Protection Of Simvastatin On Kidney Of Diabetic Rats And The Molecular Mechanism

Objective:Diabetic kidney disease is one of the most common microvascular complications of diabetes and is a major pathogeny of renal failure.The current treatment is only to alleviate the symptoms,but does not improve the potential pathophysiological changes of diabetic kidney disease.This study aimed to investigate the protective effect and the molecular mechanism of simvastatin on the kidney of diabetic rats.Methods:24 SD rats were randomly divided into normal control group(NC group,n = 8),diabetic group(DM group,n = 8)and simvastatin intragastic administration group(DM + Sim group,n = 8).The model rats were injected streptozotocin(STZ)to induced diabeties intraperitoneally.Rats in DM + Sim group were given simvastatin for 4 weeks,and the other two groups were given the same volume of saline for 4 weeks.During the experiment,the rats were weighted every day,and the blood glucose of rats was measured every three days,the 24-hour unire of rats was collected at the end of first and the fourth weekend of simvastatin intragastic administration,and 24-hour urinary protein of rats was measured.At the end of the experiment,the blood in abdominal aorta was drawn and the total cholesterol(TC)and triglyceride(TG)were measured.The bilateral kidneys were removed and the level of malondialdehyde(MDA)and the activity of superoxide dismutase(SOD)were detected.H&E staining was used to observe the morphological changes of kidney.Sirius Red staining was used to observe the renal fibrosis.Western blot and immunohistochemistry(IHC)were used to detect the expression of GRP78,p-IRE1α,IRE1α,NF-κB p65,MCP-1,nephrin,p-p53,p53,Bax and Bcl-2,and the apoptosis of rat kidney tissue was detected by TUNEL.Results:1.Compared with NC group,the body weight of DM group and DM + Sim group increased slowly,while the blood glucose in these groups increased rapidly.There was no statistical difference in body weight and blood glucose level between these two groups.2.Compared with NC group,TC and TG in DM group increased significantly(P <0.01).After simvastatin intragastic administration and compared with DM group,TC(P <0.01)and TG(P <0.05)in DM + Sim Group decreased.3.At the end of first week of simvastatin intragastic administration,compared with the NC group,the 24 h urinary protein in DM group increased significantly(P <0.01),but compared with the DM + Sim group,it has no significant difference;at the end of the fourth weekend of simvastatin intragastic administration,Compared with NC group,24-hour urinary protein in DM group and DM + Sim group increased significantly(P <0.01),but 24-hour urinary protein in DM + Sim group was lower than that in DM group(P <0.05).4.The level of MDA in kidneys of DM group was higher significantly than that in NC group(P<0.01),while the activity of SOD was significantly lower than that in NC group(P<0.01).Compared with DM group,the activity of SOD in DM + Sim group increased(P<0.05),while the level of MDA decreased(P<0.01).5.H&E staining was used to observe the structure of kidney slides.Compared with the NC group,rat kidney in DM group showed diffuse glomerulosclerosis,partial glomerular deformation and constriction,mesangial cells and mesangial matrix proliferation,the vascular lumen and Mandel’s capsule stenosis and even occlusion,renal tubular atrophy,and inflammatory cell infiltration in renal tubuar interstitial.After simvastatin intragastic administration,the structure of renal tissue in DM + Sim group was significantly improved,and there was no obvious pathological change in NC group.Rat kidney in NC group showed no pathological changes.6.Under ordinary microscope,the red collagen fibers of glomerulus and renal tubule in NC rats were evenly distributed,and the coloration was faint.The red collagen fibers in glomeruli and accessory tubules was obivious extensive,dark,tangled,and distributed inhomogeneously in DM group(P<0.01).After simvastatin intragastic administration,the red staining was only slightly stained in DM + Sim group(P <0.01).7.Western Blot and immunohistochemistry showed that the expression of GRP78,P-IRE1α,NF-κB p65,MCP-1,p-p53,p53 and Bax in DM group increased(P<0.05),while the expressions of nephrin and Bcl-2 decreased significantly(P<0.05).However,compared with DM group,the expression of GRP78,P-IRE1α,NF-κB p65,MCP-1,p-p53,p53 and Bax in DM + Sim group all decreased(P<0.05),while the expression of nephrin and Bcl-2 increased significantly(P <0.05).8.TUNEL staining showed that the apoptotic nuclei were brown and granular,and some apoptotic nuclei were pyknotic and deformed with a small volume,and the normal nuclei were purple-blue.Only a small number of apoptotic nuclei were observed in NC group.In DM group,there were a large number of apoptotic nuclei in glomeruli and accessory tubules,which were significantly more than those in NC group(P<0.01).After simvastatin intragastic administration,apoptotic nuclei were significantly reduced(P <0.01).Conclusion:1.Simvastatin has little influence on blood glucose and body weight in diabetic rats;2.Simvastatin can significantly reduce the level of blood lipid of diabetic rats,and can delay the formation of urinary protein to improve the function of kidney;3.Simvastatin can improve significantly the pathological renal changes of diabetic rats,and delay the structural damage of diabetic kidney;4.Lipid peroxidation,endoplasmic reticulum stress,inflammatory response and apoptosis are all contribute to the development of kidney injury of diabetic rats;5.Simvastatin can alleviated kidney pathological injury and interstitial fibrosis of diabetic rats through inhibition lipid peroxidation,thereby inhibiting the endoplasmic reticulum stress and inflammatory response;6.Simvastatin reduces apoptosis of kidney cells in diabetic rats by inhibiting the expression of pro-apoptotic proteins and up-regulating the expression of anti-apoptotic proteins.