达格列净和坎地沙坦联用对糖尿病大鼠肾脏调节尿浓缩功能的影响

Effect of Dapagliflozin and Candesartan in Combination on Urine Concentration in Diabetic Rat

目的:探讨达格列净和坎地沙坦联用对糖尿病肾脏尿液浓缩调节的影响。方法:尾静脉注射链脲佐菌素（STZ）制备糖尿病大鼠,以达格列净1mg/（kg·d）及坎地沙坦2mg/（kg·d）的剂量灌胃给药7d,代谢笼实验收集24h尿,监测血糖、尿糖、血Na+,K+,Cl-浓度、24h尿量、尿渗透压;分离肾皮质、外髓、内髓尖端、内髓基底段,Western Blot检测外髓钠-钾-氯共转运蛋白（NKCC2）、内髓尿素转运蛋白A1（UT-A1）、内髓水通道蛋白2（AQP2）蛋白表达。结果:与未治疗糖尿病组相比,达格列净单用,达格列净和坎地沙坦联用分别降低血糖47%和42%,而三组尿糖浓度（mmol/L）相当（513.3±22.8 vs 569.2±18.7 vs 533.3±34.6）,与正常对照组相比,三组糖尿病大鼠出现多尿、尿渗透压降低,但与未治疗糖尿病组相比,两治疗组都减轻了多尿程度[24h尿量（ml）:135±19 vs 83±5 vs 70±13,P<0.05],也改善了尿渗透压（mOsm/kg H2O）（751±41 vs 1 067±31 vs 1 189±154,P<0.05）。Western Blot分析显示糖尿病大鼠肾组织内NKCC2、UT-A1及AQP2较正常对照组明显升高。与未治疗糖尿病组相比,达格列净治疗进一步升高了内髓尖端UT-A1蛋白表达。达格列净和坎地沙坦联用组则进一步上调了内髓尖端UT-A1和外髓NKCC2蛋白表达。结论:达格列净和坎地沙坦联用进一步上调了糖尿病肾髓质UTA1和NKCC2蛋白表达,较达格列净单用进一步减轻高尿糖渗透性利尿程度,这提示钠-葡萄糖协同转运蛋白2（SGLT2）抑制剂和血管紧张素Ⅱ受体抑制剂（ARB）联用有利于防止单用SGLT2抑制剂所致的容量丢失和电解质紊乱。

Objective:To evaluate the effect of dapagliflozin in combination with candesartan on urine concentration in diabetic rats.Methods:Diabetes mellitus(DM)rat was induced by injection of streptozotocin into the tail vein,and 1 mg/(kg·d)of Dapagliflozin and 2 mg/(kg·d)of Candesartan were administrated intragastricly for successive 7 days.Serum Na^+,K^+,Cl^- concentration,blood glucose,urine glucose excretion,urine volume and urine osmolality were analyzed after the administration of dapagliflozin and candesartan.UT-A1,AQP2 and NKCC2 proteins were also detected by Western blot.Results:Blood glucose decreased by 39% in diabetic rats treated bydapagliflozin alone and 45% treated by combination of dapagliflozin and candesartan on day 7.Dapagliflozin alone or in combination with candesartan induced urine glucose excretion in diabetic rats,but there were no differences among three diabetic groups.All diabetic rats presented increased 24-h urine volume and decreased urine osmolality compared with controlled rats.Dapagliflozin alone attenuated the intensity of polyuria,and it was further attenuated by combination therapy of dapagliflozin and candesartan.Hyponatremia,hypokalemia and hypochloremia were observed in untreated diabetic rats,which were corrected by dapagliflozin alone or in combination with candesartan.Western blot analysis showed that UT-A1 and AQP2 proteins were up-regulated in DM rats over control rats at day 7;dapagliflozin treatment resulted in a further increase in IM tip UT-A1 protein abundance by 38% ,combination of dapagliflozin and candesartan further increased IM tip UT-A1 protein abundance by 35% and OM NKCC2 protein abundance by 46% .Conclusion:Dapagliflozin in combination with candesartan treatment may augment the compensatory changes in medullary transport proteins in DM.These changes will tend to conserve solute and water even with persistent glucosuria induced by dapagliflozin.