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de Sousa ME, Gusmao DO, Dos Santos WO, Moriya HT, de Lima FF, List EO, Kopchick JJ, Donato J. Fasting and prolonged food restriction differentially affect GH secretion independently of GH receptor signaling in AgRP neurons. J Neuroendocrinol 2024; 36:e13254. [PMID: 36964750 DOI: 10.1111/jne.13254] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/21/2022] [Revised: 03/02/2023] [Accepted: 03/03/2023] [Indexed: 03/14/2023]
Abstract
Growth hormone (GH) receptor (GHR) is abundantly expressed in neurons that co-release the agouti-related protein (AgRP) and neuropeptide Y (NPY) in the arcuate nucleus of the hypothalamus (ARH). Since ARHAgRP/NPY neurons regulate several hypothalamic-pituitary-endocrine axes, this neuronal population possibly modulates GH secretion via a negative feedback loop, particularly during food restriction, when ARHAgRP/NPY neurons are highly active. The present study aims to determine the importance of GHR signaling in ARHAgRP/NPY neurons on the pattern of GH secretion in fed and food-deprived male mice. Additionally, we compared the effect of two distinct situations of food deprivation: 16 h of fasting or four days of food restriction (40% of usual food intake). Overnight fasting strongly suppressed both basal and pulsatile GH secretion. Animals lacking GHR in ARHAgRP/NPY neurons (AgRP∆GHR mice) did not exhibit differences in GH secretion either in the fed or fasted state, compared to control mice. In contrast, four days of food restriction increased GH pulse frequency, basal GH secretion, and pulse irregularity/complexity (measured by sample entropy), whereas pulsatile GH secretion was not affected in both control and AgRP∆GHR mice. Hypothalamic Ghrh mRNA levels were unaffected by fasting or food restriction, but Sst expression increased in acutely fasted mice, but decreased after prolonged food restriction in both control and AgRP∆GHR mice. Our findings indicate that short-term fasting and prolonged food restriction differentially affect the pattern of GH secretion, independently of GHR signaling in ARHAgRP/NPY neurons.
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Affiliation(s)
- Maria E de Sousa
- Department of Physiology and Biophysics, Instituto de Ciencias Biomedicas, Universidade de Sao Paulo, Sao Paulo, 05508-000, Brazil
| | - Daniela O Gusmao
- Department of Physiology and Biophysics, Instituto de Ciencias Biomedicas, Universidade de Sao Paulo, Sao Paulo, 05508-000, Brazil
| | - Willian O Dos Santos
- Department of Physiology and Biophysics, Instituto de Ciencias Biomedicas, Universidade de Sao Paulo, Sao Paulo, 05508-000, Brazil
| | - Henrique T Moriya
- Biomedical Engineering Laboratory, Escola Politecnica, Universidade de Sao Paulo, Sao Paulo, 05508-010, Brazil
| | - Felipe F de Lima
- Biomedical Engineering Laboratory, Escola Politecnica, Universidade de Sao Paulo, Sao Paulo, 05508-010, Brazil
| | - Edward O List
- Edison Biotechnology Institute and Heritage College of Osteopathic Medicine, Ohio University, Athens, Ohio, 45701, USA
| | - John J Kopchick
- Edison Biotechnology Institute and Heritage College of Osteopathic Medicine, Ohio University, Athens, Ohio, 45701, USA
| | - Jose Donato
- Department of Physiology and Biophysics, Instituto de Ciencias Biomedicas, Universidade de Sao Paulo, Sao Paulo, 05508-000, Brazil
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Ghrelin proteolysis increases in plasma of men, but not women, with obesity. Life Sci 2023; 313:121305. [PMID: 36543283 DOI: 10.1016/j.lfs.2022.121305] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2022] [Revised: 12/06/2022] [Accepted: 12/14/2022] [Indexed: 12/23/2022]
Abstract
AIMS Since plasma ghrelin can undergo des-acylation and proteolysis, the aim of this study was to investigate the extent to which an enhancement of these reactions is associated to the decrease of ghrelin in plasma after food intake or in individuals with obesity. MAIN METHODS we performed an intervention cross-sectional study, in which levels of ghrelin, desacyl-ghrelin (DAG), glucose, insulin, ghrelin des-acylation and ghrelin proteolysis were assessed in plasma before and after a test meal in 40 people (n = 21 males) with normal weight (NW, n = 20) or overweight/obesity (OW/OB, n = 20). KEY FINDINGS Preprandial ghrelin and DAG levels were lower, whereas preprandial ghrelin proteolysis was ∼4.6-fold higher in plasma of males with OW/OB. In males, ghrelin proteolysis positively correlated with glycemia. Ghrelin and DAG levels were also lower in females with OW/OB, but preprandial ghrelin proteolysis was not different between females with NW or OW/OB. Ghrelin and DAG levels decreased postprandially in males and females, independently of BMI, and ghrelin proteolysis increased postprandially ∼2 folds only in individuals with NW. Ghrelin des-acylation remained unaffected by BMI or feeding status in both sexes. SIGNIFICANCE Current study shows that ghrelin proteolysis increases in males with obesity as well as after meal in lean individuals. Therefore, ghrelin proteolysis may be an important checkpoint and, consequently, a putative pharmacological target to control circulating ghrelin levels in humans.
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Sheep as a model for neuroendocrinology research. PROGRESS IN MOLECULAR BIOLOGY AND TRANSLATIONAL SCIENCE 2022; 189:1-34. [PMID: 35595346 DOI: 10.1016/bs.pmbts.2022.01.001] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Animal models remain essential to understand the fundamental mechanisms of physiology and pathology. Particularly, the complex and dynamic nature of neuroendocrine cells of the hypothalamus make them difficult to study. The neuroendocrine systems of the hypothalamus are critical for survival and reproduction, and are highly conserved throughout vertebrate evolution. Their roles in controlling body metabolism, growth and body composition, stress, electrolyte balance, and reproduction, have been intensively studied, and have yielded groundbreaking discoveries. Many of these discoveries would not have been feasible without the use of the domestic sheep (Ovis aries). The sheep has been used for decades to study the neuroendocrine systems of the hypothalamus and has become a model for human neuroendocrinology. The aim of this chapter is to review some of the profound biomedical discoveries made possible by the use of sheep. The advantages and limitations of sheep as a neuroendocrine model will be discussed. While no animal model can perfectly recapitulate a human disease or condition, sheep are invaluable for enabling manipulations not possible in human subjects and isolating physiologic variables to garner insight into neuroendocrinology and associated pathologies.
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Labarthe A, Zizzari P, Fiquet O, Lebrun N, Veldhuis JD, Roelfsema F, Chauveau C, Bohlooly-Y M, Epelbaum J, Tolle V. Effect of Growth Hormone Secretagogue Receptor Deletion on Growth, Pulsatile Growth Hormone Secretion, and Meal Pattern in Male and Female Mice. Neuroendocrinology 2022; 112:215-234. [PMID: 33774644 DOI: 10.1159/000516147] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/03/2020] [Accepted: 03/25/2021] [Indexed: 11/19/2022]
Abstract
INTRODUCTION While the vast majority of research investigating the role of ghrelin or its receptor, GHS-R1a, in growth, feeding, and metabolism has been conducted in male rodents, very little is known about sex differences in this system. Furthermore, the role of GHS-R1a signaling in the control of pulsatile GH secretion and its link with growth or metabolic parameters has never been characterized. METHODS We assessed the sex-specific contribution of GHS-R1a signaling in the activity of the GH/IGF-1 axis, metabolic parameters, and feeding behavior in adolescent (5-6 weeks old) or adult (10-19 weeks old) GHS-R KO (Ghsr-/-) and WT (Ghsr+/+) male and female mice. RESULTS Adult Ghsr-/- male and female mice displayed deficits in weight and linear growth that were correlated with reduced GH pituitary contents in males only. GHS-R1a deletion was associated with reduced meal frequency and increased meal intervals, as well as reduced hypothalamic GHRH and NPY mRNA in males, not females. In adult, GH release from Ghsr-/- mice pituitary explants ex vivo was reduced independently of the sex. However, in vivo pulsatile GH secretion decreased in adult but not adolescent Ghsr-/- females, while in males, GHS-R1a deletion was associated with reduction in pulsatile GH secretion during adolescence exclusively. In males, linear growth did not correlate with pulsatile GH secretion, but rather with ApEn, a measure that reflects irregularity of the rhythmic secretion. Fat mass, plasma leptin concentrations, or ambulatory activity did not predict differences in GH secretion. DISCUSSION/CONCLUSION These results point to a sex-dependent dimorphic effect of GHS-R1a signaling to modulate pulsatile GH secretion and meal pattern in mice with different compensatory mechanisms occurring in the hypothalamus of adult males and females after GHS-R1a deletion. Altogether, we show that GHS-R1a signaling plays a more critical role in the regulation of pulsatile GH secretion during adolescence in males and adulthood in females.
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Affiliation(s)
- Alexandra Labarthe
- Université de Paris, UMRS_1266 INSERM, Institute of Psychiatry and Neuroscience of Paris, Paris, France
| | - Philippe Zizzari
- Université de Paris, UMRS_1266 INSERM, Institute of Psychiatry and Neuroscience of Paris, Paris, France
| | - Oriane Fiquet
- Université de Paris, UMRS_1266 INSERM, Institute of Psychiatry and Neuroscience of Paris, Paris, France
| | - Nicolas Lebrun
- Université de Paris, UMRS_1266 INSERM, Institute of Psychiatry and Neuroscience of Paris, Paris, France
| | - Johannes D Veldhuis
- Endocrine Research Unit, Department of Medicine, Mayo School of Graduate Medical Education, Clinical Translational Science Center, Mayo Clinic, Rochester, New York, USA
| | - Ferdinand Roelfsema
- Department of Internal Medicine, Section of Endocrinology and Metabolism, Leiden University Medical Center, Leiden, The Netherlands
| | - Christophe Chauveau
- Marrow Adiposity and Bone Lab - MABLab ULR 4490, University Littoral Côte d'Opale, Boulogne-sur-Mer, France
- University Lille, CHU Lille, Lille, France
| | - Mohammad Bohlooly-Y
- Translational Genomics, Discovery Sciences, Biopharmaceuticals R&D, AstraZeneca, Gothenburg, Sweden
| | - Jacques Epelbaum
- Université de Paris, UMRS_1266 INSERM, Institute of Psychiatry and Neuroscience of Paris, Paris, France
- UMR CNRS/MNHN 7179, Mécanismes Adaptatifs et Evolution, Brunoy, France
| | - Virginie Tolle
- Université de Paris, UMRS_1266 INSERM, Institute of Psychiatry and Neuroscience of Paris, Paris, France
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Wang W, Huang Z, Huang L, Gao L, Cui L, Cowley M, Guo L, Chen C. Time-Restricted Feeding Restored Insulin-Growth Hormone Balance and Improved Substrate and Energy Metabolism in MC4RKO Obese Mice. Neuroendocrinology 2022; 112:174-185. [PMID: 33735897 DOI: 10.1159/000515960] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/01/2020] [Accepted: 03/01/2021] [Indexed: 11/19/2022]
Abstract
BACKGROUND Dysregulation of metabolic regulatory hormones often occurs during the progress of obesity. Key regulatory hormone insulin-growth hormone (GH) balance has recently been proposed to maintain metabolism profiles. Time-restricted feeding (TRF) is an effective strategy against obesity without detailed research on pulsatile GH releasing patterns. METHODS TRF was performed in an over-eating melanocortin 4 receptor-knockout (MC4RKO) obese mouse model using normal food. Body weight and food intake were measured. Series of blood samples were collected for 6-h pulsatile GH profile, glucose tolerance test, and insulin tolerance test at 5, 8, and 9 weeks of TRF, respectively. Indirect calorimetric recordings were performed by the Phenomaster system at 6 weeks for 1 week, and body composition was measured by nuclear magnetic resonance spectroscopy (NMR). Substrate- and energy metabolism-related gene expressions were measured in terminal liver and subcutaneous white adipose tissues. RESULTS TRF increased pulsatile GH secretion in dark phase and suppressed hyperinsulinemia in MC4RKO obese mice to reach a reduced insulin/GH ratio. This was accompanied by the improvement in insulin sensitivity, metabolic flexibility, glucose tolerance, and decreased glucose fluctuation, together with appropriate modification of gene expression involved in substrate metabolism and adipose tissue browning. NMR measurement showed that TRF decreased fat mass but increased lean mass. Indirect calorimeter recording indicated that TRF decreased the respiratory exchange ratio (RER) reflecting consumption of more fatty acid in energy production in light phase and increased the oxygen consumption during activities in dark phase. CONCLUSIONS TRF effectively decreases hyperinsulinemia and restores pulsatile GH secretion in the overeating obese mice with significant improvement in substrate and energy metabolism and body composition without reducing total caloric intake.
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Affiliation(s)
- Weihao Wang
- School of Biomedical Sciences, University of Queensland, Brisbane, Queensland, Australia
- Department of Endocrinology, Beijing Hospital, National Center of Gerontology, Institute of Geriatric Medicine, Chinese Academy of Medical Sciences, Beijing, China
- Graduate School of Peking Union Medical College, Chinese Academy of Medical Sciences, Beijing, China
| | - Zhengxiang Huang
- School of Biomedical Sciences, University of Queensland, Brisbane, Queensland, Australia
| | - Lili Huang
- School of Biomedical Sciences, University of Queensland, Brisbane, Queensland, Australia
| | - Lyn Gao
- School of Biomedical Sciences, University of Queensland, Brisbane, Queensland, Australia
| | - Ling Cui
- School of Biomedical Sciences, University of Queensland, Brisbane, Queensland, Australia
| | - Michael Cowley
- Department of Physiology, Monash University, Melbourne, Victoria, Australia
| | - Lixin Guo
- Department of Endocrinology, Beijing Hospital, National Center of Gerontology, Institute of Geriatric Medicine, Chinese Academy of Medical Sciences, Beijing, China
- Graduate School of Peking Union Medical College, Chinese Academy of Medical Sciences, Beijing, China
| | - Chen Chen
- School of Biomedical Sciences, University of Queensland, Brisbane, Queensland, Australia
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Wang W, Huang Z, Huang L, Tan C, Chen W, Roelfsema F, Chen C, Guo L. Rotating Day and Night Disturb Growth Hormone Secretion Profiles, Body Energy Metabolism, and Insulin Levels in Mice. Neuroendocrinology 2022; 112:481-492. [PMID: 34348337 DOI: 10.1159/000518338] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/24/2021] [Accepted: 07/02/2021] [Indexed: 11/19/2022]
Abstract
BACKGROUND Insulin and growth hormone (GH) - 2 vital metabolic regulatory hormones - regulate glucose, lipid, and energy metabolism. These 2 hormones determine substrate and energy metabolism under different living conditions. Shift of day and night affects the clock system and metabolism probably through altered insulin and GH secretion. METHODS Five-week-old male mice were randomly assigned to a rotating light (RL) group (3-day normal light/dark cycle followed by 4-day reversed light/dark cycle per week) and normal light (NL) group. Body weight and food intake were recorded every week. Series of blood samples were collected for pulsatile GH analysis, glucose tolerance test, and insulin tolerance test at 9, 10, and 11 weeks from the start of intervention, respectively. Indirect calorimetric measurement was performed, and body composition was tested at 12 weeks. Expressions of energy and substrate metabolism-related genes were evaluated in pituitary and liver tissues at the end of 12-week intervention. RESULTS The RL group had an increased number of GH pulsatile bursts and reduced GH mass/burst. RL also disturbed the GH secretion regularity and mode. It suppressed insulin secretion, which led to a disturbed insulin/GH balance. It was accompanied by the reduced metabolic flexibility and modified gene expression involved in energy balance and substrate metabolism. Indirect calorimeter recording revealed that RL decreased the respiratory exchange ratio (RER) and oxygen consumption at the dark phase, which resulted in an increase in fat mass and free fatty acid levels in circulation. CONCLUSION RL disturbed pulsatile GH secretion and decreased insulin secretion in male mice with significant impairment in energy, substrate metabolism, and body composition.
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Affiliation(s)
- Weihao Wang
- Graduate School of Peking Union Medical College, Chinese Academy of Medical Sciences, Beijing, China
- School of Biomedical Sciences, University of Queensland, St Lucia, Brisbane, Queensland, Australia
- Department of Endocrinology, Beijing Hospital, National Center of Gerontology, Institute of Geriatric Medicine, Chinese Academy of Medical Sciences, Beijing, China
| | - Zhengxiang Huang
- School of Biomedical Sciences, University of Queensland, St Lucia, Brisbane, Queensland, Australia
| | - Lili Huang
- School of Biomedical Sciences, University of Queensland, St Lucia, Brisbane, Queensland, Australia
| | - Chunlu Tan
- School of Biomedical Sciences, University of Queensland, St Lucia, Brisbane, Queensland, Australia
| | - Wanlin Chen
- School of Biomedical Sciences, University of Queensland, St Lucia, Brisbane, Queensland, Australia
| | | | - Chen Chen
- School of Biomedical Sciences, University of Queensland, St Lucia, Brisbane, Queensland, Australia
| | - Lixin Guo
- Graduate School of Peking Union Medical College, Chinese Academy of Medical Sciences, Beijing, China
- Department of Endocrinology, Beijing Hospital, National Center of Gerontology, Institute of Geriatric Medicine, Chinese Academy of Medical Sciences, Beijing, China
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Towards Understanding the Direct and Indirect Actions of Growth Hormone in Controlling Hepatocyte Carbohydrate and Lipid Metabolism. Cells 2021; 10:cells10102532. [PMID: 34685512 PMCID: PMC8533955 DOI: 10.3390/cells10102532] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2021] [Revised: 09/20/2021] [Accepted: 09/23/2021] [Indexed: 02/06/2023] Open
Abstract
Growth hormone (GH) is critical for achieving normal structural growth. In addition, GH plays an important role in regulating metabolic function. GH acts through its GH receptor (GHR) to modulate the production and function of insulin-like growth factor 1 (IGF1) and insulin. GH, IGF1, and insulin act on multiple tissues to coordinate metabolic control in a context-specific manner. This review will specifically focus on our current understanding of the direct and indirect actions of GH to control liver (hepatocyte) carbohydrate and lipid metabolism in the context of normal fasting (sleep) and feeding (wake) cycles and in response to prolonged nutrient deprivation and excess. Caveats and challenges related to the model systems used and areas that require further investigation towards a clearer understanding of the role GH plays in metabolic health and disease are discussed.
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Høyer KL, Høgild ML, List EO, Lee KY, Kissinger E, Sharma R, Erik Magnusson N, Puri V, Kopchick JJ, Jørgensen JOL, Jessen N. The acute effects of growth hormone in adipose tissue is associated with suppression of antilipolytic signals. Physiol Rep 2020; 8:e14373. [PMID: 32073221 PMCID: PMC7029434 DOI: 10.14814/phy2.14373] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2019] [Revised: 01/19/2020] [Accepted: 01/21/2020] [Indexed: 02/07/2023] Open
Abstract
AIM Since GH stimulates lipolysis in vivo after a 2-hr lag phase, we studied whether this involves GH signaling and gene expression in adipose tissue (AT). METHODS Human subjects (n = 9) each underwent intravenous exposure to GH versus saline with measurement of serum FFA, and GH signaling, gene array, and protein in AT biopsies after 30-120 min. Human data were corroborated in adipose-specific GH receptor knockout (FaGHRKO) mice versus wild-type mice. Expression of candidate genes identified in the array were investigated in 3T3-L1 adipocytes. RESULTS GH increased serum FFA and AT phosphorylation of STAT5b in human subjects. This was replicated in wild-type mice, but not in FaGHRKO mice. The array identified 53 GH-regulated genes, and Ingenuity Pathway analysis showed downregulation of PDE3b, an insulin-dependent antilipolytic signal, upregulation of PTEN that inhibits insulin-dependent antilipolysis, and downregulation of G0S2 and RASD1, both encoding antilipolytic proteins. This was confirmed in 3T3-L1 adipocytes, except for PDE3B, including reciprocal effects of GH and insulin on mRNA expression of PTEN, RASD1, and G0S2. CONCLUSION (a) GH directly stimulates AT lipolysis in a GHR-dependent manner, (b) this involves suppression of antilipolytic signals at the level of gene expression, (c) the underlying GH signaling pathways remain to be defined.
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Affiliation(s)
- Katrine L. Høyer
- Medical Research LaboratoryDepartment of Clinical Medicine, HealthAarhus UniversityAarhusDenmark
- Department of EndocrinologyAarhus University HospitalAarhusDenmark
| | - Morten L. Høgild
- Medical Research LaboratoryDepartment of Clinical Medicine, HealthAarhus UniversityAarhusDenmark
- Department of EndocrinologyAarhus University HospitalAarhusDenmark
| | - Edward O. List
- The Edison Biotechnology InstituteAthensOHUSA
- Heritage College of Osteopathic MedicineOhio UniversityAthensOHUSA
| | - Kevin Y. Lee
- Heritage College of Osteopathic MedicineOhio UniversityAthensOHUSA
| | - Emily Kissinger
- Heritage College of Osteopathic MedicineOhio UniversityAthensOHUSA
| | - Rita Sharma
- Heritage College of Osteopathic MedicineOhio UniversityAthensOHUSA
| | - Nils Erik Magnusson
- Medical Research LaboratoryDepartment of Clinical Medicine, HealthAarhus UniversityAarhusDenmark
- Department of EndocrinologyAarhus University HospitalAarhusDenmark
| | - Vishwajeet Puri
- Heritage College of Osteopathic MedicineOhio UniversityAthensOHUSA
| | - John J. Kopchick
- The Edison Biotechnology InstituteAthensOHUSA
- Heritage College of Osteopathic MedicineOhio UniversityAthensOHUSA
| | - Jens O. L. Jørgensen
- Medical Research LaboratoryDepartment of Clinical Medicine, HealthAarhus UniversityAarhusDenmark
- Department of EndocrinologyAarhus University HospitalAarhusDenmark
| | - Niels Jessen
- Department of Clinical PharmacologyUniversity of AarhusAarhusDenmark
- Department of BiomedicineAarhus UniversityAarhusDenmark
- Steno Diabetes Center AarhusAarhus University HospitalAarhusDenmark
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Huang L, Huang Z, Chen C. Rhythmic growth hormone secretion in physiological and pathological conditions: Lessons from rodent studies. Mol Cell Endocrinol 2019; 498:110575. [PMID: 31499134 DOI: 10.1016/j.mce.2019.110575] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/05/2019] [Revised: 09/04/2019] [Accepted: 09/04/2019] [Indexed: 02/01/2023]
Abstract
Evolutionally conserved in all mammalians, the release of GH occurs in a rhythmic pattern, characterized by several dominant surges (pulsatile GH) with tonic low inter-pulse levels (tonic GH). Such pulsatile secretion pattern is essential for many physiological actions of GH on different tissues with defined gender dimorphism. Rhythmic release of pulsatile GH is tightly controlled by hypothalamic neurons as well as peripheral metabolic factors. Changes of GH pattern occur within a range of sophisticated physiological and pathological settings and significantly contribute to growth, ageing, survival and disease predispositions. Precise analysis of GH secretion pattern is vitally important for a comprehensive understanding of the function of GH and the components that regulate GH secretion pattern.
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Affiliation(s)
- Lili Huang
- School of Biomedical Sciences, University of Queensland, St Lucia, Brisbane, Australia
| | - Zhengxiang Huang
- School of Biomedical Sciences, University of Queensland, St Lucia, Brisbane, Australia
| | - Chen Chen
- School of Biomedical Sciences, University of Queensland, St Lucia, Brisbane, Australia.
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Wasinski F, Frazão R, Donato J. Effects of growth hormone in the central nervous system. ARCHIVES OF ENDOCRINOLOGY AND METABOLISM 2019; 63:549-556. [PMID: 31939479 PMCID: PMC10522235 DOI: 10.20945/2359-3997000000184] [Citation(s) in RCA: 20] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/08/2019] [Accepted: 08/29/2019] [Indexed: 11/23/2022]
Abstract
Growth hormone (GH) is best known for its effect stimulating tissue and somatic growth through the regulation of cell division, regeneration and proliferation. However, GH-responsive neurons are spread over the entire central nervous system, suggesting that they have important roles in the brain. The objective of the present review is to summarize and discuss the potential physiological importance of GH action in the central nervous system. We provide evidence that GH signaling in the brain regulates the physiology of numerous functions such as cognition, behavior, neuroendocrine changes and metabolism. Data obtained from experimental animal models have shown that disruptions in GH signaling in specific neuronal populations can affect the reproductive axis and impair food intake during glucoprivic conditions, neuroendocrine adaptions during food restriction, and counter-regulatory responses to hypoglycemia, and they can modify gestational metabolic adaptions. Therefore, the brain is an important target tissue of GH, and changes in GH action in the central nervous system can explain some dysfunctions presented by individuals with excessive or deficient GH secretion. Furthermore, GH acts in specific neuronal populations during situations of metabolic stress to promote appropriate physiological adjustments that restore homeostasis. Arch Endocrinol Metab. 2019;63(6):549-56.
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Affiliation(s)
- Frederick Wasinski
- Departamento de Fisiologia e BiofísicaInstituto de Ciências BiomédicasUniversidade de São PauloSão PauloSPBrasilDepartamento de Fisiologia e Biofísica, Instituto de Ciências Biomédicas, Universidade de São Paulo (USP), São Paulo, SP, Brasil
| | - Renata Frazão
- Departamento de AnatomiaInstituto de Ciências BiomédicasUniversidade de São PauloSão PauloSPBrasilDepartamento de Anatomia, Instituto de Ciências Biomédicas, Universidade de São Paulo (USP), São Paulo, SP, Brasil
| | - Jose Donato
- Departamento de Fisiologia e BiofísicaInstituto de Ciências BiomédicasUniversidade de São PauloSão PauloSPBrasilDepartamento de Fisiologia e Biofísica, Instituto de Ciências Biomédicas, Universidade de São Paulo (USP), São Paulo, SP, Brasil
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Furigo IC, de Souza GO, Teixeira PDS, Guadagnini D, Frazão R, List EO, Kopchick JJ, Prada PO, Donato J. Growth hormone enhances the recovery of hypoglycemia via ventromedial hypothalamic neurons. FASEB J 2019; 33:11909-11924. [PMID: 31366244 DOI: 10.1096/fj.201901315r] [Citation(s) in RCA: 29] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Growth hormone (GH) is secreted during hypoglycemia, and GH-responsive neurons are found in brain areas containing glucose-sensing neurons that regulate the counter-regulatory response (CRR). However, whether GH modulates the CRR to hypoglycemia via specific neuronal populations is currently unknown. Mice carrying ablation of GH receptor (GHR) either in leptin receptor (LepR)- or steroidogenic factor-1 (SF1)-expressing cells were studied. We also investigated the importance of signal transducer and activator of transcription 5 (STAT5) signaling in SF1 cells for the CRR. GHR ablation in LepR cells led to impaired capacity to recover from insulin-induced hypoglycemia and to a blunted CRR caused by 2-deoxy-d-glucose (2DG) administration. GHR inactivation in SF1 cells, which include ventromedial hypothalamic neurons, also attenuated the CRR. The reduced CRR was prevented by parasympathetic blockers. Additionally, infusion of 2DG produced an abnormal hyperactivity of parasympathetic preganglionic neurons, whereas the 2DG-induced activation of anterior bed nucleus of the stria terminalis neurons was reduced in mice without GHR in SF1 cells. Mice carrying ablation of Stat5a/b genes in SF1 cells showed no defects in the CRR. In summary, GHR expression in SF1 cells is required for a normal CRR, and these effects are largely independent of STAT5 pathway.-Furigo, I. C., de Souza, G. O., Teixeira, P. D. S., Guadagnini, D., Frazão, R., List, E. O., Kopchick, J. J., Prada, P. O., Donato, J., Jr. Growth hormone enhances the recovery of hypoglycemia via ventromedial hypothalamic neurons.
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Affiliation(s)
- Isadora C Furigo
- Department of Physiology and Biophysics, Institute of Biomedical Sciences, University of São Paulo, São Paulo, Brazil
| | - Gabriel O de Souza
- Department of Physiology and Biophysics, Institute of Biomedical Sciences, University of São Paulo, São Paulo, Brazil
| | - Pryscila D S Teixeira
- Department of Physiology and Biophysics, Institute of Biomedical Sciences, University of São Paulo, São Paulo, Brazil
| | - Dioze Guadagnini
- School of Applied Sciences, State University of Campinas, Limeira, Brazil
| | - Renata Frazão
- Department of Anatomy, Institute of Biomedical Sciences, University of São Paulo, São Paulo, Brazil
| | - Edward O List
- Edison Biotechnology Institute and Heritage College of Osteopathic Medicine, Ohio University, Athens, Ohio, USA
| | - John J Kopchick
- Edison Biotechnology Institute and Heritage College of Osteopathic Medicine, Ohio University, Athens, Ohio, USA
| | - Patricia O Prada
- School of Applied Sciences, State University of Campinas, Limeira, Brazil
| | - Jose Donato
- Department of Physiology and Biophysics, Institute of Biomedical Sciences, University of São Paulo, São Paulo, Brazil
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Vestergaard ET, Hjelholt AJ, Kuhre RE, Møller N, Larraufie P, Gribble FM, Reimann F, Jessen N, Holst JJ, Jørgensen JOL. Acipimox Acutely Increases GLP-1 Concentrations in Overweight Subjects and Hypopituitary Patients. J Clin Endocrinol Metab 2019; 104:2581-2592. [PMID: 30726969 PMCID: PMC7212086 DOI: 10.1210/jc.2018-02503] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/20/2018] [Accepted: 02/01/2019] [Indexed: 12/25/2022]
Abstract
CONTEXT Glucagon-like peptide-1 (GLP-1) is an incretin hormone used therapeutically in type 2 diabetes and obesity. The interplay between ambient free fatty acids (FFAs) and GLP-1 remains unclear. Acipimox suppresses adipose tissue lipolysis via activation of the PUMA-G (also known as HCA2 and GPR109a) receptor. OBJECTIVE To investigate whether lowering of serum FFA level with acipimox affects GLP-1 secretion. DESIGN Two randomized crossover studies were performed in human subjects. Rat intestine was perfused intra-arterially and intraluminally, and l-cells were incubated with acipimox. PARTICIPANTS The participants were healthy overweight subjects and hypopituitary adult patients. INTERVENTIONS The overweight participants received acipimox 250 mg 60 minutes before an oral glucose test. The hypopituitary patients received acipimox 250 mg 12, 9, and 2 hours before and during the metabolic study day, when they were studied in the basal state and during a hyperinsulinemic euglycemic clamp. RESULTS Acipimox suppressed FFA but did not affect insulin in the clinical trials. In overweight subjects, the GLP-1 increase after the oral glucose tolerance test (area under the curve) was more than doubled [4119 ± 607 pmol/L × min (Acipimox) vs 1973 ± 375 pmol/L × min (control), P = 0.004]. In hypopituitary patients, acipimox improved insulin sensitivity (4.7 ± 0.8 mg glucose/kg/min (Acipimox) vs 3.1 ± 0.5 mg glucose/kg/min (control), P = 0.005], and GLP-1 concentrations increased ~40%. An inverse correlation between FFA and GLP-1 concentrations existed in both trials. In rat intestine, acipimox did not affect GLP-1 secretion, and l-cells did not consistently express the putative receptor for acipimox. CONCLUSIONS Acipimox treatment increases systemic GLP-1 levels in both obese subjects and hypopituitary patients. Our in vitro data indicate that the underlying mechanisms are indirect.
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Affiliation(s)
- Esben Thyssen Vestergaard
- Medical Research Laboratories Aarhus University, Palle Juul-Jensens Boulevard 99, 8200 Aarhus N, Denmark
- Department of Pediatrics, Randers Regional Hospital, 8930 Randers
| | - Astrid Johanneson Hjelholt
- Medical Research Laboratories Aarhus University, Palle Juul-Jensens Boulevard 99, 8200 Aarhus N, Denmark
- Department of Diabetes and Endocrinology, Aarhus University Hospital, Palle Juul-Jensens Boulevard 99, 8200 Aarhus N, Denmark
| | - Rune E. Kuhre
- Department of Biomedical Sciences and NNF Centre for Basic Metabolic Research, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Niels Møller
- Medical Research Laboratories Aarhus University, Palle Juul-Jensens Boulevard 99, 8200 Aarhus N, Denmark
- Department of Diabetes and Endocrinology, Aarhus University Hospital, Palle Juul-Jensens Boulevard 99, 8200 Aarhus N, Denmark
| | - Pierre Larraufie
- Metabolic Research Laboratories and Medical Research Council Metabolic Diseases Unit, Wellcome Trust-Medical Research Council Institute of Metabolic Science, Addenbrooke's Hospital, University of Cambridge, CB2 0QQ, UK
| | - Fiona M. Gribble
- Metabolic Research Laboratories and Medical Research Council Metabolic Diseases Unit, Wellcome Trust-Medical Research Council Institute of Metabolic Science, Addenbrooke's Hospital, University of Cambridge, CB2 0QQ, UK
| | - Frank Reimann
- Metabolic Research Laboratories and Medical Research Council Metabolic Diseases Unit, Wellcome Trust-Medical Research Council Institute of Metabolic Science, Addenbrooke's Hospital, University of Cambridge, CB2 0QQ, UK
| | - Niels Jessen
- Medical Research Laboratories Aarhus University, Palle Juul-Jensens Boulevard 99, 8200 Aarhus N, Denmark
- Research Laboratory for Biochemical Pathology, Aarhus University Hospital, 8000 Aarhus C, Denmark
- Department of Biomedicine, Aarhus University, Aarhus C, Denmark
- Steno Diabetes Centre Aarhus, Aarhus University Hospital, Denmark
| | - Jens Juul Holst
- Department of Biomedical Sciences and NNF Centre for Basic Metabolic Research, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Jens Otto Lunde Jørgensen
- Medical Research Laboratories Aarhus University, Palle Juul-Jensens Boulevard 99, 8200 Aarhus N, Denmark
- Department of Diabetes and Endocrinology, Aarhus University Hospital, Palle Juul-Jensens Boulevard 99, 8200 Aarhus N, Denmark
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13
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Fernandez G, Cabral A, Andreoli MF, Labarthe A, M'Kadmi C, Ramos JG, Marie J, Fehrentz JA, Epelbaum J, Tolle V, Perello M. Evidence Supporting a Role for Constitutive Ghrelin Receptor Signaling in Fasting-Induced Hyperphagia in Male Mice. Endocrinology 2018; 159:1021-1034. [PMID: 29300858 DOI: 10.1210/en.2017-03101] [Citation(s) in RCA: 49] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/01/2017] [Accepted: 12/21/2017] [Indexed: 01/22/2023]
Abstract
Ghrelin is a potent orexigenic peptide hormone that acts through the growth hormone secretagogue receptor (GHSR), a G protein-coupled receptor highly expressed in the hypothalamus. In vitro studies have shown that GHSR displays a high constitutive activity, whose physiological relevance is uncertain. As GHSR gene expression in the hypothalamus is known to increase in fasting conditions, we tested the hypothesis that constitutive GHSR activity at the hypothalamic level drives the fasting-induced hyperphagia. We found that refed wild-type (WT) mice displayed a robust hyperphagia that continued for 5 days after refeeding and changed their food intake daily pattern. Fasted WT mice showed an increase in plasma ghrelin levels, as well as in GHSR expression levels and ghrelin binding sites in the hypothalamic arcuate nucleus. When fasting-refeeding responses were evaluated in ghrelin- or GHSR-deficient mice, only the latter displayed an ∼15% smaller hyperphagia, compared with WT mice. Finally, fasting-induced hyperphagia of WT mice was significantly smaller in mice centrally treated with the GHSR inverse agonist K-(D-1-Nal)-FwLL-NH2, compared with mice treated with vehicle, whereas it was unaffected in mice centrally treated with the GHSR antagonists D-Lys3-growth hormone-releasing peptide 6 or JMV2959. Taken together, genetic models and pharmacological results support the notion that constitutive GHSR activity modulates the magnitude of the compensatory hyperphagia triggered by fasting. Thus, the hypothalamic GHSR signaling system could affect the set point of daily food intake, independently of plasma ghrelin levels, in situations of negative energy balance.
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Affiliation(s)
- Gimena Fernandez
- Laboratory of Neurophysiology of the Multidisciplinary Institute of Cell Biology (Argentine Research Council, Scientific Research Commission of the Province of Buenos Aires and National University of La Plata), La Plata, Buenos Aires, Argentina
| | - Agustina Cabral
- Laboratory of Neurophysiology of the Multidisciplinary Institute of Cell Biology (Argentine Research Council, Scientific Research Commission of the Province of Buenos Aires and National University of La Plata), La Plata, Buenos Aires, Argentina
| | - María F Andreoli
- School of Biochemistry and Biological Sciences, National University of Litoral and Institute of Environmental Health, Santa Fe, Argentina
| | - Alexandra Labarthe
- Centre de Psychiatrie et Neurosciences Unité Mixte de Recherche Scientifique_S894 INSERM Université Paris Descartes, Sorbonne Paris-Cité, Paris, France
| | - Céline M'Kadmi
- Institut des Biomolécules Max Mousseron, Unité Mixte de Recherche Scientifique 5247 Centre National de la Recherche Scientifique-Université Montpellier-École Nationale Supérieure de Chimie de Montpellier, Faculté de Pharmacie, Montpellier, France
| | - Jorge G Ramos
- School of Biochemistry and Biological Sciences, National University of Litoral and Institute of Environmental Health, Santa Fe, Argentina
| | - Jacky Marie
- Institut des Biomolécules Max Mousseron, Unité Mixte de Recherche Scientifique 5247 Centre National de la Recherche Scientifique-Université Montpellier-École Nationale Supérieure de Chimie de Montpellier, Faculté de Pharmacie, Montpellier, France
| | - Jean-Alain Fehrentz
- Institut des Biomolécules Max Mousseron, Unité Mixte de Recherche Scientifique 5247 Centre National de la Recherche Scientifique-Université Montpellier-École Nationale Supérieure de Chimie de Montpellier, Faculté de Pharmacie, Montpellier, France
| | - Jacques Epelbaum
- Centre de Psychiatrie et Neurosciences Unité Mixte de Recherche Scientifique_S894 INSERM Université Paris Descartes, Sorbonne Paris-Cité, Paris, France
- Mécanismes Adaptatifs et Evolution, Unité Mixte de Recherche Scientifique 7179 Centre National de la Recherche Scientifique, Muséum National d'Histoire Naturelle France, Brunoy, France
| | - Virginie Tolle
- Centre de Psychiatrie et Neurosciences Unité Mixte de Recherche Scientifique_S894 INSERM Université Paris Descartes, Sorbonne Paris-Cité, Paris, France
| | - Mario Perello
- Laboratory of Neurophysiology of the Multidisciplinary Institute of Cell Biology (Argentine Research Council, Scientific Research Commission of the Province of Buenos Aires and National University of La Plata), La Plata, Buenos Aires, Argentina
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14
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Abstract
Growth hormone (GH) secretory patterns emerge following birth, and changes in patterning occur throughout life. These secretory patterns are coupled to growth, reproduction and metabolism. Comparing human and animal studies, this review will highlight ultradian patterning of GH release and the mechanisms that contribute to this. Discussions will focus on the emergence in variations in the number and frequency of GH secretory events, and the amounts of GH released (peak and basal). Animal studies have contributed significantly to our understanding of the processes that regulate GH release. However, translation of knowledge from animal models to benefit our understanding of human physiology is sometimes limited. To overcome these limitations, it is critical that we reconcile the cause and consequences of differences in GH release between humans and model organisms. In doing so, we can embrace emerging technologies that will rapidly advance our knowledge of endogenous process that control GH release.
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Affiliation(s)
- Frederik J Steyn
- Centre for Clinical Research, The University of Queensland, Queensland, Australia; Australian Institute for Bioengineering and Nanotechnology, The University of Queensland, Australia.
| | - Shyuan T Ngo
- Australian Institute for Bioengineering and Nanotechnology, The University of Queensland, Australia; Queensland Brain Institute, The University of Queensland, Australia.
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15
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Foradori CD, Whitlock BK, Daniel JA, Zimmerman AD, Jones MA, Read CC, Steele BP, Smith JT, Clarke IJ, Elsasser TH, Keisler DH, Sartin JL. Kisspeptin Stimulates Growth Hormone Release by Utilizing Neuropeptide Y Pathways and Is Dependent on the Presence of Ghrelin in the Ewe. Endocrinology 2017; 158:3526-3539. [PMID: 28977590 DOI: 10.1210/en.2017-00303] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/29/2017] [Accepted: 07/13/2017] [Indexed: 12/31/2022]
Abstract
Although kisspeptin is the primary stimulator of gonadotropin-releasing hormone secretion and therefore the hypothalamic-pituitary-gonadal axis, recent findings suggest kisspeptin can also regulate additional neuroendocrine processes including release of growth hormone (GH). Here we show that central delivery of kisspeptin causes a robust rise in plasma GH in fasted but not fed sheep. Kisspeptin-induced GH secretion was similar in animals fasted for 24 hours and those fasted for 72 hours, suggesting that the factors involved in kisspeptin-induced GH secretion are responsive to loss of food availability and not the result of severe negative energy balance. Pretreatment with the neuropeptide Y (NPY) Y1 receptor antagonist, BIBO 3304, blocked the effects of kisspeptin-induced GH release, implicating NPY as an intermediary. Kisspeptin treatment induced c-Fos in NPY and GH-releasing hormone (GHRH) cells of the arcuate nucleus. The same kisspeptin treatment resulted in a reduction in c-Fos in somatostatin (SS) cells in the periventricular nucleus. Finally, blockade of systemic ghrelin release or antagonism of the ghrelin receptor eliminated or reduced the ability of kisspeptin to induce GH release, suggesting the presence of ghrelin is required for kisspeptin-induced GH release in fasted animals. Our findings support the hypothesis that during short-term fasting, systemic ghrelin concentrations and NPY expression in the arcuate nucleus rise. This permits kisspeptin activation of NPY cells. In turn, NPY stimulates GHRH cells and inhibits SS cells, resulting in GH release. We propose a mechanism by which kisspeptin conveys reproductive and hormone status onto the somatotropic axis, resulting in alterations in GH release.
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Affiliation(s)
- Chad D Foradori
- Department of Anatomy, Physiology & Pharmacology, Auburn University, Auburn, Alabama 36849
| | - Brian K Whitlock
- Department of Large Animal Clinical Sciences, University of Tennessee, Knoxville, Tennessee 37996
| | - Jay A Daniel
- Department of Animal Science, Berry College, Mt. Berry, Georgia 30149
| | - Arthur D Zimmerman
- Department of Anatomy, Physiology & Pharmacology, Auburn University, Auburn, Alabama 36849
| | - Melaney A Jones
- Department of Anatomy, Physiology & Pharmacology, Auburn University, Auburn, Alabama 36849
| | - Casey C Read
- Department of Anatomy, Physiology & Pharmacology, Auburn University, Auburn, Alabama 36849
| | - Barbara P Steele
- Department of Anatomy, Physiology & Pharmacology, Auburn University, Auburn, Alabama 36849
| | - Jeremy T Smith
- School of Anatomy, Physiology and Human Biology, University of Western Australia, Perth, Crawley, Washington 6009, Australia
| | - Iain J Clarke
- Neuroscience Program, Monash Biomedicine Discovery Institute and Department of Physiology, Monash University, Melbourne, Victoria 3800, Australia
| | - Theodore H Elsasser
- Animal Genomics and Improvement Laboratory, US Department of Agriculture, Agricultural Research Service, Beltsville, Maryland 20705
| | - Duane H Keisler
- Division of Animal Sciences, University of Missouri, Columbia, Missouri 65211
| | - James L Sartin
- Department of Anatomy, Physiology & Pharmacology, Auburn University, Auburn, Alabama 36849
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16
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Gatford KL, Muhlhausler BS, Huang L, Sim PSL, Roberts CT, Velhuis JD, Chen C. Rising maternal circulating GH during murine pregnancy suggests placental regulation. Endocr Connect 2017; 6:260-266. [PMID: 28404685 PMCID: PMC5457489 DOI: 10.1530/ec-17-0032] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/11/2017] [Accepted: 04/12/2017] [Indexed: 11/15/2022]
Abstract
Placenta-derived hormones including growth hormone (GH) in humans contribute to maternal adaptation to pregnancy, and intermittent maternal GH administration increases foetal growth in several species. Both patterns and abundance of circulating GH are important for its activity, but their changes during pregnancy have only been reported in humans and rats. The aim of the present study was to characterise circulating profiles and secretory characteristics of GH in non-pregnant female mice and throughout murine pregnancy. Circulating GH concentrations were measured in whole blood (2 μL) collected every 10 min for 6 h in non-pregnant diestrus female C57Bl/6J mice (n = 9), and pregnant females at day 8.5-9.5 (early pregnancy, n = 8), day 12.5-13.5 (mid-pregnancy, n = 7) and day 17.5 after mating (late pregnancy, n = 7). Kinetics and secretory patterns of GH secretion were determined by deconvolution analysis, while orderliness and regularity of serial GH concentrations were calculated by approximate entropy analysis. Circulating GH was pulsatile in all groups. Mean circulating GH and total and basal GH secretion rates increased markedly from early to mid-pregnancy, and then remained elevated. Pulse frequency and pulsatile GH secretion rate were similar between groups. The irregularity of GH pulses was higher in all pregnant groups than that in non-pregnant mice. Increased circulating GH in murine pregnancy is consistent with an important role for this hormone in maternal adaptation to pregnancy and placental development. The timing of increased basal secretion from mid-pregnancy, concurrent with the formation of the chorioallantoic placenta and initiation of maternal blood flow through it, suggests regulation of pituitary secretion by placenta-derived factors.
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Affiliation(s)
- Kathryn L Gatford
- Robinson Research InstituteThe University of Adelaide, Adelaide, Australia
- Adelaide Medical SchoolThe University of Adelaide, Adelaide, Australia
| | - Beverly S Muhlhausler
- FOOD plus Research CentreSchool of Agriculture, Food and Wine, The University of Adelaide, Adelaide, Australia
| | - Lili Huang
- School of Biomedical SciencesUniversity of Queensland, St Lucia, Brisbane, Australia
| | - Pamela Su-Lin Sim
- FOOD plus Research CentreSchool of Agriculture, Food and Wine, The University of Adelaide, Adelaide, Australia
| | - Claire T Roberts
- Robinson Research InstituteThe University of Adelaide, Adelaide, Australia
- Adelaide Medical SchoolThe University of Adelaide, Adelaide, Australia
| | - Johannes D Velhuis
- Endocrine Research UnitMayo School of Graduate Medical Education, Center for Translational Science Activities, Mayo Clinic, Rochester, Minnesota, USA
| | - Chen Chen
- School of Biomedical SciencesUniversity of Queensland, St Lucia, Brisbane, Australia
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17
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A Single Bout of Fasting (24 h) Reduces Basal Cytokine Expression and Minimally Impacts the Sterile Inflammatory Response in the White Adipose Tissue of Normal Weight F344 Rats. Mediators Inflamm 2016; 2016:1698071. [PMID: 28077915 PMCID: PMC5203907 DOI: 10.1155/2016/1698071] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2016] [Accepted: 11/20/2016] [Indexed: 01/10/2023] Open
Abstract
Sterile inflammation occurs when inflammatory proteins are increased in blood and tissues by nonpathogenic states and is a double-edged sword depending on its cause (stress, injury, or disease), duration (transient versus chronic), and inflammatory milieu. Short-term fasting can exert a host of health benefits through unknown mechanisms. The following experiment tested if a 24 h fast would modulate basal and stress-evoked sterile inflammation in plasma and adipose. Adult male F344 rats were either randomized to ad libitum access to food or fasted for 24 h prior to 0 (control), 10, or 100, 1.5 mA-5 s intermittent, inescapable tail shocks (IS). Glucose, nonesterified free fatty acids (NEFAs), insulin, leptin, and corticosterone were measured in plasma and tumor necrosis factor- (TNF-) α, interleukin- (IL-) 1β, IL-6, and IL-10 in plasma, and subcutaneous, intraperitoneal, and visceral compartments of white adipose tissue (WAT). In control rats, a 24 h fast reduced all measured basal cytokines in plasma and visceral WAT, IL-1β and IL-6 in subcutaneous WAT, and IL-6 in intraperitoneal WAT. In stressed rats (IS), fasting reduced visceral WAT TNF-α, subcutaneous WAT IL-1β, and plasma insulin and leptin. Short-term fasting may thus prove to be a useful dietary strategy for reducing peripheral inflammatory states associated with visceral obesity and chronic stress.
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18
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Steyn FJ, Tolle V, Chen C, Epelbaum J. Neuroendocrine Regulation of Growth Hormone Secretion. Compr Physiol 2016; 6:687-735. [PMID: 27065166 DOI: 10.1002/cphy.c150002] [Citation(s) in RCA: 71] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
This article reviews the main findings that emerged in the intervening years since the previous volume on hormonal control of growth in the section on the endocrine system of the Handbook of Physiology concerning the intra- and extrahypothalamic neuronal networks connecting growth hormone releasing hormone (GHRH) and somatostatin hypophysiotropic neurons and the integration between regulators of food intake/metabolism and GH release. Among these findings, the discovery of ghrelin still raises many unanswered questions. One important event was the application of deconvolution analysis to the pulsatile patterns of GH secretion in different mammalian species, including Man, according to gender, hormonal environment and ageing. Concerning this last phenomenon, a great body of evidence now supports the role of an attenuation of the GHRH/GH/Insulin-like growth factor-1 (IGF-1) axis in the control of mammalian aging.
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Affiliation(s)
- Frederik J Steyn
- University of Queensland Centre for Clinical Research and the School of Biomedical Sciences, University of Queensland, St. Lucia, Brisbane, Queensland, Australia
| | - Virginie Tolle
- Unité Mixte de Recherche en Santé 894 INSERM, Centre de Psychiatrie et Neurosciences, Université Paris Descartes, Sorbonne Paris Cité, Paris, France
| | - Chen Chen
- School of Biomedical Sciences, University of Queensland, St. Lucia, Brisbane, Queensland, Australia
| | - Jacques Epelbaum
- University of Queensland Centre for Clinical Research and the School of Biomedical Sciences, University of Queensland, St. Lucia, Brisbane, Queensland, Australia
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19
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Wilson CG, Tran JL, Erion DM, Vera NB, Febbraio M, Weiss EJ. Hepatocyte-Specific Disruption of CD36 Attenuates Fatty Liver and Improves Insulin Sensitivity in HFD-Fed Mice. Endocrinology 2016; 157:570-85. [PMID: 26650570 PMCID: PMC4733118 DOI: 10.1210/en.2015-1866] [Citation(s) in RCA: 297] [Impact Index Per Article: 37.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
CD36/FAT (fatty acid translocase) is associated with human and murine nonalcoholic fatty liver disease, but it has been unclear whether it is simply a marker or whether it directly contributes to disease pathogenesis. Mice with hepatocyte-specific deletion of Janus kinase 2 (JAK2L mice) have increased circulating free fatty acids (FAs), dramatically increased hepatic CD36 expression and profound fatty liver. To investigate the role of elevated CD36 in the development of fatty liver, we studied two models of hepatic steatosis, a genetic model (JAK2L mice) and a high-fat diet (HFD)-induced steatosis model. We deleted Cd36 specifically in hepatocytes of JAK2L mice to generate double knockouts and from wild-type mice to generate CD36L single-knockout mice. Hepatic Cd36 disruption in JAK2L livers significantly improved steatosis by lowering triglyceride, diacylglycerol, and cholesterol ester content. The largest differences in liver triglycerides were in species comprised of oleic acid (C18:1). Reduction in liver lipids correlated with an improvement in the inflammatory markers that were elevated in JAK2L mice, namely aspartate aminotransferase and alanine transaminase. Cd36 deletion in mice on HFD (CD36L-HFD) reduced liver lipid content and decreased hepatic 4,4-difluoro-4-bora-3a,4a-diaza-s-indacene-FA uptake as compared with CON-HFD. Additionally, CD36L-HFD mice had improved whole-body insulin sensitivity and reduced liver and serum inflammatory markers. Therefore, CD36 directly contributes to development of fatty liver under conditions of elevated free FAs by modulating the rate of FA uptake by hepatocytes. In HFD-fed animals, disruption of hepatic Cd36 protects against associated systemic inflammation and insulin resistance.
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Affiliation(s)
- Camella G Wilson
- Cardiovascular Research Institute (C.G.W., J.L.T., E.J.W.), University of California, San Francisco, San Francisco, California 94158-9001; Pfizer Pharmaceuticals (D.M.E., N.B.V.), Cambridge, Massachusetts 02139; and School of Dentistry (M.F.), University of Alberta, Edmonton AB, Canada T6G 2E1
| | - Jennifer L Tran
- Cardiovascular Research Institute (C.G.W., J.L.T., E.J.W.), University of California, San Francisco, San Francisco, California 94158-9001; Pfizer Pharmaceuticals (D.M.E., N.B.V.), Cambridge, Massachusetts 02139; and School of Dentistry (M.F.), University of Alberta, Edmonton AB, Canada T6G 2E1
| | - Derek M Erion
- Cardiovascular Research Institute (C.G.W., J.L.T., E.J.W.), University of California, San Francisco, San Francisco, California 94158-9001; Pfizer Pharmaceuticals (D.M.E., N.B.V.), Cambridge, Massachusetts 02139; and School of Dentistry (M.F.), University of Alberta, Edmonton AB, Canada T6G 2E1
| | - Nicholas B Vera
- Cardiovascular Research Institute (C.G.W., J.L.T., E.J.W.), University of California, San Francisco, San Francisco, California 94158-9001; Pfizer Pharmaceuticals (D.M.E., N.B.V.), Cambridge, Massachusetts 02139; and School of Dentistry (M.F.), University of Alberta, Edmonton AB, Canada T6G 2E1
| | - Maria Febbraio
- Cardiovascular Research Institute (C.G.W., J.L.T., E.J.W.), University of California, San Francisco, San Francisco, California 94158-9001; Pfizer Pharmaceuticals (D.M.E., N.B.V.), Cambridge, Massachusetts 02139; and School of Dentistry (M.F.), University of Alberta, Edmonton AB, Canada T6G 2E1
| | - Ethan J Weiss
- Cardiovascular Research Institute (C.G.W., J.L.T., E.J.W.), University of California, San Francisco, San Francisco, California 94158-9001; Pfizer Pharmaceuticals (D.M.E., N.B.V.), Cambridge, Massachusetts 02139; and School of Dentistry (M.F.), University of Alberta, Edmonton AB, Canada T6G 2E1
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20
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Dal J, List EO, Jørgensen JOL, Berryman DE. Glucose and Fat Metabolism in Acromegaly: From Mice Models to Patient Care. Neuroendocrinology 2016; 103:96-105. [PMID: 25925240 DOI: 10.1159/000430819] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/09/2015] [Accepted: 04/20/2015] [Indexed: 11/19/2022]
Abstract
Patients with active acromegaly are frequently insulin resistant, glucose intolerant, and at risk for developing overt type 2 diabetes. At the same time, these patients have a relatively lean phenotype associated with mobilization and oxidation of free fatty acids. These features are reversed by curative surgical removal of the growth hormone (GH)-producing adenoma. Mouse models of acromegaly share many of these characteristics, including a lean phenotype and proneness to type 2 diabetes. There are, however, also species differences with respect to oxidation rates of glucose and fat as well as the specific mechanisms underlying GH-induced insulin resistance. The impact of acromegaly treatment on insulin sensitivity and glucose tolerance depends on the treatment modality (e.g. somatostatin analogs also suppress insulin secretion, whereas the GH antagonist restores insulin sensitivity). The interplay between animal research and clinical studies has proven useful in the field of acromegaly and should be continued in order to understand the metabolic actions of GH.
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Affiliation(s)
- Jakob Dal
- Department of Endocrinology and Internal Medicine, Aarhus University Hospital, Aarhus, Denmark
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21
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Xie TY, Ngo ST, Veldhuis JD, Jeffery PL, Chopin LK, Tschöp M, Waters MJ, Tolle V, Epelbaum J, Chen C, Steyn FJ. Effect of Deletion of Ghrelin-O-Acyltransferase on the Pulsatile Release of Growth Hormone in Mice. J Neuroendocrinol 2015; 27:872-86. [PMID: 26442444 DOI: 10.1111/jne.12327] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/03/2015] [Revised: 09/30/2015] [Accepted: 10/01/2015] [Indexed: 12/21/2022]
Abstract
Ghrelin, a gut hormone originating from the post-translational cleavage of preproghrelin, is the endogenous ligand of growth hormone secretagogue receptor 1a (GHS-R1a). Within the growth hormone (GH) axis, the biological activity of ghrelin requires octanoylation by ghrelin-O-acyltransferase (GOAT), conferring selective binding to the GHS-R1a receptor via acylated ghrelin. Complete loss of preproghrelin-derived signalling (through deletion of the Ghrl gene) contributes to a decline in peak GH release; however, the selective contribution of endogenous acyl-ghrelin to pulsatile GH release remains to be established. We assessed the pulsatile release of GH in ad lib. fed male germline goat(-/-) mice, extending measures to include mRNA for key hypothalamic regulators of GH release, and peripheral factors that are modulated relative to GH release. The amount of GH released was reduced in young goat(-/-) mice compared to age-matched wild-type mice, whereas pulse frequency and irregularity increased. Altered GH release did not coincide with alterations in hypothalamic Ghrh, Srif, Npy or Ghsr mRNA expression, or pituitary GH content, suggesting that loss of Goat does not compromise canonical mechanisms that contribute to pituitary GH production and release. Although loss of Goat resulted in an irregular pattern of GH release (characterised by an increase in the number of GH pulses observed during extended secretory events), this did not contribute to a change in the expression of sexually dimorphic GH-dependent liver genes. Of interest, circulating levels of insulin-like growth factor (IGF)-1 were elevated in goat(-/-) mice. This rise in circulating levels of IGF-1 was correlated with an increase in GH pulse frequency, suggesting that sustained or increased IGF-1 release in goat(-/-) mice may occur in response to altered GH release patterning. Our observations demonstrate that germline loss of Goat alters GH release and patterning. Although the biological relevance of altered GH secretory patterning remains unclear, we propose that this may contribute to sustained IGF-1 release and growth in goat(-/-) mice.
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Affiliation(s)
- T Y Xie
- School of Biomedical Sciences, University of Queensland, St Lucia, Brisbane, Queensland, Australia
| | - S T Ngo
- School of Biomedical Sciences, University of Queensland, St Lucia, Brisbane, Queensland, Australia
- The Queensland Brain Institute, University of Queensland, St Lucia, Brisbane, Queensland, Australia
- University of Queensland Centre for Clinical Research, University of Queensland, Herston, Queensland, Australia
| | - J D Veldhuis
- Endocrine Research Unit, Department of Medicine, Mayo School of Graduate Medical Education, Clinical Translational Science Center, Mayo Clinic, Rochester, MN, USA
| | - P L Jeffery
- Ghrelin Research Group, Translational Research Institute - Institute of Health and Biomedical Innovation, Queensland University of Technology, Woolloongabba, Queensland, Australia
| | - L K Chopin
- Ghrelin Research Group, Translational Research Institute - Institute of Health and Biomedical Innovation, Queensland University of Technology, Woolloongabba, Queensland, Australia
| | - M Tschöp
- Institute for Diabetes and Obesity, Helmholtz Zentrum München, German Research Center for Environmental Health, Neuherberg, Germany
| | - M J Waters
- Institute for Molecular Bioscience, The University of Queensland, St Lucia, Brisbane, Queensland, Australia
| | - V Tolle
- UMR-S 894 INSERM, Centre de Psychiatrie et Neurosciences, Université Paris Descartes, Sorbonne Paris Cité, Paris, France
| | - J Epelbaum
- UMR-S 894 INSERM, Centre de Psychiatrie et Neurosciences, Université Paris Descartes, Sorbonne Paris Cité, Paris, France
| | - C Chen
- School of Biomedical Sciences, University of Queensland, St Lucia, Brisbane, Queensland, Australia
| | - F J Steyn
- School of Biomedical Sciences, University of Queensland, St Lucia, Brisbane, Queensland, Australia
- University of Queensland Centre for Clinical Research, University of Queensland, Herston, Queensland, Australia
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22
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Steyn FJ. Nutrient Sensing Overrides Somatostatin and Growth Hormone-Releasing Hormone to Control Pulsatile Growth Hormone Release. J Neuroendocrinol 2015; 27:577-87. [PMID: 25808924 DOI: 10.1111/jne.12278] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/20/2014] [Revised: 03/07/2015] [Accepted: 03/07/2015] [Indexed: 12/14/2022]
Abstract
Pharmacological studies reveal that interactions between hypothalamic inhibitory somatostatin and stimulatory growth hormone-releasing hormone (GHRH) govern pulsatile GH release. However, in vivo analysis of somatostatin and GHRH release into the pituitary portal vasculature and peripheral GH output demonstrates that the withdrawal of somatostatin or the appearance of GHRH into pituitary portal blood does not reliably dictate GH release. Consequently, additional intermediates acting at the level of the hypothalamus and within the anterior pituitary gland are likely to contribute to the release of GH, entraining GH secretory patterns to meet physiological demand. The identification and validation of the actions of such intermediates is particularly important, given that the pattern of GH release defines several of the physiological actions of GH. This review highlights the actions of neuropeptide Y in regulating GH release. It is acknowledged that pulsatile GH release may not occur selectively in response to hypothalamic control of pituitary function. As such, interactions between somatotroph networks, the median eminence and pituitary microvasculature and blood flow, and the emerging role of tanycytes and pericytes as critical regulators of pulsatility are considered. It is argued that collective interactions between the hypothalamus, the median eminence and pituitary vasculature, and structural components within the pituitary gland dictate somatotroph function and thereby pulsatile GH release. These interactions may override hypothalamic somatostatin and GHRH-mediated GH release, and modify pulsatile GH release relative to the peripheral glucose supply, and thereby physiological demand.
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Affiliation(s)
- F J Steyn
- The University of Queensland Centre for Clinical Research and The School of Biomedical Sciences, University of Queensland, Herston, 4029, Australia
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23
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Arisqueta L, Navarro-Imaz H, Rueda Y, Fresnedo O. Cholesterol mobilization from hepatic lipid droplets during endotoxemia is altered in obese ob/ob mice. J Biochem 2015; 158:321-9. [DOI: 10.1093/jb/mvv047] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2015] [Accepted: 03/31/2015] [Indexed: 11/12/2022] Open
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24
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Adams JM, Otero-Corchon V, Hammond GL, Veldhuis JD, Qi N, Low MJ. Somatostatin is essential for the sexual dimorphism of GH secretion, corticosteroid-binding globulin production, and corticosterone levels in mice. Endocrinology 2015; 156:1052-65. [PMID: 25551181 PMCID: PMC4330306 DOI: 10.1210/en.2014-1429] [Citation(s) in RCA: 36] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Distinct male and female patterns of pituitary GH secretion produce sexually differentiated hepatic gene expression profiles, thereby influencing steroid and xenobiotic metabolism. We used a fully automated system to obtain serial nocturnal blood samples every 15 minutes from cannulated wild-type (WT) and somatostatin knockout (Sst-KO) mice to determine the role of SST, the principal inhibitor of GH release, in the generation of sexually dimorphic GH pulsatility. WT males had lower mean and median GH values, less random GH secretory bursts, and longer trough periods between GH pulses than WT females. Each of these parameters was feminized in male Sst-KO mice, whereas female Sst-KO mice had higher GH levels than all other groups, but GH pulsatility was unaffected. We next performed hepatic mRNA profiling with high-density microarrays. Male Sst-KO mice exhibited a globally feminized pattern of GH-dependent mRNA levels, but female Sst-KO mice were largely unaffected. Among the differentially expressed female-predominant genes was Serpina6, which encodes corticosteroid-binding globulin (CBG). Increased CBG was associated with elevated diurnal peak plasma corticosterone in unstressed WT females and both sexes of Sst-KO mice compared with WT males. Sst-KO mice also had exaggerated ACTH and corticosterone responses to acute restraint stress. However, consistent with their lack of phenotypic signs of excess glucocorticoids, cerebrospinal fluid concentrations of free corticosterone in Sst-KO mice were not elevated. In summary, SST is necessary for the prolonged interpulse troughs that define masculinized pituitary GH secretion. SST also contributes to sexual dimorphism of the hypothalamic-pituitary-adrenal axis via GH-dependent regulation of hepatic CBG production.
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Affiliation(s)
- Jessica M Adams
- Neuroscience Graduate Program (J.M.A.), University of Michigan, Ann Arbor, Michigan, 48109; Department of Molecular and Integrative Physiology (J.M.A., V.O.-C., M.J.L.), University of Michigan Medical School, Ann Arbor, Michigan, 48109; Department of Cellular and Physiological Sciences (G.L.H.), University of British Columbia, Vancouver, British Columbia, Canada, V6T 1Z3; Department of Internal Medicine (J.D.V.), Endocrine Research Unit, Mayo Clinic College of Medicine, Rochester, Minnesota, 55905; and Department of Internal Medicine (N.Q., M.J.L.), Division of Metabolism, Endocrinology and Diabetes, University of Michigan Medical School, Ann Arbor, Michigan, 48109
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25
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Actions of NPY, and its Y1 and Y2 receptors on pulsatile growth hormone secretion during the fed and fasted state. J Neurosci 2015; 34:16309-19. [PMID: 25471570 DOI: 10.1523/jneurosci.4622-13.2014] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
The hypothalamic NPY system plays an important role in regulating food intake and energy expenditure. Different biological actions of NPY are assigned to NPY receptor subtypes. Recent studies demonstrated a close relationship between food intake and growth hormone (GH) secretion; however, the mechanism through which endogenous NPY modulates GH release remains unknown. Moreover, conclusive evidence demonstrating a role for NPY and Y-receptors in regulating the endogenous pulsatile release of GH does not exist. We used genetically modified mice (germline Npy, Y1, and Y2 receptor knock-out mice) to assess pulsatile GH secretion under both fed and fasting conditions. Deletion of NPY did not impact fed GH release; however, it reversed the fasting-induced suppression of pulsatile GH secretion. The recovery of GH secretion was associated with a reduction in hypothalamic somatotropin release inhibiting factor (Srif; somatostatin) mRNA expression. Moreover, observations revealed a differential role for Y1 and Y2 receptors, wherein the postsynaptic Y1 receptor suppresses GH secretion in fasting. In contrast, the presynaptic Y2 receptor maintains normal GH output under long-term ad libitum-fed conditions. These data demonstrate an integrated neural circuit that modulates GH release relative to food intake, and provide essential information to address the differential roles of Y1 and Y2 receptors in regulating the release of GH under fed and fasting states.
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26
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Báez-Ruiz A, Luna-Moreno D, Carmona-Castro A, Cárdenas-Vázquez R, Díaz-Muñoz M, Carmona-Alcocer V, Fuentes-Granados C, Manuel MA. Hypothalamic expression of anorexigenic and orexigenic hormone receptors in obese femalesNeotomodon alstoni:Effect of fasting. Nutr Neurosci 2013; 17:31-6. [DOI: 10.1179/1476830513y.0000000063] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
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27
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Tan HY, Huang L, Simmons D, Veldhuis JD, Steyn FJ, Chen C. Hypothalamic distribution of somatostatin mRNA expressing neurones relative to pubertal and adult changes in pulsatile growth hormone secretion in mice. J Neuroendocrinol 2013; 25:910-9. [PMID: 23855876 DOI: 10.1111/jne.12078] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/20/2013] [Revised: 07/08/2013] [Accepted: 07/11/2013] [Indexed: 01/03/2023]
Abstract
The age-associated decline in growth hormone (GH) secretion may be a consequence of the reduction in the number of GH-releasing hormone (GHRH) positive neurones. However, it remains unclear whether an alteration in the number or distribution of somatostatin (SST) neurones contributes to this change. In the present study, we characterised the role of SST in modulating the change in pulsatile GH secretion in male C57Bl/6J mice throughout puberty and into early adulthood. We assessed pulsatile GH secretion in mice at 4, 8 and 16 weeks of age. These ages correspond to early pubertal, early adulthood and adulthood, respectively. We show an elevation in peak, total and pulsatile GH secretion coinciding with periods of rapid linear growth. Using in situ hybridisation and morphometric methods, we mapped the distribution of Sst mRNA expression within the mouse brain relative to this change in pulsatile GH secretion. The results obtained show that altered pulsatile GH secretion in male mice from 4-16 weeks of age does not coincide with a significant change in the number of Sst mRNA expressing neurones or an abundance of Sst mRNA expression throughout the arcuate nucleus (ARC) and periventricular nucleus (PeV). Rather, we observed a progressive decline in Sst mRNA expressing neurones within subnuclei of the paraventricular nucleus at this time. We conclude that structural changes in Sst expression within the PeV and ARC may not reflect the observed decline in pulsatile GH secretion in mice from puberty into early adulthood.
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Affiliation(s)
- H Y Tan
- School of Biomedical Sciences, University of Queensland, Brisbane, Queensland, Australia
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28
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Serra D, Mera P, Malandrino MI, Mir JF, Herrero L. Mitochondrial fatty acid oxidation in obesity. Antioxid Redox Signal 2013; 19:269-84. [PMID: 22900819 PMCID: PMC3691913 DOI: 10.1089/ars.2012.4875] [Citation(s) in RCA: 163] [Impact Index Per Article: 14.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
SIGNIFICANCE Current lifestyles with high-energy diets and little exercise are triggering an alarming growth in obesity. Excess of adiposity is leading to severe increases in associated pathologies, such as insulin resistance, type 2 diabetes, atherosclerosis, cancer, arthritis, asthma, and hypertension. This, together with the lack of efficient obesity drugs, is the driving force behind much research. RECENT ADVANCES Traditional anti-obesity strategies focused on reducing food intake and increasing physical activity. However, recent results suggest that enhancing cellular energy expenditure may be an attractive alternative therapy. CRITICAL ISSUES This review evaluates recent discoveries regarding mitochondrial fatty acid oxidation (FAO) and its potential as a therapy for obesity. We focus on the still controversial beneficial effects of increased FAO in liver and muscle, recent studies on how to potentiate adipose tissue energy expenditure, and the different hypotheses involving FAO and the reactive oxygen species production in the hypothalamic control of food intake. FUTURE DIRECTIONS The present review aims to provide an overview of novel anti-obesity strategies that target mitochondrial FAO and that will definitively be of high interest in the future research to fight against obesity-related disorders.
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Affiliation(s)
- Dolors Serra
- Department of Biochemistry and Molecular Biology, Facultat de Farmàcia, Universitat de Barcelona, Institut de Biomedicina de la Universitat de Barcelona IBUB, Barcelona, Spain
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29
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Steyn FJ, Xie TY, Huang L, Ngo ST, Veldhuis JD, Waters MJ, Chen C. Increased adiposity and insulin correlates with the progressive suppression of pulsatile GH secretion during weight gain. J Endocrinol 2013; 218:233-44. [PMID: 23708999 DOI: 10.1530/joe-13-0084] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
Abstract
Pathological changes associated with obesity are thought to contribute to GH deficiency. However, recent observations suggest that impaired GH secretion relative to excess calorie consumption contributes to progressive weight gain and thus may contribute to the development of obesity. To clarify this association between adiposity and GH secretion, we investigated the relationship between pulsatile GH secretion and body weight; epididymal fat mass; and circulating levels of leptin, insulin, non-esterified free fatty acids (NEFAs), and glucose. Data were obtained from male mice maintained on a standard or high-fat diet. We confirm the suppression of pulsatile GH secretion following dietary-induced weight gain. Correlation analyses reveal an inverse relationship between measures of pulsatile GH secretion, body weight, and epididymal fat mass. Moreover, we demonstrate an inverse relationship between measures of pulsatile GH secretion and circulating levels of leptin and insulin. The secretion of GH did not change relative to circulating levels of NEFAs or glucose. We conclude that impaired pulsatile GH secretion in the mouse occurs alongside progressive weight gain and thus precedes the development of obesity. Moreover, data illustrate key interactions between GH secretion and circulating levels of insulin and reflect the potential physiological role of GH in modulation of insulin-induced lipogenesis throughout positive energy balance.
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Affiliation(s)
- F J Steyn
- School of Biomedical Sciences, University of Queensland, St Lucia, Brisbane, Queensland 4072, Australia
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30
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Steyn FJ, Ngo ST, Lee JD, Leong JW, Buckley AJ, Veldhuis JD, McCombe PA, Chen C, Bellingham MC. Impairments to the GH-IGF-I axis in hSOD1G93A mice give insight into possible mechanisms of GH dysregulation in patients with amyotrophic lateral sclerosis. Endocrinology 2012; 153:3735-46. [PMID: 22621959 DOI: 10.1210/en.2011-2171] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
GH deficiency has been found in subjects with amyotrophic lateral sclerosis (ALS). Disrupted endocrine function could contribute to the progressive muscle loss and hypermetabolism seen in ALS. It is not possible to study all the elements of the GH-IGF-I axis in ALS patients. Consequently, it remains unclear whether dysfunctional GH secretion contributes to disease pathogenesis and why GH and IGF-I directed treatment strategies are ineffective in human ALS. The hSOD1(G93A) transgenic mouse model is useful for the detailed investigation of the pathogenesis of ALS. We report that symptomatic male hSOD1(G93A) transgenic mice exhibit a deficiency in GH secretion similar to that seen in human ALS. Further characterization of the GH-IGF-I axis in hSOD1(G93A) mice reveals central and peripheral abnormalities that are not found in wild-type age-matched controls. Specifically, we observe aberrant endogenous pulsatile GH secretion, reduced pituitary GH content, and decreased circulating levels of IGF-I, indicating global GH deficiency in hSOD1(G93A) mice. Furthermore, a reduction in the expression of the IGF-I receptor α-subunit in skeletal muscle and lumbar spinal cords of hSOD1(G93A) mice suggests impaired IGF-I signaling within these tissues. This is the first account of disrupted GH secretion in a transgenic mouse model of ALS. These observations are essential for the development of effective GH and IGF-I targeted therapies in ALS.
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Affiliation(s)
- F J Steyn
- School of Biomedical Sciences, University of Queensland, St. Lucia 4072, Australia.
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