1
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Xu W, Borges K. Case for supporting astrocyte energetics in glucose transporter 1 deficiency syndrome. Epilepsia 2024; 65:2213-2226. [PMID: 38767952 DOI: 10.1111/epi.18013] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2024] [Revised: 04/30/2024] [Accepted: 05/02/2024] [Indexed: 05/22/2024]
Abstract
In glucose transporter 1 deficiency syndrome (Glut1DS), glucose transport into brain is reduced due to impaired Glut1 function in endothelial cells at the blood-brain barrier. This can lead to shortages of glucose in brain and is thought to contribute to seizures. Ketogenic diets are the first-line treatment and, among many beneficial effects, provide auxiliary fuel in the form of ketone bodies that are largely metabolized by neurons. However, Glut1 is also the main glucose transporter in astrocytes. Here, we review data indicating that glucose shortage may also impact astrocytes in addition to neurons and discuss the expected negative biochemical consequences of compromised astrocytic glucose transport for neurons. Based on these effects, auxiliary fuels are needed for both cell types and adding medium chain triglycerides (MCTs) to ketogenic diets is a biochemically superior treatment for Glut1DS compared to classical ketogenic diets. MCTs provide medium chain fatty acids (MCFAs), which are largely metabolized by astrocytes and not neurons. MCFAs supply energy and contribute carbons for glutamine and γ-aminobutyric acid synthesis, and decanoic acid can also block α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid glutamate receptors. MCTs do not compete with metabolism of ketone bodies mostly occurring in neurons. Triheptanoin, an anaplerotic but also gluconeogenic uneven MCT, may be another potential addition to ketogenic diets, although maintenance of "ketosis" can be difficult. Gene therapy has also targeted both endothelial cells and astrocytes. Other approaches to increase fuel delivery to the brain currently investigated include exchange of Glut1DS erythrocytes with healthy cells, infusion of lactate, and pharmacological improvement of glucose transport. In conclusion, although it remains difficult to assess impaired astrocytic energy metabolism in vivo, astrocytic energy needs are most likely not met by ketogenic diets in Glut1DS. Thus, we propose prospective studies including monitoring of blood MCFA levels to find optimal doses for add-on MCT to ketogenic diets and assessing of short- and long-term outcomes.
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Affiliation(s)
- Weizhi Xu
- School of Biomedical Sciences, University of Queensland, St Lucia, Queensland, Australia
| | - Karin Borges
- School of Biomedical Sciences, University of Queensland, St Lucia, Queensland, Australia
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2
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Wu K, Xie W, Chen Z, Zhou L, Wang L, Zhou Y, Liu L. Disturbed hippocampal histidine metabolism contributes to cognitive impairment induced by recurrent nonsevere hypoglycemia in diabetes. Biochem Biophys Res Commun 2023; 682:325-334. [PMID: 37837753 DOI: 10.1016/j.bbrc.2023.10.036] [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: 08/11/2023] [Revised: 09/29/2023] [Accepted: 10/09/2023] [Indexed: 10/16/2023]
Abstract
Hypoglycemia is a common adverse reaction to glucose-lowering treatment. Diabetes mellitus (DM) combined with recurrent nonsevere hypoglycemia (RH) can accelerate cognitive decline. Currently, the metabolic pattern changes in cognition-related brain regions caused by this combined effect of DM and RH (DR) remain unclear. In this study, we first characterized the metabolic profiles of the hippocampus in mice exposed to DR using non-targeted metabolomic platforms. Our results showed that DR induced a unique metabolic pattern in the hippocampus, and several significant differences in metabolite levels belonging to the histidine metabolism pathway were discovered. Based on these findings, in the follow-up experiment, we found that histidine treatment could attenuate the cognitive impairment and rescue the neuronal and synaptic damage induced by DR in the hippocampus, which are closely related to ameliorated mitochondrial injury. These findings provide new insights into the metabolic mechanisms of the hippocampus in the progression of DR, and l-histidine supplementation may be a potential metabolic therapy in the future.
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Affiliation(s)
- Kejun Wu
- Department of Endocrinology, Fujian Medical University Union Hospital, Fuzhou, China
| | - Wenhuo Xie
- Department of Clinical Pharmacy and Pharmacy Administration, School of Pharmacy, Fujian Medical University, Fuzhou, China
| | - Zhou Chen
- Department of Clinical Pharmacy and Pharmacy Administration, School of Pharmacy, Fujian Medical University, Fuzhou, China
| | - Linying Zhou
- Public Technology Service Center, Fujian Medical University, Fuzhou, China
| | - Lijing Wang
- Department of Endocrinology, Fujian Medical University Union Hospital, Fuzhou, China
| | - Yu Zhou
- Department of Clinical Pharmacy and Pharmacy Administration, School of Pharmacy, Fujian Medical University, Fuzhou, China.
| | - Libin Liu
- Department of Endocrinology, Fujian Medical University Union Hospital, Fuzhou, China.
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3
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Mortaji S, Dozières-Puyravel B, Geraldes K, Perrot C, Quéméner V, Auvin S. Uncommon use of intermittent glucose administration for infrequent non-epileptic paroxysmal events in GLUT1-DS. Eur J Paediatr Neurol 2023; 45:19-21. [PMID: 37244032 DOI: 10.1016/j.ejpn.2023.05.005] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/04/2022] [Revised: 02/28/2023] [Accepted: 05/15/2023] [Indexed: 05/29/2023]
Abstract
The ketogenic diet is the treatment of GLUT1 deficiency syndrome that provides an alternative energy source for the brain. However, there are some limitations, including compliance issues as well as patients who do not respond to the ketogenic diet. We report the case of two patients that were not on any particular diet. Both experienced infrequent paroxysmal non-epileptic events (acute ataxia and exercise-induced dystonia). Intermittent glucose intake prior to physical activity for exercise-induced symptoms and at the onset of symptoms for acute ataxia showed consistent and reproducible improvement of the symptoms. Our observations raised the question of developing a new treatment strategy with the induction of a sustained increase in blood glucose. For now, the use of this strategy should be limited to a small group of GLUT1-DS patients who are not on a ketogenic diet.
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Affiliation(s)
- Soufiane Mortaji
- AP-HP, Robert-Debré University Hospital, Pediatric Neurology Department, CRMR épilepsies rares, EpiCARE member, Paris, France
| | - Blandine Dozières-Puyravel
- AP-HP, Robert-Debré University Hospital, Pediatric Neurology Department, CRMR épilepsies rares, EpiCARE member, Paris, France
| | - Katia Geraldes
- AP-HP, Robert-Debré University Hospital, Pediatric Neurology Department, CRMR épilepsies rares, EpiCARE member, Paris, France
| | - Céline Perrot
- AP-HP, Robert-Debré University Hospital, Pediatric Neurology Department, CRMR épilepsies rares, EpiCARE member, Paris, France
| | - Virginie Quéméner
- AP-HP, Robert-Debré University Hospital, Pediatric Neurology Department, CRMR épilepsies rares, EpiCARE member, Paris, France
| | - Stéphane Auvin
- AP-HP, Robert-Debré University Hospital, Pediatric Neurology Department, CRMR épilepsies rares, EpiCARE member, Paris, France; Université Paris Cité, INSERM NeuroDiderot, Paris, France; Institut Universitaire de France, (IUF), Paris, France.
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4
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Hariharan A, Robertson CD, Garcia DCG, Longden TA. Brain capillary pericytes are metabolic sentinels that control blood flow through a K ATP channel-dependent energy switch. Cell Rep 2022; 41:111872. [PMID: 36577387 PMCID: PMC10187957 DOI: 10.1016/j.celrep.2022.111872] [Citation(s) in RCA: 12] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2022] [Revised: 10/10/2022] [Accepted: 11/30/2022] [Indexed: 12/28/2022] Open
Abstract
Despite the abundance of capillary thin-strand pericytes and their proximity to neurons and glia, little is known of the contributions of these cells to the control of brain hemodynamics. We demonstrate that the pharmacological activation of thin-strand pericyte KATP channels profoundly hyperpolarizes these cells, dilates upstream penetrating arterioles and arteriole-proximate capillaries, and increases capillary blood flow. Focal stimulation of pericytes with a KATP channel agonist is sufficient to evoke this response, mediated via KIR2.1 channel-dependent retrograde propagation of hyperpolarizing signals, whereas genetic inactivation of pericyte KATP channels eliminates these effects. Critically, we show that decreasing extracellular glucose to less than 1 mM or inhibiting glucose uptake by blocking GLUT1 transporters in vivo flips a mechanistic energy switch driving rapid KATP-mediated pericyte hyperpolarization to increase local blood flow. Together, our findings recast capillary pericytes as metabolic sentinels that respond to local energy deficits by increasing blood flow to neurons to prevent energetic shortfalls.
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Affiliation(s)
- Ashwini Hariharan
- Department of Physiology, School of Medicine, University of Maryland, Baltimore, MD, USA; Laboratory of Neurovascular Interactions, Center for Biomedical Engineering and Technology, School of Medicine, University of Maryland, Baltimore, MD, USA
| | - Colin D Robertson
- Department of Pharmacology, School of Medicine, University of Maryland, Baltimore, MD, USA
| | - Daniela C G Garcia
- Department of Physiology, School of Medicine, University of Maryland, Baltimore, MD, USA; Laboratory of Neurovascular Interactions, Center for Biomedical Engineering and Technology, School of Medicine, University of Maryland, Baltimore, MD, USA
| | - Thomas A Longden
- Department of Physiology, School of Medicine, University of Maryland, Baltimore, MD, USA; Laboratory of Neurovascular Interactions, Center for Biomedical Engineering and Technology, School of Medicine, University of Maryland, Baltimore, MD, USA.
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5
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Gao R, Chen Z, Wu Y, Chen R, Zheng W, Qi L, Liu X, Liu X, Liu L. SIRT3 alleviates mitochondrial dysfunction induced by recurrent low glucose and improves the supportive function of astrocytes to neurons. Free Radic Biol Med 2022; 193:405-420. [PMID: 36306990 DOI: 10.1016/j.freeradbiomed.2022.10.313] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/08/2022] [Revised: 09/22/2022] [Accepted: 10/20/2022] [Indexed: 11/06/2022]
Abstract
Hypoglycemia is an independent risk factor of cognitive impairment in patients with diabetes. Our previous study indicated that dysfunction of astrocytic mitochondria induced by recurrent low glucose (RLG) may account for hypoglycemia-associated neuronal injury and cognitive decline. Sirtuin 3 (SIRT3) is a key deacetylase for mitochondrial proteins and has recently been demonstrated to be an important regulator of mitochondrial function. However, whether mitochondrial dysfunction due to hypoglycemia is associated with astrocytic SIRT3 remains unclear, and few studies have focused on the impact of astrocytic SIRT3 on neuronal survival. In the present work, primary mouse cortical astrocytes cultured in normal glucose (5.5 mM) and high glucose (16.5 mM) were treated with five rounds of RLG (0.1 mM). The results showed that RLG suppressed SIRT3 expression in a glucose-dependent manner. High-glucose culture considerably increased the vulnerability of SIRT3 to RLG, leading to disrupted mitochondrial morphology in astrocytes. Overexpression of SIRT3 markedly improved astrocytic mitochondrial function and reduced RLG-induced oxidative stress. Moreover, SIRT3 suppressed a shift towards a neuroinflammatory A1-like reactive phenotype of astrocytes in response to RLG with reduced IL-1β, IL-6, and TNFα levels. Furthermore, it elevated brain-derived neurotrophic factor (BDNF) levels and promoted neurite growth by activating BDNF/TrkB signaling in the co-cultured neurons. The present study reveals the probable crosstalk between neurons and astrocytes after hypoglycemic exposure and provides a potential target in treating hypoglycemia-associated neuronal injury.
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Affiliation(s)
- Ruonan Gao
- Department of Endocrinology, Fujian Medical University Union Hospital, Fuzhou, 350001, China
| | - Zhou Chen
- Department of Clinical Pharmacy and Pharmacy Administration, School of Pharmacy, Fujian Medical University, Fuzhou, 350122, China; Fujian Key Laboratory of Natural Medicine Pharmacology, Fujian Medical University, Fuzhou, 350122, China
| | - Yubin Wu
- Department of Endocrinology, Fujian Medical University Union Hospital, Fuzhou, 350001, China
| | - Ruiyu Chen
- Department of Clinical Pharmacy and Pharmacy Administration, School of Pharmacy, Fujian Medical University, Fuzhou, 350122, China
| | - Wenrong Zheng
- Department of Clinical Pharmacy and Pharmacy Administration, School of Pharmacy, Fujian Medical University, Fuzhou, 350122, China
| | - Liqin Qi
- Department of Endocrinology, Fujian Medical University Union Hospital, Fuzhou, 350001, China
| | - Xiaoying Liu
- Department of Endocrinology, Fujian Medical University Union Hospital, Fuzhou, 350001, China
| | - Xiaohong Liu
- Department of Endocrinology, Fujian Medical University Union Hospital, Fuzhou, 350001, China
| | - Libin Liu
- Department of Endocrinology, Fujian Medical University Union Hospital, Fuzhou, 350001, China.
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6
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Dickie BR, Jin T, Wang P, Hinz R, Harris W, Boutin H, Parker GJ, Parkes LM, Matthews JC. Quantitative kinetic modelling and mapping of cerebral glucose transport and metabolism using glucoCESL MRI. J Cereb Blood Flow Metab 2022; 42:2066-2079. [PMID: 35748031 PMCID: PMC9580170 DOI: 10.1177/0271678x221108841] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Chemical-exchange spin-lock (CESL) MRI can map regional uptake and utilisation of glucose in the brain at high spatial resolution (i.e sub 0.2 mm3 voxels). We propose two quantitative kinetic models to describe glucose-induced changes in tissue R1ρ and apply them to glucoCESL MRI data acquired in tumour-bearing and healthy rats. When assuming glucose transport is saturable, the maximal transport capacity (Tmax) measured in normal tissue was 3.2 ± 0.6 µmol/min/mL, the half saturation constant (Kt) was 8.8 ± 2.2 mM, the metabolic rate of glucose consumption (MRglc) was 0.21 ± 0.13 µmol/min/mL, and the cerebral blood volume (vb) was 0.006 ± 0.005 mL/mL. Values in tumour were: Tmax = 7.1 ± 2.7 µmol/min/mL, Kt = 14 ± 1.7 mM, MRglc = 0.22 ± 0.09 µmol/min/mL, vb = 0.030 ± 0.035 mL/mL. Tmax and Kt were significantly higher in tumour tissue than normal tissue (p = 0.006 and p = 0.011, respectively). When assuming glucose uptake also occurs via free diffusion, the free diffusion rate (kd) was 0.061 ± 0.017 mL/min/mL in normal tissue and 0.12 ± 0.042 mL/min/mL in tumour. These parameter estimates agree well with literature values obtained using other approaches (e.g. NMR spectroscopy).
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Affiliation(s)
- Ben R Dickie
- Division of Neuroscience and Experimental Psychology, Faculty of Biology, Medicine and Health, The University of Manchester, Manchester, UK.,Geoffrey Jefferson Brain Research Centre, Manchester Academic Health Science Centre, Manchester, UK
| | - Tao Jin
- Department of Radiology, University of Pittsburgh, Pittsburgh, Pennsylvania, USA
| | - Ping Wang
- Department of Radiology, University of Pittsburgh, Pittsburgh, Pennsylvania, USA
| | - Rainer Hinz
- Division of Informatics, Imaging, and Data Science, Faculty of Biology Medicine and Health, University of Manchester, Manchester, UK
| | - William Harris
- Division of Neuroscience and Experimental Psychology, Faculty of Biology, Medicine and Health, The University of Manchester, Manchester, UK.,Geoffrey Jefferson Brain Research Centre, Manchester Academic Health Science Centre, Manchester, UK
| | - Hervé Boutin
- Division of Neuroscience and Experimental Psychology, Faculty of Biology, Medicine and Health, The University of Manchester, Manchester, UK.,Geoffrey Jefferson Brain Research Centre, Manchester Academic Health Science Centre, Manchester, UK
| | - Geoff Jm Parker
- Bioxydyn Limited, Manchester, UK.,Centre for Medical Image Computing, Department of Medical Physics & Biomedical Engineering and Department of Neuroinflammation, University College London, London, UK
| | - Laura M Parkes
- Division of Neuroscience and Experimental Psychology, Faculty of Biology, Medicine and Health, The University of Manchester, Manchester, UK.,Geoffrey Jefferson Brain Research Centre, Manchester Academic Health Science Centre, Manchester, UK
| | - Julian C Matthews
- Division of Neuroscience and Experimental Psychology, Faculty of Biology, Medicine and Health, The University of Manchester, Manchester, UK.,Geoffrey Jefferson Brain Research Centre, Manchester Academic Health Science Centre, Manchester, UK
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7
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Smyczyńska J, Pawelak N, Hilczer M, Lewiński A. Delayed Diagnosis of Congenital Combined Pituitary Hormone Deficiency including Severe Growth Hormone Deficiency in Children with Persistent Neonatal Hypoglycemia—Case Reports and Review. Int J Mol Sci 2022; 23:ijms231911069. [PMID: 36232371 PMCID: PMC9570002 DOI: 10.3390/ijms231911069] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2022] [Revised: 09/11/2022] [Accepted: 09/15/2022] [Indexed: 11/27/2022] Open
Abstract
Apart from stimulation of human growth and cell proliferation, growth hormone (GH) has pleiotropic metabolic effects in all periods of life. Severe GH deficiency is a common component of combined pituitary hormone deficiency (CPHD). CPHD may be caused by mutations in the genes encoding transcription factors and signaling molecules involved in normal pituitary development; however, often its genetic cause remains unknown. Symptoms depend on which hormone is deficient. The first symptom of GH or adrenocorticotropic hormone (ACTH) deficiency may be persistent hypoglycemia in apparently healthy newborns, which is often neglected. Diagnosing CPHD is based on decreased concentrations of hormones secreted by the anterior pituitary and peripheral endocrine glands. Findings in magnetic resonance imaging vary widely, including anterior pituitary hypoplasia/aplasia or pituitary stalk interruption syndrome (PSIS). Delayed diagnosis and treatment can be life-threatening. GH therapy is necessary to recover hypoglycemia and to improve auxological and psychomotor development. We present two girls, diagnosed and treated in our departments, in whom the diagnosis of CPHD was delayed, despite persistent neonatal hypoglycemia; and a review of similar cases, with attention paid to progress in the genetic assessments of such patients, since the introduction of whole exome sequencing that is especially important for PSIS.
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Affiliation(s)
- Joanna Smyczyńska
- Department of Pediatrics, Endocrinology, Diabetology and Nephrology, Medical University of Lodz, 90-419 Lodz, Poland
- Correspondence:
| | - Natalia Pawelak
- Department of Endocrinology and Metabolic Diseases, Polish Mother’s Memorial Hospital—Research Institute, 93-338 Lodz, Poland
| | - Maciej Hilczer
- Department of Endocrinology and Metabolic Diseases, Polish Mother’s Memorial Hospital—Research Institute, 93-338 Lodz, Poland
| | - Andrzej Lewiński
- Department of Endocrinology and Metabolic Diseases, Polish Mother’s Memorial Hospital—Research Institute, 93-338 Lodz, Poland
- Department of Endocrinology and Metabolic Diseases, Medical University of Lodz, 90-419 Lodz, Poland
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8
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Nartsissov YR. Application of a multicomponent model of convectional reaction-diffusion to description of glucose gradients in a neurovascular unit. Front Physiol 2022; 13:843473. [PMID: 36072843 PMCID: PMC9444140 DOI: 10.3389/fphys.2022.843473] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/26/2021] [Accepted: 07/18/2022] [Indexed: 11/16/2022] Open
Abstract
A supply of glucose to a nervous tissue is fulfilled by a cerebrovascular network, and further diffusion is known to occur at both an arteriolar and a microvascular level. Despite a direct relation, a blood flow dynamic and reaction-diffusion of metabolites are usually considered separately in the mathematical models. In the present study they are coupled in a multiphysical approach which allows to evaluate the effects of capillary blood flow changes on near-vessels nutrient concentration gradients evidently. Cerebral blood flow (CBF) was described by the non-steady-state Navier-Stokes equations for a non-Newtonian fluid whose constitutive law is given by the Carreau model. A three-level organization of blood–brain barrier (BBB) is modelled by the flux dysconnectivity functions including densities and kinetic properties of glucose transporters. The velocity of a fluid flow in brain extracellular space (ECS) was estimated using Darcy’s law. The equations of reaction-diffusion with convection based on a generated flow field for continues and porous media were used to describe spatial-time gradients of glucose in the capillary lumen and brain parenchyma of a neurovascular unit (NVU), respectively. Changes in CBF were directly simulated using smoothing step-like functions altering the difference of intracapillary pressure in time. The changes of CBF cover both the decrease (on 70%) and the increase (on 50%) in a capillary flow velocity. Analyzing the dynamics of glucose gradients, it was shown that a rapid decrease of a capillary blood flow yields an enhanced level of glucose in a near-capillary nervous tissue if the contacts between astrocytes end-feet are not tight. Under the increased CBF velocities the amplitude of glucose concentration gradients is always enhanced. The introduced approach can be used for estimation of blood flow changes influence not only on glucose but also on other nutrients concentration gradients and for the modelling of distributions of their concentrations near blood vessels in other tissues as well.
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9
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Huang J, Lai JHC, Han X, Chen Z, Xiao P, Liu Y, Chen L, Xu J, Chan KWY. Sensitivity schemes for dynamic glucose-enhanced magnetic resonance imaging to detect glucose uptake and clearance in mouse brain at 3 T. NMR IN BIOMEDICINE 2022; 35:e4640. [PMID: 34750891 DOI: 10.1002/nbm.4640] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/18/2021] [Revised: 08/30/2021] [Accepted: 10/05/2021] [Indexed: 06/13/2023]
Abstract
We investigated three dynamic glucose-enhanced (DGE) MRI methods for sensitively monitoring glucose uptake and clearance in both brain parenchyma and cerebrospinal fluid (CSF) at clinical field strength (3 T). By comparing three sequences, namely, Carr-Purcell-Meiboom-Gill (CPMG), on-resonance variable delay multipulse (onVDMP), and on-resonance spin-lock (onSL), a high-sensitivity DGE MRI scheme with truncated multilinear singular value decomposition (MLSVD) denoising was proposed. The CPMG method showed the highest sensitivity in detecting the parenchymal DGE signal among the three methods, while both onVDMP and onSL were more robust for CSF DGE imaging. Here, onVDMP was applied for CSF imaging, as it displayed the best stability of the DGE results in this study. The truncated MLSVD denoising method was incorporated to further improve the sensitivity. The proposed DGE MRI scheme was examined in mouse brain with 50%/25%/12.5% w/w D-glucose injections. The results showed that this combination could detect DGE signal changes from the brain parenchyma and CSF with as low as a 12.5% w/w D-glucose injection. The proposed DGE MRI schemes could sensitively detect the glucose signal change from brain parenchyma and CSF after D-glucose injection at a clinically relevant concentration, demonstrating high potential for clinical translation.
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Affiliation(s)
- Jianpan Huang
- Department of Biomedical Engineering, City University of Hong Kong, Hong Kong, China
| | - Joseph H C Lai
- Department of Biomedical Engineering, City University of Hong Kong, Hong Kong, China
| | - Xiongqi Han
- Department of Biomedical Engineering, City University of Hong Kong, Hong Kong, China
| | - Zilin Chen
- Department of Biomedical Engineering, City University of Hong Kong, Hong Kong, China
| | - Peng Xiao
- Department of Biomedical Engineering, City University of Hong Kong, Hong Kong, China
| | - Yang Liu
- Department of Biomedical Engineering, City University of Hong Kong, Hong Kong, China
- Hong Kong Centre for Cerebro-Cardiovascular Health Engineering (COCHE), Hong Kong, China
| | - Lin Chen
- F. M. Kirby Research Center for Functional Brain Imaging, Kennedy Krieger Research Institute, Baltimore, Maryland, USA
- Russell H. Morgan Department of Radiology and Radiological Science, The Johns Hopkins University School of Medicine, Baltimore, Maryland, USA
- Department of Electronic Science, Fujian Provincial Key Laboratory of Plasma and Magnetic Resonance, Xiamen University, Xiamen, China
| | - Jiadi Xu
- F. M. Kirby Research Center for Functional Brain Imaging, Kennedy Krieger Research Institute, Baltimore, Maryland, USA
- Russell H. Morgan Department of Radiology and Radiological Science, The Johns Hopkins University School of Medicine, Baltimore, Maryland, USA
| | - Kannie W Y Chan
- Department of Biomedical Engineering, City University of Hong Kong, Hong Kong, China
- Hong Kong Centre for Cerebro-Cardiovascular Health Engineering (COCHE), Hong Kong, China
- Russell H. Morgan Department of Radiology and Radiological Science, The Johns Hopkins University School of Medicine, Baltimore, Maryland, USA
- City University of Hong Kong Shenzhen Research Institute, Shenzhen, China
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10
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Li C, Chai X, Pan J, Huang J, Wu Y, Xue Y, Zhou W, Yang J, Zhu X, Zhao S. β-Hydroxybutyrate Alleviates Low Glucose-Induced Apoptosis via Modulation of ROS-Mediated p38 MAPK Signaling. J Mol Neurosci 2022; 72:923-938. [PMID: 35129799 DOI: 10.1007/s12031-022-01974-3] [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: 09/14/2021] [Accepted: 01/14/2022] [Indexed: 11/26/2022]
Abstract
Hypoglycemia has emerged as a prominent complication in anti-diabetic drug therapy or negative energy balance of animals, which causes brain damage, cognitive impairment, and even death. Brain injury induced by hypoglycemia is closely related to oxidative stress and the production of reactive oxygen species (ROS). The intracellular accumulation of ROS leads to neuronal damage, even death. Ketone body β-hydroxybutyrate (BHBA) not only serves as alternative energy source for glucose in extrahepatic tissues, but is also involved in cellular signaling transduction. Previous studies showed that BHBA reduces apoptosis by inhibiting the excessive production of ROS and activation of caspase-3. However, the effects of BHBA on apoptosis induced by glucose deprivation and its related molecular mechanisms have been seldom reported. In the present study, PC12 cells and primary cortical neurons were used to establish a low glucose injury model. The effects of BHBA on the survival and apoptosis in a glucose deficient condition and related molecular mechanisms were investigated by using flow cytometry, immunofluorescence, and western blotting. PC12 cells were incubated with 1 mM glucose for 24 h as a low glucose cell model, in which ROS accumulation and cell mortality were significantly increased. After 24 h and 48 h treatment with different concentrations of BHBA (0 mM, 0.05 mM, 0.5 mM, 1 mM, 2 mM), ROS production was significantly inhibited. Moreover, cell apoptosis rate was decreased and survival rate was significantly increased in 1 mM and 2 mM BHBA groups. In primary cortical neurons, at 24 h after treatment with 2 mM BHBA, the injured length and branch of neurites were significantly improved. Meanwhile, the intracellular ROS level, the proportion of c-Fos+ cells, apoptosis rate, and nuclear translocation of NF-κB protein after treatment with BHBA were significantly decreased when compared with that in low glucose cells. Importantly, the expression of p38, p-p38, NF-κB, and caspase-3 were significantly decreased, while the expression of p-ERK was significantly increased in both PC12 cells and primary cortical neurons. Our results demonstrate that BHBA decreased the accumulation of intracellular ROS, and further inhibited cell apoptosis by mediating the p38 MAPK signaling pathway and caspase-3 apoptosis cascade during glucose deprivation. In addition, BHBA inhibited apoptosis by activating ERK phosphorylation and alleviated the damage of low glucose to PC12 cells and primary cortical neurons. These results provide new insight into the anti-apoptotic effect of BHBA in a glucose deficient condition and the related signaling cascade.
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Affiliation(s)
- Cixia Li
- College of Veterinary Medicine, Northwest A&F University, Yangling, Shaanxi, 712100, People's Republic of China
| | - Xuejun Chai
- College of Basic Medicine, Xi'An Medical University, Xi'An, Shaanxi, 710021, People's Republic of China
| | - Jiarong Pan
- College of Veterinary Medicine, Northwest A&F University, Yangling, Shaanxi, 712100, People's Republic of China
| | - Jian Huang
- College of Veterinary Medicine, Northwest A&F University, Yangling, Shaanxi, 712100, People's Republic of China
| | - Yongji Wu
- College of Veterinary Medicine, Northwest A&F University, Yangling, Shaanxi, 712100, People's Republic of China
| | - Yuhuan Xue
- College of Veterinary Medicine, Northwest A&F University, Yangling, Shaanxi, 712100, People's Republic of China
| | - Wentai Zhou
- College of Veterinary Medicine, Northwest A&F University, Yangling, Shaanxi, 712100, People's Republic of China
| | - Jiping Yang
- College of Basic Medicine, Xi'An Medical University, Xi'An, Shaanxi, 710021, People's Republic of China
| | - Xiaoyan Zhu
- College of Veterinary Medicine, Northwest A&F University, Yangling, Shaanxi, 712100, People's Republic of China.
| | - Shanting Zhao
- College of Veterinary Medicine, Northwest A&F University, Yangling, Shaanxi, 712100, People's Republic of China.
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11
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Ge I, Kirschen GW, Wang X. Shifted Dynamics of Glucose Metabolism in the Hippocampus During Aging. Front Aging Neurosci 2021; 13:700306. [PMID: 34194320 PMCID: PMC8236846 DOI: 10.3389/fnagi.2021.700306] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2021] [Accepted: 05/19/2021] [Indexed: 11/13/2022] Open
Abstract
Aging is a process that adversely affects brain functions such as cognition. Brain activity is highly energy consuming, with glucose serving as the main energy source under normal circumstances. Whether the dynamics of glucose metabolism change with aging is not well understood. This study sought to investigate the activity-dependent changes in glucose metabolism of the mouse hippocampus during aging. In brief, after 1 h of contextual exploration in an enriched environmental condition or 1 h in a familiar home cage condition, metabolites were measured from the hippocampus of both young adult and aged mice with metabolomic profiling. Compared to the home cage context, the enriched contextual exploration condition resulted in changes in the concentration of 11 glucose metabolism-related metabolites in the young adult hippocampus. In contrast, glucose metabolism-related metabolite changes were more apparent in the aged group altered by contextual exploration when compared to those in the home cage condition. Importantly, in the aged groups, several key metabolites involved in glycolysis, the TCA cycle, and ketone body metabolism accumulated, suggesting the less efficient metabolization of glucose-based energy resources. Altogether, the analyses revealed that in the aged mice altered by enriched contextual exploration, the glucose resource seems to be unable to provide enough energy for hippocampal function.
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Affiliation(s)
- Ivan Ge
- Ward Melville High School, East Setauket, NY, United States
| | - Gregory Wohl Kirschen
- Department of Gynecology and Obstetrics, The Johns Hopkins Hospital, Baltimore, MD, United States
| | - Xinxing Wang
- Department of Neurobiology and Behavior, The State University of New York at Stony Brook, Stony Brook, NY, United States
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12
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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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13
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Garcia-Serrano AM, Duarte JMN. Brain Metabolism Alterations in Type 2 Diabetes: What Did We Learn From Diet-Induced Diabetes Models? Front Neurosci 2020; 14:229. [PMID: 32265637 PMCID: PMC7101159 DOI: 10.3389/fnins.2020.00229] [Citation(s) in RCA: 41] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2019] [Accepted: 03/02/2020] [Indexed: 12/27/2022] Open
Abstract
Type 2 diabetes (T2D) is a metabolic disease with impact on brain function through mechanisms that include glucose toxicity, vascular damage and blood–brain barrier (BBB) impairments, mitochondrial dysfunction, oxidative stress, brain insulin resistance, synaptic failure, neuroinflammation, and gliosis. Rodent models have been developed for investigating T2D, and have contributed to our understanding of mechanisms involved in T2D-induced brain dysfunction. Namely, mice or rats exposed to diabetogenic diets that are rich in fat and/or sugar have been widely used since they develop memory impairment, especially in tasks that depend on hippocampal processing. Here we summarize main findings on brain energy metabolism alterations underlying dysfunction of neuronal and glial cells promoted by diet-induced metabolic syndrome that progresses to a T2D phenotype.
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Affiliation(s)
- Alba M Garcia-Serrano
- Department of Experimental Medical Science, Faculty of Medicine, Lund University, Lund, Sweden.,Wallenberg Centre for Molecular Medicine, Faculty of Medicine, Lund University, Lund, Sweden
| | - João M N Duarte
- Department of Experimental Medical Science, Faculty of Medicine, Lund University, Lund, Sweden.,Wallenberg Centre for Molecular Medicine, Faculty of Medicine, Lund University, Lund, Sweden
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14
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Dobberthien BJ, Tessier AG, Stanislaus AE, Sawyer MB, Fallone BG, Yahya A. PRESS timings for resolving 13 C 4 -glutamate 1 H signal at 9.4 T: Demonstration in rat with uniformly labelled 13 C-glucose. NMR IN BIOMEDICINE 2019; 32:e4180. [PMID: 31518031 DOI: 10.1002/nbm.4180] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/14/2019] [Revised: 07/30/2019] [Accepted: 08/18/2019] [Indexed: 06/10/2023]
Abstract
MRS of 13 C4 -labelled glutamate (13 C4 -Glu) during an infusion of a carbon-13 (13 C)-labelled substrate, such as uniformly labelled glucose ([U-13 C6 ]-Glc), provides a measure of Glc metabolism. The presented work provides a single-shot indirect 13 C detection technique to quantify the approximately 2.51 ppm 13 C4 -Glu satellite proton (1 H) peak at 9.4 T. The methodology is an optimized point-resolved spectroscopy (PRESS) sequence that minimizes signal contamination from the strongly coupled protons of N-acetylaspartate (NAA), which resonate at approximately 2.49 ppm. J-coupling evolution of protons was characterized numerically and verified experimentally. A (TE1 , TE2 ) combination of (20 ms, 106 ms) was found to be suitable for minimizing NAA signal in the 2.51 ppm 1 H 13 C4 -Glu spectral region, while retaining the 13 C4 -Glu 1 H satellite peak. The efficacy of the technique was verified on phantom solutions and on two rat brains in vivo during an infusion of [U-13 C6 ]-Glc. LCModel was employed for analysis of the in vivo spectra to quantify the 2.51 ppm 1 H 13 C4 -Glu signal to obtain Glu C4 fractional enrichment time courses during the infusions. Cramér-Rao lower bounds of about 8% were obtained for the 2.51 ppm 13 C4 -Glu 1 H satellite peak with the optimal TE combination.
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Affiliation(s)
| | - Anthony G Tessier
- Department of Oncology, University of Alberta, Edmonton, Alberta, Canada
- Department of Medical Physics, Cross Cancer Institute, Edmonton, Alberta, Canada
| | | | - Michael B Sawyer
- Department of Oncology, University of Alberta, Edmonton, Alberta, Canada
| | - B Gino Fallone
- Department of Oncology, University of Alberta, Edmonton, Alberta, Canada
- Department of Medical Physics, Cross Cancer Institute, Edmonton, Alberta, Canada
| | - Atiyah Yahya
- Department of Oncology, University of Alberta, Edmonton, Alberta, Canada
- Department of Medical Physics, Cross Cancer Institute, Edmonton, Alberta, Canada
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15
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Richter J, Rabe D, Duysen K, Melchert UH, Oltmanns KM. Lactate infusion increases brain energy content during euglycemia but not hypoglycemia in healthy men. NMR IN BIOMEDICINE 2019; 32:e4167. [PMID: 31468650 DOI: 10.1002/nbm.4167] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/22/2018] [Revised: 07/04/2019] [Accepted: 07/24/2019] [Indexed: 06/10/2023]
Abstract
A special characteristic of the brain is the usage of lactate as alternative fuel instead of glucose to preserve its energy homeostasis. This physiological function is valid for sufficient cerebral glucose supply, as well as presumably during hypoglycemia, given that exogenous lactate infusion suppresses hormonal counterregulation. However, it is not yet clarified whether this effect is mediated by the use of lactate as an alternative cerebral energy substrate or any other mechanism. We hypothesized that under conditions of limited access to glucose (ie, during experimental hypoglycemia) lactate infusion would prevent hypoglycemia-induced neuroenergetic deficits in a neuroprotective way. In a randomized, double-blind, crossover study, lactate vs placebo infusion was compared during hyperinsulinemic-hypoglycemic clamps in 16 healthy young men. We measured the cerebral high-energy phosphate content - ie, adenosine triphosphate (ATP), phosphocreatine (PCr) and inorganic phosphate (Pi) levels - by 31 P-magnetic resonance spectroscopy as well as the neuroendocrine stress response. During euglycemia, lactate infusion increased ATP/Pi as well as PCr/Pi ratios compared with baseline values and placebo infusion. During hypoglycemia, there were no differences between the lactate and the placebo condition in both ratios. Hormonal counterregulation was significantly diminished upon lactate infusion. Our data demonstrate an elevated cerebral high-energy phosphate content upon lactate infusion during euglycemia, whereas there was no such effect during experimental hypoglycemia. Nevertheless, lactate infusion suppressed hypoglycemic hormonal counterregulation. Lactate thus adds to cerebral energy provision during euglycemia and may contribute to an increase in ATP reserves, which in turn protects the brain against neuroglucopenia under recurrent hypopglycemic conditions, eg, in diabetic patients.
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Affiliation(s)
- Juliane Richter
- Section of Psychoneurobiology, Center of Brain, Behavior and Metabolism, University of Luebeck, Luebeck, Germany
| | - Doerte Rabe
- Section of Psychoneurobiology, Center of Brain, Behavior and Metabolism, University of Luebeck, Luebeck, Germany
| | - Kai Duysen
- Section of Psychoneurobiology, Center of Brain, Behavior and Metabolism, University of Luebeck, Luebeck, Germany
| | - Uwe H Melchert
- Section of Psychoneurobiology, Center of Brain, Behavior and Metabolism, University of Luebeck, Luebeck, Germany
| | - Kerstin M Oltmanns
- Section of Psychoneurobiology, Center of Brain, Behavior and Metabolism, University of Luebeck, Luebeck, Germany
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16
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Lei H, Preitner F, Labouèbe G, Gruetter R, Thorens B. Glucose transporter 2 mediates the hypoglycemia-induced increase in cerebral blood flow. J Cereb Blood Flow Metab 2019; 39:1725-1736. [PMID: 29561214 PMCID: PMC6727137 DOI: 10.1177/0271678x18766743] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Glucose transporter 2 (Glut2)-positive cells are sparsely distributed in brain and play an important role in the stimulation of glucagon secretion in response to hypoglycemia. We aimed to determine if Glut2-positive cells can influence another response to hypoglycemia, i.e. increased cerebral blood flow (CBF). CBF of adult male mice devoid of Glut2, either globally (ripglut1:glut2-/-) or in the nervous system only (NG2KO), and their respective controls were studied under basal glycemia and insulin-induced hypoglycemia using quantitative perfusion magnetic resonance imaging at 9.4 T. The effect on CBF of optogenetic activation of hypoglycemia responsive Glut2-positive neurons of the paraventricular thalamic area was measured in mice expressing channelrhodopsin2 under the control of the Glut2 promoter. We found that in both ripglut1:glut2-/- mice and NG2KO mice, CBF in basal conditions was higher than in their respective controls and not further activated by hypoglycemia, as measured in the hippocampus, hypothalamus and whole brain. Conversely, optogenetic activation of Glut2-positive cells in the paraventricular thalamic nucleus induced a local increase in CBF similar to that induced by hypoglycemia. Thus, Glut2 expression in the nervous system is required for the control of CBF in response to changes in blood glucose concentrations.
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Affiliation(s)
- Hongxia Lei
- 1 AIT, Center for Biomedical Imaging (CIBM-AIT), Ecole Polytechnique Fédérale de Lausanne, Lausanne, Switzerland.,2 Department of Radiology, University of Geneva, Geneva, Switzerland
| | - Frédéric Preitner
- 3 Center for Integrative Genomics, University of Lausanne, Lausanne, Switzerland.,4 Mouse Metabolic Evaluation Facility, Center for Integrative Genomics, University of Lausanne, Lausanne, Switzerland
| | - Gwenaël Labouèbe
- 3 Center for Integrative Genomics, University of Lausanne, Lausanne, Switzerland
| | - Rolf Gruetter
- 1 AIT, Center for Biomedical Imaging (CIBM-AIT), Ecole Polytechnique Fédérale de Lausanne, Lausanne, Switzerland.,2 Department of Radiology, University of Geneva, Geneva, Switzerland.,5 Department of Radiology, University of Lausanne, Lausanne, Switzerland
| | - Bernard Thorens
- 3 Center for Integrative Genomics, University of Lausanne, Lausanne, Switzerland
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17
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Díaz-García CM, Lahmann C, Martínez-François JR, Li B, Koveal D, Nathwani N, Rahman M, Keller JP, Marvin JS, Looger LL, Yellen G. Quantitative in vivo imaging of neuronal glucose concentrations with a genetically encoded fluorescence lifetime sensor. J Neurosci Res 2019; 97:946-960. [PMID: 31106909 PMCID: PMC6565483 DOI: 10.1002/jnr.24433] [Citation(s) in RCA: 46] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2019] [Revised: 04/08/2019] [Accepted: 04/08/2019] [Indexed: 01/07/2023]
Abstract
Glucose is an essential source of energy for the brain. Recently, the development of genetically encoded fluorescent biosensors has allowed real time visualization of glucose dynamics from individual neurons and astrocytes. A major difficulty for this approach, even for ratiometric sensors, is the lack of a practical method to convert such measurements into actual concentrations in ex vivo brain tissue or in vivo. Fluorescence lifetime imaging provides a strategy to overcome this. In a previous study, we reported the lifetime glucose sensor iGlucoSnFR-TS (then called SweetieTS) for monitoring changes in neuronal glucose levels in response to stimulation. This genetically encoded sensor was generated by combining the Thermus thermophilus glucose-binding protein with a circularly permuted variant of the monomeric fluorescent protein T-Sapphire. Here, we provide more details on iGlucoSnFR-TS design and characterization, as well as pH and temperature sensitivities. For accurate estimation of glucose concentrations, the sensor must be calibrated at the same temperature as the experiments. We find that when the extracellular glucose concentration is in the range 2-10 mM, the intracellular glucose concentration in hippocampal neurons from acute brain slices is ~20% of the nominal external glucose concentration (~0.4-2 mM). We also measured the cytosolic neuronal glucose concentration in vivo, finding a range of ~0.7-2.5 mM in cortical neurons from awake mice.
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Affiliation(s)
| | - Carolina Lahmann
- Department of Neurobiology, Harvard Medical School, Boston, MA, USA
| | | | - Binsen Li
- Department of Neurobiology, Harvard Medical School, Boston, MA, USA
| | - Dorothy Koveal
- Department of Neurobiology, Harvard Medical School, Boston, MA, USA
| | - Nidhi Nathwani
- Department of Neurobiology, Harvard Medical School, Boston, MA, USA
| | - Mahia Rahman
- Department of Neurobiology, Harvard Medical School, Boston, MA, USA
| | - Jacob P. Keller
- Janelia Research Campus, Howard Hughes Medical Institute, Ashburn, VA, USA
| | - Jonathan S. Marvin
- Janelia Research Campus, Howard Hughes Medical Institute, Ashburn, VA, USA
| | - Loren L. Looger
- Janelia Research Campus, Howard Hughes Medical Institute, Ashburn, VA, USA
| | - Gary Yellen
- Department of Neurobiology, Harvard Medical School, Boston, MA, USA
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18
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Rehni AK, Dave KR. Impact of Hypoglycemia on Brain Metabolism During Diabetes. Mol Neurobiol 2018; 55:9075-9088. [PMID: 29637442 PMCID: PMC6179939 DOI: 10.1007/s12035-018-1044-6] [Citation(s) in RCA: 36] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2018] [Accepted: 03/27/2018] [Indexed: 12/24/2022]
Abstract
Diabetes is a metabolic disease afflicting millions of people worldwide. A substantial fraction of world's total healthcare expenditure is spent on treating diabetes. Hypoglycemia is a serious consequence of anti-diabetic drug therapy, because it induces metabolic alterations in the brain. Metabolic alterations are one of the central mechanisms mediating hypoglycemia-related functional changes in the brain. Acute, chronic, and/or recurrent hypoglycemia modulate multiple metabolic pathways, and exposure to hypoglycemia increases consumption of alternate respiratory substrates such as ketone bodies, glycogen, and monocarboxylates in the brain. The aim of this review is to discuss hypoglycemia-induced metabolic alterations in the brain in glucose counterregulation, uptake, utilization and metabolism, cellular respiration, amino acid and lipid metabolism, and the significance of other sources of energy. The present review summarizes information on hypoglycemia-induced metabolic changes in the brain of diabetic and non-diabetic subjects and the manner in which they may affect brain function.
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Affiliation(s)
- Ashish K Rehni
- Cerebral Vascular Disease Research Laboratories, University of Miami Miller School of Medicine, Miami, FL, 33136, USA
- Department of Neurology, University of Miami Miller School of Medicine, 1420 NW 9th Ave, NRB/203E, Miami, FL, 33136, USA
| | - Kunjan R Dave
- Cerebral Vascular Disease Research Laboratories, University of Miami Miller School of Medicine, Miami, FL, 33136, USA.
- Department of Neurology, University of Miami Miller School of Medicine, 1420 NW 9th Ave, NRB/203E, Miami, FL, 33136, USA.
- Neuroscience Program, University of Miami Miller School of Medicine, Miami, FL, 33136, USA.
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19
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Hladky SB, Barrand MA. Elimination of substances from the brain parenchyma: efflux via perivascular pathways and via the blood-brain barrier. Fluids Barriers CNS 2018; 15:30. [PMID: 30340614 PMCID: PMC6194691 DOI: 10.1186/s12987-018-0113-6] [Citation(s) in RCA: 133] [Impact Index Per Article: 22.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2018] [Accepted: 08/30/2018] [Indexed: 02/06/2023] Open
Abstract
This review considers efflux of substances from brain parenchyma quantified as values of clearances (CL, stated in µL g-1 min-1). Total clearance of a substance is the sum of clearance values for all available routes including perivascular pathways and the blood-brain barrier. Perivascular efflux contributes to the clearance of all water-soluble substances. Substances leaving via the perivascular routes may enter cerebrospinal fluid (CSF) or lymph. These routes are also involved in entry to the parenchyma from CSF. However, evidence demonstrating net fluid flow inwards along arteries and then outwards along veins (the glymphatic hypothesis) is still lacking. CLperivascular, that via perivascular routes, has been measured by following the fate of exogenously applied labelled tracer amounts of sucrose, inulin or serum albumin, which are not metabolized or eliminated across the blood-brain barrier. With these substances values of total CL ≅ 1 have been measured. Substances that are eliminated at least partly by other routes, i.e. across the blood-brain barrier, have higher total CL values. Substances crossing the blood-brain barrier may do so by passive, non-specific means with CLblood-brain barrier values ranging from < 0.01 for inulin to > 1000 for water and CO2. CLblood-brain barrier values for many small solutes are predictable from their oil/water partition and molecular weight. Transporters specific for glucose, lactate and many polar substrates facilitate efflux across the blood-brain barrier producing CLblood-brain barrier values > 50. The principal route for movement of Na+ and Cl- ions across the blood-brain barrier is probably paracellular through tight junctions between the brain endothelial cells producing CLblood-brain barrier values ~ 1. There are large fluxes of amino acids into and out of the brain across the blood-brain barrier but only small net fluxes have been observed suggesting substantial reuse of essential amino acids and α-ketoacids within the brain. Amyloid-β efflux, which is measurably faster than efflux of inulin, is primarily across the blood-brain barrier. Amyloid-β also leaves the brain parenchyma via perivascular efflux and this may be important as the route by which amyloid-β reaches arterial walls resulting in cerebral amyloid angiopathy.
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Affiliation(s)
- Stephen B. Hladky
- Department of Pharmacology, University of Cambridge, Cambridge, CB2 1PD UK
| | - Margery A. Barrand
- Department of Pharmacology, University of Cambridge, Cambridge, CB2 1PD UK
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20
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Jin T, Mehrens H, Wang P, Kim SG. Chemical exchange-sensitive spin-lock MRI of glucose analog 3-O-methyl-d-glucose in normal and ischemic brain. J Cereb Blood Flow Metab 2018; 38:869-880. [PMID: 28485194 PMCID: PMC5987935 DOI: 10.1177/0271678x17707419] [Citation(s) in RCA: 26] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
Glucose transport is important for understanding brain glucose metabolism. We studied glucose transport with a presumably non-toxic and non-metabolizable glucose analog, 3-O-methyl-d-glucose, using a chemical exchange-sensitive spin-lock MRI technique at 9.4 Tesla. 3-O-methyl-d-glucose showed comparable chemical exchange properties with d-glucose and 2-deoxy-d-glucose in phantoms, and higher and lower chemical exchange-sensitive spin-lock sensitivity than Glc and 2-deoxy-d-glucose in in vivo experiments, respectively. The changes of the spin-lattice relaxation rate in the rotating frame (Δ R1ρ) in normal rat brain peaked at ∼15 min after the intravenous injection of 1 g/kg 3-O-methyl-d-glucose and almost maintained a plateau for >1 h. Doses up to 4 g/kg 3-O-methyl-d-glucose were linearly correlated with Δ R1ρ. In rats with focal ischemic stroke, chemical exchange-sensitive spin-lock with 3-O-methyl-d-glucose injection at 1 h after stroke onset showed reduced Δ R1ρ in the ischemic core but higher Δ R1ρ in the peri-core region compared to normal tissue, which progressed into the ischemic core at 3 h after stroke onset. This suggests that the hyper-chemical exchange-sensitive spin-lock region observed at 1 h is the ischemic penumbra at-risk of infarct. In summary, 3-O-methyl-d-glucose-chemical exchange-sensitive spin-lock can be a sensitive MRI technique to probe the glucose transport in normal and ischemic brains.
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Affiliation(s)
- Tao Jin
- 1 NeuroImaging Laboratory, Department of Radiology, University of Pittsburgh, Pittsburgh, PA, USA.,2 Department of Bioengineering, University of Pittsburgh, Pittsburgh, PA, USA
| | - Hunter Mehrens
- 1 NeuroImaging Laboratory, Department of Radiology, University of Pittsburgh, Pittsburgh, PA, USA
| | - Ping Wang
- 1 NeuroImaging Laboratory, Department of Radiology, University of Pittsburgh, Pittsburgh, PA, USA
| | - Seong-Gi Kim
- 3 Center for Neuroscience Imaging Research, Institute for Basic Science (IBS), Suwon, Korea.,4 Department of Biomedical Engineering, Sungkyunkwan University, Suwon, Korea
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21
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Blood-Brain Glucose Transfer in Alzheimer's disease: Effect of GLP-1 Analog Treatment. Sci Rep 2017; 7:17490. [PMID: 29235507 PMCID: PMC5727512 DOI: 10.1038/s41598-017-17718-y] [Citation(s) in RCA: 92] [Impact Index Per Article: 13.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2017] [Accepted: 11/29/2017] [Indexed: 12/12/2022] Open
Abstract
There are fewer than normal glucose transporters at the blood-brain barrier (BBB) in Alzheimer’s disease (AD). When reduced expression of transporters aggravates the symptoms of AD, the transporters become a potential target of therapy. The incretin hormone GLP-1 prevents the decline of cerebral metabolic rate for glucose (CMRglc) in AD, and GLP-1 may serve to raise transporter numbers. We hypothesized that the GLP-1 analog liraglutide would prevent the decline of CMRglc in AD by raising blood-brain glucose transfer, depending on the duration of disease. We randomized 38 patients with AD to treatment with liraglutide (n = 18) or placebo (n = 20) for 6 months, and determined the blood-brain glucose transfer capacity (Tmax) in the two groups and a healthy age matched control group (n = 6). In both AD groups at baseline, Tmax estimates correlated inversely with the duration of AD, as did the estimates of CMRglc that in turn were positively correlated with cognition. The GLP-1 analog treatment, compared to placebo, highly significantly raised the Tmax estimates of cerebral cortex from 0.72 to 1.1 umol/g/min, equal to Tmax estimates in healthy volunteers. The result is consistent with the claim that GLP-1 analog treatment restores glucose transport at the BBB.
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22
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Lu M, Zhu XH, Zhang Y, Mateescu G, Chen W. Quantitative assessment of brain glucose metabolic rates using in vivo deuterium magnetic resonance spectroscopy. J Cereb Blood Flow Metab 2017; 37:3518-3530. [PMID: 28503999 PMCID: PMC5669347 DOI: 10.1177/0271678x17706444] [Citation(s) in RCA: 88] [Impact Index Per Article: 12.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
Quantitative assessment of cerebral glucose consumption rate (CMRglc) and tricarboxylic acid cycle flux (VTCA) is crucial for understanding neuroenergetics under physiopathological conditions. In this study, we report a novel in vivo Deuterium (2H) MRS (DMRS) approach for simultaneously measuring and quantifying CMRglc and VTCA in rat brains at 16.4 Tesla. Following a brief infusion of deuterated glucose, dynamic changes of isotope-labeled glucose, glutamate/glutamine (Glx) and water contents in the brain can be robustly monitored from their well-resolved 2H resonances. Dynamic DMRS glucose and Glx data were employed to determine CMRglc and VTCA concurrently. To test the sensitivity of this method in response to altered glucose metabolism, two brain conditions with different anesthetics were investigated. Increased CMRglc (0.46 vs. 0.28 µmol/g/min) and VTCA (0.96 vs. 0.6 µmol/g/min) were found in rats under morphine as compared to deeper anesthesia using 2% isoflurane. This study demonstrates the feasibility and new utility of the in vivo DMRS approach to assess cerebral glucose metabolic rates at high/ultrahigh field. It provides an alternative MRS tool for in vivo study of metabolic coupling relationship between aerobic and anaerobic glucose metabolisms in brain under physiopathological states.
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Affiliation(s)
- Ming Lu
- 1 Center for Magnetic Resonance Research, Department of Radiology, University of Minnesota Medical School, MN, USA
| | - Xiao-Hong Zhu
- 1 Center for Magnetic Resonance Research, Department of Radiology, University of Minnesota Medical School, MN, USA
| | - Yi Zhang
- 1 Center for Magnetic Resonance Research, Department of Radiology, University of Minnesota Medical School, MN, USA
| | - Gheorghe Mateescu
- 2 Case Center for Imaging Research, Departments of Chemistry, Case Western Reserve University, Cleveland, OH, USA
| | - Wei Chen
- 1 Center for Magnetic Resonance Research, Department of Radiology, University of Minnesota Medical School, MN, USA
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23
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Angleys H, Jespersen SN, Østergaard L. The Effects of Capillary Transit Time Heterogeneity (CTH) on the Cerebral Uptake of Glucose and Glucose Analogs: Application to FDG and Comparison to Oxygen Uptake. Front Comput Neurosci 2016; 10:103. [PMID: 27790110 PMCID: PMC5062759 DOI: 10.3389/fncom.2016.00103] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2016] [Accepted: 09/15/2016] [Indexed: 11/13/2022] Open
Abstract
Glucose is the brain's principal source of ATP, but the extent to which cerebral glucose consumption (CMRglc) is coupled with its oxygen consumption (CMRO2) remains unclear. Measurements of the brain's oxygen-glucose index OGI = CMRO2/CMRglc suggest that its oxygen uptake largely suffices for oxidative phosphorylation. Nevertheless, during functional activation and in some disease states, brain tissue seemingly produces lactate although cerebral blood flow (CBF) delivers sufficient oxygen, so-called aerobic glycolysis. OGI measurements, in turn, are method-dependent in that estimates based on glucose analog uptake depend on the so-called lumped constant (LC) to arrive at CMRglc. Capillary transit time heterogeneity (CTH), which is believed to change during functional activation and in some disease states, affects the extraction efficacy of oxygen from blood. We developed a three-compartment model of glucose extraction to examine whether CTH also affects glucose extraction into brain tissue. We then combined this model with our previous model of oxygen extraction to examine whether differential glucose and oxygen extraction might favor non-oxidative glucose metabolism under certain conditions. Our model predicts that glucose uptake is largely unaffected by changes in its plasma concentration, while changes in CBF and CTH affect glucose and oxygen uptake to different extents. Accordingly, functional hyperemia facilitates glucose uptake more than oxygen uptake, favoring aerobic glycolysis during enhanced energy demands. Applying our model to glucose analogs, we observe that LC depends on physiological state, with a risk of overestimating relative increases in CMRglc during functional activation by as much as 50%.
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Affiliation(s)
- Hugo Angleys
- Center of Functionally Integrative Neuroscience and MINDLab, Aarhus University Aarhus, Denmark
| | - Sune N Jespersen
- Center of Functionally Integrative Neuroscience and MINDLab, Aarhus UniversityAarhus, Denmark; Department of Physics and Astronomy, Aarhus UniversityAarhus, Denmark
| | - Leif Østergaard
- Center of Functionally Integrative Neuroscience and MINDLab, Aarhus UniversityAarhus, Denmark; Department of Neuroradiology, Aarhus University HospitalAarhus, Denmark
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Microdialysis as a Part of Invasive Cerebral Monitoring During Porcine Septic Shock. J Neurosurg Anesthesiol 2016; 28:323-30. [DOI: 10.1097/ana.0000000000000220] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
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Jin T, Mehrens H, Wang P, Kim SG. Glucose metabolism-weighted imaging with chemical exchange-sensitive MRI of 2-deoxyglucose (2DG) in brain: Sensitivity and biological sources. Neuroimage 2016; 143:82-90. [PMID: 27570111 DOI: 10.1016/j.neuroimage.2016.08.040] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2016] [Revised: 08/15/2016] [Accepted: 08/19/2016] [Indexed: 10/21/2022] Open
Abstract
Recent proof-of-principle studies have demonstrated the feasibility of measuring the uptake and metabolism of non-labeled 2-deoxy-D-glucose (2DG) by a chemical exchange-sensitive spin-lock (CESL) MRI approach. In order to gain better understanding of this new approach, we performed dynamic in vivo CESL MRI on healthy rat brains with an intravenous injection of 2DG under various conditions at 9.4T. For three 2DG doses of 0.25, 0.5 and 1g/kg, we found that 2DG-CESL signals increased linearly with injection dose at the initial (<20min) but not the later period (>40min) suggesting time-dependent differential weightings of 2DG transport and metabolism. Remaining 2DG-CESL studies were performed with 0.25g/kg 2DG. Since a higher isoflurane level reduces glucose metabolism and increases blood flow, 2DG-CESL was measured under 0.5%, 1.5% and 2.2% isoflurane. The 2DG-CESL signal was reduced at higher isoflurane levels correlating well with the 2DG phosphorylation in the intracellular space. To detect regional heterogeneities of glucose metabolism, 2DG-CESL with 0.33×0.33×1.50mm3 resolution was obtained, which indeed showed a higher response in the cortex compared to the corpus callosum. Lastly, unlike CESL MRI with the injection of non-transportable mannitol, the 2DG-CESL response decreased with an increased spin-lock pulse power confirming that 2DG-CESL is dominated by chemical exchange processes in the extravascular space. Taken together, our results showed that 2DG-CESL MRI signals mainly indicate glucose transport and metabolism and may be a useful biomarker for metabolic studies of normal and diseased brains.
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Affiliation(s)
- Tao Jin
- NeuroImaging Laboratory, Department of Radiology, University of Pittsburgh, Pittsburgh, PA 15203, United States; Department of Bioengineering, University of Pittsburgh, Pittsburgh, PA 15203, United States.
| | - Hunter Mehrens
- NeuroImaging Laboratory, Department of Radiology, University of Pittsburgh, Pittsburgh, PA 15203, United States
| | - Ping Wang
- NeuroImaging Laboratory, Department of Radiology, University of Pittsburgh, Pittsburgh, PA 15203, United States
| | - Seong-Gi Kim
- Center for Neuroscience Imaging Research, Institute for Basic Science (IBS), Suwon, Republic of Korea; Department of Biomedical Engineering, Sungkyunkwan University, Suwon, Republic of Korea
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Rooijackers HMM, Wiegers EC, Tack CJ, van der Graaf M, de Galan BE. Brain glucose metabolism during hypoglycemia in type 1 diabetes: insights from functional and metabolic neuroimaging studies. Cell Mol Life Sci 2016; 73:705-22. [PMID: 26521082 PMCID: PMC4735263 DOI: 10.1007/s00018-015-2079-8] [Citation(s) in RCA: 35] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2015] [Revised: 10/16/2015] [Accepted: 10/20/2015] [Indexed: 12/30/2022]
Abstract
Hypoglycemia is the most frequent complication of insulin therapy in patients with type 1 diabetes. Since the brain is reliant on circulating glucose as its main source of energy, hypoglycemia poses a threat for normal brain function. Paradoxically, although hypoglycemia commonly induces immediate decline in cognitive function, long-lasting changes in brain structure and cognitive function are uncommon in patients with type 1 diabetes. In fact, recurrent hypoglycemia initiates a process of habituation that suppresses hormonal responses to and impairs awareness of subsequent hypoglycemia, which has been attributed to adaptations in the brain. These observations sparked great scientific interest into the brain's handling of glucose during (recurrent) hypoglycemia. Various neuroimaging techniques have been employed to study brain (glucose) metabolism, including PET, fMRI, MRS and ASL. This review discusses what is currently known about cerebral metabolism during hypoglycemia, and how findings obtained by functional and metabolic neuroimaging techniques contributed to this knowledge.
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Affiliation(s)
- Hanne M M Rooijackers
- Department of Internal Medicine 463, Radboud University Medical Center, PO Box 9101, 6500 HB, Nijmegen, The Netherlands.
| | - Evita C Wiegers
- Department of Radiology and Nuclear Medicine, Radboud University Medical Center, Nijmegen, The Netherlands
| | - Cees J Tack
- Department of Internal Medicine 463, Radboud University Medical Center, PO Box 9101, 6500 HB, Nijmegen, The Netherlands
| | - Marinette van der Graaf
- Department of Radiology and Nuclear Medicine, Radboud University Medical Center, Nijmegen, The Netherlands
- Department of Pediatrics, Radboud University Medical Center, Nijmegen, The Netherlands
| | - Bastiaan E de Galan
- Department of Internal Medicine 463, Radboud University Medical Center, PO Box 9101, 6500 HB, Nijmegen, The Netherlands
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Thorn TL, He Y, Jackman NA, Lobner D, Hewett JA, Hewett SJ. A Cytotoxic, Co-operative Interaction Between Energy Deprivation and Glutamate Release From System xc- Mediates Aglycemic Neuronal Cell Death. ASN Neuro 2015; 7:1759091415614301. [PMID: 26553727 PMCID: PMC4641554 DOI: 10.1177/1759091415614301] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
The astrocyte cystine/glutamate antiporter (system xc(-)) contributes substantially to the excitotoxic neuronal cell death facilitated by glucose deprivation. The purpose of this study was to determine the mechanism by which this occurred. Using pure astrocyte cultures, as well as, mixed cortical cell cultures containing both neurons and astrocytes, we found that neither an enhancement in system xc(-) expression nor activity underlies the excitotoxic effects of aglycemia. In addition, using three separate bioassays, we demonstrate no change in the ability of glucose-deprived astrocytes--either cultured alone or with neurons--to remove glutamate from the extracellular space. Instead, we demonstrate that glucose-deprived cultures are 2 to 3 times more sensitive to the killing effects of glutamate or N-methyl-D-aspartate when compared with their glucose-containing controls. Hence, our results are consistent with the weak excitotoxic hypothesis such that a bioenergetic deficiency, which is measureable in our mixed but not astrocyte cultures, allows normally innocuous concentrations of glutamate to become excitotoxic. Adding to the burgeoning literature detailing the contribution of astrocytes to neuronal injury, we conclude that under our experimental paradigm, a cytotoxic, co-operative interaction between energy deprivation and glutamate release from astrocyte system xc(-) mediates aglycemic neuronal cell death.
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Affiliation(s)
- Trista L Thorn
- Department of Biology, Program in Neuroscience, Syracuse University, NY, USA Department of Neuroscience and Physiology, SUNY Upstate Medical University, Syracuse, NY, USA
| | - Yan He
- Department of Biology, Program in Neuroscience, Syracuse University, NY, USA
| | - Nicole A Jackman
- Department of Neuroscience, University of Connecticut Health Center, Farmington, CT, USA
| | - Doug Lobner
- Department of Biomedical Sciences, Marquette University, Milwaukee, WI, USA
| | - James A Hewett
- Department of Biology, Program in Neuroscience, Syracuse University, NY, USA Department of Neuroscience and Physiology, SUNY Upstate Medical University, Syracuse, NY, USA
| | - Sandra J Hewett
- Department of Biology, Program in Neuroscience, Syracuse University, NY, USA Department of Neuroscience and Physiology, SUNY Upstate Medical University, Syracuse, NY, USA
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Falkowska A, Gutowska I, Goschorska M, Nowacki P, Chlubek D, Baranowska-Bosiacka I. Energy Metabolism of the Brain, Including the Cooperation between Astrocytes and Neurons, Especially in the Context of Glycogen Metabolism. Int J Mol Sci 2015; 16:25959-81. [PMID: 26528968 PMCID: PMC4661798 DOI: 10.3390/ijms161125939] [Citation(s) in RCA: 177] [Impact Index Per Article: 19.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2015] [Revised: 09/27/2015] [Accepted: 10/16/2015] [Indexed: 01/15/2023] Open
Abstract
Glycogen metabolism has important implications for the functioning of the brain, especially the cooperation between astrocytes and neurons. According to various research data, in a glycogen deficiency (for example during hypoglycemia) glycogen supplies are used to generate lactate, which is then transported to neighboring neurons. Likewise, during periods of intense activity of the nervous system, when the energy demand exceeds supply, astrocyte glycogen is immediately converted to lactate, some of which is transported to the neurons. Thus, glycogen from astrocytes functions as a kind of protection against hypoglycemia, ensuring preservation of neuronal function. The neuroprotective effect of lactate during hypoglycemia or cerebral ischemia has been reported in literature. This review goes on to emphasize that while neurons and astrocytes differ in metabolic profile, they interact to form a common metabolic cooperation.
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Affiliation(s)
- Anna Falkowska
- Department of Biochemistry and Medical Chemistry, Pomeranian Medical University, Powstańców Wlkp. 72, 70-111 Szczecin, Poland.
| | - Izabela Gutowska
- Department of Biochemistry and Human Nutrition, Pomeranian Medical University, Broniewskiego 24, 71-460 Szczecin, Poland.
| | - Marta Goschorska
- Department of Biochemistry and Medical Chemistry, Pomeranian Medical University, Powstańców Wlkp. 72, 70-111 Szczecin, Poland.
| | - Przemysław Nowacki
- Department of Neurology, Pomeranian Medical University, Unii Lubelskiej 1, 71-225 Szczecin, Poland.
| | - Dariusz Chlubek
- Department of Biochemistry and Medical Chemistry, Pomeranian Medical University, Powstańców Wlkp. 72, 70-111 Szczecin, Poland.
| | - Irena Baranowska-Bosiacka
- Department of Biochemistry and Medical Chemistry, Pomeranian Medical University, Powstańców Wlkp. 72, 70-111 Szczecin, Poland.
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Patel D, Kharkar PS, Nandave M. Emerging roles of system antiporter and its inhibition in CNS disorders. Mol Membr Biol 2015; 32:89-116. [PMID: 26508554 DOI: 10.3109/09687688.2015.1096972] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Affiliation(s)
| | - Prashant S. Kharkar
- Department of Pharmaceutical Chemistry, SPP School of Pharmacy and Technology Management, SVKM’s NMIMS University, Mumbai, India
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30
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Patet C, Quintard H, Suys T, Bloch J, Daniel RT, Pellerin L, Magistretti PJ, Oddo M. Neuroenergetic Response to Prolonged Cerebral Glucose Depletion after Severe Brain Injury and the Role of Lactate. J Neurotrauma 2015; 32:1560-6. [DOI: 10.1089/neu.2014.3781] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023] Open
Affiliation(s)
- Camille Patet
- Department of Intensive Care Medicine, University of Lausanne, Switzerland
| | - Hervé Quintard
- Department of Intensive Care Medicine, University of Lausanne, Switzerland
| | - Tamarah Suys
- Department of Intensive Care Medicine, University of Lausanne, Switzerland
| | - Jocelyne Bloch
- Department of Clinical Neurosciences, University of Lausanne, Switzerland
| | - Roy T. Daniel
- Department of Clinical Neurosciences, University of Lausanne, Switzerland
| | - Luc Pellerin
- Departement of Physiology, University of Lausanne, Switzerland
| | - Pierre J. Magistretti
- Division of Biological and Environmental Sciences and Engineering, King Abdullah University of Science and Technology, Thuwal, Kingdom of Saudi Arabia
- Department of Psychiatry, Centre Hospitalier Universitaire Vaudois, Lausanne, Switzerland
- Laboratory of Neuroenergetics and Cellular Dynamics, Brain Mind Institute, Ecole Polytechnique Fédérale de Lausanne, Lausanne, Switzerland
| | - Mauro Oddo
- Department of Intensive Care Medicine, University of Lausanne, Switzerland
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GDH-Dependent Glutamate Oxidation in the Brain Dictates Peripheral Energy Substrate Distribution. Cell Rep 2015; 13:365-75. [PMID: 26440896 DOI: 10.1016/j.celrep.2015.09.003] [Citation(s) in RCA: 45] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2014] [Revised: 08/17/2015] [Accepted: 09/01/2015] [Indexed: 12/27/2022] Open
Abstract
Glucose, the main energy substrate used in the CNS, is continuously supplied by the periphery. Glutamate, the major excitatory neurotransmitter, is foreseen as a complementary energy contributor in the brain. In particular, astrocytes actively take up glutamate and may use it through oxidative glutamate dehydrogenase (GDH) activity. Here, we investigated the significance of glutamate as energy substrate for the brain. Upon glutamate exposure, astrocytes generated ATP in a GDH-dependent way. The observed lack of glutamate oxidation in brain-specific GDH null CnsGlud1(-/-) mice resulted in a central energy-deprivation state with increased ADP/ATP ratios and phospho-AMPK in the hypothalamus. This induced changes in the autonomous nervous system balance, with increased sympathetic activity promoting hepatic glucose production and mobilization of substrates reshaping peripheral energy stores. Our data reveal the importance of glutamate as necessary energy substrate for the brain and the role of central GDH in the regulation of whole-body energy homeostasis.
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Zhao F, Deng J, Yu X, Li D, Shi H, Zhao Y. Protective effects of vascular endothelial growth factor in cultured brain endothelial cells against hypoglycemia. Metab Brain Dis 2015; 30:999-1007. [PMID: 25761767 PMCID: PMC4491374 DOI: 10.1007/s11011-015-9659-z] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/13/2014] [Accepted: 02/16/2015] [Indexed: 12/21/2022]
Abstract
Hypoglycemia is a common and serious problem among patients with type 1 diabetes receiving treatment with insulin. Clinical studies have demonstrated that hypoglycemic edema is involved in the initiation of hypoglycemic brain damage. However, the mechanisms of this edema are poorly understood. Vascular endothelial growth factor (VEGF), a potent regulator of blood vessel function, has been observed an important candidate hormone induced by hypoglycemia to protect neurons by restoring plasma glucose. Whether VEGF has a protective effect against hypoglycemia-induced damage in brain endothelial cells is still unknown. To investigate the effects of hypoglycemia on cerebral microvascular endothelial cells and assess the protective effect of exogenous VEGF on endothelial cells during hypoglycemia, confluent monolayers of the brain endothelial cell line bEnd.3 were treated with normal (5.5 mM glucose), hypoglycemic (0, 0.5, 1 mM glucose) medium or hypoglycemic medium in the presence of VEGF. The results clearly showed that hypoglycemia significantly downregulated the expression of claudin-5 in bEnd.3 cells, without affecting ZO-1 and occludin expression and distribution. Besides, transendothelial permeability significantly increased under hypoglycemic conditions compared to that under control conditions. Moreover, the hypoglycemic medium in presence of VEGF decreased endothelial permeability via the inhibition of claudin-5 degradation and improved hypoglycemia-induced cell toxicity. Furthermore, Glucose transporter-1 (Glut-1) and apoptosis regulator Bcl-2 expression were significantly upregulated. Taken together, hypoglycemia can significantly increase paraendocellular permeability by downregulating claudin-5 expression. We further showed that VEGF protected brain endothelial cells against hypoglycemia by enhancing glucose passage, reducing endothelial cell death, and ameliorating paraendocellular permeability.
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Affiliation(s)
- Fei Zhao
- Neurologic Department, Shanghai Jiao Tong University Affiliated Sixth People’s Hospital, No.600, Yishan Road, Xuhui District, Shanghai, 200233 China
| | - Jiangshan Deng
- Neurologic Department, Shanghai Jiao Tong University Affiliated Sixth People’s Hospital, No.600, Yishan Road, Xuhui District, Shanghai, 200233 China
| | - Xiaoyan Yu
- Neurologic Department, Shanghai Jiao Tong University Affiliated Sixth People’s Hospital, No.600, Yishan Road, Xuhui District, Shanghai, 200233 China
| | - Dawei Li
- School of Pharmacy, Shanghai Jiao Tong University, No.800, Dongchuan Road, Minhang District, Shanghai, 200240 China
| | - Hong Shi
- Neurologic Department, Shanghai Jiao Tong University Affiliated Sixth People’s Hospital, No.600, Yishan Road, Xuhui District, Shanghai, 200233 China
| | - Yuwu Zhao
- Neurologic Department, Shanghai Jiao Tong University Affiliated Sixth People’s Hospital, No.600, Yishan Road, Xuhui District, Shanghai, 200233 China
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Dienel GA, Cruz NF. Contributions of glycogen to astrocytic energetics during brain activation. Metab Brain Dis 2015; 30:281-98. [PMID: 24515302 PMCID: PMC4130810 DOI: 10.1007/s11011-014-9493-8] [Citation(s) in RCA: 70] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/29/2013] [Accepted: 01/21/2014] [Indexed: 12/11/2022]
Abstract
Glycogen is the major store of glucose in brain and is mainly in astrocytes. Brain glycogen levels in unstimulated, carefully-handled rats are 10-12 μmol/g, and assuming that astrocytes account for half the brain mass, astrocytic glycogen content is twice as high. Glycogen turnover is slow under basal conditions, but it is mobilized during activation. There is no net increase in incorporation of label from glucose during activation, whereas label release from pre-labeled glycogen exceeds net glycogen consumption, which increases during stronger stimuli. Because glycogen level is restored by non-oxidative metabolism, astrocytes can influence the global ratio of oxygen to glucose utilization. Compensatory increases in utilization of blood glucose during inhibition of glycogen phosphorylase are large and approximate glycogenolysis rates during sensory stimulation. In contrast, glycogenolysis rates during hypoglycemia are low due to continued glucose delivery and oxidation of endogenous substrates; rates that preserve neuronal function in the absence of glucose are also low, probably due to metabolite oxidation. Modeling studies predict that glycogenolysis maintains a high level of glucose-6-phosphate in astrocytes to maintain feedback inhibition of hexokinase, thereby diverting glucose for use by neurons. The fate of glycogen carbon in vivo is not known, but lactate efflux from brain best accounts for the major metabolic characteristics during activation of living brain. Substantial shuttling coupled with oxidation of glycogen-derived lactate is inconsistent with available evidence. Glycogen has important roles in astrocytic energetics, including glucose sparing, control of extracellular K(+) level, oxidative stress management, and memory consolidation; it is a multi-functional compound.
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Affiliation(s)
- Gerald A Dienel
- Department of Neurology, University of Arkansas for Medical Sciences, Slot 500, 4301 W. Markham St., Little Rock, AR, 72205, USA,
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Khowaja A, Choi IY, Seaquist ER, Öz G. In vivo Magnetic Resonance Spectroscopy of cerebral glycogen metabolism in animals and humans. Metab Brain Dis 2015; 30:255-61. [PMID: 24676563 PMCID: PMC4392006 DOI: 10.1007/s11011-014-9530-7] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/04/2014] [Accepted: 03/12/2014] [Indexed: 01/31/2023]
Abstract
Glycogen serves as an important energy reservoir in the human body. Despite the abundance of glycogen in the liver and skeletal muscles, its concentration in the brain is relatively low, hence its significance has been questioned. A major challenge in studying brain glycogen metabolism has been the lack of availability of non-invasive techniques for quantification of brain glycogen in vivo. Invasive methods for brain glycogen quantification such as post mortem extraction following high energy microwave irradiation are not applicable in the human brain. With the advent of (13)C Magnetic Resonance Spectroscopy (MRS), it has been possible to measure brain glycogen concentrations and turnover in physiological conditions, as well as under the influence of stressors such as hypoglycemia and visual stimulation. This review presents an overview of the principles of the (13)C MRS methodology and its applications in both animals and humans to further our understanding of glycogen metabolism under normal physiological and pathophysiological conditions such as hypoglycemia unawareness.
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Affiliation(s)
- Ameer Khowaja
- Division of Diabetes, Endocrinology and Metabolism, Department of Medicine, University of Minnesota, 420 Delaware Street, SE, Minneapolis, MN 55455, USA
| | - In-Young Choi
- Hoglund Brain Imaging Center, Department of Neurology, Department of Molecular & Integrative Physiology, University of Kansas Medical Center, Kansas City, KS 66160, USA
| | - Elizabeth R. Seaquist
- Division of Diabetes, Endocrinology and Metabolism, Department of Medicine, University of Minnesota, 420 Delaware Street, SE, Minneapolis, MN 55455, USA
| | - Gülin Öz
- Center for Magnetic Resonance Research, Department of Radiology, University of Minnesota, Minneapolis, MN 55455, USA
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Sonneville R, Vanhorebeek I, den Hertog HM, Chrétien F, Annane D, Sharshar T, Van den Berghe G. Critical illness-induced dysglycemia and the brain. Intensive Care Med 2014; 41:192-202. [PMID: 25465908 DOI: 10.1007/s00134-014-3577-0] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2014] [Accepted: 11/19/2014] [Indexed: 01/04/2023]
Abstract
PURPOSE Dysglycemia is a characteristic feature of critical illness associated with adverse outcome. Whether dysglycemia contributes to brain dysfunction during critical illness and long-term neurological complications is unclear. We give an overview of glucose metabolism in the brain and review the literature on critical illness-induced dysglycemia and the brain. METHODS Medline database search using relevant search terms on dysglycemia, critical illness, acute brain injury/dysfunction, and randomized controlled trial. RESULTS Hyperglycemia has been associated with deleterious effects on the nervous system. Underlying mechanisms in critical illness remain largely speculative and are often extrapolated from knowledge in diabetes mellitus. Increased hyperglycemia-induced blood-brain barrier permeability, oxidative stress, and microglia activation may play a role and compromise neuronal and glial cell integrity. Hypoglycemia is feared as critically ill patients cannot recognize or communicate hypoglycemic symptoms, which furthermore are masked by sedation and analgesia. However, observational data on the impact of brief hypoglycemia on the brain in critical illness are controversial. Secondary analysis of two large randomized studies suggested neuroprotection by strict glycemic control with insulin during intensive care, with lowered intracranial pressure, reduction of seizures, and better long-term rehabilitation in patients with isolated brain injury, and reduced incidence of critical illness polyneuromyopathy in the general critically ill patient population. Several subsequent studies failed to reproduce neurological benefit, likely explained by methodological issues, which include divergent achieved glucose levels and inaccurate glucose monitoring tools. CONCLUSIONS Preventing hyperglycemia during critical illness holds promise as a neuroprotective strategy to preserve brain cell viability and prevent acute brain dysfunction and long-term cognitive impairment in survivors.
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Affiliation(s)
- Romain Sonneville
- Clinical Department and Laboratory of Intensive Care Medicine, Division of Cellular and Molecular Medicine, KU Leuven, Herestraat 49, 3000, Leuven, Belgium
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Mapping brain glucose uptake with chemical exchange-sensitive spin-lock magnetic resonance imaging. J Cereb Blood Flow Metab 2014; 34:1402-10. [PMID: 24865996 PMCID: PMC4126103 DOI: 10.1038/jcbfm.2014.97] [Citation(s) in RCA: 76] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/30/2014] [Revised: 04/08/2014] [Accepted: 05/10/2014] [Indexed: 11/08/2022]
Abstract
Uptake of administered D-glucose (Glc) or 2-deoxy-D-glucose (2DG) has been indirectly mapped through the chemical exchange (CE) between glucose hydroxyl and water protons using CE-dependent saturation transfer (glucoCEST) magnetic resonance imaging (MRI). We propose an alternative technique-on-resonance CE-sensitive spin-lock (CESL) MRI-to enhance responses to glucose changes. Phantom data and simulations suggest higher sensitivity for this 'glucoCESL' technique (versus glucoCEST) in the intermediate CE regime relevant to glucose. Simulations of CESL signals also show insensitivity to B0-fluctuations. Several findings are apparent from in vivo glucoCESL studies of rat brain at 9.4 Tesla with intravenous injections. First, dose-dependent responses are nearly linearly for 0.25-, 0.5-, and 1-g/kg Glc administration (obtained with 12-second temporal resolution), with changes robustly detected for all doses. Second, responses at a matched dose of 1 g/kg are much larger and persist for a longer duration for 2DG versus Glc administration, and are minimal for mannitol as an osmolality control. And third, with similar increases in steady-state blood glucose levels, glucoCESL responses are ∼2.2 times higher for 2DG versus Glc, consistent with their different metabolic properties. Overall, we show that glucoCESL MRI could be a highly sensitive and quantifiable tool for glucose transport and metabolism studies.
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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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Changes in human brain glutamate concentration during hypoglycemia: insights into cerebral adaptations in hypoglycemia-associated autonomic failure in type 1 diabetes. J Cereb Blood Flow Metab 2014; 34:876-82. [PMID: 24549182 PMCID: PMC4013769 DOI: 10.1038/jcbfm.2014.32] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/22/2013] [Revised: 01/09/2014] [Accepted: 01/13/2014] [Indexed: 01/27/2023]
Abstract
Hypoglycemia-associated autonomic failure (HAAF) is a condition in which patients with type 1 diabetes (T1D) who experience frequent hypoglycemia develop defective glucose counter-regulation and become unable to sense hypoglycemia. Brain glutamate may be involved in the mechanism of HAAF. The goal of this study was to follow the human brain glutamate concentration during experimentally induced hypoglycemia in subjects with and without HAAF. (1)H magnetic resonance spectroscopy was used to track the occipital cortex glutamate concentration throughout a euglycemic clamp followed immediately by a hypoglycemic clamp. T1D patients with HAAF were studied in comparison to two control groups, i.e., T1D patients without HAAF and healthy controls (n=5 per group). Human brain glutamate concentration decreased (P ≤ 0.01) after the initiation of hypoglycemia in the two control groups, but a smaller trend toward a decrease in patients with HAAF did not reach significance (P>0.05). These findings are consistent with a metabolic adaptation in HAAF to provide higher glucose and/or alternative fuel to the brain, eliminating the need to oxidize glutamate. In an exploratory analysis, we detected additional metabolite changes in response to hypoglycemia in the T1D patient without HAAF control group, namely, increased aspartate and decreased lactate.
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Asgari S, Vespa P, Hu X. Is there any association between cerebral vasoconstriction/vasodilatation and microdialysis Lactate to Pyruvate ratio increase? Neurocrit Care 2014; 19:56-64. [PMID: 23733172 DOI: 10.1007/s12028-013-9821-6] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
BACKGROUND Although abnormally high Lactate/Pyruvate ratio (LPR) could indicate cerebral ischemia for brain injury patients, there is a debate on what is primary factor responsible for LPR increase. METHODS A data analysis experiment is taken to test whether any association between cerebral vasodilatation/vasoconstriction and LPR increase exists. We studied 4,316 microdialysis data samples collected in an average interval of 1.3 h from 30 severe traumatic brain injury (TBI) patients. The LPR increase episodes were automatically identified using a moving time-window of 5 samples. A novel pulse morphological template matching (PMTM) algorithm was applied to the intracranial pressure (ICP) data of the corresponding patients to assess the occurrence of cerebral vasodilatation and vasoconstriction during the identified LPR increase episodes. Several analyses were performed to evaluate the association between cerebral vasoconstriction/vasodilatation and LPR increase. RESULTS Results revealed that although more than half of the LPR increase episodes are not associated with any detected cerebral vasoconstriction/vasodilatation, when a vaso-change happens in association of LPR increase, it is more likely that this vaso-change is in the form of vasoconstriction rather than vasodilatation. Also for few subjects with dominant number of vasoconstriction episodes, a causality relationship between vasoconstriction and LPR increase were observed (vasoconstriction precedes LPR increase). CONCLUSIONS Using continuous intracranial pressure monitoring and our pulse morphological template matching (PMTM) algorithm could be potentially helpful in teasing out whether culprit cerebral vascular changes precede metabolic crisis for traumatic brain injury patients and hence guiding the management of this condition.
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Affiliation(s)
- Shadnaz Asgari
- Department of Computer Engineering and Computer Science, California State University, Long Beach, CA, USA
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High-field proton magnetic resonance spectroscopy reveals metabolic effects of normal brain aging. Neurobiol Aging 2014; 35:1686-94. [PMID: 24559659 DOI: 10.1016/j.neurobiolaging.2014.01.018] [Citation(s) in RCA: 53] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2013] [Revised: 12/19/2013] [Accepted: 01/19/2014] [Indexed: 11/24/2022]
Abstract
Altered brain metabolism is likely to be an important contributor to normal cognitive decline and brain pathology in elderly individuals. To characterize the metabolic changes associated with normal brain aging, we used high-field proton magnetic resonance spectroscopy in vivo to quantify 20 neurochemicals in the hippocampus and sensorimotor cortex of young adult and aged rats. We found significant differences in the neurochemical profile of the aged brain when compared with younger adults, including lower aspartate, ascorbate, glutamate, and macromolecules, and higher glucose, myo-inositol, N-acetylaspartylglutamate, total choline, and glutamine. These neurochemical biomarkers point to specific cellular mechanisms that are altered in brain aging, such as bioenergetics, oxidative stress, inflammation, cell membrane turnover, and endogenous neuroprotection. Proton magnetic resonance spectroscopy may be a valuable translational approach for studying mechanisms of brain aging and pathology, and for investigating treatments to preserve or enhance cognitive function in aging.
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Abstract
Hypoglycemia occurs in diabetic patients as a consequence of treatment with hypoglycemic agents, in insulinoma patients as a result of excessive insulin production, and in infants as a result of abnormal regulation of metabolism. Profound hypoglycemia can cause structural and functional disturbances in both the central (CNS) and the peripheral nervous system (PNS). The brain is damaged by a short and severe episode of hypoglycemia, whereas PNS pathology appears after a mild and prolonged episode. In the CNS, damaged mitochondria, elevated intracellular Ca2(+) level, released cytochrome c to the cytosol, extensive production of superoxide, increased caspase-3 activity, release of aspartate and glutamate from presynaptic terminals, and altered biosynthetic machinery can lead to neuronal cell death in the brain. Considering the PNS, chronic hypoglycemia is associated with delayed motor and sensory conduction velocities in peripheral nerves. With respect to pathology, hypoglycemic neuropathy in the PNS is characterized by Wallerian-like axonal degeneration that starts at the nerve terminal and progresses to a more proximal part of the axon, and motor axons to the muscles may be more severely damaged than sensory axons. Since excitatory neurotransmitters primarily involve the neuron in the CNS, this "dying back" pattern of axonal damage in the PNS may involve mechanisms other than excitotoxicity.
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Affiliation(s)
- Simin Mohseni
- Department of Clinical and Experimental Medicine, Division of Cell Biology, Faculty of Health Sciences, Linköping University, Linköping, Sweden.
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The oxygen paradox of neurovascular coupling. J Cereb Blood Flow Metab 2014; 34:19-29. [PMID: 24149931 PMCID: PMC3887356 DOI: 10.1038/jcbfm.2013.181] [Citation(s) in RCA: 91] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/09/2013] [Revised: 09/12/2013] [Accepted: 09/22/2013] [Indexed: 01/09/2023]
Abstract
The coupling of cerebral blood flow (CBF) to neuronal activity is well preserved during evolution. Upon changes in the neuronal activity, an incompletely understood coupling mechanism regulates diameter changes of supplying blood vessels, which adjust CBF within seconds. The physiologic brain tissue oxygen content would sustain unimpeded brain function for only 1 second if continuous oxygen supply would suddenly stop. This suggests that the CBF response has evolved to balance oxygen supply and demand. Surprisingly, CBF increases surpass the accompanying increases of cerebral metabolic rate of oxygen (CMRO2). However, a disproportionate CBF increase may be required to increase the concentration gradient from capillary to tissue that drives oxygen delivery. However, the brain tissue oxygen content is not zero, and tissue pO2 decreases could serve to increase oxygen delivery without a CBF increase. Experimental evidence suggests that CMRO2 can increase with constant CBF within limits and decreases of baseline CBF were observed with constant CMRO2. This conflicting evidence may be viewed as an oxygen paradox of neurovascular coupling. As a possible solution for this paradox, we hypothesize that the CBF response has evolved to safeguard brain function in situations of moderate pathophysiological interference with oxygen supply.
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Tissue-type plasminogen activator mediates neuronal detection and adaptation to metabolic stress. J Cereb Blood Flow Metab 2013; 33:1761-9. [PMID: 23881246 PMCID: PMC3824174 DOI: 10.1038/jcbfm.2013.124] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/07/2013] [Revised: 07/01/2013] [Accepted: 07/02/2013] [Indexed: 12/13/2022]
Abstract
Adenosine monophosphate-activated protein kinase (AMPK) is an energy sensor that regulates cellular adaptation to metabolic stress. Tissue-type plasminogen activator (tPA) is a serine proteinase found in the intravascular space, where its main role is as thrombolytic enzyme, and in neurons, where its function is less well understood. Here, we report that glucose deprivation induces the mobilization and package of neuronal tPA into presynaptic vesicles. Mass spectrometry and immunohistochemical studies show that the release of this tPA in the synaptic space induces AMPK activation in the postsynaptic terminal, and an AMPK-mediated increase in neuronal uptake of glucose and neuronal adenosine 5'(tetrahydrogen triphosphate; ATP) synthesis. This effect is independent of tPA's proteolytic properties, and instead requires the presence of functional N-methyl-D-aspartate receptors (NMDARs). In agreement with these observations, positron emission tomography (PET) studies and biochemical analysis with synaptoneurosomes indicate that the intravenous administration of recombinant tPA (rtPA) after transient middle cerebral artery occlusion (tMCAO) induces AMPK activation in the synaptic space and NMDAR-mediated glucose uptake in the ischemic brain. These data indicate that the release of neuronal tPA or treatment with rtPA activate a cell signaling pathway in the synaptic space that promotes the detection and adaptation to metabolic stress.
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Bouzat P, Sala N, Payen JF, Oddo M. Beyond intracranial pressure: optimization of cerebral blood flow, oxygen, and substrate delivery after traumatic brain injury. Ann Intensive Care 2013; 3:23. [PMID: 23837598 PMCID: PMC3716965 DOI: 10.1186/2110-5820-3-23] [Citation(s) in RCA: 72] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2013] [Accepted: 06/25/2013] [Indexed: 02/17/2023] Open
Abstract
Monitoring and management of intracranial pressure (ICP) and cerebral perfusion pressure (CPP) is a standard of care after traumatic brain injury (TBI). However, the pathophysiology of so-called secondary brain injury, i.e., the cascade of potentially deleterious events that occur in the early phase following initial cerebral insult—after TBI, is complex, involving a subtle interplay between cerebral blood flow (CBF), oxygen delivery and utilization, and supply of main cerebral energy substrates (glucose) to the injured brain. Regulation of this interplay depends on the type of injury and may vary individually and over time. In this setting, patient management can be a challenging task, where standard ICP/CPP monitoring may become insufficient to prevent secondary brain injury. Growing clinical evidence demonstrates that so-called multimodal brain monitoring, including brain tissue oxygen (PbtO2), cerebral microdialysis and transcranial Doppler among others, might help to optimize CBF and the delivery of oxygen/energy substrate at the bedside, thereby improving the management of secondary brain injury. Looking beyond ICP and CPP, and applying a multimodal therapeutic approach for the optimization of CBF, oxygen delivery, and brain energy supply may eventually improve overall care of patients with head injury. This review summarizes some of the important pathophysiological determinants of secondary cerebral damage after TBI and discusses novel approaches to optimize CBF and provide adequate oxygen and energy supply to the injured brain using multimodal brain monitoring.
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Affiliation(s)
- Pierre Bouzat
- Department of Intensive Care Medicine, CHUV-University Hospital, Rue du Bugnon 46, BH 08,623, CH-1011 Lausanne, Switzerland.
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Amaral AI. Effects of hypoglycaemia on neuronal metabolism in the adult brain: role of alternative substrates to glucose. J Inherit Metab Dis 2013; 36:621-34. [PMID: 23109064 DOI: 10.1007/s10545-012-9553-3] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/14/2012] [Revised: 10/02/2012] [Accepted: 10/11/2012] [Indexed: 12/22/2022]
Abstract
Hypoglycaemia is characterized by decreased blood glucose levels and is associated with different pathologies (e.g. diabetes, inborn errors of metabolism). Depending on its severity, it might affect cognitive functions, including impaired judgment and decreased memory capacity, which have been linked to alterations of brain energy metabolism. Glucose is the major cerebral energy substrate in the adult brain and supports the complex metabolic interactions between neurons and astrocytes, which are essential for synaptic activity. Therefore, hypoglycaemia disturbs cerebral metabolism and, consequently, neuronal function. Despite the high vulnerability of neurons to hypoglycaemia, important neurochemical changes enabling these cells to prolong their resistance to hypoglycaemia have been described. This review aims at providing an overview over the main metabolic effects of hypoglycaemia on neurons, covering in vitro and in vivo findings. Recent studies provided evidence that non-glucose substrates including pyruvate, glycogen, ketone bodies, glutamate, glutamine, and aspartate, are metabolized by neurons in the absence of glucose and contribute to prolong neuronal function and delay ATP depletion during hypoglycaemia. One of the pathways likely implicated in the process is the pyruvate recycling pathway, which allows for the full oxidation of glutamate and glutamine. The operation of this pathway in neurons, particularly after hypoglycaemia, has been re-confirmed recently using metabolic modelling tools (i.e. Metabolic Flux Analysis), which allow for a detailed investigation of cellular metabolism in cultured cells. Overall, the knowledge summarized herein might be used for the development of potential therapies targeting neuronal protection in patients vulnerable to hypoglycaemic episodes.
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Affiliation(s)
- Ana I Amaral
- Anne McLaren Laboratory for Regenerative Medicine, Department of Clinical Neurosciences, MRC Centre for Stem Cell Biology and Regenerative Medicine, University of Cambridge, West Forvie Building, Robinson Way, CB2 0SZ Cambridge, UK.
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Kealy J, Bennett R, Lowry JP. Simultaneous recording of hippocampal oxygen and glucose in real time using constant potential amperometry in the freely-moving rat. J Neurosci Methods 2013; 215:110-20. [PMID: 23499196 DOI: 10.1016/j.jneumeth.2013.02.016] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2012] [Revised: 01/31/2013] [Accepted: 02/22/2013] [Indexed: 01/02/2023]
Abstract
Amperometric sensors for oxygen and glucose allow for real time recording from the brain in freely-moving animals. These sensors have been used to detect activity- and drug-induced changes in metabolism in a number of brain regions but little attention has been given over to the hippocampus despite its importance in cognition and disease. Sensors for oxygen and glucose were co-implanted into the hippocampus and allowed to record for several days. Baseline recordings show that basal concentrations of hippocampal oxygen and glucose are 100.26±5.76 μM and 0.60±0.06 mM respectively. Furthermore, stress-induced changes in neural activity have been shown to significantly alter concentrations of both analytes in the hippocampus. Administration of O2 gas to the animals' snouts results in significant increases in hippocampal oxygen and glucose and administration of N2 gas results in a significant decrease in hippocampal oxygen. Chloral hydrate-induced anaesthesia causes a significant increase in hippocampal oxygen whereas treatment with the carbonic anhydrase inhibitor acetazolamide significantly increases hippocampal oxygen and glucose. These findings provide real time electrochemical data for the hippocampus which has been previously impossible with traditional methods such as microdialysis or ex vivo analysis. As such, these sensors provide a window into hippocampal function which can be used in conjunction with behavioural and pharmacological interventions to further elucidate the functions and mechanisms of action of the hippocampus in normal and disease states.
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Affiliation(s)
- John Kealy
- Department of Chemistry, National University of Ireland Maynooth, Maynooth, Co. Kildare, Ireland.
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Simultaneous measurement of glucose blood-brain transport constants and metabolic rate in rat brain using in-vivo 1H MRS. J Cereb Blood Flow Metab 2012; 32:1778-87. [PMID: 22714049 PMCID: PMC3434624 DOI: 10.1038/jcbfm.2012.82] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Cerebral glucose consumption and glucose transport across the blood-brain barrier are crucial to brain function since glucose is the major energy fuel for supporting intense electrophysiological activity associated with neuronal firing and signaling. Therefore, the development of noninvasive methods to measure the cerebral metabolic rate of glucose (CMR(glc)) and glucose transport constants (K(T): half-saturation constant; T(max): maximum transport rate) are of importance for understanding glucose transport mechanism and neuroenergetics under various physiological and pathological conditions. In this study, a novel approach able to simultaneously measure CMR(glc), K(T), and T(max) via monitoring the dynamic glucose concentration changes in the brain tissue using in-vivo (1)H magnetic resonance spectroscopy (MRS) and in plasma after a brief glucose infusion was proposed and tested using an animal model. The values of CMR(glc), T(max), and K(T) were determined to be 0.44 ± 0.17 μmol/g per minute, 1.35 ± 0.47 μmol/g per minute, and 13.4 ± 6.8 mmol/L in the rat brain anesthetized with 2% isoflurane. The Monte-Carlo simulations suggest that the measurements of CMR(glc) and T(max) are more reliable than that of K(T). The overall results indicate that the new approach is robust and reliable for in-vivo measurements of both brain glucose metabolic rate and transport constants, and has potential for human application.
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Lei H, Pilloud Y, Magill AW, Gruetter R. Continuous arterial spin labeling of mouse cerebral blood flow using an actively-detuned two-coil system at 9.4T. ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. IEEE ENGINEERING IN MEDICINE AND BIOLOGY SOCIETY. ANNUAL INTERNATIONAL CONFERENCE 2012; 2011:6993-6. [PMID: 22255948 DOI: 10.1109/iembs.2011.6091768] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Among numerous magnetic resonance imaging (MRI) techniques, perfusion MRI provides insight into the passage of blood through the brain's vascular network non-invasively. Studying disease models and transgenic mice would intrinsically help understanding the underlying brain functions, cerebrovascular disease and brain disorders. This study evaluates the feasibility of performing continuous arterial spin labeling (CASL) on all cranial arteries for mapping murine cerebral blood flow at 9.4 T. We showed that with an active-detuned two-coil system, a labeling efficiency of 0.82 ± 0.03 was achieved with minimal magnetization transfer residuals in brain. The resulting cerebral blood flow of healthy mouse was 99 ± 26 mL/100g/min, in excellent agreement with other techniques. In conclusion, high magnetic fields deliver high sensitivity and allowing not only CASL but also other MR techniques, i.e. (1)H MRS and diffusion MRI etc, in studying murine brains.
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Affiliation(s)
- Hongxia Lei
- Laboratory of Functional and Metabolic Imaging, Ecole Polytechnique Federale de Lausanne, EPFL-SB-IPSB-LIFMET, CH F1 627, Station 6, Lausanne CH1015, Switzerland.
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van de Ven KC, van der Graaf M, Tack CJ, Heerschap A, de Galan BE. Steady-state brain glucose concentrations during hypoglycemia in healthy humans and patients with type 1 diabetes. Diabetes 2012; 61:1974-7. [PMID: 22688331 PMCID: PMC3402320 DOI: 10.2337/db11-1778] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
The objective of this study was to investigate the relationship between plasma and brain glucose levels during euglycemia and hypoglycemia in healthy subjects and patients with type 1 diabetes mellitus (T1DM). Hyperinsulinemic euglycemic (5 mmol/L) and hypoglycemic (3 mmol/L) [1-(13)C]glucose clamps were performed in eight healthy subjects and nine patients with uncomplicated T1DM (HbA(1c) 7.7 ± 1.4%). Brain glucose levels were measured by (13)C magnetic resonance spectroscopy. Linear regression analysis was used to fit the relationship between plasma and brain glucose levels and calculate reversible Michaelis-Menten (MM) kinetic parameters. Brain glucose values during euglycemia (1.1 ± 0.4 μmol/g vs. 1.1 ± 0.3 μmol/g; P = 0.95) and hypoglycemia (0.5 ± 0.2 μmol/g vs. 0.6 ± 0.3 μmol/g; P = 0.52) were comparable between healthy subjects and T1DM patients. MM kinetic parameters of combined data were calculated to be maximum transport rate/cerebral metabolic rate of glucose (T(max)/CMR(glc)) = 2.25 ± 0.32 and substrate concentration at half maximal transport (K(t)) = 1.53 ± 0.88 mmol/L, which is in line with previously published data obtained under hyperglycemic conditions. In conclusion, the linear MM relationship between plasma and brain glucose can be extended to low plasma glucose levels. We found no evidence that the plasma to brain glucose relationship or the kinetics describing glucose transport over the blood-brain barrier differ between healthy subjects and patients with uncomplicated, reasonably well-controlled T1DM.
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Affiliation(s)
- Kim C.C. van de Ven
- Department of Radiology, Radboud University Nijmegen Medical Centre, Nijmegen, the Netherlands
| | - Marinette van der Graaf
- Department of Radiology, Radboud University Nijmegen Medical Centre, Nijmegen, the Netherlands
- Clinical Physics Laboratory, Radboud University Nijmegen Medical Centre, Nijmegen, the Netherlands
| | - Cees J. Tack
- Department of General Internal Medicine, Radboud University Nijmegen Medical Centre, Nijmegen, the Netherlands
| | - Arend Heerschap
- Department of Radiology, Radboud University Nijmegen Medical Centre, Nijmegen, the Netherlands
| | - Bastiaan E. de Galan
- Department of General Internal Medicine, Radboud University Nijmegen Medical Centre, Nijmegen, the Netherlands
- Corresponding author: Bastiaan E. de Galan,
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Abstract
Metabolic signals are used for imaging and spectroscopic studies of brain function and disease and to elucidate the cellular basis of neuroenergetics. The major fuel for activated neurons and the models for neuron–astrocyte interactions have been controversial because discordant results are obtained in different experimental systems, some of which do not correspond to adult brain. In rats, the infrastructure to support the high energetic demands of adult brain is acquired during postnatal development and matures after weaning. The brain's capacity to supply and metabolize glucose and oxygen exceeds demand over a wide range of rates, and the hyperaemic response to functional activation is rapid. Oxidative metabolism provides most ATP, but glycolysis is frequently preferentially up-regulated during activation. Underestimation of glucose utilization rates with labelled glucose arises from increased lactate production, lactate diffusion via transporters and astrocytic gap junctions, and lactate release to blood and perivascular drainage. Increased pentose shunt pathway flux also causes label loss from C1 of glucose. Glucose analogues are used to assay cellular activities, but interpretation of results is uncertain due to insufficient characterization of transport and phosphorylation kinetics. Brain activation in subjects with low blood-lactate levels causes a brain-to-blood lactate gradient, with rapid lactate release. In contrast, lactate flooding of brain during physical activity or infusion provides an opportunistic, supplemental fuel. Available evidence indicates that lactate shuttling coupled to its local oxidation during activation is a small fraction of glucose oxidation. Developmental, experimental, and physiological context is critical for interpretation of metabolic studies in terms of theoretical models.
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