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Vila-Bedmar R, Cruces-Sande M, Lucas E, Willemen HLDM, Heijnen CJ, Kavelaars A, Mayor F, Murga C. Reversal of diet-induced obesity and insulin resistance by inducible genetic ablation of GRK2. Sci Signal 2015. [PMID: 26198359 DOI: 10.1126/scisignal.aaa4374] [Citation(s) in RCA: 47] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
Insulin resistance is a common feature of obesity and predisposes individuals to various prevalent pathological conditions. G protein (heterotrimeric guanine nucleotide-binding protein)-coupled receptor kinase 2 (GRK2) integrates several signal transduction pathways and is emerging as a physiologically relevant inhibitor of insulin signaling. GRK2 abundance is increased in humans with metabolic syndrome and in different murine models of insulin resistance. To support GRK2 as a potential drug target in type 2 diabetes and obesity, we investigated whether lowering GRK2 abundance reversed an ongoing systemic insulin-resistant phenotype, using a mouse model of tamoxifen-induced GRK2 ablation after high-fat diet-dependent obesity and insulin resistance. Tamoxifen-triggered GRK2 deletion impeded further body weight gain, normalized fasting glycemia, improved glucose tolerance, and was associated with preserved insulin sensitivity in skeletal muscle and liver, thereby maintaining whole-body glucose homeostasis. Moreover, when continued to be fed a high-fat diet, these animals displayed reduced fat mass and smaller adipocytes, were resistant to the development of liver steatosis, and showed reduced expression of proinflammatory markers in the liver. Our results indicate that GRK2 acts as a hub to control metabolic functions in different tissues, which is key to controlling insulin resistance development in vivo. These data suggest that inhibiting GRK2 could reverse an established insulin-resistant and obese phenotype, thereby putting forward this enzyme as a potential therapeutic target linking glucose homeostasis and regulation of adiposity.
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Affiliation(s)
- Rocio Vila-Bedmar
- Centro de Biología Molecular Severo Ochoa (CSIC-UAM), Madrid 28049, Spain. Instituto de Investigación Sanitaria La Princesa, Madrid 28006, Spain
| | - Marta Cruces-Sande
- Centro de Biología Molecular Severo Ochoa (CSIC-UAM), Madrid 28049, Spain. Instituto de Investigación Sanitaria La Princesa, Madrid 28006, Spain
| | - Elisa Lucas
- Centro de Biología Molecular Severo Ochoa (CSIC-UAM), Madrid 28049, Spain. Instituto de Investigación Sanitaria La Princesa, Madrid 28006, Spain
| | - Hanneke L D M Willemen
- Laboratory of Neuroimmunology and Developmental Origins of Disease, University Medical Center Utrecht, Utrecht 3584 EA, Netherlands
| | - Cobi J Heijnen
- Laboratory of Neuroimmunology and Developmental Origins of Disease, University Medical Center Utrecht, Utrecht 3584 EA, Netherlands. Laboratory of Neuroimmunology, Division of Internal Medicine, Department of Symptom Research, The University of Texas MD Anderson Cancer Center, Houston, TX 77030, USA
| | - Annemieke Kavelaars
- Laboratory of Neuroimmunology and Developmental Origins of Disease, University Medical Center Utrecht, Utrecht 3584 EA, Netherlands. Laboratory of Neuroimmunology, Division of Internal Medicine, Department of Symptom Research, The University of Texas MD Anderson Cancer Center, Houston, TX 77030, USA
| | - Federico Mayor
- Centro de Biología Molecular Severo Ochoa (CSIC-UAM), Madrid 28049, Spain. Instituto de Investigación Sanitaria La Princesa, Madrid 28006, Spain.
| | - Cristina Murga
- Centro de Biología Molecular Severo Ochoa (CSIC-UAM), Madrid 28049, Spain. Instituto de Investigación Sanitaria La Princesa, Madrid 28006, Spain.
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Lucas E, Cruces-Sande M, Briones AM, Salaices M, Mayor F, Murga C, Vila-Bedmar R. Molecular physiopathology of obesity-related diseases: multi-organ integration by GRK2. Arch Physiol Biochem 2015; 121:163-77. [PMID: 26643283 DOI: 10.3109/13813455.2015.1107589] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Obesity is a worldwide problem that has reached epidemic proportions both in developed and developing countries. The excessive accumulation of fat poses a risk to health since it favours the development of metabolic alterations including insulin resistance and tissue inflammation, which further contribute to the progress of the complex pathological scenario observed in the obese. In this review we put together the different outcomes of fat accumulation and insulin resistance in the main insulin-responsive tissues, and discuss the role of some of the key molecular routes that control disease progression both in an organ-specific and also in a more systemic manner. In particular, we focus on the importance of studying the integrated regulation of different organs and pathways that contribute to the global pathophysiology of this condition with a specific emphasis on the role of emerging key molecular nodes such as the G protein-coupled receptor kinase 2 (GRK2) signalling hub.
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Affiliation(s)
- Elisa Lucas
- a Departamento de Biología Molecular and Centro de Biología Molecular Severo Ochoa (UAM-CSIC) , Universidad Autónoma de Madrid , Madrid , Spain
- b Instituto de Investigación Sanitaria La Princesa , Madrid , Spain
| | - Marta Cruces-Sande
- a Departamento de Biología Molecular and Centro de Biología Molecular Severo Ochoa (UAM-CSIC) , Universidad Autónoma de Madrid , Madrid , Spain
- b Instituto de Investigación Sanitaria La Princesa , Madrid , Spain
| | - Ana M Briones
- c Departamento de Farmacología , Universidad Autónoma de Madrid (UAM) Madrid , Spain , and
- d Instituto de Investigación Hospital Universitario La Paz (IdiPAZ) Madrid , Spain
| | - Mercedes Salaices
- c Departamento de Farmacología , Universidad Autónoma de Madrid (UAM) Madrid , Spain , and
- d Instituto de Investigación Hospital Universitario La Paz (IdiPAZ) Madrid , Spain
| | - Federico Mayor
- a Departamento de Biología Molecular and Centro de Biología Molecular Severo Ochoa (UAM-CSIC) , Universidad Autónoma de Madrid , Madrid , Spain
- b Instituto de Investigación Sanitaria La Princesa , Madrid , Spain
| | - Cristina Murga
- a Departamento de Biología Molecular and Centro de Biología Molecular Severo Ochoa (UAM-CSIC) , Universidad Autónoma de Madrid , Madrid , Spain
- b Instituto de Investigación Sanitaria La Princesa , Madrid , Spain
| | - Rocio Vila-Bedmar
- a Departamento de Biología Molecular and Centro de Biología Molecular Severo Ochoa (UAM-CSIC) , Universidad Autónoma de Madrid , Madrid , Spain
- b Instituto de Investigación Sanitaria La Princesa , Madrid , Spain
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Guillen C, Bartolome A, Vila-Bedmar R, García-Aguilar A, Gomez-Hernandez A, Benito M. Concerted expression of the thermogenic and bioenergetic mitochondrial protein machinery in brown adipose tissue. J Cell Biochem 2014; 114:2306-13. [PMID: 23606415 DOI: 10.1002/jcb.24577] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2012] [Accepted: 04/12/2013] [Indexed: 11/08/2022]
Abstract
Brown adipose tissue (BAT) is specialized in non-shivering thermogenesis through the expression of the mitochondrial uncoupling protein-1 (UCP1). In this paper, we describe the relationship between UCP1 and proteins involved in ATP synthesis. By the use of BATIRKO mice, which have enhanced UCP1 expression in BAT, an increase in ATP synthase as well as in ubiquinol cytochrome c reductase levels was observed. Alterations in mitochondrial mass or variations in ATP levels were not observed in BAT of these mice. In addition, using a protocol of brown adipocyte differentiation, the concerted expression of UCP1 with ATP synthase was found. These two scenarios revealed that increases in the uncoupling machinery of brown adypocites must be concomitantly followed by an enhancement of proteins involved in ATP synthesis. These concerted changes reflect the need to maintain ATP production in an essentially uncoupling cell type.
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Affiliation(s)
- Carlos Guillen
- Faculty of Pharmacy, Department of Biochemistry and Molecular Biology II, Complutense University of Madrid, Madrid, Spain
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Fernández-Veledo S, Vázquez-Carballo A, Vila-Bedmar R, Ceperuelo-Mallafré V, Vendrell J. Role of energy- and nutrient-sensing kinases AMP-activated protein kinase (AMPK) and mammalian target of rapamycin (mTOR) in adipocyte differentiation. IUBMB Life 2013; 65:572-83. [PMID: 23671028 DOI: 10.1002/iub.1170] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2013] [Accepted: 03/14/2013] [Indexed: 12/14/2022]
Abstract
Recent advances have demonstrated that the adipose tissue plays a central role in regulating overall energy balance. Obesity results from a chronic deregulation of energy balance, with energy intake exceeding energy expenditure. Recently, new mechanisms that control the obesity phenotype such as the equilibrium between white and brown adipose tissue function has been identified. In this context, it is becoming increasingly clear that in addition to cellular growth, AMP-activated protein kinase (AMPK) and mammalian target of rapamycin (mTOR) also regulate lipid metabolism and adipogenesis. Here, we review recent advances in the understanding of the molecular mechanisms involved in white and brown differentiation programs focusing on AMPK and mTOR signaling pathways, which may play differential roles in white adipose tissue and brown adipose tissue development. In view of the worldwide epidemic of obesity and its associated metabolic disorders such as insulin resistance and type 2 diabetes, targeting these kinases may represent a potential approach for reducing adiposity and improving obesity-related diseases. © 2013 IUBMB Life, 65(7):572-583, 2013.
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Affiliation(s)
- Sonia Fernández-Veledo
- Research Unit, Hospital Universitari de Tarragona Joan XXIII. IISPV. Universitat Rovira i Virgili, Tarragona, Spain
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O'Neill HM, Holloway GP, Steinberg GR. AMPK regulation of fatty acid metabolism and mitochondrial biogenesis: implications for obesity. Mol Cell Endocrinol 2013; 366:135-51. [PMID: 22750049 DOI: 10.1016/j.mce.2012.06.019] [Citation(s) in RCA: 241] [Impact Index Per Article: 21.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/10/2011] [Revised: 03/13/2012] [Accepted: 06/21/2012] [Indexed: 12/25/2022]
Abstract
Skeletal muscle plays an important role in regulating whole-body energy expenditure given it is a major site for glucose and lipid oxidation. Obesity and type 2 diabetes are causally linked through their association with skeletal muscle insulin resistance, while conversely exercise is known to improve whole body glucose homeostasis simultaneously with muscle insulin sensitivity. Exercise activates skeletal muscle AMP-activated protein kinase (AMPK). AMPK plays a role in regulating exercise capacity, skeletal muscle mitochondrial content and contraction-stimulated glucose uptake. Skeletal muscle AMPK is also thought to be important for regulating fatty acid metabolism; however, direct genetic evidence in this area is currently lacking. This review will discuss the current paradigms regarding the influence of AMPK in regulating skeletal muscle fatty acid metabolism and mitochondrial biogenesis at rest and during exercise, and highlight the potential implications in the development of insulin resistance.
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Affiliation(s)
- Hayley M O'Neill
- University of Melbourne, Department of Medicine, St. Vincent's Institute of Medical Research, Melbourne, Victoria, Australia.
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Vila-Bedmar R, Garcia-Guerra L, Nieto-Vazquez I, Mayor F, Lorenzo M, Murga C, Fernández-Veledo S. GRK2 contribution to the regulation of energy expenditure and brown fat function. FASEB J 2012; 26:3503-14. [PMID: 22516294 DOI: 10.1096/fj.11-202267] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Obesity is a major health problem and an important risk factor for the development of multiple disorders. Previous studies in our laboratory have revealed that down-regulation of GRK2 decreases age-related adiposity, but the physiological and molecular mechanisms underlying this outcome remain unclear. We evaluate whether the lean phenotype results from a direct effect of GRK2 on energy homeostasis. The study of white adipose tissue (WAT) in wild-type (WT) and GRK2(+/-) littermates showed a reduced expression of lipogenic enzymes and enhanced lipolytic rate in adult GRK2(+/-) mice. Moreover, hemizygous mice display higher energy expenditure and lower respiratory exchange ratio. Analysis of brown adipose tissue (BAT) from adult GRK2(+/-) mice showed a less deteriorated morphology associated with age compared to WT, which is correlated with a higher basal core temperature. BAT from young GRK2(+/-) mice showed an increase in gene expression of thermogenesis-related genes. Accordingly, hemizygous mice displayed better thermogenic capacity and exhibited a more oxidative phenotype in both BAT and WAT than WT littermates. Overexpression of GRK2 in brown adipocytes corroborated the negative effect of this kinase in BAT function and differentiation. Collectively, our data point to GRK2 inhibition as a potential tool for the enhancement of brown fat activity, which may have important therapeutic implications for the treatment of obesity and associated metabolic disorders.
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Affiliation(s)
- Rocio Vila-Bedmar
- Department of Biochemistry and Molecular Biology II, School of Pharmacy, Complutense University-Centro de Investigación Biomédica en Red de Diabetes y Enfermedades Metabólicas Asociadas, Madrid, Spain
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Chang Y, She ZG, Sakimura K, Roberts A, Kucharova K, Rowitch DH, Stallcup WB. Ablation of NG2 proteoglycan leads to deficits in brown fat function and to adult onset obesity. PLoS One 2012; 7:e30637. [PMID: 22295099 PMCID: PMC3266271 DOI: 10.1371/journal.pone.0030637] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2011] [Accepted: 12/20/2011] [Indexed: 01/25/2023] Open
Abstract
Obesity is a major health problem worldwide. We are studying the causes and effects of obesity in C57Bl/6 mice following genetic ablation of NG2, a chondroitin sulfate proteoglycan widely expressed in progenitor cells and also in adipocytes. Although global NG2 ablation delays early postnatal adipogenesis in mouse skin, adult NG2 null mice are paradoxically heavier than wild-type mice, exhibiting larger white fat deposits. This adult onset obesity is not due to NG2-dependent effects on CNS function, since specific ablation of NG2 in oligodendrocyte progenitors yields the opposite phenotype; i.e. abnormally lean mice. Metabolic analysis reveals that, while activity and food intake are unchanged in global NG2 null mice, O2 consumption and CO2 production are decreased, suggesting a decrease in energy expenditure. Since brown fat plays important roles in regulating energy expenditure, we have investigated brown fat function via cold challenge and high fat diet feeding, both of which induce the adaptive thermogenesis that normally occurs in brown fat. In both tests, body temperatures in NG2 null mice are reduced compared to wild-type mice, indicating a deficit in brown fat function in the absence of NG2. In addition, adipogenesis in NG2 null brown pre-adipocytes is dramatically impaired compared to wild-type counterparts. Moreover, mRNA levels for PR domain containing 16 (PRDM16) and peroxisome proliferator-activated receptor γ coactivator (PGC)1-α, proteins important for brown adipocyte differentiation, are decreased in NG2 null brown fat deposits in vivo and NG2 null brown pre-adipocytes in vitro. Altogether, these results indicate that brown fat dysfunction in NG2 null mice results from deficits in the recruitment and/or development of brown pre-adipocytes. As a consequence, obesity in NG2 null mice may occur due to disruptions in brown fat-dependent energy homeostasis, with resulting effects on lipid storage in white adipocytes.
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Affiliation(s)
- Yunchao Chang
- Cancer Center, Sanford-Burnham Medical Research Institute, La Jolla, California, United States of America.
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