Ghrelin is Released from Rat Hypothalamic Explants and Stimulates Corticotrophin-releasing Hormone and Arginine-vasopressin

A. M. Mozid; G. Tringali; M. L. Forsling; M. S. Hendricks; S. Ajodha; R. Edwards; P. Navarra; A. B. Grossman; M. Korbonits

doi:10.1055/s-2003-41801

Hormone and Metabolic Research, Table of Contents

Horm Metab Res 2003; 35(8): 455-459
DOI: 10.1055/s-2003-41801

Original Basic

Ghrelin is Released from Rat Hypothalamic Explants and Stimulates Corticotrophin-releasing Hormone and Arginine-vasopressin[*]

A. M. Mozid ¹ , G. Tringali ² , M. L. Forsling ³ , M. S. Hendricks ¹ , S. Ajodha ¹ , R. Edwards ¹ , P. Navarra ² , A. B. Grossman ¹ , M. Korbonits ¹

¹Department of Endocrinology, St. Bartholomew’s Hospital, London, UK
²Department of Pharmacology, Catholic University, Rome, Italy
³Department of Physiology, UMDS, London, UK

Abstract

Ghrelin and synthetic growth hormone secretagogues have diverse effects on the hypothalamus including effects on appetite and the growth hormone axis as well as on the hypothalamus-pituitary-adrenal (HPA) axis. We previously studied the effect of synthetic growth hormone secretagogues on CRH and AVP release from rat hypothalami in vitro, and now report on the effects of ghrelin on CRH and AVP release. The ghrelin protein content and ghrelin output from rat hypothalamic explants was measured using a specific novel ghrelin enzyme immunoassay. The effect of 10 ^{- 8} M to 10 ^{- 6} M ghrelin on CRH and AVP release was studied in the rat hypothalamic explants, where stimulation with des-octanoyl ghrelin was used as control. The presence of both ghrelin mRNA and protein could be shown in the rat hypothalamus. Ghrelin output was detected in the incubation fluid of rat hypothalamic explants and could be stimulated with high potassium concentrations. Our data also demonstrated a dose-dependent effect of ghrelin on both CRH and AVP release, while des-octanoylated ghrelin showed no effect on either peptide. In summary, the current data suggest that ghrelin is expressed in the hypothalamus both at RNA and the protein levels. Ghrelin stimulates the HPA axis in the rat via stimulation of both CRH, and particularly, AVP release from the hypothalamus. The local autocrine/paracrine and endocrine effects of ghrelin in the hypothalamus could influence all the hormonal systems involved in ghrelin effects, including growth hormone release, the HPA axis and appetite.

Key words

Ghrelin - Growth hormone secretagogue receptor - Hypothalamus - Corticotrophin-releasing hormone - Arginine-vasopressin

Full Text

References

1 Kojima M, Hosoda H, Date Y, Nakazato M, Matsuo H, Kangawa K. Ghrelin is a growth-hormone-releasing acylated peptide from stomach. Nature. 1999; 402 656-660
2 Gnanapavan S, Kola B, Bustin S A, Morris D G, McGee P, Fairclough P, Bhattacharya S, Carpenter R, Grossman A B, Korbonits M. The tissue distribution of the mRNA of ghrelin and subtypes of its receptor, GHS-R, in humans. J Clin Endocrinol Metab. 2002; 87 2988
3 Howard A D, Feighner S D, Cully D F, Liberator P A, Arena J P, Rosenblum C I, Hamelin M J, Hreniuk D L, Palyha O C, Anderson J, Paress P S, Diaz C, Chou M, Liu K, Kulju McKee K, Pong S-S, Chaung L Y, Elbrecht A, Dashkevicz M, Heavens R, Rigby M, Sirinathsinghji D JS, Dean D C, Melillo D G, Patchett A A, Nargund R, Griffin P R, DeMartino J A, Gupta S K, Schaeffer J M, Smith R G, Van der Ploeg L HT. A receptor in pituitary and hypothalamus that functions in growth hormone release. Science. 1996; 273 974-977
4 Korbonits M, Kaltsas G, Perry L A, Putignano P, Grossman A B, Besser G M, Trainer P J. The growth hormone secretagogue hexarelin stimulates the hypothalamo-pituitary-adrenal axis via arginine vasopressin. J Clin Endocrinol Metab. 1999; 84 2489-2495
5 Arvat E, Maccario M, Di Vito L, Broglio F, Benso A, Gottero C, Papotti M, Muccioli G, Dieguez C, Casanueva F F, Deghenghi R, Camanni F, Ghigo E. Endocrine activities of ghrelin, a natural GH secretagogue, in humans: comparison and interactions with hexarelin, a non natural peptidyl GHS, and GH-releasing hormone. J Clin Endocrinol Metab. 2001; 86 1169-1174
6 Tschöp M, Smiley D L, Heiman M L. Ghrelin induces adiposity in rodents. Nature. 2000; 407 908-913
7 Katugampola S D, Pallikaros Z, Davenport A P. [125I-His(9)]-ghrelin, a novel radioligand for localizing GHS orphan receptors in human and rat tissue: up-regulation of receptors with athersclerosis. Br J Pharmacol. 2001; 134 143-149
8 Tolle V, Bassant M H, Zizzari P, Poindessous-Jazat F, Tomasetto C, Epelbaum J, Bluet-Pajot M T. Ultradian rhythmicity of ghrelin secretion in relation with GH, feeding behavior, and sleep-wake patterns in rats. Endocrinology. 2002; 143 1353-1361
9 Jeffery P L, Herington A C, Chopin L K. Expression and action of the growth hormone releasing peptide ghrelin and its receptor in prostate cancer cell lines. J Endocrinol. 2002; 172 R7-R11
10 Pettersson I, Muccioli G, Granata R, Deghenghi R, Ghigo E, Ohlsson C, Isgaard J. Natural (ghrelin) and synthetic (hexarelin) GH secretagogues stimulate H9c2 cardiomyocyte cell proliferation. J Endocrinol. 2002; 175 201-209
11 Korbonits M, Bustin S A, Kojima M, Jordan S, Adams E F, Lowe D G, Kangawa K, Grossman A B. The expression of the growth hormone secretagogue receptor ligand ghrelin in normal and abnormal human pituitary and other neuroendocrine tumours. J Clin Endocrinol Metab. 2001; 86 881-887
12 Hosoda H, Kojima M, Matsuo H, Kangawa K. Ghrelin and des-acyl ghrelin: Two major forms of rat ghrelin peptide in gastrointestinal tissue. Biochem Biophys Res Commun. 2000; 279 909-913
13 Korbonits M, Little J A, Forsling M L, Tringali G, Costa A, Navarra P, Trainer P J, Grossman A B. The effect of growth hormone secretagogues and neuropeptide Y on hypothalamic hormone release from acute rat hypothalamic explants. J Neuroendocrinol. 1999; 11 521-528
14 Korbonits M, Little J A, Camacho-Hübner C, Trainer P J, Besser G M, Grossman A B. Insulin-like growth factor-I and -II in combination inhibit the release of growth hormone-releasing hormone from the rat hypothalamus in vitro. . Growth Regul. 1996; 6 110-120
15 Berelowitz M, Szabo M, Frohman L A, Firestone S, Chu L, Hintz H L. Somatomedin-C mediates growth hormone negative feedback by effects on both the hypothalamus and the pituitary. Science. 1981; 212 1279-1281
16 Lengyel A M, Grossman A B, Niewenhuyzen-Kruseman A C, Ackland J, Rees L H, Besser G M. Glucose modulation of somatostatin and LHRH release from rat hypothalamic fragments in vitro. . Neuroendocrinol. 1984; 39 31-38
17 Aguila M C, McCann S M. Stimulation of somatostatin release in vitro by synthetic human growth hormone-releasing factor by a nondopaminergic mechanism. Endocrinology. 1985; 117 762-765
18 Mancuso C, Tringali G, Grossman A B, Preziosi P, Navarra P. The generation of nitric oxide and carbon monoxide produces opposite effects on the release of immunoreactive interleukin 1b from the rat hypothalamus in vitro: evidence for the involvement of the different signaling pathways. Endocrinology. 1998; 139 1031-1039
19 Pozzoli G, Tringali G, Dello R C, Vairano M, Preziosi P, Navarra P. HIV-1 Gp120 protein modulates corticotropin releasing factor synthesis and release via the stimulation of its mRNA from the rat hypothalamus in vitro: involvement of inducible nitric oxide synthase. J Neuroimmunol. 2001; 118 268-276
20 Forsling M L. Measurement of vasopressin in body fluids. In: Baylis PH, Padfield PL, (eds) Posterior Pituitary. New York; Marcel Dekker Inc 1985: 161-192
21 Korbonits M, Chitnis M M, Norman D, Rosenfelder N, Suliman M, Jones T H, Noonan K, Fabbri A, Besser G M, Burrin J M, Grossman A B. The release of leptin and its effect on hormone release from human pituitary adenomas. Clin Endocrinol (Oxf). 2001; 54 781-789
22 Galas L, Chartrel N, Kojima M, Kangawa K, Vaudry H. Immunohistochemical localization and biochemical characterization of ghrelin in the brain and stomach of the frog Rana esculenta. J Comp Neurol. 2002; 450 34-44
23 Nakazato M, Murakami N, Date Y, Kojima M, Matsuo H, Kangawa K, Matsukura S. A role for ghrelin in the central regulation of feeding. Nature. 2001; 409 194-198
24 Yasin S A, Costa A, Forsling M L, Grossman A. Interleukin-1 beta and interleukin-6 stimulate neurohypophysial hormone release in vitro. J Neuroendocrinol. 1994; 6 179-184
25 Wren A M, Small C J, Fribbens C V, Neary N M, Ward H L, Seal L J, Ghatei M A, Bloom S R. The hypothalamic mechanisms of the hypophysiotropic action of ghrelin. Neuroendocrinol. 2002; 76 316-324
26 Arvat E, Maccagno B, Ramunni J, Di Vito L, Broglio F, Deghenghi R, Camanni F, Ghigo E. Hexarelin, a synthetic growth hormone-releasing peptide, shows no interaction with corticotropin-releasing hormone and vasopressin on adrenocorticotropin and cortisol secretion in humans. Neuroendocrinol. 1997; 66 432-438

1 These data were presented at the September 2002 Meeting of the European Neuroendocrine Association, Munich, Germany.

M. Korbonits M.D., PhD.

MRC Clinician Scientist · Senior Lecturer in Endocrinology · Endocrine Oncology · Department of Endocrinology · St. Bartholomew's Hospital

59 Bartholomew Close · Unit 1.1 · London · EC1A 7BE · UK

Phone: +44(20)76018613 or 8746

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Email: m.korbonits@qmul.ac.uk