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Moult PR, Harvey J. NMDA receptor subunit composition determines the polarity of leptin-induced synaptic plasticity. Neuropharmacology 2011; 61:924-36. [PMID: 21752339 DOI: 10.1016/j.neuropharm.2011.06.021] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2011] [Revised: 06/21/2011] [Accepted: 06/22/2011] [Indexed: 11/16/2022]
Abstract
Leptin is a hormone that crosses the blood-brain barrier and regulates numerous CNS functions. The hippocampus in particular is an important site for leptin action. Indeed, leptin markedly influences excitatory synaptic transmission and synaptic plasticity in this brain region. Recent studies indicate that leptin modulation of hippocampal excitatory synaptic transmission is age-dependent however the cellular basis for this is unclear. Here we show that early in development leptin evokes a transient (P11-18) or persistent (P5-8) depression of synaptic transmission, whereas leptin evokes a long lasting increase (LTP) in synaptic strength in adulthood. The synaptic depressions induced by leptin required activation of NMDA receptor GluN2B subunits and the ERK signalling cascade. Conversely, leptin-induced LTP in adult was mediated by GluN2A subunits and involved PI 3-kinase dependent signalling. In addition, low-frequency stimulus (LFS)-evoked LTD occluded the persistent effects of leptin at P5-8 and vice versa. Similarly, synaptically-induced LTP occluded the persistent increase in synaptic transmission induced by leptin, indicating that similar expression mechanisms underlie leptin-induced LTD and LFS-induced LTD at P5-8, and leptin-induced LTP and HFS-induced LTP in adult. These findings have important implications for the role of leptin in hippocampal synaptic function during early neuronal development and in aging.
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Affiliation(s)
- Peter R Moult
- Centre for Neuroscience, Division of Medical Sciences, Ninewells Hospital and Medical School, University of Dundee, Dundee, UK
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Grillo CA, Piroli GG, Junor L, Wilson SP, Mott DD, Wilson MA, Reagan LP. Obesity/hyperleptinemic phenotype impairs structural and functional plasticity in the rat hippocampus. Physiol Behav 2011; 105:138-44. [PMID: 21354191 DOI: 10.1016/j.physbeh.2011.02.028] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2010] [Revised: 02/15/2011] [Accepted: 02/17/2011] [Indexed: 11/28/2022]
Abstract
Epidemiological studies estimate that greater than 60% of the adult US population may be categorized as either overweight or obese, and there is a growing appreciation that the complications of obesity extend to the central nervous system (CNS). While the vast majority of these studies have focused on the hypothalamus, more recent studies suggest that the complications of obesity may also affect the structural and functional integrity of the hippocampus. A potential contributor to obesity-related CNS abnormalities is the adipocyte-derived hormone leptin. In this regard, decreases in CNS leptin activity may contribute to deficits in hippocampal synaptic plasticity and suggest that leptin resistance, a well-described phenomenon in the hypothalamus, may also be observed in the hippocampus. Unfortunately, the myriad of metabolic and endocrine abnormalities in diabetes/obesity phenotypes makes it challenging to assess the role of leptin in hippocampal neuroplasticity deficits associated with obesity models. To address this question, we examined hippocampal morphological and behavioral plasticity following lentivirus-mediated downregulation of hypothalamic insulin receptors (hypo-IRAS). Hypo-IRAS rats exhibit increases in body weight, adiposity, plasma leptin and triglyceride levels. As such, hypo-IRAS rats develop a phenotype that is consistent with features of the metabolic syndrome. In addition, hippocampal morphological plasticity and performance of hippocampal-dependent tasks are adversely affected in hypo-IRAS rats. Leptin-mediated signaling is also decreased in hypo-IRAS rats. We will discuss these findings in the context of how hyperleptinemia and hypertriglyceridemia may represent mechanistic mediators of the neurological consequences of impaired hippocampal synaptic plasticity in obesity.
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Affiliation(s)
- Claudia A Grillo
- Department of Pharmacology, Physiology and Neuroscience, University of South Carolina School of Medicine, 6439 Garners Ferry Road, Columbia, SC 29208, USA
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García-Alcocer G, Rodríguez A, Moreno-Layseca P, Berumen LC, Escobar J, Miledi R. Serotonin receptor 5-HT5A in rat hippocampus decrease by leptin treatment. Neurosci Lett 2010; 486:171-3. [DOI: 10.1016/j.neulet.2010.09.045] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2010] [Revised: 08/31/2010] [Accepted: 09/15/2010] [Indexed: 10/25/2022]
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Abstract
About 60% of adults in the United States do not consume the estimated average requirement for magnesium, but widespread pathological conditions attributed to magnesium deficiency have not been reported. Nevertheless, low magnesium status has been associated with numerous pathological conditions characterized as having a chronic inflammatory stress component. In humans, deficient magnesium intakes are mostly marginal to moderate (approximately 50% to <100% of the recommended dietary allowance). Animal experiments indicate that signs of marginal-to-moderate magnesium deficiency can be compensated or exacerbated by other factors influencing inflammatory and oxidative stress; recent studies suggest a similar happening in humans. This suggestion may have significance in obesity, which is characterized as having a chronic low-grade inflammation component and an increased incidence of a low magnesium status. Marginal-to-moderate magnesium deficiency through exacerbating chronic inflammatory stress may be contributing significantly to the occurrence of chronic diseases such as atherosclerosis, hypertension, osteoporosis, diabetes mellitus, and cancer.
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Affiliation(s)
- Forrest H Nielsen
- US Department of Agriculture, Agricultural Research Service, Grand Forks Human Nutrition Research Center, Grand Forks, North Dakota 58202-9034, USA.
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Razzoli M, Andreoli M, Maraia G, Di Francesco C, Arban R. Functional role of Calcium-stimulated adenylyl cyclase 8 in adaptations to psychological stressors in the mouse: implications for mood disorders. Neuroscience 2010; 170:429-40. [PMID: 20638449 DOI: 10.1016/j.neuroscience.2010.07.022] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2010] [Revised: 06/09/2010] [Accepted: 07/10/2010] [Indexed: 01/09/2023]
Abstract
The Ca(2+)/calmodulin stimulated adenylyl cylcase 8 (AC8) is a pure Ca(2+) sensor, catalyzing the conversion of ATP to cAMP, with a critical role in neuronal plasticity. A role for AC8 in modulating complex behavioral outcomes has been demonstrated in AC8 knock out (KO) mouse models in which anxiety-like responses were differentially modulated following repeated stress experiences, suggesting an involvement of AC8 in stress adaptation and mood disorders. To further investigate the role of this enzyme in phenotypes relevant for psychiatric conditions, AC8 KO mice were assessed for baseline behavioral and hormonal parameters, responses to repeated restraint stress experience, and long-term effects of chronic social defeat stress. The lack of AC8 conferred a hyperactive-phenotype both in home-cage behaviors and the forced swim test response as well as lower leptin plasma levels and adrenal hypertrophy. AC8 KO mice showed baseline "anxiety" levels similar to wild type littermates in a variety of procedures, but displayed decreased anxiety-like responses following repeated restraint stress. This increased stress resilience was not seen during the chronic social defeat procedure. AC8 KO did not differ from wild type mice in response to social stress; similar alterations in body weight, food intake and increased social avoidance were found in all defeated subjects. Altogether these results support a complex role of cAMP signaling pathways confirming the involvement of AC8 in the modulation of stress responses. Furthermore, the hyperactivity and the increased risk taking behavior observed in AC8 KO mice could be related to a manic-like behavioral phenotype that warrants further investigation.
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Affiliation(s)
- M Razzoli
- Neurosciences CEDD, GlaxoSmithKline Medicine Research Centre, via Fleming 4, 37135 Verona, Italy.
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56
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Pachoud B, Adamantidis A, Ravassard P, Luppi PH, Grisar T, Lakaye B, Salin PA. Major impairments of glutamatergic transmission and long-term synaptic plasticity in the hippocampus of mice lacking the melanin-concentrating hormone receptor-1. J Neurophysiol 2010; 104:1417-25. [PMID: 20592115 DOI: 10.1152/jn.01052.2009] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The hypothalamic neuropeptide melanin-concentrating hormone (MCH) plays important roles in energy homeostasis, anxiety, and sleep regulation. Since the MCH receptor-1 (MCH-R1), the only functional receptor that mediates MCH functions in rodents, facilitates behavioral performance in hippocampus-dependent learning tasks, we investigated whether glutamatergic transmission in CA1 pyramidal cells could be modulated in mice lacking the MCH-R1 gene (MCH-R1(-/-)). We found that both α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) and N-methyl-d-aspartate (NMDA) receptor-mediated transmissions were diminished in the mutant mice compared with their controls. This deficit was explained, at least in part, by a postsynaptic down-regulation of these receptors since the amplitude of miniature excitatory postsynaptic currents and the NMDA/AMPA ratio were decreased. Long-term synaptic potentiation (LTP) was also impaired in MCH-R1(-/-) mice. This was due to an altered induction, rather than an impaired, expression because repeating the induction stimulus restored LTP to a normal magnitude. In addition, long-term synaptic depression was strongly diminished in MCH-R1(-/-) mice. These results suggest that MCH exerts a facilitatory effect on CA1 glutamatergic synaptic transmission and long-term synaptic plasticity. Recently, it has been shown that MCH neurons fire exclusively during sleep and mainly during rapid eye movement sleep. Thus these findings provide a mechanism by which sleep might facilitate memory consolidation.
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Affiliation(s)
- Bastien Pachoud
- Unité Mixte de Recherche 5167 du Centre National de la Recherche Scientifique, Institut Fédératif des Neurosciences de Lyon (IFR19), Université Claude, Lyon, France
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Nishio M, Watanabe Y. Hippocampal leptin suppresses methamphetamine-induced hyperlocomotion. Basic Clin Pharmacol Toxicol 2010; 107:842-6. [PMID: 20486923 DOI: 10.1111/j.1742-7843.2010.00591.x] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Leptin is an anorexigenic peptide which is synthesized in white adipose tissue. The actions of leptin are mediated by the leptin receptor which is abundantly localized in the hypothalamus and is involved in energy regulation and balance. Recently, there has been evidence suggesting that the leptin receptor is also present in the hippocampus and may be involved with hippocampal excitability and long-term depression. To investigate the physiological function of leptin signalling in the hippocampus, we studied the effects of leptin on methamphetamine-induced ambulatory hyperactivity by utilizing intra-hippocampal infusion (i.h.) in mice. Our results show that the infusion of leptin (5 ng each bilaterally i.h.) does not affect the basal ambulatory activity but significantly suppresses methamphetamine-induced ambulatory hyperactivity as compared to saline-infused controls. Interestingly, higher dose of leptin increases the suppression of the methamphetamine-induced ambulatory hyperactivity. The i.h. infusion of leptin did not activate the JAK-STAT pathway, which is the cellular signalling pathway through which leptin acts in the hypothalamus. The infusion of leptin also did not affect activation of p42/44 MAPK which is known to be another leptin-induced signalling pathway in the brain. These results demonstrate that leptin has a novel potential suppressive effect on methamphetamine-induced hyperlocomotion and also suggest that there must be an alternative pathway in the hippocampus through which leptin signalling is being mediated.
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Affiliation(s)
- Masahiro Nishio
- Department of Pharmacology, National Defense Medical College, Namiki, Tokorozawa, Japan
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Abstract
The hormone leptin can cross the blood-brain barrier and influences numerous brain functions (Harvey, 2007). Indeed, recent studies have demonstrated that leptin regulates activity-dependent synaptic plasticity in the CA1 region of the hippocampus (Shanley et al., 2001; Li et al., 2002; Durakoglugil et al., 2005; Moult et al., 2009). It is well documented that trafficking of AMPA receptors is pivotal for hippocampal synaptic plasticity (Collingridge et al., 2004), but there is limited knowledge of how hormonal systems like leptin influence this process. In this study we have examined how leptin influences AMPA receptor trafficking and in turn how this impacts on excitatory synaptic function. Here we show that leptin preferentially increases the cell surface expression of GluR1 and the synaptic density of GluR2-lacking AMPA receptors in adult hippocampal slices. The leptin-induced increase in surface GluR1 required NMDA receptor activation and was associated with an increase in cytoplasmic PtdIns(3,4,5)P(3) levels. In addition, leptin enhanced phosphorylation of the lipid phosphatase PTEN which inhibits PTEN function and elevates PtdIns(3,4,5)P(3) levels. Moreover, inhibition of PTEN mimicked and occluded the effects of leptin on GluR1 trafficking and excitatory synaptic strength. These data indicate that leptin, via a novel pathway involving PTEN inhibition, promotes GluR1 trafficking to hippocampal synapses. This process has important implications for the role of leptin in hippocampal synaptic function in health and disease.
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Fiszer U, Michałowska M, Baranowska B, Wolińska-Witort E, Jeske W, Jethon M, Piaścik-Gromada M, Marcinowska-Suchowierska E. Leptin and ghrelin concentrations and weight loss in Parkinson's disease. Acta Neurol Scand 2010; 121:230-6. [PMID: 20028343 DOI: 10.1111/j.1600-0404.2009.01185.x] [Citation(s) in RCA: 63] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
OBJECTIVES To investigate the role of leptin, ghrelin, GH and IGF-1 in energy balance disturbances in Parkinson's disease (PD). MATERIALS AND METHODS Thirty-nine patients were included: 11 PD patients with unintentional weight loss, 16 PD patients without weight loss and 12 controls. UPDRS, MMSE, MADRS, appetite scale, BMI, adipose tissue content, plasma leptin and active ghrelin concentrations and serum GH, IGF-1, TSH, T3 and T4, concentrations were evaluated. RESULTS A lower plasma leptin concentration and a higher serum IGF-1 concentration were found in PD patients with weight loss. BMI and the content of adipose tissue were positively correlated with leptin concentration in all PD patients. Paradoxically, the lower BMI was, the lower plasma active ghrelin concentration was in PD patients with the weight loss. CONCLUSION These findings confirm that changes of plasma leptin concentration occur in PD patients with loss of weight.
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Affiliation(s)
- U Fiszer
- Department of Neurology and Epileptology, Medical Center for Postgraduate Education, Warsaw, Poland.
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Lynch JJ, Shek EW, Castagné V, Mittelstadt SW. The proconvulsant effects of leptin on glutamate receptor-mediated seizures in mice. Brain Res Bull 2010; 82:99-103. [PMID: 20152888 DOI: 10.1016/j.brainresbull.2010.02.003] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2009] [Revised: 02/01/2010] [Accepted: 02/03/2010] [Indexed: 10/19/2022]
Abstract
The metabolic-related hormone, leptin has been suggested for clinical use as an anticonvulsant based upon data generated from in vitro and in vivo non-human studies. However, a number of other non-human experiments have demonstrated proconvulsant activity for leptin. The current study investigated potential pro- and anticonvulsant effects of leptin during exposure to either glutamate (the major endogenous excitatory neurotransmitter) or three subtype-selective glutamate receptor agonists (N-methyl-d-aspartic acid [NMDA], alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid [AMPA], and kainate). Male C57BL/6JRj mice were pretreated with leptin (0.1-10mg/kg, i.p.) and then administered doses of the glutamate receptor agonists (i.p.) that had been previously shown to result in clonic convulsions in approximately half of the animals tested. Leptin had no clear convulsant-related effects with either glutamate or AMPA, but it exhibited dose-related, proconvulsant activity (decreased latency to first occurrence of various convulsion-related signs, and increased percentage of animals exhibiting such signs) with both NMDA and kainate. The proconvulsant effects of leptin observed during the current study suggest that a cautious approach should be taken when administering leptin to individuals who may be prone to seizures.
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Affiliation(s)
- James J Lynch
- Department of Integrative Pharmacology, Global Pharmaceutical Research and Development, Abbott Laboratories, 100 Abbott Park Road, Abbott Park, IL 60064-6119, USA.
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61
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Abstract
It is well established that leptin is a circulating hormone that enters the brain and regulates food intake and body weight via its hypothalamic actions. However, it is also known that leptin receptors are widely expressed in the CNS (central nervous system), and evidence is accumulating that leptin modulates many neuronal functions. In particular, recent studies have indicated that leptin plays an important role in the regulation of hippocampal synaptic plasticity. Indeed leptin-insensitive rodents display impairments in hippocampal synaptic plasticity and defects in spatial memory tasks. We have also shown that leptin facilitates the induction of hippocampal LTP (long-term potentiation) via enhancing NMDA (N-methyl-D-aspartate) receptor function and that leptin has the ability to evoke a novel form of NMDA receptor-dependent LTD (long-term depression). In addition, leptin promotes rapid alterations in hippocampal dendritic morphology and synaptic density, which are likely to contribute to the effects of this hormone on excitatory synaptic strength. Recent studies have demonstrated that trafficking of AMPA (alpha-amino-3-hydroxy-5-methylisoxazole-4-propionic acid) receptors is pivotal for activity-dependent hippocampal synaptic plasticity. However, little is known about how AMPA receptor trafficking processes are regulated by hormonal systems. In the present paper, we discuss evidence that leptin rapidly alters the trafficking of AMPA receptors to and away from hippocampal CA1 synapses. The impact of these leptin-driven changes on hippocampal excitatory synaptic function are discussed.
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Affiliation(s)
- Peter R Moult
- Division of Neuroscience, Centre for Neuroscience, Ninewells Hospital, University of Dundee, Dundee DD1 9SY, UK
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62
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Solovyova N, Moult PR, Milojkovic B, Lambert JJ, Harvey J. Bi-directional modulation of fast inhibitory synaptic transmission by leptin. J Neurochem 2009; 108:190-201. [PMID: 19094063 DOI: 10.1111/j.1471-4159.2008.05751.x] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The hormone leptin has widespread actions in the CNS. Indeed, leptin markedly influences hippocampal excitatory synaptic transmission and synaptic plasticity. However, the effects of leptin on fast inhibitory synaptic transmission in the hippocampus have not been evaluated. Here, we show that leptin modulates GABA(A) receptor-mediated synaptic transmission onto hippocampal CA1 pyramidal cells. Leptin promotes a rapid and reversible increase in the amplitude of evoked GABA(A) receptor-mediated inhibitory synaptic currents (IPSCs); an effect that was paralleled by increases in the frequency and amplitude of miniature IPSCs, but with no change in paired pulse ratio or coefficient of variation, suggesting a post-synaptic expression mechanism. Following washout of leptin, a persistent depression (inhibitory long-lasting depression) of evoked IPSCs was observed. Whole-cell dialysis or bath application of inhibitors of phosphoinositide 3 (PI 3)-kinase or Akt prevented leptin-induced enhancement of IPSCs indicating involvement of a post-synaptic PI 3-kinase/Akt-dependent pathway. In contrast, blockade of PI 3-kinase or Akt activity failed to alter the ability of leptin to induce inhibitory long-lasting depression, suggesting that this process is independent of PI 3-kinase/Akt. In conclusion these data indicate that the hormone leptin bi-directionally modulates GABA(A) receptor-mediated synaptic transmission in the hippocampus. These findings have important implications for the role of this hormone in regulating hippocampal pyramidal neuron excitability.
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Affiliation(s)
- Natasha Solovyova
- Neurosciences Institute, Division of Pathology & Neuroscience, Ninewells Hospital & Medical School, University of Dundee, Dundee, UK
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Leptin signaling in brain: A link between nutrition and cognition? Biochim Biophys Acta Mol Basis Dis 2008; 1792:401-8. [PMID: 19130879 DOI: 10.1016/j.bbadis.2008.12.004] [Citation(s) in RCA: 143] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2008] [Revised: 12/05/2008] [Accepted: 12/07/2008] [Indexed: 12/22/2022]
Abstract
Leptin is a protein hormone that acts within the hypothalamus to suppress food intake and decrease body adiposity, but it is increasingly clear that the hypothalamus is not the only site of leptin action, nor food intake the only biological effect of leptin. Instead, leptin is a pleiotropic hormone that impinges on many brain areas, and in doing so alters food intake, motivation, learning, memory, cognitive function, neuroprotection, reproduction, growth, metabolism, energy expenditure, and more. This diversity of function also means that a dysregulation of leptin secretion and signaling can have far reaching effects. To date research on leptin signaling has focused primarily on the hypothalamus, and the result is a relative lack of information regarding the impact of leptin signaling and leptin resistance in non-hypothalamic areas, despite a growing literature implicating leptin in the regulation of neuronal structure and function in the hippocampus, cortex and other brain areas associated with cognition.
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Moult PR, Milojkovic B, Harvey J. Leptin reverses long-term potentiation at hippocampal CA1 synapses. J Neurochem 2008; 108:685-96. [PMID: 19054283 DOI: 10.1111/j.1471-4159.2008.05810.x] [Citation(s) in RCA: 53] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The hormone leptin crosses the blood brain barrier and regulates numerous neuronal functions, including hippocampal synaptic plasticity. Here we show that application of leptin resulted in the reversal of long-term potentiation (LTP) at hippocampal CA1 synapses. The ability of leptin to depotentiate CA1 synapses was concentration-dependent and it displayed a distinct temporal profile. Leptin-induced depotentiation was not associated with any change in the paired pulse facilitation ratio or the coefficient of variance, indicating a post-synaptic locus of expression. Moreover, the synaptic activation of NMDA receptors was required for leptin-induced depotentiation as the effects of leptin were blocked by the competitive NMDA receptor antagonist, D-aminophosphovaleric acid (D-AP5). The signaling mechanisms underlying leptin-induced depotentiation involved activation of the calcium/calmodulin-dependent protein phosphatase, calcineurin, but were independent of c-jun NH(2) terminal kinase. Furthermore, leptin-induced depotentiation was accompanied by a reduction in alpha-amino-3-hydroxy-5-methylisoxazole-4-propionate (AMPA) receptor rectification indicating that loss of glutamate receptor 2 (GluR2)-lacking AMPA receptors underlies this process. These data indicate that leptin reverses hippocampal LTP via a process involving calcineurin-dependent internalization of GluR2-lacking AMPA receptors which further highlights the key role for this hormone in regulating hippocampal synaptic plasticity and neuronal development.
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Affiliation(s)
- Peter R Moult
- Neurosciences Institute, Ninewells Hospital and Medical School, University of Dundee, Dundee, UK
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Moult PR, Harvey J. Hormonal regulation of hippocampal dendritic morphology and synaptic plasticity. Cell Adh Migr 2008; 2:269-75. [PMID: 19262152 DOI: 10.4161/cam.2.4.6354] [Citation(s) in RCA: 56] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
The peripheral functions of hormones such as leptin, insulin and estrogens are well documented. An important and rapidly expanding field is demonstrating that as well as their peripheral actions, these hormones play an important role in modulating synaptic function and structure within the CNS. The hippocampus is a major mediator of spatial learning and memory and is also an area highly susceptible to epileptic seizure. As such, the hippocampus has been extensively studied with particular regard to synaptic plasticity, a process thought to be necessary for learning and memory. Modulators of hippocampal function are therefore of particular interest, not only as potential modulators of learning and memory processes, but also with regard to CNS driven diseases such as epilepsy. Hormones traditionally thought of as only having peripheral roles are now increasingly being shown to have an important role in modulating synaptic plasticity and dendritic morphology. Here we review recent findings demonstrating that a number of hormones are capable of modulating both these phenomena.
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Affiliation(s)
- Peter R Moult
- Neurosciences Institute, Division of Pathology and Neuroscience, Ninewells Hospital and Medical School, University of Dundee, Dundee, UK
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Signore AP, Zhang F, Weng Z, Gao Y, Chen J. Leptin neuroprotection in the CNS: mechanisms and therapeutic potentials. J Neurochem 2008; 106:1977-90. [PMID: 18466320 PMCID: PMC2634657 DOI: 10.1111/j.1471-4159.2008.05457.x] [Citation(s) in RCA: 109] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Leptin is well known as a hormone important in the central control of appetitive behaviors via receptor-mediated actions in the hypothalamus, where leptin adjusts food intake to maintain homeostasis with the body's energy stores. Recent evidence has shown that leptin and its receptors are widespread in the CNS and may provide neuronal survival signals. This review summarizes our current knowledge of how leptin functions in the brain and then focuses on the ability of leptin to mitigate neuronal damage in experimental models of human neurological disorders. Damage to the brain by acute events such as stroke, or long-term loss of neurons associated with neurodegenerative diseases, including Parkinson's and Alzheimer's disease, may be amenable to treatment using leptin to limit death of susceptible cells. Leptin-mediated pro-survival signaling is now known to prevent the death of neurons in these models. The signaling cascades that leptin generates are shared by other neuroprotective molecules including insulin and erythropoietin, and are thus a component of the neurotrophic effects mediated by endogenous hormones. Coupled with evidence that leptin dysregulation in human disease also results in enhanced neuronal susceptibility to damage, development of leptin as a therapeutic methodology is an attractive and viable possibility.
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Affiliation(s)
- Armando P. Signore
- Department of Neurology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania 15261
| | - Feng Zhang
- Department of Neurology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania 15261
| | - Zhongfang Weng
- Department of Neurology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania 15261
| | - YanQing Gao
- State Key Laboratory of Medical Neurobiology, Fudan University School of Medicine, Shanghai, China 200032
| | - Jun Chen
- Department of Neurology, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania 15261
- State Key Laboratory of Medical Neurobiology, Fudan University School of Medicine, Shanghai, China 200032
- Geriatric Research, Educational and Clinical Center Veterans Affairs Pittsburgh Health Care System, Pittsburgh, Pennsylvania 15261
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Paz-Filho GJ, Babikian T, Asarnow R, Esposito K, Erol HK, Wong ML, Licinio J. Leptin replacement improves cognitive development. PLoS One 2008; 3:e3098. [PMID: 18769731 PMCID: PMC2518120 DOI: 10.1371/journal.pone.0003098] [Citation(s) in RCA: 101] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2008] [Accepted: 08/05/2008] [Indexed: 01/18/2023] Open
Abstract
Background Leptin changes brain structure, neuron excitability and synaptic plasticity. It also regulates the development and function of feeding circuits. However, the effects of leptin on neurocognitive development are unknown. Objective To evaluate the effect of leptin on neurocognitive development. Methodology A 5-year-old boy with a nonconservative missense leptin gene mutation (Cys-to-Thr in codon 105) was treated with recombinant methionyl human leptin (r-metHuLeptin) at physiologic replacement doses of 0.03 mg/kg/day. Cognitive development was assessed using the Differential Ability Scales (DAS), a measure of general verbal and nonverbal functioning; and selected subtests from the NEPSY, a measure of neuropsychological functioning in children. Principal Findings Prior to treatment, the patient was morbidly obese, hypertensive, dyslipidemic, and hyperinsulinemic. Baseline neurocognitive tests revealed slower than expected rates of development (developmental age lower than chronological age) in a majority of the areas assessed. After two years, substantial increases in the rates of development in most neurocognitive domains were apparent, with some skills at or exceeding expectations based on chronological age. We also observed marked weight loss and resolution of hypertension, dyslipidemia and hyperinsulinemia. Conclusions We concluded that replacement with r-metHuLeptin is associated with weight loss and changes in rates of development in many neurocognitive domains, which lends support to the hypothesis that, in addition to its role in metabolism, leptin may have a cognitive enhancing role in the developing central nervous system. Trial Registration ClinicalTrials.gov NCT00659828
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Affiliation(s)
- Gilberto J. Paz-Filho
- Department of Psychiatry and Behavioral Sciences, Center for Pharmacogenomics, University of Miami Miller School of Medicine, Miami, Florida, United States of America
- SEMPR – Serviço de Endocrinologia e Metabologia da UFPR, Curitiba, Parana, Brazil
| | - Talin Babikian
- Department of Psychiatry and Biobehavioral Sciences, David Geffen School of Medicine at University of California Los Angeles, Los Angeles, California, United States of America
| | - Robert Asarnow
- Department of Psychiatry and Biobehavioral Sciences, David Geffen School of Medicine at University of California Los Angeles, Los Angeles, California, United States of America
| | - Karin Esposito
- Department of Psychiatry and Behavioral Sciences, Center for Pharmacogenomics, University of Miami Miller School of Medicine, Miami, Florida, United States of America
| | - Halil K. Erol
- Department of Psychiatry and Behavioral Sciences, Center for Pharmacogenomics, University of Miami Miller School of Medicine, Miami, Florida, United States of America
| | - Ma-Li Wong
- Department of Psychiatry and Behavioral Sciences, Center for Pharmacogenomics, University of Miami Miller School of Medicine, Miami, Florida, United States of America
| | - Julio Licinio
- Department of Psychiatry and Behavioral Sciences, Center for Pharmacogenomics, University of Miami Miller School of Medicine, Miami, Florida, United States of America
- * E-mail:
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Doherty GH, Oldreive C, Harvey J. Neuroprotective actions of leptin on central and peripheral neurons in vitro. Neuroscience 2008; 154:1297-307. [PMID: 18550292 DOI: 10.1016/j.neuroscience.2008.04.052] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2008] [Revised: 04/23/2008] [Accepted: 04/25/2008] [Indexed: 11/16/2022]
Abstract
Neuronal cell death and its regulation have been extensively studied as an essential process of both neurodevelopment and neurodegenerative conditions. However it is not clear how circulating hormones influence such processes. Therefore we aimed to determine whether the anti-obesity hormone leptin could promote the survival of murine central and peripheral neurons in vitro. Thus we established primary neuronal cultures of dopaminergic midbrain neurons and trigeminal sensory neurons and induced cell death via either toxic insult or growth factor withdrawal. We demonstrate that leptin promotes the survival of developing peripheral and central neurons via activation of mitogen-activated protein kinase (MAPK) and phosphoinositide 3-kinase (PI3-kinase)/Akt/nuclear factor kappa B (NF-kappaB) -dependent signaling cascades. Specifically, leptin protects dopaminergic midbrain neurons from the apoptotic stimuli, tumor necrosis factor alpha (TNF-alpha) and 6-hydroxydopamine (6-OHDA). In addition, it promotes the survival of postnatal, but not embryonic, trigeminal sensory neurons following neurotrophin withdrawal. Our data reveal a novel neuroprotective role for leptin in the peripheral nervous system while expanding on the known anti-apoptotic role of leptin in the CNS. These findings have important implications for our understanding of neuronal viability.
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Affiliation(s)
- G H Doherty
- School of Biology, University of St Andrews, West Burn Lane, St Andrews, Fife, UK.
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69
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Xu L, Rensing N, Yang XF, Zhang HX, Thio LL, Rothman SM, Weisenfeld AE, Wong M, Yamada KA. Leptin inhibits 4-aminopyridine- and pentylenetetrazole-induced seizures and AMPAR-mediated synaptic transmission in rodents. J Clin Invest 2008; 118:272-80. [PMID: 18097472 DOI: 10.1172/jci33009] [Citation(s) in RCA: 90] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2007] [Accepted: 10/24/2007] [Indexed: 12/23/2022] Open
Abstract
Leptin is a hormone that reduces excitability in some hypothalamic neurons via leptin receptor activation of the JAK2 and PI3K intracellular signaling pathways. We hypothesized that leptin receptor activation in other neuronal subtypes would have anticonvulsant activity and that intranasal leptin delivery would be an effective route of administration. We tested leptin's anticonvulsant action in 2 rodent seizure models by directly injecting it into the cortex or by administering it intranasally. Focal seizures in rats were induced by neocortical injections of 4-aminopyridine, an inhibitor of voltage-gated K+ channels. These seizures were briefer and less frequent upon coinjection of 4-aminopyridine and leptin. In mice, intranasal administration of leptin produced elevated brain and serum leptin levels and delayed the onset of chemical convulsant pentylenetetrazole-induced generalized convulsive seizures. Leptin also reduced neuronal spiking in an in vitro seizure model. Leptin inhibited alpha-amino-3-hydroxy-5-methyl-4-isoxazole proprionic acid (AMPA) receptor-mediated synaptic transmission in mouse hippocampal slices but failed to inhibit synaptic responses in slices from leptin receptor-deficient db/db mice. JAK2 and PI3K antagonists prevented leptin inhibition of AMPAergic synaptic transmission. We conclude that leptin receptor activation and JAK2/PI3K signaling may be novel targets for anticonvulsant treatments. Intranasal leptin administration may have potential as an acute abortive treatment for convulsive seizures in emergency situations.
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Affiliation(s)
- Lin Xu
- Department of Neurology and Hope Center for Neurological Disorders, Washington University School of Medicine, St. Louis, Missouri 63110, USA
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70
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Erbayat-Altay E, Yamada KA, Wong M, Thio LL. Increased severity of pentylenetetrazol induced seizures in leptin deficient ob/ob mice. Neurosci Lett 2007; 433:82-6. [PMID: 18241989 DOI: 10.1016/j.neulet.2007.12.051] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2007] [Revised: 12/12/2007] [Accepted: 12/21/2007] [Indexed: 11/25/2022]
Abstract
Leptin modulates multiple ion channels making its net effect on brain excitability difficult to predict. One method of determining leptin's net effect on brain excitability is to examine brain excitability during chronic leptin deficiency. We compared the susceptibility of leptin deficient ob/ob and wild type mice to pentylenetetrazol (PTZ) induced seizures using continuous video electroencephalogram (EEG) recordings. We found that ob/ob mice were more likely to die and were more susceptible to generalized clonic and clonic-tonic seizures than wild type mice at submaximal PTZ doses. These findings suggest that chronic leptin deficiency in vivo increases seizure susceptibility.
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Affiliation(s)
- Ebru Erbayat-Altay
- Department of Neurology, Washington University School of Medicine, St. Louis, MO 63110, United States
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71
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Harvey J. Leptin regulation of neuronal excitability and cognitive function. Curr Opin Pharmacol 2007; 7:643-7. [PMID: 18024215 PMCID: PMC2635528 DOI: 10.1016/j.coph.2007.10.006] [Citation(s) in RCA: 116] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2007] [Accepted: 10/13/2007] [Indexed: 12/31/2022]
Abstract
Leptin, a hormone produced by adipocytes, provides signals to specific regions of the hypothalamus to control energy homeostasis. However, the past decade of research has not only revealed that leptin receptors are widely expressed in the CNS, but has also identified numerous additional functions for this hormone in the brain. In particular, there is evidence that leptin influences neuronal excitability via the activation as well as trafficking of specific potassium channels in several brain regions. Leptin-induced alterations in neuronal excitability have been implicated in the regulation of food intake, reward behaviour and anti-convulsant effects. A number of studies have also identified a role for leptin in cognitive processes that involve activation of leptin receptors in limbic structures, such as the hippocampus. Indeed, leptin influences hippocampal-dependent learning and memory, and more recently leptin has been shown to have anti-depressant properties. Characterisation of these novel actions of leptin is providing valuable insights into the role of this hormone in the regulation of diverse neuronal functions in health and disease.
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Affiliation(s)
- Jenni Harvey
- Neurosciences Institute, Ninewells Hospital and Medical School, University of Dundee, Dundee, United Kingdom.
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72
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Guo Z, Jiang H, Xu X, Duan W, Mattson MP. Leptin-mediated cell survival signaling in hippocampal neurons mediated by JAK STAT3 and mitochondrial stabilization. J Biol Chem 2007; 283:1754-1763. [PMID: 17993459 DOI: 10.1074/jbc.m703753200] [Citation(s) in RCA: 153] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Leptin plays a pivotal role in the regulation of energy homeostasis and metabolism, primarily by acting on neurons in the hypothalamus that control food intake. However, leptin receptors are more widely expressed in the brain suggesting additional, as yet unknown, functions of leptin. Here we show that both embryonic and adult hippocampal neurons express leptin receptors coupled to activation of STAT3 and phosphatidylinositol 3-kinase-Akt signaling pathways. Leptin protects hippocampal neurons against cell death induced by neurotrophic factor withdrawal and excitotoxic and oxidative insults. The neuroprotective effect of leptin is antagonized by the JAK2-STAT3 inhibitor AG-490, STAT3 decoy DNA, and phosphatidylinositol 3-kinase/Akt inhibitors but not by an inhibitor of MAPK. Leptin induces the production of manganese superoxide dismutase and the anti-apoptotic protein Bcl-xL, and stabilizes mitochondrial membrane potential and lessens mitochondrial oxidative stress. Leptin receptor-deficient mice (db/db mice) are more vulnerable to seizure-induced hippocampal damage, and intraventricular administration of leptin protects neurons against seizures. By enhancing mitochondrial resistance to apoptosis and excitotoxicity, our findings suggest that leptin signaling serves a neurotrophic function in the developing and adult hippocampus.
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Affiliation(s)
- Zhihong Guo
- Laboratory of Neurosciences and National Institute on Aging Intramural Research Program, Baltimore, Maryland 21224
| | - Haiyang Jiang
- Laboratory of Neurosciences and National Institute on Aging Intramural Research Program, Baltimore, Maryland 21224
| | - Xiangru Xu
- Laboratory of Neurosciences and National Institute on Aging Intramural Research Program, Baltimore, Maryland 21224
| | - Wenzhen Duan
- Laboratory of Neurosciences and National Institute on Aging Intramural Research Program, Baltimore, Maryland 21224
| | - Mark P Mattson
- Laboratory of Neurosciences and National Institute on Aging Intramural Research Program, Baltimore, Maryland 21224; Department of Neuroscience, The Johns Hopkins University School of Medicine, Baltimore, Maryland 21205.
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73
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Huang JS, Letendre S, Marquie-Beck J, Cherner M, McCutchan JA, Grant I, Ellis R. Low CSF leptin levels are associated with worse learning and memory performance in HIV-infected men. J Neuroimmune Pharmacol 2007; 2:352-8. [PMID: 18040853 DOI: 10.1007/s11481-007-9093-z] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2007] [Accepted: 09/13/2007] [Indexed: 10/22/2022]
Abstract
OBJECTIVE The main objective of this study was to investigate the association between human CSF leptin levels and neuropsychological (NP) performance in the setting of HIV infection. We hypothesized that human CSF leptin levels positively correlate with NP performance. BACKGROUND Leptin is an adipocyte-derived hormone that influences brain development and function, particularly learning and memory, in the mouse model. The extent to which leptin contributes to neurocognitive functioning in humans is less clear. METHOD A cross-sectional evaluation of CSF leptin and NP performance was performed. Leptin levels in CSF and serum samples from 59 HIV-positive men were measured by ELISA. Comprehensive, standardized NP testing was used to determine impairment status in global and specific domains. RESULTS Lower CSF leptin levels and reduced leptin uptake into the central nervous system (CNS) correlated with impaired learning and memory performance in both univariate and multivariate analyses. In multivariate analyses, lower CSF leptin levels and reduced CNS leptin uptake were associated with worse NP performance in learning and memory, adjusting for CD4 nadir, antiretroviral treatment exposure, and HIV RNA levels in CSF. CONCLUSIONS Low CSF leptin levels are associated with poorer performance in learning and memory among HIV-infected men adjusting for usual predictors of HIV-associated neurocognitive impairment. This association is consistent with prior in vitro and animal data suggesting leptin has a trophic or facilitatory role in the hippocampus, above and beyond its role in hypothalamic regulation.
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Affiliation(s)
- J S Huang
- Department of Pediatrics, University of California, San Diego, USA.
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74
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Liu X, Stancliffe D, Lee S, Mathur S, Gershenfeld HK. Genetic dissection of the tail suspension test: a mouse model of stress vulnerability and antidepressant response. Biol Psychiatry 2007; 62:81-91. [PMID: 17125744 DOI: 10.1016/j.biopsych.2006.08.017] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/14/2006] [Revised: 08/17/2006] [Accepted: 08/19/2006] [Indexed: 12/20/2022]
Abstract
BACKGROUND The tail suspension test (TST) is a mouse screening test for antidepressants. METHODS An F2 intercross was derived from NMRI and 129S6 inbred strains (n = 747). Mice underwent standardized TST with 2 sessions: (1) baseline and (2) imipramine (30 mg/kg, intraperitoneally) TST. RESULTS A whole genome scan of this intercross mapped significant basal TST quantitative trait loci (QTL) on chromosomes (chr) 5 (peak 61 cM, Lod 5.7), 12 (peak 43 cM, Lod 5.2), and 18 (peak 51 cM, Lod 3.0). A suggestive QTL on chr 4 (peak 62 cM; Lod 3.1) overlapped regions containing previously mapped QTLs. For TST imipramine response, QTL were mapped on chr 1, 4, and 5. The chromosome 5 locus affected basal TST, antidepressant immobility response, and tail suspension-induced hyperthermia (TSIH) behaviors. An outbred NMRI F2 population provided further evidence for a chr 5 QTL. This chr 5 region harbors a cluster of gamma aminobutyric acid (GABA)-A receptor subunits and the human syntenic region includes chr 4p, 1p11, 12q24, and 22q11.24. A significant TSIH QTL (Tsih1) mapped on chr 4 near the Leptin receptor (Lepr). CONCLUSIONS These QTL provide potential regions of interest for human genetic studies in stress-diathesis models of psychiatric illness and antidepressant responsiveness.
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MESH Headings
- Animals
- Antidepressive Agents/pharmacology
- Antidepressive Agents/therapeutic use
- Behavior, Animal/drug effects
- Behavior, Animal/physiology
- Chromosome Mapping
- Chromosomes, Mammalian/genetics
- Crosses, Genetic
- Disease Models, Animal
- Fever/genetics
- Genetic Predisposition to Disease/genetics
- Hindlimb Suspension/physiology
- Imipramine/pharmacology
- Imipramine/therapeutic use
- Immobilization/physiology
- Immobilization/psychology
- Immunohistochemistry
- Injections, Intraperitoneal
- Lod Score
- Mice
- Mice, Inbred Strains
- Quantitative Trait Loci/genetics
- Receptors, Cell Surface/genetics
- Receptors, GABA-A/drug effects
- Receptors, GABA-A/genetics
- Receptors, Leptin
- Stress, Psychological/drug therapy
- Stress, Psychological/etiology
- Stress, Psychological/genetics
- Terminology as Topic
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Affiliation(s)
- Xiaoqing Liu
- Department of Psychiatry, University of Texas Health Science Center at Houston, Houston, Texas, USA
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75
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Pinteaux E, Inoue W, Schmidt L, Molina-Holgado F, Rothwell NJ, Luheshi GN. Leptin induces interleukin-1beta release from rat microglial cells through a caspase 1 independent mechanism. J Neurochem 2007; 102:826-33. [PMID: 17419800 DOI: 10.1111/j.1471-4159.2007.04559.x] [Citation(s) in RCA: 70] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Leptin regulates energy balance by suppressing appetite and increasing energy expenditure through actions in the hypothalamus. Recently we demonstrated that the effects of leptin are, at least in part, mediated by the release of interleukin (IL)-1beta in the brain. Microglia constitute the major source of IL-1beta in the brain but it is not known whether these cells express leptin receptors, or respond to leptin to produce IL-1beta. Using RT-PCR and immunocytochemistry, we demonstrate that primary rat microglial cells express the short (non-signalling) and long (signalling) isoforms of the leptin receptors (Ob-R)s. Immunoassays performed on cell medium collected 24 h after leptin treatment (0.01-10 microg/mL) demonstrated a dose-dependent production and release of IL-1beta and its endogenously occurring receptor antagonist IL-1RA. In addition leptin-induced IL-1beta release occurs via a signal transducer and activator of transcription 3 (STAT3)-dependent mechanism. Western blot analysis demonstrated that leptin induced the synthesis of pro-IL-1beta in microglial cells and the release of mature 17 kDa isoform into the culture medium. Leptin-induced IL-1beta release was neither inhibited by the pan-caspase inhibitor BOC-D-FMK, nor by the caspase 1 inhibitor Ac-YVAD-CHO indicating that IL-1 cleavage is independent of caspase activity. These results confirm our earlier observations in vivo and demonstrate that microglia are an important source of IL-1beta in the brain in response to leptin.
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Affiliation(s)
- Emmanuel Pinteaux
- Faculty of Life Sciences, Michael Smith Building, University of Manchester, Oxford Road, Manchester, UK
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76
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Abstract
It is well documented that leptin is a circulating hormone that plays a key role in regulating food intake and body weight via its actions on specific hypothalamic nuclei. However, leptin receptors are widely expressed in the CNS, in regions not generally associated with energy homeostasis, such as the hippocampus, cortex and cerebellum. Moreover, evidence is accumulating that leptin has widespread actions in the brain. In particular, recent studies have demonstrated that leptin markedly influences the excitability of hippocampal neurons via its ability to activate large conductance Ca(2+)-activated K(+) (BK) channels, and also to promote long-term depression of excitatory synaptic transmission. Here, we review the evidence supporting a role for this hormone in regulating hippocampal excitability.
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Affiliation(s)
- Jenni Harvey
- Neurosciences Institute, Ninewells Hospital and Medical School, University of Dundee, Dundee, UK.
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77
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Oomura Y, Hori N, Shiraishi T, Fukunaga K, Takeda H, Tsuji M, Matsumiya T, Ishibashi M, Aou S, Li XL, Kohno D, Uramura K, Sougawa H, Yada T, Wayner MJ, Sasaki K. Leptin facilitates learning and memory performance and enhances hippocampal CA1 long-term potentiation and CaMK II phosphorylation in rats. Peptides 2006; 27:2738-49. [PMID: 16914228 DOI: 10.1016/j.peptides.2006.07.001] [Citation(s) in RCA: 202] [Impact Index Per Article: 11.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/05/2006] [Revised: 07/02/2006] [Accepted: 07/06/2006] [Indexed: 11/22/2022]
Abstract
Leptin, an adipocytokine encoded by an obesity gene and expressed in adipose tissue, affects feeding behavior, thermogenesis, and neuroendocrine status via leptin receptors distributed in the brain, especially in the hypothalamus. Leptin may also modulate the synaptic plasticity and behavioral performance related to learning and memory since: leptin receptors are found in the hippocampus, and both leptin and its receptor share structural and functional similarities with the interleukin-6 family of cytokines that modulate long-term potentiation (LTP) in the hippocampus. We therefore examined the effect of leptin on (1) behavioral performance in emotional and spatial learning tasks, (2) LTP at Schaffer collateral-CA1 synapses, (3) presynaptic and postsynaptic activities in hippocampal CA1 neurons, (4) the intracellular Ca(2+) concentration ([Ca(2+)](i)) in CA1 neurons, and (5) the activity of Ca(2+)/calmodulin protein kinase II (CaMK II) in the hippocampal CA1 tissue that exhibits LTP. Intravenous injection of 5 and/or 50mug/kg, but not of 500mug/kg leptin, facilitated behavioral performance in passive avoidance and Morris water-maze tasks. Bath application of 10(-12)M leptin in slice experiments enhanced LTP and increased the presynaptic transmitter release, whereas 10(-10)M leptin suppressed LTP and reduced the postsynaptic receptor sensitivity to N-methyl-d-aspartic acid. The increase in the [Ca(2+)](i) induced by 10(-10)M leptin was two times greater than that induced by 10(-12)M leptin. In addition, the facilitation (10(-12)M) and suppression (10(-10)M) of LTP by leptin was closely associated with an increase and decrease in Ca(2+)-independent activity of CaMK II. Our results show that leptin not only affects hypothalamic functions (such as feeding, thermogenesis, and neuroendocrine status), but also modulates higher nervous functions, such as the behavioral performance related to learning and memory and hippocampal synaptic plasticity.
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Affiliation(s)
- Y Oomura
- Department of Physiology, Faculty of Medicine, Kyushu University at Fukuoka, Fukuoka 812-0054, Japan
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78
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Harvey J, Solovyova N, Irving A. Leptin and its role in hippocampal synaptic plasticity. Prog Lipid Res 2006; 45:369-78. [PMID: 16678906 PMCID: PMC1762032 DOI: 10.1016/j.plipres.2006.03.001] [Citation(s) in RCA: 151] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2006] [Revised: 03/21/2006] [Accepted: 03/21/2006] [Indexed: 12/24/2022]
Abstract
It is well documented that the hormone leptin plays a pivotal role in regulating food intake and body weight via its hypothalamic actions. However, leptin receptors are expressed throughout the brain with high levels found in the hippocampus. Evidence is accumulating that leptin has widespread actions on CNS function and in particular learning and memory. Recent studies have demonstrated that leptin-deficient or-insensitive rodents have impairments in hippocampal synaptic plasticity and in spatial memory tasks performed in the Morris water maze. Moreover, direct administration of leptin into the brain facilitates hippocampal long-term potentiation (LTP), and improves memory performance in mice. There is also evidence that, at the cellular level, leptin has the capacity to convert hippocampal short-term potentiation (STP) into LTP, via enhancing NMDA receptor function. Recent data indicates that leptin can also induce a novel form of NMDA receptor-dependent hippocampal long-term depression. Here, we review the evidence implicating a key role for the hormone leptin in modulating hippocampal synaptic plasticity and discuss the role of lipid signaling cascades in this process.
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Affiliation(s)
- Jenni Harvey
- Neurosciences Institute, Ninewells Hospital and Medical School, University of Dundee, Dundee DD1 9SY, Scotland, United Kingdom.
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