BHBA对大鼠下丘脑GHRH表达和分泌的影响及其机制

发布时间：2018-10-13 15:20

【摘要】：哺乳动物的生长发育由一系列复杂的神经内分泌免疫调节系统调控，它起源于下丘脑。而下丘脑分泌两种对于脑垂体细胞很重要的肽类：促生长激素释放激素GHRH和生长抑素SST。GHRH作用于脑垂体促进生长激素GH的分泌，从而增加肝脏和其他组织中胰岛素样生长因子类IGF-1的生成，而GH在肝脏以IGF-1的形式促进机体新陈代谢。 BHBA作为一种重要的脂肪酸代谢的中间代谢物，它的作用类似于葡萄糖，能够为大脑提供能量，尤其是新生婴儿。近年来，研究显示BHBA在下丘脑中能够调节激素的合成和分泌。然而，BHBA介导激素调节或者BHBA调节CHRH的合成和分泌机制的报道比较少。研究显示，BHBA能够通过GPR109A受体抑制LPS诱导的炎症。另有研究显示，BHBA能够通过GPR109A受体促进脂连素的分泌。本课题组在前期的研究中发现，在离体培养的下丘脑神经细胞中有BHBA的受体GPR109A的表达。因此，我们假设BHBA通过GPR109A及其下游信号调控GHRH的合成分泌。在我们的实验研究中，大鼠体内实验显示BHBA使GHRH基因转录显著下调。体外实验显示，BHBA处理离体培养的下丘脑神经细胞后GHRH的合成和分泌减少，但是当PTX预处理后，这种效应被抑制。在GT1-7细胞系中，，BHBA对GHRH的合成和分泌无明显作用。而在含有GPR109A受体的GT1-7细胞系中，BHBA对GHRH的合成和分泌明显抑制，且这一效应可被PTX阻断。此外，BHBA能显著下调同源基因Gsh-1转录水平，同样PTX也能阻断这种效应。蛋白免疫印迹结果显示，离体培养的下丘脑神经细胞中BHBA能激活ERK1/2，p38和JNK MAPK信号通路。且ERK1/2信号通路抑制剂U0126能减弱BHBA抑制Gsh-1表达、GHRH合成分泌的效应。这些结果提示，BHBA通过GPR109A/ERK1/2MAPK通路能下调Gsh-1的表达和GHRH的合成分泌。
[Abstract]:Mammalian growth and development are regulated by a series of complex neuroendocrine and immunomodulatory systems, which originate from the hypothalamus. However, hypothalamus secretes two kinds of peptides that are important to pituitary cells: growth hormone releasing hormone (GHRH) and somatostatin (SST.GHRH), which promote the secretion of growth hormone (GH) in pituitary gland. Thus increasing the production of insulin-like growth factor-like IGF-1 in liver and other tissues, while GH promotes the metabolism of the body in the form of IGF-1 in the liver. BHBA is an important intermediate metabolite of fatty acid metabolism. It acts like glucose and provides energy to the brain, especially newborn babies. In recent years, studies have shown that BHBA regulates hormone synthesis and secretion in the hypothalamus. However, there are few reports of BHBA mediating hormone regulation or BHBA regulating the synthesis and secretion of CHRH. Studies have shown that BHBA can inhibit LPS-induced inflammation through GPR109A receptors. Other studies have shown that BHBA promotes adiponectin secretion through GPR109A receptors. In our previous study, we found the expression of BHBA receptor GPR109A in cultured hypothalamic neurons. Therefore, we assume that BHBA regulates the synthesis and secretion of GHRH through GPR109A and its downstream signals. In our study, in vivo experiments in rats showed that BHBA significantly down-regulated the transcription of GHRH gene. In vitro experiments showed that the synthesis and secretion of GHRH decreased after BHBA treatment of cultured hypothalamic nerve cells, but this effect was inhibited after pretreatment with PTX. In GT1-7 cell line, BHBA has no effect on the synthesis and secretion of GHRH. In GT1-7 cell line containing GPR109A receptor, BHBA significantly inhibited the synthesis and secretion of GHRH, and this effect could be blocked by PTX. In addition, BHBA significantly down-regulated the transcription level of homologous gene Gsh-1, and PTX also blocked this effect. Western blot showed that BHBA could activate ERK1/2,p38 and JNK MAPK signaling pathway in cultured hypothalamic neurons. ERK1/2 signaling pathway inhibitor U0126 can attenuate the inhibitory effect of BHBA on Gsh-1 expression and GHRH synthesis and secretion. These results suggest that BHBA can down-regulate the expression of Gsh-1 and the synthesis and secretion of GHRH through GPR109A/ERK1/2MAPK pathway.
【学位授予单位】：吉林大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：S852.21

【共引文献】