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Johnson CS, Mermelstein PG. The interaction of membrane estradiol receptors and metabotropic glutamate receptors in adaptive and maladaptive estradiol-mediated motivated behaviors in females. INTERNATIONAL REVIEW OF NEUROBIOLOGY 2023; 168:33-91. [PMID: 36868633 DOI: 10.1016/bs.irn.2022.11.001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
Estrogen receptors were initially identified as intracellular, ligand-regulated transcription factors that result in genomic change upon ligand binding. However, rapid estrogen receptor signaling initiated outside of the nucleus was also known to occur via mechanisms that were less clear. Recent studies indicate that these traditional receptors, estrogen receptor α and estrogen receptor β, can also be trafficked to act at the surface membrane. Signaling cascades from these membrane-bound estrogen receptors (mERs) can rapidly alter cellular excitability and gene expression, particularly through the phosphorylation of CREB. A principal mechanism of neuronal mER action has been shown to occur through glutamate-independent transactivation of metabotropic glutamate receptors (mGlu), which elicits multiple signaling outcomes. The interaction of mERs with mGlu has been shown to be important in many diverse functions in females, including driving motivated behaviors. Experimental evidence suggests that a large part of estradiol-induced neuroplasticity and motivated behaviors, both adaptive and maladaptive, occurs through estradiol-dependent mER activation of mGlu. Herein we will review signaling through estrogen receptors, both "classical" nuclear receptors and membrane-bound receptors, as well as estradiol signaling through mGlu. We will focus on how the interactions of these receptors and their downstream signaling cascades are involved in driving motivated behaviors in females, discussing a representative adaptive motivated behavior (reproduction) and maladaptive motivated behavior (addiction).
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Affiliation(s)
- Caroline S Johnson
- Department of Neuroscience, University of Minnesota, Minneapolis, MN, United States
| | - Paul G Mermelstein
- Department of Neuroscience, University of Minnesota, Minneapolis, MN, United States.
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2
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Johnson CS, Micevych PE, Mermelstein PG. Membrane estrogen signaling in female reproduction and motivation. Front Endocrinol (Lausanne) 2022; 13:1009379. [PMID: 36246891 PMCID: PMC9557733 DOI: 10.3389/fendo.2022.1009379] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/01/2022] [Accepted: 09/13/2022] [Indexed: 01/13/2023] Open
Abstract
Estrogen receptors were initially identified in the uterus, and later throughout the brain and body as intracellular, ligand-regulated transcription factors that affect genomic change upon ligand binding. However, rapid estrogen receptor signaling initiated outside of the nucleus was also known to occur via mechanisms that were less clear. Recent studies indicate that these traditional receptors, estrogen receptor-α and estrogen receptor-β, can also be trafficked to act at the surface membrane. Signaling cascades from these membrane-bound estrogen receptors (mERs) not only rapidly effect cellular excitability, but can and do ultimately affect gene expression, as seen through the phosphorylation of CREB. A principal mechanism of neuronal mER action is through glutamate-independent transactivation of metabotropic glutamate receptors (mGluRs), which elicits multiple signaling outcomes. The interaction of mERs with mGluRs has been shown to be important in many diverse functions in females, including, but not limited to, reproduction and motivation. Here we review membrane-initiated estrogen receptor signaling in females, with a focus on the interactions between these mERs and mGluRs.
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Affiliation(s)
- Caroline S. Johnson
- Department of Neuroscience, University of Minnesota, Minneapolis, MN, United States
- *Correspondence: Caroline S. Johnson,
| | - Paul E Micevych
- Laboratory of Neuroendocrinology, Department of Neurobiology, David Geffen School of Medicine at University of California, Los Angeles, Los Angeles, CA, United States
| | - Paul G. Mermelstein
- Department of Neuroscience, University of Minnesota, Minneapolis, MN, United States
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3
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Lakhssassi K, Lahoz B, Sarto P, Iguácel LP, Folch J, Alabart JL, Serrano M, Calvo JH. Genome-Wide Association Study Demonstrates the Role Played by the CD226 Gene in Rasa Aragonesa Sheep Reproductive Seasonality. Animals (Basel) 2021; 11:ani11041171. [PMID: 33921837 PMCID: PMC8074133 DOI: 10.3390/ani11041171] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2021] [Revised: 04/14/2021] [Accepted: 04/15/2021] [Indexed: 01/02/2023] Open
Abstract
Simple Summary To elucidate the genetic basis of reproductive seasonality in Rasa Aragonesa sheep breed, we performed a genome-wide association study (GWAS) in order to detect single nucleotide polymorphisms (SNPs) or regions associated with traits related to ovarian function and behavioural signs of estrous. The GWAS included 205 ewes with genotypes for 583882 SNPs. Only one SNP overcame the genome-wide significance level. Nine potential SNPs overcame the chromosome-wise significance level (FDR 10%). Gene annotation demonstrated that CD226molecule (CD226) and neuropeptide Y (NPY) genes that could be involved in reproductive seasonality were close to the significant SNPs. To validate the results, we sequenced the entire coding region of the NPY gene and four exons of the CD226 gene to search for polymorphisms that could be involved in the phenotypes studied. Two synonymous and two nonsynonymous SNPs in the NPY and CD226 genes, respectively, were genotyped in the whole population. We demonstrated that the AA genotype of the SNP rs404360094 located in exon 3 of the CD226 gene was associated with higher and lower total days of anoestrus and oestrous cycling months, respectively. Therefore, this SNP could be utilized as a genetic marker for assisted selection marker to reduce seasonality. Abstract A genome-wide association study (GWAS) was used to identify genomic regions influencing seasonality reproduction traits in Rasa Aragonesa sheep. Three traits associated with either ovarian function based on blood progesterone levels (total days of anoestrus and progesterone cycling months) or behavioral signs of oestrous (oestrous cycling months) were studied. The GWAS included 205 ewes genotyped using the 50k and 680k Illumina Ovine Beadchips. Only one SNP associated with the progesterone cycling months overcame the genome-wide significance level (rs404991855). Nine SNPs exhibited significant associations at the chromosome level, being the SNPs rs404991855 and rs418191944, that are located in the CD226 molecule (CD226) gene, associated with the three traits. This gene is related to reproductive diseases. Two other SNPs were located close to the neuropeptide Y (NPY) gene, which is involved in circadian rhythms. To validate the GWAS, partial characterization of both genes by Sanger sequencing, and genotyping of two synonymous and two nonsynonymous SNPs in the NPY and CD226 genes, respectively, were performed. SNP association analysis showed that only SNP rs404360094 in the exon 3 of the CD226 gene, which produces an amino acid substitution from asparagine (uncharged polar) to aspartic acid (acidic), was associated with the three seasonality traits. Our results suggest that the CD226 gene may be involved in the reproductive seasonality in Rasa Aragonesa.
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Affiliation(s)
- Kenza Lakhssassi
- Centro de Investigación y Tecnología Agroalimentaria de Aragón, Instituto Agroalimentario de Aragón (IA2) (CITA–Zaragoza University), 50059 Zaragoza, Spain; (K.L.); (B.L.); (P.S.); (L.P.I.); (J.F.); (J.L.A.)
- INRA, Instituts Morocco, 6356 Rabat, Morocco
| | - Belén Lahoz
- Centro de Investigación y Tecnología Agroalimentaria de Aragón, Instituto Agroalimentario de Aragón (IA2) (CITA–Zaragoza University), 50059 Zaragoza, Spain; (K.L.); (B.L.); (P.S.); (L.P.I.); (J.F.); (J.L.A.)
| | - Pilar Sarto
- Centro de Investigación y Tecnología Agroalimentaria de Aragón, Instituto Agroalimentario de Aragón (IA2) (CITA–Zaragoza University), 50059 Zaragoza, Spain; (K.L.); (B.L.); (P.S.); (L.P.I.); (J.F.); (J.L.A.)
| | - Laura Pilar Iguácel
- Centro de Investigación y Tecnología Agroalimentaria de Aragón, Instituto Agroalimentario de Aragón (IA2) (CITA–Zaragoza University), 50059 Zaragoza, Spain; (K.L.); (B.L.); (P.S.); (L.P.I.); (J.F.); (J.L.A.)
| | - José Folch
- Centro de Investigación y Tecnología Agroalimentaria de Aragón, Instituto Agroalimentario de Aragón (IA2) (CITA–Zaragoza University), 50059 Zaragoza, Spain; (K.L.); (B.L.); (P.S.); (L.P.I.); (J.F.); (J.L.A.)
| | - José Luis Alabart
- Centro de Investigación y Tecnología Agroalimentaria de Aragón, Instituto Agroalimentario de Aragón (IA2) (CITA–Zaragoza University), 50059 Zaragoza, Spain; (K.L.); (B.L.); (P.S.); (L.P.I.); (J.F.); (J.L.A.)
| | - Malena Serrano
- Departamento de Mejora Genética Animal INIA, 28040 Madrid, Spain;
| | - Jorge Hugo Calvo
- Centro de Investigación y Tecnología Agroalimentaria de Aragón, Instituto Agroalimentario de Aragón (IA2) (CITA–Zaragoza University), 50059 Zaragoza, Spain; (K.L.); (B.L.); (P.S.); (L.P.I.); (J.F.); (J.L.A.)
- The Aragonese Foundation for Research and Development (ARAID), 50018 Zaragoza, Spain
- Correspondence: ; Tel.: +34976716471
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Mann SN, Hadad N, Nelson Holte M, Rothman AR, Sathiaseelan R, Ali Mondal S, Agbaga MP, Unnikrishnan A, Subramaniam M, Hawse J, Huffman DM, Freeman WM, Stout MB. Health benefits attributed to 17α-estradiol, a lifespan-extending compound, are mediated through estrogen receptor α. eLife 2020; 9:59616. [PMID: 33289482 PMCID: PMC7744101 DOI: 10.7554/elife.59616] [Citation(s) in RCA: 26] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2020] [Accepted: 12/07/2020] [Indexed: 02/06/2023] Open
Abstract
Metabolic dysfunction underlies several chronic diseases, many of which are exacerbated by obesity. Dietary interventions can reverse metabolic declines and slow aging, although compliance issues remain paramount. 17α-estradiol treatment improves metabolic parameters and slows aging in male mice. The mechanisms by which 17α-estradiol elicits these benefits remain unresolved. Herein, we show that 17α-estradiol elicits similar genomic binding and transcriptional activation through estrogen receptor α (ERα) to that of 17β-estradiol. In addition, we show that the ablation of ERα completely attenuates the beneficial metabolic effects of 17α-E2 in male mice. Our findings suggest that 17α-E2 may act through the liver and hypothalamus to improve metabolic parameters in male mice. Lastly, we also determined that 17α-E2 improves metabolic parameters in male rats, thereby proving that the beneficial effects of 17α-E2 are not limited to mice. Collectively, these studies suggest ERα may be a drug target for mitigating chronic diseases in male mammals.
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Affiliation(s)
- Shivani N Mann
- Department of Nutritional Sciences, University of Oklahoma Health Sciences Center, Oklahoma City, United States.,Oklahoma Center for Geroscience, University of Oklahoma Health Sciences Center, Oklahoma City, United States.,Harold Hamm Diabetes Center, University of Oklahoma Health Sciences Center, Oklahoma City, United States
| | - Niran Hadad
- The Jackson Laboratory, Bar Harbor, United States
| | - Molly Nelson Holte
- Department of Biochemistry and Molecular Biology, Mayo Clinic, Rochester, United States
| | - Alicia R Rothman
- Department of Nutritional Sciences, University of Oklahoma Health Sciences Center, Oklahoma City, United States
| | - Roshini Sathiaseelan
- Department of Nutritional Sciences, University of Oklahoma Health Sciences Center, Oklahoma City, United States
| | - Samim Ali Mondal
- Department of Nutritional Sciences, University of Oklahoma Health Sciences Center, Oklahoma City, United States
| | - Martin-Paul Agbaga
- Harold Hamm Diabetes Center, University of Oklahoma Health Sciences Center, Oklahoma City, United States.,Department of Cell Biology, University of Oklahoma Health Sciences Center, Oklahoma City, United States.,Dean McGee Eye Institute, University of Oklahoma Health Sciences Center, Oklahoma City, United States
| | - Archana Unnikrishnan
- Harold Hamm Diabetes Center, University of Oklahoma Health Sciences Center, Oklahoma City, United States.,Department of Biochemistry and Molecular Biology, University of Oklahoma Health Sciences Center, Oklahoma City, United States
| | | | - John Hawse
- Department of Biochemistry and Molecular Biology, Mayo Clinic, Rochester, United States
| | - Derek M Huffman
- Department of Molecular Pharmacology, Albert Einstein College of Medicine, New York, United States
| | - Willard M Freeman
- Oklahoma Center for Geroscience, University of Oklahoma Health Sciences Center, Oklahoma City, United States.,Genes & Human Disease Research Program, Oklahoma Medical Research Foundation, Oklahoma City, United States.,Oklahoma City Veterans Affairs Medical Center, Oklahoma City, United States
| | - Michael B Stout
- Department of Nutritional Sciences, University of Oklahoma Health Sciences Center, Oklahoma City, United States.,Oklahoma Center for Geroscience, University of Oklahoma Health Sciences Center, Oklahoma City, United States.,Harold Hamm Diabetes Center, University of Oklahoma Health Sciences Center, Oklahoma City, United States
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5
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Tural U, Iosifescu DV. Neuropeptide Y in PTSD, MDD, and chronic stress: A systematic review and meta-analysis. J Neurosci Res 2020; 98:950-963. [PMID: 32048334 DOI: 10.1002/jnr.24589] [Citation(s) in RCA: 22] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2019] [Revised: 01/14/2020] [Accepted: 01/22/2020] [Indexed: 01/23/2023]
Abstract
Previous studies have suggested that neuropeptide Y (NPY) levels may be altered in patients with major depressive disorder (MDD), post-traumatic stress disorder (PTSD) and chronic stress. We investigated, through systematic review and meta-analysis, whether the mean levels of NPY are significantly different in patients with MDD, PTSD or chronic stress, compared to controls. The main outcome was the pooled standardized mean difference (SMD) with 95% confidence intervals between cases and controls, using the random-effects model. Heterogeneity and publication bias were evaluated. Thirty-five studies met eligibility criteria. Meta-regression determined that medication and sex could explain 27% of the between-study variance. Females and participants currently prescribed psychotropic medications had significantly higher levels of NPY. NPY levels were significantly lower in plasma and cerebrospinal fluid (CSF) in PTSD patients versus controls. Patients with MDD had significantly lower levels of NPY in plasma compared to controls, but not in the CSF. The magnitudes of the decrease in plasma NPY levels were not significantly different between PTSD and MDD. However, chronic stress patients had significantly higher plasma NPY levels compared to controls, PTSD or MDD. Our findings may imply a shared role of NPY in trauma and depression: nevertheless, it is not clear that the association is specific to these disorders. Psychotropic medications may help restore NPY levels. Further controlled studies are needed to better delineate the contribution of confounding variables such as type of depression, body mass index, appetite or sleep architecture.
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Affiliation(s)
- Umit Tural
- Clinical Research Division, The Nathan S. Kline Institute for Psychiatric Research, Orangeburg, NY, USA
| | - Dan V Iosifescu
- Clinical Research Division, The Nathan S. Kline Institute for Psychiatric Research, Orangeburg, NY, USA.,Psychiatry Department, New York University School of Medicine, New York, NY, USA
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6
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Johnson C, Hong W, Micevych P. Optogenetic Activation of β-Endorphin Terminals in the Medial Preoptic Nucleus Regulates Female Sexual Receptivity. eNeuro 2020; 7:ENEURO.0315-19.2019. [PMID: 31941660 PMCID: PMC6984809 DOI: 10.1523/eneuro.0315-19.2019] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2019] [Revised: 11/15/2019] [Accepted: 11/19/2019] [Indexed: 01/13/2023] Open
Abstract
Estrogen and progesterone (P4) act in neural circuits to elicit lordosis, the stereotypical female sexual receptivity behavior. Estradiol acts through membrane receptors to rapidly activate a limbic-hypothalamic circuit consisting of the arcuate (ARH), medial preoptic (MPN), and ventromedial (VMH) nuclei of the hypothalamus. This initial activation results in a transient but necessary inhibition of lordosis, which appears to be a result of the release of β-endorphin (β-End) from proopiomelanocortin (POMC) terminals onto cells containing the µ-opioid receptor (MOR) in the MPN. To functionally examine the role of the MOR in the hypothalamic lordosis circuit, we transfected a channelrhodopsin (ChR2) adeno-associated virus into POMC cell bodies in the ARH and photostimulated POMC/β-End axon terminals in the MPN in sexually receptive female Pomc-cre mice. Following estrogen and P4 priming, sexual receptivity was assessed by measuring the lordosis quotient (LQ). Following an initial trial for sexual receptivity, mice were photostimulated during behavioral testing, and brains were processed for MOR immunohistochemistry (IHC). Photostimulation decreased the LQ only in ChR2-expressing Pomc-cre mice. Furthermore, photostimulation of ChR2 in POMC/β-End axon terminals in the MPN resulted in the internalization of MOR, indicating activation of the receptor. Our results suggest that the activation of the MOR in the MPN is sufficient to attenuate lordosis behavior in a hormone-primed, sexually receptive female mouse. These data support a central role of MOR in female sexual behavior, and provide further insight into the hypothalamus control of sexual receptivity.
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Affiliation(s)
- Caroline Johnson
- Department of Neurobiology David Geffen School of Medicine at University of California, Los Angeles, Los Angeles, CA 90095
- Laboratory of Neuroendocrinology of the Brain Research Institute, University of California, Los Angeles, Los Angeles, CA 90095
| | - Weizhe Hong
- Department of Neurobiology David Geffen School of Medicine at University of California, Los Angeles, Los Angeles, CA 90095
- Laboratory of Neuroendocrinology of the Brain Research Institute, University of California, Los Angeles, Los Angeles, CA 90095
- Department of Biological Chemistry, David Geffen School of Medicine, University of California, Los Angeles, Los Angeles, CA 90095
| | - Paul Micevych
- Department of Neurobiology David Geffen School of Medicine at University of California, Los Angeles, Los Angeles, CA 90095
- Laboratory of Neuroendocrinology of the Brain Research Institute, University of California, Los Angeles, Los Angeles, CA 90095
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7
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Aylwin CF, Vigh-Conrad K, Lomniczi A. The Emerging Role of Chromatin Remodeling Factors in Female Pubertal Development. Neuroendocrinology 2019; 109:208-217. [PMID: 30731454 PMCID: PMC6794153 DOI: 10.1159/000497745] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/07/2018] [Accepted: 02/06/2019] [Indexed: 12/21/2022]
Abstract
To attain sexual competence, all mammalian species go through puberty, a maturational period during which body growth and development of secondary sexual characteristics occur. Puberty begins when the diurnal pulsatile gonadotropin-releasing hormone (GnRH) release from the hypothalamus increases for a prolonged period of time, driving the adenohypophysis to increase the pulsatile release of luteinizing hormone with diurnal periodicity. Increased pubertal GnRH secretion does not appear to be driven by inherent changes in GnRH neuronal activity; rather, it is induced by changes in transsynaptic and glial inputs to GnRH neurons. We now know that these changes involve a reduction in inhibitory transsynaptic inputs combined with increased transsynaptic and glial excitatory inputs to the GnRH neuronal network. Although the pubertal process is known to have a strong genetic component, during the last several years, epigenetics has been implicated as a significant regulatory mechanism through which GnRH release is first repressed before puberty and is involved later on during the increase in GnRH secretion that brings about the pubertal process. According to this concept, a central target of epigenetic regulation is the transcriptional machinery of neurons implicated in stimulating GnRH release. Here, we will briefly review the hormonal changes associated with the advent of female puberty and the role that excitatory transsynaptic inputs have in this process. In addition, we will examine the 3 major groups of epigenetic modifying enzymes expressed in the neuroendocrine hypothalamus, which was recently shown to be involved in pubertal development and progression.
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Affiliation(s)
- Carlos Francisco Aylwin
- Division of Genetics, Oregon National Primate Research Center, Oregon Health and Science University (OHSU), Beaverton, Oregon, USA
| | - Katinka Vigh-Conrad
- Division of Genetics, Oregon National Primate Research Center, Oregon Health and Science University (OHSU), Beaverton, Oregon, USA
| | - Alejandro Lomniczi
- Division of Genetics, Oregon National Primate Research Center, Oregon Health and Science University (OHSU), Beaverton, Oregon, USA,
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8
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Abstract
The hypothalamus is most often associated with innate behaviors such as is hunger, thirst and sex. While the expression of these behaviors important for survival of the individual or the species is nested within the hypothalamus, the desire (i.e., motivation) for them is centered within the mesolimbic reward circuitry. In this review, we will use female sexual behavior as a model to examine the interaction of these circuits. We will examine the evidence for a hypothalamic circuit that regulates consummatory aspects of reproductive behavior, i.e., lordosis behavior, a measure of sexual receptivity that involves estradiol membrane-initiated signaling in the arcuate nucleus (ARH), activating β-endorphin projections to the medial preoptic nucleus (MPN), which in turn modulate ventromedial hypothalamic nucleus (VMH) activity-the common output from the hypothalamus. Estradiol modulates not only a series of neuropeptides, transmitters and receptors but induces dendritic spines that are for estrogenic induction of lordosis behavior. Simultaneously, in the nucleus accumbens of the mesolimbic system, the mating experience produces long term changes in dopamine signaling and structure. Sexual experience sensitizes the response of nucleus accumbens neurons to dopamine signaling through the induction of a long lasting early immediate gene. While estrogen alone increases spines in the ARH, sexual experience increases dendritic spine density in the nucleus accumbens. These two circuits appear to converge onto the medial preoptic area where there is a reciprocal influence of motivational circuits on consummatory behavior and vice versa. While it has not been formally demonstrated in the human, such circuitry is generally highly conserved and thus, understanding the anatomy, neurochemistry and physiology can provide useful insight into the motivation for sexual behavior and other innate behaviors in humans.
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Affiliation(s)
- Paul E Micevych
- Laboratory of Neuroendocrinology, Department of Neurobiology, David Geffen School of Medicine at University of California, Los AngelesLos Angeles, CA, United States.,Brain Research Institute, University of California, Los AngelesLos Angeles, CA, United States
| | - Robert L Meisel
- Department of Neuroscience, University of MinnesotaMinneapolis, MN, United States
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9
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Rebouças ECC, Leal S, Sá SI. Regulation of NPY and α-MSH expression by estradiol in the arcuate nucleus of Wistar female rats: a stereological study. Neurol Res 2016; 38:740-7. [PMID: 27357214 DOI: 10.1080/01616412.2016.1203124] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
Abstract
OBJECTIVES Feeding behavior in both animals and humans is modulated by estrogens, as shown by the increased adiposity observed in women and rats upon the drop of estradiol levels at menopause. Estradiol action on food intake is mediated through its cognate receptors within several hypothalamic nuclei, namely the arcuate nucleus (ARN). The ARN contains two neuronal populations expressing peptides that exert opposing effects on the central control of feeding: the orexigenic neuropeptide Y (NPY) and the anorexigenic α-melanocyte-stimulating hormone (α-MSH). METHODS To understand the role played by estradiol in the modulation of food intake, we have used an animal model of cyclic 17β-estradiol benzoate (EB) administration and stereological methods to estimate the total number of neurons immunoreactive for NPY and α-MSH in the ARN of ovariectomized rats. RESULTS Present results show that the experimentally induced EB cyclicity prompted a decrease in food consumption and in body weight. Data also show that ovariectomy induced an increase in NPY expression and a decrease in α-MSH expression in the ARN that were reverted by EB administration. Conversely, EB blocked the expression of NPY and increased the synthesis of α-MSH in ARN neurons, without affecting the overall sum of NPY and α-MSH neurons. DISCUSSION These results suggest that estradiol affects food intake and, consequently, body weight gain, through an overriding mechanism superimposed in the physiological balance between both peptides in the ARN of female rats.
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Affiliation(s)
- Elce C C Rebouças
- a Department of Natural Sciences , State University of Southwest of Bahia , Bahia , Brazil.,b Faculty of Medicine, Department of Anatomy , University of Porto , Porto , Portugal.,c Faculty of Medicine, Center for Health Technology and Services Research (CINTESIS) , University of Porto , Porto , Portugal
| | - Sandra Leal
- b Faculty of Medicine, Department of Anatomy , University of Porto , Porto , Portugal.,c Faculty of Medicine, Center for Health Technology and Services Research (CINTESIS) , University of Porto , Porto , Portugal.,d Department of Sciences , Institute of Research and Advanced Training in Health Sciences and Technologies (IINFACTS) , Advanced Institute of Health Sciences-North (ISCS-N), CESPU, CRL , Gandra , Portugal
| | - Susana I Sá
- b Faculty of Medicine, Department of Anatomy , University of Porto , Porto , Portugal.,c Faculty of Medicine, Center for Health Technology and Services Research (CINTESIS) , University of Porto , Porto , Portugal
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10
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Stress-induced alterations in estradiol sensitivity increase risk for obesity in women. Physiol Behav 2016; 166:56-64. [PMID: 27182047 DOI: 10.1016/j.physbeh.2016.05.016] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2015] [Revised: 04/04/2016] [Accepted: 05/11/2016] [Indexed: 02/02/2023]
Abstract
The prevalence of obesity in the United States continues to rise, increasing individual vulnerability to an array of adverse health outcomes. One factor that has been implicated causally in the increased accumulation of fat and excess food intake is the activity of the limbic-hypothalamic-pituitary-adrenal (LHPA) axis in the face of relentless stressor exposure. However, translational and clinical research continues to understudy the effects sex and gonadal hormones and LHPA axis dysfunction in the etiology of obesity even though women continue to be at greater risk than men for stress-induced disorders, including depression, emotional feeding and obesity. The current review will emphasize the need for sex-specific evaluation of the relationship between stress exposure and LHPA axis activity on individual risk for obesity by summarizing data generated by animal models currently being leveraged to determine the etiology of stress-induced alterations in feeding behavior and metabolism. There exists a clear lack of translational models that have been used to study female-specific risk. One translational model of psychosocial stress exposure that has proven fruitful in elucidating potential mechanisms by which females are at increased risk for stress-induced adverse health outcomes is that of social subordination in socially housed female macaque monkeys. Data from subordinate female monkeys suggest that increased risk for emotional eating and the development of obesity in females may be due to LHPA axis-induced changes in the behavioral and physiological sensitivity of estradiol. The lack in understanding of the mechanisms underlying these alterations necessitate the need to account for the effects of sex and gonadal hormones in the rationale, design, implementation, analysis and interpretation of results in our studies of stress axis function in obesity. Doing so may lead to the identification of novel therapeutic targets with which to combat stress-induced obesity exclusively in females.
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11
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Rebouças ECC, Leal S, Silva SM, Sá SI. Changes in the female arcuate nucleus morphology and neurochemistry after chronic ethanol consumption and long-term withdrawal. J Chem Neuroanat 2016; 77:30-40. [PMID: 27154870 DOI: 10.1016/j.jchemneu.2016.05.001] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2016] [Revised: 05/02/2016] [Accepted: 05/02/2016] [Indexed: 12/26/2022]
Abstract
Ethanol is a macronutrient whose intake is a form of ingestive behavior, sharing physiological mechanisms with food intake. Chronic ethanol consumption is detrimental to the brain, inducing gender-dependent neuronal damage. The hypothalamic arcuate nucleus (ARN) is a modulator of food intake that expresses feeding-regulatory neuropeptides, such as alpha melanocyte-stimulating hormone (α-MSH) and neuropeptide Y (NPY). Despite its involvement in pathways associated with eating disorders and ethanol abuse, the impact of ethanol consumption and withdrawal in the ARN structure and neurochemistry in females is unknown. We used female rat models of 20% ethanol consumption for six months and of subsequent ethanol withdrawal for two months. Food intake and body weights were measured. ARN morphology was stereologically analyzed to estimate its volume, total number of neurons and total number of neurons expressing NPY, α-MSH, tyrosine hydroxylase (TH) and estrogen receptor alpha (ERα). Ethanol decreased energy intake and body weights. However, it did not change the ARN morphology or the expression of NPY, α-MSH and TH, while increasing ERα expression. Withdrawal induced a significant volume and neuron loss that was accompanied by an increase in NPY expression without affecting α-MSH and TH expression. These findings indicate that the female ARN is more vulnerable to withdrawal than to excess alcohol. The data also support the hypothesis that the same pathways that regulate the expression of NPY and α-MSH in long-term ethanol intake may regulate food intake. The present model of long-term ethanol intake and withdrawal induces new physiological conditions with adaptive responses.
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Affiliation(s)
- Elce C C Rebouças
- Department of Natural Sciences, State University of Southwestern Bahia, Praça Primavera, 40-Bairro Primavera, Itapetinga, BA 45700-000, Brazil; Department of Anatomy, Faculty of Medicine, University of Porto, Al. Prof. Hernâni Monteiro, 4200-319 Porto, Portugal; Center for Health Technology and Services Research (CINTESIS), Faculty of Medicine, University of Porto, Rua Dr. Plácido da Costa, 4200-450 Porto, Portugal.
| | - Sandra Leal
- Department of Anatomy, Faculty of Medicine, University of Porto, Al. Prof. Hernâni Monteiro, 4200-319 Porto, Portugal; Center for Health Technology and Services Research (CINTESIS), Faculty of Medicine, University of Porto, Rua Dr. Plácido da Costa, 4200-450 Porto, Portugal; Institute of Research and Advanced Training in Health Sciences and Technologies (IINFACTS), Department of Sciences, Instituto Universitário de Ciências da Saúde (IUCS), CESPU, CRL, R. Central da Gandra 1317, 4585-116 Gandra, Portugal.
| | - Susana M Silva
- Department of Anatomy, Faculty of Medicine, University of Porto, Al. Prof. Hernâni Monteiro, 4200-319 Porto, Portugal; Center for Health Technology and Services Research (CINTESIS), Faculty of Medicine, University of Porto, Rua Dr. Plácido da Costa, 4200-450 Porto, Portugal.
| | - Susana I Sá
- Department of Anatomy, Faculty of Medicine, University of Porto, Al. Prof. Hernâni Monteiro, 4200-319 Porto, Portugal; Center for Health Technology and Services Research (CINTESIS), Faculty of Medicine, University of Porto, Rua Dr. Plácido da Costa, 4200-450 Porto, Portugal.
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12
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Wellhauser L, Gojska NM, Belsham DD. Delineating the regulation of energy homeostasis using hypothalamic cell models. Front Neuroendocrinol 2015; 36:130-49. [PMID: 25223866 DOI: 10.1016/j.yfrne.2014.09.001] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/23/2014] [Revised: 08/28/2014] [Accepted: 09/02/2014] [Indexed: 12/27/2022]
Abstract
Attesting to its intimate peripheral connections, hypothalamic neurons integrate nutritional and hormonal cues to effectively manage energy homeostasis according to the overall status of the system. Extensive progress in the identification of essential transcriptional and post-translational mechanisms regulating the controlled expression and actions of hypothalamic neuropeptides has been identified through the use of animal and cell models. This review will introduce the basic techniques of hypothalamic investigation both in vivo and in vitro and will briefly highlight the key advantages and challenges of their use. Further emphasis will be place on the use of immortalized models of hypothalamic neurons for in vitro study of feeding regulation, with a particular focus on cell lines proving themselves most fruitful in deciphering fundamental basics of NPY/AgRP, Proglucagon, and POMC neuropeptide function.
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Affiliation(s)
- Leigh Wellhauser
- Department of Physiology, University of Toronto, Toronto, Ontario M5G 1A8, Canada
| | - Nicole M Gojska
- Department of Physiology, University of Toronto, Toronto, Ontario M5G 1A8, Canada
| | - Denise D Belsham
- Departments of Physiology, Medicine and OB/GYN, University of Toronto, Toronto, Ontario M5G 1A8, Canada; Division of Cellular and Molecular Biology, Toronto General Hospital Research Institute, University Health Network, Toronto, Ontario M5S 1A8, Canada.
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13
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Nestor CC, Kelly MJ, Rønnekleiv OK. Cross-talk between reproduction and energy homeostasis: central impact of estrogens, leptin and kisspeptin signaling. Horm Mol Biol Clin Investig 2014; 17:109-28. [PMID: 25372735 PMCID: PMC4959432 DOI: 10.1515/hmbci-2013-0050] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2013] [Accepted: 10/07/2013] [Indexed: 02/06/2023]
Abstract
The central nervous system receives hormonal cues (e.g., estrogens and leptin, among others) that influence reproduction and energy homeostasis. 17β-estradiol (E2) is known to regulate gonadotropin-releasing hormone (GnRH) secretion via classical steroid signaling and rapid non-classical membrane-initiated signaling. Because GnRH neurons are void of leptin receptors, the actions of leptin on these neurons must be indirect. Although it is clear that the arcuate nucleus of the hypothalamus is the primary site of overlap between these two systems, it is still unclear which neural network(s) participate in the cross-talk of E2 and leptin, two hormones essential for reproductive function and metabolism. Herein we review the progress made in understanding the interactions between reproduction and energy homeostasis by focusing on the advances made to understand the cellular signaling of E2 and leptin on three neural networks: kisspeptin, pro-opiomelanocortin (POMC) and neuropeptide Y (NPY). Although critical in mediating the actions of E2 and leptin, considerable work still remains to uncover how these neural networks interact in vivo.
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Affiliation(s)
- Casey C Nestor
- Department of Physiology and Pharmacology, Oregon Health and Science University, Portland, OR, USA
| | - Martin J. Kelly
- Department of Physiology and Pharmacology, Oregon Health and Science University, Portland, OR, USA; and Division of Neuroscience, Oregon National Primate Research Center, Oregon Health and Science University, Beaverton, OR, USA
| | - Oline K. Rønnekleiv
- Department of Physiology and Pharmacology, Oregon Health and Science University, Portland, OR, USA; and Division of Neuroscience, Oregon National Primate Research Center, Oregon Health and Science University, Beaverton, OR, USA
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14
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Micevych P, Sinchak K. Temporal and concentration-dependent effects of oestradiol on neural pathways mediating sexual receptivity. J Neuroendocrinol 2013; 25:1012-23. [PMID: 24028299 PMCID: PMC3943611 DOI: 10.1111/jne.12103] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/10/2013] [Revised: 08/13/2013] [Accepted: 09/05/2013] [Indexed: 11/27/2022]
Abstract
The acceptance of oestradiol signalling through receptors found in the cell membrane, as well as, the nucleus, has provided for a re-examination of the timing and location of the actions of oestradiol on neural circuits mediating sexual receptivity (lordosis). Oestradiol membrane signalling involves the transactivation of metabotrophic glutamate receptors (mGluRs) that transduce steroid information through protein kinase C signalling cascades producing rapid activation of lordosis-regulating circuits. It has been known for some time that oestradiol initially produces an inhibition of the medial preoptic nucleus. We have demonstrated that underlying this inhibition is oestradiol acting in the arcuate nucleus to induce β-endorphin release, which inhibits the medial preoptic nucleus through a μ-opioid receptor mechanism. This transient inhibition is relieved by either subsequent progesterone treatment or longer exposure to higher doses of oestradiol to facilitate lordosis behaviour. We review recent findings about oestradiol membrane signalling inducing dendritic spine formation in the arcuate nucleus that is critical for oestradiol induction of sexual receptivity. Moreover, we discuss the evidence that, in addition to oestrogen receptor α, several other putative membrane oestrogen receptors facilitate lordosis behaviour through regulation of the arcuate nucleus. These include the GRP30 and the STX activated Gq-mER. Finally, we report on the importance of GABA acting at GABAB receptors for oestradiol membrane signalling that regulates lordosis circuit activation and sexual receptivity.
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Affiliation(s)
- Paul Micevych
- Department of Neurobiology, David Geffen School of Medicine at UCLA, the Laboratory of Neuroendocrinology, Brain Research Institute, University of California, Los Angeles, CA 90095
| | - Kevin Sinchak
- Department of Biological Sciences, California State University, Long Beach, CA 90840
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15
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Matic I, Matthews BG, Kizivat T, Igwe JC, Marijanovic I, Ruohonen ST, Savontaus E, Adams DJ, Kalajzic I. Bone-specific overexpression of NPY modulates osteogenesis. KLIN NEUROPHYSIOL 2013. [PMID: 23196263 DOI: 10.1055/s-0032-1305278] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
OBJECTIVES Neuropeptide Y (NPY) is a peptide involved in the regulation of appetite and energy homeostasis. Genetic data indicates that NPY decreases bone formation via central and peripheral activities. NPY is produced by various cell types including osteocytes and osteoblasts and there is evidence suggesting that peripheral NPY is important for regulation of bone formation. We sought to investigate the role of bone-derived NPY in bone metabolism. METHODS We generated a mouse where NPY was over-expressed specifically in mature osteoblasts and osteocytes (Col2.3NPY) and characterized the bone phenotype of these mice in vivo and in vitro. RESULTS Trabecular and cortical bone volume was reduced in 3-month-old animals, however bone formation rate and osteoclast activity were not significantly changed. Calvarial osteoblast cultures from Col2.3NPY mice also showed reduced mineralization and expression of osteogenic marker genes. CONCLUSIONS Our data suggest that osteoblast/osteocyte-derived NPY is capable of altering osteogenesis in vivo and in vitro and may represent an important source of NPY for regulation of bone formation. However, it is possible that other peripheral sources of NPY such as the sympathetic nervous system and vasculature also contribute to peripheral regulation of bone turnover.
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Affiliation(s)
- I Matic
- Department of Reconstructive Sciences, University of Connecticut Health Center, Farmington, CT 06032, USA
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16
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Terasawa E, Kenealy BP. Neuroestrogen, rapid action of estradiol, and GnRH neurons. Front Neuroendocrinol 2012; 33:364-75. [PMID: 22940545 PMCID: PMC3496051 DOI: 10.1016/j.yfrne.2012.08.001] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/16/2012] [Revised: 07/29/2012] [Accepted: 08/15/2012] [Indexed: 02/01/2023]
Abstract
Estradiol plays a pivotal role in the control of GnRH neuronal function, hence female reproduction. A series of recent studies in our laboratory indicate that rapid excitatory actions of estradiol directly modify GnRH neuronal activity in primate GnRH neurons through GPR30 and STX-sensitive receptors. Similar rapid direct actions of estradiol through estrogen receptor beta are also described in mouse GnRH neurons. In this review, we propose two novel hypotheses as a possible physiological role of estradiol in primates. First, while ovarian estradiol initiates the preovulatory GnRH surge through interneurons expressing estrogen receptor alpha, rapid direct membrane-initiated action of estradiol may play a role in sustaining GnRH surge release for many hours. Second, locally produced neuroestrogens may contribute to pulsatile GnRH release. Either way, estradiol synthesized in interneurons in the hypothalamus may play a significant role in the control of the GnRH surge and/or pulsatility of GnRH release.
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Affiliation(s)
- Ei Terasawa
- Wisconsin National Primate Research Center, University of Wisconsin, Madison, WI 53715, United States.
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17
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Sinchak K, Wagner EJ. Estradiol signaling in the regulation of reproduction and energy balance. Front Neuroendocrinol 2012; 33:342-63. [PMID: 22981653 PMCID: PMC3496056 DOI: 10.1016/j.yfrne.2012.08.004] [Citation(s) in RCA: 65] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/02/2012] [Revised: 08/18/2012] [Accepted: 08/22/2012] [Indexed: 12/14/2022]
Abstract
Our knowledge of membrane estrogenic signaling mechanisms and their interactions that regulate physiology and behavior has grown rapidly over the past three decades. The discovery of novel membrane estrogen receptors and their signaling mechanisms has started to reveal the complex timing and interactions of these various signaling mechanisms with classical genomic steroid actions within the nervous system to regulate physiology and behavior. The activation of the various estrogenic signaling mechanisms is site specific and differs across the estrous cycle acting through both classical genomic mechanisms and rapid membrane-initiated signaling to coordinate reproductive behavior and physiology. This review focuses on our current understanding of estrogenic signaling mechanisms to promote: (1) sexual receptivity within the arcuate nucleus of the hypothalamus, (2) estrogen positive feedback that stimulates de novo neuroprogesterone synthesis to trigger the luteinizing hormone surge important for ovulation and estrous cyclicity, and (3) alterations in energy balance.
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Affiliation(s)
- Kevin Sinchak
- Department of Biological Sciences, California State University, Long Beach, 1250 Bellflower Blvd., Long Beach, CA 90840-9502, United States.
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18
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Yonezawa T, Mogi K, Li JY, Sako R, Manabe N, Yamanouchi K, Nishihara M. Effects of estrogen on growth hormone pulsatility in peripheral blood and neuropeptide profiles in the cerebrospinal fluid of goats. J Reprod Dev 2011; 57:280-7. [PMID: 21242654 DOI: 10.1262/jrd.10-118s] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
We previously reported that growth hormone (GH) pulses were negatively associated with neuropeptide Y (NPY) profiles in cerebrospinal fluid (CSF) of the third ventricle of Shiba goats. In addition, while most GH pulses were coincident with GH-releasing hormone (GHRH) pulses, there was no correlation between GH and somatostatin (SRIF) levels. The present study was performed to elucidate the relationship between GH pulses and these neuropeptide levels in CSF when estradiol (1.0 mg/head) was subcutaneously administered to ovariectomized goats. CSF and plasma samples were collected every 15 min for 18 h (from 6 h before to 12 h after injection). GH levels in peripheral blood and GHRH, SRIF and NPY levels in CSF were measured by radioimmunoassay. Pulse/trough characteristics and correlations were assessed by the ULTRA algorithm and cross-correlation analysis. Before estradiol was injected, significant coincidence was found between GHRH pulses and GH pulses, and negative coincidence was found between NPY troughs and GH pulses. Six to 12 h after estradiol injection, the amplitude and area under the curve (AUC) of the GH pulses were markedly increased. The duration and AUC of the GHRH pulses in the CSF were also increased, and stronger synchrony of GHRH with GH was observed. In contrast, the baseline of NPY was significantly decreased, and the negative correlation between the GH pulses and NPY troughs disappeared. The parameters of SRIF troughs were not clearly changed. These observations suggest that estrogen enhances the pattern of secretion of GH in the goat via enhancement of GHRH pulses and decrease of NPY levels.
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Affiliation(s)
- Tomohiro Yonezawa
- Department of Veterinary Physiology, Veterinary Medical Science, The University of Tokyo, Tokyo, Japan
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19
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Endocrine induced changes in brain function during pregnancy. Brain Res 2010; 1364:198-215. [DOI: 10.1016/j.brainres.2010.09.062] [Citation(s) in RCA: 80] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2010] [Revised: 09/10/2010] [Accepted: 09/16/2010] [Indexed: 02/05/2023]
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20
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Brown LM, Clegg DJ. Central effects of estradiol in the regulation of food intake, body weight, and adiposity. J Steroid Biochem Mol Biol 2010; 122:65-73. [PMID: 20035866 PMCID: PMC2889220 DOI: 10.1016/j.jsbmb.2009.12.005] [Citation(s) in RCA: 217] [Impact Index Per Article: 15.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/30/2009] [Revised: 11/19/2009] [Accepted: 12/15/2009] [Indexed: 12/14/2022]
Abstract
In recent years, obesity and its associated health disorders and costs have increased. Accumulation of adipose tissue, or fat, in the intra-abdominal adipose depot is associated with an increased risk of developing cardiovascular problems, type-2 diabetes mellitus, certain cancers, and other disorders like the metabolic syndrome. Males and females differ in terms of how and where their body fat is stored, in their hormonal secretions, and in their neural responses to signals regulating weight and body fat distribution. Men and post-menopausal women accumulate more fat in their intra-abdominal depots than pre-menopausal women, resulting in a greater risk of developing complications associated with obesity. The goal of this review is to discuss the current literature on sexual dimorphisms in body weight regulation, adipose tissue accrual and deposition.
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Affiliation(s)
- LM Brown
- Department of Nutrition, University of North Carolina Greensboro, Greensboro, NC 27412
| | - DJ Clegg
- Department of Internal Medicine, Touchstone Diabetes Center, University of Texas Southwestern Medical Center, Dallas, TX 75390-8854
- Corresponding author at: Deborah J. Clegg, RD, PhD, Assistant Professor, Department of Internal Medicine, Touchstone Diabetes Center, UT Southwestern Medical Center, 5323 Harry Hines Blvd., K5.252, Dallas, TX 75390-8854, Tel: 214-648-3401, Fax: 214-648-8720, (D. Clegg)
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21
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Igwe JC, Jiang X, Paic F, Ma L, Adams DJ, Baldock PA, Pilbeam CC, Kalajzic I. Neuropeptide Y is expressed by osteocytes and can inhibit osteoblastic activity. J Cell Biochem 2009; 108:621-30. [PMID: 19670271 DOI: 10.1002/jcb.22294] [Citation(s) in RCA: 82] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
Osteocytes are the most abundant osteoblast lineage cells within the bone matrix. They respond to mechanical stimulation and can participate in the release of regulatory proteins that can modulate the activity of other bone cells. We hypothesize that neuropeptide Y (NPY), a neurotransmitter with regulatory functions in bone formation, is produced by osteocytes and can affect osteoblast activity. To study the expression of NPY by the osteoblast lineage cells, we utilized transgenic mouse models in which we can identify and isolate populations of osteoblasts and osteocytes. The Col2.3GFP transgene is active in osteoblasts and osteocytes, while the DMP1 promoter drives green fluorescent protein (GFP) expression in osteocytes. Real-time PCR analysis of RNA from the isolated populations of cells derived from neonatal calvaria showed higher NPY mRNA in the preosteocytes/osteocytes fraction compared to osteoblasts. NPY immunostaining confirmed the strong expression of NPY in osteocytes (DMP1GFP(+)), and lower levels in osteoblasts. In addition, the presence of NPY receptor Y1 mRNA was detected in cavaria and long bone, as well as in primary calvarial osteoblast cultures, whereas Y2 mRNA was restricted to the brain. Furthermore, NPY expression was reduced by 30-40% in primary calvarial cultures when subjected to fluid shear stress. In addition, treatment of mouse calvarial osteoblasts with exogenous NPY showed a reduction in the levels of intracellular cAMP and markers of osteoblast differentiation (osteocalcin, BSP, and DMP1). These results highlight the potential regulation of osteoblast lineage differentiation by local NPY signaling.
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Affiliation(s)
- John C Igwe
- Department of Reconstructive Sciences, University of Connecticut Health Center, Farmington, Connecticut 06032, USA
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22
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Abstract
The control of energy homeostasis in women is correlated with the anorectic effects of oestrogen, which can attenuate body weight gain and reduce food intake in rodent models. This review investigates the multiple signalling pathways and cellular targets that oestrogen utilises to control energy homeostasis in the hypothalamus. Oestrogen affects all of the hypothalamic nuclei that control energy homeostasis. Oestrogen controls the activity of hypothalamic neurones through gene regulation and neuronal excitability. Oestrogen's primary cellular pathway is the control of gene transcription through the classical oestrogen receptors (ERs) (ERalpha and ERbeta) with ERalpha having the primary role in energy homeostasis. Oestrogen also controls energy homeostasis through membrane-mediated events via membrane-associated ERs or a novel, putative membrane ER that is coupled to G-proteins. Therefore, oestrogen is coupled to at least two receptors with multiple signalling and transcriptional pathways to mediate immediate and long-term anorectic effects. Ultimately, it is the interactions of all the receptor-mediated processes in hypothalamus and other areas of the central nervous system that will determine the anorectic effects of oestrogen and its control of energy homeostasis.
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Affiliation(s)
- T A Roepke
- Department of Physiology and Pharmacology, Oregon Health and Science University, Portland, OR 97239, USA.
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24
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Stereological analysis of estrogen receptor expression in the hypothalamic arcuate nucleus of ob/ob and agouti mice. Brain Res 2008; 1217:86-95. [DOI: 10.1016/j.brainres.2008.04.031] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2007] [Revised: 04/04/2008] [Accepted: 04/05/2008] [Indexed: 12/19/2022]
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25
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Huang W, Acosta-Martínez M, Levine JE. Ovarian steroids stimulate adenosine triphosphate-sensitive potassium (KATP) channel subunit gene expression and confer responsiveness of the gonadotropin-releasing hormone pulse generator to KATP channel modulation. Endocrinology 2008; 149:2423-32. [PMID: 18258681 PMCID: PMC2329280 DOI: 10.1210/en.2007-0830] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
The ATP-sensitive potassium (K(ATP)) channels couple intracellular metabolism to membrane potential. They are composed of Kir6.x and sulfonylurea receptor (SUR) subunits and are expressed in hypothalamic neurons that project to GnRH neurons. However, their roles in regulating GnRH secretion have not been determined. The present study first tested whether K(ATP) channels regulate pulsatile GnRH secretion, as indirectly reflected by pulsatile LH secretion. Ovariectomized rats received sc capsules containing oil, 17beta-estradiol (E(2)), progesterone (P), or E(2)+P at 24 h before blood sampling. Infusion of the K(ATP) channel blocker tolbutamide into the third ventricle resulted in increased LH pulse frequency in animals treated with E(2)+P but was without effect in all other groups. Coinfusion of tulbutamide and the K(ATP) channel opener diazoxide blocked this effect, whereas diazoxide alone suppressed LH. Effects of steroids on Kir6.2 and SUR1 mRNA expression were then evaluated. After 24hr treatment, E(2)+P produced a modest but significant increase in Kir6.2 expression in the preoptic area (POA), which was reversed by P receptor antagonism with RU486. Neither SUR1 in the POA nor both subunits in the mediobasal hypothalamus were altered by any steroid treatment. After 8 d treatment, Kir6.2 mRNA levels were again enhanced by E(2)+P but to a greater extent in the POA. Our findings demonstrate that 1) blockade of preoptic/hypothalamic K(ATP) channels produces an acceleration of the GnRH pulse generator in a steroid-dependent manner and 2) E(2)+P stimulate Kir6.2 gene expression in the POA. These observations are consistent with the hypothesis that the negative feedback actions of ovarian steroids on the GnRH pulse generator are mediated, in part, by their ability to up-regulate K(ATP) channel subunit expression in the POA.
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Affiliation(s)
- Wenyu Huang
- Department of Neurobiology and Physiology, Northwestern University, Evanston, Illinois 60208, USA
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26
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Santollo J, Eckel LA. Estradiol decreases the orexigenic effect of neuropeptide Y, but not agouti-related protein, in ovariectomized rats. Behav Brain Res 2008; 191:173-7. [PMID: 18453005 DOI: 10.1016/j.bbr.2008.03.019] [Citation(s) in RCA: 61] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2007] [Revised: 01/21/2008] [Accepted: 03/18/2008] [Indexed: 02/07/2023]
Abstract
Available data suggest that estradiol exerts an inhibitory effect on food intake by modulating the actions of multiple gut- and brain-derived peptides implicated in the control of food intake. For example, recent studies have shown that estradiol decreases the orexigenic effects of ghrelin and melanin-concentrating hormone. In the present study, we examined estradiol's ability to decrease the actions of two additional orexigenic peptides, neuropeptide Y (NPY) and agouti-related protein (AgRP). Food intake was monitored following lateral ventricular infusions of 5 microg NPY, 10 microg AgRP, or saline vehicle in ovariectomized rats treated with either 1 microg estradiol or sesame oil vehicle. NPY increased food intake for 2h in both oil- and estradiol-treated ovariectomized rats. During this interval, the orexigenic effect of NPY was significantly greater in oil-treated rats, relative to estradiol-treated rats. In contrast to the short-term action of NPY, a single injection of AgRP increased food intake for 3 days in oil- and estradiol-treated rats. Meal pattern analysis revealed that the orexigenic effect of AgRP is mediated by an increase in meal size, not meal number. Unlike that observed following NPY treatment, estradiol failed to modulate the magnitude by which AgRP increased food intake and meal size. We conclude that a physiological regimen of estradiol treatment decreases the orexigenic effect of NPY, but not AgRP, in ovariectomized rats.
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Affiliation(s)
- Jessica Santollo
- Program in Neuroscience and Department of Psychology, Florida State University, Eppes Hall, Copeland Avenue, Tallahassee, FL 32306-1270, USA
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27
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Pelletier G, Li S, Luu-The V, Labrie F. Oestrogenic regulation of pro-opiomelanocortin, neuropeptide Y and corticotrophin-releasing hormone mRNAs in mouse hypothalamus. J Neuroendocrinol 2007; 19:426-31. [PMID: 17388940 DOI: 10.1111/j.1365-2826.2007.01548.x] [Citation(s) in RCA: 72] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
It is well documented that oestrogen suppresses food intake by an action at the hypothalamic level. Using in situ hybridisation, we studied the effect of castration (CX) and short-term administration of oestradiol (E2) in CX female mice for three neuropeptides involved in feeding behaviour: two anorexigenic peptides, (i) the pro-opiomelanocortin (POMC)-derived peptide alpha-melanocyte-stimulating hormone and (ii) corticotrophin-releasing hormone (CRH), and the orexigenic peptide, (iii) neuropeptide Y (NPY). POMC-expressing neurones were mostly laterally located in the arcuate nucleus. POMC mRNA expression was decreased following CX and a single injection of E2 induced an increase in mRNA levels at 12- and 24-h time intervals. In the parvocellular area of the paraventricular nucleus, CRH mRNA levels were similarly decreased after CX and completely restored to normal levels at 12 and 24 h following E2 injection. On the other hand, the levels of NPY mRNA expressed in neurones located in the inner zone of the arcuate nucleus were increased by CX and decreased to the levels observed in intact animals by E2 injection (3-24 h). The present data suggest that oestrogen might exert an anorexigenic action by stimulating POMC and CRH mRNA expression and decreasing NPY mRNA expression in the hypothalamus.
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Affiliation(s)
- G Pelletier
- Oncology and Molecular Endocrinology Research Center, Centre de recherche du Centre Hospitalier de l'Université Laval (CRCHUL), Québec, Québec, Canada.
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28
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Hart SA, Snyder MA, Smejkalova T, Woolley CS. Estrogen mobilizes a subset of estrogen receptor-alpha-immunoreactive vesicles in inhibitory presynaptic boutons in hippocampal CA1. J Neurosci 2007; 27:2102-11. [PMID: 17314305 PMCID: PMC6673535 DOI: 10.1523/jneurosci.5436-06.2007] [Citation(s) in RCA: 85] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2005] [Revised: 01/21/2007] [Accepted: 01/22/2007] [Indexed: 01/01/2023] Open
Abstract
Although the classical mechanism of estrogen action involves activation of nuclear transcription factor receptors, estrogen also has acute effects on neuronal signaling that occur too rapidly to involve gene expression. These rapid effects are likely to be mediated by extranuclear estrogen receptors associated with the plasma membrane and/or cytoplasmic organelles. Here we used a combination of serial-section electron microscopic immunocytochemistry, immunofluorescence, and Western blotting to show that estrogen receptor-alpha is associated with clusters of vesicles in perisomatic inhibitory boutons in hippocampal CA1 and that estrogen treatment mobilizes these vesicle clusters toward synapses. Estrogen receptor-alpha is present in approximately one-third of perisomatic inhibitory boutons, and specifically in those that express cholecystokinin, not parvalbumin. We also found a high degree of extranuclear estrogen receptor-alpha colocalization with neuropeptide Y. Our results suggest a novel mode of estrogen action in which a subset of vesicles within a specific population of inhibitory boutons responds directly to estrogen by moving toward synapses. The mobilization of these vesicles may influence acute effects of estrogen mediated by estrogen receptor-alpha signaling at inhibitory synapses.
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Affiliation(s)
- Sharron A. Hart
- Department of Neurobiology and Physiology, Northwestern University, Evanston, Illinois 60208
| | - Melissa A. Snyder
- Department of Neurobiology and Physiology, Northwestern University, Evanston, Illinois 60208
| | - Tereza Smejkalova
- Department of Neurobiology and Physiology, Northwestern University, Evanston, Illinois 60208
| | - Catherine S. Woolley
- Department of Neurobiology and Physiology, Northwestern University, Evanston, Illinois 60208
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Mazumdar M, Sakharkar AJ, Singru PS, Subhedar N. Reproduction phase-related variations in neuropeptide Y immunoreactivity in the olfactory system, forebrain, and pituitary of the female catfish,Clarias batrachus (Linn.). J Comp Neurol 2007; 504:450-69. [PMID: 17701999 DOI: 10.1002/cne.21462] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
The aim of this study was to determine whether neuropeptide Y (NPY) immunoreactivity in the cells and fibers in the forebrain and pituitary of Clarias batrachus is linked to the annual reproductive cycle. A steady rise in luteinizing hormone (LH) immunoreactivity was seen in the pituitary through preparatory (February-April) and prespawning (May-June) phases; it was greatly reduced during spawning (July-August; P < 0.001) and partially replenished during postspawning (September-November; P < 0.01) through resting (December-January) phases. Although NPY immunoreactivity in olfactory receptor neurons and olfactory nerve layer in olfactory bulb was gradually augmented during resting through prespawning phases (P < 0.001), attaining a peak in spawning phase (P < 0.001), a dramatic decline was encountered during postspawning phase (P < 0.001). A similar pattern was also observed in NPY-containing fibers of the medial olfactory tract (MOT) and pituitary. However, a different pattern of NPY immunoreactivity was observed in the neurons of nucleus entopeduncularis (NE) and nucleus preopticus periventricularis (NPP). Whereas these neurons and fibers in the forebrain showed significant augmentation during the resting through prespawning phases (P < 0.001), the immunoreactivity dramatically declined during spawning (P < 0.001) and was partially replenished in the postspawning phase. Testosterone injection of juveniles significantly augmented (P < 0.001) NPY immunoreactivity in NE neurons. We suggest that NPY cells of NE and NPP, and related fiber systems, might be involved in processing of sex steroid-borne information and regulation of the gonadotropin-releasing hormone-LH axis.
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Affiliation(s)
- Minakshi Mazumdar
- Department of Pharmaceutical Sciences, R.T.M. Nagpur University Campus, Nagpur-440033, India
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Nedungadi TP, Briski KP. Effects of estradiol on acute and recurrent insulin-induced hypoglycemia-associated patterns of arcuate neuropeptide Y, proopiomelanocortin, and cocaine- and amphetamine-related transcript gene expression in the ovariectomized rat. Neuroendocrinology 2007; 86:270-6. [PMID: 17934251 DOI: 10.1159/000109678] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/09/2007] [Accepted: 07/19/2007] [Indexed: 11/19/2022]
Abstract
The ovarian steroid hormone, estradiol, is one of several peripheral metabolic signal modulators that are integrated at the level of the arcuate nucleus of the hypothalamus (ARH), and is implicated in the control of ARH neuropeptides that maintain energy balance, including neuropeptide Y (NPY) and proopiomelanocortin (POMC). The present studies utilized quantitative real-time RT-PCR techniques to examine the hypothesis that estradiol regulates ARH NPY, POMC, and cocaine- and amphetamine-related transcript (CART) gene expression during acute insulin-induced hypoglycemia (IIH) and that adaptive modifications in transcriptional reactivity during recurring exposure are steroid dependent. ARH tissue was obtained by micropunch dissection from estradiol benzoate- and oil-implanted ovariectomized (OVX) rats that were treated by subcutaneous injection of one or four doses of the intermediate insulin formulation, Humulin NPH, over as many days, or vehicle alone. Our data show that in OVX plus estradiol benzoate and OVX plus oil groups, a single injection of insulin did not modify gene expression profiles, with the exception of acute hypoglycemic reduction of ARH NPY transcripts in the presence of estrogen. Prior exposure to daily hypoglycemia significantly diminished basal NPY and POMC mRNA levels in estradiol benzoate-, but not oil-implanted OVX rats, but elevated baseline CART transcripts in oil-treated animals. Recurring IIH enhanced ARH NPY gene expression relative to baseline, irrespective of the estradiol manipulation, but net tissue levels were greater in the absence of estrogen. In contrast, reexposure to hypoglycemia decreased POMC and CART gene transcription in estradiol benzoate- and oil-implanted OVX animals, respectively, relative to the single-dose groups. These studies show that estrogen modulates the impact of precedent exposure to IIH on basal and/or hypoglycemia-associated patterns of expression of ARH neuropeptide genes of characterized significance for energy homeostasis. The novel evidence for transcriptional acclimation of NPY, POMC, and CART to recurring IIH supports the possibility that adaptation of compensatory behavioral and physiological responses to acute versus chronic exposure to this metabolic stress may reflect neural regulatory mechanisms involving one or more neurotransmitters encoded by these genes.
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Affiliation(s)
- T Prashant Nedungadi
- Department of Basic Pharmaceutical Sciences, College of Pharmacy, The University of Louisiana at Monroe, Monroe, LA 71209, USA
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Titolo D, Cai F, Belsham DD. Coordinate Regulation of Neuropeptide Y and Agouti-Related Peptide Gene Expression by Estrogen Depends on the Ratio of Estrogen Receptor (ER) α to ERβ in Clonal Hypothalamic Neurons. Mol Endocrinol 2006; 20:2080-92. [PMID: 16675543 DOI: 10.1210/me.2006-0027] [Citation(s) in RCA: 87] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
Neuropeptide Y (NPY) and agouti-related peptide (AgRP) stimulate feeding, whereas NPY also facilitates the estrogen-mediated preovulatory GnRH surge. In addition to regulating reproductive function, estrogen also acts as an anorexigenic hormone, although it is not yet known which hypothalamic neurons are involved in this process. We hypothesize that estrogen may directly control hypothalamic NPY and/or AgRP synthesis to influence energy homeostasis. Using two clonal, murine hypothalamic neuronal cell models, N-38 and N-42, we demonstrate that 17beta-estradiol differentially regulates estrogen receptor (ER)alpha and ERbeta levels, as well as NPY and AgRP gene expression in a manner that is temporally coordinated with the changes in ER abundance. The estrogen-mediated repression of NPY and AgRP mRNA levels in N-38 and N-42 neurons require either ERalpha and ERbeta or ERalpha alone, respectively, whereas the induction of NPY and AgRP in N-38 neurons is strictly ERbeta dependent, as assessed by ER-specific agonists and small interfering RNA knockdown of ERalpha or ERbeta. Through transient transfection analysis in N-38 neurons, we have mapped the estrogen-mediated repression of NPY to within -1078 of the 5' regulatory region of the NPY gene. Our results provide the first evidence that NPY and AgRP gene expression is directly regulated by estrogen in specific hypothalamic neurons, and that this regulation is dependent upon the ratio of ERbeta to ERalpha. The biphasic control of neuronal NPY/AgRP transcription may be a mechanism by which estrogen has distinct effects on both energy homeostasis and reproduction.
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Affiliation(s)
- Danny Titolo
- Department of Physiology, University of Toronto, Medical Sciences Building 3247A, 1 King's College Circle, Toronto, Ontario, Canada M5S 1A8
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Torto R, Boghossian S, Dube MG, Kalra PS, Kalra SP. Central leptin gene therapy blocks ovariectomy-induced adiposity. Obesity (Silver Spring) 2006; 14:1312-9. [PMID: 16988073 DOI: 10.1038/oby.2006.149] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
OBJECTIVE In this study, we tested the hypothesis that insufficiency of leptin restraint in the hypothalamus is responsible for promoting weight gain and adiposity after ovariectomy (ovx). Whether increasing leptin transgene expression can overcome the diminution in leptin restraint was evaluated in ovx rats. RESEARCH METHODS AND PROCEDURES Enhanced leptin or green fluorescent protein (GFP; control) transgene expression was induced by a single intracerebroventricular injection of recombinant adeno-associated viral vector encoding either leptin gene (rAAV-lep) or GFP gene (rAAV-GFP; control) in acutely and chronically ovx rats. Body weight and food intake responses were monitored weekly. White adipose tissue (WAT) mass and serum levels of WAT-derived hormones, leptin, and adiponectin were analyzed at termination of the experiments. RESULTS AND DISCUSSION An increase in leptin transgene expression in the hypothalamus initiated soon after ovx blocked hyperphagia and body weight gain and markedly suppressed WAT mass and adipokines, leptin, and adiponectin. Similar suppression of weight gain and adiposity and serum leptin and adiponectin levels after intracerebroventricular rAAV-lep injection in chronically ovx rats were observed concomitant with unchanged daily food intake. These findings are consistent with the hypothesis that in the absence of ovarian steroids, the existent insufficiency of leptin restraint at the hypothalamic level can be overcome with ectopic leptin expression, thereby reinstating central control on weight and adiposity.
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Affiliation(s)
- Rita Torto
- Departments of Physiology, University of Florida McKnight Brain Institute, P.O. Box 100244, Gainesville, FL 32610-0244, USA
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Sahu A. Alteration in hypothalamic neuropeptide Y (NPY) secretion may underlie female reproductive ageing: induction of steroid-induced luteinising hormone surge by NPY in ovariectomised aged rats. J Neuroendocrinol 2006; 18:584-93. [PMID: 16867179 DOI: 10.1111/j.1365-2826.2006.01449.x] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
A large body of evidence suggests that a defect in the hypothalamic function may be the primary cause of reproductive ageing in female rats. We have previously shown that luteinising hormone (LH)-surge associated changes in hypothalamic neuropeptide Y (NPY) gene expression and median eminence (ME) NPY levels seen in young rats do not occur in middle-aged (MA) rats. The present study examined whether hypothalamic NPY release is altered during the steroid-induced LH surge in ovariectomised (OVX) MA rats, and whether exogenous NPY initiates steroid-induced LH surge in OVX old rats. In the first study, NPY release from the ME-arcuate nucleus, as assessed by the push-pull cannula technique, was significantly increased before and during the progesterone-induced LH surge in oestrogen (E(2))-primed ovariectomised young rats (2-3 months old). This antecedent increase in NPY release seen in young rats was not apparent in MA rats (11-13 months old) in association with a delayed and attenuated LH surge. In the second study, whereas progesterone failed to induce LH surges in E(2)-primed ovariectomised old rats (23-25 months old), intracerebroventricular NPY (0.1-0.5 microg) injections at 1100, 1200 and 13.00 h resulted in LH surge induction in E(2) + progesterone-primed ovariectomised old rats. Because increased hypothalamic NPY synthesis and release is obligatory for the preovulatory LH discharge in young rats, the present findings suggest that alteration in NPY release from the ME-arcuate nucleus contributes to the delayed and reduced LH surges in MA rats and may be involved in the subsequent loss of the LH surges in old rats.
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Affiliation(s)
- A Sahu
- Department of Cell Biology and Physiology, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261, USA.
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Acuna-Goycolea C, Tamamaki N, Yanagawa Y, Obata K, van den Pol AN. Mechanisms of neuropeptide Y, peptide YY, and pancreatic polypeptide inhibition of identified green fluorescent protein-expressing GABA neurons in the hypothalamic neuroendocrine arcuate nucleus. J Neurosci 2006; 25:7406-19. [PMID: 16093392 PMCID: PMC6725307 DOI: 10.1523/jneurosci.1008-05.2005] [Citation(s) in RCA: 101] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
The fast inhibitory transmitter GABA is robustly expressed in the arcuate nucleus (ARC) and appears to play a major role in hypothalamic regulation of endocrine function and energy homeostasis. Previously, it has not been possible to record selectively from GABA cells, because they have no defining morphological or physiological characteristics. Using transgenic mice that selectively express GFP (green fluorescent protein) in GAD67 (glutamic acid decarboxylase 67)-synthesizing cells, we identified ARC GABA neurons (n > 300) and used whole-cell recording to study their physiological response to neuropeptide Y (NPY), the related peptide YY(3-36) (PYY(3-36)), and pancreatic polypeptide (PP), important modulators of ARC function. In contrast to other identified ARC cells in which NPY receptor agonists were reported to generate excitatory actions, we found that NPY consistently reduced the firing rate and hyperpolarized GABA neurons including neuroendocrine GABA neurons identified by antidromic median eminence stimulation. The inhibitory NPY actions were mediated by postsynaptic activation of G-protein-linked inwardly rectifying potassium (GIRK) and depression of voltage-gated calcium currents via Y1 and Y2 receptor subtypes. Additionally, NPY reduced spontaneous and evoked synaptic glutamate release onto GABA neurons by activation of Y1 and Y5 receptors. The peptide PYY(3-36), a peripheral endocrine signal that can act in the brain, also inhibited GABA neurons, including identified neuroendocrine cells, by activating GIRK conductances and depressing calcium currents. The endogenous Y4 agonist PP depressed the activity of GABA-expressing neurons mainly by presynaptic attenuation of glutamate release. Together, these results show that the family of neuropeptide Y modulators reduces the activity of inhibitory GABA neurons in the ARC by multiple presynaptic and postsynaptic mechanisms.
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Abstract
Ghrelin, produced in the stomach, acts on growth hormone secretagogue receptors (GHSRs) in hypothalamic neurons to potently increase food intake. However, male mice with deletions of ghrelin (Ghrl-/- mice) or GHSR (Ghsr-/- mice) display normal growth and regulation of food intake. Furthermore, adult Ghrl-/- mice display a normal sensitivity to high-fat diet-induced obesity. These findings from early studies raised the question as to whether the ghrelin system is an essential component for the regulation of food intake and body weight homeostasis. However, recent studies by Wortley et al. and Zigman et al. demonstrate that Ghrl-/- and Ghsr-/- mice are resistant to diet-induced obesity when fed a high-fat diet during the early post-weaning period. This commentary highlights 3 key issues raised by these 2 reports: (a) the impact of ghrelin on the development of metabolic systems; (b) the constitutive activity of GHSR; and (c) gender differences in the sensitivity to deletion of the ghrelin signaling system.
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Affiliation(s)
- Kevin L Grove
- Division of Neuroscience, Oregon National Primate Research Center, Oregon Health & Science University, Beaverton, Oregon 97006, USA.
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36
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Zhou W, Aoyama M, Yoshizawa F, Sugahara K. Developmental increases in hypothalamic neuropeptide Y content with the embryonic age of meat- and layer-type chicks. Brain Res 2006; 1072:26-9. [PMID: 16426585 DOI: 10.1016/j.brainres.2005.11.029] [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: 08/01/2005] [Revised: 10/31/2005] [Accepted: 11/02/2005] [Indexed: 11/15/2022]
Abstract
We determined central neuropeptide Y (NPY) content of meat- and layer-type chicks at embryonic days 7, 14, 20, and at post-hatching day 1. The central NPY was detectable at day 7; hypothalamic NPY content developmentally increased with a similar pattern but a different level between both types of chicks. These results were discussed with respect to feeding behavior early period after hatching.
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Affiliation(s)
- Weidong Zhou
- United Graduate School of Agricultural Science, Tokyo University of Agriculture and Technology, Fuchu, Tokyo 183-8509, Japan
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37
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Heikkinen AM, Niskanen LK, Salmi JA, Koulu M, Pesonen U, Uusitupa MIJ, Komulainen MH, Tuppurainen MT, Kröger H, Jurvelin J, Saarikoski S. Leucine7 to proline7 polymorphism in prepro-NPY gene and femoral neck bone mineral density in postmenopausal women. Bone 2004; 35:589-94. [PMID: 15336593 DOI: 10.1016/j.bone.2004.05.004] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/11/2003] [Revised: 04/02/2004] [Accepted: 05/05/2004] [Indexed: 10/26/2022]
Abstract
Neuropeptide Y (NPY) is a versatile neurotransmitter that has recently been shown to regulate bone metabolism in animal and in vitro studies. We studied the influence of leucine7-to-proline7 (Leu7/Pro7) polymorphism of the NPY signal peptide gene on bone mineral density (BMD) before and after a 5-year hormone replacement therapy (HRT) in 316 early postmenopausal women participating in a randomized controlled trial nested in the population-based Kuopio Osteoporosis Risk Factor and Prevention (OSTPRE) study. The participants were randomized into two treatment groups: the HRT group (n = 146) received a sequential combination of 2 mg estradiol valerate and 1 mg cyproterone acetate and calcium lactate, 500 mg/day (equal to 93 mg Ca2+) alone or in combination with vitamin D3, 100-300 IU/day. The non-HRT group (n = 170) received calcium lactate, 500 mg alone or in combination with vitamin D3, 100-300 IU/day. BMDs of the lumbar spine (L2-4) and proximal femur were measured by using dual X-ray absorptiometry (DXA). The frequency of Leu7/Pro7 polymorphism was 15.2%. At baseline, there were no significant differences in the lumbar or femoral neck BMD between the subjects who had Leu7Pro7 polymorphism and the normal subjects. After 5 years, the BMD of the femoral neck remained unaltered and that of the lumbar spine increased by 1.7% in the HRT group, whereas both BMDs were decreased by 4-5% in the non-HRT group. After 5 years, the femoral neck BMD was significantly lower in those with the wild-type NPY polymorphism than in those with Leu7/Pro7 polymorphism (P = 0.040) in the non-HRT group. In the HRT group, the changes in BMD were quite modest and not significantly modified by Leu7/Pro7 genotype. We conclude that the Leu7/Pro7 polymorphism in NPY signal gene may favorably affect femoral neck BMD in postmenopausal women.
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Affiliation(s)
- Anna-Mari Heikkinen
- Department of Obstetrics and Gynecology, Kuopio University Hospital, FIN-70211 Kuopio, Finland
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Kalra SP, Kalra PS. NPY and cohorts in regulating appetite, obesity and metabolic syndrome: beneficial effects of gene therapy. Neuropeptides 2004; 38:201-11. [PMID: 15337372 DOI: 10.1016/j.npep.2004.06.003] [Citation(s) in RCA: 131] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/10/2004] [Accepted: 06/04/2004] [Indexed: 11/16/2022]
Abstract
Neuropeptide Y is the most potent physiological appetite transducer known. The NPY network is the conductor of the hypothalamic appetite regulating orchestra in the arcuate nucleus-paraventricular nucleus (ARC-PVN) of the hypothalamus. NPY and cohorts, AgrP, GABA and adrenergic transmitters, initiate appetitive drive directly through Y1, Y5, GABAA and alpha1 receptors, co-expressed in the magnocellular PVN (mPVN) and ARC neurons and by simultaneously repressing anorexigenic melanocortin signaling in the ARC-PVN axis. The circadian and ultradian rhythmicities in NPY secretion imprint the daily circadian and episodic feeding patterns. Although a number of afferent hormonal signals from the periphery can directly modulate NPYergic signaling, the reciprocal circadian and ultradian rhythmicities of anorexigenic leptin from adipocytes and orexigenic ghrelin from stomach, encode a corresponding pattern of NPY discharge for daily meal patterning. Subtle and progressive derangements produced by environmental and genetic factors in this exquisitely intricate temporal relationship between the two opposing humoral signals and the NPY network promote hyperphagia and abnormal rate of weight gain culminating in obesity and attendant metabolic disorders. Newer insights at cellular and molecular levels demonstrate that a breakdown of the integrated circuit due both to high and low abundance of NPY at target sites, underlies hyperphagia and increased adiposity. Consequently, interruption of NPYergic signaling at a single locus with NPY receptor antagonists may not be the most efficacious therapy to suppress hyperphagia and obesity. Central leptin gene therapy in rodents has been shown to subjugate, i.e. bring under homeostatic control, NPYergic signaling and suppress the age-related and dietary obesity for extended periods and thus shows promise as a newer treatment modality to curb the pandemic of obesity and metabolic syndrome.
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Affiliation(s)
- S P Kalra
- Department of Neuroscience, University of Florida, McKnight Brain Institute, PO Box 100244, Gainesville, FL 32610, USA.
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Mills RH, Sohn RK, Micevych PE. Estrogen-induced mu-opioid receptor internalization in the medial preoptic nucleus is mediated via neuropeptide Y-Y1 receptor activation in the arcuate nucleus of female rats. J Neurosci 2004; 24:947-55. [PMID: 14749439 PMCID: PMC6729811 DOI: 10.1523/jneurosci.1366-03.2004] [Citation(s) in RCA: 94] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023] Open
Abstract
The endogenous peptides beta-endorphin (beta-END) and neuropeptide Y (NPY) have been implicated in regulating sexual receptivity. Both beta-END and NPY systems are activated by estrogen and inhibit female sexual receptivity. The initial estrogen-induced sexual nonreceptivity is correlated with the activation and internalization of mu-opioid receptors (MORs), in the medial preoptic nucleus (MPN). Progesterone reverses the estrogen-induced activation/internalization of MOR and induces the sexual receptive behavior lordosis. To determine whether NPY and endogenous opioids interact, we tested the hypothesis that estrogen-induced MOR activation is mediated through NPY-Y1 receptor (Y1R) activation. Retrograde tract tracing demonstrated Y1Ron beta-END neurons that projected to the MPN. Sex steroid modulation of MOR in the MPN acts through NPY and the Y1R. Estradiol administration or intracerebroventricular injection of NPY activated/internalized Y1R in the arcuate nucleus and MOR in the MPN of ovariectomized (OVX) rats. Moreover, the selective Y1R agonist [Leu31, Pro34]-Neuropeptide Y (LPNY) internalized MOR in the MPN of OVX rats. The Y1R antagonist (Cys31, Nva34)-Neuropeptide Y (27-36)2 prevented estrogen-induced Y1R and MOR activation/internalization. NPY reversed the progesterone blockade of estradiol-induced Y1R and MOR internalization in the arcuate nucleus and MPN, respectively. Behaviorally, LPNY inhibited estrogen plus progesterone-induced lordosis, and the MOR-selective antagonist D-Phe-Cys-Tyr-d-Trp-Orn-Thr-Pen-Thr amide reversed LPNY-induced inhibition of lordosis. These results suggest that a sequential sex steroid activation of NPY and MOR circuits regulates sexual receptivity.
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Affiliation(s)
- Richard H Mills
- Department of Neurobiology, David Geffen School of Medicine, Laboratory of Neuroendocrinology, Brain Research Institute, University of California, Los Angeles, California 90095, USA.
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Kalra SP, Kalra PS. Neuropeptide Y: a physiological orexigen modulated by the feedback action of ghrelin and leptin. Endocrine 2003; 22:49-56. [PMID: 14610298 DOI: 10.1385/endo:22:1:49] [Citation(s) in RCA: 89] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/14/2003] [Accepted: 04/14/2003] [Indexed: 01/16/2023]
Abstract
Neuropeptide Y (NPY), a 36-amino-acid neuropeptide is the most potent physiological appetite transducer known. Episodic NPY neurosecretion in hypothalamic target sites is temporally linked with onset of the daily feeding pattern. Upregulation of NPY signaling in the arcuate nucleus-paraventricular nucleus (ARC-PVN) neural axis is responsible for the hyperphagia evoked by dieting, fasting, hormonal and genetic factors, and disruption in intrahypothalamic signaling. Clusters of NPY-producing neurons in the ARC that coexpress gamma- amino butyric acid and agouti-related peptide, and those in the brain stem (BS) that coexpress catecholamines and galanin, participate in disparate manners to regulate appetitive behavior. NPY receptors, Y1, Y2, and Y5, expressed by various components of the NPY network, mediate NPY-induced feeding. Imbalance in NPY signaling due either to high or low abundance of NPY at target sites elicits hyperphagia leading to increased fat accretion and obesity. Recent studies show that intermittent, feedback action of opposing afferent hormonal signals-leptin from adipose tissue and ghrelin from stomach-regulate the episodic secretion of orexigenic NPY in the PVN-ARC. Apparently, the hypothalamic NPY network is the primary common pathway intimately involved in genesis of appetite- stimulating impulses.
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Affiliation(s)
- Satya P Kalra
- Department of Neuroscience, McKnight Brain Institute, PO Box 100244, University of Florida, Gainesville, FL 32610-0244, USA.
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Abstract
Fetal swallowing has important roles in fetal gastrointestinal development, and perhaps fetal somatic growth and maturation. Ingestive behavioral responses must develop in utero to provide for acquisition of water and food intake during the neonatal period. At birth, the rat, ovine and human fetus have developed mechanisms to acquire food via intact mechanisms of taste, suckling and swallowing. Our preliminary studies suggest that in sheep and likely in human fetuses, putative orexic-mediated ingestive responses are present near term gestation. We hypothesize that both orexic (appetite) and satiety mechanisms develop during the last third of gestation and the related neurotransmitters involved in this process are functional. The potential in utero imprinting of orexic mechanisms may influence infant, childhood and ultimately adult appetite "set-points". Thus, dysfunctional appetite, and perhaps obesity, may result from maternal environmental influences during critical stages of development.
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Affiliation(s)
- Michael G Ross
- University of California, Los Angeles, Harbor-UCLA Medical Center, 1000 West, Carson Street, Box 3, Torrance, CA 90509, USA.
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Varma A, He J, Weissfeld L, Devaskar SU. Postnatal intracerebroventricular exposure to neuropeptide Y causes weight loss in female adult rats. Am J Physiol Regul Integr Comp Physiol 2003; 284:R1560-6. [PMID: 12573978 DOI: 10.1152/ajpregu.00557.2001] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Abstract
We investigated the effect of repetitive postnatal (2-7 days) intracerebroventricular administration of neuropeptide Y (NPY) on food intake and body weight gain in the 3- to 120-day-old Sprague-Dawley rats. NPY caused a 32% transient increase in body weight gain with elevated circulating insulin concentrations within 24 h. This early intervention led to the persistence of hyperinsulinemia and relative hyperleptinemia with euglycemia in the 120-day-old female alone. This perturbation was associated with 50% suppression in adult female hypothalamic NPY concentrations and a 50-85% decline in NPY immunoreactivity in the paraventricular and arcuate nuclei. This change was paralleled by a approximately 20% decline in food intake and body weight gain at 60 and 120 days. However, when exogenous NPY was stereotaxically reinjected into the paraventricular nucleus of the approximately 120-day-old adult females who were pretreated with NPY postnatally, an increase in food intake and body weight gain was noted, attesting to no disruption in the NPY end-organ responsivity. We conclude that postnatal intracerebroventricular NPY has long-lasting effects that predetermine the resultant adult phenotype in a sex-specific manner.
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Affiliation(s)
- Amit Varma
- University of Pittsburgh Schools of Medicine; Public Health, Pittsburgh, Pennsylvania 15213-3180, USA
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Kalra SP, Bagnasco M, Otukonyong EE, Dube MG, Kalra PS. Rhythmic, reciprocal ghrelin and leptin signaling: new insight in the development of obesity. REGULATORY PEPTIDES 2003; 111:1-11. [PMID: 12609743 DOI: 10.1016/s0167-0115(02)00305-1] [Citation(s) in RCA: 127] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
The hypothalamus integrates metabolic, neural and hormonal signals to evoke an intermittent appetitive drive in the daily management of energy homeostasis. Three major players identified recently in the feedback communication between the periphery and hypothalamus are leptin, ghrelin and neuropeptide Y (NPY). We propose that reciprocal circadian and ultradian rhythmicities in the afferent humoral signals, anorexigenic leptin from adipocytes and orexigenic ghrelin from stomach, encode a corresponding discharge pattern in the appetite-stimulating neuropeptide Y network in the hypothalamus. An exquisitely intricate temporal relationship among these signaling modalities with varied sites of origin is paramount in sustenance of weight control on a daily basis. Our model envisages that subtle and progressive derangements in temporal communication, imposed by environmental shifts in energy intake, impel a positive energy balance culminating in excessive weight gain and obesity. This conceptual advance provides a new target for designing pharmacologic or gene transfer therapies that would normalize the rhythmic patterns of afferent hormonal and efferent neurochemical messages.
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Affiliation(s)
- Satya P Kalra
- Department of Neuroscience, College of Medicine, University of Florida McKnight Brain Institute, PO Box 100244, Gainesville, FL 32610-0244, USA.
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Sohn EH, Wolden-Hanson T, Matsumoto AM. Testosterone (T)-induced changes in arcuate nucleus cocaine-amphetamine-regulated transcript and NPY mRNA are attenuated in old compared to young male brown Norway rats: contribution of T to age-related changes in cocaine-amphetamine-regulated transcript and NPY gene expression. Endocrinology 2002; 143:954-63. [PMID: 11861518 DOI: 10.1210/endo.143.3.8670] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
The age-related decrease in serum T levels is associated with impairments in food intake and weight regulation and alterations in brain peptides that regulate energy balance. To test the hypothesis that reduced T levels contribute to altered hypothalamic cocaine-amphetamine-regulated transcript (CART) and NPY gene expression, the mRNA content of these neuropeptides was measured by in situ hybridization in sham-operated (intact), castrated, and T-replaced castrated young and old male Brown Norway rats. T levels in T-replaced young and old rats were similar to those in intact young animals. Compared with castrated rats, arcuate nucleus CART mRNA was lower and NPY mRNA was higher in both young and old T-replaced castrated animals, suggesting reciprocal regulation of these peptides by T; these T-induced changes were localized primarily in the rostral arcuate and were markedly attenuated in old animals. Compared with intact animals, paraventricular nucleus CART mRNA was lower in castrated animals and similar in T-replaced young and old rats. We conclude that hypothalamic CART and NPY neurons remain responsive to T regulation in old rats, albeit less so than in young animals, suggesting that the age-related reduction of T contributes in part to altered brain neuropeptide gene expression favoring anorexia and wasting with aging.
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Affiliation(s)
- Elliott H Sohn
- Geriatric Research, Education, and Clinical Center, Veterans Administration Puget Sound Health Care System, Seattle, Washington 98108-1597, USA
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Iqbal J, Pompolo S, Murakami T, Grouzmann E, Sakurai T, Meister B, Clarke IJ. Immunohistochemical characterization of localization of long-form leptin receptor (OB-Rb) in neurochemically defined cells in the ovine hypothalamus. Brain Res 2001; 920:55-64. [PMID: 11716811 DOI: 10.1016/s0006-8993(01)02932-8] [Citation(s) in RCA: 66] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
Leptin, a hormone secreted from the adipose tissue, is involved in the regulation of food intake and neuroendocrine function, by modulation of the expression and/or function of various neuropeptides in the hypothalamus. The long isoform (OB-Rb) is the major signaling form of the leptin receptor in the hypothalamus. We have used double-labeling immunohistochemistry to examine the extent of OB-Rb expression in neurochemically defined cell types in the ovine hypothalamus. OB-Rb-like immunoreactivity was widespread within cells localized to the periventricular, paraventricular, supraoptic, dorsomedial hypothalamic, ventromedial hypothalamic and arcuate nuclei, as well as the median eminence, perifornical, anterior hypothalamic and lateral hypothalamic areas and the zona incerta. Double-labeling showed expression of OB-Rb in 59.6+/-6.0% neuropeptide Y-containing cells, 60.8+/-4.7% galanin-containing cells, 89.8+/-2.65% pro-opiomelanocortin-containing cells, 73.4+/-3.5% tyrosine hydroxylase-containing cells and 31.8+/-2.8% corticotropin-releasing factor-containing cells. Interestingly 100% of melanin-concentrating hormone and orexin positive cells were also OB-Rb immunoreactive. These data provide semi-quantitative information on the extent to which various cell types express OB-Rb in the hypothalamus. Expression of OB-Rb within specific neuropeptidergic neurons provides evidence for the direct action of leptin upon the various neurochemical systems that regulate food intake, neuroendocrine and autonomic function in the brain.
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Affiliation(s)
- J Iqbal
- Prince Henry's Institute of Medical Research, P.O. Box 5152, Victoria 3168, Clayton, Australia
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Abstract
It has been recognized for some time that a number of different neuropeptides exert powerful effects on food intake. During the last few years, the neurocircuitry within which these peptides operate has also begun to be elucidated. Peptidergic feeding-regulatory neurones are found both in the hypothalamus and the brainstem, where they act as input stations for hormonal and gastrointestinal information, respectively. These cell populations both project to several other brain regions and interconnect extensively. The present review summarizes the neuroanatomy and connectivity of some prominent peptides involved in food intake control, including neuropeptide Y, melanocortin peptides, agouti gene-related protein, cocaine- and amphetamine-regulated transcript, orexin/hypocretin, melanin-concentrating hormone and cholecystokinin. Disturbances in the hypothalamic neuropeptide systems have been implicated in the phenotype of a genetic model of fatal hypophagia, the mouse anorexia (anx) mutation, which is also discussed.
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Affiliation(s)
- C Broberger
- Department of Neuroscience, Karolinska Institutet, 171 77, Stockholm, Sweden.
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Ainslie DA, Morris MJ, Wittert G, Turnbull H, Proietto J, Thorburn AW. Estrogen deficiency causes central leptin insensitivity and increased hypothalamic neuropeptide Y. Int J Obes (Lond) 2001; 25:1680-8. [PMID: 11753591 DOI: 10.1038/sj.ijo.0801806] [Citation(s) in RCA: 156] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/28/2000] [Revised: 03/13/2001] [Accepted: 05/02/2001] [Indexed: 01/21/2023]
Abstract
OBJECTIVE Altered fat distribution is a consequence of menopause, but the mechanisms responsible are unknown. Estrogen insufficiency in humans can be modeled using ovariectomized rats. We have shown that increased adiposity in these rats is due to reduced physical activity and transient hyperphagia, and can be reversed with 17beta-estradiol treatment. The aims of this study were to examine whether this altered energy balance is associated with circulating leptin insufficiency, central leptin insensitivity, decreased hypothalamic leptin receptor (Ob-Rb) expression, and/or increased hypothalamic neuropeptide Y (NPY). METHODS Plasma leptin levels, adipose tissue ob gene expression, energy balance responses to i.c.v. leptin, hypothalamic Ob-Rb expression and NPY concentration in five separate hypothalamic regions were measured in adult female rats after either ovariectomy or sham operations. RESULTS Obesity was not associated with hypoleptinemia or decreased ob gene expression in ovariectomized rats; however, it was associated with insensitivity to central leptin administration. Food intake was less suppressed and spontaneous physical activity was less stimulated by leptin. This was not due to decreased hypothalamic Ob-Rb expression. NPY concentration in the paraventricular nucleus of the hypothalamus was elevated in the ovariectomized rats, consistent with leptin insensitivity; however this effect was transient and disappeared as body fat and leptin levels increased further and hyperphagia normalized. CONCLUSION Impaired central leptin sensitivity and overproduction of NPY may contribute to excess fat accumulation caused by estrogen deficiency.
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Affiliation(s)
- D A Ainslie
- Department of Medicine, University of Melbourne, Parkville, Victoria, Australia
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Ichimaru T, Mori Y, Okamura H. A possible role of neuropeptide Y as a mediator of undernutrition to the hypothalamic gonadotropin-releasing hormone pulse generator in goats. Endocrinology 2001; 142:2489-98. [PMID: 11356698 DOI: 10.1210/endo.142.6.8002] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
To understand central mechanisms for nutritional infertility, the activity of the GnRH pulse generator was directly assessed in ovariectomized (OVX) goats under several experimental conditions by recording characteristic increases in the multiple-unit activity (volleys). When estradiol (E(2))-treated animals were fasted for 4-5 days, the activity of the GnRH pulse generator was gradually suppressed, and the volley interval at the end of fasting was significantly prolonged, compared with that during the feeding period (67.4 vs. 49.3 min, n = 5, P < 0.01). On the other hand, such a significant effect on the pulse generator was not observed in OVX goats. In the second experiment, the animals received a bolus intracerebroventricular injection of several doses (0, 2, 5, and 20 microg/400 microl) of neuropeptide Y (NPY). Exogenous NPY dose-dependently inhibited the pulse generator activity. At the highest dosage, the 1st posttreatment volley interval was significantly longer than that of the pretreatment (112.4 vs. 32.6 min, n = 5, P < 0.01) in OVX goats. The suppressive effect of NPY was similarly observed in OVX+E(2) goats. Further, when NPY was infused (10 microg/200 microl.h for 6 h) into OVX goats, the activity of the GnRH pulse generator was almost completely inhibited during the infusion period. Hypothalamic sites responding to fasting were immunohistochemically evaluated using an antibody for Fos in castrated goats. Fos-immunoreactive neurons were found in areas adjacent to the third ventricle. Double-labeling immunohistochemistry revealed that a subpopulation of NPY neurons in the arcuate nucleus was activated in response to fasting. These results demonstrate that: 1) the activity of the GnRH pulse generator is suppressed by fasting in the presence of E(2); 2) exogenous NPY inhibits the activity of the GnRH pulse generator regardless of the presence of E(2); and 3) several hypothalamic neurons or regions, including those containing NPY in the arcuate nucleus, are activated by fasting. Collectively, these observations suggest that NPY acts as a mediator of undernutrition to the GnRH pulse generator.
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Affiliation(s)
- T Ichimaru
- Department of Physiology, National Institute of Animal Industry, Ministry of Agriculture, Forestry and Fisheries, Inashiki, Ibaraki 305, Japan
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Abstract
Melanin-concentrating hormone (MCH) is an orexigenic neuropeptide produced by neurons of the lateral hypothalamic area (LHA). Because genetic MCH deficiency induces hypophagia and loss of body fat, we hypothesized that MCH neurons may represent a specific LHA pathway that, when inhibited, contributes to the pathogenesis of certain anorexia syndromes. To test this hypothesis, we measured behavioral, hormonal, and hypothalamic neuropeptide responses in two models of hyperestrogenemia in male rats, a highly reproducible anorexia paradigm. Whereas estrogen-induced weight loss engaged multiple systems that normally favor recovery of lost weight, the expected increase of MCH mRNA expression induced by energy restriction was selectively and completely abolished. These findings identify MCH neurons as specific targets of estrogen action and suggest that inhibition of these neurons may contribute to the hypophagic effect of estrogen.
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Danzer SC, McMullen NT, Rance NE. Testosterone modulates the dendritic architecture of arcuate neuroendocrine neurons in adult male rats. Brain Res 2001; 890:78-85. [PMID: 11164770 DOI: 10.1016/s0006-8993(00)03083-3] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Recent studies have demonstrated that gonadectomy of adult male rats induces dendritic growth of neuroendocrine neurons in the arcuate nucleus. We have hypothesized that these changes are secondary to the loss of testosterone negative feedback. In the present study, we examined the effects of testosterone replacement on the dendritic morphology of arcuate neuroendocrine neurons in castrated rats. Rats were orchidectomized and implanted with silastic capsules designed to produce physiological levels of plasma testosterone (n=9) or empty silastic capsules (n=9) for 2 months. Retrograde labeling with systemically injected Fluoro-Gold, followed by intracellular injection of labeled neurons in a fixed slice preparation, were used to visualize arcuate neuroendocrine neurons. Quantitative analysis of dendritic morphology was performed using three-dimensional computer reconstruction. Serum levels of LH (luteinizing hormone) and testosterone were measured by radioimmunoassay. Treatment of castrated rats with physiological levels of testosterone significantly reduced dendritic length, volume and terminal branch number relative to the castrated rats receiving empty silastic capsules. Dendritic spine density was also greater in the testosterone-treated animals, although the total numbers of spines per dendrite was not significantly different between the two groups. In addition, testosterone replacement was effective in reducing serum LH to levels found in intact rats. These studies demonstrate that testosterone replacement suppresses the dendritic outgrowth of arcuate neuroendocrine neurons that occurs in response to castration. The parallel changes in dendritic arbor and serum LH after castration and hormone replacement suggests that the suppressive effects of testosterone are related to steroid negative feedback.
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Affiliation(s)
- S C Danzer
- Department of Pathology, University of Arizona College of Medicine, 1501 N. Campbell Avenue, Tucson, AZ 85724, USA
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