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Rahman FA, Quadrilatero J. Mitochondrial network remodeling: an important feature of myogenesis and skeletal muscle regeneration. Cell Mol Life Sci 2021; 78:4653-4675. [PMID: 33751143 PMCID: PMC11072563 DOI: 10.1007/s00018-021-03807-9] [Citation(s) in RCA: 23] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2020] [Revised: 02/23/2021] [Accepted: 03/03/2021] [Indexed: 12/13/2022]
Abstract
The remodeling of the mitochondrial network is a critical process in maintaining cellular homeostasis and is intimately related to mitochondrial function. The interplay between the formation of new mitochondria (biogenesis) and the removal of damaged mitochondria (mitophagy) provide a means for the repopulation of the mitochondrial network. Additionally, mitochondrial fission and fusion serve as a bridge between biogenesis and mitophagy. In recent years, the importance of these processes has been characterised in multiple tissue- and cell-types, and under various conditions. In skeletal muscle, the robust remodeling of the mitochondrial network is observed, particularly after injury where large portions of the tissue/cell structures are damaged. The significance of mitochondrial remodeling in regulating skeletal muscle regeneration has been widely studied, with alterations in mitochondrial remodeling processes leading to incomplete regeneration and impaired skeletal muscle function. Needless to say, important questions related to mitochondrial remodeling and skeletal muscle regeneration still remain unanswered and require further investigation. Therefore, this review will discuss the known molecular mechanisms of mitochondrial network remodeling, as well as integrate these mechanisms and discuss their relevance in myogenesis and regenerating skeletal muscle.
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Affiliation(s)
- Fasih Ahmad Rahman
- Department of Kinesiology, University of Waterloo, Waterloo, ON, N2L 3G1, Canada
| | - Joe Quadrilatero
- Department of Kinesiology, University of Waterloo, Waterloo, ON, N2L 3G1, Canada.
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2
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Chambers JM, Wingert RA. PGC-1α in Disease: Recent Renal Insights into a Versatile Metabolic Regulator. Cells 2020; 9:E2234. [PMID: 33022986 PMCID: PMC7601329 DOI: 10.3390/cells9102234] [Citation(s) in RCA: 25] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2020] [Revised: 09/29/2020] [Accepted: 09/30/2020] [Indexed: 12/14/2022] Open
Abstract
Peroxisome proliferator-activated receptor gamma co-activator 1 alpha (PGC-1α) is perhaps best known as a master regulator of mitochondrial biogenesis and function. However, by virtue of its interactions as a coactivator for numerous nuclear receptors and transcription factors, PGC-1α also regulates many tissue-specific tasks that include adipogenesis, angiogenesis, gluconeogenesis, heme biosynthesis, thermogenesis, and cellular protection against degeneration. Knowledge about these functions continue to be discovered with ongoing research. Unsurprisingly, alterations in PGC-1α expression lead to a range of deleterious outcomes. In this review, we provide a brief background on the PGC-1 family with an overview of PGC-1α's roles as an adaptive link to meet cellular needs and its pathological consequences in several organ contexts. Among the latter, kidney health is especially reliant on PGC-1α. Thus, we discuss here at length how changes in PGC-1α function impact the states of renal cancer, acute kidney injury (AKI) and chronic kidney disease (CKD), as well as emerging data that illuminate pivotal roles for PGC-1α during renal development. We survey a new intriguing association of PGC-1α function with ciliogenesis and polycystic kidney disease (PKD), where recent animal studies revealed that embryonic renal cyst formation can occur in the context of PGC-1α deficiency. Finally, we explore future prospects for PGC-1α research and therapeutic implications for this multifaceted coactivator.
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Affiliation(s)
- Joseph M. Chambers
- College of Pharmacy, Natural and Health Sciences, Manchester University, Fort Wayne, IN 46845, USA
| | - Rebecca A. Wingert
- Department of Biological Sciences, Center for Stem Cells and Regenerative Medicine, Center for Zebrafish Research, Boler-Parseghian Center for Rare and Neglected Diseases, University of Notre Dame, Notre Dame, IN 46556, USA
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Paszkiewicz RL, Bergman RN, Santos RS, Frank AP, Woolcott OO, Iyer MS, Stefanovski D, Clegg DJ, Kabir M. A Peripheral CB1R Antagonist Increases Lipolysis, Oxygen Consumption Rate, and Markers of Beiging in 3T3-L1 Adipocytes Similar to RIM, Suggesting that Central Effects Can Be Avoided. Int J Mol Sci 2020; 21:E6639. [PMID: 32927872 PMCID: PMC7554772 DOI: 10.3390/ijms21186639] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2020] [Revised: 09/03/2020] [Accepted: 09/08/2020] [Indexed: 02/07/2023] Open
Abstract
With the increased prevalence of obesity and related co-morbidities, such as type 2 diabetes (T2D), worldwide, improvements in pharmacological treatments are necessary. The brain- and peripheral-cannabinoid receptor 1 (CB1R) antagonist rimonabant (RIM) has been shown to induce weight loss and improve glucose homeostasis. We have previously demonstrated that RIM promotes adipose tissue beiging and decreased adipocyte cell size, even during maintenance on a high-fat diet. Given the adverse side-effects of brain-penetrance with RIM, in this study we aimed to determine the site of action for a non-brain-penetrating CB1R antagonist AM6545. By using in vitro assays, we demonstrated the direct effects of this non-brain-penetrating CB1R antagonist on cultured adipocytes. Specifically, we showed, for the first time, that AM6545 significantly increases markers of adipose tissue beiging, mitochondrial biogenesis, and lipolysis in 3T3-L1 adipocytes. In addition, the oxygen consumption rate (OCR), consisting of baseline respiratory rate, proton leak, maximal respiratory capacity, and ATP synthase activity, was greater for cells exposed to AM6545, demonstrating greater mitochondrial uncoupling. Using a lipolysis inhibitor during real-time OCR measurements, we determined that the impact of CB1R antagonism on adipocytes is driven by increased lipolysis. Thus, our data suggest the direct role of CB1R antagonism on adipocytes does not require brain penetrance, supporting the importance of focus on peripheral CB1R antagonism pharmacology for reducing the incidence of obesity and T2D.
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Affiliation(s)
- Rebecca L. Paszkiewicz
- Sports Spectacular Diabetes and Obesity Wellness and Research Center, Cedars-Sinai Medical Center, Los Angeles, CA 90048, USA; (R.L.P.); (R.N.B.); (R.S.S.); (A.P.F.); (O.O.W.); (M.S.I.)
| | - Richard N. Bergman
- Sports Spectacular Diabetes and Obesity Wellness and Research Center, Cedars-Sinai Medical Center, Los Angeles, CA 90048, USA; (R.L.P.); (R.N.B.); (R.S.S.); (A.P.F.); (O.O.W.); (M.S.I.)
| | - Roberta S. Santos
- Sports Spectacular Diabetes and Obesity Wellness and Research Center, Cedars-Sinai Medical Center, Los Angeles, CA 90048, USA; (R.L.P.); (R.N.B.); (R.S.S.); (A.P.F.); (O.O.W.); (M.S.I.)
| | - Aaron P. Frank
- Sports Spectacular Diabetes and Obesity Wellness and Research Center, Cedars-Sinai Medical Center, Los Angeles, CA 90048, USA; (R.L.P.); (R.N.B.); (R.S.S.); (A.P.F.); (O.O.W.); (M.S.I.)
| | - Orison O. Woolcott
- Sports Spectacular Diabetes and Obesity Wellness and Research Center, Cedars-Sinai Medical Center, Los Angeles, CA 90048, USA; (R.L.P.); (R.N.B.); (R.S.S.); (A.P.F.); (O.O.W.); (M.S.I.)
| | - Malini S. Iyer
- Sports Spectacular Diabetes and Obesity Wellness and Research Center, Cedars-Sinai Medical Center, Los Angeles, CA 90048, USA; (R.L.P.); (R.N.B.); (R.S.S.); (A.P.F.); (O.O.W.); (M.S.I.)
| | - Darko Stefanovski
- School of Veterinary Medicine, University of Pennsylvania, Philadelphia, PA 19104, USA;
| | - Deborah J. Clegg
- The College of Nursing and Health Professions, Drexel University, Philadelphia, PA 19104, USA;
| | - Morvarid Kabir
- Sports Spectacular Diabetes and Obesity Wellness and Research Center, Cedars-Sinai Medical Center, Los Angeles, CA 90048, USA; (R.L.P.); (R.N.B.); (R.S.S.); (A.P.F.); (O.O.W.); (M.S.I.)
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Becerril S, Rodríguez A, Catalán V, Ramírez B, Unamuno X, Portincasa P, Gómez-Ambrosi J, Frühbeck G. Functional Relationship between Leptin and Nitric Oxide in Metabolism. Nutrients 2019; 11:nu11092129. [PMID: 31500090 PMCID: PMC6769456 DOI: 10.3390/nu11092129] [Citation(s) in RCA: 32] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2019] [Revised: 08/23/2019] [Accepted: 09/02/2019] [Indexed: 12/28/2022] Open
Abstract
Leptin, the product of the ob gene, was originally described as a satiety factor, playing a crucial role in the control of body weight. Nevertheless, the wide distribution of leptin receptors in peripheral tissues supports that leptin exerts pleiotropic biological effects, consisting of the modulation of numerous processes including thermogenesis, reproduction, angiogenesis, hematopoiesis, osteogenesis, neuroendocrine, and immune functions as well as arterial pressure control. Nitric oxide (NO) is a free radical synthesized from L-arginine by the action of the NO synthase (NOS) enzyme. Three NOS isoforms have been identified: the neuronal NOS (nNOS) and endothelial NOS (eNOS) constitutive isoforms, and the inducible NOS (iNOS). NO mediates multiple biological effects in a variety of physiological systems such as energy balance, blood pressure, reproduction, immune response, or reproduction. Leptin and NO on their own participate in multiple common physiological processes, with a functional relationship between both factors having been identified. The present review describes the functional relationship between leptin and NO in different physiological processes.
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Affiliation(s)
- Sara Becerril
- Metabolic Research Laboratory, Clínica Universidad de Navarra, 31008 Pamplona, Spain.
- CIBER Fisiopatología de la Obesidad y Nutrición (CIBEROBN), Instituto de Salud Carlos III, 31008 Pamplona, Spain.
- Obesity and Adipobiology Group, Instituto de Investigación Sanitaria de Navarra (IdiSNA), 31008 Pamplona, Spain.
| | - Amaia Rodríguez
- Metabolic Research Laboratory, Clínica Universidad de Navarra, 31008 Pamplona, Spain.
- CIBER Fisiopatología de la Obesidad y Nutrición (CIBEROBN), Instituto de Salud Carlos III, 31008 Pamplona, Spain.
- Obesity and Adipobiology Group, Instituto de Investigación Sanitaria de Navarra (IdiSNA), 31008 Pamplona, Spain.
| | - Victoria Catalán
- Metabolic Research Laboratory, Clínica Universidad de Navarra, 31008 Pamplona, Spain.
- CIBER Fisiopatología de la Obesidad y Nutrición (CIBEROBN), Instituto de Salud Carlos III, 31008 Pamplona, Spain.
- Obesity and Adipobiology Group, Instituto de Investigación Sanitaria de Navarra (IdiSNA), 31008 Pamplona, Spain.
| | - Beatriz Ramírez
- Metabolic Research Laboratory, Clínica Universidad de Navarra, 31008 Pamplona, Spain.
- CIBER Fisiopatología de la Obesidad y Nutrición (CIBEROBN), Instituto de Salud Carlos III, 31008 Pamplona, Spain.
- Obesity and Adipobiology Group, Instituto de Investigación Sanitaria de Navarra (IdiSNA), 31008 Pamplona, Spain.
| | - Xabier Unamuno
- Metabolic Research Laboratory, Clínica Universidad de Navarra, 31008 Pamplona, Spain.
- CIBER Fisiopatología de la Obesidad y Nutrición (CIBEROBN), Instituto de Salud Carlos III, 31008 Pamplona, Spain.
- Medical Engineering Laboratory, University of Navarra, 31008 Pamplona, Spain.
| | - Piero Portincasa
- Clinica Medica "A. Murri", Department of Biomedical Sciences and Human Oncology, University of Bari Medical School, Policlinico Hospital, 70124 Bari, Italy.
| | - Javier Gómez-Ambrosi
- Metabolic Research Laboratory, Clínica Universidad de Navarra, 31008 Pamplona, Spain.
- CIBER Fisiopatología de la Obesidad y Nutrición (CIBEROBN), Instituto de Salud Carlos III, 31008 Pamplona, Spain.
- Obesity and Adipobiology Group, Instituto de Investigación Sanitaria de Navarra (IdiSNA), 31008 Pamplona, Spain.
| | - Gema Frühbeck
- Metabolic Research Laboratory, Clínica Universidad de Navarra, 31008 Pamplona, Spain.
- CIBER Fisiopatología de la Obesidad y Nutrición (CIBEROBN), Instituto de Salud Carlos III, 31008 Pamplona, Spain.
- Obesity and Adipobiology Group, Instituto de Investigación Sanitaria de Navarra (IdiSNA), 31008 Pamplona, Spain.
- Department of Endocrinology & Nutrition, Clínica Universidad de Navarra, 31008 Pamplona, Spain.
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Vandenbeek R, Khan NP, Estall JL. Linking Metabolic Disease With the PGC-1α Gly482Ser Polymorphism. Endocrinology 2018; 159:853-865. [PMID: 29186342 DOI: 10.1210/en.2017-00872] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/27/2017] [Accepted: 11/20/2017] [Indexed: 12/11/2022]
Abstract
Peroxisome proliferator-activated receptor γ coactivator 1-α (PGC-1α) is a highly conserved transcriptional coactivator enriched in metabolically active tissues including liver, adipose, pancreas, and muscle. It plays a role in regulating whole body energy metabolism and its deregulation has been implicated in type 2 diabetes (T2D). A single nucleotide variant of the PPARGC1A gene (rs8192678) is associated with T2D susceptibility, relative risk of obesity and insulin resistance, and lower indices of β cell function. This common polymorphism is within a highly conserved region of the bioactive protein and leads to a single amino acid substitution (glycine 482 to serine). Its prevalence and effects on metabolic parameters appear to vary depending on factors including ethnicity and sex, suggesting important interactions between genetics and cultural/environmental factors and associated disease risk. Interestingly, carriers of the serine allele respond better to some T2D interventions, illustrating the importance of understanding functional impacts of genetic variance on PGC-1α when targeting this pathway for personalized medicine. This review summarizes a growing body of literature surrounding possible links between the PGC-1α Gly482Ser single nucleotide polymorphism and diabetes, with focus on key clinical findings, affected metabolic systems, potential molecular mechanisms, and the influence of geographical or ethnic background on associated risk.
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Affiliation(s)
- Roxanne Vandenbeek
- Institut de recherches cliniques de Montreal, Montreal, Quebec, Canada
- Division of Experimental Medicine, McGill University, Montreal, Quebec, Canada
| | - Naveen P Khan
- Institut de recherches cliniques de Montreal, Montreal, Quebec, Canada
- Division of Experimental Medicine, McGill University, Montreal, Quebec, Canada
| | - Jennifer L Estall
- Institut de recherches cliniques de Montreal, Montreal, Quebec, Canada
- Division of Experimental Medicine, McGill University, Montreal, Quebec, Canada
- Faculty of Medicine, University of Montreal, Montréal, Québec, Canada
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Dong J, Zhao J, Zhang M, Liu G, Wang X, Liu Y, Yang N, Liu Y, Zhao G, Sun J, Tian J, Cheng C, Wei L, Li Y, Li W. β3-Adrenoceptor Impairs Mitochondrial Biogenesis and Energy Metabolism During Rapid Atrial Pacing-Induced Atrial Fibrillation. J Cardiovasc Pharmacol Ther 2015; 21:114-26. [PMID: 26130614 DOI: 10.1177/1074248415590440] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/13/2015] [Accepted: 05/11/2015] [Indexed: 11/17/2022]
Abstract
BACKGROUND The β3-adrenoceptor (β3-AR) is implicated in cardiac remodeling. Since metabolic dysfunction due to loss of mitochondria plays an important role in heart diseases, we examined the effects of β3-AR on mitochondrial biogenesis and energy metabolism in atrial fibrillation (AF). METHODS Atrial fibrillation was created by rapid atrial pacing in adult rabbits. Rabbits were randomly divided into 4 groups: control, pacing (P7), β3-AR antagonist (L748337), and β3-AR agonist (BRL37344) groups. Atrial effective refractory period (AERP) and AF induction rate were measured. Atrial concentrations of adenine nucleotides and phosphocreatine were quantified through high-performance liquid chromatography. Mitochondrial DNA content was determined. Real-time polymerase chain reaction and Western blot were used to examine the expression levels of signaling intermediates related to mitochondrial biogenesis. RESULTS After pacing for 7 days, β3-AR was significantly upregulated, AERP was reduced, and the AF induction rate was increased. The total adenine nucleotides pool was significantly reduced due to the decrease in adenosine triphosphate (ATP). The P7 group showed decreased activity of F0F1-ATPase. Mitochondrial DNA content was decreased and mitochondrial respiratory chain subunits were downregulated after pacing. Furthermore, expression of transcription factors involved in mitochondrial biogenesis, including peroxisome proliferator-activated receptor γ coactivator 1α (PGC-1α), nuclear respiratory factor 1 (NRF-1), and mitochondrial transcription factor A (Tfam), was lower in the P7 group in response to β3-AR activation. Further stimulation of β3-AR with BRL37344 exacerbated these effects, together with a significant decrease in the levels of phosphocreatine. In contrast, inhibition of β3-AR with L748337 partially restored mitochondrial biogenesis and energy metabolism of atria in the paced rabbits. CONCLUSION The activation of β3-AR contributes to atrial metabolic remodeling via transcriptional downregulation of PGC-1α/NRF-1/Tfam pathway that are involved in mitochondrial biogenesis, which ultimately perturbs mitochondrial function in rapid pacing-induced AF. The β3-AR is therefore a potential novel therapeutic target for the treatment or prevention of AF.
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Affiliation(s)
- Jingmei Dong
- Department of Cardiology, First Affiliated Hospital of Harbin Medical University, Harbin, China
| | - Jingjing Zhao
- Department of Cardiology, First Affiliated Hospital of Harbin Medical University, Harbin, China
| | - Miaomiao Zhang
- Department of Cardiology, First Affiliated Hospital of Harbin Medical University, Harbin, China
| | - Guangzhong Liu
- Department of Cardiology, First Affiliated Hospital of Harbin Medical University, Harbin, China
| | - Xiaobing Wang
- Department of Cardiology, First Affiliated Hospital of Harbin Medical University, Harbin, China
| | - Yixi Liu
- Department of Cardiology, First Affiliated Hospital of Harbin Medical University, Harbin, China
| | - Ning Yang
- Ultrasonic Cardiogram Room, First Affiliated Hospital of Harbin Medical University, Harbin, China
| | - Yongwu Liu
- Centre for Drug Safety Evaluation, Heilongjiang University of Chinese Medicine, Harbin, China
| | - Guanqi Zhao
- Department of Cardiology, First Affiliated Hospital of Harbin Medical University, Harbin, China
| | - Jiayu Sun
- Department of Cardiology, First Affiliated Hospital of Harbin Medical University, Harbin, China
| | - Jingpu Tian
- Department of Cardiology, First Affiliated Hospital of Harbin Medical University, Harbin, China
| | - Cheping Cheng
- Department of Cardiology, Wake Forest University School of Medicine, Winston-Salem, North Carolina, USA
| | - Lin Wei
- Department of Cardiology, First Hospital of Harbin City, Harbin, China
| | - Yue Li
- Department of Cardiology, First Affiliated Hospital of Harbin Medical University, Harbin, China
| | - Weimin Li
- Department of Cardiology, First Affiliated Hospital of Harbin Medical University, Harbin, China
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Abstract
Transcription factors of the FoxO (forkhead box O) family regulate a wide range of cellular physiological processes, including metabolic adaptation and myogenic differentiation. The transcriptional activity of most FoxO members is inhibitory to myogenic differentiation and overexpression of FoxO1 inhibits the development of oxidative type I fibres in vivo. In this study, we found that FoxO6, the last discovered FoxO family member, is expressed ubiquitously in various tissues but with higher expression levels in oxidative tissues, such as brain and oxidative muscles. Both the expression level and promoter activity of FoxO6 were found to be enhanced by PGC-1α (peroxisome-proliferator-activated receptor γ co-activator 1α), thus explained its enriched expression in oxidative tissues. We further demonstrated that FoxO6 represses the expression of PGC-1α via direct binding to an upstream A/T-rich element (AAGATATCAAAACA,−2228–2215) in the PGC-1α promoter. Oxidative low-intensity exercise induced PGC-1α but reduced FoxO6 expression levels in hind leg muscles, and the binding of FoxO6 to PGC-1α promoter was also prevented by exercise. As FoxO6 promoter can be co-activated by PGC-1α and its promoter in turn can be repressed by FoxO6, it suggests that FoxO6 and PGC-1α form a regulatory loop for setting oxidative metabolism level in the skeletal muscle, which can be entrained by exercise.
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Tsukiyama-Kohara K, Katsume A, Kimura K, Saito M, Kohara M. 4E-BP1 regulates the differentiation of white adipose tissue. Genes Cells 2013; 18:602-7. [PMID: 23672244 DOI: 10.1111/gtc.12059] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2012] [Accepted: 03/26/2013] [Indexed: 11/29/2022]
Abstract
4E Binding protein 1 (4E-BP1) suppresses translation initiation. The absence of 4E-BP1 drastically reduces the amount of adipose tissue in mice. To address the role of 4E-BP1 in adipocyte differentiation, we characterized 4E-BP1(-/-) mice in this study. The lack of 4E-BP1 decreased the amount of white adipose tissue and increased the amount of brown adipose tissue. In 4E-BP1(-/-) MEF cells, PPARγ coactivator 1 alpha (PGC-1α) expression increased and exogenous 4E-BP1 expression suppressed PGC-1α expression. The level of 4E-BP1 expression was higher in white adipocytes than in brown adipocytes and showed significantly greater up-regulation in white adipocytes than in brown adipocytes during preadipocyte differentiation into mature adipocytes. The amount of PGC-1α was consistently higher in HB cells (a brown preadipocyte cell line) than in HW cells (a white preadipocyte cell line) during differentiation. Moreover, the ectopic over-expression of 4E-BP1 suppressed PGC-1α expression in white adipocytes, but not in brown adipocytes. Thus, the results of our study indicate that 4E-BP1 may suppress brown adipocyte differentiation and PGC-1α expression in white adipose tissues.
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Affiliation(s)
- Kyoko Tsukiyama-Kohara
- Department of Experimental Phylaxiology, Faculty of Medical and Pharmaceutical Sciences, Kumamoto University, 1-1-1 Honjo, Kumamoto-City, Kumamoto 860-8556, Japan.
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Ananda S, Wang Y, Zhu S, Wang R, Zhou X, Zhuo L, Sun T, Ren L, Liu Q, Dong H, Liu Y, Liu L. Role of neuropeptide Y and peroxisome proliferator-activated receptor γ coactivator-1α in stress cardiomyopathy. ACTA ACUST UNITED AC 2012; 32:823-828. [PMID: 23271280 DOI: 10.1007/s11596-012-1041-3] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2012] [Indexed: 10/27/2022]
Abstract
Death following situations of intense emotional stress has been linked to the cardiac pathology described as stress cardiomyopathy, whose pathomechanism is still not clear. In this study, we sought to determine, via an animal model, whether the transcriptional coactivator peroxisome proliferator-activated receptor γ coactivator-1alpha (PGC-1α) and the amino peptide neuropeptide Y (NPY) play a role in the pathogenesis of this cardiac entity. Male Sprague-Dawley rats in the experimental group were subjected to immobilization in a plexy glass box for 1 h, which was followed by low voltage electric foot shock for about 1 h at 10 s intervals in a cage fitted with metallic rods. After 25 days the rats were sacrificed and sections of their hearts were processed. Hematoxylin-eosin staining of cardiac tissues revealed the characteristic cardiac lesions of stress cardiomyopathy such as contraction band necrosis, inflammatory cell infiltration and fibrosis. The semi-quantitative RT-PCR analysis for PGC-1α mRNA expression showed significant overexpression of PGC1-α in the stress-subjected rats (P<0.05). Fluorescence immunohistochemistry revealed a higher production of NPY in the stress-subjected rats as compared to the control rats (P=0.0027). Thus, we are led to conclude that following periods of intense stress, an increased expression of PGC1-α in the heart and an overflow of NPY may lead to stress cardiomyopathy and even death in susceptible victims. Moreover, these markers can be used to identify stress cardiomyopathy as the cause of sudden death in specific cases.
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Affiliation(s)
- Sunnassee Ananda
- Department of Forensic Medicine, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, 430030, China
| | - Yunyun Wang
- Department of Forensic Medicine, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, 430030, China
| | - Shaohua Zhu
- Department of Forensic Medicine, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, 430030, China.
| | - Rongshuai Wang
- Department of Forensic Medicine, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, 430030, China
| | - Xiaowei Zhou
- Department of Forensic Medicine, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, 430030, China
| | - Luo Zhuo
- Department of Forensic Medicine, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, 430030, China
| | - Tingyi Sun
- Department of Forensic Medicine, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, 430030, China
| | - Liang Ren
- Department of Forensic Medicine, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, 430030, China
| | - Qian Liu
- Department of Forensic Medicine, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, 430030, China
| | - Hongmei Dong
- Department of Forensic Medicine, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, 430030, China
| | - Yan Liu
- Department of Forensic Medicine, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, 430030, China
| | - Liang Liu
- Department of Forensic Medicine, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, 430030, China
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Becerril S, Rodríguez A, Catalán V, Sáinz N, Ramírez B, Gómez-Ambrosi J, Frühbeck G. Transcriptional analysis of brown adipose tissue in leptin-deficient mice lacking inducible nitric oxide synthase: evidence of the role of Med1 in energy balance. Physiol Genomics 2012; 44:678-88. [PMID: 22570438 DOI: 10.1152/physiolgenomics.00039.2012] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Leptin and nitric oxide (NO) are implicated in the control of energy homeostasis. The aim of the present study was to examine the impact of the absence of the inducible NO synthase (iNOS) gene on the regulation of energy balance in ob/ob mice analyzing the changes in gene expression levels in brown adipose tissue (BAT). Double knockout (DBKO) mice simultaneously lacking the ob and iNOS genes were generated and the expression of genes involved in energy balance including fatty acid and glucose metabolism as well as mitochondrial genes were analyzed by microarrays. DBKO mice exhibited an improvement in energy balance with a decrease in body weight (P < 0.001), total fat pads (P < 0.05), and food intake (P < 0.05), as well as an enhancement in BAT function compared with ob/ob mice. To better understand the molecular events associated with this improvement, BAT gene expression was analyzed. Of particular interest, gene expression levels of the key subunit of the Mediator complex Med1 was upregulated (P < 0.05) in DBKO mice. Real-time PCR and immunohistochemistry further confirmed this data. Med1 is implicated in adipogenesis, lipid metabolic and biosynthetic processes, glucose metabolism, and mitochondrial metabolic pathways. Med1 plays an important role in the transcriptional control of genes implicated in energy homeostasis, suggesting that the improvement in energy balance and BAT function of the DBKO mice is mediated, at least in part, through the transcription coactivator Med1.
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Affiliation(s)
- Sara Becerril
- Metabolic Research Laboratory, Clínica Universidad de Navarra, Pamplona, Spain
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Chang JS, Fernand V, Zhang Y, Shin J, Jun HJ, Joshi Y, Gettys TW. NT-PGC-1α protein is sufficient to link β3-adrenergic receptor activation to transcriptional and physiological components of adaptive thermogenesis. J Biol Chem 2012; 287:9100-11. [PMID: 22282499 DOI: 10.1074/jbc.m111.320200] [Citation(s) in RCA: 60] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
PGC-1α is an inducible transcriptional coactivator that regulates cellular energy metabolism and adaptation to environmental and nutritional stimuli. In tissues expressing PGC-1α, alternative splicing produces a truncated protein (NT-PGC-1α) corresponding to the first 267 amino acids of PGC-1α. Brown adipose tissue also expresses two novel exon 1b-derived isoforms of PGC-1α and NT-PGC-1α, which are 4 and 13 amino acids shorter in the N termini than canonical PGC-1α and NT-PGC-1α, respectively. To evaluate the ability of NT-PGC-1α to substitute for PGC-1α and assess the isoform-specific role of NT-PGC-1α, adaptive thermogenic responses of adipose tissue were evaluated in mice lacking full-length PGC-1α (FL-PGC-1(-/-)) but expressing slightly shorter but functionally equivalent forms of NT-PGC-1α (NT-PGC-1α(254)). At room temperature, NT-PGC-1α and NT-PGC-1α(254) were produced from conventional exon 1a-derived transcripts in brown adipose tissue of wild type and FL-PGC-1α(-/-) mice, respectively. However, cold exposure shifted transcription to exon 1b, increasing exon 1b-derived mRNA levels. The resulting transcriptional responses produced comparable increases in energy expenditure and maintenance of core body temperature in WT and FL-PGC-1α(-/-) mice. Moreover, treatment of the two genotypes with a selective β(3)-adrenergic receptor agonist produced similar increases in energy expenditure, mitochondrial DNA, and reductions in adiposity. Collectively, these findings illustrate that the transcriptional and physiological responses to sympathetic input are unabridged in FL-PGC-1α(-/-) mice, and that NT-PGC-1α is sufficient to link β(3)-androgenic receptor activation to adaptive thermogenesis in adipose tissue. Furthermore, the transcriptional shift from exon 1a to 1b supports isoform-specific roles for NT-PGC-1α in basal and adaptive thermogenesis.
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Affiliation(s)
- Ji Suk Chang
- Laboratory of Nutrient Sensing and Adipocyte Signaling, Pennington Biomedical Research Center, Baton Rouge, Louisiana 70808, USA
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12
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Fernandez-Marcos PJ, Auwerx J. Regulation of PGC-1α, a nodal regulator of mitochondrial biogenesis. Am J Clin Nutr 2011; 93:884S-90. [PMID: 21289221 PMCID: PMC3057551 DOI: 10.3945/ajcn.110.001917] [Citation(s) in RCA: 890] [Impact Index Per Article: 68.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
Mechanisms responsible for energy management in the cell and in the whole organism require a complex network of transcription factors and cofactors. Peroxisome proliferator-activated receptor γ coactivator 1α (PGC-1α) has emerged as a master regulator of mitochondrial biogenesis and function, thus becoming a crucial metabolic node. We present an overview of the mechanisms by which PGC-1α is regulated, including the transcriptional regulation of PGC-1α expression and the fine-tuning of its final activity via posttranslational modifications.
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Affiliation(s)
- Pablo J Fernandez-Marcos
- Laboratory for Integrative and Systems Physiology, Ecole Polytechnique Fédérale de Lausanne, Switzerland
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13
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Chartoumpekis DV, Habeos IG, Ziros PG, Psyrogiannis AI, Kyriazopoulou VE, Papavassiliou AG. Brown adipose tissue responds to cold and adrenergic stimulation by induction of FGF21. Mol Med 2011; 17:736-40. [PMID: 21373720 DOI: 10.2119/molmed.2011.00075] [Citation(s) in RCA: 186] [Impact Index Per Article: 14.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2011] [Accepted: 02/25/2011] [Indexed: 12/30/2022] Open
Abstract
Fibroblast growth factor-21 (FGF21) is a pleiotropic protein involved in glucose, lipid metabolism and energy homeostasis, with main tissues of expression being the liver and adipose tissue. Brown adipose tissue (BAT) is responsible for cold-induced thermogenesis in rodents. The role of FGF21 in BAT biology has not been investigated. In the present study, wild-type C57BL/6J mice as well as a brown adipocyte cell line were used to explore the potential role of cold exposure and β3-adrenergic stimulation in the expression of FGF21 in BAT. Our results demonstrate that short-term exposure to cold, as well as β3-adrenergic stimulation, causes a significant induction of FGF21 mRNA levels in BAT, without a concomitant increase in FGF21 plasma levels. This finding opens new routes for the potential use of pharmaceuticals that could induce FGF21 and, hence, activate BAT thermogenesis.
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Affiliation(s)
- Dionysios V Chartoumpekis
- Department of Internal Medicine, Division of Endocrinology, Medical School, University of Patras, Patras, Greece
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14
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Fernandez-Marcos PJ, Auwerx J. Regulation of PGC-1α, a nodal regulator of mitochondrial biogenesis. THE AMERICAN JOURNAL OF CLINICAL NUTRITION 2011. [PMID: 21289221 DOI: 10.3945/jcn.110.001917] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Mechanisms responsible for energy management in the cell and in the whole organism require a complex network of transcription factors and cofactors. Peroxisome proliferator-activated receptor γ coactivator 1α (PGC-1α) has emerged as a master regulator of mitochondrial biogenesis and function, thus becoming a crucial metabolic node. We present an overview of the mechanisms by which PGC-1α is regulated, including the transcriptional regulation of PGC-1α expression and the fine-tuning of its final activity via posttranslational modifications.
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Affiliation(s)
- Pablo J Fernandez-Marcos
- Laboratory for Integrative and Systems Physiology, Ecole Polytechnique Fédérale de Lausanne, Switzerland
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15
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Deletion of inducible nitric-oxide synthase in leptin-deficient mice improves brown adipose tissue function. PLoS One 2010; 5:e10962. [PMID: 20532036 PMCID: PMC2881035 DOI: 10.1371/journal.pone.0010962] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2010] [Accepted: 05/16/2010] [Indexed: 01/22/2023] Open
Abstract
Background Leptin and nitric oxide (NO) on their own participate in the control of non-shivering thermogenesis. However, the functional interplay between both factors in this process has not been explored so far. Therefore, the aim of the present study was to analyze the impact of the absence of the inducible NO synthase (iNOS) gene in the regulation of energy balance in ob/ob mice. Methods and Findings Double knockout (DBKO) mice simultaneously lacking the ob and iNOS genes were generated, and the expression of molecules involved in the control of brown fat cell function was analyzed by real-time PCR, western-blot and immunohistochemistry. Twelve week-old DBKO mice exhibited reduced body weight (p<0.05), decreased amounts of total fat pads (p<0.05), lower food efficiency rates (p<0.05) and higher rectal temperature (p<0.05) than ob/ob mice. Ablation of iNOS also improved the carbohydrate and lipid metabolism of ob/ob mice. DBKO showed a marked reduction in the size of brown adipocytes compared to ob/ob mutants. In this sense, in comparison to ob/ob mice, DBKO rodents showed an increase in the expression of PR domain containing 16 (Prdm16), a transcriptional regulator of brown adipogenesis. Moreover, iNOS deletion enhanced the expression of mitochondria-related proteins, such as peroxisome proliferator-activated receptor γ coactivator-1 α (Pgc-1α), sirtuin-1 (Sirt-1) and sirtuin-3 (Sirt-3). Accordingly, mitochondrial uncoupling proteins 1 and 3 (Ucp-1 and Ucp-3) were upregulated in brown adipose tissue (BAT) of DBKO mice as compared to ob/ob rodents. Conclusion Ablation of iNOS improved the energy balance of ob/ob mice by decreasing food efficiency through an increase in thermogenesis. These effects may be mediated, in part, through the recovery of the BAT phenotype and brown fat cell function improvement.
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16
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Giacobino JP, Casteilla L. Thermogenic brown adipocytes as new targets for the treatment of obesity in humans. ACTA ACUST UNITED AC 2010. [DOI: 10.2217/clp.10.5] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
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17
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Catalán V, Gómez-Ambrosi J, Lizanzu A, Rodríguez A, Silva C, Rotellar F, Gil MJ, Cienfuegos JA, Salvador J, Frühbeck G. RIP140 gene and protein expression levels are downregulated in visceral adipose tissue in human morbid obesity. Obes Surg 2009; 19:771-6. [PMID: 19367438 DOI: 10.1007/s11695-009-9834-6] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2008] [Accepted: 03/23/2009] [Indexed: 01/03/2023]
Abstract
BACKGROUND Receptor-interacting protein 140 (RIP140) is a corepressor for nuclear receptors with an important role in the inhibition of energy expenditure. Rip140-knockout mice are lean and resistant to diet-induced obesity due to an increase in mitochondrial biogenesis, fatty acid oxidation, and oxidative phosphorylation. The aim of the present work was to evaluate the effect of morbid obesity on gene and protein expression levels of RIP140 in visceral adipose tissue (VAT). METHODS VAT biopsies obtained from 17 subjects were used in the study. Patients were classified as lean (body mass index [BMI]=21.8+/-1.3 kg/m2) or obese (BMI=48.2+/-2.6 kg/m2). Reverse transcription polymerase chain reaction and Western blot analyses were performed to quantify the expression levels of RIP140 in VAT. We also analyzed glucose and lipid profile as well as some inflammatory factors. RESULTS Obese patients exhibited significantly lower RIP140 mRNA expression levels compared to lean subjects (lean=1.00+/-0.17 arbitrary units, obese=0.65+/-0.18 arbitrary units; P<0.05). Protein expression of RIP140 followed the same trend, being significantly higher in lean volunteers (lean=1.00+/-0.18 arbitrary units, obese=0.45+/-0.11 arbitrary units; P<0.05). Furthermore, a significant negative correlation was found between RIP140 protein levels and both BMI (rho=-0.85; P<0.001) and body fat percentage (rho=-0.88; P<0.001). CONCLUSIONS The lower gene and protein expression levels of RIP140 in obese subjects may suggest a compensatory mechanism in order to favor energy expenditure and reduce fat accumulation in obesity states.
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Affiliation(s)
- Victoria Catalán
- Metabolic Research Laboratory, Department of Endocrinology, Clínica Universitaria de Navarra, University of Navarra, Pamplona, Spain
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18
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Bogacka I, Gettys TW, de Jonge L, Nguyen T, Smith JM, Xie H, Greenway F, Smith SR. The effect of beta-adrenergic and peroxisome proliferator-activated receptor-gamma stimulation on target genes related to lipid metabolism in human subcutaneous adipose tissue. Diabetes Care 2007; 30:1179-86. [PMID: 17351280 DOI: 10.2337/dc06-1962] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
OBJECTIVE The sympathetic nervous system and thiazolidinediones control lipid metabolism and have been implicated in body weight regulation. This study was conducted to determine whether the simultaneous activation of these two signaling systems might synergize to exert beneficial effects on the expression of key genes involved in lipid metabolism and mitochondrial biogenesis in subcutaneous fat in nondiabetic subjects. RESEARCH DESIGN AND METHODS A total of 57 women and men were randomized into four groups: 1) placebo/placebo (PP), 2) ephedrine HCl (25 mg, 3 times daily) plus caffeine (200 mg, 3 times daily)/placebo (ECP), 3) placebo/pioglitazone (45 mg) (PPio), and 4) ephedrine plus caffeine/pioglitazone (ECPio) for 16 weeks. Adipose tissue samples were obtained after 12 weeks of treatment to determine gene expression. RESULTS Body fat decreased by 6.0 and 4.6% in the ECP and ECPio groups, respectively, while remaining unchanged in the PPio and PP groups. Triglyceride levels decreased by -7.7, -24, -15.2, and -41 mg/dl after 16 weeks treatment in the PP, PPio, ECP, and ECPio groups, respectively. This indicates that pioglitazone groups with or without EC (ephedrine HCl plus caffeine) decreased triglycerides, and EC groups with or without pioglitazone decreased body weight. The mRNA for sirtuin 1 and CD36 increased only in the ECPio group. Carnitine palmitoyltransferase-1, medium-chain acyl CoA dehydrogenase, and malonyl-CoA decarboxylase increased with PPio and ECPio. Stearoyl-CoA desaturase decreased with ECP. CONCLUSIONS Combined activation of peroxisome proliferator-activated receptor-gamma and beta-adrenergic receptors has beneficial effects on body weight, plasma triglycerides, and lipid metabolism in subcutaneous fat by increasing the expression of genes required for fatty acid catabolism.
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Affiliation(s)
- Iwona Bogacka
- Molecular Endocrinology Laboratory, Pennington Biomedical Research Center, 6400 Perkins Rd., Baton Rouge, LA 70808, USA
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19
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Nisoli E, Clementi E, Carruba MO, Moncada S. Defective mitochondrial biogenesis: a hallmark of the high cardiovascular risk in the metabolic syndrome? Circ Res 2007; 100:795-806. [PMID: 17395885 DOI: 10.1161/01.res.0000259591.97107.6c] [Citation(s) in RCA: 185] [Impact Index Per Article: 10.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
The metabolic syndrome is a group of risk factors of metabolic origin that are accompanied by increased risk for type 2 diabetes mellitus and cardiovascular disease. These risk factors include atherogenic dyslipidemia, elevated blood pressure and plasma glucose, and a prothrombotic and proinflammatory state. The condition is progressive and is exacerbated by physical inactivity, advancing age, hormonal imbalance, and genetic predisposition. The metabolic syndrome is a particularly challenging clinical condition because its complex molecular basis is still largely undefined. Impaired cell metabolism has, however, been suggested as a relevant pathophysiological process underlying several clinical features of the syndrome. In particular, defective oxidative metabolism seems to be involved in visceral fat gain and in the development of insulin resistance in skeletal muscle. This suggests that mitochondrial function may be impaired in the metabolic syndrome and, thus, in the consequent cardiovascular disease. We have recently found that mitochondrial biogenesis and function are enhanced by nitric oxide in various cell types and tissues, including cardiac muscle. Increasing evidence suggests that this mediator acts as a metabolic sensor in cardiomyocytes. This implies that a defective production of nitric oxide might be linked to dysfunction of the cardiomyocyte metabolism. Here we summarize some recent findings and propose a hypothesis for the high cardiovascular risk linked to the metabolic syndrome.
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Affiliation(s)
- Enzo Nisoli
- Department of Pharmacology, Chemotherapy and Medical Toxicology, School of Medicine, Milan University, Milan, Italy.
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20
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McAinch A, Steinberg G, Mollica J, O’Brien P, Dixon J, Kemp B, Cameron-Smith D. Leptin stimulation of COXIV is impaired in obese skeletal muscle myotubes. Obes Res Clin Pract 2007; 1:1-78. [DOI: 10.1016/j.orcp.2006.10.003] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/16/2006] [Revised: 10/04/2006] [Accepted: 10/12/2006] [Indexed: 10/23/2022]
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21
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Lehr L, Canola K, Asensio C, Jimenez M, Kuehne F, Giacobino JP, Muzzin P. The control of UCP1 is dissociated from that of PGC-1alpha or of mitochondriogenesis as revealed by a study using beta-less mouse brown adipocytes in culture. FEBS Lett 2006; 580:4661-6. [PMID: 16876797 DOI: 10.1016/j.febslet.2006.07.037] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2006] [Revised: 07/05/2006] [Accepted: 07/11/2006] [Indexed: 10/24/2022]
Abstract
In rodent brown adipose tissue, the beta-adrenergic signaling is believed, by an action on PGC-1alpha, to control UCP1 expression and mitochondriogenesis. We addressed this hypothesis using beta(1)/beta(2)/beta(3)-adrenoceptor knockout (beta-less) brown adipocytes in primary culture. In these cells: (a) proliferation and differentiation into multilocular cells were normal; (b) UCP1 mRNA expression was dramatically decreased (by 93%), whereas PGC-1alpha and mtTFA mRNA expressions were not; (c) UCP1, PGC-1alpha and COX IV protein expressions were decreased by 97%, 62% and 22%, respectively. Altogether the data show a dissociation between the control of UCP1, which is mostly beta-adrenoceptor-dependent and that of PGC-1alpha and of mitochondriogenesis which are not.
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Affiliation(s)
- Lorenz Lehr
- Department of Cell Physiology and Metabolism, Centre Médical Universitaire, Geneva, Switzerland.
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22
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Uno K, Katagiri H, Yamada T, Ishigaki Y, Ogihara T, Imai J, Hasegawa Y, Gao J, Kaneko K, Iwasaki H, Ishihara H, Sasano H, Inukai K, Mizuguchi H, Asano T, Shiota M, Nakazato M, Oka Y. Neuronal pathway from the liver modulates energy expenditure and systemic insulin sensitivity. Science 2006; 312:1656-9. [PMID: 16778057 DOI: 10.1126/science.1126010] [Citation(s) in RCA: 186] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
Coordinated control of energy metabolism and glucose homeostasis requires communication between organs and tissues. We identified a neuronal pathway that participates in the cross talk between the liver and adipose tissue. By studying a mouse model, we showed that adenovirus-mediated expression of peroxisome proliferator-activated receptor (PPAR)-g2 in the liver induces acute hepatic steatosis while markedly decreasing peripheral adiposity. These changes were accompanied by increased energy expenditure and improved systemic insulin sensitivity. Hepatic vagotomy and selective afferent blockage of the hepatic vagus revealed that the effects on peripheral tissues involve the afferent vagal nerve. Furthermore, an antidiabetic thiazolidinedione, a PPARg agonist, enhanced this pathway. This neuronal pathway from the liver may function to protect against metabolic perturbation induced by excessive energy storage.
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Affiliation(s)
- Kenji Uno
- Division of Molecular Metabolism and Diabetes, Tohoku University Graduate School of Medicine, Sendai 980-8575, Japan
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23
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Soriano FX, Liesa M, Bach D, Chan DC, Palacín M, Zorzano A. Evidence for a mitochondrial regulatory pathway defined by peroxisome proliferator-activated receptor-gamma coactivator-1 alpha, estrogen-related receptor-alpha, and mitofusin 2. Diabetes 2006; 55:1783-91. [PMID: 16731843 DOI: 10.2337/db05-0509] [Citation(s) in RCA: 276] [Impact Index Per Article: 15.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
Mitofusin 2 (Mfn2) is a mitochondrial membrane protein that participates in mitochondrial fusion and regulates mitochondrial metabolism in mammalian cells. Here, we show that Mfn2 gene expression is induced in skeletal muscle and brown adipose tissue by conditions associated with enhanced energy expenditure, such as cold exposure or beta(3)-adrenergic agonist treatment. In keeping with the role of peroxisome proliferator-activated receptor-gamma coactivator (PGC)-1 alpha on energy expenditure, we demonstrate a stimulatory effect of PGC-1 alpha on Mfn2 mRNA and protein expression in muscle cells. PGC-1 alpha also stimulated the activity of the Mfn2 promoter, which required the integrity of estrogen-related receptor-alpha (ERR alpha)-binding elements located at -413/-398. ERR alpha also activated the transcriptional activity of the Mfn2 promoter, and the effects were synergic with those of PGC-1 alpha. Mfn2 loss of function reduced the stimulatory effect of PGC-1 alpha on mitochondrial membrane potential. Exposure to cold substantially increased Mfn2 gene expression in skeletal muscle from heterozygous Mfn2 knock-out mice, which occurred in the presence of higher levels of PGC-1 alpha mRNA compared with control mice. Our results indicate the existence of a regulatory pathway involving PGC-1 alpha, ERR alpha, and Mfn2. Alterations in this regulatory pathway may participate in the pathophysiology of insulin-resistant conditions and type 2 diabetes.
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MESH Headings
- Adipose Tissue, Brown/drug effects
- Adipose Tissue, Brown/metabolism
- Animals
- Blotting, Western
- Cells, Cultured
- Chromatin Immunoprecipitation
- Cold Temperature
- Dioxoles/pharmacology
- Electrophoretic Mobility Shift Assay
- Estrogen Receptor alpha/genetics
- Estrogen Receptor alpha/metabolism
- GTP Phosphohydrolases
- Gene Expression/drug effects
- HeLa Cells
- Heat-Shock Proteins/genetics
- Heat-Shock Proteins/metabolism
- Humans
- Male
- Membrane Proteins/genetics
- Membrane Proteins/metabolism
- Mice
- Mitochondria, Muscle/metabolism
- Mitochondrial Proteins/genetics
- Mitochondrial Proteins/metabolism
- Muscle, Skeletal/cytology
- Muscle, Skeletal/drug effects
- Muscle, Skeletal/metabolism
- Peroxisome Proliferator-Activated Receptor Gamma Coactivator 1-alpha
- Protein Binding
- RNA, Messenger/genetics
- RNA, Messenger/metabolism
- Rats
- Rats, Wistar
- Signal Transduction/drug effects
- Signal Transduction/genetics
- Signal Transduction/physiology
- Transcription Factors/genetics
- Transcription Factors/metabolism
- Transfection
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Affiliation(s)
- Francesc X Soriano
- Institute for Research in Biomedicine (IRB), Scientífic Park of Barcelona, Departament of Biochemistry and Molecular Biology, Faculty of Biology, University of Barcelona, Barelona, Spain
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24
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Chan LLY, Chen Q, Go AGG, Lam EKY, Li ETS. Reduced adiposity in bitter melon (Momordica charantia)-fed rats is associated with increased lipid oxidative enzyme activities and uncoupling protein expression. J Nutr 2005; 135:2517-23. [PMID: 16251604 DOI: 10.1093/jn/135.11.2517] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
To further explore the antiobesity effect of freeze-dried bitter melon (BM) juice, activities of mitochondrial lipid oxidative enzymes as well as the expression of uncoupling proteins and their transcription coactivator peroxisome proliferator-activated receptor-gamma coactivator-1 alpha (PGC-1alpha) were determined in diet-induced obese (DIO) rats. Rats were fed high-fat (HF) diets to induce obesity, and the effect of BM was assessed at doses of 0.75, 1.0, or 1.25% (wt:wt). In a dose-response experiment, BM-supplemented rats had lower energy efficiency (g weight gained/kJ consumed), visceral fat mass, serum glucose, and insulin resistance index, but higher plasma norepinephrine than unsupplemented rats (P < 0.05). Hepatic and skeletal muscle triglyceride concentrations were lower in supplemented HF diet-fed rats than in unsupplemented HF diet-fed rats (P < 0.05). An HF diet supplemented with BM elevated activities of hepatic and muscle mitochondrial carnitine palmitoyl transferase-I (CPT-I) and acyl-CoA dehydrogenase (AD) (P < 0.05). In another experiment, BM (1.0 g/100 g) lowered visceral fat mass but increased serum adiponectin concentration in HF diet-fed rats (P < 0.05). In the final study, rats were fed the HF diet with 0, 1.0 or 1.25% BM. Both groups of BM-supplemented rats had higher uncoupling protein 1 in brown adipose tissue (P < 0.05) and uncoupling protein 3 in red gastrocnemius muscle (P < 0.05), measured by Western blotting and RT-PCR, than the controls. The expression of the transcription coactivator PGC-1alpha in both tissues was also significantly elevated in the BM-supplemented rats (P < 0.05). The present results suggest that decreased adiposity in BM-supplemented rats may result from lower metabolic efficiency, a consequence of increased lipid oxidation and mitochondrial uncoupling.
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Affiliation(s)
- Laureen L Y Chan
- Food and Nutritional Science Program, Department of Zoology, The University of Hong Kong, Hong Kong, The People's Republic of China
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25
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Zhang P, Liu C, Zhang C, Zhang Y, Shen P, Zhang J, Zhang CY. Free fatty acids increase PGC-1alpha expression in isolated rat islets. FEBS Lett 2005; 579:1446-52. [PMID: 15733855 DOI: 10.1016/j.febslet.2005.01.046] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2004] [Revised: 01/20/2005] [Accepted: 01/21/2005] [Indexed: 10/25/2022]
Abstract
PGC-1alpha mRNA and protein are elevated in islets from multiple animal models of diabetes. Overexpression of PGC-1alpha impairs glucose-stimulated insulin secretion (GSIS). However, it is not well known which metabolic events lead to upregulation of PGC-1alpha in the beta-cells under pathophysiological condition. In present study, we have investigated effects of chronic hyperlipidemia and hyperglycemia on PGC-1alpha mRNA expression in isolated rat islets. Isolated rat islets are chronically incubated with 0, 0.2 and 0.4 mM oleic acid/palmitic acid (free fatty acids, FFA) or 5.5 and 25 mM glucose for 72 h. FFA dose-dependently increases PGC-1alpha mRNA expression level in isolated islets. FFA also increases PGC-1alpha expression in mouse beta-cell-derived beta TC3 cell line. In contrast, 25 mM glucose decreases expression level of PGC-1alpha. Inhibition of PGC-1alpha by siRNA improves FFA-induced impairment of GSIS in islets. These data suggest that hyperlipidemia and hyperglycemia regulate PGC-1alpha expression in islets differently, and elevated PGC-1alpha by FFA plays an important role in chronic hyperlipidemia-induced beta-cell dysfunction.
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Affiliation(s)
- Peixiang Zhang
- Institute of Mecular Medicine and State Key Laboratory of Pharmaceutical Biotechnology, School of Life Sciences, Nanjing University, 22 Hankou Road, Nanjing, Jiangsu 210093, PR China
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Nedergaard J, Petrovic N, Lindgren EM, Jacobsson A, Cannon B. PPARgamma in the control of brown adipocyte differentiation. Biochim Biophys Acta Mol Basis Dis 2005; 1740:293-304. [PMID: 15949696 DOI: 10.1016/j.bbadis.2005.02.003] [Citation(s) in RCA: 154] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2004] [Revised: 01/22/2005] [Accepted: 02/04/2005] [Indexed: 01/08/2023]
Abstract
The effects of fatty acids and retinoic acid (carotene) on brown adipose tissue differentiation are mediated by activation of the transcription factors PPARgamma and PPARalpha in combination with RXR. There is good support for the idea that activated PPARgamma promotes adipogenesis also in brown adipose tissue. However, the issue is more complex concerning the full differentiation to the brown adipocyte phenotype, particularly the expression of the brown-fat-specific marker UCP1. The effect of norepinephrine on PPARgamma gene expression, at least in-vitro, is negative, PPARgamma-ablated brown adipose tissue can express UCP1, and PGC-1alpha coactivates other transcription factors (including PPARalpha); thus, the significance of PPARgamma for the physiological control of UCP1 gene expression is not settled. However, importantly, the effects of PPAR agonists demonstrate the existence of a pathway for brown adipose tissue recruitment that is not dependent on chronic adrenergic stimulation and may be active in recruitment conditions such as prenatal and prehibernation recruitment. The ability of chronic PPARgamma agonist treatment to promote the occurrence of brown-fat features in white adipose tissue-like depots implies a role in anti-obesity treatment, but this will only be effective if the extra thermogenic capacity is activated by adrenergic stimulation.
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Affiliation(s)
- Jan Nedergaard
- The Wenner-Gren Institute, The Arrhenius Laboratories F3, Stockholm University, SE-106 91 Stockholm, Sweden.
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27
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McCarty MF. Up-regulation of PPARγ coactivator-1α as a strategy for preventing and reversing insulin resistance and obesity. Med Hypotheses 2005; 64:399-407. [PMID: 15607577 DOI: 10.1016/j.mehy.2004.03.034] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2004] [Accepted: 03/21/2004] [Indexed: 12/25/2022]
Abstract
Excessive accumulation of triglycerides and certain fatty acid derivatives in skeletal muscle and other tissues appears to mediate many of the adverse effects of insulin resistance syndrome. Although fatty diets and obesity can promote such accumulation, deficient capacity for fatty acid oxidation can also contribute in this regard. Indeed, in subjects who are insulin resistant, diabetic, and/or obese, fatty acid oxidation by skeletal muscle tends to be inefficient, reflecting decreased expression of mitochondria and mitochondrial enzymes in muscle. This phenomenon is not corrected by weight loss, is not simply reflective of subnormal physical activity, and is also seen in lean first-degree relatives of diabetics; thus, it appears to be primarily attributable to genetic factors. Recent studies indicate that decreased expression of PPARgamma coactivator-1alpha (PGC-1alpha), a "master switch" which induces mitochondrial biogenesis by supporting the transcriptional activity of the nuclear respiratory factors, may largely account for the diminished oxidative capacity of subjects prone to insulin resistance. Thus, feasible measures which up-regulate PGC-1alpha may be useful for preventing and treating insulin resistance and obesity. These may include exercise training, metformin and other agents which stimulate AMP-activated kinase, high-dose biotin, and PPARdelta agonists. Drugs which are specific agonists for PPARdelta show remarkable efficacy in rodent models of insulin resistance, diabetes, and obesity, and are currently being evaluated clinically. Phytanic acid, a branched-chain fatty acid found in omnivore diets, can also activate PPARdelta, and thus should be examined with respect to its impact on mitochondrial biogenesis and insulin sensitivity.
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Affiliation(s)
- Mark F McCarty
- NutriGuard Research, 1051 Hermes Ave., Encinitas, CA 92024, USA.
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Abstract
The function of brown adipose tissue is to transfer energy from food into heat; physiologically, both the heat produced and the resulting decrease in metabolic efficiency can be of significance. Both the acute activity of the tissue, i.e., the heat production, and the recruitment process in the tissue (that results in a higher thermogenic capacity) are under the control of norepinephrine released from sympathetic nerves. In thermoregulatory thermogenesis, brown adipose tissue is essential for classical nonshivering thermogenesis (this phenomenon does not exist in the absence of functional brown adipose tissue), as well as for the cold acclimation-recruited norepinephrine-induced thermogenesis. Heat production from brown adipose tissue is activated whenever the organism is in need of extra heat, e.g., postnatally, during entry into a febrile state, and during arousal from hibernation, and the rate of thermogenesis is centrally controlled via a pathway initiated in the hypothalamus. Feeding as such also results in activation of brown adipose tissue; a series of diets, apparently all characterized by being low in protein, result in a leptin-dependent recruitment of the tissue; this metaboloregulatory thermogenesis is also under hypothalamic control. When the tissue is active, high amounts of lipids and glucose are combusted in the tissue. The development of brown adipose tissue with its characteristic protein, uncoupling protein-1 (UCP1), was probably determinative for the evolutionary success of mammals, as its thermogenesis enhances neonatal survival and allows for active life even in cold surroundings.
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Affiliation(s)
- Barbara Cannon
- The Wenner-Gren Institute, The Arrhenius Laboratories F3, Stockholm University, Stockholm, Sweden
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Puigserver P, Spiegelman BM. Peroxisome proliferator-activated receptor-gamma coactivator 1 alpha (PGC-1 alpha): transcriptional coactivator and metabolic regulator. Endocr Rev 2003; 24:78-90. [PMID: 12588810 DOI: 10.1210/er.2002-0012] [Citation(s) in RCA: 1539] [Impact Index Per Article: 73.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Investigations of biological programs that are controlled by gene transcription have mainly studied the regulation of transcription factors. However, there are examples in which the primary focus of biological regulation is at the level of a transcriptional coactivator. We have reviewed here the molecular mechanisms and biological programs controlled by the transcriptional coactivator peroxisome proliferator-activated receptor-gamma coactivator 1 alpha (PGC-1 alpha). Key cellular signals that control energy and nutrient homeostasis, such as cAMP and cytokine pathways, strongly activate PGC-1 alpha. Once PGC-1 alpha is activated, it powerfully induces and coordinates gene expression that stimulates mitochondrial oxidative metabolism in brown fat, fiber-type switching in skeletal muscle, and multiple aspects of the fasted response in liver. The regulation of these metabolic and cell fate decisions by PGC-1 alpha is achieved through specific interaction with a variety of transcription factors such as nuclear hormone receptors, nuclear respiratory factors, and muscle-specific transcription factors. PGC-1 alpha therefore constitutes one of the first and clearest examples in which biological programs are chiefly regulated by a transcriptional coactivator in response to environmental stimuli. Finally, PGC-1 alpha's control of energy homeostasis suggests that it could be a target for anti-obesity or diabetes drugs.
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Affiliation(s)
- Pere Puigserver
- Dana-Farber Cancer Institute and Department of Cell Biology, Harvard Medical School, Boston, Massachusetts 02115
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Portilla D, Dai G, McClure T, Bates L, Kurten R, Megyesi J, Price P, Li S. Alterations of PPARalpha and its coactivator PGC-1 in cisplatin-induced acute renal failure. Kidney Int 2002; 62:1208-18. [PMID: 12234291 DOI: 10.1111/j.1523-1755.2002.kid553.x] [Citation(s) in RCA: 113] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
BACKGROUND In this study we examined whether a recently characterized coactivator of Peroxisome proliferator activated receptor alpha (PPARalpha), Peroxisome proliferator activated receptor-gamma-coactivator-1 (PGC-1) plays a role in the regulation of fatty acid oxidation during cisplatin-induced nephrotoxicity. METHODS Studies in mouse kidneys used quantitative reverse transcription-polymerase chain reaction (RT-PCR) to measure peroxisomal acyl coenzyme A (acyl-CoA) and PGC-1 mRNA levels and in situ hybridization to localize PGC-1 mRNA. Studies in LLCPK1 cells used quantitative RT-PCR and biochemical assays to measure mRNA levels and enzyme activities of peroxisomal acyl-CoA, mitochondrial carnitine palmitoyl transferase (CPT) and PGC-1. Eletrophoretic mobility shift assays (EMSA) and Western blot analysis of nuclear extracts, and transient transfection of PGC-1 were used to examine the effect of cisplatin on PPARalpha-regulated fatty acid oxidation. RESULTS Cisplatin decreased mRNA levels of peroxisomal acyl-CoA enzyme in mouse kidney and also reduced the mRNA levels and enzyme activities of acyl-CoA and mitochondrial CPT-1 in LLCPK1 cells. DNA-protein binding studies demonstrated that exposure to cisplatin reduces PPARalpha/retinoid X receptor (RXRalpha) binding activity. Immunoblotting studies demonstrated that cisplatin had no effect on nuclear levels of PPARalpha or RXRalpha protein. In situ hybridization studies in mouse kidney demonstrated the localization of PGC-1 mRNA to proximal tubules and thick ascending limb of Henley (TALH) cells. Cisplatin diminished the expression of PGC-1 mRNA levels in mouse kidney and also in LLCPK1 cells. Transient expression of PGC-1 shows the nuclear localization of PGC-1 protein and increased PPARalpha transcriptional activity in LLCPK1 cells. CONCLUSIONS These results demonstrate that cisplatin deactivates PPARalpha by reducing its DNA binding activity and the availability of its tissue specific coactivator PGC-1.
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Affiliation(s)
- Didier Portilla
- Division of Nephrology, Departments of Internal Medicine and Physiology, University of Arkansas for Medical Sciences, 4301 W. Markham Street, Little Rock, AR 72205, USA.
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Iwahashi H, Yamagata K, Yoshiuchi I, Terasaki J, Yang Q, Fukui K, Ihara A, Zhu Q, Asakura T, Cao Y, Imagawa A, Namba M, Hanafusa T, Miyagawa JI, Matsuzawa Y. Thyroid hormone receptor interacting protein 3 (trip3) is a novel coactivator of hepatocyte nuclear factor-4alpha. Diabetes 2002; 51:910-4. [PMID: 11916906 DOI: 10.2337/diabetes.51.4.910] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
Mutations of the hepatocyte nuclear factor-4alpha (HNF-4alpha) gene are associated with a subtype of maturity-onset diabetes of the young (MODY1) that is characterized by impaired insulin secretion in response to a glucose load. HNF-4alpha, which is a transcription factor expressed in pancreatic beta-cells, plays an important role in regulating the expression of genes involved in glucose metabolism. Thus, cofactors that interact with HNF-4alpha and modify its transcriptional activity might also play an important role in regulating the metabolic pathways in pancreatic beta-cells, and the genes of such cofactors are plausible candidate genes for MODY. In the present study, we showed, using a yeast two-hybrid screening assay, that thyroid hormone receptor interacting protein 3 (Trip3) interacted with HNF-4alpha, and their interaction was confirmed by the glutathione S-transferase pull-down assay. Human Trip3 cDNA contained an open reading frame for a protein of 155 amino acids, and the gene was expressed in both pancreatic islets and MIN6 cells. Cotransfection experiments indicated that Trip3 could enhance (two- to threefold) the transcription activity of HNF-4alpha in COS-7 cells and MIN6 cells. These results suggest that Trip3 is a coactivator of HNF-4alpha. Mutation screening revealed that variation of the Trip3 gene is not a common cause of MODY/early-onset type 2 diabetes in Japanese individuals. Trip3 may play an important role in glucose metabolism by regulating the transcription activity of HNF-4alpha.
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Affiliation(s)
- Hiromi Iwahashi
- Department of Internal Medicine and Molecular Science, Graduate School of Medicine, Osaka University, Osaka, Japan
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Gómez-Ambrosi J, Frühbeck G, Martínez JA. Interactions between an alpha2-adrenergic antagonist and a beta3-adrenergic agonist on the expression of UCP2 and UCP3 in rats. J Physiol Biochem 2002; 58:17-23. [PMID: 12222743 DOI: 10.1007/bf03179834] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
Abstract
This experimental trial was devised to assess whether selective beta3-adrenergic receptor (AR) stimulation and simultaneous blockade of alpha2-AR would affect thermoregulation. With this purpose, the individual and combined administration of a beta-AR agonist, trecadrine, and an alpha2-AR antagonist, yohimbine, were evaluated. Yohimbine produced a marked decrease (p < 0.001) in body temperature one hour after administration (5 mg kg(-1), i.p.) and blocked the thermogenic effect of trecadrine (1 mg kg(-1), i.p.) when simultaneously administered. Uncoupling protein-2 expression in skeletal muscle was downregulated (p < 0.05) by trecadrine, while yohimbine had no effect. White adipose tissue UCP2 and muscle UCP3 were not modified by either trecadrine or yohimbine administration. Liver UCP2 mRNA expression was significantly decreased by yohimbine (p < 0.05). However, this downregulation does not seem to explain the reduction in temperature produced by yohimbine given the fact that trecadrine produced a similar downregulation of hepatic UCP2 (p < 0.05). The present work indicates that alpha2-AR antagonism blocks the thermogenic effects mediated by beta3-AR stimulation, contrary to our expectations, suggesting a possible interplay between both mechanisms. Moreover, these effects are not apparently explained by changes in UCP2 and UCP3.
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Affiliation(s)
- J Gómez-Ambrosi
- Departamento de Fisiología y Nutricion, Universidad de Navarra, Spain
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Yoon JC, Puigserver P, Chen G, Donovan J, Wu Z, Rhee J, Adelmant G, Stafford J, Kahn CR, Granner DK, Newgard CB, Spiegelman BM. Control of hepatic gluconeogenesis through the transcriptional coactivator PGC-1. Nature 2001; 413:131-8. [PMID: 11557972 DOI: 10.1038/35093050] [Citation(s) in RCA: 1409] [Impact Index Per Article: 61.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Blood glucose levels are maintained by the balance between glucose uptake by peripheral tissues and glucose secretion by the liver. Gluconeogenesis is strongly stimulated during fasting and is aberrantly activated in diabetes mellitus. Here we show that the transcriptional coactivator PGC-1 is strongly induced in liver in fasting mice and in three mouse models of insulin action deficiency: streptozotocin-induced diabetes, ob/ob genotype and liver insulin-receptor knockout. PGC-1 is induced synergistically in primary liver cultures by cyclic AMP and glucocorticoids. Adenoviral-mediated expression of PGC-1 in hepatocytes in culture or in vivo strongly activates an entire programme of key gluconeogenic enzymes, including phosphoenolpyruvate carboxykinase (PEPCK) and glucose-6-phosphatase, leading to increased glucose output. Full transcriptional activation of the PEPCK promoter requires coactivation of the glucocorticoid receptor and the liver-enriched transcription factor HNF-4alpha (hepatic nuclear factor-4alpha) by PGC-1. These results implicate PGC-1 as a key modulator of hepatic gluconeogenesis and as a central target of the insulin-cAMP axis in liver.
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Affiliation(s)
- J C Yoon
- Dana-Farber Cancer Institute and Department of Cell Biology, Harvard Medical School, Boston, Massachusetts 02115, USA
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