Ghrelin
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Ghrelin is a hormone that is produced by cells lining the stomach which stimulates the appetite. Ghrelin levels are increased prior to a meal and decreased after a meal. It is considered the counterpart of the hormone leptin, produced by adipose tissue, which induces satiation when present at higher levels.
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Forms
Ghrelin exists in an inactive and and active (octanoylated) form.
Role in disease
Ghrelin levels in the plasma of obese individuals are lower than those in leaner individuals. Yildiz et al (2004) found that the level of ghrelin increases during the time of day from midnight to dawn in thinner people, suggesting a flaw in the circulatory system of obese individuals.
Those suffering from the eating disorder anorexia nervosa appear to have high plasma levels of ghrelin. Ghrelin levels are found to be increased in patients who have cancer-induced cachexia (Garcia et al 2005).
History and name
The discovery of ghrelin was reported by Masayasu Kojima et al in 1999. The name is based on its role as a "Growth Hormone RELeasing peptide", with allusion to the Proto-Indo-European root ghre meaning "to grow".
References
- Garcia JM, Garcia-Touza M, Hijazi RA, Taffet G, Epner D, Mann D, Smith RG, Cunningham GR, Marcelli M. Active ghrelin levels and active to total ghrelin ratio in cancer-induced cachexia. J Clin Endocrinol Metab 2005;90:2920-6. PMID 15713718.
- Kojima M, Hosoda H, Date Y, Nakazato M, Matsuo H, Kangawa K. Ghrelin is a growth-hormone-releasing acylated peptide from stomach. Nature 1999;402:656-60. PMID 10604470.
- Yildiz BO, Suchard MA, Wong ML, McCann SM, Licinio J. Alterations in the dynamics of circulating ghrelin, adiponectin, and leptin in human obesity. Proc Natl Acad Sci U S A 2004;101:10434-9. PMID 15231997.de:Ghrelin