microRNA-34a在硬脂酸诱导的外周组织胰岛素抵抗中的作用及机制研究

Insulin resistance (IR) has an important role in pathogenesis and evolution of type 2 diabetes. Studies have shown that free fatty acids is closely related with diabetes, especially saturated fatty acids, palmitic acid (PA) and stearic acid (SA), which cause IR in peripheral tissues, however, the mechanism is still unclear. In recent years, microRNA (miRNA) plays a crucial role in the process of IR and diabetes. Our previous study had found that compared with PA, high-SA diet induced-hyperglycemia was more significant, and SA-induced hepatic IR was also more obvious. Through miRNA microarray chip, we found that microRNA-34 (miR-34a) levels were significantly increased in liver tissue of high-SA diet-induced obesity mouse. The in vitro experiments confirmed that overexpression of miR-34a could induce IR in hepatic cells. Whether the increased miR-34a involves in the process of SA-induced hepatic IR? If so, what regulatory mechanism mediates the process? What is the mechanism of high-level expression of miR-34 promoted by SA? In addition to the liver tissue, whether miR-34a is also involved in the regulation of SA-induced IR in adipose and skeletal muscle tissues? Based on these questions, we will study systematically effects and mechanisms of miR-34a on SA-induced IR in peripheral tissues. Finally, with miR-34a as potential target, providing new therapeutic strategy to early prevention and treatment of type 2 diabetes.

胰岛素抵抗（IR）是2型糖尿病重要病理基础。游离脂肪酸与糖尿病密切相关，特别是饱和脂肪酸中的软脂酸（PA）和硬脂酸（SA），是导致IR的重要原因，然而机制尚不明确。microRNA（miRNA）在IR、糖尿病进程中扮演了重要角色。前期实验中发现与PA相比，高SA饮食引起血糖增高更为显著，且其诱导肝细胞IR也较为明显。通过miRNA芯片发现miR-34a在高SA饮食小鼠肝脏中显著增高。体外实验证实过表达miR-34a能够引起肝细胞发生IR。那么miR-34a是否参与SA诱导的肝脏IR？若参与此过程，miR-34a是通过何种机制进行调节的？SA又是如何促使miR-34a水平增高的？除了肝脏，miR-34a是否也参与调控了SA诱导的脂肪、骨骼肌IR？基于这些问题，本课题将全面系统研究miR-34a在SA诱导外周组织IR中的作用及机制，最终以miR-34a为靶点，为2型糖尿病的早期防治提供新思路。

胰岛素抵抗（IR）是多种代谢性疾病的重要病理基础，如2型糖尿病（T2DM）和非酒精性脂肪肝病（NAFLD）等，因此改善IR是防治T2DM、NAFLD等多种代谢疾病的关键。IR发生机制复杂，有证据表明游离脂肪酸，特别是饱和脂肪酸，如软脂酸（PA）和硬脂酸（SA），是导致IR的重要原因，然而机制尚不明确。通过miRNA芯片发现微小RNA-34a（miR-34a）在高脂饮食（HFD）喂养的小鼠肝脏组织中显著增高，推测miR-34a可能参与介导了高脂诱导的外周组织IR。因此本项目通过细胞、动物及人群实验，全面系统的研究了miR-34a及其靶点ENO3在高脂（SA、PA及HFD）诱导的外周组织（肝脏和骨骼肌）IR中的作用及相关机制。主要完成了以下方面的工作：1. 通过体内和体外实验，过表达或抑制miR-34a表达水平，从正反两方面证实miR-34a参与介导了高脂（SA、PA和HFD）诱导的肝脏IR过程。2. 利用iTRAQ定量蛋白质组学、TargetScan数据库、Luciferase实验和细胞转染等多种实验，找到并证实miR-34a调节的靶基因为ENO3。3. 采用体内外实验相结合的方式证实，miR-34a及其靶基因ENO3通过影响胰岛素信号传导通路关键蛋白p-IRS2和p-Akt表达，调节细胞糖代谢，进而介导高脂诱导的肝脏IR。4. 体外实验明确了p53参与介导了高脂促使的miR-34a水平增加的分子机制。5. 体外实验证实miR-34a没有参与介导骨骼肌细胞的IR过程。上述研究结果为揭示miR-34a及其靶点ENO3在高脂诱导的外周组织IR中的作用及分子机制提供了新的理论依据，并以此为基础，最终以miR-34a/ENO3作为靶点，提出与IR相关疾病的新防控策略。