The Effects Of Pioglitazone On The Autoimmune Injuries To The Kidneys And The Skeletal Muscle In STZ-induced Diabetic Rats

The effects of pioglitazone on the autoimmune injuries to the kidneys andskeletal muscle in STZ-induced diabetic ratsObjective:The chronic complications may appear in all organs in the daibetispatients,which severely damage their health.The mechanism of these chroniccomplications still remains unclear while recent studies have implied that theabnormal immune responses may play an important role in the pathogenesis ofchronic complications of diabetes.By biopsy,we also demonstrated the deposition ofimmunological complexes and complements of various kinds on the kidneys andskeletal muscle in the most patients of T2DM.Our previous studies showed thatdiabetes kidney disease(DKD) of diabetic rats (eight weeks)could be effectivelyprevented by the administration of cyclosporine A(CsA).But we did not know howabout its effects in the rats with longer course of diabetes.Recently,more and morestudies indicate Thiazolidinediones(TZDs) showed immunoregulatory effect,butthere is no report about weather they has the regulatory effects on the abnormalautoimmunity of the chronic complications of diabetes.p38 mitogen-activated protein kinase (MAPK) pathway plays an important rolein the processes of stress,inflammation,apoptosis,protein synthesis and secretion,and cell differentiation.p38MAPK activation is a feature of early stage of DKD,diabetic neuropathy and macrovascular disease.However,whether p38MAPKactivatin could be detected in advanced stages of DKD remains to be elucidated,andwhether p38MAPK is associated with the development of diabetic myopathy ofskeletal muscle had not been reported.It has been shown that TZDs may activate p38MAPK in adipocytes and liverepithelial cells,but it has no effect on p38MAPK activation of human mesangial cells.p38MAPK activation may be suppressed by CsA in cardiomyocytes throughinhibitting calcineurin(CaN) and PKC.Till now,however there is still no any reporton whether p38MAPK activation could be affected by TZDs and CsA in the renalcortex and skeletal muscle during the course of DKD and diabetic myopathy of skeletal muscle.In the current study,our investigation aimed at the abnormal deposition ofimmunoglobulins in the renal cortex and skeletal muscle of STZ-induced diabetic ratsand evaluate the protective effects of pioglitazone(PIO) and CsA against theseimmunological complexes.And the effects of pioglitazone(PIO) or CsA were studiedon the activity of p38MAPK,apoptosis,the expression of inflammatory factors andglucose transporters(GLUTs) in the diabetic rats.Materials and methods:The DM rat models were made by intravenousinjection of STZ(45mg/kg).Then,they were randomly divided into seven groups,including small-dose PIO group (group A,4mg/kg/d),large-dose PIO group (group B,20mg/kg/d),small-dose PIO combined with glargine group (group C,PIO 4mg/kg/dand glargine 4U//kg/d),CsA group (group D,lmg/kg/d),CsA combined with glarginegroup(group E,CsA lmg/kg/d and glargine 4U//kg/d),glargine trentmentgroup(group F,glargine 4U//kg/d) and no-treatment group(group G).Another groupof normal rats(group CON) was also monitored simultaneously.Sixteen weeks later,renal function,urine albumin and serum insulin were evaluated.The pathologicalchanges were studied in kidneys and skeletal muscle by light and electron microscope.The deposition of immunoglobulins was detected on the renal cortex and skeletalmuscle by immunohistochemistry and immunofluorescence.At the same time,theexpression of p-p38MAPK,TGFβ1,TNFα,Bax,Bcl-2,Fas,Fas-L,GLUT1 andGLUT4 was detected by immunohistochemistry.Results:1.In group G,glomerular sclerosis,fibrosis,widespread deposition ofglycogen granules in proximal tubular epithelial cells(PTEC) were showed by lightmicorscope.Irregular thicking of glomerular basement membrane,mesangialexpansion and fusion of epithelial cells foot processes were observed by electronmicroscope.Pathological changes of skeletal muscle were characterized primarily bywidespread myatrophy and dotted dissolving of myofilament.The above-mentionedchanges relieved to some extent in the groups treated with PIO or CsA.2.Comparedwith the control group,the deposition of IgG,IgA and IgM was remarkably increasedin renal cortex and skeletal muscle of group G rats.The immunoglobulins depositionon these organs was obviously decreased in PIO or CsA treatment groups than in group G.3.Compared with the control group,the expressions ofp-p38MAPK,TGFβ1,TNF-α,Bax,Fas,Fas-L,GLUT1 and GLUT4 in the renal cortexof diabetic rats were significantly increased in group G,and the ratio of Bax/Bcl-2was elevated.While all the values were obviously decreased in the groups treatedwith PIO or CsA than in group G.4.Compared with the control group,theexpressions of p-p38MAPK,TGFβ1,TNF-α,Bax,Fas and Fas-L in the skeletalmuscle were significantly increased,and the ratio of Bax/Bcl-2 was elevated,theexpression of GLUT1 and GLUT4 were decreased markedly in group G.Theexpressions of p-p38MAPK,TGFβ1,TNF-α,Bax,Fas and Fas-L were obviouslydecreased in the groups treated with PIO or CsA than in group G,and the expressionof GLUT4 was increased,but the expression of GLUT 1 had no change.Conclusions:1.The deposition ofimmunoglobulins on renal cortex and skeletalmuscle of STZ-induced diabetic rats suggests that the autoimmune injuries happenedto those tissues and was involved in the pathogenesis of the chronic diabeticcomplications.2.Immunoregulatory or immunosuppressive treatment with PIO orCsA have demonstrated protective effects on kidney and skeletal muscle by inhibitingthe abnormal deposition of immunoglobulins on them.3.Renal cortical p38MAPKactivity was increased in diabetic rats at advanced stages of DKD,as compared withnon-diabetic rats,and the expressions of TGFβ1,TNF-α,pro-apoptotic protein,GLUT1 and GLUT4 were demonstrated in the renal cortex.All the factors interactedwith each other and promoted the development of diabetes kidney diseases.4.Thep38MAPK pathway was activated in the rats of diabetic myopathy of skeletal muscle,at the same time,the expression of TGFβ1,TNF-α,pro-apoptotic protein wereincreased.5.p38MAPK activity and the expressions of TGFβ1,TNF-αandpro-apoptotic protein could be suppressed by treatment with PIO or CsA on the renalcortex and skeletal muscle in the diabetic rats,simultaneously,abnormal expressionsof GLUT1 and GLUT4 in the kidneys and the decreased expression of GLUT4 in theskeletal muscle could be improved.