1
|
Nakamura S, Sasaki T, Uenoyama Y, Inoue N, Nakanishi M, Yamada K, Morishima A, Suzumura R, Kitagawa Y, Morita Y, Ohkura S, Tsukamura H. Raphe glucose-sensing serotonergic neurons stimulate KNDy neurons to enhance LH pulses via 5HT2CR: rat and goat studies. Sci Rep 2024; 14:10190. [PMID: 38702366 PMCID: PMC11068885 DOI: 10.1038/s41598-024-58470-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2023] [Accepted: 03/29/2024] [Indexed: 05/06/2024] Open
Abstract
Dysfunction of central serotonergic neurons is known to cause depressive disorders in humans, who often show reproductive and/or glucose metabolism disorders. This study examined whether dorsal raphe (DR) serotonergic neurons sense high glucose availability to upregulate reproductive function via activating hypothalamic arcuate (ARC) kisspeptin neurons (= KNDy neurons), a dominant stimulator of gonadotropin-releasing hormone (GnRH)/gonadotropin pulses, using female rats and goats. RNA-seq and histological analysis revealed that stimulatory serotonin-2C receptor (5HT2CR) was mainly expressed in the KNDy neurons in female rats. The serotonergic reuptake inhibitor administration into the mediobasal hypothalamus (MBH), including the ARC, significantly blocked glucoprivic suppression of luteinizing hormone (LH) pulses and hyperglycemia induced by intravenous 2-deoxy-D-glucose (2DG) administration in female rats. A local infusion of glucose into the DR significantly increased in vivo serotonin release in the MBH and partly restored LH pulses and hyperglycemia in the 2DG-treated female rats. Furthermore, central administration of serotonin or a 5HT2CR agonist immediately evoked GnRH pulse generator activity, and central 5HT2CR antagonism blocked the serotonin-induced facilitation of GnRH pulse generator activity in ovariectomized goats. These results suggest that DR serotonergic neurons sense high glucose availability to reduce gluconeogenesis and upregulate reproductive function by activating GnRH/LH pulse generator activity in mammals.
Collapse
Affiliation(s)
- Sho Nakamura
- Laboratory of Animal Production Science, Graduate School of Bioagricultural Sciences, Nagoya University, Togo-cho, Aichi, 470-0151, Japan
| | - Takuya Sasaki
- Laboratory of Animal Production Science, Graduate School of Bioagricultural Sciences, Nagoya University, Togo-cho, Aichi, 470-0151, Japan
| | - Yoshihisa Uenoyama
- Laboratory of Animal Reproduction, Graduate School of Bioagricultural Sciences, Nagoya University, Nagoya, Aichi, 464-8601, Japan
| | - Naoko Inoue
- Laboratory of Animal Reproduction, Graduate School of Bioagricultural Sciences, Nagoya University, Nagoya, Aichi, 464-8601, Japan
| | - Marina Nakanishi
- Laboratory of Animal Reproduction, Graduate School of Bioagricultural Sciences, Nagoya University, Nagoya, Aichi, 464-8601, Japan
| | - Koki Yamada
- Laboratory of Animal Reproduction, Graduate School of Bioagricultural Sciences, Nagoya University, Nagoya, Aichi, 464-8601, Japan
| | - Ai Morishima
- Laboratory of Animal Production Science, Graduate School of Bioagricultural Sciences, Nagoya University, Togo-cho, Aichi, 470-0151, Japan
| | - Reika Suzumura
- Laboratory of Animal Production Science, Graduate School of Bioagricultural Sciences, Nagoya University, Togo-cho, Aichi, 470-0151, Japan
| | - Yuri Kitagawa
- Laboratory of Animal Production Science, Graduate School of Bioagricultural Sciences, Nagoya University, Togo-cho, Aichi, 470-0151, Japan
| | - Yasuhiro Morita
- Laboratory of Animal Production Science, Graduate School of Bioagricultural Sciences, Nagoya University, Togo-cho, Aichi, 470-0151, Japan
| | - Satoshi Ohkura
- Laboratory of Animal Production Science, Graduate School of Bioagricultural Sciences, Nagoya University, Togo-cho, Aichi, 470-0151, Japan
| | - Hiroko Tsukamura
- Laboratory of Animal Reproduction, Graduate School of Bioagricultural Sciences, Nagoya University, Nagoya, Aichi, 464-8601, Japan.
| |
Collapse
|
2
|
Li AJ, Wang Q, Rogers RC, Herman G, Ritter RC, Ritter S. Chemogenetic activation of ventral medullary astrocytes enhances feeding and corticosterone release in response to mild glucoprivation. Am J Physiol Regul Integr Comp Physiol 2023; 325:R229-R237. [PMID: 37424401 PMCID: PMC10396275 DOI: 10.1152/ajpregu.00079.2023] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2023] [Revised: 06/28/2023] [Accepted: 06/29/2023] [Indexed: 07/11/2023]
Abstract
To investigate the role of glial cells in the regulation of glucoprivic responses in rats, a chemogenetic approach was used to activate astrocytes neighboring catecholamine (CA) neurons in the ventromedial medulla (VLM) where A1 and C1 CA cell groups overlap (A1/C1). Previous results indicate that activation of CA neurons in this region is necessary and sufficient for feeding and corticosterone release in response to glucoprivation. However, it is not known whether astrocyte neighbors of CA neurons contribute to glucoregulatory responses. Hence, we made nanoinjections of AAV5-GFAP-hM3D(Gq)-mCherry to selectively transfect astrocytes in the A1/C1 region with the excitatory designer receptor exclusively activated by designer drugs (DREADDs), hM3D(Gq). After allowing time for DREADD expression, we evaluated the rats for increased food intake and corticosterone release in response to low systemic doses of the antiglycolytic agent, 2-deoxy-d-glucose (2DG), alone and in combination with the hM3D(Gq) activator clozapine-n-oxide (CNO). We found that DREADD-transfected rats ate significantly more food when 2DG and CNO were coadministered than when either 2DG or CNO was injected alone. We also found that CNO significantly enhanced 2DG-induced FOS expression in the A1/C1 CA neurons, and that corticosterone release also was enhanced when CNO and 2DG were administered together. Importantly, CNO-induced activation of astrocytes in the absence of 2DG did not trigger food intake or corticosterone release. Our results indicate that during glucoprivation, activation of VLM astrocytes cells markedly increases the sensitivity or responsiveness of neighboring A1/C1 CA neurons to glucose deficit, suggesting a potentially important role for VLM astrocytes in glucoregulation.
Collapse
Affiliation(s)
- Ai-Jun Li
- Programs in Neuroscience, Washington State University, Pullman, Washington, United States
| | - Qing Wang
- Programs in Neuroscience, Washington State University, Pullman, Washington, United States
| | - Richard C Rogers
- Autonomic Neuroscience Laboratory, Pennington Biomedical Research Center, Baton Rouge, Louisiana, United States
| | - Gerlinda Herman
- Autonomic Neuroscience Laboratory, Pennington Biomedical Research Center, Baton Rouge, Louisiana, United States
| | - Robert C Ritter
- Programs in Neuroscience, Washington State University, Pullman, Washington, United States
| | - Sue Ritter
- Programs in Neuroscience, Washington State University, Pullman, Washington, United States
| |
Collapse
|
3
|
McCosh RB, O'Bryne KT, Karsch FJ, Breen KM. Regulation of the gonadotropin-releasing hormone neuron during stress. J Neuroendocrinol 2022; 34:e13098. [PMID: 35128742 PMCID: PMC9232848 DOI: 10.1111/jne.13098] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/16/2021] [Revised: 01/14/2022] [Accepted: 01/18/2022] [Indexed: 11/30/2022]
Abstract
The effect of stress on reproduction and gonadal function has captivated investigators for almost 100 years. Following the identification of gonadotropin-releasing hormone (GnRH) 50 years ago, a niche research field emerged fixated on how stress impairs this central node controlling downstream pituitary and gonadal function. It is now clear that both episodic GnRH secretion in males and females and surge GnRH secretion in females are inhibited during a variety of stress types. There has been considerable advancement in our understanding of numerous stress-related signaling molecules and their ability to impair reproductive neuroendocrine activity during stress. Recently, much attention has turned to the effects of stress on two populations of kisspeptin neurons: the stimulatory afferents to GnRH neurons that regulate pulsatile and surge-type gonadotropin secretion. Indeed, future work is still required to fully construct the neuroanatomical framework underlying stress effects, directly or indirectly, on GnRH neuron function. The present review evaluates and synthesizes evidence related to stress-related signaling molecules acting directly on GnRH neurons. Here, we review the evidence for and against the action of a handful of signaling molecules as inhibitors of GnRH neuron function, including corticotropin-releasing hormone, urocortins, norepinephrine, cortisol/corticosterone, calcitonin gene-related peptide and arginine-phenylalanine-amide-related peptide-3.
Collapse
Affiliation(s)
- Richard B McCosh
- Department of Obstetrics, Gynecology and Reproductive Sciences, University of California, La Jolla, CA, USA
| | - Kevin T O'Bryne
- Department of Women and Children's Health, Faculty of Life Sciences and Medicine, King's College London, Guy's Campus, London, UK
| | - Fred J Karsch
- Reproductive Sciences Program and Department of Molecular and Integrative Physiology, University of Michigan, Ann Arbor, MI, USA
| | - Kellie M Breen
- Department of Obstetrics, Gynecology and Reproductive Sciences, University of California, La Jolla, CA, USA
| |
Collapse
|
4
|
Saporin as a Commercial Reagent: Its Uses and Unexpected Impacts in the Biological Sciences—Tools from the Plant Kingdom. Toxins (Basel) 2022; 14:toxins14030184. [PMID: 35324681 PMCID: PMC8952126 DOI: 10.3390/toxins14030184] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2022] [Revised: 02/23/2022] [Accepted: 02/23/2022] [Indexed: 02/02/2023] Open
Abstract
Saporin is a ribosome-inactivating protein that can cause inhibition of protein synthesis and causes cell death when delivered inside a cell. Development of commercial Saporin results in a technology termed ‘molecular surgery’, with Saporin as the scalpel. Its low toxicity (it has no efficient method of cell entry) and sturdy structure make Saporin a safe and simple molecule for many purposes. The most popular applications use experimental molecules that deliver Saporin via an add-on targeting molecule. These add-ons come in several forms: peptides, protein ligands, antibodies, even DNA fragments that mimic cell-binding ligands. Cells that do not express the targeted cell surface marker will not be affected. This review will highlight some newer efforts and discuss significant and unexpected impacts on science that molecular surgery has yielded over the last almost four decades. There are remarkable changes in fields such as the Neurosciences with models for Alzheimer’s Disease and epilepsy, and game-changing effects in the study of pain and itch. Many other uses are also discussed to record the wide-reaching impact of Saporin in research and drug development.
Collapse
|
5
|
Tsukamura H. Kobayashi Award 2019: The neuroendocrine regulation of the mammalian reproduction. Gen Comp Endocrinol 2022; 315:113755. [PMID: 33711315 DOI: 10.1016/j.ygcen.2021.113755] [Citation(s) in RCA: 28] [Impact Index Per Article: 14.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/01/2020] [Revised: 02/13/2021] [Accepted: 02/23/2021] [Indexed: 02/05/2023]
Abstract
Mammalian reproductive function is a complex system of many players orchestrated by the hypothalamus-pituitary-gonadal (HPG) axis. The hypothalamic gonadotropin-releasing hormone (GnRH) and the consequent pituitary gonadotropin release show two modes of secretory patterns, namely the surge and pulse modes. The surge mode is triggered by the positive feedback action of estrogen secreted from the mature ovarian follicle to induce ovulation in females of most mammalian species. The pulse mode of GnRH release is required for stimulating tonic gonadotropin secretion to drive folliculogenesis, spermatogenesis and steroidogenesis and is negatively fine-tuned by the sex steroids. Accumulating evidence suggests that hypothalamic kisspeptin neurons are the master regulator for animal reproduction to govern the HPG axis. Specifically, kisspeptin neurons located in the anterior hypothalamus, such as the anteroventral periventricular nucleus (AVPV) in rodents and preoptic nucleus (POA) in ruminants, primates and others, and the neurons located in the arcuate nucleus (ARC) in posterior hypothalamus in most mammals are considered to play a key role in generating the surge and pulse modes of GnRH release, respectively. The present article focuses on the role of AVPV (or POA) kisspeptin neurons as a center for GnRH surge generation and of the ARC kisspeptin neurons as a center for GnRH pulse generation to mediate estrogen positive and negative feedback mechanisms, respectively, and discusses how the estrogen epigenetically regulates kisspeptin gene expression in these two populations of neurons. This article also provides the mechanism how malnutrition and lactation suppress GnRH/gonadotropin pulses through an inhibition of the ARC kisspeptin neurons. Further, the article discusses the programming effect of estrogen on kisspeptin neurons in the developmental brain to uncover the mechanism underlying the sex difference in GnRH/gonadotropin release as well as an irreversible infertility induced by supra-physiological estrogen exposure in rodent models.
Collapse
Affiliation(s)
- Hiroko Tsukamura
- Graduate School of Bioagricultural Sciences, Nagoya University, Nagoya 464-8601, Japan.
| |
Collapse
|
6
|
Sato M, Minabe S, Sakono T, Magata F, Nakamura S, Watanabe Y, Inoue N, Uenoyama Y, Tsukamura H, Matsuda F. Morphological Analysis of the Hindbrain Glucose Sensor-Hypothalamic Neural Pathway Activated by Hindbrain Glucoprivation. Endocrinology 2021; 162:6308440. [PMID: 34161572 DOI: 10.1210/endocr/bqab125] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/06/2020] [Indexed: 01/06/2023]
Abstract
Lowered glucose availability, sensed by the hindbrain, has been suggested to enhance gluconeogenesis and food intake as well as suppress reproductive function. In fact, our previous histological and in vitro studies suggest that hindbrain ependymal cells function as a glucose sensor. The present study aimed to clarify the hindbrain glucose sensor-hypothalamic neural pathway activated in response to hindbrain glucoprivation to mediate counterregulatory physiological responses. Administration of 2-deoxy-D-glucose (2DG), an inhibitor of glucose utilization, into the fourth ventricle (4V) of male rats for 0.5 hour induced messenger RNA (mRNA) expression of c-fos, a marker for cellular activation, in ependymal cells in the 4V, but not in the lateral ventricle, the third ventricle or the central canal without a significant change in blood glucose and testosterone levels. Administration of 2DG into the 4V for 1 hour significantly increased blood glucose levels, food intake, and decreased blood testosterone levels. Simultaneously, the expression of c-Fos protein was detected in the 4V ependymal cells; dopamine β-hydroxylase-immunoreactive cells in the C1, C2, and A6 regions; neuropeptide Y (NPY) mRNA-positive cells in the C2; corticotropin-releasing hormone (CRH) mRNA-positive cells in the hypothalamic paraventricular nucleus (PVN); and NPY mRNA-positive cells in the arcuate nucleus (ARC). Taken together, these results suggest that lowered glucose availability, sensed by 4V ependymal cells, activates hindbrain catecholaminergic and/or NPY neurons followed by CRH neurons in the PVN and NPY neurons in the ARC, thereby leading to counterregulatory responses, such as an enhancement of gluconeogenesis, increased food intake, and suppression of sex steroid secretion.
Collapse
Affiliation(s)
- Marimo Sato
- Department of Veterinary Medical Sciences, The University of Tokyo, Tokyo 113-8657, Japan
| | - Shiori Minabe
- Department of Veterinary Medical Sciences, The University of Tokyo, Tokyo 113-8657, Japan
| | - Takahiro Sakono
- Department of Veterinary Medical Sciences, The University of Tokyo, Tokyo 113-8657, Japan
| | - Fumie Magata
- Department of Veterinary Medical Sciences, The University of Tokyo, Tokyo 113-8657, Japan
| | - Sho Nakamura
- Faculty of Veterinary Medicine, Okayama University of Science, Imabari, Ehime 794-8555, Japan
| | - Youki Watanabe
- Department of Veterinary Medical Sciences, The University of Tokyo, Tokyo 113-8657, Japan
| | - Naoko Inoue
- Graduate School of Bioagricultural Sciences, Nagoya University, Nagoya, Aichi 464-8601, Japan
| | - Yoshihisa Uenoyama
- Graduate School of Bioagricultural Sciences, Nagoya University, Nagoya, Aichi 464-8601, Japan
| | - Hiroko Tsukamura
- Graduate School of Bioagricultural Sciences, Nagoya University, Nagoya, Aichi 464-8601, Japan
| | - Fuko Matsuda
- Department of Veterinary Medical Sciences, The University of Tokyo, Tokyo 113-8657, Japan
| |
Collapse
|
7
|
Kreisman MJ, Tadrousse KS, McCosh RB, Breen KM. Neuroendocrine Basis for Disrupted Ovarian Cyclicity in Female Mice During Chronic Undernutrition. Endocrinology 2021; 162:bqab103. [PMID: 34037744 PMCID: PMC8272537 DOI: 10.1210/endocr/bqab103] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/02/2021] [Indexed: 11/19/2022]
Abstract
Chronic undernutrition is a type of metabolic stress that impairs reproduction in multiple species. Although energy balance and female reproductive capacity is recognized as tightly coupled, the neuroendocrine loci and molecular mechanisms that mediate ovarian cycle dysfunction during chronic undernutrition in adult females remain poorly understood. Here, we present a series of studies in which we tested the hypothesis that inhibition of kisspeptin (Kiss1) neurons, which are critical for controlling luteinizing hormone (LH) pulses and the preovulatory LH surge in females, underlies the impairment of the ovarian cycle by undernutrition. We first investigated the effect of chronic undernutrition (70% of unrestricted feed intake) on estrous cyclicity in intact female c57bl6 mice. Undernutrition caused a rapid cessation of ovarian cyclicity during the 2-week treatment, suppressing ovarian steroidogenesis and inhibiting ovulation. Using 2 well-defined estradiol-replacement paradigms, we directly tested the hypothesis that undernutrition inhibits Kiss1 neurons in the arcuate nucleus (ARCKiss1), which are required for LH pulses and in the anteroventral periventricular nucleus (AVPVKiss1), which are necessary for LH surge secretion. Undernutrition prevented LH pulses and impaired ARCKiss1 neuronal activation, using c-Fos as a marker, in ovariectomized females subcutaneously implanted with a pellet containing a diestrus-like level of estradiol. In addition, undernutrition completely blocked the estradiol-induced LH surge and diminished Kiss1 messenger RNA abundance, without decreasing estradiol receptor α (Erα), in micropunches of the AVPV. Collectively, these studies demonstrate that undernutrition disrupts ovarian cyclicity in females via impairment both of ARCKiss1 control of LH pulses and AVPVKiss1 induction of the LH surge.
Collapse
Affiliation(s)
- Michael J Kreisman
- Department of Obstetrics, Gynecology and Reproductive Sciences, University of California, San Diego, La Jolla, California 92093-0674, USA
| | - Kirollos S Tadrousse
- Department of Obstetrics, Gynecology and Reproductive Sciences, University of California, San Diego, La Jolla, California 92093-0674, USA
| | - Richard B McCosh
- Department of Obstetrics, Gynecology and Reproductive Sciences, University of California, San Diego, La Jolla, California 92093-0674, USA
| | - Kellie M Breen
- Department of Obstetrics, Gynecology and Reproductive Sciences, University of California, San Diego, La Jolla, California 92093-0674, USA
| |
Collapse
|
8
|
Tsuchida H, Mostari P, Yamada K, Miyazaki S, Enomoto Y, Inoue N, Uenoyama Y, Tsukamura H. Paraventricular Dynorphin A Neurons Mediate LH Pulse Suppression Induced by Hindbrain Glucoprivation in Female Rats. Endocrinology 2020; 161:5902463. [PMID: 32894768 DOI: 10.1210/endocr/bqaa161] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/11/2020] [Accepted: 09/03/2020] [Indexed: 12/11/2022]
Abstract
Malnutrition suppresses reproductive functions in mammals, which is considered to be mostly due to the inhibition of pulsatile gonadotropin-releasing hormone (GnRH)/gonadotropin secretion. Accumulating evidence suggests that kisspeptin neurons in the arcuate nucleus (ARC) play a critical role in the regulation of pulsatile GnRH/gonadotropin release. The present study aimed to examine if the hypothalamic dynorphin A (Dyn) neurons mediate the suppression of GnRH/luteinizing hormone (LH) pulses during malnutrition. Ovariectomized rats treated with a negative feedback level of estradiol-17β-treated (OVX+E2) were administered with intravenous (iv) or fourth cerebroventricle (4V) 2-deoxy-D-glucose (2DG), an inhibitor of glucose utilization, to serve as a malnutrition model. Central administration of a Dyn receptor antagonist blocked the iv- or 4V-2DG-induced suppression of LH pulses in OVX+E2 rats. The 4V 2DG administration significantly increased the number of Pdyn (Dyn gene)-positive cells co-expressing fos in the paraventricular nucleus (PVN), but not in the ARC and supraoptic nucleus (SON), and the iv 2DG treatment significantly increased the number of fos and Pdyn-co-expressing cells in the PVN and SON, but decreased it in the ARC. The E2 treatment significantly increased Pdyn expression in the PVN, but not in the ARC and SON. Double in situ hybridization for Kiss1 (kisspeptin gene) and Oprk1 (Dyn receptor gene) revealed that around 60% of ARC Kiss1-expressing cells co-expressed Oprk1. These results suggest that the PVN Dyn neurons, at least in part, mediate LH pulse suppression induced by the hindbrain or peripheral glucoprivation, and Dyn neurons may directly suppress the ARC kisspeptin neurons in female rats.
Collapse
Affiliation(s)
- Hitomi Tsuchida
- Laboratory of Animal Reproduction, Graduate School of Bioagricultural Sciences, Nagoya University, Nagoya, Japan
| | - Parvin Mostari
- Laboratory of Animal Reproduction, Graduate School of Bioagricultural Sciences, Nagoya University, Nagoya, Japan
| | - Koki Yamada
- Laboratory of Animal Reproduction, Graduate School of Bioagricultural Sciences, Nagoya University, Nagoya, Japan
| | - Sae Miyazaki
- Laboratory of Animal Reproduction, Graduate School of Bioagricultural Sciences, Nagoya University, Nagoya, Japan
| | - Yuki Enomoto
- Laboratory of Animal Reproduction, Graduate School of Bioagricultural Sciences, Nagoya University, Nagoya, Japan
| | - Naoko Inoue
- Laboratory of Animal Reproduction, Graduate School of Bioagricultural Sciences, Nagoya University, Nagoya, Japan
| | - Yoshihisa Uenoyama
- Laboratory of Animal Reproduction, Graduate School of Bioagricultural Sciences, Nagoya University, Nagoya, Japan
| | - Hiroko Tsukamura
- Laboratory of Animal Reproduction, Graduate School of Bioagricultural Sciences, Nagoya University, Nagoya, Japan
| |
Collapse
|
9
|
McCosh RB, Kreisman MJ, Tian K, Ho BS, Thackray VG, Breen KM. Insulin-induced hypoglycaemia suppresses pulsatile luteinising hormone secretion and arcuate Kiss1 cell activation in female mice. J Neuroendocrinol 2019; 31:e12813. [PMID: 31758872 PMCID: PMC6933080 DOI: 10.1111/jne.12813] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/04/2019] [Revised: 10/25/2019] [Accepted: 11/20/2019] [Indexed: 12/11/2022]
Abstract
Stress suppresses pulsatile luteinising hormone (LH) secretion in a variety of species, although the mechanism underlying this inhibition of reproductive function remains unclear. Metabolic stress, particularly hypoglycaemia, is a clinically-relevant stress type that is modelled with bolus insulin injection (insulin-induced hypoglycaemia). The present study utilised ovariectomised C57BL/6 mice to test the hypothesis that acute hypoglycaemia suppresses pulsatile LH secretion via central mechanisms. Pulsatile LH secretion was measured in 90-minute sampling periods immediately prior to and following i.p. injection of saline or insulin. The secretion of LH was not altered over time in fed animals or acutely fasted (5 hours) animals following an i.p. saline injection. By contrast, insulin elicited a robust suppression of pulsatile LH secretion in fasted animals, preventing LH pulses in five of six mice. To identify the neuroendocrine site of impairment, a kisspeptin challenge was performed in saline or insulin pre-treated animals in a cross-over design. LH secretion in response to exogenous kisspeptin was not different between animals pre-treated with saline or insulin, indicating normal gonadotrophin-releasing hormone cell and pituitary responses during acute hypoglycaemia. Based on this finding, the effect of insulin-induced hypoglycaemia on arcuate kisspeptin (Kiss1) cell function was determined using c-Fos as a marker of neuronal activation. Insulin caused a significant suppression in the percentage of Kiss1 cells in the arcuate nucleus that contained c-Fos compared to saline-injected controls. Taken together, these data support the hypothesis that insulin-induced hypoglycaemia suppresses pulsatile LH secretion in the female mouse via predominantly central mechanisms, which culminates in the suppression of the arcuate Kiss1 population.
Collapse
Affiliation(s)
- Richard B McCosh
- Department of Obstetrics, Gynecology and Reproductive Sciences, University of California, San Diego, CA, USA
| | - Michael J Kreisman
- Department of Obstetrics, Gynecology and Reproductive Sciences, University of California, San Diego, CA, USA
| | - Katherine Tian
- Department of Obstetrics, Gynecology and Reproductive Sciences, University of California, San Diego, CA, USA
| | - Bryan S Ho
- Department of Obstetrics, Gynecology and Reproductive Sciences, University of California, San Diego, CA, USA
| | - Varykina G Thackray
- Department of Obstetrics, Gynecology and Reproductive Sciences, University of California, San Diego, CA, USA
| | - Kellie M Breen
- Department of Obstetrics, Gynecology and Reproductive Sciences, University of California, San Diego, CA, USA
| |
Collapse
|
10
|
McCosh RB, Breen KM, Kauffman AS. Neural and endocrine mechanisms underlying stress-induced suppression of pulsatile LH secretion. Mol Cell Endocrinol 2019; 498:110579. [PMID: 31521706 PMCID: PMC6874223 DOI: 10.1016/j.mce.2019.110579] [Citation(s) in RCA: 25] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/22/2019] [Revised: 08/30/2019] [Accepted: 09/10/2019] [Indexed: 12/21/2022]
Abstract
Stress is well-known to inhibit a variety of reproductive processes, including the suppression of episodic Gonadotropin releasing hormone (GnRH) secretion, typically measured via downstream luteinizing hormone (LH) secretion. Since pulsatile secretion of GnRH and LH are necessary for proper reproductive function in both males and females, and stress is common for both human and animals, understanding the fundamental mechanisms by which stress impairs LH pulses is of critical importance. Activation of the hypothalamic-pituitary-adrenal axis, and its corresponding endocrine factors, is a key feature of the stress response, so dissecting the role of stress hormones, including corticotrophin releasing hormone (CRH) and corticosterone, in the inhibition of LH secretion has been one key research focus. However, some evidence suggests that these stress hormones alone are not sufficient for the full inhibition of LH caused by stress, implicating the additional involvement of other hormonal or neural signaling pathways in this process (including inputs from the brainstem, amygdala, parabrachial nucleus, and dorsomedial nucleus). Moreover, different stress types, such as metabolic stress (hypoglycemia), immune stress, and psychosocial stress, appear to suppress LH secretion via partially unique neural and endocrine pathways. The mechanisms underlying the suppression of LH pulses in these models offer interesting comparisons and contrasts, including the specific roles of amygdaloid nuclei and CRH receptor types. This review focuses on the most recent and emerging insights into endocrine and neural mechanisms responsible for the suppression of pulsatile LH secretion in mammals, and offers insights in important gaps in knowledge.
Collapse
Affiliation(s)
- Richard B McCosh
- Department of Obstetrics, Gynecology and Reproductive Sciences, University of California, San Diego, 9500 Gilman Drive, La Jolla, CA, 92093-0674, USA
| | - Kellie M Breen
- Department of Obstetrics, Gynecology and Reproductive Sciences, University of California, San Diego, 9500 Gilman Drive, La Jolla, CA, 92093-0674, USA
| | - Alexander S Kauffman
- Department of Obstetrics, Gynecology and Reproductive Sciences, University of California, San Diego, 9500 Gilman Drive, La Jolla, CA, 92093-0674, USA.
| |
Collapse
|
11
|
Hasegawa S, Inoue T, Inagi R. Neuroimmune interactions and kidney disease. Kidney Res Clin Pract 2019; 38:282-294. [PMID: 31422643 PMCID: PMC6727900 DOI: 10.23876/j.krcp.19.014] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2019] [Revised: 05/28/2019] [Accepted: 06/02/2019] [Indexed: 12/15/2022] Open
Abstract
The autonomic nervous system plays critical roles in maintaining homeostasis in humans, directly regulating inflammation by altering the activity of the immune system. The cholinergic anti-inflammatory pathway is a well-studied neuroimmune interaction involving the vagus nerve. CD4-positive T cells expressing β2 adrenergic receptors and macrophages expressing the alpha 7 subunit of the nicotinic acetylcholine receptor in the spleen receive neurotransmitters such as norepinephrine and acetylcholine and are key mediators of the cholinergic anti-inflammatory pathway. Recent studies have demonstrated that vagus nerve stimulation, ultrasound, and restraint stress elicit protective effects against renal ischemia-reperfusion injury. These protective effects are induced primarily via activation of the cholinergic anti-inflammatory pathway. In addition to these immunological roles, nervous systems are directly related to homeostasis of renal physiology. Whole-kidney three-dimensional visualization using the tissue clearing technique CUBIC (clear, unobstructed brain/body imaging cocktails and computational analysis) has illustrated that renal sympathetic nerves are primarily distributed around arteries in the kidneys and denervated after ischemia-reperfusion injury. In contrast, artificial renal sympathetic denervation has a protective effect against kidney disease progression in murine models. Further studies are needed to elucidate how neural networks are involved in progression of kidney disease.
Collapse
Affiliation(s)
- Sho Hasegawa
- Division of Nephrology and Endocrinology, University of Tokyo Graduate School of Medicine, Tokyo, Japan.,Division of CKD Pathophysiology, University of Tokyo Graduate School of Medicine, Tokyo, Japan
| | - Tsuyoshi Inoue
- Division of CKD Pathophysiology, University of Tokyo Graduate School of Medicine, Tokyo, Japan
| | - Reiko Inagi
- Division of CKD Pathophysiology, University of Tokyo Graduate School of Medicine, Tokyo, Japan
| |
Collapse
|
12
|
Ritter S, Li AJ, Wang Q. Hindbrain glucoregulatory mechanisms: Critical role of catecholamine neurons in the ventrolateral medulla. Physiol Behav 2019; 208:112568. [PMID: 31173784 PMCID: PMC7015674 DOI: 10.1016/j.physbeh.2019.112568] [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] [Subscribe] [Scholar Register] [Received: 12/21/2018] [Revised: 06/03/2019] [Accepted: 06/03/2019] [Indexed: 12/29/2022]
Abstract
Glucose is the required metabolic substrate for the brain. Yet the brain stores very little glucose. Therefore, the brain continuously monitors glucose availability to detect hypoglycemia and to mobilize system-wide responses to protect and restore euglycemia. Catecholamine (CA) neurons in the hindbrain are critical elements of the brain's glucoregulatory mechanisms. They project widely throughout the brain and spinal cord, innervating sites controlling behavioral, endocrine and visceral responses. Hence, CA neurons are capable of triggering a rapid, coordinated and multifaceted response to glucose challenge. This article reviews experimental data that has begun to elucidate the importance of CA neurons for glucoregulation, the functions of specific CA subpopulations in the ventrolateral medulla, and the extended circuitry through which they engage other levels of the nervous system to accomplish their essential glucoregulatory task. Hopefully, this review also suggests the vast amount of work yet to be done in this area and the justification for engaging in that effort.
Collapse
Affiliation(s)
- Sue Ritter
- Department of Integrative Physiology and Neuroscience, College of Veterinary Medicine, Washington State University, Pullman, WA 99164, United States of America.
| | - Ai-Jun Li
- Department of Integrative Physiology and Neuroscience, College of Veterinary Medicine, Washington State University, Pullman, WA 99164, United States of America
| | - Qing Wang
- Department of Integrative Physiology and Neuroscience, College of Veterinary Medicine, Washington State University, Pullman, WA 99164, United States of America
| |
Collapse
|
13
|
Inoue T, Tanaka S, Rosin DL, Okusa MD. Bioelectronic Approaches to Control Neuroimmune Interactions in Acute Kidney Injury. Cold Spring Harb Perspect Med 2019; 9:a034231. [PMID: 30126836 PMCID: PMC6546041 DOI: 10.1101/cshperspect.a034231] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Recent studies have shown renal protective effects of bioelectric approaches, including ultrasound treatment, electrical vagus nerve stimulation, and optogenetic brainstem C1 neuron stimulation. The renal protection acquired by all three modalities was lost in splenectomized mice and/or α7 subunit of the nicotinic acetylcholine receptor-deficient mice. C1 neuron-mediated renal protection was blocked by β2-adrenergic receptor antagonist. These findings indicate that all three methods commonly, at least partially, activate the cholinergic anti-inflammatory pathway, a well-studied neuroimmune pathway. In this article, we summarize the current understanding of neuroimmune axis-mediated kidney protection in preclinical models of acute kidney injury by these three modalities. Examination of the differences among these three modalities might lead to a further elucidation of the neuroimmune axis involved in renal protection and is of interest for developing new therapeutic approaches.
Collapse
Affiliation(s)
- Tsuyoshi Inoue
- Division of Nephrology and Center for Immunity, Inflammation, and Regenerative Medicine, University of Virginia Health System, Charlottesville, Virginia 22908
| | - Shinji Tanaka
- Division of Nephrology and Center for Immunity, Inflammation, and Regenerative Medicine, University of Virginia Health System, Charlottesville, Virginia 22908
| | - Diane L Rosin
- Department of Pharmacology, University of Virginia Health System Charlottesville, Virginia 22908
| | - Mark D Okusa
- Division of Nephrology and Center for Immunity, Inflammation, and Regenerative Medicine, University of Virginia Health System, Charlottesville, Virginia 22908
| |
Collapse
|
14
|
Deura C, Minabe S, Ikegami K, Inoue N, Uenoyama Y, Maeda KI, Tsukamura H. Morphological analysis for neuronal pathway from the hindbrain ependymocytes to the hypothalamic kisspeptin neurons. J Reprod Dev 2019; 65:129-137. [PMID: 30662010 PMCID: PMC6473108 DOI: 10.1262/jrd.2018-122] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
Hindbrain ependymocytes are postulated to have a glucose-sensing role in regulating gonadal functions. Previous studies have suggested that malnutrition-induced suppression of gonadotropin
secretion is mediated by noradrenergic inputs from the A2 region in the solitary tract nucleus to the paraventricular nucleus (PVN), and by corticotropin-releasing hormone (CRH) release in
the hypothalamus. However, no morphological evidence to indicate the neural pathway from the hindbrain ependymocytes to hypothalamic kisspeptin neurons, a center for reproductive function in
mammals, currently exists. The present study aimed to examine the existence of a neuronal pathway from the hindbrain ependymocytes to kisspeptin neurons in the arcuate nucleus (ARC) and
anteroventral periventricular nucleus (AVPV). To determine this, wheat-germ agglutinin (WGA), a trans-synaptic tracer, was injected into the fourth ventricle (4V) in heterozygous
Kiss1-tandem dimer Tomato (tdTomato) rats, where kisspeptin neurons were visualized by tdTomato fluorescence. 48 h after the WGA injection, brain sections were taken from
the forebrain, midbrain and hindbrain and subjected to double immunohistochemistry for WGA and dopamine β-hydroxylase (DBH) or CRH. WGA immunoreactivities were found in
vimentin-immunopositive ependymocytes of the 4V and the central canal (CC), but not in the third ventricle. The WGA immunoreactivities were detected in some tdTomato-expressing cells in the
ARC and AVPV, DBH-immunopositive cells in the A1–A7 noradrenergic nuclei, and CRH-immunopositive cells in the PVN. These results suggest that the hindbrain ependymocytes have neuronal
connections with the kisspeptin neurons, most probably via hindbrain noradrenergic and CRH neurons to relay low energetic signals for regulation of reproduction.
Collapse
Affiliation(s)
- Chikaya Deura
- Graduate School of Bioagricultural Sciences, Nagoya University, Aichi 464-8601, Japan
| | - Shiori Minabe
- Graduate School of Bioagricultural Sciences, Nagoya University, Aichi 464-8601, Japan
| | - Kana Ikegami
- Graduate School of Bioagricultural Sciences, Nagoya University, Aichi 464-8601, Japan
| | - Naoko Inoue
- Graduate School of Bioagricultural Sciences, Nagoya University, Aichi 464-8601, Japan
| | - Yoshihisa Uenoyama
- Graduate School of Bioagricultural Sciences, Nagoya University, Aichi 464-8601, Japan
| | - Kei-Ichiro Maeda
- Department of Veterinary Medical Sciences, The University of Tokyo, Tokyo 113-8657, Japan
| | - Hiroko Tsukamura
- Graduate School of Bioagricultural Sciences, Nagoya University, Aichi 464-8601, Japan
| |
Collapse
|
15
|
Hill JW, Elias CF. Neuroanatomical Framework of the Metabolic Control of Reproduction. Physiol Rev 2019; 98:2349-2380. [PMID: 30109817 DOI: 10.1152/physrev.00033.2017] [Citation(s) in RCA: 38] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
A minimum amount of energy is required for basic physiological processes, such as protein biosynthesis, thermoregulation, locomotion, cardiovascular function, and digestion. However, for reproductive function and survival of the species, extra energy stores are necessary. Production of sex hormones and gametes, pubertal development, pregnancy, lactation, and parental care all require energy reserves. Thus the physiological systems that control energy homeostasis and reproductive function coevolved in mammals to support both individual health and species subsistence. In this review, we aim to gather scientific knowledge produced by laboratories around the world on the role of the brain in integrating metabolism and reproduction. We describe essential neuronal networks, highlighting key nodes and potential downstream targets. Novel animal models and genetic tools have produced substantial advances, but critical gaps remain. In times of soaring worldwide obesity and metabolic dysfunction, understanding the mechanisms by which metabolic stress alters reproductive physiology has become crucial for human health.
Collapse
Affiliation(s)
- Jennifer W Hill
- Center for Diabetes and Endocrine Research, Departments of Physiology and Pharmacology and of Obstetrics and Gynecology, University of Toledo College of Medicine , Toledo, Ohio ; and Departments of Molecular and Integrative Physiology and of Obstetrics and Gynecology, University of Michigan , Ann Arbor, Michigan
| | - Carol F Elias
- Center for Diabetes and Endocrine Research, Departments of Physiology and Pharmacology and of Obstetrics and Gynecology, University of Toledo College of Medicine , Toledo, Ohio ; and Departments of Molecular and Integrative Physiology and of Obstetrics and Gynecology, University of Michigan , Ann Arbor, Michigan
| |
Collapse
|
16
|
Role of C1 neurons in anti-inflammatory reflex: Mediation between afferents and efferents. Neurosci Res 2018; 136:6-12. [DOI: 10.1016/j.neures.2018.05.001] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2018] [Revised: 04/24/2018] [Accepted: 05/07/2018] [Indexed: 12/21/2022]
|
17
|
Li AJ, Wang Q, Ritter S. Activation of catecholamine neurons in the ventral medulla reduces CCK-induced hypophagia and c-Fos activation in dorsal medullary catecholamine neurons. Am J Physiol Regul Integr Comp Physiol 2018; 315:R442-R452. [PMID: 29874094 DOI: 10.1152/ajpregu.00107.2018] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Catecholamine (CA) neurons within the A1 and C1 cell groups in the ventrolateral medulla (VLM) potently increase food intake when activated by glucose deficit. In contrast, CA neurons in the A2 cell group of the dorsomedial medulla are required for reduction of food intake by cholecystokinin (CCK), a peptide that promotes satiation. Thus dorsal and ventral medullary CA neurons are activated by divergent metabolic conditions and mediate opposing behavioral responses. Acute glucose deficit is a life-threatening condition, and increased feeding is a key response that facilitates survival of this emergency. Thus, during glucose deficit, responses to satiation signals, like CCK, must be suppressed to ensure glucorestoration. Here we test the hypothesis that activation of VLM CA neurons inhibits dorsomedial CA neurons that participate in satiation. We found that glucose deficit produced by the antiglycolytic glucose analog, 2-deoxy-d-glucose, attenuated reduction of food intake by CCK. Moreover, glucose deficit increased c-Fos expression by A1 and C1 neurons while reducing CCK-induced c-Fos expression in A2 neurons. We also selectively activated A1/C1 neurons in TH-Cre+ transgenic rats in which A1/C1 neurons were transfected with a Cre-dependent designer receptor exclusively activated by a designer drug (DREADD). Selective activation of A1/C1 neurons using the DREADD agonist, clozapine- N-oxide, attenuated reduction of food intake by CCK and prevented CCK-induced c-Fos expression in A2 CA neurons, even under normoglycemic conditions. Results support the hypothesis that activation of ventral CA neurons attenuates satiety by inhibiting dorsal medullary A2 CA neurons. This mechanism may ensure that satiation does not terminate feeding before restoration of normoglycemia.
Collapse
Affiliation(s)
- Ai-Jun Li
- Department of Integrative Physiology and Neuroscience, Washington State University , Pullman, Washington
| | - Qing Wang
- Department of Integrative Physiology and Neuroscience, Washington State University , Pullman, Washington
| | - Sue Ritter
- Department of Integrative Physiology and Neuroscience, Washington State University , Pullman, Washington
| |
Collapse
|
18
|
Li AJ, Wang Q, Ritter S. Selective Pharmacogenetic Activation of Catecholamine Subgroups in the Ventrolateral Medulla Elicits Key Glucoregulatory Responses. Endocrinology 2018; 159:341-355. [PMID: 29077837 PMCID: PMC5761588 DOI: 10.1210/en.2017-00630] [Citation(s) in RCA: 31] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/12/2017] [Accepted: 10/18/2017] [Indexed: 12/30/2022]
Abstract
Catecholamine (CA) neurons in the ventrolateral medulla (VLM) contribute importantly to glucoregulation during glucose deficit. However, it is not known which CA neurons elicit different glucoregulatory responses or whether selective activation of CA neurons is sufficient to elicit these responses. Therefore, to selectively activate CA subpopulations, we injected male or female Th-Cre+ transgenic rats with the Cre-dependent DREADD construct, AAV2-DIO-hSyn-hM3D(Gq)-mCherry, at one of four rostrocaudal levels of the VLM: rostral C1 (C1r), middle C1 (C1m), the area of A1 and C1 overlap (A1/C1), and A1. Transfection was highly selective for CA neurons at each site. Systemic injection of the Designer Receptor Exclusively Activated by Designer Drugs (DREADD) receptor agonist, clozapine-N-oxide (CNO), stimulated feeding in rats transfected at C1r, C1m, or A1/C1 but not A1. CNO increased corticosterone secretion in rats transfected at C1m or A1/C1 but not A1. In contrast, CNO did not increase blood glucose or induce c-Fos expression in the spinal cord or adrenal medulla after transfection of any single VLM site but required dual transfection of both C1m and C1r, possibly indicating that CA neurons mediating blood glucose responses are more sparsely distributed in C1r and C1m than those mediating feeding and corticosterone secretion. These results show that selective activation of C1 CA neurons is sufficient to increase feeding, blood glucose levels, and corticosterone secretion and suggest that each of these responses is mediated by CA neurons concentrated at different levels of the C1 cell group.
Collapse
Affiliation(s)
- Ai-Jun Li
- Programs in Neuroscience, Washington State University, Pullman, Washington 99164-7620
| | - Qing Wang
- Programs in Neuroscience, Washington State University, Pullman, Washington 99164-7620
| | - Sue Ritter
- Programs in Neuroscience, Washington State University, Pullman, Washington 99164-7620
| |
Collapse
|
19
|
GLP-1R Signaling Directly Activates Arcuate Nucleus Kisspeptin Action in Brain Slices but Does not Rescue Luteinizing Hormone Inhibition in Ovariectomized Mice During Negative Energy Balance. eNeuro 2017; 4:eN-NWR-0198-16. [PMID: 28144621 PMCID: PMC5247618 DOI: 10.1523/eneuro.0198-16.2016] [Citation(s) in RCA: 31] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2016] [Revised: 11/28/2016] [Accepted: 12/21/2016] [Indexed: 12/20/2022] Open
Abstract
Kisspeptin (Kiss1) neurons in the hypothalamic arcuate nucleus (ARC) are key components of the hypothalamic-pituitary-gonadal axis, as they regulate the basal pulsatile release of gonadotropin releasing hormone (GnRH). ARC Kiss1 action is dependent on energy status, and unmasking metabolic factors responsible for modulating ARC Kiss1 neurons is of great importance. One possible factor is glucagon-like peptide 1 (GLP-1), an anorexigenic neuropeptide produced by brainstem preproglucagon neurons. Because GLP fiber projections and the GLP-1 receptor (GLP-1R) are abundant in the ARC, we hypothesized that GLP-1R signaling could modulate ARC Kiss1 action. Using ovariectomized mice, we found that GLP-producing fibers come in close apposition with ARC Kiss1 neurons; these neurons also contain Glp1r mRNA. Electrophysiological recordings revealed that liraglutide (a long-acting GLP-1R agonist) increased action potential firing and caused a direct membrane depolarization of ARC Kiss1 cells in brain slices. We determined that brainstem preproglucagon mRNA is decreased after a 48-h fast in mice, a negative energy state in which ARC Kiss1 expression and downstream GnRH/luteinizing hormone (LH) release are potently suppressed. However, activation of GLP-1R signaling in fasted mice with liraglutide was not sufficient to prevent LH inhibition. Furthermore, chronic central infusions of the GLP-1R antagonist, exendin(9–39), in ad libitum–fed mice did not alter ARC Kiss1 mRNA or plasma LH. As a whole, these data identify a novel interaction of the GLP-1 system with ARC Kiss1 neurons but indicate that CNS GLP-1R signaling alone is not critical for the maintenance of LH during fasting or normal feeding.
Collapse
|
20
|
Minabe S, Deura C, Ikegami K, Goto T, Sanbo M, Hirabayashi M, Inoue N, Uenoyama Y, Maeda KI, Tsukamura H. Pharmacological and Morphological Evidence of AMPK-Mediated Energy Sensing in the Lower Brain Stem Ependymocytes to Control Reproduction in Female Rodents. Endocrinology 2015; 156:2278-87. [PMID: 25822714 PMCID: PMC4430616 DOI: 10.1210/en.2014-2018] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
Ependymocytes are one of the energy-sensing cells that regulate animal reproduction through their responsiveness to changes in extracellular glucose levels and the expression of pancreatic-type glucokinase and glucose transporter 2, which play a critical role in sensing blood glucose levels in pancreatic β-cells. Molecular mechanisms underlying glucose sensing in the ependymocytes remain poorly understood. The AMP-activated protein kinase (AMPK), a serine/threonine kinase highly conserved in all eukaryotic cells, has been suggested to be an intracellular fuel gauge that detects cellular energy status. The present study aims to clarify the role AMPK of the lower brainstem ependymocytes has in sensing glucose levels to regulate reproductive functions. First, we will show that administration of 5-aminoimidazole-4-carboxamide-1-β-D-ribofuranoside, an AMPK activator, into the 4th ventricle suppressed pulsatile LH release in female rats. Second, we will demonstrate the presence of AMPK catalytic subunit immunoreactivities in the rat lower brainstem ependymocytes. Third, transgenic mice were generated to visualize the ependymocytes with Venus, a green fluorescent protein, expressed under the control of the mouse vimentin promoter for further in vitro study. The Venus-labeled ependymocytes taken from the lower brainstem of transgenic mice revealed that AMPK activation by 5-aminoimidazole-4-carboxamide-1-β-D-ribofuranoside, an AMPK activator, increased in vitro intracellular calcium concentrations. Taken together, malnutrition-induced AMPK activation of ependymocytes of the lower brainstem might be involved in suppression of GnRH/LH release and then gonadal activities.
Collapse
Affiliation(s)
- Shiori Minabe
- Graduate School of Bioagricultural Sciences (S.M., C.D., K.I., T.G., N.I., Y.U., H.T.), Nagoya University, Nagoya, Aichi 464-8601, Japan; Center for Genetic Analysis of Behavior (M.S., M.H.), National Institute for Physiological Sciences, Okazaki, Aichi 444-8585, Japan; and Veterinary Medical Sciences (K.-i.M.), University of Tokyo, Tokyo 113-8657, Japan
| | | | | | | | | | | | | | | | | | | |
Collapse
|
21
|
Li AJ, Wang Q, Dinh TT, Powers BR, Ritter S. Stimulation of feeding by three different glucose-sensing mechanisms requires hindbrain catecholamine neurons. Am J Physiol Regul Integr Comp Physiol 2013; 306:R257-64. [PMID: 24381177 DOI: 10.1152/ajpregu.00451.2013] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Previous work has shown that hindbrain catecholamine neurons are required components of the brain's glucoregulatory circuitry. However, the mechanisms and circuitry underlying their glucoregulatory functions are poorly understood. Here we examined three drugs, glucosamine (GcA), phloridzin (Phl) and 5-thio-d-glucose (5TG), that stimulate food intake but interfere in different ways with cellular glucose utilization or transport. We examined feeding and blood glucose responses to each drug in male rats previously injected into the hypothalamic paraventricular nucleus with anti-dopamine-β-hydroxylase conjugated to saporin (DSAP), a retrogradely transported immunotoxin that selectively lesions noradrenergic and adrenergic neurons, or with unconjugated saporin (SAP) control. Our major findings were 1) that GcA, Phl, and 5TG all stimulated feeding in SAP controls whether injected into the lateral or fourth ventricle (LV or 4V), 2) that each drug's potency was similar for both LV and 4V injections, 3) that neither LV or 4V injection of these drugs evoked feeding in DSAP-lesioned rats, and 4) that only 5TG, which blocks glycolysis, stimulated a blood glucose response. The antagonist of the MEK/ERK signaling cascade, U0126, attenuated GcA-induced feeding, but not Phl- or 5TG-induced feeding. Thus GcA, Phl, and 5TG, although differing in mechanism and possibly activating different neural populations, stimulate feeding in a catecholamine-dependent manner. Although results do not exclude the possibility that catecholamine neurons possess glucose-sensing mechanisms responsive to all of these agents, currently available evidence favors the possibility that the feeding effects result from convergent neural circuits in which catecholamine neurons are a required component.
Collapse
Affiliation(s)
- Ai-Jun Li
- Programs in Neuroscience, Washington State University, Pullman, Washington
| | | | | | | | | |
Collapse
|
22
|
Schneider JE, Wise JD, Benton NA, Brozek JM, Keen-Rhinehart E. When do we eat? Ingestive behavior, survival, and reproductive success. Horm Behav 2013; 64:702-28. [PMID: 23911282 DOI: 10.1016/j.yhbeh.2013.07.005] [Citation(s) in RCA: 79] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/18/2013] [Revised: 07/21/2013] [Accepted: 07/22/2013] [Indexed: 12/13/2022]
Abstract
The neuroendocrinology of ingestive behavior is a topic central to human health, particularly in light of the prevalence of obesity, eating disorders, and diabetes. The study of food intake in laboratory rats and mice has yielded some useful hypotheses, but there are still many gaps in our knowledge. Ingestive behavior is more complex than the consummatory act of eating, and decisions about when and how much to eat usually take place in the context of potential mating partners, competitors, predators, and environmental fluctuations that are not present in the laboratory. We emphasize appetitive behaviors, actions that bring animals in contact with a goal object, precede consummatory behaviors, and provide a window into motivation. Appetitive ingestive behaviors are under the control of neural circuits and neuropeptide systems that control appetitive sex behaviors and differ from those that control consummatory ingestive behaviors. Decreases in the availability of oxidizable metabolic fuels enhance the stimulatory effects of peripheral hormones on appetitive ingestive behavior and the inhibitory effects on appetitive sex behavior, putting a new twist on the notion of leptin, insulin, and ghrelin "resistance." The ratio of hormone concentrations to the availability of oxidizable metabolic fuels may generate a critical signal that schedules conflicting behaviors, e.g., mate searching vs. foraging, food hoarding vs. courtship, and fat accumulation vs. parental care. In species representing every vertebrate taxa and even in some invertebrates, many putative "satiety" or "hunger" hormones function to schedule ingestive behavior in order to optimize reproductive success in environments where energy availability fluctuates.
Collapse
Affiliation(s)
- Jill E Schneider
- Department of Biological Sciences, Lehigh University, 111 Research Drive, Bethlehem, PA 18015, USA
| | | | | | | | | |
Collapse
|
23
|
Guyenet PG, Stornetta RL, Bochorishvili G, Depuy SD, Burke PGR, Abbott SBG. C1 neurons: the body's EMTs. Am J Physiol Regul Integr Comp Physiol 2013; 305:R187-204. [PMID: 23697799 DOI: 10.1152/ajpregu.00054.2013] [Citation(s) in RCA: 207] [Impact Index Per Article: 18.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
The C1 neurons reside in the rostral and intermediate portions of the ventrolateral medulla (RVLM, IVLM). They use glutamate as a fast transmitter and synthesize catecholamines plus various neuropeptides. These neurons regulate the hypothalamic pituitary axis via direct projections to the paraventricular nucleus and regulate the autonomic nervous system via projections to sympathetic and parasympathetic preganglionic neurons. The presympathetic C1 cells, located in the RVLM, are probably organized in a roughly viscerotopic manner and most of them regulate the circulation. C1 cells are variously activated by hypoglycemia, infection or inflammation, hypoxia, nociception, and hypotension and contribute to most glucoprivic responses. C1 cells also stimulate breathing and activate brain stem noradrenergic neurons including the locus coeruleus. Based on the various effects attributed to the C1 cells, their axonal projections and what is currently known of their synaptic inputs, subsets of C1 cells appear to be differentially recruited by pain, hypoxia, infection/inflammation, hemorrhage, and hypoglycemia to produce a repertoire of stereotyped autonomic, metabolic, and neuroendocrine responses that help the organism survive physical injury and its associated cohort of acute infection, hypoxia, hypotension, and blood loss. C1 cells may also contribute to glucose and cardiovascular homeostasis in the absence of such physical stresses, and C1 cell hyperactivity may contribute to the increase in sympathetic nerve activity associated with diseases such as hypertension.
Collapse
Affiliation(s)
- Patrice G Guyenet
- Department of Pharmacology, University of Virginia, Charlottesville, VA 22908-0735, USA.
| | | | | | | | | | | |
Collapse
|
24
|
Routh VH, Donovan CM, Ritter S. 2. Hypoglycemia Detection. TRANSLATIONAL ENDOCRINOLOGY & METABOLISM 2012; 3:47-87. [PMID: 24910721 PMCID: PMC4045627 DOI: 10.1210/team.9781936704200.ch2] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
|
25
|
Schneider JE, Klingerman CM, Abdulhay A. Sense and nonsense in metabolic control of reproduction. Front Endocrinol (Lausanne) 2012; 3:26. [PMID: 22649413 PMCID: PMC3355988 DOI: 10.3389/fendo.2012.00026] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/06/2011] [Accepted: 02/04/2012] [Indexed: 12/16/2022] Open
Abstract
An exciting synergistic interaction occurs among researchers working at the interface of reproductive biology and energy homeostasis. Reproductive biologists benefit from the theories, experimental designs, and methodologies used by experts on energy homeostasis while they bring context and meaning to the study of energy homeostasis. There is a growing recognition that identification of candidate genes for obesity is little more than meaningless reductionism unless those genes and their expression are placed in a developmental, environmental, and evolutionary context. Reproductive biology provides this context because metabolic energy is the most important factor that controls reproductive success and gonadal hormones affect energy intake, storage, and expenditure. Reproductive hormone secretion changes during development, and reproductive success is key to evolutionary adaptation, the process that most likely molded the mechanisms that control energy balance. It is likely that by viewing energy intake, storage, and expenditure in the context of reproductive success, we will gain insight into human obesity, eating disorders, diabetes, and other pathologies related to fuel homeostasis. This review emphasizes the metabolic hypothesis: a sensory system monitors the availability of oxidizable metabolic fuels and orchestrates behavioral motivation to optimize reproductive success in environments where energy availability fluctuates or is unpredictable.
Collapse
Affiliation(s)
- Jill E Schneider
- Department of Biological Sciences, Lehigh University Bethlehem, PA, USA.
| | | | | |
Collapse
|
26
|
Ritter S, Li AJ, Wang Q, Dinh TT. Minireview: The value of looking backward: the essential role of the hindbrain in counterregulatory responses to glucose deficit. Endocrinology 2011; 152:4019-32. [PMID: 21878511 PMCID: PMC3444967 DOI: 10.1210/en.2010-1458] [Citation(s) in RCA: 62] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Abstract
This review focuses on evidence indicating a key role for the hindbrain in mobilizing behavioral, autonomic and endocrine counterregulatory responses to acute and profound glucose deficit, and identifies hindbrain norepinephrine (NE) and epinephrine (E) neurons as essential mediators of some of these responses. It has become clear that hindbrain NE/E neurons are functionally diverse. However, considerable progress has been made in identifying the particular NE/E neurons important for particular glucoregulatory responses. Although it is not yet known whether NE/E neurons are directly activated by glucose deficit, compelling evidence indicates that if they are not, the primary glucoreceptor cells must be located in the immediate vicinity these neurons. Hindbrain studies identifying cellular markers associated with glucose-sensing functions in other brain regions are discussed, as are studies examining the relationship of these markers to counterregulatory responses of NE/E neurons. Further investigations to identify glucose-sensing cells (neurons, ependymocytes, or glia) controlling counterregulatory responses are crucial, as are studies to determine the specific functions of glucose-sensing cells throughout the brain. Likewise, examination of the roles (if any) of hindbrain counterregulatory systems in managing glucose homeostasis under basal, nonglucoprivic conditions will also be important for a full understanding of energy homeostasis. Nevertheless, the accumulated evidence demonstrates that hindbrain glucose sensors and NE/E neurons are essential players in triggering counterregulatory responses to emergencies of glucose deficit.
Collapse
Affiliation(s)
- Sue Ritter
- Department of Veterinary and Comparative Anatomy, Pharmacology, College of Veterinary Medicine, Washington State University, Pullman, Washington 99164-6520, USA.
| | | | | | | |
Collapse
|
27
|
Roland AV, Moenter SM. Regulation of gonadotropin-releasing hormone neurons by glucose. Trends Endocrinol Metab 2011; 22:443-9. [PMID: 21855365 PMCID: PMC3205187 DOI: 10.1016/j.tem.2011.07.001] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/09/2011] [Revised: 06/14/2011] [Accepted: 07/08/2011] [Indexed: 01/03/2023]
Abstract
Reproduction is influenced by energy balance, but the physiological pathways mediating their relationship have not been fully elucidated. As the central regulators of fertility, gonadotropin-releasing hormone (GnRH) neurons integrate numerous physiological signals, including metabolic cues. Circulating glucose levels regulate GnRH release and might in part mediate the effects of negative energy balance on fertility. Existing evidence suggests that neural pathways originating in the hindbrain, as well as in the hypothalamic feeding nuclei, transmit information concerning glucose availability to GnRH neurons. Here we review recent evidence suggesting that GnRH neurons might directly sense changes in glucose availability by a mechanism involving AMP-activated protein kinase. These findings expand our understanding of how metabolic signaling in the brain regulates reproduction.
Collapse
Affiliation(s)
- Alison V Roland
- Department of Animal Biology, University of Pennsylvania, Philadelphia, PA, USA.
| | | |
Collapse
|
28
|
Quennell JH, Howell CS, Roa J, Augustine RA, Grattan DR, Anderson GM. Leptin deficiency and diet-induced obesity reduce hypothalamic kisspeptin expression in mice. Endocrinology 2011; 152:1541-50. [PMID: 21325051 PMCID: PMC3206710 DOI: 10.1210/en.2010-1100] [Citation(s) in RCA: 223] [Impact Index Per Article: 17.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
The hormone leptin modulates a diverse range of biological functions, including energy homeostasis and reproduction. Leptin promotes GnRH function via an indirect action on forebrain neurons. We tested whether leptin deficiency or leptin resistance due to a high-fat diet (HFD) can regulate the potent reproductive neuropeptide kisspeptin. In mice with normalized levels of estradiol, leptin deficiency markedly reduced kisspeptin gene expression, particularly in the arcuate nucleus (ARC), and kisspeptin immunoreactive cell numbers in the rostral periventricular region of the third ventricle (RP3V). The HFD model was used to determine the effects of diet-induced obesity and central leptin resistance on kisspeptin cell number and gene expression. DBA/2J mice, which are prone to HFD-induced infertility, showed a marked decrease in kisspeptin expression in both the RP3V and ARC and cell numbers in the RP3V after HFD. This is the first evidence that kisspeptin can be regulated by HFD and/or increased body weight. Next we demonstrated that leptin does not signal (via signal transducer and activator of transcription 3 or 5, or mammalian target of rapamycin) directly on kisspeptin-expressing neurons in the RP3V. Lastly, in leptin receptor-deficient mice, neither GnRH nor kisspeptin neurons were activated during a preovulatory-like GnRH/LH surge induction regime, indicating that leptin's actions on GnRH may be upstream of kisspeptin neurons. These data provide evidence that leptin's effects on reproductive function are regulated by kisspeptin neurons in both the ARC and RP3V, although in the latter site the effects are likely to be indirect.
Collapse
Affiliation(s)
- Janette H Quennell
- Centre for Neuroendocrinology and Department of Anatomy and Structural Biology, University of Otago School of Medical Sciences, PO Box 913, Dunedin 9054, New Zealand.
| | | | | | | | | | | |
Collapse
|
29
|
I'Anson H, Jethwa PH, Warner A, Ebling FJ. Histaminergic regulation of seasonal metabolic rhythms in Siberian hamsters. Physiol Behav 2011; 103:268-78. [PMID: 21362434 PMCID: PMC3094761 DOI: 10.1016/j.physbeh.2011.02.035] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2010] [Revised: 01/28/2011] [Accepted: 02/23/2011] [Indexed: 11/24/2022]
Abstract
We investigated whether histaminergic tone contributes to the seasonal catabolic state in Siberian hamsters by determining the effect of ablation of histaminergic neurons on food intake, metabolic rate and body weight. A ribosomal toxin (saporin) conjugated to orexin-B was infused into the ventral tuberomammillary region of the hypothalamus, since most histaminergic neurons express orexin receptors. This caused not only 75–80% loss of histaminergic neurons in the posterior hypothalamus, but also some loss of other orexin-receptor expressing cells e.g. MCH neurons. In the long-day anabolic state, lesions produced a transient post-surgical decrease in body weight, but the hamsters recovered and maintained constant body weight, whereas weight gradually increased in sham-lesioned hamsters. VO2 in the dark phase was significantly higher in the lesioned hamsters compared to shams, and locomotor activity also tended to be higher. In a second study in short days, sham-treated hamsters showed the expected seasonal decrease in body weight, but weight remained constant in the lesioned hamsters, as in the long-day study. Lesioned hamsters consumed more during the early dark phase and less during the light phase due to an increase in the frequency of meals during the dark and decreased meal size during the light, and their cumulative food intake in their home cages was greater than in the control hamsters. In summary, ablation of orexin-responsive cells in the posterior hypothalamus blocks the short-day induced decline in body weight by preventing seasonal hypophagia, evidence consistent with the hypothesis that central histaminergic mechanisms contribute to long-term regulation of body weight.
Collapse
Affiliation(s)
- Helen I'Anson
- Biology Department, Washington and Lee University, Lexington, VA, USA
| | - Preeti H. Jethwa
- School of Biomedical Sciences, University of Nottingham, UK
- Division of Nutritional Sciences, School of Biosciences, University of Nottingham, UK
| | - Amy Warner
- School of Biomedical Sciences, University of Nottingham, UK
| | - Francis J.P. Ebling
- School of Biomedical Sciences, University of Nottingham, UK
- Corresponding author at: School of Biomedical Sciences, University of Nottingham Medical School, Queen's Medical Centre, Nottingham, NG7 2UH, UK. Tel.: + 44 115 8230164; fax: + 44 115 8230142.
| |
Collapse
|
30
|
Rogers RC, McDougal DH, Hermann GE. Leptin amplifies the action of thyrotropin-releasing hormone in the solitary nucleus: an in vitro calcium imaging study. Brain Res 2011; 1385:47-55. [PMID: 21334313 DOI: 10.1016/j.brainres.2011.02.029] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2010] [Revised: 02/11/2011] [Accepted: 02/11/2011] [Indexed: 12/28/2022]
Abstract
Leptin exerts a powerful permissive influence on neurogenic thermogenesis. During starvation and an absence of leptin, animals cannot produce thermogenic reactions to cold stress. However, thermogenesis is rescued by restoring leptin. We have previously observed a highly cooperative interaction between leptin and thyrotropin-releasing hormone [TRH] to activate hindbrain-generated thermogenic responses (Hermann et al., 2006). In vivo physiological studies (Rogers et al., 2009) suggested that the thermogenic impact of TRH in the hindbrain is amplified by the action of leptin through a leptin receptor-mediated production of phosphoinositol-trisphosphate [PIP3]. In turn, PIP3 can activate a tyrosine kinase whose target is the Src-SH2 regulatory site on the phospholipase C [PLC] complex. The TRH receptor signals through the PLC complex. Our immunohistochemical studies (Barnes et al., 2010) suggest that this transduction interaction between leptin and TRH occurs within neurons of the solitary nucleus [NST], though this interaction had not been verified. The present in vitro live cell calcium imaging study shows that while medial NST neurons are rarely activated by leptin alone, leptin pre-treatment significantly augments NST neurons' responsiveness to TRH. This leptin-mediated priming of NST neurons was uncoupled by pre-treatment with the phosphoinositide 3-kinase [PI3K] inhibitor [wortmannin], the phospholipase C inhibitor [U73122] and the Src-SH2 antagonist [PP2]. TTX did not eliminate the synergistic response of the agonists, thus the sensitization cannot be attributed to pre-synaptic mechanisms. It seems likely that NST neurons are involved in the leptin-mediated increase in BAT temperature by sensitizing the TRH-PLC-IP3-calcium release mechanism.
Collapse
Affiliation(s)
- Richard C Rogers
- Laboratory of Autonomic Neurosciences, Pennington Biomedical Research Center, Baton Rouge, LA 70808, USA
| | | | | |
Collapse
|
31
|
Abstract
OBJECTIVE To examine the role of AMP-activated protein kinase (AMPK) in the control of glucoprivic feeding by hindbrain catecholamine neurons. RESEARCH DESIGN AND METHODS Micropunched hindbrain samples were collected from control and 2-deoxy-d-glucose (2DG)-injected rats for Western blot analysis of phosphorylated (activated) AMPK (pAMPK). Samples also were collected from 2DG-injected rats pretreated with anti-dopamine-β-hydroxylase conjugated to saporin to lesion hindbrain catecholamine neurons. In a second experiment, rats were given a fourth-ventricle injection of compound C (CC) or 5-aminoimidazole-4-carboxyamide ribonucleoside (AICAR), an inhibitor and activator of AMPK, to identify a role for AMPK in hindbrain neurons required for elicitation of 2DG-induced feeding. RESULTS Systemic 2DG stimulated food intake in controls but not in catecholamine-lesioned rats. In controls, but not catecholamine-lesioned rats, 2DG also increased phosphorylated Thr172 at AMPKα subunits (pAMPKα) in hindbrain micropunches containing catecholaminergic cell groups A1 through the middle region of C1 (A1-C1m). Increased pAMPKα was not observed in the adjacent noncatecholaminergic ventromedial medulla or in the A2-C2 catecholamine cell groups in the dorsal hindbrain. Fourth-ventricle injection of CC attenuated 2DG-induced feeding during the first 2 h of the test, and AICAR alone increased food intake only during the first 60 min of the 4-h test. CONCLUSIONS Results indicate that AMPK in catecholaminergic A1-C1m neurons is activated by glucoprivation. Therefore, AMPK may contribute to the glucose-sensing mechanism by which these neurons detect and signal a glucose deficit in the service of systemic glucoregulation.
Collapse
Affiliation(s)
- Ai-Jun Li
- Programs in Neuroscience, Washington State University, Pullman, Washington, USA.
| | | | | |
Collapse
|
32
|
Ghuman SPS, Morris R, Scherzer J, Routly JE, Mobasheri A, Smith RF, Dobson H. Neuronal Responses in the Brainstem and Hypothalamic Nuclei Following Insulin Treatment During the Late Follicular Phase in the Ewe. Reprod Domest Anim 2011; 46:121-9. [DOI: 10.1111/j.1439-0531.2010.01605.x] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
|
33
|
True C, Grove KL, Smith MS. Beyond Leptin: Emerging Candidates for the Integration of Metabolic and Reproductive Function during Negative Energy Balance. Front Endocrinol (Lausanne) 2011; 2:53. [PMID: 22645510 PMCID: PMC3355832 DOI: 10.3389/fendo.2011.00053] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/30/2011] [Accepted: 09/29/2011] [Indexed: 12/19/2022] Open
Abstract
Reproductive status is tightly coupled to metabolic state in females, and ovarian cycling in mammals is halted when energy output exceeds energy input, a metabolic condition known as negative energy balance. This inhibition of reproductive function during negative energy balance occurs due to suppression of gonadotropin-releasing hormone (GnRH) release in the hypothalamus. The GnRH secretagogue kisspeptin is also inhibited during negative energy balance, indicating that inhibition of reproductive neuroendocrine circuits may occur upstream of GnRH itself. Understanding the metabolic signals responsible for the inhibition of reproductive pathways has been a compelling research focus for many years. A predominant theory in the field is that the status of energy balance is conveyed to reproductive neuroendocrine circuits via the adipocyte hormone leptin. Leptin is stimulatory for GnRH release and lower levels of leptin during negative energy balance are believed to result in decreased stimulatory drive for GnRH cells. However, recent evidence found that restoring leptin to physiological levels did not restore GnRH function in three different models of negative energy balance. This suggests that although leptin may be an important permissive signal for reproductive function as indicated by many years of research, factors other than leptin must critically contribute to negative energy balance-induced reproductive inhibition. This review will focus on emerging candidates for the integration of metabolic status and reproductive function during negative energy balance.
Collapse
Affiliation(s)
- Cadence True
- Division of Neuroscience, Oregon National Primate Research Center, Oregon Health and Science UniversityBeaverton, OR, USA
| | - Kevin L. Grove
- Division of Neuroscience, Oregon National Primate Research Center, Oregon Health and Science UniversityBeaverton, OR, USA
| | - M. Susan Smith
- Division of Neuroscience, Oregon National Primate Research Center, Oregon Health and Science UniversityBeaverton, OR, USA
- *Correspondence: M. Susan Smith, Division of Neuroscience, Oregon National Primate Research Center, Oregon Health and Science University, 505 NW 185th Avenue, Beaverton, OR 97006, USA. e-mail:
| |
Collapse
|
34
|
The neuroendocrine basis of lactation-induced suppression of GnRH: role of kisspeptin and leptin. Brain Res 2010; 1364:139-52. [PMID: 20727862 DOI: 10.1016/j.brainres.2010.08.038] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2010] [Revised: 08/11/2010] [Accepted: 08/12/2010] [Indexed: 11/22/2022]
Abstract
Lactation is an important physiological model of the integration of energy balance and reproduction, as it involves activation of potent appetitive neuropeptide systems coupled to a profound inhibition of pulsatile GnRH/LH secretion. There are multiple systems that contribute to the chronic hyperphagia of lactation: 1) suppression of the metabolic hormones, leptin and insulin, 2) activation of hypothalamic orexigenic neuropeptide systems NPY, AGRP, orexin (OX) and melanin concentrating hormone (MCH), 3) special induction of NPY expression in the dorsomedial hypothalamus, and 4) suppression of anorexigenic systems POMC and CART. These changes ensure adequate energy intake to meet the metabolic needs of milk production. There is significant overlap in all of the systems that regulate food intake with the regulation of GnRH, suggesting there could be several redundant factors acting to suppress GnRH/LH during lactation. In addition to an overall increase in inhibitory tone acting directly on GnRH cell bodies that is brought about by increases in orexigenic systems, there are also effects at the ARH to disrupt Kiss1/neurokinin B/dynorphin neuronal function through inhibition of Kiss1 and NKB. These changes could lead to an increase in inhibitory auto-regulation of the Kiss1 neurons and a possible disruption of pulsatile GnRH release. While the low levels of leptin and insulin contribute to the changes in ARH appetitive systems, they do not appear to contribute to the suppression of ARH Kiss1 or NKB. The inhibition of Kiss1 may be the key factor in the suppression of GnRH during lactation, although the mechanisms responsible for its inhibition are unknown.
Collapse
|
35
|
Barnes MJ, Rogers RC, Van Meter MJ, Hermann GE. Co-localization of TRHR1 and LepRb receptors on neurons in the hindbrain of the rat. Brain Res 2010; 1355:70-85. [PMID: 20691166 DOI: 10.1016/j.brainres.2010.07.094] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2010] [Revised: 07/24/2010] [Accepted: 07/27/2010] [Indexed: 02/06/2023]
Abstract
We have reported a highly cooperative interaction between leptin and thyrotropin releasing hormone (TRH) in the hindbrain to generate thermogenic responses (Hermann et al., 2006) (Rogers et al., 2009). Identifying the locus in the hindbrain where leptin and TRH act synergistically to increase thermogenesis will be necessary before we can determine the mechanism(s) by which this interaction occurs. Here, we performed heat-induced epitope recovery techniques and in situ hybridization to determine if neurons or afferent fibers in the hindbrain possess both TRH type 1 receptor and long-form leptin receptor [TRHR1; LepRb, respectively]. LepRb receptors were highly expressed in the solitary nucleus [NST], dorsal motor nucleus of the vagus [DMN] and catecholaminergic neurons of the ventrolateral medulla [VLM]. All neurons that contained LepRb also contained TRHR1. Fibers in the NST and the raphe pallidus [RP] and obscurrus [RO] that possess LepRb receptors were phenotypically identified as glutamatergic type 2 fibers (vglut2). Fibers in the NST and RP that possess TRHR1 receptors were phenotypically identified as serotonergic [i.e., immunopositive for the serotonin transporter; SERT]. Co-localization of LepRb and TRHR1 was not observed on individual fibers in the hindbrain but these two fiber types co-mingle in these nuclei. These anatomical arrangements may provide a basis for the synergy between leptin and TRH to increase thermogenesis.
Collapse
Affiliation(s)
- Maria J Barnes
- Laboratory of Autonomic Neuroscience, Pennington Biomedical Research Center, Louisiana State University System, Baton Rouge, LA 70808, USA
| | | | | | | |
Collapse
|
36
|
Schneider JE. If I only had a whole brain: the importance of extrahypothalamic areas in the energy balance equation. Endocrinology 2009; 150:5195-8. [PMID: 19933395 PMCID: PMC2795710 DOI: 10.1210/en.2009-1203] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Affiliation(s)
- Jill E Schneider
- Department of Biological Sciences, Lehigh University, Bethlehem, Pennsylvania 18015, USA.
| |
Collapse
|
37
|
Leptin "gates" thermogenic action of thyrotropin-releasing hormone in the hindbrain. Brain Res 2009; 1295:135-41. [PMID: 19643094 DOI: 10.1016/j.brainres.2009.07.063] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2009] [Revised: 07/16/2009] [Accepted: 07/18/2009] [Indexed: 12/19/2022]
Abstract
Leptin, acting as a measure of metabolic fuel availability, exerts a powerful permissive influence on neurogenic thermogenesis. During starvation and an absence of leptin, animals cannot produce thermogenic reactions to cold stress. However, thermogenesis is rescued by restoring leptin. We have previously observed (Hermann, G.E., Barnes, M.J., Rogers, R.C., 2006. Leptin and thyrotropin-releasing hormone: cooperative action in the hindbrain to activate brown adipose thermogenesis. Brain Res. 1117, 118-124.) a highly cooperative interaction between leptin and thyrotropin-releasing hormone [TRH] to activate hindbrain generated thermogenic responses. Specifically, exposure to both leptin and TRH elicited a 3.5 degrees C increase in brown adipose tissue [BAT] thermogenesis, while leptin alone did not evoke any change, and TRH alone caused only approximately 1 degrees C increase. The present study shows that the leptin-TRH synergy in controlling brown adipose [BAT] thermogenesis is order-specific and dependent on the feeding status of the animal. That is, fourth ventricular [4V] application of leptin to the food-deprived animal, before TRH injection, yields a substantial increase in BAT; while the reverse order yields a significantly smaller effect. If the animal were fed within minutes of anesthesia, then exogenous leptin was not necessary for TRH to yield a large increase in BAT temperature. The leptin-TRH synergy was uncoupled by pretreatment with the phosphoinositol-tris phosphate kinase [PI3K] inhibitor, wortmannin and the Src-SH2 antagonist, PP2. The TRH transduction mechanism utilizes phospholipase C [PLC] potently regulated by the SH2 site. Previous work in culture systems suggests that the product of PI3K activity [PIP3] potently upregulates PLC by activating the SH2 domain of the PLC complex. Perhaps leptin "gates" the thermogenic action of TRH in the hindbrain by invoking this same mechanism.
Collapse
|
38
|
Ghuman SPS, Morris R, Spiller DG, Smith RF, Dobson H. Integration Between Different Hypothalamic Nuclei Involved in Stress and GnRH Secretion in the Ewe. Reprod Domest Anim 2009; 45:1065-73. [DOI: 10.1111/j.1439-0531.2009.01496.x] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
|
39
|
Darling RA, Ritter S. 2-Deoxy-D-glucose, but not mercaptoacetate, increases food intake in decerebrate rats. Am J Physiol Regul Integr Comp Physiol 2009; 297:R382-6. [PMID: 19494173 DOI: 10.1152/ajpregu.90827.2008] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
We examined food intake in chronically maintained decerebrate rats in response to two antimetabolic drugs known to stimulate food intake, 2-mercaptoacetate (MA) and 2-deoxy-D-glucose (2DG). MA reduces fatty acid oxidation, and 2DG reduces glucose utilization. Because previous work has shown that insulin-induced hypoglycemia increases food intake in decerebrate rats, we predicted that 2DG would have this same effect. MA-induced feeding requires vagal sensory neurons that terminate in the hindbrain. Cholecystokinin-induced suppression of feeding, which likewise requires vagal sensory neurons, has been shown to suppress food intake in decerebrate rats. Therefore, we predicted that MA's effects on feeding would also persist in decerebrate rats. In our experiments, the test diet (40% milk, diluted with water) was infused intraorally through a chronic cheek fistula. We found that sham controls consumed 258% and 230% of their baseline milk intake in response to 2DG and MA, respectively. Decerebrates consumed 239% of their baseline milk intake in response to 2DG, but did not increase their intake in response to MA. Because decerebration separates the hindbrain from the forebrain, these results indicate that 2DG-induced glucoprivation is capable of acting within the hindbrain to activate fundamental reflex circuitry for consummatory feeding responses, as shown previously for hypoglycemia. In contrast, MA affects food consumption only after forebrain processing of MA-induced vagal afferent signals and in the presence of intact ascending and descending neural pathways.
Collapse
|
40
|
Quennell JH, Mulligan AC, Tups A, Liu X, Phipps SJ, Kemp CJ, Herbison AE, Grattan DR, Anderson GM. Leptin indirectly regulates gonadotropin-releasing hormone neuronal function. Endocrinology 2009; 150:2805-12. [PMID: 19179437 PMCID: PMC2732287 DOI: 10.1210/en.2008-1693] [Citation(s) in RCA: 260] [Impact Index Per Article: 17.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
The adipose-derived hormone leptin communicates information about metabolic status to the hypothalamic GnRH neuronal system. It is unclear whether leptin can act directly on GnRH neurons. To examine this, we used three approaches. First, the presence of leptin-induced signal transducer and activator of transcription-3 activation was examined in GnRH neurons in male and female rats. Intracerebroventricular treatment with 4 mug leptin-induced robust signal transducer and activator of transcription-3 expression within the anteroventral periventricular nucleus but not in GnRH neurons. Second, fertility was assessed in male and female CRE-loxP transgenic mice with conditional leptin receptor (Lepr) deletion from either all forebrain neurons or GnRH neurons only. Forebrain neuron LEPR deletion prevented the onset of puberty resulting in infertility in males and females and blocked estradiol-induced LH surge. However, mice with GnRH neuron-selective Lepr deletion exhibited normal fertility apart from a slight puberty delay in males. Lastly, the highly sensitive technique of single-cell nested PCR was used to test for Lepr transcript presence in individual GnRH neurons, identified in situ using GnRH-green fluorescent protein transgenics. Whereas 75% of positive control (proopiomelanocortin) neurons contained Lepr mRNA, no (none of 18) GnRH neurons were Lepr mRNA positive. Collectively, these results show that leptin does not act directly on GnRH neurons in rats and mice. Leptin appears to regulate GnRH function via forebrain neurons that are afferent to GnRH because forebrain neuronal LEPR deletion caused infertility. The location and phenotype of these leptin-responsive neurons remains to be elucidated.
Collapse
Affiliation(s)
- Janette H Quennell
- Department of Anatomy and Structural Biology, Centre for Neuroendocrinology, University of Otago School of Medical Sciences, Dunedin, New Zealand
| | | | | | | | | | | | | | | | | |
Collapse
|
41
|
Taylor A, Madison F, Fraley G. Galanin-like peptide stimulates feeding and sexual behavior via dopaminergic fibers within the medial preoptic area of adult male rats. J Chem Neuroanat 2009; 37:105-11. [DOI: 10.1016/j.jchemneu.2008.12.003] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2008] [Revised: 12/08/2008] [Accepted: 12/09/2008] [Indexed: 02/07/2023]
|
42
|
Li AJ, Wang Q, Dinh TT, Ritter S. Simultaneous silencing of Npy and Dbh expression in hindbrain A1/C1 catecholamine cells suppresses glucoprivic feeding. J Neurosci 2009; 29:280-7. [PMID: 19129404 PMCID: PMC2711634 DOI: 10.1523/jneurosci.4267-08.2009] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2008] [Revised: 12/04/2008] [Accepted: 12/05/2008] [Indexed: 11/21/2022] Open
Abstract
Previous data have strongly implicated hindbrain catecholamine/neuropeptide Y (NPY) coexpressing neurons as key mediators of the glucoprivic feeding response. Catecholamine/NPY cell bodies are concentrated in the A1 and caudal C1 cell cluster (A1/C1) in the ventrolateral medulla, a region highly sensitive to glucoprivic challenge. To further investigate the importance of this catecholamine subpopulation in glucoregulation, we used small interfering RNA (siRNA) technology to produce a targeted gene knockdown of NPY and dopamine-beta-hydroxylase (DBH), a catecholamine biosynthetic enzyme. Unilateral injection of NPY siRNA and DBH siRNA (0.02 nmol each) both significantly inhibited expression of the targeted genes up to 2 d, as revealed by real-time PCR, and reduced protein expression up to 8 d, as revealed by immunohistochemistry, compared with the control nontargeting siRNA (ntRNA) side. Subsequently, targeted siRNA or control ntRNA was injected bilaterally into A1/C1 and responses to 2-deoxy-D-glucose (2DG; 200 mg/kg)-induced glucoprivation were tested 3-7 d later. Silencing of either Npy or Dbh alone did not reduce glucoprivic feeding or hyperglycemic responses, compared with responses of ntRNA-injected controls. In contrast, simultaneous silencing of both Npy and Dbh reduced 2DG-induced feeding by 61%. Neither the hyperglycemic response to 2DG nor feeding elicited by mercaptoacetate (68 mg/kg)-induced blockade of fatty acid oxidation ("lipoprivic feeding") was reduced by simultaneous silencing of these two genes. These results suggest that catecholamines and NPY act conjointly to control glucoprivic feeding and that the crucial NPY/catecholamine coexpressing neurons are concentrated in the A1/C1 cell group.
Collapse
Affiliation(s)
- Ai-Jun Li
- Programs in Neuroscience, Washington State University, Pullman, Washington 99164-6520, USA.
| | | | | | | |
Collapse
|
43
|
Sajapitak S, Iwata K, Shahab M, Uenoyama Y, Yamada S, Kinoshita M, Bari FY, I'Anson H, Tsukamura H, Maeda KI. Central lipoprivation-induced suppression of luteinizing hormone pulses is mediated by paraventricular catecholaminergic inputs in female rats. Endocrinology 2008; 149:3016-24. [PMID: 18308839 DOI: 10.1210/en.2008-0016] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
The present study aims to clarify the role of fatty acids in regulating pulsatile LH secretion in rats. To produce an acute central lipoprivic condition, mercaptoacetate (MA), an inhibitor of fatty acids oxidation, was administered into the fourth cerebroventricle (4V) in ad libitum fed ovariectomized (OVX) rats (0.4, 2, and 10 micromol/rat) with or without an estradiol (E2) implant producing diestrus plasma E2 levels. Pulsatile LH secretion was suppressed by 4V MA administration in a dose-dependent manner in both OVX and OVX plus E2 rats. Mean LH levels and LH pulse frequency and amplitude were significantly reduced by the highest dose of MA in OVX rats, and by the middle and highest dose of MA in E2-treated rats, suggesting that estrogen enhanced LH suppression. Blood glucose levels increased immediately after the highest dose of MA in both groups. Fourth ventricular injection of trimetazidine (2 and 3 micromol/rat), another inhibitor of fatty acids oxidation, also inhibited pulsatile LH release, resulting in significant and dose-dependent suppression of LH pulse frequency and an increase in blood glucose levels in OVX plus E2 rats. In contrast, peripheral injection of the highest 4V dose of MA (10 micromol/rat) did not alter LH release or blood glucose levels. Microdialysis of the hypothalamic paraventricular nucleus (PVN) revealed that norepinephrine release in the region was increased by 4V MA administration. Preinjection of alpha-methyl-p-tyrosine, a catecholamine synthesis inhibitor, into the PVN completely blocked the lipoprivic inhibition of LH and the counter-regulatory increase in blood glucose levels in OVX plus E2 rats. Together, these studies indicate that fatty acid availability may be sensed by a central detector, located in the lower brainstem to maintain reproduction, and that noradrenergic inputs to the PVN mediate this lipoprivic-induced suppression of LH release.
Collapse
Affiliation(s)
- Somchai Sajapitak
- Graduate School of Bioagricultural Sciences, Nagoya University, Nagoya 464-8601, Japan
| | | | | | | | | | | | | | | | | | | |
Collapse
|
44
|
Sajapitak S, Uenoyama Y, Yamada S, Kinoshita M, Iwata K, Bari FY, I'anson H, Tsukamula H, Maeda KI. Paraventricular alpha1- and alpha2-adrenergic receptors mediate hindbrain lipoprivation-induced suppression of luteinizing hormone pulses in female rats. J Reprod Dev 2008; 54:198-202. [PMID: 18344615 DOI: 10.1262/jrd.20024] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Acute central lipoprivation suppresses pulsatile luteinizing hormone (LH) release and increases blood glucose levels through noradrenergic input to the hypothalamic paraventricular nucleus (PVN) in female rats. The present study was conducted to identify adrenergic receptor subtypes involved in central lipoprivation-induced suppression of pulsatile LH secretion and increases in plasma glucose levels in female rats. Acute hindbrain lipoprivation was produced by injection into the fourth cerebroventricle (4V) of 2-mercaptoacetate (MA), an inhibitor of fatty acid oxidation, in estradiol-implanted ovariectomized rats. Two min before MA injection, alpha1-, alpha2- or beta-adrenergic receptor antagonist was injected into the PVN. Injection of MA into the 4V suppresses pulsatile LH release in PVN vehicle-treated rats, whereas pretreatment of animals with injection of alpha1- or alpha2-adrenergic antagonist into the PVN blocked the effect of the 4V MA injection on LH pulses. beta-Adrenergic antagonist did not affect MA-induced suppression of LH pulses. The counter-regulatory increase in plasma glucose levels after 4V MA injection was also partially blocked by pretreatment with alpha1- and alpha2-adrenergic receptor antagonists. These results suggest that alpha1- and alpha2-adrenergic receptors in the PVN mediate hindbrain lipoprivation-induced suppression of LH release and counter-regulatory increases in plasma glucose levels in female rats.
Collapse
Affiliation(s)
- Somchai Sajapitak
- Laboratory of Animal Reproduction, Graduate School of Bioagricultural Sciences, Nagoya University, Nagoya, Japan
| | | | | | | | | | | | | | | | | |
Collapse
|
45
|
Abstract
PURPOSE OF REVIEW To summarize the physiological bases of infertility during undernutrition. RECENT FINDINGS When energy expenditure consistently exceeds intake, survival receives temporary priority over fertility, and reproduction is deferred until conditions are more favorable. This nutritional infertility is due to inhibition of both gonadotropin-releasing hormone secretion and copulatory behaviors. Recent work has focused on the nature of the metabolic signals to the brain, detection of these signals, and the neural circuitry involved. This work is reviewed and summarized. SUMMARY It was once erroneously believed that female mammals had to maintain a particular body fat content to remain fertile. We now know that the primary metabolic factor is short-term availability of glucose and fatty acids for oxidation. Metabolic fuel availability is detected in the caudal hindbrain and possibly elsewhere. This information is relayed to the forebrain via projections containing catecholamines and neuropeptide-Y, where they activate corticotropin-releasing hormone neurons. Acting as a neurotransmitter, this hormone inhibits gonadotropin-releasing hormone secretion and estrous behavior. Conversely, corticotropin-releasing hormone antagonists reverse the effects of food deprivation on both measures, indicating that corticotropin-releasing hormone is vital in the nutritional suppression of reproduction. Leptin may modulate reproductive responses to changes in short-term fuel availability.
Collapse
Affiliation(s)
- Maria Furman
- Division of Endocrinology, Diabetes, and Hypertension, Brigham and Women's Hospital, Boston, Massachusetts, USA
| | | |
Collapse
|
46
|
Todd BJ, Fraley GS, Peck AC, Schwartz GJ, Etgen AM. Central insulin-like growth factor 1 receptors play distinct roles in the control of reproduction, food intake, and body weight in female rats. Biol Reprod 2007; 77:492-503. [PMID: 17567960 DOI: 10.1095/biolreprod.107.060434] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/01/2022] Open
Abstract
Estradiol and progesterone induction of the LH surge in ovariectomized female rats requires concurrent activation of brain insulin-like growth factor 1 (IGF1) receptors. The present study determined whether brain IGF1 receptor signaling is required for estrous cyclicity in gonadally intact female rats. A selective IGF1 receptor antagonist (JB-1) or vehicle was continuously administered into the third ventricle by osmotic minipumps. Following surgical placement of the minipumps, all rats temporarily reduced food intake, lost weight, and suspended estrous cycles. Control rats resumed cycles within a few days and exhibited compensatory hyperphagia until they returned to presurgical body weight. Animals receiving JB-1 had severely delayed or absent estrous cycles, failed to show rebound feeding, and regained body weight more slowly. Vehicle-infused animals pair fed to JB-1-treated rats had even lower body weights but resumed estrous cycles sooner than those given drug alone. Chronic infusion of IGF1 alone had no effect on any of these parameters, but coinfusion of IGF1 with the antagonist completely reversed JB-1 effects on food intake and estrous cyclicity and partially reversed the effects on body weight. There were no significant differences in the expression of galanin-like peptide (Galp) or Kiss1 mRNA in the arcuate or periventricular hypothalamic area of control and JB-1-treated animals at a time point when food intake and estrous cycles were different between controls and JB-1-treated rats. These data suggest that brain IGF1 signaling is necessary for normal estrous cycles as well as compensatory hyperphagia and that IGF1 modulation of the reproductive axis is not secondary to reduced food intake.
Collapse
Affiliation(s)
- Brigitte J Todd
- Department of Neuroscience, Albert Einstein College of Medicine, Bronx, New York 10461, USA.
| | | | | | | | | |
Collapse
|
47
|
Schneider JE, Casper JF, Barisich A, Schoengold C, Cherry S, Surico J, DeBarba A, Fabris F, Rabold E. Food deprivation and leptin prioritize ingestive and sex behavior without affecting estrous cycles in Syrian hamsters. Horm Behav 2007; 51:413-27. [PMID: 17306262 DOI: 10.1016/j.yhbeh.2006.12.010] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/11/2006] [Revised: 12/15/2006] [Accepted: 12/18/2006] [Indexed: 11/19/2022]
Abstract
Energy consumption is critical for the energetically expensive processes related to reproduction, and thus, mechanisms that increase ingestive behavior are directly linked to reproductive success. Similarly, the mechanisms that inhibit hunger and ingestive behavior might be most adaptive when these mechanisms cause individuals to stop foraging, hoarding and eating in order to find and court potential mates. In the laboratory, ingestive behaviors are typically studied separately from reproductive behaviors even though it is likely that these behaviors evolved under conditions in which both food and mates were available. We examined the choice between paracopulatory and ingestive behaviors in a semi-natural environment in which both food and potential mates were available. Intact female Syrian hamsters showed a high preference for males on days 3 and 4 (day 4 being the day of ovulation and estrous behavior), and a 48-h period of food deprivation significantly decreased preference for sex and increased preference for eating and food hoarding on day 3 in 89% of the hamsters, although none became anestrous. The same period of food deprivation significantly decreased the level of vaginal marking without significant effects on plasma estradiol concentrations. Next, hamsters were either food deprived (FD) or fed ad libitum, and half of each group was treated with vehicle or the adipocyte hormone leptin. The percentage of females with a low preference for sex was significantly greater in the FD compared to the ad libitum-fed groups, and leptin treatment prevented this effect. Metabolic fuels, possibly acting through leptin and other hormones, might influence sensitivity to estradiol or enhance the downstream effects of estradiol, thereby increasing motivation for sex and decreasing the relative motivation to forage, hoard and eat food.
Collapse
Affiliation(s)
- Jill E Schneider
- Department of Biological Sciences, Lehigh University, 111 Research Drive, Bethlehem, PA 18015, USA.
| | | | | | | | | | | | | | | | | |
Collapse
|
48
|
Andrew SF, Dinh TT, Ritter S. Localized glucoprivation of hindbrain sites elicits corticosterone and glucagon secretion. Am J Physiol Regul Integr Comp Physiol 2007; 292:R1792-8. [PMID: 17218439 DOI: 10.1152/ajpregu.00777.2006] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Glucose is required for brain energy metabolism. Decerebration, aqueduct occlusion, and cannula mapping studies have established that glucose-sensing cells capable of eliciting feeding and adrenal medullary responses to glucoprivation are localized in the hindbrain. Glucoprivation also evokes corticosterone and glucagon secretion, but the location of receptors mediating these responses is unknown. To determine whether glucoreceptive sites controlling these responses are present in the hindbrain, we administered the antiglycolytic agent, 5-d-thioglucose (5TG, 24 microg in 200 nl) into brain stem sites through implanted cannulas and examined plasma concentrations of corticosterone and glucagon. Both hindbrain and hypothalamic sites were tested. Blood was collected remotely from intra-atrial catheters at 0, 30, 60, 90, 120, 180, and 240 min after 5TG or control injection. Caudal hindbrain 5TG injections potently increased circulating corticosterone and glucagon concentrations. For corticosterone, the mean peak response (maximum concentration minus time 0 concentration) elicited at positive sites (23 of 40 sites) was 391 ng/ml (SE = 16). For glucagon, the mean peak response at positive sites (27 of 40 sites) was 46 pg/ml (SE = 6). Glucoprivically evoked glucagon secretion was abolished by the ganglionic blocker, hexamethonium, but not by adrenal denervation. Six of twenty-five hypothalamic sites were positive for corticosterone secretion, yielding plasma levels of 279 +/- 23 ng/ml, but none of the hypothalamic injection sites elevated glucagon concentrations. Results demonstrate that receptor cells responsive to glucose deficit and capable of increasing corticosterone and glucagon concentrations exist within the hindbrain, thus further delineating central glucoregulatory neural circuitry.
Collapse
Affiliation(s)
- Shayne F Andrew
- Programs in Neuroscience, Washington State Univ, Pullman, WA 99164-6520, USA
| | | | | |
Collapse
|
49
|
Crown A, Clifton DK, Steiner RA. Neuropeptide signaling in the integration of metabolism and reproduction. Neuroendocrinology 2007; 86:175-82. [PMID: 17898535 DOI: 10.1159/000109095] [Citation(s) in RCA: 116] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/30/2006] [Accepted: 12/11/2007] [Indexed: 12/27/2022]
Abstract
Fertility is gated by nutrition and the availability of stored energy reserves, but the cellular and molecular mechanisms that link energy stores and reproduction are not well understood. Neuropeptides including galanin-like peptide (GALP), neuropeptide Y (NPY), products of the proopiomelanocortin (POMC; e.g., alpha-MSH and beta-endorphin), and kisspeptin are thought to be involved in this process for several reasons. First, the neurons that express these neuropeptides all reside in the hypothalamic arcuate nucleus, a critical site for the regulation of both metabolism and reproduction. Second, these neuropeptides are all targets for regulation by metabolic hormones, such as leptin and insulin. And third, these neuropeptides have either direct or indirect effects on feeding and metabolism, as well as on the secretion of gonadotropin-releasing hormone (GnRH) and luteinizing hormone (LH). As the target for the action of metabolic hormones and sex steroids, these neuropeptides serve as molecular motifs integrating the control of metabolism and reproduction.
Collapse
Affiliation(s)
- Angelena Crown
- Undergraduate Program in Neurobiology, University of Washington, Seattle, WA 98195-7290, USA
| | | | | |
Collapse
|
50
|
Hermann GE, Barnes MJ, Rogers RC. Leptin and thyrotropin-releasing hormone: cooperative action in the hindbrain to activate brown adipose thermogenesis. Brain Res 2006; 1117:118-24. [PMID: 16956588 DOI: 10.1016/j.brainres.2006.08.018] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2006] [Revised: 07/12/2006] [Accepted: 08/03/2006] [Indexed: 10/24/2022]
Abstract
Explanations of leptin induction of thermogenesis typically involve primary detection elements in the hypothalamus. In turn, these circuits control medullary raphe neurons that regulate spinal efferent sympathetic projections to heat-producing brown adipose tissue (BAT). The hindbrain may be capable of considerable thermoregulatory capacity independent of the hypothalamus, though little is known about the site(s), mechanism(s) of action, or the physiological consequences of leptin action in the hindbrain. Several reports describe the presence of leptin receptor in the solitary nucleus, and there is functional evidence that leptin can act in the dorsal medulla to suppress feeding. We examined the effects of leptin, applied to the dorsal medulla, on BAT thermogenesis. Leptin alone (< or =25 microg) had no independent effect on BAT thermogenesis. We hypothesized that, while leptin may not be capable of activating thermocontrol mechanisms in the hindbrain directly, it may modulate the efficacy of other neural signals involved in the control of thermogenesis such as thyrotropin-releasing hormone (TRH). We tested the hypothesis that leptin and TRH, acting in the hindbrain, co-regulate thermogenesis. As expected, TRH (0.1 microg), alone, produces a small increase (+0.75 degrees C) in BAT temperature. Co-application of leptin (5 mug) and TRH (0.1 microg) to the dorsal medulla produces an increase in BAT and core temperature more than 300% greater than TRH alone (+3.5 degrees C). This effect is undiminished in the acute decerebrate rat, suggesting that the effect is mediated entirely by the hindbrain.
Collapse
Affiliation(s)
- Gerlinda E Hermann
- Pennington Biomedical Research Center, Louisiana State University System, 6400 Perkins Rd., Baton Rouge, Louisiana 70808, USA.
| | | | | |
Collapse
|