甘草苷对妊娠糖尿病大鼠胰岛素抵抗及Ras/Raf-1/ERK信号通路的影响

The effects of glycyrrhizin on insulin resistance and Ras/Raf-1/ERK signaling pathway in gestational diabetic rats

目的探讨甘草苷对妊娠糖尿病(GDM)大鼠胰岛素抵抗及Ras/Raf-1/ERK信号通路的影响。方法以尾静脉注射链脲佐霉素的方法诱导复制GDM大鼠模型,随机分为模型组、甘草苷低剂量(10 mg/kg)组、甘草苷中剂量(20 mg/kg)组、甘草苷高剂量(40 mg/kg)组、二甲双胍(24.2 mg/kg)组,每组12只,另取12只孕鼠尾静脉注射等剂量生理盐水,设为对照组,分组给药后,测量各组孕鼠空腹血糖(FBG)、空腹胰岛素(FINS)、三酰甘油(TG)、总胆固醇(TC)与高密度脂蛋白(HDL-C)水平,算出胰岛素抵抗指数(IRI);测量各组孕鼠与其妊娠20 d时胎鼠体重;PAS染色检测各组孕鼠肝糖原合成情况;酶联免疫吸附法(ELISA)检测各组孕鼠血清炎性细胞因子IL-1β、IL-18及TNF-α水平;蛋白免疫印迹法检测各组孕鼠肝组织Ras/Raf-1/ERK通路蛋白(Ras、p-Raf-1/Raf-1、p-ERK1/2/ERK1/2)表达。结果与对照组比较,模型组孕鼠肝糖原合成显著减少,FINS、FBG、IRI、TG、TC、HDL-C、孕鼠与胎鼠体重、血清IL-1β水平、血清IL-18水平及血清TNF-α水平、肝组织Ras蛋白表达、p-Raf-1/Raf-1及p-ERK1/2/ERK1/2显著升高(P<0.05);与模型组比较,各给药组孕鼠肝糖原合成增多,FINS、FBG、IRI、TG、TC、HDL-C、孕鼠与胎鼠体重、血清IL-1β水平、血清IL-18水平及血清TNF-α水平、肝组织Ras蛋白表达、p-Raf-1/Raf-1及p-ERK1/2/ERK1/2降低,且甘草苷低、中、高剂量组之间呈剂量依赖性(P<0.05);甘草苷高剂量组与二甲双胍组比较,大鼠各指标无明显差异(P>0.05)。结论甘草苷可抑制炎症发生发展,减轻GDM大鼠胰岛素抵抗,改善其肝脏糖脂代谢,减轻母婴体重异常增重症状,可能是通过抑制Ras/Raf-1/ERK信号激活实现的。

Objective To investigate the effects of glycyrrhizin on insulin resistance and Ras/Raf-1/ERK signaling pathway in gestational diabetes(GDM)rats.Methods The GDM rat model was induced and replicated by tail vein injection of streptozotocin and randomly divided into model group,low-dose glycyrrhizin(10 mg/kg)group,middle-dose glycyrrhizin(20 mg/kg)group,and high-dose glycyrrhizin(40 mg/kg)group,metformin(24.2 mg/kg)group,with 12 rats in each group,another 12 pregnant rats were injected with the same dose of normal saline through the tail vein and set as a control group.After group administration,the levels of fasting blood glucose(FBG),fasting insulin(FINS),triglycerides(TG),total cholesterol(TC)and high-density lipoprotein(HDL-C)of pregnant rats in each group were measured,and the insulin resistance index(IRI)was calculated;the weight of each group of pregnant rats and their fetuses at 20 days of pregnancy was measured;the glycogen synthesis in the liver of pregnant rats in each group was detected with PAS staining;the levels of serum inflammatory cytokines IL-1β,IL-18 and TNF-αin pregnant rats in each group were detected with enzyme-linked immunosorbent assay(ELISA);the expression of Ras/Raf-1/ERK pathway proteins(Ras,p-Raf-1/Raf-1,p-ERK1/2/ERK1/2)in liver tissues of pregnant rats in each group was detected with Western blotting.Results Compared with the control group,the liver glycogen synthesis of pregnant rats in the model group was significantly reduced,FINS,FBG,IRI,TG,TC,HDL-C,weight of pregnant and fetal rats,serum IL-1β,IL-18 and TNF-αlevels,Ras protein expression,p-Raf-1/Raf-1 and p-ERK1/2/ERK1/2 in liver tissue increased significantly(P<0.05);compared with the model group,the liver glycogen synthesis of pregnant rats in each administration group increased,FINS,FBG,IRI,TG,TC,HDL-C,weight of pregnant and fetal rats,serum IL-1β,IL-18 and TNF-αlevels,Ras protein expression,p-Raf-1/Raf-1 and p-ERK1/2/ERK1/2 in liver tissue decreased,and the glycyrrhizin low,medium and high dose groups were dose-dependent(P<0.05);compared between the high-dose glycyrrhizin group and the metformin group,there was no significant difference in the indicators of the rats(P>0.05).Conclusion Glycyrrhizin can inhibit the occurrence and development of inflammation,reduce insulin resistance in GDM rats,improve liver glucose and lipid metabolism,and reduce the symptoms of abnormal weight gain in mothers and infants,which may be achieved by inhibiting Ras/Raf-1/ERK signal activation.