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Juras JA, Webb MB, Young LE, Markussen KH, Hawkinson TR, Buoncristiani MD, Bolton KE, Coburn PT, Williams MI, Sun LP, Sanders WC, Bruntz RC, Conroy LR, Wang C, Gentry MS, Smith BN, Sun RC. In situ microwave fixation provides an instantaneous snapshot of the brain metabolome. CELL REPORTS METHODS 2023; 3:100455. [PMID: 37159672 PMCID: PMC10163000 DOI: 10.1016/j.crmeth.2023.100455] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 10/19/2022] [Revised: 02/14/2023] [Accepted: 03/27/2023] [Indexed: 05/11/2023]
Abstract
Brain glucose metabolism is highly heterogeneous among brain regions and continues postmortem. In particular, we demonstrate exhaustion of glycogen and glucose and an increase in lactate production during conventional rapid brain resection and preservation by liquid nitrogen. In contrast, we show that these postmortem changes are not observed with simultaneous animal sacrifice and in situ fixation with focused, high-power microwave. We further employ microwave fixation to define brain glucose metabolism in the mouse model of streptozotocin-induced type 1 diabetes. Using both total pool and isotope tracing analyses, we identified global glucose hypometabolism in multiple brain regions, evidenced by reduced 13C enrichment into glycogen, glycolysis, and the tricarboxylic acid (TCA) cycle. Reduced glucose metabolism correlated with a marked decrease in GLUT2 expression and several metabolic enzymes in unique brain regions. In conclusion, our study supports the incorporation of microwave fixation for more accurate studies of brain metabolism in rodent models.
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Affiliation(s)
- Jelena A. Juras
- Department of Neuroscience, University of Kentucky, College of Medicine, Lexington, KY 40536, USA
| | - Madison B. Webb
- Department of Molecular and Cellular Biochemistry, University of Kentucky, College of Medicine, Lexington, KY 40536, USA
| | - Lyndsay E.A. Young
- Department of Molecular and Cellular Biochemistry, University of Kentucky, College of Medicine, Lexington, KY 40536, USA
- Markey Cancer Center, University of Kentucky, Lexington, KY 40536, USA
| | - Kia H. Markussen
- Department of Molecular and Cellular Biochemistry, University of Kentucky, College of Medicine, Lexington, KY 40536, USA
| | - Tara R. Hawkinson
- Department of Neuroscience, University of Kentucky, College of Medicine, Lexington, KY 40536, USA
- Department of Biochemistry and Molecular Biology, University of Florida, College of Medicine, Gainesville, FL 32611, USA
| | - Michael D. Buoncristiani
- Department of Neuroscience, University of Kentucky, College of Medicine, Lexington, KY 40536, USA
| | - Kayli E. Bolton
- Department of Molecular and Cellular Biochemistry, University of Kentucky, College of Medicine, Lexington, KY 40536, USA
| | - Peyton T. Coburn
- Department of Molecular and Cellular Biochemistry, University of Kentucky, College of Medicine, Lexington, KY 40536, USA
| | - Meredith I. Williams
- Department of Molecular and Cellular Biochemistry, University of Kentucky, College of Medicine, Lexington, KY 40536, USA
| | - Lisa P.Y. Sun
- Department of Neuroscience, University of Kentucky, College of Medicine, Lexington, KY 40536, USA
- Markey Cancer Center, University of Kentucky, Lexington, KY 40536, USA
| | - William C. Sanders
- Department of Molecular and Cellular Biochemistry, University of Kentucky, College of Medicine, Lexington, KY 40536, USA
| | - Ronald C. Bruntz
- Department of Molecular and Cellular Biochemistry, University of Kentucky, College of Medicine, Lexington, KY 40536, USA
| | - Lindsey R. Conroy
- Department of Neuroscience, University of Kentucky, College of Medicine, Lexington, KY 40536, USA
- Markey Cancer Center, University of Kentucky, Lexington, KY 40536, USA
| | - Chi Wang
- Markey Cancer Center, University of Kentucky, Lexington, KY 40536, USA
- Division of Biostatics, Department of Internal Medicine, University of Kentucky, College of Medicine, Lexington, KY 40536, USA
| | - Matthew S. Gentry
- Department of Molecular and Cellular Biochemistry, University of Kentucky, College of Medicine, Lexington, KY 40536, USA
- Markey Cancer Center, University of Kentucky, Lexington, KY 40536, USA
- Department of Biochemistry and Molecular Biology, University of Florida, College of Medicine, Gainesville, FL 32611, USA
- Center for Advanced Spatial Biomolecule Research, University of Florida, College of Medicine, Gainesville, FL 32611, USA
| | - Bret N. Smith
- Department of Neuroscience, University of Kentucky, College of Medicine, Lexington, KY 40536, USA
- Department of Biomedical Sciences, Colorado State University, Fort Collins, CO 80523, USA
| | - Ramon C. Sun
- Department of Neuroscience, University of Kentucky, College of Medicine, Lexington, KY 40536, USA
- Markey Cancer Center, University of Kentucky, Lexington, KY 40536, USA
- Department of Biochemistry and Molecular Biology, University of Florida, College of Medicine, Gainesville, FL 32611, USA
- Center for Advanced Spatial Biomolecule Research, University of Florida, College of Medicine, Gainesville, FL 32611, USA
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2
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Rafiee Z, García-Serrano AM, Duarte JMN. Taurine Supplementation as a Neuroprotective Strategy upon Brain Dysfunction in Metabolic Syndrome and Diabetes. Nutrients 2022; 14:1292. [PMID: 35334949 PMCID: PMC8952284 DOI: 10.3390/nu14061292] [Citation(s) in RCA: 34] [Impact Index Per Article: 17.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2022] [Revised: 03/14/2022] [Accepted: 03/15/2022] [Indexed: 02/07/2023] Open
Abstract
Obesity, type 2 diabetes, and their associated comorbidities impact brain metabolism and function and constitute risk factors for cognitive impairment. Alterations to taurine homeostasis can impact a number of biological processes, such as osmolarity control, calcium homeostasis, and inhibitory neurotransmission, and have been reported in both metabolic and neurodegenerative disorders. Models of neurodegenerative disorders show reduced brain taurine concentrations. On the other hand, models of insulin-dependent diabetes, insulin resistance, and diet-induced obesity display taurine accumulation in the hippocampus. Given the possible cytoprotective actions of taurine, such cerebral accumulation of taurine might constitute a compensatory mechanism that attempts to prevent neurodegeneration. The present article provides an overview of brain taurine homeostasis and reviews the mechanisms by which taurine can afford neuroprotection in individuals with obesity and diabetes. We conclude that further research is needed for understanding taurine homeostasis in metabolic disorders with an impact on brain function.
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Affiliation(s)
- Zeinab Rafiee
- Department of Experimental Medical Science, Faculty of Medicine, Lund University, 22100 Lund, Sweden; (Z.R.); (A.M.G.-S.)
- Wallenberg Centre for Molecular Medicine, Lund University, 22100 Lund, Sweden
| | - Alba M. García-Serrano
- Department of Experimental Medical Science, Faculty of Medicine, Lund University, 22100 Lund, Sweden; (Z.R.); (A.M.G.-S.)
- Wallenberg Centre for Molecular Medicine, Lund University, 22100 Lund, Sweden
| | - João M. N. Duarte
- Department of Experimental Medical Science, Faculty of Medicine, Lund University, 22100 Lund, Sweden; (Z.R.); (A.M.G.-S.)
- Wallenberg Centre for Molecular Medicine, Lund University, 22100 Lund, Sweden
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3
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Abstract
Renal diseases remain devastating illnesses with unacceptably high rates of mortality and morbidity worldwide. Animal models are essential tools to better understand the pathomechanism of kidney-related illnesses and to develop new, successful therapeutic strategies. Magnetic resonance imaging (MRI) has been actively explored in the last decades for assessing renal function, perfusion, tissue oxygenation as well as the degree of fibrosis and inflammation. This chapter aims to provide an overview of the preparation and monitoring of small animals before, during, and after surgical interventions or MR imaging. Standardization of experimental settings such as body temperature or hydration of animals and minimizing pain and distress are essential for diminishing nonexperimental variables as well as for conducting ethical research.This publication is based upon work from the COST Action PARENCHIMA, a community-driven network funded by the European Cooperation in Science and Technology (COST) program of the European Union, which aims to improve the reproducibility and standardization of renal MRI biomarkers.
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4
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Lanz B, Abaei A, Braissant O, Choi IY, Cudalbu C, Henry PG, Gruetter R, Kara F, Kantarci K, Lee P, Lutz NW, Marjańska M, Mlynárik V, Rasche V, Xin L, Valette J. Magnetic resonance spectroscopy in the rodent brain: Experts' consensus recommendations. NMR IN BIOMEDICINE 2020; 34:e4325. [PMID: 33565219 PMCID: PMC9429976 DOI: 10.1002/nbm.4325] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/11/2019] [Revised: 03/29/2020] [Accepted: 04/30/2020] [Indexed: 05/21/2023]
Abstract
In vivo MRS is a non-invasive measurement technique used not only in humans, but also in animal models using high-field magnets. MRS enables the measurement of metabolite concentrations as well as metabolic rates and their modifications in healthy animals and disease models. Such data open the way to a deeper understanding of the underlying biochemistry, related disturbances and mechanisms taking place during or prior to symptoms and tissue changes. In this work, we focus on the main preclinical 1H, 31P and 13C MRS approaches to study brain metabolism in rodent models, with the aim of providing general experts' consensus recommendations (animal models, anesthesia, data acquisition protocols). An overview of the main practical differences in preclinical compared with clinical MRS studies is presented, as well as the additional biochemical information that can be obtained in animal models in terms of metabolite concentrations and metabolic flux measurements. The properties of high-field preclinical MRS and the technical limitations are also described.
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Affiliation(s)
- Bernard Lanz
- Laboratory for Functional and Metabolic Imaging (LIFMET), Ecole Polytechnique Fédérale de Lausanne, Lausanne, Switzerland
- Sir Peter Mansfield Imaging Centre, School of Medicine, University of Nottingham, Nottingham, United Kingdom
| | - Alireza Abaei
- Core Facility Small Animal Imaging, Ulm University, Ulm, Germany
| | - Olivier Braissant
- Service of Clinical Chemistry, University of Lausanne and University Hospital of Lausanne, Lausanne, Switzerland
| | - In-Young Choi
- Department of Neurology, University of Kansas Medical Center, Kansas City, Kansas, US
| | - Cristina Cudalbu
- Centre d'Imagerie Biomedicale (CIBM), Ecole Polytechnique Fédérale de Lausanne (EPFL), Lausanne, Switzerland
| | - Pierre-Gilles Henry
- Center for Magnetic Resonance Research, Department of Radiology, University of Minnesota, Minneapolis, Minnesota, US
| | - Rolf Gruetter
- Laboratory for Functional and Metabolic Imaging (LIFMET), Ecole Polytechnique Fédérale de Lausanne, Lausanne, Switzerland
| | - Firat Kara
- Department of Radiology, Mayo Clinic, Rochester, Minnesota, US
| | - Kejal Kantarci
- Department of Radiology, Mayo Clinic, Rochester, Minnesota, US
| | - Phil Lee
- Department of Radiology, University of Kansas Medical Center, Kansas City, Kansas, US
| | - Norbert W Lutz
- CNRS, CRMBM, Aix-Marseille University, Marseille, France
| | - Małgorzata Marjańska
- Center for Magnetic Resonance Research, Department of Radiology, University of Minnesota, Minneapolis, Minnesota, US
| | - Vladimír Mlynárik
- High Field MR Centre, Department of Biomedical Imaging and Image-Guided Therapy, Medical University of Vienna, Vienna, Austria
| | - Volker Rasche
- Core Facility Small Animal Imaging, Ulm University, Ulm, Germany
| | - Lijing Xin
- Centre d'Imagerie Biomedicale (CIBM), Ecole Polytechnique Fédérale de Lausanne (EPFL), Lausanne, Switzerland
| | - Julien Valette
- Commissariat à l'Energie Atomique et aux Energies Alternatives, MIRCen, Fontenay-aux-Roses, France
- Neurodegenerative Diseases Laboratory, Centre National de la Recherche Scientifique, Université Paris-Sud, Université Paris-Saclay, UMR 9199, Fontenay-aux-Roses, France
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5
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Lei H, Gruetter R. Metabolic and perfusion responses to acute hypoglycemia in the rat cortex: A non-invasive magnetic resonance approach. J Neurochem 2020; 154:71-83. [PMID: 32306383 DOI: 10.1111/jnc.15028] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2019] [Revised: 04/10/2020] [Accepted: 04/14/2020] [Indexed: 11/30/2022]
Abstract
Hypoglycemia is critical condition during diabetic treatment that involves intensive insulin therapy, and it may impair brain function. We aimed to compare cortical responses of three hypoglycemic phases and the restoration of glycemia to control levels after a severe episode in rats using non-invasive perfusion magnetic resonance (MR) imaging and localized 1 H MR spectroscopy. Under light α-chloralose anesthesia, cortical blood flow (cCBF) was 42 ± 3 ml/100 g/min at euglycemia (~ 5 mM plasma glucose), was not altered at mild hypoglycemia I (42 ± 4 ml/100 g/min, 2-3.5 mM), increased to 60 ± 8 ml/100 g/min under moderate hypoglycemia II (1-2 mM) and amplified to 190 ± 35 ml/100 g/min at severe hypoglycemia III (< 1 mM). 1 H MRS revealed metabolic changes at hypoglycemia I without any perfusion alteration. At hypoglycemia III, glutamine and glutamate decreased, whereas aspartate increased. When animals subsequently regained glycemic control, not all metabolites returned to their control levels, for example, glutamine. Meanwhile, ascorbate was increased with amplified hypoglycemic severity, whereas glutathione was reduced; these compounds did not return to normal levels upon the restoration of glycemia. Our study is the first to report cCBF and neurochemical changes in cortex upon five glycemic stages. The cortical responses of different hypoglycemic phases would explain variable neuronal damages after hypoglycemia and might help identify the degrees of hypoglycemic insults and further improve alternative therapies.
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Affiliation(s)
- Hongxia Lei
- Animal Imaging Technology (AIT), Center for Biomedical Imaging Research (CIBM), Ecole Polytechnique Federale de Lausanne, Lausanne, Switzerland
| | - Rolf Gruetter
- Animal Imaging Technology (AIT), Center for Biomedical Imaging Research (CIBM), Ecole Polytechnique Federale de Lausanne, Lausanne, Switzerland.,Wuhan United Imaging Life Science Instruments Ltd., Wuhan, P.R.China.,Laboratory of Functional and Metabolic Imaging (LIFMET), Ecole Polytechnique Federale de Lausanne, Lausanne, Switzerland.,Department of Radiology, University of Geneva, Geneva, Switzerland
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6
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Sonnay S, Duarte JMN, Just N, Gruetter R. Energy metabolism in the rat cortex under thiopental anaesthesia measured In Vivo by 13 C MRS. J Neurosci Res 2017; 95:2297-2306. [PMID: 28316083 DOI: 10.1002/jnr.24032] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2016] [Revised: 01/05/2017] [Accepted: 01/16/2017] [Indexed: 01/05/2023]
Abstract
Barbiturates, commonly used as general anaesthetics, depress neuronal activity and thus cerebral metabolism. Moreover, they are likely to disrupt the metabolic support of astrocytes to neurons, as well as the uptake of nutrients from circulation. By employing 13 C magnetic resonance spectroscopy (MRS) in vivo at high magnetic field, we characterized neuronal and astrocytic pathways of energy metabolism in the rat cortex under thiopental anaesthesia. The neuronal tricarboxylic acid (TCA) cycle rate was 0.46 ± 0.02 µmol/g/min, and the rate of the glutamate-glutamine cycle was 0.09 ± 0.02 µmol/g/min. In astrocytes, the TCA cycle rate was 0.16 ± 0.02 µmol/g/min, accounting for a quarter of whole brain glucose oxidation, pyruvate carboxylase rate was 0.02 ± 0.01 µmol/g/min, and glutamine synthetase was 0.12 ± 0.01 µmol/g/min. Relative to previous experiments under light α-chloralose anaesthesia, thiopental reduced oxidative metabolism in neurons and even more so in astrocytes. Interestingly, total oxidative metabolism in the cortex under thiopental anaesthesia surpassed the rate of pyruvate production by glycolysis, indicating substantial utilisation of substrates other than glucose, likely plasma lactate. © 2017 Wiley Periodicals, Inc.
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Affiliation(s)
- Sarah Sonnay
- Laboratory for Functional and Metabolic Imaging, École Polytechnique Fédérale Lausanne, Switzerland
| | - João M N Duarte
- Laboratory for Functional and Metabolic Imaging, École Polytechnique Fédérale Lausanne, Switzerland
| | - Nathalie Just
- Centre d'Imagerie Biomédicale - Animal and Technology Core, Lausanne, Switzerland
| | - Rolf Gruetter
- Laboratory for Functional and Metabolic Imaging, École Polytechnique Fédérale Lausanne, Switzerland.,Department of Radiology, University of Geneva, Switzerland.,Department of Radiology, University of Lausanne, Switzerland
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7
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Yan G, Xuan Y, Dai Z, Zhang G, Xu H, Mikulis D, Wu R. Evolution of blood-brain barrier damage associated with changes in brain metabolites following acute ischemia. Neuroreport 2015; 26:945-51. [PMID: 26366833 DOI: 10.1097/wnr.0000000000000438] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Stroke is a serious medical condition that requires emergency care. In the case of ischemic stroke, ischemia may lead to damage to the blood-brain barrier (BBB); the damage in turn may exacerbate the condition. Therefore, noninvasive detection of BBB damage represents a challenge for experimental and clinical researchers. In this study, we assessed the onset of BBB disruption by means of T1-weighted images with administration of the contrast enhancement agent gadolinium-diethylenetriamine pentaacetic acid (Gd-DTPA) and related BBB breakdown to brain metabolite changes in proton magnetic resonance spectrum (H-MRS) in the infarcted site following middle cerebral artery occlusion (MCAO) in rats. It was shown that MCAO for 30 min and 1.5 h caused no Gd-DTPA signal change in the T1-weighted images, whereas MCAO for 1 h significantly altered some of H-MRS brain metabolites, suggesting that brain metabolite changes occurred earlier than BBB damage after ischemic stroke. MCAO for 2 h caused BBB breakdown, which was related to changes in the levels of some brain metabolites detected by H-MRS. Between the second and the third hour after MCAO, brain metabolite changes continued as the result of BBB breakdown and the concurrent overperfusion to the infarcted site, which may ameliorate the metabolite changes, thus compensating for the functional failures of the brain after stroke.
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Affiliation(s)
- Gen Yan
- aDepartment of Radiology, Affiliated Hospital, Jiangnan University bDepartment of Basic Medicine, Jiangnan University Medical School, Wuxi cDepartment of Radiology, the Second Affiliated Hospital, Shantou University Medical College, Shantou dDepartment of Anatomy, Shantou University Medical College, Shantou, People's Republic of China eDepartment of Medical Imaging, University of Toronto, Toronto, Canada
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8
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Abstract
A plethora of magnetic resonance (MR) techniques developed in the last two decades provide unique and noninvasive measurement capabilities for studies of basic brain function and brain diseases in humans. Animal model experiments have been an indispensible part of this development. MR imaging and spectroscopy measurements have been employed in animal models, either by themselves or in combination with complementary and often invasive techniques, to enlighten us about the information content of such MR methods and/or verify observations made in the human brain. They have also been employed, with or independently of human efforts, to examine mechanisms underlying pathological developments in the brain, exploiting the wealth of animal models available for such studies. In this endeavor, the desire to push for ever-higher spatial and/or spectral resolution, better signal-to-noise ratio, and unique image contrast has inevitably led to the introduction of increasingly higher magnetic fields. As a result, today, animal model studies are starting to be conducted at magnetic fields ranging from ~ 11 to 17 Tesla, significantly enhancing the armamentarium of tools available for the probing brain function and brain pathologies.
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Affiliation(s)
- Gülin Öz
- Center for Magnetic Resonance Research, University of Minnesota, Minneapolis, Minnesota, USA
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9
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Alf MF, Duarte JMN, Lei H, Krämer SD, Mlynarik V, Schibli R, Gruetter R. MRS glucose mapping and PET joining forces: re-evaluation of the lumped constant in the rat brain under isoflurane anaesthesia. J Neurochem 2014; 129:672-82. [PMID: 24471521 DOI: 10.1111/jnc.12667] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2013] [Revised: 01/22/2014] [Accepted: 01/24/2014] [Indexed: 12/17/2022]
Abstract
Although numerous positron emission tomography (PET) studies with (18) F-fluoro-deoxyglucose (FDG) have reported quantitative results on cerebral glucose kinetics and consumption, there is a large variation between the absolute values found in the literature. One of the underlying causes is the inconsistent use of the lumped constants (LCs), the derivation of which is often based on multiple assumptions that render absolute numbers imprecise and errors hard to quantify. We combined a kinetic FDG-PET study with magnetic resonance spectroscopic imaging (MRSI) of glucose dynamics in Sprague-Dawley rats to obtain a more comprehensive view of brain glucose kinetics and determine a reliable value for the LC under isoflurane anaesthesia. Maps of Tmax /CMRglc derived from MRSI data and Tmax determined from PET kinetic modelling allowed to obtain an LC-independent CMRglc . The LC was estimated to range from 0.33 ± 0.07 in retrosplenial cortex to 0.44 ± 0.05 in hippocampus, yielding CMRglc between 62 ± 14 and 54 ± 11 μmol/min/100 g, respectively. These newly determined LCs for four distinct areas in the rat brain under isoflurane anaesthesia provide means of comparing the growing amount of FDG-PET data available from translational studies.
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Affiliation(s)
- Malte F Alf
- Laboratory of Functional and Metabolic Imaging, Ecole Polytechnique Fédérale de Lausanne, Lausanne, Switzerland; Center for Radiopharmaceutical Sciences of ETH Zurich, Zurich, Switzerland
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10
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Lanz B, Gruetter R, Duarte JMN. Metabolic Flux and Compartmentation Analysis in the Brain In vivo. Front Endocrinol (Lausanne) 2013; 4:156. [PMID: 24194729 PMCID: PMC3809570 DOI: 10.3389/fendo.2013.00156] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/31/2013] [Accepted: 10/07/2013] [Indexed: 12/16/2022] Open
Abstract
Through significant developments and progresses in the last two decades, in vivo localized nuclear magnetic resonance spectroscopy (MRS) became a method of choice to probe brain metabolic pathways in a non-invasive way. Beside the measurement of the total concentration of more than 20 metabolites, (1)H MRS can be used to quantify the dynamics of substrate transport across the blood-brain barrier by varying the plasma substrate level. On the other hand, (13)C MRS with the infusion of (13)C-enriched substrates enables the characterization of brain oxidative metabolism and neurotransmission by incorporation of (13)C in the different carbon positions of amino acid neurotransmitters. The quantitative determination of the biochemical reactions involved in these processes requires the use of appropriate metabolic models, whose level of details is strongly related to the amount of data accessible with in vivo MRS. In the present work, we present the different steps involved in the elaboration of a mathematical model of a given brain metabolic process and its application to the experimental data in order to extract quantitative brain metabolic rates. We review the recent advances in the localized measurement of brain glucose transport and compartmentalized brain energy metabolism, and how these reveal mechanistic details on glial support to glutamatergic and GABAergic neurons.
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Affiliation(s)
- Bernard Lanz
- Laboratory for Functional and Metabolic Imaging, Ecole Polytechnique Fédérale de Lausanne, Lausanne, Switzerland
| | - Rolf Gruetter
- Laboratory for Functional and Metabolic Imaging, Ecole Polytechnique Fédérale de Lausanne, Lausanne, Switzerland
- Department of Radiology, University of Lausanne, Lausanne, Switzerland
- Department of Radiology, University of Geneva, Geneva, Switzerland
| | - João M. N. Duarte
- Laboratory for Functional and Metabolic Imaging, Ecole Polytechnique Fédérale de Lausanne, Lausanne, Switzerland
- Department of Radiology, University of Lausanne, Lausanne, Switzerland
- *Correspondence: João M. N. Duarte, Laboratory for Functional and Metabolic Imaging, Ecole Polytechnique Fédérale de Lausanne, Bâtiment CH, Station 6, CH-1015 Lausanne, Switzerland e-mail:
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11
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Smeland OB, Hadera MG, McDonald TS, Sonnewald U, Borges K. Brain mitochondrial metabolic dysfunction and glutamate level reduction in the pilocarpine model of temporal lobe epilepsy in mice. J Cereb Blood Flow Metab 2013; 33:1090-7. [PMID: 23611869 PMCID: PMC3705438 DOI: 10.1038/jcbfm.2013.54] [Citation(s) in RCA: 51] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/29/2013] [Revised: 03/14/2013] [Accepted: 03/19/2013] [Indexed: 11/10/2022]
Abstract
Although certain metabolic characteristics such as interictal glucose hypometabolism are well established for temporal lobe epilepsy (TLE), its pathogenesis still remains unclear. Here, we performed a comprehensive study of brain metabolism in a mouse model of TLE, induced by pilocarpine-status epilepticus (SE). To investigate glucose metabolism, we injected mice 3.5-4 weeks after SE with [1,2-(13)C]glucose before microwave fixation of the head. Using (1)H and (13)C nuclear magnetic resonance spectroscopy, gas chromatography-mass spectrometry and high-pressure liquid chromatography, we quantified metabolites and (13)C labeling in extracts of cortex and hippocampal formation (HF). Hippocampal levels of glutamate, glutathione and alanine were decreased in pilocarpine-SE mice compared with controls. Moreover, the contents of N-acetyl aspartate, succinate and reduced nicotinamide adenine dinucleotide (phosphate) NAD(P)H were decreased in HF indicating impairment of mitochondrial function. In addition, the reduction in (13)C enrichment of hippocampal citrate and malate suggests decreased tricarboxylic acid (TCA) cycle turnover in this region. In cortex, we found reduced (13)C labeling of glutamate, glutamine and aspartate via the pyruvate carboxylation and pyruvate dehydrogenation pathways, suggesting slower turnover of these amino acids and/or the TCA cycle. In conclusion, mitochondrial metabolic dysfunction and altered amino-acid metabolism is found in both cortex and HF in this epilepsy model.
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Affiliation(s)
- Olav B Smeland
- Department of Neuroscience, Faculty of Medicine, Norwegian University of Science and Technology, Trondheim, Norway
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12
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Nilsen LH, Rae C, Ittner LM, Götz J, Sonnewald U. Glutamate metabolism is impaired in transgenic mice with tau hyperphosphorylation. J Cereb Blood Flow Metab 2013; 33:684-91. [PMID: 23340677 PMCID: PMC3652703 DOI: 10.1038/jcbfm.2012.212] [Citation(s) in RCA: 45] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
Abstract
In neurodegenerative diseases including Alzheimer's disease and frontotemporal dementia, the protein tau is hyperphosphorylated and eventually aggregates to develop neurofibrillary tangles. Here, the consequences of tau hyperphosphorylation on both neuronal and astrocytic metabolism and amino-acid neurotransmitter homeostasis were assessed in transgenic mice expressing the pathogenic mutation P301L in the human tau gene (pR5 mice) compared with nontransgenic littermate controls. Mice were injected with the neuronal and astrocytic substrate [1-(13)C]glucose and the astrocytic substrate [1,2-(13)C]acetate. Hippocampus and cerebral cortex extracts were analyzed using (1)H and (13)C nuclear magnetic resonance spectroscopy, gas chromatography-mass spectrometry and high-performance liquid chromatography. The glutamate level was reduced in the hippocampus of pR5 mice, accompanied by reduced incorporation of (13)C label derived from [1-(13)C]glucose in glutamate. In the cerebral cortex, glucose utilization as well as turnover of glutamate, glutamine, and GABA, were increased. This was accompanied by a relative increase in production of glutamate via the pyruvate carboxylation pathway in cortex. Overall, we revealed that astrocytes as well as glutamatergic and GABAergic neurons in the cortex of pR5 mice were in a hypermetabolic state, whereas in the hippocampus, where expression levels of mutant human tau are the highest, glutamate homeostasis was impaired.
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Affiliation(s)
- Linn Hege Nilsen
- Department of Neuroscience, Faculty of Medicine, Norwegian University of Science and Technology, Trondheim, Norway
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13
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Walter B, Eiselt M, Cumming P, Xiong G, Hinz R, Uthe S, Brust P, Bauer R. Resistance of brain glucose metabolism to thiopental-induced CNS depression in newborn piglets. Int J Dev Neurosci 2013; 31:157-64. [PMID: 23305916 DOI: 10.1016/j.ijdevneu.2012.12.008] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2012] [Accepted: 12/30/2012] [Indexed: 10/27/2022] Open
Abstract
The transition from mild sedation to deep anaesthesia is marked by the phenomenon of burst suppression (BS). FDG-PET studies show that the cerebral metabolic rate for glucose (CMRglc) declines dramatically with onset of BS in the adult brain. Global CMRglc increases substantially in the post-natal period and achieves its maximum in preadolescence. However, the impact of post-natal brain development on the vulnerability of CMRglc to the onset of BS has not been documented. Therefore, cerebral blood flow and metabolism were measured using a variant of the Kety-Schmidt method, in conjunction with quantitative regional estimation of brain glucose uptake by FDG-PET in groups of neonate and juvenile pigs, under a condition of light sedation or after induction of deep anaesthesia with thiopental. Quantification of simultaneous ECoG recordings was used to establish the correlation between anaesthesia-related changes in brain electrical activity and the observed cerebrometabolic changes. In the condition of light sedation the magnitude of CMRglc was approximately 20% higher in the older pigs, with the greatest developmental increase evident in the cerebral cortex and basal ganglia (P<0.05). Onset of BS was associated with 20-40% declines in CMRglc. Subtraction of the mean parametric maps for CMRglc showed the absolute reductions in CMRglc evoked by thiopental anaesthesia to be two-fold greater in the pre-adolescent pigs than in the neonates (P<0.05). Thus, the lesser suppression of brain energy demand of neonate brain during deep anaesthesia represents a reduced part of thiopental suppressing brain metabolism in neonates.
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Affiliation(s)
- Bernd Walter
- Institute of Molecular Cell Biology, Jena University Hospital, Friedrich Schiller University, Jena, Germany
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Tremoleda JL, Kerton A, Gsell W. Anaesthesia and physiological monitoring during in vivo imaging of laboratory rodents: considerations on experimental outcomes and animal welfare. EJNMMI Res 2012; 2:44. [PMID: 22877315 PMCID: PMC3467189 DOI: 10.1186/2191-219x-2-44] [Citation(s) in RCA: 94] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2012] [Accepted: 07/16/2012] [Indexed: 12/15/2022] Open
Abstract
The implementation of imaging technologies has dramatically increased the efficiency of preclinical studies, enabling a powerful, non-invasive and clinically translatable way for monitoring disease progression in real time and testing new therapies. The ability to image live animals is one of the most important advantages of these technologies. However, this also represents an important challenge as, in contrast to human studies, imaging of animals generally requires anaesthesia to restrain the animals and their gross motion. Anaesthetic agents have a profound effect on the physiology of the animal and may thereby confound the image data acquired. It is therefore necessary to select the appropriate anaesthetic regime and to implement suitable systems for monitoring anaesthetised animals during image acquisition. In addition, repeated anaesthesia required for longitudinal studies, the exposure of ionising radiations and the use of contrast agents and/or imaging biomarkers may also have consequences on the physiology of the animal and its response to anaesthesia, which need to be considered while monitoring the animals during imaging studies. We will review the anaesthesia protocols and monitoring systems commonly used during imaging of laboratory rodents. A variety of imaging modalities are used for imaging rodents, including magnetic resonance imaging, computed tomography, positron emission tomography, single photon emission computed tomography, high frequency ultrasound and optical imaging techniques such as bioluminescence and fluorescence imaging. While all these modalities are implemented for non-invasive in vivo imaging, there are certain differences in terms of animal handling and preparation, how the monitoring systems are implemented and, importantly, how the imaging procedures themselves can affect mammalian physiology. The most important and critical adverse effects of anaesthetic agents are depression of respiration, cardiovascular system disruption and thermoregulation. When anaesthetising rodents, one must carefully consider if these adverse effects occur at the therapeutic dose required for anaesthesia, if they are likely to affect the image acquisitions and, importantly, if they compromise the well-being of the animals. We will review how these challenges can be successfully addressed through an appropriate understanding of anaesthetic protocols and the implementation of adequate physiological monitoring systems.
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Affiliation(s)
- Jordi L Tremoleda
- Biological Imaging Centre (BIC), Medical Research Council (MRC) Clinical Science Centre, Imperial College London, Hammersmith Campus, Cyclotron Building, Du Cane Road, London, W12 0NN, UK.
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15
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Smeland OB, Meisingset TW, Sonnewald U. Dietary supplementation with acetyl-l-carnitine in seizure treatment of pentylenetetrazole kindled mice. Neurochem Int 2012; 61:444-54. [PMID: 22709675 DOI: 10.1016/j.neuint.2012.06.008] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2011] [Revised: 06/01/2012] [Accepted: 06/03/2012] [Indexed: 10/28/2022]
Abstract
In spite of the availability of new antiepileptic drugs a considerable number of epilepsy patients still have pharmacoresistant seizures, and thus there is a need for novel approaches. Acetyl-l-carnitine (ALCAR), which delivers acetyl units to mitochondria for acetyl-CoA production, has been shown to improve brain energy homeostasis and protects against various neurotoxic insults. To our knowledge, this is the first study of ALCAR's effect on metabolism in pentylenetetrazole (PTZ) kindled mice. ALCAR or the commonly used antiepileptic drug valproate, was added to the drinking water of mice for 25days, and animals were injected with PTZ or saline three times a week during the last 21 days. In order to investigate ALCAR's effects on glucose metabolism, mice were injected with [1-(13)C]glucose 15 min prior to microwave fixation. Brain extracts from cortex and the hippocampal formation (HF) were studied using (1)H and (13)C NMR spectroscopy and HPLC. PTZ kindling caused glucose hypometabolism, evidenced by a reduction in both glycolysis and TCA cycle turnover in both brain regions investigated. Glutamatergic and GABAergic neurons were affected in cortex and HF, but the amount of glutamate was only reduced in HF. Slight astrocytic involvement could be detected in the cortex. Interestingly, the dopamine content was increased in the HF. ALCAR attenuated the PTZ induced reduction in [3-(13)C]alanine and the increase in dopamine in the HF. However, TCA cycle metabolism was not different from that seen in PTZ kindled animals. In conclusion, even though ALCAR did not delay the kindling process, it did show some promising ameliorative effects, worthy of further investigation.
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Affiliation(s)
- Olav B Smeland
- Dept. of Neuroscience, Faculty of Medicine, Norwegian University of Science and Technology, Trondheim, Norway
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16
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The neurochemical profile quantified by in vivo 1H NMR spectroscopy. Neuroimage 2012; 61:342-62. [DOI: 10.1016/j.neuroimage.2011.12.038] [Citation(s) in RCA: 168] [Impact Index Per Article: 14.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2011] [Accepted: 12/15/2011] [Indexed: 12/13/2022] Open
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17
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Xu S, Ji Y, Chen X, Yang Y, Gullapalli RP, Masri R. In vivo high-resolution localized (1) H MR spectroscopy in the awake rat brain at 7 T. Magn Reson Med 2012; 69:937-43. [PMID: 22570299 DOI: 10.1002/mrm.24321] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2012] [Revised: 04/10/2012] [Accepted: 04/11/2012] [Indexed: 12/26/2022]
Abstract
In vivo localized high-resolution (1) H MR spectroscopy was performed in multiple brain regions without the use of anesthetic or paralytic agents in awake head-restrained rats that were previously trained in a simulated MRI environment using a 7T MR system. Spectra were obtained using a short echo time single-voxel point-resolved spectroscopy technique with voxel size ranging from 27 to 32.4 mm(3) in the regions of anterior cingulate cortex, somatosensory cortex, hippocampus, and thalamus. Quantifiable spectra, without the need for any additional postprocessing to correct for possible motion, were reliably detected including the metabolites of interest such as γ-aminobutyric acid, glutamine, glutamate, myo-inositol, N-acetylaspartate, taurine, glycerophosphorylcholine/phosphorylcholine, creatine/phosphocreatine, and N-acetylaspartate/N-acetylaspartylglutamate. The spectral quality was comparable to spectra from anesthetized animals with sufficient spectral dispersion to separate metabolites such as glutamine and glutamate. Results from this study suggest that reliable information on major metabolites can be obtained without the confounding effects of anesthesia or paralytic agents in rodents.
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Affiliation(s)
- Su Xu
- Department of Diagnostic Radiology and Nuclear Medicine, University of Maryland School of Medicine, Baltimore, MD 20892-1527, USA
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Duarte JMN, Gruetter R. Characterization of cerebral glucose dynamics in vivo with a four-state conformational model of transport at the blood-brain barrier. J Neurochem 2012; 121:396-406. [DOI: 10.1111/j.1471-4159.2012.07688.x] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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Makaryus R, Lee H, Yu M, Zhang S, Smith SD, Rebecchi M, Glass PS, Benveniste H. The metabolomic profile during isoflurane anesthesia differs from propofol anesthesia in the live rodent brain. J Cereb Blood Flow Metab 2011; 31:1432-42. [PMID: 21266982 PMCID: PMC3130322 DOI: 10.1038/jcbfm.2011.1] [Citation(s) in RCA: 57] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
Development of noninvasive techniques to discover new biomarkers in the live brain is important to further understand the underlying metabolic pathways of significance for processes such as anesthesia-induced apoptosis and cognitive dysfunction observed in the undeveloped brain. We used in vivo proton magnetic resonance spectroscopy and two different signal processing approaches to test the hypothesis that volatile (isoflurane) and intravenous (propofol) anesthetics at equipotent doses produce distinct metabolomic profiles in the hippocampus and parietal cortex of the live rodent. For both brain regions, prolonged isoflurane anesthesia was characterized by higher levels of lactate (Lac) and glutamate compared with long-lasting propofol. In contrast, propofol anesthesia was characterized by very low concentrations of Lac ([lac]) as well as glucose. Quantitative analysis revealed that the [lac] was fivefold higher with isoflurane compared with propofol anesthesia and independent of [lac] in blood. The metabolomic profiling further demonstrated that for both brain regions, Lac was the most important metabolite for the observed differences, suggesting activation of distinct metabolic pathways that may impact mechanisms of action, background cellular functions, and possible agent-specific neurotoxicity.
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Affiliation(s)
- Rany Makaryus
- Department of Anesthesiology, Health Sciences Center, Stony Brook University, Stony Brook, New York 11794, USA
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Kulak A, Duarte JMN, Do KQ, Gruetter R. Neurochemical profile of the developing mouse cortex determined by in vivo1H NMR spectroscopy at 14.1 T and the effect of recurrent anaesthesia. J Neurochem 2010; 115:1466-77. [DOI: 10.1111/j.1471-4159.2010.07051.x] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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