CD226分子参与肥胖状态下脂肪组织慢性炎症的免疫学机制研究

Obesity is a chronic low degree of systemic inflammation, which is the pathological basis of diabetes, and has become a serious global problem more and more. Obesity is characterized by infiltration of adipose tissue by activated macrophages. White adipose tissue (WAT) plays a key role in obesity, with significantly increased number and activity of adipose tissue macrophages (ATMs), which should be the key cause of chronic adipose inflammation and diabetes. Different from other parts, WAT and ATMs have unique regional immunological characteristics. CD226 is an immune cell activating receptor, which transduces activating signals. The expression and activation of CD226 molecule on ATMs have positive correlation with diabetes, but the molecular mechanism of obesity regulation is still unclear. We found that in addition to the immune organs and cells, CD226 is also highly expressed in glucolipid metabolic organs, such as muscle, liver and adipose. A high-fat diet feeding can cause abnormal blood sugar in mice, with increased CD226 expression in WAT; meanwhile, CD226KO mice showed significantly better results in blood glucose and Intraperitoneal glucose tolerance test (IPGTT), compared with wild type mice, which hinted that CD226 may participated in the initiation and development of obesity. The aim of this study is, based on the immunological characters of white adipose tissue, to analysis the relationship between expression of CD226 and insulin resistance, diabetes in obese individuals; clarify the mechanisms of how CD226 regulating the ATMs of chronic adipose inflammation; And the possible mechanism of intervention CD226 signal to improve insulin sensitivity. This study focused on the regional immunological characteristics of adipose tissue macrophages; provide new possibilities for prevention and treatment of insulin resistance caused by obesity.

肥胖是慢性低程度系统性炎症，是糖尿病的病理基础，日益成为严重的全球化问题。关键部位白色脂肪（WAT）中脂肪巨噬细胞（ATMs）数量和活性显著增加，是脂肪慢性炎症和糖尿病的关键动因；与其他部位不同，ATMs具有独特的区域免疫学特性。ATMs膜上CD226分子与糖尿病密切相关，但其调控肥胖的分子机制尚不清楚。我们实验发现，除免疫器官外，CD226还高表达于糖脂代谢器官肌肉、肝脏和脂肪。高脂饮食饲养可致小鼠血糖异常，WAT中CD226上调；而CD226KO小鼠血糖和糖耐量实验结果均显著优于野生型小鼠，提示CD226参与了肥胖的发生发展。本课题拟深入研究肥胖个体CD226与胰岛素抵抗及糖尿病的关系；阐明CD226通过调控ATMs参与脂肪慢性炎症的机制；及干预CD226信号改善胰岛素敏感性的可能机制。本研究聚焦于脂肪局部巨噬细胞免疫学特性，从改善脂肪慢性炎症角度，为防治肥胖所致胰岛素抵抗提供新思路。

脂肪组织是一个具有重要内分泌功能的器官，在肥胖条件下，由缺氧、炎症和自由基堆积等因素导致脂肪组织各种细胞和分子重构，形成独特的区域免疫特性。脂肪组织巨噬细胞ATMs、M1型巨噬细胞极化聚集，是推动脂肪慢性炎症进展、胰岛素抵抗和2 型糖尿病发生的核心因素。.本课题实施基本按照预定方案执行，主要研究内容包括：明确肥胖诱导的白色脂肪炎症状态及机体系统胰岛素敏感性与CD226分子的关系；探讨巨噬细胞CD226分子在肥胖导致的胰岛素抵抗中的关键作用；研究CD226在巨噬细胞极化中的作用。主要发现包括：① CD226分子参与高脂饮食诱发的胰岛素抵抗和II型糖尿病发病：II型糖尿病患者（T2DM）血清CD226（soluble CD226，sCD226）水平与血糖水平正相关。CD226敲除小鼠（KO）血糖、糖耐量和胰岛素耐量显著优于WT小鼠。CD226KO小鼠胰岛增生、脂肪细胞体积、脂肪肝病变均显著较轻。敲除CD226可上调Glut1表达，增加内皮细胞摄取葡萄糖。② 阻断CD226分子信号促进Treg分化：炎症条件下APC细胞CD155、T细胞CD226/TIGIT表达水平均显著增高。CD226单抗、CD226-Fc促进Treg增高，抑制淋巴细胞增殖和杀伤。在体使用CD226单抗或TIGIT-Fc蛋白显著延长同种异体移植排斥反应，受体Treg细胞显著增高，巨噬细胞向M2型极化比例增加。③ CD226/TIGIT-CD155信号平衡调控巨噬细胞极化模式：巨噬细胞与MNC混合培养，CD3抗体加LPS刺激成熟巨噬细胞CD155、CD226、TIGIT分子表达均显著上调。CD226单抗显著抑制巨噬细胞向M1极化并上调Treg比例，TIGIT单抗则促进M1极化并下调Treg比例。TIGIT-Fc可以促进巨噬细胞ERK-MSK-CREB磷酸化，促进IL-10产生以及向M2型极化，而CD226-Fc发挥相反作用。CD226/TIGIT-CD155信号分子间的平衡对于CD155阳性APC细胞的活化机制可能是CD226参与细胞间信号调控通路的主要因素。.本课题研究内容着眼于肥胖所致白色脂肪组织炎症-2型糖尿病这一环节，集中于CD226/TIGIT-CD155信号对ATMs 极化与功能活性调控的分子机制，探讨了共刺激分子调控ATMs在2型糖尿病中的重要作用，为免疫干预策略提供新思路。