老龄大鼠肝脏和骨骼肌胰岛素受体底物-1及磷酸化蛋白激酶B的表达

Effects of Aging on the Expressions of Insulin Receptor Substrate-1,Phosphate Protein Kinase B in Rat Liver and Muscle

目的探讨老龄对胰岛素受体底物-1(IRS-1)/磷脂酰肌醇3激酶(PI3K)/蛋白激酶B(PKB,p-Akt)在肝脏和骨骼肌中表达的影响,为老年糖尿病早期干预方法提供实验依据。方法3种不同月龄SD大鼠(6、12、20～24月龄),腹腔麻醉后抽心血查血糖、血脂、游离脂肪酸(FFA);分离肝脏、骨骼肌,免疫组化观察IRS-1与p-Akt在不同月龄大鼠肝脏和骨骼肌中的表达。结果20～24月龄鼠血浆中FFA水平高于6月龄大鼠〔(419.94±93.93)vs(256.22±73.93)mmol/L,P<0.05〕;但空腹血糖及血脂水平与其它月龄大鼠相当;在肝脏或骨骼肌均未发现IRS-1表达水平的显著变化(P>0.05);p-Akt在肝细胞中的表达减少,与6月龄和12月龄组相比差异有统计学意义(P<0.05);而在骨骼肌细胞中,3组动物p-Akt表达无明显差异。结论FFA水平增高是自然衰老大鼠胰岛素抵抗的显著特征,与此相关的PI3K/Akt信号通路障碍早于血糖异常出现;Akt的磷酸化障碍可能是早期干预的靶点。Akt的磷酸化障碍主要在肝细胞中发现,肝脏可能是衰老相关胰岛素信号通路异常的主要部位。

Objectives To investigate the effects of aging on the levels of free fatty acid （FFA） ,lipid profile, the expression of IRS-1 and its downstream signal Akt phosphorylation, so to explore the mechanisms of agingassociated glucose tolerance impairment. Methods Three different age groups （6, 12, 20-24 months） of SD rats were used.. After being fasted for 12-14 h, the rats were anesthetized with sodium pentobarbital （30 mg/kg BW, ip）, then the samples of blood, liver and muscle were collected. Blood samples were used for the detection of fasting blood glucose, lipid profile and FFA. The expressions of IRS-1 and p-Akt in liver and muscle were measured by immunohistochemical staining method. Results （1） The level of FFA in 20-24 months groups was significantly higher[（419.94±93.93） vs （256.22±73.93） mmol/L, P〈0.05]than that of younger group （6 months） ; （2） IRS- 1 was expressed in liver and muscle cell of all groups. The level of IRS-1 showed no significant change in both liver and muscle. （3） p-Akt expression in liver significantly decreased in old rat when comparing to younger counterparts （2911.06±268. 13 vs 4683.72±582. 29 （12 months）＆4903.06±688.44 （6 months）, P〈0. 053, while no difference was found in muscle among three age groups. Conclusion （1） FFA was the initial metabolic change in natural aging SD rat, which might play an important role in age-related insulin resistance. （2） There was no significant difference of IRS-lexpression among three rat age groups. （3） PI3K/Akt pathway in liver of old rat is a critical signal defect of insulin dysfunction with aging. Liver might be main component organ involved to age-related insulin resistance.