| Objective:To establish the model of type 2 diabetes of rats and investigate the relationship between impaired fracture healing and the change of the expression of of TNF-a In vivo of type 2 diabetes ratsMethods:30 physical fitness male Sprague-Dawley rats were divided into control group (15 rats) fed with normal diet and experimental group (15 rats) fed with high fat and sucrosum diet.8 weeks later, we individually intraperitoneally injected rats with streptozotocin(30mg/kg) or citrate buffe.2 weeks later, we chose the rats which fasting blood sugar exceeded 16.7 mmol/L into experimental group. Onwards, we established the model of distraction osteogenesis in the left tibiae of all the rats. Distraction was initiated the following day at 0.15 mm b.i.d. and continued for 14 days. At the beginning of 15 day, we sacrificed all the rats and collected the blood and left tibiae. Both femora were harvested with germ free. We tested blood glucose,triglyceride,total cholesterol and serum insulin of blood collected at different time points. We observed callus formation in distraction gap by X ray and the formation of primary matrix front and microcolumn formation by histological examination. We tested blood Osteocalcin and Advanced glycation end products by immunohistochemistry and RT-PCR when all rats were sacrificed.Results:The levels of triglyceride, total cholesterol, and serum insulin in the experimental group were significantly higher than that of control group(P<0.01). The level of fasting blood glucose was not obviously different in experimental group(P>0.05) when compared with control rats after 8 weeks. The levels of fasting blood glucose, triglyceride, and total cholesterol in the experimental animals were obviously elevated in comparison with control group(P<0.01). The level of serum insulin was not obviously different in experiment group compared with control rats(P>0.05) at 10 week and when all the rats were sacrificed. Callus formation in distraction gap in experimental group was obviously diminished by X-ray examination. The array of microcolumn formation was disordered and the area of primary matrix front was catachromasis by histology examination in comparison with experimental group. The level of TNF-αwas obviously elevated(P<0.01) while Osteocalcin obviously reduced(P<0.01) in experimental group by immunohistochemistry and RT-PCR when all the rats were sacrificed.The expression of TNF-αwas up-regulated in experimental group (p<0.01) while Osteocalcin was obviously down-regulated(P<0.01) by the same way.Conclusion:We established the model of diabetic rats through feeding diet with high fat and sugar, and intraperitoneal injection of low doze streptozocin. These animals appeared some characters in similar with human type 2 diabetes, such as hyperglycemia, hyperlipemia and insulin resistance. The poor bone formation in distraction callus was found in type 2 diabetes rats. The expression of TNF-αwas increased in bone of type 2 diabetes rats. This change may be one of the reasons that caused impaired fracture healing in diabetic rats.
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