The Effect Of Advanced Glycation End Products For The Thyroid Tissues In Diabetic Rats

Objectives: Diabetes mellitus is a general syndrome which is caused by multitude factors. Epidemiological studies show that the prevalence of thyroid disfuction is higher 2-3 times in the patients with diabetes mellitus than without diabetes mellitus. Therefore, Study the changes and mechanisms of the thyroid in the hyperglycemia is important to prevent and cure the cardiovascular disease in the diabetes mellitus. In the mechanisms of tissue damage caused by long-term hyperglycemia , advanced glycation end products (AGEs) is important in the incidence and development of chronic complication of diabetes mellitus. Thyroglobulin(TG) could response sensitively the function of thyroid. Our study observed that the expression of AGEs, receptor of AGEs, TG, thyroid peroxidase(TPO) and thyroid-stimulating hormone receptor (TSHR) in thyroid of diabetic rats which are caused by streptozocin. Showed that the pathological changes of the thyroid tissues which damaged by diabetes mellitus. Researched that except for the immunologic mechanism. Methods: 40 male SD rats were randomly divided to diabetic group(n=20) and controls (n=20). Diabetic rats were produced in experimental group by injection of 60 mg streptozocin /kg BW via the tail vein. Control group was injected by 0. 85% saline. Blood samples were taken from canthus veins for glucose test in the third day of injection. The glucose levels of all diabetic rats were more than 16. 65mmol/L. After 8 weeks experimental term, the thyroid samples were obtained. ?Put them in the solution of the 2. 5% glutaric dialdehyde and 1% osmium tetroxide to fixate, and then observed with JE0L-100CX transmission electron microscope. â‘¡Put themin the solution of 10% formalin, and then embedded in paraffin, the sections were used to observe the general structure of the thyroid tissue by HE staining and the expressions of AGEs> RAGE, and TG, TPO\ TSHR in thyroid by immunohistochemistry. (3)Put them in the liquid nitrogen to fixate, and then do protein electrophoresis, trarsmembrane, Western Blotting. Detected the expression of above-mentioned factors by Western Blotting.Results: 1. After injection of streptozocin, the rats became polydipsia, polyphagia, polyuria and weight loss, (and) while the serum glucose increased. Compared with control group, the body weight was significantly decreased in diabetic group (P<0.01), while the fasting glucose was significantly increased (P<0. 01).2. Ultrastructural pathology: The thyroid tissues of diabetic rats were all abnormal under electron microscopy.Most of cases showed microvilli of thyroid follicle epithelial cells diminished substantially and some of them almost disappeared .The nuclear of thyroid follicle epithelial cells were flattened , cisterns of rough endoplasmic reticulum were dilated and myelin figures were conspicuous. Number of mitochondria and lysosomes were significantly decreased. 3. Under the observation with microscope, the thyroid follicle cell became applanatus and absorbed vacuolus was decreased in the diabetic group. 4. Results of immunohistochemistry: AGEs , RAGE and TG, TPO\ TSHR were expressed both in diabetic group and in control group. Positive expression of AGEs presented yellow in periplast, and positive cell of RAGE located in endochylema and colloid. Positive expression of TG located in endochylemaand colloid. The expression of TPO was found in the endochylema, and TSHR was observed in cytomembrane of thyroid follicle. 5. The result of Western Blotting: Compared with control group, the expressions of AGEs^ RAGE% TSHR in diabetic group were significant increased (P<0. 01), while the level of TG and TPO in diabetic group were significant decreased (P<0. 01). Conclusions: ?The model of diabetic rat could be made by streptozocin via the tail vein. ?Histological observation on thyroid provided a proof to the early pathological changes of thyroid causing by hyperglycemia. (DUltrastructural pathology: The thyroid tissues of diabetic rats were all abnormal under electron microscopy. Most of cases showed hypofunction of thyroid. ?Compared with control group, the expressions of AGEs and RAGE in diabetic group were increased, which suggested that the thyroid tissues may be one of the target organs of hyperglycemia lesion. (5) The changes of TG> TPO and TSHR suggested that the (effection) effect of hyperglycemia is that the function of thyroid become lower.