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Vieira-Lara MA, Bakker BM. The paradox of fatty-acid β-oxidation in muscle insulin resistance: Metabolic control and muscle heterogeneity. Biochim Biophys Acta Mol Basis Dis 2024; 1870:167172. [PMID: 38631409 DOI: 10.1016/j.bbadis.2024.167172] [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: 12/17/2023] [Revised: 03/18/2024] [Accepted: 04/09/2024] [Indexed: 04/19/2024]
Abstract
The skeletal muscle is a metabolically heterogeneous tissue that plays a key role in maintaining whole-body glucose homeostasis. It is well known that muscle insulin resistance (IR) precedes the development of type 2 diabetes. There is a consensus that the accumulation of specific lipid species in the tissue can drive IR. However, the role of the mitochondrial fatty-acid β-oxidation in IR and, consequently, in the control of glucose uptake remains paradoxical: interventions that either inhibit or activate fatty-acid β-oxidation have been shown to prevent IR. We here discuss the current theories and evidence for the interplay between β-oxidation and glucose uptake in IR. To address the underlying intricacies, we (1) dive into the control of glucose uptake fluxes into muscle tissues using the framework of Metabolic Control Analysis, and (2) disentangle concepts of flux and catalytic capacities taking into account skeletal muscle heterogeneity. Finally, we speculate about hitherto unexplored mechanisms that could bring contrasting evidence together. Elucidating how β-oxidation is connected to muscle IR and the underlying role of muscle heterogeneity enhances disease understanding and paves the way for new treatments for type 2 diabetes.
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Affiliation(s)
- Marcel A Vieira-Lara
- Laboratory of Pediatrics, University Medical Center Groningen, University of Groningen, Groningen, the Netherlands.
| | - Barbara M Bakker
- Laboratory of Pediatrics, University Medical Center Groningen, University of Groningen, Groningen, the Netherlands.
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2
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Rabbani N, Thornalley PJ. Hexokinase-linked glycolytic overload and unscheduled glycolysis in hyperglycemia-induced pathogenesis of insulin resistance, beta-cell glucotoxicity, and diabetic vascular complications. Front Endocrinol (Lausanne) 2024; 14:1268308. [PMID: 38292764 PMCID: PMC10824962 DOI: 10.3389/fendo.2023.1268308] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/27/2023] [Accepted: 12/12/2023] [Indexed: 02/01/2024] Open
Abstract
Hyperglycemia is a risk factor for the development of insulin resistance, beta-cell glucotoxicity, and vascular complications of diabetes. We propose the hypothesis, hexokinase-linked glycolytic overload and unscheduled glycolysis, in explanation. Hexokinases (HKs) catalyze the first step of glucose metabolism. Increased flux of glucose metabolism through glycolysis gated by HKs, when occurring without concomitant increased activity of glycolytic enzymes-unscheduled glycolysis-produces increased levels of glycolytic intermediates with overspill into effector pathways of cell dysfunction and pathogenesis. HK1 is saturated with glucose in euglycemia and, where it is the major HK, provides for basal glycolytic flux without glycolytic overload. HK2 has similar saturation characteristics, except that, in persistent hyperglycemia, it is stabilized to proteolysis by high intracellular glucose concentration, increasing HK activity and initiating glycolytic overload and unscheduled glycolysis. This drives the development of vascular complications of diabetes. Similar HK2-linked unscheduled glycolysis in skeletal muscle and adipose tissue in impaired fasting glucose drives the development of peripheral insulin resistance. Glucokinase (GCK or HK4)-linked glycolytic overload and unscheduled glycolysis occurs in persistent hyperglycemia in hepatocytes and beta-cells, contributing to hepatic insulin resistance and beta-cell glucotoxicity, leading to the development of type 2 diabetes. Downstream effector pathways of HK-linked unscheduled glycolysis are mitochondrial dysfunction and increased reactive oxygen species (ROS) formation; activation of hexosamine, protein kinase c, and dicarbonyl stress pathways; and increased Mlx/Mondo A signaling. Mitochondrial dysfunction and increased ROS was proposed as the initiator of metabolic dysfunction in hyperglycemia, but it is rather one of the multiple downstream effector pathways. Correction of HK2 dysregulation is proposed as a novel therapeutic target. Pharmacotherapy addressing it corrected insulin resistance in overweight and obese subjects in clinical trial. Overall, the damaging effects of hyperglycemia are a consequence of HK-gated increased flux of glucose metabolism without increased glycolytic enzyme activities to accommodate it.
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Affiliation(s)
| | - Paul J. Thornalley
- College of Health and Life Sciences, Hamad Bin Khalifa University, Doha, Qatar
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3
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The role of exercise and hypoxia on glucose transport and regulation. Eur J Appl Physiol 2023; 123:1147-1165. [PMID: 36690907 DOI: 10.1007/s00421-023-05135-1] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2022] [Accepted: 01/06/2023] [Indexed: 01/25/2023]
Abstract
Muscle glucose transport activity increases with an acute bout of exercise, a process that is accomplished by the translocation of glucose transporters to the plasma membrane. This process remains intact in the skeletal muscle of individuals with insulin resistance and type 2 diabetes mellitus (T2DM). Exercise training is, therefore, an important cornerstone in the management of individuals with T2DM. However, the acute systemic glucose responses to carbohydrate ingestion are often augmented during the early recovery period from exercise, despite increased glucose uptake into skeletal muscle. Accordingly, the first aim of this review is to summarize the knowledge associated with insulin action and glucose uptake in skeletal muscle and apply these to explain the disparate responses between systemic and localized glucose responses post-exercise. Herein, the importance of muscle glycogen depletion and the key glucoregulatory hormones will be discussed. Glucose uptake can also be stimulated independently by hypoxia; therefore, hypoxic training presents as an emerging method for enhancing the effects of exercise on glucose regulation. Thus, the second aim of this review is to discuss the potential for systemic hypoxia to enhance the effects of exercise on glucose regulation.
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4
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Faubert B, Tasdogan A, Morrison SJ, Mathews TP, DeBerardinis RJ. Stable isotope tracing to assess tumor metabolism in vivo. Nat Protoc 2021; 16:5123-5145. [PMID: 34535790 PMCID: PMC9274147 DOI: 10.1038/s41596-021-00605-2] [Citation(s) in RCA: 39] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2020] [Accepted: 07/12/2021] [Indexed: 02/08/2023]
Abstract
Cancer cells undergo diverse metabolic adaptations to meet the energetic demands imposed by dysregulated growth and proliferation. Assessing metabolism in intact tumors allows the investigator to observe the combined metabolic effects of numerous cancer cell-intrinsic and -extrinsic factors that cannot be fully captured in culture models. We have developed methods to use stable isotope-labeled nutrients (e.g., [13C]glucose) to probe metabolic activity within intact tumors in vivo, in mice and humans. In these methods, the labeled nutrient is introduced to the circulation through an intravenous catheter prior to surgical resection of the tumor and adjacent nonmalignant tissue. Metabolism within these tissues during the infusion transfers the isotope label into metabolic intermediates from pathways supplied by the infused nutrient. Extracting metabolites from surgical specimens and analyzing their isotope labeling patterns provides information about metabolism in the tissue. We provide detailed information about this technique, from introduction of the labeled tracer through data analysis and interpretation, including streamlined approaches to quantify isotope labeling in informative metabolites extracted from tissue samples. We focus on infusions with [13C]glucose and the application of mass spectrometry to assess isotope labeling in intermediates from central metabolic pathways, including glycolysis, the tricarboxylic acid cycle and nonessential amino acid synthesis. We outline practical considerations to apply these methods to human subjects undergoing surgical resections of solid tumors. We also discuss the method's versatility and consider the relative advantages and limitations of alternative approaches to introduce the tracer, harvest the tissue and analyze the data.
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Affiliation(s)
- Brandon Faubert
- Children's Research Institute and Department of Pediatrics, University of Texas Southwestern Medical Center, Dallas, TX, USA.
| | - Alpaslan Tasdogan
- Children's Research Institute and Department of Pediatrics, University of Texas Southwestern Medical Center, Dallas, TX, USA
- Department of Dermatology, University Hospital Essen & German Cancer Consortium, Partner Site, Essen, Germany
| | - Sean J Morrison
- Children's Research Institute and Department of Pediatrics, University of Texas Southwestern Medical Center, Dallas, TX, USA
- Howard Hughes Medical Institute, University of Texas Southwestern Medical Center, Dallas, TX, USA
| | - Thomas P Mathews
- Children's Research Institute and Department of Pediatrics, University of Texas Southwestern Medical Center, Dallas, TX, USA
- Howard Hughes Medical Institute, University of Texas Southwestern Medical Center, Dallas, TX, USA
| | - Ralph J DeBerardinis
- Children's Research Institute and Department of Pediatrics, University of Texas Southwestern Medical Center, Dallas, TX, USA.
- Howard Hughes Medical Institute, University of Texas Southwestern Medical Center, Dallas, TX, USA.
- Eugene McDermott Center for Human Growth and Development, University of Texas Southwestern Medical Center, Dallas, TX, USA.
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5
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Hoang G, Udupa S, Le A. Application of metabolomics technologies toward cancer prognosis and therapy. INTERNATIONAL REVIEW OF CELL AND MOLECULAR BIOLOGY 2019; 347:191-223. [PMID: 31451214 DOI: 10.1016/bs.ircmb.2019.07.003] [Citation(s) in RCA: 41] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Altered metabolism is one of the defining features of cancer. Since the discovery of the Warburg effect in 1924, research into the metabolic aspects of cancer has been reinvigorated over the past decade. Metabolomics is an invaluable tool for gaining insights into numerous biochemical processes including those related to cancer metabolism and metabolic aspects of other diseases. The combination of untargeted and targeted metabolomics approaches has greatly facilitated the discovery of many cancer biomarkers with prognostic potential. Using mass spectrometry-based stable isotope-resolved metabolomics (SIRM) with isotopic labeling, a powerful tool used in pathway analysis, researchers have discovered novel cancer metabolic pathways and metabolic targets for therapeutic application. Metabolomics technologies provide invaluable metabolic insights reflecting cancer progression in coordination with genomics and proteomics aspects. The systematic study of metabolite levels in the metabolome and their dynamics within a biological organism has been, in recent years, applied across a wide range of fields. Metabolomics technologies have been applied to both early clinical trials and pre-clinical research in several essential aspects of human health. This chapter will give an overview of metabolomics technologies and their application in the discovery of novel pathways using isotopic labeled and non-labeled metabolomics.
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Affiliation(s)
- Giang Hoang
- Department of Pathology, Johns Hopkins University School of Medicine, Baltimore, MD, United States; Department of Biomedical Engineering, Johns Hopkins University Whiting School of Engineering, Baltimore, MD, United States
| | - Sunag Udupa
- Department of Pathology, Johns Hopkins University School of Medicine, Baltimore, MD, United States
| | - Anne Le
- Department of Pathology, Johns Hopkins University School of Medicine, Baltimore, MD, United States; Department of Oncology, Johns Hopkins University School of Medicine, Baltimore, MD, United States.
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6
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Giovannetti G, Flori A, Marsigli F, De Marchi D, Frijia F, Giannoni M, Kusmic C, Positano V, Aquaro GD, Menichetti L. A radiofrequency system for in vivo hyperpolarized 13 C MRS experiments in mice with a 3T MRI clinical scanner. SCANNING 2016; 38:710-719. [PMID: 27059822 DOI: 10.1002/sca.21319] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/16/2015] [Accepted: 03/20/2016] [Indexed: 06/05/2023]
Abstract
Hyperpolarized carbon-13 magnetic resonance spectroscopy (MRS) is a powerful tool to explore tissue metabolic state, by permitting the study of intermediary metabolism of biomolecules in vivo. However, a number of technological problems still limit this technology and need innovative solutions. In particular, the low molar concentration of derivate metabolites give rise to low signal-to-noise ratio (SNR), which makes the design and development of dedicated radiofrequency (RF) coils a fundamental task. In this article, the authors describe the simulation and the design of a RF coils configuration for MR experiments in mice, constituted by a 1 H whole body volume RF coil for imaging and a 13 C single circular loop surface RF coil for performing 13 C acquisitions. After the building, the RF system was employed in an in vivo experiment in a mouse injected with hyperpolarized [1-13 C]pyruvate by using a 3 T clinical MR scanner. SCANNING 38:710-719, 2016. © 2016 Wiley Periodicals, Inc.
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Affiliation(s)
- Giulio Giovannetti
- Institute of Clinical Physiology, National Research Council (CNR), Pisa, Italy
- Fondazione CNR/Regione Toscana G. Monasterio, Pisa, Italy
| | - Alessandra Flori
- Fondazione CNR/Regione Toscana G. Monasterio, Pisa, Italy
- Institute of Life Sciences, Scuola Superiore Sant'Anna, Pisa, Italy
| | - Fabio Marsigli
- Department of Information Engineering, University of Pisa, Pisa, Italy
| | | | | | - Massimo Giannoni
- Institute of Clinical Physiology, National Research Council (CNR), Pisa, Italy
| | - Claudia Kusmic
- Institute of Clinical Physiology, National Research Council (CNR), Pisa, Italy
| | | | | | - Luca Menichetti
- Institute of Clinical Physiology, National Research Council (CNR), Pisa, Italy
- Fondazione CNR/Regione Toscana G. Monasterio, Pisa, Italy
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7
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Yahya A, De Zanche N, Allen PS. A dual-tuned transceive resonator for (13) C{(1) H} MRS: two open coils in one. NMR IN BIOMEDICINE 2013; 26:533-541. [PMID: 23401299 DOI: 10.1002/nbm.2890] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/10/2012] [Revised: 10/01/2012] [Accepted: 10/18/2012] [Indexed: 06/01/2023]
Abstract
Proton-decoupled, (13) C nuclear MRS experiments require a RF coil that operates at the Larmor frequencies of both (13) C and (1) H. In this work, we designed, built and tested a single-unit, dual-tuned coil based on a half-birdcage open coil design. It was constructed as a low-pass network with a resonant trap in series with each leg. Traps are tuned in alternate legs such that the two resonant modes arise from currents on alternate legs. The coil performance was compared with that of a dual-tuned coil consisting of two proton surface coils operating in quadrature and a single surface coil for (13) C transmission and reception. The half-birdcage coil was shown to produce a more homogeneous RF field at each frequency and was more sensitive to a (13) C signal arising from regions further from the coil surface. The applicability of the coil in vivo was demonstrated by acquiring a proton decoupled, natural abundance (13) C glycogen signal from the calf of a normal volunteer.
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Affiliation(s)
- Atiyah Yahya
- Department of Medical Physics, Cross Cancer Institute, Edmonton, Alberta, Canada.
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8
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Taşal E, Kumalar M. Structure and vibrational spectra of 6-(4-fluorobenzoyl)-3-(2-(4-methylpiperazin-1-yl)-2-oxoethyl)benzo[d]thiazol-2(3H)-one molecule. SPECTROCHIMICA ACTA. PART A, MOLECULAR AND BIOMOLECULAR SPECTROSCOPY 2012; 96:548-562. [PMID: 22885078 DOI: 10.1016/j.saa.2012.07.060] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/04/2012] [Revised: 07/11/2012] [Accepted: 07/13/2012] [Indexed: 06/01/2023]
Abstract
The molecular structure, conformational stability and vibrational frequencies of 6-(4-fluorobenzoyl)-3-(2-(4-methylpiperazin-1-yl)-2-oxoethyl)benzo[d]thiazol-2(3H)-one (abbreviated as FMOT) molecule in the ground state were calculated by DFT (B3LYP) and HF methods using different basis sets. The solid-state FT-IR spectrum was measured and compared with calculated values. FMOT was found to have four different stable conformations. The comparison of the theoretical and experimental geometries of the title compound indicated that the X-ray parameters fairly well agree with the theoretically obtained values for the most stable conformer. Energy gap of the molecule was found using HOMO and LUMO calculation, hence the less band gap, which seems to be more stable. The observed and calculated vibrational frequencies are found to be in good agreement.
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Affiliation(s)
- Erol Taşal
- Department of Physics, Faculty of Arts & Sciences, Eskişehir Osmangazi University, 26480 Eskişehir, Turkey.
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9
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Ruschkewitz Y, Gefen A. Cellular-scale transport in deformed skeletal muscle following spinal cord injury. Comput Methods Biomech Biomed Engin 2011; 14:411-24. [DOI: 10.1080/10255842.2010.529804] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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10
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The evolution of control and distribution of adaptive mutations in a metabolic pathway. Genetics 2009; 184:483-502. [PMID: 19966064 DOI: 10.1534/genetics.109.110411] [Citation(s) in RCA: 72] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
In an attempt to understand whether it should be expected that some genes tend to be used disproportionately often by natural selection, we investigated two related phenomena: the evolution of flux control among enzymes in a metabolic pathway and properties of adaptive substitutions in pathway enzymes. These two phenomena are related by the principle that adaptive substitutions should occur more frequently in enzymes with greater flux control. Predicting which enzymes will be preferentially involved in adaptive evolution thus requires an evolutionary theory of flux control. We investigated the evolution of enzyme control in metabolic pathways with two models of enzyme kinetics: metabolic control theory (MCT) and Michaelis-Menten saturation kinetics (SK). Our models generate two main predictions for pathways in which reactions are moderately to highly irreversible: (1) flux control will evolve to be highly unequal among enzymes in a pathway and (2) upstream enzymes evolve a greater control coefficient then those downstream. This results in upstream enzymes fixing the majority of beneficial mutations during adaptive evolution. Once the population has reached high fitness, the trend is reversed, with the majority of neutral/slightly deleterious mutations occurring in downstream enzymes. These patterns are the result of three factors (the first of these is unique to the MCT simulations while the other two seem to be general properties of the metabolic pathways): (1) the majority of randomly selected, starting combinations of enzyme kinetic rates generate pathways that possess greater control for the upstream enzymes compared to downstream enzymes; (2) selection against large pools of intermediate substrates tends to prevent majority control by downstream enzymes; and (3) equivalent mutations in enzyme kinetic rates have the greatest effect on flux for enzymes with high levels of flux control, and these enzymes will accumulate adaptive substitutions, strengthening their control. Prediction 1 is well supported by available data on control coefficients. Data for evaluating prediction 2 are sparse but not inconsistent with this prediction.
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11
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Chew YH, Shia YL, Lee CT, Majid FAA, Chua LS, Sarmidi MR, Aziz RA. Modeling of glucose regulation and insulin-signaling pathways. Mol Cell Endocrinol 2009; 303:13-24. [PMID: 19428987 DOI: 10.1016/j.mce.2009.01.018] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/09/2008] [Revised: 12/22/2008] [Accepted: 01/26/2009] [Indexed: 01/31/2023]
Abstract
A model of glucose regulation system was combined with a model of insulin-signaling pathways in this study. A feedback loop was added to link the transportation of glucose into cells (by GLUT4 in the insulin-signaling pathways) and the insulin-dependent glucose uptake in the glucose regulation model using the Michaelis-Menten kinetic model. A value of K(m) for GLUT4 was estimated using Genetic Algorithm. The estimated value was found to be 25.3 mM, which was in the range of K(m) values found experimentally from in vivo and in vitro human studies. Based on the results of this study, the combined model enables us to understand the overall dynamics of glucose at the systemic level, monitor the time profile of components in the insulin-signaling pathways at the cellular level and gives a good estimate of the K(m) value of glucose transportation by GLUT4. In conclusion, metabolic modeling such as displayed in this study provides a good predictive method to study the step-by-step reactions in an organism at different levels and should be used in combination with experimental approach to increase our understanding of metabolic disorders such as type 2 diabetes.
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Affiliation(s)
- Yin Hoon Chew
- Department of Bioprocess Engineering, Faculty of Chemical and Natural Resources Engineering, Universiti Teknologi Malaysia, Skudai, Johor, Malaysia
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12
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Abstract
Magnetic resonance spectroscopy (MRS) of skeletal muscle has been successfully applied by physiologists over several decades, particularly for studies of high-energy phosphates (by (31)P-MRS) and glycogen (by (13)C-MRS). Unfortunately, the observation of these heteronuclei requires equipment that is typically not available on clinical MR scanners, such as broadband capability and a second channel for decoupling and nuclear Overhauser enhancement (NOE). On the other hand, (1)H-MR spectra of skeletal muscle can be acquired on many routine MR systems and also provide a wealth of physiological information. In particular, studies of intramyocellular lipids (IMCL) attract physiologists and endocrinologists because IMCL levels are related to insulin resistance and thus can lead to a better understanding of major health problems in industrial countries. The combination of (1)H-, (13)C-, and (31)P-MRS gives access to the major long- and short-term energy sources of skeletal muscle. This review summarizes the technical aspects and unique MR-methodological features of the different nuclei. It reviews clinical studies that employed MRS of one or more nuclei, or combinations of MRS with other MR modalities. It also illustrates that MR spectra contain additional physiological information that is not yet used in routine clinical applications.
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Affiliation(s)
- Chris Boesch
- Department of Clinical Research, MR-Spectroscopy and Methodology, University of Bern, Bern, Switzerland.
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13
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Boesch C, Machann J, Vermathen P, Schick F. Role of proton MR for the study of muscle lipid metabolism. NMR IN BIOMEDICINE 2006; 19:968-88. [PMID: 17075965 DOI: 10.1002/nbm.1096] [Citation(s) in RCA: 130] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/12/2023]
Abstract
1H-MR spectroscopy (MRS) of intramyocellular lipids (IMCL) became particularly important when it was recognized that IMCL levels are related to insulin sensitivity. While this relation is rather complex and depends on the training status of the subjects, various other influences such as exercise and diet also influence IMCL concentrations. This may open insight into many metabolic interactions; however, it also requires careful planning of studies in order to control all these confounding influences. This review summarizes various historical, methodological, and practical aspects of 1H-MR spectroscopy (MRS) of muscular lipids. That includes a differentiation of bulk magnetic susceptibility effects and residual dipolar coupling that can both be observed in MRS of skeletal muscle, yet affecting different metabolites in a specific way. Fitting of the intra- (IMCL) and extramyocellular (EMCL) signals with complex line shapes and the transformation into absolute concentrations is discussed. Since the determination of IMCL in muscle groups with oblique fiber orientation or in obese subjects is still difficult, potential improvement with high-resolution spectroscopic imaging or at higher field strength is considered. Fat selective imaging is presented as a possible alternative to MRS and the potential of multinuclear MRS is discussed. 1H-MRS of muscle lipids allows non-invasive and repeated studies of muscle metabolism that lead to highly relevant findings in clinics and patho-physiology.
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Affiliation(s)
- Chris Boesch
- Department of Clinical Research (AMSM), University of Bern, Bern, Switzerland.
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Slimani L, Oikonen V, Hällsten K, Savisto N, Knuuti J, Nuutila P, Iozzo P. Exercise restores skeletal muscle glucose delivery but not insulin-mediated glucose transport and phosphorylation in obese subjects. J Clin Endocrinol Metab 2006; 91:3394-403. [PMID: 16772346 PMCID: PMC2743828 DOI: 10.1210/jc.2006-0269] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
CONTEXT/OBJECTIVE Insulin resistance in obese subjects results in the impaired disposal of glucose by skeletal muscle. The current study examined the effects of insulin and/or exercise on glucose transport and phosphorylation in skeletal muscle and the influence of obesity on these processes. SUBJECTS/METHODS Seven obese and 12 lean men underwent positron emission tomography with 2-deoxy-2-[(18)F]fluoro-d-glucose in resting and isometrically exercising skeletal muscle during normoglycemic hyperinsulinemia. Data were analyzed by two-tissue compartmental modeling. Perfusion and oxidative capacity were measured during insulin stimulation by [15O]H2O and [15O]O2. RESULTS Exercise increased glucose fractional uptake (K), inward transport rate (K(1)), and the k(3) parameter, combining transport and intracellular phosphorylation, in lean and obese subjects. In each group, there was no statistically significant difference between plasma flow and K(1). At rest, a significant defect in K(1) (P = 0.0016), k(3) (P = 0.016), and K (P = 0.022) was found in obese subjects. Exercise restored K(1), improved but did not normalize K (P = 0.03 vs. lean), and did not ameliorate the more than 60% relative impairment in k(3) in obese individuals (P = 0.002 vs. lean). The glucose oxidative potential tended to be reduced by obesity. CONCLUSIONS/INTERPRETATION The study indicates that exercise restores the impairment in insulin-mediated skeletal muscle perfusion and glucose delivery associated with obesity but does not normalize the defect involving the proximal steps regulating glucose disposal in obese individuals. Our data support the use of 2-deoxy-2-[18F]fluoro-d-glucose-positron emission tomography in the dissection between substrate supply and intrinsic tissue metabolism.
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Affiliation(s)
- Lotfi Slimani
- Turku PET Centre
University of TurkuP.O. Box 52 20521 Turku,FI
- * Correspondence should be adressed to: Lotfi Slimani
| | - Vesa Oikonen
- Turku PET Centre
University of TurkuP.O. Box 52 20521 Turku,FI
| | - Kirsti Hällsten
- Turku PET Centre
University of TurkuP.O. Box 52 20521 Turku,FI
| | - Nina Savisto
- Turku PET Centre
University of TurkuP.O. Box 52 20521 Turku,FI
| | - Juhani Knuuti
- Turku PET Centre
University of TurkuP.O. Box 52 20521 Turku,FI
| | - Pirjo Nuutila
- Turku PET Centre
University of TurkuP.O. Box 52 20521 Turku,FI
- Department of Medicine
University of TurkuTurku,FI
| | - Patricia Iozzo
- Turku PET Centre
University of TurkuP.O. Box 52 20521 Turku,FI
- Institute of Clinical Physiology
National Research Council56100 Pisa,IT
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15
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Fortpied J, Maliekal P, Vertommen D, Van Schaftingen E. Magnesium-dependent Phosphatase-1 Is a Protein-Fructosamine-6-phosphatase Potentially Involved in Glycation Repair. J Biol Chem 2006; 281:18378-85. [PMID: 16670083 DOI: 10.1074/jbc.m513208200] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023] Open
Abstract
Fructosamine-3-kinase (FN3K) is a recently described protein-repair enzyme responsible for the removal of fructosamines, which are the products of a spontaneous reaction of glucose with amines. We show here that, compared with glucose, glucose 6-phosphate (Glu-6-P) reacted 3-6-fold more rapidly with proteins and 8-fold more rapidly with N-alpha-t-Boc-lysine, being therefore a more significant intracellular glycating agent than glucose in skeletal muscle and heart. Fructosamine 6-phosphates, which result from the reaction of amines with Glu-6-P, were not substrates for FN3K. However, a phosphatase that dephosphorylates protein-bound fructosamine 6-phosphates was found to be present in rat tissues. This enzyme was purified to near homogeneity from skeletal muscle and was identified as magnesium-dependent phosphatase-1 (MDP-1), an enzyme of the haloacid dehalogenase family with a putative protein-tyrosine phosphatase function. Human recombinant MDP-1 acted on protein-bound fructosamine 6-phosphates with a catalytic efficiency >10-fold higher than those observed with its next best substrates (arabinose 5-phosphate and free fructoselysine 6-phosphate) and >100-fold higher than with protein-phosphotyrosine. It had no detectable activity on fructosamine 3-phosphates. MDP-1 dephosphorylated up to approximately 75% of the fructosamine 6-phosphates that are present on lysozyme after incubation of this protein with Glu-6-P. Furthermore, lysozyme glycated with Glu-6-P was converted by MDP-1 to a substrate for FN3K. We conclude that MDP-1 may act physiologically in conjunction with FN3K to free proteins from the glycation products derived from Glu-6-P.
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Affiliation(s)
- Juliette Fortpied
- Laboratory of Physiological Chemistry, Christian de Duve Institute of Cellular Pathology and Université Catholique de Louvain, Brussels, Belgium
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16
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Serlie MJM, de Haan JH, Tack CJ, Verberne HJ, Ackermans MT, Heerschap A, Sauerwein HP. Glycogen synthesis in human gastrocnemius muscle is not representative of whole-body muscle glycogen synthesis. Diabetes 2005; 54:1277-82. [PMID: 15855310 DOI: 10.2337/diabetes.54.5.1277] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
The introduction of 13C magnetic resonance spectroscopy (MRS) has enabled noninvasive measurement of muscle glycogen synthesis in humans. Conclusions based on measurements by the MRS technique assume that glucose metabolism in gastrocnemius muscle is representative for all skeletal muscles and thus can be extrapolated to whole-body muscle glucose metabolism. An alternative method to assess whole-body muscle glycogen synthesis is the use of [3-(3)H]glucose. In the present study, we compared this method to the MRS technique, which is a well-validated technique for measuring muscle glycogen synthesis. Muscle glycogen synthesis was measured in the gastrocnemius muscle of six lean healthy subjects by MRS and by the isotope method during a hyperinsulinemic-euglycemic clamp. Mean muscle glycogen synthesis as measured by the isotope method was 115 +/- 26 micromol x kg(-1) muscle x min(-1) vs. 178 +/- 72 micromol x kg(-1) muscle x min(-1) (P = 0.03) measured by MRS. Glycogen synthesis rates measured by MRS exceeded 100% of glucose uptake in three of the six subjects. We conclude that glycogen synthesis rates measured in gastrocnemius muscle cannot be extrapolated to whole-body muscle glycogen synthesis.
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Affiliation(s)
- Mireille J M Serlie
- Academic Medical Centre, Department of Endocrinology and Metabolism (F5-169), Meibergdreef 9, 1105AZ Amsterdam, The Netherlands.
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Figueiredo-Garutti ML, Navarro I, Capilla E, Souza RHS, Moraes G, Gutiérrez J, Vicentini-Paulino MLM. Metabolic changes in Brycon cephalus (Teleostei, Characidae) during post-feeding and fasting. Comp Biochem Physiol A Mol Integr Physiol 2002; 132:467-76. [PMID: 12020663 DOI: 10.1016/s1095-6433(02)00094-6] [Citation(s) in RCA: 42] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Metabolic changes during the transition from post-feeding to fasting were studied in Brycon cephalus, an omnivorous teleost from the Amazon Basin in Brazil. Body weight and somatic indices (liver and digestive tract), glycogen and glucose content in liver and muscle, as well as plasma glucose, free fatty acids (FFA), insulin and glucagon levels of B. cephalus, were measured at 0, 12, 24, 48, 72, 120, 168 and 336 h after the last feeding. At time 0 h (the moment of food administration, 09.00 h) plasma levels of insulin and glucagon were already high, and relatively high values were maintained until 24 h post-feeding. Glycemia was 6.42+/-0.82 mM immediately after food ingestion and 7.53+/-1.12 mM at 12 h. Simultaneously, a postprandial replenishment of liver and muscle glycogen reserves was observed. Subsequently, a sharp decrease of plasma insulin occurred, from 7.19+/-0.83 ng/ml at 24 h of fasting to 5.27+/-0.58 ng/ml at 48 h. This decrease coincided with the drop in liver glucose and liver glycogen, which reached the lowest value at 72 h of fasting (328.56+/-192.13 and 70.33+/-14.13 micromol/g, respectively). Liver glucose increased after 120 h and reached a peak 168 h post-feeding, which suggests that hepatic gluconeogenesis is occurring. Plasma FFA levels were low after 120 and 168 h and increased again at 336 h of fasting. During the transition from post-feeding to fast condition in B. cephalus, the balance between circulating insulin and glucagon quickly adjust its metabolism to the ingestion or deprivation of food.
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18
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Abstract
The study of intermediary metabolism in biomolecules has been given new directions by recent experiments in human muscle and brain by 13C NMR. Labeled substrates, generally glucose, have enabled the fluxes to be determined in vivo, whereas the naturally abundant 13C has enabled concentrations to be measured. In muscle the glycogen synthesis pathway has been measured and the flux control determined by metabolic control analysis of data, which shows that this pathway is mainly responsible for insulin-stimulated glucose disposal and that a deficiency in the glucose transporter in the pathway is responsible for hyperglycemia in non-insulin-dependent diabetics. From a physiological point of view the most surprising result was that the heavily regulated allosteric enzyme, glycogen synthase, does not control flux but is needed to maintain homeostasis during flux changes. This novel role for a phosphorylated allosteric enzyme is proposed to be a general phenomenon in metabolic and signaling pathways, which physiologically link different cellular activities. In human and rat brains 13C NMR measurements of the flow of labeled glucose into glutamate and glutamine simultaneously determine the rate of glucose oxidation and glutamate neurotransmitter cycling and reveal a 1:1 stoichiometry between the two fluxes. Implications for the interpretation of functional imaging studies and for psychology are discussed. These results demonstrate how intermediary metabolism serves to connect biochemistry with systemic physiology when measured and analyzed by in vivo NMR methods.
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Affiliation(s)
- R G Shulman
- Department of Molecular Biophysics, Yale University School of Medicine, 333 Cedar Street, New Haven, Connecticut 06510, USA.
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Shulman RG, Rothman DL. The "glycogen shunt" in exercising muscle: A role for glycogen in muscle energetics and fatigue. Proc Natl Acad Sci U S A 2001; 98:457-61. [PMID: 11209049 PMCID: PMC14608 DOI: 10.1073/pnas.98.2.457] [Citation(s) in RCA: 107] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Stimulated by recent (13)C and (31)P NMR studies of exercising muscle, we propose a model of the energetics of contraction. Previous studies of energetics have followed energy consumption. However, the rapidity of contraction, in 10-40 msec, requires that energy be delivered rapidly, so that the muscle has power requirements of rapid energy expenditure that are ultimately met by the slower averaged consumption of carbon and oxygen from blood. We propose that energy is supplied in milliseconds by glycogenolysis and that between contractions, glycogenesis refills the pools. The energy for glycogenesis is supplied by oxidative phosphorylation. This mechanism utilizes the rapid conversion of glycogen phosphorylase, the "fight-or-flight" enzyme, to its active form. Lactate is necessarily generated by this pathway to serve as a time buffer between fast and slow energy needs, which resolves the paradoxical generation of lactate in well oxygenated tissue. Consequences of the glycogen shunt are compatible with numerous biochemical and physiological experiments. The model provides a possible mechanism for muscle fatigue, suggesting that at low but nonzero glycogen concentrations, there is not enough glycogen to supply millisecond energy needs.
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Affiliation(s)
- R G Shulman
- Departments of Molecular Biophysics and Biochemistry and Diagnostic Radiology, Yale University School of Medicine, New Haven, CT 06510, USA.
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20
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Van Den Bergh AJ, Tack CJ, Van Den Boogert HJ, Vervoort G, Smits P, Heerschap A. Assessment of human muscle glycogen synthesis and total glucose content by in vivo 13C MRS. Eur J Clin Invest 2000; 30:122-8. [PMID: 10651836 DOI: 10.1046/j.1365-2362.2000.00603.x] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
BACKGROUND Obesity is often accompanied by a decreased ability of insulin to stimulate glucose uptake and glycogenesis in skeletal muscle. The aim of this study was to investigate the rate of glycogen formation and of muscular glucose content in relation to insulin sensitivity under euglycemic conditions. MATERIALS AND METHODS We applied a hyperinsulinemic (430 pmol m-2 min-1) euglycemic clamp with infusion of 20% glucose (30% enriched with 13C-1-glucose) to 8 subjects with a wide range of insulin sensitivities. Glycogen and glucose levels were monitored simultaneously by in vivo 13C MRS of the calf muscle on a clinical MR system at 1.5T field strength. RESULTS AND CONCLUSIONS Glycogen synthesis rate showed a strong correlation with whole body glucose uptake during the clamp (r = 0.93, P < 0.01). With the use of 13C MRS, total muscular glucose content could be determined in vivo, and showed a positive, linear correlation with glycogen synthesis rate (r = 0.85, P < 0.01). 13C MRS provides important information regarding in vivo insulin action. Preliminary results indicate that the glycogen synthesis rate improves after treatment with troglitazone.
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21
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Jucker BM, Barucci N, Shulman GI. Metabolic control analysis of insulin-stimulated glucose disposal in rat skeletal muscle. THE AMERICAN JOURNAL OF PHYSIOLOGY 1999; 277:E505-12. [PMID: 10484363 DOI: 10.1152/ajpendo.1999.277.3.e505] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Metabolic control analysis was used to calculate the distributed control of insulin-stimulated skeletal muscle glucose disposal in awake rats. Three separate hyperinsulinemic infusion protocols were performed: 1) protocol I was a euglycemic (approximately 6 mM)-hyperinsulinemic (10 mU. kg(-1). min(-1)) clamp, 2) protocol II was a hyperglycemic ( approximately 11 mM)-hyperinsulinemic (10 mU. kg(-1). min(-1)) clamp, and 3) protocol III was a euglycemic (approximately 6 mM)-hyperinsulinemic (10 mU. kg(-1). min(-1))-lipid/heparin (increased plasma free fatty acid) clamp. [1-13C]glucose was administered in all three protocols for a 3-h period, during which time [1-13C]glucose label incorporation into [1-13)]glycogen, [3-13C]lactate, and [3-13C]alanine was detected in the hindlimb of awake rats via 13C-NMR. Combined steady-state and kinetic data were used to calculate rates of glycogen synthesis and glycolysis. Additionally, glucose 6-phosphate (G-6-P) was measured in the hindlimb muscles with the use of in vivo 31P-NMR during the three infusion protocols. The clamped glucose infusion rates were 31.6 +/- 2.9, 49.7 +/- 1.0, and 24.0 +/- 1.5 mg. kg(-1). min(-1) at 120 min in protocols I-III, respectively. Rates of glycolysis were 62.1 +/- 10.3, 71.6 +/- 11.8, and 19.5 +/- 3.6 nmol. g(-1). min(-1) and rates of glycogen synthesis were 125 +/- 15, 224 +/- 23, and 104 +/- 17 nmol. g(-1). min(-1) in protocols I-III, respectively. Insulin-stimulated G-6-P concentrations were 217 +/- 8, 265 +/- 12, and 251 +/- 9 nmol/g in protocols I-III, respectively. A top-down approach to metabolic control analysis was used to calculate the distributed control among glucose transport/phosphorylation [GLUT-4/hexokinase (HK)], glycogen synthesis, and glycolysis from the metabolic flux and G-6-P data. The calculated values for the control coefficients (C) of these three metabolic steps (C(J)(GLUT-4/HK) = 0.55 +/- 0.10, C(J)(glycogen syn) = 0.30 +/- 0.06, and C(J)(glycolysis) = 0.15 +/- 0.02; where J is glucose disposal flux, and glycogen syn is glycogen synthesis) indicate that there is shared control of glucose disposal and that glucose transport/phosphorylation is responsible for the majority of control of insulin-stimulated glucose disposal in skeletal muscle.
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Affiliation(s)
- B M Jucker
- Department of Internal Medicine, Yale University School of Medicine, New Haven, Connecticut 06520-8020, USA.
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Abstract
Magnetic resonance imaging (MRI) is a well known diagnostic tool in radiology that produces unsurpassed images of the human body, in particular of soft tissue. However, the medical community is often not aware that MRI is an important yet limited segment of magnetic resonance (MR) or nuclear magnetic resonance (NMR) as this method is called in basic science. The tremendous morphological information of MR images sometimes conceal the fact that MR signals in general contain much more information, especially on processes on the molecular level. NMR is successfully used in physics, chemistry, and biology to explore and characterize chemical reactions, molecular conformations, biochemical pathways, solid state material, and many other applications that elucidate invisible characteristics of matter and tissue. In medical applications, knowledge of the molecular background of MRI and in particular MR spectroscopy (MRS) is an inevitable basis to understand molecular phenomenon leading to macroscopic effects visible in diagnostic images or spectra. This review shall provide the necessary background to comprehend molecular aspects of magnetic resonance applications in medicine. An introduction into the physical basics aims at an understanding of some of the molecular mechanisms without extended mathematical treatment. The MR typical terminology is explained such that reading of original MR publications could be facilitated for non-MR experts. Applications in MRI and MRS are intended to illustrate the consequences of molecular effects on images and spectra.
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Affiliation(s)
- C Boesch
- Department of Clinical Research, University of Bern, Switzerland
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Young VR, Ajami A. The Rudolf Schoenheimer Centenary Lecture. Isotopes in nutrition research. Proc Nutr Soc 1999; 58:15-32. [PMID: 10343336 DOI: 10.1079/pns19990004] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
The present lecture begins with a brief overview of the professional and scientific journey taken by Rudolf Schoenheimer, before turning to a discussion of the power of isotopic tracers in nutrition research. Schoenheimer's remarkable contributions to the study of intermediary metabolism and the turnover of body constituents, based initially on compounds tagged with 2H and later with 15N, spanned a mere decade. It is difficult, however, to overestimate the enormous impact of Schoenheimer's research on the evolution of biological science. After a relative hiatus, following Schoenheimer's death in 1941, in the use of stable nuclides as tracers in metabolism and nutrition, especially in human subjects, there is now an expanded and exciting range of techniques, experimental protocols and stable-isotope tracer compounds that are helping to probe the dynamic aspects of the metabolism of the major energy-yielding substrates, amino acids and other N-containing compounds, vitamins and mineral elements in human subjects. Various aspects of the contemporary applications of these tracers in nutrition research are covered in the present lecture.
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Affiliation(s)
- V R Young
- Laboratory of Human Nutrition, School of Science, Massachusetts Institute of Technology, Cambridge 02139, USA.
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