1
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Modder M, Coomans CP, Saaltink DJ, Tersteeg MMH, Hoogduin J, Scholten L, Pronk ACM, Lalai RA, Boelen A, Kalsbeek A, Rensen PCN, Vreugdenhil E, Kooijman S. Doublecortin-like knockdown in mice attenuates obesity by stimulating energy expenditure in adipose tissue. Sci Rep 2024; 14:19517. [PMID: 39174821 PMCID: PMC11341836 DOI: 10.1038/s41598-024-70639-5] [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: 04/24/2024] [Accepted: 08/20/2024] [Indexed: 08/24/2024] Open
Abstract
Crosstalk between peripheral metabolic organs and the central nervous system is essential for body weight control. At the base of the hypothalamus, β-tanycytes surround the portal capillaries and function as gatekeepers to facilitate transfer of substances from the circulation into the cerebrospinal fluid and vice versa. Here, we investigated the role of the neuroplasticity gene doublecortin-like (DCL), highly expressed by β-tanycytes, in body weight control and whole-body energy metabolism. We demonstrated that DCL-knockdown through a doxycycline-inducible shRNA expression system prevents body weight gain by reducing adiposity in mice. DCL-knockdown slightly increased whole-body energy expenditure possibly as a result of elevated circulating thyroid hormones. In white adipose tissue (WAT) triglyceride uptake was increased while the average adipocyte cell size was reduced. At histological level we observed clear signs of browning, and thus increased thermogenesis in WAT. We found no indications for stimulated thermogenesis in brown adipose tissue (BAT). Altogether, we demonstrate an important, though subtle, role of tanycytic DCL in body weight control through regulation of energy expenditure, and specifically WAT browning. Elucidating mechanisms underlying the role of DCL in regulating brain-peripheral crosstalk further might identify new treatment targets for obesity.
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Affiliation(s)
- Melanie Modder
- Division of Endocrinology, Department of Medicine, Leiden University Medical Center, P.O. Box 9600, 2300 RC, Leiden, The Netherlands
| | - Claudia P Coomans
- Laboratory for Neurophysiology, Department of Cell and Chemical Biology, Leiden University Medical Center, P.O. Box 9600, 2300 RC, Leiden, The Netherlands
| | - Dirk-Jan Saaltink
- Laboratory for Neurophysiology, Department of Cell and Chemical Biology, Leiden University Medical Center, P.O. Box 9600, 2300 RC, Leiden, The Netherlands
| | - Mayke M H Tersteeg
- Laboratory for Neurophysiology, Department of Cell and Chemical Biology, Leiden University Medical Center, P.O. Box 9600, 2300 RC, Leiden, The Netherlands
| | - Janna Hoogduin
- Laboratory for Neurophysiology, Department of Cell and Chemical Biology, Leiden University Medical Center, P.O. Box 9600, 2300 RC, Leiden, The Netherlands
| | - Leonie Scholten
- Laboratory for Neurophysiology, Department of Cell and Chemical Biology, Leiden University Medical Center, P.O. Box 9600, 2300 RC, Leiden, The Netherlands
| | - Amanda C M Pronk
- Division of Endocrinology, Department of Medicine, Leiden University Medical Center, P.O. Box 9600, 2300 RC, Leiden, The Netherlands
| | - Reshma A Lalai
- Division of Endocrinology, Department of Medicine, Leiden University Medical Center, P.O. Box 9600, 2300 RC, Leiden, The Netherlands
| | - Anita Boelen
- Endocrine Laboratory, Amsterdam UMC, Location AMC, University of Amsterdam, Amsterdam, The Netherlands
| | - Andries Kalsbeek
- Endocrine Laboratory, Amsterdam UMC, Location AMC, University of Amsterdam, Amsterdam, The Netherlands
- Department of Endocrinology and Metabolism, Amsterdam UMC, Location AMC, University of Amsterdam, Amsterdam, The Netherlands
- Hypothalamic Integration Mechanisms, Netherlands Institute for Neuroscience, Amsterdam, The Netherlands
| | - Patrick C N Rensen
- Division of Endocrinology, Department of Medicine, Leiden University Medical Center, P.O. Box 9600, 2300 RC, Leiden, The Netherlands
| | - Erno Vreugdenhil
- Laboratory for Neurophysiology, Department of Cell and Chemical Biology, Leiden University Medical Center, P.O. Box 9600, 2300 RC, Leiden, The Netherlands
| | - Sander Kooijman
- Division of Endocrinology, Department of Medicine, Leiden University Medical Center, P.O. Box 9600, 2300 RC, Leiden, The Netherlands.
- Leiden University Medical Center, Albinusdreef 2, 2333ZA, Leiden, The Netherlands.
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Liu D, Wang T, Zhao X, Chen J, Yang T, Shen Y, Zhou YD. Saturated fatty acids stimulate cytokine production in tanycytes via the PP2Ac-dependent signaling pathway. J Cereb Blood Flow Metab 2024; 44:985-999. [PMID: 38069840 PMCID: PMC11318396 DOI: 10.1177/0271678x231219115] [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: 06/16/2023] [Revised: 09/18/2023] [Accepted: 11/10/2023] [Indexed: 05/18/2024]
Abstract
The hypothalamic tanycytes are crucial for free fatty acids (FFAs) detection, storage, and transport within the central nervous system. They have been shown to effectively respond to fluctuations in circulating FFAs, thereby regulating energy homeostasis. However, the precise molecular mechanisms by which tanycytes modulate lipid utilization remain unclear. Here, we report that the catalytic subunit of protein phosphatase 2 A (PP2Ac), a serine/threonine phosphatase, is expressed in tanycytes and its accumulation and activation occur in response to high-fat diet consumption. In vitro, tanycytic PP2Ac responds to palmitic acid (PA) exposure and accumulates and is activated at an early stage in an AMPK-dependent manner. Furthermore, activated PP2Ac boosts hypoxia-inducible factor-1α (HIF-1α) accumulation, resulting in upregulation of an array of cytokines. Pretreatment with a PP2Ac inhibitor, LB100, prevented the PA-induced elevation of vascular endothelial growth factor (VEGF), fibroblast growth factor 1 (FGF1), hepatocyte growth factor (HGF), and dipeptidyl peptidase IV (DPPIV or CD26). Our results disclose a mechanism of lipid metabolism in tanycytes that involves the activation of PP2Ac and highlight the physiological significance of PP2Ac in hypothalamic tanycytes in response to overnutrition and efficacious treatment of obesity.
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Affiliation(s)
- Danyang Liu
- Institute of Neuroscience, NHC and CAMS Key Laboratory of Medical Neurobiology, MOE Frontier Science Center for Brain Research and Brain-Machine Integration, Zhejiang University School of Brain Science and Brain Medicine, Hangzhou, China
- Nanhu Brain-computer Interface Institute, Hangzhou 311100, China
- Department of Ophthalmology of the First Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou, China
- Zhejiang Laboratory for Systems & Precision Medicine, Zhejiang University Medical Center, Hangzhou, China
| | - Tao Wang
- Institute of Neuroscience, NHC and CAMS Key Laboratory of Medical Neurobiology, MOE Frontier Science Center for Brain Research and Brain-Machine Integration, Zhejiang University School of Brain Science and Brain Medicine, Hangzhou, China
| | - Xingqi Zhao
- Institute of Neuroscience, NHC and CAMS Key Laboratory of Medical Neurobiology, MOE Frontier Science Center for Brain Research and Brain-Machine Integration, Zhejiang University School of Brain Science and Brain Medicine, Hangzhou, China
| | - Juan Chen
- School of Mental Health, Bengbu Medical College, Bengbu, Anhui, China
| | - Tianqi Yang
- Institute of Neuroscience, NHC and CAMS Key Laboratory of Medical Neurobiology, MOE Frontier Science Center for Brain Research and Brain-Machine Integration, Zhejiang University School of Brain Science and Brain Medicine, Hangzhou, China
| | - Yi Shen
- Institute of Neuroscience, NHC and CAMS Key Laboratory of Medical Neurobiology, MOE Frontier Science Center for Brain Research and Brain-Machine Integration, Zhejiang University School of Brain Science and Brain Medicine, Hangzhou, China
- Department of Neurobiology and Department of General Intensive Care Unit of the Second Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou, China
| | - Yu-Dong Zhou
- Institute of Neuroscience, NHC and CAMS Key Laboratory of Medical Neurobiology, MOE Frontier Science Center for Brain Research and Brain-Machine Integration, Zhejiang University School of Brain Science and Brain Medicine, Hangzhou, China
- Lingang Laboratory, Shanghai 200031, China
- Department of Ophthalmology of the First Affiliated Hospital, Zhejiang University School of Medicine, Hangzhou, China
- Zhejiang Laboratory for Systems & Precision Medicine, Zhejiang University Medical Center, Hangzhou, China
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3
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Makrygianni EA, Chrousos GP. Neural Progenitor Cells and the Hypothalamus. Cells 2023; 12:1822. [PMID: 37508487 PMCID: PMC10378393 DOI: 10.3390/cells12141822] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2023] [Revised: 05/22/2023] [Accepted: 06/02/2023] [Indexed: 07/30/2023] Open
Abstract
Neural progenitor cells (NPCs) are multipotent neural stem cells (NSCs) capable of self-renewing and differentiating into neurons, astrocytes and oligodendrocytes. In the postnatal/adult brain, NPCs are primarily located in the subventricular zone (SVZ) of the lateral ventricles (LVs) and subgranular zone (SGZ) of the hippocampal dentate gyrus (DG). There is evidence that NPCs are also present in the postnatal/adult hypothalamus, a highly conserved brain region involved in the regulation of core homeostatic processes, such as feeding, metabolism, reproduction, neuroendocrine integration and autonomic output. In the rodent postnatal/adult hypothalamus, NPCs mainly comprise different subtypes of tanycytes lining the wall of the 3rd ventricle. In the postnatal/adult human hypothalamus, the neurogenic niche is constituted by tanycytes at the floor of the 3rd ventricle, ependymal cells and ribbon cells (showing a gap-and-ribbon organization similar to that in the SVZ), as well as suprachiasmatic cells. We speculate that in the postnatal/adult human hypothalamus, neurogenesis occurs in a highly complex, exquisitely sophisticated neurogenic niche consisting of at least four subniches; this structure has a key role in the regulation of extrahypothalamic neurogenesis, and hypothalamic and extrahypothalamic neural circuits, partly through the release of neurotransmitters, neuropeptides, extracellular vesicles (EVs) and non-coding RNAs (ncRNAs).
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Affiliation(s)
- Evanthia A Makrygianni
- University Research Institute of Maternal and Child Health & Precision Medicine, National and Kapodistrian University of Athens, 11527 Athens, Greece
| | - George P Chrousos
- University Research Institute of Maternal and Child Health & Precision Medicine, National and Kapodistrian University of Athens, 11527 Athens, Greece
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Kannangara H, Cullen L, Miyashita S, Korkmaz F, Macdonald A, Gumerova A, Witztum R, Moldavski O, Sims S, Burgess J, Frolinger T, Latif R, Ginzburg Y, Lizneva D, Goosens K, Davies TF, Yuen T, Zaidi M, Ryu V. Emerging roles of brain tanycytes in regulating blood-hypothalamus barrier plasticity and energy homeostasis. Ann N Y Acad Sci 2023; 1525:61-69. [PMID: 37199228 PMCID: PMC10524199 DOI: 10.1111/nyas.15009] [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] [Indexed: 05/19/2023]
Abstract
Seasonal changes in food intake and adiposity in many animal species are triggered by changes in the photoperiod. These latter changes are faithfully transduced into a biochemical signal by melatonin secreted by the pineal gland. Seasonal variations, encoded by melatonin, are integrated by third ventricular tanycytes of the mediobasal hypothalamus through the detection of the thyroid-stimulating hormone (TSH) released from the pars tuberalis. The mediobasal hypothalamus is a critical brain region that maintains energy homeostasis by acting as an interface between the neural networks of the central nervous system and the periphery to control metabolic functions, including ingestive behavior, energy homeostasis, and reproduction. Among the cells involved in the regulation of energy balance and the blood-hypothalamus barrier (BHB) plasticity are tanycytes. Increasing evidence suggests that anterior pituitary hormones, specifically TSH, traditionally considered to have unitary functions in targeting single endocrine sites, display actions on multiple somatic tissues and central neurons. Notably, modulation of tanycytic TSH receptors seems critical for BHB plasticity in relation to energy homeostasis, but this needs to be proven.
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Affiliation(s)
- Hasni Kannangara
- Center for Translational Medicine and Pharmacology, Icahn School of Medicine at Mount Sinai, New York, NY
- Department of Medicine and of Pharmacological Sciences, Icahn School of Medicine at Mount Sinai, New York, NY
| | - Liam Cullen
- Center for Translational Medicine and Pharmacology, Icahn School of Medicine at Mount Sinai, New York, NY
- Department of Medicine and of Pharmacological Sciences, Icahn School of Medicine at Mount Sinai, New York, NY
| | - Sari Miyashita
- Center for Translational Medicine and Pharmacology, Icahn School of Medicine at Mount Sinai, New York, NY
- Department of Medicine and of Pharmacological Sciences, Icahn School of Medicine at Mount Sinai, New York, NY
| | - Funda Korkmaz
- Center for Translational Medicine and Pharmacology, Icahn School of Medicine at Mount Sinai, New York, NY
- Department of Medicine and of Pharmacological Sciences, Icahn School of Medicine at Mount Sinai, New York, NY
| | - Anne Macdonald
- Center for Translational Medicine and Pharmacology, Icahn School of Medicine at Mount Sinai, New York, NY
- Department of Medicine and of Pharmacological Sciences, Icahn School of Medicine at Mount Sinai, New York, NY
| | - Anisa Gumerova
- Center for Translational Medicine and Pharmacology, Icahn School of Medicine at Mount Sinai, New York, NY
- Department of Medicine and of Pharmacological Sciences, Icahn School of Medicine at Mount Sinai, New York, NY
| | - Ronit Witztum
- Center for Translational Medicine and Pharmacology, Icahn School of Medicine at Mount Sinai, New York, NY
- Department of Medicine and of Pharmacological Sciences, Icahn School of Medicine at Mount Sinai, New York, NY
| | - Ofer Moldavski
- Center for Translational Medicine and Pharmacology, Icahn School of Medicine at Mount Sinai, New York, NY
- Department of Medicine and of Pharmacological Sciences, Icahn School of Medicine at Mount Sinai, New York, NY
| | - Steven Sims
- Center for Translational Medicine and Pharmacology, Icahn School of Medicine at Mount Sinai, New York, NY
- Department of Medicine and of Pharmacological Sciences, Icahn School of Medicine at Mount Sinai, New York, NY
| | - Jocoll Burgess
- Center for Translational Medicine and Pharmacology, Icahn School of Medicine at Mount Sinai, New York, NY
- Department of Medicine and of Pharmacological Sciences, Icahn School of Medicine at Mount Sinai, New York, NY
| | - Tal Frolinger
- Center for Translational Medicine and Pharmacology, Icahn School of Medicine at Mount Sinai, New York, NY
- Department of Medicine and of Pharmacological Sciences, Icahn School of Medicine at Mount Sinai, New York, NY
| | - Rauf Latif
- Center for Translational Medicine and Pharmacology, Icahn School of Medicine at Mount Sinai, New York, NY
- Department of Medicine and of Pharmacological Sciences, Icahn School of Medicine at Mount Sinai, New York, NY
| | - Yelena Ginzburg
- Center for Translational Medicine and Pharmacology, Icahn School of Medicine at Mount Sinai, New York, NY
- Department of Medicine and of Pharmacological Sciences, Icahn School of Medicine at Mount Sinai, New York, NY
| | - Daria Lizneva
- Center for Translational Medicine and Pharmacology, Icahn School of Medicine at Mount Sinai, New York, NY
- Department of Medicine and of Pharmacological Sciences, Icahn School of Medicine at Mount Sinai, New York, NY
| | - Ki Goosens
- Center for Translational Medicine and Pharmacology, Icahn School of Medicine at Mount Sinai, New York, NY
- Department of Psychiatry, Icahn School of Medicine at Mount Sinai, New York, NY
| | - Terry F. Davies
- Center for Translational Medicine and Pharmacology, Icahn School of Medicine at Mount Sinai, New York, NY
- Department of Medicine and of Pharmacological Sciences, Icahn School of Medicine at Mount Sinai, New York, NY
| | - Tony Yuen
- Center for Translational Medicine and Pharmacology, Icahn School of Medicine at Mount Sinai, New York, NY
- Department of Medicine and of Pharmacological Sciences, Icahn School of Medicine at Mount Sinai, New York, NY
| | - Mone Zaidi
- Center for Translational Medicine and Pharmacology, Icahn School of Medicine at Mount Sinai, New York, NY
- Department of Medicine and of Pharmacological Sciences, Icahn School of Medicine at Mount Sinai, New York, NY
| | - Vitaly Ryu
- Center for Translational Medicine and Pharmacology, Icahn School of Medicine at Mount Sinai, New York, NY
- Department of Medicine and of Pharmacological Sciences, Icahn School of Medicine at Mount Sinai, New York, NY
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5
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Dali R, Estrada-Meza J, Langlet F. Tanycyte, the neuron whisperer. Physiol Behav 2023; 263:114108. [PMID: 36740135 DOI: 10.1016/j.physbeh.2023.114108] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2022] [Revised: 01/23/2023] [Accepted: 02/01/2023] [Indexed: 02/05/2023]
Abstract
Reciprocal communication between neurons and glia is essential for normal brain functioning and adequate physiological functions, including energy balance. In vertebrates, the homeostatic process that adjusts food intake and energy expenditure in line with physiological requirements is tightly controlled by numerous neural cell types located within the hypothalamus and the brainstem and organized in complex networks. Within these neural networks, peculiar ependymoglial cells called tanycytes are nowadays recognized as multifunctional players in the physiological mechanisms of appetite control, partly by modulating orexigenic and anorexigenic neurons. Here, we review recent advances in tanycytes' impact on hypothalamic neuronal activity, emphasizing on arcuate neurons.
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Affiliation(s)
- Rafik Dali
- Department of biomedical sciences, University of Lausanne, 1005 Lausanne, Switzerland
| | - Judith Estrada-Meza
- Department of biomedical sciences, University of Lausanne, 1005 Lausanne, Switzerland
| | - Fanny Langlet
- Department of biomedical sciences, University of Lausanne, 1005 Lausanne, Switzerland.
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6
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Nampoothiri S, Nogueiras R, Schwaninger M, Prevot V. Glial cells as integrators of peripheral and central signals in the regulation of energy homeostasis. Nat Metab 2022; 4:813-825. [PMID: 35879459 PMCID: PMC7613794 DOI: 10.1038/s42255-022-00610-z] [Citation(s) in RCA: 15] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/03/2021] [Accepted: 06/15/2022] [Indexed: 01/03/2023]
Abstract
Communication between the periphery and the brain is key for maintaining energy homeostasis. To do so, peripheral signals from the circulation reach the brain via the circumventricular organs (CVOs), which are characterized by fenestrated vessels lacking the protective blood-brain barrier (BBB). Glial cells, by virtue of their plasticity and their ideal location at the interface of blood vessels and neurons, participate in the integration and transmission of peripheral information to neuronal networks in the brain for the neuroendocrine control of whole-body metabolism. Metabolic diseases, such as obesity and type 2 diabetes, can disrupt the brain-to-periphery communication mediated by glial cells, highlighting the relevance of these cell types in the pathophysiology of such complications. An improved understanding of how glial cells integrate and respond to metabolic and humoral signals has become a priority for the discovery of promising therapeutic strategies to treat metabolic disorders. This Review highlights the role of glial cells in the exchange of metabolic signals between the periphery and the brain that are relevant for the regulation of whole-body energy homeostasis.
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Affiliation(s)
- Sreekala Nampoothiri
- Univ. Lille, Inserm, CHU Lille, Laboratory of Development and Plasticity of the Neuroendocrine Brain, Lille Neuroscience & Cognition, UMR-S1172, EGID, DISTALZ, Lille, France
| | - Ruben Nogueiras
- Universidade de Santiago de Compostela-Instituto de Investigation Sanitaria, Santiago de Compostela, Spain
- CIBER Fisiopatologia de la Obesidad y Nutrition, Santiago de Compostela, Spain
| | - Markus Schwaninger
- Institute for Experimental and Clinical Pharmacology and Toxicology, University of Lübeck, Lübeck, Germany
| | - Vincent Prevot
- Univ. Lille, Inserm, CHU Lille, Laboratory of Development and Plasticity of the Neuroendocrine Brain, Lille Neuroscience & Cognition, UMR-S1172, EGID, DISTALZ, Lille, France.
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7
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Choi JH, Kim MS. Homeostatic Regulation of Glucose Metabolism by the Central Nervous System. Endocrinol Metab (Seoul) 2022; 37:9-25. [PMID: 35255598 PMCID: PMC8901968 DOI: 10.3803/enm.2021.1364] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/09/2021] [Accepted: 02/07/2022] [Indexed: 12/04/2022] Open
Abstract
Evidence for involvement of the central nervous system (CNS) in the regulation of glucose metabolism dates back to the 19th century, although the majority of the research on glucose metabolism has focused on the peripheral metabolic organs. Due to recent advances in neuroscience, it has now become clear that the CNS is indeed vital for maintaining glucose homeostasis. To achieve normoglycemia, specific populations of neurons and glia in the hypothalamus sense changes in the blood concentrations of glucose and of glucoregulatory hormones such as insulin, leptin, glucagon-like peptide 1, and glucagon. This information is integrated and transmitted to other areas of the brain where it eventually modulates various processes in glucose metabolism (i.e., hepatic glucose production, glucose uptake in the brown adipose tissue and skeletal muscle, pancreatic insulin and glucagon secretion, renal glucose reabsorption, etc.). Errors in these processes lead to hyper- or hypoglycemia. We here review the current understanding of the brain regulation of glucose metabolism.
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Affiliation(s)
- Jong Han Choi
- Division of Endocrinology and Metabolism, Konkuk University Medical Center, Seoul,
Korea
| | - Min-Seon Kim
- Division of Endocrinology and Metabolism, Asan Medical Center, University of Ulsan College of Medicine, Seoul,
Korea
- Appeptite Regulation Laboratory, Asan Institute for Life Sciences, University of Ulsan College of Medicine, Seoul,
Korea
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8
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Glial Modulation of Energy Balance: The Dorsal Vagal Complex Is No Exception. Int J Mol Sci 2022; 23:ijms23020960. [PMID: 35055143 PMCID: PMC8779587 DOI: 10.3390/ijms23020960] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2021] [Revised: 01/11/2022] [Accepted: 01/13/2022] [Indexed: 02/04/2023] Open
Abstract
The avoidance of being overweight or obese is a daily challenge for a growing number of people. The growing proportion of people suffering from a nutritional imbalance in many parts of the world exemplifies this challenge and emphasizes the need for a better understanding of the mechanisms that regulate nutritional balance. Until recently, research on the central regulation of food intake primarily focused on neuronal signaling, with little attention paid to the role of glial cells. Over the last few decades, our understanding of glial cells has changed dramatically. These cells are increasingly regarded as important neuronal partners, contributing not just to cerebral homeostasis, but also to cerebral signaling. Our understanding of the central regulation of energy balance is part of this (r)evolution. Evidence is accumulating that glial cells play a dynamic role in the modulation of energy balance. In the present review, we summarize recent data indicating that the multifaceted glial compartment of the brainstem dorsal vagal complex (DVC) should be considered in research aimed at identifying feeding-related processes operating at this level.
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Wang J, Beecher K. TSPO: an emerging role in appetite for a therapeutically promising biomarker. Open Biol 2021; 11:210173. [PMID: 34343461 PMCID: PMC8331234 DOI: 10.1098/rsob.210173] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
There is accumulating evidence that an obesogenic Western diet causes neuroinflammatory damage to the brain, which then promotes further appetitive behaviour. Neuroinflammation has been extensively studied by analysing the translocator protein of 18 kDa (TSPO), a protein that is upregulated in the inflamed brain following a damaging stimulus. As a result, there is a rich supply of TSPO-specific agonists, antagonists and positron emission tomography ligands. One TSPO ligand, etifoxine, is also currently used clinically for the treatment of anxiety with a minimal side-effect profile. Despite the neuroinflammatory pathogenesis of diet-induced obesity, and the translational potential of targeting TSPO, there is sparse literature characterizing the effect of TSPO on appetite. Therefore, in this review, the influence of TSPO on appetite is discussed. Three putative mechanisms for TSPO's appetite-modulatory effect are then characterized: the TSPO–allopregnanolone–GABAAR signalling axis, glucosensing in tanycytes and association with the synaptic protein RIM-BP1. We highlight that, in addition to its plethora of functions, TSPO is a regulator of appetite. This review ultimately suggests that the appetite-modulating function of TSPO should be further explored due to its potential therapeutic promise.
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Affiliation(s)
- Joshua Wang
- Addiction Neuroscience and Obesity Laboratory, School of Clinical Sciences, Faculty of Health, Translational Research Institute, Queensland University of Technology, Brisbane, Queensland, Australia
| | - Kate Beecher
- Addiction Neuroscience and Obesity Laboratory, School of Clinical Sciences, Faculty of Health, Translational Research Institute, Queensland University of Technology, Brisbane, Queensland, Australia
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Lhomme T, Clasadonte J, Imbernon M, Fernandois D, Sauve F, Caron E, Lima N, Heras V, Martinez-Corral I, Müller-Fielitz H, Rasika S, Schwaninger M, Nogueiras R, Prevot V. Tanycytic networks mediate energy balance by feeding lactate to glucose-insensitive POMC neurons. J Clin Invest 2021; 131:e140521. [PMID: 34324439 DOI: 10.1172/jci140521] [Citation(s) in RCA: 25] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2020] [Accepted: 07/28/2021] [Indexed: 11/17/2022] Open
Abstract
Hypothalamic glucose sensing enables an organism to match energy expenditure and food intake to circulating levels of glucose, the main energy source of the brain. Here, we established that tanycytes of the hypothalamic arcuate nucleus, specialized glia that line the wall of the third ventricle, convert brain glucose supplies into lactate that they transmit through monocarboxylate transporters to arcuate proopiomelanocortin neurons, which integrate this signal to drive their activity and to adapt the metabolic response to meet physiological demands. Furthermore, this transmission required the formation of extensive Connexin-43 gap-junction-mediated metabolic networks by arcuate tanycytes. Selectively suppressing either tanycytic monocarboxylate transporters or gap junctions resulted in altered feeding behavior and energy metabolism. Tanycytic intercellular communication and lactate production are thus integral to the mechanism by which hypothalamic neurons that regulate energy and glucose homeostasis efficiently perceive alterations in systemic glucose levels as a function of the physiological state of the organism.
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Affiliation(s)
- Tori Lhomme
- Laboratory of Development and Plasticity of the Neuroendocrine Brain, INSERM U1172, Lille, France
| | - Jerome Clasadonte
- Laboratory of Development and Plasticity of the Neuroendocrine Brain, INSERM U1172, Lille, France
| | - Monica Imbernon
- Laboratory of Development and Plasticity of the Neuroendocrine Brain, INSERM U1172, Lille, France
| | - Daniela Fernandois
- Laboratory of Development and Plasticity of the Neuroendocrine Brain, INSERM U1172, Lille, France
| | - Florent Sauve
- Laboratory of Development and Plasticity of the Neuroendocrine Brain, INSERM U1172, Lille, France
| | - Emilie Caron
- Laboratory of Development and Plasticity of the Neuroendocrine Brain, INSERM U1172, Lille, France
| | - Natalia Lima
- CIMUS, University of Santiago de Compostela, Santiago de Compostela, Spain
| | - Violeta Heras
- CIMUS, University of Santiago de Compostela, Santiago de Compostela, Spain
| | - Ines Martinez-Corral
- Laboratory of Development and Plasticity of the Neuroendocrine Brain, INSERM U1172, Lille, France
| | - Helge Müller-Fielitz
- Institute for Experimental and Clinical Pharmacology and Toxicology, University of Lübeck, Lübeck, Germany
| | - S Rasika
- Laboratory of Development and Plasticity of the Neuroendocrine Brain, INSERM U1172, Lille, France
| | - Markus Schwaninger
- Institute for Experimental and Clinical Pharmacology and Toxicology, University of Lübeck, Lübeck, Germany
| | - Ruben Nogueiras
- CIMUS, University of Santiago de Compostela, Santiago de Compostela, Spain
| | - Vincent Prevot
- Laboratory of Development and Plasticity of the Neuroendocrine Brain, INSERM U1172, Lille, France
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Rohrbach A, Caron E, Dali R, Brunner M, Pasquettaz R, Kolotuev I, Santoni F, Thorens B, Langlet F. Ablation of glucokinase-expressing tanycytes impacts energy balance and increases adiposity in mice. Mol Metab 2021; 53:101311. [PMID: 34325016 PMCID: PMC8379510 DOI: 10.1016/j.molmet.2021.101311] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/05/2021] [Accepted: 07/20/2021] [Indexed: 01/06/2023] Open
Abstract
Objectives Glucokinase (GCK) is critical for glucosensing. In rats, GCK is expressed in hypothalamic tanycytes and appears to play an essential role in feeding behavior. In this study, we investigated the distribution of GCK-expressing tanycytes in mice and their role in the regulation of energy balance. Methods In situ hybridization, reporter gene assay, and immunohistochemistry were used to assess GCK expression along the third ventricle in mice. To evaluate the impact of GCK-expressing tanycytes on arcuate neuron function and mouse physiology, Gck deletion along the ventricle was achieved using loxP/Cre recombinase technology in adult mice. Results GCK expression was low along the third ventricle, but detectable in tanycytes facing the ventromedial arcuate nucleus from bregma −1.5 to −2.2. Gck deletion induced the death of this tanycyte subgroup through the activation of the BAD signaling pathway. The ablation of GCK-expressing tanycytes affected different aspects of energy balance, leading to an increase in adiposity in mice. This phenotype was systematically associated with a defect in NPY neuron function. In contrast, the regulation of glucose homeostasis was mostly preserved, except for glucoprivic responses. Conclusions This study describes the role of GCK in tanycyte biology and highlights the impact of tanycyte loss on the regulation of energy balance. vmARH tanycytes express glucokinase. Glucokinase deletion in tanycytes induces cell death. Ablation of vmARH tanycytes alters energy balance and adiposity. Ablation of vmARH tanycytes alters NPY neuron function.
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Affiliation(s)
- Antoine Rohrbach
- Center for Integrative Genomics, Faculty of Biology and Medicine, University of Lausanne, Lausanne, Switzerland; Department of Biomedical Sciences, Faculty of Biology and Medicine, University of Lausanne, Lausanne, Switzerland
| | - Emilie Caron
- Univ. Lille, Inserm, CHU Lille, Laboratory of Development and Plasticity of the Neuroendocrine Brain, Lille Neuroscience & Cognition, UMR-S, 1172, Lille, France
| | - Rafik Dali
- Department of Biomedical Sciences, Faculty of Biology and Medicine, University of Lausanne, Lausanne, Switzerland
| | - Maxime Brunner
- Service of Endocrinology, Diabetology, and Metabolism, Lausanne University Hospital, Faculty of Biology and Medicine, 1011, Lausanne, Switzerland
| | - Roxane Pasquettaz
- Center for Integrative Genomics, Faculty of Biology and Medicine, University of Lausanne, Lausanne, Switzerland
| | - Irina Kolotuev
- Electron Microscopy Facility, Faculty of Biology and Medicine, University of Lausanne, Lausanne, Switzerland
| | - Federico Santoni
- Service of Endocrinology, Diabetology, and Metabolism, Lausanne University Hospital, Faculty of Biology and Medicine, 1011, Lausanne, Switzerland
| | - Bernard Thorens
- Center for Integrative Genomics, Faculty of Biology and Medicine, University of Lausanne, Lausanne, Switzerland
| | - Fanny Langlet
- Center for Integrative Genomics, Faculty of Biology and Medicine, University of Lausanne, Lausanne, Switzerland; Department of Biomedical Sciences, Faculty of Biology and Medicine, University of Lausanne, Lausanne, Switzerland.
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12
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Abstract
Chronic metabolic diseases, including diabetes and obesity, have become a major global health threat of the twenty-first century. Maintaining glucose homeostasis is essential for survival in mammals. Complex and highly coordinated interactions between glucose-sensing mechanisms and multiple effector systems are essential for controlling glucose levels in the blood. The central nervous system (CNS) plays a crucial role in regulating glucose homeostasis. Growing evidence indicates that disruption of glucose sensing in selective CNS areas, such as the hypothalamus, is closely interlinked with the pathogenesis of obesity and type 2 diabetes mellitus. However, the underlying intracellular mechanisms of glucose sensing in the hypothalamus remain elusive. Here, we review the current literature on hypothalamic glucose-sensing mechanisms and discuss the impact of alterations of these mechanisms on the pathogenesis of diabetes.
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Affiliation(s)
- Nal Ae Yoon
- Institute of Human Nutrition, Vagelos College of Physicians and Surgeons, Columbia University Irving Medical Center, New York, NY, USA
- Department of Molecular Pharmacology and Therapeutics, Vagelos College of Physicians and Surgeons, Columbia University Irving Medical Center, New York, NY, USA
| | - Sabrina Diano
- Institute of Human Nutrition, Vagelos College of Physicians and Surgeons, Columbia University Irving Medical Center, New York, NY, USA.
- Department of Molecular Pharmacology and Therapeutics, Vagelos College of Physicians and Surgeons, Columbia University Irving Medical Center, New York, NY, USA.
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13
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Bolborea M, Langlet F. What is the physiological role of hypothalamic tanycytes in metabolism? Am J Physiol Regul Integr Comp Physiol 2021; 320:R994-R1003. [PMID: 33826442 DOI: 10.1152/ajpregu.00296.2020] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
In vertebrates, the energy balance process is tightly controlled by complex neural circuits that sense metabolic signals and adjust food intake and energy expenditure in line with the physiological requirements of optimal conditions. Within neural networks controlling energy balance, tanycytes are peculiar ependymoglial cells that are nowadays recognized as multifunctional players in the metabolic hypothalamus. However, the physiological function of hypothalamic tanycytes remains unclear, creating a number of ambiguities in the field. Here, we review data accumulated over the years that demonstrate the physiological function of tanycytes in the maintenance of metabolic homeostasis, opening up new research avenues. The presumed involvement of tanycytes in the pathophysiology of metabolic disorders and age-related neurodegenerative diseases will be finally discussed.
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Affiliation(s)
- Matei Bolborea
- Central and Peripheral Mechanisms of Neurodegeneration, INSERM U1118, Université de Strasbourg, Strasbourg, France.,School of Life Sciences, University of Warwick, Coventry, United Kingdom
| | - Fanny Langlet
- Center for Integrative Genomics, University of Lausanne, Lausanne, Switzerland
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14
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Garcia SM, Hirschberg PR, Sarkar P, Siegel DM, Teegala SB, Vail GM, Routh VH. Insulin actions on hypothalamic glucose-sensing neurones. J Neuroendocrinol 2021; 33:e12937. [PMID: 33507001 PMCID: PMC10561189 DOI: 10.1111/jne.12937] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/27/2020] [Revised: 12/22/2020] [Accepted: 12/29/2020] [Indexed: 12/13/2022]
Abstract
Subsequent to the discovery of insulin 100 years ago, great strides have been made in understanding its function, especially in the brain. It is now clear that insulin is a critical regulator of the neuronal circuitry controlling energy balance and glucose homeostasis. This review focuses on the effects of insulin and diabetes on the activity and glucose sensitivity of hypothalamic glucose-sensing neurones. We highlight the role of electrophysiological data in understanding how insulin regulates glucose-sensing neurones. A brief introduction describing the benefits and limitations of the major electrophysiological techniques used to investigate glucose-sensing neurones is provided. The mechanisms by which hypothalamic neurones sense glucose are discussed with an emphasis on those glucose-sensing neurones already shown to be modulated by insulin. Next, the literature pertaining to how insulin alters the activity and glucose sensitivity of these hypothalamic glucose-sensing neurones is described. In addition, the effects of impaired insulin signalling during diabetes and the ramifications of insulin-induced hypoglycaemia on hypothalamic glucose-sensing neurones are covered. To the extent that it is known, we present hypotheses concerning the mechanisms underlying the effects of these insulin-related pathologies. To conclude, electrophysiological data from the hippocampus are evaluated aiming to provide clues regarding how insulin might influence neuronal plasticity in glucose-sensing neurones. Although much has been accomplished subsequent to the discovery of insulin, the work described in our review suggests that the regulation of central glucose sensing by this hormone is both important and understudied.
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Affiliation(s)
- Stephanie M Garcia
- Department of Pharmacology, Physiology and Neuroscience, Rutgers, New Jersey Medical School, The State University of New Jersey, Newark, NJ, USA
| | - Pamela R Hirschberg
- Department of Pharmacology, Physiology and Neuroscience, Rutgers, New Jersey Medical School, The State University of New Jersey, Newark, NJ, USA
| | - Pallabi Sarkar
- Department of Pharmacology, Physiology and Neuroscience, Rutgers, New Jersey Medical School, The State University of New Jersey, Newark, NJ, USA
| | - Dashiel M Siegel
- Department of Pharmacology, Physiology and Neuroscience, Rutgers, New Jersey Medical School, The State University of New Jersey, Newark, NJ, USA
| | - Suraj B Teegala
- Department of Pharmacology, Physiology and Neuroscience, Rutgers, New Jersey Medical School, The State University of New Jersey, Newark, NJ, USA
| | - Gwyndolin M Vail
- Department of Pharmacology, Physiology and Neuroscience, Rutgers, New Jersey Medical School, The State University of New Jersey, Newark, NJ, USA
| | - Vanessa H Routh
- Department of Pharmacology, Physiology and Neuroscience, Rutgers, New Jersey Medical School, The State University of New Jersey, Newark, NJ, USA
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15
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Tanycytes in the infundibular nucleus and median eminence and their role in the blood-brain barrier. HANDBOOK OF CLINICAL NEUROLOGY 2021; 180:253-273. [PMID: 34225934 DOI: 10.1016/b978-0-12-820107-7.00016-1] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
The blood-brain barrier is generally attributed to endothelial cells. However, in circumventricular organs, such as the median eminence, tanycytes take over the barrier function. These ependymoglial cells form the wall of the third ventricle and send long extensions into the parenchyma to contact blood vessels and hypothalamic neurons. The shape and location of tanycytes put them in an ideal position to connect the periphery with central nervous compartments. In line with this, tanycytes control the transport of hormones and key metabolites in and out of the hypothalamus. They function as sensors of peripheral homeostasis for central regulatory networks. This chapter discusses current evidence that tanycytes play a key role in regulating glucose balance, food intake, endocrine axes, seasonal changes, reproductive function, and aging. The understanding of how tanycytes perform these diverse tasks is only just beginning to emerge and will probably lead to a more differentiated view of how the brain and the periphery interact.
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16
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Prezotto LD, Thorson JF, Prevot V, Redmer DA, Grazul-Bilska AT. Nutritionally induced tanycytic plasticity in the hypothalamus of adult ewes. Domest Anim Endocrinol 2020; 72:106438. [PMID: 32388344 DOI: 10.1016/j.domaniend.2020.106438] [Citation(s) in RCA: 3] [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: 10/31/2019] [Revised: 12/27/2019] [Accepted: 01/16/2020] [Indexed: 02/07/2023]
Abstract
The blood-brain barrier regulates the transport of molecules that convey global energetic status to the feeding circuitry within the hypothalamus. Capillaries within the median eminence (ME) and tight junctions between tanycytes lining the third ventricle (3V) are critical components of this barrier. Herein, we tested the hypothesis that altering the plane of nutrition results in the structural reorganization of tanycytes, tight junctions, and capillary structure within the medial basal hypothalamus. Proopiomelanocortin (POMC) neuronal content within the arcuate nucleus of the hypothalamus (ARC) was also assessed to test whether reduced nutritional status improved access of nutrients to the ARC, while decreasing the access of nutrients of overfed animals. Multiparous, nongestating ewes were stratified by weight and randomly assigned to dietary treatments offered for 75 d: 200% of dietary recommendations (overfed), 100% of dietary recommendations (control), or 60% of dietary recommendations (underfed). The number of POMC-expressing neurons within the ARC was increased (P ≤ 0.002) in underfed ewes. Overfeeding increased (P ≤ 0.01) tanycyte cellular process penetration and density compared with control and underfeeding as assessed using vimentin immunostaining. Immunostaining of tight junctions along the wall of the 3V did not differ (P = 0.32) between treatments. No differences were observed in capillary density (P = 0.21) or classification (P ≥ 0.47) within the ME. These results implicate that changes within the satiety center and morphology of tanycytes within the ARC occur as an adaptation to nutrient availability.
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Affiliation(s)
- L D Prezotto
- Nutritional & Reproductive Physiology Laboratory, Northern Agricultural Research Center, Montana State University, 3710 Assinniboine Road, Havre, MT 59501, USA.
| | - J F Thorson
- Nutritional & Reproductive Physiology Laboratory, Northern Agricultural Research Center, Montana State University, 3710 Assinniboine Road, Havre, MT 59501, USA
| | - V Prevot
- INSERM, Laboratory of Development and Plasticity of the Neuroendocrine Brain, Jean-Pierre Aubert Research Centre, U1172, Lille, France
| | - D A Redmer
- Department of Animal Sciences, North Dakota State University, Fargo, ND 58108, USA
| | - A T Grazul-Bilska
- Department of Animal Sciences, North Dakota State University, Fargo, ND 58108, USA
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17
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Zhou Y, Dong Z, A R, Liao Z, Guo J, Liu C, Sun X. The prevalence of impaired glucose regulation in anxiety disorder patients and the relationship with hypothalamic-pituitary-adrenal axis and hypothalamic-pituitary-thyroid axis activity. J Evid Based Med 2019; 12:51-55. [PMID: 27792263 DOI: 10.1111/jebm.12224] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/27/2016] [Accepted: 04/27/2016] [Indexed: 01/11/2023]
Abstract
OBJECTIVE To investigate the prevalence of impaired glucose regulation (IGR) in patients with anxiety disorders and the relationship with hypothalamic-pituitary-adrenal (HPA) and hypothalamic-pituitary-thyroid (HPT) axes function. METHODS From September 2013 to May 2015, a total of 646 patients with anxiety disorders who matched the criteria of the 10th revision of the International Statistical Classification of Diseases and Related Health Problems participated in our study, which was conducted in the Psychiatric Inpatient Department of the West China Hospital of Sichuan University. The results from 75-g glucose tolerance tests, and morning (8:00 am) serum cortisol (PTC), adrenocorticotropic hormone (ACTH), thyroid-stimulating hormone (TSH), TT3, TT4, FT3, and FT4 levels were collected. The Hamilton Anxiety Scale was administered to assess the severity of anxiety. SPSS 17.0 software was used for statistical analysis. RESULTS The crude prevalence of impaired glucose regulation was 24.61% in patients with anxiety disorders patients. In the 18- to 40-year age group with impaired glucose regulation (IGR), both ACTH and PTC levels were higher than the control group (P < 0.05). In the 61- to 75-year age group with IGR, the TSH level was lower and the FT4 level was higher than the control group (P < 0.05). CONCLUSION The results herein partially confirm that the prevalence of IGR in patients with anxiety disorders is high. Impaired glucose in the younger age group is closely associated with HPA axis function, while impaired glucose in the older age group is closely associated with HPT axis alteration. Therefore, routine blood glucose and endocrine function testing in patients with anxiety disorder is of clinical importance to prevent the development of diabetes.
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Affiliation(s)
- Yaling Zhou
- Mental Health Center, West China Hospital, Sichuan University, Chengdu, China
| | - Zaiquan Dong
- Mental Health Center, West China Hospital, Sichuan University, Chengdu, China
| | - Ruhan A
- Mental Health Center, West China Hospital, Sichuan University, Chengdu, China
| | - Zongbing Liao
- Mental Health Center, West China Hospital, Sichuan University, Chengdu, China
| | - Jing Guo
- Mental Health Center, West China Hospital, Sichuan University, Chengdu, China
| | - Cancan Liu
- Mental Health Center, West China Hospital, Sichuan University, Chengdu, China
| | - Xueli Sun
- Mental Health Center, West China Hospital, Sichuan University, Chengdu, China
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18
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Langlet F. Tanycyte Gene Expression Dynamics in the Regulation of Energy Homeostasis. Front Endocrinol (Lausanne) 2019; 10:286. [PMID: 31133987 PMCID: PMC6514105 DOI: 10.3389/fendo.2019.00286] [Citation(s) in RCA: 23] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/25/2019] [Accepted: 04/18/2019] [Indexed: 01/01/2023] Open
Abstract
Animal survival relies on a constant balance between energy supply and energy expenditure, which is controlled by several neuroendocrine functions that integrate metabolic information and adapt the response of the organism to physiological demands. Polarized ependymoglial cells lining the floor of the third ventricle and sending a single process within metabolic hypothalamic parenchyma, tanycytes are henceforth described as key components of the hypothalamic neural network controlling energy balance. Their strategic position and peculiar properties convey them diverse physiological functions ranging from blood/brain traffic controllers, metabolic modulators, and neural stem/progenitor cells. At the molecular level, these functions rely on an accurate regulation of gene expression. Indeed, tanycytes are characterized by their own molecular signature which is mostly associated to their diverse physiological functions, and the detection of variations in nutrient/hormone levels leads to an adequate modulation of genetic profile in order to ensure energy homeostasis. The aim of this review is to summarize recent knowledge on the nutritional control of tanycyte gene expression.
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19
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McDougal DH, Darpolor MM, DuVall MA, Sutton EF, Morrison CD, Gadde KM, Redman LM, Carmichael OT. Glial acetate metabolism is increased following a 72-h fast in metabolically healthy men and correlates with susceptibility to hypoglycemia. Acta Diabetol 2018; 55:1029-1036. [PMID: 29931424 PMCID: PMC6153507 DOI: 10.1007/s00592-018-1180-5] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/28/2017] [Accepted: 06/11/2018] [Indexed: 12/02/2022]
Abstract
AIMS Prior exposure to insulin-induced hypoglycemia was shown to increase glial acetate metabolism (GAM) during subsequent exposure to hypoglycemia in diabetic individuals. However, it remained unclear whether this effect was dependent on the disease state or the antecedent cause of hypoglycemia. We aimed to establish whether exposure to fasting-induced hypoglycemia was sufficient to produce alterations in GAM in non-diabetic individuals. METHODS GAM was measured via carbon-13 magnetic resonance spectroscopy during infusion of [1-13C] acetate before and after a 72-h fast in six metabolically healthy men. All participants were male, aged 18-40 years, with a Body Mass Index of 20.0-27.9 kg/m2, who consented to reside at Pennington Biomedical Research Center for 4 days. The main outcome measure was the percent enhancement of cerebral [1-13C] bicarbonate (the primary metabolic byproduct of glial oxidation of [1-13C] acetate). Continuous glucose monitoring was used to measure hypoglycemic episodes during the 72-h fast. RESULTS As expected, 72 h of fasting significantly reduced blood glucose levels and resulted in a high frequency of hypoglycemic episodes. Steady-state GAM increased from 53.5 ± 3.7 to 61.9 ± 1.7% following the 72-h fast (p = 0.005). This increase correlated with greater duration of hypoglycemia experienced during the fast (r = 0.967). In addition, subjects with greater GAM at baseline experienced a greater increase in the duration of hypoglycemia experienced during the 72-h fast (r = 0.979). CONCLUSIONS GAM has potential as a biomarker for susceptibility to hypoglycemic episodes. TRAIL REGISTRATION Clinicaltrials.gov ID: NCT02690168.
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Affiliation(s)
| | | | | | - Elizabeth Frost Sutton
- Pennington Biomedical Research Center, Baton Rouge, LA, 70808, USA
- Magee-Womens Research Institute, 204 Craft Ave, Pittsburgh, PA, 15213, USA
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Prevot V, Dehouck B, Sharif A, Ciofi P, Giacobini P, Clasadonte J. The Versatile Tanycyte: A Hypothalamic Integrator of Reproduction and Energy Metabolism. Endocr Rev 2018; 39:333-368. [PMID: 29351662 DOI: 10.1210/er.2017-00235] [Citation(s) in RCA: 147] [Impact Index Per Article: 24.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/01/2017] [Accepted: 01/12/2018] [Indexed: 12/16/2022]
Abstract
The fertility and survival of an individual rely on the ability of the periphery to promptly, effectively, and reproducibly communicate with brain neural networks that control reproduction, food intake, and energy homeostasis. Tanycytes, a specialized glial cell type lining the wall of the third ventricle in the median eminence of the hypothalamus, appear to act as the linchpin of these processes by dynamically controlling the secretion of neuropeptides into the portal vasculature by hypothalamic neurons and regulating blood-brain and blood-cerebrospinal fluid exchanges, both processes that depend on the ability of these cells to adapt their morphology to the physiological state of the individual. In addition to their barrier properties, tanycytes possess the ability to sense blood glucose levels, and play a fundamental and active role in shuttling circulating metabolic signals to hypothalamic neurons that control food intake. Moreover, accumulating data suggest that, in keeping with their putative descent from radial glial cells, tanycytes are endowed with neural stem cell properties and may respond to dietary or reproductive cues by modulating hypothalamic neurogenesis. Tanycytes could thus constitute the missing link in the loop connecting behavior, hormonal changes, signal transduction, central neuronal activation and, finally, behavior again. In this article, we will examine these recent advances in the understanding of tanycytic plasticity and function in the hypothalamus and the underlying molecular mechanisms. We will also discuss the putative involvement and therapeutic potential of hypothalamic tanycytes in metabolic and fertility disorders.
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Affiliation(s)
- Vincent Prevot
- Inserm, Laboratory of Development and Plasticity of the Neuroendocrine Brain, Jean-Pierre Aubert Research Center, Lille, France.,University of Lille, FHU 1000 Days for Health, School of Medicine, Lille, France
| | - Bénédicte Dehouck
- Inserm, Laboratory of Development and Plasticity of the Neuroendocrine Brain, Jean-Pierre Aubert Research Center, Lille, France.,University of Lille, FHU 1000 Days for Health, School of Medicine, Lille, France
| | - Ariane Sharif
- Inserm, Laboratory of Development and Plasticity of the Neuroendocrine Brain, Jean-Pierre Aubert Research Center, Lille, France.,University of Lille, FHU 1000 Days for Health, School of Medicine, Lille, France
| | - Philippe Ciofi
- Inserm, Neurocentre Magendie, Bordeaux, France.,Université de Bordeaux, Bordeaux, France
| | - Paolo Giacobini
- Inserm, Laboratory of Development and Plasticity of the Neuroendocrine Brain, Jean-Pierre Aubert Research Center, Lille, France.,University of Lille, FHU 1000 Days for Health, School of Medicine, Lille, France
| | - Jerome Clasadonte
- Inserm, Laboratory of Development and Plasticity of the Neuroendocrine Brain, Jean-Pierre Aubert Research Center, Lille, France.,University of Lille, FHU 1000 Days for Health, School of Medicine, Lille, France
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21
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Ebling FJP, Lewis JE. Tanycytes and hypothalamic control of energy metabolism. Glia 2018; 66:1176-1184. [DOI: 10.1002/glia.23303] [Citation(s) in RCA: 36] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2017] [Revised: 12/21/2017] [Accepted: 01/23/2018] [Indexed: 01/15/2023]
Affiliation(s)
- Francis J. P. Ebling
- School of Life Sciences; University of Nottingham Medical School, Queen's Medical Centre; Nottingham NG7 2UH United Kingdom
| | - Jo E. Lewis
- School of Life Sciences; University of Nottingham Medical School, Queen's Medical Centre; Nottingham NG7 2UH United Kingdom
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22
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Levin BE. 10 lessons learned by a misguided physician. Physiol Behav 2017; 176:217-222. [PMID: 28034577 DOI: 10.1016/j.physbeh.2016.12.033] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2016] [Revised: 12/23/2016] [Accepted: 12/23/2016] [Indexed: 10/20/2022]
Abstract
It was a great and humbling honor to receive the 2016 Distinguished Career Award from my SSIB colleagues. This paper summarizes the major points of my DCA talk at the 2016 annual meeting. It is a reflection on my 50year medical and research career and 10 lessons I have learned over those years which might be of help to young investigators near the beginning of their own research careers. These lessons include: the value of being receptive to the opportunities provided you; how clinician-scientists can serve as critical role models for young investigators like me and a history of how my career developed as a result of their influence; the importance of carefully examining your own data, particularly when it doesn't agree with your preconceived ideas; the critical role that students, postdocs and PhD (and even veterinarian) colleagues can play in developing one's career; the likelihood that your career path will have many interesting twists and turns determined by changes in your own scientific interests and how rewarding various areas of research focus are to you; the importance of building a close-knit laboratory staff family; the fact that science and romance can mix. Finally, I offer 3 somewhat self-evident free pieces of advice for building and maintaining a rewarding career.
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Affiliation(s)
- Barry E Levin
- Department of Neurology, Rutgers New Jersey Medical School, 185 South Orange Avenue, MSB H506, Newark, NJ 07107, USA.
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23
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Abstract
Glucokinase (GK), the hexokinase involved in glucosensing in pancreatic β-cells, is also expressed in arcuate nucleus (AN) neurons and hypothalamic tanycytes, the cells that surround the basal third ventricle (3V). Several lines of evidence suggest that tanycytes may be involved in the regulation of energy homeostasis. Tanycytes have extended cell processes that contact the feeding-regulating neurons in the AN, particularly, agouti-related protein (AgRP), neuropeptide Y (NPY), cocaine- and amphetamine-regulated transcript (CART) and proopiomelanocortin (POMC) neurons. In this study, we developed an adenovirus expressing GK shRNA to inhibit GK expression in vivo. When injected into the 3V of rats, this adenovirus preferentially transduced tanycytes. qRT-PCR and Western blot assays confirmed GK mRNA and protein levels were lower in GK knockdown animals compared to the controls. In response to an intracerebroventricular glucose injection, the mRNA levels of anorexigenic POMC and CART and orexigenic AgRP and NPY neuropeptides were altered in GK knockdown animals. Similarly, food intake, meal duration, frequency of eating events and the cumulative eating time were increased, whereas the intervals between meals were decreased in GK knockdown rats, suggesting a decrease in satiety. Thus, GK expression in the ventricular cells appears to play an important role in feeding behavior.
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Conde-Sieira M, Soengas JL. Nutrient Sensing Systems in Fish: Impact on Food Intake Regulation and Energy Homeostasis. Front Neurosci 2017; 10:603. [PMID: 28111540 PMCID: PMC5216673 DOI: 10.3389/fnins.2016.00603] [Citation(s) in RCA: 60] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2016] [Accepted: 12/19/2016] [Indexed: 12/27/2022] Open
Abstract
Evidence obtained in recent years in a few species, especially rainbow trout, supports the presence in fish of nutrient sensing mechanisms. Glucosensing capacity is present in central (hypothalamus and hindbrain) and peripheral [liver, Brockmann bodies (BB, main accumulation of pancreatic endocrine cells in several fish species), and intestine] locations whereas fatty acid sensors seem to be present in hypothalamus, liver and BB. Glucose and fatty acid sensing capacities relate to food intake regulation and metabolism in fish. Hypothalamus is as a signaling integratory center in a way that detection of increased levels of nutrients result in food intake inhibition through changes in the expression of anorexigenic and orexigenic neuropeptides. Moreover, central nutrient sensing modulates functions in the periphery since they elicit changes in hepatic metabolism as well as in hormone secretion to counter-regulate changes in nutrient levels detected in the CNS. At peripheral level, the direct nutrient detection in liver has a crucial role in homeostatic control of glucose and fatty acid whereas in BB and intestine nutrient sensing is probably involved in regulation of hormone secretion from endocrine cells.
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Affiliation(s)
- Marta Conde-Sieira
- Laboratorio de Fisioloxía Animal, Departamento de Bioloxía Funcional e Ciencias da Saúde, Facultade de Bioloxía, Universidade de Vigo Vigo, Spain
| | - José L Soengas
- Laboratorio de Fisioloxía Animal, Departamento de Bioloxía Funcional e Ciencias da Saúde, Facultade de Bioloxía, Universidade de Vigo Vigo, Spain
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Argente-Arizón P, Guerra-Cantera S, Garcia-Segura LM, Argente J, Chowen JA. Glial cells and energy balance. J Mol Endocrinol 2017; 58:R59-R71. [PMID: 27864453 DOI: 10.1530/jme-16-0182] [Citation(s) in RCA: 42] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/19/2016] [Accepted: 11/18/2016] [Indexed: 12/31/2022]
Abstract
The search for new strategies and drugs to abate the current obesity epidemic has led to the intensification of research aimed at understanding the neuroendocrine control of appetite and energy expenditure. This intensified investigation of metabolic control has also included the study of how glial cells participate in this process. Glia, the most abundant cell type in the central nervous system, perform a wide spectrum of functions and are vital for the correct functioning of neurons and neuronal circuits. Current evidence indicates that hypothalamic glia, in particular astrocytes, tanycytes and microglia, are involved in both physiological and pathophysiological mechanisms of appetite and metabolic control, at least in part by regulating the signals reaching metabolic neuronal circuits. Glia transport nutrients, hormones and neurotransmitters; they secrete growth factors, hormones, cytokines and gliotransmitters and are a source of neuroprogenitor cells. These functions are regulated, as glia also respond to numerous hormones and nutrients, with the lack of specific hormonal signaling in hypothalamic astrocytes disrupting metabolic homeostasis. Here, we review some of the more recent advances in the role of glial cells in metabolic control, with a special emphasis on the differences between glial cell responses in males and females.
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Affiliation(s)
- Pilar Argente-Arizón
- Departments of Pediatrics & Pediatric EndocrinologyHospital Infantil Universitario Niño Jesús, Instituto de Investigación La Princesa, Department of Pediatrics, Universidad Autónoma de Madrid, CIBEROBN, Instituto de Salud Carlos III, Madrid, Spain
| | - Santiago Guerra-Cantera
- Departments of Pediatrics & Pediatric EndocrinologyHospital Infantil Universitario Niño Jesús, Instituto de Investigación La Princesa, Department of Pediatrics, Universidad Autónoma de Madrid, CIBEROBN, Instituto de Salud Carlos III, Madrid, Spain
| | | | - Jesús Argente
- Departments of Pediatrics & Pediatric EndocrinologyHospital Infantil Universitario Niño Jesús, Instituto de Investigación La Princesa, Department of Pediatrics, Universidad Autónoma de Madrid, CIBEROBN, Instituto de Salud Carlos III, Madrid, Spain
| | - Julie A Chowen
- Departments of Pediatrics & Pediatric EndocrinologyHospital Infantil Universitario Niño Jesús, Instituto de Investigación La Princesa, Department of Pediatrics, Universidad Autónoma de Madrid, CIBEROBN, Instituto de Salud Carlos III, Madrid, Spain
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Haythorne E, Hamilton DL, Findlay JA, Beall C, McCrimmon RJ, Ashford MLJ. Chronic exposure to K ATP channel openers results in attenuated glucose sensing in hypothalamic GT1-7 neurons. Neuropharmacology 2016; 111:212-222. [PMID: 27618741 DOI: 10.1016/j.neuropharm.2016.09.008] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2016] [Revised: 07/06/2016] [Accepted: 09/07/2016] [Indexed: 10/21/2022]
Abstract
Individuals with Type 1 diabetes (T1D) are often exposed to recurrent episodes of hypoglycaemia. This reduces hormonal and behavioural responses that normally counteract low glucose in order to maintain glucose homeostasis, with altered responsiveness of glucose sensing hypothalamic neurons implicated. Although the molecular mechanisms are unknown, pharmacological studies implicate hypothalamic ATP-sensitive potassium channel (KATP) activity, with KATP openers (KCOs) amplifying, through cell hyperpolarization, the response to hypoglycaemia. Although initial findings, using acute hypothalamic KCO delivery, in rats were promising, chronic exposure to the KCO NN414 worsened the responses to subsequent hypoglycaemic challenge. To investigate this further we used GT1-7 cells to explore how NN414 affected glucose-sensing behaviour, the metabolic response of cells to hypoglycaemia and KATP activity. GT1-7 cells exposed to 3 or 24 h NN414 exhibited an attenuated hyperpolarization to subsequent hypoglycaemic challenge or NN414, which correlated with diminished KATP activity. The reduced sensitivity to hypoglycaemia was apparent 24 h after NN414 removal, even though intrinsic KATP activity recovered. The NN414-modified glucose responsiveness was not associated with adaptations in glucose uptake, metabolism or oxidation. KATP inactivation by NN414 was prevented by the concurrent presence of tolbutamide, which maintains KATP closure. Single channel recordings indicate that NN414 alters KATP intrinsic gating inducing a stable closed or inactivated state. These data indicate that exposure of hypothalamic glucose sensing cells to chronic NN414 drives a sustained conformational change to KATP, probably by binding to SUR1, that results in loss of channel sensitivity to intrinsic metabolic factors such as MgADP and small molecule agonists.
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Affiliation(s)
- Elizabeth Haythorne
- Division of Molecular and Clinical Medicine, School of Medicine, Ninewells Hospital & Medical School, University of Dundee, Dundee, UK.
| | - D Lee Hamilton
- Division of Molecular and Clinical Medicine, School of Medicine, Ninewells Hospital & Medical School, University of Dundee, Dundee, UK.
| | - John A Findlay
- Division of Molecular and Clinical Medicine, School of Medicine, Ninewells Hospital & Medical School, University of Dundee, Dundee, UK.
| | - Craig Beall
- Division of Molecular and Clinical Medicine, School of Medicine, Ninewells Hospital & Medical School, University of Dundee, Dundee, UK.
| | - Rory J McCrimmon
- Division of Molecular and Clinical Medicine, School of Medicine, Ninewells Hospital & Medical School, University of Dundee, Dundee, UK.
| | - Michael L J Ashford
- Division of Molecular and Clinical Medicine, School of Medicine, Ninewells Hospital & Medical School, University of Dundee, Dundee, UK.
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De Backer I, Hussain SS, Bloom SR, Gardiner JV. Insights into the role of neuronal glucokinase. Am J Physiol Endocrinol Metab 2016; 311:E42-55. [PMID: 27189932 PMCID: PMC4967152 DOI: 10.1152/ajpendo.00034.2016] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/26/2016] [Accepted: 05/13/2016] [Indexed: 12/17/2022]
Abstract
Glucokinase is a key component of the neuronal glucose-sensing mechanism and is expressed in brain regions that control a range of homeostatic processes. In this review, we detail recently identified roles for neuronal glucokinase in glucose homeostasis and counterregulatory responses to hypoglycemia and in regulating appetite. We describe clinical implications from these advances in our knowledge, especially for developing novel treatments for diabetes and obesity. Further research required to extend our knowledge and help our efforts to tackle the diabetes and obesity epidemics is suggested.
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Affiliation(s)
- Ivan De Backer
- Section of Investigative Medicine, Division of Diabetes, Endocrinology and Metabolism, Imperial College London, London, United Kingdom
| | - Sufyan S Hussain
- Section of Investigative Medicine, Division of Diabetes, Endocrinology and Metabolism, Imperial College London, London, United Kingdom
| | - Stephen R Bloom
- Section of Investigative Medicine, Division of Diabetes, Endocrinology and Metabolism, Imperial College London, London, United Kingdom
| | - James V Gardiner
- Section of Investigative Medicine, Division of Diabetes, Endocrinology and Metabolism, Imperial College London, London, United Kingdom
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Grieb P. Intracerebroventricular Streptozotocin Injections as a Model of Alzheimer's Disease: in Search of a Relevant Mechanism. Mol Neurobiol 2016; 53:1741-1752. [PMID: 25744568 PMCID: PMC4789228 DOI: 10.1007/s12035-015-9132-3] [Citation(s) in RCA: 228] [Impact Index Per Article: 28.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2014] [Accepted: 02/22/2015] [Indexed: 01/26/2023]
Abstract
Streptozotocin (STZ), a glucosamine-nitrosourea compound derived from soil bacteria and originally developed as an anticancer agent, in 1963 has been found to induce diabetes in experimental animals. Since then, systemic application of STZ became the most frequently studied experimental model of insulin-dependent (type 1) diabetes. The compound is selectively toxic toward insulin-producing pancreatic beta cells, which is explained as the result of its cellular uptake by the low-affinity glucose transporter 2 (GLUT2) protein located in their cell membranes. STZ cytotoxicity is mainly due to DNA alkylation which results in cellular necrosis. Besides pancreatic beta cells, STZ applied systemically damages also other organs expressing GLUT2, such as kidney and liver, whereas brain is not affected directly because blood-brain barrier lacks this transporter protein. However, single or double intracerebroventricular (icv) STZ injection(s) chronically decrease cerebral glucose uptake and produce multiple other effects that resemble molecular, pathological, and behavioral features of Alzheimer's disease (AD). Taking into consideration that glucose hypometabolism is an early and persistent sign of AD and that Alzheimer's brains present features of impaired insulin signaling, icv STZ injections are exploited by some investigators as a non-transgenic model of this disease and used for preclinical testing of pharmacological therapies for AD. While it has been assumed that icv STZ produces cerebral glucose hypometabolism and other effects directly through desensitizing brain insulin receptors, the evidence for such mechanism is poor. On the other hand, early data on insulin immunoreactivity showed intense insulin expression in the rodent brain, and the possibility of local production of insulin in the mammalian brain has never been conclusively excluded. Also, there are GLUT2-expressing cells in the brain, in particular in the circumventricular organs and hypothalamus; some of these cells may be involved in glucose sensing. Thus, icv STZ may damage brain glucose insulin producing cells and/or brain glucose sensors. Mechanistic explanation of the mode of action of icv STZ, which is currently lacking, would provide a valuable contribution to the field of animal models of Alzheimer's disease.
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Affiliation(s)
- Paweł Grieb
- Department of Experimental Pharmacology, Mossakowski Medical Research Centre, Polish Academy of Sciences, Str. Pawinskiego 5, 02-106, Warsaw, Poland.
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Emerging role of the brain in the homeostatic regulation of energy and glucose metabolism. Exp Mol Med 2016; 48:e216. [PMID: 26964832 PMCID: PMC4892882 DOI: 10.1038/emm.2016.4] [Citation(s) in RCA: 213] [Impact Index Per Article: 26.6] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2015] [Revised: 12/07/2015] [Accepted: 12/09/2015] [Indexed: 12/12/2022] Open
Abstract
Accumulated evidence from genetic animal models suggests that the brain, particularly the hypothalamus, has a key role in the homeostatic regulation of energy and glucose metabolism. The brain integrates multiple metabolic inputs from the periphery through nutrients, gut-derived satiety signals and adiposity-related hormones. The brain modulates various aspects of metabolism, such as food intake, energy expenditure, insulin secretion, hepatic glucose production and glucose/fatty acid metabolism in adipose tissue and skeletal muscle. Highly coordinated interactions between the brain and peripheral metabolic organs are critical for the maintenance of energy and glucose homeostasis. Defective crosstalk between the brain and peripheral organs contributes to the development of obesity and type 2 diabetes. Here we comprehensively review the above topics, discussing the main findings related to the role of the brain in the homeostatic regulation of energy and glucose metabolism.
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Otlivanchik O, Sanders NM, Dunn-Meynell A, Levin BE. Orexin signaling is necessary for hypoglycemia-induced prevention of conditioned place preference. Am J Physiol Regul Integr Comp Physiol 2015; 310:R66-73. [PMID: 26511522 DOI: 10.1152/ajpregu.00066.2015] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2015] [Accepted: 10/19/2015] [Indexed: 01/24/2023]
Abstract
While the neural control of glucoregulatory responses to insulin-induced hypoglycemia is beginning to be elucidated, brain sites responsible for behavioral responses to hypoglycemia are relatively poorly understood. To help elucidate central control mechanisms associated with hypoglycemia unawareness, we first evaluated the effect of recurrent hypoglycemia on a simple behavioral measure, the robust feeding response to hypoglycemia, in rats. First, food intake was significantly, and similarly, increased above baseline saline-induced intake (1.1 ± 0.2 g; n = 8) in rats experiencing a first (4.4 ± 0.3; n = 8) or third daily episode of recurrent insulin-induced hypoglycemia (IIH, 3.7 ± 0.3 g; n = 9; P < 0.05). Because food intake was not impaired as a result of prior IIH, we next developed an alternative animal model of hypoglycemia-induced behavioral arousal using a conditioned place preference (CPP) model. We found that hypoglycemia severely blunted previously acquired CPP in rats and that recurrent hypoglycemia prevented this blunting. Pretreatment with a brain penetrant, selective orexin receptor-1 antagonist, SB-334867A, blocked hypoglycemia-induced blunting of CPP. Recurrently hypoglycemic rats also showed decreased preproorexin expression in the perifornical hypothalamus (50%) but not in the adjacent lateral hypothalamus. Pretreatment with sertraline, previously shown to prevent hypoglycemia-associated glucoregulatory failure, did not prevent blunting of hypoglycemia-induced CPP prevention by recurrent hypoglycemia. This work describes the first behavioral model of hypoglycemia unawareness and suggests a role for orexin neurons in mediating behavioral responses to hypoglycemia.
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Affiliation(s)
- Oleg Otlivanchik
- Graduate School of Biomedical Sciences, Rutgers University, Newark, New Jersey; Department of Neurology, New Jersey Medical School, Rutgers University, Newark, New Jersey
| | | | - Ambrose Dunn-Meynell
- Graduate School of Biomedical Sciences, Rutgers University, Newark, New Jersey; Department of Neurology, New Jersey Medical School, Rutgers University, Newark, New Jersey; Neurology Service, Veterans Affairs Medical Center, East Orange, New Jersey; and
| | - Barry E Levin
- Department of Neurology, New Jersey Medical School, Rutgers University, Newark, New Jersey; Neurology Service, Veterans Affairs Medical Center, East Orange, New Jersey; and
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Elizondo-Vega R, Cortes-Campos C, Barahona MJ, Oyarce KA, Carril CA, García-Robles MA. The role of tanycytes in hypothalamic glucosensing. J Cell Mol Med 2015; 19:1471-82. [PMID: 26081217 PMCID: PMC4511346 DOI: 10.1111/jcmm.12590] [Citation(s) in RCA: 58] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2015] [Accepted: 03/03/2015] [Indexed: 12/23/2022] Open
Abstract
Tanycytes are elongated hypothalamic glial cells that cover the basal walls of the third ventricle; their apical regions contact the cerebrospinal fluid (CSF), and their processes reach hypothalamic neuronal nuclei that control the energy status of an organism. These nuclei maintain the balance between energy expenditure and intake, integrating several peripheral signals and triggering cellular responses that modify the feeding behaviour and peripheral glucose homeostasis. One of the most important and well-studied signals that control this process is glucose; however, the mechanism by which this molecule is sensed remains unknown. We along with others have proposed that tanycytes play a key role in this process, transducing changes in CSF glucose concentration to the neurons that control energy status. Recent studies have demonstrated the expression and function of monocarboxylate transporters and canonical pancreatic β cell glucose sensing molecules, including glucose transporter 2 and glucokinase, in tanycytes. These and other data, which will be discussed in this review, suggest that hypothalamic glucosensing is mediated through a metabolic interaction between tanycytes and neurons through lactate. This article will summarize the recent evidence that supports the importance of tanycytes in hypothalamic glucosensing, and discuss the possible mechanisms involved in this process. Finally, it is important to highlight that a detailed analysis of this mechanism could represent an opportunity to understand the evolution of associated pathologies, including diabetes and obesity, and identify new candidates for therapeutic intervention.
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Affiliation(s)
- Roberto Elizondo-Vega
- Laboratorio de Biología Celular, Departamento de Biología Celular, Facultad de Ciencias Biológicas, Universidad de Concepción, Concepción, Chile
| | | | - Maria J Barahona
- Laboratorio de Biología Celular, Departamento de Biología Celular, Facultad de Ciencias Biológicas, Universidad de Concepción, Concepción, Chile
| | - Karina A Oyarce
- Laboratorio de Biología Celular, Departamento de Biología Celular, Facultad de Ciencias Biológicas, Universidad de Concepción, Concepción, Chile
| | - Claudio A Carril
- Laboratorio de Biología Celular, Departamento de Biología Celular, Facultad de Ciencias Biológicas, Universidad de Concepción, Concepción, Chile
| | - Maria A García-Robles
- Laboratorio de Biología Celular, Departamento de Biología Celular, Facultad de Ciencias Biológicas, Universidad de Concepción, Concepción, Chile
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32
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Argente-Arizón P, Freire-Regatillo A, Argente J, Chowen JA. Role of non-neuronal cells in body weight and appetite control. Front Endocrinol (Lausanne) 2015; 6:42. [PMID: 25859240 PMCID: PMC4374626 DOI: 10.3389/fendo.2015.00042] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/06/2015] [Accepted: 03/11/2015] [Indexed: 12/14/2022] Open
Abstract
The brain is composed of neurons and non-neuronal cells, with the latter encompassing glial, ependymal and endothelial cells, as well as pericytes and progenitor cells. Studies aimed at understanding how the brain operates have traditionally focused on neurons, but the importance of non-neuronal cells has become increasingly evident. Once relegated to supporting roles, it is now indubitable that these diverse cell types are fundamental for brain development and function, including that of metabolic circuits, and they may play a significant role in obesity onset and complications. They participate in processes of neurogenesis, synaptogenesis, and synaptic plasticity of metabolic circuits both during development and in adulthood. Some glial cells, such as tanycytes and astrocytes, transport circulating nutrients and metabolic factors that are fundamental for neuronal viability and activity into and within the hypothalamus. All of these cell types express receptors for a variety of metabolic factors and hormones, suggesting that they participate in metabolic function. They are the first line of defense against any assault to neurons. Indeed, microglia and astrocytes participate in the hypothalamic inflammatory response to high fat diet (HFD)-induced obesity, with this process contributing to inflammatory-related insulin and leptin resistance. Moreover, HFD-induced obesity and hyperleptinemia modify hypothalamic astroglial morphology, which is associated with changes in the synaptic inputs to neuronal metabolic circuits. Astrocytic contact with the microvasculature is increased by HFD intake and this could modify nutrient/hormonal uptake into the brain. In addition, progenitor cells in the hypothalamus are now known to have the capacity to renew metabolic circuits, and this can be affected by HFD intake and obesity. Here, we discuss our current understanding of how non-neuronal cells participate in physiological and physiopathological metabolic control.
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Affiliation(s)
- Pilar Argente-Arizón
- Department of Endocrinology, Hospital Infantil Universitario Niño Jesús, Instituto de Investigación La Princesa, Madrid, Spain
- Department of Pediatrics, Universidad Autónoma de Madrid, Madrid, Spain
- Fisiopatología de la Obesidad y Nutrición (CIBERobn), Centros de Investigación Biomédica en Red, Instituto de Salud Carlos III, Madrid, Spain
| | - Alejandra Freire-Regatillo
- Department of Endocrinology, Hospital Infantil Universitario Niño Jesús, Instituto de Investigación La Princesa, Madrid, Spain
- Department of Pediatrics, Universidad Autónoma de Madrid, Madrid, Spain
- Fisiopatología de la Obesidad y Nutrición (CIBERobn), Centros de Investigación Biomédica en Red, Instituto de Salud Carlos III, Madrid, Spain
| | - Jesús Argente
- Department of Endocrinology, Hospital Infantil Universitario Niño Jesús, Instituto de Investigación La Princesa, Madrid, Spain
- Department of Pediatrics, Universidad Autónoma de Madrid, Madrid, Spain
- Fisiopatología de la Obesidad y Nutrición (CIBERobn), Centros de Investigación Biomédica en Red, Instituto de Salud Carlos III, Madrid, Spain
| | - Julie A. Chowen
- Department of Endocrinology, Hospital Infantil Universitario Niño Jesús, Instituto de Investigación La Princesa, Madrid, Spain
- Fisiopatología de la Obesidad y Nutrición (CIBERobn), Centros de Investigación Biomédica en Red, Instituto de Salud Carlos III, Madrid, Spain
- *Correspondence: Julie A. Chowen, Department of Endocrinology, Hospital Infantil Universitario Niño Jesús, Avda. Menéndez Pelayo, 65, Madrid E-28009, Spain e-mail: ;
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Routh VH, Hao L, Santiago AM, Sheng Z, Zhou C. Hypothalamic glucose sensing: making ends meet. Front Syst Neurosci 2014; 8:236. [PMID: 25540613 PMCID: PMC4261699 DOI: 10.3389/fnsys.2014.00236] [Citation(s) in RCA: 122] [Impact Index Per Article: 12.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2014] [Accepted: 11/26/2014] [Indexed: 01/12/2023] Open
Abstract
The neuroendocrine system governs essential survival and homeostatic functions. For example, growth is needed for development, thermoregulation maintains optimal core temperature in a changing environment, and reproduction ensures species survival. Stress and immune responses enable an organism to overcome external and internal threats while the circadian system regulates arousal and sleep such that vegetative and active functions do not overlap. All of these functions require a significant portion of the body's energy. As the integrator of the neuroendocrine system, the hypothalamus carefully assesses the energy status of the body in order to appropriately partition resources to provide for each system without compromising the others. While doing so the hypothalamus must ensure that adequate glucose levels are preserved for brain function since glucose is the primary fuel of the brain. To this end, the hypothalamus contains specialized glucose sensing neurons which are scattered throughout the nuclei controlling distinct neuroendocrine functions. We hypothesize that these neurons play a key role in enabling the hypothalamus to partition energy to meet these peripheral survival needs without endangering the brain's glucose supply. This review will first describe the varied mechanisms underlying glucose sensing in neurons within discrete hypothalamic nuclei. We will then evaluate the way in which peripheral energy status regulates glucose sensitivity. For example, during energy deficit such as fasting specific hypothalamic glucose sensing neurons become sensitized to decreased glucose. This increases the gain of the information relay when glucose availability is a greater concern for the brain. Finally, changes in glucose sensitivity under pathological conditions (e.g., recurrent insulin-hypoglycemia, diabetes) will be addressed. The overall goal of this review is to place glucose sensing neurons within the context of hypothalamic control of neuroendocrine function.
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Affiliation(s)
- Vanessa H Routh
- Department of Pharmacology and Physiology, New Jersey Medical School, Rutgers University Newark, NJ, USA
| | - Lihong Hao
- Department of Pharmacology and Physiology, New Jersey Medical School, Rutgers University Newark, NJ, USA ; Department of Pharmacology and Physiology and Graduate School of the Biomedical Sciences, New Jersey Medical School, Rutgers University Newark, NJ, USA
| | - Ammy M Santiago
- Department of Pharmacology and Physiology, New Jersey Medical School, Rutgers University Newark, NJ, USA ; Department of Pharmacology and Physiology and Graduate School of the Biomedical Sciences, New Jersey Medical School, Rutgers University Newark, NJ, USA
| | - Zhenyu Sheng
- Department of Pharmacology and Physiology, New Jersey Medical School, Rutgers University Newark, NJ, USA
| | - Chunxue Zhou
- Department of Pharmacology and Physiology, New Jersey Medical School, Rutgers University Newark, NJ, USA ; Department of Pharmacology and Physiology and Graduate School of the Biomedical Sciences, New Jersey Medical School, Rutgers University Newark, NJ, USA
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Langlet F. Tanycytes: a gateway to the metabolic hypothalamus. J Neuroendocrinol 2014; 26:753-60. [PMID: 25131689 DOI: 10.1111/jne.12191] [Citation(s) in RCA: 64] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/12/2014] [Revised: 08/01/2014] [Accepted: 08/01/2014] [Indexed: 01/07/2023]
Abstract
The central regulation of energy balance relies on the ability of the brain to promptly and efficiently sense variations of metabolic state. To achieve this, circulating hormonal and metabolic signals have to cross the blood-brain interface, where unusual glial cells named tanycytes have been described to play a key role in this process. Tanycytes are specialised polarised ependymoglial cells that line the floor of the third ventricle and send a single process to contact hypothalamic neurones and blood vessels. Although their role in the regulation of energy balance via the modulation of neuronal activity or their chemosensitivity has been already described, recent studies ascribe a new function to tanycytes in the regulation of energy homeostasis as a result of their capacity to regulate the access of metabolic signals to the hypothalamus. This review discusses the peculiar place of tanycytes within the blood-hypothalamus interface, as well as a striking capacity to remodel their own interface to ensure an adaptive metabolic response to energy imbalances.
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Affiliation(s)
- F Langlet
- Inserm, Jean-Pierre Aubert Research Centre, U837, Development and Plasticity of the Postnatal Brain, Lille, France; UDSL, School of Medicine, Lille, France; Université de Lille, Institut de Médecine Prédictive et de Recherche Thérapeutique, Lille, France
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35
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Herwig A, Campbell G, Mayer CD, Boelen A, Anderson RA, Ross AW, Mercer JG, Barrett P. A thyroid hormone challenge in hypothyroid rats identifies T3 regulated genes in the hypothalamus and in models with altered energy balance and glucose homeostasis. Thyroid 2014; 24:1575-93. [PMID: 25087834 PMCID: PMC4229697 DOI: 10.1089/thy.2014.0169] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
BACKGROUND The thyroid hormone triiodothyronine (T3) is known to affect energy balance. Recent evidence points to an action of T3 in the hypothalamus, a key area of the brain involved in energy homeostasis, but the components and mechanisms are far from understood. The aim of this study was to identify components in the hypothalamus that may be involved in the action of T3 on energy balance regulatory mechanisms. METHODS Sprague Dawley rats were made hypothyroid by giving 0.025% methimazole (MMI) in their drinking water for 22 days. On day 21, half the MMI-treated rats received a saline injection, whereas the others were injected with T3. Food intake and body weight measurements were taken daily. Body composition was determined by magnetic resonance imaging, gene expression was analyzed by in situ hybridization, and T3-induced gene expression was determined by microarray analysis of MMI-treated compared to MMI-T3-injected hypothalamic RNA. RESULTS Post mortem serum thyroid hormone levels showed that MMI treatment decreased circulating thyroid hormones and increased thyrotropin (TSH). MMI treatment decreased food intake and body weight. Body composition analysis revealed reduced lean and fat mass in thyroidectomized rats from day 14 of the experiment. MMI treatment caused a decrease in circulating triglyceride concentrations, an increase in nonesterified fatty acids, and decreased insulin levels. A glucose tolerance test showed impaired glucose clearance in the thyroidectomized animals. In the brain, in situ hybridization revealed marked changes in gene expression, including genes such as Mct8, a thyroid hormone transporter, and Agrp, a key component in energy balance regulation. Microarray analysis revealed 110 genes to be up- or downregulated with T3 treatment (± 1.3-fold change, p<0.05). Three genes chosen from the differentially expressed genes were verified by in situ hybridization to be activated by T3 in cells located at or close to the hypothalamic ventricular ependymal layer and differentially expressed in animal models of long- and short-term body weight regulation. CONCLUSION This study identified genes regulated by T3 in the hypothalamus, a key area of the brain involved in homeostasis and neuroendocrine functions. These include genes hitherto not known to be regulated by thyroid status.
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Affiliation(s)
- Annika Herwig
- Ingestive Behaviour Group, Rowett Institute for Nutrition and Health, University of Aberdeen, Aberdeen, United Kingdom
- Zoological Institute, University of Hamburg, Hamburg, Germany
| | - Gill Campbell
- Ingestive Behaviour Group, Rowett Institute for Nutrition and Health, University of Aberdeen, Aberdeen, United Kingdom
| | - Claus-Dieter Mayer
- Biomathematics and Statistics Scotland, Rowett Institute for Nutrition and Health, University of Aberdeen, Aberdeen, United Kingdom
| | - Anita Boelen
- Department of Endocrinology, Metabolism, Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands
| | - Richard A. Anderson
- Ingestive Behaviour Group, Rowett Institute for Nutrition and Health, University of Aberdeen, Aberdeen, United Kingdom
| | - Alexander W. Ross
- Ingestive Behaviour Group, Rowett Institute for Nutrition and Health, University of Aberdeen, Aberdeen, United Kingdom
| | - Julian G. Mercer
- Ingestive Behaviour Group, Rowett Institute for Nutrition and Health, University of Aberdeen, Aberdeen, United Kingdom
| | - Perry Barrett
- Ingestive Behaviour Group, Rowett Institute for Nutrition and Health, University of Aberdeen, Aberdeen, United Kingdom
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Jokiaho AJ, Donovan CM, Watts AG. The rate of fall of blood glucose determines the necessity of forebrain-projecting catecholaminergic neurons for male rat sympathoadrenal responses. Diabetes 2014; 63:2854-65. [PMID: 24740574 PMCID: PMC4113074 DOI: 10.2337/db13-1753] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Different onset rates of insulin-induced hypoglycemia use distinct glucosensors to activate sympathoadrenal counterregulatory responses (CRRs). Glucosensory elements in the portal-mesenteric veins are dispensable with faster rates when brain elements predominate, but are essential for responses to the slower-onset hypoglycemia that is common with insulin therapy. Whether a similar rate-associated divergence exists within more expansive brain networks is unknown. Hindbrain catecholamine neurons distribute glycemia-related information throughout the forebrain. We tested in male rats whether catecholaminergic neurons that project to the medial and ventromedial hypothalamus are required for sympathoadrenal CRRs to rapid- and slow-onset hypoglycemia and whether these neurons are differentially engaged as onset rates change. Using a catecholamine-specific neurotoxin and hyperinsulinemic-hypoglycemic clamps, we found that sympathoadrenal CRRs to slow- but not rapid-onset hypoglycemia require hypothalamus-projecting catecholaminergic neurons, the majority of which originate in the ventrolateral medulla. As determined with Fos, these neurons are differentially activated by the two onset rates. We conclude that 1) catecholaminergic projections to the hypothalamus provide essential information for activating sympathoadrenal CRRs to slow- but not rapid-onset hypoglycemia, 2) hypoglycemia onset rates have a major impact on the hypothalamic mechanisms that enable sympathoadrenal CRRs, and 3) hypoglycemia-related sensory information activates hindbrain catecholaminergic neurons in a rate-dependent manner.
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Affiliation(s)
- Anne J Jokiaho
- Center for NeuroMetabolic Interactions, The Integrated and Evolutionary Biology Graduate Program, and The Department of Biological Sciences, USC Dornsife College of Letters, Arts, and Sciences, University of Southern California, Los Angeles, CA
| | - Casey M Donovan
- Center for NeuroMetabolic Interactions, The Integrated and Evolutionary Biology Graduate Program, and The Department of Biological Sciences, USC Dornsife College of Letters, Arts, and Sciences, University of Southern California, Los Angeles, CA
| | - Alan G Watts
- Center for NeuroMetabolic Interactions, The Integrated and Evolutionary Biology Graduate Program, and The Department of Biological Sciences, USC Dornsife College of Letters, Arts, and Sciences, University of Southern California, Los Angeles, CA
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Osterstock G, El Yandouzi T, Romanò N, Carmignac D, Langlet F, Coutry N, Guillou A, Schaeffer M, Chauvet N, Vanacker C, Galibert E, Dehouck B, Robinson ICAF, Prévot V, Mollard P, Plesnila N, Méry PF. Sustained alterations of hypothalamic tanycytes during posttraumatic hypopituitarism in male mice. Endocrinology 2014; 155:1887-98. [PMID: 24601879 DOI: 10.1210/en.2013-1336] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
Traumatic brain injury is a leading cause of hypopituitarism, which compromises patients' recovery, quality of life, and life span. To date, there are no means other than standardized animal studies to provide insights into the mechanisms of posttraumatic hypopituitarism. We have found that GH levels were impaired after inducing a controlled cortical impact (CCI) in mice. Furthermore, GHRH stimulation enhanced GH to lower level in injured than in control or sham mice. Because many characteristics were unchanged in the pituitary glands of CCI mice, we looked for changes at the hypothalamic level. Hypertrophied astrocytes were seen both within the arcuate nucleus and the median eminence, two pivotal structures of the GH axis, spatially remote to the injury site. In the arcuate nucleus, GHRH neurons were unaltered. In the median eminence, injured mice exhibited unexpected alterations. First, the distributions of claudin-1 and zonula occludens-1 between tanycytes were disorganized, suggesting tight junction disruptions. Second, endogenous IgG was increased in the vicinity of the third ventricle, suggesting abnormal barrier properties after CCI. Third, intracerebroventricular injection of a fluorescent-dextran derivative highly stained the hypothalamic parenchyma only after CCI, demonstrating an increased permeability of the third ventricle edges. This alteration of the third ventricle might jeopardize the communication between the hypothalamus and the pituitary gland. In conclusion, the phenotype of CCI mice had similarities to the posttraumatic hypopituitarism seen in humans with intact pituitary gland and pituitary stalk. It is the first report of a pathological status in which tanycyte dysfunctions appear as a major acquired syndrome.
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Affiliation(s)
- Guillaume Osterstock
- INSERM Unité 661 (G.O., T.E.Y., N.Co., N.R., A.G., M.S., N.Ch., E.G., P.M., P.-F.M.), Centre National de la Recherche Scientifique Unité Mixte de Recherche 5203 (G.O., T.E.Y., N.R., N.Co., A.G., M.S., N.Ch., E.G., P.M., P.-F.M.), Institut de Génomique Fonctionelle, 34094 Montpellier, France; Université Montpellier 1, 2 (G.O., T.E.Y., N.R., N.Co., A.G., M.S., N.Ch., E.G., P.M., P.-F.M.), 34967 Montpellier, France; Division of Molecular Neuroendocrinology (D.C., I.C.A.F.R.), Medical Research Council National Institute for Medical Research, The Ridgeway, Mill Hill, London NW7 1AA, United Kingdom; Royal College of Surgeons in Ireland (G.O., T.E.Y., M.S., N.P.), Dublin 2, Ireland; INSERM Unité 837 (F.L., C.V., B.D., V.P.), Department of Development and Plasticity of the Postnatal Brain, Jean-Pierre Aubert Research Center, 59045 Lille, France; and University of Lille 2 (F.L., C.V., B.D., V.P.), 59000 Lille, France
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38
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Salgado M, Tarifeño-Saldivia E, Ordenes P, Millán C, Yañez MJ, Llanos P, Villagra M, Elizondo-Vega R, Martínez F, Nualart F, Uribe E, de los Angeles García-Robles M. Dynamic localization of glucokinase and its regulatory protein in hypothalamic tanycytes. PLoS One 2014; 9:e94035. [PMID: 24739934 PMCID: PMC3989220 DOI: 10.1371/journal.pone.0094035] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2013] [Accepted: 03/11/2014] [Indexed: 11/28/2022] Open
Abstract
Glucokinase (GK), the hexokinase involved in glucose sensing in pancreatic β cells, is also expressed in hypothalamic tanycytes, which cover the ventricular walls of the basal hypothalamus and are implicated in an indirect control of neuronal activity by glucose. Previously, we demonstrated that GK was preferentially localized in tanycyte nuclei in euglycemic rats, which has been reported in hepatocytes and is suggestive of the presence of the GK regulatory protein, GKRP. In the present study, GK intracellular localization in hypothalamic and hepatic tissues of the same rats under several glycemic conditions was compared using confocal microscopy and Western blot analysis. In the hypothalamus, increased GK nuclear localization was observed in hyperglycemic conditions; however, it was primarily localized in the cytoplasm in hepatic tissue under the same conditions. Both GK and GKRP were next cloned from primary cultures of tanycytes. Expression of GK by Escherichia coli revealed a functional cooperative protein with a S0.5 of 10 mM. GKRP, expressed in Saccharomyces cerevisiae, inhibited GK activity in vitro with a Ki 0.2 µM. We also demonstrated increased nuclear reactivity of both GK and GKRP in response to high glucose concentrations in tanycyte cultures. These data were confirmed using Western blot analysis of nuclear extracts. Results indicate that GK undergoes short-term regulation by nuclear compartmentalization. Thus, in tanycytes, GK can act as a molecular switch to arrest cellular responses to increased glucose.
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Affiliation(s)
- Magdiel Salgado
- Departamento de Biología Celular, Facultad de Ciencias Biológicas, Universidad de Concepción, Concepción, Chile
| | - Estefanía Tarifeño-Saldivia
- Departamento de Biología Celular, Facultad de Ciencias Biológicas, Universidad de Concepción, Concepción, Chile
| | - Patricio Ordenes
- Departamento de Biología Celular, Facultad de Ciencias Biológicas, Universidad de Concepción, Concepción, Chile
| | - Carola Millán
- Facultad de Artes Liberales, Universidad Adolfo Ibañez, Viña del Mar, Chile
| | - María José Yañez
- Departamento de Biología Celular, Facultad de Ciencias Biológicas, Universidad de Concepción, Concepción, Chile
| | - Paula Llanos
- Departamento de Biología Celular, Facultad de Ciencias Biológicas, Universidad de Concepción, Concepción, Chile
| | - Marcos Villagra
- Departamento de Biología Celular, Facultad de Ciencias Biológicas, Universidad de Concepción, Concepción, Chile
| | - Roberto Elizondo-Vega
- Departamento de Biología Celular, Facultad de Ciencias Biológicas, Universidad de Concepción, Concepción, Chile
| | - Fernando Martínez
- Departamento de Biología Celular, Facultad de Ciencias Biológicas, Universidad de Concepción, Concepción, Chile
| | - Francisco Nualart
- Departamento de Biología Celular, Facultad de Ciencias Biológicas, Universidad de Concepción, Concepción, Chile
| | - Elena Uribe
- Departamento de Bioquímica y Biología Molecular, Facultad de Ciencias Biológicas, Universidad de Concepción, Concepción, Chile
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Jensen VFH, Bøgh IB, Lykkesfeldt J. Effect of insulin-induced hypoglycaemia on the central nervous system: evidence from experimental studies. J Neuroendocrinol 2014; 26:123-50. [PMID: 24428753 DOI: 10.1111/jne.12133] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/05/2013] [Revised: 12/13/2013] [Accepted: 01/08/2014] [Indexed: 12/12/2022]
Abstract
Insulin-induced hypoglycaemia (IIH) is a major acute complication in type 1 as well as in type 2 diabetes, particularly during intensive insulin therapy. The brain plays a central role in the counter-regulatory response by eliciting parasympathetic and sympathetic hormone responses to restore normoglycaemia. Brain glucose concentrations, being approximately 15-20% of the blood glucose concentration in humans, are rigorously maintained during hypoglycaemia through adaptions such as increased cerebral glucose transport, decreased cerebral glucose utilisation and, possibly, by using central nervous system glycogen as a glucose reserve. However, during sustained hypoglycaemia, the brain cannot maintain a sufficient glucose influx and, as the cerebral hypoglycaemia becomes severe, electroencephalogram changes, oxidative stress and regional neuronal death ensues. With particular focus on evidence from experimental studies on nondiabetic IIH, this review outlines the central mechanisms behind the counter-regulatory response to IIH, as well as cerebral adaption to avoid sequelae of cerebral neuroglycopaenia, including seizures and coma.
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Affiliation(s)
- V F H Jensen
- Department of Veterinary Disease Biology, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark; Department of Diabetes Toxicology and Safety Pharmacology, Novo Nordisk A/S, Maaloev, Denmark
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40
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Li AJ, Wang Q, Dinh TT, Powers BR, Ritter S. Stimulation of feeding by three different glucose-sensing mechanisms requires hindbrain catecholamine neurons. Am J Physiol Regul Integr Comp Physiol 2013; 306:R257-64. [PMID: 24381177 DOI: 10.1152/ajpregu.00451.2013] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Previous work has shown that hindbrain catecholamine neurons are required components of the brain's glucoregulatory circuitry. However, the mechanisms and circuitry underlying their glucoregulatory functions are poorly understood. Here we examined three drugs, glucosamine (GcA), phloridzin (Phl) and 5-thio-d-glucose (5TG), that stimulate food intake but interfere in different ways with cellular glucose utilization or transport. We examined feeding and blood glucose responses to each drug in male rats previously injected into the hypothalamic paraventricular nucleus with anti-dopamine-β-hydroxylase conjugated to saporin (DSAP), a retrogradely transported immunotoxin that selectively lesions noradrenergic and adrenergic neurons, or with unconjugated saporin (SAP) control. Our major findings were 1) that GcA, Phl, and 5TG all stimulated feeding in SAP controls whether injected into the lateral or fourth ventricle (LV or 4V), 2) that each drug's potency was similar for both LV and 4V injections, 3) that neither LV or 4V injection of these drugs evoked feeding in DSAP-lesioned rats, and 4) that only 5TG, which blocks glycolysis, stimulated a blood glucose response. The antagonist of the MEK/ERK signaling cascade, U0126, attenuated GcA-induced feeding, but not Phl- or 5TG-induced feeding. Thus GcA, Phl, and 5TG, although differing in mechanism and possibly activating different neural populations, stimulate feeding in a catecholamine-dependent manner. Although results do not exclude the possibility that catecholamine neurons possess glucose-sensing mechanisms responsive to all of these agents, currently available evidence favors the possibility that the feeding effects result from convergent neural circuits in which catecholamine neurons are a required component.
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Affiliation(s)
- Ai-Jun Li
- Programs in Neuroscience, Washington State University, Pullman, Washington
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41
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Chowen JA, Argente J, Horvath TL. Uncovering novel roles of nonneuronal cells in body weight homeostasis and obesity. Endocrinology 2013; 154:3001-7. [PMID: 23798599 PMCID: PMC3749483 DOI: 10.1210/en.2013-1303] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Glial cells, which constitute more than 50% of the mass of the central nervous system and greatly outnumber neurons, are at the vanguard of neuroendocrine research in metabolic control and obesity. Historically relegated to roles of structural support and protection, diverse functions have been gradually attributed to this heterogeneous class of cells with their protagonism in crescendo in all areas of neuroscience during the past decade. However, this dramatic increase in attention bestowed upon glial cells has also emphasized our vast lack of knowledge concerning many aspects of their physiological functions, let alone their participation in numerous pathologies. This minireview focuses on the recent advances in our understanding of how glial cells participate in the physiological regulation of appetite and systemic metabolism as well as their role in the pathophysiological response to poor nutrition and secondary complications associated with obesity. Moreover, we highlight some of the existing lagoons of knowledge in this increasingly important area of investigation.
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Affiliation(s)
- Julie A Chowen
- Hospital Infantil Universitario Niño Jesús, Department of Endocrinology, Instituto de Investigación La Princesa, 28009 Madrid, Spain.
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42
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Lanfray D, Arthaud S, Ouellet J, Compère V, Do Rego JL, Leprince J, Lefranc B, Castel H, Bouchard C, Monge-Roffarello B, Richard D, Pelletier G, Vaudry H, Tonon MC, Morin F. Gliotransmission and brain glucose sensing: critical role of endozepines. Diabetes 2013; 62:801-10. [PMID: 23160530 PMCID: PMC3581199 DOI: 10.2337/db11-0785] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Hypothalamic glucose sensing is involved in the control of feeding behavior and peripheral glucose homeostasis, and glial cells are suggested to play an important role in this process. Diazepam-binding inhibitor (DBI) and its processing product the octadecaneuropeptide (ODN), collectively named endozepines, are secreted by astroglia, and ODN is a potent anorexigenic factor. Therefore, we investigated the involvement of endozepines in brain glucose sensing. First, we showed that intracerebroventricular administration of glucose in rats increases DBI expression in hypothalamic glial-like tanycytes. We then demonstrated that glucose stimulates endozepine secretion from hypothalamic explants. Feeding experiments indicate that the anorexigenic effect of central administration of glucose was blunted by coinjection of an ODN antagonist. Conversely, the hyperphagic response elicited by central glucoprivation was suppressed by an ODN agonist. The anorexigenic effects of centrally injected glucose or ODN agonist were suppressed by blockade of the melanocortin-3/4 receptors, suggesting that glucose sensing involves endozepinergic control of the melanocortin pathway. Finally, we found that brain endozepines modulate blood glucose levels, suggesting their involvement in a feedback loop controlling whole-body glucose homeostasis. Collectively, these data indicate that endozepines are a critical relay in brain glucose sensing and potentially new targets in treatment of metabolic disorders.
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Affiliation(s)
- Damien Lanfray
- INSERM U982, DC2N Laboratory of Neuronal and Neuroendocrine Cell Differentiation and Communication, Mont-Saint-Aignan, France
- Institute for Biomedical Research and Innovation, Regional Platform for Cell Imaging (PRIMACEN), Rouen, France
- University of Rouen, Mont-Saint-Aignan, France
| | - Sébastien Arthaud
- Institute for Biomedical Research and Innovation, Regional Platform for Cell Imaging (PRIMACEN), Rouen, France
- University of Rouen, Mont-Saint-Aignan, France
- Centre National de la Recherche Scientifique Unité Mixte de Recherche 5167, University Claude Bernard Lyon 1, Lyon, France
| | - Johanne Ouellet
- Research Center in Molecular Endocrinology, Oncology and Human Genomics, Laval University, Quebec, Quebec, Canada
| | - Vincent Compère
- INSERM U982, DC2N Laboratory of Neuronal and Neuroendocrine Cell Differentiation and Communication, Mont-Saint-Aignan, France
- Institute for Biomedical Research and Innovation, Regional Platform for Cell Imaging (PRIMACEN), Rouen, France
- University of Rouen, Mont-Saint-Aignan, France
- Department of Anaesthesiology and Critical Care, Rouen University Hospital, Rouen, France
| | - Jean-Luc Do Rego
- INSERM U982, DC2N Laboratory of Neuronal and Neuroendocrine Cell Differentiation and Communication, Mont-Saint-Aignan, France
- Institute for Biomedical Research and Innovation, Regional Platform for Cell Imaging (PRIMACEN), Rouen, France
- University of Rouen, Mont-Saint-Aignan, France
| | - Jérôme Leprince
- INSERM U982, DC2N Laboratory of Neuronal and Neuroendocrine Cell Differentiation and Communication, Mont-Saint-Aignan, France
- Institute for Biomedical Research and Innovation, Regional Platform for Cell Imaging (PRIMACEN), Rouen, France
- University of Rouen, Mont-Saint-Aignan, France
| | - Benjamin Lefranc
- Institute for Biomedical Research and Innovation, Regional Platform for Cell Imaging (PRIMACEN), Rouen, France
- University of Rouen, Mont-Saint-Aignan, France
| | - Hélène Castel
- INSERM U982, DC2N Laboratory of Neuronal and Neuroendocrine Cell Differentiation and Communication, Mont-Saint-Aignan, France
- Institute for Biomedical Research and Innovation, Regional Platform for Cell Imaging (PRIMACEN), Rouen, France
- University of Rouen, Mont-Saint-Aignan, France
| | - Cynthia Bouchard
- Centre de Recherche de l’Institut Universitaire de Cardiologie et Pneumologie de Québec, Laval University, Quebec, Quebec, Canada
| | - Boris Monge-Roffarello
- Centre de Recherche de l’Institut Universitaire de Cardiologie et Pneumologie de Québec, Laval University, Quebec, Quebec, Canada
| | - Denis Richard
- Centre de Recherche de l’Institut Universitaire de Cardiologie et Pneumologie de Québec, Laval University, Quebec, Quebec, Canada
| | - Georges Pelletier
- Research Center in Molecular Endocrinology, Oncology and Human Genomics, Laval University, Quebec, Quebec, Canada
| | - Hubert Vaudry
- INSERM U982, DC2N Laboratory of Neuronal and Neuroendocrine Cell Differentiation and Communication, Mont-Saint-Aignan, France
- Institute for Biomedical Research and Innovation, Regional Platform for Cell Imaging (PRIMACEN), Rouen, France
- University of Rouen, Mont-Saint-Aignan, France
- Research Center in Molecular Endocrinology, Oncology and Human Genomics, Laval University, Quebec, Quebec, Canada
| | - Marie-Christine Tonon
- INSERM U982, DC2N Laboratory of Neuronal and Neuroendocrine Cell Differentiation and Communication, Mont-Saint-Aignan, France
- Institute for Biomedical Research and Innovation, Regional Platform for Cell Imaging (PRIMACEN), Rouen, France
- University of Rouen, Mont-Saint-Aignan, France
- Corresponding author: Marie-Christine Tonon, , or Fabrice Morin,
| | - Fabrice Morin
- INSERM U982, DC2N Laboratory of Neuronal and Neuroendocrine Cell Differentiation and Communication, Mont-Saint-Aignan, France
- Institute for Biomedical Research and Innovation, Regional Platform for Cell Imaging (PRIMACEN), Rouen, France
- University of Rouen, Mont-Saint-Aignan, France
- Corresponding author: Marie-Christine Tonon, , or Fabrice Morin,
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Moreno C, Yang L, Dacks P, Isoda F, Poplawski M, Mobbs CV. Regulation of peripheral metabolism by substrate partitioning in the brain. Endocrinol Metab Clin North Am 2013; 42:67-80. [PMID: 23391240 PMCID: PMC4501378 DOI: 10.1016/j.ecl.2012.11.007] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
All organisms must adapt to changing nutrient availability, with nutrient surplus promoting glucose metabolism and nutrient deficit promoting alternative fuels (in mammals, mainly free fatty acids). A major function of glucose-sensing neurons in the hypothalamus is to regulate blood glucose. When these neurons sense glucose levels are too low, they activate robust counterregulatory responses to enhance glucose production, primarily from liver, and reduce peripheral metabolism. Some hypothalamic neurons can metabolize free fatty acids via β-oxidation, and β-oxidation generally opposes effects of glucose on hypothalamic neurons. Thus hypothalamic β-oxidation promotes obese phenotypes, including enhanced hepatic glucose output.
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Affiliation(s)
- Cesar Moreno
- Department of Neuroscience, Mount Sinai School of Medicine, 1 Gustave Levy Pl., New York, NY 10029, Phone: 212 659 5911,
| | - Linda Yang
- Harvard Medical School, Beth Israel Deaconess Medical Center,
| | - Penny Dacks
- Alzheimer's Drug Discovery Foundation, Aging & Alzheimer's Disease Prevention, New York, NY 10019,
| | - Fumiko Isoda
- Department of Neuroscience, Mount Sinai School of Medicine, 1 Gustave Levy Pl., New York, NY 10029, Phone: 212 659 5911,
| | - Michael Poplawski
- Department of Neuroscience, New York, NY 10029, Phone: 212 659 5929,
| | - Charles V. Mobbs
- Department of Neuroscience, Mount Sinai School of Medicine, 1 Gustave Levy Pl., New York, NY 10029
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Ozaki T, Mohammad S, Morioka E, Takiguchi S, Ikeda M. Infant satiety depends on transient expression of cholecystokinin-1 receptors on ependymal cells lining the third ventricle in mice. J Physiol 2012; 591:1295-312. [PMID: 23266937 DOI: 10.1113/jphysiol.2012.247676] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023] Open
Abstract
Cholecystokinin (CCK) is a hypothetical controller for suckling and infancy body weight, although the underlying mechanisms remain unclear. Therefore, the present study analysed the mechanisms using mice lacking the CCK-1 receptor (CCK1R-/-). Although CCK1R-/- mice displayed normal weights at birth and adulthood, CCK1R-/- pups had enlarged adipocytes and were overweight from the first to second week after birth, regardless of maternal genotype. The lacZ reporter gene assay and/or calcium imaging analysis demonstrated that CCK-1 receptors were abundant in satiety-controlling regions such as the hypothalamus, brainstem, nodose ganglion and pylorus in adults, whereas these signals were few to lacking at pre-weanling stages. At postnatal day (PD) 6, the increase in cFos expression in the medullary nucleus tractus solitarius was similarly triggered by gastrointestinal milk- or saline filling in both genotypes, further indicating immature CCK-1 receptor function in an ascending satiety-controlling system during infancy. Conversely, third ventricle ependymal tanycyte-like cells expressed CCK-1 receptors with expression peaking at PD6. At PD6, wild-type but not CCK1R-/- mice had increased cFos immunoreactivity in ependymal cells following gastrointestinal milk filling whereas the response became negligible at PD12. In addition, ependymal cFos was not increased by saline filling, indicating that these responses are dependent on CCK-1 receptors, developmental stage and nutrients. Furthermore, body weights of wild-type pups were transiently increased by blocking ependymal CCK receptor function with microinjection of a CCK-1 antagonist, but not a CCK-2 antagonist. Hence, we demonstrate de novo functions of ependymal CCK-1 receptors and reveal a new aspect of infant satiety-controlling mechanisms.
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Affiliation(s)
- Tomoya Ozaki
- 1Graduate School of Innovative Life Science, University of Toyama, 3190 Gofuku, Toyama 930-8555, Japan
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45
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Routh VH, Donovan CM, Ritter S. 2. Hypoglycemia Detection. TRANSLATIONAL ENDOCRINOLOGY & METABOLISM 2012; 3:47-87. [PMID: 24910721 PMCID: PMC4045627 DOI: 10.1210/team.9781936704200.ch2] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
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Blouet C, Schwartz GJ. Brainstem nutrient sensing in the nucleus of the solitary tract inhibits feeding. Cell Metab 2012; 16:579-87. [PMID: 23123165 PMCID: PMC3537851 DOI: 10.1016/j.cmet.2012.10.003] [Citation(s) in RCA: 97] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/06/2012] [Revised: 08/23/2012] [Accepted: 10/09/2012] [Indexed: 01/16/2023]
Abstract
Direct detection of circulating nutrients by the central nervous system has been implicated in the regulation of energy balance, and the mediobasal hypothalamus is considered as the primary sensing site mediating these effects. Neurons sensitive to energyrelated signals have also been identified outside the hypothalamus, particularly within the caudomedial nucleus of the solitary tract (cmNTS) in brainstem, but the consequences of direct cmNTS nutrient detection on energy balance remain poorly characterized. Here we determined the behavioral and metabolic consequences of direct L-leucine detection by the cmNTS and investigated the intracellular signaling and neurochemical pathways implicated in cmNTS L-leucine sensing in rats. Our results support the distributed nature of central nutrient detection, evidence a role for the cmNTS S6K1 pathway in the regulation of meal size and body weight, and suggest that the cmNTS integrates direct cmNTS nutrient detection with gut-derived, descending forebrain, and adiposity signals of energy availability to regulate food intake.
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Affiliation(s)
- Clemence Blouet
- Department of Medicine, Diabetes Research Center, Albert Einstein College of Medicine, Bronx, NY 10461, USA
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García-Cáceres C, Fuente-Martín E, Argente J, Chowen JA. Emerging role of glial cells in the control of body weight. Mol Metab 2012; 1:37-46. [PMID: 24024117 DOI: 10.1016/j.molmet.2012.07.001] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/30/2012] [Revised: 07/09/2012] [Accepted: 07/09/2012] [Indexed: 12/18/2022] Open
Abstract
Glia are the most abundant cell type in the brain and are indispensible for the normal execution of neuronal actions. They protect neurons from noxious insults and modulate synaptic transmission through affectation of synaptic inputs, release of glial transmitters and uptake of neurotransmitters from the synaptic cleft. They also transport nutrients and other circulating factors into the brain thus controlling the energy sources and signals reaching neurons. Moreover, glia express receptors for metabolic hormones, such as leptin and insulin, and can be activated in response to increased weight gain and dietary challenges. However, chronic glial activation can be detrimental to neurons, with hypothalamic astrocyte activation or gliosis suggested to be involved in the perpetuation of obesity and the onset of secondary complications. It is now accepted that glia may be a very important participant in metabolic control and a possible therapeutical target. Here we briefly review this rapidly advancing field.
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Affiliation(s)
- Cristina García-Cáceres
- Institute of Diabetes and Obesity, Helmholtz Center Munich, German Research Center for Environmental Health (GmbH), Munich, Germany ; CIBER de Fisiopatología de Obesidad y Nutrición, Instituto de Salud Carlos III, Madrid, Spain
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Steinman MQ, Knight JA, Trainor BC. Effects of photoperiod and food restriction on the reproductive physiology of female California mice. Gen Comp Endocrinol 2012; 176:391-9. [PMID: 22245263 PMCID: PMC3334427 DOI: 10.1016/j.ygcen.2011.12.035] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/01/2011] [Revised: 12/24/2011] [Accepted: 12/27/2011] [Indexed: 12/21/2022]
Abstract
Many temperate-zone animals use changes in photoperiod to time breeding. Shorter term cues, like food availability, are integrated with photoperiod to adjust reproductive timing under unexpected conditions. Many mice of the genus Peromyscus breed in the summer. California mice (Peromyscus californicus), however, can breed year round, but tend to begin breeding in the winter. Glial cells may be involved in transduction of environmental signals that regulate gonadotrophin releasing hormone I (GnRH) activity. We examined the effects of diet and photoperiod on reproduction in female California mice. Mice placed on either short days (8L:16D) or long days (16L:8D) were food restricted (80% of normal intake) or fed ad libitum. Short day-food restricted mice showed significant regression of the reproductive system. GnRH-immunoreactivity was increased in the tuberal hypothalamus of long day-food restricted mice. This may be associated with the sparing effect long days have when mice are food restricted. The number of GFAP-immunoreactive fibers in proximity to GnRH nerve terminals correlated negatively with uterine size in ad libitum but not food restricted mice, suggesting diet may alter glial regulation of the reproductive axis. There was a trend towards food restriction increasing uterine expression of c-fos mRNA, an estrogen dependent gene. Similar to other seasonally breeding rodents, short days render the reproductive system of female California mice more susceptible to effects of food restriction. This may be vestigial, or it may have evolved to mitigate consequences of unexpectedly poor winter food supplies.
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Affiliation(s)
- Michael Q Steinman
- Molecular, Cellular and Integrative Physiology Graduate Group, University of California, Davis, CA 95616, USA.
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Bechtold DA, Sidibe A, Saer BRC, Li J, Hand LE, Ivanova EA, Darras VM, Dam J, Jockers R, Luckman SM, Loudon ASI. A role for the melatonin-related receptor GPR50 in leptin signaling, adaptive thermogenesis, and torpor. Curr Biol 2011; 22:70-7. [PMID: 22197240 DOI: 10.1016/j.cub.2011.11.043] [Citation(s) in RCA: 79] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2011] [Revised: 11/03/2011] [Accepted: 11/21/2011] [Indexed: 12/21/2022]
Abstract
The ability of mammals to maintain a constant body temperature has proven to be a profound evolutionary advantage, allowing members of this class to thrive in most environments on earth. Intriguingly, some mammals employ bouts of deep hypothermia (torpor) to cope with reduced food supply and harsh climates [1, 2]. During torpor, physiological processes such as respiration, cardiac function, and metabolic rate are severely depressed, yet the neural mechanisms that regulate torpor remain unclear [3]. Hypothalamic responses to energy signals, such as leptin, influence the expression of torpor [4-7]. We show that the orphan receptor GPR50 plays an important role in adaptive thermogenesis and torpor. Unlike wild-type mice, Gpr50(-/-) mice readily enter torpor in response to fasting and 2-deoxyglucose administration. Decreased thermogenesis in Gpr50(-/-) mice is not due to a deficit in brown adipose tissue, the principal site of nonshivering thermogenesis in mice [8]. GPR50 is highly expressed in the hypothalamus of several species, including man [9, 10]. In line with this, altered thermoregulation in Gpr50(-/-) mice is associated with attenuated responses to leptin and a suppression of thyrotropin-releasing hormone. Thus, our findings identify hypothalamic circuits involved in torpor and reveal GPR50 to be a novel component of adaptive thermogenesis in mammals.
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Kim HK, Shin MS, Youn BS, Namkoong C, Gil SY, Kang GM, Yu JH, Kim MS. Involvement of progranulin in hypothalamic glucose sensing and feeding regulation. Endocrinology 2011; 152:4672-82. [PMID: 21933869 DOI: 10.1210/en.2011-1221] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Progranulin (PGRN) is a secreted glycoprotein with multiple biological functions, including modulation of wound healing and inflammation. Hypothalamic PGRN has been implicated in the development of sexual dimorphism. In the present study, a potential role for PGRN in the hypothalamic regulation of appetite and body weight was investigated. In adult rodents, PGRN was highly expressed in periventricular tanycytes and in hypothalamic neurons, which are known to contain glucose-sensing machinery. Hypothalamic PGRN expression levels were decreased under low-energy conditions (starvation and 2-deoxy-D-glucose administration) but increased under high-energy condition (postprandially). Intracerebrovetricular administration of PGRN significantly suppressed nocturnal feeding as well as hyperphagia induced by 2-deoxyglucose, neuropeptide Y, and Agouti-related peptide. Moreover, the inhibition of hypothalamic PGRN expression or action increased food intake and promoted weight gain, suggesting that endogenous PGRN functions as an appetite suppressor in the hypothalamus. Investigation of the mechanism of action revealed that PGRN diminished orexigenic neuropeptide Y and Agouti-related peptide production but stimulated anorexigenic proopiomelanocortin production, at least in part through the regulation of hypothalamic AMP-activated protein kinase. Notably, PGRN was also expressed in hypothalamic microglia. In diet-induced obese mice, microglial PGRN expression was increased, and the anorectic response to PGRN was blunted. These findings highlight a physiological role for PGRN in hypothalamic glucose-sensing and appetite regulation. Alterations in hypothalamic PGRN production or action may be linked to appetite dysregulation in obesity.
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Affiliation(s)
- Hyun-Kyong Kim
- Appetite Regulation Laboratory, Asan Institute for Life Sciences, University of Ulsan College of Medicine, Pungnap-dong, Songpa-ku, Seoul 138-736, Korea
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