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Xu X, Leforestier R, Xia D, Block KT, Feng L. MRI of GlycoNOE in the human liver using GraspNOE-Dixon. Magn Reson Med 2024. [PMID: 39367632 DOI: 10.1002/mrm.30270] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2024] [Revised: 08/06/2024] [Accepted: 08/07/2024] [Indexed: 10/06/2024]
Abstract
PURPOSE The objective of this study was to develop a new MRI technique for non-invasive, free-breathing imaging of glycogen in the human liver using the nuclear Overhauser effect (NOE). METHODS The proposed method, called GraspNOE-Dixon, uses a novel MRI sequence that combines steady-state saturation-transfer preparation with multi-echo golden-angle radial stack-of-stars sampling. Multi-echo acquisition enables fat/water-separated imaging for quantification of water-specific NOE. Image reconstruction is performed using the improved golden-angle radial sparse parallel imaging (GRASP-Pro) technique to exploit spatiotemporal correlations in dynamic images. To evaluate the proposed technique, imaging experiments were first performed on glycogen phantoms, followed by in vivo studies involving healthy volunteers and patients with fatty liver disease. In addition, a comparative assessment of signal changes before and after a 12-h fasting period was performed. RESULTS Evaluation experiments on glycogen phantoms showed a robust linear correlation between the NOE signal and glycogen concentration. In vivo experiments demonstrated motion-robust NOE-weighted images, with potential for further acceleration. In subjects with varying liver fat content, the fat/water separation approach resulted in distortion-free Z-spectra, enabling the quantification of glycogen NOE. An approximately one-third reduction in the NOE signal was observed following a 12-h fasting period, consistent with a decrease in glycogen level. CONCLUSION This study introduces a clinically feasible imaging technique, GraspNOE-Dixon, for free-breathing volumetric multi-echo imaging of hepatic glycogen at 3 T. The motion robust imaging technique developed here may also have applications in other body areas beyond liver imaging.
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Affiliation(s)
- Xiang Xu
- BioMedical Engineering and Imaging Institute (BMEII), Icahn School of Medicine at Mount Sinai, New York, New York, USA
- Department of Diagnostic, Molecular and Interventional Radiology, The Icahn School of Medicine at Mount Sinai, New York, New York, USA
| | - Rodolphe Leforestier
- BioMedical Engineering and Imaging Institute (BMEII), Icahn School of Medicine at Mount Sinai, New York, New York, USA
- Department of Diagnostic, Molecular and Interventional Radiology, The Icahn School of Medicine at Mount Sinai, New York, New York, USA
| | - Ding Xia
- BioMedical Engineering and Imaging Institute (BMEII), Icahn School of Medicine at Mount Sinai, New York, New York, USA
- Department of Diagnostic, Molecular and Interventional Radiology, The Icahn School of Medicine at Mount Sinai, New York, New York, USA
| | - Kai Tobias Block
- Center for Advanced Imaging Innovation and Research (CAI2R), Department of Radiology, New York University School of Medicine, New York, New York, USA
| | - Li Feng
- BioMedical Engineering and Imaging Institute (BMEII), Icahn School of Medicine at Mount Sinai, New York, New York, USA
- Department of Diagnostic, Molecular and Interventional Radiology, The Icahn School of Medicine at Mount Sinai, New York, New York, USA
- Center for Advanced Imaging Innovation and Research (CAI2R), Department of Radiology, New York University School of Medicine, New York, New York, USA
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Valette J, Tiret B, Boumezbeur F. Experimental strategies for in vivo 13C NMR spectroscopy. Anal Biochem 2016; 529:216-228. [PMID: 27515993 DOI: 10.1016/j.ab.2016.08.003] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2016] [Revised: 05/24/2016] [Accepted: 08/04/2016] [Indexed: 11/15/2022]
Abstract
In vivo carbon-13 (13C) MRS opens unique insights into the metabolism of intact organisms, and has led to major advancements in the understanding of cellular metabolism under normal and pathological conditions in various organs such as skeletal muscles, the heart, the liver and the brain. However, the technique comes at the expense of significant experimental difficulties. In this review we focus on the experimental aspects of non-hyperpolarized 13C MRS in vivo. Some of the enrichment strategies which have been proposed so far are described; the various MRS acquisition paradigms to measure 13C labeling are then presented. Finally, practical aspects of 13C spectral quantification are discussed.
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Affiliation(s)
- Julien Valette
- Commissariat à l'Energie Atomique et aux Energies Alternatives (CEA), Direction de la Recherche Fondamentale (DRF), Institut d'Imagerie Biomédicale (I2BM), MIRCen, F-92260 Fontenay-aux-Roses, France; Centre National de la Recherche Scientifique (CNRS), Université Paris-Sud, Université Paris-Saclay, UMR 9199, Neurodegenerative Diseases Laboratory, F-92260 Fontenay-aux-Roses, France.
| | - Brice Tiret
- Commissariat à l'Energie Atomique et aux Energies Alternatives (CEA), Direction de la Recherche Fondamentale (DRF), Institut d'Imagerie Biomédicale (I2BM), MIRCen, F-92260 Fontenay-aux-Roses, France; Centre National de la Recherche Scientifique (CNRS), Université Paris-Sud, Université Paris-Saclay, UMR 9199, Neurodegenerative Diseases Laboratory, F-92260 Fontenay-aux-Roses, France
| | - Fawzi Boumezbeur
- Commissariat à l'Energie Atomique et aux Energies Alternatives (CEA), Direction de la Recherche Fondamentale (DRF), Institut d'Imagerie Biomédicale (I2BM), NeuroSpin, F-91190 Gif-sur-Yvette, France
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3
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van Heeswijk RB, Pellegrin M, Flögel U, Gonzales C, Aubert JF, Mazzolai L, Schwitter J, Stuber M. Fluorine MR Imaging of Inflammation in Atherosclerotic Plaque in Vivo. Radiology 2015; 275:421-9. [DOI: 10.1148/radiol.14141371] [Citation(s) in RCA: 42] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
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4
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Tesfaye N, Seaquist ER, Oz G. Noninvasive measurement of brain glycogen by nuclear magnetic resonance spectroscopy and its application to the study of brain metabolism. J Neurosci Res 2011; 89:1905-12. [PMID: 21732401 DOI: 10.1002/jnr.22703] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2010] [Revised: 04/19/2011] [Accepted: 05/02/2011] [Indexed: 11/11/2022]
Abstract
Glycogen is the reservoir for glucose in the brain. Beyond the general agreement that glycogen serves as an energy source in the central nervous system, its exact role in brain energy metabolism has yet to be elucidated. Experiments performed in cell and tissue culture and animals have shown that glycogen content is affected by several factors, including glucose, insulin, neurotransmitters, and neuronal activation. The study of in vivo glycogen metabolism has been hindered by the inability to measure glycogen noninvasively, but, in the past several years, the development of a noninvasive localized (13) C nuclear magnetic resonance (NMR) spectroscopy method has allowed the study of glycogen metabolism in the conscious human. With this technique, (13) C-glucose is administered intravenously, and its incorporation into and washout from brain glycogen is tracked. One application of this method has been to the study of brain glycogen metabolism in humans during hypoglycemia: data have shown that mobilization of brain glycogen is augmented during hypoglycemia, and, after a single episode of hypoglycemia, glycogen synthesis rate is increased, suggesting that glycogen stores rebound to levels greater than baseline. Such studies suggest that glycogen may serve as a potential energy reservoir in hypoglycemia and may participate in the brain's adaptation to recurrent hypoglycemia and eventual development of hypoglycemia unawareness. Beyond this focused area of study, (13) C NMR spectroscopy has a broad potential for application in the study of brain glycogen metabolism and carries the promise of a better understanding of the role of brain glycogen in diabetes and other conditions.
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Affiliation(s)
- Nolawit Tesfaye
- Department of Medicine, Division of Endocrinology and Diabetes, University of Minnesota, Minneapolis, Minnesota 55455, USA
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5
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Morgenthaler FD, van Heeswijk RB, Xin L, Laus S, Frenkel H, Lei H, Gruetter R. Non-invasive quantification of brain glycogen absolute concentration. J Neurochem 2008; 107:1414-23. [PMID: 19013831 DOI: 10.1111/j.1471-4159.2008.05717.x] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The only currently available method to measure brain glycogen in vivo is 13C NMR spectroscopy. Incorporation of 13C-labeled glucose (Glc) is necessary to allow glycogen measurement, but might be affected by turnover changes. Our aim was to measure glycogen absolute concentration in the rat brain by eliminating label turnover as variable. The approach is based on establishing an increased, constant 13C isotopic enrichment (IE). 13C-Glc infusion is then performed at the IE of brain glycogen. As glycogen IE cannot be assessed in vivo, we validated that it can be inferred from that of N-acetyl-aspartate IE in vivo: After [1-13C]-Glc ingestion, glycogen IE was 2.2 +/- 0.1 fold that of N-acetyl-aspartate (n = 11, R(2) = 0.77). After subsequent Glc infusion, glycogen IE equaled brain Glc IE (n = 6, paired t-test, p = 0.37), implying isotopic steady-state achievement and complete turnover of the glycogen molecule. Glycogen concentration measured in vivo by 13C NMR (mean +/- SD: 5.8 +/- 0.7 micromol/g) was in excellent agreement with that in vitro (6.4 +/- 0.6 micromol/g, n = 5). When insulin was administered, the stability of glycogen concentration was analogous to previous biochemical measurements implying that glycogen turnover is activated by insulin. We conclude that the entire glycogen molecule is turned over and that insulin activates glycogen turnover.
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Affiliation(s)
- Florence D Morgenthaler
- Centre d'Imagerie Biomédicale (CIBM), Ecole Polytechnique Fédérale de Lausanne (EPFL), Lausanne, Switzerland.
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Lei H, Morgenthaler F, Yue T, Gruetter R. Direct validation of in vivo localized 13C MRS measurements of brain glycogen. Magn Reson Med 2007; 57:243-8. [PMID: 17260359 PMCID: PMC1839006 DOI: 10.1002/mrm.21128] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
With the use of localized 13C MRS in conjunction with [1-(13)C]-D-glucose infusion, it is possible to study brain glycogen metabolism in vivo. The purpose of this study was to validate in vivo 13C MRS measurements by comparing them with results from a standard biochemical assay. To increase the [1-(13)C] glycogen concentration, 11 rats were subjected to an episode of acute hypoglycemia followed by a mild hyperglycemic recovery period during which [1-(13)C]-D-glucose was infused. The total brain [1-(13)C] glycogen of the same animal was determined from the enzymatically determined total brain glycogen content, which was fixed by focused microwave irradiation (4 kW in 1.4 s) immediately after the end of the in vivo NMR measurements. The corresponding isotopic enrichment (IE) of glycogen was measured by in vitro 1H MRS of protons bound to glucose C1-alpha. The in vivo [1-(13)C] glycogen concentration was strongly correlated to the in vitro [1-(13)C] glycogen content determined by biochemical measurement in a linear manner (R=0.79). The results are consistent with the notion that localized 13C MRS measurements closely reflect 13C glycogen content in the brain.
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Affiliation(s)
- Hongxia Lei
- Department of Radiology, University of Minnesota, Minneapolis, Minnesota, USA
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7
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Prompers JJ, Jeneson JAL, Drost MR, Oomens CCW, Strijkers GJ, Nicolay K. Dynamic MRS and MRI of skeletal muscle function and biomechanics. NMR IN BIOMEDICINE 2006; 19:927-53. [PMID: 17075956 DOI: 10.1002/nbm.1095] [Citation(s) in RCA: 82] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/12/2023]
Abstract
MR is a powerful technique for studying the biomechanical and functional properties of skeletal muscle in vivo in health and disease. This review focuses on 31P, 1H and 13C MR spectroscopy for assessment of the dynamics of muscle metabolism and on dynamic 1H MRI methods for non-invasive measurement of the biomechanical and functional properties of skeletal muscle. The information thus obtained ranges from the microscopic level of the metabolism of the myocyte to the macroscopic level of the contractile function of muscle complexes. The MR technology presented plays a vital role in achieving a better understanding of many basic aspects of muscle function, including the regulation of mitochondrial activity and the intricate interplay between muscle fiber organization and contractile function. In addition, these tools are increasingly being employed to establish novel diagnostic procedures as well as to monitor the effects of therapeutic and lifestyle interventions for muscle disorders that have an increasing impact in modern society.
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Affiliation(s)
- Jeanine J Prompers
- Biomedical NMR, Department of Biomedical Engineering, Eindhoven University of Technology, The Netherlands
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8
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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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9
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Goforth HW, Laurent D, Prusaczyk WK, Schneider KE, Petersen KF, Shulman GI. Effects of depletion exercise and light training on muscle glycogen supercompensation in men. Am J Physiol Endocrinol Metab 2003; 285:E1304-11. [PMID: 12902321 PMCID: PMC2995524 DOI: 10.1152/ajpendo.00209.2003] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Supercompensated muscle glycogen can be achieved by using several carbohydrate (CHO)-loading protocols. This study compared the effectiveness of two "modified" CHO-loading protocols. Additionally, we determined the effect of light cycle training on muscle glycogen. Subjects completed a depletion (D, n = 15) or nondepletion (ND, n = 10) CHO-loading protocol. After a 2-day adaptation period in a metabolic ward, the D group performed a 120-min cycle exercise at 65% peak oxygen uptake (VO2 peak) followed by 1-min sprints at 120% VO2 peak to exhaustion. The ND group performed only 20-min cycle exercise at 65% VO2 peak. For the next 6 days, both groups ate the same high-CHO diets and performed 20-min daily cycle exercise at 65% VO2 peak followed by a CHO beverage (105 g of CHO). Muscle glycogen concentrations of the vastus lateralis were measured daily with 13C magnetic resonance spectroscopy. On the morning of day 5, muscle glycogen concentrations had increased 1.45 (D) and 1.24 (ND) times baseline (P < 0.001) but did not differ significantly between groups. However, on day 7, muscle glycogen of the D group was significantly greater (p < 0.01) than that of the ND group (130 +/- 7 vs. 104 +/- 5 mmol/l). Daily cycle exercise decreased muscle glycogen by 10 +/- 2 (D) and 14 +/- 5 mmol/l (ND), but muscle glycogen was equal to or greater than preexercise values 24 h later. In conclusion, a CHO-loading protocol that begins with a glycogen-depleting exercise results in significantly greater muscle glycogen that persists longer than a CHO-loading protocol using only an exercise taper. Daily exercise at 65% VO2 peak for 20 min can be performed throughout the CHO-loading protocol without negatively affecting muscle glycogen supercompensation.
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10
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Wary C, Laforêt P, Eymard B, Fardeau M, Leroy-Willig A, Bassez G, Leroy JP, Caillaud C, Poenaru L, Carlier PG. Evaluation of muscle glycogen content by 13C NMR spectroscopy in adult-onset acid maltase deficiency. Neuromuscul Disord 2003; 13:545-53. [PMID: 12921791 DOI: 10.1016/s0960-8966(03)00069-5] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Muscle glycogen storage was measured by in vivo, natural abundance 13C nuclear magnetic resonance spectroscopy in distal and proximal lower limb segments of patients suffering from adult-onset acid maltase deficiency. Interleaved T1-weighted acquisitions of glycogen and creatine served to quantify glycogen excess. For acid maltase deficient patients (n=11), glycogen:creatine was higher than controls (n=12), (1.20+/-0.39 vs. 0.83+/-0.18, P=0.0005). Glycogen storage was above the normal 95% confidence limits in at least one site for 7/11 patients. The intra-individual coefficient of reproducibility was 12%. This totally atraumatic measurement of glycogen allows repeated measurement at different muscle sites of acid maltase deficient patients, despite selective fatty replacement of tissue. This could provide an additional parameter to follow the development of disease in individual patients, including in the perspective of forthcoming therapeutic trials. It may also offer an appropriate tool to study the role of glycogen accumulation in progression of the pathology.
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Affiliation(s)
- Claire Wary
- AFM-CEA NMR Laboratory, Institut de Myologie, IFR14, G.H. Pitié-Salpêtrière, 75651 Paris Cedex 13, France.
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11
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Oz G, Henry PG, Seaquist ER, Gruetter R. Direct, noninvasive measurement of brain glycogen metabolism in humans. Neurochem Int 2003; 43:323-9. [PMID: 12742076 DOI: 10.1016/s0197-0186(03)00019-6] [Citation(s) in RCA: 58] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
The concentration and metabolism of the primary carbohydrate store in the brain, glycogen, is unknown in the conscious human brain. This study reports the first direct detection and measurement of glycogen metabolism in the human brain, which was achieved using localized 13C NMR spectroscopy. To enhance the NMR signal, the isotopic enrichment of the glucosyl moieties was increased by administration of 80 g of 99% enriched [1-13C]glucose in four subjects. 3 h after the start of the label administration, the 13C NMR signal of brain glycogen C1 was detected (0.36+/-0.07 micromol/g, mean+/-S.D., n=4). Based on the rate of 13C label incorporation into glycogen and the isotopic enrichment of plasma glucose, the flux through glycogen synthase was estimated at 0.17+/-0.05 micromol/(gh). This study establishes that brain glycogen can be measured in humans and indicates that its metabolism is very slow in the conscious human. The noninvasive detection of human brain glycogen opens the prospect of understanding the role and function of this important energy reserve under various physiological and pathophysiological conditions.
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Affiliation(s)
- Gülin Oz
- Department of Radiology, Center for MR Research, University of Minnesota, 2021 6th St. S.E., Minneapolis, MN 55455, USA
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12
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Abstract
Cigarette smoking is a leading cause of many adverse health consequences. Chronic nicotine exposure leads to insulin resistance and may increase the risk of developing non-insulin-dependent diabetes mellitus in young otherwise healthy smokers. To evaluate smoking-induced effects on carbohydrate metabolism, we studied muscle glycogen recovery from exercise in a young healthy population of smokers. The study used 31P-13C NMR spectroscopy to compare muscle glycogen and glucose 6-phosphate levels during recovery in exercised gastrocnemius muscles of randomized cohorts of healthy male smokers (S) and controls (C). Data for the two groups were as follows: S, > or =20 cigarettes/day (n = 8), 24 +/- 2 yr, 173 +/- 3 cm, 70 +/- 4 kg and age- and weight-matched nonsmoking C (n = 10), 23 +/- 1 yr, 175 +/- 3 cm, 67 +/- 3 kg. Subjects performed single-leg toe raises to deplete glycogen to approximately 20 mmol/l, and glycogen resynthesis was measured during the first 4 h of recovery. Plasma samples were assayed for glucose and insulin at rest and during recovery. Test subjects were recruited from the general community surrounding Yale University. Glycogen was depleted to similar levels in the two groups [23.5 +/- 1.2 (S) and 19.1 +/- 1.3 (C) mmol/l]. During the 1st h of recovery, glycogen synthesis rates were similar [13.8 +/- 1.1 (S) and 15.3 +/- 1.3 (C) mmol x l-1 x h-1]. Between hours 1 and 4, glycogen synthesis was impaired in smokers [0.8 +/- 0.2 (S) and 4.5 +/- 0.5 (C) mmol x l-1 x h-1, P = 0.0002] compared with controls. Glucose 6-phosphate was reduced in smokers during hours 1-4 [0.105 +/- 0.006 (S) and 0.217 +/- 0.019 (C) mmol/l, P = 0.0212]. We conclude that cigarette smoking impairs the insulin-dependent portion of muscle recovery from glycogen-depleting exercise. This impairment likely results from a reduction in glucose uptake.
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Affiliation(s)
- Thomas B Price
- Department of Diagnostic Radiology, Yale University School of Medicine, New Haven, Connecticut 06510, USA.
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13
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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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14
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Murphy E, Hellerstein M. Is in vivo nuclear magnetic resonance spectroscopy currently a quantitative method for whole-body carbohydrate metabolism? Nutr Rev 2000; 58:304-14. [PMID: 11127969 DOI: 10.1111/j.1753-4887.2000.tb01825.x] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023] Open
Abstract
In vivo nuclear magnetic resonance (NMR) spectroscopy is a powerful tool for noninvasive metabolic research. NMR studies of tissue glycogen metabolism and glucose utilization have generated results with major implications for normal glucose homeostasis and the pathophysiology of type 2 diabetes mellitus. A key question for clinicians and physiologists reading these highly technical studies is: How accurate for whole-body carbohydrate metabolism is NMR spectroscopy? We review this topic and discuss technical, metabolic, and interpretive factors that may limit quantitative accuracy of this modality. We conclude that seeing is not yet believing regarding in vivo NMR spectroscopy; there are still important limitations to quantification of whole-body carbohydrate metabolism.
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Affiliation(s)
- E Murphy
- Department of Nutritional Sciences and Toxicology, University of California at Berkeley, 94720-4104, USA
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15
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Laurent D, Hundal RS, Dresner A, Price TB, Vogel SM, Petersen KF, Shulman GI. Mechanism of muscle glycogen autoregulation in humans. Am J Physiol Endocrinol Metab 2000; 278:E663-8. [PMID: 10751200 DOI: 10.1152/ajpendo.2000.278.4.e663] [Citation(s) in RCA: 40] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
To examine the mechanism by which muscle glycogen limits its own synthesis, muscle glycogen and glucose 6-phosphate (G-6-P) concentrations were measured in seven healthy volunteers during a euglycemic ( approximately 5.5 mM)-hyperinsulinemic ( approximately 450 pM) clamp using (13)C/(31)P nuclear magnetic resonance spectroscopy before and after a muscle glycogen loading protocol. Rates of glycogen synthase (V(syn)) and phosphorylase (V(phos)) flux were estimated during a [1-(13)C]glucose (pulse)-unlabeled glucose (chase) infusion. The muscle glycogen loading protocol resulted in a 65% increase in muscle glycogen content that was associated with a twofold increase in fasting plasma lactate concentrations (P < 0.05 vs. basal) and an approximately 30% decrease in plasma free fatty acid concentrations (P < 0.001 vs. basal). Muscle glycogen loading resulted in an approximately 30% decrease in the insulin-stimulated rate of net muscle glycogen synthesis (P < 0.05 vs. basal), which was associated with a twofold increase in intramuscular G-6-P concentration (P < 0.05 vs. basal). Muscle glycogen loading also resulted in an approximately 30% increase in whole body glucose oxidation rates (P < 0.05 vs. basal), whereas there was no effect on insulin-stimulated rates of whole body glucose uptake ( approximately 10.5 mg. kg body wt(-1). min(-1) for both clamps) or glycogen turnover (V(syn)/V(phos) was approximately 23% for both clamps). In conclusion, these data are consistent with the hypothesis that glycogen limits its own synthesis through feedback inhibition of glycogen synthase activity, as reflected by an accumulation of intramuscular G-6-P, which is then shunted into aerobic and anaerobic glycolysis.
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Affiliation(s)
- D Laurent
- Department of Internal Medicine, Yale University School of Medicine, New Haven, Connecticut 06510, USA
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Price TB, Laurent D, Petersen KF, Rothman DL, Shulman GI. Glycogen loading alters muscle glycogen resynthesis after exercise. J Appl Physiol (1985) 2000; 88:698-704. [PMID: 10658040 DOI: 10.1152/jappl.2000.88.2.698] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
This study compared muscle glycogen recovery after depletion of approximately 50 mmol/l (DeltaGly) from normal (Nor) resting levels (63.2 +/- 2.8 mmol/l) with recovery after depletion of approximately 50 mmol/l from a glycogen-loaded (GL) state (99.3 +/- 4.0 mmol/l) in 12 healthy, untrained subjects (5 men, 7 women). To glycogen load, a 7-day carbohydrate-loading protocol increased muscle glycogen 1.6 +/- 0.2-fold (P < or = 0.01). GL subjects then performed plantar flexion (single-leg toe raises) at 50 +/- 3% of maximum voluntary contraction (MVC) to yield DeltaGly = 48.0 +/- 1.3 mmol/l. The Nor trial, performed on a separate occasion, yielded DeltaGly = 47.5 +/- 4.5 mmol/l. Interleaved natural abundance (13)C-(31)P-NMR spectra were acquired and quantified before exercise and during 5 h of recovery immediately after exercise. During the initial 15 min after exercise, glycogen recovery in the GL trial was rapid (32.9 +/- 8.9 mmol. l(-1). h(-1)) compared with the Nor trial (15.9 +/- 6.9 mmol. l(-1). h(-1)). During the next 45 min, GL glycogen synthesis was not as rapid as in the Nor trial (0.9 +/- 2.5 mmol. l(-1). h(-1) for GL; 14.7 +/- 3.0 mmol. l(-1). h(-1) for Nor; P < or = 0.005) despite similar glucose 6-phosphate levels. During extended recovery (60-300 min), reduced GL recovery rates continued (1.3 +/- 0.5 mmol. l(-1). h(-1) for GL; 3.9 +/- 0.3 mmol. l(-1). h(-1) for Nor; P < or = 0.001). We conclude that glycogen recovery from heavy exercise is controlled primarily by the remaining postexercise glycogen concentration, with only a transient synthesis period when glycogen levels are not severely reduced.
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Affiliation(s)
- T B Price
- Department of Diagnostic Radiology, Yale University School of Medicine, New Haven, Connecticut 06510, USA.
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17
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Abstract
Natural-abundance 13C NMR spectroscopy is a non-invasive technique that enables in vivo assessments of muscle and/or liver glycogen concentrations. Over the last several years, 13C NMR has been developed and used to obtain information about human glycogen metabolism with diet and exercise. Since NMR is non-invasive, more data points are available over a specified time course, dramatically improving the time resolution. This improved time resolution has enabled the documentation of subtleties of muscle glycogen re-synthesis following severe glycogen depletion that were not previously observed. Muscle and liver glycogen concentrations have been tracked in several different human populations under conditions that include: (1) muscle glycogen recovery from intense localized exercise with normal insulin and with insulin suppressed; (2) muscle glycogen recovery in an insulin-resistant population; (3) muscle glycogen depletion during prolonged low-intensity exercise; (4) effect of a mixed meal on postprandial muscle and liver glycogen synthesis. The present review focuses on basic 13C NMR and gives results from selected studies.
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Affiliation(s)
- T B Price
- Department of Diagnostic Radiology, Yale University School of Medicine, New Haven, CT 06510, USA.
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18
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Boesch C, Décombaz J, Slotboom J, Kreis R. Observation of intramyocellular lipids by means of 1H magnetic resonance spectroscopy. Proc Nutr Soc 1999; 58:841-50. [PMID: 10817151 DOI: 10.1017/s0029665199001147] [Citation(s) in RCA: 81] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Magnetic resonance imaging (MRI) and magnetic resonance spectroscopy (MRS) are being increasingly used for investigations of human muscle physiology. While MRI reveals the morphology of muscles in great detail (e.g. for the determination of muscle volumes), MRS provides information on the chemical composition of the tissue. Depending on the observed nucleus, MRS allows the monitoring of high-energy phosphates (31P MRS), glycogen (13C MRS), or intramyocellular lipids (1H MRS), to give only a few examples. The observation of intramyocellular lipids (IMCL) by means of 1H MRS is non-invasive and, therefore, can be repeated many times and with a high temporal resolution. MRS has the potential to replace the biopsy for the monitoring of IMCL levels; however, the biopsy still has the advantage that other methods such as those used in molecular biology can be applied to the sample. The present study describes variations in the IMCL levels (expressed in mmol/kg wet weight and ml/100 ml) in three different muscles before and after (0, 1, 2, and 5 d) marathon runs for a well-trained individual who followed two different recovery protocols varying mainly in the diet. It was shown that the repletion of IMCL levels is strongly dependent on the diet post exercise. The monitoring of IMCL levels by means of 1H MRS is extremely promising, but several methodological limitations and pitfalls need to be considered, and these are addressed in the present review.
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Affiliation(s)
- C Boesch
- Department of Clinical Research, MR Spectroscopy and Methodology, University of Bern, Switzerland.
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19
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Choi IY, Tkác I, Ugurbil K, Gruetter R. Noninvasive measurements of [1-(13)C]glycogen concentrations and metabolism in rat brain in vivo. J Neurochem 1999; 73:1300-8. [PMID: 10461925 DOI: 10.1046/j.1471-4159.1999.0731300.x] [Citation(s) in RCA: 86] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Using a specific 13C NMR localization method, 13C label incorporation into the glycogen C1 resonance was measured while infusing [1-(13)C]glucose in intact rats. The maximal concentration of [1-(13)C]glycogen was 5.1 +/- 0.6 micromol g(-1) (mean +/- SE, n = 8). During the first 60 min of acute hyperglycemia, the rate of 13C label incorporation (synthase flux) was 2.3 +/- 0.7 micromol g(-1) h(-1) (mean +/- SE, n = 9 rats), which was higher (p < 0.01) than the rate of 0.49 +/- 0.14 micromol g(-1) h(-1) measured > or = 2 h later. To assess whether the incorporation of 13C label was due to turnover or net synthesis, the infusion was continued in seven rats with unlabeled glucose. The rate of 13C label decline (phosphorylase flux) was lower (0.33 +/- 0.10 micromol g(-1) h(-1)) than the initial rate of label incorporation (p < 0.01) and appeared to be independent of the duration of the preceding infusion of [1-(13)C]glucose (p > 0.05 for correlation). The results implied that net glycogen synthesis of approximately 3 micromol g(-1) had occurred, similar to previous reports. When infusing unlabeled glucose before [1-(13)C]glucose in three studies, the rate of glycogen C1 accumulation was 0.46 +/- 0.08 micromol g(-1) h(-1). The results suggest that steady-state glycogen turnover rates during hyperglycemia are approximately 1% of glucose consumption.
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Affiliation(s)
- I Y Choi
- Department of Radiology, Center for MR Research, University of Minnesota, Minneapolis, USA
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20
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Abstract
Prior to the advent of nuclear magnetic resonance (NMR) spectroscopy, human glucose metabolism was studied through tracer and tissue biopsy methodology. NMR spectroscopy now provides a noninvasive means to monitor metabolic flux and intracellular metabolite concentrations continuously. 13C NMR spectroscopy has shown that muscle glycogen synthesis accounts for the majority of insulin-stimulated muscle glucose uptake in normal volunteers and that defects in this process are chiefly responsible for insulin resistance in type 1 and type 2 diabetes mellitus, as well as in other insulin resistant states (obesity, insulin-resistant offspring of type 2 diabetic parents, elevation of plasma FFA concentrations). Furthermore, using 31P NMR spectroscopy to measure intracellular glucose-6-phosphate, it has been shown that defects in insulin-stimulated glucose transport/phosphorylation activity are primarily responsible for the insulin resistance in these states.
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Affiliation(s)
- M Roden
- Department of Internal Medicine III, University of Vienna Medical School, Austria.
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21
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Price TB, Gore JC. Effect of muscle glycogen content on exercise-induced changes in muscle T2 times. J Appl Physiol (1985) 1998; 84:1178-84. [PMID: 9516182 DOI: 10.1152/jappl.1998.84.4.1178] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
Effects of gastrocnemius glycogen (Gly) concentration on changes in transverse relaxation time (T2; ms) were studied after 5-min plantar flexion at 25% of maximum voluntary contraction (MVC). Gastrocnemius Gly, phosphorus metabolites, and T2 were measured in seven subjects by using interleaved 13C/31P magnetic resonance spectroscopy (MRS) at 4.7 T and magnetic resonance imaging (MRI; 1.5 T). After baseline MRS/MRI, subjects exercised for 5 min at 25% of MVC and were reexamined (MRS/MRI). Subjects then performed approximately 15 min of single-leg toe raises (50 +/- 2% of MVC), depleting gastrocnemius Gly by 43%. After a 1-h rest (for T2 return to baseline), subjects repeated the 5-min protocol, followed by a final MRI/MRS. After the initial 5-min protocol, T2 values increased by 5.9 +/- 0.8 ms (29.9 +/- 0.4 to 35.8 +/- 0.6 ms), whereas Gly did not change significantly (70.5 +/- 6.8 to 67.6 +/- 7.4 mM). After 15 min of toe raises, gastrocnemius Gly was reduced to 40.4 +/- 5.3 mM (P </= 0. 01), recovering to 45.8 +/- 5.3 mM (P </= 0.05) during a 1-h rest. After the second 5-min bout of plantar flexion (reduced Gly at 25% of MVC), T2 values increased by 5.0 +/- 0.8 ms (30.4 to 35.4 ms), whereas muscle Gly rose to 57.6 +/- 5.3 mM. We conclude that muscle Gly concentration per se does not affect exercise-induced T2 increases in the human gastrocnemius.
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Affiliation(s)
- T B Price
- Department of Diagnostic Radiology, Yale University School of Medicine, New Haven, Connecticut 06510, USA.
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22
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Laurent D, Petersen KF, Russell RR, Cline GW, Shulman GI. Effect of epinephrine on muscle glycogenolysis and insulin-stimulated muscle glycogen synthesis in humans. THE AMERICAN JOURNAL OF PHYSIOLOGY 1998; 274:E130-8. [PMID: 9458758 DOI: 10.1152/ajpendo.1998.274.1.e130] [Citation(s) in RCA: 23] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
To examine the effects of a physiological increase in plasma epinephrine concentration (approximately 800 pg/ml) on muscle glycogenolysis and insulin-stimulated glycogenesis, we infused epinephrine [1.2 micrograms.(m2 body surface)-1.min-1] for 2 h and monitored muscle glycogen and glucose 6-phosphate (G-6-P) concentrations with 13C/31P nuclear magnetic resonance (NMR) spectroscopy. Epinephrine caused an increase in plasma glucose (delta approximately 50 mg/dl), lactate (delta approximately 1.4 mM), free fatty acids (delta approximately 1,200 microM at peak), and whole body glucose oxidation (delta approximately 0.85 mg.kg-1.min-1) compared with levels in a group of control subjects (n = 4) in the presence of slight hyperinsulinemia (approximately 13 microU/ml, n = 8) or basal insulin (approximately 7 microU/ml, n = 7). However, epinephrine did not induce any detectable changes in glycogen or G-6-P concentrations, whereas muscle inorganic phosphate (Pi) decreased by 35%. Epinephrine infusion during a euglycemic-hyperinsulinemic clamp (n = 8) caused a 45% decrease in the glucose infusion rate that could be mostly attributed to a 73% decrease in muscle glycogen synthesis rate. After an initial increase to approximately 160% of basal values, G-6-P levels decreased by approximately 30% with initiation of the epinephrine infusion. We conclude that a physiological increase in plasma epinephrine concentration 1) has a negligible effect on muscle glycogenolysis at rest, 2) decreases muscle Pi, which may maintain phosphorylase activity at a low level, and 3) causes a major impairment in insulin-stimulated muscle glycogen synthesis, possibly due to inhibition of glucose transport-phosphorylation activity.
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Affiliation(s)
- D Laurent
- Department of Internal Medicine, Yale University School of Medicine, New Haven, Connecticut 06520, USA
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23
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Bertocci LA, Jones JG, Malloy CR, Victor RG, Thomas GD. Oxidation of lactate and acetate in rat skeletal muscle: analysis by 13C-nuclear magnetic resonance spectroscopy. J Appl Physiol (1985) 1997; 83:32-9. [PMID: 9216941 DOI: 10.1152/jappl.1997.83.1.32] [Citation(s) in RCA: 23] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
The balance between carbohydrate and fatty acid utilization in skeletal muscle previously has been studied in vivo by using a variety of methods such as arteriovenous concentration differences and radioactive isotope tracer techniques. However, these methodologies provide only indirect estimates of substrate oxidation. We used 13C-nuclear magnetic resonance (NMR) spectroscopy and non-steady-state isotopomer analysis to directly quantify the relative oxidation of two competing exogenous substrates in rat skeletal muscles. We infused [1,2-13C]acetate and [3-13C]lactate intravenously in anesthetized rats during the final 30 min of 35 (n = 10) or 95 (n = 10) min of intense, unilateral, rhythmic hindlimb contractions. 13C-NMR spectroscopy and isotopomer analysis were performed on extracts of gastrocnemius and soleus muscles from both the contracting and contralateral resting hindlimbs. We found that 1) [13C]lactate and [13C]acetate were taken up and oxidized by both resting and contracting skeletal muscles; and 2) high-intensity muscle contractions altered the pattern of substrate utilization such that the relative oxidation of acetate decreased while that of lactate remained unchanged or increased. Based on these findings, we propose that 13C-NMR spectroscopy in combination with isotopomer analysis can be used to study the general dynamics of substrate competition between carbohydrates and fats in rat skeletal muscle.
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Affiliation(s)
- L A Bertocci
- Institute for Exercise and Environmental Medicine, Presbyterian Hospital of Dallas, Dallas 75231, Texas 75216, USA.
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24
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Boesch C, Slotboom J, Hoppeler H, Kreis R. In vivo determination of intra-myocellular lipids in human muscle by means of localized 1H-MR-spectroscopy. Magn Reson Med 1997; 37:484-93. [PMID: 9094069 DOI: 10.1002/mrm.1910370403] [Citation(s) in RCA: 320] [Impact Index Per Article: 11.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Intra-myocellular lipids (IMCL) are stored in droplets in the cytoplasm of muscle cells and are an energy storage form readily accessed during long-term exercise. 1H-MR spectroscopy methods are presented for noninvasive determination of IMCL in human muscle. This is based on (a) the separation of two resonances in the lipid-CH2-region, with the one assigned to IMCL being independent of muscle orientation relative to the magnetic field and (b) the fact that IMCL resonances scale along with signal amplitudes of metabolites in the muscle cell (e.g., creatine) when voxel size is increased, while lipid signals of bulk fat show a disproportionate growth. Inter-individual and intra-individual reproducibility studies indicate that the error of the method is about 6% and that IMCL levels differ significantly between identical muscles in different subjects, as well as intra-individually when measured at 1 week intervals. IMCL determinations in a single subject before and after strenuous exercise indicate that lipid stores recover with a t1/2 of about 1 day.
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Affiliation(s)
- C Boesch
- Department of MR-Spectroscopy and Methodology, University of Bern, Switzerland
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25
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Nuclear magnetic resonance studies of glucose metabolism in non-insulin-dependent diabetes mellitus subjects. Mol Med 1997. [PMID: 8898370 DOI: 10.1007/bf03401638] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
In this review, the results of a series of NMR experiments investigating glucose storage and synthesis in NIDDM patients and normal controls have been summarized. These have shown: 1. The deficit in nonoxidative glucose disposal in NIDDM subjects results from a defect in the muscle glycogen synthesis pathway. 2. Reduced activity of glucose transporter/hexokinase step in this pathway accounts for the reduced rate of glycogen synthesis in NIDDM patients. 3. This reduced activity of GT/Hk is a genetic defect present before the clinical onset of disease in prediabetic descendants of diabetic parents. 4. In muscle from normal, healthy subjects the rate of glycogen synthesis is controlled by the glucose transport/hexokinase activity step and not by the activity of the muscle glycogen synthase enzyme. 5. Hepatic gluconeogenesis is responsible for most hepatic glucose production during an overnight fast in both normal and NIDDM subjects, and increases in gluconeogenic flux are responsible for the increased rate of hepatic glucose production in NIDDM subjects. 6. In contrast to human muscle, where glycogenesis ceases at rest, in the liver gluconeogenesis and glycogenolysis are always active. Numerous previous studies were considered prior to embarking in each of these NMR experiments. In the original research articles we published, the earlier studies were discussed in terms of the relevant literature. Here, however, I have chosen to present the NMR data as simply as possible, in the hope of exposing the significance of these studies by disentangling the results from the complexities of NMR methodology.
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26
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Weiss RG, de Albuquerque CP, Vandegaer K, Chacko VP, Gerstenblith G. Attenuated glycogenolysis reduces glycolytic catabolite accumulation during ischemia in preconditioned rat hearts. Circ Res 1996; 79:435-46. [PMID: 8781477 DOI: 10.1161/01.res.79.3.435] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
Prior transient episodes of ischemia ("ischemic preconditioning") reduce lactate accumulation and attenuate acidosis during a subsequent prolonged ischemic insult. The mechanisms responsible for attenuated glycolytic catabolite accumulation have not been established but may include earlier exhaustion of glycogen stores, slowed glycogenolysis before complete glycogen depletion, and/or inhibition of glycolysis. Simultaneous repeated measures of myocardial glycogen and the rates of glycolysis, glycogenolysis, glucose utilization, and glycolytic ATP production were obtained during total ischemia by 13C nuclear magnetic resonance spectroscopy in control and ischemia-preconditioned isolated rat hearts. Both [13C]glycolytic and [13C]glycogenolytic rates were significantly lower during total ischemia in preconditioned compared with control hearts (0.77 +/- 0.04 versus 1.06 +/- 0.06 mumol/min per gram wet weight [P < .01] for glycolysis and 0.15 +/- 0.07 versus 0.78 +/- 0.12 mumol/ min per gram wet weight [P < .001] for glycogenolysis, respectively, at 2.5 minutes of ischemia). Slowed glycolysis was present even during the early minutes of ischemia, when significant amounts of available [13C]glycogen were still present. Importantly, the reduction in the rate of glycogenolysis was larger and out of proportion to the reduction in glycolysis and occurred despite an increase in glucose utilization in preconditioned hearts (2.23 +/- 0.15 versus 1.5 +/- 0.10 mumol/min per gram wet weight at 1.25 minutes, P < .01). During early ischemia, conversion of glycogen phosphorylase to the a or "active" form was less in preconditioned than in control hearts (29.1 +/- 2.6% versus 41.2 +/- 9.8%, respectively; P < .05). Taken together, these findings demonstrate that ischemic preconditioning significantly depresses glycolytic catabolite accumulation during sustained ischemia not by more severe glycolytic inhibition or exhaustion of glycogen stores but by depressed glycogenolysis from the onset of ischemia.
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Affiliation(s)
- R G Weiss
- Peter Belfer Laboratory, Johns Hopkins Hospital, Baltimore, Md. 21287-6568, USA.
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27
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Abstract
This study is the first report on the multiexponential T2 relaxation of the 13C-1 carbon of glycogen. In contrast to T1 relaxation, which does not display observable multiexponential decay behavior, T2 relaxation is described by a continuous distribution of T2 times. Changes in molecular weight and sample viscosity, which affect the overall mobility of the glycogen particle have little influence on T1 and T2 relaxation times. This is in contradiction with earlier results that T2 is dominated by the overall motion of the glycogen particles [L.-H. Zang Biochemistry 29, 6815-6820 (1990)]. T1 depends strongly on the external field Bo and is almost temperature independent in the range 23-37 degrees C whereas T2 is field independent and varies appreciably with temperature. The experimental T1 and T2 relaxation data are shown to be consistent with existing theoretical models for relaxation, suitably modified to include a distribution of correlation times for the internal motions. The presence of fast decaying components (short T2) in the FID implies broad line components in the frequency spectrum and the corresponding need to appropriately set the integration limits for the quantification of the glycogen peak.
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Affiliation(s)
- K Overloop
- Biomedical NMR Unit, Faculty of Medicine, Katholieke Universiteit Leuven, Belgium
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28
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Price TB, Perseghin G, Duleba A, Chen W, Chase J, Rothman DL, Shulman RG, Shulman GI. NMR studies of muscle glycogen synthesis in insulin-resistant offspring of parents with non-insulin-dependent diabetes mellitus immediately after glycogen-depleting exercise. Proc Natl Acad Sci U S A 1996; 93:5329-34. [PMID: 8643574 PMCID: PMC39245 DOI: 10.1073/pnas.93.11.5329] [Citation(s) in RCA: 57] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023] Open
Abstract
To examine the impact of insulin resistance on the insulin-dependent and insulin-independent portions of muscle glycogen synthesis during recovery from exercise, we studied eight young, lean, normoglycemic insulin-resistant (IR) offspring of individuals with non-insulin-dependent diabetes mellitus and eight age-weight matched control (CON) subjects after plantar flexion exercise that lowered muscle glycogen to approximately 25% of resting concentration. After approximately 20 min of exercise, intramuscular glucose 6-phosphate and glycogen were simultaneously monitored with 31P and 13C NMR spectroscopies. The postexercise rate of glycogen resynthesis was nonlinear. Glycogen synthesis rates during the initial insulin independent portion (0-1 hr of recovery) were similar in the two groups (IR, 15.5 +/- 1.3 mM/hr and CON, 15.8 +/- 1.7 mM/hr); however, over the next 4 hr, insulin-dependent glycogen synthesis was significantly reduced in the IR group [IR, 0.1 +/- 0.5 mM/hr and CON, 2.9 +/- 0.2 mM/hr; (P < or = 0.001)]. After exercise there was an initial rise in glucose 6-phosphate concentrations that returned to baseline after the first hour of recovery in both groups. In summary, we found that following muscle glycogen-depleting exercise, IR offspring of parents with non-insulin-dependent diabetes mellitus had (i) normal rates of muscle glycogen synthesis during the insulin-independent phase of recovery from exercise and (ii) severely diminished rates of muscle glycogen synthesis during the subsequent recovery period (2-5 hr), which has previously been shown to be insulin-dependent in normal CON subjects. These data provide evidence that exercise and insulin stimulate muscle glycogen synthesis in humans by different mechanisms and that in the IR subjects the early response to stimulation by exercise is normal.
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Affiliation(s)
- T B Price
- Department of Internal Medicine, Yale University School of Medicine, New Haven, CT 06520, USA
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29
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Shulman RG, Bloch G, Rothman DL. In vivo regulation of muscle glycogen synthase and the control of glycogen synthesis. Proc Natl Acad Sci U S A 1995; 92:8535-42. [PMID: 7567971 PMCID: PMC41002 DOI: 10.1073/pnas.92.19.8535] [Citation(s) in RCA: 116] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
The activity of glycogen synthase (GSase; EC 2.4.1.11) is regulated by covalent phosphorylation. Because of this regulation, GSase has generally been considered to control the rate of glycogen synthesis. This hypothesis is examined in light of recent in vivo NMR experiments on rat and human muscle and is found to be quantitatively inconsistent with the data under conditions of glycogen synthesis. Our first experiments showed that muscle glycogen synthesis was slower in non-insulin-dependent diabetics compared to normals and that their defect was in the glucose transporter/hexokinase (GT/HK) part of the pathway. From these and other in vivo NMR results a quantitative model is proposed in which the GT/HK steps control the rate of glycogen synthesis in normal humans and rat muscle. The flux through GSase is regulated to match the proximal steps by "feed forward" to glucose 6-phosphate, which is a positive allosteric effector of all forms of GSase. Recent in vivo NMR experiments specifically designed to test the model are analyzed by metabolic control theory and it is shown quantitatively that the GT/HK step controls the rate of glycogen synthesis. Preliminary evidence favors the transporter step. Several conclusions are significant: (i) glucose transport/hexokinase controls the glycogen synthesis flux; (ii) the role of covalent phosphorylation of GSase is to adapt the activity of the enzyme to the flux and to control the metabolite levels not the flux; (iii) the quantitative data needed for inferring and testing the present model of flux control depended upon advances of in vivo NMR methods that accurately measured the concentration of glucose 6-phosphate and the rate of glycogen synthesis.
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Affiliation(s)
- R G Shulman
- Department of Molecular Biophysics and Biochemistry, Yale University School of Medicine, New Haven, CT 06510, USA
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30
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Rothman DL, Magnusson I, Cline G, Gerard D, Kahn CR, Shulman RG, Shulman GI. Decreased muscle glucose transport/phosphorylation is an early defect in the pathogenesis of non-insulin-dependent diabetes mellitus. Proc Natl Acad Sci U S A 1995; 92:983-7. [PMID: 7862678 PMCID: PMC42621 DOI: 10.1073/pnas.92.4.983] [Citation(s) in RCA: 218] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023] Open
Abstract
Recent studies have demonstrated that reduced insulin-stimulated muscle glycogen synthesis is the major cause of insulin resistance in patients with non-insulin-dependent diabetes mellitus (NIDDM). This reduced rate has been assigned to a defect in either glucose transport or hexokinase activity. However it is unknown whether this is a primary or acquired defect in the pathogenesis of NIDDM. To examine this question, we measured the rate of muscle glycogen synthesis and the muscle glucose 6-phosphate (G6P) concentration using 13C and 31P NMR spectroscopy as well as oxidative and nonoxidative glucose metabolism in six lean, normoglycemic offspring of parents with NIDDM and seven age/weight-matched control subjects under hyperglycemic (approximately 11 mM)-hyperinsulinemic (approximately 480 pM) clamp conditions. The offspring of parents with NIDDM had a 50% reduction in total glucose metabolism, primarily due to a decrease in the nonoxidative component. The rate of muscle glycogen synthesis was reduced by 70% (P < 0.005) and muscle G6P concentration was reduced by 40% (P < 0.003), which suggests impaired muscle glucose transport/hexokinase activity. These changes were similar to those previously observed in subjects with fully developed NIDDM. When the control subjects were studied at similar insulin levels (approximately 440 pM) but euglycemic plasma glucose concentration (approximately 5 mM), both the rate of glycogen synthesis and the G6P concentration were reduced to values similar to the offspring of parents with NIDDM. We conclude that insulin-resistant offspring of parents with NIDDM have reduced nonoxidative glucose metabolism and muscle glycogen synthesis secondary to a defect in muscle glucose transport/hexokinase activity prior to the onset of overt hyperglycemia. The presence of this defect in these subjects suggests that it may be the primary factor in the pathogenesis of NIDDM.
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Affiliation(s)
- D L Rothman
- Department of Internal Medicine, Yale Medical School, New Haven, CT 06520
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31
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Gruetter R, Magnusson I, Rothman DL, Avison MJ, Shulman RG, Shulman GI. Validation of 13C NMR measurements of liver glycogen in vivo. Magn Reson Med 1994; 31:583-8. [PMID: 8057810 DOI: 10.1002/mrm.1910310602] [Citation(s) in RCA: 59] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
The natural abundance 13C NMR intensity of the glycogen C1 resonance was measured in the surgically exposed liver of rabbits in vivo (n = 17) by integration from 98 to 104 ppm and compared double blindedly to the subsequent biochemical measurement. Coil loading was measured each time from a reference sphere at the coil center and the NMR intensity was normalized accordingly. For quantification, the normalized NMR intensity was calibrated using aqueous glycogen solutions ranging from 110 to 1100 mumol glucosyl units/g (n = 14). An in vivo range from 110 to 800 mumol glucosyl units/g wet weight was measured with a highly linear correlation with concentration (r = 0.85, P < 0.001). The in vivo NMR concentration was 0.95 +/- 0.05 (mean +/- standard error, n = 17) of the concomitant enzymatic measurement of glycogen content. We conclude that the 13C NMR signal of liver glycogen C1 is essentially 100% visible in vivo and that natural abundance 13C NMR spectroscopy can provide reliable noninvasive estimates of in vivo glycogen content over the physiological range of liver glycogen concentrations when using adequate localization and integration procedures.
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Affiliation(s)
- R Gruetter
- Department of Molecular Biophysics, Yale University and School of Medicine, New Haven, Connecticut
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32
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Magnusson I, Rothman DL, Jucker B, Cline GW, Shulman RG, Shulman GI. Liver glycogen turnover in fed and fasted humans. THE AMERICAN JOURNAL OF PHYSIOLOGY 1994; 266:E796-803. [PMID: 8203517 DOI: 10.1152/ajpendo.1994.266.5.e796] [Citation(s) in RCA: 55] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
Whether liver glycogen synthesis and breakdown occur simultaneously during net glycogen synthesis was assessed in fed and fasted healthy humans. The peak intensity of the carbon-1 (C1) resonance of the glycosyl units of glycogen was monitored with 13C nuclear magnetic resonance spectroscopy during [1-13C]glucose infusion followed by unlabeled glucose infusion. The C1 peak intensity increased almost linearly during the [1-13C]glucose infusion, reflecting a near linear rate of glycogen synthesis. When switched to unlabeled glucose, the C1 peak intensity reached a plateau in the fasted subjects and declined in the fed subjects, reflecting active glycogenolysis during a time of net glycogen synthesis. We conclude that liver glycogen synthesis and degradation occur simultaneously in humans under conditions of net glycogen synthesis. The relative turnover rate was significantly higher in the fed (57 +/- 3%) than in the fasted state (31 +/- 8%; P < 0.01). The results indicate that glycogen may regulate its rate of breakdown and that liver glycogen turnover may be an important factor in limiting the accumulation of liver glycogen in humans.
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Affiliation(s)
- I Magnusson
- Department of Internal Medicine, Yale University School of Medicine, New Haven, Connecticut 06510
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Borgs M, Van Hecke P, Overloop K, Decanniere C, Van Huffel S, Stalmans W, Vanstapel F. In situ 13C NMR quantification of hepatic glycogen. NMR IN BIOMEDICINE 1993; 6:371-376. [PMID: 8148232 DOI: 10.1002/nbm.1940060604] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
Abstract
We report on the 13C NMR visibility of the C-1 glycosidic carbon of alpha-particulate glycogen in perfused rat liver. We used rats fed ad libitum, animals refed after a 48 h fast with a sucrose supplement with or without glucocorticoid treatment, and gsd/gsd rats with a hepatic glycogen storage disease due to phosphorylase kinase deficiency. Thus we studied a wide range of glycogen levels (25-140 mg/g liver). All livers were perfused with 15 mM glucose, to maintain constant glycogen levels. Failure to activate glycogen phosphorylase ensures stable glycogen levels in gsd/gsd livers. Natural abundance 13C NMR signals were calibrated against a phantom containing a fixed amount of glycogen. Accumulated free induction decays were analysed after Fourier transformation by numerical integration, or by direct analysis of the signal in the time domain using a non-iterative method based on singular value decomposition. NMR quantification of the glycogen correlated well with the chemical determination over the whole concentration range. However, the precision (reproducibility) of glycogen determinations (be it by chemical methods or by NMR spectroscopy) may pose problems. Authors should be encouraged to report systematically on the precision of their methods.
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Affiliation(s)
- M Borgs
- Afdeling Biochemie, Faculteit Geneeskunde, Katholieke Universiteit Leuven, Belgium
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Garlick PB, Pritchard RD. Absolute quantification and NMR visibility of glycogen in the isolated, perfused rat heart using 13C NMR spectroscopy. NMR IN BIOMEDICINE 1993; 6:84-88. [PMID: 8457431 DOI: 10.1002/nbm.1940060113] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
Abstract
NMR spectroscopy, possibly, does not detect 100% of large molecules such as glycogen (mol.wt = 10(7)-10(9)). Using both NMR and chemical quantification methods, we have, therefore, determined the NMR visibility of cardiac glycogen (defined as the ratio of the NMR value to the chemical value, expressed as a percentage) in the isolated, perfused heart. Rats (n = 7) were pretreated for 60 min with 0.2 mg/kg isoproterenol (s.c.) to deplete their endogenous myocardial glycogen stores (mainly 12C). The hearts were then aerobically perfused (65 cm H2O, at 37 degrees C) in a double-walled chamber (the annulus contained a standard), for 70 min with Krebs buffer plus 3.5 mM [13C]1-glucose and 5 mM sodium acetate (natural abundance). From 70 to 175 min the sole substrate was natural abundance acetate (5 mM). 13C NMR spectra for glycogen quantification were acquired in two different ways; by applying 896, 90 degree pulses at 0.33 s intervals with 1H decoupling ('fast', practical spectra) and by applying 896, 90 degree pulses at 5 s intervals ('slow', impractical spectra). Hearts were then removed from the magnet, freeze-clamped (-196 degrees C) and analysed chemically. Cardiac glycogen, quantified from the 'fast' spectra (using conversion factors) and the 'slow' spectra was 16.8 +/- 1.1 and 16.1 +/- 1.8 (mean +/- SEM) mumol glucosyl units/heart, respectively. After correction of the chemical value for the residual [12C]glycogen (determined from 1H NMR spectra of the extracted glycogen after hydrolysis), the NMR-visibilities were calculated to be 101 +/- 6 and 109 +/- 7%, for the 'fast' and 'slow' spectra, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)
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Affiliation(s)
- P B Garlick
- Department of Radiological Sciences, United Medical School, Guy's Hospital, London, UK
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Taylor R, Price TB, Rothman DL, Shulman RG, Shulman GI. Validation of 13C NMR measurement of human skeletal muscle glycogen by direct biochemical assay of needle biopsy samples. Magn Reson Med 1992; 27:13-20. [PMID: 1435198 DOI: 10.1002/mrm.1910270103] [Citation(s) in RCA: 78] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Recent developments in 13C nuclear magnetic resonance (NMR) spectroscopy have permitted noninvasive assessment of glycogen concentration in human skeletal muscle. Before these indirect measurements could be accepted as accurate, it was essential that validation should be carried out by comparing the widely used method of muscle biopsy and direct biochemical assay for glycogen concentration with measurement by NMR. Eight normal subjects underwent six NMR scans of gastrocnemius and three biopsies of the same muscle on the same day. The overall mean for muscle glycogen concentration was 87.4 mM by NMR and 88.3 mM by biopsy. There was a close correlation between the pairs of observations on each subject (R = 0.95; P less than 0.0001). The mean coefficient of variation for NMR measurement was 4.3 +/- 2.1% and that for biopsy was 9.3 +/- 5.9%. The performance of the muscle biopsies was accompanied by a small but significant rise in plasma-free fatty acids (529 +/- 157 to 667 +/- 250; P less than 0.01), epinephrine (17 +/- 6 to 25 +/- 8 pg/ml; P less than 0.02), and norepinephrine (318 +/- 119 to 400 +/- 140 pg/ml; P less than 0.02) but no change in plasma glucose, plasma insulin, nor muscle glycogen concentration assessed by NMR. The study demonstrates that in vivo 13C NMR measurement of human muscle glycogen can be regarded as accurate, and the technique is associated with a higher precision that biopsy with direct biochemical assessment.
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Affiliation(s)
- R Taylor
- Department of Internal Medicine, Yale University, New Haven, Connecticut 06511
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Rothman DL, Magnusson I, Katz LD, Shulman RG, Shulman GI. Quantitation of hepatic glycogenolysis and gluconeogenesis in fasting humans with 13C NMR. Science 1991; 254:573-6. [PMID: 1948033 DOI: 10.1126/science.1948033] [Citation(s) in RCA: 375] [Impact Index Per Article: 11.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
The rate of net hepatic glycogenolysis was assessed in humans by serially measuring hepatic glycogen concentration at 3- to 12-hour intervals during a 68-hour fast with 13C nuclear magnetic resonance spectroscopy. The net rate of gluconeogenesis was calculated by subtracting the rate of net hepatic glycogenolysis from the rate of glucose production in the whole body measured with tritiated glucose. Gluconeogenesis accounted for 64 +/- 5% (mean +/- standard error of the mean) of total glucose production during the first 22 hours of fasting. In the subsequent 14-hour and 18-hour periods of the fast, gluconeogenesis accounted for 82 +/- 5% and 96 +/- 1% of total glucose production, respectively. These data show that gluconeogenesis accounts for a substantial fraction of total glucose production even during the first 22 hours of a fast in humans.
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Affiliation(s)
- D L Rothman
- Department of Internal Medicine, Yale University School of Medicine, New Haven, CT 06510
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