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Cognitive deficits and impaired hippocampal long-term potentiation in K ATP-induced DEND syndrome. Proc Natl Acad Sci U S A 2021; 118:2109721118. [PMID: 34732576 PMCID: PMC8609313 DOI: 10.1073/pnas.2109721118] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 09/29/2021] [Indexed: 11/18/2022] Open
Abstract
ATP-sensitive potassium (KATP) gain-of-function (GOF) mutations cause neonatal diabetes, with some individuals exhibiting developmental delay, epilepsy, and neonatal diabetes (DEND) syndrome. Mice expressing KATP-GOF mutations pan-neuronally (nKATP-GOF) demonstrated sensorimotor and cognitive deficits, whereas hippocampus-specific hKATP-GOF mice exhibited mostly learning and memory deficiencies. Both nKATP-GOF and hKATP-GOF mice showed altered neuronal excitability and reduced hippocampal long-term potentiation (LTP). Sulfonylurea therapy, which inhibits KATP, mildly improved sensorimotor but not cognitive deficits in KATP-GOF mice. Mice expressing KATP-GOF mutations in pancreatic β-cells developed severe diabetes but did not show learning and memory deficits, suggesting neuronal KATP-GOF as promoting these features. These findings suggest a possible origin of cognitive dysfunction in DEND and the need for novel drugs to treat neurological features induced by neuronal KATP-GOF.
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2
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Song N, Fang Y, Zhu H, Liu J, Jiang S, Sun S, Xu R, Ding J, Hu G, Lu M. Kir6.2 is essential to maintain neurite features by modulating PM20D1-reduced mitochondrial ATP generation. Redox Biol 2021; 47:102168. [PMID: 34673451 PMCID: PMC8577462 DOI: 10.1016/j.redox.2021.102168] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2021] [Revised: 10/13/2021] [Accepted: 10/14/2021] [Indexed: 12/28/2022] Open
Abstract
Kir6.2, a pore-forming subunit of the ATP-sensitive potassium (KATP) channels, regulates the functions of metabolically active tissues and acts as an ideal therapeutic target for multiple diseases. Previous studies have been conducted on peripheral kir6.2, but its precise physiological roles in the central nervous system (CNS) have rarely been revealed. In the current study, we evaluated the neurophenotypes and neuroethology of kir6.2 knockout (kir6.2-/-) mice. We demonstrated the beneficial effects of kir6.2 on maintaining the morphology of mesencephalic neurons and controlling the motor coordination of mice. The mechanisms underlying the abnormal neurological features of kir6.2 deficiency were analyzed by RNA sequencing (RNA-seq). Pm20d1, a gene encoding PM20D1 secretase that promotes the generation of endogenous mitochondria uncouplers in vivo, was dramatically upregulated in the midbrain of kir6.2-/- mice. Further investigations verified that PM20D1-induced increase of N-acyl amino acids (N-AAAs) from circulating fatty acids and amino acids promoted mitochondrial impairments and cut down the ATP generation, which mediated the morphological defects of the mesencephalic neurons and thus led to the behavioral impairments of kir6.2 knockout mice. This study is the first evidence to demonstrate the roles of kir6.2 in the morphological maintenance of neurite and motor coordination control of mice, which extends our understanding of kir6.2/KATP channels in regulating the neurophysiological function.
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Affiliation(s)
- Nanshan Song
- Jiangsu Key Laboratory of Neurodegeneration, Department of Pharmacology, Nanjing Medical University, Nanjing, 211166, China
| | - Yinquan Fang
- Jiangsu Key Laboratory of Neurodegeneration, Department of Pharmacology, Nanjing Medical University, Nanjing, 211166, China
| | - Hong Zhu
- Jiangsu Key Laboratory of Neurodegeneration, Department of Pharmacology, Nanjing Medical University, Nanjing, 211166, China
| | - Jiaqi Liu
- Jiangsu Key Laboratory of Neurodegeneration, Department of Pharmacology, Nanjing Medical University, Nanjing, 211166, China
| | - Siyuan Jiang
- Jiangsu Key Laboratory of Neurodegeneration, Department of Pharmacology, Nanjing Medical University, Nanjing, 211166, China
| | - Sifan Sun
- Department of Pharmacology, Nanjing University of Chinese Medicine, Nanjing, 210023, China
| | - Rong Xu
- Jiangsu Key Laboratory of Neurodegeneration, Department of Pharmacology, Nanjing Medical University, Nanjing, 211166, China
| | - Jianhua Ding
- Jiangsu Key Laboratory of Neurodegeneration, Department of Pharmacology, Nanjing Medical University, Nanjing, 211166, China
| | - Gang Hu
- Jiangsu Key Laboratory of Neurodegeneration, Department of Pharmacology, Nanjing Medical University, Nanjing, 211166, China; Department of Pharmacology, Nanjing University of Chinese Medicine, Nanjing, 210023, China.
| | - Ming Lu
- Jiangsu Key Laboratory of Neurodegeneration, Department of Pharmacology, Nanjing Medical University, Nanjing, 211166, China; Neuroprotective Drug Discovery Key Laboratory, Department of Pharmacology, Nanjing Medical University, Nanjing, 211166, China.
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Akyuz E, Villa C, Beker M, Elibol B. Unraveling the Role of Inwardly Rectifying Potassium Channels in the Hippocampus of an Aβ (1-42)-Infused Rat Model of Alzheimer's Disease. Biomedicines 2020; 8:biomedicines8030058. [PMID: 32183098 PMCID: PMC7148495 DOI: 10.3390/biomedicines8030058] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2020] [Revised: 03/10/2020] [Accepted: 03/12/2020] [Indexed: 11/24/2022] Open
Abstract
Alzheimer’s disease (AD) is a progressive neurodegenerative disorder with a complex etiology and characterized by cognitive deficits and memory loss. The pathogenesis of AD is not yet completely elucidated, and no curative treatment is currently available. Inwardly rectifying potassium (Kir) channels are important for playing a key role in maintaining the resting membrane potential and controlling cell excitability, being largely expressed in both excitable and non-excitable tissues, including neurons. Accordingly, the aim of the study is to investigate the role of neuronal Kir channels in AD pathophysiology. The mRNA and protein levels of neuronal Kir2.1, Kir3.1, and Kir6.2 were evaluated by real-time PCR and Western blot analysis from the hippocampus of an amyloid-β(Aβ)(1-42)-infused rat model of AD. Extracellular deposition of Aβ was confirmed by both histological Congo red staining and immunofluorescence analysis. Significant decreased mRNA and protein levels of Kir2.1 and Kir6.2 channels were observed in the rat model of AD, whereas no differences were found in Kir3.1 channel levels as compared with controls. Our results provide in vivo evidence that Aβ can modulate the expression of these channels, which may represent novel potential therapeutic targets in the treatment of AD.
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Affiliation(s)
- Enes Akyuz
- Department of Biophysics, Faculty of Medicine, Yozgat Bozok University, Yozgat 66100, Turkey
- Correspondence: (E.A.); (C.V.)
| | - Chiara Villa
- School of Medicine and Surgery, University of Milano-Bicocca, 20900 Monza, Italy
- Correspondence: (E.A.); (C.V.)
| | - Merve Beker
- Department of Medical Biology, Faculty of Medicine, Bezmialem Vakif University, Istanbul 34093, Turkey; (M.B.); (B.E.)
| | - Birsen Elibol
- Department of Medical Biology, Faculty of Medicine, Bezmialem Vakif University, Istanbul 34093, Turkey; (M.B.); (B.E.)
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Kir6.1 Heterozygous Mice Exhibit Aberrant Amygdala-Dependent Cued Fear Memory. Mol Neurobiol 2019; 57:1622-1635. [PMID: 31808063 DOI: 10.1007/s12035-019-01840-1] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2019] [Accepted: 11/18/2019] [Indexed: 10/25/2022]
Abstract
ATP-sensitive K+ (KATP) channels are predominantly expressed in the brain and consist of four identical inward-rectifier potassium ion channel subunits (Kir6.1 or Kir6.2) and four identical high-affinity sulfonylurea receptor subunits (SUR1, SUR2A, or SUR2B). We previously observed that chronic corticosterone-treated (CORT) mice exhibited enhanced anxiety-like behaviors and cued fear memory. In the present study, the protein and mRNA expression levels of Kir6.1, but not Kir6.2, were decreased in the lateral amygdala (LA) of CORT mice. Heterozygous Kir6.1-null (Kir6.1+/-) mice also showed enhanced tone (cued) fear memory and long-term potentiation (LTP) in the cortico-LA pathway compared to those in wild-type mice. However, LTP was not enhanced in the hippocampal CA1 regions of Kir6.1+/- mice. Consistent with increased cued fear memory, both Ca2+/calmodulin-dependent protein kinase II (CaMKII) and extracellular signal-regulated kinase (ERK) activities were significantly elevated in the LAs of Kir6.1+/- mice after tone stimulation. Our results indicate that increased CaMKII and ERK activities may induce LTP in the LA in Kir6.1+/- mice, leading to aberrant cued fear memory. The changes in neural plasticity in the LA of Kir6.1+/- mice were associated with anxiety-like behaviors and may be related to the pathogenic mechanisms of anxiety disorders in human patients.
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Tinker A, Aziz Q, Li Y, Specterman M. ATP‐Sensitive Potassium Channels and Their Physiological and Pathophysiological Roles. Compr Physiol 2018; 8:1463-1511. [DOI: 10.1002/cphy.c170048] [Citation(s) in RCA: 72] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
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6
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Ahn KC, Learman CR, Dunbar GL, Maiti P, Jang WC, Cha HC, Song MS. Characterization of Impaired Cerebrovascular Structure in APP/PS1 Mouse Brains. Neuroscience 2018; 385:246-254. [PMID: 29777753 DOI: 10.1016/j.neuroscience.2018.05.002] [Citation(s) in RCA: 25] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2017] [Revised: 04/27/2018] [Accepted: 05/02/2018] [Indexed: 01/01/2023]
Abstract
Alzheimer's disease (AD) is defined by senile plaques, tauopathy and neuronal cell death in specific area of the brain. Recent studies suggest that neurovascular dysfunction may be an integral part of AD pathogenesis, contributing to the onset and development of AD pathologies such as neuronal death, inflammatory response, and breakdown of blood-brain barrier (BBB). In addition, vascular complications caused by age-related metabolic diseases such as diabetes and high blood pressure have high incidence in development of dementia and AD. We previously reported that astrocytes, essential components of BBB, were chronically activated and some deteriorated in the brain of 5xFAD, an amyloid precursor protein/presenilin1 (APP/PS1) transgenic mouse model. Thus, it is rational to investigate if any vascular dysfunction is associated with considerable activation of astrocytes in APP/PS1 mouse model. In this study, we observed that cerebrovascular pathology was associated with large scale of reactive astrocytes and neurodegeneration in an Aβ plague-generating mouse model. Using 5xFAD mouse brains, we demonstrate damaged brain vessels and reduced expression of glucose transporter 1 (GLUT1), the main glucose transporter, and a tight junction protein zonula occludens-1 (ZO-1) of cerebrovascular endothelial cells. This vascular pathology was closely associated with astrocytic deterioration and neuronal loss due to buildup of Aβ plaques in 5xFAD mouse brains.
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Affiliation(s)
- Kee-Chan Ahn
- University of British Columbia, Vancouver, BC, Canada; EnviroBrain, Edmonton, AB, Canada
| | - Cameron R Learman
- Field Neurosciences Institute, St. Mary's of Michigan, Saginaw, MI, USA; Neuroscience Program, Central Michigan University, Mt Pleasant, MI, USA
| | - Gary L Dunbar
- Field Neurosciences Institute, St. Mary's of Michigan, Saginaw, MI, USA; Neuroscience Program, Central Michigan University, Mt Pleasant, MI, USA
| | - Panchanan Maiti
- Field Neurosciences Institute, St. Mary's of Michigan, Saginaw, MI, USA; Neuroscience Program, Central Michigan University, Mt Pleasant, MI, USA
| | | | - Hyeon-Cheol Cha
- Department of Biological Sciences, Dankook University, Cheonan, Chungnam, South Korea
| | - Mee-Sook Song
- Department of Biological Sciences, Dankook University, Cheonan, Chungnam, South Korea.
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Moriguchi S, Ishizuka T, Yabuki Y, Shioda N, Sasaki Y, Tagashira H, Yawo H, Yeh JZ, Sakagami H, Narahashi T, Fukunaga K. Blockade of the K ATP channel Kir6.2 by memantine represents a novel mechanism relevant to Alzheimer's disease therapy. Mol Psychiatry 2018; 23:211-221. [PMID: 27777420 DOI: 10.1038/mp.2016.187] [Citation(s) in RCA: 32] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/24/2015] [Revised: 08/11/2016] [Accepted: 08/22/2016] [Indexed: 01/09/2023]
Abstract
Here, we report a novel target of the drug memantine, ATP-sensitive K+ (KATP) channels, potentially relevant to memory improvement. We confirmed that memantine antagonizes memory impairment in Alzheimer's model APP23 mice. Memantine increased CaMKII activity in the APP23 mouse hippocampus, and memantine-induced enhancement of hippocampal long-term potentiation (LTP) and CaMKII activity was totally abolished by treatment with pinacidil, a specific opener of KATP channels. Memantine also inhibited Kir6.1 and Kir6.2 KATP channels and elevated intracellular Ca2+ concentrations in neuro2A cells overexpressing Kir6.1 or Kir6.2. Kir6.2 was preferentially expressed at postsynaptic regions of hippocampal neurons, whereas Kir6.1 was predominant in dendrites and cell bodies of pyramidal neurons. Finally, we confirmed that Kir6.2 mutant mice exhibit severe memory deficits and impaired hippocampal LTP, impairments that cannot be rescued by memantine administration. Altogether, our studies show that memantine modulates Kir6.2 activity, and that the Kir6.2 channel is a novel target for therapeutics to improve memory impairment in Alzheimer disease patients.
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Affiliation(s)
- S Moriguchi
- Department of Pharmacology, Graduate School of Pharmaceutical Sciences, Tohoku University, Sendai, Japan
| | - T Ishizuka
- Department of Developmental Biology and Neuroscience, Graduate School of Life Sciences, Tohoku University, Sendai, Japan
| | - Y Yabuki
- Department of Pharmacology, Graduate School of Pharmaceutical Sciences, Tohoku University, Sendai, Japan
| | - N Shioda
- Department of Pharmacology, Graduate School of Pharmaceutical Sciences, Tohoku University, Sendai, Japan
| | - Y Sasaki
- Department of Pharmacology, Graduate School of Pharmaceutical Sciences, Tohoku University, Sendai, Japan
| | - H Tagashira
- Department of Pharmacology, Graduate School of Pharmaceutical Sciences, Tohoku University, Sendai, Japan
| | - H Yawo
- Department of Developmental Biology and Neuroscience, Graduate School of Life Sciences, Tohoku University, Sendai, Japan
| | - J Z Yeh
- Department of Molecular Pharmacology and Biological Chemistry, Northwestern University Feinberg School of Medicine, Chicago, IL, USA
| | - H Sakagami
- Department of Anatomy, Kitasato University School of Medicine, Sagamihara, Japan
| | - T Narahashi
- Department of Molecular Pharmacology and Biological Chemistry, Northwestern University Feinberg School of Medicine, Chicago, IL, USA
| | - K Fukunaga
- Department of Pharmacology, Graduate School of Pharmaceutical Sciences, Tohoku University, Sendai, Japan
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Kim DY, Abdelwahab MG, Lee SH, O’Neill D, Thompson RJ, Duff HJ, Sullivan PG, Rho JM. Ketones prevent oxidative impairment of hippocampal synaptic integrity through KATP channels. PLoS One 2015; 10:e0119316. [PMID: 25848768 PMCID: PMC4388385 DOI: 10.1371/journal.pone.0119316] [Citation(s) in RCA: 45] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2014] [Accepted: 01/29/2015] [Indexed: 12/31/2022] Open
Abstract
Dietary and metabolic therapies are increasingly being considered for a variety of neurological disorders, based in part on growing evidence for the neuroprotective properties of the ketogenic diet (KD) and ketones. Earlier, we demonstrated that ketones afford hippocampal synaptic protection against exogenous oxidative stress, but the mechanisms underlying these actions remain unclear. Recent studies have shown that ketones may modulate neuronal firing through interactions with ATP-sensitive potassium (KATP) channels. Here, we used a combination of electrophysiological, pharmacological, and biochemical assays to determine whether hippocampal synaptic protection by ketones is a consequence of KATP channel activation. Ketones dose-dependently reversed oxidative impairment of hippocampal synaptic integrity, neuronal viability, and bioenergetic capacity, and this action was mirrored by the KATP channel activator diazoxide. Inhibition of KATP channels reversed ketone-evoked hippocampal protection, and genetic ablation of the inwardly rectifying K+ channel subunit Kir6.2, a critical component of KATP channels, partially negated the synaptic protection afforded by ketones. This partial protection was completely reversed by co-application of the KATP blocker, 5-hydoxydecanoate (5HD). We conclude that, under conditions of oxidative injury, ketones induce synaptic protection in part through activation of KATP channels.
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Affiliation(s)
- Do Young Kim
- Departments of Neurology and Neurobiology, Barrow Neurological Institute, St. Joseph’s Hospital & Medical Center, Phoenix, Arizona, United States of America
- * E-mail:
| | - Mohammed G. Abdelwahab
- Departments of Neurology and Neurobiology, Barrow Neurological Institute, St. Joseph’s Hospital & Medical Center, Phoenix, Arizona, United States of America
| | - Soo Han Lee
- Departments of Neurology and Neurobiology, Barrow Neurological Institute, St. Joseph’s Hospital & Medical Center, Phoenix, Arizona, United States of America
| | - Derek O’Neill
- Departments of Neurology and Neurobiology, Barrow Neurological Institute, St. Joseph’s Hospital & Medical Center, Phoenix, Arizona, United States of America
| | - Roger J. Thompson
- Departments of Cell Biology and Anatomy, Hotchkiss Brain Institute, University of Calgary, Calgary, Alberta, Canada
| | - Henry J. Duff
- Libin Cardiovascular Institute of Alberta, University of Calgary, Calgary, Alberta, Canada
| | - Patrick G. Sullivan
- Spinal Cord and Brain Injury Research Center, University of Kentucky, Lexington, Kentucky, United States of America
| | - Jong M. Rho
- Departments of Pediatrics and Clinical Neurosciences, Alberta Children’s Hospital, Calgary, Alberta, Canada
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Gandhi RM, Kogan CS, Messier C. 2-Methyl-6-(phenylethynyl) pyridine (MPEP) reverses maze learning and PSD-95 deficits in Fmr1 knock-out mice. Front Cell Neurosci 2014; 8:70. [PMID: 24701200 PMCID: PMC3965849 DOI: 10.3389/fncel.2014.00070] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/01/2014] [Accepted: 02/17/2014] [Indexed: 11/22/2022] Open
Abstract
Fragile X Syndrome (FXS) is caused by the lack of expression of the fragile X mental retardation protein (FMRP), which results in intellectual disability and other debilitating symptoms including impairment of visual-spatial functioning. FXS is the only single-gene disorder that is highly co-morbid with autism spectrum disorder and can therefore provide insight into its pathophysiology. Lack of FMRP results in altered group I metabotropic glutamate receptor (mGluR) signaling, which is a target for putative treatments. The Hebb-Williams (H-W) mazes are a set of increasingly complex spatial navigation problems that depend on intact hippocampal and thus mGluR-5 functioning. In the present investigation, we examined whether an antagonist of mGluR-5 would reverse previously described behavioral deficits in fragile X mental retardation 1 knock-out (Fmr1 KO) mice. Mice were trained on a subset of the H-W mazes and then treated with either 20 mg/kg of an mGluR-5 antagonist, 2-Methyl-6-(phenylethynyl) pyridine (MPEP; n = 11) or an equivalent dose of saline (n = 11) prior to running test mazes. Latency and errors were dependent variables recorded during the test phase. Immediately after completing each test, marble-burying behavior was assessed, which confirmed that the drug treatment was pharmacologically active during maze learning. Although latency was not statistically different between the groups, MPEP treated Fmr1 KO mice made significantly fewer errors on mazes deemed more difficult suggesting a reversal of the behavioral deficit. MPEP treated mice were also less perseverative and impulsive when navigating mazes. Furthermore, MPEP treatment reversed post-synaptic density-95 (PSD-95) protein deficits in Fmr1 KO treated mice, whereas levels of a control protein (β-tubulin) remained unchanged. These data further validate MPEP as a potentially beneficial treatment for FXS. Our findings also suggest that adapted H-W mazes may be a useful tool to document alterations in behavioral functioning following pharmacological intervention in FXS.
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Affiliation(s)
- Réno M Gandhi
- School of Psychology, University of Ottawa Ottawa, ON, Canada
| | - Cary S Kogan
- School of Psychology, University of Ottawa Ottawa, ON, Canada
| | - Claude Messier
- School of Psychology, University of Ottawa Ottawa, ON, Canada
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Gimeno-Bayón J, López-López A, Rodríguez M, Mahy N. Glucose pathways adaptation supports acquisition of activated microglia phenotype. J Neurosci Res 2014; 92:723-31. [DOI: 10.1002/jnr.23356] [Citation(s) in RCA: 111] [Impact Index Per Article: 11.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2013] [Revised: 11/04/2013] [Accepted: 12/03/2013] [Indexed: 01/25/2023]
Affiliation(s)
- J. Gimeno-Bayón
- Unitat de Bioquímica i Biologia Molecular, Facultat de Medicina; Institut d'Investigacions Biomèdiques August Pi i Sunyer (IDIBAPS), Universitat de Barcelona; Barcelona CIBERNED Spain
| | - A. López-López
- Unitat de Bioquímica i Biologia Molecular, Facultat de Medicina; Institut d'Investigacions Biomèdiques August Pi i Sunyer (IDIBAPS), Universitat de Barcelona; Barcelona CIBERNED Spain
| | - M.J. Rodríguez
- Unitat de Bioquímica i Biologia Molecular, Facultat de Medicina; Institut d'Investigacions Biomèdiques August Pi i Sunyer (IDIBAPS), Universitat de Barcelona; Barcelona CIBERNED Spain
| | - N. Mahy
- Unitat de Bioquímica i Biologia Molecular, Facultat de Medicina; Institut d'Investigacions Biomèdiques August Pi i Sunyer (IDIBAPS), Universitat de Barcelona; Barcelona CIBERNED Spain
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11
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Insulin stimulated-glucose transporter Glut 4 is expressed in the retina. PLoS One 2012; 7:e52959. [PMID: 23285235 PMCID: PMC3528717 DOI: 10.1371/journal.pone.0052959] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2012] [Accepted: 11/26/2012] [Indexed: 11/19/2022] Open
Abstract
The vertebrate retina is a very metabolically active tissue whose energy demands are normally met through the uptake of glucose and oxygen. Glucose metabolism in this tissue relies upon adequate glucose delivery from the systemic circulation. Therefore, glucose transport depends on the expression of glucose transporters. Here, we show retinal expression of the Glut 4 glucose transporter in frog and rat retinas. Immunohistochemistry and in situ hybridization studies showed Glut 4 expression in the three nuclear layers of the retina: the photoreceptor, inner nuclear and ganglionar cell layers. In the rat retina immunoprecipitation and Western blot analysis revealed a protein with an apparent molecular mass of 45 kDa. ¹⁴C-glucose accumulation by isolated rat retinas was significantly enhanced by physiological concentrations of insulin, an effect blocked by inhibitors of phosphatidyl-inositol 3-kinase (PI3K), a key enzyme in the insulin-signaling pathway in other tissues. Also, we observed an increase in ³H-cytochalasin binding sites in the presence of insulin, suggesting an increase in transporter recruitment at the cell surface. Besides, insulin induced phosphorylation of Akt, an effect also blocked by PI3K inhibition. Expression of Glut 4 was not modified in retinas of a type 1 diabetic rat model. To our knowledge, our results provide the first evidence of Glut4 expression in the retina, suggesting it as an insulin- responsive tissue.
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Newman LA, Korol DL, Gold PE. Lactate produced by glycogenolysis in astrocytes regulates memory processing. PLoS One 2011; 6:e28427. [PMID: 22180782 PMCID: PMC3236748 DOI: 10.1371/journal.pone.0028427] [Citation(s) in RCA: 357] [Impact Index Per Article: 27.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2011] [Accepted: 11/08/2011] [Indexed: 01/06/2023] Open
Abstract
When administered either systemically or centrally, glucose is a potent enhancer of memory processes. Measures of glucose levels in extracellular fluid in the rat hippocampus during memory tests reveal that these levels are dynamic, decreasing in response to memory tasks and loads; exogenous glucose blocks these decreases and enhances memory. The present experiments test the hypothesis that glucose enhancement of memory is mediated by glycogen storage and then metabolism to lactate in astrocytes, which provide lactate to neurons as an energy substrate. Sensitive bioprobes were used to measure brain glucose and lactate levels in 1-sec samples. Extracellular glucose decreased and lactate increased while rats performed a spatial working memory task. Intrahippocampal infusions of lactate enhanced memory in this task. In addition, pharmacological inhibition of astrocytic glycogenolysis impaired memory and this impairment was reversed by administration of lactate or glucose, both of which can provide lactate to neurons in the absence of glycogenolysis. Pharmacological block of the monocarboxylate transporter responsible for lactate uptake into neurons also impaired memory and this impairment was not reversed by either glucose or lactate. These findings support the view that astrocytes regulate memory formation by controlling the provision of lactate to support neuronal functions.
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Affiliation(s)
- Lori A Newman
- Neuroscience Program, University of Illinois at Urbana-Champaign, Champaign, Illinois, United States of America.
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Zhao Y, Fung C, Shin D, Shin BC, Thamotharan S, Sankar R, Ehninger D, Silva A, Devaskar SU. Neuronal glucose transporter isoform 3 deficient mice demonstrate features of autism spectrum disorders. Mol Psychiatry 2010; 15:286-99. [PMID: 19506559 PMCID: PMC4208914 DOI: 10.1038/mp.2009.51] [Citation(s) in RCA: 75] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Abstract
Neuronal glucose transporter (GLUT) isoform 3 deficiency in null heterozygous mice led to abnormal spatial learning and working memory but normal acquisition and retrieval during contextual conditioning, abnormal cognitive flexibility with intact gross motor ability, electroencephalographic seizures, perturbed social behavior with reduced vocalization and stereotypies at low frequency. This phenotypic expression is unique as it combines the neurobehavioral with the epileptiform characteristics of autism spectrum disorders. This clinical presentation occurred despite metabolic adaptations consisting of an increase in microvascular/glial GLUT1, neuronal GLUT8 and monocarboxylate transporter isoform 2 concentrations, with minimal to no change in brain glucose uptake but an increase in lactate uptake. Neuron-specific glucose deficiency has a negative impact on neurodevelopment interfering with functional competence. This is the first description of GLUT3 deficiency that forms a possible novel genetic mechanism for pervasive developmental disorders, such as the neuropsychiatric autism spectrum disorders, requiring further investigation in humans.
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Affiliation(s)
- Yuanzi Zhao
- Division of Neonatology & Developmental Biology, David Geffen School of Medicine UCLA, Los Angeles, CA 90095-1752,Department of Pediatrics, David Geffen School of Medicine UCLA, Los Angeles, CA 90095-1752
| | - Camille Fung
- Division of Neonatology & Developmental Biology, David Geffen School of Medicine UCLA, Los Angeles, CA 90095-1752,Department of Pediatrics, David Geffen School of Medicine UCLA, Los Angeles, CA 90095-1752
| | - Don Shin
- Division of Neurology, Neonatal Research Center1, David Geffen School of Medicine UCLA, Los Angeles, CA 90095-1752,Department of Pediatrics, David Geffen School of Medicine UCLA, Los Angeles, CA 90095-1752
| | - Bo-Chul Shin
- Division of Neonatology & Developmental Biology, David Geffen School of Medicine UCLA, Los Angeles, CA 90095-1752,Department of Pediatrics, David Geffen School of Medicine UCLA, Los Angeles, CA 90095-1752
| | - Shanthie Thamotharan
- Division of Neonatology & Developmental Biology, David Geffen School of Medicine UCLA, Los Angeles, CA 90095-1752,Department of Pediatrics, David Geffen School of Medicine UCLA, Los Angeles, CA 90095-1752
| | - Raman Sankar
- Division of Neurology, Neonatal Research Center1, David Geffen School of Medicine UCLA, Los Angeles, CA 90095-1752,Department of Pediatrics, David Geffen School of Medicine UCLA, Los Angeles, CA 90095-1752,Department of Neurology, David Geffen School of Medicine UCLA, Los Angeles, CA 90095-1752
| | - Dan Ehninger
- Department of Neurobiology, David Geffen School of Medicine UCLA, Los Angeles, CA 90095-1752
| | - Alcino Silva
- Department of Neurobiology, David Geffen School of Medicine UCLA, Los Angeles, CA 90095-1752
| | - Sherin U. Devaskar
- Division of Neonatology & Developmental Biology, David Geffen School of Medicine UCLA, Los Angeles, CA 90095-1752,Department of Pediatrics, David Geffen School of Medicine UCLA, Los Angeles, CA 90095-1752,Address all correspondence to: 10833, Le Conte Avenue, MDCC-B2-375, Los Angeles, CA 90095-1752, Ph. No. 310-825-9436, FAX No. 310-267-0154,
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14
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Abstract
The K+ channel, one of the determinants for neuronal excitability, is genetically heterogeneous, and various K+ channel genes are expressed in the CNS. The therapeutic potential of K+ channel blockers for cognitive enhancement has been discussed, but the contribution each K+ channel gene makes to cognitive function remains obscure. BEC1 (KCNH3) is a member of the K+ channel superfamily that shows forebrain-preferential distribution. Here, we show the critical involvement of BEC1 in cognitive function. BEC1 knock-out mice performed behavioral tasks related to working memory, reference memory, and attention better than their wild-type littermates. Enhanced performance was also observed in heterozygous mutants. The knock-out mice had neither the seizures nor the motor dysfunction that are often observed in K+ channel-deficient mice. In contrast to when it is disrupted, overexpression of BEC1 in the forebrain caused the impaired performance of those tasks. It was also found that altering BEC1 expression could change hippocampal neuronal excitability and synaptic plasticity. The results indicate that BEC1 may represent the first K+ channel that contributes preferentially and bidirectionally to cognitive function.
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Betourne A, Bertholet AM, Labroue E, Halley H, Sun HS, Lorsignol A, Feng ZP, French RJ, Penicaud L, Lassalle JM, Frances B. Involvement of hippocampal CA3 KATP channels in contextual memory. Neuropharmacology 2009; 56:615-25. [DOI: 10.1016/j.neuropharm.2008.11.001] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2008] [Revised: 10/31/2008] [Accepted: 11/03/2008] [Indexed: 11/27/2022]
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