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Rupee S, Rupee K, Singh RB, Hanoman C, Ismail AMA, Smail M, Singh J. Diabetes-induced chronic heart failure is due to defects in calcium transporting and regulatory contractile proteins: cellular and molecular evidence. Heart Fail Rev 2022; 28:627-644. [PMID: 36107271 DOI: 10.1007/s10741-022-10271-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Accepted: 09/07/2022] [Indexed: 11/04/2022]
Abstract
Heart failure (HF) is a major deteriorating disease of the myocardium due to weak myocardial muscles. As such, the heart is unable to pump blood efficiently around the body to meet its constant demand. HF is a major global health problem with more than 7 million deaths annually worldwide, with some patients dying suddenly due to sudden cardiac death (SCD). There are several risk factors which are associated with HF and SCD which can negatively affect the heart synergistically. One major risk factor is diabetes mellitus (DM) which can cause an elevation in blood glucose level or hyperglycaemia (HG) which, in turn, has an insulting effect on the myocardium. This review attempted to explain the subcellular, cellular and molecular mechanisms and to a lesser extent, the genetic factors associated with the development of diabetes- induced cardiomyopathy due to the HG which can subsequently lead to chronic heart failure (CHF) and SCD. The study first explained the structure and function of the myocardium and then focussed mainly on the excitation-contraction coupling (ECC) processes highlighting the defects of calcium transporting (SERCA, NCX, RyR and connexin) and contractile regulatory (myosin, actin, titin and troponin) proteins. The study also highlighted new therapies and those under development, as well as preventative strategies to either treat or prevent diabetic cardiomyopathy (DCM). It is postulated that prevention is better than cure.
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Glycation modulates glutamatergic signaling and exacerbates Parkinson's disease-like phenotypes. NPJ Parkinsons Dis 2022; 8:51. [PMID: 35468899 PMCID: PMC9038780 DOI: 10.1038/s41531-022-00314-x] [Citation(s) in RCA: 16] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2021] [Accepted: 03/31/2022] [Indexed: 01/17/2023] Open
Abstract
Alpha-synuclein (aSyn) is a central player in the pathogenesis of synucleinopathies due to its accumulation in typical protein aggregates in the brain. However, it is still unclear how it contributes to neurodegeneration. Type-2 diabetes mellitus is a risk factor for Parkinson's disease (PD). Interestingly, a common molecular alteration among these disorders is the age-associated increase in protein glycation. We hypothesized that glycation-induced neuronal dysfunction is a contributing factor in synucleinopathies. Here, we dissected the impact of methylglyoxal (MGO, a glycating agent) in mice overexpressing aSyn in the brain. We found that MGO-glycation potentiates motor, cognitive, olfactory, and colonic dysfunction in aSyn transgenic (Thy1-aSyn) mice that received a single dose of MGO via intracerebroventricular injection. aSyn accumulates in the midbrain, striatum, and prefrontal cortex, and protein glycation is increased in the cerebellum and midbrain. SWATH mass spectrometry analysis, used to quantify changes in the brain proteome, revealed that MGO mainly increase glutamatergic-associated proteins in the midbrain (NMDA, AMPA, glutaminase, VGLUT and EAAT1), but not in the prefrontal cortex, where it mainly affects the electron transport chain. The glycated proteins in the midbrain of MGO-injected Thy1-aSyn mice strongly correlate with PD and dopaminergic pathways. Overall, we demonstrated that MGO-induced glycation accelerates PD-like sensorimotor and cognitive alterations and suggest that the increase of glutamatergic signaling may underly these events. Our study sheds new light into the enhanced vulnerability of the midbrain in PD-related synaptic dysfunction and suggests that glycation suppressors and anti-glutamatergic drugs may hold promise as disease-modifying therapies for synucleinopathies.
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Toriumi K, Miyashita M, Suzuki K, Tabata K, Horiuchi Y, Ishida H, Itokawa M, Arai M. Role of glyoxalase 1 in methylglyoxal detoxification-the broad player of psychiatric disorders. Redox Biol 2021; 49:102222. [PMID: 34953453 PMCID: PMC8718652 DOI: 10.1016/j.redox.2021.102222] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2021] [Revised: 12/16/2021] [Accepted: 12/20/2021] [Indexed: 12/16/2022] Open
Abstract
Methylglyoxal (MG) is a highly reactive α-ketoaldehyde formed endogenously as a byproduct of the glycolytic pathway. To remove MG, various detoxification systems work together in vivo, including the glyoxalase system, which enzymatically degrades MG using glyoxalase 1 (GLO1) and GLO2. Recently, numerous reports have shown that GLO1 expression and MG accumulation in the brain are involved in the pathogenesis of psychiatric disorders, such as anxiety disorder, depression, autism, and schizophrenia. Furthermore, it has been reported that GLO1 inhibitors may be promising drugs for the treatment of psychiatric disorders. In this review, we discuss the recent findings of the effects of altered GLO1 function on mental behavior, especially focusing on results obtained from animal models.
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Affiliation(s)
- Kazuya Toriumi
- Schizophrenia Research Project, Department of Psychiatry and Behavioral Sciences, Tokyo Metropolitan Institute of Medical Science, Tokyo, 156-8506, Japan
| | - Mitsuhiro Miyashita
- Schizophrenia Research Project, Department of Psychiatry and Behavioral Sciences, Tokyo Metropolitan Institute of Medical Science, Tokyo, 156-8506, Japan; Department of Psychiatry, Tokyo Metropolitan Matsuzawa Hospital, Setagaya-ku, Tokyo, 156-0057, Japan; Department of Psychiatry, Takatsuki Hospital, Hachioji, Tokyo, 192-0005, Japan
| | - Kazuhiro Suzuki
- Schizophrenia Research Project, Department of Psychiatry and Behavioral Sciences, Tokyo Metropolitan Institute of Medical Science, Tokyo, 156-8506, Japan; Department of Psychiatry, Graduate School of Medicine, Shinshu University, Nagano, 390-8621, Japan
| | - Koichi Tabata
- Schizophrenia Research Project, Department of Psychiatry and Behavioral Sciences, Tokyo Metropolitan Institute of Medical Science, Tokyo, 156-8506, Japan; Department of Psychiatry and Behavioral Science, Tokyo Medical and Dental University Graduate School, Tokyo, Japan
| | - Yasue Horiuchi
- Schizophrenia Research Project, Department of Psychiatry and Behavioral Sciences, Tokyo Metropolitan Institute of Medical Science, Tokyo, 156-8506, Japan
| | - Hiroaki Ishida
- Schizophrenia Research Project, Department of Psychiatry and Behavioral Sciences, Tokyo Metropolitan Institute of Medical Science, Tokyo, 156-8506, Japan
| | - Masanari Itokawa
- Schizophrenia Research Project, Department of Psychiatry and Behavioral Sciences, Tokyo Metropolitan Institute of Medical Science, Tokyo, 156-8506, Japan; Department of Psychiatry, Tokyo Metropolitan Matsuzawa Hospital, Setagaya-ku, Tokyo, 156-0057, Japan
| | - Makoto Arai
- Schizophrenia Research Project, Department of Psychiatry and Behavioral Sciences, Tokyo Metropolitan Institute of Medical Science, Tokyo, 156-8506, Japan.
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Gonçalves CA, Rodrigues L, Bobermin LD, Zanotto C, Vizuete A, Quincozes-Santos A, Souza DO, Leite MC. Glycolysis-Derived Compounds From Astrocytes That Modulate Synaptic Communication. Front Neurosci 2019; 12:1035. [PMID: 30728759 PMCID: PMC6351787 DOI: 10.3389/fnins.2018.01035] [Citation(s) in RCA: 45] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2018] [Accepted: 12/20/2018] [Indexed: 12/14/2022] Open
Abstract
Based on the concept of the tripartite synapse, we have reviewed the role of glucose-derived compounds in glycolytic pathways in astroglial cells. Glucose provides energy and substrate replenishment for brain activity, such as glutamate and lipid synthesis. In addition, glucose metabolism in the astroglial cytoplasm results in products such as lactate, methylglyoxal, and glutathione, which modulate receptors and channels in neurons. Glucose has four potential destinations in neural cells, and it is possible to propose a crossroads in “X” that can be used to describe these four destinations. Glucose-6P can be used either for glycogen synthesis or the pentose phosphate pathway on the left and right arms of the X, respectively. Fructose-6P continues through the glycolysis pathway until pyruvate is formed but can also act as the initial compound in the hexosamine pathway, representing the left and right legs of the X, respectively. We describe each glucose destination and its regulation, indicating the products of these pathways and how they can affect synaptic communication. Extracellular L-lactate, either generated from glucose or from glycogen, binds to HCAR1, a specific receptor that is abundantly localized in perivascular and post-synaptic membranes and regulates synaptic plasticity. Methylglyoxal, a product of a deviation of glycolysis, and its derivative D-lactate are also released by astrocytes and bind to GABAA receptors and HCAR1, respectively. Glutathione, in addition to its antioxidant role, also binds to ionotropic glutamate receptors in the synaptic cleft. Finally, we examined the hexosamine pathway and evaluated the effect of GlcNAc-modification on key proteins that regulate the other glucose destinations.
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Affiliation(s)
- Carlos-Alberto Gonçalves
- Department of Biochemistry, Federal University of Rio Grande do Sul (UFRGS), Porto Alegre, Brazil
| | - Letícia Rodrigues
- Department of Biochemistry, Federal University of Rio Grande do Sul (UFRGS), Porto Alegre, Brazil
| | - Larissa D Bobermin
- Department of Biochemistry, Federal University of Rio Grande do Sul (UFRGS), Porto Alegre, Brazil
| | - Caroline Zanotto
- Department of Biochemistry, Federal University of Rio Grande do Sul (UFRGS), Porto Alegre, Brazil
| | - Adriana Vizuete
- Department of Biochemistry, Federal University of Rio Grande do Sul (UFRGS), Porto Alegre, Brazil
| | - André Quincozes-Santos
- Department of Biochemistry, Federal University of Rio Grande do Sul (UFRGS), Porto Alegre, Brazil
| | - Diogo O Souza
- Department of Biochemistry, Federal University of Rio Grande do Sul (UFRGS), Porto Alegre, Brazil
| | - Marina C Leite
- Department of Biochemistry, Federal University of Rio Grande do Sul (UFRGS), Porto Alegre, Brazil
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Papadaki M, Holewinski RJ, Previs SB, Martin TG, Stachowski MJ, Li A, Blair CA, Moravec CS, Van Eyk JE, Campbell KS, Warshaw DM, Kirk JA. Diabetes with heart failure increases methylglyoxal modifications in the sarcomere, which inhibit function. JCI Insight 2018; 3:121264. [PMID: 30333300 DOI: 10.1172/jci.insight.121264] [Citation(s) in RCA: 47] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2018] [Accepted: 09/04/2018] [Indexed: 12/27/2022] Open
Abstract
Patients with diabetes are at significantly higher risk of developing heart failure. Increases in advanced glycation end products are a proposed pathophysiological link, but their impact and mechanism remain incompletely understood. Methylglyoxal (MG) is a glycolysis byproduct, elevated in diabetes, and modifies arginine and lysine residues. We show that left ventricular myofilament from patients with diabetes and heart failure (dbHF) exhibited increased MG modifications compared with nonfailing controls (NF) or heart failure patients without diabetes. In skinned NF human and mouse cardiomyocytes, acute MG treatment depressed both calcium sensitivity and maximal calcium-activated force in a dose-dependent manner. Importantly, dbHF myocytes were resistant to myofilament functional changes from MG treatment, indicating that myofilaments from dbHF patients already had depressed function arising from MG modifications. In human dbHF and MG-treated mice, mass spectrometry identified increased MG modifications on actin and myosin. Cosedimentation and in vitro motility assays indicate that MG modifications on actin and myosin independently depress calcium sensitivity, and mechanistically, the functional consequence requires actin/myosin interaction with thin-filament regulatory proteins. MG modification of the myofilament may represent a critical mechanism by which diabetes induces heart failure, as well as a therapeutic target to avoid the development of or ameliorate heart failure in these patients.
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Affiliation(s)
- Maria Papadaki
- Loyola University Chicago, Department of Cell and Molecular Physiology, Chicago, Illinois, USA
| | | | - Samantha Beck Previs
- University of Vermont, Department of Molecular Physiology and Biophysics, Burlington, Vermont, USA
| | - Thomas G Martin
- Loyola University Chicago, Department of Cell and Molecular Physiology, Chicago, Illinois, USA
| | - Marisa J Stachowski
- Loyola University Chicago, Department of Cell and Molecular Physiology, Chicago, Illinois, USA
| | - Amy Li
- University of Vermont, Department of Molecular Physiology and Biophysics, Burlington, Vermont, USA
| | - Cheavar A Blair
- University of Kentucky, Department of Physiology, Lexington, Kentucky, USA
| | - Christine S Moravec
- The Cleveland Clinic, Department of Molecular Cardiology, Cleveland, Ohio, USA
| | - Jennifer E Van Eyk
- Cedars-Sinai Medical Center, Heart Institute, Los Angeles, California, USA
| | - Kenneth S Campbell
- University of Kentucky, Department of Physiology, Lexington, Kentucky, USA
| | - David M Warshaw
- University of Vermont, Department of Molecular Physiology and Biophysics, Burlington, Vermont, USA
| | - Jonathan A Kirk
- Loyola University Chicago, Department of Cell and Molecular Physiology, Chicago, Illinois, USA
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Alomar F, Singh J, Jang H, Rozanzki GJ, Shao CH, Padanilam BJ, Mayhan WG, Bidasee KR. Smooth muscle-generated methylglyoxal impairs endothelial cell-mediated vasodilatation of cerebral microvessels in type 1 diabetic rats. Br J Pharmacol 2016; 173:3307-3326. [PMID: 27611446 PMCID: PMC5738666 DOI: 10.1111/bph.13617] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2016] [Revised: 07/26/2016] [Accepted: 08/18/2016] [Indexed: 12/14/2022] Open
Abstract
BACKGROUND AND PURPOSE Endothelial cell-mediated vasodilatation of cerebral arterioles is impaired in individuals with Type 1 diabetes (T1D). This defect compromises haemodynamics and can lead to hypoxia, microbleeds, inflammation and exaggerated ischaemia-reperfusion injuries. The molecular causes for dysregulation of cerebral microvascular endothelial cells (cECs) in T1D remains poorly defined. This study tests the hypothesis that cECs dysregulation in T1D is triggered by increased generation of the mitochondrial toxin, methylglyoxal, by smooth muscle cells in cerebral arterioles (cSMCs). EXPERIMENTAL APPROACH Endothelial cell-mediated vasodilatation, vascular transcytosis inflammation, hypoxia and ischaemia-reperfusion injury were assessed in brains of male Sprague-Dawley rats with streptozotocin-induced diabetes and compared with those in diabetic rats with increased expression of methylglyoxal-degrading enzyme glyoxalase-I (Glo-I) in cSMCs. KEY RESULTS After 7-8 weeks of T1D, endothelial cell-mediated vasodilatation of cerebral arterioles was impaired. Microvascular leakage, gliosis, macrophage/neutrophil infiltration, NF-κB activity and TNF-α levels were increased, and density of perfused microvessels was reduced. Transient occlusion of a mid-cerebral artery exacerbated ischaemia-reperfusion injury. In cSMCs, Glo-I protein was decreased, and the methylglyoxal-synthesizing enzyme, vascular adhesion protein 1 (VAP-1) and methylglyoxal were increased. Restoring Glo-I protein in cSMCs of diabetic rats to control levels via gene transfer, blunted VAP-1 and methylglyoxal increases, cECs dysfunction, microvascular leakage, inflammation, ischaemia-reperfusion injury and increased microvessel perfusion. CONCLUSIONS AND IMPLICATIONS Methylglyoxal generated by cSMCs induced cECs dysfunction, inflammation, hypoxia and exaggerated ischaemia-reperfusion injury in diabetic rats. Lowering methylglyoxal produced by cSMCs may be a viable therapeutic strategy to preserve cECs function and blunt deleterious downstream consequences in T1D.
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Affiliation(s)
- Fadhel Alomar
- Department of Pharmacology and Experimental NeuroscienceUniversity of Nebraska Medical CenterOmahaNEUSA
- Department of PharmacologyUniversity of DammamDammamSaudi Arabia
| | - Jaipaul Singh
- School of Forensic and Applied ScienceUniversity of Central LancashirePrestonUK
| | - Hee‐Seong Jang
- Department of Cellular and Integrative PhysiologyUniversity of Nebraska Medical CenterOmahaNEUSA
| | - George J Rozanzki
- Department of Cellular and Integrative PhysiologyUniversity of Nebraska Medical CenterOmahaNEUSA
- Nebraska Redox Biology CenterLincolnNEUSA
| | - Chun Hong Shao
- Department of Pharmacology and Experimental NeuroscienceUniversity of Nebraska Medical CenterOmahaNEUSA
| | - Babu J Padanilam
- Department of Cellular and Integrative PhysiologyUniversity of Nebraska Medical CenterOmahaNEUSA
| | - William G Mayhan
- Department of Basic Biomedical Sciences, Sanford School of MedicineUniversity of South DakotaVermillionSDUSA
| | - Keshore R Bidasee
- Department of Pharmacology and Experimental NeuroscienceUniversity of Nebraska Medical CenterOmahaNEUSA
- Department of Environmental, Agricultural and Occupational HealthUniversity of Nebraska Medical CenterOmahaNEUSA
- Nebraska Redox Biology CenterLincolnNEUSA
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7
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Matafome P, Rodrigues T, Sena C, Seiça R. Methylglyoxal in Metabolic Disorders: Facts, Myths, and Promises. Med Res Rev 2016; 37:368-403. [DOI: 10.1002/med.21410] [Citation(s) in RCA: 55] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2016] [Revised: 08/07/2016] [Accepted: 08/12/2016] [Indexed: 01/17/2023]
Affiliation(s)
- Paulo Matafome
- Laboratory of Physiology, Institute of Biomedical Imaging and Life Sciences (IBILI); Faculty of Medicine, University of Coimbra; 3000-548 Coimbra Portugal
- Department of Complementary Sciences; Coimbra Health School (ESTeSC); Instituto Politécnico de Coimbra; 3045-601 Coimbra Portugal
| | - Tiago Rodrigues
- Laboratory of Physiology, Institute of Biomedical Imaging and Life Sciences (IBILI); Faculty of Medicine, University of Coimbra; 3000-548 Coimbra Portugal
| | - Cristina Sena
- Laboratory of Physiology, Institute of Biomedical Imaging and Life Sciences (IBILI); Faculty of Medicine, University of Coimbra; 3000-548 Coimbra Portugal
| | - Raquel Seiça
- Laboratory of Physiology, Institute of Biomedical Imaging and Life Sciences (IBILI); Faculty of Medicine, University of Coimbra; 3000-548 Coimbra Portugal
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Petit JM, Magistretti P. Regulation of neuron–astrocyte metabolic coupling across the sleep–wake cycle. Neuroscience 2016; 323:135-56. [DOI: 10.1016/j.neuroscience.2015.12.007] [Citation(s) in RCA: 60] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2015] [Revised: 12/01/2015] [Accepted: 12/04/2015] [Indexed: 11/30/2022]
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Abstract
Many current pharmacological treatments for neuropsychiatric disorders, such as anxiety and depression, are limited by a delayed onset of therapeutic effect, adverse side effects, abuse potential or lack of efficacy in many patients. These off-target effects highlight the need to identify novel mechanisms and targets for treatment. Recently, modulation of Glo1 (glyoxalase I) activity was shown to regulate anxiety-like behaviour and seizure-susceptibility in mice. These effects are likely to be mediated through the regulation of MG (methylglyoxal) by Glo1, as MG acts as a competitive partial agonist at GABA(A) (γ-aminobutyric acid A) receptors. Thus modulation of MG by Glo1 represents a novel target for treatment. In the present article, we evaluate the therapeutic potential of indirectly modulating MG concentrations through Glo1 inhibitors for the treatment of neuropsychiatric disorders.
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Allaman I, Bélanger M, Magistretti PJ. Methylglyoxal, the dark side of glycolysis. Front Neurosci 2015; 9:23. [PMID: 25709564 PMCID: PMC4321437 DOI: 10.3389/fnins.2015.00023] [Citation(s) in RCA: 339] [Impact Index Per Article: 37.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2014] [Accepted: 01/13/2015] [Indexed: 12/05/2022] Open
Abstract
Glucose is the main energy substrate for the brain. There is now extensive evidence indicating that the metabolic profile of neural cells with regard to glucose utilization and glycolysis rate is not homogenous, with a marked propensity for glycolytic glucose processing in astrocytes compared to neurons. Methylglyoxal, a highly reactive dicarbonyl compound, is inevitably formed as a by-product of glycolysis. Methylglyoxal is a major cell-permeant precursor of advanced glycation end-products (AGEs), which are associated with several pathologies including diabetes, aging and neurodegenerative diseases. In normal situations, cells are protected against methylglyoxal toxicity by different mechanisms and in particular the glyoxalase system, which represents the most important pathway for the detoxification of methylglyoxal. While the neurotoxic effects of methylglyoxal and AGEs are well characterized, our understanding the glyoxalase system in the brain is more scattered. Considering the high energy requirements (i.e., glucose) of the brain, one should expect that the cerebral glyoxalase system is adequately fitted to handle methylglyoxal toxicity. This review focuses on our actual knowledge on the cellular aspects of the glyoxalase system in brain cells, in particular with regard to its activity in astrocytes and neurons. A main emerging concept is that these two neural cell types have different and energetically adapted glyoxalase defense mechanisms which may serve as protective mechanism against methylglyoxal-induced cellular damage.
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Affiliation(s)
- Igor Allaman
- Laboratory of Neuroenergetics and Cellular Dynamics, Brain Mind Institute, Ecole Polytechnique Fédérale de Lausanne (EPFL) Lausanne, Switzerland
| | - Mireille Bélanger
- Laboratory of Neuroenergetics and Cellular Dynamics, Brain Mind Institute, Ecole Polytechnique Fédérale de Lausanne (EPFL) Lausanne, Switzerland
| | - Pierre J Magistretti
- Division of Biological and Environmental Sciences and Engineering, King Abdullah University of Science and Technology Thuwal, Saudi Arabia ; Laboratory of Neuroenergetics and Cellular Dynamics, Brain Mind Institute, Ecole Polytechnique Fédérale de Lausanne (EPFL) Lausanne, Switzerland
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Rempe MJ, Wisor JP. Cerebral lactate dynamics across sleep/wake cycles. Front Comput Neurosci 2015; 8:174. [PMID: 25642184 PMCID: PMC4294128 DOI: 10.3389/fncom.2014.00174] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2014] [Accepted: 12/23/2014] [Indexed: 12/17/2022] Open
Abstract
Cerebral metabolism varies dramatically as a function of sleep state. Brain concentration of lactate, the end product of glucose utilization via glycolysis, varies as a function of sleep state, and like slow wave activity (SWA) in the electroencephalogram (EEG), increases as a function of time spent awake or in rapid eye movement sleep and declines as a function of time spent in slow wave sleep (SWS). We sought to determine whether lactate concentration exhibits homeostatic dynamics akin to those of SWA in SWS. Lactate concentration in the cerebral cortex was measured by indwelling enzymatic biosensors. A set of equations based conceptually on Process S (previously used to quantify the homeostatic dynamics of SWA) was used to predict the sleep/wake state-dependent dynamics of lactate concentration in the cerebral cortex. Additionally, we applied an iterative parameter space-restricting algorithm (the Nelder-Mead method) to reduce computational time to find the optimal values of the free parameters. Compared to an exhaustive search, this algorithm reduced the computation time required by orders of magnitude. We show that state-dependent lactate concentration dynamics can be described by a homeostatic model, but that the optimal time constants for describing lactate dynamics are much smaller than those of SWA. This disconnect between lactate dynamics and SWA dynamics does not support the concept that lactate concentration is a biochemical mediator of sleep homeostasis. However, lactate synthesis in the cerebral cortex may nonetheless be informative with regard to sleep function, since the impact of glycolysis on sleep slow wave regulation is only just now being investigated.
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Affiliation(s)
- Michael J Rempe
- Mathematics and Computer Science, Whitworth University Spokane, WA, USA ; Department of Integrative Physiology and Neuroscience, College of Medical Sciences, Washington State University Spokane Spokane, WA, USA
| | - Jonathan P Wisor
- Department of Integrative Physiology and Neuroscience, College of Medical Sciences, Washington State University Spokane Spokane, WA, USA
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