Melanocortin

proopiomelanocortin derivatives
POMC
     
γ-MSH ACTH β-lipotropin
         
  α-MSH CLIP γ-lipotropin β-endorphin
       
    β-MSH  

The melanocortins are a group of peptide hormones which include adrenocorticotropic hormone (ACTH) and the different forms of melanocyte-stimulating hormone (MSH),[1] and are derived from proopiomelanocortin (POMC) in the pituitary gland.[2] The melanocortins exert their effects by binding to and activating the melanocortin receptors.[1]

There are 5 melanocortin receptors (MCR) and all of them are G protein–coupled receptors. In the brain, only MC3R and MC4R are expressed and their endogenous ligand is α-MSH. Agouti-related peptide (AgRP) is the endogenous antagonist.[3]

Function

The melanocortin system is one of the mammalian body's tools to regulate food intake in a push-pull fashion.[4] The only neurons known to release melanocortins are located in the arcuate nucleus of the hypothalmus. Accordingly, there is a subpopulation called POMC neurons and one called AgRP neurons.[5] When POMC neurons release α-MSH, appetite is decreased. On the other hand, when AgRP neurons release AgRP, appetite is stimulated. Leptin, the energy surfeit hormone, and Ghrelin, the hunger hormone, are upstream regulators of the melanocortin system in the brain.[5] These hormones also regulate the release of peptides other than the melanocortins.

References

  1. 1 2 Gantz I, Fong TM (March 2003). "The melanocortin system". Am. J. Physiol. Endocrinol. Metab. 284 (3): E468–74. doi:10.1152/ajpendo.00434.2002. PMID 12556347.
  2. ↑ Raffin-Sanson ML, de Keyzer Y, Bertagna X (August 2003). "Proopiomelanocortin, a polypeptide precursor with multiple functions: from physiology to pathological conditions". Eur. J. Endocrinol. 149 (2): 79–90. doi:10.1530/eje.0.1490079. PMID 12887283.
  3. ↑ Yoon, Ye Ran; Baik, Ja-Hyun (2015-12-01). "Melanocortin 4 Receptor and Dopamine D2 Receptor Expression in Brain Areas Involved in Food Intake". Endocrinology and Metabolism. 30 (4). doi:10.3803/enm.2015.30.4.576. ISSN 2093-596X.
  4. ↑ Zhou, Yingjiang; Rui, Liangyou (2013-06-01). "Leptin signaling and leptin resistance". Frontiers of Medicine. 7 (2): 207–222. doi:10.1007/s11684-013-0263-5. ISSN 2095-0217. PMC 4069066.
  5. 1 2 Klok, M. D.; Jakobsdottir, S.; Drent, M. L. (2007-01-01). "The role of leptin and ghrelin in the regulation of food intake and body weight in humans: a review". Obesity Reviews. 8 (1): 21–34. doi:10.1111/j.1467-789x.2006.00270.x. ISSN 1467-789X.


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