do not induce myogenesis. We analyzed the effects of Hrg on cellular oxidative metabolism and insulin sensitivity and explored the mechanisms of action. RESULTS Hrg increased the cell content of GLUT4 without affecting basal glucose uptake. Glucose and palmitate oxidation increased in Hrg-treated cells, whereas lactate release decreased. Hrg increased the abundance of oxidative phosphorylation (OXPHOS) subunits, enhanced mitochondrial membrane potential, and induced the expression of peroxisome proliferator-activated receptor (PPAR)gamma coactivator1alpha and PPARdelta. Furthermore, we identified PPARdelta as an essential mediator of the stimulatory effects of Hrg on the expression of OXPHOS subunits. The higher oxidative capacity of L6E9 myotubes after neuregulin treatment also paralleled an increase in insulin sensitivity and insulin signaling potency. CONCLUSIONS These results indicate that neuregulins act as key modulators of oxidative capacity and insulin sensitivity in muscle cells.
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Affiliation(s)
- Carles Cantó
- Department of Biochemistry and Molecular Biology, School of Biology, University of Barcelona, Barcelona, Spain
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15
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Bézaire V, Seifert EL, Harper ME. Uncoupling protein-3: clues in an ongoing mitochondrial mystery. FASEB J 2007; 21:312-24. [PMID: 17202247 DOI: 10.1096/fj.06-6966rev] [Citation(s) in RCA: 105] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
Uncoupling protein (UCP) 3 (UCP3) is a mitochondrial anion carrier protein with highly selective expression in skeletal muscle. Despite a great deal of interest, to date neither its molecular mechanism nor its biochemical and physiological functions are well understood. Based on its high degree of homology to the original UCP (UCP1), early studies examined a role for UCP3 in thermogenesis. However, evidence for such a function is lacking. Recent studies have focused on two distinct, but not mutually exclusive, hypotheses: 1) UCP3 mitigates reactive oxygen species (ROS) production, and 2) UCP3 is somehow involved in fatty acid (FA) translocation. While supportive evidence exists for both hypotheses, the interpretation of the corresponding evidence has created some controversy. Mechanistic studies examining mitigated ROS production have been largely conducted in vitro, and the physiological significance of the findings is questioned. Conversely, while physiological evidence exists for FA translocation hypotheses, the evidence is largely correlative, leaving causal relationships unexplored. This review critically assesses evidence for the hypotheses and attempts to link the outcomes from mechanistic studies to physiological implications. Important directions for future studies, using current and novel approaches, are discussed.
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Affiliation(s)
- Véronic Bézaire
- Department of Biochemistry, Microbiology and Immunology, Faculty of Medicine, University of Ottawa, 451 Smyth Rd., Ottawa, ON, Canada K1H 8M5
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16
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Sultan KR, Henkel B, Terlou M, Haagsman HP. Quantification of hormone-induced atrophy of large myotubes from C2C12and L6 cells: atrophy-inducible and atrophy-resistant C2C12myotubes. Am J Physiol Cell Physiol 2006; 290:C650-9. [PMID: 16176969 DOI: 10.1152/ajpcell.00163.2005] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Myofiber atrophy is the final outcome of muscle wasting induced by catabolic factors such as glucocorticoids and thyroid hormones. We set up an in vitro system to define the catabolic reaction based on myotube atrophy. Both mouse C2C12and rat L6 cells were used. C2C12myotube formation was improved by replacing horse serum with the serum substitute Ultroser G. A new method was developed to quantify size changes of large (0.5–1 mm) myotubes only, excluding remaining myoblasts and small myotubes. Dexamethasone reduced myotube size by 30% in L6 but not in C2C12myotubes. Expression of the glucocorticoid receptor was twofold higher in L6 myotubes than in C2C12myotubes. In both cell lines, 3,3′,5-triiodo-l-thyronine (T3) did not induce a significant size reduction. Expression of the major T3receptor (T3Rβ1) was higher in L6 myotubes. We investigated whether the changes in myotube size are related to changes in atrogin-1 expression, as this enzyme is thought to be a key factor in the initiation of muscle atrophy. Dexamethasone induced a twofold increase of atrogin-1 mRNA; again, only L6 myotubes were susceptible. Interestingly, atrogin-1 expression in Ultroser G-fused C2C12myotubes was lower than that in horse serum-fused myotubes. Furthermore, dexamethasone treatment increased atrogin-1 expression only in horse serum-fused myotubes but not in Ultroser G-fused myotubes. Ultroser G-induced fusion may result in atrophy-resistant C2C12myotubes. Therefore, C2C12myotubes offer an ideal system in which to study skeletal muscle atrophy because, depending on differentiation conditions, C2C12cells produce atrophy-inducible and atrophy-resistant myotubes.
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Affiliation(s)
- Karim R Sultan
- Faculty of Veterinary Medicine, Academic Biomedical Centre, Utrecht University, Utrecht, The Netherlands
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17
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Smith AG, Muscat GEO. Skeletal muscle and nuclear hormone receptors: implications for cardiovascular and metabolic disease. Int J Biochem Cell Biol 2005; 37:2047-63. [PMID: 15922648 DOI: 10.1016/j.biocel.2005.03.002] [Citation(s) in RCA: 124] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2004] [Revised: 02/22/2005] [Accepted: 03/11/2005] [Indexed: 12/18/2022]
Abstract
Skeletal muscle is a major mass peripheral tissue that accounts for approximately 40% of the total body mass and a major player in energy balance. It accounts for >30% of energy expenditure, is the primary tissue of insulin stimulated glucose uptake, disposal, and storage. Furthermore, it influences metabolism via modulation of circulating and stored lipid (and cholesterol) flux. Lipid catabolism supplies up to 70% of the energy requirements for resting muscle. However, initial aerobic exercise utilizes stored muscle glycogen but as exercise continues, glucose and stored muscle triglycerides become important energy substrates. Endurance exercise increasingly depends on fatty acid oxidation (and lipid mobilization from other tissues). This underscores the importance of lipid and glucose utilization as an energy source in muscle. Consequently skeletal muscle has a significant role in insulin sensitivity, the blood lipid profile, and obesity. Moreover, caloric excess, obesity and physical inactivity lead to skeletal muscle insulin resistance, a risk factor for the development of type II diabetes. In this context skeletal muscle is an important therapeutic target in the battle against cardiovascular disease, the worlds most serious public health threat. Major risk factors for cardiovascular disease include dyslipidemia, hypertension, obesity, sedentary lifestyle, and diabetes. These risk factors are directly influenced by diet, metabolism and physical activity. Metabolism is largely regulated by nuclear hormone receptors which function as hormone regulated transcription factors that bind DNA and mediate the patho-physiological regulation of gene expression. Metabolism and activity, which directly influence cardiovascular disease risk factors, are primarily driven by skeletal muscle. Recently, many nuclear receptors expressed in skeletal muscle have been shown to improve glucose tolerance, insulin resistance, and dyslipidemia. Skeletal muscle and nuclear receptors are rapidly emerging as critical targets in the battle against cardiovascular disease risk factors. Understanding the function of nuclear receptors in skeletal muscle has enormous pharmacological utility for the treatment of cardiovascular disease. This review focuses on the molecular regulation of metabolism by nuclear receptors in skeletal muscle in the context of dyslipidemia and cardiovascular disease.
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MESH Headings
- Cardiovascular Diseases/metabolism
- Cholesterol/metabolism
- DNA-Binding Proteins/metabolism
- Dyslipidemias/metabolism
- Glucose/metabolism
- Humans
- Insulin Resistance/physiology
- Metabolic Diseases/metabolism
- Models, Biological
- Muscle, Skeletal/metabolism
- Muscle, Skeletal/physiopathology
- Nuclear Receptor Subfamily 4, Group A, Member 1
- Peroxisome Proliferator-Activated Receptors/metabolism
- Receptors, Cytoplasmic and Nuclear/metabolism
- Receptors, Estrogen/metabolism
- Receptors, Glucocorticoid/metabolism
- Receptors, Steroid/metabolism
- Receptors, Thyroid Hormone/metabolism
- Transcription Factors/metabolism
- Tretinoin/metabolism
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Affiliation(s)
- Aaron G Smith
- Institute for Molecular Bioscience, University of Queensland, St Lucia, 4072 Qld, Australia
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18
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Szanto A, Narkar V, Shen Q, Uray IP, Davies PJA, Nagy L. Retinoid X receptors: X-ploring their (patho)physiological functions. Cell Death Differ 2005; 11 Suppl 2:S126-43. [PMID: 15608692 DOI: 10.1038/sj.cdd.4401533] [Citation(s) in RCA: 207] [Impact Index Per Article: 10.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Retinoid X receptor (RXR) belongs to a family of ligand-activated transcription factors that regulate many aspects of metazoan life. A class of nuclear receptors requires RXR as heterodimerization partner for their function. This places RXR in the crossroad of multiple distinct biological pathways. This and the fact that the debate on the endogenous ligand requirement for RXR is not yet settled make RXR still an enigmatic transcription factor. Here, we review some of the biology of RXR. We place RXR into the evolution of nuclear receptors, review structural details and ligands of the receptor. Then processes regulated by RXR are discussed focusing on the developmental roles deduced from studies on knockout animals and metabolic roles in diseases such as diabetes and atherosclerosis deduced from pharmacological studies. Finally, aspects of RXR's involvement in myeloid differentiation and apoptosis are summarized along with issues on RXR's suitability as a therapeutic target.
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Affiliation(s)
- A Szanto
- Department of Biochemistry and Molecular Biology, Research Center for Molecular Medicine, University of Debrecen, Nagyerdei krt. 98, Debrecen H-4012, Hungary
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19
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Ramsay TG, Rosebrough RW. Regulation of uncoupling proteins 2 and 3 in porcine adipose tissue. Domest Anim Endocrinol 2005; 28:351-66. [PMID: 15826771 DOI: 10.1016/j.domaniend.2004.12.003] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/18/2004] [Accepted: 12/22/2004] [Indexed: 11/22/2022]
Abstract
This study was performed to determine whether or not uncoupling protein 2 (UCP2) and UCP3 expression in porcine subcutaneous adipose tissue are hormonally regulated in vitro and whether their expression is correlated with changes in metabolic activity. Tissue slices (approximately 100 mg) were placed in 12-well plates containing 1 mL of DMEM/F12 with 25 mM Hepes, 0.5% BSA, pH 7.4. Triplicate slices were incubated with basal medium or hormone supplemented media at 37 degrees C with 95% air/5% CO2. Parallel cultures were maintained for either 2 or 24 h to evaluate metabolic viability of the tissue. Slices were transferred to test tubes containing 1 mL of DMEM/F12 with 25 mM Hepes, 3% BSA, 5.5 mM glucose, 1 microCi 14C-U-glucose/mL and incubated for an additional 2 h at 37 degrees C. Glucose metabolism in 2-h incubations did not differ from 24-h (chronic) incubations, indicating viability was maintained (P>0.05). Expression of UCP2 and UCP3 was assessed in slices following 24h of incubation with various combinations of hormones by semi-quantitative RT-PCR. Expression of UCP2 was induced by leptin (100 ng/mL; P<0.05). Growth hormone (100 ng/mL) inhibited UCP2 expression (P<0.05). Expression of UCP3 was inhibited by growth hormone (100 ng/mL; P<0.05), tri-iodothyronine (10 nM; P<0.05) or leptin (100 ng/mL; P<0.05). Changes in UCP expression could not be associated with overall changes in glucose metabolism by adipose tissue slices in chronic culture.
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Affiliation(s)
- T G Ramsay
- Growth Biology Laboratory, USDA-ARS, BARC-East, Bldg. 200, Rm. 207, Beltsville, MD 20705, USA.
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20
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Bezaire V, Spriet LL, Campbell S, Sabet N, Gerrits M, Bonen A, Harper ME. Constitutive UCP3 overexpression at physiological levels increases mouse skeletal muscle capacity for fatty acid transport and oxidation. FASEB J 2005; 19:977-9. [PMID: 15814607 DOI: 10.1096/fj.04-2765fje] [Citation(s) in RCA: 103] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Uncoupling protein 3 (UCP3) expression is directly correlated to fatty acid oxidation in skeletal muscle. UCP3 has been hypothesized to facilitate high rates of fatty acid oxidation, but evidence thus far is lacking. Our aim was to investigate the effects of UCP3 overexpression and ablation on fatty acid uptake and metabolism in muscle of mice having congenic backgrounds. In mice constitutively expressing the UCP3 protein (human form) at levels just over twofold higher than normal (230% of wild-type levels), indirect calorimetry demonstrated no differences in total energy expenditure (VO2), but a shift toward increased fat oxidation compared with wild-type (WT) mice. Metabolic efficiency (gram weight gain/kcal ingested) was similar between Ucp3 overexpressors, WT and Ucp3 (-/-) mice. In muscle of Ucp3-tg mice, plasma membrane fatty acid binding protein (FABPpm) content was increased compared with WT mice. Although hormone-sensitive lipase activity was unchanged across the genotypes, there were increases in carnitine palmitoyltransferase I, beta-hydroxyacylCoA dehydrogenase, and citrate synthase activities and decreases in intramuscular triacylglycerol in muscle of Ucp3-tg mice. There were no differences in muscle mitochondrial content. High-energy phosphates and total muscle carnitine and CoA were also greater in Ucp3-tg compared with WT mice. Taken together, the findings demonstrate an increased capacity for fat oxidation in the absence of significant increases in thermogenesis in Ucp3-tg mice. Findings from Ucp3 (-/-) mice revealed few differences compared with WT mice, consistent with the possibility of compensatory mechanisms. In conjunction with our observed increases in CoA and carnitine in muscle of Ucp3 overexpressors, the findings support the hypothesized role for Ucp3 in facilitating fatty acid oxidation in muscle.
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Affiliation(s)
- V Bezaire
- Department of Human Biology and Nutritional Sciences, University of Guelph, Ontario, Canada
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21
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Solanes G, Pedraza N, Calvo V, Vidal-Puig A, Lowell BB, Villarroya F. Thyroid hormones directly activate the expression of the human and mouse uncoupling protein-3 genes through a thyroid response element in the proximal promoter region. Biochem J 2005; 386:505-13. [PMID: 15496137 PMCID: PMC1134869 DOI: 10.1042/bj20041073] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2004] [Revised: 10/06/2004] [Accepted: 10/21/2004] [Indexed: 01/07/2023]
Abstract
The transcription of the human UCP3 (uncoupling protein-3) gene in skeletal muscle is tightly regulated by metabolic signals related to fatty acid availability. However, changes in thyroid status also modulate UCP3 gene expression, albeit by unknown mechanisms. We created transgenic mice bearing the entire human UCP3 gene to investigate the effect of thyroid hormones on human UCP3 gene expression. Treatment of human UCP3 transgenic mice with thyroid hormones induced the expression of the human gene in skeletal muscle. In addition, transient transfection experiments demonstrate that thyroid hormones activate the transcription of the human UCP3 gene promoter when MyoD and the TR (thyroid hormone receptor) were co-transfected. The action of thyroid hormones on UCP3 gene transcription is mediated by the binding of the TR to a proximal region in the UCP3 gene promoter that contains a direct repeat structure. An intact DNA sequence of this site is required for thyroid hormone responsiveness and TR binding. Chromatin immunoprecipitation assays revealed that the TR binds this element in vivo. The murine Ucp3 gene promoter was also dependent on MyoD and responsive to thyroid hormone in transient transfection assays. However, it was much less sensitive to thyroid hormone than the human UCP3 promoter. In summary, UCP3 gene transcription is activated by thyroid hormone treatment in vivo, and this activation is mediated by a TRE (thyroid hormone response element) in the proximal promoter region. Such regulation suggests a link between UCP3 gene expression and the effects of thyroid hormone on mitochondrial function in skeletal muscle.
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Key Words
- promoter regulation
- thyroid hormone
- transgenic mouse
- uncoupling protein-3 (ucp3)
- c/ebpα, ccaat/enhancer-binding protein
- chip, chromatin immunoprecipitation
- emsa, electrophoretic mobility-shift assay
- ppar, peroxisome-proliferator-activated receptor
- ros, reactive oxygen species
- rxr, retinoid x receptor
- t3, thyroid hormone
- tr, thyroid hormone receptor
- tre, thyroid hormone response element
- ucp3, uncoupling protein-3
- ucp3l, long form of ucp3
- ucp3s, short form of ucp3
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Affiliation(s)
- Gemma Solanes
- Departament de Bioquímica i Biologia Molecular, Universitat de Barcelona, Avda Diagonal 645, E-08028 Barcelona, Spain.
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22
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Rusyniak DE, Tandy SL, Hekmatyar SK, Mills E, Smith DJ, Bansal N, MacLellan D, Harper ME, Sprague JE. The role of mitochondrial uncoupling in 3,4-methylenedioxymethamphetamine-mediated skeletal muscle hyperthermia and rhabdomyolysis. J Pharmacol Exp Ther 2005; 313:629-39. [PMID: 15644431 DOI: 10.1124/jpet.104.079236] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Use of the popular club drug ecstasy (3,4-methylenedioxymethamphetamine, MDMA) can result in life-threatening hyperthermia and rhabdomyolysis. Recent studies show a link between skeletal muscle uncoupling proteins in MDMA-mediated hyperthermia. The mechanisms by which MDMA interacts with skeletal muscle mitochondria are largely unknown. The present study was designed to comprehensively evaluate the effects of MDMA on bioenergetics and toxicity of skeletal muscle. Using (31)P nuclear magnetic resonance (NMR) and serum creatine kinase levels, we demonstrate evidence for uncoupling of oxidative phosphorylation in the skeletal muscle of MDMA (40 mg/kg)-treated rats. In vivo, rats treated with MDMA had significantly elevated serum creatine kinase levels, a marker of rhabdomyolysis, 4 h post-MDMA treatment (955 +/- 132 IU/l) compared with saline-treated controls (373.2 +/- 59 IU/l). beta-ATP signal areas after MDMA treatment showed significant reductions (15%) from the baseline values with corresponding increases in inorganic phosphate (88% increases) and decreases in intracellular pH. Clark electrode experiments on isolated skeletal muscle mitochondria in vitro (1-5 mM MDMA) and ex vivo in MDMA-treated animals demonstrated no evidence of uncoupling of oxidative phosphorylation. In vitro experiments using L6 myotubules cocultured with primary hepatocytes demonstrated the presence of uncoupling protein-3 in the L6 myotubules, but no evidence of a direct effect of MDMA or its potential metabolites on cellular creatine kinase concentrations. These findings suggest that MDMA uncouples skeletal muscle mitochondria in vivo but that this uncoupling is the result of indirect mechanisms.
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Affiliation(s)
- Daniel E Rusyniak
- Department of Emergency Medicine, Indiana University School of Medicine, Indianapolis, 46202, USA.
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23
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Felipe F, Mercader J, Ribot J, Palou A, Bonet ML. Effects of retinoic acid administration and dietary vitamin A supplementation on leptin expression in mice: lack of correlation with changes of adipose tissue mass and food intake. Biochim Biophys Acta Mol Basis Dis 2004; 1740:258-65. [PMID: 15949693 DOI: 10.1016/j.bbadis.2004.11.014] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2004] [Revised: 11/15/2004] [Accepted: 11/22/2004] [Indexed: 10/26/2022]
Abstract
Retinoic acid (RA) administration and chronic vitamin A supplementation were reported to inhibit adipose tissue leptin expression in rodents, but the impact of this effect on food intake and its relationship with changes of body adiposity was not analyzed. Here, we have studied the effects of RA administration at three different doses on body weight, adipose tissue mass, food intake, adipose tissue leptin expression and circulating leptin levels in NMRI mice; the effects of chronic vitamin A supplementation with a 40-fold excess retinyl palmitate on the same parameters in NMRI and C57BL/6J mice; and the effects of RA and retinoid receptors agonists on leptin expression in brown and white adipocyte cell model systems. The results show that vitamin A down-regulates leptin expression in white and brown adipose tissue and circulating leptin levels independently of changes of adipose tissue mass and, for the first time to our knowledge, that this effect does not correlate with increased food intake. They also demonstrate a direct inhibitory effect of RA on leptin expression in both white and brown adipocyte cell cultures, and constitute first proof of the involvement of both RA receptors (RARs) and rexinoid receptors (RXRs) in this effect. Reduction of leptin levels by specific nutrients is of potential interest from a clinical point of view.
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Affiliation(s)
- Francisco Felipe
- Laboratory of Molecular Biology, Nutrition and Biotechnology, Department of Fundamental Biology and Health Sciences, University of the Balearic Islands, Crta. Valldemossa Km 7.5, 07122 Palma de Mallorca, Spain
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24
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Verma NK, Singh J, Dey CS. PPAR-gamma expression modulates insulin sensitivity in C2C12 skeletal muscle cells. Br J Pharmacol 2004; 143:1006-13. [PMID: 15504754 PMCID: PMC1575957 DOI: 10.1038/sj.bjp.0706002] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2004] [Revised: 08/23/2004] [Accepted: 09/08/2004] [Indexed: 11/09/2022] Open
Abstract
Peroxisome proliferator-activated receptor-gamma (PPAR-gamma) expression is very low in skeletal muscle cells, which is one of the most important target tissues for insulin and plays a predominant role in glucose homeostasis. It has recently been shown that muscle-specific PPAR-gamma deletion in mouse causes insulin resistance. However, it is likely that the observed effects might be due to secondary interaction in whole animal. The aim of the study was to explore the role of muscle PPAR-gamma in insulin sensitivity. We stably transfected C2C12 skeletal muscle cells with plasmids containing sense or antisense constructs of PPAR-gamma and examined the effect of modulation of PPAR-gamma expression in terms of glucose uptake. Effect was also examined in insulin-resistant C2C12 skeletal muscle cells. In transfected C2C12 cell line, the inhibition of PPAR-gamma expression (23.0 +/-0.005%) was observed to induce insulin resistance as determined by functional assessment of 2-deoxyglucose incorporation. Overexpression of PPAR-gamma (28.5 +/- 0.008%) produced an additional effect on insulin (100 nM) and Pioglitazone (50 microM), resulting in 42.7 +/- 3.5% increase in glucose uptake as against 29.2+/-2.8% in wild-type C2C12 skeletal muscle cells differentiated under normal (2% horse serum) condition. Under similar treatment, PPAR-gamma overexpressing cells resistant to insulin exhibited enhanced glucose uptake upto 60.7 +/- 4.08%, as compared to 23.8 +/- 5.1% observed in wild-type C2C12 skeletal muscle cells. These data demonstrate a direct involvement of PPAR-gamma in insulin sensitization of TZD action on skeletal muscle cells, and suggest that pharmacological overexpression of muscle PPAR-gamma gene in skeletal muscle might be a useful strategy for the treatment of insulin resistance.
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Affiliation(s)
- Navin K Verma
- Signal Transduction Research Laboratory, Department of Biotechnology, National Institute of Pharmaceutical Education and Research (NIPER), Sector 67, S.A.S. Nagar, Punjab 160 062, India
| | - Jaskirat Singh
- Signal Transduction Research Laboratory, Department of Biotechnology, National Institute of Pharmaceutical Education and Research (NIPER), Sector 67, S.A.S. Nagar, Punjab 160 062, India
| | - Chinmoy S Dey
- Signal Transduction Research Laboratory, Department of Biotechnology, National Institute of Pharmaceutical Education and Research (NIPER), Sector 67, S.A.S. Nagar, Punjab 160 062, India
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25
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Thompson MP, Kim D. Links between fatty acids and expression of UCP2 and UCP3 mRNAs. FEBS Lett 2004; 568:4-9. [PMID: 15196910 DOI: 10.1016/j.febslet.2004.05.011] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2004] [Accepted: 05/03/2004] [Indexed: 12/31/2022]
Abstract
Physiological and pathological states that are associated with elevated plasma fatty acids (FAs) increase uncoupling protein 2 (UCP2) mRNA in white adipose tissue and UCP3 mRNA in skeletal muscle and heart. A direct effect of unsaturated fatty acids from all classes has been shown in various cultured cells. There is evidence that FAs could induce expression of UCPs by acting as ligands for peroxisome proliferator-activated receptors, influencing the function of sterol responsive element binding protein or activating 5'-AMP-activated protein kinase. Oleic acid has been shown to stimulate the activity of the promoter regions of UCP2 and UCP3 genes and the FA responsive regions are beginning to be characterised.
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Affiliation(s)
- Mary P Thompson
- Department of Biochemistry, University of Otago, P.O. Box 56, Dunedin, New Zealand.
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26
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Liebig M, von Praun C, Heldmaier G, Klingenspor M. Absence of UCP3 in brown adipose tissue does not impair nonshivering thermogenesis. Physiol Biochem Zool 2004; 77:116-26. [PMID: 15057722 DOI: 10.1086/381464] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 09/11/2003] [Indexed: 11/03/2022]
Abstract
We report on a novel Djungarian hamster mutant lineage that exhibits a loss of uncoupling protein (UCP) 3 mRNA and protein in brown adipose tissue (BAT), whereas UCP3 expression in skeletal muscle is only mildly diminished. In response to 2 d of cold exposure, UCP3 mRNA was 4.5-fold elevated in BAT of wild-type hamsters but remained undetectable in mutant hamsters. Notably, in BAT of warm- and cold-exposed mutant hamsters, UCP1 and UCP2 mRNA levels were increased. The tissue specificity of UCP3 deficiency suggests that the underlying unknown mutation impairs a factor controlling UCP3 gene expression selectively in brown adipocytes. In wild-type but not mutant primary brown adipocytes, UCP3 gene expression was stimulated by treatment with peroxisome proliferator activated receptor (PPAR) ligands. This implies that the underlying mutation causing UCP3 deficiency is expressed within brown adipocytes and disrupts PPAR-dependent transactivation of the UCP3 gene. On the functional level, we found no direct phenotypic consequences of altered UCP expression in BAT. The absence of UCP3 in BAT of cold-acclimated mutant hamsters affected neither maximal nonshivering thermogenesis elicited by noradrenaline nor the uncoupled respiration of isolated mitochondria in the presence of oligomycin and in response to palmitate.
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Affiliation(s)
- Michaela Liebig
- Animal Physiology, Department of Biology, Philipps University Marburg, D-35032 Marburg, Germany
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27
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Depieri TZ, Pinto RR, Catarin JK, de Carli MCL, Garcia Júnior JR. UCP-3: regulação da expressão gênica no músculo esquelético e possível relação com o controle do peso corporal. ACTA ACUST UNITED AC 2004; 48:337-44. [PMID: 15640895 DOI: 10.1590/s0004-27302004000300003] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
As UCPs constituem um subgrupo das proteínas carreadoras mitocondriais que estão localizadas na membrana mitocondrial interna. Por meio da dissipação do gradiente de próton, elas desacoplam a fosforilação oxidativa e convertem combustível em calor. Foram identificadas quatro isoformas da UCP. A UCP-1 foi a primeira a ser descoberta, sendo encontrada exclusivamente no tecido adiposo marrom, a UCP-2 é encontrada em vários tecidos, a UCP-3 encontra-se no músculo esquelético em humanos e tecido adiposo marrom e músculo esquelético em roedores, enquanto a UCP-4 é expressa no cérebro. A expressão da UCP-3 no músculo esquelético e no tecido adiposo marrom pode fazer destes tecidos importantes mediadores da termogênese adaptativa. No entanto, o papel da UCP-3 quanto ao gasto de energia e como causa da obesidade ainda não passa de uma hipótese. Há evidências de que a UCP-3 seja regulada pelos substratos energéticos, tais como ácidos graxos e glicose que, ao entrarem no músculo, provocam aumento da UCP-3 e aumento no gasto de energia. Nosso objetivo nesta revisão foi descrever e discutir as informações disponíveis sobre a regulação da UCP-3, e sua possível relação com o controle do peso corporal.
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Affiliation(s)
- Tatiane Z Depieri
- Pró-Reitoria de Pesquisa e Pós-Graduação, UNOESTE, Presidente Prudente, SP
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Sun X, Wray C, Tian X, Hasselgren PO, Lu J. Expression of uncoupling protein 3 is upregulated in skeletal muscle during sepsis. Am J Physiol Endocrinol Metab 2003; 285:E512-20. [PMID: 12721157 DOI: 10.1152/ajpendo.00446.2002] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Uncoupling protein 3 (UCP3) is a member of the mitochondrial transporter superfamily that is expressed primarily in skeletal muscle. UCP3 is upregulated in various conditions characterized by skeletal muscle atrophy, including hyperthyroidism, fasting, denervation, diabetes, cancer, lipopolysaccharide (LPS), and treatment with glucocorticoids (GCs). The influence of sepsis, another condition characterized by muscle cachexia, on UCP3 expression and activity is not known. We examined UCP3 gene and protein expression in skeletal muscles from rats after cecal ligation and puncture and from sham-operated control rats. Sepsis resulted in a two- to threefold increase in both mRNA and protein levels of UCP3 in skeletal muscle. Treatment of rats with the glucocorticoid receptor antagonist RU-38486 prevented the sepsis-induced increase in gene and protein expression of UCP3. The UCP3 mRNA and protein levels were increased 2.4- to 3.6-fold when incubated muscles from normal rats were treated with dexamethasone (DEX) and/or free fatty acids (FFA) ex vivo. In addition, UCP3 mRNA and protein levels were significantly increased in normal rat muscles in vivo with treatment of either DEX or FFA. The results suggest that sepsis upregulates the gene and protein expression of UCP3 in skeletal muscle, which may at least in part be mediated by GCs and FFA.
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Affiliation(s)
- Xiaoyan Sun
- Department of Surgery, University of Cincinnati, 231 Albert Sabin Way, Mail Location 0558, Cincinnati, Ohio 45267-0558, USA.
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Mingrone G, Rosa G, Greco AV, Manco M, Vega N, Hesselink MK, Castagneto M, Schrauwen P, Vidal H. Decreased uncoupling protein expression and intramyocytic triglyceride depletion in formerly obese subjects. OBESITY RESEARCH 2003; 11:632-40. [PMID: 12740453 DOI: 10.1038/oby.2003.91] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
OBJECTIVE To examine the muscular uncoupling protein expression 2 (UCP2) and UCP3 gene expression in morbid obese subjects before and after bariatric surgery [bilio-pancreatic diversion (BPD)]. RESEARCH METHODS AND PROCEDURES Eleven obese subjects (BMI = 49 +/- 2 kg/m(2)) were studied before BPD and 24 months after BPD. Skeletal muscle UCP2 and UCP3 mRNA was measured using reverse transcriptase-competitive polymerase chain reaction and UCP3 protein by Western blotting. Intramyocytic triglycerides were quantified by high-performance liquid chromatography. Twenty-four-hour energy expenditure and respiratory quotient (RQ) were measured in a respiratory chamber. RESULTS After BPD, the average weight loss was approximately 38%. Nonprotein RQ was increased in the postobese subjects (0.73 +/- 0.00 vs. 0.83 +/- 0.02, p < 0.001). The intramyocytic triglyceride level dropped (3.66 +/- 0.16 to 1.60 +/- 0.29 mg/100 mg of fresh tissue, p < 0.0001) after BPD. Expression of UCP2 and UCP3 mRNA was significantly reduced (from 35.9 +/- 6.1% to 18.6 +/- 4.5% of cyclophilin, p = 0.02; from 60.2 +/- 14.0% to 33.4 +/- 8.5%, p = 0.03; respectively). UCP3 protein content was also significantly reduced (272.19 +/- 84.13 vs. 175.78 +/- 60.31, AU, p = 0.04). A multiple regression analysis (R(2) = 0.90) showed that IMTG levels (p = 0.007) represented the most powerful independent variable for predicting UCP3 variation. DISCUSSION The strong correlation of UCP expression and decrease in IMTG levels suggests that triglyceride content plays an even more important role in the regulation of UCP gene expression than the circulating levels of free fatty acids or the achieved degree of weight loss.
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Affiliation(s)
- Geltrude Mingrone
- Istituto di Clinica Medica and. Clinica Chirurgica and Centro CNR Fisiopatologia Shock, Università Cattolica S Cuore, Rome, Italy.
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30
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Gilde AJ, van der Lee KAJM, Willemsen PHM, Chinetti G, van der Leij FR, van der Vusse GJ, Staels B, van Bilsen M. Peroxisome proliferator-activated receptor (PPAR) alpha and PPARbeta/delta, but not PPARgamma, modulate the expression of genes involved in cardiac lipid metabolism. Circ Res 2003; 92:518-24. [PMID: 12600885 DOI: 10.1161/01.res.0000060700.55247.7c] [Citation(s) in RCA: 304] [Impact Index Per Article: 14.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Abstract
Long-chain fatty acids (FA) coordinately induce the expression of a panel of genes involved in cellular FA metabolism in cardiac muscle cells, thereby promoting their own metabolism. These effects are likely to be mediated by peroxisome proliferator-activated receptors (PPARs). Whereas the significance of PPARalpha in FA-mediated expression has been demonstrated, the role of the PPARbeta/delta and PPARgamma isoforms in cardiac lipid metabolism is unknown. To explore the involvement of each of the PPAR isoforms, neonatal rat cardiomyocytes were exposed to FA or to ligands specific for either PPARalpha (Wy-14,643), PPARbeta/delta (L-165041, GW501516), or PPARgamma (ciglitazone and rosiglitazone). Their effect on FA oxidation rate, expression of metabolic genes, and muscle-type carnitine palmitoyltransferase-1 (MCPT-1) promoter activity was determined. Consistent with the PPAR isoform expression pattern, the FA oxidation rate increased in cardiomyocytes exposed to PPARalpha and PPARbeta/delta ligands, but not to PPARgamma ligands. Likewise, the FA-mediated expression of FA-handling proteins was mimicked by PPARalpha and PPARbeta/delta, but not by PPARgamma ligands. As expected, in embryonic rat heart-derived H9c2 cells, which only express PPARbeta/delta, the FA-induced expression of genes was mimicked by the PPARbeta/delta ligand only, indicating that FA also act as ligands for the PPARbeta/delta isoform. In cardiomyocytes, MCPT-1 promoter activity was unresponsive to PPARgamma ligands. However, addition of PPARalpha and PPARbeta/delta ligands dose-dependently induced promoter activity. Collectively, the present findings demonstrate that, next to PPARalpha, PPARbeta/delta, but not PPARgamma, plays a prominent role in the regulation of cardiac lipid metabolism, thereby warranting further research into the role of PPARbeta/delta in cardiac disease.
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Affiliation(s)
- Andries J Gilde
- Department of Physiology, Cardiovascular Research Institute Maastricht, Maastricht University, PO Box 616, 6200 MD Maastricht, The Netherlands
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31
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Abstract
AIMS The regulation of uncoupling protein-3 (UCP-3) expression in muscle remains unclear, specifically in relation to dietary and drug treatments. The present study evaluated the effects of oleic acid and rosiglitazone on UCP-3 mRNA expression in differentiated L6 myotubes. METHODS L6 myocytes were cultured and differentiated prior to exposure to rosiglitazone 10 micro mol/l, oleic acid 100 micro mol/l, or the combination, for 24 h, prior to semiquantitative evaluation of UCP-3 mRNA relative to GAPDH mRNA by RT-PCR. RESULTS Exposure to oleic acid produced a significant increase in UCP-3 mRNA (0.012 +/- 0.007 vs. 0.0011 +/- 0.0006 for untreated cells, relative to GAPDH mRNA, p < 0.001). Rosiglitazone alone had no effect on UCP-3 expression and nor did the glitazone affect oleic-acid-induced upregulation of UCP-3. CONCLUSIONS In L6 myotubes, 24-h exposure to oleic acid produced a 10-fold increase in UCP-3 mRNA expression, but rosiglitazone had no effect. Oleic-acid-induced upregulation of UCP-3 was not affected (positively or negatively) by glitazone exposure.
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Affiliation(s)
- A Costello
- School of Medical and Surgical Sciences, University of Nottingham
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Kumar N, Dey CS. Development of insulin resistance and reversal by thiazolidinediones in C2C12 skeletal muscle cells. Biochem Pharmacol 2003; 65:249-57. [PMID: 12504800 DOI: 10.1016/s0006-2952(02)01509-5] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
AIM/HYPOTHESIS The aim of this study was to develop an insulin-resistant cell culture model in skeletal muscle cell line by chronic presence of insulin in serum-free medium and to determine the effect of thiazolidinediones on insulin signaling. METHODS We differentiated C2C12 in a combination of serum-free medium in presence or absence of insulin and determined differentiation by creatine kinase activity, myogenin and MyoD expression. The development of insulin resistance was determined by tyrosine phosphorylation of insulin receptor and insulin receptor substrate-1, phosphatidylinositol 3-kinase activity associated with insulin receptor substrate-1 and glucose uptake. We treated the cells with 50 microM of thiazolidinediones to determine the effect on these parameters. RESULTS C2C12 cells were differentiated normally in the serum-free medium in the absence or presence of insulin. Chronic treatment of insulin resulted in reduced tyrosine phosphorylation of insulin receptor and insulin receptor substrate-1; activation of phosphatidylinositol 3-kinase was impaired and insulin-stimulated glucose uptake was reduced. The treatment of insulin-resistant cells with thiazolidinediones resulted in the enhancement of insulin signaling pathway by increasing tyrosine phosphorylation of insulin receptor, insulin receptor substrate-1, phosphatidylinositol 3-kinase activity and glucose uptake. CONCLUSION/INTERPRETATION These results indicate that insulin resistance can be developed in C2C12 skeletal muscle cell line. These findings implicate a direct mechanism of action of thiazolidinediones on skeletal muscle.
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Affiliation(s)
- Naresh Kumar
- Signal Transduction Research Laboratory, Department of Biotechnology, National Institute of Pharmaceutical Education and Research, Sector 67, S.A.S. Nagar, Punjab 160062, India
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Felipe F, Bonet ML, Ribot J, Palou A. Up-regulation of muscle uncoupling protein 3 gene expression in mice following high fat diet, dietary vitamin A supplementation and acute retinoic acid-treatment. Int J Obes (Lond) 2003; 27:60-9. [PMID: 12532155 DOI: 10.1038/sj.ijo.0802188] [Citation(s) in RCA: 56] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/27/2002] [Revised: 07/15/2002] [Accepted: 08/01/2002] [Indexed: 11/08/2022]
Abstract
OBJECTIVE To analyse the impact of vitamin A supplementation of both a normal fat (NF) diet and a high fat (HF) diet and of acute retinoic acid (RA)-treatment on the expression of uncoupling protein 3 (UCP3) in mice. DESIGN C57BL/6J mice were fed for 18 weeks a NF or a HF diet (10 and 45 energy% as fat, respectively), both with the normal vitamin A content or an excess vitamin A (8 mg and 320 mg retinyl palmitate/kg diet, respectively). Body weight and energy intake were recorded periodically. UCP3 mRNA and UCP3 protein levels in skeletal muscle (soleus/gastrocnemius) were analysed, as well as UCP1, UCP2 and UCP3 mRNA levels in interscapular brown adipose tissue (BAT), and UCP2 mRNA, UCP2 protein and leptin mRNA levels in white adipose tissue (WAT) depots. The effect of acute RA-treatment (100 mg/kg/day, 4 days) on UCP3 mRNA levels in skeletal muscle and BAT of NMRI mice was also assessed. RESULTS Vitamin A supplementation of a NF diet led to increased levels of UCP3 mRNA and UCP3 protein in muscle, UCP1 mRNA in BAT, and UCP2 mRNA in inguinal WAT, but had no impact on body weight or adiposity of B6 mice. HF diet promoted obesity and increased levels of UCP3 mRNA and UCP3 protein in skeletal muscle, and of the mRNAs for all three UCPs in BAT. Supplementing the HF diet with vitamin A had little effect on the final obesity reached and did not lead to further increases of muscle UCP3 mRNA nor BAT UCP1 mRNA over the levels achieved with the non-supplemented HF diet. Adipose leptin mRNA levels were down regulated after vitamin A supplementation, independently of the fat content of the diet. Up-regulation of muscle, but not BAT, UCP3 mRNA levels was also found after acute RA-treatment in NMRI mice. CONCLUSION The results provide evidence of a stimulatory effect of retinoids on muscle UCP3 expression in vivo, and a differential retinoid-regulation of the UCP3 gene in muscle and BAT.
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Affiliation(s)
- F Felipe
- Laboratori de Biologia Molecular, Nutrició i Biotecnologia, Departament de Biologia Fonamental i Ciències de la Salut, Universitat de les Illes Balears, Palma de Mallorca, Spain
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Guigal N, Rodriguez M, Cooper RN, Dromaint S, Di Santo JP, Mouly V, Boutin JA, Galizzi JP. Uncoupling protein-3 (UCP3) mRNA expression in reconstituted human muscle after myoblast transplantation in RAG2-/-/gamma c/C5(-) immunodeficient mice. J Biol Chem 2002; 277:47407-11. [PMID: 12351640 DOI: 10.1074/jbc.m208048200] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Uncoupling protein-3 (UCP3), which is expressed abundantly in skeletal muscle, is one of the carrier proteins dissipating the transmitochondrial electrochemical gradient as heat and has therefore been implicated in the regulation of energy metabolism. Myoblasts or differentiated muscle cells in vitro expressed little if any UCP3, compared with the levels detected in biopsies of skeletal muscle. In the present report, we sought to investigate UCP3 mRNA expression in human muscle generated by myoblast transplantation in the skeletal muscle of an immunodeficient mouse model. Time course experiments demonstrated that 7-8 weeks following transplantation fully differentiated human muscle fibers were formed. The presence of differentiated human muscle fibers was assessed by quantitative PCR measurement of the human alpha-actin mRNA together with immunohistochemical staining using specific antibodies for spectrin and the slow adult myosin heavy chain. Interestingly, we found that the expression of UCP3 mRNA was dependant on human muscle differentiation and that the UCP3 mRNA level was comparable with that found in human muscle biopsies. Moreover, the human UCP3 (hUCP3) promoter seems to be fully functional, since triiodothyronine treatment of the mice not only stimulated the mouse UCP3 (mUCP3) mRNA expression but also strongly stimulated the hUCP3 mRNA expression in human fibers formed after myoblast transplantation. To our knowledge, this is the first time that primary myoblasts could be induced to express the UCP3 gene at a level comparable of that found in human muscle fibers.
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Affiliation(s)
- Nolwen Guigal
- Institut de Recherches Servier, Division de Pharmacologie Moléculaire et Cellulaire, 125 Chemin de Ronde, 78290 Croissy-sur-Seine, France
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López-Solache I, Marie V, Camirand A, Silva JE. Regulation of uncoupling protein-2 mRNA in L6 myotubules: II: Thyroid hormone amplifies stimulation of uncoupling protein-2 gene by thiazolidinediones and other peroxisome proliferator-activated receptor ligands in L6 myotubules: evidence for a priming effect. Endocrine 2002; 19:209-17. [PMID: 12588052 DOI: 10.1385/endo:19:2:209] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/23/2002] [Revised: 10/02/2002] [Accepted: 10/02/2002] [Indexed: 11/11/2022]
Abstract
The stimulation of the uncoupling protein-2 gene (ucp2) by thyroid hormone (triiodothyronine [T3]) in vivo is variable, suggesting complex interactions and even the possibility of indirect effects. We investigated the effect of T3 on ucp2 expression in L6 myotubules. Alone, T3 did not significantly stimulate ucp2 expression in L6 cells, but it amplified the stimulation by thiazolidinediones (TZDs). L6 cells expressed both alpha1 and beta1 thyroid hormone receptors and the data were consistent with the effect being mediated by these receptors. T3 also enhanced the stimulation of ucp2 by the nonselective peroxisome proliferator-activated receptor (PPAR) ligands bezafibrate and carbacyclin, but not that by oleic acid or norepinephrine. L6 cells expressed PPARbeta and PPARgamma, but not PPARalpha. As short as a 1-h preexposure of L6 cells to T3 was sufficient to amplify the effect of PPAR ligands. Neither transcription nor translation was needed for this effect of T3. T3 did not affect the t1/2 of UCP2 mRNA. The histone deacetylases inhibitor trichostatin A (TSA) stimulated the expression of ucp2 but did not add to the effect of T3 nor did this hormone enhance the effect of TSA. These results suggest that T3 selectively enhances the transcriptional stimulation of ucp2 by TZDs and nonselective PPAR ligands by priming the gene to a transactivating signal(s) generated by such ligands.
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Affiliation(s)
- Irma López-Solache
- Department of Medicine, Division of Endocrinology, Jewish General Hospital, Lady Davis Institute, McGill University, Montreal, Quebec, Canada
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Tsutsumi K, Inoue Y, Kondo Y. The relationship between lipoprotein lipase activity and respiratory quotient of rats in circadian rhythms. Biol Pharm Bull 2002; 25:1360-3. [PMID: 12392095 DOI: 10.1248/bpb.25.1360] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Plasma lipid levels and lipoprotein lipase (LPL) are known to follow circadian rhythms in rats. However, very little information is available on the variations in respiratory quotient (RQ) during the 24-h period in rats. The aims of this study were to provide an overall view of the effects of circadian rhythm on RQ and to determine the relationship of LPL and RQ with metabolic parameters in these animals. Male rats were fed ad libitum and were kept under a 12 :12-h light-dark cycle. Rats were killed every 2 h over a 24-h period for measurement of metabolic parameters and tissue LPL activity. The RQ was measured every 4 h over the same 24-h period. The gastric contents increased during the dark phase and decreased during the light phase. For the metabolic parameters, circadian rhythms were detected for plasma glucose, triglycerides, high-density lipoprotein cholesterol and non esterified free fatty acids, but not for plasma total cholesterol or phospholipids. The RQ and adipose tissue LPL activity increased during the dark phase, while skeletal muscle LPL activity decreased during this phase. The RQ was inversely correlated with skeletal muscle LPL activity (r = -0.880) and positively correlated with adipose tissue LPL activity (r = 0.937). These results appear to show that rats tend toward consumption of fat by accelerating fat oxidation, resulting in suppression of fat accumulation in the light phase, while tending toward fat accumulation by the suppression of fat oxidation in the dark phase.
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Affiliation(s)
- Kazuhiko Tsutsumi
- Nutrition Research Institute, Otsuka Pharmaceutical Factory, Inc, Naruto, Tokushima, Japan.
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Delerive P, Chin WW, Suen CS. Identification of Reverb(alpha) as a novel ROR(alpha) target gene. J Biol Chem 2002; 277:35013-8. [PMID: 12114512 DOI: 10.1074/jbc.m202979200] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The nuclear receptor superfamily comprises a large number of ligand-activated transcription factors that are involved in numerous biological processes such as cell proliferation, differentiation, and homeostasis. ROR(alpha) (NR1F1) and Reverb(alpha) (NR1D1) are two members of this family whose biological functions are largely unknown. In addition, no ligand has been yet identified for these two receptors; therefore, they are referred as orphan receptors. Here, we show that ROR(alpha) and Reverb(alpha) are expressed with a similar tissue distribution and are both induced during the differentiation of rat L6 myoblastic cells. Ectopic expression of ROR(alpha)1 in L6 cells significantly induces Reverb(alpha) expression as demonstrated by Northern blot analysis. Using reverse transcription-PCR to analyze Reverb(alpha) gene expression from staggerer mice, we found that there was a significant reduction of Reverb(alpha) mRNA in the skeletal muscle comparing it with the wild-type mice, which suggests that ROR(alpha) is involved in the regulation of Reverb(alpha) gene expression. Transient transfection assays using the Reverb(alpha) promoter demonstrate that ROR(alpha) regulates the Reverb(alpha) gene at the transcriptional level. Furthermore, mutagenesis experiments indicate that ROR(alpha) regulates Reverb(alpha) transcription via a monomeric ROR response element located in the Reverb(alpha) gene promoter. Electrophoretic mobility shift assays show that ROR(alpha) binds strongly to this site in a specific-manner. Finally, overexpression of GRIP-1/TIF-2, but not SRC-1, potentiates ROR(alpha)-stimulated Reverb(alpha) promoter activity in transient transfection experiments. Together, our results identify Reverb(alpha) as a novel target gene for ROR(alpha).
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Affiliation(s)
- Philippe Delerive
- Department of Gene Regulation, Bone and Inflammation Research, Eli Lilly Research Laboratories, Lilly Corporate Center, Indianapolis, Indiana 46285, USA.
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Khurana A, Dey CS. Subtype specific roles of mitogen activated protein kinases in L6E9 skeletal muscle cell differentiation. Mol Cell Biochem 2002; 238:27-39. [PMID: 12349907 DOI: 10.1023/a:1019957602038] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Role of mitogen activated protein kinases (MAPK) in skeletal muscle differentiation is not fully understood. We investigated subtype-specific functions and their interactions, if any, in the regulation of myogenic differentiation in L6E9 skeletal muscle cells. We show inhibition of extracellular signal-regulated kinase-1 and -2 (ERK-1/-2) and activation of p38 MAP kinase during the differentiation of L6E9 rat skeletal muscle cells under low serum condition. Inhibition of ERK-1/-2 activity dramatically enhanced differentiation as was evident from cellular morphology, expression of muscle differentiation specific marker proteins, suggesting that ERK-1/-2 activation may be inhibitory to initiation and progression of differentiation. In contrast, inhibition of p38 MAP kinase completely prevented differentiation; meaning p38 activation is required from the initiation till terminal differentiation of L6E9 cells. Moreover, inhibition of ERK-1/-2 activities enhanced the activation of p38 MAP kinase that resulted in enhancement of differentiation; whereas inhibition of p38 MAP kinase activity enhanced the ERK-1/-2 activities culminating in abrogation of differentiation. We conclude that ERK-1/-2 andp38 MAPkinase cascades oppositelyregulate each other's function(s) thereby regulating L6E9 skeletal muscle differentiation.
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Affiliation(s)
- Ashwani Khurana
- Department of Biotechnology, National Institute of Pharmaceutical Education and Research, Punjab, India
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Sbraccia P, D'Adamo M, Leonetti F, Buongiorno A, Silecchia G, Basso MS, Tamburrano G, Lauro D, Federici M, Di Daniele N, Lauro R. Relationship between plasma free fatty acids and uncoupling protein-3 gene expression in skeletal muscle of obese subjects: in vitro evidence of a causal link. Clin Endocrinol (Oxf) 2002; 57:199-207. [PMID: 12153598 DOI: 10.1046/j.1365-2265.2002.01593.x] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
OBJECTIVE To investigate whether skeletal muscle uncoupling protein-2 (UCP2) and uncoupling protein-3 (UCP3) gene expression is altered in massive obesity and whether it correlates with in vivo insulin sensitivity and with metabolic and hormonal status. DESIGN Quantification of UCP2 and UCP3 gene expression in skeletal muscle of obese and lean subjects displaying different degrees of insulin sensitivity. PATIENTS Fourteen obese and 10 age- and sex-matched healthy control subjects with a mean body mass index (BMI) of 43.6 +/- 1.4 and 22.8 +/- 1.8 (+/- SEM), respectively. MEASUREMENTS Insulin sensitivity by glucose clamp, body composition by bio-impedance, fasting plasma glucose, insulin, leptin and free fatty acids (FFA). Skeletal muscle UCP2 and UCP3 mRNA levels by quantitative reverse transcription polymerase chain reaction (RT-PCR). RESULTS No significant differences in UCP2 or UCP3 mRNA levels were found between obese and control subjects. No significant correlation was observed, in both groups, between UCP2 or UCP3 mRNA levels and both anthropometrical and metabolic parameters. In contrast, a highly significant correlation was observed between skeletal muscle UCP3, but not UCP2, mRNA levels and plasma FFA in the obese, but not in the lean, group. Furthermore, exposure of human myocytes to FFA for 24 h strongly induced both UCP3 and peroxisome proliferator-activated receptor-gamma (PPARgamma) but not UCP2 gene expression. CONCLUSIONS FFA levels correlate strongly with skeletal muscle UCP3 mRNA levels in obese, but not in lean, subjects; in addition, in human myocytes, high FFA concentrations promote UCP3 expression. Our studies therefore provide evidence that supports a role for increased plasma FFA concentrations in the regulation of human skeletal muscle UCP3 gene expression.
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Affiliation(s)
- Paolo Sbraccia
- Loboratory of Molecular Medicine, Department of Internal Medicine, University of Rome 'Tor Vergata', Italy.
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Brown HR, Ni H, Benavides G, Yoon L, Hyder K, Giridhar J, Gardner G, Tyler RD, Morgan KT. Correlation of simultaneous differential gene expression in the blood and heart with known mechanisms of adriamycin-induced cardiomyopathy in the rat. Toxicol Pathol 2002; 30:452-69. [PMID: 12187937 DOI: 10.1080/01926230290105604] [Citation(s) in RCA: 41] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
As the genomes of mammalian species become sequenced and gene functions are ascribed, the use of differential gene expression (DGE) to evaluate organ function will become common in the experimental evaluation of new drug therapies. The ability to translate this technology into useful information for human exposures depends on tissue sampling that is impractical or generally not possible in man. The possibility that the DGE of nucleated cells, reticulocytes, or platelets in blood may present the necessary link with target organ toxicity provides an opportunity to correlate preclinical with clinical outcomes. Adriamycin is highly effective alone and more frequently in combination with other chemotherapeutic agents in the treatment of a variety of susceptible malignancies. Adriamycin-induced cardiomyopathy was examined as an endpoint to measure the utility of DOE on whole blood as a predictor of cardiac toxicity. Statistically significant gene changes were observed between relevant blood and cardiac gene profiles that corroborated the accepted mechanisms of toxicity (oxidative stress, effects on carnitine transport, DNA intercalation). There were, however, clear indications that other target organs (bone marrow and intestinal tract) were affected. The divergent expression of some genes between the blood and the heart on day 7 may also indicate the timing and mechanism of development of the cardiomyopathy and confirm current therapeutic approaches for its prevention. The data demonstrate that whole blood gene expression particularly in relation to oxidative stress, in conjunction with standard hematology and clinical chemistry, may be useful in monitoring and predicting cardiac damage secondary to adriamycin administration. Appendices A & B, referenced in this paper, are not printed in this issue of Toxicologic Pathology. They are available as downloadable text files at http://taylorandfrancis.metapress.com/openurl.asp?genre=journal&issn=0192-6233. To access them, click on the issue link for 30(4), then select this article. A download option appears at the bottom of this abstract. In order to access the full article online, you must either have an individual subscription or a member subscription accessed through www.toxpath.org.
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Affiliation(s)
- H Roger Brown
- Drug Safety, GlaxoSmithKline, Inc, Research Triangle Park, North Carolina 27709, USA.
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41
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Guillet-Deniau I, Mieulet V, Le Lay S, Achouri Y, Carré D, Girard J, Foufelle F, Ferré P. Sterol regulatory element binding protein-1c expression and action in rat muscles: insulin-like effects on the control of glycolytic and lipogenic enzymes and UCP3 gene expression. Diabetes 2002; 51:1722-8. [PMID: 12031958 DOI: 10.2337/diabetes.51.6.1722] [Citation(s) in RCA: 98] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
Sterol regulatory element binding protein-1c (SREBP-1c) is a transcription factor that mediates insulin effects on hepatic gene expression. It is itself transcriptionally stimulated by insulin in hepatocytes. Here we show that SREBP-1c mRNA is expressed in adult rat skeletal muscles and that this expression is decreased by diabetes. The regulation of SREBP-1c expression was then assessed in cultures of adult muscle satellite cells. These cells form spontaneously contracting multinucleated myotubes within 7 days of culture. SREBP-1c mRNA is expressed in contracting myotubes. A 4-h treatment with 100 nmol/l insulin increases SREBP-1c expression and nuclear abundance by two- to threefold in myotubes. In cultured myotubes, insulin increases the expression of glycolytic and lipogenic enzyme genes and inhibits the 9-cis retinoic acid-induced UCP3 expression. These effects of insulin are mimicked by adenovirus-mediated expression of a transcriptionally active form of SREBP-1c. We conclude that in skeletal muscles, SREBP-1c expression is sensitive to insulin and can transduce the positive and negative actions of the hormone on specific genes and thus has a pivotal role in long-term muscle insulin sensitivity.
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Argilés JM, Busquets S, López-Soriano FJ. The role of uncoupling proteins in pathophysiological states. Biochem Biophys Res Commun 2002; 293:1145-52. [PMID: 12054495 DOI: 10.1016/s0006-291x(02)00355-8] [Citation(s) in RCA: 75] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
Until very recently, the uncoupling protein-1 (UCP1), present only in brown adipose tissue (BAT), was considered to be the only mitochondrial carrier protein that stimulated heat production by dissipating the proton gradient generated during respiration across the inner mitochondrial membrane and therefore uncoupling respiration from ATP synthesis. Recently, new uncoupling proteins, UCP2, UCP3, and UCP4, and brain mitochondrial carrier protein-1 (BMCP-1) have been described in mammalian tissues. The present review deals with the possible role of these proteins in different pathological conditions involving alterations in energy balance such as obesity or cachexia. In conclusion, the emergence of the UCP family has altered the approaches to bioenergetics and stressed the importance of uncoupling respiration in different pathophysiological conditions. An extensive qualitative and quantitative characterization of the new members of the UCP family in mammalian tissues will allow a better understanding of the molecular and regulatory mechanisms of thermogenesis and energy metabolism. At this point, we hope that the knowledge presented in the present review will not only stimulate a debate about the role of the UCP family in disease but also lead to applications beneficial for human health.
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Affiliation(s)
- Josep M Argilés
- Cancer Research Group, Departament de Bioquímica i Biologia Molecular, Facultat de Biologia, Universitat de Barcelona, Diagonal 645, 08028 Barcelona, Spain.
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43
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Kogure A, Sakane N, Takakura Y, Umekawa T, Yoshioka K, Nishino H, Yamamoto T, Kawada T, Yoshikawa T, Yoshida T. Effects of caffeine on the uncoupling protein family in obese yellow KK mice. Clin Exp Pharmacol Physiol 2002; 29:391-4. [PMID: 12010181 DOI: 10.1046/j.1440-1681.2002.03675.x] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
1. The hypothesis that caffeine upregulates uncoupling protein (UCP)-1, UCP-2 and UCP-3 expression, which contribute to thermogenesis, was investigated in obese mice. 2. The mRNA levels of UCP-1, -2 and -3 in brown adipose tissue (BAT), UCP-2 in white adipose tissue (WAT), and UCP-2 and -3 in skeletal muscle were measured using real-time quantitative reverse transcription-polymerase chain reaction analysis in obese yellow KK mice 4 h after the subcutaneous administration of either 60 mg/kg caffeine or physiological saline. Plasma free fatty acids, adrenaline, noradrenaline and dopamine levels were also measured. 3. In caffeine-injected obese mice, UCP-1 mRNA levels were significantly increased by 1.5-fold in BAT, UCP-2 mRNA levels were increased by 1.8- and 2.5-fold in BAT and skeletal muscles, respectively, and UCP-3 mRNA levels were increased 1.7- and 3.4-fold in BAT and skeletal muscles, respectively, compared with control mice injected with physiological saline. There was no difference in UCP-2 mRNA levels in WAT between the two groups. 4. Plasma free fatty acids and adrenaline levels were significantly elevated in mice treated with caffeine compared with those injected with physiological saline. 5. It was concluded that caffeine upregulates the expression of UCP-1, UCP-2 and UCP-3 in BAT and UCP-2 and UCP-3 in skeletal muscles, which may contribute to thermogenesis in obese mice.
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Affiliation(s)
- Akinori Kogure
- First Department of Internal Medicine, Kyoto Prefectural University of Medicine, Kyoto, Japan.
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44
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Muoio DM, Way JM, Tanner CJ, Winegar DA, Kliewer SA, Houmard JA, Kraus WE, Dohm GL. Peroxisome proliferator-activated receptor-alpha regulates fatty acid utilization in primary human skeletal muscle cells. Diabetes 2002; 51:901-9. [PMID: 11916905 DOI: 10.2337/diabetes.51.4.901] [Citation(s) in RCA: 177] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
In humans, skeletal muscle is a major site of peroxisome proliferator-activated receptor-alpha (PPAR-alpha) expression, but its function in this tissue is unclear. We investigated the role of hPPAR-alpha in regulating muscle lipid utilization by studying the effects of a highly selective PPAR-alpha agonist, GW7647, on [(14)C]oleate metabolism and gene expression in primary human skeletal muscle cells. Robust induction of PPAR-alpha protein expression occurred during muscle cell differentiation and corresponded with differentiation-dependent increases in oleate oxidation. In mature myotubes, 48-h treatment with 10-1,000 nmol/l GW7647 increased oleate oxidation dose-dependently, up to threefold. Additionally, GW7647 decreased oleate esterification into myotube triacylglycerol (TAG), up to 45%. This effect was not abolished by etomoxir, a potent inhibitor of beta-oxidation, indicating that PPAR-alpha-mediated TAG depletion does not depend on reciprocal changes in fatty acid catabolism. Consistent with its metabolic actions, GW7647 induced mRNA expression of mitochondrial enzymes that promote fatty acid catabolism; carnitine palmityltransferase 1 and malonyl-CoA decarboxylase increased approximately 2-fold, whereas pyruvate dehydrogenase kinase 4 increased 45-fold. Expression of several genes that regulate glycerolipid synthesis was not changed by GW7647 treatment, implicating involvement of other targets to explain the TAG-depleting effect of the compound. These results demonstrate a role for hPPAR-alpha in regulating muscle lipid homeostasis.
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MESH Headings
- Butyrates/pharmacology
- Carboxy-Lyases/genetics
- Carboxy-Lyases/metabolism
- Cell Differentiation
- Cells, Cultured
- DNA-Binding Proteins/metabolism
- Fatty Acids, Nonesterified/metabolism
- Gene Expression Regulation, Enzymologic/drug effects
- Homeostasis
- Humans
- Kinetics
- Microscopy, Phase-Contrast
- Mitochondria/drug effects
- Mitochondria/metabolism
- Muscle, Skeletal/cytology
- Muscle, Skeletal/drug effects
- Muscle, Skeletal/metabolism
- Oleic Acid/metabolism
- Phenylurea Compounds/pharmacology
- Protein Kinases/genetics
- Protein Kinases/metabolism
- Protein Serine-Threonine Kinases
- Pyruvate Dehydrogenase Acetyl-Transferring Kinase
- RNA, Messenger/genetics
- Receptors, Cytoplasmic and Nuclear/agonists
- Receptors, Cytoplasmic and Nuclear/physiology
- Transcription Factors/agonists
- Transcription Factors/physiology
- Transcription, Genetic
- Triglycerides/metabolism
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Affiliation(s)
- Deborah M Muoio
- Department of Medicine and Cell Biology, Duke University Medical Center, Durham, North Carolina 27710, USA.
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45
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Hatakeyama Y, Scarpace PJ. Transcriptional regulation of uncoupling protein-2 gene expression in L6 myotubes. Int J Obes (Lond) 2001; 25:1619-24. [PMID: 11753581 DOI: 10.1038/sj.ijo.0801812] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/09/2000] [Revised: 04/23/2001] [Accepted: 05/08/2001] [Indexed: 01/04/2023]
Abstract
OBJECTIVE To increase the understanding of the transcriptional regulation of UCP2 gene expression in skeletal muscle cells, we examined the effect of all-trans-retinoic acid (tRA), a ligand (after the conversion to 9-cis-RA) of the retinoid X receptor (RXR), and linolenic acid, a polyunsaturated fatty acid and peroxisome proliferator-activated receptors (PPARs) ligand, on the expression of UCP2 mRNA in cultured L6 myotubes. RESEARCH METHODS AND PROCEDURES UCP2 gene expression in L6 myotubes was confirmed by Northern blot analysis. The time- and concentration-dependency of tRA and linolenic acid on UCP2 gene expression was assessed by dot blot quantification. The mRNA levels of PPAR subtypes (alpha, gamma and delta) were determined by RT-PCR. RESULTS tRA induced UCP2 gene expression in a time- and concentration-dependent manner. Similar to tRA, UCP2 mRNA was markedly increased by 0.5 mM linolenic acid. In L6 myotubes, PPARdelta mRNA was abundant, whereas PPARalpha mRNA was lower and PPARgamma mRNA was minimal. CONCLUSIONS UCP2 mRNA expression in L6 myotubes is up-regulated by tRA and linolenic acid, possibly through a mechanism involving PPAR and RXRs.
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MESH Headings
- Animals
- Blotting, Northern
- Cells, Cultured
- DNA Primers
- Dose-Response Relationship, Drug
- Gene Expression Regulation
- Ion Channels
- Membrane Transport Proteins
- Mitochondrial Proteins
- Muscle, Skeletal/cytology
- Proteins/genetics
- RNA, Messenger/drug effects
- RNA, Messenger/genetics
- Rats
- Receptors, Cytoplasmic and Nuclear/administration & dosage
- Receptors, Retinoic Acid/drug effects
- Receptors, Retinoic Acid/genetics
- Retinoid X Receptors
- Reverse Transcriptase Polymerase Chain Reaction
- Transcription Factors/administration & dosage
- Transcription Factors/drug effects
- Transcription Factors/genetics
- Transcription Factors/pharmacology
- Transcription, Genetic
- Tretinoin/administration & dosage
- Tretinoin/pharmacology
- Uncoupling Protein 2
- alpha-Linolenic Acid/administration & dosage
- alpha-Linolenic Acid/pharmacology
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Affiliation(s)
- Y Hatakeyama
- Department of Metabolic Diseases, Medicinal Biology Research Laboratories, Fujisawa Pharmaceutical Co. Ltd, Osaka, Japan.
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46
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Saito M, Ohashi A. [Mitochondrial uncoupling protein as a target of pharmacotherapy for obesity]. Nihon Yakurigaku Zasshi 2001; 118:327-33. [PMID: 11729636 DOI: 10.1254/fpj.118.327] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Abstract
Uncoupling protein (UCP) is a transporter family present in the mitochondrial inner membrane, and as its name suggests, it uncouples respiration from ATP synthesis by dissipating the transmembrane proton gradient as heat. UCP is now recognized as a key molecule in metabolic thermogenesis such as cold- and diet-induced heat production, which is a significant component of energy expenditure, and its dysfunction contributes to the development of obesity. Among the UCP family, UCP-1 is expressed exclusively in brown adipose tissue (BAT), while UCP-2 is present in many organs and UCP-3 is in skeletal muscle. BAT thermogenesis by UCP-1, which has been studied most extensively, is controlled directly by sympathetic nerves principally through the beta-adrenergic action of norepinephrine. Since the beta 3-adrenoceptor is present primarily in adipose tissues, its selective agonists stimulate BAT thermogenesis and also lipid mobilization in white adipose tissue without any noticeable effect on beta 1- and beta 2-adrenoceptos. Therefore, beta 3-adrenoceptor agonists would be promising for the pharmacotherapy of obesity. UCP gene expression is up regulated by ligands for nuclear receptors such as thyroid hormone receptor, peroxisome proliferator-activated receptors (PPAR) and retinoid-X receptor. Long chain fatty acids and some of their metabolites are known to activate PPAR and thereby lead to abundant expression of UCP, which may also contribute to increase in energy expenditure and prevention of obesity. The activity of UCP is suppressed by purine nucleotides but activated by fatty acids. Thus, fatty acids increase UCP-mediated thermogenesis by direct activation of UCP and also by increased gene expression, implying some specific fatty acids or their derivatives as an effective anti-obesity tool.
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Affiliation(s)
- M Saito
- Department of Biomedical Sciences, Graduate School of Veterinary Medicine, Hokkaido University, Sapporo 060-0818, Japan.
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47
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Son C, Hosoda K, Matsuda J, Fujikura J, Yonemitsu S, Iwakura H, Masuzaki H, Ogawa Y, Hayashi T, Itoh H, Nishimura H, Inoue G, Yoshimasa Y, Yamori Y, Nakao K. Up-regulation of uncoupling protein 3 gene expression by fatty acids and agonists for PPARs in L6 myotubes. Endocrinology 2001; 142:4189-94. [PMID: 11564673 DOI: 10.1210/endo.142.10.8446] [Citation(s) in RCA: 56] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Uncoupling protein 3 (UCP3), which uncouples electron transport from ATP synthesis, is expressed at high levels in the skeletal muscle, an important organ in glucose and lipid metabolism. Because several reports proposed that fatty acids induced UCP3 gene expression in skeletal muscle in vivo, in the present study we examined the regulation of UCP3 gene expression by various fatty acids using L6 myotubes. UCP3 gene expression was increased in L6 myotubes by various fatty acids or by alpha-bromopalmitate, a nonmetabolized derivative of palmitic acid. Because fatty acids are also known as agonists for PPARs, we examined the involvement of PPARs in the regulation of the UCP3 gene expression. L-165041, a PPAR delta agonist, increased UCP3 gene expression in L6 myotubes, whereas neither Wy 14,643, a PPAR alpha agonist, nor Pioglitazone, a PPAR gamma agonist, increased it. Therefore, we conclude that UCP3 gene expression is increased by the activation of PPAR delta in L6 myotubes and postulate that PPAR delta mediates at least some part of the increased UCP3 gene expression by fatty acids in skeletal muscle in vivo.
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Affiliation(s)
- C Son
- Department of Medicine and Clinical Science, Kyoto University Graduate School of Medicine, Kyoto 606-8507, Japan
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48
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Huppertz C, Fischer BM, Kim YB, Kotani K, Vidal-Puig A, Slieker LJ, Sloop KW, Lowell BB, Kahn BB. Uncoupling protein 3 (UCP3) stimulates glucose uptake in muscle cells through a phosphoinositide 3-kinase-dependent mechanism. J Biol Chem 2001; 276:12520-9. [PMID: 11278970 DOI: 10.1074/jbc.m011708200] [Citation(s) in RCA: 64] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023] Open
Abstract
UCP3 is a mitochondrial membrane protein expressed in humans selectively in skeletal muscle. To determine the mechanisms by which UCP3 plays a role in regulating glucose metabolism, we expressed human UCP3 in L6 myotubes by adenovirus-mediated gene transfer and in H(9)C(2) cardiomyoblasts by stable transfection with a tetracycline-repressible UCP3 construct. Expression of UCP3 in L6 myotubes increased 2-deoxyglucose uptake 2-fold and cell surface GLUT4 2.3-fold, thereby reaching maximally insulin-stimulated levels in control myotubes. Wortmannin, LY 294002, or the tyrosine kinase inhibitor genistein abolished the effect of UCP3 on glucose uptake, and wortmannin inhibited UCP3-induced GLUT4 cell surface recruitment. UCP3 overexpression increased phosphotyrosine-associated phosphoinositide 3-kinase (PI3K) activity 2.2-fold compared with control cells (p < 0.05). UCP3 overexpression increased lactate release 1.5- to 2-fold above control cells, indicating increased glucose metabolism. In H(9)C(2) cardiomyoblasts stably transfected with UCP3 under control of a tetracycline-repressible promotor, removal of doxycycline resulted in detectable levels of UCP3 at 12 h and 2.2-fold induction at 7 days compared with 12 h. In parallel, glucose transport increased 1.3- and 2-fold at 12 h and 7 days, respectively, and the stimulation was inhibited by wortmannin or genistein. p85 association with membranes was increased 5.5-fold and phosphotyrosine-associated PI3K activity 3.8-fold. In contrast, overexpression of UCP3 in 3T3-L1 adipocytes did not alter glucose uptake, suggesting tissue-specific effects of human UCP3. Thus, UCP3 stimulates glucose transport and GLUT4 translocation to the cell surface in cardiac and skeletal muscle cells by activating a PI3K dependent pathway.
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Affiliation(s)
- C Huppertz
- Diabetes Unit, Department of Medicine, Division of Endocrinology and Metabolism, Beth Israel Deaconess Medical Center and Harvard Medical School, Boston, Massachusetts 02215, USA
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49
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Nagase I, Yoshida T, Saito M. Up-regulation of uncoupling proteins by beta-adrenergic stimulation in L6 myotubes. FEBS Lett 2001; 494:175-80. [PMID: 11311236 DOI: 10.1016/s0014-5793(01)02341-9] [Citation(s) in RCA: 41] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Catecholamine-induced and beta-adrenergic receptor (beta-AR)-mediated thermogenesis in skeletal muscle is a significant component of whole-body energy expenditure. Skeletal muscle expresses uncoupling protein (UCP) 2 and UCP3, which can dissipate the transmitochondrial electrochemical gradient and thereby may be involved in regulation of energy metabolism. We investigated the effects of beta-AR stimulation on UCP2 and UCP3 expression in L6 myotubes. Stimulation of the cells with epinephrine increased the UCP3 mRNA level transiently at 6 h, and also the UCP2 mRNA level at 6-24 h. The stimulatory effects of epinephrine were also observed in the presence of carbacyclin and 9-cis retinoic acid, and mimicked by isoproterenol and salbutamol (beta2-AR agonists), but abolished by propranolol and ICI-118,551 (beta2-AR antagonists). Pharmacological and mRNA analyses revealed the existence of beta2-AR, but not beta1- and beta3-ARs, in L6 myotubes. These results suggested that catecholamines up-regulate UCP2 and UCP3 expression through direct action on the beta2-AR in skeletal muscle.
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MESH Headings
- Adrenergic beta-Agonists/pharmacology
- Adrenergic beta-Antagonists/pharmacology
- Albuterol/pharmacology
- Alitretinoin
- Animals
- Carrier Proteins/genetics
- Cell Line
- Cyclic AMP/metabolism
- Energy Metabolism
- Epinephrine/pharmacology
- Epoprostenol/analogs & derivatives
- Epoprostenol/pharmacology
- Ion Channels
- Isoproterenol/pharmacology
- Membrane Transport Proteins
- Mitochondrial Proteins
- Muscle, Skeletal/cytology
- Muscle, Skeletal/drug effects
- Muscle, Skeletal/metabolism
- Propanolamines/pharmacology
- Propranolol/pharmacology
- Proteins/genetics
- RNA, Messenger/genetics
- RNA, Messenger/metabolism
- Rats
- Receptors, Adrenergic, beta/genetics
- Receptors, Adrenergic, beta/metabolism
- Receptors, Cytoplasmic and Nuclear/metabolism
- Receptors, Retinoic Acid/metabolism
- Retinoid X Receptors
- Time Factors
- Transcription Factors/metabolism
- Tretinoin/pharmacology
- Uncoupling Protein 2
- Uncoupling Protein 3
- Up-Regulation/drug effects
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Affiliation(s)
- I Nagase
- Department of Biomedical Sciences, Laboratory of Biochemistry, Graduate School of Veterinary Medicine, Hokkaido University, Sapporo 060-0818, Japan
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50
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Chevillotte E, Rieusset J, Roques M, Desage M, Vidal H. The regulation of uncoupling protein-2 gene expression by omega-6 polyunsaturated fatty acids in human skeletal muscle cells involves multiple pathways, including the nuclear receptor peroxisome proliferator-activated receptor beta. J Biol Chem 2001; 276:10853-60. [PMID: 11278377 DOI: 10.1074/jbc.m008010200] [Citation(s) in RCA: 62] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Fatty acids have been postulated to regulate uncoupling protein (UCP) gene expression in skeletal muscle in vivo. We have identified, at least in part, the mechanism by which polyunsaturated fatty acids increase UCP-2 expression in primary culture of human muscle cells. omega-6 fatty acids and arachidonic acid induced a 3-fold rise in UCP-2 mRNA levels possibly through transcriptional activation. This effect was prevented by indomethacin and mimicked by prostaglandin (PG) E(2) and carbaprostacyclin PGI(2), consistent with a cyclooxygenase-mediated process. Incubation of myotubes for 6 h with 100 micrometer arachidonic acid resulted in a 150-fold increase in PGE(2) and a 15-fold increase in PGI(2) in the culture medium. Consistent with a role of cAMP and protein kinase A, both prostaglandins induced a marked accumulation of cAMP in human myotubes, and forskolin reproduced the effect of arachidonic acid on UCP-2 mRNA expression. Inhibition of protein kinase A with H-89 suppressed the effect of PGE(2), whereas cPGI(2) and arachidonic acid were still able to increase ucp-2 gene expression, suggesting additional mechanisms. We found, however, that the MAP kinase pathway was not involved. Prostaglandins, particularly PGI(2), are potent activators of the peroxisome proliferator-activated receptors. A specific agonist of peroxisome proliferator-activated receptor (PPAR) beta (L165041) increased UCP-2 mRNA levels in myotubes, whereas activation of PPARalpha or PPARgamma was ineffective. These results suggest thus that ucp-2 gene expression is regulated by omega-6 fatty acids in human muscle cells through mechanisms involving at least protein kinase A and the nuclear receptor PPARbeta.
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Affiliation(s)
- E Chevillotte
- INSERM U449, Faculté de Médecine René Laennec, Université Claude Bernard Lyon-1, and CRNHL Faculté de Médecine René Laennec, Université Claude Bernard Lyon-1, 69372 Lyon, France
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