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目的探讨2型糖尿病对雄性小鼠听力脑干反应(ABR)和耳蜗带状突触的作用。方法将24只健康6周龄清洁级雄性C57BL/6J小鼠按体重随机分为2组,分别为对照[饲料含铁量为(8.26±2.67)mg/kg]组和糖尿病[饲料含铁量为(8.39±1.03)g/kg]组,每组12只。分别于喂养第0、4、8、12、16周监测血糖,第16周测定血红蛋白、血清铁、血清铁蛋白、总铁结合力、转铁蛋白饱和度,并进行葡萄糖耐量及胰岛素耐量测验,采用ABR检测。应用免疫荧光检测左侧耳蜗基底膜C末端结合蛋白2(Ct BP2)、囊泡谷氨酸转运体3(VGLUT3)、肌球蛋白Ⅶa(MyosinⅦa)在耳蜗内外毛细胞分布,分离右侧耳蜗进行HE染色。结果与对照组比较,糖尿病组小鼠血清铁、血清铁蛋白、转铁蛋白饱和度均升高,差异有统计学意义(P<0.05);而血红蛋白、总铁结合力均无明显改变。与对照组比较,糖尿病组小鼠血糖水平在喂养8周后明显升高,喂养16周时胰岛素抵抗指数(HOMA-IR)明显升高,差异均有统计学意义(P<0.05)。与对照组比较,糖尿病组小鼠血糖水平在葡萄糖耐量试验的60、120 min时较高,差异有统计学意义(P<0.05);而在15、30 min时仅略有升高。与对照组比较,胰岛素耐量实验各检测时间点糖尿病组小鼠血糖水平均较高,差异有统计学意义(P<0.05)。与对照组比较,糖尿病组小鼠在2、3 k Hz下的ABR阈值较高,差异均有统计学意义(P<0.05);而在1、4 k Hz下的ABR阈值仅略有升高。糖尿病可造成小鼠内毛细胞Ct BP2标记带状突触数量减少,但在耳蜗毛细胞中VGLUT3、MyosinⅦa免疫荧光阳性反应未受影响,另外,耳蜗Corti氏器、螺旋神经节细胞及神经丝未见损伤。结论膳食铁过量诱导的2型糖尿病小鼠可能出现内耳毛细胞带状突触数量减少,从而扰乱小鼠听力脑干反应,呈现高频段小鼠听力损伤。
Objective To investigate the effects of type 2 diabetes on auditory brainstem response (ABR) and cochlear banded synapse in male mice. Methods Twenty-four healthy 6-week-old male C57BL / 6J mice were randomly divided into two groups according to body weight: control group (8.26 ± 2.67 mg / kg) and diabetic group (8.39 ± 1.03) g / kg], with 12 rats in each group. Blood glucose was monitored at the 0, 4, 8, 12 and 16 weeks of feeding, hemoglobin, serum iron, serum ferritin, total iron binding capacity and transferrin saturation were measured at week 16, and glucose tolerance and insulin tolerance test were performed. Using ABR test. Immunofluorescence was used to detect the distribution of CtBP2, VGLUT3 and MyosinⅦa in the cochlear inner and outer hair cells, and the right cochlea was isolated HE staining. Results Compared with the control group, the levels of serum iron, serum ferritin and transferrin in diabetic group were significantly increased (P <0.05), while hemoglobin and total iron binding capacity did not change significantly. Compared with the control group, the blood glucose level of diabetic mice increased significantly after 8 weeks of feeding, and the level of HOMA-IR increased significantly at 16 weeks of feeding (P <0.05). Compared with the control group, the blood glucose level of diabetic mice was significantly higher at 60 and 120 minutes of glucose tolerance test (P <0.05), and only slightly increased at 15 and 30 minutes. Compared with the control group, the blood glucose levels of diabetic mice were significantly higher at each time point of insulin resistance test (P <0.05). Compared with the control group, ABR thresholds of diabetic mice at 2,3 k Hz were higher (P <0.05), while ABR thresholds at 1 and 4 kHz were only slightly increased . Diabetes mellitus can cause the number of Ct BP2-labeled ribbon synapses in the hair cells of mice decreased, but the positive immunofluorescence of VGLUT3 and Myosin VIIa in cochlear hair cells was not affected. In addition, Corti’s cells, spiral ganglion cells and neurofibers See damage. Conclusion Type 2 diabetic mice induced by dietary iron overload may reduce the number of ribbon synapses in the inner ear hair cells, thereby disrupting the auditory brainstem response in mice and presenting the hearing impairment in high frequency mice.