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Samira Kabli¹, Herman P. Spaink¹, Huub J. M de Groot¹, A Alia¹

¹Leiden University, Leiden, Netherlands

Zebrafish is increasingly used as model organism for understanding brain diseases especially due to similar organization of brain components as that of human. In this study we optimized ο MRI and localized 1H MRS sequences at 9.4T to get metabolic profile of the zebrafish brain in vivo.  A high resolution spectrum was obtained from a voxel as small as 3.3 οl placed in the middle of the zebrafish brain which gave excellent separation of resonances from various brain metabolites. Our study suggests that zebrafish brain has similar metabolite profile as that of human brain which proves zebrafish as a good model organism for human brain disorders

Ivan Tkac¹, Erik S. Carlson¹, Anna Petryk¹, Michael K. Georgieff¹

¹University of Minnesota, Minneapolis, Minnesota, USA

In vivo ¹H NMR spectroscopy at 9.4 T was used to investigate neurochemical changes in hippocampus of CamKII α -cre/S1c11a2 flox/flox double-mutant mice with knock-out of the iron transporter Slc11a2 in forebrain neurons. Iron content was selectively reduced in hippocampus by 40% in knock-out (KO) relative to wild type (WT) mice. Behavioral tests showed cognitive deficit of KO mice relative to WT. Of all 17 metabolites quantified in hippocampus only Lac levels were significantly reduced in KO mice relative to WT controls, which may indicate reduced energy production.

Shaolin Yang¹, D. Bruce Vaupel¹, Hanbing Lu¹, Thomas J. Ross¹, William Rea¹, Steven M. Demny¹, Elliot A. Stein¹, Yihong Yang¹

¹National Institute on Drug Abuse, NIH, Baltimore, Maryland, USA

Seizures were induced in rats by intraperitoneal injection of pentylenetetrazole (PTZ, 70 mg/kg). The time series of metabolite concentrations in the frontal cortex of adult rat brain were measured in vivo before and after the injection by localized 1H MRS spectroscopy at 9.4T (3 time points before the injection and 4 time points after, 25 minutes for each time point). Compared to the baseline levels, the average concentrations of glutamine (Gln) and ã-aminobutyric acid (GABA) (n = 7) significantly increased post injection but reached peaks at different time.

Ines R. Violante¹, Jelena Anastasovska², Gina J. Sanchez-Canon², Tiago B. Rodrigues¹, Laura Nieto¹, Stephen R. Bloom³, James R. Parkinson³, Jimmy Bell², Sebastian Cerdan¹

¹CSIC, Madrid, Spain; ²Hammersmith Hospital, London, UK; ³Imperial College, London, UK

We investigate the neuroglial metabolic interactions underlying appetite control during the feeding/fasting cycles. We administered an i.p. injection of (1-¹³C) glucose (20 µmol/g) to C57BL/6 mice, fixed the brain with high power microwaves (5kW), dissect the hypothalamus from the remaining cerebral structures and analyzed the ¹³C distribution in these regions by ¹³C HRMAS. Our results indicate that cerebral activation by fasting results in increased (3-¹³C) lactate and decreased (4-¹³C) glutamate levels in the hypothalamus. This finding suggests that the activation by fasting occurs most probably through the Astrocyte to Neuron Lactate Redox Shuttle, as in other sensorial activation processes.

Lihong Jiang¹, Robin A. de Graaf, Kevin L. Behar

¹Yale University, New Haven, Connecticut, USA

In this study, we combined brain temperature mapping using the temperature-dependent frequency shift of water relative to NAA with ¹H-[¹³C] MRS measurements of ¹³C turnover following acute MDMA-induced hyperthermia. The SI temperature map showed regional differences in temperature elevation, lower values in cortex and higher values in hippocampus. Glutamate and glutamine ¹³C turnover from [1,6-¹³C] glucose appeared faster during MDMA hyperthermia suggest increased oxidative metabolism.

Christine Nabuurs¹, Dennis Klomp¹, Andor Veltien¹, Bart Van de Bank¹, Arend Heerschap¹

¹Radboud University Nijmegen Medical Center, Nijmegen, Netherlands

One of the largest hurdles in the assessment of metabolic conversion by MRS with ¹³C labeled glucose infusion in mouse brain, is the determination of time resolved ¹³C  enrichment of labeled metabolites in vivo during the MR experiment. These preliminary results demonstrate a coil setup and method, that allows for detection of glutamate and glutamine signals using POCE and DEPT methods sequentially to obtain spectra in the same VOI in a mouse brain. This enables both good separate detection of labeled metabolites and evaluation of isotopic enrichment.

Anant Bahadur Patel¹, ², Robin A. de Graaf¹, Douglas L. Rothman¹, Robert G. Shulman¹, Kevin L. Behar¹, Graeme F. Mason¹

¹Yale University School of Medicine, New Haven, USA; ²Centre for Cellular and Molecular Biology, Hyderabad, India

In the present study we investigated transport and metabolism of acetate in rat brain in vivo. Cerebral metabolite levels and ¹³C labeling were measured in vivo at 7 Tesla using ¹H-[¹³C]-NMR spectroscopy in halothane-anesthetized rats receiving intravenous infusions of [2-¹³C]acetate. Steady-state brain acetate increased linearly with plasma level, whereas Gln-C4 labeling, which reflects the oxidation of acetate by the astroglial TCA cycle, reached saturation for plasma levels ¡Ý15 mM. The maximum rate of acetate utilization was ~14% of total (neuronal + glial) oxidative metabolism.

Xiao-Hong Zhu¹, Fei Du¹, Yi Zhang¹, Wei Chen¹

¹Center for Magnetic Resonance Research, Minneapolis, Minnesota, USA

In vivo ³¹P MRS provides useful measures of a large number of cerebral phosphate metabolites and tissue pH. It is particularly important for studying the ATP metabolism and bioenergetics in the brain noninvasively. The reliability of ³¹P MRS measurement can be significantly improved at high field. We have conducted a study to determine the brain phosphate metabolite profiles in human and two animal species of cat and rat at high fields (7-9.4T). Significant differences were found in the measured metabolite concentrations and tissue pH among the human and animal brains. Our results provide the standard phosphate metabolite profiles of the healthy human, cat and rat brains. This information should be valuable for cerebral metabolic study in these species, especially when comparing physiology versus pathology states in a specific brain of interest.

Niels Braakman¹, Thomas Oerther², Huub de Groot¹, A Alia¹

¹Leiden University, Leiden, Netherlands; ²Bruker BioSpin GmbH, Rheinstetten, Germany

Localized two-dimensional magnetic resonance spectroscopy (2D MRS) is revolutionizing the in vivo studies of brain metabolites due to improved spectral resolution and unambiguous assignment opportunities. Despite the fact that there are large numbers of transgenic mouse models available for neurological disorders, localized 2D MRS has not yet been implemented in the mouse brain due to size constraints. In this study we optimized a localized 2D proton chemical shift correlated spectroscopic sequence at 9.4T to obtain highly resolved 2D spectra from localized regions in the mouse brain in vivo. To our knowledge this is the first in vivo application of 2D MRS in mouse brain. The L-COSY method yields consistent, reproducible results, and thus allows the clear and unambiguous identification of multiple brain metabolites from a single measurement. Such information will prove invaluable in future studies of brain disorders in mouse models.

Fei Du¹, Yi Zhang¹, Xiao-Hong Zhu¹, Wei Chen¹

¹University of Minnesota, Minneapolis, Minnesota, USA

Increases in neuronal activity are accompanied by elevated cerebral metabolic rates of glucose and oxygen consumption (CMRglc, CMRO₂) at the activated sites. The end result of glucose and oxygen consumptions is the production of ATP molecules in mitochondria through ATPase. ATP is the fundamental cellular energy currency, and its hydrolysis to inorganic phosphate (Pi) and ADP is coupled to all energy requiring process in the cells. It is, thus, interesting to understand the neuro-metabolic coupling in the brain. In this comparative study, we investigated the correlations between the varied EEG activity through changing the anesthesia depth and the cerebral metabolite concentrations and metabolic rates which can be measured by in vivo ³¹P and/or ¹H MRS. We found that the ATP and glucose metabolic rates are more closely coupled with the varied EEG activity in the resting rat brain as compared to steady-state metabolite concentrations. Thus, the imaging of these rates should provide sensitive and quantitative measures of brain bioenergetics associated with neuronal activity. Finally, this comparison study also supports a tight neuro-metabolic coupling in the rat brain.