Mechanism of appetite regulating peptides

1、人ghrelin启动子活性的调控为了检测胃产生的生长激素释放和食欲刺激激素ghrelin的基因表达，我们构建了人ghrelin启动子报告载体并分析了启动子活性。在内源性表达Ghrelin mRNA的培养细胞（如TT或ECC10细胞）中，Ghrelin启动子活性较高，表明这些细胞含有充分表达人Ghrelin所需的因子。人胃促生长素启动子包含正调控元件和负调控元件。将含有人饥饿素启动子-1600片段的报告载体转染培养细胞后，观察到启动子活性瞬间下降。我们研究了几种转录因子对胃饥饿素启动子活性的影响；NF-kB被抑制，而Nkx2.2（一种含有同源结构域的转录因子，对胰腺中生长素产生细胞的发育很重要）则激活启动子活性。脂多糖（LPS）结合toll样受体4，其下游信号激活NF-kB。由于LPS抑制ghrelin表达水平，LPS可能通过激活NF-kB抑制ghrelin基因表达。UNeuromedin U （NMU）是1985年首次从猪脊髓中分离到的一种无氧肽。由于脑垂体前叶中大量存在NMU，我们研究了NMU对促性腺激素分泌的影响。脑垂体中均表达NMU及其受体NMUR1和NMUR2。NMU抑制大鼠垂体前细胞LH和FSH的释放。此外，nmu缺陷小鼠表现出阴道开口早发性。LHbeta/FSHbeta比率是青春期开始的一个指标，在年轻的nmu缺陷小鼠中很高。这些结果表明，NMU抑制促性腺激素分泌并调节青春期的发生。

1, Regulation of the human ghrelin promoter activityTo examine the gene expression of ghrelin, a growth hormone-releasing and appetite-stimulating hormone produced by the stomach, we constructed human ghrelin promoter-reporter vectors and analyzed promoter activity. Ghrelin promoter activity was high in cultured cells that endogenously express ghrelin mRNA, such as TT or ECC10 cells, indicating that these cells contain the factors necessary for full expression of human ghrelin. The human ghrelin promoter contains both positive and negative regulatory elements. A transient decrease in promoter activity was observed following transfection of a reporter vector containing the -1600 fragment of the human ghrelin promoter into cultured cells. We examined the effect of several transcription factors on ghrelin promoter activity ; NF-kB suppressed, while Nkx2.2, a homeodomain-containing transcription factor important for ghrelin-producing cell development in the pancreas, activates promoter activity. Lipopolysaccharide (LPS) binds Toll-like receptor 4, whose downstream signaling activates NF-kB. As LPS suppresses ghrelin expression levels, LPS may suppress ghrelin gene expression by activating NF-kB.2, Regulation of gonadotropin secretion and puberty onset by neuromedin UNeuromedin U (NMU), an anorexigenic peptide, was originally isolated from porcine spinal cord in 1985. As NMU is abundant in the anterior pituitary gland, we investigated the effects of NMU on gonadotropin secretion. Both NMU and its receptors, NMUR1 and NMUR2, were expressed in the pituitary gland. NMU suppressed LH and FSH releases from rat anterior pituitary cells. Moreover, NMU-deficient mice exhibit an early onset of vaginal opening. The LHbeta/FSHbeta ratio, which is an index of puberty onset, is high in young NMU-deficient mice. These results indicate that NMU suppresses gonadotropin secretion and regulates the onset of puberty.