| Objective: The study observed the expression of PEDF and VEGF inkidney tissues of Type1diabetic rats which were induced bystreptozotocin,the intervention effects of candesartan to examine the role ofPEDF and VEGF in the development of diabetic nephropathy (DN) and themechanism of candesartan’s renoprotection.Methods:1.Thirty-six male Wistar rats were divided into3groupsrandomly: normal control rats (NC group,n=12),diabetic model rats (DMgroup,n=12) and diabetic model rats treated with candesartan(DM-Cgroup,n=12). The rats of DM and DM-C group were induced diabetes byintraperitoneal injection of streptozotocin (STZ,50mg/kg) singly after anovernight fast. The rats of NC group received an injection of citrate buffer ofthe same volume alone.72hours after STZ injection,the rats with the bloodglucose higher than16.7mmol/l were demmed successful diabetes modeling.The rats of DM-C group were treated with candesartan5mg·kg-1·d-1and theother groups were treated with the equal volume of normal saline. At the endof12weeks of intervention,all rats were put in metabolic cages to collect the24-hour urine,which was used to measure urinary albumin excretion(UAE).The rats were weighted and collected plasma samples for the assay offasting blood glucose (FBG),serum creatinine（Scr）,blood urea nitrogen（BUN）. Cut right kidney,removed capsule and weighed. Pathologicalchanges of the kidney was observed by microscope and transmission electronmicroscope. The protein expression of PEDF and VEGF in glomeruli andtubulars were determined by immunohistochemistry. The left kidney wereisolated,and stored in-70°C refrigerator.The mRNA expression of PEDF andVEGF was detected by reverse transcription polymerase chain reaction(RT-PCR). Results: At the end of the study,12rats in NC group,10rats in DM groupand9rats in DM-C group survived.1FBG， BW：FBG and BW in DM and DM-C group were higher thanthat in NC group(P＜0.01). There were no significant differences betweenDM and DM-C group in FBG and BW (P＞0.05).2Scr,BUN,KW/BW,UAE: Scr,BUN in DM and DM-C group werehigher than that in NC group (P＜0.01). There were no significant differencesbetween DM and DM-C group in Scr,BUN (P＞0.05).24-hour UAE andkidney index(kidney weight/body weight，KW/BW) in DM and DM-C groupwere higher than that in NC group (P＜0.01). After candesartanintervention,24-hour UAE and kidney index were significantly decreasedcompared with that in DM group (P＜0.01,P＜0.05).3Immunohistochemistry:①PEDF was expressed at high levels inglomeruli and tubulars in NC group,and mainly in mesangial and basementmembrane area. The expression of PEDF in glomeruli and tubulars in DM andDM-C group was lower than that in NC group（P <0.01）,the expression ofPEDF in DM-C was higher than that in DM group（P <0.01）.②Theexpression of VEGF in glomeruli and tubulars in NC group was very few.Theexpression of VEGF in kidney in DM group was higher than that in the rats ofNC group（P <0.01）,but lower than that in DM-C group（P <0.01）.4Pathomorphological changes of the kidney：HE and PAS stainingshowed that there were no obvious abnormalities in the kidneys of NC group.In the rats of DM group, there were structural disorder in glomeruli andtubulars,glomerular hypertrophy,mesangial area expansion,extracellular matrixincreased,part of the glomeruli were smaller in size,some tubulars atrophy.PAS-positive materials increased in DM and DM-C group,which meant thatthe basement membrane was thickening and the mesangial area expanded indiabetic rats compared with in NC group. Transmission electron microscoperevealed that the glomerular basement membrane was thickening and the footprocess were converged and damaged in diabetic rats. The abnormal changeswere alleviated after candesartan intervention,although not normalized. 5The mRNA expression of PEDF and VEGF in kidney tissues: ThemRNA expression of PEDF in DM and DM-C group was lower than that inNC group（P<0.01）,but it was higher in DM-C group than that in DM group（P<0.05）.The mRNA expression of VEGF in DM and DM-C group washigher than that in NC group（P<0.01）,but it was lower in DM-C group thanthat in DM group（P <0.05）.6Pearson correlation analysis showed that the mRNA expression ofPEDF was negatively correlated with24-hour UAE（r=-0.696,P<0.01）,themRNA expression of VEGF was positively correlated with24-hour UAE（r=0.767,P<0.01）.Conclusions:1In the kidney tissue of diabetic rats，the expression of PEDF wassignificantly decreased,the expression of VEGF was significantly increasedand24-hour UAE was significantly increased， accompanied with theabnormality of renal function.2Candesartan decreased24-hour UAE, reduced the pathologicaldamage of kidney.3Candesartan may play renoprotective effect through maintaining thedynamic balance of PEDF and VEGF via up-regulating the expression ofPEDF and down-regulating the expression of VEGF. |
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