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14-September-2008 18:02:46 - Ghrelin Ghrelin/obestatin preprohormone Identifiers Symbols GHRL; MTLRP; ghrelin; obestatin External IDs OMIM: 605353 MGI: 1930008 HomoloGene: 9487 Gene ontology Molecular function: growth hormone-releasing hormone activity ghrelin receptor binding Cellular component: extracellular region extracellular space cytoplasm Biological process: G-protein coupled receptor protein signaling pathway adult feeding behavior hormone-mediated signaling growth hormone secretion positive regulation of appetite positive regulation of body size Orthologs Human Mouse Entrez 51738 58991 Ensembl ENSG00000157017 ENSMUSG00000064177 Uniprot Q9UBU3 Q9EQX0 Refseq NM_016362 mRNA NP_057446 protein NM_021488 mRNA NP_067463 protein Location Chr 3: 10.3 - 10.31 Mb Chr 6: 113.68 - 113.69 Mb Pubmed search 1 2 Ghrelin is a hormone produced mainly by P/D1 cells lining the fundus of the human stomach and epsilon cells of the pancreas that stimulates appetite.1 Ghrelin levels increase before meals and decrease after meals. It is considered the counterpart of the hormone leptin, produced by adipose tissue, which induces satiation when present at higher levels. In some bariatric procedures, the level of ghrelin is reduced in patients, thus causing satiation before it would normally occur. Ghrelin is also produced in the hypothalamic arcuate nucleus where it stimulates the secretion of growth hormone from the anterior pituitary gland.2. Receptors for ghrelin are expressed by neurons in the arcuate nucleus and the ventromedial hypothalamus. The ghrelin receptor is a G protein-coupled receptor, formerly known as the GHS receptor growth hormone secretagogue receptor. Ghrelin plays a significant role in neurotrophy, particularly in the hippocampus, and is essential for cognitive adaptation to changing environments and the process of learning.3 Recently, ghrelin has been shown to activate the endothelial isoform of nitric oxide synthase in a pathway that depends on various kinases including Akt.citation needed Contents 1 Forms 2 Mechanism of action 3 Roles of Ghrelin 4 Role in Disease 5 Relation to obestatin 6 History and name 7 Anti-obesity vaccine 8 References 9 External links Forms Ghrelin exists in an endocrinological inactive pure peptide and an active octanoylated form see Hexatropin. Other side chains than octanoyl were also observed. Mechanism of action Ghrelin has emerged as the first circulating hunger hormone. Ghrelin and synthetic ghrelin mimetics the growth hormone secretagogues increase food intake and increase fat mass45 by an action exerted at the level of the hypothalamus. They activate cells in the arcuate nucleus67 that include the orexigenic neuropeptide Y NPY neurones8. Ghrelin-responsiveness of these neurones is both leptin and insulin sensitive9. Ghrelin also activates the mesolimbic cholinergic-dopaminergic reward link, a circuit that communicates the hedonic and reinforcing aspects of natural rewards, such as food, as well as of addictive drugs, such as ethanol.1011 12 Roles of Ghrelin Lung Development In the fetuses, it seems that ghrelin is early produced by the lung and promotes its growth.13 Learning and Memory Animal models indicate that ghrelin may enter the hippocampus from the bloodstream, enhancing learning and memory.14 It is suggested that learning may be best during the day and when the stomach is empty, since ghrelin levels are higher at these times. In rodents, X/A-like cells produce ghrelin. Stress-Induced Depression A study appearing in the journal Nature Neuroscience June 15, 2008 online suggests that the hormone might help defend against symptoms of stress-induced depression and anxiety.15 To test whether ghrelin could regulate depressive symptoms brought on by chronic stress, the researchers subjected mice to daily bouts of social stress, using a standard laboratory technique that induces stress by exposing normal mice to very aggressive bully mice. Such animals have been shown to be good models for studying depression in humans. The researchers stressed both wild-type mice and altered mice that were unable to respond to ghrelin. They found that after experiencing stress, both types of mice had significantly elevated levels of ghrelin that persisted at least four weeks after their last defeat encounter. The altered mice, however, displayed significantly greater social avoidance than their wild-type counterparts, indicating an exacerbation of depression-like symptoms. They also ate less than the wild-type mice.16 Role in Disease Ghrelin levels in the plasma of obese individuals are lower than those in leaner individuals3 except in the case of Prader-Willi syndrome-induced obesity. Those suffering from the eating disorder anorexia nervosa have high plasma levels of ghrelin compared to both the constitutionally thin and normal-weight controls4. These findings suggest that ghrelin plays a role in both anorexia and obesity. Yildiz and colleagues found that the level of ghrelin increases during the time of day from midnight to dawn in thinner people, suggesting a flaw in the circadian system of obese individuals.17 Professor Cappuccio of the University of Warwick has recently discovered that short sleep duration may also lead to obesity, through an increase of appetite via hormonal changes. Lack of sleep produces ghrelin, which stimulates appetite and creates less leptin which, amongst its many other effects, suppresses appetite. Ghrelin levels are also high in patients who have cancer-induced cachexia.18 Prader-Willi syndrome is also characterized by high fasting levels of ghrelin; here the ghrelin levels are associated with high food intake.19 At least one study found that gastric bypass surgery not only reduces the gut's capacity for food, but also dramatically lowers ghrelin levels compared to both lean controls and those who lost weight through dieting alone.20 Relation to obestatin Obestatin is a hormone that was found, in late 2005, to decrease appetite. Both obestatin and ghrelin are encoded by the same gene; the gene's product breaks apart to yield the two peptide hormones.21 The purpose of this mechanism is unknown. History and name The discovery of ghrelin was reported by Masayasu Kojima and colleagues in 1999.22 The name is based on its role as a growth hormone-releasing peptide, with reference to the Proto-Indo-European root ghre, meaning to grow. Anti-obesity vaccine Recently Scripps research scientists have developed an anti-obesity vaccine, which is directed against the hormone ghrelin.23 24The vaccine uses the immune system, specifically antibodies, to bind to selected targets, directing the body's own immune response against them. This prevents ghrelin from reaching the central nervous system, thus producing a desired reduction in weight gain. References ^ Inui A, Asakawa A, Bowers CY, et al 2004. Ghrelin, appetite, and gastric motility: the emerging role of the stomach as an endocrine organ. FASEB J. 18 3: 439-56. doi:10.1096/fj.03-0641rev. PMID 15003990. ^ Mondal, M.S., Date, Y., Yamaguchi, H., Toshinai, K., Tsuruta, T., Kangawa, K., Nakazato, M. 2005. Identification of ghrelin and its receptor in neurons of the rat arcuate nucleus. Regul. Pept 126: 55-59. doi:10.1016/j.regpep.2004.08.038. ^ Hunger hormone tied to learning. Retrieved on 2007-06-01. at The Scientist ^ Lall S, Tung LY, Ohlsson C, Jansson JO, Dickson SL 2001. Growth hormone GH-independent stimulation of adiposity by GH secretagogues. Biochem Biophys Res Commun 280 1: 132-138. doi:10.1006/bbrc.2000.4065. PMID 11162489. ^ Tschöp M, Smiley DL, Heiman ML 2000. Ghrelin induces adiposity in rodents. Nature 407 6806: 908-913. doi:10.1038/35038090. ^ Hewson AK, Dickson SL. 2000. Systemic administration of ghrelin induces Fos and Egr-1 proteins in the hypothalamic arcuate nucleus of fasted and fed rats. J Neuroendocrinol. 12 11: 1047-1049. doi:10.1046/j.1365-2826.2000.00584.x. PMID 11069119. ^ Dickson SL, Leng G, Robinson ICAF. 1993. Systemic administration of growth hormone-releasing peptide activates hypothalamic arcuate neurons. Neuroscience 54 2: 303-306. doi:10.1016/0306-45229390197-N. PMID 8492908. ^ Dickson SL, Luckman SM. 1997. Induction of c-fos messenger ribonucleic acid in neuropeptide Y and growth hormone GH-releasing factor neurons in the rat arcuate nucleus following systemic injection of the GH secretagogue, GH-releasing peptide-6. Endocrinology. 138 2: 771-777. doi:10.1210/en.138.2.771. PMID 9003014. ^ Hewson AK, Tung LY, Connell DW, Tookman L, Dickson SL. 2002. The rat arcuate nucleus integrates peripheral signals provided by leptin, insulin, and a ghrelin mimetic. Diabetes. 51 12: 3412-3419. year=2002. doi:10.2337/diabetes.51.12.3412. PMID 12453894. ^ Jerlhag E, Egecioglu, E, Dickson SL, Andersson M, Svensson L, Engel JA. 2004. Ghrelin Stimulates Locomotor Activity and Accumbal Dopamine-Overflow via Central Cholinergic Systems in Mice: Implications for its Involvement in Brain Reward. Addiction Biology 11 1: 45-54. doi:10.1111/j.1369-1600.2006.00002.x. PMID 16759336. ^ Jerlhag E, Egecioglu E, Dickson SL, Douhan A, Svensson L, Engel JA. 2007. Ghrelin administration into tegmental areas stimulates locomotor activity and increases extracellular concentration of dopamine in the nucleus accumbens. Addiction Biology 12: 6-16. doi:10.1111/j.1369-1600.2006.00041.x. PMID 17407492. ^ Hewson AK, Tung LY, Connell DW, Tookman L, Dickson SL. 2002. The rat arcuate nucleus integrates peripheral signals provided by leptin, insulin, and a ghrelin mimetic. Diabetes. 51 12: 3412-3419.. doi:10.2337/diabetes.51.12.3412. PMID 12453894. ^ Santos M, Bastos P, Gonzaga S, Roriz JM, Baptista MJ, Nogueira-Silva C, Melo-Rocha G, Henriques-Coelho T, Roncon-Albuquerque R Jr, Leite-Moreira AF, De Krijger RR, Tibboel D, Rottier R, Correia-Pinto J. 2006. Ghrelin expression in human and rat fetal lungs and the effect of ghrelin administration in nitrofen-induced congenital diaphragmatic hernia. Pediatr Res 59 4: 531-7. doi:10.1203/01.pdr.0000202748.66359.a9. PMID 16549524. ^ Learning and memory stimulated by gut hormone | Science Blog ^ Lutter M, Sakata I, Osborne-Lawrence S, Rovinsky SA, Anderson JG, Jung S, Birnbaum S, Yanagisawa M, Elmquist JK, Nestler EJ, Zigman JM June 15. The orexigenic hormone ghrelin defends against depressive symptoms of chronic stress. J Nat Neurosci. 11: 752. doi:10.1038/nn.2139. PMID 18552842. ^ Newswise: Hunger Hormone Increases During Stress, May Have Antidepressant Effect Retrieved on June 18, 2008. ^ Yildiz B, Suchard M, Wong M, McCann S, Licinio J 2004. Alterations in the dynamics of circulating ghrelin, adiponectin, and leptin in human obesity. Proc Natl Acad Sci U S A 101 28: 10434-9. doi:10.1073/pnas.0403465101. PMID 15231997. ^ Garcia J, Garcia-Touza M, Hijazi R, Taffet G, Epner D, Mann D, Smith R, Cunningham G, Marcelli M 2005. Active ghrelin levels and active to total ghrelin ratio in cancer-induced cachexia. J Clin Endocrinol Metab 90 5: 2920-6. doi:10.1210/jc.2004-1788. PMID 15713718. ^ Goldstone A, Thomas E, Brynes A, Castroman G, Edwards R, Ghatei M, Frost G, Holland A, Grossman A, Korbonits M, Bloom S, Bell J 2004. Elevated fasting plasma ghrelin in prader-willi syndrome adults is not solely explained by their reduced visceral adiposity and insulin resistance. J Clin Endocrinol Metab 89 4: 1718-26. doi:10.1210/jc.2003-031118. PMID 15070936. ^ Cummings D, Weigle D, Frayo R, Breen P, Ma M, Dellinger E, Purnell J 2002. Plasma ghrelin levels after diet-induced weight loss or gastric bypass surgery. N Engl J Med 346 21: 1623-30. doi:10.1056/NEJMoa012908. PMID 12023994. ^ Zhang J, Ren P, Avsian-Kretchmer O, Luo C, Rauch R, Klein C, Hsueh A 2005. Obestatin, a peptide encoded by the ghrelin gene, opposes ghrelin's effects on food intake. Science 310 5750: 996-9. doi:10.1126/science.1117255. PMID 16284174. ^ Kojima M, Hosoda H, Date Y, Nakazato M, Matsuo H, Kangawa K 1999. Ghrelin is a growth-hormone-releasing acylated peptide from stomach. Nature 402 6762: 656-60. doi:10.1038/45230. PMID 10604470. ^ Scripps.edu - 'Scripps Research Scientists Successfully Test New Anti-Obesity Vaccine' at The Scripps Research Institute ^ From the Cover: Vaccination against weight gain - Zorrilla et al. 103 35: 13226 - Proceedings of the National Academy of Sciences External links Ghrelin at Colorado State University InfoBiogen.fr - 'Ghrelin/MTLRP' motilin-related peptide NeuroEndo.org.uk - 'Ghrelin: A newly discovered hormone', Dr. Suzanne L. Dickson, University of Cambridge June 14, 2005 ScienceNews.org - 'Still Hungry? Fattening revelations-and new mysteries-about the hunger hormone', Janet Raloff, Science News, vol 167, no 14, p 216 April 2, 2005 Balancing Hunger Hormones - Web site reviewing role of ghrelin and leptin in obesity. Feeling Hungry Can Make You Happy MeSH ghrelin Retrieved from http://en..org/wiki/Ghrelin Categories: Genes on chromosome 3 | Human proteins | Neuropeptides | ObesityHidden categories: Protein pages needing a picture | All articles with statements | Articles with statements since August 2008 Views Article Discussion this page History Personal tools Log in / create account Navigation Main page Contents Featured content Current events Random article Search Go Search Interaction Community portal Recent changes Contact Donate to Help Toolbox What links here Related changes Upload file Special pages Printable version Permanent link Cite this page Languages Deutsch Þ‹Þ¨ÞˆÞ¬Þ€Þ¨Þ„Þ¦Þ?Þ° Français Italiano Nederlands 日本語 Polski РуÑ?Ñ?кий Suomi УкраїнÑ?ька This page was last modified on 25 August 2008, at 02:56
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