| Objectives:Diabetic nephropathy is the most common cause of end-stage of renal disease in the world. It is a serious hazard to human health. Diabetic nephropathy is characterized by glomerular hypertrophy, mesangial matrix expansion and glomerular basement membrane thickening followed by glomerulosclerosis. In recent years, Smads super family protein in glomerulosclerosis has been concerned. In this study, we investigated expression of Smadl in kidney of diabetic nephropathy rat to explore the relationship between Smadl and mesangial matrix expansion. At the same time diabetic rat were treated with olmesartan to boserve the expression of Smadl to prove possible mechanisms of angiotensin II type 1 receptor blocker(ARB)in slowing the progression of renal disease.Methods:64 Sprague-Dawley rats were randomly divided into three group, control group included 16 rats, diabetic group and treatment group were 24 rats. Intraperitoneal injection Streptozotocin (55mg/kg) induced diabetics, rats receiving an injection of citrate buffer were used as controls. Treatment group rats were treated with the ARB, olmesarta (0.6mg/kg.d) after three weeks, other rats treated with nomal saline. The rats were sacrificed at 3 w, 4w,12w and 20w respectinely. Glycosylated hemoglobin, serum creatinine and kidney weight index were measured in each rats, while creatinine and albumin were measured from a 24-h urine collection, meanwhile kidney sections were observed by electron microscopy, masson staining, periodic acid silver methenamine (PASM) and periodic acid Schiff (PAS) used to monitor the renal pathological changes. The protein expression of Smadl and collagen IV in kidney were detected by immunohistochemistry and western blot, the mRNA expression of Smadl and collagen IV were detected by reverse transcription polymerase chain reaction. Using an image analyzer with microscopy to analyse the correlation.Results:1. The levels of glycosylated hemoglobin, serum creatinine, kidney weight index,24h Albuminuria of diabetic rats were all progressive during the period of the experiment. The levels of HBA1c,24h urine volume and 24h albuminuria in diabetic group were remarkably higher than those in control group(p<0.05, p<0.01)meanwhile it showed that diabetic modal was successful.2. The results of immunohistochemistry showed that diabetic rats Smadl mainly expressed in the mesangial area, with little expression in renal tubules, decreased expression in the control group. The results of western blot indicated that the protein levels of Smadl were increased 16-fold (p<0.01) in diabetic rats as compared with that of the controls at 3w, expression of Smadl in treatment group decreased 8.3-fold compared with diabetic group at 20w. The results of reverse transcription polymerase chain reaction reveal that the mRNA levels of Smad1 in treatment group were decreased 1.7-fold compared with diabetic rats at 20w. They were indicated that expression of Smadl in the diabetic rat increased, olmesarta decreased expression of Smadl.3. The results of immunohistochemistry showed that there is collagen IV expresses mesangial area, but in diabetic group were remarkably higher than those in control group, they were all progressive during the period of the experiment, The results of reverse transcription polymerase chain reaction show that the mRNA levels of collagen IV in treatment group were decreased 2.3-fold compared with diabetic rats at 20w(p<0.05).4. Expression of Smadl and collagen IV increased in 3 weeks compared with control group (p<0.05)by immunohistochemistry and western blot, meanwhile albumin in the urineit was increased in 3 weeks. Using Image-Pro PLUS analyzed that Smadl of diabetic rats was nicely correlated with collagen IV (r=0.68, p<0.01), while albuminuria showed a weaker association (r=0.45, p=0.043).Conclusions:1. Expression of Smad1 in the diabetic rats show that Smadl may play a role in the progression of early diabetic nephropathy, whether Smadl in an early phase of diabetes can predict later development of glomerulosclerosis in diabetic nephropathy2. Angiotensin II typel receptor blocker (significantly ameliorates glomeruloscrelosis possibly through Smadl signaling pathway. |
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