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，并分析了启动子的活性。在内源性表达Ghrelin mRNA的培养细胞中，如TT或ECC10细胞中，Ghrelin启动子活性很高，表明这些细胞含有充分表达人Ghrelin所需的因子。人类Ghrelin启动子包含正性和负性调控元件。将含有人Ghrelin启动子-1600片段的报告载体导入培养细胞后，发现启动子活性一过性下降。我们研究了几种转录因子对ghrelin启动子活性的影响；NF-kB抑制了启动子的活性，而Nkx2.2，一种含有同源结构域的转录因子，对胰腺中ghrelin产生细胞的发育至关重要，激活了启动子的活性。脂多糖与Toll样受体4结合，Toll样受体4的下游信号转导激活了核因子-kB。由于内毒素抑制ghrelin的表达水平，因此内毒素可能通过激活核因子-kB来抑制ghrelin基因的表达。2.神经内分泌调节促性腺激素分泌和青春期启动的神经内酯U(NMU)最初是1985年从猪脊髓中分离得到的。由于NMU在垂体前叶中含量丰富，我们研究了NMU对促性腺激素分泌的影响。NMU及其受体NMUR1和NMUR2在脑下垂体均有表达。NMU抑制大鼠垂体前叶细胞释放黄体生成素和卵泡刺激素。此外，NMU缺陷的小鼠表现出较早的阴道开放。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抑制促性腺激素的分泌，调节青春期的开始。

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.