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López-Gambero AJ, Martínez F, Salazar K, Cifuentes M, Nualart F. Brain Glucose-Sensing Mechanism and Energy Homeostasis. Mol Neurobiol 2018; 56:769-796. [PMID: 29796992 DOI: 10.1007/s12035-018-1099-4] [Citation(s) in RCA: 72] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2018] [Accepted: 04/25/2018] [Indexed: 01/02/2023]
Abstract
The metabolic and energy state of the organism depends largely on the availability of substrates, such as glucose for ATP production, necessary for maintaining physiological functions. Deregulation in glucose levels leads to the appearance of pathological signs that result in failures in the cardiovascular system and various diseases, such as diabetes, obesity, nephropathy, and neuropathy. Particularly, the brain relies on glucose as fuel for the normal development of neuronal activity. Regions adjacent to the cerebral ventricles, such as the hypothalamus and brainstem, exercise central control in energy homeostasis. These centers house nuclei of neurons whose excitatory activity is sensitive to changes in glucose levels. Determining the different detection mechanisms, the phenotype of neurosecretion, and neural connections involving glucose-sensitive neurons is essential to understanding the response to hypoglycemia through modulation of food intake, thermogenesis, and activation of sympathetic and parasympathetic branches, inducing glucagon and epinephrine secretion and other hypothalamic-pituitary axis-dependent counterregulatory hormones, such as glucocorticoids and growth hormone. The aim of this review focuses on integrating the current understanding of various glucose-sensing mechanisms described in the brain, thereby establishing a relationship between neuroanatomy and control of physiological processes involved in both metabolic and energy balance. This will advance the understanding of increasingly prevalent diseases in the modern world, especially diabetes, and emphasize patterns that regulate and stimulate intake, thermogenesis, and the overall synergistic effect of the neuroendocrine system.
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Affiliation(s)
- A J López-Gambero
- Laboratory of Neurobiology and Stem Cells NeuroCellT, Department of Cellular Biology, Center for Advanced Microscopy CMA BIO BIO, Faculty of Biological Sciences, University of Concepcion, Concepcion, Chile.,Department of Cell Biology, Genetics and Physiology, University of Malaga, IBIMA, BIONAND, Andalusian Center for Nanomedicine and Biotechnology and Networking Research Center on Bioengineering, Biomaterials and Nanomedicine, Málaga, Spain
| | - F Martínez
- Laboratory of Neurobiology and Stem Cells NeuroCellT, Department of Cellular Biology, Center for Advanced Microscopy CMA BIO BIO, Faculty of Biological Sciences, University of Concepcion, Concepcion, Chile
| | - K Salazar
- Laboratory of Neurobiology and Stem Cells NeuroCellT, Department of Cellular Biology, Center for Advanced Microscopy CMA BIO BIO, Faculty of Biological Sciences, University of Concepcion, Concepcion, Chile
| | - M Cifuentes
- Department of Cell Biology, Genetics and Physiology, University of Malaga, IBIMA, BIONAND, Andalusian Center for Nanomedicine and Biotechnology and Networking Research Center on Bioengineering, Biomaterials and Nanomedicine, Málaga, Spain.
| | - F Nualart
- Laboratory of Neurobiology and Stem Cells NeuroCellT, Department of Cellular Biology, Center for Advanced Microscopy CMA BIO BIO, Faculty of Biological Sciences, University of Concepcion, Concepcion, Chile. .,Departamento de Biología Celular, Facultad de Ciencias Biológicas, Universidad de Concepción, Casilla 160-C, Concepción, Chile.
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52
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Yasumoto Y, Miyazaki H, Ogata M, Kagawa Y, Yamamoto Y, Islam A, Yamada T, Katagiri H, Owada Y. Glial Fatty Acid-Binding Protein 7 (FABP7) Regulates Neuronal Leptin Sensitivity in the Hypothalamic Arcuate Nucleus. Mol Neurobiol 2018; 55:9016-9028. [PMID: 29623545 DOI: 10.1007/s12035-018-1033-9] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2017] [Accepted: 03/23/2018] [Indexed: 10/17/2022]
Abstract
The hypothalamus is involved in the regulation of food intake and energy homeostasis. The arcuate nucleus (ARC) and median eminence (ME) are the primary hypothalamic sites that sense leptin and nutrients in the blood, thereby mediating food intake. Recently, studies demonstrating a role for non-neuronal cell types, including astrocytes and tanycytes, in these regulatory processes have begun to emerge. However, the molecular mechanisms involved in these activities remain largely unknown. In this study, we examined in detail the localization of fatty acid-binding protein 7 (FABP7) in the hypothalamic ARC and sought to determine its role in the hypothalamus. We performed a phenotypic analysis of diet-induced FABP7 knockout (KO) obese mice and of FABP7 KO mice treated with a single leptin injection. Immunohistochemistry revealed that FABP7+ cells are NG2+ or GFAP+ in the ARC and ME. In mice fed a high-fat diet, weight gain and food intake were lower in FABP7 KO mice than in wild-type (WT) mice. FABP7 KO mice also had lower food intake and weight gain after a single injection of leptin, and we consistently confirmed that the number of pSTAT3+ cells in the ARC indicated that the leptin-induced activation of neurons was significantly more frequent in FABP7 KO mice than in WT mice. In FABP7 KO mice-derived primary astrocyte cultures, the level of ERK phosphorylation was lower after leptin treatment. Collectively, these results indicate that in hypothalamic astrocytes, FABP7 might be involved in sensing neuronal leptin via glia-mediated mechanisms and plays a pivotal role in controlling systemic energy homeostasis.
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Affiliation(s)
- Yuki Yasumoto
- Department of Organ Anatomy, Tohoku University Graduate School of Medicine, 2-1, Seiryo-machi, Aoba-ku, Sendai, Miyagi, 980-8575, Japan.
| | - Hirofumi Miyazaki
- Department of Organ Anatomy, Tohoku University Graduate School of Medicine, 2-1, Seiryo-machi, Aoba-ku, Sendai, Miyagi, 980-8575, Japan
| | - Masaki Ogata
- Department of Organ Anatomy, Tohoku University Graduate School of Medicine, 2-1, Seiryo-machi, Aoba-ku, Sendai, Miyagi, 980-8575, Japan
| | - Yoshiteru Kagawa
- Department of Organ Anatomy, Tohoku University Graduate School of Medicine, 2-1, Seiryo-machi, Aoba-ku, Sendai, Miyagi, 980-8575, Japan
| | - Yui Yamamoto
- Department of Organ Anatomy, Tohoku University Graduate School of Medicine, 2-1, Seiryo-machi, Aoba-ku, Sendai, Miyagi, 980-8575, Japan
| | - Ariful Islam
- Department of Organ Anatomy, Tohoku University Graduate School of Medicine, 2-1, Seiryo-machi, Aoba-ku, Sendai, Miyagi, 980-8575, Japan
| | - Tetsuya Yamada
- Department of Metabolism and Diabetes, Tohoku University Graduate School of Medicine, 2-1, Seiryo-machi, Aoba-ku, Sendai, Miyagi, 980-8575, Japan
| | - Hideki Katagiri
- Department of Metabolism and Diabetes, Tohoku University Graduate School of Medicine, 2-1, Seiryo-machi, Aoba-ku, Sendai, Miyagi, 980-8575, Japan
| | - Yuji Owada
- Department of Organ Anatomy, Tohoku University Graduate School of Medicine, 2-1, Seiryo-machi, Aoba-ku, Sendai, Miyagi, 980-8575, Japan.
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53
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Heeley N, Kirwan P, Darwish T, Arnaud M, Evans ML, Merkle FT, Reimann F, Gribble FM, Blouet C. Rapid sensing of l-leucine by human and murine hypothalamic neurons: Neurochemical and mechanistic insights. Mol Metab 2018; 10:14-27. [PMID: 29439854 PMCID: PMC5985239 DOI: 10.1016/j.molmet.2018.01.021] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/05/2018] [Revised: 01/24/2018] [Accepted: 01/29/2018] [Indexed: 11/27/2022] Open
Abstract
Objective Dietary proteins are sensed by hypothalamic neurons and strongly influence multiple aspects of metabolic health, including appetite, weight gain, and adiposity. However, little is known about the mechanisms by which hypothalamic neural circuits controlling behavior and metabolism sense protein availability. The aim of this study is to characterize how neurons from the mediobasal hypothalamus respond to a signal of protein availability: the amino acid l-leucine. Methods We used primary cultures of post-weaning murine mediobasal hypothalamic neurons, hypothalamic neurons derived from human induced pluripotent stem cells, and calcium imaging to characterize rapid neuronal responses to physiological changes in extracellular l-Leucine concentration. Results A neurochemically diverse subset of both mouse and human hypothalamic neurons responded rapidly to l-leucine. Consistent with l-leucine's anorexigenic role, we found that 25% of mouse MBH POMC neurons were activated by l-leucine. 10% of MBH NPY neurons were inhibited by l-leucine, and leucine rapidly reduced AGRP secretion, providing a mechanism for the rapid leucine-induced inhibition of foraging behavior in rodents. Surprisingly, none of the candidate mechanisms previously implicated in hypothalamic leucine sensing (KATP channels, mTORC1 signaling, amino-acid decarboxylation) were involved in the acute activity changes produced by l-leucine. Instead, our data indicate that leucine-induced neuronal activation involves a plasma membrane Ca2+ channel, whereas leucine-induced neuronal inhibition is mediated by inhibition of a store-operated Ca2+ current. Conclusions A subset of neurons in the mediobasal hypothalamus rapidly respond to physiological changes in extracellular leucine concentration. Leucine can produce both increases and decreases in neuronal Ca2+ concentrations in a neurochemically-diverse group of neurons, including some POMC and NPY/AGRP neurons. Our data reveal that leucine can signal through novel mechanisms to rapidly affect neuronal activity. A neurochemically diverse group of mouse and human hypothalamic neurons rapidly sense and respond to l-leucine. Leucine can produce neuronal activation or neuronal inhibition via distinct and novel Ca2+ signaling mechanisms. Leucine activates 25% ARH POMC neurons. Leucine inhibits 10% ARH NPY/AGRP neurons and reduces AGRP secretion from fasted mediobasal hypothalamic slices.
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Affiliation(s)
- Nicholas Heeley
- MRC Metabolic Diseases Unit, University of Cambridge Metabolic Research Laboratories, WT-MRC Institute of Metabolic Science, University of Cambridge, Cambridge CB2 OQQ, UK
| | - Peter Kirwan
- MRC Metabolic Diseases Unit, University of Cambridge Metabolic Research Laboratories, WT-MRC Institute of Metabolic Science, University of Cambridge, Cambridge CB2 OQQ, UK
| | - Tamana Darwish
- MRC Metabolic Diseases Unit, University of Cambridge Metabolic Research Laboratories, WT-MRC Institute of Metabolic Science, University of Cambridge, Cambridge CB2 OQQ, UK
| | - Marion Arnaud
- MRC Metabolic Diseases Unit, University of Cambridge Metabolic Research Laboratories, WT-MRC Institute of Metabolic Science, University of Cambridge, Cambridge CB2 OQQ, UK
| | - Mark L Evans
- MRC Metabolic Diseases Unit, University of Cambridge Metabolic Research Laboratories, WT-MRC Institute of Metabolic Science, University of Cambridge, Cambridge CB2 OQQ, UK
| | - Florian T Merkle
- MRC Metabolic Diseases Unit, University of Cambridge Metabolic Research Laboratories, WT-MRC Institute of Metabolic Science, University of Cambridge, Cambridge CB2 OQQ, UK
| | - Frank Reimann
- MRC Metabolic Diseases Unit, University of Cambridge Metabolic Research Laboratories, WT-MRC Institute of Metabolic Science, University of Cambridge, Cambridge CB2 OQQ, UK
| | - Fiona M Gribble
- MRC Metabolic Diseases Unit, University of Cambridge Metabolic Research Laboratories, WT-MRC Institute of Metabolic Science, University of Cambridge, Cambridge CB2 OQQ, UK
| | - Clemence Blouet
- MRC Metabolic Diseases Unit, University of Cambridge Metabolic Research Laboratories, WT-MRC Institute of Metabolic Science, University of Cambridge, Cambridge CB2 OQQ, UK.
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54
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Szabó I, Hormay E, Csetényi B, Nagy B, Lénárd L, Karádi Z. Multiple functional attributes of glucose-monitoring neurons in the medial orbitofrontal (ventrolateral prefrontal) cortex. Neurosci Biobehav Rev 2018; 85:44-53. [DOI: 10.1016/j.neubiorev.2017.04.024] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2017] [Revised: 04/11/2017] [Accepted: 04/21/2017] [Indexed: 11/28/2022]
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55
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Khodai T, Nunn N, Worth AA, Feetham CH, Belle MDC, Piggins HD, Luckman SM. PACAP Neurons in the Ventromedial Hypothalamic Nucleus Are Glucose Inhibited and Their Selective Activation Induces Hyperglycaemia. Front Endocrinol (Lausanne) 2018; 9:632. [PMID: 30425681 PMCID: PMC6218416 DOI: 10.3389/fendo.2018.00632] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/25/2018] [Accepted: 10/05/2018] [Indexed: 01/22/2023] Open
Abstract
Background: Glucose-sensing neurons are located in several parts of the brain, but are concentrated in the ventromedial nucleus of the hypothalamus (VMH). The importance of these VMH neurons in glucose homeostasis is well-established, however, little is known about their individual identity. In the present study, we identified a distinct glucose-sensing population in the VMH and explored its place in the glucose-regulatory network. Methods: Using patch-clamp electrophysiology on Pacap-cre::EYFP cells, we explored the glucose-sensing ability of the pituitary adenylate cyclase-activating peptide (PACAP) neurons both inside and outside the VMH. We also mapped the efferent projections of these neurons using anterograde and retrograde tracing techniques. Finally, to test the functionality of PACAPVMH in vivo, we used DREADD technology and measured systemic responses. Results: We demonstrate that PACAP neurons inside (PACAPVMH), but not outside the VMH are intrinsically glucose inhibited (GI). Anatomical tracing techniques show that PACAPVMH neurons project to several areas that can influence autonomic output. In vivo, chemogenetic stimulation of these neurons inhibits insulin secretion leading to reduced glucose tolerance, implicating their role in systemic glucose regulation. Conclusion: These findings are important as they identify, for the first time, a specific VMH neuronal population involved in glucose homeostasis. Identifying the different glucose-sensing populations in the VMH will help piece together the different arms of glucose regulation providing vital information regarding central responses to glucose metabolic disorders including hypoglycaemia.
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Affiliation(s)
- Tansi Khodai
- Faculty of Biology, Medicine and Health, University of Manchester, Manchester, United Kingdom
| | - Nicolas Nunn
- Faculty of Biology, Medicine and Health, University of Manchester, Manchester, United Kingdom
| | - Amy A. Worth
- Faculty of Biology, Medicine and Health, University of Manchester, Manchester, United Kingdom
| | - Claire H. Feetham
- Faculty of Biology, Medicine and Health, University of Manchester, Manchester, United Kingdom
| | | | - Hugh D. Piggins
- Faculty of Biology, Medicine and Health, University of Manchester, Manchester, United Kingdom
| | - Simon M. Luckman
- Faculty of Biology, Medicine and Health, University of Manchester, Manchester, United Kingdom
- *Correspondence: Simon M. Luckman
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56
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Koekkoek LL, Mul JD, la Fleur SE. Glucose-Sensing in the Reward System. Front Neurosci 2017; 11:716. [PMID: 29311793 PMCID: PMC5742113 DOI: 10.3389/fnins.2017.00716] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2017] [Accepted: 12/07/2017] [Indexed: 01/14/2023] Open
Abstract
Glucose-sensing neurons are neurons that alter their activity in response to changes in extracellular glucose. These neurons, which are an important mechanism the brain uses to monitor changes in glycaemia, are present in the hypothalamus, where they have been thoroughly investigated. Recently, glucose-sensing neurons have also been identified in brain nuclei which are part of the reward system. However, little is known about the molecular mechanisms by which they function, and their role in the reward system. We therefore aim to provide an overview of molecular mechanisms that have been studied in the hypothalamic glucose-sensing neurons, and investigate which of these transporters, enzymes and channels are present in the reward system. Furthermore, we speculate about the role of glucose-sensing neurons in the reward system.
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Affiliation(s)
- Laura L Koekkoek
- Department of Endocrinology and Metabolism, Academic Medical Center, University of Amsterdam, Amsterdam, Netherlands.,Laboratory of Endocrinology, Department of Clinical Chemistry, Academic Medical Center, University of Amsterdam, Amsterdam, Netherlands.,Metabolism and Reward Group, Netherlands Institute for Neuroscience, Institute of the Royal Netherlands Academy of Arts and Sciences (KNAW), Amsterdam, Netherlands
| | - Joram D Mul
- Department of Endocrinology and Metabolism, Academic Medical Center, University of Amsterdam, Amsterdam, Netherlands.,Laboratory of Endocrinology, Department of Clinical Chemistry, Academic Medical Center, University of Amsterdam, Amsterdam, Netherlands.,Metabolism and Reward Group, Netherlands Institute for Neuroscience, Institute of the Royal Netherlands Academy of Arts and Sciences (KNAW), Amsterdam, Netherlands
| | - Susanne E la Fleur
- Department of Endocrinology and Metabolism, Academic Medical Center, University of Amsterdam, Amsterdam, Netherlands.,Laboratory of Endocrinology, Department of Clinical Chemistry, Academic Medical Center, University of Amsterdam, Amsterdam, Netherlands.,Metabolism and Reward Group, Netherlands Institute for Neuroscience, Institute of the Royal Netherlands Academy of Arts and Sciences (KNAW), Amsterdam, Netherlands
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57
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Fioramonti X, Chrétien C, Leloup C, Pénicaud L. Recent Advances in the Cellular and Molecular Mechanisms of Hypothalamic Neuronal Glucose Detection. Front Physiol 2017; 8:875. [PMID: 29184506 PMCID: PMC5694446 DOI: 10.3389/fphys.2017.00875] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2017] [Accepted: 10/18/2017] [Indexed: 11/18/2022] Open
Abstract
The hypothalamus have been recognized for decades as one of the major brain centers for the control of energy homeostasis. This area contains specialized neurons able to detect changes in nutrients level. Among them, glucose-sensing neurons use glucose as a signaling molecule in addition to its fueling role. In this review we will describe the different sub-populations of glucose-sensing neurons present in the hypothalamus and highlight their nature in terms of neurotransmitter/neuropeptide expression. This review will particularly discuss whether pro-opiomelanocortin (POMC) neurons from the arcuate nucleus are directly glucose-sensing. In addition, recent observations in glucose-sensing suggest a subtle system with different mechanisms involved in the detection of changes in glucose level and their involvement in specific physiological functions. Several data point out the critical role of reactive oxygen species (ROS) and mitochondria dynamics in the detection of increased glucose. This review will also highlight that ATP-dependent potassium (KATP) channels are not the only channels mediating glucose-sensing and discuss the new role of transient receptor potential canonical channels (TRPC). We will discuss the recent advances in the determination of glucose-sensing machinery and propose potential line of research needed to further understand the regulation of brain glucose detection.
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Affiliation(s)
- Xavier Fioramonti
- NutriNeuro, Institut National de la Recherche Agronomique, Université de Bordeaux, Bordeaux, France.,Centre des Sciences du Goût et de l'Alimentation, Centre National de la Recherche Scientifique, Institut National de la Recherche Agronomique, Université Bourgogne Franche-Comté, Dijon, France
| | - Chloé Chrétien
- Centre des Sciences du Goût et de l'Alimentation, Centre National de la Recherche Scientifique, Institut National de la Recherche Agronomique, Université Bourgogne Franche-Comté, Dijon, France
| | - Corinne Leloup
- Centre des Sciences du Goût et de l'Alimentation, Centre National de la Recherche Scientifique, Institut National de la Recherche Agronomique, Université Bourgogne Franche-Comté, Dijon, France
| | - Luc Pénicaud
- Centre des Sciences du Goût et de l'Alimentation, Centre National de la Recherche Scientifique, Institut National de la Recherche Agronomique, Université Bourgogne Franche-Comté, Dijon, France.,Stromalab, Centre National de la Recherche Scientifique, Institut National de la Santé et de la Recherche Médicale, Université de Toulouse, Toulouse, France
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58
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Devarakonda K, Stanley S. Investigating metabolic regulation using targeted neuromodulation. Ann N Y Acad Sci 2017; 1411:83-95. [PMID: 29106710 DOI: 10.1111/nyas.13468] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2017] [Revised: 08/11/2017] [Accepted: 08/18/2017] [Indexed: 01/13/2023]
Abstract
The central nervous system (CNS) plays a vital role in regulating energy balance and metabolism. Over the last 50 years, studies in animal models have allowed us to identify critical CNS regions involved in these processes and even crucial cell populations. Now, techniques for genetically and anatomically targeted manipulation of specific neural populations using light (optogenetic), ligands (chemogenetic), or magnetic fields (radiogenetic/magnetogenetic) allow detailed investigation of circuits involved in metabolic regulation. In this review, we provide a brief overview of recent studies using light- and magnetic field-regulated neural activity to investigate the neural circuits contributing to metabolic control.
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Affiliation(s)
- Kavya Devarakonda
- Department of Neuroscience, Icahn School of Medicine at Mount Sinai, New York, New York
| | - Sarah Stanley
- Department of Neuroscience, Icahn School of Medicine at Mount Sinai, New York, New York.,Diabetes, Obesity and Metabolism Institute, Department of Medicine, Icahn School of Medicine at Mount Sinai, New York, New York
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59
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van den Top M, Zhao FY, Viriyapong R, Michael NJ, Munder AC, Pryor JT, Renaud LP, Spanswick D. The impact of ageing, fasting and high-fat diet on central and peripheral glucose tolerance and glucose-sensing neural networks in the arcuate nucleus. J Neuroendocrinol 2017; 29. [PMID: 28834571 DOI: 10.1111/jne.12528] [Citation(s) in RCA: 6] [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: 04/11/2017] [Revised: 08/01/2017] [Accepted: 08/17/2017] [Indexed: 12/14/2022]
Abstract
Obesity and ageing are risk factors for diabetes. In the present study, we investigated the effects of ageing, obesity and fasting on central and peripheral glucose tolerance and on glucose-sensing neuronal function in the arcuate nucleus of rats, with a view to providing insight into the central mechanisms regulating glucose homeostasis and how they change or are subject to dysfunction with ageing and obesity. We show that, following a glucose load, central glucose tolerance at the level of the cerebrospinal fluid (CSF) and plasma is significantly reduced in rats maintained on a high-fat diet (HFD). With ageing, up to 2 years, central glucose tolerance was impaired in an age-dependent manner, whereas peripheral glucose tolerance remained unaffected. Ageing-induced peripheral glucose intolerance was improved by a 24-hour fast, whereas central glucose tolerance was not corrected. Pre-wean, immature animals have elevated basal plasma glucose levels and a delayed increase in central glucose levels following peripheral glucose injection compared to mature animals. Electrophysiological recording techniques revealed an energy-status-dependent role for glucose-excited, inhibited and adapting neurones, along with glucose-induced changes in synaptic transmission. We conclude that ageing affects central glucose tolerance, whereas HFD profoundly affects central and peripheral glucose tolerance and, in addition, glucose-sensing neurones adapt function in an energy-status-dependent manner.
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Affiliation(s)
| | - F-Y Zhao
- NeuroSolutions Ltd, Coventry, UK
| | - R Viriyapong
- Warwick Medical School, University of Warwick, Coventry, UK
- MOAC DTC, University of Warwick, Coventry, UK
| | - N J Michael
- Metabolic Disease and Obesity Program, Biomedicine Discovery Institute, Monash University, Melbourne, VIC, Australia
- Department of Physiology, Monash University, Clayton, VIC, Australia
| | - A C Munder
- Metabolic Disease and Obesity Program, Biomedicine Discovery Institute, Monash University, Melbourne, VIC, Australia
- Department of Physiology, Monash University, Clayton, VIC, Australia
| | - J T Pryor
- Warwick Medical School, University of Warwick, Coventry, UK
- Metabolic Disease and Obesity Program, Biomedicine Discovery Institute, Monash University, Melbourne, VIC, Australia
- Department of Physiology, Monash University, Clayton, VIC, Australia
| | - L P Renaud
- Ottawa Hospital Research Institute, Ottawa Civic Hospital, Ottawa, ON, Canada
| | - D Spanswick
- NeuroSolutions Ltd, Coventry, UK
- Warwick Medical School, University of Warwick, Coventry, UK
- Metabolic Disease and Obesity Program, Biomedicine Discovery Institute, Monash University, Melbourne, VIC, Australia
- Department of Physiology, Monash University, Clayton, VIC, Australia
- Neuroscience Program, Biomedicine Discovery Institute, Monash University, Melbourne, VIC, Australia
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60
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Julliard AK, Al Koborssy D, Fadool DA, Palouzier-Paulignan B. Nutrient Sensing: Another Chemosensitivity of the Olfactory System. Front Physiol 2017; 8:468. [PMID: 28747887 PMCID: PMC5506222 DOI: 10.3389/fphys.2017.00468] [Citation(s) in RCA: 38] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2017] [Accepted: 06/19/2017] [Indexed: 12/31/2022] Open
Abstract
Olfaction is a major sensory modality involved in real time perception of the chemical composition of the external environment. Olfaction favors anticipation and rapid adaptation of behavioral responses necessary for animal survival. Furthermore, recent studies have demonstrated that there is a direct action of metabolic peptides on the olfactory network. Orexigenic peptides such as ghrelin and orexin increase olfactory sensitivity, which in turn, is decreased by anorexigenic hormones such as insulin and leptin. In addition to peptides, nutrients can play a key role on neuronal activity. Very little is known about nutrient sensing in olfactory areas. Nutrients, such as carbohydrates, amino acids, and lipids, could play a key role in modulating olfactory sensitivity to adjust feeding behavior according to metabolic need. Here we summarize recent findings on nutrient-sensing neurons in olfactory areas and delineate the limits of our knowledge on this topic. The present review opens new lines of investigations on the relationship between olfaction and food intake, which could contribute to determining the etiology of metabolic disorders.
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Affiliation(s)
- A-Karyn Julliard
- Univ Lyon, Université Claude Bernard Lyon1, Centre de Recherche en Neurosciences de Lyon (CRNL), INSERM U1028/Centre National de la Recherche Scientifique UMR5292 Team Olfaction: From Coding to MemoryLyon, France
| | - Dolly Al Koborssy
- Department of Biological Science, Florida State UniversityTallahassee, FL, United States.,Program in Neuroscience, Florida State UniversityTallahassee, FL, United States
| | - Debra A Fadool
- Department of Biological Science, Florida State UniversityTallahassee, FL, United States.,Program in Neuroscience, Florida State UniversityTallahassee, FL, United States.,Institute of Molecular Biophysics, Florida State UniversityTallahassee, FL, United States
| | - Brigitte Palouzier-Paulignan
- Univ Lyon, Université Claude Bernard Lyon1, Centre de Recherche en Neurosciences de Lyon (CRNL), INSERM U1028/Centre National de la Recherche Scientifique UMR5292 Team Olfaction: From Coding to MemoryLyon, France
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61
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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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62
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Pozo M, Rodríguez-Rodríguez R, Ramírez S, Seoane-Collazo P, López M, Serra D, Herrero L, Casals N. Hypothalamic Regulation of Liver and Muscle Nutrient Partitioning by Brain-Specific Carnitine Palmitoyltransferase 1C in Male Mice. Endocrinology 2017; 158:2226-2238. [PMID: 28472467 DOI: 10.1210/en.2017-00151] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/10/2017] [Accepted: 04/28/2017] [Indexed: 11/19/2022]
Abstract
Carnitine palmitoyltransferase (CPT) 1C, a brain-specific protein localized in the endoplasmic reticulum of neurons, is expressed in almost all brain regions. Based on global knockout (KO) models, CPT1C has demonstrated relevance in hippocampus-dependent spatial learning and in hypothalamic regulation of energy balance. Specifically, it has been shown that CPT1C is protective against high-fat diet-induced obesity (DIO), and that CPT1C KO mice show reduced peripheral fatty acid oxidation (FAO) during both fasting and DIO. However, the mechanisms mediating CPT1C-dependent regulation of energy homeostasis remain unclear. Here, we focus on the mechanistic understanding of hypothalamic CPT1C on the regulation of fuel selection in liver and muscle of male mice during energy deprivation situations, such as fasting. In CPT1C-deficient mice, modulation of the main hypothalamic energy sensors (5' adenosine monophosphate-activated protein kinase, Sirtuin 1, and mammalian target of rapamycin) was impaired and plasma catecholamine levels were decreased. Consequently, CPT1C-deficient mice presented defective fasting-induced FAO in liver, leading to higher triacylglycerol accumulation and lower glycogen levels. Moreover, muscle pyruvate dehydrogenase activity was increased, which was indicative of glycolysis enhancement. The respiratory quotient did not decrease in CPT1C KO mice after 48 hours of fasting, confirming a defective switch on fuel substrate selection under hypoglycemia. Phenotype reversion studies identified the mediobasal hypothalamus (MBH) as the main area mediating CPT1C effects on fuel selection. Overall, our data demonstrate that CPT1C in the MBH is necessary for proper hypothalamic sensing of a negative energy balance and fuel partitioning in liver and muscle.
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Affiliation(s)
- Macarena Pozo
- Basic Sciences Department, Faculty of Medicine and Health Sciences, Universitat Internacional de Catalunya, 08195 Sant Cugat del Vallès, Barcelona, Spain
| | - Rosalía Rodríguez-Rodríguez
- Basic Sciences Department, Faculty of Medicine and Health Sciences, Universitat Internacional de Catalunya, 08195 Sant Cugat del Vallès, Barcelona, Spain
| | - Sara Ramírez
- Basic Sciences Department, Faculty of Medicine and Health Sciences, Universitat Internacional de Catalunya, 08195 Sant Cugat del Vallès, Barcelona, Spain
| | - Patricia Seoane-Collazo
- NeurObesity Group, Department of Physiology, CIMUS, University of Santiago de Compostela-Instituto de Investigación Sanitaria, 15782 Santiago de Compostela, Spain
| | - Miguel López
- NeurObesity Group, Department of Physiology, CIMUS, University of Santiago de Compostela-Instituto de Investigación Sanitaria, 15782 Santiago de Compostela, Spain
- Centro de Investigación Biomédica en Red de Fisiopatología de la Obesidad y la Nutrición (CIBEROBN), Instituto de Salud Carlos III, 28029 Madrid, Spain
| | - Dolors Serra
- Centro de Investigación Biomédica en Red de Fisiopatología de la Obesidad y la Nutrición (CIBEROBN), Instituto de Salud Carlos III, 28029 Madrid, Spain
- Department of Biochemistry and Physiology, Faculty of Pharmacy, Institut de Biomedicina de la Universitat de Barcelona, Universitat de Barcelona, 08028 Barcelona, Spain
| | - Laura Herrero
- Centro de Investigación Biomédica en Red de Fisiopatología de la Obesidad y la Nutrición (CIBEROBN), Instituto de Salud Carlos III, 28029 Madrid, Spain
- Department of Biochemistry and Physiology, Faculty of Pharmacy, Institut de Biomedicina de la Universitat de Barcelona, Universitat de Barcelona, 08028 Barcelona, Spain
| | - Núria Casals
- Basic Sciences Department, Faculty of Medicine and Health Sciences, Universitat Internacional de Catalunya, 08195 Sant Cugat del Vallès, Barcelona, Spain
- Centro de Investigación Biomédica en Red de Fisiopatología de la Obesidad y la Nutrición (CIBEROBN), Instituto de Salud Carlos III, 28029 Madrid, Spain
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63
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Müller TD, Finan B, Clemmensen C, DiMarchi RD, Tschöp MH. The New Biology and Pharmacology of Glucagon. Physiol Rev 2017; 97:721-766. [PMID: 28275047 DOI: 10.1152/physrev.00025.2016] [Citation(s) in RCA: 206] [Impact Index Per Article: 29.4] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
In the last two decades we have witnessed sizable progress in defining the role of gastrointestinal signals in the control of glucose and energy homeostasis. Specifically, the molecular basis of the huge metabolic benefits in bariatric surgery is emerging while novel incretin-based medicines based on endogenous hormones such as glucagon-like peptide 1 and pancreas-derived amylin are improving diabetes management. These and related developments have fostered the discovery of novel insights into endocrine control of systemic metabolism, and in particular a deeper understanding of the importance of communication across vital organs, and specifically the gut-brain-pancreas-liver network. Paradoxically, the pancreatic peptide glucagon has reemerged in this period among a plethora of newly identified metabolic macromolecules, and new data complement and challenge its historical position as a gut hormone involved in metabolic control. The synthesis of glucagon analogs that are biophysically stable and soluble in aqueous solutions has promoted biological study that has enriched our understanding of glucagon biology and ironically recruited glucagon agonism as a central element to lower body weight in the treatment of metabolic disease. This review summarizes the extensive historical record and the more recent provocative direction that integrates the prominent role of glucagon in glucose elevation with its under-acknowledged effects on lipids, body weight, and vascular health that have implications for the pathophysiology of metabolic diseases, and the emergence of precision medicines to treat metabolic diseases.
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Affiliation(s)
- T D Müller
- Institute for Diabetes and Obesity, Helmholtz Diabetes Center, Helmholtz Zentrum München, German Research Center for Environmental Health, Neuherberg, Germany; German Center for Diabetes Research, Neuherberg, Germany; Department of Chemistry, Indiana University, Bloomington, Indiana; Division of Metabolic Diseases, Technische Universität München, Munich, Germany
| | - B Finan
- Institute for Diabetes and Obesity, Helmholtz Diabetes Center, Helmholtz Zentrum München, German Research Center for Environmental Health, Neuherberg, Germany; German Center for Diabetes Research, Neuherberg, Germany; Department of Chemistry, Indiana University, Bloomington, Indiana; Division of Metabolic Diseases, Technische Universität München, Munich, Germany
| | - C Clemmensen
- Institute for Diabetes and Obesity, Helmholtz Diabetes Center, Helmholtz Zentrum München, German Research Center for Environmental Health, Neuherberg, Germany; German Center for Diabetes Research, Neuherberg, Germany; Department of Chemistry, Indiana University, Bloomington, Indiana; Division of Metabolic Diseases, Technische Universität München, Munich, Germany
| | - R D DiMarchi
- Institute for Diabetes and Obesity, Helmholtz Diabetes Center, Helmholtz Zentrum München, German Research Center for Environmental Health, Neuherberg, Germany; German Center for Diabetes Research, Neuherberg, Germany; Department of Chemistry, Indiana University, Bloomington, Indiana; Division of Metabolic Diseases, Technische Universität München, Munich, Germany
| | - M H Tschöp
- Institute for Diabetes and Obesity, Helmholtz Diabetes Center, Helmholtz Zentrum München, German Research Center for Environmental Health, Neuherberg, Germany; German Center for Diabetes Research, Neuherberg, Germany; Department of Chemistry, Indiana University, Bloomington, Indiana; Division of Metabolic Diseases, Technische Universität München, Munich, Germany
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64
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Zilberter Y, Zilberter M. The vicious circle of hypometabolism in neurodegenerative diseases: Ways and mechanisms of metabolic correction. J Neurosci Res 2017; 95:2217-2235. [PMID: 28463438 DOI: 10.1002/jnr.24064] [Citation(s) in RCA: 131] [Impact Index Per Article: 18.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2016] [Revised: 03/17/2017] [Accepted: 03/17/2017] [Indexed: 12/13/2022]
Abstract
Hypometabolism, characterized by decreased brain glucose consumption, is a common feature of many neurodegenerative diseases. Initial hypometabolic brain state, created by characteristic risk factors, may predispose the brain to acquired epilepsy and sporadic Alzheimer's and Parkinson's diseases, which are the focus of this review. Analysis of available data suggests that deficient glucose metabolism is likely a primary initiating factor for these diseases, and that resulting neuronal dysfunction further promotes the metabolic imbalance, establishing an effective positive feedback loop and a downward spiral of disease progression. Therefore, metabolic correction leading to the normalization of abnormalities in glucose metabolism may be an efficient tool to treat the neurological disorders by counteracting their primary pathological mechanisms. Published and preliminary experimental results on this approach for treating Alzheimer's disease and epilepsy models support the efficacy of metabolic correction, confirming the highly promising nature of the strategy. © 2017 Wiley Periodicals, Inc.
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Affiliation(s)
- Yuri Zilberter
- Aix-Marseille Université, INSERM UMR1106, Institut de Neurosciences des Systèmes, Marseille, France
| | - Misha Zilberter
- Gladstone Institute of Neurological Disease, 1650 Owens Street, San Francisco, California, 94158, USA
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65
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Tups A, Benzler J, Sergi D, Ladyman SR, Williams LM. Central Regulation of Glucose Homeostasis. Compr Physiol 2017; 7:741-764. [DOI: 10.1002/cphy.c160015] [Citation(s) in RCA: 39] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
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66
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Reno CM, Puente EC, Sheng Z, Daphna-Iken D, Bree AJ, Routh VH, Kahn BB, Fisher SJ. Brain GLUT4 Knockout Mice Have Impaired Glucose Tolerance, Decreased Insulin Sensitivity, and Impaired Hypoglycemic Counterregulation. Diabetes 2017; 66:587-597. [PMID: 27797912 PMCID: PMC5319720 DOI: 10.2337/db16-0917] [Citation(s) in RCA: 65] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/27/2016] [Accepted: 10/12/2016] [Indexed: 12/12/2022]
Abstract
GLUT4 in muscle and adipose tissue is important in maintaining glucose homeostasis. However, the role of insulin-responsive GLUT4 in the central nervous system has not been well characterized. To assess its importance, a selective knockout of brain GLUT4 (BG4KO) was generated by crossing Nestin-Cre mice with GLUT4-floxed mice. BG4KO mice had a 99% reduction in GLUT4 protein expression throughout the brain. Despite normal feeding and fasting glycemia, BG4KO mice were glucose intolerant, demonstrated hepatic insulin resistance, and had reduced glucose uptake in the brain. In response to hypoglycemia, BG4KO mice had impaired glucose sensing, noted by impaired epinephrine and glucagon responses and impaired c-fos activation in the hypothalamic paraventricular nucleus. Moreover, in vitro glucose sensing of glucose-inhibitory neurons from the ventromedial hypothalamus was impaired in BG4KO mice. In summary, BG4KO mice are glucose intolerant, insulin resistant, and have impaired glucose sensing, indicating a critical role for brain GLUT4 in sensing and responding to changes in blood glucose.
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Affiliation(s)
- Candace M Reno
- Division of Endocrinology, Metabolism, and Lipid Research, Department of Medicine, Washington University in St. Louis, St. Louis, MO
- Division of Endocrinology, Metabolism, and Diabetes, Department of Internal Medicine, University of Utah, Salt Lake City, UT
| | - Erwin C Puente
- Division of Endocrinology, Metabolism, and Lipid Research, Department of Medicine, Washington University in St. Louis, St. Louis, MO
| | - Zhenyu Sheng
- Department of Pharmacology and Physiology, Rutgers New Jersey Medical School, Newark, NJ
| | - Dorit Daphna-Iken
- Division of Endocrinology, Metabolism, and Lipid Research, Department of Medicine, Washington University in St. Louis, St. Louis, MO
| | - Adam J Bree
- Division of Endocrinology, Metabolism, and Lipid Research, Department of Medicine, Washington University in St. Louis, St. Louis, MO
| | - Vanessa H Routh
- Department of Pharmacology and Physiology, Rutgers New Jersey Medical School, Newark, NJ
| | - Barbara B Kahn
- Division of Endocrinology, Diabetes and Metabolism, Department of Medicine, Beth Israel Deaconess Medical Center, Boston, MA
| | - Simon J Fisher
- Division of Endocrinology, Metabolism, and Lipid Research, Department of Medicine, Washington University in St. Louis, St. Louis, MO
- Division of Endocrinology, Metabolism, and Diabetes, Department of Internal Medicine, University of Utah, Salt Lake City, UT
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67
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Nagy B, Szabó I, Takács G, Csetényi B, Hormay E, Karádi Z. Impaired glucose tolerance after streptozotocin microinjection into the mediodorsal prefrontal cortex of the rat. Physiol Int 2017; 103:403-412. [PMID: 28229628 DOI: 10.1556/2060.103.2016.4.5] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
The mediodorsal prefrontal cortex (mdPFC) is a key structure of the central glucose-monitoring (GM) neural network. Previous studies indicate that intracerebral streptozotocin (STZ) microinjection-induced destruction of local chemosensory neurons results in feeding and metabolic alterations. The present experiments aimed to examine whether STZ microinjection into the mdPFC causes metabolic deficits. To do so, glucose tolerance test (GTT) and measurements of plasma metabolites were performed in STZ-treated or control rats. Intraperitoneal D-glucose load was delivered 20 min or 4 weeks following the intracerebral microinjection of STZ or saline (acute or subacute GTT, respectively). The STZ-treated rats displayed acute glucose intolerance: at the 120th min of the test, blood glucose level of these rats was significantly higher than that of the ones in the control group. When determining the plasma level of various metabolites, 30 min following the intracerebral STZ or saline microinjection, the triglyceride concentration of the STZ-treated rats was found to be reduced compared with that of the control rats. The GM neurons of the mdPFC are suggested to be involved in the organization of complex metabolic processes by which these chemosensory cells contribute to adaptive control mechanisms of the maintenance of homeostasis.
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Affiliation(s)
- B Nagy
- 1 Institute of Physiology, School of Medicine, University of Pécs , Pécs, Hungary
| | - I Szabó
- 1 Institute of Physiology, School of Medicine, University of Pécs , Pécs, Hungary
| | - G Takács
- 1 Institute of Physiology, School of Medicine, University of Pécs , Pécs, Hungary
| | - B Csetényi
- 1 Institute of Physiology, School of Medicine, University of Pécs , Pécs, Hungary
| | - E Hormay
- 1 Institute of Physiology, School of Medicine, University of Pécs , Pécs, Hungary
| | - Z Karádi
- 1 Institute of Physiology, School of Medicine, University of Pécs , Pécs, Hungary
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68
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The Na+-D-glucose cotransporters SGLT1 and SGLT2 are targets for the treatment of diabetes and cancer. Pharmacol Ther 2017; 170:148-165. [DOI: 10.1016/j.pharmthera.2016.10.017] [Citation(s) in RCA: 69] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
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69
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Chrétien C, Fenech C, Liénard F, Grall S, Chevalier C, Chaudy S, Brenachot X, Berges R, Louche K, Stark R, Nédélec E, Laderrière A, Andrews ZB, Benani A, Flockerzi V, Gascuel J, Hartmann J, Moro C, Birnbaumer L, Leloup C, Pénicaud L, Fioramonti X. Transient Receptor Potential Canonical 3 (TRPC3) Channels Are Required for Hypothalamic Glucose Detection and Energy Homeostasis. Diabetes 2017; 66:314-324. [PMID: 27899482 DOI: 10.2337/db16-1114] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/14/2016] [Accepted: 11/17/2016] [Indexed: 11/13/2022]
Abstract
The mediobasal hypothalamus (MBH) contains neurons capable of directly detecting metabolic signals such as glucose to control energy homeostasis. Among them, glucose-excited (GE) neurons increase their electrical activity when glucose rises. In view of previous work, we hypothesized that transient receptor potential canonical type 3 (TRPC3) channels are involved in hypothalamic glucose detection and the control of energy homeostasis. To investigate the role of TRPC3, we used constitutive and conditional TRPC3-deficient mouse models. Hypothalamic glucose detection was studied in vivo by measuring food intake and insulin secretion in response to increased brain glucose level. The role of TRPC3 in GE neuron response to glucose was studied by using in vitro calcium imaging on freshly dissociated MBH neurons. We found that whole-body and MBH TRPC3-deficient mice have increased body weight and food intake. The anorectic effect of intracerebroventricular glucose and the insulin secretory response to intracarotid glucose injection are blunted in TRPC3-deficient mice. TRPC3 loss of function or pharmacological inhibition blunts calcium responses to glucose in MBH neurons in vitro. Together, the results demonstrate that TRPC3 channels are required for the response to glucose of MBH GE neurons and the central effect of glucose on insulin secretion and food intake.
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Affiliation(s)
- Chloé Chrétien
- Centre des Sciences du Goût et de l'Alimentation, CNRS, Institut National de la Recherche Agronomique, University of Bourgogne Franche-Comté, Dijon, France
| | - Claire Fenech
- Centre des Sciences du Goût et de l'Alimentation, CNRS, Institut National de la Recherche Agronomique, University of Bourgogne Franche-Comté, Dijon, France
| | - Fabienne Liénard
- Centre des Sciences du Goût et de l'Alimentation, CNRS, Institut National de la Recherche Agronomique, University of Bourgogne Franche-Comté, Dijon, France
| | - Sylvie Grall
- Centre des Sciences du Goût et de l'Alimentation, CNRS, Institut National de la Recherche Agronomique, University of Bourgogne Franche-Comté, Dijon, France
| | - Charlène Chevalier
- Centre des Sciences du Goût et de l'Alimentation, CNRS, Institut National de la Recherche Agronomique, University of Bourgogne Franche-Comté, Dijon, France
| | - Sylvie Chaudy
- Centre des Sciences du Goût et de l'Alimentation, CNRS, Institut National de la Recherche Agronomique, University of Bourgogne Franche-Comté, Dijon, France
| | - Xavier Brenachot
- Centre des Sciences du Goût et de l'Alimentation, CNRS, Institut National de la Recherche Agronomique, University of Bourgogne Franche-Comté, Dijon, France
| | - Raymond Berges
- Centre des Sciences du Goût et de l'Alimentation, CNRS, Institut National de la Recherche Agronomique, University of Bourgogne Franche-Comté, Dijon, France
| | - Katie Louche
- INSERM UMR1048, Institute of Metabolic and Cardiovascular Diseases, Obesity Research Laboratory, University of Toulouse, Toulouse, France
| | - Romana Stark
- Biomedicine Discovery Institute, Metabolic Disease and Obesity Program, Department of Physiology, Monash University, Clayton, VIC, Australia
| | - Emmanuelle Nédélec
- Centre des Sciences du Goût et de l'Alimentation, CNRS, Institut National de la Recherche Agronomique, University of Bourgogne Franche-Comté, Dijon, France
| | - Amélie Laderrière
- Centre des Sciences du Goût et de l'Alimentation, CNRS, Institut National de la Recherche Agronomique, University of Bourgogne Franche-Comté, Dijon, France
| | - Zane B Andrews
- Biomedicine Discovery Institute, Metabolic Disease and Obesity Program, Department of Physiology, Monash University, Clayton, VIC, Australia
| | - Alexandre Benani
- Centre des Sciences du Goût et de l'Alimentation, CNRS, Institut National de la Recherche Agronomique, University of Bourgogne Franche-Comté, Dijon, France
| | - Veit Flockerzi
- Experimental and Clinical Pharmacology and Toxicology, Saarland University School of Medicine, Homburg, Germany
| | - Jean Gascuel
- Centre des Sciences du Goût et de l'Alimentation, CNRS, Institut National de la Recherche Agronomique, University of Bourgogne Franche-Comté, Dijon, France
| | - Jana Hartmann
- Institute of Neuroscience and Center for Integrated Protein Science, Technical University Munich, Munich, Germany
| | - Cédric Moro
- INSERM UMR1048, Institute of Metabolic and Cardiovascular Diseases, Obesity Research Laboratory, University of Toulouse, Toulouse, France
| | - Lutz Birnbaumer
- Neurobiology Laboratory, National Institute of Environmental Health Sciences, Research Triangle Park, NC
- Institute of Biomedical Research, Catholic University of Argentina, Buenos Aires, Argentina
| | - Corinne Leloup
- Centre des Sciences du Goût et de l'Alimentation, CNRS, Institut National de la Recherche Agronomique, University of Bourgogne Franche-Comté, Dijon, France
| | - Luc Pénicaud
- Centre des Sciences du Goût et de l'Alimentation, CNRS, Institut National de la Recherche Agronomique, University of Bourgogne Franche-Comté, Dijon, France
| | - Xavier Fioramonti
- Centre des Sciences du Goût et de l'Alimentation, CNRS, Institut National de la Recherche Agronomique, University of Bourgogne Franche-Comté, Dijon, France
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70
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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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71
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Larsen L, Le Foll C, Dunn-Meynell AA, Levin BE. IL-6 ameliorates defective leptin sensitivity in DIO ventromedial hypothalamic nucleus neurons. Am J Physiol Regul Integr Comp Physiol 2016; 311:R764-R770. [PMID: 27534878 DOI: 10.1152/ajpregu.00258.2016] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2016] [Accepted: 08/11/2016] [Indexed: 12/25/2022]
Abstract
Rats selectively bred to develop diet-induced obesity (DIO) have an early onset reduction in the sensitivity of their ventromedial hypothalamic nucleus (VMN) neurons to leptin compared with diet-resistant (DR) rats. This reduced sensitivity includes decreased leptin receptor (Lepr-b) mRNA expression, leptin receptor binding, leptin-induced phosphorylation of STAT3 (pSTAT3), and impaired leptin excitation (LepE) of VMN neurons. When administered exogenously, the pancreatic peptide, amylin, acts synergistically to reduce food intake and body weight in obese, leptin-resistant DIO rats by increasing VMN leptin signaling, likely by stimulation of microglia IL-6, which acts on its receptor to increase leptin-induced pSTAT3. Here, we demonstrate that incubation of cultured VMN neurons of outbred rats with IL-6 increases their leptin sensitivity. Control, dissociated DIO VMN neurons express 66% less Lepr-b and 75% less Bardet Biedl Syndrome-6 (BBS6) mRNA and have reduced leptin-induced activation of LepE neurons compared with DR neurons. Incubation for 4 days with IL-6 increased DIO neuron Lepr-b expression by 77% and BBS6 by 290% and corrected their defective leptin activation of LepE neurons to DR levels. Since BBS6 enhances trafficking of Lepr-b to the cell membrane, the increases in Lepr-b and BBS6 expression appear to account for correction of the reduced leptin excitation of DIO LepE neurons to that of control DR rats. These data support prior findings suggesting that IL-6 mediates the leptin-sensitizing effects of amylin on VMN neurons and that the inherent leptin resistance of DIO rats can be effectively reversed at a cellular level by IL-6.
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Affiliation(s)
| | - Christelle Le Foll
- Institute of Veterinary Physiology, University of Zurich, Zurich, Switzerland
| | | | - Barry E Levin
- Department of Neurology, Rutgers, New Jersey Medical School, Newark, New Jersey
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72
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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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73
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Le Foll C, Levin BE. Fatty acid-induced astrocyte ketone production and the control of food intake. Am J Physiol Regul Integr Comp Physiol 2016; 310:R1186-92. [PMID: 27122369 PMCID: PMC4935491 DOI: 10.1152/ajpregu.00113.2016] [Citation(s) in RCA: 55] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2016] [Accepted: 04/22/2016] [Indexed: 11/22/2022]
Abstract
Obesity and Type 2 diabetes are major worldwide public health issues today. A relationship between total fat intake and obesity has been found. In addition, the mechanisms of long-term and excessive high-fat diet (HFD) intake in the development of obesity still need to be elucidated. The ventromedial hypothalamus (VMH) is a major site involved in the regulation of glucose and energy homeostasis where "metabolic sensing neurons" integrate metabolic signals from the periphery. Among these signals, fatty acids (FA) modulate the activity of VMH neurons using the FA translocator/CD36, which plays a critical role in the regulation of energy and glucose homeostasis. During low-fat diet (LFD) intake, FA are oxidized by VMH astrocytes to fuel their ongoing metabolic needs. However, HFD intake causes VMH astrocytes to use FA to generate ketone bodies. We postulate that these astrocyte-derived ketone bodies are exported to neurons where they produce excess ATP and reactive oxygen species, which override CD36-mediated FA sensing and act as a signal to decrease short-term food intake. On a HFD, VMH astrocyte-produced ketones reduce elevated caloric intake to LFD levels after 3 days in rats genetically predisposed to resist (DR) diet-induced obesity (DIO), but not leptin-resistant DIO rats. This suggests that, while VMH ketone production on a HFD can contribute to protection from obesity, the inherent leptin resistance overrides this inhibitory action of ketone bodies on food intake. Thus, astrocytes and neurons form a tight metabolic unit that is able to monitor circulating nutrients to alter food intake and energy homeostasis.
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Affiliation(s)
- Christelle Le Foll
- Institute of Veterinary Physiology, University of Zurich, Zurich, Switzerland; and
| | - Barry E Levin
- Department of Neurology, Rutgers, New Jersey Medical School, Newark, New Jersey
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74
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Kovach CP, Al Koborssy D, Huang Z, Chelette BM, Fadool JM, Fadool DA. Mitochondrial Ultrastructure and Glucose Signaling Pathways Attributed to the Kv1.3 Ion Channel. Front Physiol 2016; 7:178. [PMID: 27242550 PMCID: PMC4871887 DOI: 10.3389/fphys.2016.00178] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2015] [Accepted: 05/04/2016] [Indexed: 12/20/2022] Open
Abstract
Gene-targeted deletion of the potassium channel Kv1.3 (Kv1.3−∕−) results in “Super-smeller” mice with a sensory phenotype that includes an increased olfactory ability linked to changes in olfactory circuitry, increased abundance of olfactory cilia, and increased expression of odorant receptors and the G-protein, Golf. Kv1.3−∕− mice also have a metabolic phenotype including lower body weight and decreased adiposity, increased total energy expenditure (TEE), increased locomotor activity, and resistance to both diet- and genetic-induced obesity. We explored two cellular aspects to elucidate the mechanism by which loss of Kv1.3 channel in the olfactory bulb (OB) may enhance glucose utilization and metabolic rate. First, using in situ hybridization we find that Kv1.3 and the insulin-dependent glucose transporter type 4 (GLUT4) are co-localized to the mitral cell layer of the OB. Disruption of Kv1.3 conduction via construction of a pore mutation (W386F Kv1.3) was sufficient to independently translocate GLUT4 to the plasma membrane in HEK 293 cells. Because olfactory sensory perception and the maintenance of action potential (AP) firing frequency by mitral cells of the OB is highly energy demanding and Kv1.3 is also expressed in mitochondria, we next explored the structure of this organelle in mitral cells. We challenged wildtype (WT) and Kv1.3−∕− male mice with a moderately high-fat diet (MHF, 31.8 % kcal fat) for 4 months and then examined OB ultrastructure using transmission electron microscopy. In WT mice, mitochondria were significantly enlarged following diet-induced obesity (DIO) and there were fewer mitochondria, likely due to mitophagy. Interestingly, mitochondria were significantly smaller in Kv1.3−∕− mice compared with that of WT mice. Similar to their metabolic resistance to DIO, the Kv1.3−∕− mice had unchanged mitochondria in terms of cross sectional area and abundance following a challenge with modified diet. We are very interested to understand how targeted disruption of the Kv1.3 channel in the OB can modify TEE. Our study demonstrates that Kv1.3 regulates mitochondrial structure and alters glucose utilization; two important metabolic changes that could drive whole system changes in metabolism initiated at the OB.
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Affiliation(s)
- Christopher P Kovach
- Program in Neuroscience, Florida State UniversityTallahassee, FL, USA; Department of Biological Science, Florida State UniversityTallahassee, FL, USA
| | - Dolly Al Koborssy
- Program in Neuroscience, Florida State University Tallahassee, FL, USA
| | - Zhenbo Huang
- Program in Neuroscience, Florida State University Tallahassee, FL, USA
| | | | - James M Fadool
- Program in Neuroscience, Florida State UniversityTallahassee, FL, USA; Department of Biological Science, Florida State UniversityTallahassee, FL, USA
| | - Debra A Fadool
- Program in Neuroscience, Florida State UniversityTallahassee, FL, USA; Department of Biological Science, Florida State UniversityTallahassee, FL, USA; Institute of Molecular Biophysics, Florida State UniversityTallahassee, FL, USA
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75
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Stanley SA, Kelly L, Latcha KN, Schmidt SF, Yu X, Nectow AR, Sauer J, Dyke JP, Dordick JS, Friedman JM. Bidirectional electromagnetic control of the hypothalamus regulates feeding and metabolism. Nature 2016; 531:647-50. [PMID: 27007848 PMCID: PMC4894494 DOI: 10.1038/nature17183] [Citation(s) in RCA: 154] [Impact Index Per Article: 19.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2015] [Accepted: 01/28/2016] [Indexed: 12/16/2022]
Abstract
Targeted, temporally regulated neural modulation is invaluable in determining the physiological roles of specific neural populations or circuits. Here we describe a system for non-invasive, temporal activation or inhibition of neuronal activity in vivo and its use to study central nervous system control of glucose homeostasis and feeding in mice. We are able to induce neuronal activation remotely using radio waves or magnetic fields via Cre-dependent expression of a GFP-tagged ferritin fusion protein tethered to the cation-conducting transient receptor potential vanilloid 1 (TRPV1) by a camelid anti-GFP antibody (anti-GFP-TRPV1). Neuronal inhibition via the same stimuli is achieved by mutating the TRPV1 pore, rendering the channel chloride-permeable. These constructs were targeted to glucose-sensing neurons in the ventromedial hypothalamus in glucokinase-Cre mice, which express Cre in glucose-sensing neurons. Acute activation of glucose-sensing neurons in this region increases plasma glucose and glucagon, lowers insulin levels and stimulates feeding, while inhibition reduces blood glucose, raises insulin levels and suppresses feeding. These results suggest that pancreatic hormones function as an effector mechanism of central nervous system circuits controlling blood glucose and behaviour. The method we employ obviates the need for permanent implants and could potentially be applied to study other neural processes or used to regulate other, even dispersed, cell types.
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Affiliation(s)
- Sarah A Stanley
- Laboratory of Molecular Genetics, Rockefeller University, New York, New York 10065, USA
| | - Leah Kelly
- Laboratory of Molecular Genetics, Rockefeller University, New York, New York 10065, USA
| | - Kaamashri N Latcha
- Laboratory of Molecular Genetics, Rockefeller University, New York, New York 10065, USA
| | - Sarah F Schmidt
- Laboratory of Molecular Genetics, Rockefeller University, New York, New York 10065, USA
| | - Xiaofei Yu
- Laboratory of Molecular Genetics, Rockefeller University, New York, New York 10065, USA
| | - Alexander R Nectow
- Laboratory of Molecular Genetics, Rockefeller University, New York, New York 10065, USA
| | - Jeremy Sauer
- Department of Chemical &Biological Engineering, Center for Biotechnology &Interdisciplinary Studies, Rensselaer Polytechnic Institute, Troy, New York 12180, USA
| | - Jonathan P Dyke
- Department of Radiology, Weill Cornell Medical College, New York, New York 10065, USA
| | - Jonathan S Dordick
- Department of Chemical &Biological Engineering, Center for Biotechnology &Interdisciplinary Studies, Rensselaer Polytechnic Institute, Troy, New York 12180, USA
| | - Jeffrey M Friedman
- Laboratory of Molecular Genetics, Rockefeller University, New York, New York 10065, USA
- Howard Hughes Medical Institute, New York, New York 10065, USA
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76
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Foster NN, Azam S, Watts AG. Rapid-onset hypoglycemia suppresses Fos expression in discrete parts of the ventromedial nucleus of the hypothalamus. Am J Physiol Regul Integr Comp Physiol 2016; 310:R1177-85. [PMID: 27030665 DOI: 10.1152/ajpregu.00042.2016] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2016] [Accepted: 03/23/2016] [Indexed: 01/12/2023]
Abstract
The consensus view of the ventromedial nucleus of the hypothalamus (VMH) is that it is a key node in the rodent brain network controlling sympathoadrenal counterregulatory responses to hypoglycemia. To identify the location of hypoglycemia-responsive neurons in the VMH, we performed a high spatial resolution Fos analysis in the VMH of rats made hypoglycemic with intraperitoneal injections of insulin. We examined Fos expression in the four constituent parts of VMH throughout its rostrocaudal extent and determined their relationship to blood glucose concentrations. Hypoglycemia significantly decreased Fos expression only in the dorsomedial and central parts of the VMH, but not its anterior or ventrolateral parts. Moreover, the number of Fos-expressing neurons was significantly and positively correlated in the two responsive regions with terminal blood glucose concentrations. We also measured Fos responses in the paraventricular nucleus of the hypothalamus (PVH) and in several levels of the periaqueductal gray (PAG), which receives strong projections from the VMH. We found the expected and highly significant increase in Fos in the neuroendocrine PVH, which was negatively correlated to terminal blood glucose concentrations, but no significant differences were seen in any part of the PAG. Our results show that there are distinct populations of VMH neurons whose Fos expression is suppressed by hypoglycemia, and their numbers correlate with blood glucose. These findings support a clear division of glycemic control functions within the different parts of the VMH.
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Affiliation(s)
- Nicholas N Foster
- Department of Biological Sciences, USC Dornsife College of Letters, Arts, and Sciences, University of Southern California, Los Angeles, California
| | - Sana Azam
- Department of Biological Sciences, USC Dornsife College of Letters, Arts, and Sciences, University of Southern California, Los Angeles, California
| | - Alan G Watts
- Department of Biological Sciences, USC Dornsife College of Letters, Arts, and Sciences, University of Southern California, Los Angeles, California
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77
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Heeley N, Blouet C. Central Amino Acid Sensing in the Control of Feeding Behavior. Front Endocrinol (Lausanne) 2016; 7:148. [PMID: 27933033 PMCID: PMC5120084 DOI: 10.3389/fendo.2016.00148] [Citation(s) in RCA: 35] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/16/2016] [Accepted: 11/03/2016] [Indexed: 11/13/2022] Open
Abstract
Dietary protein quantity and quality greatly impact metabolic health via evolutionary-conserved mechanisms that ensure avoidance of amino acid imbalanced food sources, promote hyperphagia when dietary protein density is low, and conversely produce satiety when dietary protein density is high. Growing evidence supports the emerging concept of protein homeostasis in mammals, where protein intake is maintained within a tight range independently of energy intake to reach a target protein intake. The behavioral and neuroendocrine mechanisms underlying these adaptations are unclear. While peripheral factors are able to signal amino acid deficiency and abundance to the brain, the brain itself is exposed to and can detect changes in amino acid concentrations, and subsequently engages acute and chronic responses modulating feeding behavior and food preferences. In this review, we will examine the literature describing the mechanisms by which the brain senses changes in amino acids concentrations, and how these changes modulate feeding behavior.
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Affiliation(s)
- Nicholas Heeley
- Medical Research Council Metabolic Disease Unit, Institute of Metabolic Science, University of Cambridge, Cambridge, UK
| | - Clemence Blouet
- Medical Research Council Metabolic Disease Unit, Institute of Metabolic Science, University of Cambridge, Cambridge, UK
- *Correspondence: Clemence Blouet,
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78
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Glucose Induces Slow-Wave Sleep by Exciting the Sleep-Promoting Neurons in the Ventrolateral Preoptic Nucleus: A New Link between Sleep and Metabolism. J Neurosci 2015; 35:9900-11. [PMID: 26156991 DOI: 10.1523/jneurosci.0609-15.2015] [Citation(s) in RCA: 46] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
UNLABELLED Sleep-active neurons located in the ventrolateral preoptic nucleus (VLPO) play a crucial role in the induction and maintenance of slow-wave sleep (SWS). However, the cellular and molecular mechanisms responsible for their activation at sleep onset remain poorly understood. Here, we test the hypothesis that a rise in extracellular glucose concentration in the VLPO can promote sleep by increasing the activity of sleep-promoting VLPO neurons. We find that infusion of a glucose concentration into the VLPO of mice promotes SWS and increases the density of c-Fos-labeled neurons selectively in the VLPO. Moreover, we show in patch-clamp recordings from brain slices that VLPO neurons exhibiting properties of sleep-promoting neurons are selectively excited by glucose within physiological range. This glucose-induced excitation implies the catabolism of glucose, leading to a closure of ATP-sensitive potassium (KATP) channels. The extracellular glucose concentration monitors the gating of KATP channels of sleep-promoting neurons, highlighting that these neurons can adapt their excitability according to the extracellular energy status. Together, these results provide evidence that glucose may participate in the mechanisms of SWS promotion and/or consolidation. SIGNIFICANCE STATEMENT Although the brain circuitry underlying vigilance states is well described, the molecular mechanisms responsible for sleep onset remain largely unknown. Combining in vitro and in vivo experiments, we demonstrate that glucose likely contributes to sleep onset facilitation by increasing the excitability of sleep-promoting neurons in the ventrolateral preoptic nucleus (VLPO). We find here that these neurons integrate energetic signals such as ambient glucose directly to regulate vigilance states accordingly. Glucose-induced excitation of sleep-promoting VLPO neurons should therefore be involved in the drowsiness that one feels after a high-sugar meal. This novel mechanism regulating the activity of VLPO neurons reinforces the fundamental and intimate link between sleep and metabolism.
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79
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Steinbusch L, Labouèbe G, Thorens B. Brain glucose sensing in homeostatic and hedonic regulation. Trends Endocrinol Metab 2015; 26:455-66. [PMID: 26163755 DOI: 10.1016/j.tem.2015.06.005] [Citation(s) in RCA: 57] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/15/2015] [Revised: 06/15/2015] [Accepted: 06/16/2015] [Indexed: 11/21/2022]
Abstract
Glucose homeostasis as well as homeostatic and hedonic control of feeding is regulated by hormonal, neuronal, and nutrient-related cues. Glucose, besides its role as a source of metabolic energy, is an important signal controlling hormone secretion and neuronal activity, hence contributing to whole-body metabolic integration in coordination with feeding control. Brain glucose sensing plays a key, but insufficiently explored, role in these metabolic and behavioral controls, which when deregulated may contribute to the development of obesity and diabetes. The recent introduction of innovative transgenic, pharmacogenetic, and optogenetic techniques allows unprecedented analysis of the complexity of central glucose sensing at the molecular, cellular, and neuronal circuit levels, which will lead to a new understanding of the pathogenesis of metabolic diseases.
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Affiliation(s)
- Laura Steinbusch
- Center for Integrative Genomics, University of Lausanne, Lausanne, Switzerland
| | - Gwenaël Labouèbe
- Center for Integrative Genomics, University of Lausanne, Lausanne, Switzerland
| | - Bernard Thorens
- Center for Integrative Genomics, University of Lausanne, Lausanne, Switzerland.
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80
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Veedfald S, Plamboeck A, Hartmann B, Svendsen LB, Vilsbøll T, Knop FK, Holst JJ. Pancreatic polypeptide responses to isoglycemic oral and intravenous glucose in humans with and without intact vagal innervation. Peptides 2015. [PMID: 26218807 DOI: 10.1016/j.peptides.2015.07.020] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
Abstract
Secretion of pancreatic polypeptide (PP) from the pancreatic PP cells is controlled partly by vagal mechanisms. Release is stimulated by cephalic stimulation and enteral but not parenteral nutrients. Ambient glucose levels modulate circulating PP levels as hypoglycemia stimulates while hyperglycemia inhibits secretion. The glucose sensing mechanism has yet to be determined but may involve a vagal pathway. To investigate the role of enteral stimuli with or without intact vagal innervation, while controlling for the glucose excursion caused by the OGTT, we measured PP plasma levels by an in-house radioimmunoassay in truncally vagotomized (n=15) and control individuals (n=10). All participants were studied by a 50-g oral glucose tolerance test (OGTT) with or without dipeptidyl peptidase 4 (DPP-4) inhibition (DPP-4i) and a subsequent isoglycemic intravenous glucose infusion (IGII). We included measurements from the DPP-4i day to determine the potential effect of DPP-4-cleaved peptides on PP secretion. In both vagotomized and controls, oral glucose elicited PP secretion. In controls, but not in the vagotomized participants, intravenous glucose significantly inhibited PP secretion suggesting a vagal glucose sensing mechanism dependent on intact vagal innervation. DPP-4i did not alter PP secretion in either group.
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Affiliation(s)
- Simon Veedfald
- Center for Diabetes Research, Gentofte Hospital, University of Copenhagen, Denmark; The NNF Center for Basic Metabolic Research and The Department of Biomedical Sciences, University of Copenhagen, Denmark; Department of Surgical Gastroenterology C, Rigshospitalet, University of Copenhagen, Denmark
| | - Astrid Plamboeck
- Center for Diabetes Research, Gentofte Hospital, University of Copenhagen, Denmark; The NNF Center for Basic Metabolic Research and The Department of Biomedical Sciences, University of Copenhagen, Denmark
| | - Bolette Hartmann
- The NNF Center for Basic Metabolic Research and The Department of Biomedical Sciences, University of Copenhagen, Denmark
| | - Lars B Svendsen
- Department of Surgical Gastroenterology C, Rigshospitalet, University of Copenhagen, Denmark
| | - Tina Vilsbøll
- Center for Diabetes Research, Gentofte Hospital, University of Copenhagen, Denmark
| | - Filip K Knop
- Center for Diabetes Research, Gentofte Hospital, University of Copenhagen, Denmark; The NNF Center for Basic Metabolic Research and The Department of Biomedical Sciences, University of Copenhagen, Denmark
| | - Jens J Holst
- The NNF Center for Basic Metabolic Research and The Department of Biomedical Sciences, University of Copenhagen, Denmark.
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81
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Boychuk CR, Gyarmati P, Xu H, Smith BN. Glucose sensing by GABAergic neurons in the mouse nucleus tractus solitarii. J Neurophysiol 2015; 114:999-1007. [PMID: 26084907 DOI: 10.1152/jn.00310.2015] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2015] [Accepted: 06/15/2015] [Indexed: 12/23/2022] Open
Abstract
Changes in blood glucose concentration alter autonomic function in a manner consistent with altered neural activity in brain regions controlling digestive processes, including neurons in the brain stem nucleus tractus solitarii (NTS), which process viscerosensory information. With whole cell or on-cell patch-clamp recordings, responses to elevating glucose concentration from 2.5 to 15 mM were assessed in identified GABAergic NTS neurons in slices from transgenic mice that express EGFP in a subset of GABA neurons. Single-cell real-time RT-PCR was also performed to detect glutamic acid decarboxylase (GAD67) in recorded neurons. In most identified GABA neurons (73%), elevating glucose concentration from 2.5 to 15 mM resulted in either increased (40%) or decreased (33%) neuronal excitability, reflected by altered membrane potential and/or action potential firing. Effects on membrane potential were maintained when action potentials or fast synaptic inputs were blocked, suggesting direct glucose sensing by GABA neurons. Glucose-inhibited GABA neurons were found predominantly in the lateral NTS, whereas glucose-excited cells were mainly in the medial NTS, suggesting regional segregation of responses. Responses were prevented in the presence of glucosamine, a glucokinase (GCK) inhibitor. Depolarizing responses were prevented when KATP channel activity was blocked with tolbutamide. Whereas effects on synaptic input to identified GABAergic neurons were variable in GABA neurons, elevating glucose increased glutamate release subsequent to stimulation of tractus solitarius in unlabeled, unidentified neurons. These results indicate that GABAergic NTS neurons act as GCK-dependent glucose sensors in the vagal complex, providing a means of modulating central autonomic signals when glucose is elevated.
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Affiliation(s)
- Carie R Boychuk
- Department of Physiology, University of Kentucky College of Medicine, Lexington, Kentucky
| | - Peter Gyarmati
- Department of Physiology, University of Kentucky College of Medicine, Lexington, Kentucky
| | - Hong Xu
- Department of Physiology, University of Kentucky College of Medicine, Lexington, Kentucky
| | - Bret N Smith
- Department of Physiology, University of Kentucky College of Medicine, Lexington, Kentucky
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82
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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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83
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Dus M, Lai JSY, Gunapala KM, Min S, Tayler TD, Hergarden AC, Geraud E, Joseph CM, Suh GSB. Nutrient Sensor in the Brain Directs the Action of the Brain-Gut Axis in Drosophila. Neuron 2015; 87:139-51. [PMID: 26074004 DOI: 10.1016/j.neuron.2015.05.032] [Citation(s) in RCA: 146] [Impact Index Per Article: 16.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2014] [Revised: 03/30/2015] [Accepted: 05/07/2015] [Indexed: 11/15/2022]
Abstract
Animals can detect and consume nutritive sugars without the influence of taste. However, the identity of the taste-independent nutrient sensor and the mechanism by which animals respond to the nutritional value of sugar are unclear. Here, we report that six neurosecretory cells in the Drosophila brain that produce Diuretic hormone 44 (Dh44), a homolog of the mammalian corticotropin-releasing hormone (CRH), were specifically activated by nutritive sugars. Flies in which the activity of these neurons or the expression of Dh44 was disrupted failed to select nutritive sugars. Manipulation of the function of Dh44 receptors had a similar effect. Notably, artificial activation of Dh44 receptor-1 neurons resulted in proboscis extensions and frequent episodes of excretion. Conversely, reduced Dh44 activity led to decreased excretion. Together, these actions facilitate ingestion and digestion of nutritive foods. We propose that the Dh44 system directs the detection and consumption of nutritive sugars through a positive feedback loop.
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Affiliation(s)
- Monica Dus
- Department of Cell Biology, Skirball Institute of Biomolecular Medicine, New York University School of Medicine, 540 First Avenue, New York, NY 10016, USA
| | - Jason Sih-Yu Lai
- Department of Cell Biology, Skirball Institute of Biomolecular Medicine, New York University School of Medicine, 540 First Avenue, New York, NY 10016, USA
| | - Keith M Gunapala
- Department of Cell Biology, Skirball Institute of Biomolecular Medicine, New York University School of Medicine, 540 First Avenue, New York, NY 10016, USA
| | - Soohong Min
- Department of Cell Biology, Skirball Institute of Biomolecular Medicine, New York University School of Medicine, 540 First Avenue, New York, NY 10016, USA
| | - Timothy D Tayler
- Division of Biology 156-29, California Institute of Technology, 1200 E. California Boulevard, Pasadena, CA 91125, USA
| | - Anne C Hergarden
- Division of Biology 156-29, California Institute of Technology, 1200 E. California Boulevard, Pasadena, CA 91125, USA
| | - Eliot Geraud
- Department of Cell Biology, Skirball Institute of Biomolecular Medicine, New York University School of Medicine, 540 First Avenue, New York, NY 10016, USA
| | - Christina M Joseph
- Department of Cell Biology, Skirball Institute of Biomolecular Medicine, New York University School of Medicine, 540 First Avenue, New York, NY 10016, USA
| | - Greg S B Suh
- Department of Cell Biology, Skirball Institute of Biomolecular Medicine, New York University School of Medicine, 540 First Avenue, New York, NY 10016, USA.
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84
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Donovan CM, Watts AG. Peripheral and central glucose sensing in hypoglycemic detection. Physiology (Bethesda) 2015; 29:314-24. [PMID: 25180261 DOI: 10.1152/physiol.00069.2013] [Citation(s) in RCA: 54] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023] Open
Abstract
Hypoglycemia poses a serious threat to the integrity of the brain, owing to its reliance on blood glucose as a fuel. Protecting against hypoglycemia is an extended network of glucose sensors located within the brain and in the periphery that serve to mediate responses restoring euglycemia, i.e., counterregulatory responses. This review examines the various glucose sensory loci involved in hypoglycemic detection, with a particular emphasis on peripheral glucose sensory loci and their contribution to hypoglycemic counterregulation.
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Affiliation(s)
- Casey M Donovan
- Department of Biological Sciences, The Center for NeuroMetabolic Interactions, USC Dornsife College of Letters, Arts and Sciences, University of Southern California, Los Angeles, California
| | - Alan G Watts
- Department of Biological Sciences, The Center for NeuroMetabolic Interactions, USC Dornsife College of Letters, Arts and Sciences, University of Southern California, Los Angeles, California
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85
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Le Foll C, Dunn-Meynell AA, Miziorko HM, Levin BE. Role of VMH ketone bodies in adjusting caloric intake to increased dietary fat content in DIO and DR rats. Am J Physiol Regul Integr Comp Physiol 2015; 308:R872-8. [PMID: 25786485 DOI: 10.1152/ajpregu.00015.2015] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2015] [Accepted: 03/11/2015] [Indexed: 01/06/2023]
Abstract
The objective of this study was to determine the potential role of astrocyte-derived ketone bodies in regulating the early changes in caloric intake of diet induced-obese (DIO) versus diet-resistant (DR) rats fed a 31.5% fat high-energy (HE) diet. After 3 days on chow or HE diet, DR and DIO rats were assessed for their ventromedial hypothalamic (VMH) ketone bodies levels and neuronal ventromedial hypothalamic nucleus (VMN) sensing using microdialysis coupled to continuous food intake monitoring and calcium imaging in dissociated neurons, respectively. DIO rats ate more than DR rats over 3 days of HE diet intake. On day 3 of HE diet intake, DR rats reduced their caloric intake while DIO rats remained hyperphagic. Local VMH astrocyte ketone bodies production was similar between DR and DIO rats during the first 6 h after dark onset feeding but inhibiting VMH ketone body production in DR rats on day 3 transiently returned their intake of HE diet to the level of DIO rats consuming HE diet. In addition, dissociated VMN neurons from DIO and DR rats were equally sensitive to the largely excitatory effects of β-hydroxybutyrate. Thus while DR rats respond to increased VMH ketone levels by decreasing their intake after 3 days of HE diet, this is not the case of DIO rats. These data suggest that DIO inherent leptin resistance prevents ketone bodies inhibitory action on food intake.
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Affiliation(s)
- Christelle Le Foll
- Department Neurology and Neurosciences, New Jersey Medical School, Newark, New Jersey;
| | | | - Henry M Miziorko
- School of Biological Sciences, University of Missouri-Kansas City, Kansas City, Missouri
| | - Barry E Levin
- Department Neurology and Neurosciences, New Jersey Medical School, Newark, New Jersey; Neurology Service, Veterans Affairs Center, East Orange, New Jersey; and
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86
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Bouret S, Levin BE, Ozanne SE. Gene-environment interactions controlling energy and glucose homeostasis and the developmental origins of obesity. Physiol Rev 2015; 95:47-82. [PMID: 25540138 PMCID: PMC4281588 DOI: 10.1152/physrev.00007.2014] [Citation(s) in RCA: 97] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
Obesity and type 2 diabetes mellitus (T2DM) often occur together and affect a growing number of individuals in both the developed and developing worlds. Both are associated with a number of other serious illnesses that lead to increased rates of mortality. There is likely a polygenic mode of inheritance underlying both disorders, but it has become increasingly clear that the pre- and postnatal environments play critical roles in pushing predisposed individuals over the edge into a disease state. This review focuses on the many genetic and environmental variables that interact to cause predisposed individuals to become obese and diabetic. The brain and its interactions with the external and internal environment are a major focus given the prominent role these interactions play in the regulation of energy and glucose homeostasis in health and disease.
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Affiliation(s)
- Sebastien Bouret
- The Saban Research Institute, Neuroscience Program, Childrens Hospital Los Angeles, University of Southern California, Los Angeles, California; Inserm U837, Jean-Pierre Aubert Research Center, University Lille 2, Lille, France; Neurology Service, Veterans Administration Medical Center, East Orange, New Jersey; Department of Neurology and Neurosciences, Rutgers, New Jersey Medical School, Newark, New Jersey; and University of Cambridge Institute of Metabolic Science and MRC Metabolic Diseases Unit, Cambridge, United Kingdom
| | - Barry E Levin
- The Saban Research Institute, Neuroscience Program, Childrens Hospital Los Angeles, University of Southern California, Los Angeles, California; Inserm U837, Jean-Pierre Aubert Research Center, University Lille 2, Lille, France; Neurology Service, Veterans Administration Medical Center, East Orange, New Jersey; Department of Neurology and Neurosciences, Rutgers, New Jersey Medical School, Newark, New Jersey; and University of Cambridge Institute of Metabolic Science and MRC Metabolic Diseases Unit, Cambridge, United Kingdom
| | - Susan E Ozanne
- The Saban Research Institute, Neuroscience Program, Childrens Hospital Los Angeles, University of Southern California, Los Angeles, California; Inserm U837, Jean-Pierre Aubert Research Center, University Lille 2, Lille, France; Neurology Service, Veterans Administration Medical Center, East Orange, New Jersey; Department of Neurology and Neurosciences, Rutgers, New Jersey Medical School, Newark, New Jersey; and University of Cambridge Institute of Metabolic Science and MRC Metabolic Diseases Unit, Cambridge, United Kingdom
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87
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GLUT2-mediated glucose uptake and availability are required for embryonic brain development in zebrafish. J Cereb Blood Flow Metab 2015; 35:74-85. [PMID: 25294126 PMCID: PMC4294397 DOI: 10.1038/jcbfm.2014.171] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/16/2014] [Revised: 08/14/2014] [Accepted: 09/12/2014] [Indexed: 11/18/2022]
Abstract
Glucose transporter 2 (GLUT2; gene name SLC2A2) has a key role in the regulation of glucose dynamics in organs central to metabolism. Although GLUT2 has been studied in the context of its participation in peripheral and central glucose sensing, its role in the brain is not well understood. To decipher the role of GLUT2 in brain development, we knocked down slc2a2 (glut2), the functional ortholog of human GLUT2, in zebrafish. Abrogation of glut2 led to defective brain organogenesis, reduced glucose uptake and increased programmed cell death in the brain. Coinciding with the observed localization of glut2 expression in the zebrafish hindbrain, glut2 deficiency affected the development of neural progenitor cells expressing the proneural genes atoh1b and ptf1a but not those expressing neurod. Specificity of the morphant phenotype was demonstrated by the restoration of brain organogenesis, whole-embryo glucose uptake, brain apoptosis, and expression of proneural markers in rescue experiments. These results indicate that glut2 has an essential role during brain development by facilitating the uptake and availability of glucose and support the involvement of glut2 in brain glucose sensing.
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88
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Otlivanchik O, Le Foll C, Levin BE. Perifornical hypothalamic orexin and serotonin modulate the counterregulatory response to hypoglycemic and glucoprivic stimuli. Diabetes 2015; 64:226-35. [PMID: 25114294 PMCID: PMC4274798 DOI: 10.2337/db14-0671] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Previous reports suggested an important role for serotonin (5-hydroxytryptamine [5-HT]) in enhancing the counterregulatory response (CRR) to hypoglycemia. To elucidate the sites of action mediating this effect, we initially found that insulin-induced hypoglycemia stimulates 5-HT release in widespread forebrain regions, including the perifornical hypothalamus (PFH; 30%), ventromedial hypothalamus (34%), paraventricular hypothalamus (34%), paraventricular thalamic nucleus (64%), and cerebral cortex (63%). Of these, we focused on the PFH because of its known modulation of diverse neurohumoral and behavioral responses. In awake, behaving rats, bilateral PFH glucoprivation with 5-thioglucose stimulated adrenal medullary epinephrine (Epi) release (3,153%) and feeding (400%), while clamping PFH glucose at postprandial brain levels blunted the Epi response to hypoglycemia by 30%. The PFH contained both glucose-excited (GE) and glucose-inhibited (GI) neurons; GE neurons were primarily excited, while GI neurons were equally excited or inhibited by 5-HT at hypoglycemic glucose levels in vitro. Also, 5-HT stimulated lactate production by cultured hypothalamic astrocytes. Depleting PFH 5-HT blunted the Epi (but not feeding) response to focal PFH (69%) and systemic glucoprivation (39%), while increasing PFH 5-HT levels amplified the Epi response to hypoglycemia by 32%. Finally, the orexin 1 receptor antagonist SB334867A attenuated both the Epi (65%) and feeding (47%) responses to focal PFH glucoprivation. Thus we have identified the PFH as a glucoregulatory region where both 5-HT and orexin modulate the CRR and feeding responses to glucoprivation.
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Affiliation(s)
- Oleg Otlivanchik
- Graduate School of Biomedical Sciences, Rutgers, Newark, NJ Department of Neurology and Neurosciences, New Jersey Medical School, Rutgers, Newark, NJ
| | - Christelle Le Foll
- Department of Neurology and Neurosciences, New Jersey Medical School, Rutgers, Newark, NJ
| | - Barry E Levin
- Department of Neurology and Neurosciences, New Jersey Medical School, Rutgers, Newark, NJ Neurology Service, Veterans Affairs Medical Center, East Orange, NJ
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89
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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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90
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Langlet F. [Role of tanycytes within the blood-hypothalamus interface]. Biol Aujourdhui 2014; 208:225-235. [PMID: 25474004 DOI: 10.1051/jbio/2014025] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2014] [Indexed: 06/04/2023]
Abstract
Information exchanges between the brain and the periphery are key stages in the regulation of various physiological functions. The mediobasal hypothalamus, which ensures a large part of these functions, must be permanently informed about the physiological state of the body to guarantee the maintaining of homeostasis. For that purpose, it possesses a peculiar blood-brain interface due to the presence of specialized glial cells called tanycytes. This review describes the organization of the blood-hypothalamus interface and characterizes the peculiar place of tanycytes within it, as well as their striking capacity to remodel their own interface in order to ensure the regulation of various physiological functions.
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Affiliation(s)
- Fanny Langlet
- Inserm, Centre de recherche Jean-Pierre Aubert, U837, Développement et plasticité du cerveau post-natal, 59000 Lille, France - Université de Lille, Faculté de médecine, Institut de Médecine Prédictive et de Recherche Thérapeutique, 59000 Lille, France
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91
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Le Foll C, Dunn-Meynell AA, Levin BE. Role of FAT/CD36 in fatty acid sensing, energy, and glucose homeostasis regulation in DIO and DR rats. Am J Physiol Regul Integr Comp Physiol 2014; 308:R188-98. [PMID: 25477422 DOI: 10.1152/ajpregu.00367.2014] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
Hypothalamic fatty acid (FA) sensing neurons alter their activity utilizing the FA translocator/receptor, FAT/CD36. Depletion of ventromedial hypothalamus (VMH) CD36 with adeno-associated viral vector expressing CD36 shRNA (AAV CD36 shRNA) leads to redistribution of adipose stores and insulin resistance in outbred rats. This study assessed the requirement of VMH CD36-mediated FA sensing for the regulation of energy and glucose homeostasis in postnatal day 5 (P5) and P21 selectively bred diet-induced obese (DIO) and diet-resistant (DR) rats using VMH AAV CD36 shRNA injections. P5 CD36 depletion altered VMH neuronal FA sensing predominantly in DIO rats. After 10 wk on a 45% fat diet, DIO rats injected with VMH AAV CD36 shRNA at P21 ate more and gained more weight than DIO AAV controls, while DR AAV CD36 shRNA-injected rats gained less weight than DR AAV controls. VMH CD36 depletion increased inguinal fat pad weights and leptin levels in DIO and DR rats. Although DR AAV CD36 shRNA-injected rats became as obese as DIO AAV controls, only DIO control and CD36 depleted rats became insulin-resistant on a 45% fat diet. VMH CD36 depletion stunted linear growth in DIO and DR rats. DIO rats injected with AAV CD36 shRNA at P5 had increased fat mass, mostly due to a 45% increase in subcutaneous fat. They were also insulin-resistant with an associated 71% increase of liver triglycerides. These results demonstrate that VMH CD36-mediated FA sensing is a critical factor in the regulation of energy and glucose homeostasis and fat deposition in DIO and DR rats.
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Affiliation(s)
- Christelle Le Foll
- Department of Neurology and Neurosciences, Rutgers New Jersey Medical School, Newark, New Jersey; and
| | | | - Barry E Levin
- Department of Neurology and Neurosciences, Rutgers New Jersey Medical School, Newark, New Jersey; and Neurology Service, Veterans Affairs Medical Center, East Orange, New Jersey
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92
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Al Koborssy D, Palouzier-Paulignan B, Salem R, Thevenet M, Romestaing C, Julliard AK. Cellular and molecular cues of glucose sensing in the rat olfactory bulb. Front Neurosci 2014; 8:333. [PMID: 25400540 PMCID: PMC4212682 DOI: 10.3389/fnins.2014.00333] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2014] [Accepted: 10/03/2014] [Indexed: 11/13/2022] Open
Abstract
In the brain, glucose homeostasis of extracellular fluid is crucial to the point that systems specifically dedicated to glucose sensing are found in areas involved in energy regulation and feeding behavior. Olfaction is a major sensory modality regulating food consumption. Nutritional status in turn modulates olfactory detection. Recently it has been proposed that some olfactory bulb (OB) neurons respond to glucose similarly to hypothalamic neurons. However, the precise molecular cues governing glucose sensing in the OB are largely unknown. To decrypt these molecular mechanisms, we first used immunostaining to demonstrate a strong expression of two neuronal markers of glucose-sensitivity, insulin-dependent glucose transporter type 4 (GLUT4), and sodium glucose co-transporter type 1 (SGLT1) in specific OB layers. We showed that expression and mapping of GLUT4 but not SGLT1 were feeding state-dependent. In order to investigate the impact of metabolic status on the delivery of blood-borne glucose to the OB, we measured extracellular fluid glucose concentration using glucose biosensors simultaneously in the OB and cortex of anesthetized rats. We showed that glucose concentration in the OB is higher than in the cortex, that metabolic steady-state glucose concentration is independent of feeding state in the two brain areas, and that acute changes in glycemic conditions affect bulbar glucose concentration alone. These data provide new evidence of a direct relationship between the OB and peripheral metabolism, and emphasize the importance of glucose for the OB network, providing strong arguments toward establishing the OB as a glucose-sensing organ.
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Affiliation(s)
- Dolly Al Koborssy
- Team "Olfaction: From Coding to Memory," Lyon Neuroscience Center, INSERM U1028-CNRS, University Lyon 1 Lyon, France
| | - Brigitte Palouzier-Paulignan
- Team "Olfaction: From Coding to Memory," Lyon Neuroscience Center, INSERM U1028-CNRS, University Lyon 1 Lyon, France
| | - Rita Salem
- Team "Olfaction: From Coding to Memory," Lyon Neuroscience Center, INSERM U1028-CNRS, University Lyon 1 Lyon, France
| | - Marc Thevenet
- Team "Olfaction: From Coding to Memory," Lyon Neuroscience Center, INSERM U1028-CNRS, University Lyon 1 Lyon, France
| | - Caroline Romestaing
- Laboratoire d'Ecologie des Hydrosystèmes Naturels et Anthropisés CNRS 5023, University Lyon 1, Bâtiments Darwin C and Forel Villeurbanne, France
| | - A Karyn Julliard
- Team "Olfaction: From Coding to Memory," Lyon Neuroscience Center, INSERM U1028-CNRS, University Lyon 1 Lyon, France
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93
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Ogunnowo-Bada EO, Heeley N, Brochard L, Evans ML. Brain glucose sensing, glucokinase and neural control of metabolism and islet function. Diabetes Obes Metab 2014; 16 Suppl 1:26-32. [PMID: 25200293 PMCID: PMC4405079 DOI: 10.1111/dom.12334] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/29/2014] [Accepted: 06/05/2014] [Indexed: 11/30/2022]
Abstract
It is increasingly apparent that the brain plays a central role in metabolic homeostasis, including the maintenance of blood glucose. This is achieved by various efferent pathways from the brain to periphery, which help control hepatic glucose flux and perhaps insulin-stimulated insulin secretion. Also, critically important for the brain given its dependence on a constant supply of glucose as a fuel--emergency counter-regulatory responses are triggered by the brain if blood glucose starts to fall. To exert these control functions, the brain needs to detect rapidly and accurately changes in blood glucose. In this review, we summarize some of the mechanisms postulated to play a role in this and examine the potential role of the low-affinity hexokinase, glucokinase, in the brain as a key part of some of this sensing. We also discuss how these processes may become altered in diabetes and related metabolic diseases.
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Affiliation(s)
- E O Ogunnowo-Bada
- Wellcome Trust-MRC Institute of Metabolic Science, IMS Metabolic Research Laboratories, University of CambridgeCambridge, UK
| | - N Heeley
- Wellcome Trust-MRC Institute of Metabolic Science, IMS Metabolic Research Laboratories, University of CambridgeCambridge, UK
| | - L Brochard
- Wellcome Trust-MRC Institute of Metabolic Science, IMS Metabolic Research Laboratories, University of CambridgeCambridge, UK
| | - M L Evans
- Wellcome Trust-MRC Institute of Metabolic Science, IMS Metabolic Research Laboratories, University of CambridgeCambridge, UK
- Correspondence to: Mark Evans, Wellcome Trust-MRC Institute of Metabolic Science, University of Cambridge, IMS Metabolic Research Laboratories, Box 289 Addenbrookes Hospital, Hills Road, Cambridge CB2 0QQ, UK. E-mail:
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94
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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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95
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The neuroanatomical function of leptin in the hypothalamus. J Chem Neuroanat 2014; 61-62:207-20. [PMID: 25007719 DOI: 10.1016/j.jchemneu.2014.05.004] [Citation(s) in RCA: 54] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2013] [Revised: 05/09/2014] [Accepted: 05/28/2014] [Indexed: 02/07/2023]
Abstract
The anorexigenic hormone leptin plays an important role in the control of food intake and feeding-related behavior, for an important part through its action in the hypothalamus. The adipose-derived hormone modulates a complex network of several intercommunicating orexigenic and anorexigenic neuropeptides in the hypothalamus to reduce food intake and increase energy expenditure. In this review we present an updated overview of the functional role of leptin in respect to feeding and feeding-related behavior per distinct hypothalamic nuclei. In addition to the arcuate nucleus, which is a major leptin sensitive hub, leptin-responsive neurons in other hypothalamic nuclei, including the, dorsomedial-, ventromedial- and paraventricular nucleus and the lateral hypothalamic area, are direct targets of leptin. However, leptin also modulates hypothalamic neurons in an indirect manner, such as via the melanocortin system. The dissection of the complexity of leptin's action on the networks involved in energy balance is subject of recent and future studies. A full understanding of the role of hypothalamic leptin in the regulation of energy balance requires cell-specific manipulation using of conditional deletion and expression of leptin receptors. In addition, optogenetic and pharmacogenetic tools in combination with other pharmacological (such as the recent discovery of a leptin receptor antagonist) and neuronal tracing techniques to map the circuit, will be helpful to understand the role of leptin receptor expressing neurons. Better understanding of these circuits and the involvement of leptin could provide potential sites for therapeutic interventions in obesity and metabolic diseases characterized by dysregulation of energy balance.
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96
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Long-term increased carnitine palmitoyltransferase 1A expression in ventromedial hypotalamus causes hyperphagia and alters the hypothalamic lipidomic profile. PLoS One 2014; 9:e97195. [PMID: 24819600 PMCID: PMC4018328 DOI: 10.1371/journal.pone.0097195] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2014] [Accepted: 04/16/2014] [Indexed: 12/22/2022] Open
Abstract
Lipid metabolism in the ventromedial hypothalamus (VMH) has emerged as a crucial pathway in the regulation of feeding and energy homeostasis. Carnitine palmitoyltransferase (CPT) 1A is the rate-limiting enzyme in mitochondrial fatty acid β-oxidation and it has been proposed as a crucial mediator of fasting and ghrelin orexigenic signalling. However, the relationship between changes in CPT1A activity and the intracellular downstream effectors in the VMH that contribute to appetite modulation is not fully understood. To this end, we examined the effect of long-term expression of a permanently activated CPT1A isoform by using an adeno-associated viral vector injected into the VMH of rats. Peripherally, this procedure provoked hyperghrelinemia and hyperphagia, which led to overweight, hyperglycemia and insulin resistance. In the mediobasal hypothalamus (MBH), long-term CPT1AM expression in the VMH did not modify acyl-CoA or malonyl-CoA levels. However, it altered the MBH lipidomic profile since ceramides and sphingolipids increased and phospholipids decreased. Furthermore, we detected increased vesicular γ-aminobutyric acid transporter (VGAT) and reduced vesicular glutamate transporter 2 (VGLUT2) expressions, both transporters involved in this orexigenic signal. Taken together, these observations indicate that CPT1A contributes to the regulation of feeding by modulating the expression of neurotransmitter transporters and lipid components that influence the orexigenic pathways in VMH.
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97
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Le Foll C, Dunn-Meynell AA, Miziorko HM, Levin BE. Regulation of hypothalamic neuronal sensing and food intake by ketone bodies and fatty acids. Diabetes 2014; 63:1259-69. [PMID: 24379353 PMCID: PMC3964505 DOI: 10.2337/db13-1090] [Citation(s) in RCA: 84] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Metabolic sensing neurons in the ventromedial hypothalamus (VMH) alter their activity when ambient levels of metabolic substrates, such as glucose and fatty acids (FA), change. To assess the relationship between a high-fat diet (HFD; 60%) intake on feeding and serum and VMH FA levels, rats were trained to eat a low-fat diet (LFD; 13.5%) or an HFD in 3 h/day and were monitored with VMH FA microdialysis. Despite having higher serum levels, HFD rats had lower VMH FA levels but ate less from 3 to 6 h of refeeding than did LFD rats. However, VMH β-hydroxybutyrate (β-OHB) and VMH-to-serum β-OHB ratio levels were higher in HFD rats during the first 1 h of refeeding, suggesting that VMH astrocyte ketone production mediated their reduced intake. In fact, using calcium imaging in dissociated VMH neurons showed that ketone bodies overrode normal FA sensing, primarily by exciting neurons that were activated or inhibited by oleic acid. Importantly, bilateral inhibition of VMH ketone production with a 3-hydroxy-3-methylglutaryl-CoA synthase inhibitor reversed the 3- to 6-h HFD-induced inhibition of intake but had no effect in LFD-fed rats. These data suggest that a restricted HFD intake regimen inhibits caloric intake as a consequence of FA-induced VMH ketone body production by astrocytes.
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Affiliation(s)
- Christelle Le Foll
- Department of Neurology and Neurosciences, Rutgers New Jersey Medical School, Newark, NJ
- Corresponding author: Christelle Le Foll,
| | | | - Henri M. Miziorko
- School of Biological Sciences, University of Missouri–Kansas City, Kansas City, MO
| | - Barry E. Levin
- Department of Neurology and Neurosciences, Rutgers New Jersey Medical School, Newark, NJ
- Neurology Service, Veterans Affairs Medical Center, East Orange, NJ
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98
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Lamy CM, Sanno H, Labouèbe G, Picard A, Magnan C, Chatton JY, Thorens B. Hypoglycemia-activated GLUT2 neurons of the nucleus tractus solitarius stimulate vagal activity and glucagon secretion. Cell Metab 2014; 19:527-38. [PMID: 24606905 DOI: 10.1016/j.cmet.2014.02.003] [Citation(s) in RCA: 101] [Impact Index Per Article: 10.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/25/2012] [Revised: 12/17/2013] [Accepted: 01/24/2014] [Indexed: 12/20/2022]
Abstract
Glucose-sensing neurons in the brainstem participate in the regulation of energy homeostasis but have been poorly characterized because of the lack of specific markers to identify them. Here we show that GLUT2-expressing neurons of the nucleus of the tractus solitarius form a distinct population of hypoglycemia-activated neurons. Their response to low glucose is mediated by reduced intracellular glucose metabolism, increased AMP-activated protein kinase activity, and closure of leak K(+) channels. These are GABAergic neurons that send projections to the vagal motor nucleus. Light-induced stimulation of channelrhodospin-expressing GLUT2 neurons in vivo led to increased parasympathetic nerve firing and glucagon secretion. Thus GLUT2 neurons of the nucleus tractus solitarius link hypoglycemia detection to counterregulatory response. These results may help identify the cause of hypoglycemia-associated autonomic failure, a major threat in the insulin treatment of diabetes.
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Affiliation(s)
- Christophe M Lamy
- Department of Fundamental Neurosciences, University of Lausanne, rue du Bugnon 9, 1005 Lausanne, Switzerland; Department of Medicine, University of Fribourg, Rte Albert Gockel 1, 1700 Fribourg, Switzerland
| | - Hitomi Sanno
- Center for Integrative Genomics, University of Lausanne, Genopode Building, 1015 Lausanne, Switzerland
| | - Gwenaël Labouèbe
- Center for Integrative Genomics, University of Lausanne, Genopode Building, 1015 Lausanne, Switzerland
| | - Alexandre Picard
- Center for Integrative Genomics, University of Lausanne, Genopode Building, 1015 Lausanne, Switzerland
| | - Christophe Magnan
- CNRS-University Paris Diderot, Case courrier 7126, 4 rue Marie Andrée Lagroua Weill-Halle, 75205 Paris Cedex 13, France
| | - Jean-Yves Chatton
- Department of Fundamental Neurosciences, University of Lausanne, rue du Bugnon 9, 1005 Lausanne, Switzerland.
| | - Bernard Thorens
- Center for Integrative Genomics, University of Lausanne, Genopode Building, 1015 Lausanne, Switzerland.
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99
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Hypothalamic dysfunction of the thrombospondin receptor α2δ-1 underlies the overeating and obesity triggered by brain-derived neurotrophic factor deficiency. J Neurosci 2014; 34:554-65. [PMID: 24403154 DOI: 10.1523/jneurosci.1572-13.2014] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
Brain-derived neurotrophic factor (BDNF) and its receptor, TrkB, are critical components of the neural circuitry controlling appetite and body weight. Diminished BDNF signaling in mice results in severe hyperphagia and obesity. In humans, BDNF haploinsufficiency and the functional Bdnf Val66Met polymorphism have been linked to elevated food intake and body weight. The mechanisms underlying this dysfunction are poorly defined. We demonstrate a chief role of α2δ-1, a calcium channel subunit and thrombospondin receptor, in triggering overeating in mice with central BDNF depletion. We show reduced α2δ-1 cell-surface expression in the BDNF mutant ventromedial hypothalamus (VMH), an energy balance-regulating center. This deficit contributes to the hyperphagia exhibited by BDNF mutant mice because selective inhibition of α2δ-1 by gabapentin infusion into wild-type VMH significantly increases feeding and body weight gain. Importantly, viral-mediated α2δ-1 rescue in BDNF mutant VMH significantly mitigates their hyperphagia, obesity, and liver steatosis and normalizes deficits in glucose homeostasis. Whole-cell recordings in BDNF mutant VMH neurons revealed normal calcium currents but reduced frequency of EPSCs. These results suggest calcium channel-independent effects of α2δ-1 on feeding and implicate α2δ-1-thrombospondin interactions known to facilitate excitatory synapse assembly. Our findings identify a central mechanism mediating the inhibitory effects of BDNF on feeding. They also demonstrate a novel and critical role for α2δ-1 in appetite control and suggest a mechanism underlying weight gain in humans treated with gabapentinoid drugs.
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100
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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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