PT - JOURNAL ARTICLE AU - Peter Kirwan AU - Richard Kay AU - Bas Brouwers AU - Vicente Herranz-Perez AU - Magdalena Jura AU - Pierre Larraufie AU - Jason Pembroke AU - Theresa Bartels AU - Anne White AU - Fiona Gribble AU - Frank Reimann AU - I. Sadaf Farooqi AU - Stephen O’Rahilly AU - Florian T. Merkle TI - Human POMC processing <em>in vitro</em> and <em>in vivo</em> revealed by quantitative peptidomics AID - 10.1101/257121 DP - 2018 Jan 01 TA - bioRxiv PG - 257121 4099 - http://biorxiv.org/content/early/2018/01/31/257121.short 4100 - http://biorxiv.org/content/early/2018/01/31/257121.full AB - Human obesity can result from the aberrant production or processing of proopiomelanocortin (POMC) in hypothalamic neurons, but it is unclear which human POMC-derived peptides are most relevant to body weight regulation. To address this question, we analysed both hypothalamic neurons derived from human pluripotent stem cells (hPSCs) and primary human hypothalamic tissue using quantitative liquid chromatography tandem mass spectroscopy (LC-MS/MS). In both in vitro- and in vivo-derived samples, we found that POMC was processed into β-melanocyte stimulating hormone (β-MSH), whose existence in the human brain has been controversial. β-MSH and desacetyl α-MSH (d-α-MSH) were produced at roughly equimolar concentrations and in vast excess to acetylated α-MSH (5-to 200-fold), suggesting that the importance of both d-α-MSH and β-MSH to human obesity has been underestimated. Since body weight is sensitive to changes in MSH concentration, we asked whether hPSC-derived hypothalamic neurons could provide mechanistic insights into the processing and secretion of MSH peptides. We found that cultured human hypothalamic neurons appropriately trafficked POMC and its derivatives, and robustly (P&lt;0.0001) secreted them when depolarised. Furthermore, the adipocyte-derived hormone leptin significantly (P&lt;0.01) promoted their production of both d-α-MSH and β-MSH. These results establish hPSC-derived hypothalamic neurons as a model system for studying human-specific aspects of POMC processing that might be therapeutically harnessed to treat obesity.