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Packer M. Are the benefits of SGLT2 inhibitors in heart failure and a reduced ejection fraction influenced by background therapy? Expectations and realities of a new standard of care. Eur Heart J 2021; 41:2393-2396. [PMID: 32350522 PMCID: PMC7327531 DOI: 10.1093/eurheartj/ehaa344] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Affiliation(s)
- Milton Packer
- Baylor Heart and Vascular Institute, Baylor University Medical Center, Dallas, TX, USA.,Imperial College, London, UK
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Bertrand L, Auquier J, Renguet E, Angé M, Cumps J, Horman S, Beauloye C. Glucose transporters in cardiovascular system in health and disease. Pflugers Arch 2020; 472:1385-1399. [PMID: 32809061 DOI: 10.1007/s00424-020-02444-8] [Citation(s) in RCA: 30] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2020] [Revised: 07/28/2020] [Accepted: 07/31/2020] [Indexed: 12/13/2022]
Abstract
Glucose transporters are essential for the heart to sustain its function. Due to its nature as a high energy-consuming organ, the heart needs to catabolize a huge quantity of metabolic substrates. For optimized energy production, the healthy heart constantly switches between various metabolites in accordance with substrate availability and hormonal status. This metabolic flexibility is essential for the maintenance of cardiac function. Glucose is part of the main substrates catabolized by the heart and its use is fine-tuned via complex molecular mechanisms that include the regulation of the glucose transporters GLUTs, mainly GLUT4 and GLUT1. Besides GLUTs, glucose can also be transported by cotransporters of the sodium-glucose cotransporter (SGLT) (SLC5 gene) family, in which SGLT1 and SMIT1 were shown to be expressed in the heart. This SGLT-mediated uptake does not seem to be directly linked to energy production but is rather associated with intracellular signalling triggering important processes such as the production of reactive oxygen species. Glucose transport is markedly affected in cardiac diseases such as cardiac hypertrophy, diabetic cardiomyopathy and heart failure. These alterations are not only fingerprints of these diseases but are involved in their onset and progression. The present review will depict the importance of glucose transport in healthy and diseased heart, as well as proposed therapies targeting glucose transporters.
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Affiliation(s)
- Luc Bertrand
- Institut de Recherche Expérimentale et Clinique, Pole of Cardiovascular Research, Université catholique de Louvain, Avenue Hippocrate 55, B1.55.05, B-1200, Brussels, Belgium.
| | - Julien Auquier
- Institut de Recherche Expérimentale et Clinique, Pole of Cardiovascular Research, Université catholique de Louvain, Avenue Hippocrate 55, B1.55.05, B-1200, Brussels, Belgium
| | - Edith Renguet
- Institut de Recherche Expérimentale et Clinique, Pole of Cardiovascular Research, Université catholique de Louvain, Avenue Hippocrate 55, B1.55.05, B-1200, Brussels, Belgium
| | - Marine Angé
- Institut de Recherche Expérimentale et Clinique, Pole of Cardiovascular Research, Université catholique de Louvain, Avenue Hippocrate 55, B1.55.05, B-1200, Brussels, Belgium
| | - Julien Cumps
- Institut de Recherche Expérimentale et Clinique, Pole of Cardiovascular Research, Université catholique de Louvain, Avenue Hippocrate 55, B1.55.05, B-1200, Brussels, Belgium
| | - Sandrine Horman
- Institut de Recherche Expérimentale et Clinique, Pole of Cardiovascular Research, Université catholique de Louvain, Avenue Hippocrate 55, B1.55.05, B-1200, Brussels, Belgium
| | - Christophe Beauloye
- Institut de Recherche Expérimentale et Clinique, Pole of Cardiovascular Research, Université catholique de Louvain, Avenue Hippocrate 55, B1.55.05, B-1200, Brussels, Belgium.,Division of Cardiology, Cliniques Universitaires Saint-Luc, Brussels, Belgium
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Packer M. Role of Deranged Energy Deprivation Signaling in the Pathogenesis of Cardiac and Renal Disease in States of Perceived Nutrient Overabundance. Circulation 2020; 141:2095-2105. [DOI: 10.1161/circulationaha.119.045561] [Citation(s) in RCA: 30] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Sodium-glucose cotransporter 2 inhibitors reduce the risk of serious heart failure and adverse renal events, but the mechanisms that underlie this benefit are not understood. Treatment with SGLT2 inhibitors is distinguished by 2 intriguing features: ketogenesis and erythrocytosis. Both reflect the induction of a fasting-like and hypoxia-like transcriptional paradigm that is capable of restoring and maintaining cellular homeostasis and survival. In the face of perceived nutrient and oxygen deprivation, cells activate low-energy sensors, which include sirtuin-1 (SIRT1), AMP-activated protein kinase (AMPK), and hypoxia inducible factors (HIFs; especially HIF-2α); these enzymes and transcription factors are master regulators of hundreds of genes and proteins that maintain cellular homeostasis. The activation of SIRT1 (through its effects to promote gluconeogenesis and fatty acid oxidation) drives ketogenesis, and working in concert with AMPK, it can directly inhibit inflammasome activation and maintain mitochondrial capacity and stability. HIFs act to promote oxygen delivery (by stimulating erythropoietin and erythrocytosis) and decrease oxygen consumption. The activation of SIRT1, AMPK, and HIF-2α enhances autophagy, a lysosome-dependent degradative pathway that removes dangerous constituents, particularly damaged mitochondria and peroxisomes, which are major sources of oxidative stress and triggers of cellular dysfunction and death. SIRT1 and AMPK also act on sodium transport mechanisms to reduce intracellular sodium concentrations. It is interesting that type 2 diabetes mellitus, obesity, chronic heart failure, and chronic kidney failure are characterized by the accumulation of intracellular glucose and lipid intermediates that are perceived by cells as indicators of energy overabundance. The cells respond by downregulating SIRT1, AMPK, and HIF-2α, thus leading to an impairment of autophagic flux and acceleration of cardiomyopathy and nephropathy. SGLT2 inhibitors reverse this maladaptive signaling by triggering a state of fasting and hypoxia mimicry, which includes activation of SIRT1, AMPK, and HIF-2α, enhanced autophagic flux, reduced cellular stress, decreased sodium influx into cells, and restoration of mitochondrial homeostasis. This mechanistic framework clarifies the findings of large-scale randomized trials and the close association of ketogenesis and erythrocytosis with the cardioprotective and renoprotective benefits of these drugs.
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Affiliation(s)
- Milton Packer
- Baylor Heart and Vascular Institute, Baylor University Medical Center, Dallas, TX. Imperial College, London, United Kingdom
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Packer M. Autophagy-dependent and -independent modulation of oxidative and organellar stress in the diabetic heart by glucose-lowering drugs. Cardiovasc Diabetol 2020; 19:62. [PMID: 32404204 PMCID: PMC7222526 DOI: 10.1186/s12933-020-01041-4] [Citation(s) in RCA: 66] [Impact Index Per Article: 16.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/31/2019] [Accepted: 05/09/2020] [Indexed: 02/07/2023] Open
Abstract
Autophagy is a lysosome-dependent intracellular degradative pathway, which mediates the cellular adaptation to nutrient and oxygen depletion as well as to oxidative and endoplasmic reticulum stress. The molecular mechanisms that stimulate autophagy include the activation of energy deprivation sensors, sirtuin-1 (SIRT1) and adenosine monophosphate-activated protein kinase (AMPK). These enzymes not only promote organellar integrity directly, but they also enhance autophagic flux, which leads to the removal of dysfunctional mitochondria and peroxisomes. Type 2 diabetes is characterized by suppression of SIRT1 and AMPK signaling as well as an impairment of autophagy; these derangements contribute to an increase in oxidative stress and the development of cardiomyopathy. Antihyperglycemic drugs that signal through insulin may further suppress autophagy and worsen heart failure. In contrast, metformin and SGLT2 inhibitors activate SIRT1 and/or AMPK and promote autophagic flux to varying degrees in cardiomyocytes, which may explain their benefits in experimental cardiomyopathy. However, metformin and SGLT2 inhibitors differ meaningfully in the molecular mechanisms that underlie their effects on the heart. Whereas metformin primarily acts as an agonist of AMPK, SGLT2 inhibitors induce a fasting-like state that is accompanied by ketogenesis, a biomarker of enhanced SIRT1 signaling. Preferential SIRT1 activation may also explain the ability of SGLT2 inhibitors to stimulate erythropoiesis and reduce uric acid (a biomarker of oxidative stress)—effects that are not seen with metformin. Changes in both hematocrit and serum urate are the most important predictors of the ability of SGLT2 inhibitors to reduce the risk of cardiovascular death and hospitalization for heart failure in large-scale trials. Metformin and SGLT2 inhibitors may also differ in their ability to mitigate diabetes-related increases in intracellular sodium concentration and its adverse effects on mitochondrial functional integrity. Differences in the actions of SGLT2 inhibitors and metformin may reflect the distinctive molecular pathways that explain differences in the cardioprotective effects of these drugs.
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Affiliation(s)
- Milton Packer
- Baylor Heart and Vascular Institute, Baylor University Medical Center, 621 N. Hall Street, Dallas, TX, 75226, USA. .,Imperial College, London, UK.
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Packer M. Role of Impaired Nutrient and Oxygen Deprivation Signaling and Deficient Autophagic Flux in Diabetic CKD Development: Implications for Understanding the Effects of Sodium-Glucose Cotransporter 2-Inhibitors. J Am Soc Nephrol 2020; 31:907-919. [PMID: 32276962 DOI: 10.1681/asn.2020010010] [Citation(s) in RCA: 77] [Impact Index Per Article: 19.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Growing evidence indicates that oxidative and endoplasmic reticular stress, which trigger changes in ion channels and inflammatory pathways that may undermine cellular homeostasis and survival, are critical determinants of injury in the diabetic kidney. Cells are normally able to mitigate these cellular stresses by maintaining high levels of autophagy, an intracellular lysosome-dependent degradative pathway that clears the cytoplasm of dysfunctional organelles. However, the capacity for autophagy in both podocytes and renal tubular cells is markedly impaired in type 2 diabetes, and this deficiency contributes importantly to the intensity of renal injury. The primary drivers of autophagy in states of nutrient and oxygen deprivation-sirtuin-1 (SIRT1), AMP-activated protein kinase (AMPK), and hypoxia-inducible factors (HIF-1α and HIF-2α)-can exert renoprotective effects by promoting autophagic flux and by exerting direct effects on sodium transport and inflammasome activation. Type 2 diabetes is characterized by marked suppression of SIRT1 and AMPK, leading to a diminution in autophagic flux in glomerular podocytes and renal tubules and markedly increasing their susceptibility to renal injury. Importantly, because insulin acts to depress autophagic flux, these derangements in nutrient deprivation signaling are not ameliorated by antihyperglycemic drugs that enhance insulin secretion or signaling. Metformin is an established AMPK agonist that can promote autophagy, but its effects on the course of CKD have been demonstrated only in the experimental setting. In contrast, the effects of sodium-glucose cotransporter-2 (SGLT2) inhibitors may be related primarily to enhanced SIRT1 and HIF-2α signaling; this can explain the effects of SGLT2 inhibitors to promote ketonemia and erythrocytosis and potentially underlies their actions to increase autophagy and mute inflammation in the diabetic kidney. These distinctions may contribute importantly to the consistent benefit of SGLT2 inhibitors to slow the deterioration in glomerular function and reduce the risk of ESKD in large-scale randomized clinical trials of patients with type 2 diabetes.
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Affiliation(s)
- Milton Packer
- Baylor Heart and Vascular Institute, Baylor University Medical Center, Dallas, Texas .,Imperial College, London, United Kingdom
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Pedersen SF, Counillon L. The SLC9A-C Mammalian Na +/H + Exchanger Family: Molecules, Mechanisms, and Physiology. Physiol Rev 2019; 99:2015-2113. [PMID: 31507243 DOI: 10.1152/physrev.00028.2018] [Citation(s) in RCA: 103] [Impact Index Per Article: 20.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
Na+/H+ exchangers play pivotal roles in the control of cell and tissue pH by mediating the electroneutral exchange of Na+ and H+ across cellular membranes. They belong to an ancient family of highly evolutionarily conserved proteins, and they play essential physiological roles in all phyla. In this review, we focus on the mammalian Na+/H+ exchangers (NHEs), the solute carrier (SLC) 9 family. This family of electroneutral transporters constitutes three branches: SLC9A, -B, and -C. Within these, each isoform exhibits distinct tissue expression profiles, regulation, and physiological roles. Some of these transporters are highly studied, with hundreds of original articles, and some are still only rudimentarily understood. In this review, we present and discuss the pioneering original work as well as the current state-of-the-art research on mammalian NHEs. We aim to provide the reader with a comprehensive view of core knowledge and recent insights into each family member, from gene organization over protein structure and regulation to physiological and pathophysiological roles. Particular attention is given to the integrated physiology of NHEs in the main organ systems. We provide several novel analyses and useful overviews, and we pinpoint main remaining enigmas, which we hope will inspire novel research on these highly versatile proteins.
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Affiliation(s)
- S F Pedersen
- Section for Cell Biology and Physiology, Department of Biology, University of Copenhagen, Copenhagen, Denmark; and Université Côte d'Azur, CNRS, Laboratoire de Physiomédecine Moléculaire, LP2M, France, and Laboratories of Excellence Ion Channel Science and Therapeutics, Nice, France
| | - L Counillon
- Section for Cell Biology and Physiology, Department of Biology, University of Copenhagen, Copenhagen, Denmark; and Université Côte d'Azur, CNRS, Laboratoire de Physiomédecine Moléculaire, LP2M, France, and Laboratories of Excellence Ion Channel Science and Therapeutics, Nice, France
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Ramírez MA, Beltrán AR, Araya JE, Cornejo M, Toledo F, Fuentes G, Sobrevia L. Involvement of Intracellular pH in Vascular Insulin Resistance. Curr Vasc Pharmacol 2019; 17:440-446. [DOI: 10.2174/1570161116666180911104012] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2018] [Revised: 08/02/2018] [Accepted: 08/04/2018] [Indexed: 12/25/2022]
Abstract
The maintenance of the pH homeostasis is maintained by several mechanisms including the
efflux of protons (H+) via membrane transporters expressed in almost all mammalian cells. Along these
membrane transporters the sodium/H+ exchangers (NHEs), mainly NHE isoform 1 (NHE1), plays a key
role in this phenomenon. NHE1 is under modulation by several environmental conditions (e.g. hyperglycaemia,
protein kinase C activity) as well as hormones, including insulin. NHE1 activation causes
intracellular alkalization in human endothelial cells leading to activation of the endothelial Nitric Oxide
Synthase (eNOS) to generate NO. Intracellular alkalization is a phenomenon that also results in upregulation
of the glucose transporter GLUT4 in cells that are responsive to insulin. A reduction in the removal
of the extracellular D-glucose is seen in states of insulin resistance, such as in diabetes mellitus
and obesity. Since insulin is a potent activator of eNOS in human endothelium, therefore causing vasodilation,
and its vascular effect is reduced in insulin resistance it is likely that a defective signal to activate
NHE1 in insulin target cells is expected. This phenomenon results in lower redistribution and activation
of GLUT4 leading to reduced uptake of D-glucose and hyperglycaemia. The general concept of a
role for NHE1, and perhaps other NHEs isoforms, in insulin resistance in the human vasculature is proposed.
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Affiliation(s)
- Marco A. Ramírez
- Cellular and Molecular Physiology Laboratory (CMPL), Department of Obstetrics, Division of Obstetrics and Gynaecology, School of Medicine, Faculty of Medicine, Pontifical Catholic University of Chile, Santiago 8330024, Chile
| | - Ana R. Beltrán
- Laboratorio de Fisiologia Celular, Departamento Biomedico, Facultad de Ciencias de la Salud, Universidad de Antofagasta, Antofagasta 1270300, Chile
| | - Jorge E. Araya
- Laboratorio de Fisiologia Celular, Departamento Biomedico, Facultad de Ciencias de la Salud, Universidad de Antofagasta, Antofagasta 1270300, Chile
| | - Marcelo Cornejo
- Cellular and Molecular Physiology Laboratory (CMPL), Department of Obstetrics, Division of Obstetrics and Gynaecology, School of Medicine, Faculty of Medicine, Pontifical Catholic University of Chile, Santiago 8330024, Chile
| | - Fernando Toledo
- Cellular and Molecular Physiology Laboratory (CMPL), Department of Obstetrics, Division of Obstetrics and Gynaecology, School of Medicine, Faculty of Medicine, Pontifical Catholic University of Chile, Santiago 8330024, Chile
| | - Gonzalo Fuentes
- Cellular and Molecular Physiology Laboratory (CMPL), Department of Obstetrics, Division of Obstetrics and Gynaecology, School of Medicine, Faculty of Medicine, Pontifical Catholic University of Chile, Santiago 8330024, Chile
| | - Luis Sobrevia
- Cellular and Molecular Physiology Laboratory (CMPL), Department of Obstetrics, Division of Obstetrics and Gynaecology, School of Medicine, Faculty of Medicine, Pontifical Catholic University of Chile, Santiago 8330024, Chile
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Chronic AICAR treatment prevents metabolic changes in cardiomyocytes exposed to free fatty acids. Pflugers Arch 2019; 471:1219-1234. [PMID: 31152240 DOI: 10.1007/s00424-019-02285-0] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2019] [Revised: 04/27/2019] [Accepted: 05/15/2019] [Indexed: 01/09/2023]
Abstract
The stimulation of glucose transport by metabolic stress is an important determinant of myocardial susceptibility to ischemia and reperfusion injury. Stimulation of glucose transport is markedly impaired in cardiomyocytes chronically exposed to excess free fatty acids (FFA), as occurs in vivo in type 2 diabetes. To determine whether chronic low-grade activation of AMP-activated kinase (AMPK) improves substrate metabolism in cardiomyocytes exposed to FFA, isolated cultured cardiomyocytes were exposed for 7 days to FFA ± the AMPK agonist 5-aminoimidazole-4-carboxamide ribonucleoside (AICAR). Glucose transport and glycolysis were then measured during acute metabolic stress provoked by oligomycin. Chronic treatment with AICAR improved basal and oligomycin-stimulated glucose transport in FFA-exposed but not in control cardiomyocytes. Similarly, basal and oligomycin-stimulated glycolysis was reduced in FFA-exposed cardiomyocytes but restored by chronic AICAR treatment. Conversely, fatty acid oxidation was increased in FFA-exposed cardiomyocytes and reduced by chronic AICAR treatment. Chronic AICAR treatment induced in FFA-exposed cardiomyocytes the biogenesis of numerous lipid droplets. Curiously, whereas acute treatment of cardiomyocytes with AICAR increased phosphorylation of the AMPKα subunit on T172, a classical marker of AMPK activation, chronic AICAR treatment almost completely obliterated T172 phosphorylation. However, phosphorylation of the AMPK target protein raptor on S792 was reduced in FFA-exposed cardiomyocytes but restored by AICAR treatment. In conclusion, chronic AICAR treatment induces a metabolic shift in FFA-exposed cardiomyocytes, characterized by improved glucose transport and glycolysis and redirection of fatty acids towards neutral storage. Such metabolic changes in vivo could protect the hearts of patients with type 2 diabetes against ischemia-reperfusion injury.
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Sun XL, Lessard SJ, An D, Koh HJ, Esumi H, Hirshman MF, Goodyear LJ. Sucrose nonfermenting AMPK-related kinase (SNARK) regulates exercise-stimulated and ischemia-stimulated glucose transport in the heart. J Cell Biochem 2018; 120:685-696. [PMID: 30256437 DOI: 10.1002/jcb.27425] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2018] [Accepted: 07/12/2018] [Indexed: 01/15/2023]
Abstract
The signaling mechanisms mediating myocardial glucose transport are not fully understood. Sucrose nonfermenting AMP-activated protein kinase (AMPK)-related kinase (SNARK) is an AMPK-related protein kinase that is expressed in the heart and has been implicated in contraction-stimulated glucose transport in mouse skeletal muscle. We first determined if SNARK is phosphorylated on Thr208 , a site critical for SNARK activity. Mice were treated with exercise, ischemia, submaximal insulin, or maximal insulin. Treadmill exercise slightly, but significantly increased SNARK Thr208 phosphorylation. Ischemia also increased SNARK Thr208 phosphorylation, but there was no effect of submaximal or maximal insulin. HL1 cardiomyocytes were used to overexpress wild-type (WT) SNARK and to knockdown endogenous SNARK. Overexpression of WT SNARK had no effect on ischemia-stimulated glucose transport; however, SNARK knockdown significantly decreased ischemia-stimulated glucose transport. SNARK overexpression or knockdown did not alter insulin-stimulated glucose transport or glycogen concentrations. To study SNARK function in vivo, SNARK heterozygous knockout mice (SNARK+/- ) and WT littermates performed treadmill exercise. Exercise-stimulated glucose transport was decreased by ~50% in hearts from SNARK+/- mice. In summary, exercise and ischemia increase SNARK Thr208 phosphorylation in the heart and SNARK regulates exercise-stimulated and ischemia-stimulated glucose transport. SNARK is a novel mediator of insulin-independent glucose transport in the heart.
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Affiliation(s)
- Xiang-Lan Sun
- Department of Endocrinology, Shandong Provincial Hospital Affiliated to Shandong University, Jinan, China.,Integrative Physiology and Metabolism Section, Joslin Diabetes Center and Department of Medicine, Harvard Medical School, Boston, Massachusetts
| | - Sarah J Lessard
- Integrative Physiology and Metabolism Section, Joslin Diabetes Center and Department of Medicine, Harvard Medical School, Boston, Massachusetts
| | - Ding An
- Integrative Physiology and Metabolism Section, Joslin Diabetes Center and Department of Medicine, Harvard Medical School, Boston, Massachusetts
| | - Ho-Jin Koh
- Integrative Physiology and Metabolism Section, Joslin Diabetes Center and Department of Medicine, Harvard Medical School, Boston, Massachusetts
| | - Hiroyasu Esumi
- Cancer Physiology Project, Research Center for Innovative Oncology, National Cancer Center Hospital East, Kashiwa, Japan
| | - Michael F Hirshman
- Integrative Physiology and Metabolism Section, Joslin Diabetes Center and Department of Medicine, Harvard Medical School, Boston, Massachusetts
| | - Laurie J Goodyear
- Integrative Physiology and Metabolism Section, Joslin Diabetes Center and Department of Medicine, Harvard Medical School, Boston, Massachusetts
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Spangenburg EE, Jackson KC, Schuh RA. AICAR inhibits oxygen consumption by intact skeletal muscle cells in culture. J Physiol Biochem 2013; 69:909-17. [PMID: 23813470 DOI: 10.1007/s13105-013-0269-0] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2012] [Accepted: 06/14/2013] [Indexed: 11/30/2022]
Abstract
Activation of 5' adenosine monophosphate-activated protein kinase (AMPK) with aminoimidazole carboxamide ribonucleotide (AICAR) increases skeletal muscle glucose uptake and fatty acid oxidation. The purpose of these experiments was to utilize AICAR to enhance palmitate consumption by mitochondria in cultured skeletal muscle cells. In these experiments, we treated C2C12 myotubes or adult single skeletal muscle fibers with varying concentrations of AICAR for different lengths of time. Surprisingly, acute AICAR exposure at most concentrations (0.25-1.5 mM), but not all (0.1 mM), modestly inhibited oxygen consumption even though AICAR increased AMPK phosphorylation. The data suggest that AICAR inhibited oxygen consumption by the cultured muscle in a non-specific manner. The results of these experiments are expected to provide valuable information to investigators interested in using AICAR in cell culture studies.
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Affiliation(s)
- Espen E Spangenburg
- Department of Kinesiology, School of Public Health, University of Maryland, College Park, MD, 21045, USA,
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Sgk1 sensitivity of Na(+)/H(+) exchanger activity and cardiac remodeling following pressure overload. Basic Res Cardiol 2012; 107:236. [PMID: 22212557 DOI: 10.1007/s00395-011-0236-2] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/19/2011] [Revised: 11/15/2011] [Accepted: 12/04/2011] [Indexed: 01/08/2023]
Abstract
Sustained increase of cardiac workload is known to trigger cardiac remodeling with eventual development of cardiac failure. Compelling evidence points to a critical role of enhanced cardiac Na(+)/H(+) exchanger (NHE1) activity in the underlying pathophysiology. The signaling triggering up-regulation of NHE1 remained, however, ill defined. The present study explored the involvement of the serum- and glucocorticoid-inducible kinase Sgk1 in cardiac remodeling due to transverse aortic constriction (TAC). To this end, experiments were performed in gene targeted mice lacking functional Sgk1 (sgk1 (-/-)) and their wild-type controls (sgk1 (+/+)). Transcript levels have been determined by RT-PCR, cytosolic pH (pH( i )) utilizing 2',7'-bis-(2-carboxyethyl)-5-(and-6)-carboxyfluorescein (BCECF) fluorescence, Na(+)/H(+) exchanger activity by the Na(+)-dependent realkalinization after an ammonium pulse, ejection fraction (%) utilizing cardiac cine magnetic resonance imaging and cardiac glucose uptake by PET imaging. As a result, TAC increased the mRNA expression of Sgk1 in sgk1 (+/+) mice, paralleled by an increase in Nhe1 transcript levels as well as Na(+)/H(+) exchanger activity, all effects virtually abrogated in sgk1 (-/-) mice. In sgk1 (+/+) mice, TAC induced a decrease in Pgc1a mRNA expression, while Spp1 mRNA expression was increased, both effects diminished in the sgk1 (-/-) mice. TAC was followed by a significant increase of heart and lung weight in sgk1 (+/+) mice, an effect significantly blunted in sgk1 (-/-) mice. TAC increased the transcript levels of Anp and Bnp, effects again significantly blunted in sgk1 (-/-) mice. TAC increased transcript levels of Collagen I and III as well as Ctgf mRNA and CTGF protein abundance, effects significantly blunted in sgk1 (-/-) mice. TAC further decreased the ejection fraction in sgk1 (+/+) mice, an effect again attenuated in sgk1 (-/-) mice. Also, cardiac FDG-glucose uptake was increased to a larger extent in sgk1 (+/+) mice than in sgk1 (-/-) mice after TAC. These observations point to an important role for SGK1 in cardiac remodeling and development of heart failure following an excessive work load.
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Ginion A, Auquier J, Benton CR, Mouton C, Vanoverschelde JL, Hue L, Horman S, Beauloye C, Bertrand L. Inhibition of the mTOR/p70S6K pathway is not involved in the insulin-sensitizing effect of AMPK on cardiac glucose uptake. Am J Physiol Heart Circ Physiol 2011; 301:H469-77. [DOI: 10.1152/ajpheart.00986.2010] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
The AMP-activated protein kinase (AMPK) is known to increase cardiac insulin sensitivity on glucose uptake. AMPK also inhibits the mammalian target of rapamycin (mTOR)/p70 ribosomal S6 kinase (p70S6K) pathway. Once activated by insulin, mTOR/p70S6K phosphorylates insulin receptor substrate-1 (IRS-1) on serine residues, resulting in its inhibition and reduction of insulin signaling. AMPK was postulated to act on insulin by inhibiting this mTOR/p70S6K-mediated negative feedback loop. We tested this hypothesis in cardiomyocytes. The stimulation of glucose uptake by AMPK activators and insulin correlated with AMPK and protein kinase B (PKB/Akt) activation, respectively. Both treatments induced the phosphorylation of Akt substrate 160 (AS160) known to control glucose uptake. Together, insulin and AMPK activators acted synergistically to induce PKB/Akt overactivation, AS160 overphosphorylation, and glucose uptake overstimulation. This correlated with p70S6K inhibition and with a decrease in serine phosphorylation of IRS-1, indicating the inhibition of the negative feedback loop. We used the mTOR inhibitor rapamycin to confirm these results. Mimicking AMPK activators in the presence of insulin, rapamycin inhibited p70S6K and reduced IRS-1 phosphorylation on serine, resulting in the overphosphorylation of PKB/Akt and AS160. However, rapamycin did not enhance the insulin-induced stimulation of glucose uptake. In conclusion, although the insulin-sensitizing effect of AMPK on PKB/Akt is explained by the inhibition of the insulin-induced negative feedback loop, its effect on glucose uptake is independent of this mechanism. This disconnection revealed that the PKB/Akt/AS160 pathway does not seem to be the rate-limiting step in the control of glucose uptake under insulin treatment.
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Affiliation(s)
- Audrey Ginion
- Pole of Cardiovascular Research, Institut de Recherche Expérimentale et Clinique, Université catholique de Louvain, Brussels, Belgium
| | - Julien Auquier
- Pole of Cardiovascular Research, Institut de Recherche Expérimentale et Clinique, Université catholique de Louvain, Brussels, Belgium
| | - Carley R. Benton
- Pole of Cardiovascular Research, Institut de Recherche Expérimentale et Clinique, Université catholique de Louvain, Brussels, Belgium
| | - Céline Mouton
- Pole of Cardiovascular Research, Institut de Recherche Expérimentale et Clinique, Université catholique de Louvain, Brussels, Belgium
| | - Jean-Louis Vanoverschelde
- Pole of Cardiovascular Research, Institut de Recherche Expérimentale et Clinique, Université catholique de Louvain, Brussels, Belgium
| | - Louis Hue
- Pole of Cardiovascular Research, Institut de Recherche Expérimentale et Clinique, Université catholique de Louvain, Brussels, Belgium
| | - Sandrine Horman
- Pole of Cardiovascular Research, Institut de Recherche Expérimentale et Clinique, Université catholique de Louvain, Brussels, Belgium
| | - Christophe Beauloye
- Pole of Cardiovascular Research, Institut de Recherche Expérimentale et Clinique, Université catholique de Louvain, Brussels, Belgium
| | - Luc Bertrand
- Pole of Cardiovascular Research, Institut de Recherche Expérimentale et Clinique, Université catholique de Louvain, Brussels, Belgium
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Sarigianni M, Tsapas A, Mikhailidis DP, Kaloyianni M, Koliakos G, Paletas K. Involvement of signaling molecules on na/h exchanger-1 activity in human monocytes. Open Cardiovasc Med J 2010; 4:181-8. [PMID: 21160910 PMCID: PMC3002055 DOI: 10.2174/1874192401004010181] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2010] [Revised: 07/30/2010] [Accepted: 08/02/2010] [Indexed: 12/27/2022] Open
Abstract
Background: Sodium/hydrogen exchanger-1 (NHE-1) contributes to maintaining intracellular pH (pHi). We assessed the effect of glucose, insulin, leptin and adrenaline on NHE-1 activity in human monocytes in vitro. These cells play a role in atherogenesis and disturbances in the hormones evaluated are associated with obesity and diabetes. Methods and Results: Monocytes were isolated from 16 healthy obese and 10 lean healthy subjects. NHE-1 activity was estimated by measuring pHi with a fluorescent dye. pHi was assessed pre- and post-incubation with glucose, insulin, leptin and adrenaline. Experiments were repeated after adding a NHE-1 inhibitor (cariporide) or an inhibitor of protein kinase C (PKC), nitric oxide synthase (NOS), nicotinamide adenine dinucleotide phosphate (NADPH) oxidase, phosphoinositide 3-kinases (PI3K) or actin polymerization. Within the whole study population, glucose enhanced NHE-1 activity by a processes involving PKC, NOS, PI3K and actin polymerization (p = 0.0006 to 0.01). Insulin-mediated activation of NHE-1 (p = <0.0001 to 0.02) required the classical isoforms of PKC, NOS, NADPH oxidase and PI3K. Leptin increased NHE-1 activity (p = 0.0004 to 0.04) through the involvement of PKC and actin polymerization. Adrenaline activated NHE-1 (p = <0.0001 to 0.01) by a process involving the classical isoforms of PKC, NOS and actin polymerization. There were also some differences in responses when lean and obese subjects were compared. Incubation with cariporide attenuated the observed increase in NHE-1 activity. Conclusions: Selective inhibition of NHE-1 in monocytes could become a target for drug action in atherosclerotic vascular disease.
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Affiliation(s)
- Maria Sarigianni
- Metabolic Diseases Unit, Second Department of Internal Medicine, Medical School, Aristotle University of Thessaloniki, Greece
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Harada S, Fujita-Hamabe W, Tokuyama S. RETRACTED: The importance of regulation of blood glucose levels through activation of peripheral 5′-AMP-activated protein kinase on ischemic neuronal damage. Brain Res 2010; 1351:254-263. [DOI: 10.1016/j.brainres.2010.06.052] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2010] [Revised: 06/17/2010] [Accepted: 06/21/2010] [Indexed: 01/17/2023]
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Vila-Bedmar R, Lorenzo M, Fernández-Veledo S. Adenosine 5'-monophosphate-activated protein kinase-mammalian target of rapamycin cross talk regulates brown adipocyte differentiation. Endocrinology 2010; 151:980-92. [PMID: 20133456 DOI: 10.1210/en.2009-0810] [Citation(s) in RCA: 90] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Abstract
Brown adipose tissue (BAT) is considered of metabolic significance in mammalian physiology, because it plays an important role in regulating energy balance. Alterations in this tissue have been associated with obesity and type 2 diabetes. The molecular mechanisms modulating brown adipocyte differentiation are not fully understood. Using a murine brown preadipocyte cell line, primary cultures, and 3T3-L1 cells, we analyzed the contribution of various intracellular signaling pathways to adipogenic and thermogenic programs. Sequential activation of p38MAPK and LKB1-AMPK-tuberous sclerosis complex 2 (TSC2) as well as significant attenuation of ERK1/2 and mammalian target of rapamycin (mTOR)-p70 S6 kinase 1 (p70S6K1) activation was observed through the brown differentiation process. This study demonstrates a critical role for AMPK in controlling the mTOR-p70S6K1 signaling cascade in brown but not in 3T3-L1 adipocytes. We observed that mTOR activity is essential in the first stages of differentiation. Nevertheless, subsequent inhibition of this cascade by AMPK activation is also necessary at later stages. An in vivo study showed that prolonged 5-aminoimidazole-4-carboxamide ribonucleoside (AICAR)-induced AMPK activation increases uncoupling protein 1 expression and induces an accumulation of brown adipocytes in white adipose tissue (WAT), as revealed by immunohistology. Moreover, the induction of brown adipogenesis in areas of white fat partially correlates with the body weight reduction detected in response to treatment with AICAR. Taken together, our study reveals that differentiation of brown adipocytes employs different signaling pathways from white adipocytes, with AMPK-mTOR cross talk a central mediator of this process. Promotion of BAT development in WAT by pharmacological activation of AMPK may have potential in treating obesity by acting on energy dissipation.
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Affiliation(s)
- Rocio Vila-Bedmar
- Department of Biochemistry and Molecular Biology II, Faculty of Pharmacy, Complutense University, 28040 Madrid, Spain
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Abstract
Mimetics of hormetic agents offer a novel approach to adjust dose to minimize the risk of toxic response, and maximize the benefit of induction of at least partial physiological conditioning. Nature selected and preserved those organisms and triggers that promote tolerance to stress. The induced tolerance can serve to resist that challenge and can repair previous age, disease, and trauma damage as well to provide a more youthful response to other stresses. The associated physiological conditioning may include youthful restoration of DNA repair, resistance to oxidizing pollutants, protein structure and function repair, improved immunity, tissue remodeling, adjustments in central and peripheral nervous systems, and altered metabolism. By elucidating common pathways activated by hormetic agent's mimetics, new strategies for intervention in aging, disease, and trauma emerge. Intervention potential in cancer, diabetes, age-related diseases, infectious diseases, cardiovascular diseases, and Alzheimer's disease are possible. Some hormetic mimetics exist in pathways in primitive organisms and are active or latent in humans. Peptides, oligonucleotides, and hormones are among the mimetics that activate latent resistance to radiation, physical endurance, strength, and immunity to physiological condition tolerance to stress. Co-activators may be required for expression of the desired physiological conditioning health and rejuvenation benefits.
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Affiliation(s)
- Joan Smith Sonneborn
- Department of Zoology and Physiology, University of Wyoming, 1000 E. University Avenue, Laramie, WY 82071, USA
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Affiliation(s)
- Luigi Saccà
- Department of Internal Medicine and Cardiovascular Sciences, University Federico II, Naples, Italy.
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Bracci A, Colombo G, Ronchetti F, Compostella F. 2′-O-Alkyl Derivatives and 5′-Analogues of 5-Aminoimidazole-4-carboxamide-1-β-D-ribofuranoside (AICAR) as Potential Hsp90 Inhibitors. European J Org Chem 2009. [DOI: 10.1002/ejoc.200900797] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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Benziane B, Björnholm M, Lantier L, Viollet B, Zierath JR, Chibalin AV. AMP-activated protein kinase activator A-769662 is an inhibitor of the Na(+)-K(+)-ATPase. Am J Physiol Cell Physiol 2009; 297:C1554-66. [PMID: 19828836 DOI: 10.1152/ajpcell.00010.2009] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Muscle contraction and metabolic stress are potent activators of AMP-activated protein kinase (AMPK). AMPK restores energy balance by activating processes that produce energy while inhibiting those that consume energy. The role of AMPK in the regulation of active ion transport is unclear. Our aim was to determine the effect of the AMPK activator A-769662 on Na(+)-K(+)-ATPase function in skeletal muscle cells. Short-term incubation of differentiated rat L6 myotubes with 100 microM A-769662 increased AMPK and acetyl-CoA carboxylase (ACC) phosphorylation in parallel with decreased Na(+)-K(+)-ATPase alpha(1)-subunit abundance at the plasma membrane and ouabain-sensitive (86)Rb(+) uptake. Notably, the effect of A-769662 on Na(+)-K(+)-ATPase was similar in muscle cells that do not express AMPK alpha(1)- and alpha(2)-catalytic subunits. A-769662 directly inhibits the alpha(1)-isoform of the Na(+)-K(+)-ATPase, purified from rat and human kidney cells in vitro with IC(50) 57 microM and 220 microM, respectively. Inhibition of the Na(+)-K(+)-ATPase by 100 microM ouabain decreases sodium pump activity and cell surface abundance, similar to the effect of A-769662, without affecting AMPK and ACC phosphorylation. In conclusion, the AMPK activator A-769662 inhibits Na(+)-K(+)-ATPase activity and decreases the sodium pump cell surface abundance in L6 skeletal muscle cells. The effect of A-769662 on sodium pump is due to direct inhibition of the Na(+)-K(+)-ATPase activity, rather than AMPK activation. This AMPK-independent effect on Na(+)-K(+)-ATPase calls into question the use of A-769662 as a specific AMPK activator for metabolic studies.
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Affiliation(s)
- Boubacar Benziane
- Dept. of Molecular Medicine and Surgery, Karolinska Institutet, Stockholm, Sweden
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Differential regulation of NHE1 phosphorylation and glucose uptake by inhibitors of the ERK pathway and p90RSK in 3T3-L1 adipocytes. Cell Signal 2009; 21:1984-93. [PMID: 19765648 DOI: 10.1016/j.cellsig.2009.09.009] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2009] [Accepted: 09/09/2009] [Indexed: 01/12/2023]
Abstract
Insulin stimulates trafficking of GLUT4 to the cell surface for glucose uptake into target cells, and phosphorylation of Ser703 of the Na+/H+ exchanger NHE1, which activates proton efflux. The latter has been proposed to facilitate optimal glucose uptake into cardiomyocytes. We found that the insulin-stimulated phosphorylation of Ser703 of NHE1 is mediated by p90RSK but not directly coupled to glucose uptake in 3T3-L1 adipocytes in the short-term. Inhibiting Erk1/2 activation prevented NHE1 phosphorylation but not glucose uptake in 3T3-L1 adipocytes. In contrast, both NHE1 phosphorylation and insulin-stimulated uptake of glucose into 3T3-L1 adipocytes were blocked by inhibitors of the N-terminal kinase domain of p90RSK, namely BI-D1870 and SL0101, but not the FMK inhibitor of the C-terminal kinase domain of p90RSK, though in our hands FMK did not inhibit p90RSK in 3T3-L1 adipocytes. Further experiments were consistent with phosphorylation of AS160 by PKB/Akt mediating insulin-stimulated trafficking of GLUT4 to the plasma membrane. BI-D1870 and SL0101 however, inhibited glucose uptake without blocking GLUT4 translocation. While BI-D1870 partially inhibited insulin-stimulated PKB activation in these cells, this only partially inhibited AS160 phosphorylation and did not block GLUT4 trafficking, suggesting that p90RSK might regulate glucose transport after GLUT4 translocation. Moreover, BI-D1870 also prevented PMA-induced glucose transport in 3T3-L1 adipocytes further suggesting a role for p90RSK in regulating uptake of glucose into the cells. Kinetic experiments are consistent with SL0101 being a direct competitor of 2-deoxyglucose entry into cells, and this compound might also inhibit uptake of glucose into cells via inhibiting p90RSK, as revealed by comparison with the inactive form of the inhibitor. Taken together, we propose that BI-D1870 and SL0101 might exert their inhibitory effects on glucose uptake in 3T3-L1 adipocytes at least partially through a p90RSK dependent step after GLUT4 becomes associated with the plasma membrane.
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Javadov S, Rajapurohitam V, Kilić A, Zeidan A, Choi A, Karmazyn M. Anti-hypertrophic effect of NHE-1 inhibition involves GSK-3beta-dependent attenuation of mitochondrial dysfunction. J Mol Cell Cardiol 2009; 46:998-1007. [PMID: 19318234 DOI: 10.1016/j.yjmcc.2008.12.023] [Citation(s) in RCA: 53] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/29/2008] [Revised: 12/23/2008] [Accepted: 12/24/2008] [Indexed: 11/24/2022]
Abstract
Although Na(+)-H(+) exchanger 1 (NHE-1) inhibition has been demonstrated to have anti-hypertrophic effect indirectly through mitochondria, the detailed cellular mechanisms mediating this effect remain elusive. In this study we sought to determine whether NHE-1 inhibition exerts an anti-hypertrophic effect by modulating the mitochondrial permeability transition pore (mPTP) opening through the AMP-activated protein kinase (AMPK)/glycogen synthase kinase 3beta (GSK-3beta) pathway during hypertrophy in cardiomyocytes. An in vivo model of hypertrophy was induced in male Sprague-Dawley rats by subjecting them to 3, 7 or 28 days of coronary artery ligation (CAL). To induce hypertrophy in vitro, cardiomyocytes isolated from hearts of neonatal (1-3 days) Sprague-Dawley rats were exposed to endothelin-1 (ET-1, 10 nM) in the presence or absence of various treatments. The results demonstrate that CAL affected both AMPKalpha and GSK-3beta phosphorylation in a time-dependent manner. In cultured cardiomyocytes, ET-1 increased phosphorylation of AMPKalpha(1)/alpha(2)(Ser485/Ser491) and GSK-3beta(Ser9) by 80% (P<0.05) and 225% (P<0.05) respectively, both of which were significantly blunted by the NHE-1 inhibitor AVE-4890 (5 microM). ET-1-induced phosphorylation of GSK-3beta(Ser9) was attenuated by inhibitors of phosphatidylinositol 3-kinase (LY294002), Akt (Akt inhibitor VIII), ERK1/2 (PD98059) and by the AMPK agonist 5-aminoimidazole-4-carboxamide-1-beta-D-ribofuranoside (AICAR). Prevention of GSK-3beta(Ser9) phosphorylation was also accompanied by suppression of ET-1-induced increases in cell surface area, ANP and alpha-skeletal actin gene expression. Co-immunoprecipitation studies revealed that GSK-3beta interacts with components of the mPTP, voltage-dependent anion channel (VDAC) and adenine nucleotide translocase. Furthermore, ET-1 reduced phosphorylation of VDAC, which was associated with both mPTP opening and mitochondrial membrane depolarization. These effects were mimicked by the GSK-3beta inhibitor SB216763, thus showing that modulation of mPTP formation is GSK-3beta-dependent. In conclusion, anti-hypertrophic effect of NHE-1 inhibition can be mediated through activation of GSK-3beta which in turn induces inhibition of mPTP opening due to VDAC phosphorylation.
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Affiliation(s)
- Sabzali Javadov
- Department of Physiology and Pharmacology Schulich School of Medicine and Dentistry University of Western Ontario London, Ontario, Canada.
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