1
|
Advancing reproductive neuroendocrinology through research on the regulation of GnIH and on its diverse actions on reproductive physiology and behavior. Front Neuroendocrinol 2022; 64:100955. [PMID: 34767778 DOI: 10.1016/j.yfrne.2021.100955] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/15/2021] [Revised: 10/25/2021] [Accepted: 11/05/2021] [Indexed: 01/03/2023]
Abstract
The discovery of gonadotropin-inhibitory hormone (GnIH) in 2000 has led to a new research era of reproductive neuroendocrinology because, for a long time, researchers believed that only gonadotropin-releasing hormone (GnRH) regulated reproduction as a neurohormone. Later studies on GnIH demonstrated that it acts as a new key neurohormone inhibiting reproduction in vertebrates. GnIH reduces gonadotropin release andsynthesis via the GnIH receptor GPR147 on gonadotropes and GnRH neurons. Furthermore, GnIH inhibits reproductive behavior, in addition to reproductive neuroendocrine function. The modification of the synthesis of GnIH and its release by the neuroendocrine integration of environmental and internal factors has also been demonstrated. Thus, the discovery of GnIH has facilitated advances in reproductive neuroendocrinology. Here, we describe the advances in reproductive neuroendocrinology driven by the discovery of GnIH, research on the effects of GnIH on reproductive physiology and behavior, and the regulatory mechanisms underlying GnIH synthesis and release.
Collapse
|
2
|
Tsutsui K, Ubuka T. Gonadotropin-inhibitory hormone (GnIH): A new key neurohormone controlling reproductive physiology and behavior. Front Neuroendocrinol 2021; 61:100900. [PMID: 33450199 DOI: 10.1016/j.yfrne.2021.100900] [Citation(s) in RCA: 20] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/05/2020] [Revised: 01/04/2021] [Accepted: 01/10/2021] [Indexed: 11/17/2022]
Abstract
The discovery of novel neurohormones is important for the advancement of neuroendocrinology. In early 1970s, gonadotropin-releasing hormone (GnRH), a hypothalamic neuropeptide that promotes gonadotropin release, was identified to be an endogenous neurohormone in mammals. In 2000, thirty years later, another hypothalamic neuropeptide, gonadotropin-inhibitory hormone (GnIH), that inhibits gonadotropin release, was found in quail. GnIH acts via GPR147 and inhibits gonadotropin release and synthesis and reproductive function in birds through actions on GnRH neurons in the hypothalamus and pituitary gonadotrophs. Later, GnIH was found in other vertebrates including humans. GnIH studies have advanced the progress of reproductive neuroendocrinology. Furthermore, recent GnIH studies have indicated that abnormal changes in GnIH expression may cause pubertal disorder and reproductive dysfunction. Here, we describe GnIH discovery and its impact on the progress of reproductive neuroendocrinology. This review also highlights advancement and perspective of GnIH studies on drug development for pubertal disorder and reproductive dysfunction. (149/150).
Collapse
Affiliation(s)
- Kazuyoshi Tsutsui
- Department of Biology and Center for Medical Life Science, Waseda University, Shinjuku-ku, Tokyo 162-8480, Japan; Graduate School of Integrated Sciences for Life, Hiroshima University, Kagamiyama 1-7-1, Higashi-Hiroshima 739-8521, Japan.
| | - Takayoshi Ubuka
- Department of Biology and Center for Medical Life Science, Waseda University, Shinjuku-ku, Tokyo 162-8480, Japan
| |
Collapse
|
3
|
Majarune S, Nima P, Sugimoto A, Nagae M, Inoue N, Tsukamura H, Uenoyama Y. Ad libitum feeding triggers puberty onset associated with increases in arcuate Kiss1 and Pdyn expression in growth-retarded rats. J Reprod Dev 2019; 65:397-406. [PMID: 31155522 PMCID: PMC6815743 DOI: 10.1262/jrd.2019-048] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Increasing evidence shows that puberty onset is largely dependent on body weight rather than chronological age. To investigate the mechanism involved in the energetic control of puberty
onset, the present study examined effects of chronic food restriction during the prepubertal period and the resumption of ad libitum feeding for 24 and 48 h on estrous
cyclicity, Kiss1 (kisspeptin gene), Tac3 (neurokinin B gene) and Pdyn (dynorphin A gene) expression in the hypothalamus, luteinizing
hormone (LH) secretion and follicular development in female rats. When animals weighed 75 g, they were subjected to a restricted feeding to retard growth to 70–80 g by 49 days of age. Then,
animals were subjected to ad libitum feeding or remained food-restricted. The growth-retarded rats did not show puberty onset associated with suppression of both
Kiss1 and Pdyn expression in the arcuate nucleus (ARC). 24-h ad libitum feeding increased tonic LH secretion and the number of Graafian
and non-Graafian tertiary follicles with an increase in the numbers of ARC Kiss1- and Pdyn-expressing cells. 48-h ad libitum feeding
induced the vaginal proestrus and a surge-like LH increase with an increase in Kiss1-expressing cells in the anteroventral periventricular nucleus (AVPV). These results
suggest that the negative energy balance causes pubertal failure with suppression of ARC Kiss1 and Pdyn expression and then subsequent gonadotropin
secretion and ovarian function, while the positive energetic cues trigger puberty onset via an increase in ARC Kiss1 and Pdyn expression and thus
gonadotropin secretion and follicular development in female rats.
Collapse
Affiliation(s)
- Sutisa Majarune
- Laboratory of Animal Reproduction, Graduate School of Bioagricultural Sciences, Nagoya University, Nagoya 464-8601, Japan
| | - Pelden Nima
- Laboratory of Animal Reproduction, Graduate School of Bioagricultural Sciences, Nagoya University, Nagoya 464-8601, Japan
| | - Arisa Sugimoto
- Laboratory of Animal Reproduction, Graduate School of Bioagricultural Sciences, Nagoya University, Nagoya 464-8601, Japan
| | - Mayuko Nagae
- Laboratory of Animal Reproduction, Graduate School of Bioagricultural Sciences, Nagoya University, Nagoya 464-8601, Japan
| | - Naoko Inoue
- Laboratory of Animal Reproduction, Graduate School of Bioagricultural Sciences, Nagoya University, Nagoya 464-8601, Japan
| | - Hiroko Tsukamura
- Laboratory of Animal Reproduction, Graduate School of Bioagricultural Sciences, Nagoya University, Nagoya 464-8601, Japan
| | - Yoshihisa Uenoyama
- Laboratory of Animal Reproduction, Graduate School of Bioagricultural Sciences, Nagoya University, Nagoya 464-8601, Japan
| |
Collapse
|
4
|
Muteka SP, Chimimba CT, Bastos AD, Bennett NC. The reproductive pattern of the Gerbilliscus cf. leucogaster (Rodentia: Muridae) from Namibia. CAN J ZOOL 2019. [DOI: 10.1139/cjz-2018-0090] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Very little is known about the reproductive biology of the Gerbilliscus cf. leucogaster (Peters, 1852) despite its wide distribution throughout the southern African subregion. Body mass, reproductive tract morphometrics, and gonadal histology were studied over 12 months in wild caught Gerbilliscus cf. leucogaster from the central part of Namibia to gain insights into the reproductive pattern of this species. The number of Graafian follicles and corpora lutea in 93 females increased at the end of the dry period (September) and throughout the wet months of the year (October–May) relative to that of the dry season (June–August). Pregnant and lactating females were recorded during the wet months of the year, with a peak observed during February. Testicular mass relative to body mass, testicular volume, and seminiferous tubule diameter in 64% of males increased significantly during the rainfall period (October–June). In addition, 8% of males exhibited little spermatogenesis and 28% showed no spermatogenesis or presence of sperm in the epididymis during the dry period (June–August). These findings suggest that the Gerbilliscus cf. leucogaster breeds predominantly during the rainfall period in Namibia when the food resources are more abundant.
Collapse
Affiliation(s)
- Sachariah P. Muteka
- Department of Animal Science, University of Namibia, Windhoek, Namibia
- Mammal Research Institute, Department of Zoology and Entomology, University of Pretoria, Pretoria 0002, South Africa
| | - Christian T. Chimimba
- Mammal Research Institute, Department of Zoology and Entomology, University of Pretoria, Pretoria 0002, South Africa
| | - Armanda D. Bastos
- Mammal Research Institute, Department of Zoology and Entomology, University of Pretoria, Pretoria 0002, South Africa
| | - Nigel C. Bennett
- Mammal Research Institute, Department of Zoology and Entomology, University of Pretoria, Pretoria 0002, South Africa
- South African Research Chair of Behavioural Ecology and Physiology, Department of Zoology and Entomology, University of Pretoria, Pretoria 0002, South Africa
| |
Collapse
|
5
|
Uenoyama Y, Inoue N, Nakamura S, Tsukamura H. Central Mechanism Controlling Pubertal Onset in Mammals: A Triggering Role of Kisspeptin. Front Endocrinol (Lausanne) 2019; 10:312. [PMID: 31164866 PMCID: PMC6536648 DOI: 10.3389/fendo.2019.00312] [Citation(s) in RCA: 50] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/17/2018] [Accepted: 04/30/2019] [Indexed: 01/29/2023] Open
Abstract
Pubertal onset is thought to be timed by an increase in pulsatile gonadotropin-releasing hormone (GnRH)/gonadotropin secretion in mammals. The underlying mechanism of pubertal onset in mammals is still an open question. Evidence accumulated in the last 15 years suggests that kisspeptin/neurokinin B/dynorphin A (KNDy) neurons in the hypothalamic arcuate nucleus play a key role in pubertal onset by triggering pulsatile GnRH/gonadotropin secretin in mammals. Specifically, KNDy neurons are now considered a part of GnRH pulse generator, in which neurokinin B facilitates and dynorphin A inhibits, the synchronized discharge of KNDy neurons in autocrine and/or paracrine manners. Kisspeptin serves as a potent secretagogue of GnRH secretion and thus its release is fundamental to pubertal increase in GnRH/gonadotropin secretion in mammals. Proposed mechanisms inhibiting Kiss1 (kisspeptin gene) expression during childhood to juvenile varies from species to species: we envisage that negative feedback action of estrogen plays a key role in the inhibition of Kiss1 expression in KNDy neurons in rodents and sheep, whereas estrogen-independent inhibition of kisspeptin secretion by γ-amino butyric acid or neuropeptide Y are suggested to be responsible for the pre-pubertal suppression of GnRH/gonadotropin secretion in primates. Taken together, the timing of pubertal onset is postulated to be controlled by upstream regulators for kisspeptin biosynthesis and secretion in mammals.
Collapse
Affiliation(s)
- Yoshihisa Uenoyama
- Laboratory of Animal Reproduction, Graduate School of Bioagricultural Sciences, Nagoya University, Nagoya, Japan
- *Correspondence: Yoshihisa Uenoyama
| | - Naoko Inoue
- Laboratory of Animal Reproduction, Graduate School of Bioagricultural Sciences, Nagoya University, Nagoya, Japan
| | - Sho Nakamura
- Faculty of Veterinary Medicine, Okayama University of Science, Imabari, Japan
| | - Hiroko Tsukamura
- Laboratory of Animal Reproduction, Graduate School of Bioagricultural Sciences, Nagoya University, Nagoya, Japan
| |
Collapse
|
6
|
Tsutsui K, Ubuka T. How to Contribute to the Progress of Neuroendocrinology: Discovery of GnIH and Progress of GnIH Research. Front Endocrinol (Lausanne) 2018; 9:662. [PMID: 30483217 PMCID: PMC6241250 DOI: 10.3389/fendo.2018.00662] [Citation(s) in RCA: 30] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/05/2018] [Accepted: 10/23/2018] [Indexed: 01/14/2023] Open
Abstract
It is essential to discover novel neuropeptides that regulate the functions of pituitary, brain and peripheral secretory glands for the progress of neuroendocrinology. Gonadotropin-releasing hormone (GnRH), a hypothalamic neuropeptide stimulating gonadotropin release was isolated and its structure was determined by Schally's and Guillemin's groups at the beginning of the 1970s. It was subsequently shown that GnRH is highly conserved among vertebrates. GnRH was assumed the sole hypothalamic neuropeptide that regulates gonadotropin release in vertebrates based on extensive studies of GnRH over the following three decades. However, in 2000, Tsutsui's group isolated and determined the structure of a novel hypothalamic neuropeptide, which inhibits gonadotropin release, in quail, an avian species, and named it gonadotropin-inhibitory hormone (GnIH). Following studies by Tsutsui's group demonstrated that GnIH is highly conserved among vertebrates, from humans to agnathans, and acts as a key neuropeptide inhibiting reproduction. Intensive research on GnIH demonstrated that GnIH inhibits gonadotropin synthesis and release by acting on gonadotropes and GnRH neurons via GPR147 in birds and mammals. Fish GnIH also regulates gonadotropin release according to its reproductive condition, indicating the conserved role of GnIH in the regulation of the hypothalamic-pituitary-gonadal (HPG) axis in vertebrates. Therefore, we can now say that GnRH is not the only hypothalamic neuropeptide controlling vertebrate reproduction. In addition, recent studies by Tsutsui's group demonstrated that GnIH acts in the brain to regulate behaviors, including reproductive behavior. The 18 years of GnIH research with leading laboratories in the world have significantly advanced our knowledge of the neuroendocrine control mechanism of reproductive physiology and behavior as well as interactions of the HPG, hypothalamic-pituitary-adrenal and hypothalamic-pituitary-thyroid axes. This review describes how GnIH was discovered and GnIH research progressed in this new research era of reproductive neuroendocrinology.
Collapse
Affiliation(s)
- Kazuyoshi Tsutsui
- Laboratory of Integrative Brain Sciences, Department of Biology and Center for Medical Life Science, Waseda University, Tokyo, Japan
| | - Takayoshi Ubuka
- Laboratory of Integrative Brain Sciences, Department of Biology and Center for Medical Life Science, Waseda University, Tokyo, Japan
| |
Collapse
|
7
|
Leakey JEA, Seng JE, Barnas CR, Baker VM, Hart RW. A Mechanistic Basis for the Beneficial Effects of Caloric Restriction On Longevity and Disease: Consequences for the Interpretation of Rodent Toxicity Studies. Int J Toxicol 2016. [DOI: 10.1177/109158189801700203] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Caloric restriction in rodents has been repeatedly shown to increase life span while reducing the severity and retarding the onset of both spontaneous and chemically induced neoplasms. These effects of caloric restriction are associated with a spectrum of biochemical and physiological changes that characterize the organism's adaptation to reduced caloric intake and provide the mechanistic basis for caloric restriction's effect on longevity. Here, we review evidence suggesting that the primary adaptation appears to be a rhythmic hypercorticism in the absence of elevated adrenocorticotropin (ACTH) levels. This characteristic hypercorticism evokes a spectrum of responses, including reduced body temperature and increased metabolic efficiency, decreased mitogenic response coupled with increased rates of apoptosis, reduced inflammatory response, reduced oxidative damage to proteins and DNA, reduced reproductive capacity, and altered drug-metabolizing enzyme expression. The net effect of these changes is to (1) decrease growth and metabolism in peripheral tissues to spare energy for central functions, and (2) increase the organism's capacity to withstand stress and chemical toxicity. Thus, caloric restriction research has uncovered an evolutionary mechanism that provides rodents with an adaptive advantage in conditions of fluctuating food supply. During periods of abundance, body growth and fecundity are favored over endurance and longevity. Conversely, during periods of famine, reproductive performance and growth are sacrificed to ensure survival of individuals to breed in better times. This phenomena can be observed in rodent populations that are used in toxicity testing. Improvements over the last 30 years in animal husbandry and nutrition, coupled with selective breeding for growth and fecundity, have resulted in several strains now exhibiting larger animals with reduced survival and increased incidence of background lesions. The mechanistic data from caloric restriction studies suggest that these large animals will also be more susceptible to chemically induced toxicity. This creates a problem in comparing tests performed on animals of different weights and comparing data generated today with the historical database. The rational use of caloric restriction to control body weight to within preset guidelines is a possible way of alleviating this problem.
Collapse
Affiliation(s)
- Julian E. A. Leakey
- Office of Research, National Center for Toxicological
Research, Jefferson, Arkansas, USA
| | - John E. Seng
- Office of Research, National Center for Toxicological
Research, Jefferson, Arkansas, USA
| | - Crissy R. Barnas
- Office of Research, National Center for Toxicological
Research, Jefferson, Arkansas, USA, Department of Clinical Pharmacology and Geriatrics,
Northwestern University, 303 E. Superior St., Chicago, IL 60611, USA
| | - Vanessa M. Baker
- Office of Research, National Center for Toxicological
Research, Jefferson, Arkansas, USA
| | - Ronald W. Hart
- Office of Research, National Center for Toxicological
Research, Jefferson, Arkansas, USA
| |
Collapse
|
8
|
Ullah R, Shen Y, Zhou YD, Huang K, Fu JF, Wahab F, Shahab M. Expression and actions of GnIH and its orthologs in vertebrates: Current status and advanced knowledge. Neuropeptides 2016; 59:9-20. [PMID: 27255391 DOI: 10.1016/j.npep.2016.05.004] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/02/2016] [Revised: 05/01/2016] [Accepted: 05/23/2016] [Indexed: 12/20/2022]
Abstract
The physiology of reproduction is very complex and is regulated by multiple factors, including a number of hypothalamic neuropeptides. In last few decades, various neuropeptides have been discovered to be involved in stimulation or inhibition of reproduction. In 2000, Tsutsui and colleagues uncovered gonadotropin-inhibitory hormone (GnIH), a neuropeptide generating inhibitory drive to the reproductive axis, in the brain of Coturnix quail. Afterward, GnIH orthologs were discovered in other vertebrates from fish to mammals including human. In these vertebrates, all the discovered GnIH and its ortholgs have LPXRFamide (X=L or Q) sequence at C-terminus. GnIH orthologs of mammals and primates are also termed as RFamide-related peptide (RFRP)-1 and -3 that too have an LPXRFamide (X=L or Q) motif at their C-terminus. GnIH and its orthologs form a member of the RFamide peptide family. GnIH signals via its canonical G protein coupled receptor 147 (GPR147). Both GnIH and GPR147 are expressed in hypothalamus and other brain regions. Besides actions through the hypothalamic GnRH and kisspeptinergic neurons, GnIH-GPR147 signaling exerts inhibitory effect on the reproductive axis via pituitary gonadotropes and directly at gonadal level. Various factors including availability and quality of food, photoperiod, temperature, social interaction, various stresses and some diseases modulate GnIH-GPR147 signaling. In this review, we have discussed expression and actions of GnIH and its orthologs in vertebrates. Special emphasis is given on the role of GnIH-GPR147 signaling pathway in the regulation of reproduction. We have also reviewed and discussed currently available literature on the participation of GnIH-GPR147 signaling pathway in the stress modulation of reproduction.
Collapse
Affiliation(s)
- Rahim Ullah
- Department of Endocrinology, Children Hospital of Zhejiang University, School of Medicine, Zhejiang University, Hangzhou, China; Laboratory of Reproductive Neuroendocrinology, Department of Animal Sciences, Faculty of Biological Sciences, Quaid-i-Azam University, Islamabad, Pakistan; Key Laboratory of Medical Neurobiology of Ministry of Health and Zhejiang Province, Department of Neurobiology, School of Medicine, Zhejiang University, Hangzhou 310058, PR China
| | - Yi Shen
- Key Laboratory of Medical Neurobiology of Ministry of Health and Zhejiang Province, Department of Neurobiology, School of Medicine, Zhejiang University, Hangzhou 310058, PR China
| | - Yu-Dong Zhou
- Key Laboratory of Medical Neurobiology of Ministry of Health and Zhejiang Province, Department of Neurobiology, School of Medicine, Zhejiang University, Hangzhou 310058, PR China
| | - Ke Huang
- Laboratory of Reproductive Neuroendocrinology, Department of Animal Sciences, Faculty of Biological Sciences, Quaid-i-Azam University, Islamabad, Pakistan; Laboratory of Reproductive Neuroendocrinology, Department of Animal Sciences, Faculty of Biological Sciences, Quaid-i-Azam University, Islamabad, Pakistan
| | - Jun-Fen Fu
- Department of Endocrinology, Children Hospital of Zhejiang University, School of Medicine, Zhejiang University, Hangzhou, China.
| | - Fazal Wahab
- Stem Cell Biology Unit, German Primate Center, Leibniz-Institute for Primate Research, Kellnerweg 4, 37077 Gottingen, Germany
| | - Muhammad Shahab
- Laboratory of Reproductive Neuroendocrinology, Department of Animal Sciences, Faculty of Biological Sciences, Quaid-i-Azam University, Islamabad, Pakistan.
| |
Collapse
|
9
|
Tsutsui K, Ubuka T. GnIH Control of Feeding and Reproductive Behaviors. Front Endocrinol (Lausanne) 2016; 7:170. [PMID: 28082949 PMCID: PMC5186799 DOI: 10.3389/fendo.2016.00170] [Citation(s) in RCA: 41] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/25/2016] [Accepted: 12/16/2016] [Indexed: 11/13/2022] Open
Abstract
In 2000, Tsutsui and colleagues discovered a neuropeptide gonadotropin-inhibitory hormone (GnIH) that inhibits gonadotropin release in birds. Subsequently, extensive studies during the last 15 years have demonstrated that GnIH is a key neurohormone that regulates reproduction in vertebrates, acting in the brain and on the pituitary to modulate reproduction and reproductive behavior. On the other hand, deprivation of food and other metabolic challenges inhibit the reproductive axis as well as sexual motivation. Interestingly, recent studies have further indicated that GnIH controls feeding behavior in vertebrates, such as in birds and mammals. This review summarizes the discovery of GnIH and its conservation in vertebrates and the neuroendocrine control of feeding behavior and reproductive behavior by GnIH.
Collapse
Affiliation(s)
- Kazuyoshi Tsutsui
- Laboratory of Integrative Brain Sciences, Department of Biology and Center for Medical Life Science, Waseda University, Tokyo, Japan
- *Correspondence: Kazuyoshi Tsutsui,
| | - Takayoshi Ubuka
- Laboratory of Integrative Brain Sciences, Department of Biology and Center for Medical Life Science, Waseda University, Tokyo, Japan
- Jeffrey Cheah School of Medicine and Health Sciences, Brain Research Institute Monash Sunway, Monash University Malaysia, Bandar Sunway, Malaysia
| |
Collapse
|
10
|
Méquinion M, Chauveau C, Viltart O. The use of animal models to decipher physiological and neurobiological alterations of anorexia nervosa patients. Front Endocrinol (Lausanne) 2015; 6:68. [PMID: 26042085 PMCID: PMC4436882 DOI: 10.3389/fendo.2015.00068] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/12/2015] [Accepted: 04/15/2015] [Indexed: 12/18/2022] Open
Abstract
Extensive studies were performed to decipher the mechanisms regulating feeding due to the worldwide obesity pandemy and its complications. The data obtained might be adapted to another disorder related to alteration of food intake, the restrictive anorexia nervosa. This multifactorial disease with a complex and unknown etiology is considered as an awful eating disorder since the chronic refusal to eat leads to severe, and sometimes, irreversible complications for the whole organism, until death. There is an urgent need to better understand the different aspects of the disease to develop novel approaches complementary to the usual psychological therapies. For this purpose, the use of pertinent animal models becomes a necessity. We present here the various rodent models described in the literature that might be used to dissect central and peripheral mechanisms involved in the adaptation to deficient energy supplies and/or the maintenance of physiological alterations on the long term. Data obtained from the spontaneous or engineered genetic models permit to better apprehend the implication of one signaling system (hormone, neuropeptide, neurotransmitter) in the development of several symptoms observed in anorexia nervosa. As example, mutations in the ghrelin, serotonin, dopamine pathways lead to alterations that mimic the phenotype, but compensatory mechanisms often occur rendering necessary the use of more selective gene strategies. Until now, environmental animal models based on one or several inducing factors like diet restriction, stress, or physical activity mimicked more extensively central and peripheral alterations decribed in anorexia nervosa. They bring significant data on feeding behavior, energy expenditure, and central circuit alterations. Animal models are described and criticized on the basis of the criteria of validity for anorexia nervosa.
Collapse
Affiliation(s)
- Mathieu Méquinion
- INSERM UMR-S1172, Development and Plasticity of Postnatal Brain, Lille, France
| | - Christophe Chauveau
- Pathophysiology of Inflammatory Bone Diseases, EA 4490, University of the Littoral Opal Coast, Boulogne sur Mer, France
| | - Odile Viltart
- INSERM UMR-S1172, Early stages of Parkinson diseases, University Lille 1, Lille, France
| |
Collapse
|
11
|
Kriegsfeld LJ, Ubuka T, Bentley GE, Tsutsui K. Seasonal control of gonadotropin-inhibitory hormone (GnIH) in birds and mammals. Front Neuroendocrinol 2015; 37:65-75. [PMID: 25511257 PMCID: PMC4405439 DOI: 10.1016/j.yfrne.2014.12.001] [Citation(s) in RCA: 85] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/17/2014] [Revised: 12/05/2014] [Accepted: 12/07/2014] [Indexed: 12/14/2022]
Abstract
Animals inhabiting temperate and boreal latitudes experience marked seasonal changes in the quality of their environments and maximize reproductive success by phasing breeding activities with the most favorable time of year. Whereas the specific mechanisms driving seasonal changes in reproductive function vary across species, converging lines of evidence suggest gonadotropin-inhibitory hormone (GnIH) serves as a key component of the neuroendocrine circuitry driving seasonal changes in reproduction and sexual motivation in some species. In addition to anticipating environmental change through transduction of photoperiodic information and modifying reproductive state accordingly, GnIH is also positioned to regulate acute changes in reproductive status should unpredictable conditions manifest throughout the year. The present overview summarizes the role of GnIH in avian and mammalian seasonal breeding while considering the similarities and disparities that have emerged from broad investigations across reproductively photoperiodic species.
Collapse
Affiliation(s)
- Lance J Kriegsfeld
- Department of Psychology and Helen Wills Neuroscience Institute, University of California at Berkeley, Berkeley, CA 94720-1650, USA.
| | - Takayoshi Ubuka
- Laboratory of Integrative Brain Sciences, Department of Biology, Waseda University, Center for Medical Life Science of Waseda University, 2-2 Wakamatsu-cho, Shinjuku-ku, Tokyo 162-8480, Japan
| | - George E Bentley
- Department of Integrative Biology and Helen Wills Neuroscience Institute, University of California at Berkeley, Berkeley, CA 94720-3140, USA
| | - Kazuyoshi Tsutsui
- Laboratory of Integrative Brain Sciences, Department of Biology, Waseda University, Center for Medical Life Science of Waseda University, 2-2 Wakamatsu-cho, Shinjuku-ku, Tokyo 162-8480, Japan
| |
Collapse
|
12
|
Tsutsui K, Ubuka T, Son YL, Bentley GE, Kriegsfeld LJ. Contribution of GnIH Research to the Progress of Reproductive Neuroendocrinology. Front Endocrinol (Lausanne) 2015; 6:179. [PMID: 26635728 PMCID: PMC4655308 DOI: 10.3389/fendo.2015.00179] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/18/2015] [Accepted: 11/05/2015] [Indexed: 12/17/2022] Open
Abstract
Since the discovery of gonadotropin-releasing hormone (GnRH) in mammals at the beginning of the 1970s, it was generally accepted that GnRH is the only hypothalamic neuropeptide regulating gonadotropin release in mammals and other vertebrates. In 2000, however, gonadotropin-inhibitory hormone (GnIH), a novel hypothalamic neuropeptide that actively inhibits gonadotropin release, was discovered in quail. Numerous studies over the past decade and a half have demonstrated that GnIH serves as a key player regulating reproduction across vertebrates, acting on the brain and pituitary to modulate reproductive physiology and behavior. In the latter case, recent evidence indicates that GnIH can regulate reproductive behavior through changes in neurosteroid, such as neuroestrogen, biosynthesis in the brain. This review summarizes the discovery of GnIH, and the contributions to GnIH research focused on its mode of action, regulation of biosynthesis, and how these findings advance our understanding of reproductive neuroendocrinology.
Collapse
Affiliation(s)
- Kazuyoshi Tsutsui
- Laboratory of Integrative Brain Sciences, Department of Biology and Center for Medical Life Science, Waseda University, Tokyo, Japan
- *Correspondence: Kazuyoshi Tsutsui,
| | - Takayoshi Ubuka
- Laboratory of Integrative Brain Sciences, Department of Biology and Center for Medical Life Science, Waseda University, Tokyo, Japan
- Brain Research Institute Monash Sunway of the Jeffrey Cheah School of Medicine and Health Sciences, Monash University Malaysia, Petaling Jaya, Malaysia
| | - You Lee Son
- Laboratory of Integrative Brain Sciences, Department of Biology and Center for Medical Life Science, Waseda University, Tokyo, Japan
| | - George E. Bentley
- Department of Integrative Biology, Helen Wills Neuroscience Institute, University of California at Berkeley, Berkeley, CA, USA
| | - Lance J. Kriegsfeld
- Department of Psychology, Helen Wills Neuroscience Institute, University of California at Berkeley, Berkeley, CA, USA
| |
Collapse
|
13
|
Regulation of gonadotropin secretion by monitoring energy availability. Reprod Med Biol 2014; 14:39-47. [PMID: 29259401 DOI: 10.1007/s12522-014-0194-0] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2014] [Accepted: 09/06/2014] [Indexed: 10/24/2022] Open
Abstract
Nutrition is a principal environmental factor influencing fertility in animals. Energy deficit causes amenorrhea, delayed puberty, and suppression of copulatory behaviors by inhibiting gonadal activity. When gonadal activity is impaired by malnutrition, the signals originating from an undernourished state are ultimately conveyed to the gonadotropin-releasing hormone (GnRH) pulse generator, leading to suppressed secretion of GnRH and luteinizing hormone (LH). The mechanism responsible for energetic control of gonadotropin release is believed to involve metabolic signals, sensing mechanisms, and neuroendocrine pathways. The availabilities of blood-borne energy substrates such as glucose, fatty acids, and ketone bodies, which fluctuate in parallel with changes in nutritional status, act as metabolic signals that regulate the GnRH pulse generator activity and GnRH/LH release. As components of the specific sensing system, the ependymocytes lining the cerebroventricular wall in the lower brainstem integrate the information derived from metabolic signals to control gonadotropin release. One of the pathways responsible for the energetic control of gonadal activity consists of noradrenergic neurons from the solitary tract nucleus in the lower brainstem, projecting to the paraventricular nucleus of the hypothalamus. Further studies are needed to elucidate the mechanisms underlying energetic control of reproductive function.
Collapse
|
14
|
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: 76] [Impact Index Per Article: 6.9] [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
|
15
|
Dooley JC, Prendergast BJ. Photorefractoriness and energy availability interact to permit facultative timing of spring breeding. ACTA ACUST UNITED AC 2012; 23:1049-1058. [PMID: 22936842 DOI: 10.1093/beheco/ars074] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2011] [Revised: 04/02/2012] [Accepted: 04/02/2012] [Indexed: 11/13/2022]
Abstract
In seasonally breeding mammals, vernal reproductive development is not directly triggered by increases in day length, rather, an endogenous program of photorefractoriness to short winter days initiates spontaneous development in advance of spring. The transition to the reproductive phenotype is energetically demanding. How food availability in late winter and early spring impacts the onset and expression of photorefractoriness is not known. In this study, male Siberian hamsters were born into a simulated natural photoperiod, and at the winter solstice, they were subjected to a restricted feeding protocol in which a daily food ration was provided in an amount equal to ad libitum (AL) intake during the weeks preceding the solstice. Over the next several months, AL-fed control hamsters exhibited spontaneous recrudescence or spontaneous development. In contrast, vernal reproductive development was abolished in most food-rationed hamsters. In food-rationed hamsters that did exhibit recrudescence, conspicuous delays in the onset of gonadal development and decreases in the magnitude of growth were evident. In all hamsters, the termination of food rationing triggered rapid gonadal development. The data indicate that late winter/early spring increases in environmental food availability are required for the normal manifestation of photorefractoriness-induced reproductive development and suggest that a function of photorefractoriness may be merely to disinhibit the reproductive axis from photoperiodic suppression. Vernal gonadal development or recrudescence appears to be strongly affected by proximate energy availability.
Collapse
Affiliation(s)
- James C Dooley
- Department of Psychology, University of Chicago, 940 E. 57th St., Chicago, IL 60637, USA
| | | |
Collapse
|
16
|
Glad CAM, Kitchen EEJ, Russ GC, Harris SM, Davies JS, Gevers EF, Gabrielsson BG, Wells T. Reverse feeding suppresses the activity of the GH axis in rats and induces a preobesogenic state. Endocrinology 2011; 152:869-82. [PMID: 21209022 DOI: 10.1210/en.2010-0713] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
Reversed feeding (RF) is known to disrupt hormone rhythmicity and metabolism. Although these effects may be mediated in part by phase inversion of glucocorticoid secretion, the precise mechanism is incompletely characterized. In this study, we demonstrate that acute nocturnal food deprivation in male rats suppressed the amplitude of spontaneous GH secretion during the dark phase by 62% (P < 0.001), without affecting baseline secretion. Prolonged RF, which reduced pituitary weight (by 22%; P < 0.05), also suppressed GH pulse height sufficiently to reduce skeletal growth (by 4-5%; P < 0.01) and terminal liver weight (by 11%; P < 0.001). Despite this suppression of the GH axis, proportionate adiposity was not elevated, probably due to the accompanying 16% reduction in cumulative food intake (P < 0.01). We demonstrate that RF also resulted in phase inversion of core clock gene expression in liver, abdominal white adipose tissue (WAT) and skeletal muscle, without affecting their expression patterns in the suprachiasmatic nucleus. In addition, RF resulted in phase inversion of hepatic peroxisome proliferator-activated receptor γ2 mRNA expression, a 3- to 5-fold elevation in fatty acid synthase mRNA in WAT in both light- and dark-phase samples (P < 0.01) and an elevation in muscle uncoupling protein 3 mRNA expression at the beginning of the light phase (P < 0.01). Consumption of a high-fat diet increased inguinal (by 36%; P < 0.05) and retroperitoneal WAT weight (by 72%; P < 0.01) only in RF-maintained rats, doubling the efficiency of lipid accumulation (P < 0.05). Thus, RF not only desynchronizes central and peripheral circadian clocks, and suppresses nocturnal GH secretion, but induces a preobesogenic state.
Collapse
Affiliation(s)
- Camilla A-M Glad
- Department of Endocrinology, Institute of Medicine, The Sahlgrenska Academy at the University of Gothenburg, SE-413 45 Göteborg, Sweden
| | | | | | | | | | | | | | | |
Collapse
|
17
|
Robinson ICAF, Hindmarsh PC. The Growth Hormone Secretory Pattern and Statural Growth. Compr Physiol 2011. [DOI: 10.1002/cphy.cp070512] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
|
18
|
Abou Heif HM, Deif MM, Abdel Aziz HK. Effect of food restriction on ghrelin in adult male rats and its relation to male reproductive hormones. Andrologia 2010; 42:97-105. [DOI: 10.1111/j.1439-0272.2009.00962.x] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
|
19
|
Ciccone NA, Dunn IC, Sharp PJ. Increased food intake stimulates GnRH-I, glycoprotein hormone alpha-subunit and follistatin mRNAs, and ovarian follicular numbers in laying broiler breeder hens. Domest Anim Endocrinol 2007; 33:62-76. [PMID: 16737793 DOI: 10.1016/j.domaniend.2006.04.008] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/18/2006] [Accepted: 04/25/2006] [Indexed: 11/18/2022]
Abstract
The aim of this study, in 36 week-old laying broiler breeder hens, was to establish the effects on reproductive neuroendocrine gene expression of reinstating ad libitum food intake after moderate food restriction from 2 weeks of age. Seven days of ad libitum feeding increased the number of large pre-ovulatory ovarian follicles and gonadotropin releasing hormone-I (GnRH-I), glycoprotein hormone alpha-subunit and follistatin mRNAs. Plasma luteinizing hormone (LH) was also increased while plasma follicle-stimulating hormone (FSH) was reduced. There were no associated changes in gonadotropin inhibitory hormone (GnIH), LHbeta or FSHbeta mRNAs. The mechanism underlying the increased expression of alpha-subunit and follistatin mRNAs was investigated in vitro by incubating pituitary fragments with pulses of GnRH-I. This treatment increased alpha-subunit and follistatin mRNAs but did not affect gonadotropin beta-subunit mRNAs. It is concluded that lifting food restriction in laying hens increases GnRH-I gene transcription or mRNA stability which may be a consequence, or cause of increased GnRH-I release. This, in turn, increases glycoprotein hormone alpha-subunit and follistatin mRNAs, resulting in increased plasma LH and decreased plasma FSH, respectively.
Collapse
Affiliation(s)
- N A Ciccone
- Division of Genetics and Genomics, Roslin Institute, Roslin, Midlothian EH25 9PS, United Kingdom
| | | | | |
Collapse
|
20
|
Szymanski LA, Schneider JE, Friedman MI, Ji H, Kurose Y, Blache D, Rao A, Dunshea FR, Clarke IJ. Changes in insulin, glucose and ketone bodies, but not leptin or body fat content precede restoration of luteinising hormone secretion in ewes. J Neuroendocrinol 2007; 19:449-60. [PMID: 17504439 DOI: 10.1111/j.1365-2826.2007.01551.x] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
The reproductive system, including pulsatile luteinising hormone (LH) secretion, is inhibited by deficits in energy availability and restored by energy surfeits. Plasma LH, insulin, leptin, ghrelin, glucose, ketone body, and nonesterified fatty acid concentrations were measured in ovariectomised, food-restricted ewes before and after return to ad libitum feeding to determine the factors that change in time to account for the restoration of pulsatile LH secretion. At 07.00 h, blood was sampled every 10 min for 5 h from ovariectomised, hypogonadotrophic, chronically food-restricted and ad libitum-fed ewes (Fed). At 12.00 h, four of the food-restricted sheep were given ad libitum access to food (Re-Fed), while three ewes continued to be food restricted (Restricted). Sampling continued for 5 h and resumed again on the mornings of days 2, 4, and 9. A pulse of LH was seen within 1 h of re-feeding in all Re-Fed ewes, and interpulse interval (IPI) was significantly shorter in Re-Fed compared to Restricted ewes and longer than in Fed ewes during the period after re-feeding. Re-Fed LH IPI was not restored to that of Fed ewes until sometime between days 4 and 9. The first pulse occurred within minutes, whereas restoration of IPI occurred after 4-8 days. Prior to the initial LH pulses seen in Re-Fed ewes, plasma ketone bodies first fell and then rose to levels significantly above those in Restricted ewes. Significant changes in circulating insulin, ghrelin, glucose, and total ketone body concentrations, daily food intake and lean body mass preceded restoration of Re-Fed LH IPI some time between days 4 and 9, but there were no significant changes in adiposity or circulating leptin concentrations, consistent with the hypothesis that LH pulses are reinitiated by changes in the availability of oxidisable metabolic fuels and possibly insulin, but not leptin concentrations.
Collapse
|
21
|
Perfito N, Bentley G, Hau M. Tonic Activation of Brain GnRH Immunoreactivity despite Reduction of Peripheral Reproductive Parameters in Opportunistically Breeding Zebra Finches. BRAIN, BEHAVIOR AND EVOLUTION 2006; 67:123-34. [PMID: 16415568 DOI: 10.1159/000090977] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/27/2005] [Accepted: 09/13/2005] [Indexed: 11/19/2022]
Abstract
Opportunistically breeding species offer the unique opportunity to understand mechanisms in reproductive physiology that allow for extreme flexibility in the regulation of reproduction. We studied a well-known opportunistic breeder, the zebra finch (Taeniopygia guttata) to test the hypothesis that the reproductive axis of opportunists is in a constant state of 'near-readiness'. In wild zebra finches, reproduction is highly correlated with rainfall, and in the laboratory, water availability and humidity are the strongest cues to affect reproductive activation. We therefore subjected individuals to water restriction for eleven weeks followed by a two week period of ad libitum access to water. The control group had water freely available for the entire experiment. We measured the state of activation of the hypothalamo-pituitary gonad (HPG) axis at three levels: in the hypothalamus by measuring immunoreactive (ir) cGnRH-I and cGnRH-II; in the anterior pituitary gland by measuring plasma luteinizing hormone (LH); and in the gonads by measuring gonadal volume and function. We found that water restriction caused a reduction in circulating LH concentrations and that testis volume was more likely to decrease in water restricted than in control birds. Subsequent short-term return to ad libitum water availability caused LH to return to baseline in water restricted birds. These changes occurred without significant changes in ir-cGnRH-I, ir-cGnRH-II, or in testis function. These data suggest that in these opportunistic breeders, an inhibition of parts of the reproductive axis is not necessarily correlated with full inactivation of reproductive potential. GnRH-ir cells in the hypothalamus appear to remain active and able to respond to subsequent stimulation.
Collapse
Affiliation(s)
- Nicole Perfito
- Department of Ecology and Evolutionary Biology, Princeton University, Princeton, NJ 08544-1003, USA.
| | | | | |
Collapse
|
22
|
Kim HH, DiVall SA, Deneau RM, Wolfe A. Insulin regulation of GnRH gene expression through MAP kinase signaling pathways. Mol Cell Endocrinol 2005; 242:42-9. [PMID: 16144737 DOI: 10.1016/j.mce.2005.07.002] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/25/2005] [Revised: 07/12/2005] [Accepted: 07/13/2005] [Indexed: 12/27/2022]
Abstract
In mammals, reproduction is acutely regulated by metabolic status. Insulin is an important nutritional signal from the periphery that may regulate the reproductive axis. To determine whether insulin acts directly on the GnRH neuron, we performed studies in mouse-derived GnRH-expressing cell lines. Both insulin receptor protein and mRNA were detected in these cells. A saturation radioligand binding assay revealed high affinity, low capacity binding sites for insulin in GnRH neurons. Insulin also stimulated GnRH promoter activity in GnRH neurons. This effect was blocked by pretreatment with the MEK inhibitor, PD98059, indicating a role for MAP kinase signaling. In transient transfection studies, insulin treatment stimulated expression of a 1250 bp mouse GnRH gene promoter fragment four-fold when compared to promoter activity in untreated cells. In contrast, insulin did not stimulate activity of a 587 bp fragment of the mGnRH gene promoter, indicating that the promoter elements mediating insulin stimulation of the GnRH promoter are located between -1250 and -587 bp. Our studies suggest that insulin may regulate reproductive function by direct effects on the GnRH neurons and specifically by stimulating GnRH gene expression.
Collapse
Affiliation(s)
- Helen H Kim
- University of Chicago, Department of Obstetrics and Gynecology, 5839 South Maryland Avenue MC5053, Chicago, IL 60637, USA
| | | | | | | |
Collapse
|
23
|
Karakaş A, Camsari C, Serin E, Gündüz B. Effects of Photoperiod and Food Availability on Growth, Leptin, Sexual Maturation and Maintenance in the Mongolian Gerbils (Meriones unguiculatus). Zoolog Sci 2005; 22:665-70. [PMID: 15988161 DOI: 10.2108/zsj.22.665] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Reproductive activity of Mongolian gerbils is regulated by photoperiod nevertheless body weight regulation is controlled without ambient photoperiod. Food intake is a major factor affecting rodent reproductive efficiency. Leptin is a hormone secreted by adipose tissue and modulates food intake, energy expenditure and body fat stores. In this study we studied the interaction of photoperiod and food availability on growth, sexual maturation and leptin concentration in the male and female gerbils. Gerbils were gestated and reared in either 14L:10D or 2L:22D. At weaning, gerbils were housed individually and divided into three groups: fed ad libitum, fed 80% of ad libitum or fed 60% of ad libitum. Body weights were recorded at weaning and every week thereafter. After twelve weeks of treatment, animals were sacrificed and testes and uterine weights were determined and blood was collected for leptin measurement. Food restriction reduced body weight and inhibited reproductive development. Absolute paired testis weights were similar in ad lib and 80% of ad lib groups but significantly different compared with the 60% of ad lib group in both photoperiods. Body weights were also directly dependent upon the level of food restriction. Uterine mass was only affected in the 60% of ad lib group in 14L but both food restriction levels significantly affected the uterine weights in 2L. Significant variations were found in leptin profiles. Leptin concentration was highest in ad lib and 80% of ad lib groups and lowest in 60% of ad lib groups. These results suggest that the reproductive activity of Mongolian gerbils is sensitive to food intake and multiple potential environmental cues (e.g., food availability, temperature) can be utilized.
Collapse
Affiliation(s)
- Alper Karakaş
- Department of Biology, Faculty of Arts and Sciences, Abant Izzet Baysal University, Bolu, Turkey
| | | | | | | |
Collapse
|
24
|
Morrison CD, Daniel JA, Hampton JH, Buff PR, McShane TM, Thomas MG, Keisler DH. Luteinizing hormone and growth hormone secretion in ewes infused intracerebroventricularly with neuropeptide Y. Domest Anim Endocrinol 2003; 24:69-80. [PMID: 12450626 DOI: 10.1016/s0739-7240(02)00206-0] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Neuropeptide Y (NPY) provides an important hypothalamic link between nutritional status and neuroendocrine mechanisms regulating growth and reproduction. The objective of the following series of experiments was to determine the effects of single or continuous administration of NPY on secretion of luteinizing hormone (LH) and (or) growth hormone (GH). In experiment 1, four ovariectomized (OVX) ewes and four OVX + estrogen-treated ewes each received, in a 4 x 4 Latin Square arrangement of treatments, a single injection of 0, 0.5, 5, or 50 microg NPY via an intracerebroventricular (i.c.v.) cannulae to determine the effects on secretion of GH. NPY significantly elevated serum GH at the 50 microg dose regardless of estrogen exposure (P = 0.003). In experiment 2, eight OVX ewes were infused i.c.v. with NPY or saline (n = 4/trmt) continuously for 20 h in a linearly increasing dose, ending at 50 microg/h NPY. Blood samples were collected via jugular cannulae every 10 min during hour -4-0 (interval 1, pre-treatment), hour 6-10 (interval 2) and hour 16-20 (interval 3) relative to the initiation of infusion (0 h). Mean LH and LH pulse frequency were lower in NPY- versus saline-infused ewes during intervals 2 and 3 (P < 0.01), but NPY had no discernable effect on serum GH (P > 0.10). In experiment 3, four OVX ewes were continuously infused with NPY as in experiment 2, except that the maximum 50 microg/h dose was achieved after only 10 h of infusion. Blood samples were collected every 10 min, beginning 4 h before and continuing until 4h after the NPY infusion. Mean serum LH changed significantly over time (P = 0.0001), decreasing below pre-treatment levels by hour 3 of NPY infusion (P < 0.01), and returning to pre-treatment concentrations following the end of infusion (P > 0.15). Serum GH also changed significantly over time (P < 0.001). Mean GH levels tended to be greater than pre-treatment levels by hour 2 of infusion (P < 0.08), but thereafter returned to basal levels. Serum GH also increased following the end of NPY infusion (P < 0.03). From these data we conclude that NPY exerts a persistent inhibitory effect on secretion of LH, and may stimulate the secretion of GH during the initiation and cessation of infusion of NPY. These observations support a role for NPY in mediating the effects of undernutrition on both LH and GH, and also provide evidence for potential mechanisms by which leptin, acting through NPY, may stimulate the secretion of GH.
Collapse
Affiliation(s)
- C D Morrison
- Department of Animal Sciences, 160 Animal Science Research Center, University of Missouri, Columbia, MO 65211, USA
| | | | | | | | | | | | | |
Collapse
|
25
|
Azooz OG, Farthing MJ, Savage MO, Ballinger AB. Delayed puberty and response to testosterone in a rat model of colitis. Am J Physiol Regul Integr Comp Physiol 2001; 281:R1483-91. [PMID: 11641119 DOI: 10.1152/ajpregu.2001.281.5.r1483] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Delayed puberty is a frequent complication of inflammatory bowel disease. The precise etiological mechanisms are not known. In this study, we wanted to determine the relative contribution of undernutrition and inflammation to delayed puberty and the effect of inflammation on the reproductive axis. Puberty was assessed in rats with 2,4,6-trinitrobenzenesulfonic acid induced-colitis, healthy controls, and animals pair fed to match the food intake of the colitic group. The response to testosterone administration was assessed in colitic rats. We found that induction of colitis was associated with hypophagia and reduced weight gain, and undernutrition in healthy females (i.e., pair fed) resulted in a delay in the onset (by 4.8 days, P < 0.001) and progression of puberty (normal estrous cycles in 42%, P = 0.04) compared with controls. However, puberty was further delayed in the colitic group (1.4 days after pair fed) with the absence of normal estrous cycling in all rats. In males, the onset of puberty was also delayed, and weights of accessory sex organs were reduced compared with pair-fed controls. Plasma testosterone concentrations were low, and gonadotropin concentrations were normal in colitic rats. Testosterone treatment normalized puberty in male rats with colitis. In conclusion, in rats with experimental colitis, inflammation appears to potentiate the effect of undernutrition on puberty. The weights of secondary sex organs and the onset of puberty were normalized by testosterone treatment.
Collapse
Affiliation(s)
- O G Azooz
- Department of Adult and Pediatric Gastroenterology, St. Bartholomew's and The Royal London School of Medicine and Dentistry, London E1 2AT, United Kingdom
| | | | | | | |
Collapse
|
26
|
Kriegsfeld LJ, Ranalli NJ, Trasy AG, Nelson RJ. Food restriction affects the gonadotropin releasing hormone neuronal system of male prairie voles (Microtus ochrogaster). J Neuroendocrinol 2001; 13:791-8. [PMID: 11578529 DOI: 10.1046/j.1365-2826.2001.00704.x] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Individuals of species inhabiting temperate and boreal latitudes optimize the timing of energetically costly processes by curtailing nonessential energetically demanding processes when environmental conditions are not favourable. One proximate environmental variable used to fine-tune moment-to-moment changes in reproductive physiology and behaviour is food intake. The neuroendocrine mechanisms by which food restriction leads to the cessation of reproduction in seasonally breeding rodent species remain largely unspecified. The present study sought to determine the effects of extended food restriction on the gonadotropin releasing hormone (GnRH) neuronal system. Male prairie voles (Microtus ochrogaster) were either fed ad libitum or were exposed to either 1, 2 or 3 weeks of moderate (70% of daily mean) food restriction. In accordance with previous studies of food restriction, gross reproductive organ masses and body mass were unaffected by food deprivation. Although 1 week of food restriction did not result in alterations in the GnRH neuronal system, food restriction for 2 weeks was associated with increased GnRH-immunoreactive (GnRH-ir) neurone soma size. Three weeks of food restriction resulted in a pronounced increase in GnRH-ir neurone numbers, as well as an increase in fibre intensity in the main fibre pathway to the median eminence. Taken together, these findings suggest that extended food restriction leads to modifications in the GnRH neuronal system, providing a means for temporary cessation of reproduction without gross alterations in reproductive physiology. This transient change in the hypothalmo-pituitary-gonadal axis, without pronounced changes in reproductive organ morphology, likely provides a mechanism for the rapid reinitiation of breeding in nature when local conditions provide adequate food availability.
Collapse
Affiliation(s)
- L J Kriegsfeld
- Department of Psychology, The Johns Hopkins University, Baltimore, MD, USA
| | | | | | | |
Collapse
|
27
|
Meikle D, Westberg M. Social dominance rank and accessory sex glands in wild adult male house mice born to food-deprived mothers. Physiol Behav 2001; 72:359-64. [PMID: 11274678 DOI: 10.1016/s0031-9384(00)00420-0] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Food deprivation after weaning often has greater effects on the reproduction of females than males. However, if animals are deprived prenatally (i.e., through deprivation of the mother during gestation), the reproduction of males may be more negatively impacted because it may decrease their ability to compete with other males and their attractiveness to females. We tested the predictions that adult sons of females that are food-deprived during gestation would tend to lose agonistic encounters with sons of well-nourished (control) females and would have smaller accessory sex glands as well. Sons of control mothers were more frequently dominant to sons of deprived mothers. They also had heavier vesicular-coagulating gland complexes and tended to have heavier preputial glands. However, among males that had not been tested for social dominance rank, there were no such differences in accessory gland weights. These data indicate that maternal food deprivation affects sons only if they engage in agonistic encounters. These effects may be due to a disruption of the organizational effects of testosterone that occur in neonatal male mice and they are likely to have a strong negative impact on the reproduction of the sons of deprived mothers.
Collapse
Affiliation(s)
- D Meikle
- Department of Zoology, Miami University, Oxford, OH 45056, USA.
| | | |
Collapse
|
28
|
Roemmich JN, Li X, Rogol AD, Rissman EF. Food availability affects neural estrogen receptor immunoreactivity in prepubertal mice. Endocrinology 1997; 138:5366-73. [PMID: 9389522 DOI: 10.1210/endo.138.12.5590] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
How underfeeding delays maturation of the central mechanisms affecting GnRH release at the onset of puberty, and why females are more sensitive to underfeeding than males are not well understood. We tested the hypothesis that the sexually dimorphic effects of underfeeding on GnRH release are mediated in part through the estrogen receptor (ER). We investigated the influence of underfeeding on the number of ER-immunoreactive (ER-ir) cells in the medial preoptic area (mPOA), ventromedial nucleus (VMN), and arcuate nucleus (ARH) of prepubertal CF-1 mice, neural areas known to influence GnRH release. In females, 7 days of underfeeding reduced detectable ER-ir cells in the mPOA and VMN, but not in the ARH. Also, we noted a direct relationship between the percent body weight change the last 24 h before perfusion and the numbers of ER-ir cells in the mPOA (r = 0.69; P = 0.0008) and VMN (r = 0.56; P = 0.01). In males, 17 days of underfeeding did not affect ER-ir cell numbers in any region. A subsequent investigation of the time course of alterations in ER immunoreactivity revealed that in female mice ER-ir cell numbers were reduced within 48 h of underfeeding in the mPOA, VMN, and ARH. ER-ir cell number was not changed in male mice. When female mice were underfed for 48 h and then refed, ER-ir cell numbers normalized by 24 h in the mPOA, VMN, and ARH. For the time-course experiments, the percent body weight change the last 24 h before perfusion and the number of ER-ir cells were related in the mPOA (r = 0.47; P < 0.001) and VMN (r = 0.49; P < 0.001), but not in the the ARH (r = 0.23; P < 0.12) in female mice, and in the mPOA (r = 0.66; P < 0.001), VMN (r = 0.33; P = 0.06), and ARH (r = 0.45; P = 0.007) in male mice. Thus, despite no significant change in ER-ir cell number in the male mice, there was a relationship between the percent body weight change during the last 24 h before perfusion and the number of ER-ir cells. We conclude that in male mice, correlation analyses between the percent body weight change before perfusion and ER-ir cell number may be a more sensitive marker of the metabolic condition at the time of perfusion. In female mice, underfeeding may stall puberty by reducing the number of ER-ir cells in brain areas important for signal transmission of GnRH release.
Collapse
Affiliation(s)
- J N Roemmich
- Department of Pediatrics, University of Virginia, Charlottesville 22903, USA.
| | | | | | | |
Collapse
|
29
|
Adams NR, Briegel JR, Sanders MR, Blackberry MA, Martin GB. Level of nutrition modulates the dynamics of oestradiol feedback on plasma FSH in ovariectomized ewes. Anim Reprod Sci 1997; 47:59-70. [PMID: 9233506 DOI: 10.1016/s0378-4320(96)01629-6] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
The frequency of multiple ovulations in mature, cyclic ewes is strongly influenced by the level of nutrition, but it is difficult to demonstrate concurrent changes in plasma concentrations of gonadotropins. The failure to do so might be a consequence of rapid compensation by the homeostatic feedback mechanism linking secretion by the hypothalamus/pituitary gland and ovarian hormones. Most experimental models have examined the components of the homeostatic feedback system after steady state relationships had been established. We hypothesised that the effects of nutrition might be observed more readily if the system were disrupted and then examined while equilibrium was being re-established. This hypothesis was tested in three experiments in Merino ewes by allowing gonadotropin secretion to escape feedback for 5 days after ovariectomy and then replacing ovarian hormones and examining effects of feeding regimen on the return of plasma concentrations of FSH to baseline values. In all three experiments, oestrogen replacement caused plasma concentrations of FSH to decline more rapidly (P < 0.05) in ewes fed at 0.5x maintenance, than in ewes fed at 1.4x maintenance, with groups fed at maintenance being intermediate. No effect of diet was observed on plasma FSH concentrations in the absence of oestradiol, and neither progesterone nor charcoal-treated bovine follicular fluid influenced the effect of nutrition. Plasma concentrations of oestradiol were 9.8% lower on average (NS) in ewes fed above maintenance than in the sheep fed below maintenance over the three experiments, suggesting that there may have been a reduced clearance of oestradiol which contributed to the result. We conclude that feeding regimen affects the secretion or clearance of gonadotropins in mature ewes, as in the mature ram, and that this is one mechanism by which ovulation rate may be affected.
Collapse
Affiliation(s)
- N R Adams
- Division of Animal Production, CSIRO, Wembley, W.A., Australia.
| | | | | | | | | |
Collapse
|
30
|
Deligeorgis S, Chadio S, Menegatos J. Pituitary responsiveness to GnRH in lambs undernourished during fetal life. Anim Reprod Sci 1996. [DOI: 10.1016/0378-4320(96)01471-6] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
|
31
|
Bergendahl M, Veldhuis JD. Altered pulsatile gonadotropin signaling in nutritional deficiency in the male. Trends Endocrinol Metab 1995; 6:145-59. [PMID: 18406696 DOI: 10.1016/1043-2760(95)00081-r] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
Abstract
Reproduction cannot occur without adequate nutrition. Diets that are nutritionally inadequate delay and disrupt the pubertal development of the reproductive processes of immature experimental animals and humans, and impair the function of the hypothalamic-pituitary-gonadal axis in adults. Although there is a general understanding of the linkages between nutrition and reproduction, there is a lack of detailed knowledge of the exact mechanisms that couple these two systems. The major effects of malnutrition on the hypothalamic-pituitary-gonadal axis reported in the literature are, for the most part, manifested as reduced gonadotropin secretion. Malnutrition results in decreased circulating gonadotropin concentrations. These changes in the reproductive system are associated with impaired gonadal function and subsequent secondary sex organ atrophy and lead, ultimately, to poor reproduction. Decreased hypothalamic release of gonadotropin-releasing hormone (GnRH) has been proposed as the most important etiologic factor for the fasting-induced suppression of pituitary-testicular function. In the human, hypogonadism and infertility develop in both sexes during chronic malnutrition. Most studies on the effects of malnutrition on the reproductive hormones have been performed in women, perhaps because malnutrition in women is promptly accompanied by amenorrhea, whereas in men hypogonadism develops gradually and becomes clinically evident only during more severe malnutrition. With the advent of sensitive assays for measuring reproductive hormones and of modern computerized methods for analyzing the pulsatile secretion of these hormones, however, the function of the hypothalamic-pituitary-testicular axis has been scrutinized and it has, indeed, been observed that this system is disturbed even during acute malnutrition. Here, we review the effects of malnutrition on reproductive function, especially on the pulsatile pattern of LH secretion, in humans and in experimental animals.
Collapse
Affiliation(s)
- M Bergendahl
- The Division of Endocrinology and Metabolism, Department of Internal Medicine, University of Virginia Health Sciences Center, Charlottesville, VA 22908, USA
| | | |
Collapse
|
32
|
Meikle D, Kruper J, Browning C. Adult male house mice born to undernourished mothers are unattractive to oestrous females. Anim Behav 1995. [DOI: 10.1016/0003-3472(95)80135-9] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
|
33
|
Adam CL, Robinson JJ. The role of nutrition and photoperiod in the timing of puberty. Proc Nutr Soc 1994; 53:89-102. [PMID: 7913222 DOI: 10.1079/pns19940013] [Citation(s) in RCA: 26] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Affiliation(s)
- C L Adam
- Rowett Research Institute, Bucksburn, Aberdeen
| | | |
Collapse
|
34
|
Bergendahl M, Huhtaniemi I. Acute fasting is ineffective in suppressing pituitary-gonadal function of pubertal male rats. THE AMERICAN JOURNAL OF PHYSIOLOGY 1993; 264:E717-22. [PMID: 7684566 DOI: 10.1152/ajpendo.1993.264.5.e717] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
Effects of short-term fasting (3-4 days) on pituitary-testicular functions were studied during sexual maturation in male rats at 25, 35, 45, 55, and 65 days of age. Among the main findings, testicular testosterone decreased by 41-68% at all ages (P < 0.01-0.05). The pituitary steady-state mRNA levels of the common alpha-subunit (28-55%) and follicle-stimulating hormone (FSH) beta-subunit (25-50%) decreased (P < 0.01-0.05) at 25, 55, and 65 days of age but not at 35 and 45 days; the luteinizing hormone (LH) beta-subunit did not respond at any age. Fasting decreased serum LH (P < 0.01) at 25, 55, and 65 days of age but not at 35 and 45 days. Likewise, fasting decreased pituitary and/or serum FSH only in the 25- and 65-day-old rats (P < 0.01-0.05). In conclusion, LH and FSH secretion, and the gene expression of common alpha- and FSH beta-subunits, decreased consistently during short-term fasting only in prepubertal (25 days) and adult (65 days) but not in peripubertal animals (35 and 45 days). Hence, the pubertal rise in gonadotropins represents such a strong positive induction that it largely overrides the antigonadotropic effect of fasting.
Collapse
Affiliation(s)
- M Bergendahl
- Department of Physiology, University of Turku, Finland
| | | |
Collapse
|
35
|
|
36
|
Lilburn MS, Burke WH, Mashaly MM. The effect of different feed restriction treatments during rearing on the luteinizing hormone concentrations, body weight, and fertility of broiler-breeder cockerels. Poult Sci 1990; 69:860-3. [PMID: 2367276 DOI: 10.3382/ps.0690860] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Broiler breeder cockerels were reared on four feed-restriction programs from 3 to 23 wk of age (Experiment 1). Excessive BW restriction (85% of the controls) throughout rearing significantly decreased fertility at 28 wk of age, but not at 31 or 35 wk of age. There were no carryover treatment effects on BW at 30, 35, or 45 wk of age. Significant peaks occurred in the concentration of the serum luteinizing hormone (Experiment 1, 7.05 ng per mL; Experiment 2, 7.36 ng per mL) at 33 to 35 wk of age.
Collapse
Affiliation(s)
- M S Lilburn
- Department of Poultry Science, Ohio Agricultural Research and Development Center, Wooster 44691
| | | | | |
Collapse
|
37
|
Nordio M, Vaughan MK, Sabry I, Reiter RJ. Undernutrition potentiates melatonin effects in maturing female rats. J Endocrinol Invest 1989; 12:103-10. [PMID: 2502571 DOI: 10.1007/bf03349933] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Prepubertal (21-22 days) female Sprague-Dawley rats were caged singly in either long (LP; 14:10 LD) or short (SP; 8:16 LD) photoperiod and fed ad libitum or underfed (1/2 the food intake of controls). Additionally, a fed and underfed group in LP received a daily sc injection of saline or 100 micrograms melatonin at 1700 h. Food restriction delayed vaginal opening and resulted in a reduction in body weight and in the weights of the pituitary, ovary and uterus in all underfed groups. Melatonin treatment (but not SP exposure) significantly enhanced the reduction in pituitary, ovarian and uterine weight compared to the underfed saline-treated controls. Thyroid weights were significantly increased in underfed LP and SP groups compared to their respective controls where melatonin treatment in either fed or underfed animals was ineffective. Underfeeding caused a significant rise in pituitary LH (except for SP-underfed group) and FSH concentrations and a fall in pituitary prolactin concentrations and plasma T3 levels. Melatonin injections in underfed rats significantly increased pituitary LH and FSH and decreased prolactin concentrations compared to underfed saline-treated animals. Plasma prolactin levels increased after melatonin administration in both fed and underfed rats. These observations emphasize that environmental influences such as undernutrition can alter the physiological status of immature animals and enhance the sensitivity of the neuroendocrine axis to the pineal and one of its hormones, melatonin.
Collapse
Affiliation(s)
- M Nordio
- Department of Cellular and Structural Biology, University of Texas Health Science Center, San Antonio 78284
| | | | | | | |
Collapse
|
38
|
Sisk CL, Nunez AA, Thebert MM. Differential effects of electrolytic and chemical hypothalamic lesions on LH pulses in rats. THE AMERICAN JOURNAL OF PHYSIOLOGY 1988; 255:E583-90. [PMID: 3056029 DOI: 10.1152/ajpendo.1988.255.5.e583] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
Electrolytic lesions of the arcuate nucleus were made in anesthetized adult castrated male rats. Luteinizing hormone (LH) pulse frequency averaged 2.4 pulses/h in controls but declined to a mean of 0.5 pulses/h in rats with bilateral damage to the arcuate nucleus. Because these lesions also damaged the median eminence, we tested the possibility that this disruption of LH secretion was due to coincidental damage to fibers of passage projecting to median eminence. Axon-sparing chemical lesions of the arcuate nucleus were made by intracranial injections of N-methyl-DL-aspartate (NMA) in anesthetized adult castrated rats. Mean LH pulse frequency was 2.3 and 2.5 pulses/h in control and NMA-injected rats, respectively. NMA injections destroyed arcuate neuronal cell bodies and produced a proliferation of glial cells within the nucleus. There was no apparent difference in the immunocytochemical staining intensity and distribution of luteinizing hormone-releasing hormone (LHRH) fibers in median eminence in rats receiving NMA or sham injections. These results suggest that the disruptive effects of electrolytic lesions of the arcuate nucleus on pulsatile LH secretion are a result of coincidental damage to LHRH neuronal projections to the median eminence and that neuronal cell bodies within the arcuate nucleus are not necessary for normal pulsatile LH secretion in male rats.
Collapse
Affiliation(s)
- C L Sisk
- Neuroscience Program, Michigan State University, East Lansing 48824
| | | | | |
Collapse
|