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Veedfald S, Plamboeck A, Hartmann B, Vilsbøll T, Knop FK, Deacon CF, Svendsen LB, Holst JJ. Ghrelin secretion in humans - a role for the vagus nerve? Neurogastroenterol Motil 2018; 30:e13295. [PMID: 29392854 DOI: 10.1111/nmo.13295] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/20/2017] [Accepted: 12/25/2017] [Indexed: 02/08/2023]
Abstract
BACKGROUND Ghrelin, an orexigenic peptide, is secreted from endocrine cells in the gastric mucosa. Circulating levels rise in the preprandial phase, suggesting an anticipatory or cephalic phase of release, and decline in the postprandial phase, suggesting either the loss of a stimulatory factor or inhibition by factors released when nutrients enter the intestine. We hypothesized that vagal signals are not required for the (i) preprandial increase or (ii) postprandial suppression of ghrelin levels. Further, we wanted to investigate the hypothesis that (iii) glucagon-like peptide-1 might be implicated in the postprandial decline in ghrelin levels. METHODS We measured ghrelin levels in plasma from sham-feeding and meal studies carried out in vagotomized individuals and controls, and from a GLP-1 infusion study carried out in fasting healthy young individuals. KEY RESULTS We find that (i) ghrelin secretion is unchanged during indirect vagal stimulation as elicited by modified sham-feeding in vagotomized individuals and matched controls, (ii) ghrelin secretion is similarly suppressed after meal ingestion in vagotomized individuals and controls, and (iii) infusion of GLP-1 does not lower ghrelin levels. CONCLUSIONS & INFERENCES We conclude that for postprandial suppression of circulating ghrelin levels, a circulating factor (but not GLP-1) or short (duodeno-gastric) reflexes seem to be implicated.
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Affiliation(s)
- S Veedfald
- Endocrinology Research Section, Department of Biomedical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark.,Section for Translational Metabolic Physiology, Novo Nordisk Foundation Center for Basic Metabolic Research, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark.,Center for Diabetes Research, Gentofte Hospital, University of Copenhagen, Hellerup, Denmark.,Department of Surgical Gastroenterology, Rigshospitalet, University of Copenhagen, Copenhagen, Denmark
| | - A Plamboeck
- Endocrinology Research Section, Department of Biomedical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark.,Section for Translational Metabolic Physiology, Novo Nordisk Foundation Center for Basic Metabolic Research, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - B Hartmann
- Endocrinology Research Section, Department of Biomedical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark.,Section for Translational Metabolic Physiology, Novo Nordisk Foundation Center for Basic Metabolic Research, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - T Vilsbøll
- Center for Diabetes Research, Gentofte Hospital, University of Copenhagen, Hellerup, Denmark.,Steno Diabetes Center Copenhagen, University of Copenhagen, Gentofte, Denmark.,Department of Clinical Medicine, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - F K Knop
- Section for Translational Metabolic Physiology, Novo Nordisk Foundation Center for Basic Metabolic Research, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark.,Center for Diabetes Research, Gentofte Hospital, University of Copenhagen, Hellerup, Denmark.,Department of Clinical Medicine, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - C F Deacon
- Endocrinology Research Section, Department of Biomedical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark.,Section for Translational Metabolic Physiology, Novo Nordisk Foundation Center for Basic Metabolic Research, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - L B Svendsen
- Department of Surgical Gastroenterology, Rigshospitalet, University of Copenhagen, Copenhagen, Denmark
| | - J J Holst
- Endocrinology Research Section, Department of Biomedical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark.,Section for Translational Metabolic Physiology, Novo Nordisk Foundation Center for Basic Metabolic Research, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
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Huda MSB, Mani H, Durham BH, Dovey TM, Halford JCG, Aditya BS, Pinkney JH, Wilding JP, Hart IK. Plasma obestatin and autonomic function are altered in orexin-deficient narcolepsy, but ghrelin is unchanged. Endocrine 2013. [PMID: 23179778 DOI: 10.1007/s12020-012-9838-1] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
Narcolepsy-cataplexy is characterised by orexin deficiency, sleep disturbance, obesity and dysautonomia. Ghrelin and obestatin affect both energy intake and sleep. Our aim was to investigate ghrelin, obestatin and metabolic/autonomic function in narcolepsy-cataplexy. Eight narcolepsy-cataplexy patients (seven CSF orexin-deficient) and eight matched controls were studied. The subjects had a fixed energy meal with serial blood samples and measurement of heart rate variability (HRV). Fasting plasma obestatin was more than threefold higher in narcolepsy subjects (narcolepsy 89.6 ± 16 pg/ml vs. control 24.9 ± 3 pg/ml, p < 0.001). There was no change in HRV total power, but post-prandial low-frequency (LF) power and high-frequency (HF) power were lower in the narcolepsy group [area under the curve (AUC): HF power narcolepsy 1.4 × 10(5) ± 0.2 × 10(5) vs. control 3.3 × 10(5) ± 0.6 × 10(5 )ms(2)/h, p < 0.001]. On multiple regression analyses, the only significant predictor of plasma obestatin was HF power, which was inversely correlated with obestatin (β = -0.65 R (2) = 38 %, p = 0.009). Fasting and post-prandial plasma ghrelin were similar in both groups (narcolepsy 589.5 ± 88 pg/ml vs. control 686.9 ± 81 pg/ml, p = 0.5; post-prandial AUC-narcolepsy 161.3 ± 22 ng/ml/min vs. control 188.6 ± 62 ng/ml/min, p = 0.4). Only the narcolepsy group had significant suppression of plasma ghrelin after the meal (ANOVA, p = 0.004). In orexin-deficient narcolepsy, fasting plasma ghrelin is unaltered, and post-prandial suppression is preserved. Fasting plasma obestatin is increased and correlates with autonomic dysfunction. As obestatin affects NREM sleep, we suggest that increased plasma levels contribute to the disrupted sleep-state control in narcolepsy.
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Affiliation(s)
- M S B Huda
- University of Liverpool Diabetes and Endocrinology Research Group, Clinical Sciences Centre, University Hospital Aintree, Liverpool, L9 7AL, UK.
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Grönberg M, Tsolakis AV, Holmbäck U, Stridsberg M, Grimelius L, Janson ET. Ghrelin and obestatin in human neuroendocrine tumors: expression and effect on obestatin levels after food intake. Neuroendocrinology 2013; 97:291-9. [PMID: 23147274 DOI: 10.1159/000345366] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/12/2012] [Accepted: 10/24/2012] [Indexed: 11/19/2022]
Abstract
BACKGROUND Ghrelin and obestatin are derived from the same peptide hormone precursor and are mainly produced by the gastric mucosa. Ghrelin is involved in many biological processes, whereas the physiological function of obestatin needs further investigation. The aims of the present study were to establish the incidence of ghrelin- and obestatin-immunoreactive cells in a comprehensive panel of human neuroendocrine tumors (NETs) and to investigate if blood obestatin concentrations are influenced during a standardized meal stimulation test in healthy individuals and patients with NETs. MATERIALS AND METHODS The expression of ghrelin and obestatin was investigated in NETs (n = 149) and other endocrine-related disorders (n = 3) using immunohistochemistry with specific polyclonal antibodies. Coexpression of the peptides was evaluated by double immunofluorescence. Concentrations of obestatin in blood were measured during a meal test in 6 healthy individuals and 5 patients with pancreatic NETs. RESULTS Ghrelin and obestatin were expressed in 14/152 and 19/152 tumor tissues, respectively, mainly representing NETs of foregut origin and in pancreatic tissue from a nesidioblastosis patient. Double immunofluorescence staining showed colocalization of the peptides. During the meal test, obestatin levels in blood were unchanged in all patients but decreased significantly in the healthy individuals. CONCLUSION Only a minority of NETs express ghrelin and obestatin. However, analysis of patients with tumors originating from tissues that express the peptides in normal conditions could be of importance. The results from the meal test indicate that the hormone levels are affected by food intake in healthy individuals, whereas obestatin levels remained unchanged in pancreatic NET patients.
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Affiliation(s)
- Malin Grönberg
- Section of Endocrine Oncology, Department of Medical Sciences, Uppsala University, Uppsala, Sweden. malin.gronberg @ medsci.uu.se
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Satou M, Nakamura Y, Ando H, Sugimoto H. Understanding the functional significance of ghrelin processing and degradation. Peptides 2011; 32:2183-90. [PMID: 21763742 DOI: 10.1016/j.peptides.2011.06.029] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/02/2011] [Revised: 06/08/2011] [Accepted: 06/30/2011] [Indexed: 10/18/2022]
Abstract
Post-translational modification, cleavage and processing of circulating hormones are common themes in the control of hormone activities. Full-length ghrelin is a 28 amino acid protein that exists in several modified and processed forms, including addition of an acyl moiety at the third serine of the N-terminus. When modified with octanoic acid, the first five N-terminal residues of ghrelin can modulate a signaling pathway via the ghrelin receptor GHSR1a. Although modification via a lipid moiety is essential for binding and activation of GHSR1a by ghrelin, many reports suggest that a desacyl form of ghrelin exists and has synergistic, opposing and distinct properties as compared to the acyl form. Therefore, it is important to clarify the physiological relevance of ghrelin derivatives. Based on lines of evidence from various studies, we propose that a larger proportion of secreted ghrelin is present in the deacylated form and furthermore, that circulating acyl and desacyl forms of ghrelin may be hydrolyzed to form short peptide fragments. Here, we summarize the results of studies aimed at understanding ghrelin processing and its implications for physiological function, as well as our recent findings regarding enzymes in the blood capable of generating processed forms of ghrelin.
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Affiliation(s)
- Motoyasu Satou
- Departments of Biochemistry, Dokkyo Medical University School of Medicine, 880 Kitakobayashi, Mibu, Tochigi 321-0293, Japan
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Stengel A, Wang L, Taché Y. Stress-related alterations of acyl and desacyl ghrelin circulating levels: mechanisms and functional implications. Peptides 2011; 32:2208-17. [PMID: 21782868 PMCID: PMC3220774 DOI: 10.1016/j.peptides.2011.07.002] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/20/2011] [Revised: 07/04/2011] [Accepted: 07/05/2011] [Indexed: 12/11/2022]
Abstract
Ghrelin is the only known peripherally produced and centrally acting peptide hormone that stimulates food intake and digestive functions. Ghrelin circulates as acylated and desacylated forms and recently the acylating enzyme, ghrelin-O-acyltransferase (GOAT) and the de-acylating enzyme, thioesterase 1/lysophospholipase 1 have been identified adding new layers of complexity to the regulation of ghrelin. Stress is known to alter gastrointestinal motility and food intake and was recently shown to modify circulating ghrelin and GOAT levels with differential responses related to the type of stressors including a reduction induced by physical stressors (abdominal surgery and immunological/endotoxin injection, exercise) and elevation by metabolic (cold exposure, acute fasting and caloric restriction) and psychological stressors. However, the pathways underlying the alterations of ghrelin under these various stress conditions are still largely to be defined and may relate to stress-associated autonomic changes. There is evidence that alterations of circulating ghrelin may contribute to the neuroendocrine and behavioral responses along with sustaining the energetic requirement needed upon repeated exposure to stressors. A better understanding of these mechanisms will allow targeting components of ghrelin signaling that may improve food intake and gastric motility alterations induced by stress.
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Affiliation(s)
- Andreas Stengel
- CURE: Digestive Diseases Research Center, David Geffen School of Medicine, University of California Los Angeles and Veterans Affairs Greater Los Angeles Healthcare System, Los Angeles, CA 90073, United States.
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Nedvidkova J, Smitka K, Papezova H, Vondra K, Hill M, Hainer V. Acipimox during exercise points to an inhibitory feedback of GH on ghrelin secretion in bulimic and healthy women. ACTA ACUST UNITED AC 2011; 167:134-9. [PMID: 21237212 DOI: 10.1016/j.regpep.2010.12.012] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2010] [Revised: 11/17/2010] [Accepted: 12/29/2010] [Indexed: 11/30/2022]
Abstract
OBJECTIVE Ghrelin is predominantly produced by the stomach and the growth hormone (GH)-ghrelin feedback loop between the stomach and the pituitary gland has recently been suggested. The disruption of the gut-brain axis might be involved in bulimia nervosa (BN). METHODS We investigated responses of plasma GH, ghrelin, and neuropeptide Y (NPY) concentrations to exercise or to exercise after the administration of the antilipolytic drug Acipimox (Aci) in seven BN patients and seven healthy women (C). Aci was administered 1h before exercise (45 min, 2 W/kg of lean body mass/LBM/). Ghrelin, GH, NPY, free fatty acids (FFA) and glycerol plasma levels were measured during the test using commercial kits. RESULTS The exercise induced an increase in plasma GH, NPY and FFA in both groups and a decrease in plasma ghrelin levels only in BN patients. Exercise after Aci administration resulted in an increase in plasma GH, and a decrease in plasma ghrelin in both groups; NPY increased more in BN patients. Exercise-induced FFA increase was depressed after Aci. CONCLUSIONS We conclude that the Aci-induced suppression in plasma ghrelin levels during exercise in both groups suggests a negative feedback of GH on ghrelin secretion. Observed changes in plasma FFA levels were not related to changes in GH and ghrelin levels.
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Affiliation(s)
- Jara Nedvidkova
- Institute of Endocrinology, Narodni 8, 116 94 Prague 1, Czech Republic.
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