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Glucose metabolism following human traumatic brain injury: methods of assessment and pathophysiological findings.

Jalloh I, Carpenter KL, Helmy A, Carpenter TA, Menon DK, Hutchinson PJ - Metab Brain Dis (2014)

Bottom Line: A recent novel development is the use of microdialysis to deliver glucose and other energy substrates labelled with carbon-13, which allows the metabolism of glucose and other substrates to be tracked.Positron emission tomography and magnetic resonance spectroscopy allow regional differences in metabolism to be assessed.We summarise the data published from these techniques and review their potential uses in the clinical setting.

View Article: PubMed Central - PubMed

Affiliation: Division of Neurosurgery, Department of Clinical Neurosciences, University of Cambridge, Box 167 Cambridge Biomedical Campus, Cambridge, CB2 0QQ, UK, ij232@cam.ac.uk.

ABSTRACT
The pathophysiology of traumatic brain (TBI) injury involves changes to glucose uptake into the brain and its subsequent metabolism. We review the methods used to study cerebral glucose metabolism with a focus on those used in clinical TBI studies. Arterio-venous measurements provide a global measure of glucose uptake into the brain. Microdialysis allows the in vivo sampling of brain extracellular fluid and is well suited to the longitudinal assessment of metabolism after TBI in the clinical setting. A recent novel development is the use of microdialysis to deliver glucose and other energy substrates labelled with carbon-13, which allows the metabolism of glucose and other substrates to be tracked. Positron emission tomography and magnetic resonance spectroscopy allow regional differences in metabolism to be assessed. We summarise the data published from these techniques and review their potential uses in the clinical setting.

No MeSH data available.


Related in: MedlinePlus

Methods for measuring glucose metabolism in the human brain: Various techniques lend themselves to measuring glucose metabolism in the human brain. (1) Microdialysis, which allows metabolites in the extracellular fluid to be measured, is an invasive technique requiring insertion of a microdialysis catheter (possessing a semipermeable membrane, with nominal molecular weight cut-off typically 20 kDa or 100 kDa) into brain parenchyma. A pump is used to infuse perfusion fluid at a low flow rate (e.g. 0.3 μl/min) into the catheter and returned microdialysate is collected into small vials for subsequent analysis. (2) Imaging techniques include positron emission tomography (PET), which uses detectors to measure ionising radiation emitted from the glucose analogue FDG administered intravenously. This provides a measure of the uptake and phosphorylation of glucose. (3) 1H and 31P magnetic resonance spectroscopy (MRS) can be used to measure lactate and high-energy phosphate compounds respectively, in different regions of the brain. (4) A global measure of uptake or release from the brain can be achieved by using a jugular bulb catheter, which allows the venous outflow of the brain to be sampled. Measured concentrations in blood sampled from the venous catheter can be compared with arterial concentrations of metabolites, typically measured in blood taken from an arterial line. This enables the net uptake or release of metabolites by the brain to be calculated and, if cerebral blood flow is known, the cerebral metabolic rate to be calculated
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Fig1: Methods for measuring glucose metabolism in the human brain: Various techniques lend themselves to measuring glucose metabolism in the human brain. (1) Microdialysis, which allows metabolites in the extracellular fluid to be measured, is an invasive technique requiring insertion of a microdialysis catheter (possessing a semipermeable membrane, with nominal molecular weight cut-off typically 20 kDa or 100 kDa) into brain parenchyma. A pump is used to infuse perfusion fluid at a low flow rate (e.g. 0.3 μl/min) into the catheter and returned microdialysate is collected into small vials for subsequent analysis. (2) Imaging techniques include positron emission tomography (PET), which uses detectors to measure ionising radiation emitted from the glucose analogue FDG administered intravenously. This provides a measure of the uptake and phosphorylation of glucose. (3) 1H and 31P magnetic resonance spectroscopy (MRS) can be used to measure lactate and high-energy phosphate compounds respectively, in different regions of the brain. (4) A global measure of uptake or release from the brain can be achieved by using a jugular bulb catheter, which allows the venous outflow of the brain to be sampled. Measured concentrations in blood sampled from the venous catheter can be compared with arterial concentrations of metabolites, typically measured in blood taken from an arterial line. This enables the net uptake or release of metabolites by the brain to be calculated and, if cerebral blood flow is known, the cerebral metabolic rate to be calculated

Mentions: There are various methods for investigating metabolism after TBI in patients (Fig. 1). Measuring arterial, jugular and/or cerebrospinal fluid (CSF) concentrations of metabolites provides a measure of how much the brain as a whole imports or exports. Microdialysis, which samples extracellular fluid, is a focal technique that allows the immediate microenvironment of the brain to be sampled in vivo. Microdialysis can also be used to deliver substances and in this way has been used to deliver glucose and other metabolites labelled with carbon-13 (13C). This is combined with ex vivo nuclear magnetic resonance (NMR) spectroscopy of the microdialysis-collected extracellular fluid yielding information on different intracellular pathways. Autoradiography experiments in animals, and analogous positron emission tomography (PET) studies in humans, use glucose labelled with a radioactive tracer. These experiments allow regional differences in glucose uptake and metabolism to be measured. In vivo magnetic resonance spectroscopy (MRS) has also been used to measure the combined extra- and intracellular regional concentrations of lactate and high-energy phosphate compounds. Our ability to study cerebral metabolism using these techniques has greatly improved our understanding of the pathophysiology of TBI. Importantly, there is also the potential for these techniques to help in the management of patients with TBI and improve clinical outcomes although their role in the clinical setting is still being defined.Fig. 1


Glucose metabolism following human traumatic brain injury: methods of assessment and pathophysiological findings.

Jalloh I, Carpenter KL, Helmy A, Carpenter TA, Menon DK, Hutchinson PJ - Metab Brain Dis (2014)

Methods for measuring glucose metabolism in the human brain: Various techniques lend themselves to measuring glucose metabolism in the human brain. (1) Microdialysis, which allows metabolites in the extracellular fluid to be measured, is an invasive technique requiring insertion of a microdialysis catheter (possessing a semipermeable membrane, with nominal molecular weight cut-off typically 20 kDa or 100 kDa) into brain parenchyma. A pump is used to infuse perfusion fluid at a low flow rate (e.g. 0.3 μl/min) into the catheter and returned microdialysate is collected into small vials for subsequent analysis. (2) Imaging techniques include positron emission tomography (PET), which uses detectors to measure ionising radiation emitted from the glucose analogue FDG administered intravenously. This provides a measure of the uptake and phosphorylation of glucose. (3) 1H and 31P magnetic resonance spectroscopy (MRS) can be used to measure lactate and high-energy phosphate compounds respectively, in different regions of the brain. (4) A global measure of uptake or release from the brain can be achieved by using a jugular bulb catheter, which allows the venous outflow of the brain to be sampled. Measured concentrations in blood sampled from the venous catheter can be compared with arterial concentrations of metabolites, typically measured in blood taken from an arterial line. This enables the net uptake or release of metabolites by the brain to be calculated and, if cerebral blood flow is known, the cerebral metabolic rate to be calculated
© Copyright Policy - OpenAccess
Related In: Results  -  Collection

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Fig1: Methods for measuring glucose metabolism in the human brain: Various techniques lend themselves to measuring glucose metabolism in the human brain. (1) Microdialysis, which allows metabolites in the extracellular fluid to be measured, is an invasive technique requiring insertion of a microdialysis catheter (possessing a semipermeable membrane, with nominal molecular weight cut-off typically 20 kDa or 100 kDa) into brain parenchyma. A pump is used to infuse perfusion fluid at a low flow rate (e.g. 0.3 μl/min) into the catheter and returned microdialysate is collected into small vials for subsequent analysis. (2) Imaging techniques include positron emission tomography (PET), which uses detectors to measure ionising radiation emitted from the glucose analogue FDG administered intravenously. This provides a measure of the uptake and phosphorylation of glucose. (3) 1H and 31P magnetic resonance spectroscopy (MRS) can be used to measure lactate and high-energy phosphate compounds respectively, in different regions of the brain. (4) A global measure of uptake or release from the brain can be achieved by using a jugular bulb catheter, which allows the venous outflow of the brain to be sampled. Measured concentrations in blood sampled from the venous catheter can be compared with arterial concentrations of metabolites, typically measured in blood taken from an arterial line. This enables the net uptake or release of metabolites by the brain to be calculated and, if cerebral blood flow is known, the cerebral metabolic rate to be calculated
Mentions: There are various methods for investigating metabolism after TBI in patients (Fig. 1). Measuring arterial, jugular and/or cerebrospinal fluid (CSF) concentrations of metabolites provides a measure of how much the brain as a whole imports or exports. Microdialysis, which samples extracellular fluid, is a focal technique that allows the immediate microenvironment of the brain to be sampled in vivo. Microdialysis can also be used to deliver substances and in this way has been used to deliver glucose and other metabolites labelled with carbon-13 (13C). This is combined with ex vivo nuclear magnetic resonance (NMR) spectroscopy of the microdialysis-collected extracellular fluid yielding information on different intracellular pathways. Autoradiography experiments in animals, and analogous positron emission tomography (PET) studies in humans, use glucose labelled with a radioactive tracer. These experiments allow regional differences in glucose uptake and metabolism to be measured. In vivo magnetic resonance spectroscopy (MRS) has also been used to measure the combined extra- and intracellular regional concentrations of lactate and high-energy phosphate compounds. Our ability to study cerebral metabolism using these techniques has greatly improved our understanding of the pathophysiology of TBI. Importantly, there is also the potential for these techniques to help in the management of patients with TBI and improve clinical outcomes although their role in the clinical setting is still being defined.Fig. 1

Bottom Line: A recent novel development is the use of microdialysis to deliver glucose and other energy substrates labelled with carbon-13, which allows the metabolism of glucose and other substrates to be tracked.Positron emission tomography and magnetic resonance spectroscopy allow regional differences in metabolism to be assessed.We summarise the data published from these techniques and review their potential uses in the clinical setting.

View Article: PubMed Central - PubMed

Affiliation: Division of Neurosurgery, Department of Clinical Neurosciences, University of Cambridge, Box 167 Cambridge Biomedical Campus, Cambridge, CB2 0QQ, UK, ij232@cam.ac.uk.

ABSTRACT
The pathophysiology of traumatic brain (TBI) injury involves changes to glucose uptake into the brain and its subsequent metabolism. We review the methods used to study cerebral glucose metabolism with a focus on those used in clinical TBI studies. Arterio-venous measurements provide a global measure of glucose uptake into the brain. Microdialysis allows the in vivo sampling of brain extracellular fluid and is well suited to the longitudinal assessment of metabolism after TBI in the clinical setting. A recent novel development is the use of microdialysis to deliver glucose and other energy substrates labelled with carbon-13, which allows the metabolism of glucose and other substrates to be tracked. Positron emission tomography and magnetic resonance spectroscopy allow regional differences in metabolism to be assessed. We summarise the data published from these techniques and review their potential uses in the clinical setting.

No MeSH data available.


Related in: MedlinePlus