DPP4通过下调Foxp3基因表达抑制Treg细胞免疫调节作用的机制研究

The onset and development of type 2 diabetes are promoted by chronic low-grade inflammation, however, the underlying mechanism remains unclear. Our previous research indicated that 1. DPP4 promote the onset and development of type 2 diabetes through its interaction with IGF-2 receptor to enhance the proinflammatory state. 2. Treg cell surface express IGF-2 receptor. 3. DPP4 downregulate the expression of Foxp3 in Treg cell. 4. DPP4 inhibits the differentiation of Treg cell. Furthermore, recent studies showed that relatively low activity of the PI3K/Akt/mTOR pathway is essential for the normal expression of Foxp3 and function of Treg cell，DPP4 inhibitors downregulate the PI3K/Akt/mTOR pathway. Consequently, we speculate that DPP4 interacts with IGF-2 receptor on the surface of Treg cell and results in the upregulation of PI3K/Akt/mTOR pathway, which leads to a decrease in the expression of Foxp3. This, ultimately inhibits the anti-inflammatory function of Treg. Accordingly, in this study we will perform mainly randomized controlled trial, ex vivo T cell culture, followed by flow cytometry (FACS),etc, to prove the enzymatic and nonenzymatic inhibitory effects of DPP4 exerted on the differentiation, proliferation and anti-inflammatory function of Treg and its related mechanism. This research is crucial for prevention and treatment of type 2 diabetes by attenuating the proinflammatory state in such disease.

慢性低度炎症促进2型糖尿病发生发展，但具体机制不清。我们前期研究表明：1.二肽基肽酶4(DPP4)与IGF-2受体作用发挥促炎功能进而促进2型糖尿病发生2.调节性 T 细胞（Treg）表面表达IGF-2受体3.DPP4下调Treg细胞关键功能基因Foxp3表达4.DPP4抑制Treg细胞分化。既往研究还表明，Foxp3基因表达和Treg细胞功能发挥需胞内PI3K-Akt-mTOR信号通路处于抑制状态，DPP4抑制剂可下调PI3K-Akt-mTOR信号通路。据此，我们推测，DPP4可能作用Treg细胞表面IGF-2受体，激活胞内PI3K/Akt/mTOR通路，下调Foxp3基因表达，抑制Treg细胞抗炎功能。本课题采用RCT研究、T 细胞培养、流式细胞仪等方法，在活体和细胞水平，阐明DPP4酶学与非酶学特性对Treg细胞分化、增殖及抑炎功能的影响和机制，旨在改善2型糖尿病的慢性低度炎症状态。

2 型糖尿病（T2D）是一种慢性低度炎症性疾病，机体炎症水平增加可促进 2 型糖尿病发生发展，2型糖尿病患者高糖环境下具有抑炎作用的调节性T细胞显著下降是导致2型糖尿病机体慢性低度炎症状态的可能发病机制之一。既往已有研究表明2型糖尿病患者外周血DPP4酶学活性增高可以刺激机体产生慢性低度炎症状态，但其具体分子机制目前尚未完全明确。本项目主要研究内容包括：1.2型糖尿病患者外周血DPP4水平变化对Treg细胞数量、功能及其细胞内信号通路的影响。2. DPP4抑制Treg细胞发挥促炎作用。3. DPP4抑制Treg细胞促炎作用的机制。研究结果如下：1. 2型糖尿病患者外周血DPP4水平明显增高，Treg细胞数量减少，且伴有磷酸化PI3K/Akt/ mTOR水平上调，外周血IL-10水平下降，TGF-β和TNF-α水平增加。使用DPP4抑制剂后，上述效应均减弱。2. DPP4可以通过发挥非酶学功能与Treg表面的IGF-2受体结合，进而上调细胞内PI3K/Akt/ mTOR磷酸化水平，抑制Treg发挥介导接触依赖性和非接触依赖性的双重免疫抑制作用，最终促进机体慢性炎症水平的发生发展。该研究进一步阐明2型糖尿病患者高糖环境下慢性低度炎症状态的发病机制，为后续进一步研究2型糖尿病胰腺功能受损，胰岛素抵抗及其相关大小血管并发症提供进一步的研究方向及可能的药物作用靶点。