增龄对Wistar大鼠胰岛β细胞胰岛素受体的影响

Effect of aging on insulin receptor in islet beta-cells of Wistar rats

目的观察增龄对大鼠胰岛β细胞胰岛素受体的影响,探讨老年糖耐量受损的机制。方法将Wistar大鼠30只分为青年组(15只)和老年组(15只),观察空腹血糖、空腹胰岛素、血清游离脂肪酸(FFA)、血脂的变化,同时进行高胰岛素-正葡萄糖钳夹实验观察胰岛素敏感性。两组大鼠胰腺石蜡切片,免疫荧光双标染色,标染胰岛β细胞上胰岛素受体,利用软件进行荧光强度分析。结果青年组和老年组的大鼠体重分别为(490.6±7.72)g和(728.9±7.57)g,有明显统计学意义(P<0.01);两组大鼠空腹血糖无明显差异,空腹胰岛素青年组为(0.59±0.14)ng/ml,老年组为(2.37±0.04)ng/ml,差异有统计学意义(P<0.01);空腹血清FFA水平青年组为(0.76±0.14)mmol/L,老年组为(1.51±0.04)mmol/L,有统计学差异(P<0.01);高胰岛素-正葡萄糖钳夹结果显示青年组大鼠葡萄糖输出速率为(26.02±2.83)mg/(kg·min),老年组为(10.73±0.72)mg/(kg·min),差异有统计学意义(P<0.01);使用稳态模型评估胰岛素分泌指数(HOMA-β)随年龄增长呈递增趋势,未达到统计学差异;而胰岛素抵抗指数(HOMA-IR)在青年组和老年组分别为3.09±0.80和13.14±1.59,差异有统计学意义(P<0.01);免疫荧光染色显示老年组胰岛β细胞上胰岛素受体荧光强度减弱,荧光强度分析值青年组为63.55±5.20、老年组为23.26±2.50,差异有统计学意义(p<0.01)。结论随着年龄的增长,老年大鼠存在一定的胰岛素抵抗和代偿性胰岛素分泌增加,同时胰岛β细胞胰岛素受体减少,可能存在胰岛β细胞自身胰岛素抵抗。

Objective To evaluate the effect of aging on the insulin receptor in islet beta-cells of Wistar rats, so as to investigate the mechanism of impaired glucose tolerance in elderly population. Methods Thirty healthy male Wistar rats were divided into young group（4-month old, n= 15） and elderly group（24-month old, n= 15）. The fasting blood glucose, blood insulin, free fatty acid, and blood lipid were observed. Insulin sensitivity and the function of islet ceils were assessed by the euglycaemic-hyperinsulinaemic clamp technique. The insulin receptor in islet beta-cells was observed using immunofluorescence staining, and the fluorescence intensity was analyzed using software. Results The body mass of rats in young group and elderly group was （490.60 ±7.72）g and （728.90 ± 7.57）g respectively（P 〈 0.01）. There was no significant difference in fasting blood glucose between the two groups（P〉0.05）. The fasting blood insulin was （0.59±0.14）ng/ml and （2.37 ± 0.04）ng/ml in young group and elderly group respectively （P 〈 0.01）. The blood free fatty acid was significantly lower in young group than in elderly group[（0.76 ± 0.14） vs （1.51 ±0.04） mmol/L,P 〈 0.01]. The euglycaemic-hyperinsulinaemic clamp test displayed that the glucose infusion rate was significantly higher in young group than in elderly group[（ 26.02 ± 2.83） vs （10.73± 0.72）mg/（kg· min）,P 〈 0.01]. Homeostasis model insulin resistance index（HOMA-IR） was （3.09 ± 0.80） and （13.14 ± 1.59） in young group and elderly group（P 〈 0.01）. The fluorescence intensity was （63.55 ±5.20） and （23.26± 2.50） respectively in young group and elderly group respectively（P 〈 0.01）. Conclusion The elderly rats present with insulin resistance and compensatory high level insulin secretion. Meanwhile, insulin receptor in islet beta-cells is decreased. It is possible that the peripheral insulin resistance and the insulin resistance in islet beta-cells itself coexist in elderly rats.