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Ziegs T, Ruhm L, Wright A, Henning A. Mapping of glutamate metabolism using 1H FID-MRSI after oral administration of [1-13C]Glc at 9.4 T. Neuroimage 2023; 270:119940. [PMID: 36787828 PMCID: PMC10030312 DOI: 10.1016/j.neuroimage.2023.119940] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2022] [Revised: 02/10/2023] [Accepted: 02/11/2023] [Indexed: 02/14/2023] Open
Abstract
Glutamate is the major excitatory transmitter in the brain and malfunction of the related metabolism is associated with various neurological diseases and disorders. The observation of labeling changes in the spectra after the administration of a 13C labelled tracer is a common tool to gain better insights into the function of the metabolic system. But so far, only a very few studies presenting the labeling effects in more than two voxels to show the spatial dependence of metabolism. In the present work, the labeling effects were measured in a transversal plane in the human brain using ultra-short TE and TR 1H FID-MRSI. The measurement set-up was most simple: The [1-13C]Glc was administered orally instead of intravenous and the spectra were measured with a pure 1H technique without the need of a 13C channel (as Boumezbeur et al. demonstrated in 2004). Thus, metabolic maps and enrichment curves could be obtained for more metabolites and in more voxels than ever before in human brain. Labeling changes could be observed in [4-13C]glutamate, [3-13C]glutamate+glutamine, [2-13C]glutamate+glutamine, [4-13C]glutamine, and [3-13C]aspartate with a high temporal (3.6 min) and spatial resolution (32 × 32 grid with nominal voxel size of 0.33 µL) in five volunteers.
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Affiliation(s)
- Theresia Ziegs
- High-Field MR Center, Max Planck Institute for Biological Cybernetics, Max-Planck-Ring 11, 72076 Tübingen, Germany; IMPRS for Cognitive and Systems Neuroscience, Otfried-Müller-Str. 27, 72076 Tübingen, Germany.
| | - Loreen Ruhm
- High-Field MR Center, Max Planck Institute for Biological Cybernetics, Max-Planck-Ring 11, 72076 Tübingen, Germany; IMPRS for Cognitive and Systems Neuroscience, Otfried-Müller-Str. 27, 72076 Tübingen, Germany
| | - Andrew Wright
- High-Field MR Center, Max Planck Institute for Biological Cybernetics, Max-Planck-Ring 11, 72076 Tübingen, Germany; IMPRS for Cognitive and Systems Neuroscience, Otfried-Müller-Str. 27, 72076 Tübingen, Germany
| | - Anke Henning
- High-Field MR Center, Max Planck Institute for Biological Cybernetics, Max-Planck-Ring 11, 72076 Tübingen, Germany; Advanced Imaging Research Center, University of Texas Southwestern Medical Center, 5323 Harry Hines Blvd., Dallas, TX 75390, United States
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2
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Choi IY, Taylor MK, Lee P, Alhayek SA, Bechtel M, Hamilton-Reeves J, Spaeth K, Adany P, Sullivan DK. Milk intake enhances cerebral antioxidant (glutathione) concentration in older adults: A randomized controlled intervention study. Front Nutr 2022; 9:811650. [PMID: 36046132 PMCID: PMC9421260 DOI: 10.3389/fnut.2022.811650] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2021] [Accepted: 07/18/2022] [Indexed: 11/25/2022] Open
Abstract
Background A major antioxidant, glutathione (GSH), is a key factor in the antioxidant defense mechanism against oxidative stress and aging-related functional declines. Our previous observational study showed positive correlations between brain GSH concentrations and dairy food consumption, particularly milk (p < 0.001), in older adults. Objective To investigate whether a recommended amount of milk intake (3 cups/day) in low dairy consumers enhances brain GSH concentrations through an intervention trial. Methods Seventy-three older adults (60–89 years) with a low dairy intake (≤1.5 servings/day) were randomized (5:2 ratio) in this 3-month randomized clinical trial. The intervention group was provided 1% milk weekly and instructed to consume 3 cups of milk/day for 3 months while the control group continued their habitual intake of total dairy ≤ 1.5 servings/day (<1 cup of milk/day). Brain GSH concentrations were measured in the fronto-parietal region using our unique 3 T magnetic resonance chemical shift imaging technique at baseline and 3 months. Results Among 73 randomized participants, 66 participants (49 intervention; 17 controls) completed the study. Milk intake in the intervention group increased from 0.2 ± 0.3 cups/day to 3.0 ± 0.6 cups/day (p < 0.001) between baseline and the end of the study, while milk intake in the control group did not differ throughout the study duration (0.4 ± 0.4 cups/day). The intervention group showed increases in brain GSH concentrations by 7.4 ± 11.7% (p < 0.001) in parietal and 4.7 ± 9.8% (p = 0.003) in fronto-parietal regions, and 4.6 ± 8.7% (p < 0.001) in overall brain concentration after the intervention compared with baseline, while the control group showed no changes. Conclusion This study provides evidence that milk serves as a good dietary source to increase and/or restore brain GSH concentrations in older adults. Identifying dietary sources that effectively enhance antioxidant defenses and neuroprotection could lead to the development of new strategies to promote brain health in the aging population. Clinical trial registration [https://ClinicalTrials.gov], identifier [NCT02957422].
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Affiliation(s)
- In-Young Choi
- Department of Neurology, University of Kansas Medical Center, Kansas City, KS, United States.,Hoglund Biomedical Imaging Center, University of Kansas Medical Center, Kansas City, KS, United States.,Department of Radiology, University of Kansas Medical Center, Kansas City, KS, United States.,Department of Molecular and Integrative Physiology, University of Kansas Medical Center, Kansas City, KS, United States
| | - Matthew K Taylor
- Department of Dietetics and Nutrition, University of Kansas Medical Center, Kansas City, KS, United States
| | - Phil Lee
- Hoglund Biomedical Imaging Center, University of Kansas Medical Center, Kansas City, KS, United States.,Department of Radiology, University of Kansas Medical Center, Kansas City, KS, United States.,Department of Molecular and Integrative Physiology, University of Kansas Medical Center, Kansas City, KS, United States
| | - Sibelle Alwatchi Alhayek
- Department of Dietetics and Nutrition, University of Kansas Medical Center, Kansas City, KS, United States
| | - Misty Bechtel
- Department of Urology, University of Kansas Medical Center, Kansas City, KS, United States
| | - Jill Hamilton-Reeves
- Department of Urology, University of Kansas Medical Center, Kansas City, KS, United States
| | - Kendra Spaeth
- Department of Dietetics and Nutrition, University of Kansas Medical Center, Kansas City, KS, United States
| | - Peter Adany
- Hoglund Biomedical Imaging Center, University of Kansas Medical Center, Kansas City, KS, United States
| | - Debra K Sullivan
- Department of Dietetics and Nutrition, University of Kansas Medical Center, Kansas City, KS, United States
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Jaiswal D, Nenwani M, Mishra V, Wangikar PP. Probing the metabolism of γ-glutamyl peptides in cyanobacteria via metabolite profiling and 13 C labeling. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2022; 109:708-726. [PMID: 34727398 DOI: 10.1111/tpj.15564] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/29/2021] [Revised: 10/20/2021] [Accepted: 10/25/2021] [Indexed: 06/13/2023]
Abstract
Cyanobacteria are attractive model organisms for the study of photosynthesis and diurnal metabolism and as hosts for photoautotrophic production of chemicals. Exposure to bright light or environmental pollutants and a diurnal lifestyle of these prokaryotes may result in significant oxidative stress. Glutathione is a widely studied γ-glutamyl peptide that plays a key role in managing oxidative stress and detoxification of xenobiotics in cyanobacteria. The functional role and biosynthesis pathways of this tripeptide have been studied in detail in various phyla, including cyanobacteria. However, other γ-glutamyl peptides remain largely unexplored. We use an integrated approach to identify a number of γ-glutamyl peptides based on signature mass fragments and mass shifts in them in 13 C and 15 N enriched metabolite extracts. The newly identified compounds include γ-glutamyl dipeptides and derivatives of glutathione. Carbon backbones of the former turn over much faster than that of glutathione, suggesting that they follow a distinct biosynthesis pathway. Further, transients of isotopic 13 C enrichment show positional labeling in these peptides, which allows us to delineate the alternative biosynthesis pathways. Importantly, the amino acid of γ-glutamyl dipeptides shows much faster turnover compared to the glutamate moiety. The significant accumulation of γ-glutamyl dipeptides under slow-growth conditions combined with the results from dynamic 13 C labeling suggests that these compounds may act as reservoirs of amino acids in cyanobacteria.
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Affiliation(s)
- Damini Jaiswal
- Department of Chemical Engineering, Indian Institute of Technology Bombay, Powai, Mumbai, 400076, India
| | - Minal Nenwani
- Department of Chemical Engineering, Indian Institute of Technology Bombay, Powai, Mumbai, 400076, India
| | - Vivek Mishra
- Department of Chemical Engineering, Indian Institute of Technology Bombay, Powai, Mumbai, 400076, India
| | - Pramod P Wangikar
- Department of Chemical Engineering, Indian Institute of Technology Bombay, Powai, Mumbai, 400076, India
- DBT-PAN IIT Centre for Bioenergy, Indian Institute of Technology Bombay, Powai, Mumbai, 400076, India
- Wadhwani Research Centre for Bioengineering, Indian Institute of Technology Bombay, Powai, Mumbai, 400076, India
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4
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Guo M, Fang Y, Zhu J, Chen C, Zhang Z, Tian X, Xiang H, Manyande A, Ehsanifar M, Jafari AJ, Xu F, Wang J, Peng M. Investigation of metabolic kinetics in different brain regions of awake rats using the [ 1H- 13C]-NMR technique. J Pharm Biomed Anal 2021; 204:114240. [PMID: 34246879 DOI: 10.1016/j.jpba.2021.114240] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2021] [Revised: 06/30/2021] [Accepted: 07/02/2021] [Indexed: 12/12/2022]
Abstract
Energy metabolism and neurotransmission are necessary for sustaining normal life activities. Hence, neurological or psychiatric disorders are always associated with changes in neurotransmitters and energy metabolic states in the brain. Most studies have only focused on the most important neurotransmitters, particularly GABA and Glu, however, other metabolites such as NAA and aspartate which are also very important for cerebral function are rarely investigated. In this study, most of the metabolic kinetics information of different brain regions was investigated in awake rats using the [1H-13C]-NMR technique. Briefly, rats (n = 8) were infused [1-13C] glucose through the tail vein for two minutes. After 20 min of glucose metabolism, the animals were sacrificed and the brain tissue was extracted and treated. Utilizing the 1H observed/13C-edited nuclear magnetic resonance (POCE-NMR), the enrichment of neurochemicals was detected which reflected the metabolic changes in different brain regions and the metabolic connections between neurons and glial cells in the brain. The results suggest that the distribution of every metabolite differed from every brain region and the metabolic rate of NAA was relatively low at 8.64 ± 2.37 μmol/g/h. In addition, there were some correlations between several 13C enriched metabolites, such as Glu4-Gln4 (p = 0.062), Glu4-GABA2 (p < 0.01), Glx2-Glx3 (p < 0.001), Asp3-NAA3 (p < 0.001). This correlativity reflects the signal transmission between astrocytes and neurons, as well as the potential interaction between energy metabolism and neurotransmission. In conclusion, the current study systematically demonstrated the metabolic kinetics in the brain which shed light on brain functions and the mechanisms of various pathophysiological states.
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Affiliation(s)
- Meimei Guo
- Department of Anesthesiology, Zhongnan Hospital of Wuhan University, Wuhan, Hubei, 430071, PR China; Key Laboratory of Magnetic Resonance in Biological Systems, State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics, National Center for Magnetic Resonance in Wuhan, Wuhan Institute of Physics and Mathematics, Innovation Academy for Precision Measurement Science and Technology, Chinese Academy of Sciences-Wuhan National Laboratory for Optoelectronics, 430071, Wuhan, PR China
| | - Yuanyuan Fang
- Department of Anesthesiology, Zhongnan Hospital of Wuhan University, Wuhan, Hubei, 430071, PR China; Key Laboratory of Magnetic Resonance in Biological Systems, State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics, National Center for Magnetic Resonance in Wuhan, Wuhan Institute of Physics and Mathematics, Innovation Academy for Precision Measurement Science and Technology, Chinese Academy of Sciences-Wuhan National Laboratory for Optoelectronics, 430071, Wuhan, PR China
| | - Jinpiao Zhu
- Department of Anesthesiology, Zhongnan Hospital of Wuhan University, Wuhan, Hubei, 430071, PR China; Key Laboratory of Magnetic Resonance in Biological Systems, State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics, National Center for Magnetic Resonance in Wuhan, Wuhan Institute of Physics and Mathematics, Innovation Academy for Precision Measurement Science and Technology, Chinese Academy of Sciences-Wuhan National Laboratory for Optoelectronics, 430071, Wuhan, PR China
| | - Chang Chen
- Department of Anesthesiology, Zhongnan Hospital of Wuhan University, Wuhan, Hubei, 430071, PR China
| | - Zongze Zhang
- Department of Anesthesiology, Zhongnan Hospital of Wuhan University, Wuhan, Hubei, 430071, PR China
| | - Xuebi Tian
- Department of Anesthesiology, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, 430070, PR China
| | - Hongbing Xiang
- Department of Anesthesiology, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, 430070, PR China
| | - Anne Manyande
- School of Human and Social Sciences, University of West London, London, UK
| | - Mojtaba Ehsanifar
- Department of Environmental Health Engineering, School of Public Health, Iran University of Medical Sciences, Tehran, Iran
| | - Ahmad Jonidi Jafari
- Department of Environmental Health Engineering, School of Public Health, Iran University of Medical Sciences, Tehran, Iran
| | - Fuqiang Xu
- Key Laboratory of Magnetic Resonance in Biological Systems, State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics, National Center for Magnetic Resonance in Wuhan, Wuhan Institute of Physics and Mathematics, Innovation Academy for Precision Measurement Science and Technology, Chinese Academy of Sciences-Wuhan National Laboratory for Optoelectronics, 430071, Wuhan, PR China; University of Chinese Academy of Sciences, Beijing, 100049, PR China
| | - Jie Wang
- Key Laboratory of Magnetic Resonance in Biological Systems, State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics, National Center for Magnetic Resonance in Wuhan, Wuhan Institute of Physics and Mathematics, Innovation Academy for Precision Measurement Science and Technology, Chinese Academy of Sciences-Wuhan National Laboratory for Optoelectronics, 430071, Wuhan, PR China; University of Chinese Academy of Sciences, Beijing, 100049, PR China; Hebei Provincial Key Laboratory of Basic Medicine for Diabetes, 2nd Hospital of Shijiazhuang, Shijiazhuang, Hebei, 050051, PR China.
| | - Mian Peng
- Department of Anesthesiology, Zhongnan Hospital of Wuhan University, Wuhan, Hubei, 430071, PR China.
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Moffett JR, Puthillathu N, Vengilote R, Jaworski DM, Namboodiri AM. Acetate Revisited: A Key Biomolecule at the Nexus of Metabolism, Epigenetics and Oncogenesis-Part 1: Acetyl-CoA, Acetogenesis and Acyl-CoA Short-Chain Synthetases. Front Physiol 2020; 11:580167. [PMID: 33281616 PMCID: PMC7689297 DOI: 10.3389/fphys.2020.580167] [Citation(s) in RCA: 57] [Impact Index Per Article: 14.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2020] [Accepted: 09/23/2020] [Indexed: 12/19/2022] Open
Abstract
Acetate is a major end product of bacterial fermentation of fiber in the gut. Acetate, whether derived from the diet or from fermentation in the colon, has been implicated in a range of health benefits. Acetate is also generated in and released from various tissues including the intestine and liver, and is generated within all cells by deacetylation reactions. To be utilized, all acetate, regardless of the source, must be converted to acetyl coenzyme A (acetyl-CoA), which is carried out by enzymes known as acyl-CoA short-chain synthetases. Acyl-CoA short-chain synthetase-2 (ACSS2) is present in the cytosol and nuclei of many cell types, whereas ACSS1 is mitochondrial, with greatest expression in heart, skeletal muscle, and brown adipose tissue. In addition to acting to redistribute carbon systemically like a ketone body, acetate is becoming recognized as a cellular regulatory molecule with diverse functions beyond the formation of acetyl-CoA for energy derivation and lipogenesis. Acetate acts, in part, as a metabolic sensor linking nutrient balance and cellular stress responses with gene transcription and the regulation of protein function. ACSS2 is an important task-switching component of this sensory system wherein nutrient deprivation, hypoxia and other stressors shift ACSS2 from a lipogenic role in the cytoplasm to a regulatory role in the cell nucleus. Protein acetylation is a critical post-translational modification involved in regulating cell behavior, and alterations in protein acetylation status have been linked to multiple disease states, including cancer. Improving our fundamental understanding of the "acetylome" and how acetate is generated and utilized at the subcellular level in different cell types will provide much needed insight into normal and neoplastic cellular metabolism and the epigenetic regulation of phenotypic expression under different physiological stressors. This article is Part 1 of 2 - for Part 2 see doi: 10.3389/fphys.2020.580171.
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Affiliation(s)
- John R Moffett
- Department of Anatomy, Physiology and Genetics, and Neuroscience Program, Uniformed Services University of the Health Sciences, Bethesda, MD, United States
| | - Narayanan Puthillathu
- Department of Anatomy, Physiology and Genetics, and Neuroscience Program, Uniformed Services University of the Health Sciences, Bethesda, MD, United States
| | - Ranjini Vengilote
- Department of Anatomy, Physiology and Genetics, and Neuroscience Program, Uniformed Services University of the Health Sciences, Bethesda, MD, United States
| | - Diane M Jaworski
- Department of Neurological Sciences, University of Vermont College of Medicine, Burlington, VT, United States
| | - Aryan M Namboodiri
- Department of Anatomy, Physiology and Genetics, and Neuroscience Program, Uniformed Services University of the Health Sciences, Bethesda, MD, United States
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6
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Interplay between NAD + and acetyl‑CoA metabolism in ischemia-induced mitochondrial pathophysiology. Biochim Biophys Acta Mol Basis Dis 2018; 1865:2060-2067. [PMID: 30261291 DOI: 10.1016/j.bbadis.2018.09.025] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2018] [Revised: 09/17/2018] [Accepted: 09/19/2018] [Indexed: 12/11/2022]
Abstract
Brain injury caused by ischemic insult due to significant reduction or interruption in cerebral blood flow leads to disruption of practically all cellular metabolic pathways. This triggers a complex stress response followed by overstimulation of downstream enzymatic pathways due to massive activation of post-translational modifications (PTM). Mitochondria are one of the most sensitive organelle to ischemic conditions. They become dysfunctional due to extensive fragmentation, inhibition of acetyl‑CoA production, and increased activity of NAD+ consuming enzymes. These pathologic conditions ultimately lead to inhibition of oxidative phosphorylation and mitochondrial ATP production. Both acetyl‑CoA and NAD+ are essential intermediates in cellular bioenergetics metabolism and also serve as substrates for post-translational modifications such as acetylation and ADP‑ribosylation. In this review we discuss ischemia/reperfusion-induced changes in NAD+ and acetyl‑CoA metabolism, how these affect relevant PTMs, and therapeutic approaches that restore the physiological levels of these metabolites leading to promising neuroprotection.
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Carlson HL, MacMaster FP, Harris AD, Kirton A. Spectroscopic biomarkers of motor cortex developmental plasticity in hemiparetic children after perinatal stroke. Hum Brain Mapp 2017; 38:1574-1587. [PMID: 27859933 PMCID: PMC6866903 DOI: 10.1002/hbm.23472] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2016] [Revised: 10/20/2016] [Accepted: 11/07/2016] [Indexed: 01/26/2023] Open
Abstract
Perinatal stroke causes hemiparetic cerebral palsy and lifelong motor disability. Bilateral motor cortices are key hubs within the motor network and their neurophysiology determines clinical function. Establishing biomarkers of motor cortex function is imperative for developing and evaluating restorative interventional strategies. Proton magnetic resonance spectroscopy (MRS) quantifies metabolite concentrations indicative of underlying neuronal health and metabolism in vivo. We used functional magnetic resonance imaging (MRI)-guided MRS to investigate motor cortex metabolism in children with perinatal stroke. Children aged 6-18 years with MRI-confirmed perinatal stroke and hemiparetic cerebral palsy were recruited from a population-based cohort. Metabolite concentrations were assessed using a PRESS sequence (3T, TE = 30 ms, voxel = 4 cc). Voxel location was guided by functional MRI activations during finger tapping tasks. Spectra were analysed using LCModel. Metabolites were quantified, cerebral spinal fluid corrected and compared between groups (ANCOVA) controlling for age. Associations with clinical motor performance (Assisting Hand, Melbourne, Box-and-Blocks) were assessed. Fifty-two participants were studied (19 arterial, 14 venous, 19 control). Stroke participants demonstrated differences between lesioned and nonlesioned motor cortex N-acetyl-aspartate [NAA mean concentration = 10.8 ± 1.9 vs. 12.0 ± 1.2, P < 0.01], creatine [Cre 8.0 ± 0.9 vs. 7.4 ± 0.9, P < 0.05] and myo-Inositol [Ins 6.5 ± 0.84 vs. 5.8 ± 1.1, P < 0.01]. Lesioned motor cortex NAA and creatine were strongly correlated with motor performance in children with arterial but not venous strokes. Interrogation of motor cortex by fMRI-guided MRS is feasible in children with perinatal stroke. Metabolite differences between hemispheres, stroke types and correlations with motor performance support functional relevance. MRS may be valuable in understanding the neurophysiology of developmental neuroplasticity in cerebral palsy. Hum Brain Mapp 38:1574-1587, 2017. © 2016 Wiley Periodicals, Inc.
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Affiliation(s)
- Helen L. Carlson
- Calgary Pediatric Stroke ProgramAlberta Children's HospitalCalgaryABCanada
- Alberta Children's Hospital Research Institute (ACHRI)ABCanadaCalgary
- NeurosciencesAlberta Children's HospitalCalgaryABCanada
- Department of PediatricsUniversity of CalgaryCalgaryABCanada
| | - Frank P. MacMaster
- Alberta Children's Hospital Research Institute (ACHRI)ABCanadaCalgary
- Department of PediatricsUniversity of CalgaryCalgaryABCanada
- Hotchkiss Brain Institute, University of CalgaryCalgaryABCanada
- Department of PsychiatryUniversity of CalgaryABCanada
- The Mathison Centre for Mental Health Research and Education, University of CalgaryCalgaryABCanada
- Child and Adolescent Imaging Research (CAIR) Programs, Alberta Children's HospitalCalgaryABCanada
- Strategic Clinical Network for Addictions and Mental HealthAlberta Health ServicesCalgaryABCanada
| | - Ashley D. Harris
- Alberta Children's Hospital Research Institute (ACHRI)ABCanadaCalgary
- Hotchkiss Brain Institute, University of CalgaryCalgaryABCanada
- Child and Adolescent Imaging Research (CAIR) Programs, Alberta Children's HospitalCalgaryABCanada
- Department of RadiologyUniversity of CalgaryCalgaryABCanada
| | - Adam Kirton
- Calgary Pediatric Stroke ProgramAlberta Children's HospitalCalgaryABCanada
- Alberta Children's Hospital Research Institute (ACHRI)ABCanadaCalgary
- NeurosciencesAlberta Children's HospitalCalgaryABCanada
- Department of PediatricsUniversity of CalgaryCalgaryABCanada
- Hotchkiss Brain Institute, University of CalgaryCalgaryABCanada
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I Amaral A, Hadera MG, Kotter M, Sonnewald U. Oligodendrocytes Do Not Export NAA-Derived Aspartate In Vitro. Neurochem Res 2017; 42:827-837. [PMID: 27394419 PMCID: PMC5357468 DOI: 10.1007/s11064-016-1985-y] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2016] [Revised: 06/15/2016] [Accepted: 06/20/2016] [Indexed: 12/24/2022]
Abstract
Oligodendroglial cells are known to de-acetylate the N-acetylaspartate (NAA) synthesized and released by neurons and use it for lipid synthesis. However, the role of NAA regarding their intermediary metabolism remains poorly understood. Two hypotheses were proposed regarding the fate of aspartate after being released by de-acetylation: (1) aspartate is metabolized in the mitochondria of oligodendrocyte lineage cells; (2) aspartate is released to the medium. We report here that aspartoacylase mRNA expression increases when primary rat oligodendrocyte progenitor cells (OPCs) differentiate into mature cells in culture. Moreover, characterising metabolic functions of acetyl coenzyme A and aspartate from NAA catabolism in mature oligodendrocyte cultures after 5 days using isotope-labelled glucose after 5-days of differentiation we found evidence of extensive NAA metabolism. Incubation with [1,6-13C]glucose followed by gas chromatography-mass spectrometry and high performance liquid chromatography analyses of cell extracts and media in the presence and absence of NAA established that the acetate moiety produced by hydrolysis of NAA does not enter mitochondrial metabolism in the form of acetyl coenzyme A. We also resolved the controversy concerning the possible release of aspartate to the medium: aspartate is not released to the medium by oligodendrocytes in amounts detectable by our methods. Therefore we propose that: aspartate released from NAA joins the cytosolic aspartate pool rapidly and takes part in the malate-aspartate shuttle, which transports reducing equivalents from glycolysis into the mitochondria for ATP production and enters the tricarboxylic acid cycle at a slow rate.
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Affiliation(s)
- Ana I Amaral
- Wellcome Trust-Medical Research Council Cambridge Stem Cell Institute, Anne McLaren Laboratory and Department of Clinical Neurosciences, University of Cambridge, West Forvie Building, Robinson Way, Cambridge, CB2 0SZ, UK
| | - Mussie Ghezu Hadera
- Department of Pharmacy, College of Health Sciences, Mekelle University, Tigray, Ethiopia
| | - Mark Kotter
- Wellcome Trust-Medical Research Council Cambridge Stem Cell Institute, Anne McLaren Laboratory and Department of Clinical Neurosciences, University of Cambridge, West Forvie Building, Robinson Way, Cambridge, CB2 0SZ, UK.
| | - Ursula Sonnewald
- Department of Neuroscience, Faculty of Medicine, Norwegian University of Science and Technology (NTNU), PO Box 8905, MTFS, 7491, Trondheim, Norway.
- Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, 2100, Denmark.
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9
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Patel AB, Lai JCK, Chowdhury GIM, Rothman DL, Behar KL. Comparison of Glutamate Turnover in Nerve Terminals and Brain Tissue During [1,6- 13C 2]Glucose Metabolism in Anesthetized Rats. Neurochem Res 2016; 42:173-190. [PMID: 28025798 DOI: 10.1007/s11064-016-2103-x] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2016] [Revised: 11/06/2016] [Accepted: 11/08/2016] [Indexed: 01/05/2023]
Abstract
The 13C turnover of neurotransmitter amino acids (glutamate, GABA and aspartate) were determined from extracts of forebrain nerve terminals and brain homogenate, and fronto-parietal cortex from anesthetized rats undergoing timed infusions of [1,6-13C2]glucose or [2-13C]acetate. Nerve terminal 13C fractional labeling of glutamate and aspartate was lower than those in whole cortical tissue at all times measured (up to 120 min), suggesting either the presence of a constant dilution flux from an unlabeled substrate or an unlabeled (effectively non-communicating on the measurement timescale) glutamate pool in the nerve terminals. Half times of 13C labeling from [1,6-13C2]glucose, as estimated by least squares exponential fitting to the time course data, were longer for nerve terminals (GluC4, 21.8 min; GABAC2 21.0 min) compared to cortical tissue (GluC4, 12.4 min; GABAC2, 14.5 min), except for AspC3, which was similar (26.5 vs. 27.0 min). The slower turnover of glutamate in the nerve terminals (but not GABA) compared to the cortex may reflect selective effects of anesthesia on activity-dependent glucose use, which might be more pronounced in the terminals. The 13C labeling ratio for glutamate-C4 from [2-13C]acetate over that of 13C-glucose was twice as large in nerve terminals compared to cortex, suggesting that astroglial glutamine under the 13C glucose infusion was the likely source of much of the nerve terminal dilution. The net replenishment of most of the nerve terminal amino acid pools occurs directly via trafficking of astroglial glutamine.
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Affiliation(s)
- Anant B Patel
- Department of Diagnostic Radiology and Biomedical Imaging, Magnetic Resonance Research Center, Yale University School of Medicine, New Haven, CT, 06520, USA. .,CSIR-Centre for Cellular and Molecular Biology, Uppal Road, Hyderabad, 500007, India.
| | - James C K Lai
- Department of Biomedical and Pharmaceutical Sciences, College of Pharmacy, Idaho State University, Pocatello, ID, 83209, USA
| | - Golam I M Chowdhury
- Department of Psychiatry, Magnetic Resonance Research Center, Yale University School of Medicine, 300 Cedar Street, PO Box 208043, New Haven, CT, 06520, USA
| | - Douglas L Rothman
- Department of Diagnostic Radiology and Biomedical Imaging, Magnetic Resonance Research Center, Yale University School of Medicine, New Haven, CT, 06520, USA
| | - Kevin L Behar
- Department of Psychiatry, Magnetic Resonance Research Center, Yale University School of Medicine, 300 Cedar Street, PO Box 208043, New Haven, CT, 06520, USA.
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Glutathione in the human brain: Review of its roles and measurement by magnetic resonance spectroscopy. Anal Biochem 2016; 529:127-143. [PMID: 28034792 DOI: 10.1016/j.ab.2016.12.022] [Citation(s) in RCA: 107] [Impact Index Per Article: 13.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2016] [Revised: 12/21/2016] [Accepted: 12/23/2016] [Indexed: 12/12/2022]
Abstract
We review the transport, synthesis and catabolism of glutathione in the brain as well as its compartmentation and biochemistry in different brain cells. The major reactions involving glutathione are reviewed and the factors limiting its availability in brain cells are discussed. We also describe and critique current methods for measuring glutathione in the human brain using magnetic resonance spectroscopy, and review the literature on glutathione measurements in healthy brains and in neurological, psychiatric, neurodegenerative and neurodevelopmental conditions In summary: Healthy human brain glutathione concentration is ∼1-2 mM, but it varies by brain region, with evidence of gender differences and age effects; in neurological disease glutathione appears reduced in multiple sclerosis, motor neurone disease and epilepsy, while being increased in meningiomas; in psychiatric disease the picture is complex and confounded by methodological differences, regional effects, length of disease and drug-treatment. Both increases and decreases in glutathione have been reported in depression and schizophrenia. In Alzheimer's disease and mild cognitive impairment there is evidence for a decrease in glutathione compared to age-matched healthy controls. Improved methods to measure glutathione in vivo will provide better precision in glutathione determination and help resolve the complex biochemistry of this molecule in health and disease.
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Wu Y, Pearce PS, Rapuano A, Hitchens TK, de Lanerolle NC, Pan JW. Metabolic changes in early poststatus epilepticus measured by MR spectroscopy in rats. J Cereb Blood Flow Metab 2015; 35:1862-70. [PMID: 26104287 PMCID: PMC4635243 DOI: 10.1038/jcbfm.2015.145] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/11/2015] [Revised: 05/17/2015] [Accepted: 05/20/2015] [Indexed: 11/09/2022]
Abstract
There is little experimental in vivo data on how differences in seizure duration in experimental status epilepticus influence metabolic injury. This is of interest given that in humans, status duration is a factor that influences the probability of subsequent development of epilepsy. This question is studied using 7-T magnetic resonance (MR) spectroscopy, T2 relaxometry in the incremented kainate rodent model of temporal lobe epilepsy, using two durations of status epilepticus, 1.5 and 3 hours. Histologic evaluation was performed in a subset of animals. Three days after status, single-voxel (8 mm(3)) point resolved spectroscopy (PRESS) MR spectroscopic measurements were acquired at 7 T to assess the cerebral metabolites measured as a ratio to total creatine (tCr). The status injury resulted in decreased N-acetylaspartate NAA/tCr, increased myo-inositol/tCr and glutamine/tCr, increased T2, and significant declines in NeuN-stained neuronal counts in both status groups. Regressions were identified in the status groups that provide evidence for neuronal injury and astrocytic reaction after status in both the short and long status duration groups. The long status group displays changes in glutathione/tCr that are not identified in the short status group, this difference possibly representing a maturation of injury and antioxidant response that occurs in synchrony with glutamatergic injury and glial activation.
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Affiliation(s)
- Yijen Wu
- Department of Developmental Biology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, USA
| | - Patrice S Pearce
- Departments of Neurology and Radiology, University of Pittsburgh, Pittsburgh, Pennsylvania, USA
| | - Amedeo Rapuano
- Department of Neurosurgery, Yale University School of Medicine, New Haven, Connecticut, USA
| | - T Kevin Hitchens
- Pittsburgh NMR Center for Biomedical Research, Carnegie Mellon University, Pittsburgh, Pennsylvania, USA
| | - Nihal C de Lanerolle
- Department of Neurosurgery, Yale University School of Medicine, New Haven, Connecticut, USA
| | - Jullie W Pan
- Departments of Neurology and Radiology, University of Pittsburgh, Pittsburgh, Pennsylvania, USA
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Chawla S, Ge Y, Lu H, Marshall O, Davitz MS, Fatterpekar G, Soher BJ, Gonen O. Whole-Brain N-Acetylaspartate Concentration Is Preserved during Mild Hypercapnia Challenge. AJNR Am J Neuroradiol 2015; 36:2055-61. [PMID: 26294651 PMCID: PMC4644678 DOI: 10.3174/ajnr.a4424] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2015] [Accepted: 04/01/2015] [Indexed: 11/07/2022]
Abstract
BACKGROUND AND PURPOSE Although NAA is often used as a marker of neuronal health and integrity in neurologic disorders, its normal response to physiologic challenge is not well-established and its changes are almost always attributed exclusively to brain pathology. The purpose of this study was to test the hypothesis that the neuronal cell marker NAA, often used to assess neuronal health and integrity in neurologic disorders, is not confounded by (possibly transient) physiologic changes. Therefore, its decline, when observed by using (1)H-MR spectroscopy, can almost always be attributed exclusively to brain pathology. MATERIALS AND METHODS Twelve healthy young male adults underwent a transient hypercapnia challenge (breathing 5% CO2 air mixture), a potent vasodilator known to cause a substantial increase in CBF and venous oxygenation. We evaluated their whole-brain NAA by using nonlocalizing proton MR spectroscopy, venous oxygenation with T2-relaxation under spin-tagging MR imaging, CBF with pseudocontinuous arterial spin-labeling, and the cerebral metabolic rate of oxygen, during normocapnia (breathing room air) and hypercapnia. RESULTS There was insignificant whole-brain NAA change (P = .88) from normocapnia to hypercapnia and back to normocapnia in this cohort, as opposed to highly significant increases: 28.0 ± 10.3% in venous oxygenation and 49.7 ± 16.6% in global CBF (P < 10(-4)); and a 6.4 ± 10.9% decrease in the global cerebral metabolic rate of oxygen (P = .04). CONCLUSIONS Stable whole-brain NAA during normocapnia and hypercapnia, despite significant global CBF and cerebral metabolic rate of oxygen changes, supports the hypothesis that global NAA changes are insensitive to transient physiology. Therefore, when observed, they most likely reflect underlying pathology resulting from neuronal cell integrity/viability changes, instead of a response to physiologic changes.
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Affiliation(s)
- S Chawla
- From the Department of Radiology (S.C., Y.G., O.M., M.S.D., G.F., O.G.), Center for Advanced Imaging Innovation and Research and Bernard and Irene Schwartz Center for Biomedical Imaging, New York University School of Medicine, New York, New York
| | - Y Ge
- From the Department of Radiology (S.C., Y.G., O.M., M.S.D., G.F., O.G.), Center for Advanced Imaging Innovation and Research and Bernard and Irene Schwartz Center for Biomedical Imaging, New York University School of Medicine, New York, New York
| | - H Lu
- The Russell H. Morgan Department of Radiology and Radiological Science (H.L.), Johns Hopkins University School of Medicine, Baltimore, Maryland
| | - O Marshall
- From the Department of Radiology (S.C., Y.G., O.M., M.S.D., G.F., O.G.), Center for Advanced Imaging Innovation and Research and Bernard and Irene Schwartz Center for Biomedical Imaging, New York University School of Medicine, New York, New York
| | - M S Davitz
- From the Department of Radiology (S.C., Y.G., O.M., M.S.D., G.F., O.G.), Center for Advanced Imaging Innovation and Research and Bernard and Irene Schwartz Center for Biomedical Imaging, New York University School of Medicine, New York, New York
| | - G Fatterpekar
- From the Department of Radiology (S.C., Y.G., O.M., M.S.D., G.F., O.G.), Center for Advanced Imaging Innovation and Research and Bernard and Irene Schwartz Center for Biomedical Imaging, New York University School of Medicine, New York, New York
| | - B J Soher
- Department of Radiology (B.J.S.), Center for Advanced MR Development, Duke University Medical Center, Durham, North Carolina
| | - O Gonen
- From the Department of Radiology (S.C., Y.G., O.M., M.S.D., G.F., O.G.), Center for Advanced Imaging Innovation and Research and Bernard and Irene Schwartz Center for Biomedical Imaging, New York University School of Medicine, New York, New York
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13
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Choi IY, Lee P, Denney DR, Spaeth K, Nast O, Ptomey L, Roth AK, Lierman JA, Sullivan DK. Dairy intake is associated with brain glutathione concentration in older adults. Am J Clin Nutr 2015; 101:287-93. [PMID: 25646325 PMCID: PMC4307202 DOI: 10.3945/ajcn.114.096701] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
BACKGROUND A reduction in key antioxidants such as glutathione has been noted in brain tissue undergoing oxidative stress in aging and neurodegeneration. To date, no dietary factor has been linked to a higher glutathione concentration. However, in an earlier pilot study, we showed evidence of a positive association between cerebral glutathione and dairy intake. OBJECTIVE We tested the hypothesis that dairy food consumption is associated with cerebral glutathione concentrations in older adults. DESIGN In this observational study, we measured cerebral glutathione concentrations in 60 healthy subjects (mean ± SD age: 68.7 ± 6.2 y) whose routine dairy intakes varied. Glutathione concentrations were measured by using a unique, noninvasive magnetic resonance chemical shift imaging technique at 3 T and compared with dairy intakes reported in 7-d food records. RESULTS Glutathione concentrations in the frontal [Spearman's rank-order correlation (rs) = 0.39, P = 0.013], parietal (rs = 0.50, P = 0.001), and frontoparietal regions (rs = 0.47, P = 0.003) were correlated with average daily dairy servings. In particular, glutathione concentrations in all 3 regions were positively correlated with milk servings (P ≤ 0.013), and those in the parietal region were also correlated with cheese servings (P = 0.015) and calcium intake (P = 0.039). Dairy intake was related to sex, fat-free mass, and daily intakes of energy, protein, and carbohydrates. However, when these factors were controlled through a partial correlation, correlations between glutathione concentrations and dairy and milk servings remained significant. CONCLUSIONS Higher cerebral glutathione concentrations were associated with greater dairy consumption in older adults. One possible explanation for this association is that dairy foods may serve as a good source of substrates for glutathione synthesis in the human brain.
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Affiliation(s)
- In-Young Choi
- From the Hoglund Brain Imaging Center (I-YC, PL, and JAL) and the Departments of Neurology (I-YC), Molecular & Integrative Physiology (I-YC and PL), and Dietetics and Nutrition (KS, ON, LP, and DKS), University of Kansas Medical Center, Kansas City, KS, and the Department of Psychology, University of Kansas, Lawrence, KS (DRD and AKR)
| | - Phil Lee
- From the Hoglund Brain Imaging Center (I-YC, PL, and JAL) and the Departments of Neurology (I-YC), Molecular & Integrative Physiology (I-YC and PL), and Dietetics and Nutrition (KS, ON, LP, and DKS), University of Kansas Medical Center, Kansas City, KS, and the Department of Psychology, University of Kansas, Lawrence, KS (DRD and AKR)
| | - Douglas R Denney
- From the Hoglund Brain Imaging Center (I-YC, PL, and JAL) and the Departments of Neurology (I-YC), Molecular & Integrative Physiology (I-YC and PL), and Dietetics and Nutrition (KS, ON, LP, and DKS), University of Kansas Medical Center, Kansas City, KS, and the Department of Psychology, University of Kansas, Lawrence, KS (DRD and AKR)
| | - Kendra Spaeth
- From the Hoglund Brain Imaging Center (I-YC, PL, and JAL) and the Departments of Neurology (I-YC), Molecular & Integrative Physiology (I-YC and PL), and Dietetics and Nutrition (KS, ON, LP, and DKS), University of Kansas Medical Center, Kansas City, KS, and the Department of Psychology, University of Kansas, Lawrence, KS (DRD and AKR)
| | - Olivia Nast
- From the Hoglund Brain Imaging Center (I-YC, PL, and JAL) and the Departments of Neurology (I-YC), Molecular & Integrative Physiology (I-YC and PL), and Dietetics and Nutrition (KS, ON, LP, and DKS), University of Kansas Medical Center, Kansas City, KS, and the Department of Psychology, University of Kansas, Lawrence, KS (DRD and AKR)
| | - Lauren Ptomey
- From the Hoglund Brain Imaging Center (I-YC, PL, and JAL) and the Departments of Neurology (I-YC), Molecular & Integrative Physiology (I-YC and PL), and Dietetics and Nutrition (KS, ON, LP, and DKS), University of Kansas Medical Center, Kansas City, KS, and the Department of Psychology, University of Kansas, Lawrence, KS (DRD and AKR)
| | - Alexandra K Roth
- From the Hoglund Brain Imaging Center (I-YC, PL, and JAL) and the Departments of Neurology (I-YC), Molecular & Integrative Physiology (I-YC and PL), and Dietetics and Nutrition (KS, ON, LP, and DKS), University of Kansas Medical Center, Kansas City, KS, and the Department of Psychology, University of Kansas, Lawrence, KS (DRD and AKR)
| | - Jo Ann Lierman
- From the Hoglund Brain Imaging Center (I-YC, PL, and JAL) and the Departments of Neurology (I-YC), Molecular & Integrative Physiology (I-YC and PL), and Dietetics and Nutrition (KS, ON, LP, and DKS), University of Kansas Medical Center, Kansas City, KS, and the Department of Psychology, University of Kansas, Lawrence, KS (DRD and AKR)
| | - Debra K Sullivan
- From the Hoglund Brain Imaging Center (I-YC, PL, and JAL) and the Departments of Neurology (I-YC), Molecular & Integrative Physiology (I-YC and PL), and Dietetics and Nutrition (KS, ON, LP, and DKS), University of Kansas Medical Center, Kansas City, KS, and the Department of Psychology, University of Kansas, Lawrence, KS (DRD and AKR)
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Direct evidence for activity-dependent glucose phosphorylation in neurons with implications for the astrocyte-to-neuron lactate shuttle. Proc Natl Acad Sci U S A 2014; 111:5385-90. [PMID: 24706914 DOI: 10.1073/pnas.1403576111] [Citation(s) in RCA: 143] [Impact Index Per Article: 14.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Previous (13)C magnetic resonance spectroscopy experiments have shown that over a wide range of neuronal activity, approximately one molecule of glucose is oxidized for every molecule of glutamate released by neurons and recycled through astrocytic glutamine. The measured kinetics were shown to agree with the stoichiometry of a hypothetical astrocyte-to-neuron lactate shuttle model, which predicted negligible functional neuronal uptake of glucose. To test this model, we measured the uptake and phosphorylation of glucose in nerve terminals isolated from rats infused with the glucose analog, 2-fluoro-2-deoxy-D-glucose (FDG) in vivo. The concentrations of phosphorylated FDG (FDG6P), normalized with respect to known neuronal metabolites, were compared in nerve terminals, homogenate, and cortex of anesthetized rats with and without bicuculline-induced seizures. The increase in FDG6P in nerve terminals agreed well with the increase in cortical neuronal glucose oxidation measured previously under the same conditions in vivo, indicating that direct uptake and oxidation of glucose in nerve terminals is substantial under resting and activated conditions. These results suggest that neuronal glucose-derived pyruvate is the major oxidative fuel for activated neurons, not lactate-derived from astrocytes, contradicting predictions of the original astrocyte-to-neuron lactate shuttle model under the range of study conditions.
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Moffett JR, Arun P, Ariyannur PS, Namboodiri AMA. N-Acetylaspartate reductions in brain injury: impact on post-injury neuroenergetics, lipid synthesis, and protein acetylation. FRONTIERS IN NEUROENERGETICS 2013; 5:11. [PMID: 24421768 PMCID: PMC3872778 DOI: 10.3389/fnene.2013.00011] [Citation(s) in RCA: 123] [Impact Index Per Article: 11.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/23/2013] [Accepted: 12/09/2013] [Indexed: 12/22/2022]
Abstract
N-Acetylaspartate (NAA) is employed as a non-invasive marker for neuronal health using proton magnetic resonance spectroscopy (MRS). This utility is afforded by the fact that NAA is one of the most concentrated brain metabolites and that it produces the largest peak in MRS scans of the healthy human brain. NAA levels in the brain are reduced proportionately to the degree of tissue damage after traumatic brain injury (TBI) and the reductions parallel the reductions in ATP levels. Because NAA is the most concentrated acetylated metabolite in the brain, we have hypothesized that NAA acts in part as an extensive reservoir of acetate for acetyl coenzyme A synthesis. Therefore, the loss of NAA after TBI impairs acetyl coenzyme A dependent functions including energy derivation, lipid synthesis, and protein acetylation reactions in distinct ways in different cell populations. The enzymes involved in synthesizing and metabolizing NAA are predominantly expressed in neurons and oligodendrocytes, respectively, and therefore some proportion of NAA must be transferred between cell types before the acetate can be liberated, converted to acetyl coenzyme A and utilized. Studies have indicated that glucose metabolism in neurons is reduced, but that acetate metabolism in astrocytes is increased following TBI, possibly reflecting an increased role for non-glucose energy sources in response to injury. NAA can provide additional acetate for intercellular metabolite trafficking to maintain acetyl CoA levels after injury. Here we explore changes in NAA, acetate, and acetyl coenzyme A metabolism in response to brain injury.
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Affiliation(s)
- John R. Moffett
- Neuroscience Program, Department of Anatomy, Physiology and Genetics, Uniformed Services University of the Health SciencesBethesda, MD, USA
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16
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Aoyama K, Nakaki T. Impaired glutathione synthesis in neurodegeneration. Int J Mol Sci 2013; 14:21021-44. [PMID: 24145751 PMCID: PMC3821656 DOI: 10.3390/ijms141021021] [Citation(s) in RCA: 151] [Impact Index Per Article: 13.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2013] [Revised: 09/30/2013] [Accepted: 10/01/2013] [Indexed: 12/20/2022] Open
Abstract
Glutathione (GSH) was discovered in yeast cells in 1888. Studies of GSH in mammalian cells before the 1980s focused exclusively on its function for the detoxication of xenobiotics or for drug metabolism in the liver, in which GSH is present at its highest concentration in the body. Increasing evidence has demonstrated other important roles of GSH in the brain, not only for the detoxication of xenobiotics but also for antioxidant defense and the regulation of intracellular redox homeostasis. GSH also regulates cell signaling, protein function, gene expression, and cell differentiation/proliferation in the brain. Clinically, inborn errors in GSH-related enzymes are very rare, but disorders of GSH metabolism are common in major neurodegenerative diseases showing GSH depletion and increased levels of oxidative stress in the brain. GSH depletion would precipitate oxidative damage in the brain, leading to neurodegenerative diseases. This review focuses on the significance of GSH function, the synthesis of GSH and its metabolism, and clinical disorders of GSH metabolism. A potential approach to increase brain GSH levels against neurodegeneration is also discussed.
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Affiliation(s)
- Koji Aoyama
- Department of Pharmacology, Teikyo University School of Medicine, 2-11-1 Kaga, Itabashi, Tokyo 173-8605, Japan.
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Marin-Valencia I, Good LB, Ma Q, Jeffrey FM, Malloy CR, Pascual JM. High-resolution detection of ¹³C multiplets from the conscious mouse brain by ex vivo NMR spectroscopy. J Neurosci Methods 2011; 203:50-5. [PMID: 21946227 DOI: 10.1016/j.jneumeth.2011.09.006] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2011] [Revised: 08/10/2011] [Accepted: 09/07/2011] [Indexed: 10/17/2022]
Abstract
Glucose readily supplies the brain with the majority of carbon needed to sustain neurotransmitter production and utilization. The rate of brain glucose metabolism can be computed using (13)C nuclear magnetic resonance (NMR) spectroscopy by detecting changes in (13)C contents of products generated by cerebral metabolism. As previously observed, scalar coupling between adjacent (13)C carbons (multiplets) can provide additional information to (13)C contents for the computation of metabolic rates. Most NMR studies have been conducted in large animals (often under anesthesia) because the mass of the target organ is a limiting factor for NMR. Yet, despite the challengingly small size of the mouse brain, NMR studies are highly desirable because the mouse constitutes a common animal model for human neurological disorders. We have developed a method for the ex vivo resolution of NMR multiplets arising from the brain of an awake mouse after the infusion of [1,6-(13)C(2)]glucose. NMR spectra obtained by this method display favorable signal-to-noise ratios. With this infusion protocol, the (13)C multiplets of glutamate, glutamine, GABA and aspartate achieved steady state after 150 min. The method enables the accurate resolution of multiplets over time in the awake mouse brain. We anticipate that this method can be broadly applicable to compute brain fluxes in normal and transgenic mouse models of neurological disorders.
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Affiliation(s)
- Isaac Marin-Valencia
- Rare Brain Disorders Clinic and Research Laboratory, Department of Neurology and Neurotherapeutics, The University of Texas Southwestern Medical Center, 5323 Harry Hines Boulevard, Dallas, TX 75390, USA
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Mangia S, Liimatainen T, Garwood M, Tkac I, Henry PG, Deelchand D, Michaeli S. Frequency offset dependence of adiabatic rotating frame relaxation rate constants: relevance to MRS investigations of metabolite dynamics in vivo. NMR IN BIOMEDICINE 2011; 24:807-14. [PMID: 21264976 PMCID: PMC3121927 DOI: 10.1002/nbm.1626] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/01/2010] [Revised: 07/16/2010] [Accepted: 09/21/2010] [Indexed: 05/24/2023]
Abstract
In this work, we investigated the frequency-offset dependence of the rotating frame longitudinal (R(1ρ)) and transverse (R(2ρ)) relaxation rate constants when using hyperbolic-secant adiabatic full passage pulses or continuous-wave spin-lock irradiation. Phantom and in vivo measurements were performed to validate theoretical predictions of the dominant relaxation mechanisms existing during adiabatic full passage pulses when using different settings of the frequency offset relative to the carrier. In addition, adiabatic R(1ρ) and R(2ρ) values of total creatine and N-acetylaspartate were measured in vivo from the human brain at 4 T. When the continuous-wave pulse power was limited to safe specific absorption rates for humans, simulations revealed a strong dependence of R(1ρ) and R(2ρ) values on the frequency offset for both dipolar interactions and anisochronous exchange mechanisms. By contrast, theoretical and experimental results showed adiabatic R(1ρ) and R(2ρ) values to be practically invariant within the large subregion of the bandwidth of the hyperbolic-secant pulse where complete inversion was achieved. However, adiabatic R(1ρ) and R(2ρ) values of the methyl protons of total creatine (at 3.03 ppm) were almost doubled when compared with those of the methyl protons of N-acetylaspartate (at 2.01 ppm) in spite of the fact that these resonances were in the flat region of the inversion band of the adiabatic full passage pulses. We conclude that differences in adiabatic R(1ρ) and R(2ρ) values of human brain metabolites are not a result of their chemical shifts, but instead reflect differences in dynamics.
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Affiliation(s)
- Silvia Mangia
- Center for Magnetic Resonance Research and Department of Radiology, University of Minnesota School of Medicine, Minneapolis, MN 55455, USA.
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Altered 13C glucose metabolism in the cortico-striato-thalamo-cortical loop in the MK-801 rat model of schizophrenia. J Cereb Blood Flow Metab 2011; 31:976-85. [PMID: 21081956 PMCID: PMC3063632 DOI: 10.1038/jcbfm.2010.193] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
Using a modified MK-801 (dizocilpine) N-methyl-D-aspartic acid (NMDA) receptor hypofunction model for schizophrenia, we analyzed glycolysis, as well as glutamatergic, GABAergic, and monoaminergic neurotransmitter synthesis and degradation. Rats received an injection of MK-801 daily for 6 days and on day 6, they also received an injection of [1-(13)C]glucose. Extracts of frontal cortex (FCX), parietal and temporal cortex (PTCX), thalamus, striatum, nucleus accumbens (NAc), and hippocampus were analyzed using (13)C nuclear magnetic resonance spectroscopy, high-performance liquid chromatography, and gas chromatography-mass spectrometry. A pronounced reduction in glycolysis was found only in PTCX, in which (13)C labeling of glucose, lactate, and alanine was decreased. (13)C enrichment in lactate, however, was reduced in all areas investigated. The largest reductions in glutamate labeling were detected in FCX and PTCX, whereas in hippocampus, striatum, and Nac, (13)C labeling of glutamate was only slightly but significantly reduced. The thalamus was the only region with unaffected glutamate labeling. γ-Aminobutyric acid (GABA) labeling was reduced in all areas, but most significantly in FCX. Glutamine and aspartate labeling was unchanged. Mitochondrial metabolites were also affected. Fumarate labeling was reduced in FCX and thalamus, whereas malate labeling was reduced in FCX, PTCX, striatum, and NAc. Dopamine turnover was decreased in FCX and thalamus, whereas that of serotonin was unchanged in all regions. In conclusion, neurotransmitter metabolism in the cortico-striato-thalamo-cortical loop is severely impaired in the MK-801 (dizocilpine) NMDA receptor hypofunction animal model for schizophrenia.
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21
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Gamcsik MP, Clark MD, Ludeman SM, Springer JB, D'Alessandro MA, Simpson NE, Pourdeyhimi R, Johnson CB, Teeter SD, Blackband SJ, Thelwall PE. Non-invasive monitoring of L-2-oxothiazolidine-4-carboxylate metabolism in the rat brain by in vivo 13C magnetic resonance spectroscopy. Neurochem Res 2010; 36:443-51. [PMID: 21161591 DOI: 10.1007/s11064-010-0362-5] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 12/04/2010] [Indexed: 12/01/2022]
Abstract
The cysteine precursor L-2-oxothiazolidine-4-carboxylate (OTZ, procysteine) can raise cysteine concentration, and thus glutathione levels, in some tissues. OTZ has therefore been proposed as a prodrug for combating oxidative stress. We have synthesized stable isotope labeled OTZ (i.e. L-2-oxo-[5-(13)C]-thiazolidine-4-carboxylate, (13)C-OTZ) and tracked its uptake and metabolism in vivo in rat brain by (13)C magnetic resonance spectroscopy. Although uptake and clearance of (13)C-OTZ was detectable in rat brain following a bolus dose by in vivo spectroscopy, no incorporation of isotope label into brain glutathione was detectable. Continuous infusion of (13)C-OTZ over 20 h, however, resulted in (13)C-label incorporation into glutathione, taurine, hypotaurine and lactate at levels sufficient for detection by in vivo magnetic resonance spectroscopy. Examination of brain tissue extracts by mass spectrometry confirmed only low levels of isotope incorporation into glutathione in rats treated with a bolus dose and much higher levels after 20 h of continuous infusion. In contrast to some previous studies, bolus administration of OTZ did not alter brain glutathione levels. Even a continuous infusion of OTZ over 20 h failed to raise brain glutathione levels. These studies demonstrate the utility of in vivo magnetic resonance for non-invasive monitoring of antioxidant uptake and metabolism in intact brain. These types of experiments can be used to evaluate the efficacy of various interventions for maintenance of brain glutathione.
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Affiliation(s)
- Michael P Gamcsik
- UNC/NCSU Joint Department of Biomedical Engineering, Campus Box 7115, Raleigh, NC 27695, USA.
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22
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Choi IY, Lee SP, Denney DR, Lynch SG. Lower levels of glutathione in the brains of secondary progressive multiple sclerosis patients measured by 1H magnetic resonance chemical shift imaging at 3 T. Mult Scler 2010; 17:289-96. [PMID: 20921235 DOI: 10.1177/1352458510384010] [Citation(s) in RCA: 79] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Abstract
BACKGROUND Disability levels for patients with secondary progressive multiple sclerosis (SPMS) often worsen despite a stable MRI T(2) lesion burden. The presence of oxidative stress in the absence of measurable inflammation could help explain this phenomenon. In this study, the assessment of an in vivo marker of oxidative stress, cerebral glutathione (GSH), using magnetic resonance chemical shift imaging (CSI) is described, and GSH levels were compared in patients with SPMS and healthy controls. OBJECTIVE To assess whether GSH, a key antioxidant in the brain, is lower in the SPMS patients compared to matched controls. METHODS Seventeen patients with SPMS (Expanded Disability Status Scale=4.0-7.0; length of MS diagnosis=19.4 ± 7 years) and 17 age- and gender-matched healthy controls were studied. GSH levels were measured in the fronto-parietal regions of the brain using a specially designed magnetic resonance spectroscopy technique, CSI of GSH, at 3T. RESULTS The levels of GSH were lower for SPMS patients than for controls, the largest reduction (18.5%) being in the frontal region (p=0.001). CONCLUSION The lower GSH levels in these patients indicate the presence of oxidative stress in SPMS. This process could be at least partially responsible for ongoing functional decline in SPMS.
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Affiliation(s)
- I-Y Choi
- Hoglund Brain Imaging Center, Department of Neurology, University of Kansas Medical Center, Kansas City, KS 66160, USA.
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Brennan BP, Hudson JI, Jensen JE, McCarthy J, Roberts JL, Prescot AP, Cohen BM, Pope HG, Renshaw PF, Öngür D. Rapid enhancement of glutamatergic neurotransmission in bipolar depression following treatment with riluzole. Neuropsychopharmacology 2010; 35:834-46. [PMID: 19956089 PMCID: PMC3055603 DOI: 10.1038/npp.2009.191] [Citation(s) in RCA: 113] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
Glutamatergic abnormalities may underlie bipolar disorder (BD). The glutamate-modulating drug riluzole may be efficacious in bipolar depression, but few in vivo studies have examined its effect on glutamatergic neurotransmission. We conducted an exploratory study of the effect of riluzole on brain glutamine/glutamate (Gln/Glu) ratios and levels of N-acetylaspartate (NAA). We administered open-label riluzole 100-200 mg daily for 6 weeks to 14 patients with bipolar depression and obtained imaging data from 8-cm(3) voxels in the anterior cingulate cortex (ACC) and parieto-occipital cortex (POC) at baseline, day 2, and week 6 of treatment, using two-dimensional J-resolved proton magnetic resonance spectroscopy at 4 T. Imaging data were analyzed using the spectral-fitting package, LCModel; statistical analysis used random effects mixed models. Riluzole significantly reduced Hamilton Depression Rating Scale (HAM-D) scores (d=3.4; p<0.001). Gln/Glu ratios increased significantly by day 2 of riluzole treatment (Cohen's d=1.2; p=0.023). NAA levels increased significantly from baseline to week 6 (d=1.2; p=0.035). Reduction in HAM-D scores was positively associated with increases in NAA from baseline to week 6 in the ACC (d=1.4; p=0.053), but was negatively associated in the POC (d=9.6; p<0.001). Riluzole seems to rapidly increase Gln/Glu ratios-suggesting increased glutamate-glutamine cycling, which may subsequently enhance neuronal plasticity and reduce depressive symptoms. Further investigation of the Gln/Glu ratio as a possible early biomarker of response to glutamate-modulating therapies is warranted.
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Affiliation(s)
- Brian P Brennan
- Biological Psychiatry Laboratory, McLean Hospital, Belmont, MA 02478, USA.
| | - James I Hudson
- Biological Psychiatry Laboratory, McLean Hospital, Belmont, MA, USA,Department of Psychiatry, Harvard Medical School, Boston, MA, USA
| | - J Eric Jensen
- Department of Psychiatry, Harvard Medical School, Boston, MA, USA,Brain Imaging Center, McLean Hospital, Belmont, MA, USA
| | - Julie McCarthy
- Schizophrenia and Bipolar Disorder Program, McLean Hospital, Belmont, MA, USA
| | | | - Andrew P Prescot
- The Brain Institute, University of Utah School of Medicine, Salt Lake City, UT, USA
| | - Bruce M Cohen
- Department of Psychiatry, Harvard Medical School, Boston, MA, USA,Shervert Frazier Research Institute, McLean Hospital, Belmont, MA, USA
| | - Harrison G Pope
- Biological Psychiatry Laboratory, McLean Hospital, Belmont, MA, USA,Department of Psychiatry, Harvard Medical School, Boston, MA, USA
| | - Perry F Renshaw
- The Brain Institute, University of Utah School of Medicine, Salt Lake City, UT, USA
| | - Dost Öngür
- Department of Psychiatry, Harvard Medical School, Boston, MA, USA,Shervert Frazier Research Institute, McLean Hospital, Belmont, MA, USA,Schizophrenia and Bipolar Disorder Program, McLean Hospital, Belmont, MA, USA
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24
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Abstract
Acetate, a glial-specific substrate, is an attractive alternative to glucose for the study of neuronal-glial interactions. The present study investigates the kinetics of acetate uptake and utilization in the rat brain in vivo during infusion of [2-13C]acetate using NMR spectroscopy. When plasma acetate concentration was increased, the rate of brain acetate utilization (CMR(ace)) increased progressively and reached close to saturation for plasma acetate concentration > 2-3 mM, whereas brain acetate concentration continued to increase. The Michaelis-Menten constant for brain acetate utilization (K(M)(util) = 0.01 +/- 0.14 mM) was much smaller than for acetate transport through the blood-brain barrier (BBB) (K(M)(t) = 4.18 +/- 0.83 mM). The maximum transport capacity of acetate through the BBB (V(max)(t) = 0.96 +/- 0.18 micromol/g/min) was nearly twofold higher than the maximum rate of brain acetate utilization (V(max)(util) = 0.50 +/- 0.08 micromol/g/min). We conclude that, under our experimental conditions, brain acetate utilization is saturated when plasma acetate concentrations increase above 2-3 mM. At such high plasma acetate concentration, the rate-limiting step for glial acetate metabolism is not the BBB, but occurs after entry of acetate into the brain.
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Affiliation(s)
- Dinesh K Deelchand
- Center for Magnetic Resonance Research, Department of Radiology, University of Minnesota Medical School, Minneapolis, Minnesota 55455, USA.
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25
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Morgenthaler FD, Lanz BR, Petit JM, Frenkel H, Magistretti PJ, Gruetter R. Alteration of brain glycogen turnover in the conscious rat after 5h of prolonged wakefulness. Neurochem Int 2009; 55:45-51. [PMID: 19428806 DOI: 10.1016/j.neuint.2009.02.023] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2008] [Revised: 02/23/2009] [Accepted: 02/27/2009] [Indexed: 02/04/2023]
Abstract
Although glycogen (Glyc) is the main carbohydrate storage component, the role of Glyc in the brain during prolonged wakefulness is not clear. The aim of this study was to determine brain Glyc concentration ([]) and turnover time (tau) in euglycemic conscious and undisturbed rats, compared to rats maintained awake for 5h. To measure the metabolism of [1-(13)C]-labeled Glc into Glyc, 23 rats received a [1-(13)C]-labeled Glc solution as drink (10% weight per volume in tap water) ad libitum as their sole source of exogenous carbon for a "labeling period" of either 5h (n=13), 24h (n=5) or 48 h (n=5). Six of the rats labeled for 5h were continuously maintained awake by acoustic, tactile and olfactory stimuli during the labeling period, which resulted in slightly elevated corticosterone levels. Brain [Glyc] measured biochemically after focused microwave fixation in the rats maintained awake (3.9+/-0.2 micromol/g, n=6) was not significantly different from that of the control group (4.0+/-0.1 micromol/g, n=7; t-test, P>0.5). To account for potential variations in plasma Glc isotopic enrichment (IE), Glyc IE was normalized by N-acetyl-aspartate (NAA) IE. A simple mathematical model was developed to derive brain Glyc turnover time as 5.3h with a fit error of 3.2h and NAA turnover time as 15.6h with a fit error of 6.5h, in the control rats. A faster tau(Glyc) (2.9h with a fit error of 1.2h) was estimated in the rats maintained awake for 5h. In conclusion, 5h of prolonged wakefulness mainly activates glycogen metabolism, but has minimal effect on brain [Glyc].
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Affiliation(s)
- Florence D Morgenthaler
- Centre d'Imagerie Biomédicale, Ecole Polytechnique Fédérale de Lausanne, Lausanne, Switzerland.
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26
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Xin L, Frenkel H, Mlynárik V, Morgenthaler FD, Gruetter R. Selective resonance suppression1H-[13C] NMR spectroscopy with asymmetric adiabatic RF pulses. Magn Reson Med 2009; 61:260-6. [DOI: 10.1002/mrm.21829] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
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27
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Xu S, Yang J, Shen J. Measuring N-acetylaspartate synthesis in vivo using proton magnetic resonance spectroscopy. J Neurosci Methods 2008; 172:8-12. [PMID: 18486230 DOI: 10.1016/j.jneumeth.2008.04.001] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2007] [Revised: 03/31/2008] [Accepted: 04/01/2008] [Indexed: 11/28/2022]
Abstract
N-Acetylaspartate (NAA) is an important marker of neuronal function and viability that can be measured using magnetic resonance spectroscopy (MRS). In this paper, we proposed a method to measure NAA synthesis using proton MRS with infusion of uniformly (13)C-labeled glucose, and demonstrated its feasibility in an in vivo study of the rat brain. The rate of (13)C-label incorporation into the acetyl group of NAA was measured using a localized, long echo-time proton MRS method. Signals from the (13)C satellites of the main NAA methyl protons at 2.02 ppm were continuously monitored for 10h. Quantification of the data based on a linear kinetic model showed that NAA synthesis rate in isoflurane-anesthetized rats was 0.19+/-0.02 micromol/g/h (mean+/-standard deviation, n=12).
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Affiliation(s)
- Su Xu
- Molecular Imaging Branch, National Institute of Mental Health, 9000 Rockville Pike, Bethesda, MD 20892-1527, USA.
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28
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Satrústegui J, Contreras L, Ramos M, Marmol P, del Arco A, Saheki T, Pardo B. Role of aralar, the mitochondrial transporter of aspartate-glutamate, in brain N-acetylaspartate formation and Ca(2+) signaling in neuronal mitochondria. J Neurosci Res 2008; 85:3359-66. [PMID: 17497669 DOI: 10.1002/jnr.21299] [Citation(s) in RCA: 54] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Aralar, the Ca(2+)-dependent mitochondrial aspartate-glutamate carrier expressed in brain and skeletal muscle, is a member of the malate-aspartate NADH shuttle. Disrupting the gene for aralar, SLC25a12, in mice has enabled the discovery of two new roles of this carrier. On the one hand, it is required for synthesis of brain aspartate and N-acetylaspartate, a neuron-born metabolite that supplies acetate for myelin lipid synthesis; and on the other, it is essential for the transmission of small Ca(2+) signals to mitochondria via an increase in mitochondrial NADH.
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Affiliation(s)
- Jorgina Satrústegui
- Departamento de Biología Molecular, Centro de Biología Molecular Severo Ochoa, Facultad de Ciencias, Universidad Autónoma, 28049, Cantoblanco, Madrid, Spain
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29
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Uffmann K, Gruetter R. Mathematical modeling of (13)C label incorporation of the TCA cycle: the concept of composite precursor function. J Neurosci Res 2008; 85:3304-17. [PMID: 17600827 DOI: 10.1002/jnr.21392] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
A novel approach for the mathematical modeling of (13)C label incorporation into amino acids via the TCA cycle that eliminates the explicit calculation of the labeling of the TCA cycle intermediates is described, resulting in one differential equation per measurable time course of labeled amino acid. The equations demonstrate that both glutamate C4 and C3 labeling depend in a predictable manner on both transmitochondrial exchange rate, V(X), and TCA cycle rate, V(TCA). For example, glutamate C4 labeling alone does not provide any information on either V(X) or V(TCA) but rather a composite "flux". Interestingly, glutamate C3 simultaneously receives label not only from pyruvate C3 but also from glutamate C4, described by composite precursor functions that depend in a probabilistic way on the ratio of V(X) to V(TCA): An initial rate of labeling of glutamate C3 (or C2) being close to zero is indicative of a high V(X)/V(TCA). The derived analytical solution of these equations shows that, when the labeling of the precursor pool pyruvate reaches steady state quickly compared with the turnover rate of the measured amino acids, instantaneous labeling can be assumed for pyruvate. The derived analytical solution has acceptable errors compared with experimental uncertainty, thus obviating precise knowledge on the labeling kinetics of the precursor. In conclusion, a substantial reformulation of the modeling of label flow via the TCA cycle turnover into the amino acids is presented in the current study. This approach allows one to determine metabolic rates by fitting explicit mathematical functions to measured time courses.
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Affiliation(s)
- Kai Uffmann
- Laboratory of Functional and Metabolic Imaging, Ecole Polytechnique Fédérale de Lausanne, Lausanne, Switzerland.
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30
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Gomes WA, Lado FA, de Lanerolle NC, Takahashi K, Pan C, Hetherington HP. Spectroscopic imaging of the pilocarpine model of human epilepsy suggests that early NAA reduction predicts epilepsy. Magn Reson Med 2007; 58:230-5. [PMID: 17654595 DOI: 10.1002/mrm.21310] [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: 11/12/2022]
Abstract
Reduced hippocampal N-acetyl aspartate (NAA) is commonly observed in patients with advanced, chronic temporal lobe epilepsy (TLE). It is unclear, however, whether an NAA deficit is also present during the clinically quiescent latent period that characterizes early TLE. This question has important implications for the use of MR spectroscopic imaging (MRSI) in the early identification of patients at risk for TLE. To determine whether NAA is diminished during the latent period, we obtained high-resolution (1)H spectroscopic imaging during the latent period of the rat pilocarpine model of human TLE. We used actively detuneable surface reception and volume transmission coils to enhance sensitivity and a semiautomated voxel shifting method to accurately position voxels within the hippocampi. During the latent period, 2 and 7 d following pilocarpine treatment, hippocampal NAA was significantly reduced by 27.5 +/- 6.9% (P < 0.001) and 17.3 +/- 6.9% (P < 0.001) at 2 and 7 d, respectively. Quantitative estimates of neuronal loss at 7 d (2.3 +/- 7.7% reduction; P = 0.58, not significant) demonstrate that the NAA deficit is not due to neuron loss and therefore likely represents metabolic impairment of hippocampal neurons during the latent phase. Therefore, spectroscopic imaging provides an early marker for metabolic dysfunction in this model of TLE.
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Affiliation(s)
- W A Gomes
- Department of Radiology, Montefiore Medical Center, Bronx, New York 10467, USA.
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31
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Choi JK, Dedeoglu A, Jenkins BG. Application of MRS to mouse models of neurodegenerative illness. NMR IN BIOMEDICINE 2007; 20:216-37. [PMID: 17451183 DOI: 10.1002/nbm.1145] [Citation(s) in RCA: 95] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/15/2023]
Abstract
The rapid development of transgenic mouse models of neurodegenerative diseases, in parallel with the rapidly expanding growth of MR techniques for assessing in vivo, non-invasive, neurochemistry, offers the potential to develop novel markers of disease progression and therapy. In this review we discuss the interpretation and utility of MRS for the study of these transgenic mouse and rodent models of neurodegenerative diseases such as Alzheimer's (AD), Huntington's (HD) and Parkinson's disease (PD). MRS studies can provide a wealth of information on various facets of in vivo neurochemistry, including neuronal health, gliosis, osmoregulation, energy metabolism, neuronal-glial cycling, and molecular synthesis rates. These data provide information on the etiology, natural history and therapy of these diseases. Mouse models enable longitudinal studies with useful time frames for evaluation of neuroprotection and therapeutic interventions using many of the potential MRS markers. In addition, the ability to manipulate the genome in these models allows better mechanistic understanding of the roles of the observable neurochemicals, such as N-acetylaspartate, in the brain. The argument is made that use of MRS, combined with correlative histology and other MRI techniques, will enable objective markers with which potential therapies can be followed in a quantitative fashion.
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Affiliation(s)
- Ji-Kyung Choi
- Department of Radiology, Athinoula A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital and Harvard Medical School, Charlestown, MA 02129, USA
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32
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Moffett JR, Ross B, Arun P, Madhavarao CN, Namboodiri AMA. N-Acetylaspartate in the CNS: from neurodiagnostics to neurobiology. Prog Neurobiol 2007; 81:89-131. [PMID: 17275978 PMCID: PMC1919520 DOI: 10.1016/j.pneurobio.2006.12.003] [Citation(s) in RCA: 977] [Impact Index Per Article: 57.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2006] [Revised: 12/07/2006] [Accepted: 12/11/2006] [Indexed: 01/02/2023]
Abstract
The brain is unique among organs in many respects, including its mechanisms of lipid synthesis and energy production. The nervous system-specific metabolite N-acetylaspartate (NAA), which is synthesized from aspartate and acetyl-coenzyme A in neurons, appears to be a key link in these distinct biochemical features of CNS metabolism. During early postnatal central nervous system (CNS) development, the expression of lipogenic enzymes in oligodendrocytes, including the NAA-degrading enzyme aspartoacylase (ASPA), is increased along with increased NAA production in neurons. NAA is transported from neurons to the cytoplasm of oligodendrocytes, where ASPA cleaves the acetate moiety for use in fatty acid and steroid synthesis. The fatty acids and steroids produced then go on to be used as building blocks for myelin lipid synthesis. Mutations in the gene for ASPA result in the fatal leukodystrophy Canavan disease, for which there is currently no effective treatment. Once postnatal myelination is completed, NAA may continue to be involved in myelin lipid turnover in adults, but it also appears to adopt other roles, including a bioenergetic role in neuronal mitochondria. NAA and ATP metabolism appear to be linked indirectly, whereby acetylation of aspartate may facilitate its removal from neuronal mitochondria, thus favoring conversion of glutamate to alpha ketoglutarate which can enter the tricarboxylic acid cycle for energy production. In its role as a mechanism for enhancing mitochondrial energy production from glutamate, NAA is in a key position to act as a magnetic resonance spectroscopy marker for neuronal health, viability and number. Evidence suggests that NAA is a direct precursor for the enzymatic synthesis of the neuron specific dipeptide N-acetylaspartylglutamate, the most concentrated neuropeptide in the human brain. Other proposed roles for NAA include neuronal osmoregulation and axon-glial signaling. We propose that NAA may also be involved in brain nitrogen balance. Further research will be required to more fully understand the biochemical functions served by NAA in CNS development and activity, and additional functions are likely to be discovered.
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Affiliation(s)
- John R Moffett
- Department of Anatomy, Physiology and Genetics, Uniformed Services University of the Health Sciences, Building C, 4301 Jones Bridge Rd., Bethesda, MD 20814, USA.
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33
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Li S, Shen J. Integrated RF probe for in vivo multinuclear spectroscopy and functional imaging of rat brain using an 11.7 Tesla 89 mm bore vertical microimager. MAGNETIC RESONANCE MATERIALS IN PHYSICS BIOLOGY AND MEDICINE 2005; 18:119-27. [PMID: 16007474 DOI: 10.1007/s10334-005-0103-y] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/03/2005] [Revised: 03/21/2005] [Accepted: 04/15/2005] [Indexed: 11/27/2022]
Abstract
To acquire high quality in vivo NMR data from rat brain using a vertical 89-mm bore magnet, specially designed NMR probes with integrated RF coils and animal handling capability are required. An RF probe design that is also capable of rat head fixation, body support and suitable for physiology monitoring and maintenance was constructed for an 89 mm bore, 11.7 T, vertical microimager which is equipped with a 57-mm i.d. gradient insert. Design concept and practical aspects of probe construction are described in detail. The device allows accurate and highly reproducible positioning of rat head inside the magnet while providing excellent RF performance. Typical results from fMRI, localized in vivo proton and multinuclear spectroscopy using this probe system are presented.
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Affiliation(s)
- S Li
- NIMH Magnetic Resonance Spectroscopy Core Facility, National Institute of Mental Health, National Institute of Health, 9000 Rockville Pike, Bethesda, MD 20892-1527, USA
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