The Effect Of Atorvastatin On SIRT1 Expression In Diabetic Rat Kidney And Its Possible Protective Role In Diabetic Kidney

Objective:With the incidence of diabetes increases gradually,diabetic complications have attracted more and more attention.As a severe diabetic microvascular complication,diabetic nephropathy is the main cause of end-stage renal disease,because of its high mortality and disability rate,it has done severe harm to diabetics and our society^[1].In recent years,it has been found that the occurrence of diabetic nephropathy is related to the combined action of oxidative stress,inflammatory reaction,energy metabolism,renin angiotensin,heredity and so on^[2].SIRT1?silent mating type information regulation homolog 1,2 mechanisms 1?is mostly studied in the SIR Family of7 histone deacetylase,it is a protein highly homologous with silencing information regulator 2?Sir2?in mammals,and a kind of histone deacetylase dependent on nicotinamide adenine dinucleotide?NAD+?.Researches suggest that SIRTl plays an important role in neurodegeneration,metabolic diseases,cardiovascular diseases,cancer and the pathological process,disease progression and treatment process of aging-related diseases^[3].Chuang PY and others believe that the activation of SIRT1 has protective effect on high glucose induced mesangial cells and podocytes^[4-5],animal experiments and clinical studies have demonstrated that SIRT1 activation can delay the occurrence and development of diabetic nephropathy^[6-7].Atorvastatin is the third generation of?-hydroxy beta-methyl amyl two acyl coenzyme A?HMG-CoA?reductase inhibitor and is widely used in in clinical practice.In addition to lipid-lowering,anti-oxidant,anti-inflammatory,anti-aging,improve athero-sclerosis,it also has renal protection not dependent on lipid-lowering^[8-9].Whether atorvastatin may protect kidney by regulating the expression of SIRT1 is rarely reported,the purpose of this study is to explore the effect of atorvastatin on the expression of SIRT1 in renal tissue of diabetic rats and to investigate the protective effect of atorvastatin on renal injury in diabetic rats and its possible mechanism.Methods:54 healthy female Sprague-Dawley?SD?rats weighed 160-200g were divided randomly into two groups.Rats of the normal control group?NC group?received standard chow.The experimental rats were given a high carbohydrate and high fat diet all through and an intraperitoneal injection of streptozotocin?STZ?at the dose of 30mg/kg.At week 10,we measured the body weight?BW?and biochemical index,including the fasting blood glucose?FBG?,fasting insulin?FINS?,total cholestero1?TC?and triglycerides?TG?,insulin resistance of the diabetic rats was confirmed by HOMA-IR.Then the rats were randomly divided into two groups:diabetes mellitus group?DM group?and atorvastatin group?A group?.We measured their blood glucose and body weight weekly.At week 21,FBG,FINS,TC,TG,glycosylated hemoglobin?HbA1c?,alanine transaminase?ALT?,aspartate aminotransferase?AST?,serum creatine?SCr?,UREA,HOMA-IR and BW were measured totally.The kidneys were resected and weighed after tissues outside the kidney,such as the capsule,fat,etc.were removed?kidney weight,KW?.Kidney index?KI??KW/BW?was calculated for each rat.Kidney specimens were PAS-stained to observe morphology changes.The expression of sirt1 in kidney were assessed by immunohistochemical staining.Western Blot method was used to determine the protein trace of sirt1 in each group.Data analysis was performed by SPSS 21.0,and P<0.05 was considered statistically significant difference.Results:1.BW changes At week 10,BW of the diabetic rats was apparently higher than the NC group?P<0.05?.At week 21,compared with the NC group,BW of the rats in DM group and A group was significantly lower?P<0.01?.No significant difference was observed between DM group and A group?P>0.05?.2.Biochemical index At week 10,FBG,FINS,TG,TC of the diabetic rats were significantly higher than NC group?P<0.01?.At week 21,compared with NC group,FBG,FINS,TG,TC and HbAlc of the rats in DM group and A group increased significantly?P<0.01,P<0.05?,UREA level in DM group and A group was higher than NC group?P<0.05?,but there was no significant difference between DM group and A group?P>0.05?.No difference was found between the DM group and A group?P>0.05?.Among the three groups,there was no significant difference in levels of SCr,ALT and AST?P>0.05?.3.Sensitivity to insulin At week 10,HOMA-IR of the diabetic rats was much higher that of NC group?P<0.01?.This proved diabetic rats had insulin resistance and the rats were type 2 diabetic rats.At week 21,HOMA-IR in DM group and A group was obviously higher than NC group?P<0.01?.No HOMA-IR difference was confirmed between DM group and A group?P>0.05?.4.Kidney Index?KI? At week 21,KI and Kw of both DM group and A group was significantly higher?P<0.01?than that of NC group,KI and Kw of A group was lower?P<0.01?than that of DM group.5.Morphology changes:The volume of glomeruli increased,the basilar membrane of capillaries thickened,and thickening of the mesenchymal area was more obvious than that in the normal group,and the renal interstitium showed partial renal tubular dilation,and the renal tubular epithelial cells shed and regenerated.A group rats kidney disease than DM group slightly.6.Immumohistochemical staining SIRTl positive expression for tan dye,The expression of SIRT1 was found in the Glomeruli and proximal convoluted tubule and distal convoluted tubules.Sirt1 is mainly expressed in the nucleus and a small amount of expression in the cytoplasm.In group DM and group A,the expression of SIRT1 in renal cortex was significantly lower than that in group NC?P<0.01,P<0.05?.SIRT1 expression in renal cortex of A group was higher than that of DM group,with statistically significant difference?P<0.05?.7.SIRT1 Western blot result in renal cortex Compared with the NC group,sirt1 expression in the renal cortex of the DM group was reduced?P<0.01?.The expression of sirt1 in group A was higher than that in DM group?P<0.01?.Conclusions:Compared with the normal control group,diabetic rats'kidney weight?KW?and kidney index?KI?were higher,and their glomerular volume increased and basement membrane thickened,which indicates kidney damage.The immunohistochemical results showed expression of SIRT1 in renal tissue of diabetic rats decreased,while after atorvastatin is used,the expression of SIRT1 increased,KW and KI decreased,glomerular lesions and renal damage were reduced in diabetic rats.It suggests a possible cholesterol-indepe.