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Effect of Ghrelin on the Cardiovascular System. BIOLOGY 2022; 11:biology11081190. [PMID: 36009817 PMCID: PMC9405061 DOI: 10.3390/biology11081190] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/21/2022] [Revised: 08/03/2022] [Accepted: 08/05/2022] [Indexed: 11/19/2022]
Abstract
Simple Summary Ghrelin is an octanoylated peptide that was initially isolated from rat and human stomachs in the process of searching for an endogenous ligand to the orphan growth hormone secretagogue receptor (GHS-R), a G-protein-coupled receptor. Exogenous or endogenous ghrelin secreted from the stomach binds to GHS-R on gastric vagal nerve terminals, and the signals are transmitted to the central nervous system via the vagal afferent nerve to facilitate growth hormone (GH) secretion, feeding, sympathetic inhibition, parasympathetic activation, and anabolic effects. Ghrelin also binds directly to the pituitary GHS-R and stimulates GH secretion. Ghrelin has beneficial effects on the cardiovascular system, including cardioprotective effects such as anti-heart failure, anti-arrhythmic, and anti-inflammatory actions, and it enhances vascular activity via GHS-R-dependent stimulation of GH/IGF-1 (insulin-like growth factor-1) and modulation of the autonomic nervous system. The anti-heart failure effects of ghrelin could be useful as a new therapeutic strategy for chronic heart failure. Abstract Ghrelin, an n-octanoyl-modified 28-amino-acid-peptide, was first discovered in the human and rat stomach as an endogenous ligand for the growth hormone secretagogue receptor (GHS-R). Ghrelin-GHS-R1a signaling regulates feeding behavior and energy balance, promotes vascular activity and angiogenesis, improves arrhythmia and heart failure, and also protects against cardiovascular disease by suppressing cardiac remodeling after myocardial infarction. Ghrelin’s cardiovascular protective effects are mediated by the suppression of sympathetic activity; activation of parasympathetic activity; alleviation of vascular endothelial dysfunction; and regulation of inflammation, apoptosis, and autophagy. The physiological functions of ghrelin should be clarified to determine its pharmacological potential as a cardiovascular medication.
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Thomas AS, Sassi M, Angelini R, Morgan AH, Davies JS. Acylation, a Conductor of Ghrelin Function in Brain Health and Disease. Front Physiol 2022; 13:831641. [PMID: 35845996 PMCID: PMC9280358 DOI: 10.3389/fphys.2022.831641] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2021] [Accepted: 03/31/2022] [Indexed: 11/22/2022] Open
Abstract
Acyl-ghrelin (AG) is an orexigenic hormone that has a unique octanoyl modification on its third serine residue. It is often referred to as the “hunger hormone” due to its involvement in stimulating food intake and regulating energy homeostasis. The discovery of the enzyme ghrelin-O-acyltransferase (GOAT), which catalyses ghrelin acylation, provided further insights into the relevance of this lipidation process for the activation of the growth hormone secretagogue receptor (GHS-R) by acyl-ghrelin. Although acyl-ghrelin is predominantly linked with octanoic acid, a range of saturated fatty acids can also bind to ghrelin possibly leading to specific functions. Sources of ghrelin acylation include beta-oxidation of longer chain fatty acids, with contributions from fatty acid synthesis, the diet, and the microbiome. In addition, both acyl-ghrelin and unacyl-ghrelin (UAG) have feedback effects on lipid metabolism which in turn modulate their levels. Recently we showed that whilst acyl-ghrelin promotes adult hippocampal neurogenesis and enhances memory function, UAG inhibits these processes. As a result, we postulated that the circulating acyl-ghrelin:unacyl-ghrelin (AG:UAG) ratio might be an important regulator of neurogenesis and cognition. In this review, we discuss emerging evidence behind the relevance of ghrelin acylation in the context of brain physiology and pathology, as well as the current challenges of identifying the provenance of the acyl moiety.
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Kimura R, Kondo D, Takemi S, Fujishiro M, Tsukahara S, Sakai T, Sakata I. The role of central corticotrophin-releasing factor receptor signalling in plasma glucose maintenance through ghrelin secretion in calorie-restricted mice. J Neuroendocrinol 2021; 33:e12961. [PMID: 33675127 DOI: 10.1111/jne.12961] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/02/2020] [Revised: 02/11/2021] [Accepted: 02/12/2021] [Indexed: 11/27/2022]
Abstract
Under severe calorie restriction (CR), the ghrelin-growth hormone axis in mice is involved in the maintenance of plasma glucose levels. Ghrelin, a stomach-derived acylated peptide, is up-regulated by the sympathetic nerve in the negative energy status. Central corticotrophin-releasing factor receptor (CRF-R) signalling stimulates the sympathetic tone. The present study aimed to examine the effect of central CRF-R signalling on the maintenance of plasma glucose concentrations in severe calorie-restricted mice with the involvement of ghrelin. Intracerebroventricular injections of urocorin-1 and urocorin-2, which are natural ligands for CRF-R1 and CRF-R2, elevated plasma ghrelin concentrations and ghrelin elevation with an i.c.v. injection of urocorin-1 was cancelled by atenolol (β1 adrenergic receptor antagonist) administration. We then established a mice model of 60% CR and found that the administration of [d-Lys3]-GHRP-6 (a ghrelin receptor antagonist) in mice under 60% CR reduced the plasma glucose concentration more compared to the vehicle mice. Similarly, the atenolol injection in mice under 60% CR significantly reduced the plasma glucose concentration, which was rescued by the co-administration of ghrelin. An i.c.v. injection of the alpha helical CRH, a non-selective corticotrophin-releasing factor receptor antagonist, in mice under 60% CR significantly reduced the plasma glucose concentration, although the co-administration of α-helical CRH with ghrelin maintained plasma glucose levels. These results suggest that central CRF-R signalling is involved in the maintenance of plasma glucose levels in mice under severe CR via the sympathetic-ghrelin pathway.
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Affiliation(s)
- Risa Kimura
- Area of Regulatory Biology, Division of Life Science, Graduate School of Science and Engineering, Saitama University, Saitama, Japan
| | - Daisuke Kondo
- Area of Regulatory Biology, Division of Life Science, Graduate School of Science and Engineering, Saitama University, Saitama, Japan
| | - Shota Takemi
- Area of Regulatory Biology, Division of Life Science, Graduate School of Science and Engineering, Saitama University, Saitama, Japan
| | - Miyuki Fujishiro
- Area of Regulatory Biology, Division of Life Science, Graduate School of Science and Engineering, Saitama University, Saitama, Japan
- Nikkol Group Cosmos Technical Center Co., Ltd, Tokyo, Japan
| | - Shinji Tsukahara
- Area of Regulatory Biology, Division of Life Science, Graduate School of Science and Engineering, Saitama University, Saitama, Japan
- Division of Strategy Research, Graduate School of Science and Engineering, Area of Life-NanoBio, Saitama University, Saitama, Japan
| | | | - Ichiro Sakata
- Area of Regulatory Biology, Division of Life Science, Graduate School of Science and Engineering, Saitama University, Saitama, Japan
- Division of Strategy Research, Graduate School of Science and Engineering, Area of Life-NanoBio, Saitama University, Saitama, Japan
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Abstract
Eating food is one of the most complicated behaviours in mammals, especially humans. The primary function of ghrelin is regulation of the appetite level and its stimulation. It is also responsible for the body's energy balance and glucose homeostasis. Ghrelin has been shown to affect many brain structures, which confirms the presence of ghrelin receptors in the brain. Studies are also conducted to assess the possible role of ghrelin in anxiety states and in memory disorders and motor dysfunctions. Ghrelin has been found in saliva and salivary glands, teeth and gums, and in the taste buds of the tongue epithelium; it is also secreted by mucosal cells and gingival fibroblasts. The presence of ghrelin in developmental enamel, especially in odontoblasts and ameloblasts, may suggest its regulatory role in the development of teeth. Patients with chronic periodontitis have significantly higher concentrations of ghrelin in the peripheral blood serum, as compared to the control group. Ghrelin plays a special role in the proliferation of cancer cells and in the development of neoplastic metastases. The abundant presence of ghrelin receptors in cancer cells is considered an important target in the treatment of neoplasms. Ghrelin is a hormone whose multidirectional mechanism of action has not yet been fully understood. However, its ubiquitous occurrence in the human body and its very diverse participation in metabolic processes may prove to be a significant obstacle in achieving the expected clinical effect of ghrelin as an effective drug in selected disease units.
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Tzanavari T, Tasoulas J, Vakaki C, Mihailidou C, Tsourouflis G, Theocharis S. The Role of Adipokines in the Establishment and Progression of Head and Neck Neoplasms. Curr Med Chem 2018; 26:4726-4748. [PMID: 30009699 DOI: 10.2174/0929867325666180713154505] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2017] [Revised: 03/13/2018] [Accepted: 07/06/2018] [Indexed: 12/15/2022]
Abstract
Adipokines constitute a family of protein factors secreted by white adipose tissue (WAT), that regulate the functions of WAT and other sites. Leptin, adiponectin and resistin, are the main adipokines present in serum and saliva, targeting several tissues and organs, including vessels, muscles, liver and pancreas. Besides body mass regulation, adipokines affect glucose homeostasis, inflammation, angiogenesis, cell proliferation and apoptosis, and other crucial cell procedures. Their involvement in tumor formation and growth is well established and deregulation of adipokine and adipokine receptors' expression is observed in several malignancies including those located in the head and neck region. Intracellular effects of adipokines are mediated by a plethora of receptors that activate several signaling cascades including Janus kinase/ Signal transducer and activator of transcription (JAK/ STAT pathway), Phospatidylinositol kinase (PI3/ Akt/ mTOR) and Peroxisome proliferator-activated receptor (PPAR). The present review summarizes the current knowledge on the role of adipokines family members in carcinogenesis of the head and neck region. The diagnostic and prognostic significance of adipokines and their potential role as serum and saliva biomarkers are also discussed.
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Affiliation(s)
- Theodora Tzanavari
- First Department of Pathology, Medical School, National and Kapodistrian University of Athens, Athens, 11527, Greece
| | - Jason Tasoulas
- First Department of Pathology, Medical School, National and Kapodistrian University of Athens, Athens, 11527, Greece
| | - Chrysoula Vakaki
- First Department of Pathology, Medical School, National and Kapodistrian University of Athens, Athens, 11527, Greece
| | - Chrysovalantou Mihailidou
- First Department of Pathology, Medical School, National and Kapodistrian University of Athens, Athens, 11527, Greece
| | - Gerasimos Tsourouflis
- Second Department of Propaedeutic Surgery, Medical School, National and Kapodistrian, University of Athens, Athens, 11527, Greece
| | - Stamatios Theocharis
- First Department of Pathology, Medical School, National and Kapodistrian University of Athens, Athens, 11527, Greece
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Zhu J, Yao J, Huang R, Wang Y, Jia M, Huang Y. Ghrelin promotes human non-small cell lung cancer A549 cell proliferation through PI3K/Akt/mTOR/P70S6K and ERK signaling pathways. Biochem Biophys Res Commun 2018. [PMID: 29524402 DOI: 10.1016/j.bbrc.2018.03.031] [Citation(s) in RCA: 25] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Ghrelin is a gastric acyl-peptide that plays an important role in cell proliferation. In the present study, we explored the role of ghrelin in A549 cell proliferation and the possible molecular mechanisms. We found that ghrelin promotes A549 cell proliferation, knockdown of the growth hormone secretagogue receptor (GHSR) attenuated A549 cell proliferation caused by ghrelin. Ghrelin induced the rapid phosphorylation of phosphatidylinositol 3-kinase (PI3K), Akt, ERK, mammalian target of rapamycin (mTOR) and P70S6K. PI3K inhibitor (LY 294002), ERK inhibitor (PD98059) and mTOR inhibitor (Rapamycin) inhibited ghrelin-induced A549 cell proliferation. Moreover, GHSR siRNA inhibited phosphorylation of PI3K, Akt, ERK, mTOR and P70S6K induced by ghrelin. Akt and mTOR/P70S6K phosphorylation was inhibited by LY 294002 but not by PD98059. These results indicate that ghrelin promotes A549 cell proliferation via GHSR-dependent PI3K/Akt/mTOR/P70S6K and ERK signaling pathways.
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Affiliation(s)
- Jianhua Zhu
- Laboratory of Clinical Immunology, Wuhan No. 1 Hospital, Tongji Medical College, Huazhong University of Science and Technology (HUST), Wuhan, Hubei, PR China.
| | - Jianfeng Yao
- Quanzhou Maternal and Child Health Care Hospital, Quanzhou, Fujian, PR China
| | - Rongfu Huang
- The Second Affiliated Hospital, Fujian Medical University, Quanzhou, Fujian, PR China
| | - Yueqin Wang
- Laboratory of Clinical Immunology, Wuhan No. 1 Hospital, Tongji Medical College, Huazhong University of Science and Technology (HUST), Wuhan, Hubei, PR China
| | - Min Jia
- Laboratory of Clinical Immunology, Wuhan No. 1 Hospital, Tongji Medical College, Huazhong University of Science and Technology (HUST), Wuhan, Hubei, PR China
| | - Yan Huang
- Laboratory of Clinical Immunology, Wuhan No. 1 Hospital, Tongji Medical College, Huazhong University of Science and Technology (HUST), Wuhan, Hubei, PR China
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Molecular Ghrelin System in the Pancreatic Acinar Cells: The Role of the Polypeptide, Caerulein and Sensory Nerves. Int J Mol Sci 2017; 18:ijms18050929. [PMID: 28468316 PMCID: PMC5454842 DOI: 10.3390/ijms18050929] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2017] [Revised: 04/09/2017] [Accepted: 04/19/2017] [Indexed: 12/25/2022] Open
Abstract
Ghrelin (GHRL) is an endogenous ligand for the growth hormone secretagogue receptor (GHS-R). Experimental studies showed that GHRL protects the stomach and pancreas against acute damage, but the effect of GHRL on pancreatic acinar cells was still undetermined. Aim: To investigate the effect of GHRL and caerulein on the functional ghrelin system in pancreatic acinar cells taking into account the role of sensory nerves (SN). Methods: Experiments were carried out on isolated pancreatic acinar cells and AR42J cells. Before acinar cells isolation, GHRL was administered intraperitoneally at a dose of 50 µg/kg to rats with intact SN or with capsaicin deactivation of SN (CDSN). After isolation, pancreatic acinar cells were incubated in caerulein-free or caerulein containing solution. AR42J cells were incubated under basal conditions and stimulated with caerulein, GHRL or a combination of the above. Results: Incubation of isolated acinar cells with caerulein inhibited GHS-R and GHRL expression at the level of mRNA and protein in those cells. Either in rats with intact SN or with CDSN, administration of GHRL before isolation of acinar cells increased expression of GHRL and GHS-R in those cells and reversed the caerulein-induced reduction in expression of those parameters. Similar upregulation of GHS-R and GHRL was observed after administration of GHRL in AR42J cells. Conclusions: GHRL stimulates its own expression and expression of its receptor in isolated pancreatic acinar cells and AR42J cells on the positive feedback pathway. This mechanism seems to participate in the pancreatoprotective effect of GHRL in the course of acute pancreatitis.
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Zhu CZ, Liu D, Kang WM, Yu JC, Ma ZQ, Ye X, Li K. Ghrelin and gastrointestinal stromal tumors. World J Gastroenterol 2017; 23:1758-1763. [PMID: 28348480 PMCID: PMC5352915 DOI: 10.3748/wjg.v23.i10.1758] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/27/2016] [Revised: 11/28/2016] [Accepted: 01/11/2017] [Indexed: 02/06/2023] Open
Abstract
Ghrelin, as a kind of multifunctional protein polypeptide, is mainly produced in the fundus of the stomach and can promote occurrence and development of many tumors, including gastrointestinal tumors, which has been proved by the relevant researches. Most gastrointestinal stromal tumors (GISTs, about 80%), as the most common mesenchymal tumor, also develop in the fundus. Scientific research has confirmed that ghrelin, its receptors and mRNA respectively can be found in GISTs, which demonstrated the existence of a ghrelin autocrine/paracrine loop in GIST tissues. However, no reports to date have specified the mechanism whether ghrelin can promote the occurrence and development of GISTs. Studies of pulmonary artery endothelial cells in a low-oxygen environment and cardiac muscle cells in an ischemic environment have shown that ghrelin can activate the phosphatidylinositol 3-kinase/AKT/mammalian target of rapamycin (PI3K/AKT/mTOR) signaling pathway. Moreover, some studies of GISTs have confirmed that activation of the PI3K/AKT/mTOR pathway can indeed promote the growth and progression of GISTs. Whether ghrelin is involved in the development or progression of GISTs through certain pathways remains unknown. Can we find a new target for the treatment of GISTs? This review explores and summaries the relationship among ghrelin, the PI3K/AKT/mTOR pathway and the development of GISTs.
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Ghrelin and cancer progression. Biochim Biophys Acta Rev Cancer 2017; 1868:51-57. [PMID: 28238732 DOI: 10.1016/j.bbcan.2017.02.002] [Citation(s) in RCA: 50] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2016] [Revised: 01/27/2017] [Accepted: 02/18/2017] [Indexed: 12/22/2022]
Abstract
Ghrelin is a small peptide with 28 amino acids, and has been characterized as the ligand of the growth hormone secretagogue receptor (GHSR). In addition to its original function in stimulating pituitary growth hormone release, ghrelin is multifunctional and plays a role in the regulation of energy balance, gastric acid release, appetite, insulin secretion, gastric motility and the turnover of gastric and intestinal mucosa. The discovery of ghrelin and GHSR expression beyond normal tissues suggests its role other than physiological function. Emerging evidences have revealed ghrelin's function in regulating several processes related to cancer progression, especially in metastasis and proliferation. We further show the relative GHRL and GHSR expression in pan-cancers from The Cancer Genome Atlas (TCGA), suggesting the potential pathological role of the axis in cancers. This review focuses on ghrelin's biological function in cancer progression, and reveals its clinical significance especially the impact on cancer patient outcome.
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Eslami Z, Ghassempour A, Aboul-Enein HY. Recent developments in liquid chromatography-mass spectrometry analyses of ghrelin and related peptides. Biomed Chromatogr 2016; 31. [DOI: 10.1002/bmc.3796] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2016] [Revised: 07/18/2016] [Accepted: 07/21/2016] [Indexed: 12/12/2022]
Affiliation(s)
- Zahra Eslami
- Faculty of Phytochemistry, Medicinal Plants and Drug Research Institute; Shahid Beheshti University, Evin; Tehran Iran
| | - Alireza Ghassempour
- Faculty of Phytochemistry, Medicinal Plants and Drug Research Institute; Shahid Beheshti University, Evin; Tehran Iran
| | - Hassan Y. Aboul-Enein
- Pharmaceutical and Medicinal Chemistry Department; Pharmaceutical and Drug Industries Research Division; National Research Center, Dokki; Giza 12622 Egypt
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Jung CH. Response: Serum Concentrations of Ghrelin and Leptin according to Thyroid Hormone Condition, and Their Correlations with Insulin Resistance (Endocrinol Metab 2015;30:318-25, Kyu-Jin Kim et al.). Endocrinol Metab (Seoul) 2015; 30:633-4. [PMID: 26790388 PMCID: PMC4722423 DOI: 10.3803/enm.2015.30.4.633] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/03/2022] Open
Affiliation(s)
- Chan Hee Jung
- Division of Endocrinology and Metabolism, Department of Internal Medicine, Soonchunhyang University Bucheon Hospital, Soonchunhyang University College of Medicine, Bucheon, Korea.
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Radiometric assay of ghrelin hydrolase activity and 3H-ghrelin distribution into mouse tissues. Biochem Pharmacol 2015; 98:732-9. [PMID: 26514871 DOI: 10.1016/j.bcp.2015.10.016] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2015] [Accepted: 10/21/2015] [Indexed: 11/24/2022]
Abstract
A high-throughput radiometric assay was developed to characterize enzymatic hydrolysis of ghrelin and to track the peptide's fate in vivo. The assay is based on solvent partitioning of [(3)H]-octanoic acid liberated from [(3)H]-octanoyl ghrelin during enzymatic hydrolysis. This simple and cost-effective method facilitates kinetic analysis of ghrelin hydrolase activity of native and mutated butyrylcholinesterases or carboxylesterases from multiple species. In addition, the assay's high sensitivity facilitates ready evaluation of ghrelin's pharmacokinetics and tissue distribution in mice after i.v. bolus administration of radiolabeled peptide.
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Gilloteaux J, Pardhan D. Crinophagy in Thyroid Follicular and Parafollicular Cells of Male Obese Zucker Rat. Ultrastruct Pathol 2015; 39:255-69. [PMID: 25867801 DOI: 10.3109/01913123.2015.1014611] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
Comparison between lean (Fa/?) and obese (fa/fa) young adult male Zucker rat thyroids reveals that obese rats display larger clusters of parafollicular cells than the lean ones with a lesser blood supply. Fa/? thyroid typically shows single or "twin" C cells in follicles; fa/fa parafollicular cells appear with three functional aspects. Crinophagy is found in the fa/fa C cells amassing numerous aberrant calcitonin-containing vesicles among which lysosomes build these autophagic bodies by capturing vesicle contents, other organelles and, fusing with each other, increase their size. Other C cells contain many secretory vesicles but show few or no crinophagic structures. Another parafollicular cell type is revealed with scant organelles and highly contrasted secretory vesicles, different from calcitonin. Hypercalcemia of fa/fa rats corresponds to increased C cells population with accrued calcitonin production but a low calcitonin plasma level - verified by others - is likely caused by crinophagy of the altered vesicles. In addition, the T thyrocytes of fa/fa rats exhibit crinophagy bodies; this can confirm their hypothyroidism. Possibly, the known leptin mutation along with other unknown paracrine secretions alter both T and C thyrocytes' functions of the fa/fa rats, allowing high intracellular calcium and lower pH favoring autophagocytosis. Other longitudinal, interdisciplinary studies should further clarify the complex paracrine interactions existing between these endocrine structures because this animal model could be useful to understand human defects, such as the metabolic syndrome that involves obesity, cardiovascular, renal, hepatic, non-insulin dependent diabetes mellitus (NIDDM), hypothyroidism defects, as well as the etiology of thyroid medullary tumors.
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Affiliation(s)
- Jacques Gilloteaux
- Department of Anatomical Sciences, St George's University School of Medicine, KB Taylor Global Scholar's Programme at Northumbria University , Newcastle upon Tyne , UK
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Iwakura H, Kangawa K, Nakao K. The regulation of circulating ghrelin - with recent updates from cell-based assays. Endocr J 2015; 62:107-22. [PMID: 25273611 DOI: 10.1507/endocrj.ej14-0419] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
Abstract
Ghrelin is a stomach-derived orexigenic hormone with a wide range of physiological functions. Elucidation of the regulation of the circulating ghrelin level would lead to a better understanding of appetite control in body energy homeostasis. Earlier studies revealed that circulating ghrelin levels are under the control of both acute and chronic energy status: at the acute scale, ghrelin levels are increased by fasting and decreased by feeding, whereas at the chronic scale, they are high in obese subjects and low in lean subjects. Subsequent studies revealed that nutrients, hormones, or neural activities can influence circulating ghrelin levels in vivo. Recently developed in vitro assay systems for ghrelin secretion can assess whether and how individual factors affect ghrelin secretion from cells. In this review, on the basis of numerous human, animal, and cell-based studies, we summarize current knowledge on the regulation of circulating ghrelin levels and enumerate the factors that influence ghrelin levels.
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Affiliation(s)
- Hiroshi Iwakura
- Medical Innovation Center, Kyoto University Graduate School of Medicine, Kyoto 606-8507, Japan
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Shiimura Y, Ohgusu H, Sato T, Kojima M. Regulation of the Human Ghrelin Promoter Activity by Transcription Factors, NF-κB and Nkx2.2. Int J Endocrinol 2015; 2015:580908. [PMID: 25699080 PMCID: PMC4324914 DOI: 10.1155/2015/580908] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/20/2014] [Accepted: 12/24/2014] [Indexed: 11/24/2022] Open
Abstract
To examine the gene expression of ghrelin, a growth hormone releasing and appetite stimulating hormone from stomach, we constructed human ghrelin promoter-reporter vectors and analyzed the promoter activity. The ghrelin promoter activity was high when cultured cells that express ghrelin mRNA endogenously like TT or ECC10 cells were used, indicating that these cells contain factors necessary for full expression of the human ghrelin gene. The human ghrelin promoter contains both positive and negative regulatory regions. A transient decrease of the promoter activity was found when the reporter vector with the -1600 fragment of the human ghrelin promoter was transfected into cultured cells. We then examined the effect of several transcription factors on the ghrelin promoter activity and found that NF-κB suppressed and that Nkx2.2, a homeodomain-containing transcription factor that is important for ghrelin cell development in pancreas, activates the promoter activity. These transcription factors may be possible targets for the control of ghrelin gene expression.
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Affiliation(s)
- Yuki Shiimura
- Molecular Genetics, Institute of Life Science, Kurume University, Kurume, Fukuoka 839-0864, Japan
| | - Hideko Ohgusu
- Molecular Genetics, Institute of Life Science, Kurume University, Kurume, Fukuoka 839-0864, Japan
| | - Takahiro Sato
- Molecular Genetics, Institute of Life Science, Kurume University, Kurume, Fukuoka 839-0864, Japan
| | - Masayasu Kojima
- Molecular Genetics, Institute of Life Science, Kurume University, Kurume, Fukuoka 839-0864, Japan
- *Masayasu Kojima:
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Physiological roles of ghrelin on obesity. Obes Res Clin Pract 2014; 8:e405-13. [DOI: 10.1016/j.orcp.2013.10.002] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/04/2013] [Revised: 08/28/2013] [Accepted: 10/08/2013] [Indexed: 02/06/2023]
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Mao Y, Tokudome T, Kishimoto I. Ghrelin as a treatment for cardiovascular diseases. Hypertension 2014; 64:450-4. [PMID: 24958496 DOI: 10.1161/hypertensionaha.114.03726] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
Affiliation(s)
- Yuanjie Mao
- From the Department of Biochemistry (Y.M., T.T.) and Department of Endocrinology and Metabolism (I.K.), National Cerebral and Cardiovascular Center, Osaka, Japan
| | - Takeshi Tokudome
- From the Department of Biochemistry (Y.M., T.T.) and Department of Endocrinology and Metabolism (I.K.), National Cerebral and Cardiovascular Center, Osaka, Japan
| | - Ichiro Kishimoto
- From the Department of Biochemistry (Y.M., T.T.) and Department of Endocrinology and Metabolism (I.K.), National Cerebral and Cardiovascular Center, Osaka, Japan.
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Ruchala M, Gurgul E, Stangierski A, Wrotkowska E, Moczko J. Individual plasma ghrelin changes in the same patients in hyperthyroid, hypothyroid and euthyroid state. Peptides 2014; 51:31-4. [PMID: 24184592 DOI: 10.1016/j.peptides.2013.10.018] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/02/2013] [Revised: 10/21/2013] [Accepted: 10/21/2013] [Indexed: 12/17/2022]
Abstract
Ghrelin is a multifunctional peptide of widespread expression. Since it has been shown to influence energy homeostatis, its potential role in thyroid dysfunction may have clinical significance. In this study, plasma ghrelin changes have been analyzed in the same patients in three different thyroid states for the first time. The study group consisted of 16 patients who had been diagnosed with hyperthyroidism, were treated with radioiodine, developed hypothyroidism after treatment, and finally became euthyroid on l-thyroxine substitution. In the initial state of hyperthyroidism plasma ghrelin levels correlated negatively with fT3 and fT4. In hypothyroidism ghrelin concentration increased significantly (p<0.05). Although the mean value of plasma ghrelin tended to decrease in the euthyroid state, the individual difference between hypothyroidism and euthyroidism was not significant. Plasma ghrelin in euthyroidism was still significantly higher than in hyperthyroidism (p<0.05), and correlated positively with ghrelin levels in hyperthyroidism and hypothyroidism. In our opinion, plasma ghrelin fluctuations may reflect metabolic changes in patients with thyroid dysfunction. Moreover, it cannot be excluded that in thyroid disorders ghrelin acts as a compensatory factor, helping to balance metabolic disturbances.
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Affiliation(s)
- Marek Ruchala
- Department of Endocrinology, Metabolism and Internal Medicine, Poznan University of Medical Sciences, 49 Przybyszewskiego St., 60-355 Poznan, Poland
| | - Edyta Gurgul
- Department of Endocrinology, Metabolism and Internal Medicine, Poznan University of Medical Sciences, 49 Przybyszewskiego St., 60-355 Poznan, Poland.
| | - Adam Stangierski
- Department of Endocrinology, Metabolism and Internal Medicine, Poznan University of Medical Sciences, 49 Przybyszewskiego St., 60-355 Poznan, Poland
| | - Elzbieta Wrotkowska
- Department of Endocrinology, Metabolism and Internal Medicine, Poznan University of Medical Sciences, 49 Przybyszewskiego St., 60-355 Poznan, Poland
| | - Jerzy Moczko
- Department of Computer Science and Statistics, Poznan University of Medical Sciences, 79 Dabrowskiego St., 60-529 Poznan, Poland
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Utrilla JC, Morillo-Bernal J, Gordillo-Martínez F, García-Marín R, Herrera JL, Fernández-Santos JM, Díaz-Parrado E, Garnacho C, De Miguel M, Martín-Lacave I. Expression of hypothalamic regulatory peptides in thyroid C cells of different mammals. Gen Comp Endocrinol 2013; 187:6-14. [PMID: 23524276 DOI: 10.1016/j.ygcen.2013.02.048] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/18/2012] [Revised: 02/19/2013] [Accepted: 02/20/2013] [Indexed: 10/27/2022]
Abstract
Besides intervening in calcium homeostasis by means of calcitonin, C cells are also implicated in the synthesis of an increasing number of regulatory peptides that could exert a paracrine regulation on the neighbouring follicular cells. Among the latest peptides reported in C cells, there are several characteristic hypothalamic peptides, such as TRH, CART, and ghrelin, which are mainly involved in the regulation of the metabolism at hypothalamic-pituitary-thyroid axis. The main aim of the present work has been to study the synthesis of the referred hypothalamic peptides by normal and neoplastic C cells of different mammals as well as in C-cell lines of both rat (CA-77, 6-23) and human (TT) origins in order to elucidate whether this is a fact in this kind of vertebrates. With that objective, we have applied the immunoperoxidase technique to analyze the presence of TRH, CART, ghrelin, and somatostatin in thyroid tissues of different species, and immunofluorescence to study those same peptides in C-cell cultures. Furthermore, we have investigated their expression at mRNA level by RT-PCR analysis. Our results demonstrate immunocolocalization of CART, ghrelin, somatostatin and TRH with calcitonin in normal C cells of different mammals, as well as in rat and human neoplastic C cells. We also confirm the expression of those peptides in rat and human C-cell lines by RT-PCR. Consequently, we can conclude that the synthesis of those peptides by C cells is a general event characteristic of the thyroid gland in mammals.
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Affiliation(s)
- José C Utrilla
- Dpt. Cytology and Histology, School of Medicine, University of Seville, Spain
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20
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Tvarijonaviciute A, Martínez-Subiela S, Ceron JJ. Influence of different storage conditions and anticoagulants on the measurement of total and acylated ghrelin in dogs: a preliminary study. Vet Rec 2013; 172:289. [PMID: 23322544 DOI: 10.1136/vr.100961] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
The objective of this study was to evaluate and compare different sample treatments and storage conditions in order to determine optimal conditions for total and acylated canine ghrelin measurement using ELISA assays. Under the conditions assessed in this study, total ghrelin concentration was stable when stored at room temperature or under cooled conditions (4°C) for approximately six hours regardless of the type of anticoagulant used. When samples were stored at under -20°C, three freeze/thaw cycles during storage did not alter total ghrelin concentration if serum or plasma treated with EDTA or with EDTA-aprotinin is used. When samples were stored at under -80°C, no significant differences were observed after three freeze/thaw cycles in total ghrelin concentrations in serum or plasma treated with EDTA, EDTA-aprotinin or heparin. While acylated ghrelin showed to be very instable, its analysis should be performed within an hour of sample collection or stored at -80°C preferably in serum in order to acquire accurate data. Addition of HCl did not improve total or acylated ghrelin stability. Furthermore, acidification of plasma samples decreased the stability of total ghrelin and impeded determination of acylated ghrelin with the ELISA used in this study.
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Affiliation(s)
- A Tvarijonaviciute
- Department of Animal Medicine and Surgery, Faculty of Veterinary Medicine, Regional Campus of International Excellence Campus Mare Nostrum, University of Murcia, Espinardo, Murcia 30100, Spain
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21
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Chopin LK, Seim I, Walpole CM, Herington AC. The ghrelin axis--does it have an appetite for cancer progression? Endocr Rev 2012; 33:849-91. [PMID: 22826465 DOI: 10.1210/er.2011-1007] [Citation(s) in RCA: 61] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Ghrelin, the endogenous ligand for the GH secretagogue receptor (GHSR), is a peptide hormone with diverse physiological roles. Ghrelin regulates GH release, appetite and feeding, gut motility, and energy balance and also has roles in the cardiovascular, immune, and reproductive systems. Ghrelin and the GHSR are expressed in a wide range of normal and tumor tissues, and a fluorescein-labeled, truncated form of ghrelin is showing promise as a biomarker for prostate cancer. Plasma ghrelin levels are generally inversely related to body mass index and are unlikely to be useful as a biomarker for cancer, but may be useful as a marker for cancer cachexia. Some single nucleotide polymorphisms in the ghrelin and GHSR genes have shown associations with cancer risk; however, larger studies are required. Ghrelin regulates processes associated with cancer, including cell proliferation, apoptosis, cell migration, cell invasion, inflammation, and angiogenesis; however, the role of ghrelin in cancer is currently unclear. Ghrelin has predominantly antiinflammatory effects and may play a role in protecting against cancer-related inflammation. Ghrelin and its analogs show promise as treatments for cancer-related cachexia. Further studies using in vivo models are required to determine whether ghrelin has a role in cancer progression.
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Affiliation(s)
- Lisa K Chopin
- Ghrelin Research Group, Institute of Health and Biomedical Innovation, Queensland University of Technology and Australian Prostate Cancer Research Centre-Queensland, Brisbane, Queensland 4001, Australia.
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23
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Morillo-Bernal J, Fernández-Santos JM, De Miguel M, García-Marín R, Gordillo-Martínez F, Díaz-Parrado E, Utrilla JC, Martín-Lacave I. Ghrelin potentiates TSH-induced expression of the thyroid tissue-specific genes thyroglobulin, thyroperoxidase and sodium-iodine symporter, in rat PC-Cl3 Cells. Peptides 2011; 32:2333-9. [PMID: 21945915 DOI: 10.1016/j.peptides.2011.09.013] [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: 07/22/2011] [Revised: 09/08/2011] [Accepted: 09/13/2011] [Indexed: 01/08/2023]
Abstract
Ghrelin is a 28-amino-acid peptide that stimulates pituitary growth-hormone secretion and modulates food-intake and energy metabolism in mammals. It is mainly secreted by the stomach, but it is also expressed in many other tissues such as cartilage or the thyroid gland. In the present study we have analyzed by RT-PCR and using immunohistochemistry and immunofluorescence the expression and tissue distribution of ghrelin and its functional receptor (GHS-R type 1α) in thyroid cell-lines and in normal and pathological rat thyroid tissue. Additionally, by measuring the incorporation of BrdU, we have investigated if, as previously noted for FRTL-5 cells, ghrelin enhances the proliferation rate in the PC-Cl3 rat-thyrocyte cell-line. Finally, we have determined the stimulatory effect of ghrelin on TSH-induced expression of the tissue-specific key genes involved in the synthesis of thyroid hormone: thyroglobulin, thyroperoxidase and sodium-iodine symporter. Our data provide direct evidence that C-cell secreted ghrelin may be involved in the paracrine regulation of the thyroid follicular cell function.
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Affiliation(s)
- J Morillo-Bernal
- Department of Cytology and Histology, School of Medicine, University of Seville, 41009 Sevilla, Spain
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24
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Endocrine factors in the hypothalamic regulation of food intake in females: a review of the physiological roles and interactions of ghrelin, leptin, thyroid hormones, oestrogen and insulin. Nutr Res Rev 2011; 24:132-54. [DOI: 10.1017/s0954422411000035] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
Controlling energy homeostasis involves modulating the desire to eat and regulating energy expenditure. The controlling machinery includes a complex interplay of hormones secreted at various peripheral endocrine endpoints, such as the gastrointestinal tract, the adipose tissue, thyroid gland and thyroid hormone-exporting organs, the ovary and the pancreas, and, last but not least, the brain itself. The peripheral hormones that are the focus of the present review (ghrelin, leptin, thyroid hormones, oestrogen and insulin) play integrated regulatory roles in and provide feedback information on the nutritional and energetic status of the body. As peripheral signals, these hormones modulate central pathways in the brain, including the hypothalamus, to influence food intake, energy expenditure and to maintain energy homeostasis. Since the growth of the literature on the role of various hormones in the regulation of energy homeostasis shows a remarkable and dynamic expansion, it is now becoming increasingly difficult to understand the individual and interactive roles of hormonal mechanisms in their true complexity. Therefore, our goal is to review, in the context of general physiology, the roles of the five best-known peripheral trophic hormones (ghrelin, leptin, thyroid hormones, oestrogen and insulin, respectively) and discuss their interactions in the hypothalamic regulation of food intake.
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Noguchi H, Masaki T, Kakuma T, Nakazato M, Yoshimatsu H. Ghrelin in small intestine, its contribution to regulation of food intake and body weight in cross-intestinal parabiotic rats. Endocr J 2011; 58:625-32. [PMID: 21617329 DOI: 10.1507/endocrj.k11e-085] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
Abstract
Ghrelin has been shown to be associated with feeding behavior in humans and rodents. It has been suggested that ghrelin may play a role behind the effect of bariatric surgery. Inbred rats were made into parabiotic pairs so that they shared a single abdominal cavity. A further operation is performed later in which the small intestines are transected and re-connected so that one rat continually lost nutrition to its partner. Changes in food intake and body weight were recorded. Seven weeks later, content of ghrelin in the plasma, stomach and upper intestines were measured in the paired rats. Rats which lost nutrients to its counterpart (Loss rats) ingested significantly more food than sham control rats (p<0.001). Rats which gained nutrient (Gain rats) ingested less than controls (p<0.001). There was no significant difference in body weight, blood glucose, insulin, free fatty acids and triglycerides between the paired rats. There was significantly higher levels of ghrelin in the plasma (p<0.008) and the intestine of the Loss rats (p<0.02). There were no difference in ghrelin in the stomach between parabiotic rats and sham operated controls. The ghrelin content of the plasma and intestines were significantly higher in the Loss rats, which ate more, and normal in the Gain rats, which ate less than controls. Because no remarkable changes in the ghrelin content were observed in the stomach, difference in the quality of the chime may affect the local synthesis and release of ghrelin.
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Affiliation(s)
- Hitoshi Noguchi
- Noguchi Thyroid Clinic and Hospital Foundation, Beppu, Japan.
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26
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Iwakura H, Li Y, Ariyasu H, Hosoda H, Kanamoto N, Bando M, Yamada G, Hosoda K, Nakao K, Kangawa K, Akamizu T. Establishment of a novel ghrelin-producing cell line. Endocrinology 2010; 151:2940-5. [PMID: 20375182 DOI: 10.1210/en.2010-0090] [Citation(s) in RCA: 53] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
To establish a tool to study ghrelin production and secretion in vitro, we developed a novel ghrelin-producing cell line, MGN3-1 (mouse ghrelinoma 3-1) cells from a gastric ghrelin-producing cell tumor derived from ghrelin-promoter Simian virus 40-T-antigen transgenic mice. MGN3-1 cells preserve three essential characteristics required for the in vitro tool for ghrelin research. First, MGN3-1 cells produce a substantial amount of ghrelin at levels approximately 5000 times higher than that observed in TT cells. Second, MGN3-1 cell expressed two key enzymes for acyl modification and maturation of ghrelin, namely ghrelin O-acyltransferase for acylation and prohormone convertase 1/3 for maturation and the physiological acyl modification and maturation of ghrelin were confirmed. Third, MGN3-1 cells retain physiological regulation of ghrelin secretion, at least in regard to the suppression by somatostatin and insulin, which is well established in in vivo studies. Thus, MGN3-1 cells are the first cell line derived from a gastric ghrelin-producing cell preserving secretion of substantial amounts of ghrelin under physiological regulation. This cell line will be a useful tool for both studying the production and secretion of ghrelin and screening of ghrelin-modulating drugs.
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27
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Takahashi T, Ida T, Sato T, Nakashima Y, Nakamura Y, Tsuji A, Kojima M. Production of n-octanoyl-modified Ghrelin in Cultured Cells Requires Prohormone Processing Protease and Ghrelin O-acyltransferase, as well as n-octanoic Acid. ACTA ACUST UNITED AC 2009; 146:675-82. [DOI: 10.1093/jb/mvp112] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022]
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28
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Karaoglu A, Aydin S, Dagli AF, Cummings DE, Ozercan İH, Canatan H, Ozkan Y. Expression of obestatin and ghrelin in papillary thyroid carcinoma. Mol Cell Biochem 2008; 323:113-8. [DOI: 10.1007/s11010-008-9969-0] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2008] [Accepted: 11/13/2008] [Indexed: 10/21/2022]
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29
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Abstract
The recently identified gastric hormone ghrelin was initially described as a natural Growth Hormone Secretagogue Receptor ligand. Apart from ghrelin's first discovered action, which was the stimulation of Growth Hormone release, implications for many other functions have been reported. It seems that ghrelin exhibits an important role in conditions related to processes regulating nutrition, body composition and growth, as well as heart, liver, thyroid or kidney dysfunction. In this review, current available knowledge about ghrelin's role in various pathological conditions is presented.
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Affiliation(s)
- Simoni A Katergari
- Laboratory of Physiology, Medical School, Democritus University of Thrace, Alexandroupolis, Greece
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30
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Gastric O-acyl transferase activates hunger signal to the brain. Proc Natl Acad Sci U S A 2008; 105:6213-4. [PMID: 18443299 DOI: 10.1073/pnas.0802461105] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023] Open
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31
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Abstract
The peptide hormone ghrelin is the only known protein modified with an O-linked octanoyl side group, which occurs on its third serine residue. This modification is crucial for ghrelin's physiological effects including regulation of feeding, adiposity, and insulin secretion. Despite the crucial role for octanoylation in the physiology of ghrelin, the lipid transferase that mediates this novel modification has remained unknown. Here we report the identification and characterization of human GOAT, the ghrelin O-acyl transferase. GOAT is a conserved orphan membrane-bound O-acyl transferase (MBOAT) that specifically octanoylates serine-3 of the ghrelin peptide. Transcripts for both GOAT and ghrelin occur predominantly in stomach and pancreas. GOAT is conserved across vertebrates, and genetic disruption of the GOAT gene in mice leads to complete absence of acylated ghrelin in circulation. The occurrence of ghrelin and GOAT in stomach and pancreas tissues demonstrates the relevance of GOAT in the acylation of ghrelin and further implicates acylated ghrelin in pancreatic function.
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32
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Park YJ, Lee YJ, Kim SH, Joung DS, Kim BJ, So I, Park DJ, Cho BY. Ghrelin enhances the proliferating effect of thyroid stimulating hormone in FRTL-5 thyroid cells. Mol Cell Endocrinol 2008; 285:19-25. [PMID: 18313206 DOI: 10.1016/j.mce.2008.01.003] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/19/2007] [Revised: 01/07/2008] [Accepted: 01/10/2008] [Indexed: 11/16/2022]
Abstract
Ghrelin regulates cell proliferation through the growth hormone secretagogue receptor (GHS-R). We confirmed the expression of GHS-R in FRTL-5 thyroid cells and investigated the effects of ghrelin in thyrocytes using FRTL-5 cells. Ghrelin increased intracellular calcium levels but not intracellular cyclic AMP levels. Ghrelin activated Erk within 2min, then activated Akt and STAT3. Erk phosphorylation was inhibited by the calcium inhibitor cyclopiazonic acid (CPA). Ghrelin alone did not stimulate FRTL-5 cell proliferation but enhanced the effects of thyroid stimulating hormone (TSH). Pretreatment with TSH potentiates the growth effects of ghrelin in thyroid cells, and p66Shc, a growth factor receptor adaptor protein, might mediate these synergistic effects. Ghrelin phosphorylated TSH-induced p66Shc, which was inhibited by CPA. Ghrelin did not affect the proliferation of ARO cells, which showed no increased expression of p66Shc after TSH treatment. Thus, ghrelin-induced intracellular calcium signaling enhanced the TSH-induced proliferation of thyrocytes, possibly mediated by the p66Shc pathway.
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Affiliation(s)
- Young Joo Park
- Department of Internal Medicine, Seoul National University College of Medicine, 28 Yeongeon-dong, Jongno-gu, Seoul, Republic of Korea
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Delhanty PJD, van Koetsveld PM, Gauna C, van de Zande B, Vitale G, Hofland LJ, van der Lely AJ. Ghrelin and its unacylated isoform stimulate the growth of adrenocortical tumor cells via an anti-apoptotic pathway. Am J Physiol Endocrinol Metab 2007; 293:E302-9. [PMID: 17405826 DOI: 10.1152/ajpendo.00377.2006] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Ghrelin is expressed in normal human adrenocortical cells and induces their proliferation through growth hormone secretagogue receptor 1a (GHS-R1a). Consequently, it was of interest to us to determine whether acylated ghrelin and its predominant serum isoform, unacylated ghrelin, also act as factors for adrenocortical carcinoma cell growth. To examine a potential ghrelin-regulated system in adrenocortical tumors, we measured proliferative effects of acylated and unacylated ghrelin in the adrenocortical carcinoma cell lines SW-13 and NCI-H295R. We also examined the expression of ghrelin, GHS-R1a, and corticotrophin-releasing factor receptor 2 (CRF-R2). Acylated and unacylated ghrelin in the nanomolar range dose-dependently induced adrenocortical cell growth up to 200% of untreated controls, as measured by thymidine uptake and WST1 assay. The proliferative effects of acylated and unacylated ghrelin in SW-13 cells was blocked by [D-Lys(3)]growth hormone-releasing peptide 6 (GHRP6), but a CRF-R2 antagonist had no effect on unacylated ghrelin growth stimulation. Cell cycle analysis suggests that acylated and unacylated ghrelin suppress the sub-G(0)/apoptotic fraction by up to 50%. Measurement of DNA fragmentation and caspase-3 and -7 activity in SW-13 cells confirmed that acylated and unacylated ghrelin suppress apoptotic rate. SW-13 cells express preproghrelin mRNA and secrete ghrelin, and [D-Lys(3)]GHRP6 suppresses their basal proliferation rate, strongly suggesting that ghrelin could act as an auto/paracrine growth factor. Acylated and unacylated ghrelin are potential auto/paracrine factors acting through an antiapoptotic pathway to stimulate adrenocortical tumor cell growth. Unacylated ghrelin-stimulated growth is suppressed by an antagonist of GHS-R1a, suggesting either that unacylated ghrelin is acylated before its action or that ghrelin, unacylated ghrelin, and [D-Lys(3)]GHRP-6 bind to a novel receptor in these cells.
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Affiliation(s)
- P J D Delhanty
- Department of Internal Medicine, Rm. Ee542, Erasmus Medical Centre, Dr. Molewaterplein 50, 3015 GE Rotterdam, The Netherlands.
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Vestergaard ET, Hansen TK, Gormsen LC, Jakobsen P, Moller N, Christiansen JS, Jorgensen JOL. Constant intravenous ghrelin infusion in healthy young men: clinical pharmacokinetics and metabolic effects. Am J Physiol Endocrinol Metab 2007; 292:E1829-36. [PMID: 17311892 DOI: 10.1152/ajpendo.00682.2006] [Citation(s) in RCA: 73] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Ghrelin levels fluctuate rapidly and dynamically with surges before meal times and postprandial troughs, and ghrelin increases appetite and food intake. Circulating ghrelin correlates negatively with body mass index (BMI), but obese individuals have a reduced postprandial decrease in ghrelin levels. Whether this reflects changes in secretion or clearance of ghrelin is uncertain. We therefore studied the pharmacokinetics of ghrelin in relation to anthropometric and biochemical measures. We also studied the effects of ghrelin on hormones and metabolites. In fasting humans, we used a constant infusion rate of ghrelin lasting 180 min at 5 pmol.kg body wt(-1).min(-1) in a randomized, double-blind, placebo-controlled crossover study. Serum ghrelin (s-ghrelin; total levels) was distributed and eliminated according to a two-compartment model. s-Ghrelin initial half-life was 24 +/- 2 min and terminal half-life 146 +/- 36 min, respectively. Mean residence time (MRT) of ghrelin was 93 +/- 16 min. MRT correlated positively with both BMI (r = 0.51, P < 0.001) and high-density cholesterol (HDL) levels (r = 0.75, P < 0.001). Serum insulin levels remained constant during ghrelin infusion, whereas plasma glucose increased 0.3 +/- 0.1 mmol/l (P < 0.01) and free fatty acid levels more than doubled (to 1.03 +/- 0.08 mmol/l, P < 0.001), translating into a significant reduction of insulin sensitivity (P < 0.001). In conclusion, 1) we describe novel pharmacokinetics of ghrelin that are useful when tailoring ghrelin infusion rates in clinical experiments, 2) BMI and HDL correlate positively with MRT of infused ghrelin, and 3) supraphysiological ghrelin levels impair insulin sensitivity.
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Affiliation(s)
- Esben Thyssen Vestergaard
- Medical Department M (Endocrinology and Diabetes), Aarhus University Hospital, Dk-8000 Aarhus C, Denmark.
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Abstract
Ghrelin is a 28 amino-acid hormone with multiple functions. It is predominantly produced by the stomach but has also been detected in other organs, including the small intestine, pancreas, hypothalamus and pituitary, as well as in the immune system and almost every other normal human tissue examined. It is also present in neuroendocrine tumours, pituitary adenomas, endocrine tumours of the pancreas, breast tumours, and thyroid and medullary thyroid carcinomas. Ghrelin is a brain-gut peptide with growth hormone-releasing and appetite-inducing activities, and is the endogenous ligand of the G protein-coupled growth hormone secretagogue receptor (GHS-R). In this review we comprehensively summarize the available data regarding (a) the expression of ghrelin and the GHS-R in normal endocrine tissues and in pituitary adenomas and neuroendocrine tumours, (b) the levels of circulating ghrelin in patients with pituitary adenomas and neuroendocrine tumours and (c) the effects of ghrelin administration in these patients on the levels of other hormones and on the rate of proliferation of the tumour. It is clear that ghrelin has many more functions and is involved in many more processes than was initially postulated, and its endocrine, paracrine and autocrine effects play a role in its physiological and pathophysiological functions.
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Affiliation(s)
- Chrysanthia A Leontiou
- Department of Endocrinology, William Harvey Research Institute, Barts and the London Medical School, John Vane Science Centre, Charterhouse Square, London, EC1M 6BQ, UK
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36
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Altinova AE, Toruner F, Karakoc A, Yetkin I, Ayvaz G, Cakir N, Arslan M. Serum Ghrelin Levels in patients with Hashimoto's thyroiditis. Thyroid 2006; 16:1259-64. [PMID: 17199436 DOI: 10.1089/thy.2006.16.1259] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
OBJECTIVE Hypothyroidism is associated with changes in appetite and body weight. Ghrelin is an orexigenic peptide, and it stimulates appetite and increases food intake. However, the potential relationship between circulating ghrelin levels, hypothyroidism, and thyroid antibodies has not been adequately studied. DESIGN Forty-seven patients with hypothyroidism due to Hashimoto's thyroiditis and 48 euthyroid subjects were enrolled in the study. Thyroid hormones and antibodies, insulin, glucose, ghrelin levels, and lipid parameters were measured in all the subjects. MAIN OUTCOME Hypothyroid group showed significantly decreased serum levels of ghrelin and ghrelin=body mass index (BMI) compared to euthyroid group (31.9 +/- 21.5 pg/mL vs. 50.5 +/- 34.8 pg/mL, p < 0.001; and 1.24 +/- 0.93 vs. 2.12 +/- 1.53, p < 0.0001). In hypothyroid group, 6 months after treatment, ghrelin levels and ghrelin/BMI remained lower than euthyroid group (33.2 +/- 21.1 pg/mL vs. 50.5 +/- 34.8 pg/mL, p < 0.001; and 1.27 +/- 0.86 vs. 2.12 +/- 1.53, p < 0.0001). Ghrelin levels were decreased in hypothyroid patients with high thyroid peroxidase antibody (TPOAb) titre compared to hypothyroid patients with low TPOAb titre (19.1 +/- 23.1 pg/ mL vs. 35.3 +/- 17.4 pg/mL, p < 0.01). Ghrelin levels correlated positively with free triiodothyronine (FT3) and free thyroxine (FT4), and negatively with age, thyroglobulin antibody (TAb), TPOAb, total cholesterol (T-C), low-density lipoprotein cholesterol (LDL-C), very low-density lipoprotein cholesterol (VLDL-C), and triglycerides (TG) in hypothyroid group. In euthyroid group, circulating ghrelin levels correlated negatively with age, FT3, FT4, TG, and VLDL-C levels. No significant correlation was observed between ghrelin and homeostasis model assessment for insulin resistance (HOMA-IR) and between ghrelin and quantitative insulin sensitivity check index (QUICKI) in both groups. Regression analysis revealed that FT3 level is the most important predictor of ghrelin levels. CONCLUSION Thyroid hormones and antibodies seem to have a potential effect on serum ghrelin levels in patients with hypothyroidism.
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Affiliation(s)
- Alev E Altinova
- Department of Endocrinology and Metabolism, Gazi University Medical Faculty, Ankara, Turkey.
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Cassoni P, Allia E, Marrocco T, Ghè C, Ghigo E, Muccioli G, Papotti M. Ghrelin and cortistatin in lung cancer: expression of peptides and related receptors in human primary tumors and in vitro effect on the H345 small cell carcinoma cell line. J Endocrinol Invest 2006; 29:781-90. [PMID: 17114908 DOI: 10.1007/bf03347371] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
Ghrelin, a natural GH secretagogue (GHS) acylated peptide, and cortistatin (CST), a natural SRIF-like peptide, interfere with neoplastic growth in different cancers. We tested forty-one lung carcinomas and the H345 small cell lung carcinoma (SCLC) cell line by RT-PCR to investigate the presence of ghrelin and CST and related receptors, including type 1a GHS receptor (GHS-R1a), all SRIF-receptor subtypes (sst 1-5) and MRGX2. Moreover, the presence of ghrelin and CST peptides was studied in both tumors and H345 cells. Ghrelin and CST mRNA were present in the majority of tested tumors, but ghrelin and CST proteins were revealed only in tumors with a neuroendocrine phenotype. All the receptors mRNA had a heterogeneous expression without correlation between ghrelin (or CST) and their receptor distribution. All the transcripts, but not GHS-R1a, were expressed in H345 cells. However, ghrelin and desacyl ghrelin induced in vitro a dose-dependent inhibition on the H345 cell proliferation and increased apoptosis. Conversely, neither CST nor SRIF affected H345 cell growth, despite the presence of their specific receptors. The anti-proliferative and the pro-apoptotic effects of ghrelin were consistent with binding experiments on H345 cell, where either acylated or des-acylated ghrelin recognized a common binding site. In conclusion, the present study indicates that: a) ghrelin and CST mRNAs are expressed in lung cancers, although some neuroendocrine tumors contain detectable amounts of the peptides; b) GHSR-1a mRNA is present exclusively in neuroendocrine tumors, whereas MRGX2 mRNA (but not peptide) is expressed in all histological types; c) both ghrelin forms inhibit H345 cell proliferation, both directly and enhancing apoptosis, despite the absence of GHS-R1a, whereas CST and its receptors do not interfere with cell growth.
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Affiliation(s)
- P Cassoni
- Department of Biomedical Sciences and Human Oncology, University of Turin, Turin, Italy.
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38
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Dixit VD, Weeraratna AT, Yang H, Bertak D, Cooper-Jenkins A, Riggins GJ, Eberhart CG, Taub DD. Ghrelin and the growth hormone secretagogue receptor constitute a novel autocrine pathway in astrocytoma motility. J Biol Chem 2006; 281:16681-90. [PMID: 16527811 PMCID: PMC2271047 DOI: 10.1074/jbc.m600223200] [Citation(s) in RCA: 56] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Abstract
Originally thought of as a stomach-derived endocrine peptide acting via its receptors in the central nervous system to stimulate food intake and growth hormone expression, ghrelin and its receptor (growth hormone secretagogue receptor (GHS-R)) are widely expressed in a number of organ systems, including cancer cells. However, the direct functional role of ghrelin and its receptor in tumors of central nervous system origin remains to be defined. Here, we demonstrate that the human astrocytoma cell lines U-118, U-87, CCF-STTG1, and SW1088 express 6-, 11-, 15-, and 29-fold higher levels of GHS-R compared with primary normal human astrocytes. The ligation of GHS-R by ghrelin on these cells resulted in an increase in intracellular calcium mobilization, protein kinase C activation, actin polymerization, matrix metalloproteinase-2 activity, and astrocytoma motility. In addition, ghrelin led to actin polymerization and membrane ruffling on cells, with the specific co-localization of the small GTPase Rac1 with GHS-R on the leading edge of the astrocytoma cells and imparting the tumor cells with a motile phenotype. Disruption of the endogenous ghrelin/GHS-R pathway by RNA interference resulted in diminished motility, matrix metalloproteinase activity, and Rac expression, whereas tumor cells stably overexpressing GHS-R exhibited increased cell motility. The relevance of ghrelin and GHS-R expression was verified in clinically relevant tissues from 20 patients with oligodendrogliomas and grade II-IV astrocytomas. Analysis of a central nervous system tumor tissue microarray revealed that strong GHS-R and ghrelin expression was significantly more common in high grade tumors compared with low grade ones. Together, these findings suggest a novel role for the ghrelin/GHS-R axis in astrocytoma cell migration and invasiveness of cancers of central nervous system origin.
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Affiliation(s)
- Vishwa Deep Dixit
- Laboratory of Immunology, NIA Intramural Research Program, National Institutes of Health, Johns Hopkins University, Baltimore, Maryland 21224
| | - Ashani T. Weeraratna
- Laboratory of Immunology, NIA Intramural Research Program, National Institutes of Health, Johns Hopkins University, Baltimore, Maryland 21224
| | - Hyunwon Yang
- Laboratory of Immunology, NIA Intramural Research Program, National Institutes of Health, Johns Hopkins University, Baltimore, Maryland 21224
| | - Dorothy Bertak
- Laboratory of Immunology, NIA Intramural Research Program, National Institutes of Health, Johns Hopkins University, Baltimore, Maryland 21224
| | - Anthony Cooper-Jenkins
- Laboratory of Immunology, NIA Intramural Research Program, National Institutes of Health, Johns Hopkins University, Baltimore, Maryland 21224
| | - Gregory J. Riggins
- Departments of Neurosurgery and Pathology, Johns Hopkins University, Baltimore, Maryland 21224
| | - Charles G. Eberhart
- Departments of Neurosurgery and Pathology, Johns Hopkins University, Baltimore, Maryland 21224
| | - Dennis D. Taub
- Laboratory of Immunology, NIA Intramural Research Program, National Institutes of Health, Johns Hopkins University, Baltimore, Maryland 21224
- To whom correspondence should be addressed: Clinical Immunology Section, Lab. of Immunology, NIA Intramural Research Program, NIH, 5600 Nathan Shock Dr., Baltimore, MD 21224. Tel.: 410-558-8159; Fax: 410-558-8284; E-mail:
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Bhatti SF, Van Ham LM, Mol JA, Kooistra HS. Ghrelin, an endogenous growth hormone secretagogue with diverse endocrine and nonendocrine effects. Am J Vet Res 2006; 67:180-8. [PMID: 16426229 DOI: 10.2460/ajvr.67.1.180] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Affiliation(s)
- Sofie F Bhatti
- Department of Small Animal Medicine and Clinical Biology, Faculty of Veterinary Medicine, Ghent University, Salisburylaan 133, B-9820 Merelbeke, Belgium
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Raghay K, García-Caballero T, Nogueiras R, Morel G, Beiras A, Diéguez C, Gallego R. Ghrelin localization in rat and human thyroid and parathyroid glands and tumours. Histochem Cell Biol 2005; 125:239-46. [PMID: 16187069 DOI: 10.1007/s00418-005-0044-6] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 07/13/2005] [Indexed: 11/25/2022]
Abstract
Ghrelin, the endogenous ligand of the growth hormone secretagogue receptor (GHS-R), is a 28 amino acid peptide originally isolated from rat stomach that has been primarily involved in the central neuroregulation of GH secretion and food intake. Previous studies demonstrated that ghrelin has a widespread expression in different normal cells and tissues, as well as in gastric, thyroid, testicular, breast and lung neoplasias. In the current study, we use molecular biology to detect ghrelin transcripts expression in rats, and immunohistochemical techniques to investigate the cellular distribution of this peptide in rat and human thyroid and parathyroid glands and tumours. Ghrelin was localized in thyroid C cells and in parathyroid cells. Thyroid carcinomas (medullar, follicular and papillary) and parathyroid adenomas also showed intense and diffuse immunostaining for ghrelin. These data provide direct morphological evidence that ghrelin may well be acting in a paracrine fashion in the regulation of thyroid follicular cell function. The diffuse ghrelin immunostaining found in the parathyroid gland opens up the possibility of its secretion to the bloodstream or its involvement in the regulation of the parathyroid function. Overall, expression of ghrelin in human and rat thyroid and parathyroid glands is highly suggestive of a conserved role of this molecule in the regulation of thyroid and parathyroid cell function.
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Affiliation(s)
- Kawtar Raghay
- Department of Morphological Sciences, University Clinical Hospital, University of Santiago de Compostela, c/S. Francisco, 15782 Santiago de Compostela, Spain
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Abstract
Small synthetic molecules called growth hormone secretagogues (GHSs) stimulate the release of growth hormone (GH) from the pituitary. They act through the GHS-R, a G protein-coupled receptor whose ligand has only been discovered recently. Using a reverse pharmacology paradigm with a stable cell line expressing GHS-R, we purified an endogenous ligand for GHS-R from rat stomach and named it "ghrelin," after a word root ("ghre") in Proto-Indo-European languages meaning "grow." Ghrelin is a peptide hormone in which the third amino acid, usually a serine but in some species a threonine, is modified by a fatty acid; this modification is essential for ghrelin's activity. The discovery of ghrelin indicates that the release of GH from the pituitary might be regulated not only by hypothalamic GH-releasing hormone, but also by ghrelin derived from the stomach. In addition, ghrelin stimulates appetite by acting on the hypothalamic arcuate nucleus, a region known to control food intake. Ghrelin is orexigenic; it is secreted from the stomach and circulates in the bloodstream under fasting conditions, indicating that it transmits a hunger signal from the periphery to the central nervous system. Taking into account all these activities, ghrelin plays important roles for maintaining GH release and energy homeostasis in vertebrates.
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Affiliation(s)
- Masayasu Kojima
- Molecular Genetics, Institute of Life Science, Kurume University, Hyakunenkouen 1-1, Kurume, Fukuoka 839-0864, Japan.
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Wei W, Wang G, Qi X, Englander EW, Greeley GH. Characterization and regulation of the rat and human ghrelin promoters. Endocrinology 2005; 146:1611-25. [PMID: 15604212 DOI: 10.1210/en.2004-1306] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Ghrelin is a recently discovered stomach hormone and endogenous ligand for the GH secretagogue receptor. The aim of these studies is to elucidate molecular mechanisms underlying regulation of the ghrelin gene. Distal and proximal transcription initiation sites are present. A short transcript, a product of the proximal site, showed a more widespread distribution. Two sets of 5'-upstream segments of the rat and human ghrelin genes were cloned and sequenced. Rat promoter segments upstream of the distal site showed highest activity in kidney (COS-7) and stomach (AGS) cells, whereas human promoter segments upstream of the proximal site showed highest activity in AGS and pituitary (GH3) cells in transient transfection assays. For the human, the core promoter spanned -667 to -468 bp, including the noncoding exon 1 and a short 5' sequence of intron 1. For the rat, the core promoter spanned -581 to -469 bp, and inclusion of exon 1 and a short 5'-sequence of intron 1 reduced activity by 67%. Mutation of initiator-like elements in the rat lowered activity by 20-50%, whereas in the human, all activity was abolished. Overexpression of upstream stimulatory factors increased ghrelin core promoter activity. Fasting increases stomach ghrelin expression, glucagon-a fasting-induced hormone, increased ghrelin expression in vivo in rats, and promoter activity by approximately 25-50%. Together, these findings indicate that structural differences between the rat and human ghrelin core promoters may account in part for the differences in their transcriptional regulation. Nonetheless, upstream stimulatory factor and glucagon exert similar effects on regulation of rat and human ghrelin promoters.
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Affiliation(s)
- Wei Wei
- Department of Surgery, The University of Texas Medical Branch, 301 University Boulevard, Galveston, Texas 77555-0725, USA
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43
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De Vriese C, Grégoire F, De Neef P, Robberecht P, Delporte C. Ghrelin is produced by the human erythroleukemic HEL cell line and involved in an autocrine pathway leading to cell proliferation. Endocrinology 2005; 146:1514-22. [PMID: 15564328 DOI: 10.1210/en.2004-0964] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Ghrelin, a ligand of the GH secretagogue receptor (GHS-R 1a), is a 28-amino acid peptide with an unusual octanoyl group on Ser3, crucial for its biological activity. For the first time, ghrelin and GHS-R 1b, a truncated variant of the receptor resulting from alternative splicing, but not GHS-R 1a, mRNAs were detected in the human erythroleukemic cell line HEL. Two antibodies, used for RIA, were directed against octanoylated and total (octanoylated and desoctanoylated) ghrelin, and the recognized epitopes were characterized. Using reverse phase HPLC analysis followed by RIA, we demonstrated that octanoylated and desoctanoylated ghrelins were present in HEL cells and their culture medium, of which more than 90% was octanoylated. The ghrelin levels were not affected after 24 h treatment with sodium butyrate, phorbol 12-myristate 13-acetate, or forskolin, but a significant 3-fold increase in desoctanoylated ghrelin was detected in the culture medium after 48 h treatment with sodium butyrate. The antighrelin SB801 and SB969 antisera inhibited HEL cell proliferation by 24% and 39%, respectively, after 72 h. Taken together, these data suggested that endogenous ghrelin stimulated HEL cell proliferation by an autocrine pathway involving an unidentified receptor, distinct from GHS-R1a, and that the HEL cell line represents a unique model to study the octanoylation of ghrelin.
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Affiliation(s)
- Carine De Vriese
- Department of Biochemistry and Nutrition, Faculty of Medicine, Université Libre de Bruxelles, Bat G/E, CP 611, 808 route de Lennik, B-1070 Brussels, Belgium
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44
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Ghigo E, Broglio F, Arvat E, Maccario M, Papotti M, Muccioli G. Ghrelin: more than a natural GH secretagogue and/or an orexigenic factor. Clin Endocrinol (Oxf) 2005; 62:1-17. [PMID: 15638864 DOI: 10.1111/j.1365-2265.2004.02160.x] [Citation(s) in RCA: 149] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Ghrelin, an acylated peptide produced predominantly by the stomach, has been discovered to be a natural ligand of the growth hormone secretagogue receptor type 1a (GHS-R1a). Ghrelin has recently attracted considerable interest as a new orexigenic factor. However, ghrelin exerts several other neuroendocrine, metabolic and also nonendocrine actions that are explained by the widespread distribution of ghrelin and GHS-R expression. The likely existence of GHS-R subtypes and evidence that the neuroendocrine actions, but not all the other actions, of ghrelin depend on its acylation in serine-3 revealed a system whose complexity had not been completely explored by studying synthetic GHS. Ghrelin secretion is mainly regulated by metabolic signals and, in turn, the modulatory action of ghrelin on the control of food intake and energy metabolism seems to be among its most important biological actions. However, according to a recent study, ghrelin-null mice are neither anorectics nor dwarfs and this evidence clearly depicts a remarkable difference from leptin null mice. Nevertheless, the original and fascinating story of ghrelin, as well as its potential pathophysiological implications in endocrinology and internal medicine, is not definitively cancelled by these data as GHS-R1a null aged mice show significant alterations in body composition and growth, in glucose metabolism, cardiac function and contextual memory. Besides potential clinical implications for natural or synthetic ghrelin analogues acting as agonists or antagonists, there are several open questions awaiting an answer. How many ghrelin receptor subtypes exist? Is ghrelin 'the' or just 'a' GHS-R ligand? That is, are there other natural GHS-R ligands? Is there a functional balance between acylated and unacylated ghrelin forms, potentially with different actions? Within the next few years suitable answers to these questions will probably be found, making it possible to gain a better knowledge of ghrelin's potential clinical perspectives.
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Affiliation(s)
- E Ghigo
- Division of Endocrinology and Metabolism, Department of Internal Medicine, University of Turin, Italy.
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45
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Kanamoto N, Akamizu T, Tagami T, Hataya Y, Moriyama K, Takaya K, Hosoda H, Kojima M, Kangawa K, Nakao K. Genomic structure and characterization of the 5'-flanking region of the human ghrelin gene. Endocrinology 2004; 145:4144-53. [PMID: 15142980 DOI: 10.1210/en.2003-1718] [Citation(s) in RCA: 55] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Ghrelin, an endogenous ligand for the GH secretagogue receptor, induces GH secretion, food intake, and positive energy balance. Although ghrelin exhibits a variety of hormonal actions, the mechanisms regulating ghrelin expression and secretion remain unclear. To understand regulation of human ghrelin gene expression, we examined the genomic structure of approximately 5,000 bp of the 5'-flanking region of the human ghrelin gene. We performed rapid amplification of cDNA ends to estimate transcriptional start sites, indicating that there are two transcriptional initiation sites within the human ghrelin gene. Both transcripts were equally expressed in the human stomach, whereas the longer transcript was mainly expressed in a human medullary thyroid carcinoma (TT) cell line. Functional analysis using promoter-reporter constructs containing the 5'-flanking region of the gene indicated that the sequence residing within the -349 to -193 region is necessary for human ghrelin promoter function in TT cells. Within this region existed several consensus sequences for a number of transactivating regulatory proteins, including an E-box site. Destruction of this site decreased to 40% of the promoter activity. The upstream region of the promoter has two additional putative E-box sites, and site-directed mutagenesis suggested that these are also involved in promoter activation. Electrophoretic mobility shift assays demonstrated that the upstream stimulatory factor specifically bound to these E-box elements. These results suggest a potential role for upstream stimulatory factor transcription factors in the regulation of human ghrelin expression.
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Affiliation(s)
- Naotetsu Kanamoto
- Department of Medicine and Clinical Science, Kyoto University Graduate School of Medicine, Kyoto, Japan
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Hosoda H, Doi K, Nagaya N, Okumura H, Nakagawa E, Enomoto M, Ono F, Kangawa K. Optimum collection and storage conditions for ghrelin measurements: octanoyl modification of ghrelin is rapidly hydrolyzed to desacyl ghrelin in blood samples. Clin Chem 2004; 50:1077-80. [PMID: 15161728 DOI: 10.1373/clinchem.2003.025841] [Citation(s) in RCA: 177] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Affiliation(s)
- Hiroshi Hosoda
- Department of Biochemistry, National Cardiovascular Center Research Institute, Osaka 565-8565, Japan
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van der Lely AJ, Tschöp M, Heiman ML, Ghigo E. Biological, physiological, pathophysiological, and pharmacological aspects of ghrelin. Endocr Rev 2004; 25:426-57. [PMID: 15180951 DOI: 10.1210/er.2002-0029] [Citation(s) in RCA: 802] [Impact Index Per Article: 40.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Ghrelin is a peptide predominantly produced by the stomach. Ghrelin displays strong GH-releasing activity. This activity is mediated by the activation of the so-called GH secretagogue receptor type 1a. This receptor had been shown to be specific for a family of synthetic, peptidyl and nonpeptidyl GH secretagogues. Apart from a potent GH-releasing action, ghrelin has other activities including stimulation of lactotroph and corticotroph function, influence on the pituitary gonadal axis, stimulation of appetite, control of energy balance, influence on sleep and behavior, control of gastric motility and acid secretion, and influence on pancreatic exocrine and endocrine function as well as on glucose metabolism. Cardiovascular actions and modulation of proliferation of neoplastic cells, as well as of the immune system, are other actions of ghrelin. Therefore, we consider ghrelin a gastrointestinal peptide contributing to the regulation of diverse functions of the gut-brain axis. So, there is indeed a possibility that ghrelin analogs, acting as either agonists or antagonists, might have clinical impact.
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Affiliation(s)
- Aart J van der Lely
- Department of Internal Medicine, Erasmus Medical Center, 3015 GD Rotterdam, The Netherlands.
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Abstract
OBJECTIVE Ghrelin is a novel gastric hormone recognized in 1999 as a mediator of growth hormone release. Since growth hormone is anabolic, an important function of ghrelin may be to coordinate energy needs with the growth process. Newly discovered biologic roles of ghrelin imply that it may have other important physiological functions as well. This is a review of recent clinically relevant, yet less well-known, physiologic actions of ghrelin. SUMMARY BACKGROUND DATA Ghrelin has profound orexigenic, adipogenic, and somatotrophic properties, increasing food intake and body weight. Secreted predominantly from the stomach, ghrelin is the natural ligand for the growth hormone secretagogue receptor in the pituitary gland, thus fulfilling criteria of a brain-gut peptide. The brain-gut axis is the effector of anabolism by regulating growth, feeding, and metabolism via vagal afferents mediating ghrelin signaling. However, the wide tissue distribution of ghrelin suggests that it may have other functions as well. METHODS Systematic literature review of all PubMed citations between 1999 and August 2003 focusing on clinically relevant biochemical and physiological characteristics of ghrelin. RESULTS Ghrelin is an important component of an integrated regulatory system of growth and metabolism acting via the vagus nerve, and is implicated in a variety of altered energy states such as obesity, eating disorders, neoplasia, and cachexia. It also enhances immune responses and potentially down-regulates anti-inflammatory molecules. Ghrelin's role as a brain-gut peptide emphasizes the significance of afferent vagal fibers as a major pathway to the brain, serving the purpose of maintaining physiologic homeostasis. CONCLUSIONS The discovery of ghrelin has increased our understanding of feeding regulation, nutritional homeostasis, and metabolic processes. Further characterization of ghrelin's functions will likely generate new pharmacological approaches to diagnose and treat different disease entities including those related to the over-nutrition of obesity and the catabolic response to surgical trauma.
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Affiliation(s)
- James T Wu
- Department of Surgery, SUNY Downstate Medical Center, Brooklyn, NY 11203, USA.
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Srivastava A, Kamath A, Barry SA, Dayal Y. Ghrelin expression in hyperplastic and neoplastic proliferations of the enterochromaffin-like (ECL) cells. Endocr Pathol 2004; 15:47-54. [PMID: 15067176 DOI: 10.1385/ep:15:1:47] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Abstract
Ghrelin, a recently discovered peptide isolated from the gastric corpus mucosa, is believed to be important in the regulation of growth hormone secretion and has been shown to increase appetite and food intake as well. It may also have other gastrointestinal and cardiac functions. Because a cell of origin for ghrelin has not been convincingly identified in the gastric mucosa thus far, we studied the immunohistochemical expression of ghrelin in proliferative lesions of the enterochromaffin-like (ECL) cells-a cell that is not only exclusively confined to the gastric corpus mucosa but is its dominant endocrine cell type as well. Formalin-fixed, paraffin embedded tissues from three cases of gastric ECL cell hyperplasia and five ECL carcinoids (three with coexisting foci of diffuse, linear, and micronodular hyperplasia) were immunohistochemically stained for ghrelin, using a commercially available antibody. The Sevier-Munger stain for ECL cells and immunohistochemical stains for chromogranin, gastrin, serotonin, somatostatin, and vesicular monoamine transporter-2 (VMAT-2) were performed on parallel sections for correlation with the ghrelin staining results. All ECL cell carcinoids and hyperplastic lesions were positive for both the Sevier-Munger and the immunohistochemical stains for chromogranin and VMAT-2. Immunoreactivity for ghrelin was seen in 4/5 ECL carcinoids, all cases of ECL cell hyperplasia, as well as in all areas with linear and micronodular hyperplasia adjacent to the ECL cell carcinoids. In each instance, such staining was confined to the Sevier-Munger, and VMAT-2 positive cells only. Our findings indicate that the ECL cells are either the ghrelin-producing cells of the gastric mucosa or acquire the capability to synthesize ghrelin during proliferative states encompassing the entire hyperplasia to neoplasia spectrum. In view of the orexigenic and other known actions of ghrelin, the functional and/or biologic significance of ghrelin production in such ECL cell proliferations needs to be investigated further.
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Affiliation(s)
- Amitabh Srivastava
- Department of Pathology, Tufts-New England Medical Center, Boston, MA 02111, USA
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50
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Hataya Y, Akamizu T, Hosoda H, Kanamoto N, Moriyama K, Kangawa K, Takaya K, Nakao K. Alterations of plasma ghrelin levels in rats with lipopolysaccharide-induced wasting syndrome and effects of ghrelin treatment on the syndrome. Endocrinology 2003; 144:5365-71. [PMID: 12960078 DOI: 10.1210/en.2003-0427] [Citation(s) in RCA: 72] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Ghrelin not only strongly stimulates GH secretion, but is also involved in energy homeostasis by stimulating food intake and promoting adiposity through a GH-independent mechanism. These effects of ghrelin may play an important role in the pathophysiology of inflammatory wasting syndrome, in which both the somatotropic axis and energy balance are altered. In this study we investigated plasma ghrelin concentrations after lipopolysaccharide (LPS) administration to rats, a model of the wasting syndrome and critical illness. In addition, the therapeutic potential of the antiwasting effects of ghrelin was explored using LPS-injected rats. A single LPS injection suppressed plasma ghrelin levels 6 and 12 h later. Maximal reduction was observed 12 h after LPS injection, in a dose-dependent manner. In contrast, plasma ghrelin levels were elevated after repeated LPS injections on d 2 and 5. Peripheral administration of ghrelin twice daily (10 nmol/rat) for 5 d increased body weight gain in repeated LPS-injected rats. Furthermore, both adipose tissue weight and plasma leptin concentrations were increased after ghrelin administration in these rats. In conclusion, plasma ghrelin levels are altered in LPS-injected rats, and ghrelin treatment may provide a new therapeutic approach to the wasting syndrome and critical illness.
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Affiliation(s)
- Yuji Hataya
- Department of Medicine and Clinical Science, Kyoto University Graduate School of Medicine, Kyoto 606-8507, Japan
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