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Nakaya Y, Kosukegawa S, Kobayashi S, Hirose K, Kitano K, Mayahara K, Takei H, Motoyoshi M, Kobayashi M. Insulin potentiates inhibitory synaptic currents between fast-spiking and pyramidal neurons in the rat insular cortex. Neuropharmacology 2023:109649. [PMID: 37393988 DOI: 10.1016/j.neuropharm.2023.109649] [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: 04/28/2023] [Revised: 06/27/2023] [Accepted: 06/30/2023] [Indexed: 07/04/2023]
Abstract
Insulin plays roles in brain functions such as neural development and plasticity and is reported to be involved in dementia and depression. However, little information is available on the insulin-mediated modulation of electrophysiological activities, especially in the cerebral cortex. This study examined how insulin modulates the neural activities of inhibitory neurons and inhibitory postsynaptic currents (IPSCs) in rat insular cortex (IC; either sex) by multiple whole-cell patch-clamp recordings. We demonstrated that insulin increased the repetitive spike firing rate with a decrease in the threshold potential without changing the resting membrane potentials and input resistance of fast-spiking GABAergic neurons (FSNs). Next, we found a dose-dependent enhancement of unitary IPSCs (uIPSCs) by insulin in the connections from FSNs to pyramidal neurons (PNs). The insulin-induced enhancement of uIPSCs accompanied decreases in the paired-pulse ratio, suggesting that insulin increases GABA release from presynaptic terminals. The finding of miniature IPSC recordings of the increased frequency without changing the amplitude supports this hypothesis. Insulin had little effect on uIPSCs under the coapplication of S961, an insulin receptor antagonist, or lavendustin A, an inhibitor of tyrosine kinase. The PI3-K inhibitor wortmannin or the PKB/Akt inhibitors, deguelin and Akt inhibitor VIII, blocked the insulin-induced enhancement of uIPSCs. Intracellular application of Akt inhibitor VIII to presynaptic FSNs also blocked insulin-induced enhancement of uIPSCs. In contrast, uIPSCs were enhanced by insulin in combination with the MAPK inhibitor PD98059. These results suggest that insulin facilitates the inhibition of PNs by increases in FSN firing frequency and IPSCs from FSNs to PNs. (250 words).
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Affiliation(s)
- Yuka Nakaya
- Department of Pharmacology, Nihon University School of Dentistry, 1-8-13 Kanda-Surugadai, Chiyoda-ku, Tokyo, 101-8310, Japan; Division of Oral and Craniomaxillofacial Research, Dental Research Center, Nihon University School of Dentistry, 1-8-13 Kanda-Surugadai, Chiyoda-ku, Tokyo, 101-8310, Japan
| | - Satoshi Kosukegawa
- Department of Pharmacology, Nihon University School of Dentistry, 1-8-13 Kanda-Surugadai, Chiyoda-ku, Tokyo, 101-8310, Japan; Department of Orthodontics, Nihon University School of Dentistry, 1-8-13 Kanda-Surugadai, Chiyoda-ku, Tokyo, 101-8310, Japan
| | - Satomi Kobayashi
- Department of Pharmacology, Nihon University School of Dentistry, 1-8-13 Kanda-Surugadai, Chiyoda-ku, Tokyo, 101-8310, Japan; Division of Oral and Craniomaxillofacial Research, Dental Research Center, Nihon University School of Dentistry, 1-8-13 Kanda-Surugadai, Chiyoda-ku, Tokyo, 101-8310, Japan; Department of Biology, Nihon University School of Dentistry, 1-8-13 Kanda-Surugadai, Chiyoda-ku, Tokyo, 101-8310, Japan
| | - Kensuke Hirose
- Department of Pharmacology, Nihon University School of Dentistry, 1-8-13 Kanda-Surugadai, Chiyoda-ku, Tokyo, 101-8310, Japan; Department of Pedodontics, Nihon University School of Dentistry, 1-8-13 Kanda-Surugadai, Chiyoda-ku, Tokyo, 101-8310, Japan
| | - Kouhei Kitano
- Department of Pharmacology, Nihon University School of Dentistry, 1-8-13 Kanda-Surugadai, Chiyoda-ku, Tokyo, 101-8310, Japan
| | - Kotoe Mayahara
- Division of Oral and Craniomaxillofacial Research, Dental Research Center, Nihon University School of Dentistry, 1-8-13 Kanda-Surugadai, Chiyoda-ku, Tokyo, 101-8310, Japan; Department of Orthodontics, Nihon University School of Dentistry, 1-8-13 Kanda-Surugadai, Chiyoda-ku, Tokyo, 101-8310, Japan
| | - Hiroki Takei
- Department of Dentistry, Saitama Prefectural Children's Medical Center, 1-2, Shintoshin, Chuo-ku, Saitama-shi, 3330-8777, Japan
| | - Mitsuru Motoyoshi
- Division of Oral and Craniomaxillofacial Research, Dental Research Center, Nihon University School of Dentistry, 1-8-13 Kanda-Surugadai, Chiyoda-ku, Tokyo, 101-8310, Japan; Department of Orthodontics, Nihon University School of Dentistry, 1-8-13 Kanda-Surugadai, Chiyoda-ku, Tokyo, 101-8310, Japan
| | - Masayuki Kobayashi
- Department of Pharmacology, Nihon University School of Dentistry, 1-8-13 Kanda-Surugadai, Chiyoda-ku, Tokyo, 101-8310, Japan; Division of Oral and Craniomaxillofacial Research, Dental Research Center, Nihon University School of Dentistry, 1-8-13 Kanda-Surugadai, Chiyoda-ku, Tokyo, 101-8310, Japan.
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2
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Yamaguchi ST, Tomita J, Kume K. Insulin signaling in clock neurons regulates sleep in Drosophila. Biochem Biophys Res Commun 2021; 591:44-49. [PMID: 34998032 DOI: 10.1016/j.bbrc.2021.12.100] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2021] [Accepted: 12/26/2021] [Indexed: 12/12/2022]
Abstract
Sleep relates to numerous biological functions, including metabolism. Both dietary conditions and genes related to metabolism are known to affect sleep behavior. Insulin signaling is well conserved across species including the fruit fly and relates to both metabolism and sleep. However, the neural mechanism of sleep regulation by insulin signaling is poorly understood. Here, we report that insulin signaling in specific neurons regulates sleep in Drosophila melanogaster. We analyzed the sleep behavior of flies with the mutation in insulin-like ligands expressed in the brain and found that three insulin-like ligands participate in sleep regulation with some redundancy. We next used 21 Gal4 drivers to express a dominant-negative form of the insulin receptor (InR DN) in various neurons including circadian clock neurons, which express the clock gene, and the pars intercerebralis (PI). Inhibition of insulin signaling in the anterior dorsal neuron group 1 (DN1a) decreased sleep. Additionally, the same manipulation in PI also decreased sleep. Pan-neuronal induced expression of InR DN also decreased sleep. These results suggested that insulin signaling in DN1a and PI regulates sleep.
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Affiliation(s)
- Sho T Yamaguchi
- Department of Neuropharmacology, Graduate School of Pharmaceutical Sciences, Nagoya City University, Nagoya, 467-8603, Japan.
| | - Jun Tomita
- Department of Neuropharmacology, Graduate School of Pharmaceutical Sciences, Nagoya City University, Nagoya, 467-8603, Japan.
| | - Kazuhiko Kume
- Department of Neuropharmacology, Graduate School of Pharmaceutical Sciences, Nagoya City University, Nagoya, 467-8603, Japan.
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3
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Internal state effects on behavioral shifts in freely behaving praying mantises (Tenodera sinensis). PLoS Comput Biol 2021; 17:e1009618. [PMID: 34928939 PMCID: PMC8751982 DOI: 10.1371/journal.pcbi.1009618] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2021] [Revised: 01/11/2022] [Accepted: 11/05/2021] [Indexed: 11/19/2022] Open
Abstract
How we interact with our environment largely depends on both the external cues presented by our surroundings and the internal state from within. Internal states are the ever-changing physiological conditions that communicate the immediate survival needs and motivate the animal to behaviorally fulfill them. Satiety level constitutes such a state, and therefore has a dynamic influence on the output behaviors of an animal. In predatory insects like the praying mantis, hunting tactics, grooming, and mating have been shown to change hierarchical organization of behaviors depending on satiety. Here, we analyze behavior sequences of freely hunting praying mantises (Tenodera sinensis) to explore potential differences in sequential patterning of behavior as a correlate of satiety. First, our data supports previous work that showed starved praying mantises were not just more often attentive to prey, but also more often attentive to further prey. This was indicated by the increased time fraction spent in attentive bouts such as prey monitoring, head turns (to track prey), translations (closing the distance to the prey), and more strike attempts. With increasing satiety, praying mantises showed reduced time in these behaviors and exhibited them primarily towards close-proximity prey. Furthermore, our data demonstrates that during states of starvation, the praying mantis exhibits a stereotyped pattern of behavior that is highly motivated by prey capture. As satiety increased, the sequenced behaviors became more variable, indicating a shift away from the necessity of prey capture to more fluid presentations of behavior assembly.
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Tingley D, McClain K, Kaya E, Carpenter J, Buzsáki G. A metabolic function of the hippocampal sharp wave-ripple. Nature 2021; 597:82-86. [PMID: 34381214 PMCID: PMC9214835 DOI: 10.1038/s41586-021-03811-w] [Citation(s) in RCA: 41] [Impact Index Per Article: 13.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2020] [Accepted: 07/07/2021] [Indexed: 02/07/2023]
Abstract
The hippocampus has previously been implicated in both cognitive and endocrine functions1-15. We simultaneously measured electrophysiological activity from the hippocampus and interstitial glucose concentrations in the body of freely behaving rats to identify an activity pattern that may link these disparate functions of the hippocampus. Here we report that clusters of sharp wave-ripples recorded from the hippocampus reliably predicted a decrease in peripheral glucose concentrations within about 10 min. This correlation was not dependent on circadian, ultradian or meal-triggered fluctuations, could be mimicked with optogenetically induced ripples in the hippocampus (but not in the parietal cortex) and was attenuated to chance levels by pharmacogenetically suppressing activity of the lateral septum, which is the major conduit between the hippocampus and the hypothalamus. Our findings demonstrate that a function of the sharp wave-ripple is to modulate peripheral glucose homeostasis, and offer a mechanism for the link between sleep disruption and blood glucose dysregulation in type 2 diabetes16-18.
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Affiliation(s)
- David Tingley
- Neuroscience Institute, New York University, New York, NY, USA.,Correspondence and requests for materials should be addressed to D.T. or G.B. ;
| | - Kathryn McClain
- Center for Neural Science, New York University, New York, NY, USA
| | - Ekin Kaya
- Neuroscience Institute, New York University, New York, NY, USA.,Department of Psychology, Bogazici University, Istanbul, Turkey
| | - Jordan Carpenter
- Neuroscience Institute, New York University, New York, NY, USA.,Kavli Institute for Systems Neuroscience and Centre for Neural Computation, Norwegian University of Science and Technology, Trondheim, Norway
| | - György Buzsáki
- Neuroscience Institute, New York University, New York, NY, USA.,Center for Neural Science, New York University, New York, NY, USA.,Department of Neurology, New York University, New York, NY, USA.,Langone Medical Center, New York University, New York, NY, USA.,Correspondence and requests for materials should be addressed to D.T. or G.B. ;
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Torabi N, Noursadeghi E, Shayanfar F, Nazari M, Fahanik-Babaei J, Saghiri R, Khodagholi F, Eliassi A. Intranasal insulin improves the structure-function of the brain mitochondrial ATP-sensitive Ca 2+ activated potassium channel and respiratory chain activities under diabetic conditions. Biochim Biophys Acta Mol Basis Dis 2021; 1867:166075. [PMID: 33444710 DOI: 10.1016/j.bbadis.2021.166075] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2020] [Revised: 12/06/2020] [Accepted: 12/30/2020] [Indexed: 11/21/2022]
Abstract
Although it is well established that diabetes impairs mitochondrial respiratory chain activity, little is known of the effects of intranasal insulin (INI) on the mitochondrial respiratory chain and structure-function of mitoBKCa channel in diabetes. We have investigated this mechanism in an STZ-induced early type 2 diabetic model. Single ATP-sensitive mitoBKCa channel activity was considered in diabetic and INI-treated rats using a channel incorporated into the bilayer lipid membrane. Because mitoBKCa channels have been involved in mitochondrial respiratory chain activity, a study was undertaken to investigate whether the NADH, complexes I and IV, mitochondrial ROS production, and ΔΨm are altered in an early diabetic model. In this work, we provide evidence for a significant decrease in channel open probability and conductance in diabetic rats. Evidence has been shown that BKCa channel β2 subunits induce a left shift in the BKCa channel voltage dependent curve in low Ca2+ conditions,; our results indicated a significant decrease in mitoBKCa β2 subunits using Western blot analysis. Importantly, INI treatment improved mitoBKCa channel behaviors and β2 subunits expression up to ~70%. We found that early diabetes decreased activities of complex I and IV and increased NADH, ROS production, and ΔΨm. Surprisingly, INI modified the mitochondrial respiratory chain, ROS production, and ΔΨm up to ~70%. Our results thus demonstrate an INI improvement in respiratory chain activity and ROS production in brain mitochondrial preparations coming from the STZ early diabetic rat model, an effect potentially linked to INI improvement in mitoBKCa channel activity and channel β2 subunit expression.
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Affiliation(s)
- Nihad Torabi
- Neurophysiology Research Center, Shahid Beheshti University of Medical Sciences, Tehran, Iran; Department of Physiology, Shahid Beheshti University of Medical Sciences, Tehran, Iran
| | - Elham Noursadeghi
- Neurophysiology Research Center, Shahid Beheshti University of Medical Sciences, Tehran, Iran
| | - Farzad Shayanfar
- Department of Physiology, Shahid Beheshti University of Medical Sciences, Tehran, Iran
| | - Maryam Nazari
- Department of Physiology, Shahid Beheshti University of Medical Sciences, Tehran, Iran
| | - Javad Fahanik-Babaei
- Electrophysiology Research Center, Neuroscience Institute, Tehran University of Medical Sciences, Tehran, Iran
| | - Reza Saghiri
- Department of Biochemistry, Pasteur Institute of Iran, Tehran, Iran
| | - Fariba Khodagholi
- Neuroscience Research Center, Shahid Beheshti University of Medical Sciences, Evin, Tehran, Iran
| | - Afsaneh Eliassi
- Neurophysiology Research Center, Shahid Beheshti University of Medical Sciences, Tehran, Iran; Department of Physiology, Shahid Beheshti University of Medical Sciences, Tehran, Iran.
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Wingrove JO, O'Daly O, Forbes B, Swedrowska M, Amiel SA, Zelaya FO. Intranasal insulin administration decreases cerebral blood flow in cortico-limbic regions: A neuropharmacological imaging study in normal and overweight males. Diabetes Obes Metab 2021; 23:175-185. [PMID: 33026175 DOI: 10.1111/dom.14213] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/27/2020] [Revised: 09/17/2020] [Accepted: 09/27/2020] [Indexed: 12/13/2022]
Abstract
AIM To assess and compare the effects of 160 IU intranasal insulin (IN-INS) administration on regional cerebral blood flow (rCBF) in healthy male individuals with normal weight and overweight phenotypes. METHODS Thirty young male participants (mean age 25.9 years) were recruited and stratified into two cohorts based on body mass index: normal weight (18.5-24.9 kg/m2 ) and overweight (25.0-29.9 kg/m2 ). On separate mornings participants received 160 IU of IN-INS using an intranasal protocol and intranasal placebo as part of a double-blind crossover design. Thirty minutes following administration rCBF data were collected using a magnetic resonance imaging method called pseudocontinuous arterial spin labelling. Blood samples were collected to assess insulin sensitivity and changes over time in peripheral glucose, insulin and C-peptide. RESULTS Insulin sensitivity did not significantly differ between groups. Compared with placebo, IN-INS administration reduced rCBF in parts of the hippocampus, insula, putamen, parahippocampal gyrus and fusiform gyrus in the overweight group. No effect was seen in the normal weight group. Insula rCBF was greater in the overweight group versus normal weight only under placebo conditions. Peripheral glucose and insulin levels were not affected by IN-INS. C-peptide levels in the normal weight group decreased significantly over time following IN-INS administration but not placebo. CONCLUSION Insulin-induced changes within key regions of the brain involved in gustation, memory and reward were observed in overweight healthy male individuals. Following placebo administration, differences in gustatory rCBF were observed between overweight and normal weight healthy individuals.
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Affiliation(s)
- Jed O Wingrove
- Centre for Neuroimaging Sciences, King's College London, London, UK
- Centre for Obesity Research, University College London, London, UK
- Diabetes Research Group, King's College Hospital Campus, Weston Education Central, King's College London, London, UK
| | - Owen O'Daly
- Centre for Neuroimaging Sciences, King's College London, London, UK
| | - Ben Forbes
- Institute of Pharmaceutical Science, King's College London, London, UK
| | - Magda Swedrowska
- Institute of Pharmaceutical Science, King's College London, London, UK
| | - Stephanie A Amiel
- Diabetes Research Group, King's College Hospital Campus, Weston Education Central, King's College London, London, UK
- Institute of Diabetes and Obesity, King's Health Partners, London, UK
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De Sousa RAL, Harmer AR, Freitas DA, Mendonça VA, Lacerda ACR, Leite HR. An update on potential links between type 2 diabetes mellitus and Alzheimer's disease. Mol Biol Rep 2020; 47:6347-6356. [PMID: 32740795 DOI: 10.1007/s11033-020-05693-z] [Citation(s) in RCA: 25] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2020] [Accepted: 07/26/2020] [Indexed: 12/14/2022]
Abstract
Alzheimer's disease (AD) and type 2 diabetes (T2D) major feature is insulin resistance. Brain and peripheral insulin resistance lead to hyperglycemia, which contributes to the development of T2D-linked comorbidities, such as obesity and dyslipidemia. Individuals with hyperglycemia in AD present with neuronal loss, formation of plaques and tangles and reduced neurogenesis. Inflammation seems to play an essential role in the development of insulin resistance in AD and T2D. We conducted a literature review about the links between AD and T2D. Alterations in glucose metabolism result from changes in the expression of the insulin receptor substrates 1 and 2 (IRS-1 and IRS-2), and seem to be mediated by several inflammatory pathways being present in both pathologies. Although there are some similarities in the insulin resistance of AD and T2D, brain and peripheral insulin resistance also have their discrete features. Failure to activate IRS-1 is the hallmark of AD, while inhibition of IRS-2 is the main feature in T2D. Inflammation mediates the alterations in glucose metabolism in AD and T2D. Targeting inflammation and insulin receptors may be a successful strategy to prevent and ameliorate T2D and AD symptoms.
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Affiliation(s)
- Ricardo Augusto Leoni De Sousa
- Programa Multicêntrico de Pós-Graduação em Ciências Fisiológicas- Sociedade Brasileira de Fisiologia (SBFis), Universidade Federal dos Vales do Jequitinhonha E Mucuri (UFVJM), Campus JK, Rodovia MGT 367, Km 583, Alto da Jacuba, no 5000, Diamantina, MG, CEP 39100-000, Brazil.
| | - Alison R Harmer
- Faculty of Medicine and Health, Sydney School of Health Sciences, The University of Sydney, Sydney, Australia
| | - Daniel Almeida Freitas
- Programa Multicêntrico de Pós-Graduação em Ciências Fisiológicas- Sociedade Brasileira de Fisiologia (SBFis), Universidade Federal dos Vales do Jequitinhonha E Mucuri (UFVJM), Campus JK, Rodovia MGT 367, Km 583, Alto da Jacuba, no 5000, Diamantina, MG, CEP 39100-000, Brazil
| | - Vanessa Amaral Mendonça
- Programa Multicêntrico de Pós-Graduação em Ciências Fisiológicas- Sociedade Brasileira de Fisiologia (SBFis), Universidade Federal dos Vales do Jequitinhonha E Mucuri (UFVJM), Campus JK, Rodovia MGT 367, Km 583, Alto da Jacuba, no 5000, Diamantina, MG, CEP 39100-000, Brazil
| | - Ana Cristina Rodrigues Lacerda
- Programa Multicêntrico de Pós-Graduação em Ciências Fisiológicas- Sociedade Brasileira de Fisiologia (SBFis), Universidade Federal dos Vales do Jequitinhonha E Mucuri (UFVJM), Campus JK, Rodovia MGT 367, Km 583, Alto da Jacuba, no 5000, Diamantina, MG, CEP 39100-000, Brazil
| | - Hércules Ribeiro Leite
- Programa Multicêntrico de Pós-Graduação em Ciências Fisiológicas- Sociedade Brasileira de Fisiologia (SBFis), Universidade Federal dos Vales do Jequitinhonha E Mucuri (UFVJM), Campus JK, Rodovia MGT 367, Km 583, Alto da Jacuba, no 5000, Diamantina, MG, CEP 39100-000, Brazil
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8
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Gralle M, Labrecque S, Salesse C, De Koninck P. Spatial dynamics of the insulin receptor in living neurons. J Neurochem 2020; 156:88-105. [PMID: 31886886 DOI: 10.1111/jnc.14950] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2019] [Revised: 12/11/2019] [Accepted: 12/27/2019] [Indexed: 12/23/2022]
Abstract
Insulin signaling through the insulin receptor has long been studied in classic target organs, such as adipose tissue and skeletal muscle, where one of its effects is to increase glucose uptake. Insulin and insulin receptor are present in many areas of the brain, but the functions of brain insulin signaling outside feeding circuits are not well defined. It has been proposed that hippocampal insulin signaling is important for memory, that brain insulin signaling is deficient in Alzheimer's disease, and that intranasal insulin treatment improves cognition, but the mechanisms remain unclear and do not seem to involve increased glucose uptake by neurons. The molecular behavior of the insulin receptor itself is not well known in living neurons; therefore, we investigated the spatial dynamics of the insulin receptor on somatodendritic membranes of live rat hippocampal neurons in culture. Using single-molecule tracking of quantum dot-tagged insulin receptors and single-particle tracking photoactivation localization microscopy, we show that the insulin receptor is distributed over both dendritic shafts and spines. Using colocalization with synaptic markers, we also show that in contrast to the glutamate receptor subunit glutamate receptor subunit A1, the dynamics of the insulin receptor are not affected by association with excitatory synapses; however, the insulin receptor is immobilized by components of inhibitory synapses. The mobility of the insulin receptor is reduced both by low concentrations of the pro-inflammatory cytokine tumor necrosis factor α and by cholesterol depletion, suggesting an association with sphingolipid-rich membrane domains. On the other hand, the insulin receptor dynamics in hippocampal neurons are not affected by increased excitatory signaling. Finally, using real-time single-event quantification, we find evidence of strong insulin receptor exocytosis on dendritic shafts. Our results suggest an association of the neuronal insulin receptor with specific elements of the dendritic shaft, rather than excitatory synapses.
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Affiliation(s)
- Matthias Gralle
- Instituto de Bioquímica Médica Leopoldo de Meis, Universidade Federal do Rio de Janeiro, Rio de Janeiro, Brazil.,CERVO Brain Research Center, Québec, QC, Canada
| | | | | | - Paul De Koninck
- CERVO Brain Research Center, Québec, QC, Canada.,Département de biochimie, microbiologie et bio-informatique, Université Laval, Québec, QC, Canada
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Ghasemi M, Mehranfard N. Mechanisms underlying anticonvulsant and proconvulsant actions of norepinephrine. Neuropharmacology 2018; 137:297-308. [DOI: 10.1016/j.neuropharm.2018.05.015] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2018] [Revised: 05/09/2018] [Accepted: 05/10/2018] [Indexed: 01/02/2023]
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10
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Identification of Insulin Receptor Splice Variant B in Neurons by in situ Detection in Human Brain Samples. Sci Rep 2018; 8:4070. [PMID: 29511314 PMCID: PMC5840297 DOI: 10.1038/s41598-018-22434-2] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2017] [Accepted: 02/22/2018] [Indexed: 12/28/2022] Open
Abstract
Insulin and its receptor are widely expressed in a variety of tissues throughout the body including liver, adipose tissue, liver and brain. The insulin receptor is expressed as two functionally distinct isoforms, differentiated by a single 12 amino acid exon. The two receptor isoforms, designated IR/A and IR/B, are expressed in a highly tissue and cell specific manner and relative proportions of the different isoforms vary during development, aging and disease states. The high degree of similarity between the two isoforms has prevented detailed studies as differentiation of the two isoforms by traditional immunological methods cannot be achieved. We describe here a new in situ RT-PCR/ FISH assay that allows for the visualization of IR/A and IR/B in tissue along with tissue specific markers. We used this new method to show for the first time that IR/A and IR/B are both expressed in neurons in the adult human brain. Thus, we present a method that enables the investigation of IR/A and IR/B insulin receptor isoform expression in situ in various tissues.
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11
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Navidhamidi M, Ghasemi M, Mehranfard N. Epilepsy-associated alterations in hippocampal excitability. Rev Neurosci 2018; 28:307-334. [PMID: 28099137 DOI: 10.1515/revneuro-2016-0059] [Citation(s) in RCA: 30] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2016] [Accepted: 11/03/2016] [Indexed: 11/15/2022]
Abstract
The hippocampus exhibits a wide range of epilepsy-related abnormalities and is situated in the mesial temporal lobe, where limbic seizures begin. These abnormalities could affect membrane excitability and lead to overstimulation of neurons. Multiple overlapping processes refer to neural homeostatic responses develop in neurons that work together to restore neuronal firing rates to control levels. Nevertheless, homeostatic mechanisms are unable to restore normal neuronal excitability, and the epileptic hippocampus becomes hyperexcitable or hypoexcitable. Studies show that there is hyperexcitability even before starting recurrent spontaneous seizures, suggesting although hippocampal hyperexcitability may contribute to epileptogenesis, it alone is insufficient to produce epileptic seizures. This supports the concept that the hippocampus is not the only substrate for limbic seizure onset, and a broader hyperexcitable limbic structure may contribute to temporal lobe epilepsy (TLE) seizures. Nevertheless, seizures also occur in conditions where the hippocampus shows a hypoexcitable phenotype. Since TLE seizures most often originate in the hippocampus, it could therefore be assumed that both hippocampal hypoexcitability and hyperexcitability are undesirable states that make the epileptic hippocampal network less stable and may, under certain conditions, trigger seizures.
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12
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Kim JE, Park JY, Kang TC. TRPC6-mediated ERK1/2 Activation Regulates Neuronal Excitability via Subcellular Kv4.3 Localization in the Rat Hippocampus. Front Cell Neurosci 2017; 11:413. [PMID: 29326557 PMCID: PMC5742353 DOI: 10.3389/fncel.2017.00413] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2017] [Accepted: 12/11/2017] [Indexed: 01/02/2023] Open
Abstract
Recently, we have reported that transient receptor potential channel-6 (TRPC6) plays an important role in the regulation of neuronal excitability and synchronization of spiking activity in the dentate granule cells (DGC). However, the underlying mechanisms of TRPC6 in these phenomena have been still unclear. In the present study, we investigated the role of TRPC6 in subcellular localization of Kv4.3 and its relevance to neuronal excitability in the rat hippocampus. TRPC6 knockdown increased excitability and inhibitory transmission in the DGC and the CA1 neurons in response to a paired-pulse stimulus. However, TRPC6 knockdown impaired γ-aminobutyric acid (GABA)ergic inhibition in the hippocampus during and after high-frequency stimulation (HFS). TRPC6 knockdown reduced the Kv4.3 clusters in membrane fractions and its dendritic localization on DGC and GABAergic interneurons. TRPC6 knockdown also decreased extracellular signal-regulated kinase 1/2 (ERK1/2) phosphorylation and the efficacy of 4-aminopyridine (4-AP) in neuronal excitability. An ERK1/2 inhibitor generated multiple population spikes in response to a paired-pulse stimulus, concomitant with reduced membrane Kv4.3 translocation. A TRPC6 activator (hyperforin) reversed the effects of TRPC knockdown, except paired-pulse inhibition. These findings provide valuable clues indicating that TRPC6-mediated ERK1/2 activation may regulate subcellular Kv4.3 localization in DGC and interneurons, which is cause-effect relationship between neuronal excitability and seizure susceptibility.
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Affiliation(s)
- Ji-Eun Kim
- Department of Anatomy and Neurobiology, Institute of Epilepsy Research, College of Medicine, Hallym University, Chuncheon, South Korea
| | - Jin-Young Park
- Department of Anatomy and Neurobiology, Institute of Epilepsy Research, College of Medicine, Hallym University, Chuncheon, South Korea
| | - Tae-Cheon Kang
- Department of Anatomy and Neurobiology, Institute of Epilepsy Research, College of Medicine, Hallym University, Chuncheon, South Korea
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13
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Steiner J, Guest PC, Martins-de-Souza D. Application of Proteomic Techniques for Improved Stratification and Treatment of Schizophrenia Patients. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2017; 974:3-19. [PMID: 28353222 DOI: 10.1007/978-3-319-52479-5_1] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
For major psychiatric disorders such as schizophrenia, there have been shortcomings in the translation of scientific findings into new treatments and this has led to diminished interest for large pharmaceutical companies. This chapter describes how incorporation of proteomic approaches into the clinical pipeline can lead to identification and implementation of biomarker tests for improved patient characterization, prediction of treatment response and monitoring treatment effects to help revitalize efforts in this important area. In addition, the construction of specific biomarker tests for disease prediction should smooth the progress of early intervention strategies which, in turn, may help to slow disease onset or progression. Finally, the development of purpose-built biomarker tests using lab-on-a-chip platforms with smartphone readouts will help to shift the diagnosis and treatment of this major psychiatric disorder into point-of-care settings for increased effectiveness and improved patient outcomes.
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Affiliation(s)
- Johann Steiner
- Department of Psychiatry, University of Magdeburg, Leipziger Strasse 44, 39120, Magdeburg, Germany.
| | - Paul C Guest
- Laboratory of Neuroproteomics, Department of Biochemistry and Tissue Biology, Institute of Biology, University of Campinas (UNICAMP), Rua Monteiro Lobato 255 F/01, Cidade Universitária Zeferino Vaz, 13083-862, Campinas, Brazil
| | - Daniel Martins-de-Souza
- Laboratory of Neuroproteomics, Department of Biochemistry and Tissue Biology, Institute of Biology, University of Campinas (UNICAMP), Rua Monteiro Lobato 255 F/01, Cidade Universitária Zeferino Vaz, 13083-862, Campinas, Brazil.,UNICAMP's Neurobiology Center, Rua Monteiro Lobato 255, Cidade Universitária Zeferino Vaz, 13083-862, Campinas, Brazil
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14
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Kania A, Gugula A, Grabowiecka A, de Ávila C, Blasiak T, Rajfur Z, Lewandowski MH, Hess G, Timofeeva E, Gundlach AL, Blasiak A. Inhibition of oxytocin and vasopressin neuron activity in rat hypothalamic paraventricular nucleus by relaxin-3-RXFP3 signalling. J Physiol 2017; 595:3425-3447. [PMID: 28098344 DOI: 10.1113/jp273787] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2016] [Accepted: 12/23/2016] [Indexed: 12/21/2022] Open
Abstract
KEY POINTS Relaxin-3 is a stress-responsive neuropeptide that acts at its cognate receptor, RXFP3, to alter behaviours including feeding. In this study, we have demonstrated a direct, RXFP3-dependent, inhibitory action of relaxin-3 on oxytocin and vasopressin paraventricular nucleus (PVN) neuron electrical activity, a putative cellular mechanism of orexigenic actions of relaxin-3. We observed a Gαi/o -protein-dependent inhibitory influence of selective RXFP3 activation on PVN neuronal activity in vitro and demonstrated a direct action of RXFP3 activation on oxytocin and vasopressin PVN neurons, confirmed by their abundant expression of RXFP3 mRNA. Moreover, we demonstrated that RXFP3 activation induces a cadmium-sensitive outward current, which indicates the involvement of a characteristic magnocellular neuron outward potassium current. Furthermore, we identified an abundance of relaxin-3-immunoreactive axons/fibres originating from the nucleus incertus in close proximity to the PVN, but associated with sparse relaxin-3-containing fibres/terminals within the PVN. ABSTRACT The paraventricular nucleus of the hypothalamus (PVN) plays an essential role in the control of food intake and energy expenditure by integrating multiple neural and humoral inputs. Recent studies have demonstrated that intracerebroventricular and intra-PVN injections of the neuropeptide relaxin-3 or selective relaxin-3 receptor (RXFP3) agonists produce robust feeding in satiated rats, but the cellular and molecular mechanisms of action associated with these orexigenic effects have not been identified. In the present studies, using rat brain slices, we demonstrated that relaxin-3, acting through its cognate G-protein-coupled receptor, RXFP3, hyperpolarized a majority of putative magnocellular PVN neurons (88%, 22/25), including cells producing the anorexigenic neuropeptides, oxytocin and vasopressin. Importantly, the action of relaxin-3 persisted in the presence of tetrodotoxin and glutamate/GABA receptor antagonists, indicating its direct action on PVN neurons. Similar inhibitory effects on PVN oxytocin and vasopressin neurons were produced by the RXFP3 agonist, RXFP3-A2 (82%, 80/98 cells). In situ hybridization histochemistry revealed a strong colocalization of RXFP3 mRNA with oxytocin and vasopressin immunoreactivity in rat PVN neurons. A smaller percentage of putative parvocellular PVN neurons was sensitive to RXFP3-A2 (40%, 16/40 cells). These data, along with a demonstration of abundant peri-PVN and sparse intra-PVN relaxin-3-immunoreactive nerve fibres, originating from the nucleus incertus, the major source of relaxin-3 neurons, identify a strong inhibitory influence of relaxin-3-RXFP3 signalling on the electrical activity of PVN oxytocin and vasopressin neurons, consistent with the orexigenic effect of RXFP3 activation observed in vivo.
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Affiliation(s)
- Alan Kania
- Department of Neurophysiology and Chronobiology, Institute of Zoology, Jagiellonian University, 30-387, Krakow, Poland
| | - Anna Gugula
- Department of Neurophysiology and Chronobiology, Institute of Zoology, Jagiellonian University, 30-387, Krakow, Poland
| | - Agnieszka Grabowiecka
- Department of Neurophysiology and Chronobiology, Institute of Zoology, Jagiellonian University, 30-387, Krakow, Poland
| | - Camila de Ávila
- Faculté de Médecine, Département de Psychiatrie et de Neurosciences, Centre de Recherche de l'Institut Universitaire de Cardiologie et de Pneumologie de Québec, Université Laval, Québec, QC, Canada, G1V 0A6
| | - Tomasz Blasiak
- Department of Neurophysiology and Chronobiology, Institute of Zoology, Jagiellonian University, 30-387, Krakow, Poland
| | - Zenon Rajfur
- Faculty of Physics, Astronomy and Applied Computer Science, Institute of Physics, Jagiellonian University, 30-348, Krakow, Poland
| | - Marian H Lewandowski
- Department of Neurophysiology and Chronobiology, Institute of Zoology, Jagiellonian University, 30-387, Krakow, Poland
| | - Grzegorz Hess
- Department of Neurophysiology and Chronobiology, Institute of Zoology, Jagiellonian University, 30-387, Krakow, Poland.,Institute of Pharmacology, Polish Academy of Sciences, 31-343, Krakow, Poland
| | - Elena Timofeeva
- Faculté de Médecine, Département de Psychiatrie et de Neurosciences, Centre de Recherche de l'Institut Universitaire de Cardiologie et de Pneumologie de Québec, Université Laval, Québec, QC, Canada, G1V 0A6
| | - Andrew L Gundlach
- The Florey Institute of Neuroscience and Mental Health, Parkville, VIC, 3052, Australia.,Florey Department of Neuroscience and Mental Health, The University of Melbourne, VIC, 3010, Australia.,Department of Anatomy and Neuroscience, The University of Melbourne, VIC, 3010, Australia
| | - Anna Blasiak
- Department of Neurophysiology and Chronobiology, Institute of Zoology, Jagiellonian University, 30-387, Krakow, Poland
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15
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Steiner J, Guest PC, Rahmoune H, Martins-de-Souza D. The Application of Multiplex Biomarker Techniques for Improved Stratification and Treatment of Schizophrenia Patients. Methods Mol Biol 2017; 1546:19-35. [PMID: 27896755 DOI: 10.1007/978-1-4939-6730-8_2] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
In the case of major psychiatric disorders such as schizophrenia, shortcomings in the conversion of scientific discoveries into newer and safer treatment options has led to a loss of confidence and precipitated a crisis for large pharmaceutical companies. This chapter describes how incorporation of multiplex biomarker approaches into the clinical pipeline can lead to better patient characterization, delivery of novel treatment approaches and help to renew efforts in this important area. The development of specific biomarker test panels for disease prediction should facilitate early intervention strategies, which may help to slow disease development or progression. Furthermore, the development of such tests using lab-on-a-chip and smartphone platforms will help to shift diagnosis and treatment of this major disorder into a point-of-care setting for improved patient outcomes.
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Affiliation(s)
- Johann Steiner
- Department of Psychiatry, University of Magdeburg, Leipziger Strasse 44, 39120, Magdeburg, Germany.
| | - Paul C Guest
- Laboratory of Neuroproteomics, Department of Biochemistry and Tissue Biology, Institute of Biology, University of Campinas (UNICAMP), Rua Monteiro Lobato 255, Cidade Universitária Zeferino Vaz, 13083-862, Campinas, Brazil
| | - Hassan Rahmoune
- Department of Chemical Engineering and Biotechnology, University of Cambridge, Pembroke Street, Cambridge, UK
| | - Daniel Martins-de-Souza
- Laboratory of Neuroproteomics, Department of Biochemistry and Tissue Biology, Institute of Biology, University of Campinas (UNICAMP), Rua Monteiro Lobato 255, Cidade Universitária Zeferino Vaz, 13083-862, Campinas, SP, Brazil
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16
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Gralle M. The neuronal insulin receptor in its environment. J Neurochem 2016; 140:359-367. [PMID: 27889917 DOI: 10.1111/jnc.13909] [Citation(s) in RCA: 36] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2016] [Revised: 10/31/2016] [Accepted: 11/21/2016] [Indexed: 01/01/2023]
Abstract
Insulin is known mainly for its effects in peripheral tissues, such as the liver, skeletal muscles and adipose tissue, where the activation of the insulin receptor (IR) has both short-term and long-term effects. Insulin and the IR are also present in the brain, and since there is evidence that neuronal insulin signaling regulates synaptic plasticity and that it is impaired in disease, this pathway might be the key to protection or reversal of symptoms, especially in Alzheimer's disease. However, there are controversies about the importance of the neuronal IR, partly because biophysical data on its activation and signaling are much less complete than for the peripheral IR. This review briefly summarizes the neuronal IR signaling in health and disease, and then focuses on known differences between the neuronal and peripheral IR with regard to alternative splicing and glycosylation, and lack of data with respect to phosphorylation and membrane subdomain localization. Particularities in the neuronal IR itself and its environment may have consequences for downstream signaling and impact synaptic plasticity. Furthermore, establishing the relative importance of insulin signaling through IR or through hybrids with its homolog, the insulin-like growth factor 1 receptor, is crucial for evaluating the consequences of brain IR activation. An improved biophysical understanding of the neuronal IR may help predict the consequences of insulin-targeted interventions.
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Affiliation(s)
- Matthias Gralle
- Instituto de Bioquímica Médica Leopoldo de Meis, Universidade Federal do Rio de Janeiro, Rio de Janeiro, Brazil
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17
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Suliman NA, Mat Taib CN, Mohd Moklas MA, Adenan MI, Hidayat Baharuldin MT, Basir R. Establishing Natural Nootropics: Recent Molecular Enhancement Influenced by Natural Nootropic. EVIDENCE-BASED COMPLEMENTARY AND ALTERNATIVE MEDICINE : ECAM 2016; 2016:4391375. [PMID: 27656235 PMCID: PMC5021479 DOI: 10.1155/2016/4391375] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/31/2016] [Accepted: 07/18/2016] [Indexed: 01/24/2023]
Abstract
Nootropics or smart drugs are well-known compounds or supplements that enhance the cognitive performance. They work by increasing the mental function such as memory, creativity, motivation, and attention. Recent researches were focused on establishing a new potential nootropic derived from synthetic and natural products. The influence of nootropic in the brain has been studied widely. The nootropic affects the brain performances through number of mechanisms or pathways, for example, dopaminergic pathway. Previous researches have reported the influence of nootropics on treating memory disorders, such as Alzheimer's, Parkinson's, and Huntington's diseases. Those disorders are observed to impair the same pathways of the nootropics. Thus, recent established nootropics are designed sensitively and effectively towards the pathways. Natural nootropics such as Ginkgo biloba have been widely studied to support the beneficial effects of the compounds. Present review is concentrated on the main pathways, namely, dopaminergic and cholinergic system, and the involvement of amyloid precursor protein and secondary messenger in improving the cognitive performance.
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Affiliation(s)
- Noor Azuin Suliman
- Department of Human Anatomy, Faculty of Medicine and Health Sciences, Universiti Putra Malaysia, 43400 Serdang, Malaysia
| | - Che Norma Mat Taib
- Department of Human Anatomy, Faculty of Medicine and Health Sciences, Universiti Putra Malaysia, 43400 Serdang, Malaysia
| | - Mohamad Aris Mohd Moklas
- Department of Human Anatomy, Faculty of Medicine and Health Sciences, Universiti Putra Malaysia, 43400 Serdang, Malaysia
| | - Mohd Ilham Adenan
- Atta-ur-Rahman Institute for Natural Product Discovery, Aras 9 Bangunan FF3, UiTM Puncak Alam, Bandar Baru Puncak Alam, 42300 Selangor Darul Ehsan, Malaysia
| | | | - Rusliza Basir
- Department of Human Anatomy, Faculty of Medicine and Health Sciences, Universiti Putra Malaysia, 43400 Serdang, Malaysia
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18
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Leo A, Citraro R, Constanti A, De Sarro G, Russo E. Are big potassium-type Ca2+-activated potassium channels a viable target for the treatment of epilepsy? Expert Opin Ther Targets 2015; 19:911-26. [DOI: 10.1517/14728222.2015.1026258] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
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19
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Maimaiti S, Anderson KL, DeMoll C, Brewer LD, Rauh BA, Gant JC, Blalock EM, Porter NM, Thibault O. Intranasal Insulin Improves Age-Related Cognitive Deficits and Reverses Electrophysiological Correlates of Brain Aging. J Gerontol A Biol Sci Med Sci 2015; 71:30-9. [PMID: 25659889 DOI: 10.1093/gerona/glu314] [Citation(s) in RCA: 60] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2014] [Accepted: 12/23/2014] [Indexed: 12/25/2022] Open
Abstract
Peripheral insulin resistance is a key component of metabolic syndrome associated with obesity, dyslipidemia, hypertension, and type 2 diabetes. While the impact of insulin resistance is well recognized in the periphery, it is also becoming apparent in the brain. Recent studies suggest that insulin resistance may be a factor in brain aging and Alzheimer's disease (AD) whereby intranasal insulin therapy, which delivers insulin to the brain, improves cognition and memory in AD patients. Here, we tested a clinically relevant delivery method to determine the impact of two forms of insulin, short-acting insulin lispro (Humalog) or long-acting insulin detemir (Levemir), on cognitive functions in aged F344 rats. We also explored insulin effects on the Ca(2+)-dependent hippocampal afterhyperpolarization (AHP), a well-characterized neurophysiological marker of aging which is increased in the aged, memory impaired animal. Low-dose intranasal insulin improved memory recall in aged animals such that their performance was similar to that seen in younger animals. Further, because ex vivo insulin also reduced the AHP, our results suggest that the AHP may be a novel cellular target of insulin in the brain, and improved cognitive performance following intranasal insulin therapy may be the result of insulin actions on the AHP.
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Affiliation(s)
- Shaniya Maimaiti
- Department of Pharmacology and Nutritional Sciences, University of Kentucky Medical Center, Lexington, Kentucky
| | - Katie L Anderson
- Department of Pharmacology and Nutritional Sciences, University of Kentucky Medical Center, Lexington, Kentucky
| | - Chris DeMoll
- Department of Pharmacology and Nutritional Sciences, University of Kentucky Medical Center, Lexington, Kentucky
| | - Lawrence D Brewer
- Department of Pharmacology and Nutritional Sciences, University of Kentucky Medical Center, Lexington, Kentucky
| | - Benjamin A Rauh
- Department of Pharmacology and Nutritional Sciences, University of Kentucky Medical Center, Lexington, Kentucky
| | - John C Gant
- Department of Pharmacology and Nutritional Sciences, University of Kentucky Medical Center, Lexington, Kentucky
| | - Eric M Blalock
- Department of Pharmacology and Nutritional Sciences, University of Kentucky Medical Center, Lexington, Kentucky
| | - Nada M Porter
- Department of Pharmacology and Nutritional Sciences, University of Kentucky Medical Center, Lexington, Kentucky
| | - Olivier Thibault
- Department of Pharmacology and Nutritional Sciences, University of Kentucky Medical Center, Lexington, Kentucky.
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20
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TRPV4 channels activity in bovine articular chondrocytes: Regulation by obesity-associated mediators. Cell Calcium 2014; 56:493-503. [DOI: 10.1016/j.ceca.2014.10.006] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2014] [Revised: 10/14/2014] [Accepted: 10/16/2014] [Indexed: 01/22/2023]
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21
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Abraham MA, Filippi BM, Kang GM, Kim MS, Lam TKT. Insulin action in the hypothalamus and dorsal vagal complex. Exp Physiol 2014; 99:1104-9. [DOI: 10.1113/expphysiol.2014.079962] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Affiliation(s)
- Mona A. Abraham
- Toronto General Research Institute and Department of Medicine; University Health Network; Toronto Ontario Canada
- Department of Physiology; University of Toronto; Toronto Ontario Canada
| | - Beatrice M. Filippi
- Toronto General Research Institute and Department of Medicine; University Health Network; Toronto Ontario Canada
| | - Gil Myoung Kang
- Asan Medical Center; University of Ulsan College of Medicine; Seoul Republic of Korea
| | - Min-Seon Kim
- Asan Medical Center; University of Ulsan College of Medicine; Seoul Republic of Korea
| | - Tony K. T. Lam
- Toronto General Research Institute and Department of Medicine; University Health Network; Toronto Ontario Canada
- Department of Physiology; University of Toronto; Toronto Ontario Canada
- Asan Medical Center; University of Ulsan College of Medicine; Seoul Republic of Korea
- Department of Medicine; University of Toronto; Toronto Ontario Canada
- Banting and Best Diabetes Centre; University of Toronto; Toronto Ontario Canada
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22
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Guest PC, Chan MK, Gottschalk MG, Bahn S. The use of proteomic biomarkers for improved diagnosis and stratification of schizophrenia patients. Biomark Med 2014; 8:15-27. [DOI: 10.2217/bmm.13.83] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
Schizophrenia is characterized by a wide spectrum of clinical manifestations, including strong effects on mood and behavior. Patients can also suffer from serious comorbidities including immune system or metabolic abnormalities. Recent advances using proteomic profiling approaches have increased our understanding of these molecular effects and have laid the groundwork for unraveling the heterogeneity of this broadly defined disease. These findings could lead to improved diagnosis and stratification of patients through identification of biochemically different disease subtypes and personalized medicine approaches. The inclusion of molecular signatures in psychiatry will be an important leap forward in providing more effective treatment of patients suffering from this debilitating disorder.
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Affiliation(s)
- Paul C Guest
- Department of Chemical Engineering & Biotechnology, University of Cambridge, Cambridge, UK
| | - Man K Chan
- Department of Chemical Engineering & Biotechnology, University of Cambridge, Cambridge, UK
| | - Michael G Gottschalk
- Department of Chemical Engineering & Biotechnology, University of Cambridge, Cambridge, UK
| | - Sabine Bahn
- Department of Neuroscience, Erasmus Medical Centre, Rotterdam, The Netherlands
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23
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Thibault O, Anderson KL, DeMoll C, Brewer LD, Landfield PW, Porter NM. Hippocampal calcium dysregulation at the nexus of diabetes and brain aging. Eur J Pharmacol 2013; 719:34-43. [PMID: 23872402 DOI: 10.1016/j.ejphar.2013.07.024] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2013] [Accepted: 07/11/2013] [Indexed: 01/19/2023]
Abstract
Recently it has become clear that conditions of insulin resistance/metabolic syndrome, obesity and diabetes, are linked with moderate cognitive impairment in normal aging and elevated risk of Alzheimer's disease. It appears that a common feature of these conditions is impaired insulin signaling, affecting the brain as well as peripheral target tissues. A number of studies have documented that insulin directly affects brain processes and that reduced insulin signaling results in impaired learning and memory. Several studies have also shown that diabetes induces Ca(2+) dysregulation in neurons. Because brain aging is associated with substantial Ca(2+) dyshomeostasis, it has been proposed that impaired insulin signaling exacerbates or accelerates aging-related Ca(2+) dyshomeostasis. However, there have been few studies examining insulin interactions with Ca(2+) regulation in aging animals. We have been testing predictions of the Ca(2+) dysregulation/diabetes/brain aging hypothesis and have found that insulin and insulin-sensitizers (thiazolidinediones) target several hippocampal Ca(2+)-related processes affected by aging. The drugs appear able to reduce the age-dependent increase in Ca(2+) transients and the Ca(2+) -sensitive afterhyperpolarization. Thus, while additional testing is needed, the results to date are consistent with the view that strategies that enhance insulin signaling can counteract the effect of aging on Ca(2+) dysregulation.
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Affiliation(s)
- Olivier Thibault
- Department of Molecular and Biomedical Pharmacology, MS 313, 800 Rose Street, University of Kentucky Medical Center, Lexington, KY 40536, United States.
| | - Katie L Anderson
- Department of Molecular and Biomedical Pharmacology, MS 313, 800 Rose Street, University of Kentucky Medical Center, Lexington, KY 40536, United States
| | - Chris DeMoll
- Department of Molecular and Biomedical Pharmacology, MS 313, 800 Rose Street, University of Kentucky Medical Center, Lexington, KY 40536, United States
| | - Lawrence D Brewer
- Department of Molecular and Biomedical Pharmacology, MS 313, 800 Rose Street, University of Kentucky Medical Center, Lexington, KY 40536, United States
| | - Philip W Landfield
- Department of Molecular and Biomedical Pharmacology, MS 313, 800 Rose Street, University of Kentucky Medical Center, Lexington, KY 40536, United States
| | - Nada M Porter
- Department of Molecular and Biomedical Pharmacology, MS 313, 800 Rose Street, University of Kentucky Medical Center, Lexington, KY 40536, United States
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24
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Harris LW, Guest PC, Wayland MT, Umrania Y, Krishnamurthy D, Rahmoune H, Bahn S. Schizophrenia: metabolic aspects of aetiology, diagnosis and future treatment strategies. Psychoneuroendocrinology 2013; 38:752-66. [PMID: 23084727 DOI: 10.1016/j.psyneuen.2012.09.009] [Citation(s) in RCA: 70] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/08/2012] [Revised: 09/12/2012] [Accepted: 09/12/2012] [Indexed: 10/27/2022]
Abstract
Despite decades of research, the pathophysiology and aetiology of schizophrenia remains incompletely understood. The disorder is frequently accompanied by metabolic symptoms including dyslipidaemia, hyperinsulinaemia, type 2 diabetes and obesity. These symptoms are a common side effect of currently available antipsychotic medications. However, reports of metabolic dysfunction in schizophrenia predate the antipsychotic era and have also been observed in first onset patients prior to antipsychotic treatment. Here, we review the evidence for abnormalities in metabolism in schizophrenia patients, both in the central nervous system and periphery. Molecular analysis of post mortem brain tissue has pointed towards alterations in glucose metabolism and insulin signalling pathways, and blood-based molecular profiling analyses have demonstrated hyperinsulinaemia and abnormalities in secretion of insulin and co-released factors at first presentation of symptoms. Nonetheless, such features are not observed for all subjects with the disorder and not all individuals with such abnormalities suffer the symptoms of schizophrenia. One interpretation of these data is the presence of an underlying metabolic vulnerability in a subset of individuals which interacts with environmental or genetic factors to produce the overt symptoms of the disorder. Further investigation of metabolic aspects of schizophrenia may prove critical for diagnosis, improvement of existing treatment based on patient stratification/personalised medicine strategies and development of novel antipsychotic agents.
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Affiliation(s)
- Laura W Harris
- Department of Chemical Engineering and Biotechnology, University of Cambridge, Tennis Court Road, Cambridge, United Kingdom.
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25
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Guest PC, Martins-de-Souza D, Schwarz E, Rahmoune H, Alsaif M, Tomasik J, Turck CW, Bahn S. Proteomic profiling in schizophrenia: enabling stratification for more effective treatment. Genome Med 2013; 5:25. [PMID: 23531373 PMCID: PMC3706977 DOI: 10.1186/gm429] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
Schizophrenia is a heterogeneous psychiatric disorder characterized by an array of clinical manifestations. Although the best known manifestations include serious effects on mood and behavior, patients can also display co-morbidities, including immune system or metabolic abnormalities. Thorough characterization of these conditions using proteomic profiling methods has increased our knowledge of these molecular differences and has helped to unravel the complexity and heterogeneity of this debilitating condition. This could lead to patient stratification through characterization of biochemically different subtypes of the disease. In addition, proteomic methods have recently been used for molecular characterization of the mechanism of action of antipsychotic medications in both preclinical models and patients. This has resulted in identification of molecular panels that show some promise for prediction of response or for monitoring treatment outcome. This review describes how proteomic profiling methods can impact the future of schizophrenia diagnosis and therapeutics, and facilitate personalized medicine approaches for more effective treatment management of schizophrenia patients.
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Affiliation(s)
- Paul C Guest
- Department of Chemical Engineering and Biotechnology, University of Cambridge, Tennis Court Road, Cambridge, CB2 1QT, UK
| | - Daniel Martins-de-Souza
- Max Planck Institute of Psychiatry, Proteomics and Biomarkers, Kraepelinstr. 2-10 80804, Munich, Germany ; Department of Psychiatry, Ludwig-Maximilians-University (LMU), Nussbaumstr. 7, 80336, Munich, Germany ; Laboratório de Neurociências (LIM-27), Instituto de Psiquiatria, Faculdade de Medicina, Universidade de São Paulo, CP 8091 05403-010 São Paulo - SP - Brasil
| | - Emanuel Schwarz
- Department of Chemical Engineering and Biotechnology, University of Cambridge, Tennis Court Road, Cambridge, CB2 1QT, UK
| | - Hassan Rahmoune
- Department of Chemical Engineering and Biotechnology, University of Cambridge, Tennis Court Road, Cambridge, CB2 1QT, UK
| | - Murtada Alsaif
- Department of Chemical Engineering and Biotechnology, University of Cambridge, Tennis Court Road, Cambridge, CB2 1QT, UK
| | - Jakub Tomasik
- Department of Chemical Engineering and Biotechnology, University of Cambridge, Tennis Court Road, Cambridge, CB2 1QT, UK
| | - Christoph W Turck
- Max Planck Institute of Psychiatry, Proteomics and Biomarkers, Kraepelinstr. 2-10 80804, Munich, Germany
| | - Sabine Bahn
- Department of Chemical Engineering and Biotechnology, University of Cambridge, Tennis Court Road, Cambridge, CB2 1QT, UK ; Department of Neuroscience, Erasmus Medical Centre, NL-3000 CA Rotterdam, The Netherlands
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26
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Hypothalamic hormones and metabolism. Epilepsy Res 2012; 100:245-51. [PMID: 21856125 DOI: 10.1016/j.eplepsyres.2011.07.009] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2011] [Revised: 07/11/2011] [Accepted: 07/12/2011] [Indexed: 12/14/2022]
Abstract
The ketogenic diet is an effective treatment for medically intractable epilepsy and may have antiepileptogenic, neuroprotective, and antitumor properties. While on a ketogenic diet, the body obtains most of its calories from fat rather than carbohydrates. This dramatic change in caloric composition results in a unique metabolic state. In turn, these changes in caloric composition and metabolism alter some of the neurohormones that participate in the complex neuronal network regulating energy homeostasis. Two observed changes are an increase in serum leptin and a decrease in serum insulin. These opposing changes in leptin and insulin are unique compared to other metabolic stimuli and may modify the activity of several cell signaling cascades including phosphoinositidyl-3 kinase (PI3K), adenosine monophosphate activated protein kinase (AMPK), and mammalian target of rapamycin (mTOR). These cell signaling pathways may mediate the anticonvulsant and other beneficial effects of the diet, though the neurohormonal changes induced by the ketogenic diet and the physiological consequences of these changes remain poorly characterized.
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27
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Filippi BM, Yang CS, Tang C, Lam TKT. Insulin activates Erk1/2 signaling in the dorsal vagal complex to inhibit glucose production. Cell Metab 2012; 16:500-10. [PMID: 23040071 DOI: 10.1016/j.cmet.2012.09.005] [Citation(s) in RCA: 85] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/30/2012] [Revised: 08/01/2012] [Accepted: 09/11/2012] [Indexed: 01/07/2023]
Abstract
Insulin activates PI3-kinase (PI3K)/AKT to regulate glucose homeostasis in the peripheral tissues and the mediobasal hypothalamus (MBH) of rodents. We report that insulin infusion into the MBH or dorsal vagal complex (DVC) activated insulin receptors. The same dose of insulin that activated MBH PI3K/AKT did not in the DVC. DVC insulin instead activated Erk1/2 and lowered glucose production in rats and mice. Molecular and chemical inhibition of DVC Erk1/2 negated, while activation of DVC Erk1/2 recapitulated, the effects of DVC insulin. Circulating insulin failed to inhibit glucose production when DVC Erk1/2 was inhibited in normal rodents, while DVC insulin action was disrupted in high-fat-fed rodents. Activation of DVC ATP-sensitive potassium channels was necessary for insulin-Erk1/2 and sufficient to inhibit glucose production in normal and high-fat-fed rodents. DVC is a site of insulin action where insulin triggers Erk1/2 signaling to inhibit glucose production and of insulin resistance in high-fat feeding.
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Affiliation(s)
- Beatrice M Filippi
- Toronto General Research Institute, University Health Network, Toronto, M5G 1L7, Canada
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Costello DA, Claret M, Al-Qassab H, Plattner F, Irvine EE, Choudhury AI, Giese KP, Withers DJ, Pedarzani P. Brain deletion of insulin receptor substrate 2 disrupts hippocampal synaptic plasticity and metaplasticity. PLoS One 2012; 7:e31124. [PMID: 22383997 PMCID: PMC3287998 DOI: 10.1371/journal.pone.0031124] [Citation(s) in RCA: 53] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2011] [Accepted: 01/03/2012] [Indexed: 01/17/2023] Open
Abstract
Objective Diabetes mellitus is associated with cognitive deficits and an increased risk of dementia, particularly in the elderly. These deficits and the corresponding neurophysiological structural and functional alterations are linked to both metabolic and vascular changes, related to chronic hyperglycaemia, but probably also defects in insulin action in the brain. To elucidate the specific role of brain insulin signalling in neuronal functions that are relevant for cognitive processes we have investigated the behaviour of neurons and synaptic plasticity in the hippocampus of mice lacking the insulin receptor substrate protein 2 (IRS-2). Research Design and Methods To study neuronal function and synaptic plasticity in the absence of confounding factors such as hyperglycaemia, we used a mouse model with a central nervous system- (CNS)-restricted deletion of IRS-2 (NesCreIrs2KO). Results We report a deficit in NMDA receptor-dependent synaptic plasticity in the hippocampus of NesCreIrs2KO mice, with a concomitant loss of metaplasticity, the modulation of synaptic plasticity by the previous activity of a synapse. These plasticity changes are associated with reduced basal phosphorylation of the NMDA receptor subunit NR1 and of downstream targets of the PI3K pathway, the protein kinases Akt and GSK-3β. Conclusions These findings reveal molecular and cellular mechanisms that might underlie cognitive deficits linked to specific defects of neuronal insulin signalling.
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Affiliation(s)
- Derek A. Costello
- Research Department of Neuroscience, Physiology and Pharmacology, University College London, London, United Kingdom
| | - Marc Claret
- Department of Medicine, University College London, London, United Kingdom
| | - Hind Al-Qassab
- Department of Medicine, University College London, London, United Kingdom
| | - Florian Plattner
- Wolfson Institute of Biomedical Research, University College London, London, United Kingdom
| | - Elaine E. Irvine
- Department of Medicine, University College London, London, United Kingdom
- Wolfson Institute of Biomedical Research, University College London, London, United Kingdom
- Metabolic Signalling Group, MRC Clinical Sciences Centre, Imperial College London, London, United Kingdom
| | - Agharul I. Choudhury
- Department of Medicine, University College London, London, United Kingdom
- Metabolic Signalling Group, MRC Clinical Sciences Centre, Imperial College London, London, United Kingdom
| | - K. Peter Giese
- Wolfson Institute of Biomedical Research, University College London, London, United Kingdom
| | - Dominic J. Withers
- Department of Medicine, University College London, London, United Kingdom
- Metabolic Signalling Group, MRC Clinical Sciences Centre, Imperial College London, London, United Kingdom
| | - Paola Pedarzani
- Research Department of Neuroscience, Physiology and Pharmacology, University College London, London, United Kingdom
- * E-mail:
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Mielke JG, Wang YT. Insulin, synaptic function, and opportunities for neuroprotection. PROGRESS IN MOLECULAR BIOLOGY AND TRANSLATIONAL SCIENCE 2011; 98:133-86. [PMID: 21199772 DOI: 10.1016/b978-0-12-385506-0.00004-1] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
A steadily growing number of studies have begun to establish that the brain and insulin, while traditionally viewed as separate, do indeed have a relationship. The uptake of pancreatic insulin, along with neuronal biosynthesis, provides neural tissue with the hormone. As well, insulin acts upon a neuronal receptor that, although a close reflection of its peripheral counterpart, is characterized by unique structural and functional properties. One distinction is that the neural variant plays only a limited part in neuronal glucose transport. However, a number of other roles for neural insulin are gradually emerging; most significant among these is the modulation of ligand-gated ion channel (LGIC) trafficking. Notably, insulin has been shown to affect the tone of synaptic transmission by regulating cell-surface expression of inhibitory and excitatory receptors. The manner in which insulin regulates receptor movement may provide a cellular mechanism for insulin-mediated neuroprotection in the absence of hypoglycemia and stimulate the exploration of new therapeutic opportunities.
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Affiliation(s)
- John G Mielke
- Faculty of Applied Health Sciences, Department of Health Studies and Gerontology, University of Waterloo, Waterloo, Ontario, Canada
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30
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Guest PC, Martins-de-Souza D, Vanattou-Saifoudine N, Harris LW, Bahn S. Abnormalities in Metabolism and Hypothalamic–Pituitary–Adrenal Axis Function in Schizophrenia. INTERNATIONAL REVIEW OF NEUROBIOLOGY 2011; 101:145-68. [DOI: 10.1016/b978-0-12-387718-5.00006-7] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
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Insulin facilitates repetitive spike firing in rat insular cortex via phosphoinositide 3-kinase but not mitogen activated protein kinase cascade. Neuroscience 2010; 170:1199-208. [PMID: 20691771 DOI: 10.1016/j.neuroscience.2010.07.061] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2010] [Revised: 07/28/2010] [Accepted: 07/29/2010] [Indexed: 11/22/2022]
Abstract
The insular cortex (IC) processes gustatory and visceral information, which functionally correlate to feeding behavior. Insulin, a well-known hormone controlling glucose metabolism, is released by elevation of blood glucose concentration following feeding behavior. The IC expresses dense insulin receptors and receives projection from the hypothalamus, which monitors changes in glucose concentration. Therefore, it is likely that insulin modulates neural properties in the IC. However, little is known about the effects of insulin on electrophysiological properties of the neocortex including the IC. To explore the effects of insulin on subthreshold responses and action potential properties in the IC, intracellular recording with sharp glass electrodes was performed from IC pyramidal cells using slice preparations. Although application of insulin (100 nM) had little effect on the resting membrane potential, input resistance and rheobase, insulin significantly increased the frequency of repetitive spike firing in response to a long depolarizing current pulse injection: the slope of the frequency-current curve was increased from 23.7±2.3 Hz/nA to 29.5±3.4 Hz/nA. Insulin slightly decreased the action potential threshold without affecting the amplitude of medium-duration and slow afterhyperpolarization (sAHP) s. The insulin-induced facilitation of repetitive spike firing was dose-dependent and blocked by pre-application of 200 nM lavendustin A, a tyrosine kinase inhibitor. Moreover, when combined with 200 nM wortmannin, a phosphoinositide 3-kinase (PI3-K) inhibitor, or 500 nM deguelin, an inhibitor of protein kinase B (PKB/Akt) downstream of PI3-K, insulin failed to increase the frequency of repetitive spike firing. In contrast, co-application of insulin and (10 μM) PD 98059, an inhibitor of mitogen activated protein kinase (MAPK), exerted facilitation of repetitive spike firing. These results suggest that acute insulin-induced facilitation of firing frequency is at least partially induced by hyperpolarizing effects on the action potential threshold, and that this facilitation is induced by activation of PI3-K but not MAPK cascade.
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32
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Yang MJ, Wang F, Wang JH, Wu WN, Hu ZL, Cheng J, Yu DF, Long LH, Fu H, Xie N, Chen JG. PI3K integrates the effects of insulin and leptin on large-conductance Ca2+-activated K+ channels in neuropeptide Y neurons of the hypothalamic arcuate nucleus. Am J Physiol Endocrinol Metab 2010; 298:E193-201. [PMID: 19671839 DOI: 10.1152/ajpendo.00155.2009] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
The adipocyte-derived hormone leptin and the pancreatic beta-cell-derived hormone insulin function as afferent signals to the hypothalamus in an endocrine feedback loop that regulates body adiposity. They act in hypothalamic centers to modulate the function of specific neuronal subtypes, such as neuropeptide Y (NPY) neurons, by modifying neuronal electrical activity. To investigate the intrinsic activity of these neurons and their responses to insulin and leptin, we used a combination of morphological features and immunocytochemical technique to identify the NPY neurons of hypothalamic arcuate nucleus (ARC) and record whole cell large-conductance Ca(2+)-activated potassium (BK) currents on them. We found that both of the hormones increase the peak amplitude of BK currents, shifting the steady-state activation curve to the left. The effect of both insulin and leptin can be prevented by pretreatment with inhibitors of tyrosine kinase and phosphatidylinositol 3-kinase (PI3K) but not MAPK. These data indicate that PI3K-mediated signals are the common regulators of BK channels by insulin and leptin and mediated the two hormones' identical activatory effects on ARC NPY neurons. The effect of insulin and leptin together was similar to that of insulin or leptin alone, and leptin or insulin pretreatment did not lead to insulin- or leptin-sensitizing effects, respectively. These intracellular signaling mechanisms may play key roles in regulating ARC NPY neuron activity and physiological processes such as the control of food intake and body weight, which are under the combined control of insulin and leptin.
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Affiliation(s)
- Meng-Jie Yang
- Dept. of Pharmacology, Tongji Medical College, Huazhong Univ. of Science and Technology, Wuhan, Hubei 430030 China
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Lima PA, Vicente MI, Alves FM, Dionísio JC, Costa PF. Insulin increases excitability via a dose-dependent dual inhibition of voltage-activated K+ currents in differentiated N1E-115 neuroblastoma cells. Eur J Neurosci 2008; 27:2019-32. [PMID: 18412623 DOI: 10.1111/j.1460-9568.2008.06150.x] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
A role in the control of excitability has been attributed to insulin via modulation of potassium (K(+)) currents. To investigate insulin modulatory effects on voltage-activated potassium currents in a neuronal cell line with origin in the sympathetic system, we performed whole-cell voltage-clamp recordings in differentiated N1E-115 neuroblastoma cells. Two main voltage-activated K(+) currents were identified: (a) a relatively fast inactivating current (I(fast) - time constant 50-300 ms); (b) a slow delayed rectifying K(+) current (I(slow) - time constant 1-4 s). The kinetics of inactivation of I(fast), rather than I(slow), showed clear voltage dependence. I(fast) and I(slow) exhibited different activation and inactivation dependence for voltage, and have different but nevertheless high sensitivities to tetraethylammonium, 4-aminopyridine and quinidine. In differentiated cells - rather than in non-differentiated cells - application of up to 300 nm insulin reduced I(slow) only (IC(50) = 6.7 nm), whereas at higher concentrations I(fast) was also affected (IC(50) = 7.7 microm). The insulin inhibitory effect is not due to a change in the activation or inactivation current-voltage profiles, and the time-dependent inactivation is also not altered; this is not likely to be a result of activation of the insulin-growth-factor-1 (IGF1) receptors, as application of IGF1 did not result in significant current alteration. Results suggest that the current sensitive to low concentrations of insulin is mediated by erg-like channels. Similar observations concerning the insulin inhibitory effect on slow voltage-activated K(+) currents were also made in isolated rat hippocampal pyramidal neurons, suggesting a widespread neuromodulator role of insulin on K(+) channels.
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Affiliation(s)
- Pedro A Lima
- Faculdade de Ciências Médicas, Universidade Nova de Lisboa, Campo Mártires da Pátria, 130. 1169-056 Lisboa, Portugal.
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Foutz RM, Grimm PR, Sansom SC. Insulin increases the activity of mesangial BK channels through MAPK signaling. Am J Physiol Renal Physiol 2008; 294:F1465-72. [PMID: 18367663 DOI: 10.1152/ajprenal.00012.2008] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Glomerular hyperfiltration and mesangial expansion have been described in mouse models of a hyperinsulinemic early stage of type 2 diabetes mellitus (DM). Large-conductance Ca(2+)-activated K(+) channels (BK) have been linked to relaxation of human mesangial cells (MC) and may contribute to MC expansion and hyperfiltration. We hypothesized that high insulin levels increase BK activity in MC by increasing the number and/or open probability (P(o)) of BK in the plasma membrane. With the use of the patch-clamp technique, BK activity was analyzed in cultured MC exposed to normal insulin (1 nM) and high insulin (100 nM) for a 48-h period. The mean P(o) and the percentage of patches (cell attached) with detected BK increased by 100% in the insulin-treated cells. Real-time PCR revealed that insulin increased mRNA of BK-alpha. Western blot revealed an insulin-stimulated increase in BK-alpha from both total cellular and plasma membrane protein fractions. The mitogen-activated protein kinase (MAPK) inhibitors PD-098059 and U-0126 attenuated the insulin-induced increase in BK-alpha expression. PD-098059 inhibited insulin-stimulated phosphorylation of extracellular signal-regulated kinase 1/2 in MC. An insulin-stimulated increase also was found for total cellular BK-beta(1), the accessory subunit of BK in MC. A similar increase in BK-alpha mRNA and protein was evoked by an insulin-like growth factor I analog. Glomeruli, isolated from hyperinsulinemic early stage type 2 DM mice, exhibited increased BK-alpha mRNA by real-time PCR and protein by immunohistochemical staining and Western blot. These results indicate that insulin activates BK in the plasma membrane of MC and stimulates, via MAPK, an increase in cellular and plasma membrane BK-alpha.
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Affiliation(s)
- Ruth M Foutz
- Dept. of Cellular and Integrative Physiology, Univ. of Nebraska Medical Center, 985850 Nebraska Medical Center, Omaha, NE 68198-5850, USA
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35
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Pacheco Otalora LF, Hernandez EF, Arshadmansab MF, rancisco SF, Willis M, Ermolinsky B, Zarei M, Knaus HG, Garrido-Sanabria ER. Down-regulation of BK channel expression in the pilocarpine model of temporal lobe epilepsy. Brain Res 2008; 1200:116-31. [PMID: 18295190 PMCID: PMC2346580 DOI: 10.1016/j.brainres.2008.01.017] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2007] [Revised: 12/23/2007] [Accepted: 01/03/2008] [Indexed: 11/24/2022]
Abstract
In the hippocampus, BK channels are preferentially localized in presynaptic glutamatergic terminals including mossy fibers where they are thought to play an important role regulating excessive glutamate release during hyperactive states. Large conductance calcium-activated potassium channels (BK, MaxiK, Slo) have recently been implicated in the pathogenesis of genetic epilepsy. However, the role of BK channels in acquired mesial temporal lobe epilepsy (MTLE) remains unknown. Here we used immunohistochemistry, laser scanning confocal microscopy (LSCM), Western immunoblotting and RT-PCR to investigate the expression pattern of the alpha-pore-forming subunit of BK channels in the hippocampus and cortex of chronically epileptic rats obtained by the pilocarpine model of MTLE. All epileptic rats experiencing recurrent spontaneous seizures exhibited a significant down-regulation of BK channel immunostaining in the mossy fibers at the hilus and stratum lucidum of the CA3 area. Quantitative analysis of immunofluorescence signals by LSCM revealed a significant 47% reduction in BK channel immunofluorescent signals in epileptic rats when compared to age-matched non-epileptic control rats. These data correlate with a similar reduction in BK channel protein levels and transcripts in the cortex and hippocampus. Our data indicate a seizure-related down-regulation of BK channels in chronically epileptic rats. Further functional assays are necessary to determine whether altered BK channel expression is an acquired channelopathy or a compensatory mechanism affecting the network excitability in MTLE. Moreover, seizure-mediated BK down-regulation may disturb neuronal excitability and presynaptic control at glutamatergic terminals triggering exaggerated glutamate release and seizures.
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Affiliation(s)
- Luis F. Pacheco Otalora
- Department of Biological Sciences at the University of Texas at Brownsville/Texas Southmost College, Brownsville, Texas 78520 USA
| | - Eder F. Hernandez
- Department of Biological Sciences at the University of Texas at Brownsville/Texas Southmost College, Brownsville, Texas 78520 USA
| | - Massoud F. Arshadmansab
- Department of Biological Sciences at the University of Texas at Brownsville/Texas Southmost College, Brownsville, Texas 78520 USA
| | - Sebastian F rancisco
- Department of Biological Sciences at the University of Texas at Brownsville/Texas Southmost College, Brownsville, Texas 78520 USA
| | - Michael Willis
- Department of General Psychiatry, Medical University Innsbruck, Anichstrasse 35, 6020 Innsbruck, Austria
- Department of Molecular and Cellular Pharmacology, Medical University Innsbruck, Peter-Mayr Strasse 1, 6020 Innsbruck, Austria
| | - Boris Ermolinsky
- Department of Biological Sciences at the University of Texas at Brownsville/Texas Southmost College, Brownsville, Texas 78520 USA
| | - Masoud Zarei
- Department of Biological Sciences at the University of Texas at Brownsville/Texas Southmost College, Brownsville, Texas 78520 USA
- The Center for Biomedical Studies, Medical University Innsbruck, Anichstrasse 35, 6020 Innsbruck, Austria
| | - Hans-Guenther Knaus
- Department of Molecular and Cellular Pharmacology, Medical University Innsbruck, Peter-Mayr Strasse 1, 6020 Innsbruck, Austria
| | - Emilio R. Garrido-Sanabria
- Department of Biological Sciences at the University of Texas at Brownsville/Texas Southmost College, Brownsville, Texas 78520 USA
- The Center for Biomedical Studies, Medical University Innsbruck, Anichstrasse 35, 6020 Innsbruck, Austria
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Insulin and ghrelin: peripheral hormones modulating memory and hippocampal function. Curr Opin Pharmacol 2007; 7:628-32. [PMID: 18023257 DOI: 10.1016/j.coph.2007.10.009] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2007] [Accepted: 10/13/2007] [Indexed: 11/20/2022]
Abstract
Peptide hormones, initially identified in the periphery and best known for regulation of food intake and appetite, have increasingly been shown to regulate brain functions not only within the hypothalamus but elsewhere. The hippocampus, in particular, expresses receptors for many hormones. Both insulin and ghrelin are now known to enhance hippocampal memory processes; in addition, insulin acts to increase local hippocampal metabolism and regulate synaptic plasticity, while administration of ghrelin has been shown to promote dendritic spine synaptic formation and to increase anxiety. While insulin's effects appear to be specifically within the hippocampus, ghrelin may act at a range of sites within the limbic system.
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Daubert DL, Chung MY, Brooks VL. Insulin resistance and impaired baroreflex gain during pregnancy. Am J Physiol Regul Integr Comp Physiol 2007; 292:R2188-95. [PMID: 17303682 DOI: 10.1152/ajpregu.00614.2006] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Pregnancy decreases baroreflex gain, but the underlying mechanism is unclear. Insulin resistance, which has been associated with reduced transport of insulin into the brain, is a consistent feature of many conditions exhibiting impaired baroreflex gain, including pregnancy. Therefore, using conscious pregnant and nonpregnant rabbits, we tested the novel hypothesis that the pregnancy-induced impairment in baroreflex gain is due to insulin resistance and reduced brain insulin. Baroreflex gain was determined by quantifying changes in heart rate in response to stepwise steady-state changes in arterial pressure, secondary to infusion of nitroprusside and phenylephrine. We found that insulin sensitivity and baroreflex gain were strongly correlated in nonpregnant and term pregnant rabbits (r2 = 0.59). The decrease in insulin sensitivity and in baroreflex gain exhibited similar time courses throughout pregnancy, reaching significantly lower levels at 3 wk of gestation and remaining reduced at 4 wk (term is 31 days). Treatment of rabbits with the insulin-sensitizing drug rosiglitazone during pregnancy almost completely normalized baroreflex gain. Finally, pregnancy significantly lowered cerebrospinal fluid insulin concentrations. These data identify insulin resistance as a mechanism underlying pregnancy-induced baroreflex impairment and suggest, for the first time in any condition, that decreased brain insulin concentrations may be the link between reductions in peripheral insulin sensitivity and baroreflex gain.
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Affiliation(s)
- Daisy L Daubert
- Oregon Health & Science University, Department of Physiology and Pharmacology, Portland, Oregon 97239, USA
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O'Malley D, Harvey J. MAPK-dependent actin cytoskeletal reorganization underlies BK channel activation by insulin. Eur J Neurosci 2007; 25:673-82. [PMID: 17298596 DOI: 10.1111/j.1460-9568.2007.05347.x] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Numerous brain regions are enriched with insulin and insulin receptors, and several lines of evidence indicate that insulin is an important modulator of neuronal function. Indeed, recent studies have demonstrated that insulin inhibits hippocampal epileptiform-like activity, in part by activating large-conductance Ca2+-activated potassium (BK) channels. Moreover, the mitogen-activated protein kinase (MAPK) signalling cascade has been found to couple insulin to BK channel activation. However, the cellular events downstream of MAPK that underlie this action of insulin are unknown. Here we demonstrate that in hippocampal neurons, BK channel activation by insulin is blocked by actin filament stabilization, suggesting that this process is dependent on the actin cytoskeleton. Stabilizing actin filaments also markedly attenuated the ability of insulin to inhibit the aberrant hippocampal synaptic activity evoked following Mg2+ removal. Insulin also promoted rapid reorganization of fluorescently labelled polymerized actin filaments; an action that was prevented by inhibitors of MAPK activation. Moreover, in parallel studies, insulin increased the level of phospho-MAPK immunostaining in hippocampal neurons. These data are consistent with BK channel activation by insulin involving MAPK-dependent alterations in actin dynamics. This process may have important implications for the role of insulin in regulating hippocampal excitability.
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Affiliation(s)
- Dervla O'Malley
- Neurosciences Institute, Division of Pathology & Neuroscience, Ninewells Hospital & Medical School, University of Dundee, Dundee DD1 9SY, UK
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Moosavi M, Naghdi N, Maghsoudi N, Zahedi Asl S. The effect of intrahippocampal insulin microinjection on spatial learning and memory. Horm Behav 2006; 50:748-52. [PMID: 16890939 DOI: 10.1016/j.yhbeh.2006.06.025] [Citation(s) in RCA: 62] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/10/2006] [Revised: 06/19/2006] [Accepted: 06/25/2006] [Indexed: 11/27/2022]
Abstract
Insulin is best known for its action on peripheral target tissues such as the adipocyte, muscle and liver to regulate glucose homeostasis. Insulin and its receptor are found in specific area of CNS with a variety of region-specific functions different from its direct glucose regulation in the periphery. The hippocampus and cerebral cortex distributed insulin/insulin receptor has been shown to be involved in brain cognitive functions. Previous studies about the effect of insulin on memory are controversial. In the present study, the effect of insulin microinjection into CA1 region of rat hippocampus on water maze performance has been investigated. Insulin had a discrepant effect dose dependently. The spatial learning and memory were impaired with lower dose of insulin, had not changed with intermediate doses, while they improved with higher doses. These results suggest that insulin may have a dose-dependent effect on spatial learning and memory.
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Affiliation(s)
- M Moosavi
- Department of Physiology, School of Medicine, Shahid Beheshti University of Medical Sciences, Tehran, Iran
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40
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Wuttke TV, Lerche H. Novel anticonvulsant drugs targeting voltage-dependent ion channels. Expert Opin Investig Drugs 2006; 15:1167-77. [PMID: 16989594 DOI: 10.1517/13543784.15.10.1167] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
Epilepsy is one of the most common neurological disorders with a prevalence of 0.5-1%. About two-thirds of epilepsy patients respond well to anticonvulsant pharmacotherapy and become seizure free. There is a third who remain pharmacoresistant, demonstrating the pressing need for novel treatment options that could be drugs with a different mechanism of action compared with those that are currently in clinical use. During the past, many new substances have been screened for blocking or activating effects on specific ion channels, particularly those that are not targets for currently used antiepileptic drugs. This review provides an overview of new anticonvulsant compounds targeting voltage-dependent ion channels.
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Affiliation(s)
- Thomas V Wuttke
- University of Ulm, Department of Neurology, Zentrum Klinische Forschung, Helmholtzstrasse 8/1, D-89081 Ulm, Germany
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41
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Xu WH, Huber R, Riepe MW. Gender- and region-specific expression of insulin receptor protein in mouse brain: effect of mild inhibition of oxidative phosphorylation. J Neural Transm (Vienna) 2006; 114:373-7. [PMID: 17086487 DOI: 10.1007/s00702-006-0588-1] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2006] [Accepted: 09/23/2006] [Indexed: 10/23/2022]
Abstract
Insulin receptors (IR) and inhibition of oxidative metabolism have been suggested to partake in the pathophysiological cascade of neurodegenerative disorders. The goal of this study was to investigate gender- and region-specificity of insulin receptor protein expression in mouse brain subsequent to a mild hypoxic episode. Tissue was prepared from untreated male and female mice and animals pretreated in vivo with 20 mg/kg body weight i.p. 3-nitroproprionic acid (3-np; an inhibitor of succinic dehydrogenase) 1 hr prior to tissue preparation. IR expression in control animals was alike in males and females during proestrus and estrus but reduced during diestrus. On pretreatment, IR protein expression decrease in hippocampus in males but remained alike in other regions and females. In summary, IR protein expression is regionally different in males and females, gender-dependent, and modulated during the stages of the estrus cycle in females. Contrary to expectations it is not modified on mild inhibition of oxidative phosphorylation in any region in females and altered in hippocampus solely in males. The latter effect, however, warrants further scrutiny concerning participation in pathophysiological cascades affecting the hippocampus such as in Alzheimer's disease.
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Affiliation(s)
- W H Xu
- Department of Neurology, Peking Union Medical College Hospital, Chinese Academy of Medicine, Beijing, China
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Abstract
Migraine is a chronic episodic disorder that has been linked to abnormalities in serotonin signaling and abnormal function of a presynaptic voltage-gated calcium channel, CACNA1A. Although the importance of serotonin to migraine tendency suggests a link between serotonergic signaling and CACNA1A function, the nature of this connection remains unclear in vertebrate studies. This article reviews findings, based on an invertebrate model of CACNA1A dysfunction, which suggest a potential connection between serotonergic and calcium channel abnormalities in migraine. Neurons of the invertebrate species Caenorhabditis elegans express a voltage-gated calcium channel, UNC-2, which is the closest ortholog in C. elegans of human CACNA1A. Mutations in unc-2, the gene that encodes this invertebrate channel, cause the animals to be lethargic and uncoordinated. By identifying the genes that could be altered in such a way as to suppress the lethargic phenotype of unc-2, a signaling pathway has been identified through which UNC-2 calcium channel function antagonizes a transforming growth factor-beta (TGF-beta) pathway modulating locomotion. In C. elegans, serotonergic signaling can inhibit the rate of movement. The UNC-2/transforming growth factor-beta pathway identified regulates the expression of a gene encoding the rate-limiting enzyme for serotonin synthesis, tryptophan hydroxylase. The evolutionary and functional relationship between the UNC-2 channel and the migraine-associated CACNA1A channel was further confirmed through experiments showing that transgenic expression of human CACNA1A can suppress the lethargic and serotonin-deficient phenotypes of unc-2 mutant animals. The findings in this invertebrate model constitute the first direct demonstration of how CACNA1A function might affect the levels of serotonin, a neurotransmitter known to be important in migraine.
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Affiliation(s)
- Miguel Estevez
- Veterans Administration Hospital and University of Pittsburgh School of Medicine, Pittsburgh, PA 15213, USA
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Missan S, Zhabyeyev P, Linsdell P, McDonald TF. Insensitivity of cardiac delayed-rectifier I(Kr) to tyrosine phosphorylation inhibitors and stimulators. Br J Pharmacol 2006; 148:724-31. [PMID: 16715119 PMCID: PMC1751861 DOI: 10.1038/sj.bjp.0706776] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
1. The rapidly activating delayed-rectifying K+ current (I(Kr)) in heart cells is an important determinant of repolarisation, and decreases in its density are implicated in acquired and inherited long QT syndromes. The objective of the present study on I(Kr) in guinea-pig ventricular myocytes was to evaluate whether the current is acutely regulated by tyrosine phosphorylation. 2. Myocytes configured for ruptured-patch or perforated-patch voltage-clamp were depolarised with 200-ms steps to 0 mV for measurement of I(Kr) tail amplitude on repolarisations to -40 mV. 3. I(Kr) in both ruptured-patch and perforated-patch myocytes was only moderately (14-20%) decreased by 100 microM concentrations of protein tyrosine kinase (PTK) inhibitors tyrphostin A23, tyrphostin A25, and genistein. However, similar-sized decreases were induced by PTK-inactive analogues tyrphostin A1 and daidzein, suggesting that they were unrelated to inhibition of PTK. 4. Ruptured-patch and perforated-patch myocytes were also treated with promoters of tyrosine phosphorylation, including phosphotyrosyl phosphatase (PTP) inhibitor orthovanadate, exogenous c-Src PTK, and four receptor PTK activators (insulin, insulin-like growth factor-1, epidermal growth factor, and basic fibroblast growth factor). None of these treatments had a significant effect on the amplitude of I(Kr). 5. We conclude that Kr channels in guinea-pig ventricular myocytes are unlikely to be regulated by PTK and PTP.
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Affiliation(s)
- Sergey Missan
- Department of Physiology and Biophysics, Dalhousie University, Halifax, Nova Scotia, Canada B3H 4H7
| | - Pavel Zhabyeyev
- Department of Physiology and Biophysics, Dalhousie University, Halifax, Nova Scotia, Canada B3H 4H7
| | - Paul Linsdell
- Department of Physiology and Biophysics, Dalhousie University, Halifax, Nova Scotia, Canada B3H 4H7
| | - Terence F McDonald
- Department of Physiology and Biophysics, Dalhousie University, Halifax, Nova Scotia, Canada B3H 4H7
- Author for correspondence:
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Porte D, Baskin DG, Schwartz MW. Insulin signaling in the central nervous system: a critical role in metabolic homeostasis and disease from C. elegans to humans. Diabetes 2005; 54:1264-76. [PMID: 15855309 DOI: 10.2337/diabetes.54.5.1264] [Citation(s) in RCA: 260] [Impact Index Per Article: 13.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
Insulin and its signaling systems are implicated in both central and peripheral mechanisms governing the ingestion, distribution, metabolism, and storage of nutrients in organisms ranging from worms to humans. Input from the environment regarding the availability and type of nutrients is sensed and integrated with humoral information (provided in part by insulin) regarding the sufficiency of body fat stores. In response to these afferent inputs, neuronal pathways are activated that influence energy flux and nutrient metabolism in the body and ensure reproductive competency. Growing evidence supports the hypothesis that reduced central nervous system insulin signaling from either defective secretion or action contributes to the pathogenesis of common metabolic disorders, including diabetes and obesity, and may therefore help to explain the close association between these two disorders. These considerations implicate insulin action in the brain, an organ previously considered to be insulin independent, as a key determinant of both glucose and energy homeostasis.
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Affiliation(s)
- Daniel Porte
- Division of Metabolism, Diabetes, and Endocrinology, University of California San Diego, USA.
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Farr SA, Banks WA, Uezu K, Gaskin FS, Morley JE. DHEAS improves learning and memory in aged SAMP8 mice but not in diabetic mice. Life Sci 2004; 75:2775-85. [PMID: 15464829 DOI: 10.1016/j.lfs.2004.05.026] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2004] [Accepted: 05/07/2004] [Indexed: 10/26/2022]
Abstract
Dehydroepiandrosterone sulfate (DHEAS) has been reported to improve memory in aged animals and suggested as a treatment for age-related dementias. The SAMP8 mouse, a model of Alzheimer's disease, has an age-related impairment in learning and memory and an increase in brain levels of amyloid precursor protein (APP) and amyloid beta protein (Abeta). Male SAMP8 mice also have a decrease in testosterone, to which DHEA is a precursor. Diabetes has been suggested as a model of aging and to be linked to Alzheimer's disease. Diabetics can have memory deficits and lower DHEAS levels. Here, we examined the effects of chronic oral DHEAS on acquisition and retention for T-maze footshock avoidance in 12 mo male SAMP8 mice and in CD-1 mice with streptozocin-induced diabetes. Learning and memory were improved in aged SAMP8 mice, but not in CD-1 mice with streptozocin-induced diabetes. These findings suggest that DHEAS is more effective in reversing the cognitive impairments associated with overexpression of Abeta than with diabetes.
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Affiliation(s)
- Susan A Farr
- Geriatric Research Education and Clinical Center (GRECC), VA Medical Center, St. Louis, MO, USA.
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Xing Y, Sonner J, Laster MJ, Abaigar W, Caraiscos VB, Orser B, Eger EI. Insulin decreases isoflurane minimum alveolar anesthetic concentration in rats independently of an effect on the spinal cord. Anesth Analg 2004; 98:1712-1717. [PMID: 15155333 DOI: 10.1213/01.ane.0000113550.47942.47] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
UNLABELLED The observation that insulin supplies an element of analgesia suggests that insulin administration might decrease the concentration of inhaled anesthetic required to produce MAC (the minimum alveolar anesthetic concentration required to eliminate movement in response to noxious stimulation in 50% of subjects). We hypothesized that insulin decreases MAC by directly affecting the nervous system, by decreasing blood glucose, or both. To test these hypotheses, we infused increasing doses of insulin either intrathecally or IV in rats anesthetized with isoflurane and determined the resulting MAC change (assessing forelimb and hindlimb movement separately). Infusion of insulin produced a dose-related decrease in MAC that did not differ among groups. That is, the IV and intrathecal infusions caused similar decreases in MAC at a given infusion rate. Blood glucose concentrations were larger in the rats given insulin with 5% dextrose. However, the percentage change in MAC determined from forelimb versus hindlimb movement did not differ. For a given insulin infusion rate, MAC changes and glucose levels did not correlate with each other, except, possibly, for the most rapid infusion rate, for which smaller glucose concentrations were associated with a marginally larger decrease in MAC. Intrathecal infusions of insulin did not produce spinal cord injury. In summary, we found that insulin decreases isoflurane MAC in a dose-related manner independently of its effects on the blood concentration of glucose. The sites at which insulin acts to decrease MAC appear to be supraspinal rather than spinal. The effect may be due to a capacity of insulin to produce analgesia through an action on one or more neurotransmitter receptors. IMPLICATIONS Intrathecal and IV insulin administration equally decrease isoflurane MAC in rats, regardless of the concentration of blood sugar. These findings indicate that although insulin decreases MAC, the decrease is not mediated by actions on the spinal cord.
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Affiliation(s)
- Yilei Xing
- *Department of Anesthesia and Perioperative Care, University of California, San Francisco, California; and †Department of Anesthesia, University of Toronto, Toronto, Ontario, Canada
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O'Malley D, Harvey J. Insulin activates native and recombinant large conductance Ca(2+)-activated potassium channels via a mitogen-activated protein kinase-dependent process. Mol Pharmacol 2004; 65:1352-63. [PMID: 15155829 DOI: 10.1124/mol.65.6.1352] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Evidence is accumulating that, in addition to regulating peripheral energy metabolism, insulin is an important modulator of neuronal function. Indeed, high levels of insulin and insulin receptors are expressed in several brain regions including the hippocampus. We have shown previously that insulin inhibits aberrant synaptic activity in hippocampal neurons via activation of large conductance Ca(2+)-activated K+ (BK) channels. In this study, we have examined further the effects of insulin on native hippocampal and recombinant (hSlo) BK channels expressed in human embryonic kidney (HEK) 293 cells. Pipette or bath application of insulin evoked a rapid increase in hippocampal BK channel activity, an action caused by activation of insulin receptors because insulin-like growth factor 1 (IGF-1) failed to mimic insulin action. In parallel studies, insulin, applied via the pipette or bath, also activated hSlo channels expressed in HEK293 cells. Although phosphoinositide 3-kinase is a key component of insulin and IGF-1 receptor signaling pathways, activation of this lipid kinase does not underlie the effects of insulin because neither 2-(4-morpholinyl)-8-phenyl-4H-1-benzopyran-4-one (LY294002) nor wortmannin inhibited or reversed insulin action. However, specific inhibitors of mitogen-activated protein kinase (MAPK) activation, 2'-amino-3'-methoxyflavone (PD98059) or 1,4-diamino-2,3-dicyano-1,4-bis(2-aminophenylthio)-butadiene (U0126), attenuated insulin action, indicating that a MAPK-dependent mechanism underlies this process. Furthermore, insulin activation of this pathway enhances BK channel activity by shifting the Ca(2+)-sensitivity such that BK channels are active at more hyperpolarized membrane potentials. Because postsynaptic BK channels are important regulators of neuronal hyperexcitability, insulin-induced activation of BK channels, via stimulation of a MAPK-dependent pathway, may be an important process for regulating hippocampal function under normal and pathological conditions.
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Affiliation(s)
- Dervla O'Malley
- Department of Pharmacology and Neuroscience, Ninewells Hospital and Medical School, University of Dundee, Dundee, UK
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