Distinct functions of neuromedin u and neuromedin s in orange-spotted grouper.

Neuromedin U (NMU) and neuromedin S (NMS) play inhibitory roles in the regulation of food intake and energy homeostasis in mammals. However, their functions are not clearly established in teleost fish. In the present study, nmu and nms homologs were identified in several fish species. Subsequently, their cDNA sequences were cloned from the orange-spotted grouper (Epinephelus coioides). Sequence analysis showed that the orange-spotted grouper Nmu proprotein contains a 21-amino acid mature Nmu peptide (Nmu-21). The Nms proprotein lost the typical mature Nms peptide, but it retains a putative 34-amino acid peptide (Nmsrp). In situ hybridization revealed that nmu- and nms-expressing cells are mainly localized in the hypothalamic regions associated with appetite regulation. Food deprivation decreased the hypothalamic nmu mRNA levels but induced an increase of nms mRNA levels. Periprandial expression analysis showed that hypothalamic expression of nmu increased significantly at 3 h post-feeding, while nms expression was elevated at the normal feeding time. I.p. injection of synthetic Nmu-21 peptide suppressed the hypothalamic neuropeptide y (npy) expression, while Nmsrp administration significantly increased the expression of npy and orexin in orange-spotted grouper. Furthermore, the mRNA levels of LH beta subunit (lhβ) and gh in the pituitary were significantly down-regulated after Nmu-21 peptide administration, while Nmsrp was able to significantly stimulate the expression of FSH beta subunit (fshβ), prolactin (prl), and somatolaction (sl). Our results indicate that nmu and nms possess distinct neuroendocrine functions and pituitary functions in the orange spotted grouper.