长期酒精暴露引起小鼠胰岛素抵抗:神经酰胺的可能作用

Chronic alcohol exposure induces insulin resistance in mice:the possible mechanism of ceramide

目的探讨长期酒精暴露与胰岛素敏感性之间的关系并探讨其相关的分子机制;观察神经酰胺在酒精引起胰岛素抵抗过程中的可能作用。方法建立C57BL/6J野生型(WT)小鼠和神经鞘磷脂合成酶2基因敲除(SMS-/-2)3月龄小鼠的长期酒精暴露模型,两基因型小鼠又分为对照组、中剂量酒精组和高剂量酒精组,共计90只。建模5个月后,用血糖仪测定小鼠空腹血糖值,用酶学法检测血清胰岛素浓度,并计算胰岛素抵抗指数。利用免疫荧光染色法观察各组小鼠海马CA1区胰岛素受体底物2(IRS2)阳性细胞表达情况,免疫印迹法检测小鼠海马组织IRS2蛋白的相对表达量。结果 1.长期酒精暴露导致WT和SMS-/-2小鼠空腹血糖值和胰岛素抵抗指数升高,且具有剂量依赖性(P<0.05);但SMS-/-2小鼠随着酒精剂量的增加胰岛素抵抗指数升高幅度较小。2.免疫组织化学染色显示,酒精暴露诱导WT和SMS-/-2小鼠海马IRS2阳性细胞数降低,有剂量依赖性(P<0.05);与相同处理条件的WT小鼠相比,酒精诱导SMS-/-2小鼠海马IRS2阳性细胞数降低增多(P<0.05)。3.免疫印迹法检测各组间小鼠海马组织IRS2蛋白相对表达量与上述结果一致。结论长期酒精暴露可引起胰岛素抵抗,IRS2蛋白表达降低,且存在剂量依赖性,因此酒精导致IRS2表达下降可能是胰岛素抵抗的分子机制之一;神经酰胺可能参与酒精暴露诱导IRS2表达下降的过程,且有促进胰岛素抵抗形成的作用。

Objective To investigate the relationship among chronic alcohol exposure, insulin sensitivity and ceramide during the alcohol toxicological effect. Methods Wide type （WT） and sphingomyelin synthetase 2 knockout （SMS2^-/-） mice （about 3 month old） were used to establish the chronic alcohol exposure model. A total of 90 mice of the two genotypes were divided into the control group, moderate EtOH group and high EtOH group. After alcohol exposure for 5 months, fasting plasma glucose（FPG） and levels of fasting insulin （Fins） were measured. The insulin resistance index （HOMA-IR） was calculated. The expression of insulin receptor substrate 2 （IRS2） in hippocampus was tested with immunofluorescent labeling and Western blotting analysis. Results 1. Alcohol exposure caused WT mice FPG and HOMA-IR index increased with dose-dependency （P 〈 0. 05）. Comparing with the control group, Fins values increased in the treatment dose group （ P 〈 0. 05 ）. 2. FPG in SMS2^-/- mice increased with dose-dependency （ P 〈 0. 05 ） , but HOMA- IR index had little changes, comparing with WT mice. In addition, the immunohistochemieal staining showed that, in both WT and SMS2-/- mice, the number of IRS2-positive cells reduced in CA1 area after alcohol exposure with dose-dependency （P 〈 0. 05）. However, comparing with the WT mice, the number of IRS2-positive cells of hippocampus in SMS2^-/- mice reduced greatly （P 〈 0. 05）. 3. Immunoblotting evidence of IRS2 supported the results of immunohistochemistry in both WT and SMS~/- mice. Conclusion Chronic alcohol exposure can cause insulin resistance in both WT and SMS2^-/-mice. IRS2 protein expression decreased with dose-dependency after alcohol exposure. IRS2 loss probably is one of the causes of insulin resistance. Ceramide may be involved in the reduction of IRS2 expression and may promote the formation of insulin resistance after alcohol exposure.