二甲双胍对2型糖尿病大鼠胆汁酸代谢FXR-MAFG-CYP8B1信号通路的影响

Effect of metformin on FXR-MAFG-CYP8B1 signaling pathway in bile acid metabolism of type 2 diabetic rats

目的观察二甲双胍对2型糖尿病(T2DM)大鼠胆汁酸(BA)代谢途径中胆汁酸受体(FXR)-V-Maf肌肉腱膜纤维肉瘤癌基因同源物G(MAFG)-胆固醇12α羟化酶(CYP8B1)信号通路的影响,旨在从BA代谢途径阐述二甲双胍的治疗机制。方法将60只雄性Wistar大鼠随机分为3组各20只,模型组和干预组给予高脂饮食10周后腹腔注射小剂量STZ以诱导T2DM模型,对照组给予标准饮食并腹腔注射等量生理盐水。造模成功后,干预组给予二甲双胍500 mg/(kg·d)灌胃,其余两组给予等量生理盐水灌胃。干预12周后,计算体质量、饮食、饮水量变化,检测空腹血糖(FBG)、胰岛素(FINS)、总胆固醇(TC)、总甘油三酯(TG)、高密度脂蛋白胆固醇(HDL-C)、低密度脂蛋白胆固醇(LDL-C)、BA,计算胰岛素抵抗指数(HOMA-IR);取肝组织,采用Western blotting法、PCR技术分别检测FXR、MAFG、CYP8B1蛋白及mRNA,ELISA法测定胆酸(CA)。结果与对照组比较,模型组和干扰组体质量减轻,饮食和饮水增加(P均<0. 05);与模型组比较,干扰组二甲双胍治疗后体质量、饮食和饮水均减少(P均<0. 05)。与对照组比较,模型组FBG、FINS、HOMA-IR、TC、TG、LDL-C、BA均升高而HDL-C降低(P均<0. 05);与模型组比较,干扰组FBG、FINS、HOMA-IR、TC、TG、LDL-C、BA均降低而HDL-C升高(P均<0. 05)。与对照组比较,模型组肝组织FXR、MAFG表达下调而CYP8B1表达上调(P均<0. 05);与模型组比较,干扰组肝组织FXR、MAFG表达上调而CYP8B1表达下调(P均<0. 05)。肝组织CA表达量模型组>干扰组>对照组(P均<0. 05)。结论二甲双胍通过上调FXR和MAFG表达、下调CYP8B1表达干扰BA代谢,从而影响糖脂代谢、胰岛素敏感性以改善T2DM大鼠临床症状。

Objective To observe the effect of metformin on the FXR-V-Maf musculoaponeurotic fibrosarcoma oncogene homolog G (MAFG)-cholesterol 12α hydroxylase (CYP8B1) signaling pathway in the bile acid (BA) metabolic pathway of type 2 diabetes mellitus (T2DM) rats in order to elucidate the therapeutic mechanism of metformin from the BA metabolic pathway. Methods Sixty male Wistar rats were randomly divided into 3 groups,with 20 in each.The rats in the model group and the intervention group were given a high-fat diet for 10 weeks,and a small dose of STZ was intraperitoneally injected to induce the T2DM models;the rats in the control group were given a standard diet and were intraperitoneally injected with the same amount of normal saline.After successful modeling,the intervention group was given metformin 500 mg/(kg·d),and the other two groups were given the same amount of normal saline.After 12 weeks of intervention,we calculated the changes in body weight,diet,and water intake,and measured the serum fasting blood glucose (FPG),insulin (FINS),total cholesterol (TC),triglyceride (TG),and high-density lipoprotein cholesterol (HDL-C),low-density lipoprotein cholesterol (LDL-C),and BA,and calculated the homeostasis model assessment of insulin resistance (HOMA-IR) index;the liver tissues were obtained,and FXR,MAFG,and CYP8B1 protein and mRNA were detected by Western blotting and PCR,respectively;and cholic acid (CA) was determined by enzyme-linked immunosorbent assay (ELISA). Results Compared with the control group,the body weight decreased,diet and drinking water increased in the model group and the interference group (all P <0.05).Compared with the model group,the body weight,diet and drinking water of the intervention group decreased after treatment with metformin (all P <0.05).Compared with the control group,the FPG,FINS,HOMA-IR,TC,TG,LDL-C,and BA increased,but the HDL-C decreased in the model group (all P < 0.05 ).Compared with the model group,the FPG,FINS,HOMA-IR,TC,TG,LDL-C,and BA decreased and HDL-C was elevated in the interference group (all P <0.05).Compared with the control group,the expression of FXR and MAFG in the model group was down-regulated and the expression of CYP8B1 was up-regulated (all P <0.05).Compared with the model group,the expression of FXR and MAFG in the interference group was up-regulated and the expression of CYP8B1 was down-regulated (all P <0.05).CA expression was in the following order:model group>interference group>control group (all P <0.05). Conclusion Metformin interferes with BA metabolism by up-regulating FXR and MAFG expression and down-regulating CYP8B1 expression,thereby affecting glycolipid metabolism and insulin sensitivity to improve clinical symptoms in T2DM rats.