Melanocyte-stimulating hormone
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The melanocyte-stimulating hormones, known collectively as MSH, also known as melanotropins or intermedins, are a family of
Biosynthesis
The various forms of MSH are generated from different cleavages of the
Function
Acting through
: 1210Acting in the hypothalamus, α-MSH suppresses appetite.[4]: 419 α-MSH secreted in the hypothalamus also contributes to sexual arousal.[6]
In amphibians
In some animals (such as the claw-toed frog
In humans
An increase in MSH will cause darker skin in humans too. MSH increases in humans during pregnancy. This, along with increased estrogens, causes increased pigmentation in pregnant women. Cushing's disease due to excess adrenocorticotropic hormone (ACTH) may also result in hyperpigmentation, such as acanthosis nigricans in the axilla. Most people with primary Addison's disease have darkening (hyperpigmentation) of the skin, including areas not exposed to the sun; characteristic sites are skin creases (e.g. of the hands), nipple, and the inside of the cheek (buccal mucosa), new scars become hyperpigmented, whereas older ones do not darken. This occurs because MSH and ACTH share the same precursor molecule, proopiomelanocortin (POMC).
Different levels of MSH are not the major cause of variation in
Structure of MSH
| POMC | |||||||||
| γ-MSH | ACTH | β-lipotropin | |||||||
| α-MSH | CLIP | γ-lipotropin | β-endorphin |
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| β-MSH | |||||||||
The different forms of MSH belong to a group called the melanocortins. This group includes ACTH, α-MSH, β-MSH, and γ-MSH; these peptides are all cleavage products of a large precursor peptide called proopiomelanocortin (POMC). α-MSH is the most important melanocortin for pigmentation.
The different forms of MSH have the following
| α-MSH: | Ac-Ser-Tyr-Ser-Met-Glu-His-Phe-Arg-Trp-Gly-Lys-Pro-Val |
| β-MSH (human): | Ala-Glu-Lys-Lys-Asp-Glu-Gly-Pro-Tyr-Arg-Met-Glu-His-Phe-Arg-Trp-Gly-Ser-Pro-Pro-Lys-Asp |
| β-MSH (porcine): | Asp-Glu-Gly-Pro-Tyr-Lys-Met-Glu-His-Phe-Arg-Trp-Gly-Ser-Pro-Pro-Lys-Asp |
| γ-MSH: | Tyr-Val-Met-Gly-His-Phe-Arg-Trp-Asp-Arg-Phe-Gly |
Synthetic MSH
Synthetic
- squamous cell carcinoma (a form of skin cancer).[7]
- An additional analogue called melanotan II causes enhanced libido and erections in most male test subjects and arousal with corresponding genital involvement in most female test subjects.[8] Bremelanotide (formerly PT-141) which stemmed from melanotan II research is currently under development for its aphrodisiac effects. These effects are mediated by actions in the hypothalamus on neurons that express MC3 and MC4 receptors.
See also
- Melanocyte-inhibiting factor
- Agouti-related peptide
- Agouti signalling peptide
- Nelson's syndrome
References
- ISBN 978-0-07-176401-8.
- PMID 15383650.
- ^ ISBN 978-0-07-174889-6.
- ^ ISBN 978-0-205-23981-8.
- ^ ISBN 978-0-07-162442-8.
- PMID 17584130.
- ^ Clinuvel FAQs Archived 2008-04-11 at the Wayback Machine
- S2CID 22559801.
Further reading
- Millington GW (May 2006). "Proopiomelanocortin (POMC): the cutaneous roles of its melanocortin products and receptors". Clin. Exp. Dermatol. 31 (3): 407–12. S2CID 25213876.
- Millington GW (2007). "The role of proopiomelanocortin (POMC) neurones in feeding behaviour". Nutr Metab (Lond). 4: 18. PMID 17764572.
External links
- Melanocyte-Stimulating+Hormones at the U.S. National Library of Medicine Medical Subject Headings (MeSH)