二甲双胍对2型糖尿病小鼠附睾脂肪组织巨噬细胞浸润及胰岛素抵抗的影响

摘要

目的:研究二甲双胍对2型糖尿病(T2DM)小鼠附睾脂肪组织巨噬细胞浸润、炎症及胰岛素敏感性的影响,并探讨其可能机制.方法:将8～10周龄雄性C57BL/6J小鼠21只随机分为3组(n=7):对照组、模型组和二甲双胍组.模型组和二甲双胍组通过高脂饮食+腹腔注射链脲佐菌素建立T2DM小鼠模型.对照组给予普通饲料喂养.二甲双胍组小鼠通过灌胃给予二甲双胍(250mg/kg)28 d.各组小鼠行ITT胰岛素耐量和OTT葡萄糖耐量实验,血糖仪测量各组小鼠血糖水平,苏木精—伊红(HE)染色观察附睾脂肪病理变化,免疫荧光染色观察附睾脂肪组织巨噬细胞浸润,qPCR检测脂肪组织炎症因子(TNF-α、IL-6)、趋化因子CCL2和巨噬细胞CD68 mRNA水平,Western blotting法检测CCL2、胰岛素受体物质(IRS)1、蛋白激酶B(AKT)蛋白水平.结果:二甲双胍可降低模型组小鼠血糖、胰岛素水平,降低注射胰岛素后的血糖—时间曲线下面积,提高葡萄糖清除率,缓解胰岛素抵抗(P＜0.01).与模型组相比,二甲双胍组脂肪组织TNF-α、IL-6及CCL2表达水平显著降低,附睾脂肪细胞体积增大,巨噬细胞浸润数量明显增加,同时磷酸化(P)-IRS1和P-AKT表达水平升高(P＜0.01).结论:二甲双胍可减少T2DM小鼠巨噬细胞浸润,减轻胰岛素抵抗,其机制可能与抑制炎症反应以及促进胰岛信号通路IRS1/AKT的激活有关.%Objective:To study the effects and mechanisms of metformin on macrophage infiltration into epididymal adipose tissue and insulin resistance in type 2 diabetes (T2DM) mice.Methods:Twenty-one male C57BL/6J mice were randomly divided into 3 groups (n=7 each):control group,model group and metformin group.The rat model of T2DM was established by feeding with high-fat diet and intraperitoneal injection of streptozotoc in model group and metformin group.The control group mice were fed normal diet.Metformin (250 mg/kg) was given via gavage for 28 days.Insulin tolerance test (ITT) and oral triglyceride tolerance (OTT) test were conducted.The blood glucose level was measured.Size of epididymal fat cells and number of macrophage infiltrated epididymal adipose tissue were observed by hematoxylin-eosin (HE) staining and immunofluorescence staining,respectively.The mRNA levels of tumor necrosis factor (TNF)-α,interleukin (IL)-6,chemokine (C-C motif) ligand 2 (CCL2)and CD68 (a macrophage marker) were determined by qPCR.The protein expressions of CCL2,insulin receptor substance 1 (IRS1) and protein kinase B (AKT) were detected by western blotting.Results:Metformin reduced blood glucose and insulin levels,decreased the area under the blood glucose-time curve after insulin injection,increased glucose clearance,and alleviated insulin resistance in T2DM mice (P ＜0.01).Larger adipocytes from epididymal fat pads and large number of macrophage infiltrated obese epididymal adipose tissue were found in the model group,whereas all the changes were significantly recovered after metformin treatment.The expressions of TNF-α,IL-6,CD68 and CCL2 were down-regulated,while the phosphorylated (P)-IRS1 and P-AKT expressions were up-regulated in the metformin group compared with the model group (P ＜ 0.01).Conclusion:Metformin could reduce macrophage infiltration and alleviate insulin resistance in T2DM mice,and the mechanisms might be related to the inhibition of inflammatory response and the activation of IRS1/AKT signaling pathway.