Shandong Provincial Hospital Affiliated to Shandong University, Shandong 250021, China.
Exp Mol Med. 2010 Mar 31;42(3):205-15. doi: 10.3858/emm.2010.42.3.021.
Chronic and heavy alcohol consumption is one of the causes of heart diseases. However, the effects of ethanol on insulin sensitivity in myocardium has been unclear. To investigate the effects of ethanol on the expression of AMP-activated protein kinase (AMPK), myocyte enhancer factor 2 (MEF2) and glucose transporter 4 (GLUT4), all of which are involved in the regulation of insulin sensitivity, in the myocardium, we performed three parts of experiments in vivo and in vitro. I: Rats were injected with 5-amino-4-imidazolecarboxamide ribonucleotide (AICAR, 0.8 mg.kg(-l)) for 2 h. II: Rats received different dose (0.5, 2.5 or 5 g.kg(-l).d(-l)) of ethanol for 22-week. III: Primary neonatal rat cardiomyocytes were isolated and treated with or without 100 mM ethanol or 1 mM AICAR for 4 h. The cardiac protein and mRNA expression of AMPKalpha subunits, MEF2 and GLUT4 were observed by western-blotting and RT-PCR, respectively. Serum TNFalpha levels were assessed by ELISA. The results showed chronic ethanol exposure induced insulin resistance. Ethanol decreased the mRNA levels of AMPKalpha1 and alpha2, the protein levels of total- and phospho-AMPKalpha in cardiomyocytes. Similarly, ethanol showed inhibitory effects on both the mRNA and protein levels of MEF2A and 2D, and GLUT4 in a dose-response-like fashion. Correlation analysis implied an association between phospho-AMPKalpha and MEF2A or MEF2D, and between the levels of MEF2 protein and GLUT4 transcription. In addition, ethanol elevated serum TNFalpha level. Taken together, chronic ethanol exposure decreases the expression of AMPKalpha and MEF2, and is associated with GLUT4 decline in rat myocardium.
慢性和大量饮酒是心脏病的原因之一。然而，乙醇对心肌胰岛素敏感性的影响尚不清楚。为了研究乙醇对调节胰岛素敏感性的 AMP 激活蛋白激酶（AMPK）、肌细胞增强因子 2（MEF2）和葡萄糖转运蛋白 4（GLUT4）的表达的影响，我们在体内和体外进行了三部分实验。I：大鼠注射 5-氨基-4-咪唑甲酰胺核苷酸（AICAR，0.8mg·kg(-1)）2 小时。II：大鼠接受不同剂量（0.5、2.5 或 5g·kg(-1)·d(-1)）的乙醇 22 周。III：分离原代新生大鼠心肌细胞，用或不用 100mM 乙醇或 1mM AICAR 处理 4 小时。通过 Western-blotting 和 RT-PCR 分别观察 AMPKalpha 亚单位、MEF2 和 GLUT4 的心脏蛋白和 mRNA 表达，通过 ELISA 评估血清 TNFalpha 水平。结果显示慢性乙醇暴露诱导胰岛素抵抗。乙醇降低心肌细胞中 AMPKalpha1 和 alpha2 的 mRNA 水平以及总磷酸化 AMPKalpha 的蛋白水平。同样，乙醇以剂量反应方式对 MEF2A 和 2D 以及 GLUT4 的 mRNA 和蛋白水平均表现出抑制作用。相关分析表明磷酸化 AMPKalpha 与 MEF2A 或 MEF2D 之间以及 MEF2 蛋白水平与 GLUT4 转录之间存在关联。此外，乙醇升高血清 TNFalpha 水平。总之，慢性乙醇暴露降低了大鼠心肌中 AMPKalpha 和 MEF2 的表达，并与 GLUT4 的下降有关。
