SIK1介导的糖脂代谢在2型糖尿病NAFLD发病中的作用及贞清方干预的机制研究

Type 2 diabetes mellitus complicated with nonalcoholic fatty liver disease (NAFLD) is called NAFLD of type 2 diabetes. Its main features are elevated fasting glucose and triglyceride (TG), fat accumulation in the liver. Recent studies found that salt inducible kinase 1 (SIK1) affected fasting blood glucose and hepatic lipid synthesis by phosphorylated CRTC2 and SREBP-1c respectively. Thus the SIK1 signaling pathway plays an important role in disorder of glucose and lipid metabolism and fatty liver in diabetes mellitus. Our recent studies showed that SIK1 expression is reduced in the liver of NAFLD in type 2 diabetic rats and hepatocytes cultured in high glucose. Our clinical prescription Zhenqing Recipe and Fructus Ligustri Lucidi in Zhenqing Recipe significantly alleviated NAFLD of type 2 diabetes rats. We also observed that Zhenqing Recipe could upregulate the expression of SIK1 in the liver, but its mechanism needs further study. We intend to study the role and the mechanism of SIK1/CRTC2 and SIK1/SREBP-1c signaling pathways in the pathogenesis of NAFLD in type 2 diabetes rats and high glucose cultured liver cells by using molecular biological and immunological technology， and also study the effect of Zhenqing Recipe and Oleanolic acid on regulating SIK1 signaling pathways. This project puts forward new insights for the pathogenesis of diabetic NAFLD, and provides new target for traditional Chinese medicine in the treatment of NAFLD in type 2 diabetes.

2型糖尿病并发非酒精性脂肪肝简称2型糖尿病NAFLD, 其主要特征有空腹血糖和TG升高，肝脏脂肪积聚。近年发现SIK1通过磷酸化CRTC2影响空腹血糖，磷酸化SREBP-1c影响肝脏脂质合成，SIK1信号通路在糖尿病糖脂代谢紊乱和脂肪肝形成方面起着重要作用。我们近期的研究显示2型糖尿病NAFLD大鼠的肝脏和高糖培养的肝细胞SIK1表达降低，我们的临床验方贞清方及方中女贞子对2型糖尿病NAFLD大鼠的肝脏脂肪病变有明显的减轻作用，贞清方可上调肝脏SIK1的表达，但其机制有待深入研究。本项目拟采用分子生物学和实验免疫学等技术，研究SIK1/CRTC2和SIK1/SREBP-1c两条信号通路在2型糖尿病NAFLD发病过程中的作用；并研究中药复方贞清方及女贞子的有效成分齐墩果酸对SIK1信号通路的调节作用。本项目对糖尿病NAFLD的发病机制提出新的见解，为中药治疗2型糖尿病NAFLD提供新的靶点。

２型糖尿病伴发非酒精性脂肪肝（简称糖尿病NAFLD）的发病机制与糖脂代谢紊乱有关，目前没有特效的药物治疗。近期研究显示SIK1在脂肪肝形成方面起着重要作用，但其调控机制有待阐明。我们的临床验方贞清方对2型糖尿病NAFLD大鼠的肝脏脂肪病变有明显的减轻作用，其药理机制有待深入研究。本项目建立2型糖尿病NAFLD大鼠模型、采用高糖培养的HepG2细胞系和原代小鼠肝细胞，研究SIK1信号通路对肝糖脂代谢的影响，揭示贞清方及方中有效成分齐墩果酸改善肝糖脂代谢、干预糖尿病NAFLD的分子机制。我们的研究发现：SIK1在糖尿病NAFLD大鼠肝脏和高糖培养的肝细胞的活性和表达降低，可促进糖异生相关基因CRTC2、G6Pase和PEPCK的表达，亦同时上调脂质合成相关基因SREBP1c、FAS和ACC的表达，肝的糖异生和脂质合成增加；过表达SIK1后，SIK1的活性增加，糖异生及脂质合成相关基因表达下调，糖尿病大鼠肝组织和高糖培养的肝细胞内TG含量减少，血糖和细胞培养液中葡萄糖的含量降低；抑制SIK1会促进上述糖异生及脂质合成基因的表达；贞清方和齐墩果酸可以上调SIK1的表达，提高SIK1的活性，抑制糖异生和脂质合成基因的表达，减少TG在肝脏和肝细胞中的沉积， 降低血糖和细胞培养液中葡萄糖含量，改善2型糖尿病大鼠非酒精性脂肪肝病变。本项目的系列研究，揭示了SIK1在肝细胞以及全身糖脂代谢中的作用和调控机制，这将为SIK1基因功能的阐释带来新的证据，进一步丰富了糖尿病NAFLD的发病机制。贞清方及齐墩果酸改善糖尿病NAFLD，其主要机制与调 节 SIK1/CRTC2和SIK1/SREBP-1c信号通路有关，实验结果为中药复方及其有效单体治疗2型糖尿病NAFLD带来新的药物干预靶点。