Tph1在CREB调控胰岛β细胞功能中的作用研究

Pancreatic β-cell dysfunction plays an important role in the development of type 2 diabetes. It has been demonstrated that tryptophan hydroxylase 1(Tph1) plays a key role in pregnancy-induced pancreatic β-cell functional adaptation. Our previous data showed that Tph1 overexpression in rat islets significantly potentiated glucose-stimulated insulin secretion. cAMP and calcium signals synergistically triggered Tph1 expression in rat islets. In addition, Exendin-4, a long-term analog of glucagon-like peptide 1, increased Tph1 expression in a glucose-dependent manner. It has been reported that cAMP and calcium can increase the transcriptional activity of CREB by inducing CREB phosphorylation and CRTC de-phosphorylation. In this study, we will use various activators and inhibitors of signal pathways, lenti-virus, reporter gene, ChIP, β-cell specific Tph1 transgenic rats and knockout mice to explore the mechanisms underlying cAMP and calcium-induced Tph1 expression, and the possible role of Tph1 as the target gene for CREB and GLP-1 analogues. This will provide possible therapeutic targets for type 2 diabetes.

胰岛功能缺陷是2型糖尿病发病的重要环节，近年研究发现色氨酸羟化酶1（Tph1）在妊娠诱导的胰岛功能代偿中起重要作用。本课题组前期研究发现胰岛β细胞过表达Tph1显著促进胰岛素分泌；cAMP和钙信号能协同上调大鼠胰岛Tph1表达。另外，GLP-1长效类似物Exendin-4葡萄糖依赖性地增加Tph1表达。已有文献报道，cAMP和钙信号可通过刺激cAMP反应元件结合蛋白（CREB）磷酸化以及其转录共激活因子（CRTC）去磷酸化的双重机制促进CREB下游靶基因的转录，本研究拟用多种信号通路活性调节剂、慢病毒转染、报告基因、ChIP、胰岛β细胞特异性Tph1转基因和基因敲除鼠模型，探索cAMP和钙信号协同调节胰岛Tph1表达的分子机制以及Tph1作为CREB的靶基因和GLP-1类似物作用靶点的可能性，最终为寻求具有胰岛β细胞保护作用的2型糖尿病治疗药物提供理论依据。

胰岛功能缺陷是2型糖尿病发病的重要环节，色氨酸羟化酶1（Tph1）在胰岛功能代偿中起重要作用。我们的研究发现，去乙酰化酶抑制剂可以显著增加胰岛功能并对胰岛细胞的基因表达进行重编程，其中Tph1的基因表达上调最为显著。体内外实验均证实，Tph1表达上升伴有血清素的合成和分泌增加，同时胰岛素分泌显著增加。胰岛β细胞特异性Tph1过表达大鼠的葡萄糖耐量显著增加，葡萄糖刺激的胰岛素分泌显著增强。胰岛β细胞特异性Tph1敲除胰岛经去乙酰化酶抑制剂处理后，其促泌能力显著降低。随着年龄的增加，敲除小鼠的糖耐量降低。进一步研究发现，HDAC1能去乙酰化并降低PKA催化亚基的活性，使CREB的磷酸化水平降低，转录活性随之降低。抑制HDAC1则能增加葡萄糖和Exendin-4诱导的Tph1表达。我们的研究结果揭示了HDAC1-PKA-Tph1信号系统在胰岛β细胞功能代偿中的重要作用。