黄芪多糖对肥胖大鼠骨骼肌胰岛素信号转导的影响

Effects of astragalus polysaccharide on insulin signal transduction in skeletal muscle of obese rats

目的探讨黄芪多糖(APS)对肥胖大鼠骨骼肌胰岛素信号转导的影响。方法将48只雄性Sprague Dawley大鼠随机分为对照组、模型组、APS组和吡格列酮组,每组12只;对照组大鼠给予常规饲料喂养6周,模型组、APS组、吡格列酮组大鼠给予高脂饲料喂养6周制备肥胖模型;造模后,APS组、吡格列酮组大鼠分别给予APS 400 mg·kg^-1·d^-1及吡格列酮10 mg·kg^-1·d^-1,连续灌胃4周;对照组和模型组大鼠均给予生理盐水2 mL·kg^-1·d^-1,连续灌胃4周;药物干预第4周末采集各组大鼠血液标本、脂肪及腓肠肌组织标本,采用全自动生物化学分析仪测空腹血糖(FBG)、三酰甘油(TG)、胆固醇(TC)水平,酶联免疫吸附试验测空腹胰岛素(FINS),并计算胰岛素敏感指数(ISI)及内脏脂肪垫相对质量,实时荧光定量聚合酶链反应(PCR)检测腓肠肌组织中胰岛素受体底物1(IRS-1)mRNA水平,Western blot法检测腓肠肌组织中IRS-1及其丝氨酸307(IRS-1 Ser307)蛋白表达水平,计算IRS-1 Ser307/IRS-1比值。结果药物干预4周后,对照组、模型组、APS组及吡格列酮组大鼠FBG水平两两比较差异无统计学意义(P>0.05)。与对照组比较,模型组大鼠血清TG、TC、FINS水平及内脏脂肪垫相对质量升高,ISI下降(P<0.05);与模型组比较,APS组及吡格列酮组大鼠TG、FINS水平降低,ISI水平升高(P<0.05);APS组、吡格列酮组大鼠TC水平及内脏脂肪垫相对质量与模型组比较差异无统计学意义(P>0.05)。APS组大鼠血清TG、TC、FINS水平及ISI、内脏脂肪垫相对质量与吡格列酮组比较差异均无统计学意义(P>0.05)。与对照组比较,模型组大鼠腓肠肌组织中IRS-1 mRNA和蛋白表达量降低,IRS-1 Ser307蛋白表达量和IRS-1 Ser307/IRS-1比值升高(P<0.05)。与模型组比较,吡格列酮组、APS组大鼠腓肠肌组织中IRS-1mRNA和蛋白表达量升高,IRS-1 Ser307蛋白表达量及IRS-1 Ser307/IRS-1比值降低(P<0.05)。APS组大鼠腓肠肌组织中IRS-1 mRNA和蛋白表达量、IRS-1 Ser307蛋白表达量及IRS-1 Ser307/IRS-1比值与吡格列酮组比较差异无统计学意义(P>0.05)。结论APS能有效调节肥胖大鼠血脂水平并改善胰岛素抵抗;APS改善胰岛素抵抗的作用机制可能是通过增加大鼠腓肠肌组织中IRS-1水平、降低IRS-1 Ser307水平实现的。

Objective To investigate the effect of astragalus polysaccharide(APS)on insulin signal transduction in skeletal muscle of obese rats.Methods Forty-eight male Sprague Dawley rats were randomly divided into control group,model group,APS group and pioglitazone group,with 12 rats in each group.The rats in the control group were fed with conventional feed for 6 weeks;the rats in the model group,APS group and pioglitazone group were fed with high-fat feed for 6 weeks to prepare the obesity model.After modeling,the rats in APS group and pioglitazone group were given APS 400 mg·kg^-1·d^-1 and pioglitazone 10 mg·kg^-1·d^-1 by gavage for 4 weeks continuously;the rats in the control group and the model group were given normal saline 2 mg·kg^-1·d^-1 by gavage for 4 weeks continuously.Blood samples,fat and gastrocnemius tissue samples were collected at the end of the fourth week after drug intervention.Fasting blood glucose(FBG),triglyceride(TG)and cholesterol(TC)levels were measured by automatic biochemical analyzer.The fasting insulin(FINS)was determined by enzyme-linked immunosorbent assay,and the insulin sensitivity index(ISI)and visceral fat pad relative weight was calculated.Real-time fluorescence quantitative polymerase chain reaction was used to detect the insulin receptor substrate 1(IRS-1)mRNA levels in gastrocnemius tissues,and the expression levels of IRS-1 and serine 307(IRS-1 Ser307)protein in gastrocnemius tissues were detected by Western blot,and the IRS-1 Ser307/IRS-1 ratio was calculated.Results After 4 weeks of drug intervention,there was no significant difference in the FBG level among the control group,the model group,the APS group and the pioglitazone group(P<0.05).Compared with the control group,the serum level of TG,TC,FINS and the relative mass of visceral fat pad of rats in model group increased,and the ISI decreased(P<0.05).Compared with the model group,the TG and FINS levels of rats in the APS group and the pioglitazone group were lower,and the ISI level was higher(P<0.05);there was no significant difference in the TC level and the relative mass of visceral fat pad between the APS group,the pioglitazone group and the model group(P>0.05).There was no significant difference in the TC level model the APS group,the pioglitazone group and the model group(P>0.05).There was no statistically significant difference in TG,TC,FINS levels,ISI and visceral fat pad relative weight between the APS group and the pioglazone group(P>0.05).Compared with the control group,the expression of IRS-1 mRNA and protein in the gastrocnemius muscle tissues of rats in the model group were lower,and the expression of IRS-1 Ser307 protein and IRS-1 Ser307/IRS-1 ratio were higher(P<0.05).Compared with the model group,the expression of IRS-1 mRNA and protein in the gastrocnemius tissues of rats in the piogliazone group and the APS group were higher,the expression of IRS-1 Ser307 protein and IRS-1 Ser307/IRS-1 ratio were lower(P<0.05).There was no statistic difference in the expression of IRS-1 mRNA and protein,IRS-1 Ser307 protein and IRS-1 Ser307/IRS-1 ratio in the gastrocnemius muscle tissues of rats between the APS group and the pioglazone group(P>0.05).Conclusion APS can effectively regulate lipid level and improve insulin resistance in obese rats.The mechanism of improving insulin resistance by APS may be involve in increasing the level of IRS-1 and decreasing the level of IRS-1 Ser307 in gastrocnemius tissues of rats.