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Solis EM, Good LB, Vázquez RG, Patnaik S, Hernandez-Reynoso AG, Ma Q, Angulo G, Dobariya A, Cogan SF, Pancrazio JJ, Pascual JM, Jakkamsetti V. Isolation of the murine Glut1 deficient thalamocortical circuit: wavelet characterization and reverse glucose dependence of low and gamma frequency oscillations. Front Neurosci 2023; 17:1191492. [PMID: 37829723 PMCID: PMC10565352 DOI: 10.3389/fnins.2023.1191492] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2023] [Accepted: 08/25/2023] [Indexed: 10/14/2023] Open
Abstract
Glucose represents the principal brain energy source. Thus, not unexpectedly, genetic glucose transporter 1 (Glut1) deficiency (G1D) manifests with encephalopathy. G1D seizures, which constitute a prominent disease manifestation, often prove refractory to medications but may respond to therapeutic diets. These seizures are associated with aberrant thalamocortical oscillations as inferred from human electroencephalography and functional imaging. Mouse electrophysiological recordings indicate that inhibitory neuron failure in thalamus and cortex underlies these abnormalities. This provides the motivation to develop a neural circuit testbed to characterize the mechanisms of thalamocortical synchronization and the effects of known or novel interventions. To this end, we used mouse thalamocortical slices on multielectrode arrays and characterized spontaneous low frequency oscillations and less frequent 30-50 Hz or gamma oscillations under near-physiological bath glucose concentration. Using the cortical recordings from layer IV among other regions recorded, we quantified oscillation epochs via an automated wavelet-based algorithm. This method proved analytically superior to power spectral density, short-time Fourier transform or amplitude-threshold detection. As expected from human observations, increased bath glucose reduced the lower frequency oscillations while augmenting the gamma oscillations, likely reflecting strengthened inhibitory neuron activity, and thus decreasing the low:high frequency ratio (LHR). This approach provides an ex vivo method for the evaluation of mechanisms, fuels, and pharmacological agents in a crucial G1D epileptogenic circuit.
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Affiliation(s)
- Elysandra M. Solis
- Department of Bioengineering, The University of Texas at Dallas, Richardson, TX, United States
| | - Levi B. Good
- Department of Bioengineering, The University of Texas at Dallas, Richardson, TX, United States
- Rare Brain Disorders Program, The University of Texas Southwestern Medical Center, Dallas, TX, United States
- Department of Neurology, The University of Texas Southwestern Medical Center, Dallas, TX, United States
| | - Rafael Granja Vázquez
- Department of Neuroscience and the Center for Advanced Pain Studies, The University of Texas Southwestern Medical Center, Dallas, TX, United States
| | - Sourav Patnaik
- Department of Bioengineering, The University of Texas at Dallas, Richardson, TX, United States
| | | | - Qian Ma
- Rare Brain Disorders Program, The University of Texas Southwestern Medical Center, Dallas, TX, United States
- Department of Neurology, The University of Texas Southwestern Medical Center, Dallas, TX, United States
| | - Gustavo Angulo
- Rare Brain Disorders Program, The University of Texas Southwestern Medical Center, Dallas, TX, United States
- Department of Neurology, The University of Texas Southwestern Medical Center, Dallas, TX, United States
| | - Aksharkumar Dobariya
- Rare Brain Disorders Program, The University of Texas Southwestern Medical Center, Dallas, TX, United States
- Department of Neurology, The University of Texas Southwestern Medical Center, Dallas, TX, United States
| | - Stuart F. Cogan
- Department of Bioengineering, The University of Texas at Dallas, Richardson, TX, United States
| | - Joseph J. Pancrazio
- Department of Bioengineering, The University of Texas at Dallas, Richardson, TX, United States
| | - Juan M. Pascual
- Rare Brain Disorders Program, The University of Texas Southwestern Medical Center, Dallas, TX, United States
- Department of Neurology, The University of Texas Southwestern Medical Center, Dallas, TX, United States
- Department of Physiology, The University of Texas Southwestern Medical Center, Dallas, TX, United States
- Department of Pediatrics, The University of Texas Southwestern Medical Center, Dallas, TX, United States
- Eugene McDermott Center for Human Growth & Development/Center for Human Genetics, The University of Texas Southwestern Medical Center, Dallas, TX, United States
| | - Vikram Jakkamsetti
- Rare Brain Disorders Program, The University of Texas Southwestern Medical Center, Dallas, TX, United States
- Department of Neurology, The University of Texas Southwestern Medical Center, Dallas, TX, United States
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Solis EM, Good LB, Granja Vázquez R, Patnaik S, Hernandez-Reynoso AG, Ma Q, Angulo G, Dobariya A, Cogan SF, Pancrazio JJ, Pascual JM, Jakkamsetti V. Isolation of the murine Glut1 deficient thalamocortical circuit: wavelet characterization and reverse glucose dependence of low and gamma frequency oscillations. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.06.05.543611. [PMID: 37645928 PMCID: PMC10461930 DOI: 10.1101/2023.06.05.543611] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 08/31/2023]
Abstract
Glucose represents the principal brain energy source. Thus, not unexpectedly, genetic glucose transporter 1 (Glut1) deficiency (G1D) manifests with encephalopathy. G1D seizures, which constitute a prominent disease manifestation, often prove refractory to medications but may respond to therapeutic diets. These seizures are associated with aberrant thalamocortical oscillations as inferred from human electroencephalography and functional imaging. Mouse electrophysiological recordings indicate that inhibitory neuron failure in thalamus and cortex underlies these abnormalities. This provides the motivation to develop a neural circuit testbed to characterize the mechanisms of thalamocortical synchronization and the effects of known or novel interventions. To this end, we used mouse thalamocortical slices on multielectrode arrays and characterized spontaneous low frequency oscillations and less frequent 30-50 Hz or gamma oscillations under near-physiological bath glucose concentration. Using the cortical recordings from layer IV, we quantified oscillation epochs via an automated wavelet-based algorithm. This method proved analytically superior to power spectral density, short-time Fourier transform or amplitude-threshold detection. As expected from human observations, increased bath glucose reduced the lower frequency oscillations while augmenting the gamma oscillations, likely reflecting strengthened inhibitory neuron activity. This approach provides an ex vivo method for the evaluation of mechanisms, fuels, and pharmacological agents in a crucial G1D epileptogenic circuit.
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Affiliation(s)
- Elysandra M. Solis
- Department of Bioengineering; The University of Texas at Dallas, Richardson, Texas, USA
| | - Levi B. Good
- Department of Bioengineering; The University of Texas at Dallas, Richardson, Texas, USA
- Rare Brain Disorders Program, The University of Texas Southwestern Medical Center, Dallas, Texas, USA
- Department of Neurology; The University of Texas Southwestern Medical Center, Dallas, Texas, USA
| | - Rafael Granja Vázquez
- Department of Bioengineering; The University of Texas at Dallas, Richardson, Texas, USA
| | - Sourav Patnaik
- Department of Bioengineering; The University of Texas at Dallas, Richardson, Texas, USA
| | | | - Qian Ma
- Rare Brain Disorders Program, The University of Texas Southwestern Medical Center, Dallas, Texas, USA
- Department of Neurology; The University of Texas Southwestern Medical Center, Dallas, Texas, USA
| | - Gustavo Angulo
- Rare Brain Disorders Program, The University of Texas Southwestern Medical Center, Dallas, Texas, USA
- Department of Neurology; The University of Texas Southwestern Medical Center, Dallas, Texas, USA
| | - Aksharkumar Dobariya
- Rare Brain Disorders Program, The University of Texas Southwestern Medical Center, Dallas, Texas, USA
- Department of Neurology; The University of Texas Southwestern Medical Center, Dallas, Texas, USA
| | - Stuart F. Cogan
- Department of Bioengineering; The University of Texas at Dallas, Richardson, Texas, USA
| | - Joseph J. Pancrazio
- Department of Bioengineering; The University of Texas at Dallas, Richardson, Texas, USA
| | - Juan M. Pascual
- Rare Brain Disorders Program, The University of Texas Southwestern Medical Center, Dallas, Texas, USA
- Department of Neurology; The University of Texas Southwestern Medical Center, Dallas, Texas, USA
- Department of Physiology; The University of Texas Southwestern Medical Center, Dallas, Texas, USA
- Department of Pediatrics; The University of Texas Southwestern Medical Center, Dallas, Texas, USA
- Eugene McDermott Center for Human Growth & Development / Center for Human Genetics; The University of Texas Southwestern Medical Center, Dallas, Texas, USA
| | - Vikram Jakkamsetti
- Department of Bioengineering; The University of Texas at Dallas, Richardson, Texas, USA
- Rare Brain Disorders Program, The University of Texas Southwestern Medical Center, Dallas, Texas, USA
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Rajasekaran K, Ma Q, Good LB, Kathote G, Jakkamsetti V, Liu P, Avila A, Primeaux S, Enciso Alva J, Markussen KH, Marin-Valencia I, Sirsi D, Hacker PMS, Gentry MS, Su J, Lu H, Pascual JM. Metabolic modulation of synaptic failure and thalamocortical hypersynchronization with preserved consciousness in Glut1 deficiency. Sci Transl Med 2022; 14:eabn2956. [PMID: 36197967 DOI: 10.1126/scitranslmed.abn2956] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
Individuals with glucose transporter type I deficiency (G1D) habitually experience nutrient-responsive epilepsy associated with decreased brain glucose. However, the mechanistic association between blood glucose concentration and brain excitability in the context of G1D remains to be elucidated. Electroencephalography (EEG) in G1D individuals revealed nutrition time-dependent seizure oscillations often associated with preserved volition despite electrographic generalization and uniform average oscillation duration and periodicity, suggesting increased facilitation of an underlying neural loop circuit. Nonlinear EEG ictal source localization analysis and simultaneous EEG/functional magnetic resonance imaging converged on the thalamus-sensorimotor cortex as one potential circuit, and 18F-deoxyglucose positron emission tomography (18F-DG-PET) illustrated decreased glucose accumulation in this circuit. This pattern, reflected in a decreased thalamic to striatal 18F signal ratio, can aid with the PET imaging diagnosis of the disorder, whereas the absence of noticeable ictal behavioral changes challenges the postulated requirement for normal thalamocortical activity during consciousness. In G1D mice, 18F-DG-PET and mass spectrometry also revealed decreased brain glucose and glycogen, but preserved tricarboxylic acid cycle intermediates, indicating no overall energy metabolism failure. In brain slices from these animals, synaptic inhibition of cortical pyramidal neurons and thalamic relay neurons was decreased, and neuronal disinhibition was mitigated by metabolic sources of carbon; tonic-clonic seizures were also suppressed by α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptor inhibition. These results pose G1D as a thalamocortical synaptic disinhibition disease associated with increased glucose-dependent neuronal excitability, possibly in relation to reduced glycogen. Together with findings in other metabolic defects, inhibitory neuron dysfunction is emerging as a modulable mechanism of hyperexcitability.
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Affiliation(s)
- Karthik Rajasekaran
- Rare Brain Disorders Program, Department of Neurology, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA
| | - Qian Ma
- Rare Brain Disorders Program, Department of Neurology, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA
| | - Levi B Good
- Rare Brain Disorders Program, Department of Neurology, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA
| | - Gauri Kathote
- Rare Brain Disorders Program, Department of Neurology, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA
| | - Vikram Jakkamsetti
- Rare Brain Disorders Program, Department of Neurology, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA
| | - Peiying Liu
- Advanced Imaging Research Center, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA
| | - Adrian Avila
- Rare Brain Disorders Program, Department of Neurology, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA
| | - Sharon Primeaux
- Rare Brain Disorders Program, Department of Neurology, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA
| | - Julio Enciso Alva
- Department of Mathematics, University of Texas at Arlington, Arlington, TX 76019, USA
| | - Kia H Markussen
- Department of Molecular and Cellular Biochemistry, University of Kentucky, Lexington, KY 40506, USA
| | - Isaac Marin-Valencia
- Rare Brain Disorders Program, Department of Neurology, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA
| | - Deepa Sirsi
- Department of Pediatrics, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA
| | - Peter M S Hacker
- St. John's College and Department of Philosophy, University of Oxford, Oxford OX1 3JP, UK.,University College London Queen's Square Institute of Neurology, London WC1N 3BG, UK
| | - Matthew S Gentry
- Department of Molecular and Cellular Biochemistry, University of Kentucky, Lexington, KY 40506, USA
| | - Jianzhong Su
- Department of Mathematics, University of Texas at Arlington, Arlington, TX 76019, USA
| | - Hanzhang Lu
- Advanced Imaging Research Center, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA
| | - Juan M Pascual
- Rare Brain Disorders Program, Department of Neurology, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA.,Department of Pediatrics, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA.,Department of Physiology, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA.,Eugene McDermott Center for Human Growth and Development/Center for Human Genetics, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA
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Effect of hypoxia on heart rate variability and baroreflex sensitivity during hypoglycemia in type 1 diabetes mellitus. Clin Auton Res 2015; 25:243-50. [PMID: 26141615 DOI: 10.1007/s10286-015-0301-2] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2015] [Accepted: 05/12/2015] [Indexed: 10/23/2022]
Abstract
PURPOSE Patients with type 1 diabetes mellitus exhibit impairments in autonomic and cardiovascular control which are worsened with acute hypoglycemia--thus increasing the risk of adverse cardiovascular events. Hypoxia, as seen with the common comorbidity of sleep apnea, may lead to further autonomic dysfunction and an increased risk of ventricular arrhythmias. Therefore, we hypothesized that heart rate variability (HRV) and baroreflex sensitivity (BRS) would be reduced during hypoglycemia in adults with type 1 diabetes, with a further decline when combined with hypoxia. METHODS Subjects with type 1 diabetes (n = 13; HbA1c = 7.5 ± 0.3 %, duration of diabetes = 17 ± 5 yrs) completed two 180 min hyperinsulinemic (2 mU/kg TBW/min), hypoglycemic (~3.3 µmol/mL) clamps separated by a minimum of 1 week and randomized to normoxia (SpO2 ~98 %) or hypoxia (SpO2 ~85 %). Heart rate (electrocardiogram) and blood pressure (finger photoplethysmography) were analyzed at baseline and during the hypoglycemic clamp for measures of HRV and spontaneous cardiac BRS (sCBRS). RESULTS Hypoglycemia resulted in significant reductions in HRV and sCBRS when compared with baseline levels (main effect of hypoglycemia: p < 0.05). HRV and sCBRS were further impaired during hypoxia (main effect of hypoxia: p < 0.05). CONCLUSIONS Acute hypoxia worsens hypoglycemia-mediated impairments in autonomic and cardiovascular control in patients with type 1 diabetes and may increase the risk of cardiovascular mortality. These results highlight the potential cumulative dangers of hypoglycemia and hypoxia in this vulnerable population.
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Florez CM, Lukankin V, Sugumar S, McGinn R, Zhang ZJ, Zhang L, Carlen PL. Hypoglycemia-induced alterations in hippocampal intrinsic rhythms: Decreased inhibition, increased excitation, seizures and spreading depression. Neurobiol Dis 2015; 82:213-225. [PMID: 26093168 DOI: 10.1016/j.nbd.2015.06.005] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2014] [Revised: 06/09/2015] [Accepted: 06/12/2015] [Indexed: 12/16/2022] Open
Abstract
UNLABELLED Seizures are the most common clinical presentation of severe hypoglycemia, usually as a side effect of insulin treatment for juvenile onset type 1 diabetes mellitus and advanced type 2 diabetes. We used the mouse thick hippocampal slice preparation to study the pathophysiology of hypoglycemia-induced seizures and the effects of severe glucose depletion on the isolated hippocampal rhythms from the CA3 circuitry. METHODS AND RESULTS Dropping the glucose perfusate concentration from the standard 10 mM to 1 mM produced epileptiform activity in 14/16 of the slices. Seizure-like events (SLEs) originated in the CA3 region and then spread into the CA1 region. Following the SLE, a spreading-depression (SD)-like event occurred (12/16 slices) with irreversible synaptic failure in the CA1 region (8/12 slices). CA3 SD-like events followed ~30 s after the SD-like event in the CA1 region. Less commonly, SD-like events originated in the CA3 region (4/12). Additionally, prior to the onset of the SLE in the CA3 area, there was decreased GABA correlated baseline SPW activity (bSPW), while there was increased large-amplitude sharp wave (LASW) activity, thought to originate from synchronous pyramidal cell firing. CA3 pyramidal cells displayed progressive tonic depolarization prior to the seizure which was resistant to synaptic transmission blockade. The initiation of hypoglycemic seizures and SD was prevented by AMPA/kainate or NMDA receptor blockade. CONCLUSIONS Severe glucose depletion induces rapid changes initiated in the intrinsic CA3 rhythms of the hippocampus including depressed inhibition and enhanced excitation, which may underlie the mechanisms of seizure generation and delayed spreading depression.
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Affiliation(s)
- C M Florez
- Departments of Medicine (Neurology) and Physiology, University of Toronto, Toronto, Canada; Division of Fundamental Neurobiology, TWRI, UHN, Toronto, Canada
| | - V Lukankin
- Departments of Medicine (Neurology) and Physiology, University of Toronto, Toronto, Canada
| | - S Sugumar
- Departments of Medicine (Neurology) and Physiology, University of Toronto, Toronto, Canada
| | - R McGinn
- Departments of Medicine (Neurology) and Physiology, University of Toronto, Toronto, Canada
| | - Z J Zhang
- Departments of Medicine (Neurology) and Physiology, University of Toronto, Toronto, Canada
| | - L Zhang
- Departments of Medicine (Neurology) and Physiology, University of Toronto, Toronto, Canada
| | - P L Carlen
- Departments of Medicine (Neurology) and Physiology, University of Toronto, Toronto, Canada; Division of Fundamental Neurobiology, TWRI, UHN, Toronto, Canada.
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Galeffi F, Shetty PK, Sadgrove MP, Turner DA. Age-related metabolic fatigue during low glucose conditions in rat hippocampus. Neurobiol Aging 2014; 36:982-92. [PMID: 25443286 DOI: 10.1016/j.neurobiolaging.2014.09.016] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2014] [Revised: 09/03/2014] [Accepted: 09/17/2014] [Indexed: 12/14/2022]
Abstract
Previous reports have indicated that with aging, intrinsic brain tissue changes in cellular bioenergetics may hamper the brain's ability to cope with metabolic stress. Therefore, we analyzed the effects of age on neuronal sensitivity to glucose deprivation by monitoring changes in field excitatory postsynaptic potentials (fEPSPs), tissue Po2, and NADH fluorescence imaging in the CA1 region of hippocampal slices obtained from F344 rats (1-2, 3-6, 12-20, and >22 months). Forty minutes of moderate low glucose (2.5 mM) led to approximately 80% decrease of fEPSP amplitudes and NADH decline in all 4 ages that reversed after reintroduction of 10 mM glucose. However, tissue slices from 12 to 20 months and >22-month-old rats were more vulnerable to low glucose: fEPSPs decreased by 50% on average 8 minutes faster compared with younger slices. Tissue oxygen utilization increased after onset of 2.5 mM glucose in all ages of tissue slices, which persisted for 40 minutes in younger tissue slices. But, in older tissue slices the increased oxygen utilization slowly faded and tissue Po2 levels increased toward baseline values after approximately 25 minutes of glucose deprivation. In addition, with age the ability to regenerate NADH after oxidation was diminished. The NAD(+)/NADH ratio remained relatively oxidized after low glucose, even during recovery. In young slices, glycogen levels were stable throughout the exposure to low glucose. In contrast, with aging utilization of glycogen stores was increased during low glucose, particularly in hippocampal slices from >22 months old rats, indicating both inefficient metabolism and increased demand for glucose. Lactate addition (20 mM) improved oxidative metabolism by directly supplementing the mitochondrial NADH pool and maintained fEPSPs in young as well as aged tissue slices, indicating that inefficient metabolism in the aging tissue can be improved by directly enhancing NADH regeneration.
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Affiliation(s)
- Francesca Galeffi
- Department of Surgery (Neurosurgery), Duke University Medical Center, Durham, NC, USA; Research and Surgery Services, Durham VAMC, Durham NC, USA.
| | - Pavan K Shetty
- Department of Surgery (Neurosurgery), Duke University Medical Center, Durham, NC, USA; Research and Surgery Services, Durham VAMC, Durham NC, USA
| | - Matthew P Sadgrove
- Department of Surgery (Neurosurgery), Duke University Medical Center, Durham, NC, USA; Research and Surgery Services, Durham VAMC, Durham NC, USA
| | - Dennis A Turner
- Department of Surgery (Neurosurgery), Duke University Medical Center, Durham, NC, USA; Research and Surgery Services, Durham VAMC, Durham NC, USA; Department of Neurobiology, Duke University Medical Center, Durham, NC, USA
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7
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Abstract
In the gray matter of the brain, astrocytes have been suggested to export lactate (derived from glucose or glycogen) to neurons to power their mitochondria. In the white matter, lactate can support axon function in conditions of energy deprivation, but it is not known whether lactate acts by preserving energy levels in axons or in oligodendrocytes, the myelinating processes of which are damaged rapidly in low energy conditions. Studies of cultured cells suggest that oligodendrocytes are the cell type in the brain that consumes lactate at the highest rate, in part to produce membrane lipids presumably for myelin. Here, we use pH imaging to show that oligodendrocytes in the white matter of the rat cerebellum and corpus callosum take up lactate via monocarboxylate transporters (MCTs), which we identify as MCT1 by confocal immunofluorescence and electron microscopy. Using cultured slices of developing cerebral cortex from mice in which oligodendrocyte lineage cells express GFP (green fluorescent protein) under the control of the Sox10 promoter, we show that a low glucose concentration reduces the number of oligodendrocyte lineage cells and myelination. Myelination is rescued when exogenous l-lactate is supplied. Thus, lactate can support oligodendrocyte development and myelination. In CNS diseases involving energy deprivation at times of myelination or remyelination, such as periventricular leukomalacia leading to cerebral palsy, stroke, and secondary ischemia after spinal cord injury, lactate transporters in oligodendrocytes may play an important role in minimizing the inhibition of myelination that occurs.
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Page KA, Williamson A, Yu N, McNay EC, Dzuira J, McCrimmon RJ, Sherwin RS. Medium-chain fatty acids improve cognitive function in intensively treated type 1 diabetic patients and support in vitro synaptic transmission during acute hypoglycemia. Diabetes 2009; 58:1237-44. [PMID: 19223595 PMCID: PMC2671041 DOI: 10.2337/db08-1557] [Citation(s) in RCA: 103] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
OBJECTIVE We examined whether ingestion of medium-chain triglycerides could improve cognition during hypoglycemia in subjects with intensively treated type 1 diabetes and assessed potential underlying mechanisms by testing the effect of beta-hydroxybutyrate and octanoate on rat hippocampal synaptic transmission during exposure to low glucose. RESEARCH DESIGN AND METHODS A total of 11 intensively treated type 1 diabetic subjects participated in stepped hyperinsulinemic- (2 mU x kg(-1) x min(-1)) euglycemic- (glucose approximately 5.5 mmol/l) hypoglycemic (glucose approximately 2.8 mmol/l) clamp studies. During two separate sessions, they randomly received either medium-chain triglycerides or placebo drinks and performed a battery of cognitive tests. In vitro rat hippocampal slice preparations were used to assess the ability of beta-hydroxybutyrate and octanoate to support neuronal activity when glucose levels are reduced. RESULTS Hypoglycemia impaired cognitive performance in tests of verbal memory, digit symbol coding, digit span backwards, and map searching. Ingestion of medium-chain triglycerides reversed these effects. Medium-chain triglycerides also produced higher free fatty acids and beta-hydroxybutyrate levels compared with placebo. However, the increase in catecholamines and symptoms during hypoglycemia was not altered. In hippocampal slices beta-hydroxybutyrate supported synaptic transmission under low-glucose conditions, whereas octanoate could not. Nevertheless, octanoate improved the rate of recovery of synaptic function upon restoration of control glucose concentrations. CONCLUSIONS Medium-chain triglyceride ingestion improves cognition without adversely affecting adrenergic or symptomatic responses to hypoglycemia in intensively treated type 1 diabetic subjects. Medium-chain triglycerides offer the therapeutic advantage of preserving brain function under hypoglycemic conditions without causing deleterious hyperglycemia.
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Affiliation(s)
- Kathleen A Page
- Section of Endocrinology, Yale School of Medicine, New Haven, Connecticut, USA.
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9
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Krnjević K. Electrophysiology of cerebral ischemia. Neuropharmacology 2008; 55:319-33. [DOI: 10.1016/j.neuropharm.2008.01.002] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2007] [Revised: 12/31/2007] [Accepted: 01/08/2008] [Indexed: 12/20/2022]
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10
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Sadgrove MP, Beaver CJ, Turner DA. Effects of relative hypoglycemia on LTP and NADH imaging in rat hippocampal slices. Brain Res 2007; 1165:30-9. [PMID: 17651706 PMCID: PMC2075092 DOI: 10.1016/j.brainres.2007.06.052] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2007] [Revised: 06/15/2007] [Accepted: 06/21/2007] [Indexed: 01/13/2023]
Abstract
Cognitive and neuronal impairment in diabetes may be associated with iatrogenic hypoglycemia, particularly at low serum glucose levels (<3 mM). To evaluate cellular impairment, we assessed acute hippocampal slice functioning during decreased ambient glucose, by monitoring evoked field excitatory post-synaptic potentials (fEPSP), and slice nicotinamide adenine dinucleotide (NADH) fluorescence. The effects of lowered glucose levels (60 min) were analyzed by examining the induction and maintenance of long-term potentiation (LTP), and NADH metabolic imaging in the CA1 region. The basal fEPSP response was reduced by lowered ambient glucose, an effect that was reversible in 2.5 mM glucose, partially reversible in 1.25 mM glucose and irreversible in 0 mM glucose, after 25 min recovery. LTP induction and maintenance declined during glucose restriction, demonstrating reversibly failed maintenance in 5 mM and 2.5 mM ambient glucose, and absent induction in 1.25 mM glucose. Peak NADH levels observed during train-induced biphasic transients were significantly reduced during 1.25 mM and 2.5 mM glucose. Significant functional compromise in our slice model occurred at 2.5 mM ambient glucose, equivalent to <1 mM tissue glucose in the slice center, due to diffusion limitations and active glucose utilization. This tissue glucose level correlates with human observations of a serum threshold of <3 mM for cognitive impairment, since brain tissue glucose is approximately one third of serum levels. The physiological effects of hypoglycemia in our slice model, assessed through fEPSP, LTP, and NADH responses, replicate closely the in vivo situation, confirming the usefulness of this model in assessing consequences of relative hypoglycemia.
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Affiliation(s)
- Matthew P Sadgrove
- Neurosurgery and Neurobiology, Duke University Medical Center, Research and Surgery Services, Durham VAMC, Durham, NC 27710, USA.
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11
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Abdelmalik PA, Shannon P, Yiu A, Liang P, Adamchik Y, Weisspapir M, Samoilova M, Burnham WM, Carlen PL. Hypoglycemic seizures during transient hypoglycemia exacerbate hippocampal dysfunction. Neurobiol Dis 2007; 26:646-60. [PMID: 17459717 DOI: 10.1016/j.nbd.2007.03.002] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2006] [Revised: 02/26/2007] [Accepted: 03/07/2007] [Indexed: 10/23/2022] Open
Abstract
Severe hypoglycemia constitutes a medical emergency, involving seizures, coma and death. We hypothesized that seizures, during limited substrate availability, aggravate hypoglycemia-induced brain damage. Using immature isolated, intact hippocampi and frontal neocortical blocks subjected to low glucose perfusion, we characterized hypoglycemic (neuroglycopenic) seizures in vitro during transient hypoglycemia and their effects on synaptic transmission and glycogen content. Hippocampal hypoglycemic seizures were always followed by an irreversible reduction (>60% loss) in synaptic transmission and were occasionally accompanied by spreading depression-like events. Hypoglycemic seizures occurred more frequently with decreasing "hypoglycemic" extracellular glucose concentrations. In contrast, no hypoglycemic seizures were generated in the neocortex during transient hypoglycemia, and the reduction of synaptic transmission was reversible (<60% loss). Hypoglycemic seizures in the hippocampus were abolished by NMDA and non-NMDA antagonists. The anticonvulsant, midazolam, but neither phenytoin nor valproate, also abolished hypoglycemic seizures. Non-glycolytic, oxidative substrates attenuated, but did not abolish, hypoglycemic seizure activity and were unable to support synaptic transmission, even in the presence of the adenosine (A1) antagonist, DPCPX. Complete prevention of hypoglycemic seizures always led to the maintenance of synaptic transmission. A quantitative glycogen assay demonstrated that hypoglycemic seizures, in vitro, during hypoglycemia deplete hippocampal glycogen. These data suggest that suppressing seizures during hypoglycemia may decrease subsequent neuronal damage and dysfunction.
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Affiliation(s)
- Peter A Abdelmalik
- Division of Fundamental Neurobiology, Toronto Western Research Institute, University Health Network MCL12-413, Toronto Western Hospital, 399 Bathurst St., Toronto, Ontario, 416-603-5040, Canada M5T2S8
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Carlesimo GA, Perri R, Costa A, Serra L, Caltagirone C. Priming for novel between-word associations in patients with organic amnesia. J Int Neuropsychol Soc 2005; 11:566-73. [PMID: 16212683 DOI: 10.1017/s1355617705050678] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/05/2004] [Revised: 04/21/2005] [Accepted: 04/21/2005] [Indexed: 11/05/2022]
Abstract
Ten amnesic patients of various etiologies and 10 matched normal controls participated in this study. On 2 consecutive days, subjects studied 30 novel word-word associations 6 times. Using a cued recall task, we assessed episodic learning and delayed retention of the study material immediately after each study phase and again 24 hr after the final study phase. Further, we evaluated implicit memory for new between-word associations by means of an automatic relational priming paradigm immediately after the delayed cued recall trial. Amnesic patients performed poorly on the cued recall task. Moreover, in the overall group of amnesics the priming effect failed to reach statistical significance. When the overall group of amnesics was split according to mean performance on the cued recall task, those in the low performer subgroup--comprised of 6 patients with direct or indirect involvement of the hippocampi--were particularly poor at episodically remembering the associations and did not reveal any relational priming. These data support the hypothesis of similar impairment of new episodic and implicit learning in amnesic patients and suggest that the hippocampus is crucial for both kinds of new learning.
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Affiliation(s)
- G A Carlesimo
- Clinica Neurologica, Università Tor Vergata, Roma, Italy.
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Affiliation(s)
- Silvio E Inzucchi
- Dallas Diabetes and Endocrine Center, Medical City Dallas, 7777 Forest Lane, Suite C-618, Dallas, TX 75230, USA
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Jonas EA, Hickman JA, Hardwick JM, Kaczmarek LK. Exposure to hypoxia rapidly induces mitochondrial channel activity within a living synapse. J Biol Chem 2004; 280:4491-7. [PMID: 15561723 DOI: 10.1074/jbc.m410661200] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
One of the earliest effects of hypoxia on neuronal function is to produce a run-down of synaptic transmission, and more prolonged hypoxia results in neuronal death. An increase in the permeability of the outer mitochondrial membrane, controlled by BCL-2 family proteins, occurs in response to stimuli that trigger cell death. By patch clamping mitochondrial membranes inside the presynaptic terminal of a squid giant synapse, we have now found that several minutes of hypoxia trigger the opening of large multiconductance channels. The channel activity is induced concurrently with the attenuation of synaptic responses that occurs under hypoxic conditions. Hypoxia-induced channels are inhibited by NADH, an agent that inhibits large conductance channels produced by a pro-apoptotic fragment of BCL-xL in these synaptic mitochondria. The appearance of hypoxia-induced channels was also prevented by the caspase/cysteine protease inhibitor benzyloxycarbonyl-VAD-fluoromethyl ketone (Z-VAD-fmk), which inhibits proteolysis of BCL-xL during hypoxia. Both NADH and Z-VAD-fmk reduced significantly the rate of decline of synaptic responses during hypoxia. Our results indicate that an increase in outer mitochondrial channel activity is a very early event in the response of neurons to hypoxia and suggest that this increase in activity may contribute to the decline in synaptic function during hypoxia.
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Affiliation(s)
- Elizabeth A Jonas
- Department of Pharmacology, Yale University School of Medicine, New Haven, Connecticut 06520, USA.
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Jonas EA, Hickman JA, Chachar M, Polster BM, Brandt TA, Fannjiang Y, Ivanovska I, Basañez G, Kinnally KW, Zimmerberg J, Hardwick JM, Kaczmarek LK. Proapoptotic N-truncated BCL-xL protein activates endogenous mitochondrial channels in living synaptic terminals. Proc Natl Acad Sci U S A 2004; 101:13590-5. [PMID: 15342906 PMCID: PMC518799 DOI: 10.1073/pnas.0401372101] [Citation(s) in RCA: 89] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
Abstract
Neuronal death is often preceded by functional alterations at nerve terminals. Anti- and proapoptotic BCL-2 family proteins not only regulate the neuronal death pathway but also affect excitability of healthy neurons. We found that exposure of squid stellate ganglia to hypoxia, a death stimulus for neurons, causes a cysteine protease-dependent loss of full-length antiapoptotic BCL-xL, similar to previous findings in mammalian cells. Therefore, to determine the direct effect of the naturally occurring proapoptotic cleavage product of BCL-xL on mitochondria, recombinant N-truncated BCL-xL was applied to mitochondria inside the squid presynaptic terminal and to purified mitochondria isolated from yeast. N-truncated BCL-xL rapidly induced large multi-conductance channels with a maximal conductance significantly larger than those produced by full-length BCL-xL. This activity required the hydrophobic C terminus and the BH3 domain of BCL-xL. Moreover, N-truncated BCL-xL failed to produce any channel activity when applied to plasma membranes, suggesting that a component of the mitochondrial membrane is necessary for its actions. Consistent with this idea, the large channels induced by N-truncated BCL-xL are inhibited by NADH and require the presence of VDAC, a voltage-dependent anion channel present in the outer mitochondrial membrane. These observations suggest that the mitochondrial channels specific to full-length and N-truncated BCL-xL contribute to their opposite effects on synaptic transmission, and are consistent with their opposite effects on the cell death pathway.
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Affiliation(s)
- Elizabeth A Jonas
- Department of Pharmacology, Yale University School of Medicine, 333 Cedar Street, New Haven, CT 06520, USA
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Abstract
Axon function in the CNS has been reported to fail rapidly during anoxia, implying that there is no anaerobic capacity. This phenomenon was reassessed in rodent white matter using mouse or rat optic nerve. Axon function was semiquantitatively measured as area under the compound action potential. Mouse optic nerves exposed to anoxia (30-180 minutes) or cyanide (30-60 minutes) at 37 degrees C exhibited significant persistent function that was abolished by removing glucose. Reduction in compound action potential area increased with anoxia duration reaching a maximum of about 70% after 90 min. Rat optic nerves exposed to anoxia, in contrast to mouse optic nerves, showed rapid and complete loss of function. When artificial CSF glucose was increased from 10 to 30 mmol/L, rat optic nerves responded to anoxia in a similar manner to mouse optic nerves in 10-mmol/L glucose. The authors conclude that white matter is resistant to anoxia with a subset of axons able to subsist exclusively on anaerobically derived energy. Because the rat optic nerve is about twice the diameter of the mouse optic nerve, glucose diffusion into the rat optic nerve was inadequate during anoxia when artificial CSF glucose was 10 mmol/L but became adequate when artificial CSF glucose was 30 mmol/L. These observations have implications for white matter energy metabolism and susceptibility to injury during focal ischemia.
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Affiliation(s)
- Selva Baltan Tekkök
- Department of Neurology, University of Washington School of Medicine, Seattle, Washington, USA.
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