1
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Fulghum KL, Collins HE, Lorkiewicz PK, Cassel TA, Fan TWM, Hill BG. Exercise-induced changes in myocardial glucose utilization during periods of active cardiac growth. J Mol Cell Cardiol 2024; 191:50-62. [PMID: 38703412 PMCID: PMC11135805 DOI: 10.1016/j.yjmcc.2024.04.014] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/08/2023] [Revised: 04/08/2024] [Accepted: 04/26/2024] [Indexed: 05/06/2024]
Abstract
Exercise training can promote physiological cardiac growth, which has been suggested to involve changes in glucose metabolism to facilitate hypertrophy of cardiomyocytes. In this study, we used a dietary, in vivo isotope labeling approach to examine how exercise training influences the metabolic fate of carbon derived from dietary glucose in the heart during acute, active, and established phases of exercise-induced cardiac growth. Male and female FVB/NJ mice were subjected to treadmill running for up to 4 weeks and cardiac growth was assessed by gravimetry. Cardiac metabolic responses to exercise were assessed via in vivo tracing of [13C6]-glucose via mass spectrometry and nuclear magnetic resonance. We found that the half-maximal cardiac growth response was achieved by approximately 1 week of daily exercise training, with near maximal growth observed in male mice with 2 weeks of training; however, female mice were recalcitrant to exercise-induced cardiac growth and required a higher daily intensity of exercise training to achieve significant, albeit modest, increases in cardiac mass. We also found that increases in the energy charge of adenylate and guanylate nucleotide pools precede exercise-induced changes in cardiac size and were associated with higher glucose tracer enrichment in the TCA pool and in amino acids (aspartate, glutamate) sourced by TCA intermediates. Our data also indicate that the activity of collateral biosynthetic pathways of glucose metabolism may not be markedly altered by exercise. Overall, this study provides evidence that metabolic remodeling in the form of heightened energy charge and increased TCA cycle activity and cataplerosis precedes cardiac growth caused by exercise training in male mice.
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Affiliation(s)
- Kyle L Fulghum
- Center for Cardiometabolic Science, Christina Lee Brown Envirome Institute, Division of Environmental Medicine, Department of Medicine, University of Louisville, Louisville, KY, United States of America
| | - Helen E Collins
- Center for Cardiometabolic Science, Christina Lee Brown Envirome Institute, Division of Environmental Medicine, Department of Medicine, University of Louisville, Louisville, KY, United States of America
| | - Pawel K Lorkiewicz
- Center for Cardiometabolic Science, Christina Lee Brown Envirome Institute, Division of Environmental Medicine, Department of Medicine, University of Louisville, Louisville, KY, United States of America
| | - Teresa A Cassel
- Center for Environmental and Systems Biochemistry, University of Kentucky, Lexington, KY, United States of America
| | - Teresa W M Fan
- Center for Environmental and Systems Biochemistry, University of Kentucky, Lexington, KY, United States of America
| | - Bradford G Hill
- Center for Cardiometabolic Science, Christina Lee Brown Envirome Institute, Division of Environmental Medicine, Department of Medicine, University of Louisville, Louisville, KY, United States of America.
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2
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Liu B, Liu X, Hu S, Mao S, Yang M, Wu B, Wu G. Effect of SH2B1 on glucose metabolism during pressure overload-induced cardiac hypertrophy and cardiac dysfunction. Clin Exp Pharmacol Physiol 2023; 50:815-825. [PMID: 37401170 DOI: 10.1111/1440-1681.13807] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2022] [Revised: 06/14/2023] [Accepted: 06/16/2023] [Indexed: 07/05/2023]
Abstract
This study mainly explored the effect and mechanism of Src homology 2 (SH2) B adaptor protein 1 (SH2B1) on cardiac glucose metabolism during pressure overload-induced cardiac hypertrophy and dysfunction. A pressure-overloaded cardiac hypertrophy model was constructed, and SH2B1-siRNA was injected through the tail vein. Haematoxylin and eosin (H&E) staining was used to detect myocardial morphology. ANP, BNP, β-MHC and the diameter of myocardial fibres were quantitatively measured to evaluate the degree of cardiac hypertrophy, respectively. GLUT1, GLUT4, and IR were detected to assess cardiac glucose metabolism. Cardiac function was determined by echocardiography. Then, glucose oxidation and uptake, glycolysis and fatty acid metabolism were assessed in Langendorff perfusion of hearts. Finally, PI3K/AKT activator was used to further explore the relevant mechanism. The results showed that during cardiac pressure overload, with the aggravation of cardiac hypertrophy and dysfunction, cardiac glucose metabolism and glycolysis increased, and fatty acid metabolism decreased. After SH2B1-siRNA transfection, cardiac SH2B1 expression was knocked down, and the degree of cardiac hypertrophy and dysfunction was alleviated compared with the Control-siRNA transfected group. Simultaneously, cardiac glucose metabolism and glycolysis were reduced, and fatty acid metabolism was enhanced. The SH2B1 expression knockdown mitigated the cardiac hypertrophy and dysfunction by reducing cardiac glucose metabolism. After using PI3K/AKT activator, the effect of SH2B1 expression knockdown on cardiac glucose metabolism was reversed during cardiac hypertrophy and dysfunction. Collectively, SH2B1 regulated cardiac glucose metabolism by activating the PI3K/AKT pathway during pressure overload-induced cardiac hypertrophy and cardiac dysfunction.
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Affiliation(s)
- Beilei Liu
- Department of Cardiology, Hubei Provincial Hospital of Traditional Chinese Medicine, Wuhan, China
- Affiliated Hospital of Hubei University of Chinese Medicine, Wuhan, China
- Hubei Province Academy of Traditional Chinese Medicine, Wuhan, China
| | - Xuguang Liu
- Department of Cardiology, Hubei Provincial Hospital of Traditional Chinese Medicine, Wuhan, China
- Affiliated Hospital of Hubei University of Chinese Medicine, Wuhan, China
- Hubei Province Academy of Traditional Chinese Medicine, Wuhan, China
| | - Shan Hu
- Department of Cardiology, Hubei Key Laboratory of Cardiology, Renmin Hospital of Wuhan University, Cardiovascular Research Institute, Wuhan University, Wuhan, China
| | - Shuai Mao
- Department of Cardiology, Hubei Key Laboratory of Cardiology, Renmin Hospital of Wuhan University, Cardiovascular Research Institute, Wuhan University, Wuhan, China
| | - Manqi Yang
- Department of Cardiology, Hubei Key Laboratory of Cardiology, Renmin Hospital of Wuhan University, Cardiovascular Research Institute, Wuhan University, Wuhan, China
| | - Bin Wu
- Department of Cardiology, Hubei Provincial Hospital of Traditional Chinese Medicine, Wuhan, China
- Affiliated Hospital of Hubei University of Chinese Medicine, Wuhan, China
- Hubei Province Academy of Traditional Chinese Medicine, Wuhan, China
| | - Gang Wu
- Department of Cardiology, Hubei Key Laboratory of Cardiology, Renmin Hospital of Wuhan University, Cardiovascular Research Institute, Wuhan University, Wuhan, China
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3
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Abstract
The adult mammalian heart is recalcitrant to regeneration after injury, in part due to the postmitotic nature of cardiomyocytes. Accumulating evidence suggests that cardiomyocyte proliferation in fetal or neonatal mammals and in regenerative non-mammalian models depends on a conducive metabolic state. Results from numerous studies in adult hearts indicate that conditions of relatively low fatty acid oxidation, low reactive oxygen species generation, and high glycolysis are required for induction of cardiomyocyte proliferation. Glycolysis appears particularly important because it provides branchpoint metabolites for several biosynthetic pathways that are essential for synthesis of nucleotides and nucleotide sugars, amino acids, and glycerophospholipids, all of which are required for daughter cell formation. In addition, the proliferative cardiomyocyte phenotype is supported in part by relatively low oxygen tensions and through the actions of critical transcription factors, coactivators, and signaling pathways that promote a more glycolytic and proliferative cardiomyocyte phenotype, such as hypoxia inducible factor 1α (Hif1α), Yes-associated protein (Yap), and ErbB2. Interventions that inhibit glycolysis or its integrated biosynthetic pathways almost universally impair cardiomyocyte proliferative capacity. Furthermore, metabolic enzymes that augment biosynthetic capacity such as phosphoenolpyruvate carboxykinase 2 and pyruvate kinase M2 appear to be amplifiers of cardiomyocyte proliferation. Collectively, these studies suggest that acquisition of a glycolytic and biosynthetic metabolic phenotype is a sine qua non of cardiomyocyte proliferation. Further knowledge of the regulatory mechanisms that control substrate partitioning to coordinate biosynthesis with energy provision could be leveraged to prompt or augment cardiomyocyte division and to promote cardiac repair.
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Affiliation(s)
- Tamer M A Mohamed
- Division of Cardiovascular Medicine, Institute of Molecular Cardiology, University of Louisville, Louisville, KY, USA
- Corresponding authors: Tamer M.A. Mohamed, PhD, Department of Medicine, Division of Cardiovascular Medicine, Institute of Molecular Cardiology, 580 S. Preston Street, Rm 121A, Louisville, KY 40202, USA.
| | - Riham Abouleisa
- Division of Cardiovascular Medicine, Institute of Molecular Cardiology, University of Louisville, Louisville, KY, USA
| | - Bradford G Hill
- Division of Environmental Medicine, Christina Lee Brown Envirome Institute, Diabetes and Obesity Center, University of Louisville, Louisville, KY, USA
- Bradford G. Hill, PhD, Department of Medicine, Christina Lee Brown Envirome Institute, Diabetes and Obesity Center, University of Louisville, 580 S. Preston Street, Rm 321E, Louisville, KY 40202, USA.
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4
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Jin ES, Lee MH, Malloy CR. 13 C NMR of glutamate for monitoring the pentose phosphate pathway in myocardium. NMR IN BIOMEDICINE 2021; 34:e4533. [PMID: 33900680 DOI: 10.1002/nbm.4533] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/31/2020] [Revised: 04/05/2021] [Accepted: 04/13/2021] [Indexed: 06/12/2023]
Abstract
After administration of 13 C-labeled glucose, the activity of the pentose phosphate pathway (PPP) is often assessed by the distribution of 13 C in lactate. However, in some tissues, such as the well-oxygenated heart, the concentration of lactate may be too low for convenient analysis by NMR. Here, we examined 13 C-labeled glutamate as an alternative biomarker of the PPP in the heart. Isolated rat hearts were perfused with media containing [2,3-13 C2 ]glucose and the tissue extracts were analyzed. Metabolism of [2,3-13 C2 ]glucose yields [1,2-13 C2 ]pyruvate via glycolysis and [2,3-13 C2 ]pyruvate via the PPP. Pyruvate is in exchange with lactate or is further metabolized to glutamate through pyruvate dehydrogenase and the TCA cycle. A doublet from [4,5-13 C2 ]glutamate, indicating flux through the PPP, was readily detected in 13 C NMR of heart extracts even when the corresponding doublet from [2,3-13 C2 ]lactate was minimal. Benfotiamine, known to induce the PPP, caused an increase in production of [4,5-13 C2 ]glutamate. In rats receiving [2,3-13 C2 ]glucose, brain extracts showed well-resolved signals from both [2,3-13 C2 ]lactate and [4,5-13 C2 ]glutamate in 13 C NMR spectra. Assessment of the PPP in the brain based on glutamate had a strong linear correlation with lactate-based assessment. In summary, 13 C NMR analysis of glutamate enabled detection of the low PPP activity in isolated hearts. This analyte is an alternative to lactate for monitoring the PPP with the use of [2,3-13 C2 ]glucose.
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Affiliation(s)
- Eunsook S Jin
- Advanced Imaging Research Center, University of Texas Southwestern Medical Center, Dallas, Texas, USA
- Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, Texas, USA
| | - Min H Lee
- Advanced Imaging Research Center, University of Texas Southwestern Medical Center, Dallas, Texas, USA
| | - Craig R Malloy
- Advanced Imaging Research Center, University of Texas Southwestern Medical Center, Dallas, Texas, USA
- Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, Texas, USA
- Radiology, University of Texas Southwestern Medical Center, Dallas, Texas, USA
- VA North Texas Health Care System, Dallas, Texas, USA
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5
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Pasqua T, Rocca C, Giglio A, Angelone T. Cardiometabolism as an Interlocking Puzzle between the Healthy and Diseased Heart: New Frontiers in Therapeutic Applications. J Clin Med 2021; 10:721. [PMID: 33673114 PMCID: PMC7918460 DOI: 10.3390/jcm10040721] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2020] [Revised: 02/05/2021] [Accepted: 02/07/2021] [Indexed: 12/14/2022] Open
Abstract
Cardiac metabolism represents a crucial and essential connecting bridge between the healthy and diseased heart. The cardiac muscle, which may be considered an omnivore organ with regard to the energy substrate utilization, under physiological conditions mainly draws energy by fatty acids oxidation. Within cardiomyocytes and their mitochondria, through well-concerted enzymatic reactions, substrates converge on the production of ATP, the basic chemical energy that cardiac muscle converts into mechanical energy, i.e., contraction. When a perturbation of homeostasis occurs, such as an ischemic event, the heart is forced to switch its fatty acid-based metabolism to the carbohydrate utilization as a protective mechanism that allows the maintenance of its key role within the whole organism. Consequently, the flexibility of the cardiac metabolic networks deeply influences the ability of the heart to respond, by adapting to pathophysiological changes. The aim of the present review is to summarize the main metabolic changes detectable in the heart under acute and chronic cardiac pathologies, analyzing possible therapeutic targets to be used. On this basis, cardiometabolism can be described as a crucial mechanism in keeping the physiological structure and function of the heart; furthermore, it can be considered a promising goal for future pharmacological agents able to appropriately modulate the rate-limiting steps of heart metabolic pathways.
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Affiliation(s)
- Teresa Pasqua
- Department of Health Science, University Magna Graecia of Catanzaro, 88100 Catanzaro, Italy;
| | - Carmine Rocca
- Laboratory of Cellular and Molecular Cardiovascular Pathophysiology, Department of Biology, E. and E.S. (Di.B.E.S.T.), University of Calabria, 87036 Rende (CS), Italy
| | - Anita Giglio
- Department of Biology, E. and E.S. (Di.B.E.S.T.), University of Calabria, 87036 Rende (CS), Italy;
| | - Tommaso Angelone
- Laboratory of Cellular and Molecular Cardiovascular Pathophysiology, Department of Biology, E. and E.S. (Di.B.E.S.T.), University of Calabria, 87036 Rende (CS), Italy
- National Institute of Cardiovascular Research (I.N.R.C.), 40126 Bologna, Italy
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6
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McNally LA, Altamimi TR, Fulghum K, Hill BG. Considerations for using isolated cell systems to understand cardiac metabolism and biology. J Mol Cell Cardiol 2020; 153:26-41. [PMID: 33359038 DOI: 10.1016/j.yjmcc.2020.12.007] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/31/2020] [Revised: 12/13/2020] [Accepted: 12/16/2020] [Indexed: 12/11/2022]
Abstract
Changes in myocardial metabolic activity are fundamentally linked to cardiac health and remodeling. Primary cardiomyocytes, induced pluripotent stem cell-derived cardiomyocytes, and transformed cardiomyocyte cell lines are common models used to understand how (patho)physiological conditions or stimuli contribute to changes in cardiac metabolism. These cell models are helpful also for defining metabolic mechanisms of cardiac dysfunction and remodeling. Although technical advances have improved our capacity to measure cardiomyocyte metabolism, there is often heterogeneity in metabolic assay protocols and cell models, which could hinder data interpretation and discernment of the mechanisms of cardiac (patho)physiology. In this review, we discuss considerations for integrating cardiomyocyte cell models with techniques that have become relatively common in the field, such as respirometry and extracellular flux analysis. Furthermore, we provide overviews of metabolic assays that complement XF analyses and that provide information on not only catabolic pathway activity, but biosynthetic pathway activity and redox status as well. Cultivating a more widespread understanding of the advantages and limitations of metabolic measurements in cardiomyocyte cell models will continue to be essential for the development of coherent metabolic mechanisms of cardiac health and pathophysiology.
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Affiliation(s)
- Lindsey A McNally
- Department of Medicine, Division of Environmental Medicine, Christina Lee Brown Envirome Institute, Diabetes and Obesity Center, University of Louisville, Louisville, KY, USA
| | - Tariq R Altamimi
- Department of Medicine, Division of Environmental Medicine, Christina Lee Brown Envirome Institute, Diabetes and Obesity Center, University of Louisville, Louisville, KY, USA
| | - Kyle Fulghum
- Department of Medicine, Division of Environmental Medicine, Christina Lee Brown Envirome Institute, Diabetes and Obesity Center, University of Louisville, Louisville, KY, USA
| | - Bradford G Hill
- Department of Medicine, Division of Environmental Medicine, Christina Lee Brown Envirome Institute, Diabetes and Obesity Center, University of Louisville, Louisville, KY, USA.
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7
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Li J, Kemp BA, Howell NL, Massey J, Mińczuk K, Huang Q, Chordia MD, Roy RJ, Patrie JT, Davogustto GE, Kramer CM, Epstein FH, Carey RM, Taegtmeyer H, Keller SR, Kundu BK. Metabolic Changes in Spontaneously Hypertensive Rat Hearts Precede Cardiac Dysfunction and Left Ventricular Hypertrophy. J Am Heart Assoc 2020; 8:e010926. [PMID: 30764689 PMCID: PMC6405673 DOI: 10.1161/jaha.118.010926] [Citation(s) in RCA: 51] [Impact Index Per Article: 12.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Background Sustained pressure overload leads to changes in cardiac metabolism, function, and structure. Both time course and causal relationships between these changes are not fully understood. Therefore, we studied spontaneously hypertensive rats (SHR) during early hypertension development and compared them to control Wistar Kyoto rats. Methods and Results We serially evaluated myocardial glucose uptake rates (Ki) with dynamic 2‐[18F] fluoro‐2‐deoxy‐D‐glucose positron emission tomography, and ejection fraction and left ventricular mass to body weight ratios with cardiac magnetic resonance imaging in vivo, determined glucose uptake and oxidation rates in isolated perfused hearts, and analyzed metabolites, mammalian target of rapamycin activity and endoplasmic reticulum stress in dissected hearts. When compared with Wistar Kyoto rats, SHR demonstrated increased glucose uptake rates (Ki) in vivo, and reduced ejection fraction as early as 2 months of age when hypertension was established. Isolated perfused SHR hearts showed increased glucose uptake and oxidation rates starting at 1 month. Cardiac metabolite analysis at 2 months of age revealed elevated pyruvate, fatty acyl‐ and branched chain amino acid‐derived carnitines, oxidative stress, and inflammation. Mammalian target of rapamycin activity increased in SHR beginning at 2 months. Left ventricular mass to body weight ratios and endoplasmic reticulum stress were elevated in 5 month‐old SHR. Conclusions Thus, in a genetic hypertension model, chronic cardiac pressure overload promptly leads to increased myocardial glucose uptake and oxidation, and to metabolite abnormalities. These coincide with, or precede, cardiac dysfunction while left ventricular hypertrophy develops only later. Myocardial metabolic changes may thus serve as early diagnostic markers for hypertension‐induced left ventricular hypertrophy.
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Affiliation(s)
- Jie Li
- 1 Department of Radiology and Medical Imaging University of Virginia Charlottesville VA
| | - Brandon A Kemp
- 2 Division of Endocrinology and Metabolism Department of Medicine University of Virginia Charlottesville VA
| | - Nancy L Howell
- 2 Division of Endocrinology and Metabolism Department of Medicine University of Virginia Charlottesville VA
| | - James Massey
- 1 Department of Radiology and Medical Imaging University of Virginia Charlottesville VA.,3 Department of Biomedical Engineering University of Virginia Charlottesville VA
| | - Krzysztof Mińczuk
- 1 Department of Radiology and Medical Imaging University of Virginia Charlottesville VA
| | - Qiao Huang
- 1 Department of Radiology and Medical Imaging University of Virginia Charlottesville VA
| | - Mahendra D Chordia
- 1 Department of Radiology and Medical Imaging University of Virginia Charlottesville VA
| | - R Jack Roy
- 1 Department of Radiology and Medical Imaging University of Virginia Charlottesville VA
| | - James T Patrie
- 4 Department of Public Health Sciences University of Virginia Charlottesville VA
| | - Giovanni E Davogustto
- 5 McGovern Medical School University of Texas Health Science Center in Houston Houston TX
| | - Christopher M Kramer
- 6 Department of Cardiovascular Medicine University of Virginia Charlottesville VA
| | - Frederick H Epstein
- 3 Department of Biomedical Engineering University of Virginia Charlottesville VA
| | - Robert M Carey
- 2 Division of Endocrinology and Metabolism Department of Medicine University of Virginia Charlottesville VA
| | - Heinrich Taegtmeyer
- 5 McGovern Medical School University of Texas Health Science Center in Houston Houston TX
| | - Susanna R Keller
- 2 Division of Endocrinology and Metabolism Department of Medicine University of Virginia Charlottesville VA
| | - Bijoy K Kundu
- 1 Department of Radiology and Medical Imaging University of Virginia Charlottesville VA.,3 Department of Biomedical Engineering University of Virginia Charlottesville VA.,7 Cardiovascular Research Center University of Virginia Charlottesville VA
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8
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Chen X, Sherman JW, Wang R. Radioisotope-Based Protocol for Determination of Central Carbon Metabolism in T Cells. Methods Mol Biol 2020; 2111:257-265. [PMID: 31933213 DOI: 10.1007/978-1-0716-0266-9_20] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/25/2023]
Abstract
T lymphocytes are the major components of the adaptive immune system. It's been known that T cells are able to engage a diverse range of metabolic programs to meet the metabolic demands during their life cycle from early development, activation to functional differentiation. Central carbon metabolic pathways provide energy, reducing power, and biosynthetic precursors to support T cell homeostasis, proliferation, and immune functions. As such, quantitative or semiquantitative analysis of central carbon metabolic flux activities offers mechanistic details, as well as insights into the regulation of metabolic pathways and the impact of changing metabolic programs on T cell life cycle. Global profiling of cellular metabolites by mass spectrometry-based metabolomics and metabolic flux analysis (MFA) using radioactive and nonradioactive/stable isotope approaches are powerful tools for determination of central carbon metabolic pathway activity. Here, we describe in detail the procedure for the radioisotope-based approach of analyzing central carbon metabolic fluxes in T cells.
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Affiliation(s)
- Xuyong Chen
- Center for Childhood Cancer & Blood Diseases, Hematology/Oncology & BMT, The Research Institute at Nationwide Children's Hospital, Ohio State University, Columbus, OH, USA
| | - John William Sherman
- Center for Childhood Cancer & Blood Diseases, Hematology/Oncology & BMT, The Research Institute at Nationwide Children's Hospital, Ohio State University, Columbus, OH, USA
| | - Ruoning Wang
- Center for Childhood Cancer & Blood Diseases, Hematology/Oncology & BMT, The Research Institute at Nationwide Children's Hospital, Ohio State University, Columbus, OH, USA.
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9
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Abstract
Metabolic pathways integrate to support tissue homeostasis and to prompt changes in cell phenotype. In particular, the heart consumes relatively large amounts of substrate not only to regenerate ATP for contraction but also to sustain biosynthetic reactions for replacement of cellular building blocks. Metabolic pathways also control intracellular redox state, and metabolic intermediates and end products provide signals that prompt changes in enzymatic activity and gene expression. Mounting evidence suggests that the changes in cardiac metabolism that occur during development, exercise, and pregnancy as well as with pathological stress (eg, myocardial infarction, pressure overload) are causative in cardiac remodeling. Metabolism-mediated changes in gene expression, metabolite signaling, and the channeling of glucose-derived carbon toward anabolic pathways seem critical for physiological growth of the heart, and metabolic inefficiency and loss of coordinated anabolic activity are emerging as proximal causes of pathological remodeling. This review integrates knowledge of different forms of cardiac remodeling to develop general models of how relationships between catabolic and anabolic glucose metabolism may fortify cardiac health or promote (mal)adaptive myocardial remodeling. Adoption of conceptual frameworks based in relational biology may enable further understanding of how metabolism regulates cardiac structure and function.
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Affiliation(s)
- Andrew A Gibb
- From the Center for Translational Medicine, Lewis Katz School of Medicine, Temple University, Philadelphia, PA (A.A.G.)
| | - Bradford G Hill
- the Department of Medicine, Institute of Molecular Cardiology, Diabetes and Obesity Center, University of Louisville School of Medicine, KY (B.G.H.).
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10
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Rabin-Court A, Rodrigues MR, Zhang XM, Perry RJ. Obesity-associated, but not obesity-independent, tumors respond to insulin by increasing mitochondrial glucose oxidation. PLoS One 2019; 14:e0218126. [PMID: 31188872 PMCID: PMC6561592 DOI: 10.1371/journal.pone.0218126] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2019] [Accepted: 05/27/2019] [Indexed: 12/17/2022] Open
Abstract
Obesity is associated with increased incidence and worse prognosis of more than one dozen tumor types; however, the molecular mechanisms for this association remain under debate. We hypothesized that insulin, which is elevated in obesity-driven insulin resistance, would increase tumor glucose oxidation in obesity-associated tumors. To test this hypothesis, we applied and validated a stable isotope method to measure the ratio of pyruvate dehydrogenase flux to citrate synthase flux (VPDH/VCS, i.e. the percent of total mitochondrial oxidation fueled by glucose) in tumor cells. Using this method, we found that three tumor cell lines associated with obesity (colon cancer [MC38], breast cancer [4T1], and prostate cancer [TRAMP-C3] cells) increase VPDH/VCS in response to physiologic concentrations of insulin. In contrast, three tumor cell lines that are not associated with obesity (melanoma [YUMM1.7], B cell lymphoma [BCL1 clone 5B1b], and small cell lung cancer [NCI-H69] cells) exhibited no oxidative response to insulin. The observed increase in glucose oxidation in response to insulin correlated with a dose-dependent increase in cell division in obesity-associated tumor cell lines when grown in insulin, whereas no alteration in cell division was seen in tumor types not associated with obesity. These data reveal that a shift in substrate preference in the setting of physiologic insulin may comprise a metabolic signature of obesity-associated tumors that differs from that of those not associated with obesity.
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Affiliation(s)
- Aviva Rabin-Court
- Department of Internal Medicine, Yale University School of Medicine, New Haven, Connecticut, United States of America
- Department of Cellular & Molecular Physiology, Yale University School of Medicine, New Haven, Connecticut, United States of America
| | - Marcos R. Rodrigues
- Department of Internal Medicine, Yale University School of Medicine, New Haven, Connecticut, United States of America
| | - Xian-Man Zhang
- Department of Internal Medicine, Yale University School of Medicine, New Haven, Connecticut, United States of America
| | - Rachel J. Perry
- Department of Internal Medicine, Yale University School of Medicine, New Haven, Connecticut, United States of America
- Department of Cellular & Molecular Physiology, Yale University School of Medicine, New Haven, Connecticut, United States of America
- * E-mail:
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11
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Fulghum K, Hill BG. Metabolic Mechanisms of Exercise-Induced Cardiac Remodeling. Front Cardiovasc Med 2018; 5:127. [PMID: 30255026 PMCID: PMC6141631 DOI: 10.3389/fcvm.2018.00127] [Citation(s) in RCA: 46] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2018] [Accepted: 08/23/2018] [Indexed: 12/13/2022] Open
Abstract
Exercise has a myriad of physiological benefits that derive in part from its ability to improve cardiometabolic health. The periodic metabolic stress imposed by regular exercise appears fundamental in driving cardiovascular tissue adaptation. However, different types, intensities, or durations of exercise elicit different levels of metabolic stress and may promote distinct types of tissue remodeling. In this review, we discuss how exercise affects cardiac structure and function and how exercise-induced changes in metabolism regulate cardiac adaptation. Current evidence suggests that exercise typically elicits an adaptive, beneficial form of cardiac remodeling that involves cardiomyocyte growth and proliferation; however, chronic levels of extreme exercise may increase the risk for pathological cardiac remodeling or sudden cardiac death. An emerging theme underpinning acute as well as chronic cardiac adaptations to exercise is metabolic periodicity, which appears important for regulating mitochondrial quality and function, for stimulating metabolism-mediated exercise gene programs and hypertrophic kinase activity, and for coordinating biosynthetic pathway activity. In addition, circulating metabolites liberated during exercise trigger physiological cardiac growth. Further understanding of how exercise-mediated changes in metabolism orchestrate cell signaling and gene expression could facilitate therapeutic strategies to maximize the benefits of exercise and improve cardiac health.
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Affiliation(s)
- Kyle Fulghum
- Department of Medicine, Envirome Institute, Institute of Molecular Cardiology, Diabetes and Obesity Center, Louisville, KY, United States
- Department of Physiology, University of Louisville, Louisville, KY, United States
| | - Bradford G. Hill
- Department of Medicine, Envirome Institute, Institute of Molecular Cardiology, Diabetes and Obesity Center, Louisville, KY, United States
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12
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Kajimoto M, Nuri M, Isern NG, Robillard-Frayne I, Des Rosiers C, Portman MA. Metabolic Response of the Immature Right Ventricle to Acute Pressure Overloading. J Am Heart Assoc 2018; 7:JAHA.118.008570. [PMID: 29848498 PMCID: PMC6015375 DOI: 10.1161/jaha.118.008570] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
BACKGROUND Surgical palliation or repair of complex congenital heart disease in early infancy can produce right ventricular (RV) pressure overload, often leading to acute hemodynamic decompensation. The mechanisms causing this acute RV dysfunction remain unclear. We tested the hypothesis that the immature right ventricle lacks the ability to modify substrate metabolism in order to meet increased energy demands induced by acute pressure overloading. METHODS AND RESULTS Twenty-two infant male mixed breed Yorkshire piglets were randomized to a sham operation (Control) or pulmonary artery banding yielding >2-fold elevation over baseline RV systolic pressure. We used carbon 13 (13C)-labeled substrates and proton nuclear magnetic resonance to assess RV energy metabolism. [Phosphocreatine]/[ATP] was significantly lower after pulmonary artery banding. [Phosphocreatine]/[ATP] inversely correlated with energy demand indexed by maximal sustained RV systolic pressure/left ventricular systolic pressure. Fractional contributions of fatty acids to citric acid cycle were significantly lower in the pulmonary artery banding group than in the Control group (medium-chain fatty acids; 14.5±1.6 versus 8.2±1.0%, long-chain fatty acids; 9.3±1.5 versus 5.1±1.1%). 13C-flux analysis showed that flux via pyruvate decarboxylation did not increase during RV pressure overloading. CONCLUSIONS Acute RV pressure overload yielded a decrease in [phosphocreatine]/[ATP] ratio, implying that ATP production did not balance the increasing ATP requirement. Relative fatty acids oxidation decreased without a reciprocal increase in pyruvate decarboxylation. The data imply that RV inability to adjust substrate oxidation contributes to energy imbalance, and potentially to contractile failure. The data suggest that interventions directed at increasing RV pyruvate decarboxylation flux could ameliorate contractile dysfunction associated with acute pressure overloading.
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Affiliation(s)
- Masaki Kajimoto
- Center for Integrative Brain Research, Seattle Children's Research Institute, Seattle, WA
| | - Muhammad Nuri
- Center for Integrative Brain Research, Seattle Children's Research Institute, Seattle, WA.,Division of Pediatric Cardiac Surgery, Seattle Children's Hospital, Seattle, WA
| | - Nancy G Isern
- Environmental Molecular Sciences Laboratory, Pacific Northwest National Laboratories, Richland, WA
| | - Isabelle Robillard-Frayne
- Department of Nutrition, Université de Montréal and Montreal Heart Institute, Montréal, Quebec, Canada
| | - Christine Des Rosiers
- Department of Nutrition, Université de Montréal and Montreal Heart Institute, Montréal, Quebec, Canada
| | - Michael A Portman
- Center for Integrative Brain Research, Seattle Children's Research Institute, Seattle, WA .,Division of Cardiology, Department of Pediatrics, University of Washington, Seattle, WA
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13
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Shen Y, Sherman JW, Chen X, Wang R. Phosphorylation of CDC25C by AMP-activated protein kinase mediates a metabolic checkpoint during cell-cycle G 2/M-phase transition. J Biol Chem 2018; 293:5185-5199. [PMID: 29467227 PMCID: PMC5892595 DOI: 10.1074/jbc.ra117.001379] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2017] [Revised: 02/01/2018] [Indexed: 12/30/2022] Open
Abstract
From unicellular to multicellular organisms, cell-cycle progression is tightly coupled to biosynthetic and bioenergetic demands. Accumulating evidence has demonstrated the G1/S-phase transition as a key checkpoint where cells respond to their metabolic status and commit to replicating the genome. However, the mechanism underlying the coordination of metabolism and the G2/M-phase transition in mammalian cells remains unclear. Here, we show that the activation of AMP-activated protein kinase (AMPK), a highly conserved cellular energy sensor, significantly delays mitosis entry. The cell-cycle G2/M-phase transition is controlled by mitotic cyclin-dependent kinase complex (CDC2-cyclin B), which is inactivated by WEE1 family protein kinases and activated by the opposing phosphatase CDC25C. AMPK directly phosphorylates CDC25C on serine 216, a well-conserved inhibitory phosphorylation event, which has been shown to mediate DNA damage–induced G2-phase arrest. The acute induction of CDC25C or suppression of WEE1 partially restores mitosis entry in the context of AMPK activation. These findings suggest that AMPK-dependent phosphorylation of CDC25C orchestrates a metabolic checkpoint for the cell-cycle G2/M-phase transition.
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Affiliation(s)
- Yuqing Shen
- From the Center for Childhood Cancer and Blood Diseases, Hematology/Oncology and BMT, Research Institute at Nationwide Children's Hospital, Ohio State University, Columbus, Ohio 43205 and.,the Department of Microbiology and Immunology, Key Laboratory of Developmental Genes and Human Disease, Ministry of Education, Medical School, Southeast University, Nanjing 210009, China
| | - John William Sherman
- From the Center for Childhood Cancer and Blood Diseases, Hematology/Oncology and BMT, Research Institute at Nationwide Children's Hospital, Ohio State University, Columbus, Ohio 43205 and
| | - Xuyong Chen
- From the Center for Childhood Cancer and Blood Diseases, Hematology/Oncology and BMT, Research Institute at Nationwide Children's Hospital, Ohio State University, Columbus, Ohio 43205 and
| | - Ruoning Wang
- From the Center for Childhood Cancer and Blood Diseases, Hematology/Oncology and BMT, Research Institute at Nationwide Children's Hospital, Ohio State University, Columbus, Ohio 43205 and
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Integration of flux measurements to resolve changes in anabolic and catabolic metabolism in cardiac myocytes. Biochem J 2017; 474:2785-2801. [PMID: 28706006 PMCID: PMC5545928 DOI: 10.1042/bcj20170474] [Citation(s) in RCA: 50] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2017] [Revised: 07/11/2017] [Accepted: 07/12/2017] [Indexed: 12/18/2022]
Abstract
Although ancillary pathways of glucose metabolism are critical for synthesizing cellular building blocks and modulating stress responses, how they are regulated remains unclear. In the present study, we used radiometric glycolysis assays, [13C6]-glucose isotope tracing, and extracellular flux analysis to understand how phosphofructokinase (PFK)-mediated changes in glycolysis regulate glucose carbon partitioning into catabolic and anabolic pathways. Expression of kinase-deficient or phosphatase-deficient 6-phosphofructo-2-kinase/fructose-2,6-bisphosphatase in rat neonatal cardiomyocytes co-ordinately regulated glycolytic rate and lactate production. Nevertheless, in all groups, >40% of glucose consumed by the cells was unaccounted for via catabolism to pyruvate, which suggests entry of glucose carbons into ancillary pathways branching from metabolites formed in the preparatory phase of glycolysis. Analysis of 13C fractional enrichment patterns suggests that PFK activity regulates glucose carbon incorporation directly into the ribose and the glycerol moieties of purines and phospholipids, respectively. Pyrimidines, UDP-N-acetylhexosamine, and the fatty acyl chains of phosphatidylinositol and triglycerides showed lower 13C incorporation under conditions of high PFK activity; the isotopologue 13C enrichment pattern of each metabolite indicated limitations in mitochondria-engendered aspartate, acetyl CoA and fatty acids. Consistent with this notion, high glycolytic rate diminished mitochondrial activity and the coupling of glycolysis to glucose oxidation. These findings suggest that a major portion of intracellular glucose in cardiac myocytes is apportioned for ancillary biosynthetic reactions and that PFK co-ordinates the activities of the pentose phosphate, hexosamine biosynthetic, and glycerolipid synthesis pathways by directly modulating glycolytic intermediate entry into auxiliary glucose metabolism pathways and by indirectly regulating mitochondrial cataplerosis.
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Abstract
The heart is a biological pump that converts chemical to mechanical energy. This process of energy conversion is highly regulated to the extent that energy substrate metabolism matches energy use for contraction on a beat-to-beat basis. The biochemistry of cardiac metabolism includes the biochemistry of energy transfer, metabolic regulation, and transcriptional, translational as well as posttranslational control of enzymatic activities. Pathways of energy substrate metabolism in the heart are complex and dynamic, but all of them conform to the First Law of Thermodynamics. The perspectives expand on the overall idea that cardiac metabolism is inextricably linked to both physiology and molecular biology of the heart. The article ends with an outlook on emerging concepts of cardiac metabolism based on new molecular models and new analytical tools. © 2016 American Physiological Society. Compr Physiol 6:1675-1699, 2016.
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Affiliation(s)
- Heinrich Taegtmeyer
- Division of Cardiology, Department of Internal Medicine, McGovern Medical School at The University of Texas Health Science Center at Houston
| | - Truong Lam
- Division of Cardiology, Department of Internal Medicine, McGovern Medical School at The University of Texas Health Science Center at Houston
| | - Giovanni Davogustto
- Division of Cardiology, Department of Internal Medicine, McGovern Medical School at The University of Texas Health Science Center at Houston
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Bouzier-Sore AK, Bolaños JP. Uncertainties in pentose-phosphate pathway flux assessment underestimate its contribution to neuronal glucose consumption: relevance for neurodegeneration and aging. Front Aging Neurosci 2015; 7:89. [PMID: 26042035 PMCID: PMC4436897 DOI: 10.3389/fnagi.2015.00089] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2015] [Accepted: 05/01/2015] [Indexed: 11/13/2022] Open
Affiliation(s)
| | - Juan P Bolaños
- Institute of Functional Biology and Genomics, University of Salamanca-CSIC Salamanca, Spain
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17
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Jin ES, Sherry AD, Malloy CR. Evidence for transaldolase activity in the isolated heart supplied with [U-13C3]glycerol. J Biol Chem 2012; 288:2914-22. [PMID: 23235149 DOI: 10.1074/jbc.m112.409441] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Studies of glycerol metabolism in the heart have largely emphasized its role in triglyceride synthesis. However, glycerol may also be oxidized in the citric acid cycle, and glycogen synthesis from glycerol has been reported in the nonmammalian myocardium. The intent of this study was to test the hypothesis that glycerol may be metabolized to glycogen in mammalian heart. Isolated rat hearts were supplied with a mixture of substrates including glucose, lactate, pyruvate, octanoate, [U-(13)C(3)]glycerol, and (2)H(2)O to probe various metabolic pathways including glycerol oxidation, glycolysis, the pentose phosphate pathway, and carbon sources of stored glycogen. NMR analysis confirmed that glycogen production from the level of the citric acid cycle did not occur and that the glycerol contribution to oxidation in the citric acid cycle was negligible in the presence of alternative substrates. Quite unexpectedly, (13)C from [U-(13)C(3)]glycerol appeared in glycogen in carbon positions 4-6 of glucosyl units but none in positions 1-3. The extent of [4,5,6-(13)C(3)]glucosyl unit enrichment in glycogen was enhanced by insulin but decreased by H(2)O(2). Given that triose phosphate isomerase is generally assumed to fully equilibrate carbon tracers in the triose pool, the marked (13)C asymmetry in glycogen can only be attributed to conversion of [U-(13)C(3)]glycerol to [U-(13)C(3)]dihydroxyacetone phosphate and [U-(13)C(3)]glyceraldehyde 3-phosphate followed by rearrangements in the nonoxidative branch of the pentose phosphate pathway involving transaldolase that places this (13)C-enriched 3-carbon unit only in the bottom half of hexose phosphate molecules contributing to glycogen.
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Affiliation(s)
- Eunsook S Jin
- Advanced Imaging Research Center, University of Texas Southwestern Medical Center, Dallas, Texas 75390, USA.
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Karlstädt A, Fliegner D, Kararigas G, Ruderisch HS, Regitz-Zagrosek V, Holzhütter HG. CardioNet: a human metabolic network suited for the study of cardiomyocyte metabolism. BMC SYSTEMS BIOLOGY 2012; 6:114. [PMID: 22929619 PMCID: PMC3568067 DOI: 10.1186/1752-0509-6-114] [Citation(s) in RCA: 50] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/13/2012] [Accepted: 08/16/2012] [Indexed: 02/08/2023]
Abstract
Background Availability of oxygen and nutrients in the coronary circulation is a crucial determinant of cardiac performance. Nutrient composition of coronary blood may significantly vary in specific physiological and pathological conditions, for example, administration of special diets, long-term starvation, physical exercise or diabetes. Quantitative analysis of cardiac metabolism from a systems biology perspective may help to a better understanding of the relationship between nutrient supply and efficiency of metabolic processes required for an adequate cardiac output. Results Here we present CardioNet, the first large-scale reconstruction of the metabolic network of the human cardiomyocyte comprising 1793 metabolic reactions, including 560 transport processes in six compartments. We use flux-balance analysis to demonstrate the capability of the network to accomplish a set of 368 metabolic functions required for maintaining the structural and functional integrity of the cell. Taking the maintenance of ATP, biosynthesis of ceramide, cardiolipin and further important phospholipids as examples, we analyse how a changed supply of glucose, lactate, fatty acids and ketone bodies may influence the efficiency of these essential processes. Conclusions CardioNet is a functionally validated metabolic network of the human cardiomyocyte that enables theorectical studies of cellular metabolic processes crucial for the accomplishment of an adequate cardiac output.
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Affiliation(s)
- Anja Karlstädt
- Institute of Biochemistry, Charité-Universitätsmedizin Berlin, Charitéplatz 1/Virchowweg 6, 10117 Berlin, Germany.
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Inactivation of the AMP-activated protein kinase by glucose in cardiac myocytes: a role for the pentose phosphate pathway. Biosci Rep 2011; 32:229-39. [DOI: 10.1042/bsr20110075] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
Abstract
Incubation of adult rat cardiac myocytes with increasing glucose concentrations decreased phosphorylation (αThr172) and activity of AMPK (AMP-activated protein kinase). The effect could be demonstrated without measurable changes in adenine nucleotide contents. The glucose effect was additive to the decrease in AMPK activity caused by insulin, was attenuated by adrenaline, was not mimicked by glucose analogues, lactate or pyruvate and was not due to changes in myocyte glycogen content. AMPK activity was decreased by xylitol and PMS (phenazine methosulfate) and was increased by the glucose-6-phosphate dehydrogenase inhibitor DHEA (dehydroepiandrosterone) and by thiamine. PMS and DHEA respectively, increased and decreased CO2 formation by the PPP (pentose phosphate pathway). AMPK activity was inversely related to the myocyte content of Xu5P (xylulose 5-phosphate), an intermediate of the non-oxidative arm of the PPP. Endothall, an inhibitor of PP2A (protein phosphatase 2A), abolished the glucose effect on AMPK activity. Further studies are needed to define the ‘active component’ that mediates the glucose effect and whether its site of action is PP2A.
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Taegtmeyer H, Stanley WC. Too much or not enough of a good thing? Cardiac glucolipotoxicity versus lipoprotection. J Mol Cell Cardiol 2010; 50:2-5. [PMID: 20869969 DOI: 10.1016/j.yjmcc.2010.09.014] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/14/2010] [Revised: 09/15/2010] [Accepted: 09/16/2010] [Indexed: 01/24/2023]
Affiliation(s)
- Heinrich Taegtmeyer
- The University of Texas Medical School at Houston, Department of Internal Medicine, Division of Cardiology, Houston, TX 77030, USA.
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Pound KM, Sorokina N, Ballal K, Berkich DA, Fasano M, Lanoue KF, Taegtmeyer H, O'Donnell JM, Lewandowski ED. Substrate-enzyme competition attenuates upregulated anaplerotic flux through malic enzyme in hypertrophied rat heart and restores triacylglyceride content: attenuating upregulated anaplerosis in hypertrophy. Circ Res 2009; 104:805-12. [PMID: 19213957 DOI: 10.1161/circresaha.108.189951] [Citation(s) in RCA: 118] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
Recent work identifies the recruitment of alternate routes for carbohydrate oxidation, other than pyruvate dehydrogenase (PDH), in hypertrophied heart. Increased carboxylation of pyruvate via cytosolic malic enzyme (ME), producing malate, enables "anaplerotic" influx of carbon into the citric acid cycle. In addition to inefficient NADH production from pyruvate fueling this anaplerosis, ME also consumes NADPH necessary for lipogenesis. Thus, we tested the balance between PDH and ME fluxes in hypertrophied hearts and examined whether low triacylglyceride (TAG) was linked to ME-catalyzed anaplerosis. Sham-operated (SHAM) and aortic banded rat hearts (HYP) were perfused with buffer containing either 13C-palmitate plus glucose or (13)C glucose plus palmitate for 30 minutes. Hearts remained untreated or received dichloroacetate (DCA) to activate PDH and increase substrate competition with ME. HYP showed a 13% to 26% reduction in rate pressure product (RPP) and impaired dP/dt versus SHAM (P<0.05). DCA did not affect RPP but normalized dP/dt in HYP. HYP had elevated ME expression with a 90% elevation in anaplerosis over SHAM. Increasing competition from PDH reduced anaplerosis in HYP+DCA by 18%. Correspondingly, malate was 2.2-fold greater in HYP than SHAM but was lowered with PDH activation: HYP=1419+/-220 nmol/g dry weight; HYP+DCA=343+/-56 nmol/g dry weight. TAG content in HYP (9.7+/-0.7 micromol/g dry weight) was lower than SHAM (13.5+/-1.0 micromol/g dry weight). Interestingly, reduced anaplerosis in HYP+DCA corresponded with normalized TAG (14.9+/-0.6 micromol/g dry weight) and improved contractility. Thus, we have determined partial reversibility of increased anaplerosis in HYP. The findings suggest anaplerosis through NADPH-dependent, cytosolic ME limits TAG formation in hypertrophied hearts.
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Affiliation(s)
- Kayla M Pound
- Department of Physiology and Biophysics, MC 901, UIC College of Medicine, 835 S Wolcott Ave, Chicago, IL 60612, USA.
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Young ME, Yan J, Razeghi P, Cooksey RC, Guthrie PH, Stepkowski SM, McClain DA, Tian R, Taegtmeyer H. Proposed regulation of gene expression by glucose in rodent heart. GENE REGULATION AND SYSTEMS BIOLOGY 2007; 1:251-62. [PMID: 19936093 PMCID: PMC2759127 DOI: 10.4137/grsb.s222] [Citation(s) in RCA: 54] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Background During pressure overload-induced hypertrophy, unloading-induced atrophy, and diabetes mellitus, the heart induces ‘fetal’ genes (e.g. myosin heavy chain β; mhcβ). Hypothesis We propose that altered glucose homeostasis within the cardiomyocyte acts as a central mechanism for the regulation of gene expression in response to environmental stresses. The evidence is as follows. Methods and Results Forced glucose uptake both ex vivo and in vivo results in mhc isoform switching. Restricting dietary glucose prevents mhc isoform switching in hearts of both GLUT1-Tg mice and rats subjected to pressure overload-induced hypertrophy. Thus, glucose availability correlates with mhc isoform switching under all conditions investigated. A potential mechanism by which glucose affects gene expression is through O-linked glycosylation of specific transcription factors. Glutamine:fructose-6-phosphate amidotransferase (GFAT) catalyzes the flux generating step in UDP-N-acetylglucosamine biosynthesis, the rate determining metabolite in protein glycosylation. Ascending aortic constriction increased intracellular levels of UDP-N-acetylglucosamine, and the expression of gfat2, but not gfat1, in the rat heart. Conclusions Collectively, the results strongly suggest glucose-regulated gene expression in the heart, and the involvement of glucose metabolites in isoform switching of sarcomeric proteins characteristic for the fetal gene program.
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Affiliation(s)
- Martin E Young
- USDA/ARS Children's Nutrition Research Center, Baylor College of Medicine, Houston, Texas, USA
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Sharma S, Guthrie P, Chan S, Haq S, Taegtmeyer H. Glucose phosphorylation is required for insulin-dependent mTOR signalling in the heart. Cardiovasc Res 2007; 76:71-80. [PMID: 17553476 PMCID: PMC2257479 DOI: 10.1016/j.cardiores.2007.05.004] [Citation(s) in RCA: 70] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/13/2007] [Revised: 04/26/2007] [Accepted: 05/07/2007] [Indexed: 01/03/2023] Open
Abstract
OBJECTIVE Insulin regulates both glucose uptake and postnatal cardiac growth. The anabolic effects of insulin are mediated by the mammalian target of rapamycin (mTOR), an evolutionarily conserved kinase which is also a convergence point between nutrient sensing and cell growth. We postulated that mTOR signalling in the heart requires the metabolism of glucose. METHODS We interrogated the insulin-mediated mTOR signalling pathway in response to different metabolic interventions regulating substrate metabolism in the isolated working rat heart and in isolated cardiomyocytes. RESULTS Although insulin enhanced Akt activity, phosphorylation of mTOR and its downstream targets (p70S6K and 4EBP1) required the addition of glucose. Glucose-dependent p70S6K phosphorylation was independent of the hexosamine biosynthetic pathway, the AMP kinase pathway, and the pentose phosphate pathway. However, inhibition of glycolysis downstream of hexokinase markedly enhanced p70S6K phosphorylation. Furthermore, 2-deoxyglucose activated p70S6K suggesting that phosphorylation of glucose is required for carbohydrate-mediated mTOR signalling in the heart. Lastly, we also found enhanced p70S6K phosphorylation in the hearts of diabetic rats. CONCLUSION Phosphorylation of glucose is necessary for insulin-dependent mTOR activity in the heart, suggesting a link between intermediary metabolism and cardiac growth.
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Affiliation(s)
- Saumya Sharma
- Division of Cardiology, The University of Texas Houston Medical School, Houston, Texas
| | - Patrick Guthrie
- Division of Cardiology, The University of Texas Houston Medical School, Houston, Texas
| | - Suzanne Chan
- Division of Cardiology, The University of Texas Houston Medical School, Houston, Texas
| | - Syed Haq
- Molecular Cardiology Research Institute, Tufts-New England Medical Center and Department of Medicine, Tufts University
| | - Heinrich Taegtmeyer
- Division of Cardiology, The University of Texas Houston Medical School, Houston, Texas
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Suh JH, Wang H, Liu RM, Liu J, Hagen TM. (R)-alpha-lipoic acid reverses the age-related loss in GSH redox status in post-mitotic tissues: evidence for increased cysteine requirement for GSH synthesis. Arch Biochem Biophys 2004; 423:126-35. [PMID: 14871476 PMCID: PMC4696556 DOI: 10.1016/j.abb.2003.12.020] [Citation(s) in RCA: 113] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2003] [Revised: 12/02/2003] [Indexed: 11/22/2022]
Abstract
Age-related depletion of GSH levels and perturbations in its redox state may be especially deleterious to metabolically active tissues, such as the heart and brain. We examined the extent and the mechanisms underlying the potential age-related changes in cerebral and myocardial GSH status in young and old F344 rats and whether administration of (R)-alpha-lipoic acid (LA) can reverse these changes. Our results show that GSH/GSSG ratios in the aging heart and the brain declined by 58 and 66% relative to young controls, respectively (p < 0.001). Despite a consistent loss in GSH redox status in both tissues, only cerebral GSH levels declined with age (p < 0.001). To discern the potential mechanisms underlying this differential loss, the levels and the activities of gamma-glutamylcysteine ligase (GCL) and cysteine availability were determined. There were no significant age-related changes in substrate or enzyme levels, or GCL activity when saturating amounts of substrates were provided. However, kinetic analysis of GCL in brains of old rats displayed a significant increase (p < 0.05) in the apparent [Km] for cysteine (Km cys) vs. young rats (84.3+/-25.4 vs. 179.0+/-49.0; young and old, respectively), resulting in a 40% loss in apparent catalytic turnover of the enzyme. Thus, the age-related decline in total GSH appears to be mediated, in part, by a general decrement in GCL catalytic efficiency. Treating old rats with LA (40 mg/kg body wt; by i.p.) markedly increased tissue cysteine levels by 54% 12 h following treatment and subsequently restored the cerebral GSH levels. Moreover, LA improved the age-related changes in the tissue GSH/GSSG ratios in both heart and the brain. These results demonstrate that LA is an effective agent to restore both the age-associated decline in thiol redox ratio as well as increase cerebral GSH levels that otherwise decline with age.
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Affiliation(s)
- Jung H. Suh
- Department of Biochemistry and Biophysics, Linus Pauling Institute, Oregon State University, Corvallis, OR, USA
- Children’s Hospital Oakland Research Institute, Oakland, CA, USA
| | - Hong Wang
- Department of Immunology, University of Alabama at Birmingham, School of Public Health, Birmingham, AL, USA
| | - Rui-Ming Liu
- Department of Environmental Health Sciences, University of Alabama at Birmingham, School of Public Health, Birmingham, AL, USA
| | - JianKang Liu
- Children’s Hospital Oakland Research Institute, Oakland, CA, USA
| | - Tory M. Hagen
- Department of Biochemistry and Biophysics, Linus Pauling Institute, Oregon State University, Corvallis, OR, USA
- Corresponding author: Fax: 1-541-737-5077. (T.M. Hagen)
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Jain M, Brenner DA, Cui L, Lim CC, Wang B, Pimentel DR, Koh S, Sawyer DB, Leopold JA, Handy DE, Loscalzo J, Apstein CS, Liao R. Glucose-6-phosphate dehydrogenase modulates cytosolic redox status and contractile phenotype in adult cardiomyocytes. Circ Res 2003; 93:e9-16. [PMID: 12829617 DOI: 10.1161/01.res.0000083489.83704.76] [Citation(s) in RCA: 142] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Reactive oxygen species (ROS)-mediated cell injury contributes to the pathophysiology of cardiovascular disease and myocardial dysfunction. Protection against ROS requires maintenance of endogenous thiol pools, most importantly, reduced glutathione (GSH), by NADPH. In cardiomyocytes, GSH resides in two separate cellular compartments: the mitochondria and cytosol. Although mitochondrial GSH is maintained largely by transhydrogenase and isocitrate dehydrogenase, the mechanisms responsible for sustaining cytosolic GSH remain unclear. Glucose-6-phosphate dehydrogenase (G6PD) functions as the first and rate-limiting enzyme in the pentose phosphate pathway, responsible for the generation of NADPH in a reaction coupled to the de novo production of cellular ribose. We hypothesized that G6PD is required to maintain cytosolic GSH levels and protect against ROS injury in cardiomyocytes. We found that in adult cardiomyocytes, G6PD activity is rapidly increased in response to cellular oxidative stress, with translocation of G6PD to the cell membrane. Furthermore, inhibition of G6PD depletes cytosolic GSH levels and subsequently results in cardiomyocyte contractile dysfunction through dysregulation of calcium homeostasis. Cardiomyocyte dysfunction was reversed through treatment with either a thiol-repleting agent (L-2-oxothiazolidine-4-carboxylic acid) or antioxidant treatment (Eukarion-134), but not with exogenous ribose. Finally, in a murine model of G6PD deficiency, we demonstrate the development of in vivo adverse structural remodeling and impaired contractile function over time. We, therefore, conclude that G6PD is a critical cytosolic antioxidant enzyme, essential for maintenance of cytosolic redox status in adult cardiomyocytes. Deficiency of G6PD may contribute to cardiac dysfunction through increased susceptibility to free radical injury and impairment of intracellular calcium transport. The full text of this article is available online at http://www.circresaha.org.
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Affiliation(s)
- Mohit Jain
- Cardiac Muscle Research Laboratory, Whitaker Cardiovascular Institute and Evans Department of Medicine, Boston University School of Medicine, Boston, Mass, USA
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Leong HS, Grist M, Parsons H, Wambolt RB, Lopaschuk GD, Brownsey R, Allard MF. Accelerated rates of glycolysis in the hypertrophied heart: are they a methodological artifact? Am J Physiol Endocrinol Metab 2002; 282:E1039-45. [PMID: 11934668 DOI: 10.1152/ajpendo.00507.2001] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Glycolysis, measured by (3)H(2)O production from [5-(3)H]glucose, is accelerated in isolated working hypertrophied rat hearts. However, nonglycolytic detritiation of [5-(3)H]glucose via the nonoxidative pentose phosphate pathway (PPP) could potentially lead to an overestimation of true glycolytic rates, especially in hypertrophied hearts where the PPP may be upregulated. To address this concern, we measured glycolysis using [5-(3)H]glucose and a second, independent method in isolated working hearts from halothane-anesthetized, sham-operated and aortic-constricted rats. Glycolysis was accelerated in hypertrophied hearts compared with control hearts regardless of the method used. There was also excellent concordance in glycolytic rates between the different methods. Moreover, activity of glucose-6-phosphate dehydrogenase and expression of transaldolase, enzymes controlling key steps in the oxidative and nonoxidative PPP, respectively, were not different between control and hypertrophied hearts. Thus nonglycolytic detritiation of [5-(3)H]glucose in the PPP is insignificant, and (3)H(2)O production from [5-(3)H]glucose is an accurate means to measure glycolysis in isolated working normal and hypertrophied rat hearts. Furthermore, the PPP does not appear to be increased in cardiac hypertrophy induced by abdominal aortic constriction.
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Affiliation(s)
- Hon Sing Leong
- McDonald Research Laboratories/The iCAPTUR, University of British Columbia-St. Paul's Hospital, Vancouver, British Columbia, V6Z 1Y6
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29
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Affiliation(s)
- Martin E Young
- Department of Internal Medicine, Division of Cardiology, University of Texas-Houston Medical School, Houston, Tex 77030, USA
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