载脂蛋白A4抑制肥胖相关低度炎症改善胰岛素抵抗的作用及机制

Obesity accompanied low-grade inflammation which promotes insulin resistance is recognized as the pathogenesis of the obesity associated type 2 diabetes and the relative metabolic syndrome. It was reported that Apolipoprotein A4 (APOA4) gene expression level is associated with obesity and diabetes. We previously found that. APOA4 improves insulin sensitivity by injection of recombinant APOA4 to diabetic mice and with APOA4 knockout mice. Currently we found APOA4 inhibits the activation of inflammatory pathway and the expression of inflammatory cytokines. Furthermore, M1 macrophage and inflammatory T lymphocyte infiltrating in the white adipose tissue in APOA4 knockout mice with high-fat-diet were increased. These data indicates APOA4 deletion results in worse low-grade inflammation. Based on these results we hypothesize that APOA4 improves insulin sensitivity through inhibiting the low-grade inflammation induced by high-fat-diet is one of the mechanisms of its inhibitory role on insulin resistance. This project focus on the white adipose tissue metabolic inflammation and the aims are: 1) establish the fat induced low-grade inflammation and insulin resistance animal models with APOA4 deleted mice, APOA4 transgenic mice and WT mice; and then test the protection effects of APOA4 from low-grade inflammation and insulin resistance and correlation analysis ; 2) explore the regulating profiles and lymphocyte subsets of APOA4 with above mice by using the Transcript-omics and Immune repertoire; confirm the key factors of down-stream of APOA4 and the subsets of Immune cells on anti-inflammation and anti-insulin resistance by in vitro APOA4 specific cell factors and cell interactions, cell and cell interactions and lymphocytes transplantation technology; 3) Confirm APOA4’s effect on the immunological regulation in the metabolic inflammation of T2D patients by correlation analysis between T2D patient clinical indications and newly discovered APOA4 specific factors and the cell subsets. These study results will provide scientific theoretical basis for APOA4 in clinical diagnosis and the novel strategy for the therapy of type 2 diabetes.

低度炎症导致胰岛素抵抗是糖尿病一个主要病理机制。载脂蛋白A4（APOA4）是由小肠分泌，其血清水平与胰岛素抵抗及糖尿病呈负相关。我们前期发现APOA4缺失加重高脂诱导胰岛素抵抗，给予外源APOA4可改善该小鼠及糖尿病KKAy模型鼠胰岛素敏感性；新近发现APOA4抑制细胞炎性信号通路及促炎因子表达，APOA4敲除加剧高脂诱导小鼠低度炎症。推测，APOA4抑制低度炎症是其改善胰岛素抵抗的机制之一。本研究拟分别在APOA4基因敲除和转基因小鼠建立高脂诱导低度炎症模型，比较APOA4有无对小鼠低度炎症的影响及其与胰岛素抵抗的关系；用转录组和免疫组库技术探寻APOA4调控低度炎症相关因子和T淋巴细胞亚群；通过APOA4调控因子和细胞互作、细胞间互作及细胞亚群移植技术，揭示APOA4抑制低度炎症改善胰岛素抵抗的作用机制；并取T2D患者样本进行APOA4作用靶点验证。为糖尿病诊治提供实验依据。

低度炎症导致胰岛素抵抗是肥胖、糖尿病、脂肪肝等肥胖相关代谢病一个主要病理机制。载脂蛋白A4（ApoA4）是由小肠分分泌，其血清水平与胰岛素抵抗及糖尿病呈负相关。我们前期发现ApoA44缺失加重高脂诱导胰岛素抵抗，给予外源ApoA4可改善该小鼠及糖尿病小鼠模型胰岛素敏感性；预实验发现ApoA4抑制细胞炎性信号通路及促炎因子表达，APOA4敲除加剧高脂诱导小鼠低度炎症。推测，ApoA4抑制度炎症是其改善胰岛素抵抗的机制之一。本项目用肥胖-糖尿病-脂肪肝模型鼠，结合ApoA4基因缺失、过表达及外源注射ApoA4纯化重组蛋白的实验方式，用代谢病表型观测、代谢性炎症、胰岛素敏感性、脂肪肝相关已知指标及可能机制的检测，同时进行了白色脂肪组织和肝组织转录组、肝脏单细胞组学检测、生物信息数据分析的多途径及最先进的研究方法，研究ApoA4是否通过调节免疫抑制肥胖、糖尿病、脂肪肝的作用及机制。本项目研究发现如下：①首次证明ApoA4抑制肥胖、抑制糖代谢异常、抑制代谢性炎症及抑制脂肪肝的同时抑制多种代谢病的作用；②首次发现了ApoA4 通过IL-7/TNF-IKK/JNK通路抑制代谢性炎症，进而抑制胰岛素抵抗的作用机制；③首次发现了ApoA4 通过SREBP1抑制脂合成及氧化磷酸化，进而抑制NAFLD的作用机制；④首次发现了ApoA4 缺失导致肝脏肝巨噬细胞比例增加，炎性相关通路上调。促炎Cxcl9+Mφ和Cxcl2+Mφ亚群增加；初始Ets1+Gran粒细胞几乎消失，而NAFLD相关Wfdc17+Gran亚群增加。⑤首次提出NAFLD发病与发展相关生物标志物模块。⑥综合研究结果，首次提出ApoA4通过影响肝脏巨噬细胞和粒细胞细胞互作抑制NAFLD可能的细胞分子机制。