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Gilad AA, Bar-Shir A, Bricco AR, Mohanta Z, McMahon MT. Protein and peptide engineering for chemical exchange saturation transfer imaging in the age of synthetic biology. NMR IN BIOMEDICINE 2023; 36:e4712. [PMID: 35150021 PMCID: PMC10642350 DOI: 10.1002/nbm.4712] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/08/2021] [Revised: 02/02/2022] [Accepted: 02/05/2022] [Indexed: 05/23/2023]
Abstract
At the beginning of the millennium, the first chemical exchange saturation transfer (CEST) contrast agents were bio-organic molecules. However, later, metal-based CEST agents (paraCEST agents) took center stage. This did not last too long as paraCEST agents showed limited translational potential. By contrast, the CEST field gradually became dominated by metal-free CEST agents. One branch of research stemming from the original work by van Zijl and colleagues is the development of CEST agents based on polypeptides. Indeed, in the last 2 decades, tremendous progress has been achieved in this field. This includes the design of novel peptides as biosensors, genetically encoded recombinant as well as synthetic reporters. This was a result of extensive characterization and elucidation of the theoretical requirements for rational designing and engineering of such agents. Here, we provide an extensive overview of the evolution of more precise protein-based CEST agents, review the rationalization of enzyme-substrate pairs as CEST contrast enhancers, discuss the theoretical considerations to improve peptide selectivity, specificity and enhance CEST contrast. Moreover, we discuss the strong influence of synthetic biology on the development of the next generation of protein-based CEST contrast agents.
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Affiliation(s)
- Assaf A. Gilad
- Department of Chemical Engineering and Materials Science, Michigan State University, East Lansing, Michigan, USA
- Department of Radiology, Michigan State University, East Lansing, Michigan, USA
| | - Amnon Bar-Shir
- Department of Molecular Chemistry and Materials Science, Weizmann Institute of Science, Rehovot, Israel
| | - Alexander R. Bricco
- Department of Biomedical Engineering, Michigan State University, East Lansing, Michigan, USA
| | - Zinia Mohanta
- Division of MR Research, The Russell H. Morgan Department of Radiology and Radiological Science, Johns Hopkins University, Baltimore, Maryland, USA
- F.M. Kirby Research Center for Functional Brain Imaging, Kennedy Krieger Institute, Baltimore, Maryland, USA
| | - Michael T. McMahon
- Division of MR Research, The Russell H. Morgan Department of Radiology and Radiological Science, Johns Hopkins University, Baltimore, Maryland, USA
- F.M. Kirby Research Center for Functional Brain Imaging, Kennedy Krieger Institute, Baltimore, Maryland, USA
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2
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Tomar JS, Shen J. Characterization of Carbonic Anhydrase In Vivo Using Magnetic Resonance Spectroscopy. Int J Mol Sci 2020; 21:E2442. [PMID: 32244610 PMCID: PMC7178054 DOI: 10.3390/ijms21072442] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2020] [Revised: 03/29/2020] [Accepted: 03/30/2020] [Indexed: 01/30/2023] Open
Abstract
Carbonic anhydrase is a ubiquitous metalloenzyme that catalyzes the reversible interconversion of CO2/HCO3-. Equilibrium of these species is maintained by the action of carbonic anhydrase. Recent advances in magnetic resonance spectroscopy have allowed, for the first time, in vivo characterization of carbonic anhydrase in the human brain. In this article, we review the theories and techniques of in vivo 13C magnetization (saturation) transfer magnetic resonance spectroscopy as they are applied to measuring the rate of exchange between CO2 and HCO3- catalyzed by carbonic anhydrase. Inhibitors of carbonic anhydrase have a wide range of therapeutic applications. Role of carbonic anhydrases and their inhibitors in many diseases are also reviewed to illustrate future applications of in vivo carbonic anhydrase assessment by magnetic resonance spectroscopy.
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Affiliation(s)
| | - Jun Shen
- Molecular Imaging Branch, National Institute of Mental Health, NIH, Bethesda, MD 20892, USA
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Determining the Rate of Carbonic Anhydrase Reaction in the Human Brain. Sci Rep 2018; 8:2328. [PMID: 29396553 PMCID: PMC5797079 DOI: 10.1038/s41598-018-20746-x] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2017] [Accepted: 01/22/2018] [Indexed: 01/13/2023] Open
Abstract
Carbonic anhydrase plays important role in life. This study sought to demonstrate the feasibility of detecting carbonic anhydrase activity in the human brain in vivo. After oral administration of [U-13C6]glucose, 13C saturation transfer experiments were performed with interleaved control spectra and carbon dioxide saturation spectra. Proton nuclear Overhauser effect pulses were used to increase signal to noise ratio; no proton decoupling was applied. Results showed that the 13C signal of bicarbonate was reduced by 72% ± 0.03 upon saturating carbon dioxide. The unidirectional dehydration rate constant of the carbonic anhydrase reaction was found to be 0.28 ± 0.02 sec−1 in the human brain. These findings demonstrate the feasibility of measuring carbonic anhydrase activity in vivo in the human brain, which makes it possible to characterize this important enzyme in patients with brain disorders.
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Non-invasive assessment of hepatic mitochondrial metabolism by positional isotopomer NMR tracer analysis (PINTA). Nat Commun 2017; 8:798. [PMID: 28986525 PMCID: PMC5630596 DOI: 10.1038/s41467-017-01143-w] [Citation(s) in RCA: 39] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2017] [Accepted: 08/22/2017] [Indexed: 01/03/2023] Open
Abstract
Hepatic mitochondria play a central role in the regulation of intermediary metabolism and maintenance of normoglycemia, and there is great interest in assessing rates of hepatic mitochondrial citrate synthase flux (VCS) and pyruvate carboxylase flux (VPC) in vivo. Here, we show that a positional isotopomer NMR tracer analysis (PINTA) method can be used to non-invasively assess rates of VCS and VPC fluxes using a combined NMR/gas chromatography-mass spectrometry analysis of plasma following infusion of [3-13C]lactate and glucose tracer. PINTA measures VCS and VPC fluxes over a wide range of physiological conditions with minimal pyruvate cycling and detects increased hepatic VCS following treatment with a liver-targeted mitochondrial uncoupler. Finally, validation studies in humans demonstrate that the VPC/VCS ratio measured by PINTA is similar to that determined by in vivo NMR spectroscopy. This method will provide investigators with a relatively simple tool to non-invasively examine the role of altered hepatic mitochondrial metabolism. Liver mitochondrial metabolism plays an important role for glucose and lipid homeostasis and its alterations contribute to metabolic disorders, including fatty liver and diabetes. Here Perry et al. develop a method for the measurement of hepatic fluxes by using lactate and glucose tracers in combination with NMR spectroscopy.
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Perry RJ, Zhang XM, Zhang D, Kumashiro N, Camporez JPG, Cline GW, Rothman DL, Shulman GI. Leptin reverses diabetes by suppression of the hypothalamic-pituitary-adrenal axis. Nat Med 2014; 20:759-63. [PMID: 24929951 PMCID: PMC4344321 DOI: 10.1038/nm.3579] [Citation(s) in RCA: 145] [Impact Index Per Article: 14.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2014] [Accepted: 04/21/2014] [Indexed: 12/14/2022]
Abstract
Leptin treatment reverses hyperglycemia in animal models of poorly controlled type 1 diabetes (T1D), spurring great interest in the possibility of treating patients with this hormone. The antidiabetic effect of leptin has been postulated to occur through suppression of glucagon production, suppression of glucagon responsiveness or both; however, there does not appear to be a direct effect of leptin on the pancreatic alpha cell. Thus, the mechanisms responsible for the antidiabetic effect of leptin remain poorly understood. We quantified liver-specific rates of hepatic gluconeogenesis and substrate oxidation in conjunction with rates of whole-body acetate, glycerol and fatty acid turnover in three rat models of poorly controlled diabetes, including a model of diabetic ketoacidosis. We show that the higher rates of hepatic gluconeogenesis in all these models could be attributed to hypoleptinemia-induced activity of the hypothalamic-pituitary-adrenal (HPA) axis, resulting in higher rates of adipocyte lipolysis, hepatic conversion of glycerol to glucose through a substrate push mechanism and conversion of pyruvate to glucose through greater hepatic acetyl-CoA allosteric activation of pyruvate carboxylase flux. Notably, these effects could be dissociated from changes in plasma insulin and glucagon concentrations and hepatic gluconeogenic protein expression. All the altered systemic and hepatic metabolic fluxes could be mimicked by infusing rats with Intralipid or corticosterone and were corrected by leptin replacement. These data demonstrate a critical role for lipolysis and substrate delivery to the liver, secondary to hypoleptinemia and HPA axis activity, in promoting higher hepatic gluconeogenesis and hyperglycemia in poorly controlled diabetes.
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Affiliation(s)
- Rachel J. Perry
- Howard Hughes Medical Institute, Yale University School of Medicine, New Haven, CT
- Department of Internal Medicine, Yale University School of Medicine, New Haven, CT
- Department of Cellular and Molecular Physiology, Yale University School of Medicine, New Haven, CT
| | - Xian-Man Zhang
- Department of Internal Medicine, Yale University School of Medicine, New Haven, CT
| | - Dongyan Zhang
- Howard Hughes Medical Institute, Yale University School of Medicine, New Haven, CT
| | - Naoki Kumashiro
- Department of Internal Medicine, Yale University School of Medicine, New Haven, CT
| | | | - Gary W. Cline
- Department of Internal Medicine, Yale University School of Medicine, New Haven, CT
| | - Douglas L. Rothman
- Department of Diagnostic Radiology, Yale University School of Medicine, New Haven, CT
- Department of Biomedical Engineering, Yale University School of Medicine, New Haven, CT
| | - Gerald I. Shulman
- Howard Hughes Medical Institute, Yale University School of Medicine, New Haven, CT
- Department of Internal Medicine, Yale University School of Medicine, New Haven, CT
- Department of Cellular and Molecular Physiology, Yale University School of Medicine, New Haven, CT
- Novo Nordisk Center for Basic Metabolic Research, Copenhagen, DK
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Gallagher FA, Kettunen MI, Day SE, Hu DE, Karlsson M, Gisselsson A, Lerche MH, Brindle KM. Detection of tumor glutamate metabolism in vivo using 13
C magnetic resonance spectroscopy and hyperpolarized [1-13
C]glutamate. Magn Reson Med 2011; 66:18-23. [DOI: 10.1002/mrm.22851] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2010] [Revised: 12/15/2010] [Accepted: 12/20/2010] [Indexed: 01/08/2023]
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Xu S, Shen J. Studying Enzymes by In Vivo C Magnetic Resonance Spectroscopy. PROGRESS IN NUCLEAR MAGNETIC RESONANCE SPECTROSCOPY 2009; 55:266-283. [PMID: 20161496 PMCID: PMC2796782 DOI: 10.1016/j.pnmrs.2009.06.002] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/03/2023]
Affiliation(s)
- Su Xu
- Molecular Imaging Branch, National Institute of Mental Health, National Institutes of Health, Bethesda, MD 20892, USA
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Fast isotopic exchange between mitochondria and cytosol in brain revealed by relayed 13C magnetization transfer spectroscopy. J Cereb Blood Flow Metab 2009; 29:661-9. [PMID: 19156161 PMCID: PMC2845910 DOI: 10.1038/jcbfm.2008.170] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
In vivo 13C magnetic resonance spectroscopy has been applied to studying brain metabolic processes by measuring 13C label incorporation into cytosolic pools such as glutamate and aspartate. However, the rate of exchange between mitochondrial alpha-ketoglutarate/oxaloacetate and cytosolic glutamate/aspartate (Vx) extracted from metabolic modeling has been controversial. Because brain fumarase is exclusively located in the mitochondria, and mitochondrial fumarate is connected to cytosolic aspartate through a chain of fast exchange reactions, it is possible to directly measure Vx from the four-carbon side of the tricarboxylic acid cycle by magnetization transfer. In isoflurane-anesthetized adult rat brain, a relayed 13C magnetization transfer effect on cytosolic aspartate C2 at 53.2 ppm was detected after extensive signal averaging with fumarate C2 at 136.1 ppm irradiated using selective radiofrequency pulses. Quantitative analysis using Bloch-McConnell equations and a four-site exchange model found that Vx approximately 13-19 micromol per g per min (>>VTCA, the tricarboxylic acid cycle rate) when the longitudinal relaxation time of malate C2 was assumed to be within +/-33% of that of aspartate C2. If Vx approximately VTCA, the isotopic exchange between mitochondria and cytosol would be too slow on the time scale of 13C longitudinal relaxation to cause a detectable magnetization transfer effect.
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Yang J, Singh S, Shen J. 13C saturation transfer effect of carbon dioxide–bicarbonate exchange catalyzed by carbonic anhydrase in vivo. Magn Reson Med 2008; 59:492-8. [DOI: 10.1002/mrm.21501] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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Li S, Yang J, Shen J. Novel strategy for cerebral 13C MRS using very low RF power for proton decoupling. Magn Reson Med 2007; 57:265-71. [PMID: 17260369 DOI: 10.1002/mrm.21148] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
One of the major difficulties of in vivo 13C MRS is the need to decouple the large, one-bond, 1H-13C scalar couplings in order to obtain useful signal-to-noise ratios (SNRs) and spectral resolution at magnetic field strengths that are accessible to clinical studies. In this report a new strategy for in vivo cerebral 13C MRS is proposed. We realized that the turnover kinetics of glutamate (Glu) C5 from exogenous [2-(13)C]glucose (Glc) is identical to that of Glu C4 from exogenous [1-(13)C]Glc. The carboxylic/amide carbons are only coupled to protons via very weak long-range 1H-13C scalar couplings. As such, they can be effectively decoupled at very low RF power. Therefore, decoupling of the large 1H-13C scalar couplings can be avoided by the use of [2-(13)C]Glc. An additional advantage of this strategy is the lack of contamination from subcutaneous lipids because there are no overlapping fat signals in the vicinity of the Glu C5 and glutamine (Gln) C5 peaks. The feasibility of this strategy was demonstrated using 13C MRS on rhesus monkey brains at 4.7T.
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Affiliation(s)
- Shizhe Li
- Magnetic Resonance Spectroscopy Core Facility, National Institute of Mental Health, National Institutes of Health, Bethesda, Maryland 20892-1527, USA
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11
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Xu S, Yang J, Shen J. In vivo 13C saturation transfer effect of the lactate dehydrogenase reaction. Magn Reson Med 2007; 57:258-64. [PMID: 17260357 DOI: 10.1002/mrm.21137] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Lactate dehydrogenase (LDH, EC 1.1.1.27) catalyzes an exchange reaction between pyruvate and lactate. It is demonstrated here that this reaction is sufficiently fast to cause a significant magnetization (saturation) transfer effect when the 13C resonance of pyruvate is saturated by a continuous-wave (CW) RF pulse. Infusion of [2-(13)C]glucose was used to allow labeling of pyruvate C2 at 207.9 ppm to determine the pseudo first-order rate constant of the unidirectional lactate-->pyruvate flux in vivo. During systemic administration of GABAA receptor antagonist bicuculline, this pseudo first-order rate constant was determined to be 0.08+/-0.01 s-1 (mean+/-SD, N=4) in halothane-anesthetized adult rat brains. In 9L and C6 rat glioma models, the 13C saturation transfer effect of the LDH reaction was also detected in vivo. Our results demonstrate that the 13C magnetization transfer effect of the LDH reaction may be useful as a novel marker for utilizing noninvasive in vivo MRS to study many physiological and pathological conditions, such as cancer.
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Affiliation(s)
- Su Xu
- Molecular Imaging Branch, National Institute of Mental Health, Bethesda, Maryland 20892-1527, USA
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12
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Yang J, Shen J. Relayed (13)C magnetization transfer: detection of malate dehydrogenase reaction in vivo. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2007; 184:344-9. [PMID: 17126047 PMCID: PMC2800356 DOI: 10.1016/j.jmr.2006.11.002] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/01/2006] [Revised: 11/03/2006] [Accepted: 11/03/2006] [Indexed: 05/12/2023]
Abstract
Malate dehydrogenase catalyzes rapid interconversion between dilute metabolites oxaloacetate and malate. Both oxaloacetate and malate are below the detection threshold of in vivo MRS. Oxaloacetate is also in rapid exchange with aspartate catalyzed by aspartate aminotransferase, the latter metabolite is observable in vivo using (13)C MRS. We hypothesized that the rapid turnover of oxaloacetate can effectively relay perturbation of magnetization between malate and aspartate. Here, we report indirect observation of the malate dehydrogenase reaction by saturating malate C2 resonance at 71.2 ppm and detecting a reduced aspartate C2 signal at 53.2 ppm due to relayed magnetization transfer via oxaloacetate C2 at 201.3 ppm. Using this strategy the rate of the cerebral malate dehydrogenase reaction was determined to be 9+/-2 micromol/g wet weight/min (means+/-SD, n=5) at 11.7 Tesla in anesthetized adult rats infused with [1,6-(13)C(2)]glucose.
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Affiliation(s)
- Jehoon Yang
- Molecular Imaging Branch, National Institute of Mental Health Intramural Research Program, National Institutes of Health, 9000 Rockville Pike, Bethesda, MD 20892-1527, USA
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