
Originally Posted by
fred9
Melanin-concentrating hormone (MCH [?]), a 19-amino acid orexigenic (appetite-stimulating) hypothalamic peptide, is an important regulator of energy homeostasis. It is cleaved from its precursor prepro-MCH (ppMCH) along with several other neuropeptides whose roles are not fully defined. Because pituitary hormones such as growth hormone (GH), ACTH, and thyroid-stimulating hormone affect body weight and composition, appetite, insulin sensitivity, and lipoprotein metabolism, we investigated whether MCH [?] exerts direct effects on the human pituitary to regulate energy balance using dispersed human fetal pituitaries (21-22 wk gestation) and cultured GH-secreting adenomas. We found that MCH receptor-1 [?] (MCH-R1 [?]), but not MCH receptor-2, is expressed in both normal (fetal and adult) human pituitary tissues and in GH cell adenomas. MCH [?] (10 nM) stimulated GH release from human fetal pituitary cultures by up to 62% during a 4-h incubation (P < 0.05). Interestingly, neuropeptide EI (10 nM), which is also cleaved from ppMCH, increased human GH secretion by up to 124% in fetal pituitaries. A milder, albeit significant, induction of GH secretion by MCH [?] (20%) was seen in cultured GH-secreting pituitary adenomas. A comparable stimulation of GH secretion was seen when cultured mouse pituitary cells were treated with MCH [?]. Treatment of cultured GH adenoma cells with MCH [?] (100 nM) induced extracellular signal-regulated kinases 1 and 2 phosphorylation, suggesting activation of MCH-R1 [?]. In aggregate, these data suggest that MCH [?] may regulate pituitary GH secretion and imply a potential cross-talk mechanism between appetite-regulating neuropeptides and pituitary hormones.