孤儿核受体Nr5a1通过调控自噬溶酶体降解途径影响胰岛β细胞功能及其分子机制研究

Insulin secretory dysfunction of pancreatic β cell induced by lipotoxicity is important for type 2 diabetes. Orphan nuclear receptors are protein family important for lipid metabolism. But it remains largely unknown about how orphan nuclear receptors affect insulin secretion. In our previous studies, palmitate induced β cell insulin secretion deficiency, during which quantitative RT-PCR showed one of the receptors Nr5a1 was down-regulated obviously. Overexpression of Nr5a1 in Min6 promoted insulin secretion inhibited by palmitate. To answer the scientific question “How Nr5a1 regulates lipotoxicity induced β cell Insulin secretory dysfunction?”, we found that overexpression of Nr5a1 regulated some genes related to autophagy through RNA-seq and quantitative RT-PCR. A series experiments indicated that Nr5a1 binds to the promotors of these genes, which mediated autophagy-lysosome degradation pathway. Based on these previous studies, we are going to illustrate whether Nr5a1 regulates insulin secretion deficiency induced by lipotoxicity through autophagy-lysosome degradation pathway”, by performing ChIP, fluorescence assay of RFP-GFP-LC3B and immunofluorescence assay, aiming at exploring the mechanisms of how obesity induced diabetes and leading to new therapeutic target.

脂毒性作用下胰岛β细胞的功能异常在2型糖尿病中起重要作用。孤儿核受体对脂代谢有重要作用，本团队前期研究中用棕榈酸酯诱导脂毒性β细胞模型，通过实时荧光定量PCR筛选出明显下调的家族成员Nr5a1，而过表达Nr5a1可促进脂毒性β细胞模型的胰岛素分泌功能。围绕“Nr5a1如何调控脂毒性β细胞模型胰岛素分泌”这一问题，本团队对Nr5a1高表达的β细胞行RNA-seq及实时荧光定量PCR发现自噬相关基因表达改变，经一系列实验证明Nr5a1结合相应启动子调控靶基因，通过其靶基因调控自噬溶酶体降解途径。基于前期研究，本团队拟利用染色体免疫共沉淀及自噬双标荧光报告系统等技术手段深入阐明“Nr5a1是否通过促进自噬溶酶体降解途径调控β细胞胰岛素分泌功能及其分子机制”，旨在为肥胖相关2型糖尿病的发病机制提供新的理论依据，寻找新的治疗靶点。

NR5A1（SF1）是一种核受体，作为潜在的药物靶点，表达在下丘脑腹内侧核发挥调控肥胖和胰岛素抵抗的作用。本研究探究SF1在人类及小鼠胰岛中的表达和及其功能。SF1在普通C57BL/6J小鼠的胰岛中几乎不表达，而在短期内高脂饮食（HFD）喂养的小鼠胰岛中高表达；长期HFD后胰岛中的SF1表达下降。在HFD喂养组，与βSF1+/+及杂合子相比，βSF1-/-雄性及雌性小鼠表现出提早出现的糖耐量异常及葡萄糖刺激胰岛素分泌（GSIS）减弱。同样地，以腺相关病毒为载体在HFD及db/db小鼠胰β细胞特异性过表达SF1，通过促胰岛素作用改善糖代谢。进一步通过小鼠胰岛及MIN6细胞系验证了SF1是通过改善线粒体ATP合成从而促进GSIS。同时我们也探索了：1）Nr2a1通过促进PGC1-α的表达抑制棕榈酸诱导的Min6细胞系凋亡；2）抗疟药氯喹（CQ）及其衍生物羟氯喹（HCQ）对眶周成纤维细胞的作用及其机制；3）GIP调控人网膜脂肪组织ADSCs在脂肪可塑性的作用及机制；4）miR-1275靶向PRDM16调控人大网膜脂肪来源干细胞棕色化的作用及机制；5）短期胰岛素强化治疗相关研究。