The Effects Of Pioglitazone On The Autoimmune Injuries To The Spinal And Sural Nerves In STZ-induced Diabetic Rats

Objective: Diabetic neuropathy (DN) is a common complication of diabetes. Currently, more and more patients suffered from DN as the incidence of diabetic mellitus is increasing. The pathogenesis of DN remains unclear and the clinical therapy still focus on the strict glycemic control,which turned out ineffective. The study on the pathogenesis of DN will help us to get better results in preventing the development of DN.Recent studies in our clinical works have implied that autoimmune may play an important role in the pathogenesis of chronic complications of diabetes. We demonstrated the deposition of immunocomplexes and complements on the kidneys and skeletal muscle in most of patients with T2DM through biopsy.Our previous studies have showed that autoimmune and inflammation played a role in the injuries to the spinal and the sciatic nerves in STZ-induced diabetic rats and the use of cyclosporine A(CsA) can effectively inhibit the progression of the autoimmune injuries.Pioglitazone is one of the Thiazolidinediones(TZDs) drugs and is used as insulin sensitizer for several years. Recently, more and more studies indicate Thiazolidinediones(TZDs) can regulate the immunoreaction and inhibit the inflammation in some autoimmune diseases.so we designed the study to see if Pioglitazone has immunodepressive and anti-inflammatory effects in the spinal and the sural nerves of STZ-induced diabetic ratsMaterials and methods: The DM rat models were established by intravenous injection of STZ(45mg/kg).Then, they were randomly divided into eight groups, including small-dose PIO group (group PioH,4mg/kg/d), large-dose PIO group (group PioL,20mg/kg/d), small-dose PIO combined with glargine group (group PiI, PIO4mg/kg/d and glargine4U//kg/d), CsA group (group CSA, lmg/kg/d), CsA combined with glargine group(group CSI, CsA lmg/kg/d and glargine4U//kg/d), glargine trentment group(group INS, glargine4U//kg/d) nontreatment group(group DM) and the CON group. The hepatic and renal function, serume insulin were monitored along with the time. Sixteen weeks later, the rats were put to death and the specimens were got. HE stain were used to observe the pathological changes in the spinal and the sural nerves.The immunohistochemistry and immunofluorescence technology were employed to reveal the deposition of immunoglobulins and the expression of p-p38MAPK, NF-κB and TNFa proteins.Results:1. After STZ injection (45mg/kg) the blood glucose of the experimental rats were higher than16.7mmol/l,and we successfully established the diabetic rats model.2. After sixteen weeks, compared with the DM group, the blood glucose level of the rats in the group PioH,PioL and the group CSA have no statistic significance(p<0.05).3. After sixteen weeks, compared with the group DM,the serum ALT,AST and TB1L level of the rats in the group PioH,PioL and the group CSA did not increase, and the difference of the data showed no statistic significance(p<0.05). The serum ALB level of the rats in the group PioH,PioL and the group CSA were increased, while the serum BUN,and Cr level were decreased. Compared with the group DM, the difference had statistic significance(p<0.05).4. the HE stain of the spinal specimen slides in the groupDM showed no obvious pathological chages while the sural nerve specimen slides showed axon atrophy and myelin swelling. The pathological changes of the sural nerves in group PioH,PioL and the group CSA were slighter than the group DM.5. The immunohistochemistry and the immunofluorence stain showed the deposition of IgG、IgA、IgM in the group PioH,PioL and the group CSA were less than the group DM.Among the group PioH,PioL and the group CSA deposition of IgG、IgA、IgM in group CSA were the least,and the difference in the IOD value beween the group PioH and the group CSA were not significant(p<0.05).6. The immunohistochemistry stain showed the expression of p-p38MAPK, NF-kB and TNFa proteins in group PioH,PioL and group CSA were less than the group DM.Among the group PioH,PioL and group CSA, the expression level of these three proteins in the group CSA were the lowest,and the difference of the IOD value beween the group PioH and the group CSA were not significant(p<0.05).Conclusions:1. The diabetic rats model were successfully established by intravenous injection of STZ.2. the deposition of the immunoglobulin and the activation of the inflammation in the spinal and the sural nerves of the STZ induced diabetic rats were observed,which indicate that the autoimmune injuries were involved in the pathogenesis of diabetic neuropathy.3. CSA can decrese the deposition of the immunoglobulin and inhibit the inflammation in the spinal and the sural nerves of the STZ induced diabetic rats.Using pioglitazone in dosage of20mg/kg/d can get the same effect as the CSA.4. Pioglitazone and CSA have glycemic independent protective effects in autoimmune injuried in the spinal and the sural nerves in STZ induced diabetic rats.5. The dosage and the therapeutic duration of pioglitazone and CSA showed no hepatic or renal toxicity.