101
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Chen TT, Maevsky EI, Uchitel ML. Maintenance of homeostasis in the aging hypothalamus: the central and peripheral roles of succinate. Front Endocrinol (Lausanne) 2015; 6:7. [PMID: 25699017 PMCID: PMC4313775 DOI: 10.3389/fendo.2015.00007] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/18/2014] [Accepted: 01/14/2015] [Indexed: 12/20/2022] Open
Abstract
Aging is the phenotype resulting from accumulation of genetic, cellular, and molecular damages. Many factors have been identified as either the cause or consequence of age-related decline in functions and repair mechanisms. The hypothalamus is the source and a target of many of these factors and hormones responsible for the overall homeostasis in the body. With advanced age, the sensitivity of the hypothalamus to various feedback signals begins to decline. In recent years, several aging-related genes have been identified and their signaling pathways elucidated. These gene products include mTOR, IKK-β/NF-κB complex, and HIF-1α, an important cellular survival signal. All of these activators/modulators of the aging process have also been identified in the hypothalamus and shown to play crucial roles in nutrient sensing, metabolic regulation, energy balance, reproductive function, and stress adaptation. This illustrates the central role of the hypothalamus in aging. Inside the mitochondria, succinate is one of the most prominent intermediates of the Krebs cycle. Succinate oxidation in mitochondria provides the most powerful energy output per unit time. Extra-mitochondrial succinate triggers a host of succinate receptor (SUCN1 or GPR91)-mediated signaling pathways in many peripheral tissues including the hypothalamus. One of the actions of succinate is to stabilize the hypoxia and cellular stress conditions by inducing the transcriptional regulator HIF-1α. Through these actions, it is hypothesized that succinate has the potential to restore the gradual but significant loss in functions associated with cellular senescence and systemic aging.
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Affiliation(s)
- Thomas T. Chen
- Institute of Theoretical and Experimental Biophysics, Russian Academy of Sciences, Moscow, Russia
- *Correspondence: Thomas T. Chen, Department of Life Sciences, Santa Monica College, 1900 Pico Boulevard, Santa Monica, CA 90405, USA e-mail:
| | - Eugene I. Maevsky
- Institute of Theoretical and Experimental Biophysics, Russian Academy of Sciences, Moscow, Russia
| | - Mikhail L. Uchitel
- Institute of Theoretical and Experimental Biophysics, Russian Academy of Sciences, Moscow, Russia
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102
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Vázquez MJ, Romero-Ruiz A, Tena-Sempere M. Roles of leptin in reproduction, pregnancy and polycystic ovary syndrome: consensus knowledge and recent developments. Metabolism 2015; 64:79-91. [PMID: 25467843 DOI: 10.1016/j.metabol.2014.10.013] [Citation(s) in RCA: 45] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/11/2014] [Revised: 10/15/2014] [Accepted: 10/17/2014] [Indexed: 12/15/2022]
Abstract
As an essential function for perpetuation of species, reproduction, including puberty onset, is sensitive to the size of body energy stores and the metabolic state of the organism. Accordingly, impaired energy homeostasis, ranging from extreme leanness, such as in anorexia or cachexia, to morbid obesity has an impact on the timing of puberty and is often associated to fertility problems. The neuroendocrine basis for such phenomenon is the close connection between numerous metabolic hormones and nutritional cues with the various elements of the so-called hypothalamic-pituitary-gonadal (HPG) axis. Yet, despite previous fragmentary knowledge, it was only the discovery of the adipose-hormone, leptin, in 1994 what revolutionized our understanding on how metabolic and reproductive systems closely interplay and allowed the definition of the neurohormonal causes of perturbations of puberty and fertility in conditions of impaired body energy homeostasis. In this article, we aim to provide a synoptic view of the mechanisms whereby leptin engages in the regulation of different elements of the HPG axis, with special attention to its effects and mechanisms of action on the different elements of the reproductive brain and its proven direct effects in the gonads. In addition, we will summarize the state-of-the-art regarding the putative roles of leptin during gestation, including its potential function as placental hormone. Finally, comments will be made on the eventual leptin alterations in reproductive disorders, with special attention to the polycystic ovary syndrome (PCOS), a disease in which reproductive, metabolic and neuroendocrine alterations are commonly observed. All in all, we intend to provide an updated account of our knowledge on the physiological roles of leptin in the metabolic regulation of the reproductive axis and its eventual pathophysiological implications in prevalent reproductive disorders, such as PCOS.
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Affiliation(s)
- María Jesús Vázquez
- Department of Cell Biology, Physiology and Immunology, University of Córdoba, Spain; CIBER Fisiopatología de la Obesidad y Nutrición, Instituto de Salud Carlos III, Spain; Instituto Maimónides de Investigación Biomédica de Córdoba (IMIBIC)/Hospital Universitario Reina Sofia, 14004 Córdoba, Spain
| | - Antonio Romero-Ruiz
- Department of Cell Biology, Physiology and Immunology, University of Córdoba, Spain; CIBER Fisiopatología de la Obesidad y Nutrición, Instituto de Salud Carlos III, Spain; Instituto Maimónides de Investigación Biomédica de Córdoba (IMIBIC)/Hospital Universitario Reina Sofia, 14004 Córdoba, Spain
| | - Manuel Tena-Sempere
- Department of Cell Biology, Physiology and Immunology, University of Córdoba, Spain; CIBER Fisiopatología de la Obesidad y Nutrición, Instituto de Salud Carlos III, Spain; Instituto Maimónides de Investigación Biomédica de Córdoba (IMIBIC)/Hospital Universitario Reina Sofia, 14004 Córdoba, Spain.
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103
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Fergani C, Routly J, Jones D, Pickavance L, Smith R, Dobson H. Co-expression of c-Fos with oestradiol receptor α or somatostatin in the arcuate nucleus, ventromedial nucleus and medial preoptic area in the follicular phase of intact ewes: alteration after insulin-induced hypoglycaemia. Reprod Domest Anim 2014; 50:68-75. [PMID: 25399917 DOI: 10.1111/rda.12450] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2014] [Accepted: 10/07/2014] [Indexed: 11/29/2022]
Abstract
The aim of this study was to investigate how acute insulin-induced hypoglycaemia (IIH) alters the activity of cells containing oestradiol receptor α (ERα) or somatostatin (SST) in the arcuate nucleus (ARC) and ventromedial nucleus (VMN), and ERα cells in the medial preoptic area (mPOA) of intact ewes. Follicular phases were synchronized with progesterone vaginal pessaries. Control animals were killed at 0 h or 31 h (n = 5 and 6, respectively) after progesterone withdrawal (PW; time zero). At 28 h, five other animals received insulin (INS; 4 iu/kg) and were subsequently killed at 31 h. Hypothalamic sections were immunostained for ERα or SST each with c-Fos, a marker of neuronal transcriptional activation. Insulin did not alter the percentage of activated ERα cells in the ARC; however, it appeared visually that two insulin-treated animals (INS responders, with no LH surge) had an increase in the VMN (from 32 to 78%) and a decrease in the mPOA (from 40 to 12%) compared to no increase in the two INS non-responders (with an LH surge). The percentage of activated SST cells in the ARC was greater in all four insulin-treated animals (from 10 to 60%), whereas it was visually estimated that activated SST cells in the VMN increased only in the two insulin responders (from 10 to 70%). From these results, we suggest that IIH stimulates SST activation in the ARC as part of the glucose-sensing mechanism but ERα activation is unaffected in this region. We present evidence to support a hypothesis that disruption of the GnRH/LH surge may occur in insulin responders via a mechanism that involves, at least in part, SST cell activation in the VMN along with decreased ERα cell activation in the mPOA.
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Affiliation(s)
- C Fergani
- School of Veterinary Science, University of Liverpool, Leahurst Campus, Neston, Wirral, UK
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104
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Roa J, Tena-Sempere M. Connecting metabolism and reproduction: roles of central energy sensors and key molecular mediators. Mol Cell Endocrinol 2014; 397:4-14. [PMID: 25289807 DOI: 10.1016/j.mce.2014.09.027] [Citation(s) in RCA: 93] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/25/2014] [Revised: 09/26/2014] [Accepted: 09/26/2014] [Indexed: 12/15/2022]
Abstract
It is well established that pubertal activation of the reproductive axis and maintenance of fertility are critically dependent on the magnitude of body energy reserves and the metabolic state of the organism. Hence, conditions of impaired energy homeostasis often result in deregulation of puberty and reproduction, whereas gonadal dysfunction can be associated with the worsening of the metabolic profile and, eventually, changes in body weight. While much progress has taken place in our knowledge about the neuroendocrine mechanisms linking metabolism and reproduction, our understanding of how such dynamic interplay happens is still incomplete. As paradigmatic example, much has been learned in the last two decades on the reproductive roles of key metabolic hormones (such as leptin, insulin and ghrelin), their brain targets and the major transmitters and neuropeptides involved. Yet, the molecular mechanisms whereby metabolic information is translated and engages into the reproductive circuits remain largely unsolved. In this work, we will summarize recent developments in the characterization of the putative central roles of key cellular energy sensors, such as mTOR, in this phenomenon, and will relate these with other molecular mechanisms likely contributing to the brain coupling of energy balance and fertility. In doing so, we aim to provide an updated view of an area that, despite still underdeveloped, may be critically important to fully understand how reproduction and metabolism are tightly connected in health and disease.
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Affiliation(s)
- Juan Roa
- Department of Cell Biology, Physiology and Immunology, University of Córdoba, Cordoba, Spain; CIBER Fisiopatología de la Obesidad y Nutrición, Instituto de Salud Carlos III, Córdoba, Spain; Instituto Maimónides de Investigación Biomédica de Córdoba (IMIBIC)/Hospital Universitario Reina Sofia, 14004 Córdoba, Spain
| | - Manuel Tena-Sempere
- Department of Cell Biology, Physiology and Immunology, University of Córdoba, Cordoba, Spain; CIBER Fisiopatología de la Obesidad y Nutrición, Instituto de Salud Carlos III, Córdoba, Spain; Instituto Maimónides de Investigación Biomédica de Córdoba (IMIBIC)/Hospital Universitario Reina Sofia, 14004 Córdoba, Spain.
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105
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Abstract
The association between leptin and reproduction originated with the leptin-mediated correction of sterility in ob/ob mice and initiation of reproductive function in normal female mice. The uncovering of a central leptin pathway regulating food intake prompted the dissection of neuroendocrine mechanisms involving leptin in the metabolic control of reproduction. The absence of leptin receptors on GnRH neurons incited a search for intermediary neurons situated between leptin-responsive and GnRH neurons. This review addresses the most significant findings that have furthered our understanding of recent progress in this new field. The role of leptin in puberty was impacted by the discovery of neurons that co-express kisspeptin, neurokinin B, and dynorphin and these could act as leptin intermediates. Furthermore, the identification of first-order leptin-responsive neurons in the premammilary ventral nucleus and other brain regions opens new avenues to explore their relationship to GnRH neurons. Central to these advances is the unveiling that agouti-related protein/neuropeptide Y neurons project onto GnRH and kisspeptin neurons, allowing for a crosstalk between food intake and reproduction. Finally, while puberty is a state of leptin sensitivity, mid-gestation represents a state of leptin resistance aimed at building energy stores to sustain pregnancy and lactation. The mechanisms underlying leptin resistance in pregnancy have lagged; however, the establishment of this natural state is significant. Reproduction and energy balance are tightly controlled and backed up by redundant mechanisms that are critical for the survival of our species. It will be the goal of the following decade to shed new light on these complex and essential pathways.
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Affiliation(s)
- Farid F Chehab
- Department of Laboratory MedicineUniversity of California, San Francisco, San Francisco, California 94132, USA
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106
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Rønnekleiv OK, Fang Y, Zhang C, Nestor CC, Mao P, Kelly MJ. Research resource: Gene profiling of G protein-coupled receptors in the arcuate nucleus of the female. Mol Endocrinol 2014; 28:1362-80. [PMID: 24933249 PMCID: PMC4116592 DOI: 10.1210/me.2014-1103] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
The hypothalamic arcuate nucleus controls many critical homeostatic functions including energy homeostasis, reproduction, and motivated behavior. Although G protein-coupled receptors (GPCRs) are involved in the regulation of these functions, relatively few of the GPCRs have been identified specifically within the arcuate nucleus. Here, using TaqMan low-density arrays we quantified the mRNA expression of nonolfactory GPCRs in mouse arcuate nucleus. An unprecedented number of GPCRs (total of 292) were found to be expressed, of which 183 were known and 109 were orphan GPCRs. The known GPCR genes expressed were classified into several functional clusters including hormone/neurotransmitter, growth factor, angiogenesis and vasoactivity, inflammation and immune system, and lipid messenger receptors. The plethora of orphan genes expressed in the arcuate nucleus were classified into 5 structure-related classes including class A (rhodopsin-like), class B (adhesion), class C (other GPCRs), nonsignaling 7-transmembrane chemokine-binding proteins, and other 7-transmembrane proteins. Therefore, for the first time, we provide a quantitative estimate of the numerous GPCRs expressed in the hypothalamic arcuate nucleus. Finally, as proof of principle, we documented the expression and function of one of these receptor genes, the glucagon-like peptide 1 receptor (Glp1r), which was highly expressed in the arcuate nucleus. Single-cell RT-PCR revealed that Glp1r mRNA was localized in proopiomelanocortin neurons, and using whole-cell recording we found that the glucagon-like peptide 1-selective agonist exendin-4 robustly excited proopiomelanocortin neurons. Thus, the quantitative GPCR data emphasize the complexity of the hypothalamic arcuate nucleus and furthermore provide a valuable resource for future neuroendocrine/endocrine-related experiments.
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Affiliation(s)
- Oline K Rønnekleiv
- Department of Physiology and Pharmacology (O.K.R., Y.F., C.Z., C.CN., P.M., M.J.K.), Oregon Health and Science University, Portland, Oregon 97239; and Division of Neuroscience (O.K.R., P.M., M.J.K.), Oregon National Primate Research Center, Oregon Health and Science University, Beaverton, Oregon 97006
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107
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Skrapits K, Borsay BÁ, Herczeg L, Ciofi P, Bloom SR, Ghatei MA, Dhillo WS, Liposits Z, Hrabovszky E. Colocalization of cocaine- and amphetamine-regulated transcript with kisspeptin and neurokinin B in the human infundibular region. PLoS One 2014; 9:e103977. [PMID: 25084101 PMCID: PMC4118993 DOI: 10.1371/journal.pone.0103977] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2014] [Accepted: 07/08/2014] [Indexed: 01/08/2023] Open
Abstract
Kisspeptin (KP)- and neurokinin B (NKB)- synthesizing neurons of the hypothalamic arcuate nucleus play a pivotal role in the regulation of pulsatile gonadotropin-releasing hormone (GnRH) secretion. Unlike in rodents and sheep, the homologous KP and NKB neurons in the human infundibular region rarely express dynorphin- but often exhibit Substance P (SP) immunoreactivity, indicating remarkable species differences in the neurochemical phenotype of these neurons. In search for additional neuropeptides in human KP and NKB neurons, we carried out immunofluorescent studies on hypothalamic sections obtained from five postmenopausal women. Colocalization experiments provided evidence for the presence of cocaine- and amphetamine-regulated transcript (CART) in 47.9±6.6% of KP-immunoreactive (IR) and 30.0±4.9% of NKB-IR perikarya and in 17.0±2.3% of KP-IR and 6.2±2.0% of NKB-IR axon varicosities. All three neuropeptides were present in 33.3±4.9% of KP-IR and 28.2±4.6% of NKB-IR somata, respectively, whereas triple-labeling showed lower incidences in KP-IR (14.3±1.8%) and NKB-IR (5.9±2.0%) axon varicosities. CART-IR KP and NKB neurons established contacts with other peptidergic cells, including GnRH-IR neurons and also sent projections to the infundibular stalk. KP and NKB fibers with CART often contained SP as well, while being distinct from CART fibers co-containing the orexigenic peptide agouti-related protein. Presence of CART in human, but not rodent, KP and NKB neurons represents a new example of species differences in the neuropeptide repertoire of mediobasal hypothalamic KP and NKB neurons. Target cells, receptor sites and physiological significance of CART in the efferent communication of KP and NKB neurons in primates require clarification.
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Affiliation(s)
- Katalin Skrapits
- Laboratory of Endocrine Neurobiology, Institute of Experimental Medicine, Hungarian Academy of Sciences, Budapest, Hungary
| | - Beáta Á. Borsay
- Department of Forensic Medicine, Faculty of Medicine of the University of Debrecen, Debrecen, Hungary
| | - László Herczeg
- Department of Forensic Medicine, Faculty of Medicine of the University of Debrecen, Debrecen, Hungary
| | | | - Stephen R. Bloom
- Department of Investigative Medicine, Hammersmith Hospital, Imperial College London, London, United Kingdom
| | - Mohammad A. Ghatei
- Department of Investigative Medicine, Hammersmith Hospital, Imperial College London, London, United Kingdom
| | - Waljit S. Dhillo
- Department of Investigative Medicine, Hammersmith Hospital, Imperial College London, London, United Kingdom
| | - Zsolt Liposits
- Laboratory of Endocrine Neurobiology, Institute of Experimental Medicine, Hungarian Academy of Sciences, Budapest, Hungary
- Department of Neuroscience, Faculty of Information Technology, Pázmány Péter Catholic University, Budapest, Hungary
| | - Erik Hrabovszky
- Laboratory of Endocrine Neurobiology, Institute of Experimental Medicine, Hungarian Academy of Sciences, Budapest, Hungary
- * E-mail:
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108
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Amstalden M, Cardoso RC, Alves BRC, Williams GL. Reproduction Symposium: hypothalamic neuropeptides and the nutritional programming of puberty in heifers. J Anim Sci 2014; 92:3211-22. [PMID: 24894003 DOI: 10.2527/jas.2014-7808] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023] Open
Abstract
Nutrition during the juvenile period has a major impact on timing reproductive maturity in heifers. Restricted growth delays puberty, whereas elevated BW gain advances the onset of puberty. The initiation of high-frequency episodic release of GnRH and, consequently, LH during the peripubertal period is crucial for maturation of the reproductive axis and establishment of normal estrous cycles. Nutritional signals are perceived by metabolic-sensing cells in the hypothalamus, which interact with estradiol-receptive neurons to regulate the secretory activity of GnRH neurons. The orexigenic peptide, neuropeptide Y (NPY), and the anorexigenic peptide derived from the proopiomelanocortin (POMC) gene, melanocyte-stimulating hormone α (αMSH), are believed to be major afferent pathways that transmit inhibitory (NPY) and excitatory (αMSH) inputs to GnRH neurons. The neuropeptide kisspeptin is considered a major stimulator of GnRH secretion and has been shown to mediate estradiol's effect on GnRH neuronal activity. Kisspeptin may also integrate the neuronal pathways mediating the metabolic and gonadal steroid hormone control of gonadotropin secretion. Recent studies in our laboratories indicate that functional and structural changes in the pathways involving NPY, POMC, and kisspeptin neurons occur in response to high rates of BW gain during the juvenile period in heifers. Changes include regulation of expression in NPY, POMC, and KISS1 and plasticity in the neuronal projections to GnRH neurons and within the neuronal network comprising these cells. Moreover, an intricate pattern of differential gene expression in the arcuate nucleus of the hypothalamus occurs in response to feeding high concentrate diets that promote elevated BW gain. Genes involved include those controlling feeding intake and cell metabolism, neuronal growth and remodeling, and synaptic transmission. Characterizing the cellular pathways and molecular networks involved in the mechanisms that control the timing of pubertal onset will assist in improving existing strategies and facilitate the development of novel approaches to program puberty in heifers. These include the use of diets that elevate BW gain during strategic periods of prepubertal development.
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Affiliation(s)
- M Amstalden
- Department of Animal Science, Texas A&M University, College Station 77843
| | - R C Cardoso
- Department of Animal Science, Texas A&M University, College Station 77843 Animal Reproduction Laboratory, Texas A&M AgriLife Research, Beeville 78102
| | - B R C Alves
- Department of Animal Science, Texas A&M University, College Station 77843
| | - G L Williams
- Department of Animal Science, Texas A&M University, College Station 77843 Animal Reproduction Laboratory, Texas A&M AgriLife Research, Beeville 78102
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109
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Fontana R, Della Torre S, Meda C, Longo A, Eva C, Maggi AC. Estrogen replacement therapy regulation of energy metabolism in female mouse hypothalamus. Endocrinology 2014; 155:2213-21. [PMID: 24635349 DOI: 10.1210/en.2013-1731] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
Abstract
Estrogens play an important role in the regulation of energy homeostasis in female mammals and a reduced ovarian function, due to natural aging or surgery, is associated with body weight increase and fat redistribution. This disruption of energy homeostasis may constitute a trigger for several pathologies known to be associated with climacterium; however, so far, limited attention has been devoted to the ability of estrogen replacement therapies (ERT) to reinstate the balanced energy metabolism characteristic of cycling female mammals. The purpose of the present study was to compare the efficacy of selected ERTs in reversing the ovariectomy-induced gain in body weight. To this aim female ERE-Luc mice were ovariectomized and, after 3 weeks, treated per os for 21 days with: conjugated estrogens, two selective estrogen receptor modulators (bazedoxifene and raloxifene), and the combination of bazedoxifene plus conjugated estrogens (tissue-selective estrogen complex, TSEC). The study shows that the therapy based on TSEC was the most efficacious in reducing the body weight accrued by ovariectomy (OVX). In addition, by means of in vivo imaging, the TSEC treatment was shown to increase estrogen receptor (ER) transcriptional activity selectively in the arcuate nucleus, which is a key area for the control of energy homeostasis. Finally, quantitative analysis of the mRNAs encoding orexigenic and anorexigenic peptides indicated that following ERT with TSEC there was a significant change in Agrp, NPY, and Kiss-1 mRNA accumulation in the whole hypothalamus. Considering that prior studies showed that ERT with TSEC was able to mimic the rhythm of ER oscillatory activity during the reproductive cycle and that such fluctuations were relevant for energy metabolism, the present observations further point to the ER tetradian oscillation as an important component of the ER signaling necessary for the full hormone action and therefore for an efficacious ERT.
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Affiliation(s)
- Roberta Fontana
- Center of Excellence on Neurodegenerative Diseases and Department of Pharmacological and Biomolecular Sciences (R.F., S.D.T, C.M., A.M), University of Milan, 21022 Milan, Italy; Department of Drug Discovery and Development, Italian Institute of Technology, 16163 Genova, Italy (R.F.); Neuroscience Institute Cavalieri Ottolenghi, (A.L., E.C.) 10043 Turin, Italy
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110
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Cardoso RC, Alves BRC, Prezotto LD, Thorson JF, Tedeschi LO, Keisler DH, Park CS, Amstalden M, Williams GL. Use of a stair-step compensatory gain nutritional regimen to program the onset of puberty in beef heifers. J Anim Sci 2014; 92:2942-9. [PMID: 24879767 DOI: 10.2527/jas.2014-7713] [Citation(s) in RCA: 47] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023] Open
Abstract
It was hypothesized that metabolic programming of processes underlying puberty can be shifted temporally through the use of a stair-step compensatory growth model such that puberty is optimally timed to occur at 11 to 12 mo of age. Forty crossbred beef heifers were weaned at approximately 3.5 mo of age and, after a 2-wk acclimation period, were assigned randomly to 1 of 4 nutritional groups: 1) low control (LC), restricted feed intake of a forage-based diet to promote BW gain of 0.5 kg/d until 14 mo of age, 2) high control (HC), controlled feed intake of a high-concentrate diet to promote BW gain of 1 kg/d until 14 mo of age, 3) stair-step 1 (SS-1), ad libitum feed intake of a high-concentrate diet until 6.5 mo of age followed by restricted access to a high-forage diet to promote BW gain of 0.35 kg/d until 9 mo of age, ad libitum feed intake of a high-concentrate diet until 11.5 mo of age, and restricted intake of a high-forage diet to promote BW gain of 0.35 kg/d until 14 mo of age, and 4) stair-step 2 (SS-2), reverse sequence of SS-1, beginning with restricted access to a high-forage diet. Body weight (every 2 wk) and circulating concentrations of leptin (monthly) were determined throughout the experiment. Concentrations of progesterone in blood samples collected twice weekly beginning at 8 mo of age were used to determine pubertal status. Body weight gain followed a pattern similar to that proposed in our experimental design. Circulating concentrations of leptin increased following distinct elevations in BW but decreased abruptly after feed intake restriction. Survival analysis indicated that the percentage of pubertal heifers in the LC group was lower (P < 0.05) than all other groups throughout the experiment. Although heifers in SS-1 were nutritionally restricted between 6.5 and 9 mo of age, the proportion pubertal by 12 mo of age did not differ (P = 0.36) from that of the HC group, with 80% and 70% pubertal in SS-1 and HC, respectively. In contrast, the proportion of heifers pubertal by 12 mo of age in the SS-2 group (40%) was lower (P < 0.05) than both HC and SS-1. However, by 14 mo of age, 90% of heifers in the SS-2 group had also attained puberty compared to only 40% of the LC group. In summary, these data provide evidence that changes in the nutritional and metabolic status during the early juvenile period can program the onset of puberty that occurs months later, allowing optimal timing of sexual maturation in replacement beef heifers.
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Affiliation(s)
- R C Cardoso
- Animal Reproduction Laboratory, Texas A&M AgriLife Research, Beeville 78102 Department of Animal Science, Texas A&M University, College Station 77843
| | - B R C Alves
- Department of Animal Science, Texas A&M University, College Station 77843
| | - L D Prezotto
- Animal Reproduction Laboratory, Texas A&M AgriLife Research, Beeville 78102 Department of Animal Science, Texas A&M University, College Station 77843
| | - J F Thorson
- Animal Reproduction Laboratory, Texas A&M AgriLife Research, Beeville 78102 Department of Animal Science, Texas A&M University, College Station 77843
| | - L O Tedeschi
- Department of Animal Science, Texas A&M University, College Station 77843
| | - D H Keisler
- Division of Animal Sciences, University of Missouri, Columbia 65211
| | - C S Park
- Department of Animal Sciences, North Dakota State University, Fargo 58108
| | - M Amstalden
- Department of Animal Science, Texas A&M University, College Station 77843
| | - G L Williams
- Animal Reproduction Laboratory, Texas A&M AgriLife Research, Beeville 78102 Department of Animal Science, Texas A&M University, College Station 77843
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111
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Sliwowska JH, Fergani C, Gawałek M, Skowronska B, Fichna P, Lehman MN. Insulin: its role in the central control of reproduction. Physiol Behav 2014; 133:197-206. [PMID: 24874777 DOI: 10.1016/j.physbeh.2014.05.021] [Citation(s) in RCA: 62] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2013] [Revised: 05/13/2014] [Accepted: 05/19/2014] [Indexed: 12/11/2022]
Abstract
Insulin has long been recognized as a key regulator of energy homeostasis via its actions at the level of the brain, but in addition, plays a role in regulating neural control of reproduction. In this review, we consider and compare evidence from animal models demonstrating a role for insulin for physiological control of reproduction by effects on GnRH/LH secretion. We also review the role that insulin plays in prenatal programming of adult reproduction, and consider specific candidate neurons in the adult hypothalamus by which insulin may act to regulate reproductive function. Finally, we review clinical evidence of the role that insulin may play in adult human fertility and reproductive disorders. Overall, while insulin appears to have a significant impact on reproductive neuroendocrine function, there are many unanswered questions regarding its precise sites and mechanisms of action, and their impact on developing and adult reproductive neuroendocrine function.
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Affiliation(s)
- Joanna H Sliwowska
- Laboratory of Neurobiology, Institute of Zoology, Poznan University of Life Sciences, ul. Wojska Polskiego 71 C, 60-625 Poznan, Poland.
| | - Chrysanthi Fergani
- Department of Neurobiology and Anatomical Sciences, University of Mississippi Medical Center, Jackson, MS 39232, USA.
| | - Monika Gawałek
- Laboratory of Neurobiology, Institute of Zoology, Poznan University of Life Sciences, ul. Wojska Polskiego 71 C, 60-625 Poznan, Poland.
| | - Bogda Skowronska
- Department of Pediatric Diabetes and Obesity, Poznan University of Medical Sciences, Szpitalna Str. 27/33, 60-572 Poznan, Poland.
| | - Piotr Fichna
- Department of Pediatric Diabetes and Obesity, Poznan University of Medical Sciences, Szpitalna Str. 27/33, 60-572 Poznan, Poland.
| | - Michael N Lehman
- Department of Neurobiology and Anatomical Sciences, University of Mississippi Medical Center, Jackson, MS 39232, USA.
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112
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Fergani C, Routly JE, Jones DN, Pickavance LC, Smith RF, Dobson H. Kisspeptin, c-Fos and CRFR type 2 co-expression in the hypothalamus after insulin-induced hypoglycaemia. Reprod Domest Anim 2014; 49:433-40. [PMID: 24716653 DOI: 10.1111/rda.12293] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2013] [Accepted: 01/21/2014] [Indexed: 11/27/2022]
Abstract
Normal reproductive function is dependent upon availability of glucose and insulin-induced hypoglycaemia is a metabolic stressor known to disrupt the ovine oestrous cycle. We have recently shown that IIH has the ability to delay the LH surge of intact ewes. In the present study, we examined brain tissue to determine: (i) which hypothalamic regions are activated with respect to IIH and (ii) the effect of IIH on kisspeptin cell activation and CRFR type 2 immunoreactivity, all of which may be involved in disruptive mechanisms. Follicular phases were synchronized with progesterone vaginal pessaries and at 28 h after progesterone withdrawal (PW), animals received saline (n = 6) or insulin (4 IU/kg; n = 5) and were subsequently killed at 31 h after PW (i.e., 3 h after insulin administration). Peripheral hormone concentrations were evaluated, and hypothalamic sections were immunostained for either kisspeptin and c-Fos (a marker of neuronal activation) or CRFR type 2. Within 3 h of treatment, cortisol concentrations had increased whereas plasma oestradiol concentrations decreased in peripheral plasma (p < 0.05 for both). In the arcuate nucleus (ARC), insulin-treated ewes had an increased expression of c-Fos. Furthermore, the percentage of kisspeptin cells co-expressing c-Fos increased in the ARC (from 11 to 51%; p < 0.05), but there was no change in the medial pre-optic area (mPOA; 14 vs 19%). CRFR type 2 expression in the lower part of the ARC and the median eminence was not altered by insulin treatment. Thus, disruption of the LH surge after IIH in the follicular phase is not associated with decreased kisspeptin cell activation or an increase in CRFR type 2 in the ARC but may involve other cell types located in the ARC nucleus which are activated in response to IIH.
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Affiliation(s)
- C Fergani
- School of Veterinary Science, University of Liverpool, Neston, UK
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113
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Rizwan MZ, Harbid AA, Inglis MA, Quennell JH, Anderson GM. Evidence that hypothalamic RFamide related peptide-3 neurones are not leptin-responsive in mice and rats. J Neuroendocrinol 2014; 26:247-57. [PMID: 24612072 DOI: 10.1111/jne.12140] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/30/2013] [Revised: 02/05/2014] [Accepted: 02/22/2014] [Indexed: 12/22/2022]
Abstract
Leptin, a permissive hormonal regulator of fertility, provides information about the body's energy reserves to the hypothalamic gonadotrophin-releasing hormone (GnRH) neuronal system that drives reproduction. Leptin does not directly act on GnRH neurones, and the neuronal pathways that it uses remain unclear. RFamide-related peptide-3 (RFRP-3) neurones project to GnRH neurones and primarily inhibit their activity. We tested whether leptin could act via RFRP-3 neurones to potentially modulate GnRH activity. First, the effects of leptin deficiency or high-fat diet-induced obesity on RFRP-3 cell numbers and gene expression were assessed in male and female mice. There was no significant difference in Rfrp mRNA levels or RFRP-3-immunoreactive cell counts in wild-type versus leptin-deficient ob/ob animals, or in low-fat versus high-fat diet fed wild-type mice. Second, the presence of leptin-induced signalling in RFRP-3 neurones was examined in male and female wild-type mice and rats. Dual label immunohistochemistry revealed leptin-induced phosphorylated signal transducer and activator of transcription-3 in close proximity to RFRP-3 neurones, although there was very little (2-13%) colocalisation and no significant differences between vehicle and leptin-treated animals. Furthermore, we were unable to detect leptin receptor mRNA in a semi-purified RFRP-3 cell preparation. Because GABA neurones form critical leptin-responsive GnRH inputs, we also determined whether RFRP-3 and GABA cells were colocalised. No such colocalisation was detected. These results support the concept that leptin has little or no effects on RFRP-3 neurones, and that these neurones are unlikely to be an important neuronal pathway for the metabolic regulation of fertility by leptin.
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Affiliation(s)
- M Z Rizwan
- Centre for Neuroendocrinology and Department of Anatomy, University of Otago School of Medical Sciences, Dunedin, New Zealand
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114
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Abstract
Kisspeptin is vital for the neuroendocrine regulation of GNRH secretion. Kisspeptin neurons are now recognized as a central pathway responsible for conveying key homeostatic information to GNRH neurons. This pathway is likely to mediate the well-established link between energy balance and reproductive function. Thus, in states of severely altered energy balance (either negative or positive), fertility is compromised, as isKiss1expression in the arcuate nucleus. A number of metabolic modulators have been proposed as regulators of kisspeptin neurons including leptin, ghrelin, pro-opiomelanocortin (POMC), and neuropeptide Y (NPY). Whether these regulate kisspeptin neurons directly or indirectly will be discussed. Moreover, whether the stimulatory role of leptin on reproduction is mediated by kisspeptin directly will be questioned. Furthermore, in addition to being expressed in GNRH neurons, the kisspeptin receptor (Kiss1r) is also expressed in other areas of the brain, as well as in the periphery, suggesting alternative roles for kisspeptin signaling outside of reproduction. Interestingly, kisspeptin neurons are anatomically linked to, and can directly excite, anorexigenic POMC neurons and indirectly inhibit orexigenic NPY neurons. Thus, kisspeptin may have a direct role in regulating energy balance. Although data fromKiss1rknockout and WT mice found no differences in body weight, recent data indicate that kisspeptin may still play a role in food intake and glucose homeostasis. Thus, in addition to regulating reproduction, and mediating the effect of energy balance on reproductive function, kisspeptin signaling may also be a direct regulator of metabolism.
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115
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Bhattarai JP, Roa J, Herbison AE, Han SK. Serotonin acts through 5-HT1 and 5-HT2 receptors to exert biphasic actions on GnRH neuron excitability in the mouse. Endocrinology 2014; 155:513-24. [PMID: 24265447 DOI: 10.1210/en.2013-1692] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
The effect of serotonin (5-HT) on the electrical excitability of GnRH neurons was examined using gramicidin perforated-patch electrophysiology in transgenic GnRH-green fluorescent protein mice. In diestrous female, the predominant effect of 5-HT was inhibition (70%) with 50% of these cells also exhibiting a late-onset excitation. Responses were dose dependent (EC(50) = 1.2μM) and persisted in the presence of amino acid receptor antagonists and tetrodotoxin, indicating a predominant postsynaptic action of 5-HT. Studies in neonatal, juvenile, peripubertal, and adult mice revealed that 5-HT exerted less potent responses from GnRH neurons with advancing postnatal age in both sexes. In adult male mice, 5-HT exerted less potent hyperpolarizing responses with more excitations compared with females. In addition, adult proestrous female GnRH neurons exhibited reduced inhibition and a complete absence of biphasic hyperpolarization-excitation responses. Studies using 5-HT receptor antagonists demonstrated that the activation of 5-HT(1A) receptors mediated the inhibitory responses, whereas the excitation was mediated by the activation of 5-HT(2A) receptors. The 5-HT-mediated hyperpolarization involved both potassium channels and adenylate cyclase activation, whereas the 5-HT excitation was dependent on protein kinase C. The effects of exogenous 5-HT were replicated using fluoxetine, which enhances endogenous 5-HT levels. These studies demonstrate that 5-HT exerts a biphasic action on most GnRH neurons whereby a fast 5HT(1A)-mediated inhibition occurs alongside a slow 5-HT(2A) excitation. The balance of 5-HT-evoked inhibition vs excitation is developmentally regulated, sexually differentiated, and variable across the estrous cycle and may play a role in regulation of hypothalamic-pituitary-gonadal axis throughout postnatal development.
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Affiliation(s)
- Janardhan P Bhattarai
- Department of Oral Physiology (J.P.B., S.K.H.), School of Dentistry and Institute of Oral Bioscience, Chonbuk National University, Jeonju 561-756, Republic of Korea; and Centre for Neuroendocrinology and Department of Physiology (J.R., A.E.H.), University of Otago School of Medical Sciences, Dunedin 9054, New Zealand
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116
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Ramos CF, Zamoner A. Thyroid hormone and leptin in the testis. Front Endocrinol (Lausanne) 2014; 5:198. [PMID: 25505448 PMCID: PMC4243692 DOI: 10.3389/fendo.2014.00198] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/03/2014] [Accepted: 11/10/2014] [Indexed: 12/18/2022] Open
Abstract
Leptin is primarily expressed in white adipose tissue; however, it is expressed in the hypothalamus and reproductive tissues as well. Leptin acts by activating the leptin receptors (Ob-Rs). Additionally, the regulation of several neuroendocrine and reproductive functions, including the inhibition of glucocorticoids and enhancement of thyroxine and sex hormone concentrations in human beings and mice are leptin functions. It has been suggested that thyroid hormones (TH) could directly regulate leptin expression. Additionally, hypothyroidism compromises the intracellular integration of leptin signaling specifically in the arcuate nucleus. Two TH receptor isoforms are expressed in the testis, TRa and TRb, with TRa being the predominant one that is present in all stages of development. The effects of TH involve the proliferation and differentiation of Sertoli and Leydig cells during development, spermatogenesis, and steroidogenesis. In this context, TH disorders are associated with sexual dysfunction. An endocrine and/or direct paracrine effect of leptin on the gonads inhibits testosterone production in Leydig cells. Further studies are necessary to clarify the effects of both hormones in the testis during hypothyroidism. The goal of this review is to highlight the current knowledge regarding leptin and TH in the testis.
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Affiliation(s)
- Cristiane Fonte Ramos
- Laboratory of Morphometry, Metabolism and Cardiovascular Disease, Department of Anatomy, Biomedical Center, Institute of Biology, State University of Rio de Janeiro, Rio de Janeiro, Brazil
- *Correspondence: Cristiane Fonte Ramos, Laboratório de Morfometria, Metabolismo e Doença Cardiovascular, Centro Biomédico, Instituto de Biologia, Universidade do Estado do Rio de Janeiro. Av 28 de Setembro 87 fds, Rio de Janeiro 20551-030, RJ, Brazil e-mail:
| | - Ariane Zamoner
- Departamento de Bioquímica, Centro de Ciências Biológicas, Universidade Federal de Santa Catarina, Florianópolis, Brazil
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Verma S, Kirigiti M, Millar RP, Grove KL, Smith MS. Endogenous kisspeptin tone is a critical excitatory component of spontaneous GnRH activity and the GnRH response to NPY and CART. Neuroendocrinology 2014; 99:190-203. [PMID: 25011649 PMCID: PMC4201869 DOI: 10.1159/000365419] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/18/2013] [Accepted: 06/22/2014] [Indexed: 12/17/2022]
Abstract
BACKGROUND/AIMS Kisspeptin is the major excitatory regulator of gonadotropin-releasing hormone (GnRH) neurons and is responsible for basal GnRH/LH release and the GnRH/LH surge. Although it is widely assumed, based on mutations in kisspeptin and Kiss1R, that kisspeptin acts to sustain basal GnRH neuronal activity, there have been no studies to investigate whether endogenous basal kisspeptin tone plays a direct role in basal spontaneous GnRH neuronal excitability. It is also of interest to examine possible interactions between endogenous kisspeptin tone and other neuropeptides that have direct effects on GnRH neurons, such as neuropeptide Y (NPY) or cocaine- and amphetamine-regulated transcript (CART), since the activity of all these neuropeptides changes during states of negative energy balance. METHODS Loose cell-attached and whole-cell current patch-clamp recordings were made from GnRH-GFP neurons in hypothalamic slices from female and male rats. RESULTS Kisspeptin activated GnRH neurons in a concentration-dependent manner with an EC50 of 3.32 ± 0.02 nM. Surprisingly, a kisspeptin antagonist, Peptide 347, suppressed spontaneous activity in GnRH neurons, demonstrating the essential nature of the endogenous kisspeptin tone. Furthermore, inhibition of endogenous kisspeptin tone blocked the direct activation of GnRH cells that occurs in response to antagonism of NPY Y5 receptor or by CART. CONCLUSIONS Our electrophysiology studies suggest that basal endogenous kisspeptin tone is not only essential for spontaneous GnRH neuronal firing, but it is also required for the net excitatory effects of other neuropeptides, such as CART or NPY antagonism, on GnRH neurons. Therefore, endogenous kisspeptin tone could serve as the linchpin in GnRH activation or inhibition.
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Affiliation(s)
- Saurabh Verma
- Division of Diabetes, Obesity and Metabolism, Oregon National Primate Research Center, Oregon Health & Science University, Beaverton, Oregon 97006
| | - Melissa Kirigiti
- Division of Diabetes, Obesity and Metabolism, Oregon National Primate Research Center, Oregon Health & Science University, Beaverton, Oregon 97006
| | - Robert P. Millar
- MRC Receptor Biology & Reproductive Health, University of Pretoria, Pretoria, South Africa
| | - Kevin L. Grove
- Division of Diabetes, Obesity and Metabolism, Oregon National Primate Research Center, Oregon Health & Science University, Beaverton, Oregon 97006
| | - M. Susan Smith
- Division of Diabetes, Obesity and Metabolism, Oregon National Primate Research Center, Oregon Health & Science University, Beaverton, Oregon 97006
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118
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Leptin signaling in GABA neurons, but not glutamate neurons, is required for reproductive function. J Neurosci 2013; 33:17874-83. [PMID: 24198376 DOI: 10.1523/jneurosci.2278-13.2013] [Citation(s) in RCA: 66] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
The adipocyte-derived hormone leptin acts in the brain to modulate the central driver of fertility: the gonadotropin releasing hormone (GnRH) neuronal system. This effect is indirect, as GnRH neurons do not express leptin receptors (LEPRs). Here we test whether GABAergic or glutamatergic neurons provide the intermediate pathway between the site of leptin action and the GnRH neurons. Leptin receptors were deleted from GABA and glutamate neurons using Cre-Lox transgenics, and the downstream effects on puberty onset and reproduction were examined. Both mouse lines displayed the expected increase in body weight and region-specific loss of leptin signaling in the hypothalamus. The GABA neuron-specific LEPR knock-out females and males showed significantly delayed puberty onset. Adult fertility observations revealed that these knock-out animals have decreased fecundity. In contrast, glutamate neuron-specific LEPR knock-out mice displayed normal fertility. Assessment of the estrogenic hypothalamic-pituitary-gonadal axis regulation in females showed that leptin action on GABA neurons is not necessary for estradiol-mediated suppression of tonic luteinizing hormone secretion (an indirect measure of GnRH neuron activity) but is required for regulation of a full preovulatory-like luteinizing hormone surge. In conclusion, leptin signaling in GABAergic (but not glutamatergic neurons) plays a critical role in the timing of puberty onset and is involved in fertility regulation throughout adulthood in both sexes. These results form an important step in explaining the role of central leptin signaling in the reproductive system. Limiting the leptin-to-GnRH mediators to GABAergic cells will enable future research to focus on a few specific types of neurons.
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119
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Abstract
This paper is the thirty-fifth consecutive installment of the annual review of research concerning the endogenous opioid system. It summarizes papers published during 2012 that studied the behavioral effects of molecular, pharmacological and genetic manipulation of opioid peptides, opioid receptors, opioid agonists and opioid antagonists. The particular topics that continue to be covered include the molecular-biochemical effects and neurochemical localization studies of endogenous opioids and their receptors related to behavior (Section 2), and the roles of these opioid peptides and receptors in pain and analgesia (Section 3); stress and social status (Section 4); tolerance and dependence (Section 5); learning and memory (Section 6); eating and drinking (Section 7); alcohol and drugs of abuse (Section 8); sexual activity and hormones, pregnancy, development and endocrinology (Section 9); mental illness and mood (Section 10); seizures and neurologic disorders (Section 11); electrical-related activity and neurophysiology (Section 12); general activity and locomotion (Section 13); gastrointestinal, renal and hepatic functions (Section 14); cardiovascular responses (Section 15); respiration and thermoregulation (Section 16); and immunological responses (Section 17).
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Affiliation(s)
- Richard J Bodnar
- Department of Psychology and Neuropsychology Doctoral Sub-Program, Queens College, City University of New York, Flushing, NY 11367, United States.
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120
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Abstract
PURPOSE OF REVIEW Reproduction is a tightly regulated function in which many mechanisms contribute to ensure the survival of the species. Among those, due to the elevated energy requirements of reproduction, metabolic factors exert a pivotal role in the control of hypothalamic-pituitary-gonadal axis. Although this control may occur at multiple levels of the axis, the majority of interactions between metabolic and reproductive systems take place in the hypothalamus. In this article, we present an overview of the state-of-the-art knowledge regarding the metabolic regulation of reproduction at the central level. We aim to identify the neuroanatomical location where both functions interconnect by discussing the likelihood of each component of the neuronal hierarchical network controlling gonadotropin-releasing hormone (GnRH) release to be first-order responders to metabolic cues, especially the peripheral metabolic signals leptin, insulin, and ghrelin. RECENT FINDINGS Latest evidence suggests that the primary action of leptin, insulin, and ghrelin to regulate reproduction is located upstream of the main central elicitors of gonadotropin release, Kiss1 and GnRH neurons, and neuroanatomically separated from their metabolic action. SUMMARY The study of the neuronal interactions between the mechanisms governing metabolism and reproduction offers the platform to overcome or treat a number of prevailing metabolic and/or reproductive conditions.
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Affiliation(s)
- Víctor M Navarro
- Division of Endocrinology, Diabetes and Hypertension, Department of Medicine, Brigham and Women's Hospital and Harvard Medical School, Boston, Massachusetts 02115, USA.
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121
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Abstract
Reproductive hormones affect all stages of life from gamete production, fertilization, fetal development and parturition, neonatal development and puberty through to adulthood and senescence. The reproductive hormone cascade has, therefore, been the target for the development of numerous drugs that modulate its activity at many levels. As the central regulator of the cascade, gonadotropin-releasing hormone (GnRH) agonists and antagonists have found extensive applications in treating a wide range of hormone-dependent diseases, such as precocious puberty, prostate cancer, benign prostatic hyperplasia, endometriosis and uterine fibroids, as well as being an essential component of in vitro fertilization protocols. The neuroendocrine peptides that regulate GnRH neurons, kisspeptin and neurokinin B, have also been identified as therapeutic targets, and novel agonists and antagonists are being developed as modulators of the cascade upstream of GnRH. Here, we review the development and applications of analogues of the major neuroendocrine peptide regulators of the reproductive hormone cascade: GnRH, kisspeptin and neurokinin B.
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Affiliation(s)
- Robert P Millar
- Mammal Research Institute, Department of Zoology and Entomology, Faculty of Natural and Agricultural Sciences, University of Pretoria, South Africa.
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122
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True C, Verma S, Grove KL, Smith MS. Cocaine- and amphetamine-regulated transcript is a potent stimulator of GnRH and kisspeptin cells and may contribute to negative energy balance-induced reproductive inhibition in females. Endocrinology 2013; 154:2821-32. [PMID: 23736294 PMCID: PMC3713223 DOI: 10.1210/en.2013-1156] [Citation(s) in RCA: 69] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Cocaine- and amphetamine-regulated transcript (CART) is a hypothalamic neuropeptide implicated in both metabolic and reproductive regulation, raising the possibility that CART plays a role in reproductive inhibition during negative metabolic conditions. The current study characterized CART's regulatory influence on GnRH and kisspeptin (Kiss1) cells and determined the sensitivity of different CART populations to negative energy balance. CART fibers made close appositions to 60% of GnRH cells, with the majority of the fibers (>80%) originating from the arcuate nucleus (ARH) CART/pro-opiomelanocortin population. Electrophysiological recordings in GnRH-green fluorescent protein rats demonstrated that CART postsynaptically depolarizes GnRH cells. CART fibers from the ARH were also observed in close contact with Kiss1 cells in the ARH and anteroventral periventricular nucleus (AVPV). Recordings in Kiss1-GFP mice demonstrated CART also postsynaptically depolarizes ARH Kiss1 cells, suggesting CART may act directly and indirectly, via Kiss1 populations, to stimulate GnRH neurons. CART protein and mRNA levels were analyzed in 2 models of negative energy balance: caloric restriction (CR) and lactation. Both CART mRNA levels and the number of CART-immunoreactive cells were suppressed in the ARH during CR but not during lactation. AVPV CART mRNA was suppressed during CR, but not during lactation when there was a dramatic increase in CART-immunoreactive cells. These data suggest differing regulatory signals of CART between the models. In conclusion, both morphological and electrophysiological methods identify CART as a novel and potent stimulator of Kiss1 and GnRH neurons and suppression of CART expression during negative metabolic conditions could contribute to inhibition of the reproductive axis.
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Affiliation(s)
- Cadence True
- Divisions of Diabetes, Obesity, & Metabolism, and Neuroscience, Oregon National Primate Research Center, Oregon Health & Science University, Beaverton, OR 97006, USA
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123
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Roa J. Role of GnRH Neurons and Their Neuronal Afferents as Key Integrators between Food Intake Regulatory Signals and the Control of Reproduction. Int J Endocrinol 2013; 2013:518046. [PMID: 24101924 PMCID: PMC3786537 DOI: 10.1155/2013/518046] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/28/2013] [Accepted: 08/07/2013] [Indexed: 11/17/2022] Open
Abstract
Reproductive function is regulated by a plethora of signals that integrate physiological and environmental information. Among others, metabolic factors are key components of this circuit since they inform about the propitious timing for reproduction depending on energy availability. This information is processed mainly at the hypothalamus that, in turn, modulates gonadotropin release from the pituitary and, thereby, gonadal activity. Metabolic hormones, such as leptin, insulin, and ghrelin, act as indicators of the energy status and convey this information to the reproductive axis regulating its activity. In this review, we will analyse the central mechanisms involved in the integration of this metabolic information and their contribution to the control of the reproductive function. Particular attention will be paid to summarize the participation of GnRH, Kiss1, NPY, and POMC neurons in this process and their possible interactions to contribute to the metabolic control of reproduction.
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Affiliation(s)
- Juan Roa
- Department of Cell Biology, Physiology and Immunology, University of Córdoba, Avenida Menéndez Pidal s/n, 14004 Córdoba, Spain
- CIBER Fisiopatología de la Obesidad y Nutrición, Instituto de Salud Carlos III, Spain
- Instituto Maimónides de Investigaciones Biomédicas (IMIBIC)/Hospital Universitario Reina Sofia, Córdoba, Spain
- *Juan Roa:
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