内皮细胞6-磷酸果糖-2激酶（亚型3）对肥胖和胰岛素敏感性的调控研究

Adipocyte hyperplasia is usually accompanied by the infiltration of inflammatory cells and angiogenesis in the development of obesity. Although angiogenesis improves tissue hypoxia and metabolism, it may also promote adiposity and tissue inflammation. These two contradictory phenomena complicate the role of angiogenesis in obesity and metabolic diseases. Therefore, much effort should be taken to mechanistically decipher these outcomes of angiogenesis in obesity. PFKFB3, the key regulatory enzyme of glycolysis, plays a pivotal role in cell energy metabolism and endothelial sprouting. Our pilot experiments indicated that the expression of PFKFB3 was upregulated in endothelial cells following the treatment of saturated free fatty acid (palmitate), and knockdown of PFKFB3 suppressed proliferation of endothelial cells and inflammatory response of HUVEC, implicating the critical roles of endothelial PFKFB3 in the regulation of obesity and systemic insulin sensitivity. In this project we will utilize the in vivo model of feeding the PFKFB3flox/flox and PFKFB3flox/flox/Cdh5cre mice with high fat diet to disclose whether and how endothelial PFKFB3 regulates obesity and insulin sensitivity. We are also interested in the signaling pathways by which palmitate regulates PFKFB3 expression, as well as PFKFB3 modulates inflammatory responses of endothelial cells. The overall objective of this proposal is to disclose the mechanisms underlying the regulation of endothelial PFKFB3 in the progression of diet-induced obesity and metabolic disorders, and thereafter leading to the development of novel therapeutic approaches for above diseases.

在肥胖症的发生发展中，脂肪组织中脂肪细胞增加伴随着炎性细胞浸润及血管新生。尽管脂肪组织中新生血管改善脂肪组织的氧供及代谢，但也促进脂肪组织累积及脂肪组织的炎症。因此新生血管在肥胖症的发生发展中是利是弊尚无定论。6-磷酸果糖-2激酶亚型3（PFKFB3）调节内皮细胞的糖酵解并主导内皮的多项重要功能。我们的结果显示饱和脂肪酸诱导内皮细胞PFKFB3表达。PFKFB3的过表达促进血管再生及提高内皮细胞的炎症反应。干扰PFKFB3表达可减少血管增生和炎症反应。本课题拟高脂喂养内皮细胞特异性敲除PFKFB3小鼠，从血管新生和炎症两方面深入研究在体情况下内皮细胞PFKFB3对肥胖及胰岛素敏感性的调节作用。另外，本项目亦探讨饱和脂肪酸诱导PFKFB3表达的机制以及PFKFB3调控内皮炎症状态的信号传导机制。本项目的实施将从在体及离体水平揭示内皮细胞参与肥胖症发生发展的新机制，为相关疾病的防治提供新思路。

本项目计划研究内皮细胞6-磷酸果糖-2激酶（亚型3，PFKFB3）是否参与到肥胖和胰岛素敏感性及糖尿病发生发展的进程中。在项目进行过程中，结果显示内皮细胞PFKFB3敲除后，对小鼠内皮细胞在高糖高脂喂养后的糖脂代谢的影响不甚显著。我们进一步发现内皮细胞腺苷受体2A（ADORA2A）敲除可影响PFKFB3表达及后续的糖酵解过程，由于ADORA2A是细胞表面受体，是一潜在的药物靶标（如咖啡因即为一非特异性的腺苷受体2类抑制剂），也由于我们认为内皮细胞腺苷受体2A相关糖酵解通路对血管新生存在较大的影响，其中增殖性糖尿病视网膜病变（proliferative diabetic retinopathy, PDR）的主要病理特征是视网膜组织相对缺氧导致的病理性视网膜新生血管。其高糖、炎症和缺血缺氧等病理环境可诱导视网膜一系列分子信号转导通路激活和代谢方式的改变，如促增殖相关分子表达上调、糖酵解相关酶活性增强、腺苷受体系统激活等。缺血缺氧等病理条件下，ATP释放增多，转录因子SP1和缺氧诱导因子HIF激活，并介导腺苷生成关键酶CD39和CD73以及腺苷受体（主要为A2A和A2B）表达上调，同时抑制腺苷代谢酶ADK和腺苷转运体ENT1的表达和活性，细胞外腺苷浓度从基础状态下20-300 nM急剧上升至30 μM，最终导致腺苷信号系统过度活化。视网膜组织缺氧时腺苷生成显著增加，腺苷信号系统过度激活，提示在PDR的调节过程中腺苷信号系统相关基因可能发挥了关键性作用。