Objective To investigate the protective effect of quercetin on diabetic nephropathy and to explore its possible mechanism.Methods Type 2 diabetes mellitus rat model was established by feeding high-carbonhydrate-fat diet and injecting with streptozotocin.At 72 hour after injection,blood samples were collected from the tail veins of all rats.Those rats with blood glucose level ≥ 16.7 mmol/L were considered as the diabetes model been successfully established.The model rats were randomly divided into type 2 diabetic group ( group DM,n =9 ) and quercetin group ( group QUE,n =9 ).Other rats were used as normal controls (group NC,n =8).All rats were performed by intragastric administration for 8 weeks.At the end of experiment,the rats were sacrificed and fasting plasma glucose( FPG),fasting insulin( Flns),serum creatinine (SCr),blood urea nitrogen(BUN),TG,TC,LDL-C,24 h urine protein (24 h UP),and kidney index ( KI ) were evaluated.Pathological changes of kidney were observed by periodic acid-silver metheramine( PASM ).The expressions of ubiquitin and NF-κB p65 on glomeruli w ere examined by immunohistochemical method,and its association with the incidence of proteinuria was analyzed.Results In groups DM and QUE,the level of FPG [ ( 25.45 ± 1.23 ) mmol/L and ( 19.99 ± 1.20 ) mmoL/L],FIns [ ( 25.67 ± 2.58 ) mU/L and ( 19.29 ± 1.80 ) mU/L ],SCr[ ( 44.00 ± 2.53 ) μmol/L and ( 34.43 ± 2.23 )μmol/L],BUN[ ( 11.60 ± 0.39 )mmol/L and (8.20 ± 0.37) mmoL/L],TG [ (3.32 ± 0.22 ) mmol/L and (2.43±0.25)mmol/L],TC[(2.95 ±0.21) mmol/L and (2.24 ±0.17)mmol/L],LDL-C[(2.03 ±0.22 ) mmol/L and ( 1.49 ± 0.13 ) mmol/L ],24 h UP [ ( 46.67 ± 2.50 ) mg/24 h and ( 25.57 ± 2.82 )mg/24 h]and KI[ (9.76 ±0.30) × 103 and (8.44 ±0.26) × 103 ] were significantly increased than the indexes of group NC [ (6.56 ± 0.41 ) mmol/L,( 12.63 ± 1.41 ) mU/L,( 22.88 ± 2.36 ) μmol/L,( 5.45 ±0.51 ) mmoL/L,( 1.64 ± 0.1 1 ) mmol/L,( 1.33 ± 0.17 ) mmol/L,(0.46 ± 0.05 ) mmol/L,( 12.38 ±1.19)/24 h and (6.78 ±0.12) × 103].Moreover,the above indexes in group QUE were obviously lower than group DM.There was evidence of pathological changes associated with diabetes,such as focal and segmental sclerosis and thickened basement and mesangial expansion.The expressions of ubiquitin and NF-κB p65 in renal tissues of group DM increased significantly ( P ＜ 0.01 ).The expression of ubiquitin and NF-κB p65 were positively related with the level of 24 h UP ( r =0.893,0.879,P ＜ 0.01 ).Compared with group DM,all above indexes in group QUE were markedly alleviated ( P ＜ 0.01 ).The expression of ubiquitin and NF-κB p65 was reduced but didn't reach level in group NC ( P ＜ 0.01 ).Conclusion The increased expression of NF-κB induced by ubiquitin-proteasome system may participate in the pathogenesis of proteinuria in diabetic nephropathy.Quercetin has renal protective effects partly through reducing NF-κB p65 expression.%目的 探讨槲皮素对2型糖尿病大鼠肾脏损害的保护作用及其机制.方法 清洁级SD雄性大鼠采用高糖高脂饲料喂养及腹腔注射小剂量链脲佐菌素建立2型糖尿病大鼠模型,72 h后断尾法采血检测血糖≥16.7 mmol/L视为模型用鼠.成模大鼠按数字表法随机分组,其中糖尿病模型组(DM组)9只,槲皮素治疗组(QUE组)9只,另设正常对照组(NC组)8只.8周处死大鼠,检测空腹血糖(FPG)、空腹胰岛素(FIns)、血肌酐(SCr)、尿素氮(BUN)、TG、TC、LDL-C、24 h尿蛋白(24h UP)、肾脏肥大指数(KI).过碘酸六胺银染色观察肾脏病理改变,免疫组化方法检测肾脏组织中泛素、NF-κB p65蛋白表达,并分析其与蛋白尿发生的相关性.结果 DM组和QUE组FPG[ (25.45±1.23) mmol/L和(19.99±1.20) mmol/L]、FIns[( 25.67±2.58) mU/L和(19.29±1.80)mU/L、SCr[ (44.00±2.53) μmoL/L和(34.43±2.23) μmol/L]、BUN[(11.60±0.39) mmol/L和(8.20 ±0.37) mmol/L]、TG[(3.32±0.22) mmol/L和(2.43±0.25) mmol/L]、TC[ (2.95±0.21)mmol/L和(2.24±0.17) mmol/L]、LDL-C[(2.03±0.22) mmol/L和(1.49±0.13) mmol/L]及24 h UP[ (46.67±2.50) mg/24 h和(25.57±2.82) mg/24 h]及KI[ (9.76±0.30)×103和(8.44±0.26)×103]均显著高于NC组[(6.56±0.41) mmol/L、( 12.63±1.41) mU/L、( 22.88±2.36) μmol/L、(5.45±0.51) mmol/L、(1.64±0.11) mmol/L、(1.33±0.17) mmol/L、(0.46 ±0.05) mmol/L、( 12.38±1.19)/24 h和(6.78±0.12) ×103];而QUE组上述指标均明显低于DM组,P值均＜0.05.DM组大鼠肾脏组织主要表现为肾小球基底膜不规则增厚,系膜细胞增生及系膜基质增多等病理改变,且肾小球泛素、NF-κB p65蛋白的表达均上调(p＜0.01),并与蛋白尿发生呈正相关(r=0.893,0.879,P＜0.01)；QUE组肾脏组织病理改变明显减轻,肾小球泛素、NF-κB p65蛋白的表达下调(P值均＜0.01),但均未能达到NC组水平.结论 泛素蛋白酶复合体系统介导的炎症因子NF-κB p65过度表达可能导致2型糖尿病肾病的进展,而槲皮素可以抑制NF-κB p65表达而发挥保护作用.
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