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Sharma AK, Khandelwal R, Wolfrum C. Futile cycles: Emerging utility from apparent futility. Cell Metab 2024; 36:1184-1203. [PMID: 38565147 DOI: 10.1016/j.cmet.2024.03.008] [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: 01/05/2024] [Revised: 02/15/2024] [Accepted: 03/11/2024] [Indexed: 04/04/2024]
Abstract
Futile cycles are biological phenomena where two opposing biochemical reactions run simultaneously, resulting in a net energy loss without appreciable productivity. Such a state was presumed to be a biological aberration and thus deemed an energy-wasting "futile" cycle. However, multiple pieces of evidence suggest that biological utilities emerge from futile cycles. A few established functions of futile cycles are to control metabolic sensitivity, modulate energy homeostasis, and drive adaptive thermogenesis. Yet, the physiological regulation, implication, and pathological relevance of most futile cycles remain poorly studied. In this review, we highlight the abundance and versatility of futile cycles and propose a classification scheme. We further discuss the energetic implications of various futile cycles and their impact on basal metabolic rate, their bona fide and tentative pathophysiological implications, and putative drug interactions.
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Affiliation(s)
- Anand Kumar Sharma
- Laboratory of Translational Nutrition Biology, Institute of Food, Nutrition and Health, ETH Zurich, Schwerzenbach, Switzerland.
| | - Radhika Khandelwal
- Laboratory of Translational Nutrition Biology, Institute of Food, Nutrition and Health, ETH Zurich, Schwerzenbach, Switzerland
| | - Christian Wolfrum
- Laboratory of Translational Nutrition Biology, Institute of Food, Nutrition and Health, ETH Zurich, Schwerzenbach, Switzerland.
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2
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Barahona MJ, Ferrada L, Vera M, Nualart F. Tanycytes release glucose using the glucose-6-phosphatase system during hypoglycemia to control hypothalamic energy balance. Mol Metab 2024; 84:101940. [PMID: 38641253 PMCID: PMC11060961 DOI: 10.1016/j.molmet.2024.101940] [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: 01/10/2024] [Revised: 04/09/2024] [Accepted: 04/09/2024] [Indexed: 04/21/2024] Open
Abstract
OBJECTIVE The liver releases glucose into the blood using the glucose-6-phosphatase (G6Pase) system, a multiprotein complex located in the endoplasmic reticulum (ER). Here, we show for the first time that the G6Pase system is also expressed in hypothalamic tanycytes, and it is required to regulate energy balance. METHODS Using automatized qRT-PCR and immunohistochemical analyses, we evaluated the expression of the G6Pase system. Fluorescent glucose analogue (2-NBDG) uptake was evaluated by 4D live-cell microscopy. Glucose release was tested using a glucose detection kit and high-content live-cell analysis instrument, Incucyte s3. In vivo G6pt knockdown in tanycytes was performed by AAV1-shG6PT-mCherry intracerebroventricular injection. Body weight gain, adipose tissue weight, food intake, glucose metabolism, c-Fos, and neuropeptide expression were evaluated at 4 weeks post-transduction. RESULTS Tanycytes sequester glucose-6-phosphate (G6P) into the ER through the G6Pase system and release glucose in hypoglycaemia via facilitative glucose transporters (GLUTs). Strikingly, in vivo tanycytic G6pt knockdown has a powerful peripheral anabolic effect observed through decreased body weight, white adipose tissue (WAT) tissue mass, and strong downregulation of lipogenesis genes. Selective deletion of G6pt in tanycytes also decreases food intake, c-Fos expression in the arcuate nucleus (ARC), and Npy mRNA expression in fasted mice. CONCLUSIONS The tanycyte-associated G6Pase system is a central mechanism involved in controlling metabolism and energy balance.
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Affiliation(s)
- María José Barahona
- Laboratory of Neurobiology and Stem Cells, NeuroCellT, Department of Cellular Biology, Faculty of Biological Sciences, University of Concepcion, Concepcion, Chile; Center for Advanced Microscopy CMA BIO BIO, University of Concepcion, Concepcion, Chile; Laboratory of Appetite Physiology (FIDELA), Faculty of Medicine and Sciences, University San Sebastián, Concepción Campus, Concepción, Chile
| | - Luciano Ferrada
- Center for Advanced Microscopy CMA BIO BIO, University of Concepcion, Concepcion, Chile
| | - Matías Vera
- Laboratory of Neurobiology and Stem Cells, NeuroCellT, Department of Cellular Biology, Faculty of Biological Sciences, University of Concepcion, Concepcion, Chile; Center for Advanced Microscopy CMA BIO BIO, University of Concepcion, Concepcion, Chile
| | - Francisco Nualart
- Laboratory of Neurobiology and Stem Cells, NeuroCellT, Department of Cellular Biology, Faculty of Biological Sciences, University of Concepcion, Concepcion, Chile; Center for Advanced Microscopy CMA BIO BIO, University of Concepcion, Concepcion, Chile.
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3
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Cullen PF, Gammerdinger WJ, Ho Sui SJ, Mazumder AG, Sun D. Transcriptional profiling of retinal astrocytes identifies a specific marker and points to functional specialization. Glia 2024. [PMID: 38785355 DOI: 10.1002/glia.24571] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2024] [Revised: 04/19/2024] [Accepted: 05/13/2024] [Indexed: 05/25/2024]
Abstract
Astrocyte heterogeneity is an increasingly prominent research topic, and studies in the brain have demonstrated substantial variation in astrocyte form and function, both between and within regions. In contrast, retinal astrocytes are not well understood and remain incompletely characterized. Along with optic nerve astrocytes, they are responsible for supporting retinal ganglion cell axons and an improved understanding of their role is required. We have used a combination of microdissection and Ribotag immunoprecipitation to isolate ribosome-associated mRNA from retinal astrocytes and investigate their transcriptome, which we also compared to astrocyte populations in the optic nerve. Astrocytes from these regions are transcriptionally distinct, and we identified retina-specific astrocyte genes and pathways. Moreover, although they share much of the "classical" gene expression patterns of astrocytes, we uncovered unexpected variation, including in genes related to core astrocyte functions. We additionally identified the transcription factor Pax8 as a highly specific marker of retinal astrocytes and demonstrated that these astrocytes populate not only the retinal surface, but also the prelaminar region at the optic nerve head. These findings are likely to contribute to a revised understanding of the role of astrocytes in the retina.
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Affiliation(s)
- Paul F Cullen
- Department of Ophthalmology, Schepens Eye Research Institute of Massachusetts Eye and Ear Infirmary, Harvard Medical School, Boston, Massachusetts, USA
| | - William J Gammerdinger
- Department of Biostatistics, Harvard T.H. Chan School of Public Health, Boston, Massachusetts, USA
| | - Shannan J Ho Sui
- Department of Biostatistics, Harvard T.H. Chan School of Public Health, Boston, Massachusetts, USA
| | - Arpan Guha Mazumder
- Department of Ophthalmology, Schepens Eye Research Institute of Massachusetts Eye and Ear Infirmary, Harvard Medical School, Boston, Massachusetts, USA
| | - Daniel Sun
- Department of Ophthalmology, Schepens Eye Research Institute of Massachusetts Eye and Ear Infirmary, Harvard Medical School, Boston, Massachusetts, USA
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Edison P. Astroglial activation: Current concepts and future directions. Alzheimers Dement 2024; 20:3034-3053. [PMID: 38305570 PMCID: PMC11032537 DOI: 10.1002/alz.13678] [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: 08/24/2023] [Revised: 11/27/2023] [Accepted: 12/11/2023] [Indexed: 02/03/2024]
Abstract
Astrocytes are abundantly and ubiquitously expressed cell types with diverse functions throughout the central nervous system. Astrocytes show remarkable plasticity and exhibit morphological, molecular, and functional remodeling in response to injury, disease, or infection of the central nervous system, as evident in neurodegenerative diseases. Astroglial mediated inflammation plays a prominent role in the pathogenesis of neurodegenerative diseases. This review focus on the role of astrocytes as essential players in neuroinflammation and discuss their morphological and functional heterogeneity in the normal central nervous system and explore the spatial and temporal variations in astroglial phenotypes observed under different disease conditions. This review discusses the intimate relationship of astrocytes to pathological hallmarks of neurodegenerative diseases. Finally, this review considers the putative therapeutic strategies that can be deployed to modulate the astroglial functions in neurodegenerative diseases. HIGHLIGHTS: Astroglia mediated neuroinflammation plays a key role in the pathogenesis of neurodegenerative diseases. Activated astrocytes exhibit diverse phenotypes in a region-specific manner in brain and interact with β-amyloid, tau, and α-synuclein species as well as with microglia and neuronal circuits. Activated astrocytes are likely to influence the trajectory of disease progression of neurodegenerative diseases, as determined by the stage of disease, individual susceptibility, and state of astroglial priming. Modulation of astroglial activation may be a therapeutic strategy at various stages in the trajectory of neurodegenerative diseases to modify the disease course.
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Affiliation(s)
- Paul Edison
- Division of NeurologyDepartment of Brain SciencesFaculty of Medicine, Imperial College LondonLondonUK
- Division of Psychological medicine and clinical neurosciencesSchool of Medicine, Cardiff UniversityWalesUK
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Mandal S, Faizan S, Raghavendra NM, Kumar BRP. Molecular dynamics articulated multilevel virtual screening protocol to discover novel dual PPAR α/γ agonists for anti-diabetic and metabolic applications. Mol Divers 2023; 27:2605-2631. [PMID: 36437421 DOI: 10.1007/s11030-022-10571-w] [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: 07/13/2022] [Accepted: 11/11/2022] [Indexed: 11/29/2022]
Abstract
PPARα and PPARγ are isoforms of the nuclear receptor superfamily which regulate glucose and lipid metabolism. Activation of PPARα and PPARγ receptors by exogenous ligands could transactivate the expression of PPARα and PPARγ-dependent genes, and thereby, metabolic pathways get triggered, which are helpful to ameliorate treatment for the type 2 diabetes mellitus, and related metabolic complications. Herein, by understanding the structural requirements for ligands to activate PPARα and PPARγ proteins, we developed a multilevel in silico-based virtual screening protocol to identify novel chemical scaffolds and further design and synthesize two distinct series of glitazone derivatives with advantages over the classical PPARα and PPARγ agonists. Moreover, the synthesized compounds were biologically evaluated for PPARα and PPARγ transactivation potency from nuclear extracts of 3T3-L1 cell. Furthermore, glucose uptake assay on L6 cells confirmed the potency of the synthesized compounds toward glucose regulation. Percentage lipid-lowering potency was also assessed through triglyceride estimate from 3T3-L1 cell extracts. Results suggested the ligand binding mode was in orthosteric fashion as similar to classical agonists. Thus molecular docking and molecular dynamics (MD) simulation experiments were executed to validate our hypothesis on mode of ligands binding and protein complex stability. Altogether, the present study developed a newer protocol for virtual screening and enables to design of novel glitazones for activation of PPARα and PPARγ-mediated pathways. Accordingly, present approach will offer benefit as a therapeutic strategy against type 2 diabetes mellitus and associated metabolic complications.
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Affiliation(s)
- Subhankar Mandal
- Department of Pharmaceutical Chemistry, JSS College of Pharmacy, S. S. Nagar, Mysuru, Karnataka, 570015, India
- JSS Academy of Higher Education and Research, Mysuru, Karnataka, 570015, India
| | - Syed Faizan
- Department of Pharmaceutical Chemistry, JSS College of Pharmacy, S. S. Nagar, Mysuru, Karnataka, 570015, India
- JSS Academy of Higher Education and Research, Mysuru, Karnataka, 570015, India
| | | | - B R Prashantha Kumar
- Department of Pharmaceutical Chemistry, JSS College of Pharmacy, S. S. Nagar, Mysuru, Karnataka, 570015, India.
- JSS Academy of Higher Education and Research, Mysuru, Karnataka, 570015, India.
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Torabidastgerdooei S, Roy ME, Annabi B. A molecular signature for the G6PC3/SLC37A2/SLC37A4 interactors in glioblastoma disease progression and in the acquisition of a brain cancer stem cell phenotype. Front Endocrinol (Lausanne) 2023; 14:1265698. [PMID: 38034009 PMCID: PMC10687460 DOI: 10.3389/fendo.2023.1265698] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/23/2023] [Accepted: 10/31/2023] [Indexed: 12/02/2023] Open
Abstract
Background Glycogen plays an important role in glucose homeostasis and contributes to key functions related to brain cancer cell survival in glioblastoma multiforme (GBM) disease progression. Such adaptive molecular mechanism is dependent on the glycogenolytic pathway and intracellular glucose-6-phosphate (G6P) sensing by brain cancer cells residing within those highly hypoxic tumors. The involvement of components of the glucose-6-phosphatase (G6Pase) system remains however elusive. Objective We questioned the gene expression levels of components of the G6Pase system in GBM tissues and their functional impact in the control of the invasive and brain cancer stem cells (CSC) phenotypes. Methods In silico analysis of transcript levels in GBM tumor tissues was done by GEPIA. Total RNA was extracted and gene expression of G6PC1-3 as well as of SLC37A1-4 members analyzed by qPCR in four human brain cancer cell lines and from clinically annotated brain tumor cDNA arrays. Transient siRNA-mediated gene silencing was used to assess the impact of TGF-β-induced epithelial-to-mesenchymal transition (EMT) and cell chemotaxis. Three-dimensional (3D) neurosphere cultures were generated to recapitulate the brain CSC phenotype. Results Higher expression in G6PC3, SLC37A2, and SLC37A4 was found in GBM tumor tissues in comparison to low-grade glioma and healthy tissue. The expression of these genes was also found elevated in established human U87, U251, U118, and U138 GBM cell models compared to human HepG2 hepatoma cells. SLC37A4/G6PC3, but not SLC37A2, levels were induced in 3D CD133/SOX2-positive U87 neurospheres when compared to 2D monolayers. Silencing of SLC37A4/G6PC3 altered TGF-β-induced EMT biomarker SNAIL and cell chemotaxis. Conclusion Two members of the G6Pase system, G6PC3 and SLC37A4, associate with GBM disease progression and regulate the metabolic reprogramming of an invasive and CSC phenotype. Such molecular signature may support their role in cancer cell survival and chemoresistance and become future therapeutic targets.
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Affiliation(s)
| | | | - Borhane Annabi
- Laboratoire d’Oncologie Moléculaire, Centre de recherche CERMO-FC, Département de Chimie, Université du Québec à Montréal, Montreal, QC, Canada
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Panchenko PE, Hippauf L, Konsman JP, Badaut J. Do astrocytes act as immune cells after pediatric TBI? Neurobiol Dis 2023; 185:106231. [PMID: 37468048 PMCID: PMC10530000 DOI: 10.1016/j.nbd.2023.106231] [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: 04/13/2023] [Revised: 06/28/2023] [Accepted: 07/15/2023] [Indexed: 07/21/2023] Open
Abstract
Astrocytes are in contact with the vasculature, neurons, oligodendrocytes and microglia, forming a local network with various functions critical for brain homeostasis. One of the primary responders to brain injury are astrocytes as they detect neuronal and vascular damage, change their phenotype with morphological, proteomic and transcriptomic transformations for an adaptive response. The role of astrocytic responses in brain dysfunction is not fully elucidated in adult, and even less described in the developing brain. Children are vulnerable to traumatic brain injury (TBI), which represents a leading cause of death and disability in the pediatric population. Pediatric brain trauma, even with mild severity, can lead to long-term health complications, such as cognitive impairments, emotional disorders and social dysfunction later in life. To date, the underlying pathophysiology is still not fully understood. In this review, we focus on the astrocytic response in pediatric TBI and propose a potential immune role of the astrocyte in response to trauma. We discuss the contribution of astrocytes in the local inflammatory cascades and secretion of various immunomodulatory factors involved in the recruitment of local microglial cells and peripheral immune cells through cerebral blood vessels. Taken together, we propose that early changes in the astrocytic phenotype can alter normal development of the brain, with long-term consequences on neurological outcomes, as described in preclinical models and patients.
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Affiliation(s)
| | - Lea Hippauf
- CNRS UMR 5536 RMSB-University of Bordeaux, Bordeaux, France
| | | | - Jerome Badaut
- CNRS UMR 5536 RMSB-University of Bordeaux, Bordeaux, France; Department of Basic Sciences, Loma Linda University School of Medicine, Loma Linda, CA, USA.
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8
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Li Z, Jiang Y, Long C, Peng Q, Yue R. The gut microbiota-astrocyte axis: Implications for type 2 diabetic cognitive dysfunction. CNS Neurosci Ther 2023; 29 Suppl 1:59-73. [PMID: 36601656 PMCID: PMC10314112 DOI: 10.1111/cns.14077] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2022] [Revised: 11/20/2022] [Accepted: 12/18/2022] [Indexed: 01/06/2023] Open
Abstract
BACKGROUND Diabetic cognitive dysfunction (DCD) is one of the most insidious complications of type 2 diabetes mellitus, which can seriously affect the ability to self-monitoring of blood glucose and the quality of life in the elderly. Previous pathological studies of cognitive dysfunction have focused on neuronal dysfunction, characterized by extracellular beta-amyloid deposition and intracellular tau hyperphosphorylation. In recent years, astrocytes have been recognized as a potential therapeutic target for cognitive dysfunction and important participants in the central control of metabolism. The disorder of gut microbiota and their metabolites have been linked to a series of metabolic diseases such as diabetes mellitus. The imbalance of intestinal flora has the effect of promoting the occurrence and deterioration of several diabetes-related complications. Gut microbes and their metabolites can drive astrocyte activation. AIMS We reviewed the pathological progress of DCD related to the "gut microbiota-astrocyte" axis in terms of peripheral and central inflammation, intestinal and blood-brain barrier (BBB) dysfunction, systemic and brain energy metabolism disorders to deepen the pathological research progress of DCD and explore the potential therapeutic targets. CONCLUSION "Gut microbiota-astrocyte" axis, unique bidirectional crosstalk in the brain-gut axis, mediates the intermediate pathological process of neurocognitive dysfunction secondary to metabolic disorders in diabetes mellitus.
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Affiliation(s)
- Zi‐Han Li
- Hospital of Chengdu University of Traditional Chinese MedicineChengduChina
| | - Ya‐Yi Jiang
- Hospital of Chengdu University of Traditional Chinese MedicineChengduChina
| | - Cai‐Yi Long
- Hospital of Chengdu University of Traditional Chinese MedicineChengduChina
| | - Qian Peng
- Hospital of Chengdu University of Traditional Chinese MedicineChengduChina
| | - Ren‐Song Yue
- Hospital of Chengdu University of Traditional Chinese MedicineChengduChina
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9
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Mattar P, Toledo-Valenzuela L, Hernández-Cáceres MP, Peña-Oyarzún D, Morselli E, Perez-Leighton C. Integrating the effects of sucrose intake on the brain and white adipose tissue: Could autophagy be a possible link? Obesity (Silver Spring) 2022; 30:1143-1155. [PMID: 35578809 DOI: 10.1002/oby.23411] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/12/2021] [Revised: 01/07/2022] [Accepted: 01/07/2022] [Indexed: 01/18/2023]
Abstract
Excess dietary sucrose is associated with obesity and metabolic diseases. This relationship is driven by the malfunction of several cell types and tissues critical for the regulation of energy balance, including hypothalamic neurons and white adipose tissue (WAT). However, the mechanisms behind these effects of dietary sucrose are still unclear and might be independent of increased adiposity. Accumulating evidence has indicated that dysregulation of autophagy, a fundamental process for maintenance of cellular homeostasis, alters energy metabolism in hypothalamic neurons and WAT, but whether autophagy could mediate the detrimental effects of dietary sucrose on hypothalamic neurons and WAT that contribute to weight gain is a matter of debate. In this review, we examine the hypothesis that dysregulated autophagy in hypothalamic neurons and WAT is an adiposity-independent effect of sucrose that contributes to increased body weight gain. We propose that excess dietary sucrose leads to autophagy unbalance in hypothalamic neurons and WAT, which increases caloric intake and body weight, favoring the emergence of obesity and metabolic diseases.
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Affiliation(s)
- Pamela Mattar
- Department of Physiology, Faculty of Biological Sciences, Pontificia Universidad Católica de Chile, Santiago, Chile
| | - Lilian Toledo-Valenzuela
- Department of Physiology, Faculty of Biological Sciences, Pontificia Universidad Católica de Chile, Santiago, Chile
| | - María Paz Hernández-Cáceres
- Department of Physiology, Faculty of Biological Sciences, Pontificia Universidad Católica de Chile, Santiago, Chile
- Institute for Research in Dental Sciences, Faculty of Dentistry, Universidad de Chile, Santiago, Chile
- Advanced Center for Chronic Diseases (ACCDiS), Universidad de Chile, Santiago, Chile
| | - Daniel Peña-Oyarzún
- Department of Physiology, Faculty of Biological Sciences, Pontificia Universidad Católica de Chile, Santiago, Chile
- Institute for Research in Dental Sciences, Faculty of Dentistry, Universidad de Chile, Santiago, Chile
- Advanced Center for Chronic Diseases (ACCDiS), Universidad de Chile, Santiago, Chile
- Interdisciplinary Center for Research in Territorial Health of the Aconcagua Valley (CIISTe Aconcagua, School of Medicine, Faculty of Medicine, San Felipe Campus, University of Valparaiso, Valparaíso, Chile
| | - Eugenia Morselli
- Department of Physiology, Faculty of Biological Sciences, Pontificia Universidad Católica de Chile, Santiago, Chile
| | - Claudio Perez-Leighton
- Department of Physiology, Faculty of Biological Sciences, Pontificia Universidad Católica de Chile, Santiago, Chile
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Antidiabetic activity of phytosynthesized Ag/CuO nanocomposites using Murraya koenigii and Zingiber officinale extracts. J Drug Deliv Sci Technol 2022. [DOI: 10.1016/j.jddst.2021.102838] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
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Zhang S, Lachance BB, Mattson MP, Jia X. Glucose metabolic crosstalk and regulation in brain function and diseases. Prog Neurobiol 2021; 204:102089. [PMID: 34118354 DOI: 10.1016/j.pneurobio.2021.102089] [Citation(s) in RCA: 54] [Impact Index Per Article: 18.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2020] [Revised: 04/08/2021] [Accepted: 06/01/2021] [Indexed: 01/11/2023]
Abstract
Brain glucose metabolism, including glycolysis, the pentose phosphate pathway, and glycogen turnover, produces ATP for energetic support and provides the precursors for the synthesis of biological macromolecules. Although glucose metabolism in neurons and astrocytes has been extensively studied, the glucose metabolism of microglia and oligodendrocytes, and their interactions with neurons and astrocytes, remain critical to understand brain function. Brain regions with heterogeneous cell composition and cell-type-specific profiles of glucose metabolism suggest that metabolic networks within the brain are complex. Signal transduction proteins including those in the Wnt, GSK-3β, PI3K-AKT, and AMPK pathways are involved in regulating these networks. Additionally, glycolytic enzymes and metabolites, such as hexokinase 2, acetyl-CoA, and enolase 2, are implicated in the modulation of cellular function, microglial activation, glycation, and acetylation of biomolecules. Given these extensive networks, glucose metabolism dysfunction in the whole brain or specific cell types is strongly associated with neurologic pathology including ischemic brain injury and neurodegenerative disorders. This review characterizes the glucose metabolism networks of the brain based on molecular signaling and cellular and regional interactions, and elucidates glucose metabolism-based mechanisms of neurological diseases and therapeutic approaches that may ameliorate metabolic abnormalities in those diseases.
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Affiliation(s)
- Shuai Zhang
- Department of Neurosurgery, University of Maryland School of Medicine, Baltimore, MD, 21201, United States
| | - Brittany Bolduc Lachance
- Program in Trauma, Department of Neurology, University of Maryland School of Medicine, Baltimore, MD, 21201, United States
| | - Mark P Mattson
- Department of Neuroscience, Johns Hopkins University School of Medicine, Baltimore, MD, 21205, United States
| | - Xiaofeng Jia
- Department of Neurosurgery, University of Maryland School of Medicine, Baltimore, MD, 21201, United States; Department of Orthopedics, University of Maryland School of Medicine, Baltimore, MD, 21201, United States; Department of Anatomy and Neurobiology, University of Maryland School of Medicine, Baltimore, MD, 21201, United States; Department of Biomedical Engineering, Johns Hopkins University School of Medicine, Baltimore, MD, 21205, United States; Department of Anesthesiology and Critical Care Medicine, Johns Hopkins University School of Medicine, Baltimore, MD, 21205, United States.
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12
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Sommariva S, Scussolini M, Cossu V, Marini C, Sambuceti G, Caviglia G, Piana M. The role of endoplasmic reticulum in in vivo cancer FDG kinetics. PLoS One 2021; 16:e0252422. [PMID: 34061902 PMCID: PMC8168898 DOI: 10.1371/journal.pone.0252422] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2021] [Accepted: 05/17/2021] [Indexed: 11/18/2022] Open
Abstract
A recent result obtained by means of an in vitro experiment with cancer cultured cells has configured the endoplasmic reticulum as the preferential site for the accumulation of 2-deoxy-2-[18F]fluoro-D-glucose (FDG). Such a result is coherent with cell biochemistry and is made more significant by the fact that the reticular accumulation rate of FDG is dependent upon extracellular glucose availability. The objective of the present paper is to confirm in vivo the result obtained in vitro concerning the crucial role played by the endoplasmic reticulum in FDG cancer metabolism. This study utilizes data acquired by means of a Positron Emission Tomography scanner for small animals in the case of CT26 models of cancer tissues. The recorded concentration images are interpreted within the framework of a three-compartment model for FDG kinetics, which explicitly assumes that the endoplasmic reticulum is the dephosphorylation site for FDG in cancer cells. The numerical reduction of the compartmental model is performed by means of a regularized Gauss-Newton algorithm for numerical optimization. This analysis shows that the proposed three-compartment model equals the performance of a standard Sokoloff’s two-compartment system in fitting the data. However, it provides estimates of some of the parameters, such as the phosphorylation rate of FDG, more consistent with prior biochemical information. These results are made more solid from a computational viewpoint by proving the identifiability and by performing a sensitivity analysis of the proposed compartment model.
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Affiliation(s)
- Sara Sommariva
- Dipartimento di Matematica, Università di Genova, Genova, Italy
| | - Mara Scussolini
- Dipartimento di Matematica, Università di Genova, Genova, Italy
| | - Vanessa Cossu
- Dipartimento di Medicina Nucleare, Policlinico San Martino IRCCS, Genova, Italy
| | | | - Gianmario Sambuceti
- Dipartimento di Medicina Nucleare, Policlinico San Martino IRCCS, Genova, Italy
- Dipartimento di Scienze della Salute, Università di Genova, Genova, Italy
| | | | - Michele Piana
- Dipartimento di Matematica, Università di Genova, Genova, Italy
- CNR - SPIN, Genova, Italy
- * E-mail:
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13
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D'Adamo P, Horvat A, Gurgone A, Mignogna ML, Bianchi V, Masetti M, Ripamonti M, Taverna S, Velebit J, Malnar M, Muhič M, Fink K, Bachi A, Restuccia U, Belloli S, Moresco RM, Mercalli A, Piemonti L, Potokar M, Bobnar ST, Kreft M, Chowdhury HH, Stenovec M, Vardjan N, Zorec R. Inhibiting glycolysis rescues memory impairment in an intellectual disability Gdi1-null mouse. Metabolism 2021; 116:154463. [PMID: 33309713 PMCID: PMC7871014 DOI: 10.1016/j.metabol.2020.154463] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/18/2020] [Revised: 11/30/2020] [Accepted: 12/04/2020] [Indexed: 01/08/2023]
Abstract
OBJECTIVES GDI1 gene encodes for αGDI, a protein controlling the cycling of small GTPases, reputed to orchestrate vesicle trafficking. Mutations in human GDI1 are responsible for intellectual disability (ID). In mice with ablated Gdi1, a model of ID, impaired working and associative short-term memory was recorded. This cognitive phenotype worsens if the deletion of αGDI expression is restricted to neurons. However, whether astrocytes, key homeostasis providing neuroglial cells, supporting neurons via aerobic glycolysis, contribute to this cognitive impairment is unclear. METHODS We carried out proteomic analysis and monitored [18F]-fluoro-2-deoxy-d-glucose uptake into brain slices of Gdi1 knockout and wild type control mice. d-Glucose utilization at single astrocyte level was measured by the Förster Resonance Energy Transfer (FRET)-based measurements of cytosolic cyclic AMP, d-glucose and L-lactate, evoked by agonists selective for noradrenaline and L-lactate receptors. To test the role of astrocyte-resident processes in disease phenotype, we generated an inducible Gdi1 knockout mouse carrying the Gdi1 deletion only in adult astrocytes and conducted behavioural tests. RESULTS Proteomic analysis revealed significant changes in astrocyte-resident glycolytic enzymes. Imaging [18F]-fluoro-2-deoxy-d-glucose revealed an increased d-glucose uptake in Gdi1 knockout tissue versus wild type control mice, consistent with the facilitated d-glucose uptake determined by FRET measurements. In mice with Gdi1 deletion restricted to astrocytes, a selective and significant impairment in working memory was recorded, which was rescued by inhibiting glycolysis by 2-deoxy-d-glucose injection. CONCLUSIONS These results reveal a new astrocyte-based mechanism in neurodevelopmental disorders and open a novel therapeutic opportunity of targeting aerobic glycolysis, advocating a change in clinical practice.
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Affiliation(s)
- Patrizia D'Adamo
- Division of Neuroscience, IRCCS San Raffaele Scientific Institute, Milan, Italy; University of Ljubljana, Faculty of Medicine, Institute of Pathophysiology, Laboratory of Neuroendocrinology - Molecular Cell Physiology, Ljubljana, Slovenia; Celica Biomedical, Laboratory for Cell Engineering, Ljubljana, Slovenia.
| | - Anemari Horvat
- University of Ljubljana, Faculty of Medicine, Institute of Pathophysiology, Laboratory of Neuroendocrinology - Molecular Cell Physiology, Ljubljana, Slovenia; Celica Biomedical, Laboratory for Cell Engineering, Ljubljana, Slovenia
| | - Antonia Gurgone
- Division of Neuroscience, IRCCS San Raffaele Scientific Institute, Milan, Italy
| | | | - Veronica Bianchi
- Division of Neuroscience, IRCCS San Raffaele Scientific Institute, Milan, Italy
| | - Michela Masetti
- Division of Neuroscience, IRCCS San Raffaele Scientific Institute, Milan, Italy
| | - Maddalena Ripamonti
- Division of Neuroscience, IRCCS San Raffaele Scientific Institute, Milan, Italy
| | - Stefano Taverna
- Division of Neuroscience, IRCCS San Raffaele Scientific Institute, Milan, Italy
| | - Jelena Velebit
- University of Ljubljana, Faculty of Medicine, Institute of Pathophysiology, Laboratory of Neuroendocrinology - Molecular Cell Physiology, Ljubljana, Slovenia; Celica Biomedical, Laboratory for Cell Engineering, Ljubljana, Slovenia
| | - Maja Malnar
- University of Ljubljana, Faculty of Medicine, Institute of Pathophysiology, Laboratory of Neuroendocrinology - Molecular Cell Physiology, Ljubljana, Slovenia
| | - Marko Muhič
- University of Ljubljana, Faculty of Medicine, Institute of Pathophysiology, Laboratory of Neuroendocrinology - Molecular Cell Physiology, Ljubljana, Slovenia
| | - Katja Fink
- University of Ljubljana, Faculty of Medicine, Institute of Pathophysiology, Laboratory of Neuroendocrinology - Molecular Cell Physiology, Ljubljana, Slovenia
| | - Angela Bachi
- IFOM, the FIRC Institute of Molecular Oncology, Milan, Italy
| | | | - Sara Belloli
- Institute of Bioimaging and Physiology, CNR, Segrate (MI), Italy; Experimental Imaging Center (EIC), San Raffaele Scientific Institute, Milan, Italy
| | - Rosa Maria Moresco
- Experimental Imaging Center (EIC), San Raffaele Scientific Institute, Milan, Italy; Medicine and Surgery Department, University of Milano-Bicocca, Monza (MB), Italy
| | - Alessia Mercalli
- Diabetes Research Institute, IRCCS Ospedale San Raffaele, Milano, Italy
| | - Lorenzo Piemonti
- Diabetes Research Institute, IRCCS Ospedale San Raffaele, Milano, Italy; Università Vita-Salute San Raffaele, Milano, Italy
| | - Maja Potokar
- University of Ljubljana, Faculty of Medicine, Institute of Pathophysiology, Laboratory of Neuroendocrinology - Molecular Cell Physiology, Ljubljana, Slovenia; Celica Biomedical, Laboratory for Cell Engineering, Ljubljana, Slovenia
| | - Saša Trkov Bobnar
- University of Ljubljana, Faculty of Medicine, Institute of Pathophysiology, Laboratory of Neuroendocrinology - Molecular Cell Physiology, Ljubljana, Slovenia; Celica Biomedical, Laboratory for Cell Engineering, Ljubljana, Slovenia
| | - Marko Kreft
- University of Ljubljana, Faculty of Medicine, Institute of Pathophysiology, Laboratory of Neuroendocrinology - Molecular Cell Physiology, Ljubljana, Slovenia; Celica Biomedical, Laboratory for Cell Engineering, Ljubljana, Slovenia; University of Ljubljana, Biotechnical Faculty, Department of Biology, Ljubljana, Slovenia
| | - Helena H Chowdhury
- University of Ljubljana, Faculty of Medicine, Institute of Pathophysiology, Laboratory of Neuroendocrinology - Molecular Cell Physiology, Ljubljana, Slovenia; Celica Biomedical, Laboratory for Cell Engineering, Ljubljana, Slovenia
| | - Matjaž Stenovec
- University of Ljubljana, Faculty of Medicine, Institute of Pathophysiology, Laboratory of Neuroendocrinology - Molecular Cell Physiology, Ljubljana, Slovenia; Celica Biomedical, Laboratory for Cell Engineering, Ljubljana, Slovenia
| | - Nina Vardjan
- University of Ljubljana, Faculty of Medicine, Institute of Pathophysiology, Laboratory of Neuroendocrinology - Molecular Cell Physiology, Ljubljana, Slovenia; Celica Biomedical, Laboratory for Cell Engineering, Ljubljana, Slovenia.
| | - Robert Zorec
- University of Ljubljana, Faculty of Medicine, Institute of Pathophysiology, Laboratory of Neuroendocrinology - Molecular Cell Physiology, Ljubljana, Slovenia; Celica Biomedical, Laboratory for Cell Engineering, Ljubljana, Slovenia.
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14
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Horvat A, Muhič M, Smolič T, Begić E, Zorec R, Kreft M, Vardjan N. Ca 2+ as the prime trigger of aerobic glycolysis in astrocytes. Cell Calcium 2021; 95:102368. [PMID: 33621899 DOI: 10.1016/j.ceca.2021.102368] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2020] [Revised: 02/05/2021] [Accepted: 02/08/2021] [Indexed: 12/17/2022]
Abstract
Astroglial aerobic glycolysis, a process during which d-glucose is converted to l-lactate, a brain fuel and signal, is regulated by the plasmalemmal receptors, including adrenergic receptors (ARs) and purinergic receptors (PRs), modulating intracellular Ca2+ and cAMP signals. However, the extent to which the two signals regulate astroglial aerobic glycolysis is poorly understood. By using agonists to stimulate intracellular α1-/β-AR-mediated Ca2+/cAMP signals, β-AR-mediated cAMP and P2R-mediated Ca2+ signals and genetically encoded fluorescence resonance energy transfer-based glucose and lactate nanosensors in combination with real-time microscopy, we show that intracellular Ca2+, but not cAMP, initiates a robust increase in the concentration of intracellular free d-glucose ([glc]i) and l-lactate ([lac]i), both depending on extracellular d-glucose, suggesting Ca2+-triggered glucose uptake and aerobic glycolysis in astrocytes. When the glycogen shunt, a process of glycogen remodelling, was inhibited, the α1-/β-AR-mediated increases in [glc]i and [lac]i were reduced by ∼65 % and ∼30 %, respectively, indicating that at least ∼30 % of the utilization of d-glucose is linked to glycogen remodelling and aerobic glycolysis. Additional activation of β-AR/cAMP signals aided to α1-/β-AR-triggered [lac]i increase, whereas the [glc]i increase was unaltered. Taken together, an increase in intracellular Ca2+ is the prime mechanism of augmented aerobic glycolysis in astrocytes, while cAMP has only a moderate role. The results provide novel information on the signals regulating brain metabolism and open new avenues to explore whether astroglial Ca2+ signals are dysregulated and contribute to neuropathologies with impaired brain metabolism.
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Affiliation(s)
- Anemari Horvat
- Laboratory of Neuroendocrinology - Molecular Cell Physiology, Institute of Pathophysiology, Faculty of Medicine, University of Ljubljana, Ljubljana, Slovenia; Laboratory of Cell Engineering, Celica Biomedical, Ljubljana, Slovenia
| | - Marko Muhič
- Laboratory of Neuroendocrinology - Molecular Cell Physiology, Institute of Pathophysiology, Faculty of Medicine, University of Ljubljana, Ljubljana, Slovenia
| | - Tina Smolič
- Laboratory of Neuroendocrinology - Molecular Cell Physiology, Institute of Pathophysiology, Faculty of Medicine, University of Ljubljana, Ljubljana, Slovenia
| | - Ena Begić
- Laboratory of Neuroendocrinology - Molecular Cell Physiology, Institute of Pathophysiology, Faculty of Medicine, University of Ljubljana, Ljubljana, Slovenia
| | - Robert Zorec
- Laboratory of Neuroendocrinology - Molecular Cell Physiology, Institute of Pathophysiology, Faculty of Medicine, University of Ljubljana, Ljubljana, Slovenia; Laboratory of Cell Engineering, Celica Biomedical, Ljubljana, Slovenia
| | - Marko Kreft
- Laboratory of Neuroendocrinology - Molecular Cell Physiology, Institute of Pathophysiology, Faculty of Medicine, University of Ljubljana, Ljubljana, Slovenia; Laboratory of Cell Engineering, Celica Biomedical, Ljubljana, Slovenia; Department of Biology, Biotechnical Faculty, University of Ljubljana, Ljubljana, Slovenia
| | - Nina Vardjan
- Laboratory of Neuroendocrinology - Molecular Cell Physiology, Institute of Pathophysiology, Faculty of Medicine, University of Ljubljana, Ljubljana, Slovenia; Laboratory of Cell Engineering, Celica Biomedical, Ljubljana, Slovenia.
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15
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Petit JM, Eren-Koçak E, Karatas H, Magistretti P, Dalkara T. Brain glycogen metabolism: A possible link between sleep disturbances, headache and depression. Sleep Med Rev 2021; 59:101449. [PMID: 33618186 DOI: 10.1016/j.smrv.2021.101449] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2020] [Revised: 11/26/2020] [Accepted: 11/27/2020] [Indexed: 12/27/2022]
Abstract
The functions of sleep and its links with neuropsychiatric diseases have long been questioned. Among the numerous hypotheses on sleep function, early studies proposed that sleep helps to replenish glycogen stores consumed during waking. Later studies found increased brain glycogen after sleep deprivation, leading to "glycogenetic" hypothesis, which states that there is a parallel increase in synthesis and utilization of glycogen during wakefulness, whereas decrease in the excitatory transmission creates an imbalance causing accumulation of glycogen during sleep. Glycogen is a vital energy reservoir to match the synaptic demand particularly for re-uptake of potassium and glutamate during intense glutamatergic transmission. Therefore, sleep deprivation-induced transcriptional changes may trigger migraine by reducing glycogen availability, which slows clearance of extracellular potassium and glutamate, hence, creates susceptibility to cortical spreading depolarization, the electrophysiological correlate of migraine aura. Interestingly, chronic stress accompanied by increased glucocorticoid levels and locus coeruleus activity and leading to mood disorders in which sleep disturbances are prevalent, also affects brain glycogen turnover via glucocorticoids, noradrenaline, serotonin and adenosine. These observations altogether suggest that inadequate astrocytic glycogen turnover may be one of the mechanisms linking migraine, mood disorders and sleep.
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Affiliation(s)
- J-M Petit
- Lausanne University Hospital, Center for Psychiatric Neuroscience, Prilly, Switzerland.
| | - E Eren-Koçak
- Hacettepe University, Institute of Neurological Sciences and Psychiatry, and Faculty of Medicine, Department of Psychiatry, Ankara, Turkey.
| | - H Karatas
- Hacettepe University, Institute of Neurological Sciences and Psychiatry, Ankara, Turkey.
| | - P Magistretti
- King Abdullah University of Science and Technology, Saudi Arabia.
| | - T Dalkara
- Hacettepe University, Institute of Neurological Sciences and Psychiatry, Ankara, Turkey.
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16
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Fink K, Velebit J, Vardjan N, Zorec R, Kreft M. Noradrenaline-induced l-lactate production requires d-glucose entry and transit through the glycogen shunt in single-cultured rat astrocytes. J Neurosci Res 2021; 99:1084-1098. [PMID: 33491223 DOI: 10.1002/jnr.24783] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2020] [Revised: 12/07/2020] [Accepted: 12/10/2020] [Indexed: 12/21/2022]
Abstract
During cognitive efforts mediated by local neuronal networks, approximately 20% of additional energy is required; this is mediated by chemical messengers such as noradrenaline (NA). NA targets astroglial aerobic glycolysis, the hallmark of which is the end product l-lactate, a fuel for neurons. Biochemical studies have revealed that astrocytes exhibit a prominent glycogen shunt, in which a portion of d-glucose molecules entering the cytoplasm is transiently incorporated into glycogen, a buffer and source of d-glucose during increased energy demand. Here, we studied single astrocytes by measuring cytosolic L-lactate ([lac]i ) with the FRET nanosensor Laconic. We examined whether NA-induced increase in [lac]i is influenced by: (a) 2-deoxy-d-glucose (2-DG, 3 mM), a molecule that enters the cytosol and inhibits the glycolytic pathway; (b) 1,4-dideoxy-1,4-imino-d-arabinitol (DAB, 300 µM), a potent inhibitor of glycogen phosphorylase and glycogen degradation; and (c) 3-nitropropionic acid (3-NPA, 1 mM), an inhibitor of the Krebs cycle. The results of these pharmacological experiments revealed that d-glucose uptake is essential for the NA-induced increase in [lac]i , and that this exclusively arises from glycogen degradation, indicating that most, if not all, d-glucose molecules in NA-stimulated cells transit the glycogen shunt during glycolysis. Moreover, under the defined transmembrane d-glucose gradient, the glycolytic intermediates were not only used to produce l-lactate, but also to significantly support oxidative phosphorylation, as demonstrated by an elevation in [lac]i when Krebs cycle was inhibited. We conclude that l-lactate production via aerobic glycolysis is an essential energy pathway in NA-stimulated astrocytes; however, oxidative metabolism is important at rest.
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Affiliation(s)
- Katja Fink
- Laboratory of Neuroendocrinology-Molecular Cell Physiology, Faculty of Medicine, Institute of Pathophysiology, University of Ljubljana, Ljubljana, Slovenia
| | - Jelena Velebit
- Laboratory of Neuroendocrinology-Molecular Cell Physiology, Faculty of Medicine, Institute of Pathophysiology, University of Ljubljana, Ljubljana, Slovenia.,Celica Biomedical, Ljubljana, Slovenia
| | - Nina Vardjan
- Laboratory of Neuroendocrinology-Molecular Cell Physiology, Faculty of Medicine, Institute of Pathophysiology, University of Ljubljana, Ljubljana, Slovenia.,Celica Biomedical, Ljubljana, Slovenia
| | - Robert Zorec
- Laboratory of Neuroendocrinology-Molecular Cell Physiology, Faculty of Medicine, Institute of Pathophysiology, University of Ljubljana, Ljubljana, Slovenia.,Celica Biomedical, Ljubljana, Slovenia
| | - Marko Kreft
- Laboratory of Neuroendocrinology-Molecular Cell Physiology, Faculty of Medicine, Institute of Pathophysiology, University of Ljubljana, Ljubljana, Slovenia.,Celica Biomedical, Ljubljana, Slovenia.,Department of Biology, Biotechnical Faculty, University of Ljubljana, Ljubljana, Slovenia
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17
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Rose J, Brian C, Pappa A, Panayiotidis MI, Franco R. Mitochondrial Metabolism in Astrocytes Regulates Brain Bioenergetics, Neurotransmission and Redox Balance. Front Neurosci 2020; 14:536682. [PMID: 33224019 PMCID: PMC7674659 DOI: 10.3389/fnins.2020.536682] [Citation(s) in RCA: 71] [Impact Index Per Article: 17.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2020] [Accepted: 10/14/2020] [Indexed: 01/17/2023] Open
Abstract
In the brain, mitochondrial metabolism has been largely associated with energy production, and its dysfunction is linked to neuronal cell loss. However, the functional role of mitochondria in glial cells has been poorly studied. Recent reports have demonstrated unequivocally that astrocytes do not require mitochondria to meet their bioenergetics demands. Then, the question remaining is, what is the functional role of mitochondria in astrocytes? In this work, we review current evidence demonstrating that mitochondrial central carbon metabolism in astrocytes regulates overall brain bioenergetics, neurotransmitter homeostasis and redox balance. Emphasis is placed in detailing carbon source utilization (glucose and fatty acids), anaplerotic inputs and cataplerotic outputs, as well as carbon shuttles to neurons, which highlight the metabolic specialization of astrocytic mitochondria and its relevance to brain function.
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Affiliation(s)
- Jordan Rose
- Redox Biology Center, University of Nebraska-Lincoln, Lincoln, NE, United States.,School of Veterinary Medicine and Biomedical Sciences, University of Nebraska-Lincoln, Lincoln, NE, United States
| | - Christian Brian
- Redox Biology Center, University of Nebraska-Lincoln, Lincoln, NE, United States.,School of Veterinary Medicine and Biomedical Sciences, University of Nebraska-Lincoln, Lincoln, NE, United States
| | - Aglaia Pappa
- Department of Molecular Biology and Genetics, Democritus University of Thrace, Alexandroupolis, Greece
| | - Mihalis I Panayiotidis
- Department of Electron Microscopy & Molecular Pathology, Cyprus Institute of Neurology & Genetics, Nicosia, Cyprus
| | - Rodrigo Franco
- Redox Biology Center, University of Nebraska-Lincoln, Lincoln, NE, United States.,School of Veterinary Medicine and Biomedical Sciences, University of Nebraska-Lincoln, Lincoln, NE, United States
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18
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Chowdhury HH. Differences in cytosolic glucose dynamics in astrocytes and adipocytes measured by FRET-based nanosensors. Biophys Chem 2020; 261:106377. [PMID: 32302866 DOI: 10.1016/j.bpc.2020.106377] [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: 02/08/2020] [Revised: 04/08/2020] [Accepted: 04/08/2020] [Indexed: 11/17/2022]
Abstract
The cellular response to fluctuations in blood glucose levels consists of integrative regulation of cell glucose uptake and glucose utilization in the cytosol, resulting in altered levels of glucose in the cytosol. Cytosolic glucose is difficult to be measured in the intact tissue, however recently methods have become available that allow measurements of glucose in single living cells with fluorescence resonance energy transfer (FRET) based protein sensors. By studying the dynamics of cytosolic glucose levels in different experimental settings, we can gain insights into the properties of plasma membrane permeability to glucose and glucose utilization in the cytosol, and how these processes are modulated by different environmental conditions, agents and enzymes. In this review, we compare the cytosolic regulation of glucose in adipocytes and astrocytes - two important regulators of energy balance and glucose homeostasis in whole body and brain, respectively, with particular emphasis on the data obtained with FRET based protein sensors as well as other biochemical and molecular approaches.
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Affiliation(s)
- Helena H Chowdhury
- Laboratory of Neuroendocrinology - Molecular Cell Physiology, Institute of Pathophysiology, University of Ljubljana, Faculty of Medicine, 1000 Ljubljana, Slovenia; Laboratory of Cell Engineering, Celica Biomedical, 1000 Ljubljana, Slovenia.
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19
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Velebit J, Horvat A, Smolič T, Prpar Mihevc S, Rogelj B, Zorec R, Vardjan N. Astrocytes with TDP-43 inclusions exhibit reduced noradrenergic cAMP and Ca 2+ signaling and dysregulated cell metabolism. Sci Rep 2020; 10:6003. [PMID: 32265469 PMCID: PMC7138839 DOI: 10.1038/s41598-020-62864-5] [Citation(s) in RCA: 43] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2019] [Accepted: 03/20/2020] [Indexed: 12/12/2022] Open
Abstract
Most cases of amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD) have cytoplasmic inclusions of TAR DNA-binding protein 43 (TDP-43) in neurons and non-neuronal cells, including astrocytes, which metabolically support neurons with nutrients. Neuronal metabolism largely depends on the activation of the noradrenergic system releasing noradrenaline. Activation of astroglial adrenergic receptors with noradrenaline triggers cAMP and Ca2+ signaling and augments aerobic glycolysis with production of lactate, an important neuronal energy fuel. Astrocytes with cytoplasmic TDP-43 inclusions can cause motor neuron death, however, whether astroglial metabolism and metabolic support of neurons is altered in astrocytes with TDP-43 inclusions, is unclear. We measured lipid droplet and glucose metabolisms in astrocytes expressing the inclusion-forming C-terminal fragment of TDP-43 or the wild-type TDP-43 using fluorescent dyes or genetically encoded nanosensors. Astrocytes with TDP-43 inclusions exhibited a 3-fold increase in the accumulation of lipid droplets versus astrocytes expressing wild-type TDP-43, indicating altered lipid droplet metabolism. In these cells the noradrenaline-triggered increases in intracellular cAMP and Ca2+ levels were reduced by 35% and 31%, respectively, likely due to the downregulation of β2-adrenergic receptors. Although noradrenaline triggered a similar increase in intracellular lactate levels in astrocytes with and without TDP-43 inclusions, the probability of activating aerobic glycolysis was facilitated by 1.6-fold in astrocytes with TDP-43 inclusions and lactate MCT1 transporters were downregulated. Thus, while in astrocytes with TDP-43 inclusions noradrenergic signaling is reduced, aerobic glycolysis and lipid droplet accumulation are facilitated, suggesting dysregulated astroglial metabolism and metabolic support of neurons in TDP-43-associated ALS and FTD.
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Affiliation(s)
- Jelena Velebit
- Laboratory of Cell Engineering, Celica Biomedical, 1000, Ljubljana, Slovenia
| | - Anemari Horvat
- Laboratory of Cell Engineering, Celica Biomedical, 1000, Ljubljana, Slovenia.,Laboratory of Neuroendocrinology - Molecular Cell Physiology, Institute of Pathophysiology, Faculty of Medicine, University of Ljubljana, 1000, Ljubljana, Slovenia
| | - Tina Smolič
- Laboratory of Neuroendocrinology - Molecular Cell Physiology, Institute of Pathophysiology, Faculty of Medicine, University of Ljubljana, 1000, Ljubljana, Slovenia
| | - Sonja Prpar Mihevc
- Department of Biotechnology, Jožef Stefan Institute, 1000, Ljubljana, Slovenia
| | - Boris Rogelj
- Department of Biotechnology, Jožef Stefan Institute, 1000, Ljubljana, Slovenia.,Biomedical Research Institute BRIS, 1000, Ljubljana, Slovenia.,Faculty of Chemistry and Chemical Technology, University of Ljubljana, 1000, Ljubljana, Slovenia
| | - Robert Zorec
- Laboratory of Cell Engineering, Celica Biomedical, 1000, Ljubljana, Slovenia.,Laboratory of Neuroendocrinology - Molecular Cell Physiology, Institute of Pathophysiology, Faculty of Medicine, University of Ljubljana, 1000, Ljubljana, Slovenia
| | - Nina Vardjan
- Laboratory of Cell Engineering, Celica Biomedical, 1000, Ljubljana, Slovenia. .,Laboratory of Neuroendocrinology - Molecular Cell Physiology, Institute of Pathophysiology, Faculty of Medicine, University of Ljubljana, 1000, Ljubljana, Slovenia.
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20
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Öztürk Z, O’Kane CJ, Pérez-Moreno JJ. Axonal Endoplasmic Reticulum Dynamics and Its Roles in Neurodegeneration. Front Neurosci 2020; 14:48. [PMID: 32116502 PMCID: PMC7025499 DOI: 10.3389/fnins.2020.00048] [Citation(s) in RCA: 69] [Impact Index Per Article: 17.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2019] [Accepted: 01/13/2020] [Indexed: 12/13/2022] Open
Abstract
The physical continuity of axons over long cellular distances poses challenges for their maintenance. One organelle that faces this challenge is endoplasmic reticulum (ER); unlike other intracellular organelles, this forms a physically continuous network throughout the cell, with a single membrane and a single lumen. In axons, ER is mainly smooth, forming a tubular network with occasional sheets or cisternae and low amounts of rough ER. It has many potential roles: lipid biosynthesis, glucose homeostasis, a Ca2+ store, protein export, and contacting and regulating other organelles. This tubular network structure is determined by ER-shaping proteins, mutations in some of which are causative for neurodegenerative disorders such as hereditary spastic paraplegia (HSP). While axonal ER shares many features with the tubular ER network in other contexts, these features must be adapted to the long and narrow dimensions of axons. ER appears to be physically continuous throughout axons, over distances that are enormous on a subcellular scale. It is therefore a potential channel for long-distance or regional communication within neurons, independent of action potentials or physical transport of cargos, but involving its physiological roles such as Ca2+ or organelle homeostasis. Despite its apparent stability, axonal ER is highly dynamic, showing features like anterograde and retrograde transport, potentially reflecting continuous fusion and breakage of the network. Here we discuss the transport processes that must contribute to this dynamic behavior of ER. We also discuss the model that these processes underpin a homeostatic process that ensures both enough ER to maintain continuity of the network and repair breaks in it, but not too much ER that might disrupt local cellular physiology. Finally, we discuss how failure of ER organization in axons could lead to axon degenerative diseases, and how a requirement for ER continuity could make distal axons most susceptible to degeneration in conditions that disrupt ER continuity.
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Affiliation(s)
| | - Cahir J. O’Kane
- Department of Genetics, University of Cambridge, Cambridge, United Kingdom
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21
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Lagos-Cabré R, Burgos-Bravo F, Avalos AM, Leyton L. Connexins in Astrocyte Migration. Front Pharmacol 2020; 10:1546. [PMID: 32009957 PMCID: PMC6974553 DOI: 10.3389/fphar.2019.01546] [Citation(s) in RCA: 31] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2019] [Accepted: 11/29/2019] [Indexed: 12/18/2022] Open
Abstract
Astrocytes have long been considered the supportive cells of the central nervous system, but during the last decades, they have gained much more attention because of their active participation in the modulation of neuronal function. For example, after brain damage, astrocytes become reactive and undergo characteristic morphological and molecular changes, such as hypertrophy and increase in the expression of glial fibrillary acidic protein (GFAP), in a process known as astrogliosis. After severe damage, astrocytes migrate to the lesion site and proliferate, which leads to the formation of a glial scar. At this scar-forming stage, astrocytes secrete many factors, such as extracellular matrix proteins, cytokines, growth factors and chondroitin sulfate proteoglycans, stop migrating, and the process is irreversible. Although reactive gliosis is a normal physiological response that can protect brain cells from further damage, it also has detrimental effects on neuronal survival, by creating a hostile and non-permissive environment for axonal repair. The transformation of astrocytes from reactive to scar-forming astrocytes highlights migration as a relevant regulator of glial scar formation, and further emphasizes the importance of efficient communication between astrocytes in order to orchestrate cell migration. The coordination between astrocytes occurs mainly through Connexin (Cx) channels, in the form of direct cell-cell contact (gap junctions, GJs) or contact between the extracellular matrix and the astrocytes (hemichannels, HCs). Reactive astrocytes increase the expression levels of several proteins involved in astrocyte migration, such as αvβ3 Integrin, Syndecan-4 proteoglycan, the purinergic receptor P2X7, Pannexin1, and Cx43 HCs. Evidence has indicated that Cx43 HCs play a role in regulating astrocyte migration through the release of small molecules to the extracellular space, which then activate receptors in the same or adjacent cells to continue the signaling cascades required for astrocyte migration. In this review, we describe the communication of astrocytes through Cxs, the role of Cxs in inflammation and astrocyte migration, and discuss the molecular mechanisms that regulate Cx43 HCs, which may provide a therapeutic window of opportunity to control astrogliosis and the progression of neurodegenerative diseases.
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Affiliation(s)
- Raúl Lagos-Cabré
- Cellular Communication Laboratory, Programa de Biología Celular y Molecular, Instituto de Ciencias Biomédicas (ICBM), Facultad de Medicina, Universidad de Chile, Santiago, Chile.,Advanced Center for Chronic Diseases (ACCDiS), Center for Studies on Exercise, Metabolism and Cancer (CEMC), Facultad de Medicina, Instituto de Ciencias Biomédicas (ICBM), Universidad de Chile, Santiago, Chile
| | - Francesca Burgos-Bravo
- Cellular Communication Laboratory, Programa de Biología Celular y Molecular, Instituto de Ciencias Biomédicas (ICBM), Facultad de Medicina, Universidad de Chile, Santiago, Chile.,Advanced Center for Chronic Diseases (ACCDiS), Center for Studies on Exercise, Metabolism and Cancer (CEMC), Facultad de Medicina, Instituto de Ciencias Biomédicas (ICBM), Universidad de Chile, Santiago, Chile
| | - Ana María Avalos
- Facultad de Ciencias de la Salud, Instituto de Ciencias Biomédicas, Universidad Autónoma de Chile, Santiago, Chile
| | - Lisette Leyton
- Cellular Communication Laboratory, Programa de Biología Celular y Molecular, Instituto de Ciencias Biomédicas (ICBM), Facultad de Medicina, Universidad de Chile, Santiago, Chile.,Advanced Center for Chronic Diseases (ACCDiS), Center for Studies on Exercise, Metabolism and Cancer (CEMC), Facultad de Medicina, Instituto de Ciencias Biomédicas (ICBM), Universidad de Chile, Santiago, Chile
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22
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Westermeier F, Holyoak T, Asenjo JL, Gatica R, Nualart F, Burbulis I, Bertinat R. Gluconeogenic Enzymes in β-Cells: Pharmacological Targets for Improving Insulin Secretion. Trends Endocrinol Metab 2019; 30:520-531. [PMID: 31213347 DOI: 10.1016/j.tem.2019.05.004] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/18/2019] [Revised: 05/14/2019] [Accepted: 05/16/2019] [Indexed: 02/06/2023]
Abstract
Pancreatic β-cells express the gluconeogenic enzymes glucose 6-phosphatase (G6Pase), fructose 1,6-bisphosphatase (FBP), and phosphoenolpyruvate (PEP) carboxykinase (PCK), which modulate glucose-stimulated insulin secretion (GSIS) through their ability to reverse otherwise irreversible glycolytic steps. Here, we review current knowledge about the expression and regulation of these enzymes in the context of manipulating them to improve insulin secretion in diabetics. Because the regulation of gluconeogenic enzymes in β-cells is so poorly understood, we propose novel research avenues to study these enzymes as modulators of insulin secretion and β-cell dysfunction, with especial attention to FBP, which constitutes an attractive target with an inhibitor under clinical evaluation at present.
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Affiliation(s)
- Francisco Westermeier
- FH JOANNEUM Gesellschaft mbH University of Applied Sciences, Institute of Biomedical Science, Eggenberger Allee 13, 8020 Graz, Austria
| | - Todd Holyoak
- Department of Biology, University of Waterloo, Waterloo, ON N2L 3G1, Canada
| | - Joel L Asenjo
- Instituto de Bioquímica y Microbiología, Facultad de Ciencias, Universidad Austral de Chile, Independencia 631, 5110566 Valdivia, Chile
| | - Rodrigo Gatica
- Escuela de Veterinaria, Facultad de Ciencias, Universidad Mayor, La Pirámide 5750, 8580745 Santiago, Chile
| | - Francisco Nualart
- Centro de Microscopía Avanzada, CMA BIO, Facultad de Ciencias Biológicas, Universidad de Concepción, Casilla 160 C, 4030000 Concepción, Chile
| | - Ian Burbulis
- Department of Biochemistry and Molecular Genetics, School of Medicine, University of Virginia, Jordan Hall Room 6022, 1340 Jefferson Park Avenue, Charlottesville, VA 22908, USA; Escuela de Medicina, Universidad San Sebastián, Sede Patagonia, Lago Panguipulli 1390, 5501842 Puerto Montt, Chile
| | - Romina Bertinat
- Centro de Microscopía Avanzada, CMA BIO, Facultad de Ciencias Biológicas, Universidad de Concepción, Casilla 160 C, 4030000 Concepción, Chile.
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23
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The median eminence as the hypothalamic area involved in rapid transfer of glucose to the brain: functional and cellular mechanisms. J Mol Med (Berl) 2019; 97:1085-1097. [PMID: 31129757 DOI: 10.1007/s00109-019-01799-5] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2019] [Revised: 05/03/2019] [Accepted: 05/13/2019] [Indexed: 12/15/2022]
Abstract
Our data proposes that glucose is transferred directly to the cerebrospinal fluid (CSF) of the hypothalamic ventricular cavity through a rapid "fast-track-type mechanism" that would efficiently stimulate the glucosensing areas. This mechanism would occur at the level of the median eminence (ME), a periventricular hypothalamic zone with no blood-brain barrier. This "fast-track" mechanism would involve specific glial cells of the ME known as β2 tanycytes that could function as "inverted enterocytes," expressing low-affinity glucose transporters GLUT2 and GLUT6 in order to rapidly transfer glucose to the CSF. Due to the large size of tanycytes, the presence of a high concentration of mitochondria and the expression of low-affinity glucose transporters, it would be expected that these cells accumulate glucose in the endoplasmic reticulum (ER) by sequestering glucose-6-phosphate (G-6-P), in a similar way to that recently demonstrated in astrocytes. Glucose could diffuse through the cells by micrometric distances to be released in the apical region of β2 tanycytes, towards the CSF. Through this mechanism, levels of glucose would increase inside the hypothalamus, stimulating glucosensing mechanisms quickly and efficiently. KEY MESSAGES: • Glucose diffuses through the median eminence cells (β2 tanycytes), towards the hypothalamic CSF. • Glucose is transferred through a rapid "fast-track-type mechanism" via GLUT2 and GLUT6. • Through this mechanism, hypothalamic glucose levels increase, stimulating glucosensing.
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24
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Dienel GA. The “protected” glucose transport through the astrocytic endoplasmic reticulum is too slow to serve as a quantitatively‐important highway for nutrient delivery. J Neurosci Res 2019; 97:854-862. [DOI: 10.1002/jnr.24432] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2019] [Revised: 04/04/2019] [Accepted: 04/08/2019] [Indexed: 01/05/2023]
Affiliation(s)
- Gerald A. Dienel
- Department of Neurology University of Arkansas for Medical Sciences Little Rock Arkansas
- Department of Cell Biology and Physiology University of New Mexico Albuquerque New Mexico
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25
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Souza DG, Almeida RF, Souza DO, Zimmer ER. The astrocyte biochemistry. Semin Cell Dev Biol 2019; 95:142-150. [PMID: 30951895 DOI: 10.1016/j.semcdb.2019.04.002] [Citation(s) in RCA: 31] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2018] [Revised: 03/19/2019] [Accepted: 04/01/2019] [Indexed: 02/06/2023]
Abstract
Astrocytes are a unique and dynamic subtype of glial cells in the central nervous system (CNS). Understanding their biochemical reactions and their influence in the surrounding cells is extremely important in the neuroscience field. They exert important influence in the neurotransmission, ionic homeostasis and also release neuroactive molecules termed gliotransmitters. Additionally, they metabolize, store and release metabolic substrates to meet high brain energy requirements. In this review, we highlight the main biochemical reactions regarding energy metabolism that take place in astrocytes. Special attention is given to synthesis, storage and catabolism of glucose, release of lactate, oxidation of fatty acids, production of ketone bodies, and metabolism of the main neurotransmitters, glutamate and GABA. The recent findings allow proposing these cells as key players controlling the energetic homeostasis in the CNS.
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Affiliation(s)
- Débora G Souza
- Graduate Program in Biological Sciences: Biochemistry, Universidade Federal do Rio Grande do Sul (UFRGS), Porto Alegre, Brazil
| | - Roberto F Almeida
- Graduate Program in Biological Sciences: Biochemistry, Universidade Federal do Rio Grande do Sul (UFRGS), Porto Alegre, Brazil; Exact and Biological Sciences Institute, Biological Sciences Department, Federal University of Ouro Preto, Ouro Preto, Brazil
| | - Diogo O Souza
- Graduate Program in Biological Sciences: Biochemistry, Universidade Federal do Rio Grande do Sul (UFRGS), Porto Alegre, Brazil; Department of Biochemistry, UFRGS, Porto Alegre, Brazil
| | - Eduardo R Zimmer
- Graduate Program in Biological Sciences: Biochemistry, Universidade Federal do Rio Grande do Sul (UFRGS), Porto Alegre, Brazil; Department of Pharmacology, UFRGS, Porto Alegre, Brazil; Graduate Program in Biological Sciences: Pharmacology and Therapeutics, UFRGS, Porto Alegre, Brazil; Brain Institute of Rio Grande do Sul (BraIns), Pontifical Catholic University of Rio Grande do Sul, Porto Alegre, Brazil.
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26
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Hirase H, Akther S, Wang X, Oe Y. Glycogen distribution in mouse hippocampus. J Neurosci Res 2019; 97:923-932. [PMID: 30675919 DOI: 10.1002/jnr.24386] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2018] [Revised: 01/04/2019] [Accepted: 01/07/2019] [Indexed: 12/31/2022]
Abstract
The hippocampus is a limbic structure involved in the consolidation of episodic memory. In the recent decade, glycogenolysis in the rodent hippocampus has been shown critical for synaptic plasticity and memory formation. Astrocytes are the primary cells that store glycogen which is subject to degradation in hypoglycemic conditions. Focused microwave application to the brain halts metabolic activities, and therefore preserves brain glycogen. Immunohistochemistry against glycogen on focused microwave-assisted brain samples is suitable for both macroscopic and microscopic investigation of glycogen distribution. Glycogen immunohistochemistry in the hippocampus showed a characteristic punctate signal pattern that depended on hippocampal layers. In particular, the hilus is the most glycogen-rich subregion of the hippocampus. Moreover, large glycogen puncta (>0.5 µm in diameter) observed in neuropil areas are organized in a patchy pattern consisting of puncta-rich and -poor astrocytes. These observations are discussed with respect to distinct hippocampal neural activity states observed in live animals.
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Affiliation(s)
- Hajime Hirase
- RIKEN Center for Brain Science, Wako, Japan.,Saitama University Brain Science Institute, Saitama, Japan.,Center for Translational Neuromedicine, Faculty of Medical and Health Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Sonam Akther
- RIKEN Center for Brain Science, Wako, Japan.,Saitama University Brain Science Institute, Saitama, Japan
| | | | - Yuki Oe
- RIKEN Center for Brain Science, Wako, Japan
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27
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