Experimental Study On The Relationship Between TLR4and Diabetic Cardiopathy In Type2Diabetic Rats And The Effects Of Simvastatin

Objective:Type2diabetes mellitus is a polygenic inheritance metabolicdisease,its chronic complications can be widely involved in heart,liver,kidney,retina,blood vessels,nervous system,skeletal muscle,skin and so on,anddiabetic cardiopathy is a serious threat to the lives of patients with diabetes.Itspathogenesis has not yet been systematically clarified,it is thought to beclosely related to oxidative stress,inflammatory reaction,the metabolicdisorder of sugar and lipid,insulin resistance,vascular dysfunction, abnormalmicrocirculation,myocardial membrane dysfunction,glycosylation end-products and so on.In recent years, inflammation and immune theory haveattracted the attention of the people.Toll-like receptor4(TLR4) is the mainreceptor mediated inflammation and the immune response that can recognizemany kinds of exogenous ligand,but also can identify the endogenous ligandregarding inflammation,stress,body injury.After combinding with ligand,it canactivate the cell signal transduction pathway and lead to a series ofinflammatory and immune response.TLR4signal transduction pathway havean important role in the regulation of gene expression in inflammation andimmune response,so the TLR4can be the treatment target of inflammationand autoimmune disease.Simvastatin is a HMG-CoA reductase inhibitor thatcan improve endothelial function,anti-inflammatory,stabilize plaque,anti-thrombotic,anti-cell withered death and so on,aparting from reducing theformation of cholesterol and low density lipoprotein.It has broad applicationprospects in immune and inflammatory diseases.In this experiment,the ratmodels of type2diabetes were prepared,the expression of TLR4in the heartof rats was detected in order to explore the relationship between TLR4andT2DM heart disease and the effects of simvastatin in diabetic cardiopathy. Methods:Fourty male healthy sprague-Dawley rats were randomlydivided into normal control group (group A,n=10) and test group (n=30) bythe application of the random number tables.The control group rats were fedwith normal food,but the test group rats were fed with high-sugar-fat food(mixed with20%sugar,2.5%cholesterin,l5%cooked lard in general food).Four weeks later,the test group rats were induced to diabetes by injectingstreptozotocin at a dosage of30mg/kg,but the control group rats were injectedthe same dose of citric acid buffer.At the end of the6week,the rats whosefasting blood glucose (FBG) were higher by7.8mmol/L and present in thestate of insulin resistance were choosed to be the type2diabetes models.Thenthe diabetic models were divided into two groups:the diabetic group (groupB,n=13) and the Simvastatin intervention group (group C,n=13).The rats inSimvastatin group were given Simvastatin at a dosage of20mg/kg by dailygavage and the ones in control group and diabetic group were received theequal volume normal saline,the gavage was continued for8weeks.At the endof the14week,the body weight of all rats was measured.Then the rats werekilled to collect the blood sample and the heart.FBG,triglyceride (TG),totalcholesterol (TC),low-density lipoprotein cholesterol (LDL-C),high-densitylipoprotein cholesterol (HDL-C),creatine kinase (CK) were measured.Theprotein expression of TLR4in the heart was detected byimmunohistochemistry staining.The TLR4mRNA were measured byRT-PCR.The data was dealt with SPSS13.0.Results:1The experimental data after6weeks:The FBG11.98±1.97mmol/L intest group was higher than5.85±1.11mmol/L in control group (P<0.05).There was no significant difference between the FINS17.90(3.63) mIU/L intest group and17.00(5.14) mIU/L in control group (P＞0.05).The ISI0.0051(0.0018) in test group was lower than the ISI0.0110(0.0051) in controlgroup (P<0.05).(Table1,Fig.1-3)2Various biochemical indexes after14weeks:FBG12.04±2.04mmol/Lin the diabetic group and11.23±2.61mmol/L in the Simvastatin group were higher than5.92±1.28mmol/L in the control group (P<0.05),but the FBGbetween diabetic group and Simvastatin group was not statistically distinction(P＞0.05).TG,TC,LDL-C in the diabetic group and Simvastatin group werehigher than that in the control group (P<0.05),but HDL-C,CK among the threegroups were no significant difference (P＞0.05).(Table2,3)(Fig.4-6)3Morphology:The myocardial cells in control group were in order,kary-ons and intercellular space were normal,with no significant inflammatory cellsinfiltrating.While in T2DM model rats,the myocardial cells were disorganizedwhich show edema, degeneration and necrosis.There was breakage ofextensive myocardial fibers and interstitial hyperemia with significantinflammatory cells infiltrating.The situation in Simvastatin group was relievedthan that in diabetic group.(Fig.7-9)4The protein expression of TLR4:Immunohistochemistry staining resultsshowed that the expression of TLR4in diabetic group and Simvastatin groupwas significantly increased than that in control group (P<0.05).The expressionof TLR4in Simvastatin group was decreased than that in diabetic group(P<0.05).(Table4,Fig.10-12)5The mRNA expression of the TLR4:Compared with the control group,the TLR4mRNA in diabetic group and Simvastatin group was significantlyincreased (P<0.05).The expression of the TLR4mRNA in Simvastatin groupwas decreased than that in diabetic group (P<0.05).(Table5,Fig.13)Conclusion:1The expression of TLR4in the heart of type2diabetic rats wassignificantly increased,which may involved in the development of the diabeticcardiopathy.So it is deduced that the occurrence and development of T2DMheart disease may be delay by intervening some links in the TLR4signaltransduction pathway.2The expression of TLR4in Simvastatin group rats was significantlydecreased,so Simvastatin may have protective effect on the heart of type2diabetic rats,partly by reducing the expression of TLR4.