Gao Feng, Gao Erhe, Yue Tian-Li, Ohlstein Eliot H, Lopez Bernard L, Christopher Theodore A, Ma Xin-Liang
Department of Emergency Medicine, Thomas Jefferson University, Philadelphia, Pa, USA.
Circulation. 2002 Mar 26;105(12):1497-502. doi: 10.1161/01.cir.0000012529.00367.0f.
Recent evidence from cultured endothelial cell studies suggests that phosphorylation of endothelial nitric oxide synthase (eNOS) through the PI3-kinase-Akt pathway increases NO production. This study was designed to elucidate the signaling pathway involved in the antiapoptotic effect of insulin in vivo and to test the hypothesis that phosphorylation of eNOS by insulin may participate in the cardioprotective effect of insulin after myocardial ischemia and reperfusion.
Male Sprague-Dawley rats were subjected to 30 minutes of myocardial ischemia and 4 hours of reperfusion. Rats were randomized to receive vehicle, insulin, insulin plus wortmannin, or insulin plus L-NAME. Treatment with insulin resulted in 2.6-fold and 4.3-fold increases in Akt and eNOS phosphorylation and a significant increase in NO production in ischemic/reperfused myocardial tissue. Phosphorylation of Akt and eNOS and increase of NO production by insulin were completely blocked by wortmannin, a PI3-kinase inhibitor. Pretreatment with L-NAME, a nonselective NOS inhibitor, had no effect on Akt and eNOS phosphorylation but significantly reduced NO production. Moreover, treatment with insulin markedly reduced myocardial apoptotic death (P<0.01 versus vehicle). Pretreatment with wortmannin abolished the antiapoptotic effect of insulin. Most importantly, pretreatment with L-NAME also significantly reduced the antiapoptotic effect of insulin (P<0.01 versus insulin).
These results demonstrated that in vivo administration of insulin activated Akt through the PI3-kinase-dependent mechanism and reduced postischemic myocardial apoptotic death. Phosphorylation of eNOS and the concurrent increase of NO production contribute significantly to the antiapoptotic effect of insulin.
来自培养内皮细胞研究的最新证据表明，通过PI3激酶-Akt途径使内皮型一氧化氮合酶（eNOS）磷酸化可增加一氧化氮（NO）的生成。本研究旨在阐明胰岛素在体内抗凋亡作用所涉及的信号通路，并验证胰岛素使eNOS磷酸化可能参与心肌缺血再灌注后胰岛素心脏保护作用的假说。
雄性Sprague-Dawley大鼠经历30分钟心肌缺血和4小时再灌注。大鼠被随机分为接受溶剂、胰岛素、胰岛素加渥曼青霉素或胰岛素加L-精氨酸甲酯（L-NAME）。胰岛素治疗使缺血/再灌注心肌组织中Akt和eNOS磷酸化增加2.6倍和4.3倍，且NO生成显著增加。PI3激酶抑制剂渥曼青霉素完全阻断了胰岛素引起的Akt和eNOS磷酸化以及NO生成增加。非选择性一氧化氮合酶（NOS）抑制剂L-NAME预处理对Akt和eNOS磷酸化无影响，但显著降低了NO生成。此外，胰岛素治疗显著减少了心肌凋亡死亡（与溶剂相比，P<0.01）。渥曼青霉素预处理消除了胰岛素的抗凋亡作用。最重要的是，L-NAME预处理也显著降低了胰岛素的抗凋亡作用（与胰岛素相比，P<0.01）。
这些结果表明，体内给予胰岛素通过PI3激酶依赖性机制激活Akt，并减少缺血后心肌凋亡死亡。eNOS磷酸化以及同时增加的NO生成对胰岛素的抗凋亡作用有显著贡献。
