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Zhao J, Zhang Z, Nie D, Ma H, Yuan G, Su S, Liu S, Liu S, Tang G. PET Imaging of Hepatocellular Carcinomas: 18F-Fluoropropionic Acid as a Complementary Radiotracer for 18F-Fluorodeoxyglucose. Mol Imaging 2019; 18:1536012118821032. [PMID: 30799682 PMCID: PMC6322104 DOI: 10.1177/1536012118821032] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Objective: To evaluate the preclinical value of 18F-fluoropropionic acid (18F-FPA) and 18F-fluorodeoxyglucose (18F-FDG) positron emission tomography (PET) for imaging HCCs. Methods: The 18F-FPA and 18F-FDG uptake patterns in 3 HCC cell lines (Hep3B, HepG2, and SK-Hep1) were assessed in vitro and in vivo. The 18F-FPA uptake mechanism was investigated using inhibition experiments with orlistat and 5-tetradecyloxy-2-furoic acid. The 18F-FPA PET imaging was performed in different tumor animal models and compared with 18F-FDG. We also evaluated the expressions of glucose transporter-1 (GLUT1), fatty acid synthase (FASN), and matrix metalloproteinase-2 (MMP2) in these cell lines. Results: In vitro experiments showed that the radiotracer uptake patterns were complementary in the HCC cell lines. Orlistat and 5-tetradecyloxy-2-furoic acid decreased the uptake of 18F-FPA. The tumor-to-liver ratio of 18F-FPA was superior to that of 18F-FDG in the SK-Hep1 and HepG2 tumors (P < .05). However, in the Hep3B tumors, the tumor-to-liver normalized uptake of 18F-FDG was higher than 18F-FPA (P < .01). FASN was highly expressed in cell lines with high 18F-FPA uptake, whereas GLUT1 was highly expressed in cell lines with high 18F-FDG uptake. The 18F-FPA uptake correlated with FASN (r = 0.89, P = .014) and MMP2 (r = 0.77, P = .002) expressions. Conclusions: PET imaging with 18F-FPA combined with 18F-FDG can be an alternative for detecting HCC.
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Affiliation(s)
- Jing Zhao
- 1 Guangdong Provincial Key Laboratory of Malignant Tumor Epigenetics and Gene Regulation, Guangzhou, China.,2 Department of Nuclear Medicine, Sun Yat-sen Memorial Hospital, Sun Yat-sen University, Guangzhou, China.,3 Guangdong Engineering Research Center for Translational Application of Medical Radiopharmaceuticals, The First Affiliated Hospital, Sun Yat-sen University, Guangzhou, China
| | - Zhanwen Zhang
- 3 Guangdong Engineering Research Center for Translational Application of Medical Radiopharmaceuticals, The First Affiliated Hospital, Sun Yat-sen University, Guangzhou, China.,4 Department of Nuclear Medicine and Imaging Medicine, The First Affiliated Hospital, Sun Yat-sen University, Guangzhou, China.,5 Department of Nuclear Medicine, The Sixth Affiliated Hospital, Sun Yat-sen University, Guangzhou, China
| | - Dahong Nie
- 3 Guangdong Engineering Research Center for Translational Application of Medical Radiopharmaceuticals, The First Affiliated Hospital, Sun Yat-sen University, Guangzhou, China.,6 Department of Radiation Oncology, The First Affiliated Hospital, Sun Yat-sen University, Guangzhou, China
| | - Hui Ma
- 3 Guangdong Engineering Research Center for Translational Application of Medical Radiopharmaceuticals, The First Affiliated Hospital, Sun Yat-sen University, Guangzhou, China.,4 Department of Nuclear Medicine and Imaging Medicine, The First Affiliated Hospital, Sun Yat-sen University, Guangzhou, China
| | - Gongjun Yuan
- 3 Guangdong Engineering Research Center for Translational Application of Medical Radiopharmaceuticals, The First Affiliated Hospital, Sun Yat-sen University, Guangzhou, China.,4 Department of Nuclear Medicine and Imaging Medicine, The First Affiliated Hospital, Sun Yat-sen University, Guangzhou, China
| | - Shu Su
- 3 Guangdong Engineering Research Center for Translational Application of Medical Radiopharmaceuticals, The First Affiliated Hospital, Sun Yat-sen University, Guangzhou, China.,4 Department of Nuclear Medicine and Imaging Medicine, The First Affiliated Hospital, Sun Yat-sen University, Guangzhou, China
| | - Shaoyu Liu
- 3 Guangdong Engineering Research Center for Translational Application of Medical Radiopharmaceuticals, The First Affiliated Hospital, Sun Yat-sen University, Guangzhou, China.,4 Department of Nuclear Medicine and Imaging Medicine, The First Affiliated Hospital, Sun Yat-sen University, Guangzhou, China
| | - Sheng Liu
- 1 Guangdong Provincial Key Laboratory of Malignant Tumor Epigenetics and Gene Regulation, Guangzhou, China.,2 Department of Nuclear Medicine, Sun Yat-sen Memorial Hospital, Sun Yat-sen University, Guangzhou, China
| | - Ganghua Tang
- 3 Guangdong Engineering Research Center for Translational Application of Medical Radiopharmaceuticals, The First Affiliated Hospital, Sun Yat-sen University, Guangzhou, China.,4 Department of Nuclear Medicine and Imaging Medicine, The First Affiliated Hospital, Sun Yat-sen University, Guangzhou, China
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Alger JR, Sherry AD, Malloy CR. tcaSIM: A Simulation Program for Optimal Design of 13C Tracer Experiments for Analysis of Metabolic Flux by NMR and Mass Spectroscopy. ACTA ACUST UNITED AC 2019; 6:176-187. [PMID: 31745452 DOI: 10.2174/2213235x07666181219115856] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Increasingly sophisticated instrumentation for chemical separations and identification has facilitated rapid advancements in our understanding of the metabolome. Since many analyses are performed using either mass spectroscopy (MS) or nuclear magnetic resonance (NMR) spectroscopy, the spin ½ stable 13C isotope is now widely used as a metabolic tracer. There is strong interest in quantitative analysis of metabolic flux through pathways in vivo, particularly in human patients. Although instrumentation advances and scientific interests in metabolism are increasing in parallel, a practical and rational design of a 13C tracer study can be challenging. Prior to planning the details of a tracer experiment, is it important to consider whether the analytical results will be sensitive to flux through the pathways of interest. Here, we briefly summarize the various approaches that have been used to design carbon tracer experiments, outline the sources of complexity, and illustrate the use of a software tool, tcaSIM, to aid in the experimental design of both MS and NMR data in complex systems including patients.
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Affiliation(s)
- Jeffry R Alger
- Advanced Imaging Research Center, University of Texas Southwestern Medical Center, Dallas, Texas.,NeuroSpectroScopics LLC, Sherman Oaks, California
| | - A Dean Sherry
- Advanced Imaging Research Center, University of Texas Southwestern Medical Center, Dallas, Texas.,Department of Radiology, University of Texas Southwestern Medical Center, Dallas, Texas.,Department of Chemistry, University of Texas at Dallas, Richardson, Texas
| | - Craig R Malloy
- Advanced Imaging Research Center, University of Texas Southwestern Medical Center, Dallas, Texas.,Department of Radiology, University of Texas Southwestern Medical Center, Dallas, Texas.,Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, Texas.,Veterans Affairs North Texas Healthcare System, Dallas, Texas
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Comparison of three ¹⁸F-labeled carboxylic acids with ¹⁸F-FDG of the differentiation tumor from inflammation in model mice. BMC Med Imaging 2016; 16:2. [PMID: 26754531 PMCID: PMC4709996 DOI: 10.1186/s12880-016-0110-7] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2015] [Accepted: 01/07/2016] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND The aim of this study was to compare the properties and feasibility of the glucose analog, 2-(18)F-fluoro-2-deoxy-D-glucose ((18)F-FDG), three short (18)F-labeled carboxylic acids, (18)F-fluoroacetate ((18)F-FAC), 2-(18)F-fluoropropionic acid ((18)F-FPA) and 4-((18)F)fluorobenzoic acid ((18)F-FBA), for differentiating tumors from inflammation. METHODS Biodistributions of (18)F-FAC, (18)F-FPA and (18)F-FBA were determined on normal Kunming mice, and positron emission tomography (PET) imaging with these tracers were performed on the separate tumor-bearing mice model and inflammation mice model in comparison with (18)F-FDG. RESULTS Biodistribution results showed that (18)F-FAC and (18)F-FPA had similar biodistribution profiles and the slow radioactivity clearance from most tissues excluding the in vivo defluorination of (18)F-FAC, and (18)F-FBA demonstrated a lower uptake and fast clearance in most tissues. PET imaging with (18)F-FDG, (18)F-FAC and (18)F-FPA revealed the high uptake in both tumor and inflammatory lesions. The ratios of tumor-to-inflammation were 1.63 ± 0.28 for (18)F-FDG, 1.20 ± 0.38 for (18)F-FAC, and 1.41 ± 0.33 for (18)F-FPA at 60 min postinjection, respectively. While clear tumor images with high contrast between tumor and inflammation lesion were observed in (18)F-FBA/PET with the highest ratio of tumor-to-inflammation (1.98 ± 0.15). CONCLUSIONS Our data demonstrated (18)F-FBA is a promising PET probe to distinguish tumor from inflammation. But the further modification of (18)F-FBA structure is required to improve its pharmacokinetics.
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Billingsley KL, Josan S, Park JM, Tee SS, Spielman-Sun E, Hurd R, Mayer D, Spielman D. Hyperpolarized [1,4-(13)C]-diethylsuccinate: a potential DNP substrate for in vivo metabolic imaging. NMR IN BIOMEDICINE 2014; 27:356-62. [PMID: 24421249 PMCID: PMC4005842 DOI: 10.1002/nbm.3071] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/08/2013] [Revised: 12/10/2013] [Accepted: 12/11/2013] [Indexed: 05/22/2023]
Abstract
The tricarboxylic acid (TCA) cycle performs an essential role in the regulation of energy and metabolism, and deficiencies in this pathway are commonly correlated with various diseases. However, the development of non-invasive techniques for the assessment of the cycle in vivo has remained challenging. In this work, the applicability of a novel imaging agent, [1,4-(13)C]-diethylsuccinate, for hyperpolarized (13)C metabolic imaging of the TCA cycle was explored. In vivo spectroscopic studies were conducted in conjunction with in vitro analyses to determine the metabolic fate of the imaging agent. Contrary to previous reports (Zacharias NM et al. J. Am. Chem. Soc. 2012; 134: 934-943), [(13)C]-labeled diethylsuccinate was primarily metabolized to succinate-derived products not originating from TCA cycle metabolism. These results illustrate potential issues of utilizing dialkyl ester analogs of TCA cycle intermediates as molecular probes for hyperpolarized (13)C metabolic imaging.
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Affiliation(s)
- Kelvin L. Billingsley
- San Francisco State University, Department of Chemistry and Biochemistry, San Francisco, CA, 94132
| | - Sonal Josan
- Stanford University, Department of Radiology, Stanford, CA 94305
- SRI International, Neuroscience Program, Menlo Park, CA 94025
| | - Jae Mo Park
- Stanford University, Department of Radiology, Stanford, CA 94305
| | - Sui Seng Tee
- Stanford University, Department of Radiology, Stanford, CA 94305
| | | | - Ralph Hurd
- GE Healthcare, Applied Sciences Laboratory, Menlo Park, CA 94025
| | - Dirk Mayer
- University of Maryland-Baltimore, Department of Diagnostic Radiology and Nuclear Medicine, Baltimore, MD, 21201
| | - Daniel Spielman
- Stanford University, Department of Radiology, Stanford, CA 94305
- Stanford University, Department of Electrical Engineering, Stanford, CA 94305
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Zacharias NM, Chan HR, Sailasuta N, Ross BD, Bhattacharya P. Real-time molecular imaging of tricarboxylic acid cycle metabolism in vivo by hyperpolarized 1-(13)C diethyl succinate. J Am Chem Soc 2011; 134:934-43. [PMID: 22146049 DOI: 10.1021/ja2040865] [Citation(s) in RCA: 121] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
The Krebs tricarboxylic acid cycle (TCA) is central to metabolic energy production and is known to be altered in many disease states. Real-time molecular imaging of the TCA cycle in vivo will be important in understanding the metabolic basis of several diseases. Positron emission tomography (PET) with FDG-glucose (2-[(18)F]fluoro-2-deoxy-d-glucose) is already being used as a metabolic imaging agent in clinics. However, FDG-glucose does not reveal anything past glucose uptake and phosphorylation. We have developed a new metabolic imaging agent, hyperpolarized diethyl succinate-1-(13)C-2,3-d(2) , that allows for real-time in vivo imaging and spectroscopy of the TCA cycle. Diethyl succinate can be hyperpolarized via parahydrogen-induced polarization (PHIP) in an aqueous solution with signal enhancement of 5000 compared to Boltzmann polarization. (13)C magnetic resonance spectroscopy (MRS) and magnetic resonance imaging (MRI) were achieved in vivo seconds after injection of 10-20 μmol of hyperpolarized diethyl succinate into normal mice. The downstream metabolites of hyperpolarized diethyl succinate were identified in vivo as malate, succinate, fumarate, and aspartate. The metabolism of diethyl succinate was altered after exposing the animal to 3-nitropropionate, a known irreversible inhibitor of succinate dehydrogenase. On the basis of our results, hyperpolarized diethyl succinate allows for real-time in vivo MRI and MRS with a high signal-to-noise ratio and with visualization of multiple steps of the TCA cycle. Hyperpolarization of diethyl succinate and its in vivo applications may reveal an entirely new regime wherein the local status of TCA cycle metabolism is interrogated on the time scale of seconds to minutes with unprecedented chemical specificity and MR sensitivity.
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Affiliation(s)
- Niki M Zacharias
- Enhanced MR Laboratory, Huntington Medical Research Institutes, Pasadena, California, USA
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Bioenergetic pathways in tumor mitochondria as targets for cancer therapy and the importance of the ROS-induced apoptotic trigger. Mol Aspects Med 2010; 31:29-59. [DOI: 10.1016/j.mam.2009.12.006] [Citation(s) in RCA: 125] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2009] [Accepted: 12/11/2009] [Indexed: 12/22/2022]
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Maier K, Hofmann U, Bauer A, Niebel A, Vacun G, Reuss M, Mauch K. Quantification of statin effects on hepatic cholesterol synthesis by transient (13)C-flux analysis. Metab Eng 2009; 11:292-309. [PMID: 19555774 DOI: 10.1016/j.ymben.2009.06.001] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2009] [Revised: 06/17/2009] [Accepted: 06/17/2009] [Indexed: 10/20/2022]
Abstract
The present work is the first to deal with the determination of cholesterol synthesis rates in primary rat hepatocytes using transient (13)C-flux analysis. The effects of statins on cholesterol biosynthesis and central carbon fluxes were quantified at a therapeutic concentration of 50 nM atorvastatin using carbon-labeled glutamine. The flux through the cholesterol pathway decreased from 0.27 to 0.08 mmol/l(cv)h in response to the administration of the hypolipidemic drug. Isotopic steady state was reached within 4h in the central carbon metabolism but not in the cholesterol pathway, regardless of whether atorvastatin was administered or not. Marked channeling was observed for the symmetrical tricarboxylic acid cycle intermediates, succinate and fumarate. Non-stationary (13)C-based flux identification delivers both intracellular fluxes and intermediate levels, which was for the first time utilized for investigating systems-level effects of the administered drug by quantifying the flux control of the 3-hydroxy-3-methylglutaryl-coenzyme A reductase.
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Affiliation(s)
- Klaus Maier
- Institute of Biochemical Engineering, University of Stuttgart, Allmandring 31, 70569 Stuttgart, Germany
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Maier K, Hofmann U, Reuss M, Mauch K. Identification of metabolic fluxes in hepatic cells from transient 13C-labeling experiments: Part II. Flux estimation. Biotechnol Bioeng 2008; 100:355-70. [PMID: 18095336 DOI: 10.1002/bit.21746] [Citation(s) in RCA: 68] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
This contribution addresses the identification of metabolic fluxes and metabolite concentrations in mammalian cells from transient (13)C-labeling experiments. Whilst part I describes experimental set-up and acquisition of required metabolite and (13)C-labeling data, part II focuses on setting up network models and the estimation of intracellular fluxes. Metabolic fluxes were determined in glycolysis, pentose-phosphate pathway (PPP), and citric acid cycle (TCA) in a hepatoma cell line grown in aerobic batch cultures. In glycolytic and PPP metabolite pools isotopic stationarity was observed within 30 min, whereas in the TCA cycle the labeling redistribution did not reach isotopic steady state even within 180 min. In silico labeling dynamics were in accordance with in vivo (13)C-labeling data. Split ratio between glycolysis and PPP was 57%:43%; intracellular glucose concentration was estimated at 101.6 nmol per 10(6) cells. In contrast to isotopic stationary (13)C-flux analysis, transient (13)C-flux analysis can also be applied to industrially relevant mammalian cell fed-batch and batch cultures.
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Affiliation(s)
- Klaus Maier
- Institute of Biochemical Engineering, University of Stuttgart, Allmandring 31, 70569 Stuttgart, Germany
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Malaisse WJ, Zhang Y, Jijakli H, Courtois P, Sener A. Enzyme-to-enzyme channelling in the early steps of glycolysis in rat pancreatic islets. Int J Biochem Cell Biol 2005; 36:1510-20. [PMID: 15147730 DOI: 10.1016/j.biocel.2003.12.013] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2003] [Revised: 10/27/2003] [Accepted: 12/05/2003] [Indexed: 11/22/2022]
Abstract
The metabolism of D-glucose displays anomeric specificity in rat pancreatic islets. The aim of the present report is to investigate whether such a situation implies enzyme-to-enzyme tunnelling of metabolites in the early steps of glycolysis. For such a purpose, the modelling of alpha- and beta-D-glucose catabolism, itself based on available information concerning both the utilisation of these two anomers and the intrinsic properties of phosphoglucoisomerase, was first examined. According to a theoretical model with enzyme-to-enzyme channelling, the generation of 3HOH from D-[2-3H]glucose should be higher in islets exposed to beta-D-glucose rather than alpha-D-glucose, whilst the opposite situation should prevail in the case of D-[5-3H]glucose conversion to 3HOH. Experimental data collected in rat islets incubated for 60 min at 4 degrees C in the presence of either alpha- or beta-D-glucose mixed with tracer amounts of either alpha- or beta-D-[2- 3H]glucose and alpha- or beta-D-[5-3H]glucose indicate that the beta/alpha ratio for D-[2-3H]glucose conversion to 3HOH is indeed higher than the beta/alpha ratio for D-[5-3H]glucose conversion to 3HOH. These findings are consistent with the postulated enzyme-to-enzyme tunnelling of glycolytic intermediates between hexokinase isoenzyme(s), phosphoglucoisomerase and, possibly, phosphofructokinase.
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Affiliation(s)
- W J Malaisse
- Laboratory of Experimental Hormonology, Faculty of Medicine, Brussels Free University, 808 Route de Lennik, B-1070 Brussels, Belgium.
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Malaisse WJ, Zhang Y, Sener A. Enzyme-to-enzyme channeling in the early steps of glycolysis in rat pancreatic islets. Endocrine 2004; 24:105-9. [PMID: 15347834 DOI: 10.1385/endo:24:2:105] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/19/2004] [Revised: 06/24/2004] [Accepted: 07/07/2004] [Indexed: 11/11/2022]
Abstract
The enzyme-to-enzyme channeling of metabolic intermediates is not an uncommon process. The present review draws attention to recent experimental work documenting, in rat pancreatic islets, the enzyme-to-enzyme channeling of alpha-D-glucose 6-phosphate between hexokinase isoenzyme(s), mainly glucokinase, and phosphoglucoisomerase. Likewise, the possible enzyme-to-enzyme channeling of beta-D-fructose 6-phosphate between phosphoglucoisomerase and phosphofructokinase is briefly evoked. These considerations are relevant to the anomeric specificity of D-glucose metabolism, even in islets exposed to equilibrated D-glucose, to the perturbation of such an anomeric specificity in the phenomenon of so-called B-cell glucotoxicity, and to the correct interpretation of 3HOH generation from D-[2-(3H)]glucose.
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Affiliation(s)
- Willy J Malaisse
- Laboratory of Experimental Hormonology, Brussels Free University, Brussels, Belgium.
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Burgess SC, Carvalho RA, Merritt ME, Jones JG, Malloy CR, Sherry AD. 13C isotopomer analysis of glutamate by J-resolved heteronuclear single quantum coherence spectroscopy. Anal Biochem 2001; 289:187-95. [PMID: 11161312 DOI: 10.1006/abio.2000.4930] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
13C NMR isotopomer analysis is a powerful method for measuring metabolic fluxes through pathways intersecting in the tricarboxylic acid cycle. However, the inherent insensitivity of 13C NMR spectroscopy makes application of isotopomer analysis to small tissue samples (mouse tissue, human biopsies, or cells grown in tissue culture) problematic. (1)H NMR is intrinsically more sensitive than 13C NMR and can potentially supply the same information via indirect detection of 13C providing that isotopomer information can be preserved. We report here the use of J-resolved HSQC (J-HSQC) for 13C isotopomer analysis of tissue samples. We show that J-HSQC reports isotopomer multiplet patterns identical to those reported by direct 13C detection but with improved sensitivity.
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Affiliation(s)
- S C Burgess
- Department of Chemistry, University of Texas at Dallas, TX 75235, USA
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Verbruggen I, Ladrière L, Willem R, Malaisse WJ. Asymmetrical labeling of D-glucose generated from [3(-13)C]pyruvate in rat hepatocytes. BIOCHEMICAL AND MOLECULAR MEDICINE 1997; 61:229-35. [PMID: 9259988 DOI: 10.1006/bmme.1997.2604] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
The generation of 13C-labeled D-glucose isotopomers by rat hepatocytes incubated for 30 or 120 min in the presence of 10 mM [3-(13)C]pyruvate was assessed by 13C NMR. The amount of C1-labeled D-glucose exceeded that of C2-labeled hexose, which was itself higher than that of C3-labeled D-glucose. A comparable hierarchy was observed in the C6-C5-C4 moiety of the hexose. The latter moiety of D-glucose was more efficiently labeled, however, than the C3-C2-C1 moiety. This finding is similar to that both previously reported and again observed in the present study when hepatocytes were exposed to [2(-13)C]pyruvate. These converging observations thus support the concept of enzyme-to-enzyme channeling of D-glyceraldehyde 3-phosphate between glyceraldehyde-3-phosphate dehydrogenase and phospho-fructoaldolase.
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Affiliation(s)
- I Verbruggen
- High Resolution NMR Centre, Free University of Brussels (VUB), Belgium
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