摘要
非编码RNA(non-coding RNA,ncRNA)是一类没有或只有有限编码蛋白能力的RNA,主要包括微小RNA(microRNA,miRNA)、长链非编码RNA(long non-coding RNA,lncRNA)、环状RNA(circular RNA,circRNA)、转运RNA(transfer RNA,tRNA)、PIWI相互作用RNA(PIWI-interacting RNA,piRNA)和核小RNA(small nucleolar RNA,snoRNA)。目前,研究已经发现ncRNA在调控胰岛β细胞功能及胰岛素信号通路传导过程中发挥着核心作用,而胰岛素信号传导阻滞是糖尿病发生的重要原因。因此,本文综述了近年来ncRNA与胰岛素信号通路之间的调控关系的研究进展,同时探讨了ncRNA作为糖尿病潜在治疗靶点及临床诊断标志物的可能性,以期为糖尿病的治疗与诊断提供参考。
糖尿病是一种由于胰岛素抵抗、胰岛素分泌不足或胰高血糖素分泌过多而引起的代谢性疾
随着测序技术的发展和相关研究的不断深入,大量非编码RNA(non-coding RNA,ncRNA)被证实与糖尿病的发病存在明显的相关性。与健康人群相比,大量的ncRNA在糖尿病患者中的表达水平发生显著变化,并通过调控胰岛素信号通路参与糖尿病的发生和发展。已有研究证实多种类别的ncRNA在调控肥胖和糖尿病的过程中发挥着重要作
ncRNA是一类没有或只有有限编码能力的RNA,主要包括微小RNA(microRNA,miRNA)、长链非编码RNA(long non-codingRNA,lncRNA)、环状RNA(circular RNA,circRNA)、转运RNA(transfer RNA,tRNA)、PIWI相互作用RNA(PIWI-interacting RNA,piRNA)和核小RNA(small nucleolar RNA,snoRNA
miRNA是一种长度为18~21 nt的ncRNA。其体内产生过程是由DNA聚合酶Ⅱ将miRNA基因从DNA转录为pri-miRNA,pri-miRNA经过两次加工后将变成miRNA。众所周知,miRNA通过与mRNA的3′UTR区进行完全或非完全互补配对结合来干扰靶基因的表达进而影响蛋白质的翻
lncRNA是长度超过200 nt的不具有或者只有部分编码能力的RNA,同样具有调控基因表达的生物学功能。根据基因组上与蛋白编码基因的位置关系,lncRNA主要分为5类:①正义lncRNA(sense lncRNA);②反义lncRNA(antisense lncRNA);③双向lncRNA(bidirectional lncRNA);④内含子lncRNA(intronic lncRNA);⑤基因间lncRNA(long intergenic noncoding RNA,lincRNA
circRNA是一种通过非经典反向剪接形成的具有环状结构的非编码RNA,由于没有5′端帽子结构和3′端poly(A)结构,其比线性RNA具有更好的稳定
众所周知,tRNA主要作用是携带氨基酸进入核糖体,在mRNA指导下参与蛋白质的合成过程。在大多数细胞中,tRNA占总RNA的4%~10%,是一类相当稳定的RNA。然而越来越多的证据表明,在各种病理条件(比如糖尿病)下,tRNA的转录后修饰会失调甚至可能会被降解产生tRNA衍生片段(tRNA fragment,tRF
除了miRNA、lncRNA、circRNA、tRNA之外,piRNA和snoRNA也是最近被发现的非编码RNA。piRNA是一类近年在动物生殖系中发现的、长度约为24~35 nt的小分子ncRNA。piRNA含有2′-O-甲基修饰的3′端,并通过与PIWI亚家族的Argonautes蛋白发生相互作用进而使目标基因转录本沉
胰岛素抵抗是糖尿病发生的一个重要因素。胰岛素抵抗主要发生在特定的外周靶组织中,如肝脏、肌肉和脂肪组织,但也发生在胰岛β细胞
胰岛素与胰岛素受体(insulin receptor,INSR)结合后激活的INSR信号会募集胰岛素受体底物(insulin receptor substrate,IRS)家族的分子,尽管已知有6种IRS亚型,但在代谢过程中功能最强的是IRS1和IRS

图1 胰岛素信号通路示意图
INSR:胰岛素受体;IRS:胰岛素受体底物;PI3K:磷脂酰肌醇-3激酶;PIP2:磷脂酰肌醇-4,5-二磷酸;PIP3:磷脂酰肌醇-3,4,5-三磷酸;PDK1:3-磷酸肌醇依赖性蛋白激酶1;PKB/AKT:蛋白激酶B;mTORC2:mTOR复合物2;AS160/TBC1D4:TBC1域家族成员4;GSK-3β:糖原合成酶激酶-3β;FOXO:叉头转录因子;GLUT4:葡萄糖转运蛋白4
在过去的几年中,miRNA被认为是控制包括胰岛素信号通路在内的许多信号通路的关键阻滞器。miRNA通过调节胰岛素信号通路中关键基因的表达发挥作用,这在肝脏、肌肉和脂肪组织等多个胰岛素靶器官中都得到了印证。
肝脏是人体重要的代谢器官,在糖脂代谢中有核心作用,肝脏胰岛素抵抗是T2D的一个标志。在肝细胞中,可被胰岛素激活的AKT蛋白主要抑制葡萄糖的产生和促进糖原的合成。研究发现,在HepG2人肝细胞中miR-424-5p与INSR的3′UTR序列能直接结合,miR-424-5p的过表达诱导了INSR基因转录水平和蛋白水平的降
肌肉是人体内最大的胰岛素敏感组织,对全身新陈代谢非常重要。肌肉胰岛素抵抗的特征是胰岛素刺激下的葡萄糖摄取和利用受损。Zhu
脂肪细胞是胰岛素的靶器官之一。Teleman
虽然仅有少数lncRNA被证实参与了胰岛素信号通路的级联过程(
Goyal
lncRNA H19除了能调控肝脏胰岛素信号传导,也能影响肌肉中的胰岛素信号传导。Gao
Degirmenci
circRNA是缺乏5′帽子结构和3′poly(A)结构的共价闭合连续环状RNA。该特点使circRNA非常稳定,并且对核酸外切酶和RNase R酶具有抵抗力。因此,近年来人们对circRNA给予了更多的关注,circRNA已被建议作为新一代的生物标志物和许多疾病的潜在治疗靶标。
Cai
circRNA在肌肉胰岛素抵抗和脂肪组织胰岛素抵抗中的研究还鲜有报道。但Liu
尽管tRNA、piRNA、snoRNA直接作用于胰岛素信号通路的研究还鲜有报道,但是已经有一些关于这些类型ncRNA在代谢性疾病中的生物学功能和发病机制的研究(
tRNA突变、tRNA修饰异常、tRNA氨酰化异常均会加速糖尿病的发生与发展。tRNA修饰可能影响tRNA的稳定性、功能以及翻译准确性和效率,因此tRNA修饰缺陷可能对蛋白质合成产生深远的影
Henaoui
除了piRNA,也有少量文献报道了snoRNA在糖尿病中的作用。Lee
越来越多的证据表明,不同类别的ncRNA直接参与了胰岛素信号通路、胰岛功能的控制和糖尿病的发生。事实上,在动物模型中改变选定的ncRNA在体内的含量可以成功地预防或治疗糖尿
前期研究人员所做的工作为ncRNA能够调控胰岛素信号通路及糖尿病的发生与发展提供了有力的证据。值得注意的是,ncRNA除了能独立地在多个代谢器官中发挥作用外,不同类别的ncRNA之间也存在着相互作用。随着糖尿病分子机制研究的不断深入,纠正失调ncRNA水平的治疗策略研究也逐步在动物实验中展开。目前,已有研究人员使用miRNA模拟物或miRNA抑制剂来调节疾病条件下miRNA的表
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