|Locus||Chr. 2 p23|
Lipotropin is the name for two hormones produced by the cleavage of pro-opiomelanocortin (POMC). The anterior pituitary gland produces the pro-hormone POMC, which is then cleaved again to form adrenocorticotropin (ACTH) and β-lipotropin (β-LPH).
β-Lipotropin is a 90-amino acid polypeptide that is the carboxy-terminal fragment of POMC. It was initially reported to stimulate melanocytes to produce melanin. It was also reported to perform lipid-mobilizing functions such as lipolysis and steroidogenesis. However, no subsequent studies have been published that support these early findings and no receptor has been identified for β-lipotropin.
β-Lipotropin can be cleaved into smaller peptides. In humans, γ-lipotropin, β-MSH, and β-endorphin, are all possible fragments of β-lipotropin. β-Lipotropin is the predominant opioid of the anterior human and rat pituitary gland. It is found in essentially equimolar concentrations to that of corticotropin. Evidence shows that β-Lipotropin is metabolized into endorphins that can greatly affect mood and behavior and is thus regarded as a prohormone.
γ-lipotropin is the amino-terminal peptide fragment of β-lipotropin. In humans, it has 56 amino acids. Gamma lipotropin is identical to the first 56 amino acid sequences of β-lipotropin. It can be cleaved to β-melanocyte stimulating hormone.
Use in sport
Lipotropin has also, under its alternate name AOD-9604 (Anti-Obesity Drug-9604), been connected with controversies in Australian Rules Football. Allegations have arisen around the use of the drug and its administration to players of the Essendon Football Club as a supplement, including weekly administration to players in the 2012 season. The matters are currently under investigation due to the relationship between Lipotropin and growth hormones, as noted by club medical staff.
- Li CH, Chung D (April 1976). "Isolation and structure of an untriakontapeptide with opiate activity from camel pituitary glands". Proceedings of the National Academy of Sciences of the United States of America. 73 (4): 1145–8. Bibcode:1976PNAS...73.1145L. doi:10.1073/pnas.73.4.1145. PMC 430217. PMID 1063395.
- Spiess J, Mount CD, Nicholson WE, Orth DN (August 1982). "NH2-terminal amino acid sequence and peptide mapping of purified human beta-lipotropin: comparison with previously proposed sequences". Proceedings of the National Academy of Sciences of the United States of America. 79 (16): 5071–5. Bibcode:1982PNAS...79.5071S. doi:10.1073/pnas.79.16.5071. PMC 346829. PMID 6956916.
- Lazarus LH, Ling N, Guillemin R (June 1976). "beta-Lipotropin as a prohormone for the morphinomimetic peptides endorphins and enkephalins". Proceedings of the National Academy of Sciences of the United States of America. 73 (6): 2156–9. Bibcode:1976PNAS...73.2156L. doi:10.1073/pnas.73.6.2156. PMC 430469. PMID 1064883.
- Peptides Direct information page, accessed 26 August 2013
- AFL Statement of Charges against James Hird and Essendon Football Club, accessed 26 August 2013 
- beta-Lipotropin at the US National Library of Medicine Medical Subject Headings (MeSH)
- gamma-Lipotropin at the US National Library of Medicine Medical Subject Headings (MeSH)
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