miR27a作为巨噬细胞活化以及脂肪前体细胞重编程调控靶点在肥胖诱导胰岛素抵抗中的作用

In a state of resident immune function disorder, chronic inflammation of adipose tissue is an initial factor of insulin resistance caused by obesity and overnutrition. This kind of resident immune function disorder is characterized by a progressive infiltration of immune cells, particularly macrophages/monocytes, into obese adipose tissue. However, M1 polarization of macrophages and macrophages-like preadipocytes are also enhanced during obesity, and directly associated with the degree of chronic low-grade adipose tissue inflammation. All of the three procedures are regulated by peroxisome proliferator activated receptor-γ (PPARγ). Our previous and others’ studies reported that the level of miR27a was correlated with obesity. The studies also illustrated that miR27a could inhibit target genes PPARγ and regulate macrophages infiltration, macrophages polarization as well as the macrophages-like reprogramming of preadipocytes. Meanwhile, the expression of miR27a was increased in the serum of patients or mice adipose tissue. So we presume that miR27a plays a key role in macrophages activation and macrophages-like reprogramming of preadipocytes in the molecular level, acting as a key mediator on controlling chronic low-grade adipose tissue inflammation. In this study, both in vitro and in vivo studies were conducted, and mimicking the microenvironment condition of adipose tissue clarify that miR27a (inhibitor of PPARγ) participates in the process of macrophages infiltration and polarization pathways and macrophages-like reprogramming of preadipocytes pathway. Therefore, these experiments and viewpoints illuminate that miR27a as a critical signal molecule plays a key role in chronic low-grade adipose tissue inflammation and insulin resistance. Moreover, miR27a gives the novel target of intervention for insulin resistance induced by obesity.

脂肪组织区域免疫异常引起的慢性炎症是肥胖胰岛素抵抗的关键因素，巨噬细胞募集/极化及脂肪前体细胞重编程是脂肪组织区域免疫异常的中心环节，核转录因子PPARγ是其关键调控分子。我们前期工作表明，miR27a可抑制PPARγ表达，肥胖患者血清及肥胖小鼠脂肪组织中miR27a表达增加，并对巨噬细胞募集/极化以及脂肪前体细胞重编程具有调控作用。因此推测，miR27a作为巨噬细胞活化以及脂肪前体细胞重编程的分子开关，调控肥胖诱导的胰岛素抵抗。本研究通过建立肥胖小鼠模型、脂肪特异敲除miR27a小鼠以及细胞共培养模型，探讨miR27a调控巨噬细胞募集/极化以及脂肪前体细胞重编程的分子机制，阐明miR27a参与脂肪组织区域免疫的细胞及分子网络调控，揭示miR27a在肥胖诱导胰岛素抵抗中的关键作用，为肥胖诱导胰岛素抵抗提供新的干预靶点。

脂肪组织区域免疫异常引起的慢性炎症是肥胖诱导胰岛素抵抗的关键因素，巨噬细胞募集、极化及脂肪前体细胞重编程是脂肪组织区域免疫异常的中心环节，而核转录因子PPARγ是其关键调控分子。我们的前期工作表明，与脂肪细胞分化相关的miR27a在肥胖人群血液中表达明显增加，且PPARγ是miR27a直接调控下游靶点之一，因此我们推测，miR27a作为巨噬细胞活化及脂肪前体细胞重编程的分子开关，通过下调PPARγ诱导肥胖胰岛素抵抗的发生。本研究建立miR27a慢病毒敲降肥胖小鼠、miR27a慢病毒过表达小鼠以及细胞共培养模型，探讨miR27a调控巨噬细胞募集、极化以及脂肪前体细胞重编程的分子机制，阐明miR27a参与调控脂肪组织区域免疫的细胞及分子网络，揭示miR27a在肥胖诱导胰岛素抵抗中的关键作用。结果显示，在4w，8w和12w高脂饮食和miR27a过表达小鼠中观察到葡萄糖耐量异常和胰岛素耐量受损，血清miR27a水平以及炎性细胞因子时间依赖性增加，且脂肪组织中M1型巨噬细胞数量明显升高，PPARγ的蛋白水平下降，NF-κB炎症信号通路被激活。细胞实验结果显示，miR27a过表达显著促进巨噬细胞炎性因子分泌，增加细胞迁移率，棕榈酸刺激肥大脂肪细胞miR27a分泌水平升高，并促进巨噬细胞迁移。miR27a过表达促进脂肪前体细胞吞噬作用和迁移能力，表达M1型巨噬细胞表面抗原F4/80和MHC，并促进细胞炎性因子MCP-1，TNF-α和IL-1β的分泌，PPARγ表达水平受到抑制，同时，NF-κB被激活。以上结果表明，miR27a作为脂肪细胞与巨噬细胞间的关键信号通讯分子，通过抑制PPARγ解除其对NF-κB的抑制作用，激活NF-κB通路，促进巨噬细胞极化及募集，并使脂肪前体细胞发生巨噬样重编程，引起脂肪组织区域免疫异常，进而诱导胰岛素抵抗的发生。