Investigation On DM Rat Thyroid Structure And RAGE,TSHR,NIS Protein Expression Change And Intervention

Object:As two main diseases in endocrine and metabolic system,diabetic mellitus (DM) and thyroid disease often coexistent and react with each other. Domestic and abroad investigation found that the prevalence of thyroid dysfunction in DM patients are higher than that in controls, mechanism research mainly focus on autoimmune aspects. Hyperglycemia toxicity can lead to multiple organ injury,but investigations on its relationship with thyroid injury are rare.Abnormal expression of advanced glycosylated endproducts(AGEs) and Receptor for AGEs(RAGE) in hyperglycemia is correlated with the beginning and development of multiple DM chronic complications. Thyrotropin receptor(TSHR) is the specific receptor for TSH that can regulate the growth,differentiation and function of thyroid cells,sodium-iodide symporter(NIS) is a kind of glyprotein on the basilemma of thyroid follicular cells,it can mediate iodide uptake that the rate-limiting step of thyroid hormone biosynthesis. The abnormal expression of them are correlated with multiple thyroid disease.Aminoguanidine(AG) is nucleophilic hydrazide derivatives, it can inhibit AGEs formation,decrease RAGE activation and expression, protect organ from DM injury.Insulin can lower blood sugar,extenuate glyco-toxicity,play permissive effects on the thyroid regualtion by TSH.The purpose of the investigation is to approach the mechanism of DM thyroid injury through the observation on change of DM rats thyroid ultrastructure and RAGE,TSHR,NIS protein expression and to research the therapeutic efficacy of AG and insulin through observation on the change of DM rats thyroid ultrastructure and protein expression after AG and insulin intervention.Method:112 adult male Wistar rats were divided randomly into control group (N group n=25) and experimental group(n=87).The experimental group were fed with high lipid stuff for 8 weeks and injected with 30mg/kg streptozotocin(STZ) into vena caudalis to establish DM animal model.N group were fed with ordinary stuff and injected with isodose citrate buffer.The blood sugar of all the rats in experimental group are higher than 16.65mmol/L.Then the experimental group were divided into DM rats with no intervention group(DM group,n=27),DM rats treated with aminoguanidine group(DA group,n=28,intragastric administrated with 50mg/kg.d AG),DM rats treated with insulin group (DI group,n=32,hypodermic injected with 6U/kg.d insulin).12 and 20 weeks later,the rats were killed, thyroid tissue were dissected and①fixed in 2.5% glutaraldehyde and 1%osmium tetroxide and observed ultrastructure with JEM100CXⅡtransmission electron microscope.②fixed in liquid nitrogen,taken protein and detected the RAGE,NIS and TSHR protein expression with Western Blotting skills.Results:①Body weight:DM group are lower than DA group,DI group and N group (p<0.01),there are no statistical difference among the three latter groups;Blood sugar:DM group,DA group and DI group are higher than N group(p<0.01),there are no statistical difference between DA group and DM group,but they are higher than DI group(p<0.01)②Ultrastructure:The thyroid tissue of DM group rats displayed that follicular epithelial microvilli decreased,endothelium dilated and heterochromatin increased, vascular endothelium are injured, basilemma are thickened,fiber hyperplasia.The degree of injury increase with the disease course;The thyroid ultrastruture injury of DA group are ligher than DM group,and that of DI group are ligher than DM and DA group.③Western Blotting:TSHR:DM group are higher than DI group(12weeks:p=0.178,20weeks:p=0.473),DA group(12weeks:p<0.01,20weeks:p<0.05)and N group (12weeks:p<0.01,20weeks: p=0.473),but there are no statistical difference among the latter three groups.NIS: DM group are lower than DA group(12weeks:p=0.059,20weeks:p=0.053),DI group(12weeks:p<0.05,20weeks:p<0.01)and N group (p<0.01),there are no statistical difference between DA group and DI group,but they are lower than N group(p<0.01)。RAGE:DM group are higher than DI group(p<0.05),DA group(p<0.01)and N group(p<0.01),DI group are higher than DA group and N group(12weeks:p<0.05,20weeks:p<0.01),DA group than N group(12weeks: p=0.902,20weeks:p<0.05)Conclusion:①High lipid stuff feeding combined with small dose STZ once injection into vena caudalis can establish DM rat model successfully.②DM group rats thyroid tissue ultrastructure revealed that follicular epithelial cells are injured, vascular endothelium are injured,basilemma are thickened, fiber hyperplasia.RAGE and TSHR expression increased,NIS expression decreased. It is indicated that protein expression alteration are consistent with mophological changes,and the mophological and functional changes of thyroid may be related with RAGE overexpression.③When compared with DM group,DA group thyroid ultrastructure injury extenuate,function related protein expression are improved,RAGE expression decreased. This demonstrated further the relationship between RAGE overexpression and DM thyroid injury,and that AG can decrease thyroid RAGE expression, extenuate thyroid injury that caused by hyperglycemia toxicity.④DI group rats blood sugar decreased markedly,thyroid ultrastructure injury extenuate,function related protein expression are improved,RAGE expression decreased.It is indicated that insulin supplement can lower blood sugar,decrease RAGE expression,protect thyroid from DM injury.⑤When compared with DA group,DI group displayed that blood sugar are lower, thyroid ultrastructure injury are ligher,RAGE expression are higher,but there are no statistical difference on the NIS and TSHR expression between DA group and DI group.This is indicated that insulin can extenuate DM thyroid injury through antihyperglycemia mechanisms.