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Audano M, Ferrari A, Fiorino E, Kuenzl M, Caruso D, Mitro N, Crestani M, De Fabiani E. Energizing Genetics and Epi-genetics: Role in the Regulation of Mitochondrial Function. Curr Genomics 2015; 15:436-56. [PMID: 25646072 PMCID: PMC4311388 DOI: 10.2174/138920291506150106151119] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2014] [Revised: 11/11/2014] [Accepted: 11/18/2014] [Indexed: 12/15/2022] Open
Abstract
Energy metabolism and mitochondrial function hold a core position in cellular homeostasis. Oxidative metabolism is regulated at multiple levels, ranging from gene transcription to allosteric modulation. To accomplish the fine tuning of these multiple regulatory circuits, the nuclear and mitochondrial compartments are tightly and reciprocally controlled. The fact that nuclear encoded factors, PPARγ coactivator 1α and mitochondrial transcription factor A, play pivotal roles in the regulation of oxidative metabolism and mitochondrial biogenesis is paradigmatic of this crosstalk. Here we provide an updated survey of the genetic and epigenetic mechanisms involved in the control of energy metabolism and mitochondrial function. Chromatin dynamics highly depends on post-translational modifications occurring at specific amino acids in histone proteins and other factors associated to nuclear DNA. In addition to the well characterized enzymes responsible for histone methylation/demethylation and acetylation/deacetylation, other factors have gone on the "metabolic stage". This is the case of the new class of α-ketoglutarate-regulated demethylases (Jumonji C domain containing demethylases) and of the NAD+-dependent deacetylases, also known as sirtuins. Moreover, unexpected features of the machineries involved in mitochondrial DNA (mtDNA) replication and transcription, mitochondrial RNA processing and maturation have recently emerged. Mutations or defects of any component of these machineries profoundly affect mitochondrial activity and oxidative metabolism. Finally, recent evidences support the importance of mtDNA packaging in replication and transcription. These observations, along with the discovery that non-classical CpG islands present in mtDNA undergo methylation, indicate that epigenetics also plays a role in the regulation of the mitochondrial genome function.
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Affiliation(s)
- Matteo Audano
- Dipartimento di Scienze Farmacologiche e Biomolecolari, Università degli Studi di Milano, Italy
| | - Alessandra Ferrari
- Dipartimento di Scienze Farmacologiche e Biomolecolari, Università degli Studi di Milano, Italy
| | - Erika Fiorino
- Dipartimento di Scienze Farmacologiche e Biomolecolari, Università degli Studi di Milano, Italy
| | - Martin Kuenzl
- Dipartimento di Scienze Farmacologiche e Biomolecolari, Università degli Studi di Milano, Italy
| | - Donatella Caruso
- Dipartimento di Scienze Farmacologiche e Biomolecolari, Università degli Studi di Milano, Italy
| | - Nico Mitro
- Dipartimento di Scienze Farmacologiche e Biomolecolari, Università degli Studi di Milano, Italy
| | - Maurizio Crestani
- Dipartimento di Scienze Farmacologiche e Biomolecolari, Università degli Studi di Milano, Italy
| | - Emma De Fabiani
- Dipartimento di Scienze Farmacologiche e Biomolecolari, Università degli Studi di Milano, Italy
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52
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Blaauw B, Schiaffino S, Reggiani C. Mechanisms modulating skeletal muscle phenotype. Compr Physiol 2014; 3:1645-87. [PMID: 24265241 DOI: 10.1002/cphy.c130009] [Citation(s) in RCA: 155] [Impact Index Per Article: 15.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Mammalian skeletal muscles are composed of a variety of highly specialized fibers whose selective recruitment allows muscles to fulfill their diverse functional tasks. In addition, skeletal muscle fibers can change their structural and functional properties to perform new tasks or respond to new conditions. The adaptive changes of muscle fibers can occur in response to variations in the pattern of neural stimulation, loading conditions, availability of substrates, and hormonal signals. The new conditions can be detected by multiple sensors, from membrane receptors for hormones and cytokines, to metabolic sensors, which detect high-energy phosphate concentration, oxygen and oxygen free radicals, to calcium binding proteins, which sense variations in intracellular calcium induced by nerve activity, to load sensors located in the sarcomeric and sarcolemmal cytoskeleton. These sensors trigger cascades of signaling pathways which may ultimately lead to changes in fiber size and fiber type. Changes in fiber size reflect an imbalance in protein turnover with either protein accumulation, leading to muscle hypertrophy, or protein loss, with consequent muscle atrophy. Changes in fiber type reflect a reprogramming of gene transcription leading to a remodeling of fiber contractile properties (slow-fast transitions) or metabolic profile (glycolytic-oxidative transitions). While myonuclei are in postmitotic state, satellite cells represent a reserve of new nuclei and can be involved in the adaptive response.
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Affiliation(s)
- Bert Blaauw
- Department of Biomedical Sciences, University of Padova, Padova, Italy
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53
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Whole exome sequencing of insulinoma reveals recurrent T372R mutations in YY1. Nat Commun 2014; 4:2810. [PMID: 24326773 DOI: 10.1038/ncomms3810] [Citation(s) in RCA: 100] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2013] [Accepted: 10/23/2013] [Indexed: 12/24/2022] Open
Abstract
Functional pancreatic neuroendocrine tumours (PNETs) are mainly represented by insulinoma, which secrete insulin independent of glucose and cause hypoglycaemia. The major genetic alterations in sporadic insulinomas are still unknown. Here we identify recurrent somatic T372R mutations in YY1 by whole exome sequencing of 10 sporadic insulinomas. Further screening in 103 additional insulinomas reveals this hotspot mutation in 30% (34/113) of all tumours. T372R mutation alters the expression of YY1 target genes in insulinomas. Clinically, the T372R mutation is associated with the later onset of tumours. Genotyping of YY1, a target of mTOR inhibitors, may contribute to medical treatment of insulinomas. Our findings highlight the importance of YY1 in pancreatic β-cells and may provide therapeutic targets for PNETs.
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54
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Meynet O, Ricci JE. Caloric restriction and cancer: molecular mechanisms and clinical implications. Trends Mol Med 2014; 20:419-27. [PMID: 24916302 DOI: 10.1016/j.molmed.2014.05.001] [Citation(s) in RCA: 88] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2014] [Revised: 04/30/2014] [Accepted: 05/07/2014] [Indexed: 01/23/2023]
Abstract
Caloric restriction (CR) is currently the most robust environmental intervention known to increase healthy life and prolong lifespan in several models, from yeast to mice. Although the protective effect of CR on the incidence of cancer is well established, its impact on tumor cell responses to chemotherapeutic treatment is currently being investigated. Interestingly, the molecular mechanisms required to extend lifespan upon reduced food intake are being evaluated, and these mechanisms may offer new opportunities for therapeutic intervention. In addition, new findings suggest a beneficial effect of CR in enhancing the efficiency of tumor cell killing by chemotherapeutic drugs and inducing an anticancer immune response.
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Affiliation(s)
- Ophélie Meynet
- Inserm, U1065, Centre Méditerranéen de Médecine Moléculaire (C3M), Équipe "Contrôle Métabolique des Morts Cellulaires", 06204 Cedex 3, Nice, France; Université de Nice Sophia-Antipolis, Faculté de Médecine, 06100, Nice, France
| | - Jean-Ehrland Ricci
- Inserm, U1065, Centre Méditerranéen de Médecine Moléculaire (C3M), Équipe "Contrôle Métabolique des Morts Cellulaires", 06204 Cedex 3, Nice, France; Université de Nice Sophia-Antipolis, Faculté de Médecine, 06100, Nice, France; Centre Hospitalier Universitaire de Nice, Département d'Anesthésie Réanimation, 06204 Cedex 3, Nice, France.
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55
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Soares RJ, Cagnin S, Chemello F, Silvestrin M, Musaro A, De Pitta C, Lanfranchi G, Sandri M. Involvement of microRNAs in the regulation of muscle wasting during catabolic conditions. J Biol Chem 2014; 289:21909-25. [PMID: 24891504 PMCID: PMC4139209 DOI: 10.1074/jbc.m114.561845] [Citation(s) in RCA: 113] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Loss of muscle proteins and the consequent weakness has important clinical consequences in diseases such as cancer, diabetes, chronic heart failure, and in aging. In fact, excessive proteolysis causes cachexia, accelerates disease progression, and worsens life expectancy. Muscle atrophy involves a common pattern of transcriptional changes in a small subset of genes named atrophy-related genes or atrogenes. Whether microRNAs play a role in the atrophy program and muscle loss is debated. To understand the involvement of miRNAs in atrophy we performed miRNA expression profiling of mouse muscles under wasting conditions such as fasting, denervation, diabetes, and cancer cachexia. We found that the miRNA signature is peculiar of each catabolic condition. We then focused on denervation and we revealed that changes in transcripts and microRNAs expression did not occur simultaneously but were shifted. Indeed, whereas transcriptional control of the atrophy-related genes peaks at 3 days, changes of miRNA expression maximized at 7 days after denervation. Among the different miRNAs, microRNA-206 and -21 were the most induced in denervated muscles. We characterized their pattern of expression and defined their role in muscle homeostasis. Indeed, in vivo gain and loss of function experiments revealed that miRNA-206 and miRNA-21 were sufficient and required for atrophy program. In silico and in vivo approaches identified transcription factor YY1 and the translational initiator factor eIF4E3 as downstream targets of these miRNAs. Thus miRNAs are important for fine-tuning the atrophy program and their modulation can be a novel potential therapeutic approach to counteract muscle loss and weakness in catabolic conditions.
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Affiliation(s)
- Ricardo José Soares
- From the Dulbecco Telethon Institute, Venetian Institute of Molecular Medicine, 35129 Padova, Italy, the Ph.D. Programme in Experimental Biology and Biomedicine, Center for Neuroscience and Cell Biology, University of Coimbra, 3004-517 Coimbra, Portugal
| | - Stefano Cagnin
- the Department of Biology and CRIBI Biotechnology Centre, University of Padova, 35121 Padova, Italy
| | - Francesco Chemello
- the Department of Biology and CRIBI Biotechnology Centre, University of Padova, 35121 Padova, Italy
| | - Matteo Silvestrin
- the Department of Biology and CRIBI Biotechnology Centre, University of Padova, 35121 Padova, Italy
| | - Antonio Musaro
- the DAHFMO-Unit of Histology and Medical Embryology, Sapienza University, 00161 Roma, Italy, and
| | - Cristiano De Pitta
- the Department of Biology and CRIBI Biotechnology Centre, University of Padova, 35121 Padova, Italy,
| | - Gerolamo Lanfranchi
- the Department of Biology and CRIBI Biotechnology Centre, University of Padova, 35121 Padova, Italy,
| | - Marco Sandri
- From the Dulbecco Telethon Institute, Venetian Institute of Molecular Medicine, 35129 Padova, Italy, the Department of Biomedical Sciences and the Institute of Neuroscience, Consiglio Nazionale delle Ricerche, 35121 Padova, Italy, the Telethon Institute of Genetics and Medicine (TIGEM), 80131 Napoli, Italy
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56
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Abstract
The intestinal stem cell fuels the highest rate of tissue turnover in the body and has been implicated in intestinal disease and cancer; understanding the regulatory mechanisms controlling intestinal stem cell physiology is of great importance. Here, we provide evidence that the transcription factor YY1 is essential for intestinal stem cell renewal. We observe that YY1 loss skews normal homeostatic cell turnover, with an increase in proliferating crypt cells and a decrease in their differentiated villous progeny. Increased crypt cell numbers come at the expense of Lgr5(+) stem cells. On YY1 deletion, Lgr5(+) cells accelerate their commitment to the differentiated population, exhibit increased levels of apoptosis, and fail to maintain stem cell renewal. Loss of Yy1 in the intestine is ultimately fatal. Mechanistically, YY1 seems to play a role in stem cell energy metabolism, with mitochondrial complex I genes bound directly by YY1 and their transcript levels decreasing on YY1 loss. These unappreciated YY1 functions broaden our understanding of metabolic regulation in intestinal stem cell homeostasis.
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57
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Hançer NJ, Qiu W, Cherella C, Li Y, Copps KD, White MF. Insulin and metabolic stress stimulate multisite serine/threonine phosphorylation of insulin receptor substrate 1 and inhibit tyrosine phosphorylation. J Biol Chem 2014; 289:12467-84. [PMID: 24652289 PMCID: PMC4007441 DOI: 10.1074/jbc.m114.554162] [Citation(s) in RCA: 69] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2014] [Revised: 03/18/2014] [Indexed: 12/27/2022] Open
Abstract
IRS1 and IRS2 are key substrates of the insulin receptor tyrosine kinase. Mass spectrometry reveals more than 50 phosphorylated IRS1 serine and threonine residues (Ser(P)/Thr(P) residues) in IRS1 from insulin-stimulated cells or human tissues. We investigated a subset of IRS1 Ser(P)/Thr(P) residues using a newly developed panel of 25 phospho-specific monoclonal antibodies (αpS/TmAb(Irs1)). CHO cells overexpressing the human insulin receptor and rat IRS1 were stimulated with insulin in the absence or presence of inhibitors of the PI3K → Akt → mechanistic target of rapamycin (mTOR) → S6 kinase or MEK pathways. Nearly all IRS1 Ser(P)/Thr(P) residues were stimulated by insulin and significantly suppressed by PI3K inhibition; fewer were suppressed by Akt or mTOR inhibition, and none were suppressed by MEK inhibition. Insulin-stimulated Irs1 tyrosine phosphorylation (Tyr(P)(Irs1)) was enhanced by inhibition of the PI3K → Akt → mTOR pathway and correlated with decreased Ser(P)-302(Irs1), Ser(P)-307(Irs1), Ser(P)-318(Irs1), Ser(P)-325(Irs1), and Ser(P)-346(Irs1). Metabolic stress modeled by anisomycin, thapsigargin, or tunicamycin increased many of the same Ser(P)/Thr(P) residues as insulin, some of which (Ser(P)-302(Irs1), Ser(P)-307(Irs1), and four others) correlated significantly with impaired insulin-stimulated Tyr(P)(Irs1). Thus, IRS1 Ser(P)/Thr(P) is an integrated response to insulin stimulation and metabolic stress, which associates with reduced Tyr(P)(Irs1) in CHO(IR)/IRS1 cells.
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Affiliation(s)
- Nancy J. Hançer
- From the Division of Endocrinology, Department of Medicine, Boston Children's Hospital, Harvard Medical School, Boston, Massachusetts 02115
| | - Wei Qiu
- From the Division of Endocrinology, Department of Medicine, Boston Children's Hospital, Harvard Medical School, Boston, Massachusetts 02115
| | - Christine Cherella
- From the Division of Endocrinology, Department of Medicine, Boston Children's Hospital, Harvard Medical School, Boston, Massachusetts 02115
| | - Yedan Li
- From the Division of Endocrinology, Department of Medicine, Boston Children's Hospital, Harvard Medical School, Boston, Massachusetts 02115
| | - Kyle D. Copps
- From the Division of Endocrinology, Department of Medicine, Boston Children's Hospital, Harvard Medical School, Boston, Massachusetts 02115
| | - Morris F. White
- From the Division of Endocrinology, Department of Medicine, Boston Children's Hospital, Harvard Medical School, Boston, Massachusetts 02115
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58
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Tabata M, Rodgers JT, Hall JA, Lee Y, Jedrychowski MP, Gygi SP, Puigserver P. Cdc2-like kinase 2 suppresses hepatic fatty acid oxidation and ketogenesis through disruption of the PGC-1α and MED1 complex. Diabetes 2014; 63:1519-32. [PMID: 24458359 PMCID: PMC3994960 DOI: 10.2337/db13-1304] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Hepatic ketogenesis plays an important role in catabolism of fatty acids during fasting along with dietary lipid overload, but the mechanisms regulating this process remain poorly understood. Here, we show that Cdc2-like kinase 2 (Clk2) suppresses fatty acid oxidation and ketone body production during diet-induced obesity. In lean mice, hepatic Clk2 protein is very low during fasting and strongly increased during feeding; however, in diet-induced obese mice, Clk2 protein remains elevated through both fed and fasted states. Liver-specific Clk2 knockout mice fed a high-fat diet exhibit increased fasting levels of blood ketone bodies, reduced respiratory exchange ratio, and increased gene expression of fatty acid oxidation and ketogenic pathways. This effect of Clk2 is cell-autonomous, because manipulation of Clk2 in hepatocytes controls genes and rates of fatty acid utilization. Clk2 phosphorylation of peroxisome proliferator-activated receptor γ coactivator (PGC-1α) disrupts its interaction with Mediator subunit 1, which leads to a suppression of PGC-1α activation of peroxisome proliferator-activated receptor α target genes in fatty acid oxidation and ketogenesis. These data demonstrate the importance of Clk2 in the regulation of fatty acid metabolism in vivo and suggest that inhibition of hepatic Clk2 could provide new therapies in the treatment of fatty liver disease.
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Affiliation(s)
- Mitsuhisa Tabata
- Department of Cancer Biology, Dana-Farber Cancer Institute, Harvard Medical School, Boston, MA
- Department of Cell Biology, Harvard Medical School, Boston, MA
| | - Joseph T. Rodgers
- Department of Cancer Biology, Dana-Farber Cancer Institute, Harvard Medical School, Boston, MA
- Department of Cell Biology, Harvard Medical School, Boston, MA
| | - Jessica A. Hall
- Department of Cancer Biology, Dana-Farber Cancer Institute, Harvard Medical School, Boston, MA
- Department of Cell Biology, Harvard Medical School, Boston, MA
| | - Yoonjin Lee
- Department of Cancer Biology, Dana-Farber Cancer Institute, Harvard Medical School, Boston, MA
- Department of Cell Biology, Harvard Medical School, Boston, MA
| | | | - Steven P. Gygi
- Department of Cell Biology, Harvard Medical School, Boston, MA
| | - Pere Puigserver
- Department of Cancer Biology, Dana-Farber Cancer Institute, Harvard Medical School, Boston, MA
- Department of Cell Biology, Harvard Medical School, Boston, MA
- Corresponding author: Pere Puigserver,
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59
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Lu Y, Belin S, He Z. Signaling regulations of neuronal regenerative ability. Curr Opin Neurobiol 2014; 27:135-42. [PMID: 24727245 DOI: 10.1016/j.conb.2014.03.007] [Citation(s) in RCA: 81] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2013] [Revised: 03/13/2014] [Accepted: 03/14/2014] [Indexed: 10/25/2022]
Abstract
Different from physiological axon growth during development, a major limiting factor for successful axon regeneration is the poor intrinsic regenerative capacity in mature neurons in the adult mammalian central nervous system (CNS). Recent studies identified several molecular pathways, including PTEN/mTOR, Jak/STAT, DLK/JNK, providing important probes in investigating the mechanisms by which the regenerative ability is regulated. This review will summarize these recent findings and speculate their implications.
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Affiliation(s)
- Yi Lu
- Department of Neurosurgery, Brigham and Women's Hospital, Harvard Medical School, Boston, MA 02115, USA; F.M. Kirby Neurobiology Center, Boston Children's Hospital, and Department of Neurology, Harvard Medical School, Boston, MA 02115, USA
| | - Stéphane Belin
- F.M. Kirby Neurobiology Center, Boston Children's Hospital, and Department of Neurology, Harvard Medical School, Boston, MA 02115, USA
| | - Zhigang He
- F.M. Kirby Neurobiology Center, Boston Children's Hospital, and Department of Neurology, Harvard Medical School, Boston, MA 02115, USA.
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60
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Dyle MC, Ebert SM, Cook DP, Kunkel SD, Fox DK, Bongers KS, Bullard SA, Dierdorff JM, Adams CM. Systems-based discovery of tomatidine as a natural small molecule inhibitor of skeletal muscle atrophy. J Biol Chem 2014; 289:14913-24. [PMID: 24719321 PMCID: PMC4031541 DOI: 10.1074/jbc.m114.556241] [Citation(s) in RCA: 101] [Impact Index Per Article: 10.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Skeletal muscle atrophy is a common and debilitating condition that lacks an effective therapy. To address this problem, we used a systems-based discovery strategy to search for a small molecule whose mRNA expression signature negatively correlates to mRNA expression signatures of human skeletal muscle atrophy. This strategy identified a natural small molecule from tomato plants, tomatidine. Using cultured skeletal myotubes from both humans and mice, we found that tomatidine stimulated mTORC1 signaling and anabolism, leading to accumulation of protein and mitochondria, and ultimately, cell growth. Furthermore, in mice, tomatidine increased skeletal muscle mTORC1 signaling, reduced skeletal muscle atrophy, enhanced recovery from skeletal muscle atrophy, stimulated skeletal muscle hypertrophy, and increased strength and exercise capacity. Collectively, these results identify tomatidine as a novel small molecule inhibitor of muscle atrophy. Tomatidine may have utility as a therapeutic agent or lead compound for skeletal muscle atrophy.
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Affiliation(s)
- Michael C Dyle
- From the Departments of Internal Medicine and Molecular Physiology and Biophysics, and Fraternal Order of Eagles Diabetes Research Center, Roy J. and Lucille A. Carver College of Medicine, University of Iowa, Iowa City, Iowa 52242 and
| | - Scott M Ebert
- From the Departments of Internal Medicine and Molecular Physiology and Biophysics, and Fraternal Order of Eagles Diabetes Research Center, Roy J. and Lucille A. Carver College of Medicine, University of Iowa, Iowa City, Iowa 52242 and
| | - Daniel P Cook
- From the Departments of Internal Medicine and Molecular Physiology and Biophysics, and Fraternal Order of Eagles Diabetes Research Center, Roy J. and Lucille A. Carver College of Medicine, University of Iowa, Iowa City, Iowa 52242 and
| | - Steven D Kunkel
- From the Departments of Internal Medicine and Molecular Physiology and Biophysics, and Fraternal Order of Eagles Diabetes Research Center, Roy J. and Lucille A. Carver College of Medicine, University of Iowa, Iowa City, Iowa 52242 and
| | - Daniel K Fox
- From the Departments of Internal Medicine and Molecular Physiology and Biophysics, and Fraternal Order of Eagles Diabetes Research Center, Roy J. and Lucille A. Carver College of Medicine, University of Iowa, Iowa City, Iowa 52242 and
| | - Kale S Bongers
- From the Departments of Internal Medicine and Molecular Physiology and Biophysics, and Fraternal Order of Eagles Diabetes Research Center, Roy J. and Lucille A. Carver College of Medicine, University of Iowa, Iowa City, Iowa 52242 and
| | - Steven A Bullard
- From the Departments of Internal Medicine and Molecular Physiology and Biophysics, and Fraternal Order of Eagles Diabetes Research Center, Roy J. and Lucille A. Carver College of Medicine, University of Iowa, Iowa City, Iowa 52242 and the Iowa City Veterans Affairs Medical Center, Iowa City, Iowa 52246
| | - Jason M Dierdorff
- From the Departments of Internal Medicine and Molecular Physiology and Biophysics, and Fraternal Order of Eagles Diabetes Research Center, Roy J. and Lucille A. Carver College of Medicine, University of Iowa, Iowa City, Iowa 52242 and
| | - Christopher M Adams
- From the Departments of Internal Medicine and Molecular Physiology and Biophysics, and Fraternal Order of Eagles Diabetes Research Center, Roy J. and Lucille A. Carver College of Medicine, University of Iowa, Iowa City, Iowa 52242 and the Iowa City Veterans Affairs Medical Center, Iowa City, Iowa 52246
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61
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Neguembor MV, Jothi M, Gabellini D. Long noncoding RNAs, emerging players in muscle differentiation and disease. Skelet Muscle 2014; 4:8. [PMID: 24685002 PMCID: PMC3973619 DOI: 10.1186/2044-5040-4-8] [Citation(s) in RCA: 83] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2014] [Accepted: 03/11/2014] [Indexed: 12/18/2022] Open
Abstract
The vast majority of the mammalian genome is transcribed giving rise to many different types of noncoding RNAs. Among them, long noncoding RNAs are the most numerous and functionally versatile class. Indeed, the lncRNA repertoire might be as rich as the proteome. LncRNAs have emerged as key regulators of gene expression at multiple levels. They play important roles in the regulation of development, differentiation and maintenance of cell identity and they also contribute to disease. In this review, we present recent advances in the biology of lncRNAs in muscle development and differentiation. We will also discuss the contribution of lncRNAs to muscle disease with a particular focus on Duchenne and facioscapulohumeral muscular dystrophies.
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Affiliation(s)
| | | | - Davide Gabellini
- Dulbecco Telethon Institute at San Raffaele Scientific Institute, Division of Regenerative Medicine, Stem cells, and Gene therapy, DIBIT2, 5A3, Via Olgettina 58, 20132 Milano, Italy.
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62
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Zarrouki B, Benterki I, Fontés G, Peyot ML, Seda O, Prentki M, Poitout V. Epidermal growth factor receptor signaling promotes pancreatic β-cell proliferation in response to nutrient excess in rats through mTOR and FOXM1. Diabetes 2014; 63:982-93. [PMID: 24194502 PMCID: PMC3931394 DOI: 10.2337/db13-0425] [Citation(s) in RCA: 43] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
The cellular and molecular mechanisms underpinning the compensatory increase in β-cell mass in response to insulin resistance are essentially unknown. We previously reported that a 72-h coinfusion of glucose and Intralipid (GLU+IL) induces insulin resistance and a marked increase in β-cell proliferation in 6-month-old, but not in 2-month-old, Wistar rats. The aim of the current study was to identify the mechanisms underlying nutrient-induced β-cell proliferation in this model. A transcriptomic analysis identified a central role for the forkhead transcription factor FOXM1 and its targets, and for heparin-binding epidermal growth factor (EGF)-like growth factor (HB-EGF), a ligand of the EGF receptor (EGFR), in nutrient-induced β-cell proliferation. Phosphorylation of ribosomal S6 kinase, a mammalian target of rapamycin (mTOR) target, was increased in islets from GLU+IL-infused 6-month-old rats. HB-EGF induced proliferation of insulin-secreting MIN6 cells and isolated rat islets, and this effect was blocked in MIN6 cells by the EGFR inhibitor AG1478 or the mTOR inhibitor rapamycin. Coinfusion of either AG1478 or rapamycin blocked the increase in FOXM1 signaling, β-cell proliferation, and β-cell mass and size in response to GLU+IL infusion in 6-month-old rats. We conclude that chronic nutrient excess promotes β-cell mass expansion via a pathway that involves EGFR signaling, mTOR activation, and FOXM1-mediated cell proliferation.
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Affiliation(s)
- Bader Zarrouki
- Montreal Diabetes Research Center, University of Montréal, Montréal, Québec, Canada
- University of Montréal Hospital Research Centre, Montréal, Québec, Canada
- Department of Medicine, University of Montréal, Montréal, Québec, Canada
| | - Isma Benterki
- Montreal Diabetes Research Center, University of Montréal, Montréal, Québec, Canada
- University of Montréal Hospital Research Centre, Montréal, Québec, Canada
- Department of Biochemistry, University of Montréal, Montréal, Québec, Canada
| | - Ghislaine Fontés
- Montreal Diabetes Research Center, University of Montréal, Montréal, Québec, Canada
- University of Montréal Hospital Research Centre, Montréal, Québec, Canada
| | - Marie-Line Peyot
- Montreal Diabetes Research Center, University of Montréal, Montréal, Québec, Canada
- University of Montréal Hospital Research Centre, Montréal, Québec, Canada
| | - Ondrej Seda
- Montreal Diabetes Research Center, University of Montréal, Montréal, Québec, Canada
- University of Montréal Hospital Research Centre, Montréal, Québec, Canada
| | - Marc Prentki
- Montreal Diabetes Research Center, University of Montréal, Montréal, Québec, Canada
- University of Montréal Hospital Research Centre, Montréal, Québec, Canada
- Department of Biochemistry, University of Montréal, Montréal, Québec, Canada
- Department of Nutrition, University of Montréal, Montréal, Québec, Canada
| | - Vincent Poitout
- Montreal Diabetes Research Center, University of Montréal, Montréal, Québec, Canada
- University of Montréal Hospital Research Centre, Montréal, Québec, Canada
- Department of Medicine, University of Montréal, Montréal, Québec, Canada
- Department of Biochemistry, University of Montréal, Montréal, Québec, Canada
- Department of Nutrition, University of Montréal, Montréal, Québec, Canada
- Corresponding author: Vincent Poitout,
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63
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Greene NP, Nilsson MI, Washington TA, Lee DE, Brown LA, Papineau AM, Shimkus KL, Greene ES, Crouse SF, Fluckey JD. Impaired exercise-induced mitochondrial biogenesis in the obese Zucker rat, despite PGC-1α induction, is due to compromised mitochondrial translation elongation. Am J Physiol Endocrinol Metab 2014; 306:E503-11. [PMID: 24398401 DOI: 10.1152/ajpendo.00671.2013] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Previously, we demonstrated that high-volume resistance exercise stimulates mitochondrial protein synthesis (a measure of mitochondrial biogenesis) in lean but not obese Zucker rats. Here, we examined factors involved in regulating mitochondrial biogenesis in the same animals. PGC-1α was 45% higher following exercise in obese but not lean animals compared with sedentary counterparts. Interestingly, exercised animals demonstrated greater PPARδ protein in both lean (47%) and obese (>200%) animals. AMPK phosphorylation (300%) and CPT-I protein (30%) were elevated by exercise in lean animals only, indicating improved substrate availability/flux. These findings suggest that, despite PGC-1α induction, obese animals were resistant to exercise-induced synthesis of new mitochondrial and oxidative protein. Previously, we reported that most anabolic processes are upregulated in these same obese animals regardless of exercise, so the purpose of this study was to assess specific factors associated with the mitochondrial genome as possible culprits for impaired mitochondrial biogenesis. Exercise resulted in higher mRNA contents of mitochondrial transcription factor A (∼50% in each phenotype) and mitochondrial translation initiation factor 2 (31 and 47% in lean and obese, respectively). However, mitochondrial translation elongation factor-Tu mRNA was higher following exercise in lean animals only (40%), suggesting aberrant regulation of mitochondrial translation elongation as a possible culprit in impaired mitochondrial biogenesis following exercise with obesity.
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Affiliation(s)
- Nicholas P Greene
- Applied Exercise Science Laboratory, Department of Health and Kinesiology, Texas A & M University, College Station, Texas
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Shivaswamy V, Bennett RG, Clure CC, Ottemann B, Davis JS, Larsen JL, Hamel FG. Tacrolimus and sirolimus have distinct effects on insulin signaling in male and female rats. Transl Res 2014; 163:221-31. [PMID: 24361102 DOI: 10.1016/j.trsl.2013.12.002] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/25/2013] [Revised: 11/14/2013] [Accepted: 12/01/2013] [Indexed: 10/25/2022]
Abstract
Although the contribution of the immunosuppressants tacrolimus (TAC) and sirolimus (SIR) to the development of posttransplant diabetes mellitus (PTDM) are being increasingly recognized, the mechanisms of immunosuppressant-induced hyperglycemia are unclear. SIR induces insulin resistance predominantly, but is associated with β-cell dysfunction in rodents. TAC affects islet function but is associated with worsening insulin sensitivity in a few, and improvement in some, clinical studies. We sought to clarify the contributions of TAC and SIR to insulin resistance and islet function. Four groups of male and female Sprague-Dawley rats received TAC, SIR, TAC and SIR, or control for 2 weeks. All rats were administered an oral glucose challenge at the end of treatment. Half the groups were sacrificed 10 minutes after administration of regular insulin whereas the other half did not receive insulin before sacrifice. Liver, pancreas, fat, and muscle were harvested subsequently. Quantification of Western blots revealed that SIR and TAC plus SIR suppressed the phospho-Akt (pAkt)-to-Akt ratios in liver, muscle, and fat compared with control, regardless of sex. TAC alone did not impair the pAkt-to-Akt ratios in any of the tissues in male and female rats. β-Cell mass was reduced significantly after TAC treatment in male rats. SIR did not affect β-cell mass, regardless of sex. Our study demonstrated very clearly that SIR impairs insulin signaling, without any effect on β-cell mass, and TAC does not impair insulin signaling but reduces β-cell mass. Our efforts are key to understanding the mechanisms of immunosuppressant-induced hyperglycemia and to tailoring treatments for PTDM.
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Affiliation(s)
- Vijay Shivaswamy
- VA Nebraska-Western Iowa Health Care System, University of Nebraska Medical Center, Omaha, Neb; Department of Internal Medicine, University of Nebraska Medical Center, Omaha, Neb.
| | - Robert G Bennett
- VA Nebraska-Western Iowa Health Care System, University of Nebraska Medical Center, Omaha, Neb; Department of Internal Medicine, University of Nebraska Medical Center, Omaha, Neb; Biochemistry and Molecular Biology, University of Nebraska Medical Center, Omaha, Neb
| | - Cara C Clure
- Department of Internal Medicine, University of Nebraska Medical Center, Omaha, Neb
| | - Brendan Ottemann
- Department of Internal Medicine, University of Nebraska Medical Center, Omaha, Neb
| | - John S Davis
- VA Nebraska-Western Iowa Health Care System, University of Nebraska Medical Center, Omaha, Neb; Biochemistry and Molecular Biology, University of Nebraska Medical Center, Omaha, Neb; Obstetrics and Gynecology, University of Nebraska Medical Center, Omaha, Neb
| | - Jennifer L Larsen
- VA Nebraska-Western Iowa Health Care System, University of Nebraska Medical Center, Omaha, Neb; Department of Internal Medicine, University of Nebraska Medical Center, Omaha, Neb
| | - Frederick G Hamel
- VA Nebraska-Western Iowa Health Care System, University of Nebraska Medical Center, Omaha, Neb; Department of Internal Medicine, University of Nebraska Medical Center, Omaha, Neb
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Palikaras K, Tavernarakis N. Mitochondrial homeostasis: the interplay between mitophagy and mitochondrial biogenesis. Exp Gerontol 2014; 56:182-8. [PMID: 24486129 DOI: 10.1016/j.exger.2014.01.021] [Citation(s) in RCA: 291] [Impact Index Per Article: 29.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2013] [Revised: 01/15/2014] [Accepted: 01/20/2014] [Indexed: 12/29/2022]
Abstract
Mitochondria are highly dynamic organelles and their proper function is crucial for the maintenance of cellular homeostasis. Mitochondrial biogenesis and mitophagy are two pathways that regulate mitochondrial content and metabolism preserving homeostasis. The tight regulation between these opposing processes is essential for cellular adaptation in response to cellular metabolic state, stress and other intracellular or environmental signals. Interestingly, imbalance between mitochondrial proliferation and degradation process results in progressive development of numerous pathologic conditions. Here we review recent studies that highlight the intricate interplay between mitochondrial biogenesis and mitophagy, mainly focusing on the molecular mechanisms that govern the coordination of these processes and their involvement in age-related pathologies and ageing.
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Affiliation(s)
- Konstantinos Palikaras
- Institute of Molecular Biology and Biotechnology, Foundation for Research and Technology-Hellas, Heraklion 71110, Crete, Greece
| | - Nektarios Tavernarakis
- Institute of Molecular Biology and Biotechnology, Foundation for Research and Technology-Hellas, Heraklion 71110, Crete, Greece.
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Verdeguer F, Blättler SM, Cunningham JT, Hall JA, Chim H, Puigserver P. Decreased genetic dosage of hepatic Yin Yang 1 causes diabetic-like symptoms. Mol Endocrinol 2014; 28:308-16. [PMID: 24467246 DOI: 10.1210/me.2013-1173] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
Insulin sensitivity in liver is characterized by the ability of insulin to efficiently inhibit glucose production and fatty acid oxidation as well as promote de novo lipid biosynthesis. Specific dysregulation of glucose and lipid metabolism in liver is sufficient to cause insulin resistance and type 2 diabetes; this is seen by a selective inability of insulin to suppress glucose production while remaining insulin-sensitive to de novo lipid biosynthesis. We have previously shown that the transcription factor Yin Yang 1 (YY1) controls diabetic-linked glucose and lipid metabolism gene sets in skeletal muscle, but whether liver YY1-targeted metabolic genes impact a diabetic phenotype is unknown. Here we show that decreased genetic dosage of YY1 in liver causes insulin resistance, hepatic lipid accumulation, and dyslipidemia. Indeed, YY1 liver-specific heterozygous mice exhibit blunted activation of hepatic insulin signaling in response to insulin. Mechanistically, YY1, through direct recruitment to promoters, functions as a suppressor of genes encoding for metabolic enzymes of the gluconeogenic and lipogenic pathways and as an activator of genes linked to fatty acid oxidation. These counterregulatory transcriptional activities make targeting hepatic YY1 an attractive approach for treating insulin-resistant diabetes.
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Affiliation(s)
- Francisco Verdeguer
- Department of Cancer Biology (F.V., S.M.B., J.T.C., J.A.H., H.C., P.P.), Dana-Farber Cancer Institute, and Department of Cell Biology (F.V., S.M.B., J.T.C., J.A.H., H.C., P.P.), Harvard Medical School, Boston, Massachusetts 02115
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67
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Lu Y, Ma Z, Zhang Z, Xiong X, Wang X, Zhang H, Shi G, Xia X, Ning G, Li X. Yin Yang 1 promotes hepatic steatosis through repression of farnesoid X receptor in obese mice. Gut 2014; 63:170-8. [PMID: 23348961 DOI: 10.1136/gutjnl-2012-303150] [Citation(s) in RCA: 75] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
BACKGROUND Non-alcoholic fatty liver disease (NAFLD) is characterised by accumulation of excessive triglycerides in the liver. Obesity is usually associated with NAFLD through an unknown mechanism. OBJECTIVE To investigate the roles of Yin Yang 1 (YY1) in the progression of obesity-associated hepatosteatosis. METHODS Expression levels of hepatic YY1 were identified by microarray analysis in high-fat-diet (HFD)-induced obese mice. Liver triglyceride metabolism was analysed in mice with YY1 overexpression and suppression. RESULTS YY1 expression was markedly upregulated in HFD-induced obese mice and NAFLD patients. Overexpression of YY1 in healthy mice promoted hepatosteatosis under high-fat dietary conditions, whereas liver-specific ablation of YY1 using adenoviral shRNA ameliorated triglyceride accumulation in obese mice. At the molecular level, YY1 suppressed farnesoid X receptor (FXR) expression through binding to the YY1 responsive element at intron 1 of the FXR gene. CONCLUSIONS These findings indicate that YY1 plays a crucial role in obesity-associated hepatosteatosis, through repression of FXR expression.
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Affiliation(s)
- Yan Lu
- Department of Endocrine and Metabolic Diseases, Shanghai Institute of Endocrinology and Metabolism, Ruijin Hospital, Shanghai Jiao Tong University School of Medicine, , Shanghai, China
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Legry V, Schaap FG, Delire B, Horsmans Y, Leclercq IA. Yin Yang 1 and farnesoid X receptor: a balancing act in non-alcoholic fatty liver disease? Gut 2014; 63:1-2. [PMID: 23474422 DOI: 10.1136/gutjnl-2012-304338] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Affiliation(s)
- Vanessa Legry
- Laboratory of Hepato-Gastroenterology, Institut de Recherche Expérimentale et Clinique, Université catholique de Louvain, , Brussels, Belgium
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69
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Korean mistletoe (Viscum album coloratum) extract extends the lifespan of nematodes and fruit flies. Biogerontology 2013; 15:153-64. [DOI: 10.1007/s10522-013-9487-7] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2013] [Accepted: 12/06/2013] [Indexed: 12/20/2022]
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Abstract
Caloric restriction is the most reliable intervention to prevent age-related disorders and extend lifespan. The reduction of calories by 10-30% compared to an ad libitum diet is known to extend the longevity of various species from yeast to rodents. The underlying mechanisms by which the benefits of caloric restriction occur have not yet been clearly defined. However, many studies are being conducted in an attempt to elucidate these mechanisms, and there are indications that the benefits of caloric restriction are related to alteration of the metabolic rate and the accumulation of reactive oxygen species. During molecular signaling, insulin/insulin-like growth factor signaling, target of rapamycin pathway, adenosine monophosphate activated protein kinase signaling, and Sirtuin are focused as underlying pathways that mediate the benefits of caloric restriction. Here, we will review the current status of caloric restriction.
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Affiliation(s)
- Shin-Hae Lee
- Department of Biological Sciences, Inha University, Incheon 402-751, Korea
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71
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Genome-wide survey by ChIP-seq reveals YY1 regulation of lincRNAs in skeletal myogenesis. EMBO J 2013; 32:2575-88. [PMID: 23942234 DOI: 10.1038/emboj.2013.182] [Citation(s) in RCA: 115] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2012] [Accepted: 07/09/2013] [Indexed: 11/09/2022] Open
Abstract
Skeletal muscle differentiation is orchestrated by a network of transcription factors, epigenetic regulators, and non-coding RNAs. The transcription factor Yin Yang 1 (YY1) silences multiple target genes in myoblasts (MBs) by recruiting Ezh2 (Enhancer of Zeste Homologue2). To elucidate genome-wide YY1 binding in MBs, we performed chromatin immunoprecipitation (ChIP)-seq and found 1820 specific binding sites in MBs with a large portion residing in intergenic regions. Detailed analysis demonstrated that YY1 acts as an activator for many loci in addition to its known repressor function. No significant co-occupancy was found between YY1 and Ezh2, suggesting an additional Ezh2-independent function for YY1 in MBs. Further analysis of intergenic binding sites showed that YY1 potentially regulates dozens of large intergenic non-coding RNAs (lincRNAs), whose function in myogenesis is underexplored. We characterized a novel muscle-associated lincRNA (Yam-1) that is positively regulated by YY1. Yam-1 is downregulated upon differentiation and acts as an inhibitor of myogenesis. We demonstrated that Yam-1 functions through in cis regulation of miR-715, which in turn targets Wnt7b. Our findings not only provide the first genome-wide picture of YY1 association in muscle cells, but also uncover the functional role of lincRNA Yam-1.
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72
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Lamming DW, Ye L, Astle CM, Baur JA, Sabatini DM, Harrison DE. Young and old genetically heterogeneous HET3 mice on a rapamycin diet are glucose intolerant but insulin sensitive. Aging Cell 2013; 12:712-8. [PMID: 23648089 DOI: 10.1111/acel.12097] [Citation(s) in RCA: 53] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 04/24/2013] [Indexed: 11/28/2022] Open
Abstract
Rapamycin, an inhibitor of the mechanistic target of rapamycin (mTOR) signaling pathway, extends the life span of yeast, worms, flies, and mice. Interventions that promote longevity are often correlated with increased insulin sensitivity, and it therefore is surprising that chronic rapamycin treatment of mice, rats, and humans is associated with insulin resistance (J Am Soc Nephrol., 19, 2008, 1411; Diabetes, 00, 2010, 00; Science, 335, 2012, 1638). We examined the effect of dietary rapamycin treatment on glucose homeostasis and insulin resistance in the genetically heterogeneous HET3 mouse strain, a strain in which dietary rapamycin robustly extends mean and maximum life span. We find that rapamycin treatment leads to glucose intolerance in both young and old HET3 mice, but in contrast to the previously reported effect of injected rapamycin in C57BL/6 mice, HET3 mice treated with dietary rapamycin responded normally in an insulin tolerance test. To gauge the overall consequences of rapamycin treatment on average blood glucose levels, we measured HBA1c. Dietary rapamycin increased HBA1c over the first 3 weeks of treatment in young animals, but the effect was lost by 3 months, and no effect was detected in older animals. Our results demonstrate that the extended life span of HET3 mice on a rapamycin diet occurs in the absence of major changes in insulin sensitivity and highlight the importance of strain background and delivery method in testing effects of longevity interventions.
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Affiliation(s)
- Dudley W. Lamming
- Whitehead Institute for Biomedical Research Cambridge MA 02142 USA
- Department of Biology MIT Cambridge MA 02139 USA
- Howard Hughes Medical Institute MIT Cambridge MA 02139 USA
- Broad Institute of Harvard and MIT Seven Cambridge Center Cambridge MA 02142 USA
- The David H. Koch Institute for Integrative Cancer Research at MIT Cambridge MA 02139 USA
| | - Lan Ye
- Department of Physiology Institute for Diabetes, Obesity, and Metabolism Perelman School of Medicine University of Pennsylvania Philadelphia PA 19104 USA
| | | | - Joseph A. Baur
- Department of Physiology Institute for Diabetes, Obesity, and Metabolism Perelman School of Medicine University of Pennsylvania Philadelphia PA 19104 USA
| | - David M. Sabatini
- Whitehead Institute for Biomedical Research Cambridge MA 02142 USA
- Department of Biology MIT Cambridge MA 02139 USA
- Howard Hughes Medical Institute MIT Cambridge MA 02139 USA
- Broad Institute of Harvard and MIT Seven Cambridge Center Cambridge MA 02142 USA
- The David H. Koch Institute for Integrative Cancer Research at MIT Cambridge MA 02139 USA
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73
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Inhibition of Notch uncouples Akt activation from hepatic lipid accumulation by decreasing mTorc1 stability. Nat Med 2013; 19:1054-60. [PMID: 23832089 PMCID: PMC3737382 DOI: 10.1038/nm.3259] [Citation(s) in RCA: 123] [Impact Index Per Article: 11.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2013] [Accepted: 04/04/2013] [Indexed: 12/16/2022]
Abstract
Increased hepatic lipid content is an early correlate of insulin resistance, and can be caused by nutrient-induced mTor activation. The latter increases basal Akt activity, leading to a self-perpetuating lipogenic cycle. We have previously shown that the developmental Notch pathway has metabolic functions in adult liver. Acute or chronic inhibition of Notch dampens hepatic glucose production and increases Akt tone, and might therefore be predicted to increase hepatic lipid content. Surprisingly, we show that constitutive liver-specific ablation of Notch signaling, or its acute inhibition with a decoy Notch1 receptor, prevents hepatosteatosis by blocking mTorc1. Conversely, Notch gain-of-function causes fatty liver through constitutive activation of mTorc1, an effect reversible by rapamycin treatment. We demonstrate that Notch signaling increases mTorc1 complex stability, augmenting mTorc1 function and Srebp1c-mediated lipogenesis. The data identify Notch as a therapeutically actionable branch point of metabolic signaling, where hepatic Akt activation can be uncoupled from steatosis.
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74
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Dominy JE, Puigserver P. Mitochondrial biogenesis through activation of nuclear signaling proteins. Cold Spring Harb Perspect Biol 2013; 5:5/7/a015008. [PMID: 23818499 DOI: 10.1101/cshperspect.a015008] [Citation(s) in RCA: 175] [Impact Index Per Article: 15.9] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
The dynamics of mitochondrial biogenesis and function is a complex interplay of cellular and molecular processes that ultimately shape bioenergetics capacity. Mitochondrial mass, by itself, represents the net balance between rates of biogenesis and degradation. Mitochondrial biogenesis is dependent on different signaling cascades and transcriptional complexes that promote the formation and assembly of mitochondria--a process that is heavily dependent on timely and coordinated transcriptional control of genes encoding for mitochondrial proteins. In this article, we discuss the major signals and transcriptional complexes, programming mitochondrial biogenesis, and bioenergetic activity. This regulatory network represents a new therapeutic window into the treatment of the wide spectrum of mitochondrial and neurodegenerative diseases characterized by dysregulation of mitochondrial dynamics and bioenergetic deficiencies.
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Affiliation(s)
- John E Dominy
- Department of Cancer Biology, Dana-Farber Cancer Institute and Department of Cell Biology, Harvard Medical School, Boston, Massachusetts 02215, USA
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75
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Schiaffino S, Dyar KA, Ciciliot S, Blaauw B, Sandri M. Mechanisms regulating skeletal muscle growth and atrophy. FEBS J 2013; 280:4294-314. [PMID: 23517348 DOI: 10.1111/febs.12253] [Citation(s) in RCA: 942] [Impact Index Per Article: 85.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2013] [Revised: 03/13/2013] [Accepted: 03/14/2013] [Indexed: 12/11/2022]
Abstract
Skeletal muscle mass increases during postnatal development through a process of hypertrophy, i.e. enlargement of individual muscle fibers, and a similar process may be induced in adult skeletal muscle in response to contractile activity, such as strength exercise, and specific hormones, such as androgens and β-adrenergic agonists. Muscle hypertrophy occurs when the overall rates of protein synthesis exceed the rates of protein degradation. Two major signaling pathways control protein synthesis, the IGF1-Akt-mTOR pathway, acting as a positive regulator, and the myostatin-Smad2/3 pathway, acting as a negative regulator, and additional pathways have recently been identified. Proliferation and fusion of satellite cells, leading to an increase in the number of myonuclei, may also contribute to muscle growth during early but not late stages of postnatal development and in some forms of muscle hypertrophy in the adult. Muscle atrophy occurs when protein degradation rates exceed protein synthesis, and may be induced in adult skeletal muscle in a variety of conditions, including starvation, denervation, cancer cachexia, heart failure and aging. Two major protein degradation pathways, the proteasomal and the autophagic-lysosomal pathways, are activated during muscle atrophy and variably contribute to the loss of muscle mass. These pathways involve a variety of atrophy-related genes or atrogenes, which are controlled by specific transcription factors, such as FoxO3, which is negatively regulated by Akt, and NF-κB, which is activated by inflammatory cytokines.
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76
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Chaveroux C, Eichner LJ, Dufour CR, Shatnawi A, Khoutorsky A, Bourque G, Sonenberg N, Giguère V. Molecular and genetic crosstalks between mTOR and ERRα are key determinants of rapamycin-induced nonalcoholic fatty liver. Cell Metab 2013; 17:586-98. [PMID: 23562079 DOI: 10.1016/j.cmet.2013.03.003] [Citation(s) in RCA: 109] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/07/2012] [Revised: 11/16/2012] [Accepted: 03/06/2013] [Indexed: 10/27/2022]
Abstract
mTOR and ERRα are key regulators of common metabolic processes, including lipid homeostasis. However, it is currently unknown whether these factors cooperate in the control of metabolism. ChIP-sequencing analyses of mouse liver reveal that mTOR occupies regulatory regions of genes on a genome-wide scale including enrichment at genes shared with ERRα that are involved in the TCA cycle and lipid biosynthesis. Genetic ablation of ERRα and rapamycin treatment, alone or in combination, alter the expression of these genes and induce the accumulation of TCA metabolites. As a consequence, both genetic and pharmacological inhibition of ERRα activity exacerbates hepatic hyperlipidemia observed in rapamycin-treated mice. We further show that mTOR regulates ERRα activity through ubiquitin-mediated degradation via transcriptional control of the ubiquitin-proteasome pathway. Our work expands the role of mTOR action in metabolism and highlights the existence of a potent mTOR/ERRα regulatory axis with significant clinical impact.
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Affiliation(s)
- Cédric Chaveroux
- Rosalind and Morris Goodman Cancer Research Centre, McGill University, 1160 Pine Avenue West, Montréal, QC H3A 1A3, Canada
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77
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Lu Y, Xiong X, Wang X, Zhang Z, Li J, Shi G, Yang J, Zhang H, Ning G, Li X. Yin Yang 1 promotes hepatic gluconeogenesis through upregulation of glucocorticoid receptor. Diabetes 2013; 62. [PMID: 23193188 PMCID: PMC3609554 DOI: 10.2337/db12-0744] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
Gluconeogenesis is critical in maintaining blood glucose levels in a normal range during fasting. In this study, we investigated the role of Yin Yang 1 (YY1), a key transcription factor involved in cell proliferation and differentiation, in the regulation of hepatic gluconeogenesis. Our data showed that hepatic YY1 expression levels were induced in mice during fasting conditions and in a state of insulin resistance. Overexpression of YY1 in livers augmented gluconeogenesis, raising fasting blood glucose levels in C57BL/6 mice, whereas liver-specific ablation of YY1 using adenoviral shRNA ameliorated hyperglycemia in wild-type and diabetic db/db mice. At the molecular level, we further demonstrated that the major mechanism of YY1 in the regulation of hepatic glucose production is to modulate the expression of glucocorticoid receptor. Therefore, our study uncovered for the first time that YY1 participates in the regulation of hepatic gluconeogenesis, which implies that YY1 might serve as a potential therapeutic target for hyperglycemia in diabetes.
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Affiliation(s)
- Yan Lu
- Department of Endocrine and Metabolic Diseases, Shanghai Institute of Endocrinology and Metabolism, Shanghai Clinical Center for Endocrine and Metabolic Diseases, Ruijin Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Xuelian Xiong
- Department of Endocrine and Metabolic Diseases, Shanghai Institute of Endocrinology and Metabolism, Shanghai Clinical Center for Endocrine and Metabolic Diseases, Ruijin Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Xiaolin Wang
- Department of Endocrine and Metabolic Diseases, Shanghai Institute of Endocrinology and Metabolism, Shanghai Clinical Center for Endocrine and Metabolic Diseases, Ruijin Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Zhijian Zhang
- Department of Endocrine and Metabolic Diseases, Shanghai Institute of Endocrinology and Metabolism, Shanghai Clinical Center for Endocrine and Metabolic Diseases, Ruijin Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Jin Li
- Department of Endocrine and Metabolic Diseases, Shanghai Institute of Endocrinology and Metabolism, Shanghai Clinical Center for Endocrine and Metabolic Diseases, Ruijin Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Guojun Shi
- Department of Endocrine and Metabolic Diseases, Shanghai Institute of Endocrinology and Metabolism, Shanghai Clinical Center for Endocrine and Metabolic Diseases, Ruijin Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Jian Yang
- Department of Endocrine and Metabolic Diseases, Shanghai Institute of Endocrinology and Metabolism, Shanghai Clinical Center for Endocrine and Metabolic Diseases, Ruijin Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Huijie Zhang
- Department of Endocrine and Metabolic Diseases, Shanghai Institute of Endocrinology and Metabolism, Shanghai Clinical Center for Endocrine and Metabolic Diseases, Ruijin Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Guang Ning
- Department of Endocrine and Metabolic Diseases, Shanghai Institute of Endocrinology and Metabolism, Shanghai Clinical Center for Endocrine and Metabolic Diseases, Ruijin Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China
- Key Laboratory of Endocrine Tumors and the Division of Endocrine and Metabolic Diseases, E-Institute of Shanghai Universities, Shanghai, China
- Corresponding author: Guang Ning, , or Xiaoying Li,
| | - Xiaoying Li
- Department of Endocrine and Metabolic Diseases, Shanghai Institute of Endocrinology and Metabolism, Shanghai Clinical Center for Endocrine and Metabolic Diseases, Ruijin Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China
- Key Laboratory of Endocrine Tumors and the Division of Endocrine and Metabolic Diseases, E-Institute of Shanghai Universities, Shanghai, China
- Chinese-French Laboratory of Genomics and Life Sciences, Ruijin Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China
- Corresponding author: Guang Ning, , or Xiaoying Li,
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78
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Ge Y, Chen J. Mammalian target of rapamycin (mTOR) signaling network in skeletal myogenesis. J Biol Chem 2012; 287:43928-35. [PMID: 23115234 DOI: 10.1074/jbc.r112.406942] [Citation(s) in RCA: 81] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
Mammalian (or mechanistic) target of rapamycin (mTOR) regulates a wide range of cellular and developmental processes by coordinating signaling responses to mitogens, nutrients, and various stresses. Over the last decade, mTOR has emerged as a master regulator of skeletal myogenesis, controlling multiple stages of the myofiber formation process. In this minireview, we present an emerging view of the signaling network underlying mTOR regulation of myogenesis, which contrasts with the well established mechanisms in the regulation of cell and muscle growth. Current questions for future studies are also highlighted.
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Affiliation(s)
- Yejing Ge
- Department of Cell and Developmental Biology, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA
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79
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Ye L, Varamini B, Lamming DW, Sabatini DM, Baur JA. Rapamycin has a biphasic effect on insulin sensitivity in C2C12 myotubes due to sequential disruption of mTORC1 and mTORC2. Front Genet 2012; 3:177. [PMID: 22973301 PMCID: PMC3438685 DOI: 10.3389/fgene.2012.00177] [Citation(s) in RCA: 60] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2012] [Accepted: 08/23/2012] [Indexed: 12/11/2022] Open
Abstract
Rapamycin, an inhibitor of mTOR complex 1 (mTORC1), improves insulin sensitivity in acute studies in vitro and in vivo by disrupting a negative feedback loop mediated by S6 kinase. We find that rapamycin has a clear biphasic effect on insulin sensitivity in C2C12 myotubes, with enhanced responsiveness during the first hour that declines to almost complete insulin resistance by 24-48 h. We and others have recently observed that chronic rapamycin treatment induces insulin resistance in rodents, at least in part due to disruption of mTORC2, an mTOR-containing complex that is not acutely sensitive to the drug. Chronic rapamycin treatment may also impair insulin action via the inhibition of mTORC1-dependent mitochondrial biogenesis and activity, which could result in a buildup of lipid intermediates that are known to trigger insulin resistance. We confirmed that rapamycin inhibits expression of PGC-1α, a key mitochondrial transcription factor, and acutely reduces respiration rate in myotubes. However, rapamycin did not stimulate phosphorylation of PKCθ, a central mediator of lipid-induced insulin resistance. Instead, we found dramatic disruption of mTORC2, which coincided with the onset of insulin resistance. Selective inhibition of mTORC1 or mTORC2 by shRNA-mediated knockdown of specific components (Raptor and Rictor, respectively) confirmed that mitochondrial effects of rapamycin are mTORC1-dependent, whereas insulin resistance was recapitulated only by knockdown of mTORC2. Thus, mTORC2 disruption, rather than inhibition of mitochondria, causes insulin resistance in rapamycin-treated myotubes, and this system may serve as a useful model to understand the effects of rapamycin on mTOR signaling in vivo.
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Affiliation(s)
- Lan Ye
- Institute for Diabetes, Obesity, and Metabolism, Perelman School of Medicine, University of Pennsylvania Philadelphia, PA, USA
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Defective mitochondrial morphology and bioenergetic function in mice lacking the transcription factor Yin Yang 1 in skeletal muscle. Mol Cell Biol 2012; 32:3333-46. [PMID: 22711985 DOI: 10.1128/mcb.00337-12] [Citation(s) in RCA: 68] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
The formation, distribution, and maintenance of functional mitochondria are achieved through dynamic processes that depend strictly on the transcription of nuclear genes encoding mitochondrial proteins. A large number of these mitochondrial genes contain binding sites for the transcription factor Yin Yang 1 (YY1) in their proximal promoters, but the physiological relevance is unknown. We report here that skeletal-muscle-specific YY1 knockout (YY1mKO) mice have severely defective mitochondrial morphology and oxidative function associated with exercise intolerance, signs of mitochondrial myopathy, and short stature. Gene set enrichment analysis (GSEA) revealed that the top pathways downregulated in YY1mKO mice were assigned to key metabolic and regulatory mitochondrial genes. This analysis was consistent with a profound decrease in the level of mitochondrial proteins and oxidative phosphorylation (OXPHOS) bioenergetic function in these mice. In contrast to the finding for wild-type mice, inactivation of the mammalian target of rapamycin (mTOR) did not suppress mitochondrial genes in YY1mKO mice. Mechanistically, mTOR-dependent phosphorylation of YY1 resulted in a strong interaction between YY1 and the transcriptional coactivator peroxisome proliferator-activated receptor gamma coactivator 1α (PGC1α), a major regulator of mitochondrial function. These results underscore the important role of YY1 in the maintenance of mitochondrial function and explain how its inactivation might contribute to exercise intolerance and mitochondrial myopathies.
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