α7nAchR调节M1/M2巨噬细胞表型转化以优化棕色/米色脂肪产热及黄芪桂枝五物汤的作用及机制

Although it is a potential method to prevent obesity by promoting thermogenesis of brown (BAT) and beige adipose tissue, there have several problems that hinders its practical application. In the adipose tissue of obesity, infiltration of pro-inflammatory M1 macrophages leads to thermogenesis dysfunction of brown adipose tissue and suppresses beiging of white adipose tissue (WAT); moreover, M1 macrophages involves in the pathological statement of impaired adipose tissue homeostasis, which caused by excessive lipolysis in thermogenesis process of brown/beige adipose tissue. In contrast to M1 macrophages, M2 macrophages exhibits anti-inflammatory effects by secreting cytokines, and it promotes beiging of WAT. There have studies have shown that activation of α7nAchR could decreased the ratio of M1/M2 macrophages. In our previous study, we have demonstrated that Astragali Radix has effect of anti-obesity, and its main bioactive compounds Astragaloside IV could prevent occurrence of obesity-associated hypertension by up-regulating expression of α7nAchR in diet-induced obese rat. According to the above, in cultured M1 macrophages in vitro and models of cold exposure/β3 adrenergic receptor agonist-induced brown and beige adipose thermogenesis in obese mice, we will test the conversion of M1/M2 macrophages, α7nAchR expression levels and relative inflammatory signaling, capability of beiging of WAT and brown/beige adipose tissue thermogenesis. Our study will demonstrate the following hypnosis: Activating α7nAchR could promote the M1 macrophages transform into M2 macrophages, which optimize the application of brown/beige fat thermogenesis in treatment of obesity by increasing thermogenesis of brown/beige adipose and maintaining white adipose tissue homeostasis. In addition, we will study the effect and mechanism of Huang Qi Gui Zhi Wu Wu Tang in optimizing brown/beige fat thermogenesis.

促进棕色/米色脂肪产热虽是治疗肥胖的潜在方法，但存在实际应用障碍。肥胖时，脂肪中促炎的M1型巨噬细胞增多，可降低棕色脂肪产热能力，抑制白色脂肪米色化，引起白色脂肪加速脂解造成脂肪稳态受损。巨噬细胞M2型可对抗M1型，抑制炎症和促进米色化。相关研究显示激活α7nAchR可降低M1/M2型比值。申请人既往发现黄芪可抑制肥胖，黄芪甲苷可上调α7nAchR表达。据此，本项目在体外培养的M1巨噬细胞和寒冷/β3受体激动剂刺激的肥胖小鼠中，通过激活和抑制α7nAchR，检测M1/M2巨噬细胞转化、α7nAchR及有关炎症通路、米色化程度、棕色/米色脂肪产热能力。证明以下假说：激活α7nAchR可促进脂肪组织巨噬细胞M1型向M2型转化，增加产热并维持产热时白色脂肪组织稳态，优化棕色/米色脂肪产热在肥胖治疗中的应用。基于中医营卫理论，探索证明黄芪桂枝五物汤在优化棕色/米色脂肪产热的作用及机制。

肥胖时，脂肪中M1型巨噬细胞增多，可降低棕色脂肪产热，抑制白色脂肪米色化。巨噬细胞M2型可对抗M1型，抑制炎症和促进棕色脂肪产热和白色脂肪米色化产热。研究显示激活α7 nAchR可降低M1/M2比值。据此，探索激活α7 nAchR可促进脂肪组织巨噬细胞M1型向M2 型转化，优化棕色/米色脂肪产热在肥胖治疗中的治疗作用。本研究结果显示：肥胖小鼠脂肪组织M1/M2型巨噬细胞比值增高，寒冷/β3受体激动剂促进产热的过程中，脂质代谢紊乱、白色脂肪组织内质网应激加重，M1/M2型巨噬细胞失衡加剧，炎症反应加重。使用α7 nAchR选择性激动剂/抑制剂干预后，上调α7 nAchR可改善交感神经激活导致的脂质代谢紊乱、白色脂肪内质网应激，增加棕色脂肪血管密度，恢复M1/M2巨噬细胞平衡，进一步提高棕色脂肪产热和白色脂肪米色化产热。证明黄芪桂枝五物汤可上调α7 nAchR，促进巨噬细胞M1型向M2型转化，优化棕色脂肪产热和白色脂肪米色化产热对肥胖的治疗作用。本研究证明激活α7 nAchR可恢复交感神经刺激加剧的M1/M2巨噬细胞失衡，优化棕色脂肪产热和白色脂肪米色化产热，阐释了经方黄芪桂枝五物汤优化棕色脂肪产热和白色脂肪米色化产热的作用机制，为中医“营卫”理论防治肥胖提供新思路和科学依据。