scholarly journals Cortical Substrate Oxidation during Hyperketonemia in the Fasted Anesthetized Rat in Vivo

2011 ◽  
Vol 31 (12) ◽  
pp. 2313-2323 ◽  
Author(s):  
Lihong Jiang ◽  
Graeme F Mason ◽  
Douglas L Rothman ◽  
Robin A de Graaf ◽  
Kevin L Behar
Keyword(s):  
Time Course ◽  
Ketone Bodies ◽  
Tricarboxylic Acid Cycle ◽  
Metabolic Model ◽  
Substrate Oxidation ◽  
Resonance Spectroscopy ◽  
Neural Function ◽  
Anesthetized Rats ◽  
Time Courses

Ketone bodies are important alternate brain fuels, but their capacity to replace glucose and support neural function is unclear. In this study, the contributions of ketone bodies and glucose to cerebral cortical metabolism were measured in vivo in halothane-anesthetized rats fasted for 36 hours ( n=6) and receiving intravenous [2,4-13C2]-d- β-hydroxybutyrate (BHB). Time courses of 13C-enriched brain amino acids (glutamate-C4, glutamine-C4, and glutamate and glutamine-C3) were measured at 9.4 Tesla using spatially localized 1H-[13C]-nuclear magnetic resonance spectroscopy. Metabolic rates were estimated by fitting a constrained, two-compartment (neuron–astrocyte) metabolic model to the 13C time-course data. We found that ketone body oxidation was substantial, accounting for 40% of total substrate oxidation (glucose plus ketone bodies) by neurons and astrocytes. d- β-Hydroxybutyrate was oxidized to a greater extent in neurons than in astrocytes (∼70:30), and followed a pattern closely similar to the metabolism of [1-13C]glucose reported in previous studies. Total neuronal tricarboxylic acid cycle (TCA) flux in hyperketonemic rats was similar to values reported for normal (nonketotic) anesthetized rats infused with [1-13C]glucose, but neuronal glucose oxidation was 40% to 50% lower, indicating that ketone bodies had compensated for the reduction in glucose use.

scholarly journals In vivo 13C MRS in the mouse brain at 14.1 Tesla and metabolic flux quantification under infusion of [1,6-13C2]glucose

2017 ◽  
Vol 38 (10) ◽  
pp. 1701-1714 ◽  
Author(s):  
Marta Lai ◽  
Bernard Lanz ◽  
Carole Poitry-Yamate ◽  
Jackeline F Romero ◽  
Corina M Berset ◽  
...  
Keyword(s):  
Mouse Brain ◽  
Metabolic Flux ◽  
Direct Detection ◽  
Tricarboxylic Acid Cycle ◽  
Quantitative Information ◽  
Glutamine Metabolism ◽  
Resonance Spectroscopy ◽  
Flux Analysis ◽  
Carboxylase Activity

In vivo 13C magnetic resonance spectroscopy (MRS) enables the investigation of cerebral metabolic compartmentation while, e.g. infusing 13C-labeled glucose. Metabolic flux analysis of 13C turnover previously yielded quantitative information of glutamate and glutamine metabolism in humans and rats, while the application to in vivo mouse brain remains exceedingly challenging. In the present study, 13C direct detection at 14.1 T provided highly resolved in vivo spectra of the mouse brain while infusing [1,6-13C2]glucose for up to 5 h. 13C incorporation to glutamate and glutamine C4, C3, and C2 and aspartate C3 were detected dynamically and fitted to a two-compartment model: flux estimation of neuron-glial metabolism included tricarboxylic acid cycle (TCA) flux in astrocytes (Vg = 0.16 ± 0.03 µmol/g/min) and neurons (VTCAn = 0.56 ± 0.03 µmol/g/min), pyruvate carboxylase activity (VPC = 0.041 ± 0.003 µmol/g/min) and neurotransmission rate (VNT = 0.084 ± 0.008 µmol/g/min), resulting in a cerebral metabolic rate of glucose (CMRglc) of 0.38 ± 0.02 µmol/g/min, in excellent agreement with that determined with concomitant 18F-fluorodeoxyglucose positron emission tomography (18FDG PET).We conclude that modeling of neuron-glial metabolism in vivo is accessible in the mouse brain from 13C direct detection with an unprecedented spatial resolution under [1,6-13C2]glucose infusion.

scholarly journals Fast Isotopic Exchange between Mitochondria and Cytosol in Brain Revealed by Relayed 13C Magnetization Transfer Spectroscopy

2009 ◽  
Vol 29 (4) ◽  
pp. 661-669 ◽  
Author(s):  
Jehoon Yang ◽  
Su Xu ◽  
Jun Shen
Keyword(s):  
Isotopic Exchange ◽  
Tricarboxylic Acid Cycle ◽  
Magnetization Transfer ◽  
Tricarboxylic Acid ◽  
Transfer Effect ◽  
Resonance Spectroscopy ◽  
Exchange Reactions ◽  
Acid Cycle ◽  
Longitudinal Relaxation

In vivo13C magnetic resonance spectroscopy has been applied to studying brain metabolic processes by measuring 13C label incorporation into cytosolic pools such as glutamate and aspartate. However, the rate of exchange between mitochondrial α-ketoglutarate/oxaloacetate and cytosolic glutamate/aspartate ( Vx) extracted from metabolic modeling has been controversial. Because brain fumarase is exclusively located in the mitochondria, and mitochondrial fumarate is connected to cytosolic aspartate through a chain of fast exchange reactions, it is possible to directly measure Vx from the four-carbon side of the tricarboxylic acid cycle by magnetization transfer. In isoflurane-anesthetized adult rat brain, a relayed 13C magnetization transfer effect on cytosolic aspartate C2 at 53.2ppm was detected after extensive signal averaging with fumarate C2 at 136.1ppm irradiated using selective radiofrequency pulses. Quantitative analysis using Bloch–McConnell equations and a four-site exchange model found that VxE13–19 µmol per g per min (≫ VTCA, the tricarboxylic acid cycle rate) when the longitudinal relaxation time of malate C2 was assumed to be within ±33% of that of aspartate C2. If VxE VTCA, the isotopic exchange between mitochondria and cytosol would be too slow on the time scale of 13C longitudinal relaxation to cause a detectable magnetization transfer effect.

scholarly journals Early pH Changes in Musculoskeletal Tissues upon Injury—Aerobic Catabolic Pathway Activity Linked to Inter-Individual Differences in Local pH

2020 ◽  
Vol 21 (7) ◽  
pp. 2513 ◽  
Author(s):  
Julia C. Berkmann ◽  
Aaron X. Herrera Martin ◽  
Agnes Ellinghaus ◽  
Claudia Schlundt ◽  
Hanna Schell ◽  
...  
Keyword(s):  
Individual Differences ◽  
Animal Models ◽  
Time Course ◽  
Tricarboxylic Acid Cycle ◽  
Controlled Drug Release ◽  
Post Injury ◽  
Ph Changes ◽  
Ph Values ◽  
Local Ph

Local pH is stated to acidify after bone fracture. However, the time course and degree of acidification remain unknown. Whether the acidification pattern within a fracture hematoma is applicable to adjacent muscle hematoma or is exclusive to this regenerative tissue has not been studied to date. Thus, in this study, we aimed to unravel the extent and pattern of acidification in vivo during the early phase post musculoskeletal injury. Local pH changes after fracture and muscle trauma were measured simultaneously in two pre-clinical animal models (sheep/rats) immediately after and up to 48 h post injury. The rat fracture hematoma was further analyzed histologically and metabolomically. In vivo pH measurements in bone and muscle hematoma revealed a local acidification in both animal models, yielding mean pH values in rats of 6.69 and 6.89, with pronounced intra- and inter-individual differences. The metabolomic analysis of the hematomas indicated a link between reduction in tricarboxylic acid cycle activity and pH, thus, metabolic activity within the injured tissues could be causative for the different pH values. The significant acidification within the early musculoskeletal hematoma could enable the employment of the pH for novel, sought-after treatments that allow for spatially and temporally controlled drug release.

scholarly journals Interactions between Pyruvate and Lactate Metabolism in Propionibacterium freudenreichii subsp.shermanii: In Vivo 13C Nuclear Magnetic Resonance Studies

2000 ◽  
Vol 66 (5) ◽  
pp. 2012-2020 ◽  
Author(s):  
Catherine Deborde ◽  
Patrick Boyaval
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Tricarboxylic Acid Cycle ◽  
Dry Weight ◽  
Resonance Spectroscopy ◽  
Propionibacterium Freudenreichii ◽  
Pyruvate Metabolism ◽  
13C Nuclear Magnetic Resonance ◽  
Nuclear Magnetic

ABSTRACT In vivo 13C nuclear magnetic resonance spectroscopy was used to elucidate the pathways and the regulation of pyruvate metabolism and pyruvate-lactate cometabolism noninvasively in living-cell suspensions of Propionibacterium freudenreichiisubsp. shermanii. The most important result of this work concerns the modification of fluxes of pyruvate metabolism induced by the presence of lactate. Pyruvate was temporarily converted to lactate and alanine; the flux to acetate synthesis was maintained, but the flux to propionate synthesis was increased; and the reverse flux of the first part of the Wood-Werkman cycle, up to acetate synthesis, was decreased. Pyruvate was consumed at apparent initial rates of 148 and 90 μmol · min−1 · g−1 (cell dry weight) when it was the sole substrate or cometabolized with lactate, respectively. Lactate was consumed at an apparent initial rate of 157 μmol · min−1 · g−1when it was cometabolized with pyruvate. P. shermanii used several pathways, namely, the Wood-Werkman cycle, synthesis of acetate and CO2, succinate synthesis, gluconeogenesis, the tricarboxylic acid cycle, and alanine synthesis, to manage its pyruvate pool sharply. In both types of experiments, acetate synthesis and the Wood-Werkman cycle were the metabolic pathways used most.

scholarly journals Calculating Event-Triggered Average Synaptic Conductances From the Membrane Potential

2007 ◽  
Vol 97 (3) ◽  
pp. 2544-2552 ◽  
Author(s):  
Martin Pospischil ◽  
Zuzanna Piwkowska ◽  
Michelle Rudolph ◽  
Thierry Bal ◽  
Alain Destexhe
Keyword(s):  
Membrane Potential ◽  
Cortical Neurons ◽  
Time Course ◽  
Spike Generation ◽  
Nonlinear Contribution ◽  
Central Neurons ◽  
Time Courses ◽  
Model Subject ◽  
Synaptic Conductances

The optimal patterns of synaptic conductances for spike generation in central neurons is a subject of considerable interest. Ideally such conductance time courses should be extracted from membrane potential ( Vm) activity, but this is difficult because the nonlinear contribution of conductances to the Vm renders their estimation from the membrane equation extremely sensitive. We outline here a solution to this problem based on a discretization of the time axis. This procedure can extract the time course of excitatory and inhibitory conductances solely from the analysis of Vm activity. We test this method by calculating spike-triggered averages of synaptic conductances using numerical simulations of the integrate-and-fire model subject to colored conductance noise. The procedure was also tested successfully in biological cortical neurons using conductance noise injected with dynamic clamp. This method should allow the extraction of synaptic conductances from Vm recordings in vivo.

scholarly journals Time Course of Postischemic Intracellular Alkalosis Reflects the Duration of Ischemia

1990 ◽  
Vol 10 (6) ◽  
pp. 860-865 ◽  
Author(s):  
Michael Chopp ◽  
Hua Chen ◽  
Ana M. Q. Vande Linde ◽  
Eileen Brown ◽  
K. M. A. Welch
Keyword(s):  
Specific Gravity ◽  
Brain Tissue ◽  
Cerebral Edema ◽  
Time Course ◽  
High Energy ◽  
Resonance Spectroscopy ◽  
Ph Profile ◽  
Tissue Ph ◽  
Tissue Edema

We investigated the long-term (up to 1 week) relationships between the duration of cerebral ischemia and postischemic energy metabolic profile, pH, and tissue edema in the rat. Ten rats each were subjected to 8 or 12 min of forebrain ischemia induced by bicarotid occlusion concurrent with systemic hypotension, and the results were compared with those of 10 sham-operated rat controls. In vivo 31P nuclear magnetic resonance spectroscopy was performed prior to ischemia and at intervals up to 168 h after ischemia. Cerebral edema (measured by specific gravity) was assessed prior to ischemia and at 24, 72, and 168 h after ischemia. The data revealed significant differences in the brain tissue pH profile over time between the ischemic groups (p < 0.03). The 12-min ischemic animals exhibited brain tissue alkalosis (pH = 7.27 ± 0.12) at 24 h compared with both sham (pH = 7.09 ± 0.08) at 24 h and preischemic (pH = 7.06 ± 0.04) pH values. The pH remained alkalotic (pH = 7.23 ± 0.15) through the 48-h time period. In contrast, in the 8-min group, the onset of alkalosis was delayed until 48 h after ischemia (pH = 7.24 ± 0.15), and pH remained alkalotic for only 24 h. No difference in high-energy phosphate metabolism was detected between groups. A different time dependence of tissue pH and specific gravity changes after 12 min of ischemia was detected. The present study suggests that the duration of an ischemic event marks the time of onset of brain tissue alkalosis and its duration and that cerebral edema alone cannot explain the pH changes.

Effect of acute hyperketonemia on the cerebral uptake of ketone bodies in nondiabetic subjects and IDDM patients

2002 ◽  
Vol 283 (1) ◽  
pp. E20-E28 ◽  
Author(s):  
G. Blomqvist ◽  
M. Alvarsson ◽  
V. Grill ◽  
G. Von Heijne ◽  
M. Ingvar ◽  
...  
Keyword(s):  
Time Course ◽  
Ketone Body ◽  
Ketone Bodies ◽  
Tissue Concentration ◽  
Insulin Dependent Diabetes Mellitus ◽  
Dependent Diabetes Mellitus ◽  
Utilization Rate ◽  
Resonance Spectroscopy ◽  
Significant Difference ◽  
The Brain

Using R-β-[1-11C]hydroxybutyrate and positron emission tomography, we studied the effect of acute hyperketonemia (range 0.7–1.7 μmol/ml) on cerebral ketone body utilization in six nondiabetic subjects and six insulin-dependent diabetes mellitus (IDDM) patients with average metabolic control (HbA1c = 8.1 ± 1.7%). An infusion of unlabeled R-β-hydroxybutyrate was started 1 h before the bolus injection of R-β-[1-11C]hydroxybutyrate. The time course of the radioactivity in the brain was measured during 10 min. For both groups, the utilization rate of ketone bodies was found to increase nearly proportionally with the plasma concentration of ketone bodies (1.0 ± 0.3 μmol/ml for nondiabetic subjects and 1.3 ± 0.3 μmol/ml for IDDM patients). No transport of ketone bodies from the brain could be detected. This result, together with a recent study of the tissue concentration of R-β-hydroxybutyrate in the brain by magnetic resonance spectroscopy, indicate that, also at acute hyperketonemia, the rate-limiting step for ketone body utilization is the transport into the brain. No significant difference in transport and utilization of ketone bodies could be detected between the nondiabetic subjects and the IDDM patients.

scholarly journals Maximum activities of some enzymes of glycolysis, the tricarboxylic acid cycle and ketone-body and glutamine utilization pathways in lymphocytes of the rat

1982 ◽  
Vol 208 (3) ◽  
pp. 743-748 ◽  
Author(s):  
M. Salleh M. Ardawi ◽  
Eric A. Newsholme
Keyword(s):  
Ketone Body ◽  
Citrate Synthase ◽  
Ketone Bodies ◽  
Tricarboxylic Acid Cycle ◽  
Tricarboxylic Acid ◽  
Maximum Activity ◽  
Graft Versus Host Reaction ◽  
Acid Cycle ◽  
Oxoglutarate Dehydrogenase

1. The maximum activity of hexokinase in lymphocytes is similar to that of 6-phosphofructokinase, but considerably greater than that of phosphorylase, suggesting that glucose rather than glycogen is the major carbohydrate fuel for these cells. Starvation increased slightly the activities of some of the glycolytic enzymes. A local immunological challenge in vivo (a graft-versus-host reaction) increased the activities of hexokinase, 6-phosphofructokinase, pyruvate kinase and lactate dehydrogenase, confirming the importance of the glycolytic pathway in cell division. 2. The activities of the ketone-body-utilizing enzymes were lower than those of hexokinase or 6-phosphofructokinase, unlike in muscle and brain, and were not affected by starvation. It is suggested that the ketone bodies will not provide a quantitatively important alternative fuel to glucose in lymphocytes. 3. Of the enzymes of the tricarboxylic acid cycle whose activities were measured, that of oxoglutarate dehydrogenase was the lowest, yet its activity (about 4.0μmol/min per g dry wt. at 37°C) was considerably greater than the flux through the cycle (0.5μmol/min per g calculated from oxygen consumption by incubated lymphocytes). The activity was decreased by starvation, but that of citrate synthase was increased by the local immunological challenge in vivo. It is suggested that the rate of the cycle would increase towards the capacity indicated by oxoglutarate dehydrogenase in proliferating lymphocytes. 4. Enzymes possibly involved in the pathway of glutamine oxidation were measured in lymphocytes, which suggests that an aminotransferase reaction(s) (probably aspartate aminotransferase) is important in the conversion of glutamate into oxoglutarate rather than glutamate dehydrogenase, and that the maximum activity of glutaminase is markedly in excess of the rate of glutamine utilization by incubated lymphocytes. The activity of glutaminase is increased by both starvation and the local immunological challenge in vivo. This last finding suggests that metabolism of glutamine via glutaminase is important in proliferating lymphocytes.

scholarly journals Quantitative analysis of intermediary metabolism in rat hepatocytes incubated in the presence and absence of ethanol with a substrate mixture including ketoleucine

1989 ◽  
Vol 258 (1) ◽  
pp. 121-140 ◽  
Author(s):  
J M Baranyai ◽  
J J Blum
Keyword(s):  
Ketone Bodies ◽  
Rat Hepatocytes ◽  
Metabolic Model ◽  
Oxygen Utilization ◽  
Acetyl Coa ◽  
Atp Production ◽  
Considerable Excess ◽  
Metabolic Conditions ◽  
Label Incorporation

Hepatocytes isolated from livers of fed rats were incubated with a mixture of glucose (10 mM), ribose (1.0 mM), acetate (1.25 mM), alanine (3.5 mM), glutamate (2.0 mM), aspartate (2.0 mM), 4-methyl-2-oxovaleric acid (ketoleucine) (3.0 mM), and, in paired flasks, 10 mM-ethanol. One substrate was 14C-radiolabelled in any given incubation. Incorporation of 14C into glucose, glycogen, CO2, lactate, alanine, aspartate, glutamate, acetate, urea, lipid glycerol, fatty acids and the 1- and 2,3,4-positions of ketone bodies was measured after 20 and 40 min of incubation under quasi-steady-state conditions. Data were analysed with the aid of a realistic structural metabolic model. In each of the four conditions examined, there were approx. 77 label incorporation measurements and several measurements of changes in metabolite concentrations. The considerable excess of measurements over the 37 independent flux parameters allowed for a stringent test of the model. A satisfactory fit to these data was obtained for each condition. There were large bidirectional fluxes along the gluconeogenic/glycolytic pathways, with net gluconeogenesis. Rates of ureagenesis, oxygen consumption and ketogenesis were high under all four conditions studied. Oxygen utilization was accurately predicted by three of the four models. There was complete equilibration between mitochondrial and cytosolic pools of acetate and of CO2, but for several of the metabolic conditions, two incompletely equilibrated pools of mitochondrial acetyl-CoA and oxaloacetate were required. Ketoleucine was utilized at a rate comparable to that reported by others in perfused liver and entered the mitochondrial pool of acetyl-CoA directly associated with ketone body formation. Ethanol, which was metabolized at rates comparable to those in vivo, caused relatively few changes in overall flux patterns. Several effects related to the increased NADH/NAD+ ratio were observed. Pyruvate dehydrogenase was completely inhibited and the ratio of acetoacetate to 3-hydroxybutyrate was decreased; flux through glutamate dehydrogenase, the citric acid cycle, and ketoleucine dehydrogenase were, however, only slightly inhibited. Net production of ATP occurred in all conditions studied and was increased by ethanol. Futile cycling was quantified at the glucose/glucose 6-phosphate, glycogen/glucose 6-phosphate, fructose 6-phosphate/fructose 1,6-bis-phosphate, and phosphoenolpyruvate/pyruvate/oxaloacetate substrate cycles. Cycling at these four loci consumed about 22% of cellular ATP production in control hepatocytes and 14% in ethanol-treated cells.

scholarly journals Altered Neurochemical Profile after Traumatic Brain Injury: 1H-MRS Biomarkers of Pathological Mechanisms

2012 ◽  
Vol 32 (12) ◽  
pp. 2122-2134 ◽  
Author(s):  
Janna L Harris ◽  
Hung-Wen Yeh ◽  
In-Young Choi ◽  
Phil Lee ◽  
Nancy E Berman ◽  
...  
Keyword(s):  
Traumatic Brain Injury ◽  
Brain Injury ◽  
Time Course ◽  
Resonance Spectroscopy ◽  
Cellular Mechanisms ◽  
1H Mrs ◽  
Neurochemical Profile ◽  
Cell Membrane Disruption ◽  
Neurochemical Changes

Specific neurochemicals measured with proton magnetic resonance spectroscopy (1H-MRS) may serve as biomarkers of pathological mechanism in the brain. We used high field in vivo1H-MRS to measure a detailed neurochemical profile after experimental traumatic brain injury (TBI) in rats. We characterized neurochemical changes in the contused cortex and the normal-appearing perilesional hippocampus over a time course from 1 hour to 2 weeks after injury. We found significant changes in 19 out of 20 neurochemicals in the cortex, and 9 out of 20 neurochemicals in the hippocampus. These changes provide evidence of altered cellular metabolic status after TBI, with specific compounds proposed to reflect edema, excitotoxicity, neuronal and glial integrity, mitochondrial status and bioenergetics, oxidative stress, inflammation, and cell membrane disruption. Our results support the utility of 1H-MRS for monitoring cellular mechanisms of TBI pathology in animal models, and the potential of this approach for preclinical evaluation of novel therapies.

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