Stuck Bettina Johanna, Lenski Matthias, Böhm Michael, Laufs Ulrich
Klinik für Innere Medizin III, Kardiologie, Angiologie und Internistische Intensivmedizin, Universitätsklinikum des Saarlandes, Homburg/Saar, D-66421 Homburg/Saar, Germany.
J Biol Chem. 2008 Nov 21;283(47):32562-9. doi: 10.1074/jbc.M801904200. Epub 2008 Sep 12.
Angiotensin II induces cardiomyocyte hypertrophy, but its consequences on cardiomyocyte metabolism and energy supply are not completely understood. Here we investigate the effect of angiotensin II on glucose and fatty acid utilization and the modifying role of AMP-activated protein kinase (AMPK), a key regulator of metabolism and proliferation. Treatment of H9C2 cardiomyocytes with angiotensin II (Ang II, 1 microm, 4 h) increased [(3)H]leucine incorporation, up-regulated the mRNA expression of the hypertrophy marker genes MLC, ANF, BNP, and beta-MHC, and decreased the phosphorylation of the negative mTOR-regulator tuberin (TSC-2). Rat neonatal cardiomyocytes showed similar results. Western blot analysis revealed a time- and concentration-dependent down-regulation of AMPK-phosphorylation in the presence of angiotensin II, whereas the protein expression of the catalytic alpha-subunit remained unchanged. This was paralleled by membrane translocation of glucose-transporter type 4 (GLUT4), increased uptake of [(3)H]glucose and transient down-regulation of phosphorylation of acetyl-CoA carboxylase (ACC), whereas fatty acid uptake remained unchanged. Similarly, short-term transaortic constriction in mice resulted in down-regulation of P-AMPK and P-ACC but up-regulation of GLUT4 membrane translocation in the heart. Preincubation of cardiomyocytes with the AMPK stimulator 5-aminoimidazole-4-carboxamide-1-beta-D-ribofuranoside (AICAR; 1 mM, 4 h) completely prevented the angiotensin II-induced cardiomyocytes hypertrophy. In addition, AICAR reversed the metabolic effects of angiotensin II: GLUT4 translocation was reduced, but ACC phosphorylation and TSC phosphorylation were elevated. In summary, angiotensin II-induced hypertrophy of cardiomyocytes is accompanied by decreased activation of AMPK, increased glucose uptake, and decreased mTOR inhibition. Stimulation with the AMPK activator AICAR reverses these metabolic changes, increases fatty acid utilization, and inhibits cardiomyocyte hypertrophy.
血管紧张素II可诱导心肌细胞肥大，但其对心肌细胞代谢和能量供应的影响尚未完全明确。在此，我们研究血管紧张素II对葡萄糖和脂肪酸利用的影响以及AMP激活的蛋白激酶（AMPK）的调节作用，AMPK是代谢和增殖的关键调节因子。用血管紧张素II（Ang II，1微摩尔，4小时）处理H9C2心肌细胞可增加[³H]亮氨酸掺入，上调肥大标志物基因MLC、ANF、BNP和β-MHC的mRNA表达，并降低负性mTOR调节因子结节性硬化蛋白（TSC-2）的磷酸化。大鼠新生心肌细胞也得到类似结果。蛋白质印迹分析显示，在血管紧张素II存在的情况下，AMPK磷酸化呈时间和浓度依赖性下调，而催化性α亚基的蛋白表达保持不变。这与4型葡萄糖转运蛋白（GLUT4）的膜转位、[³H]葡萄糖摄取增加以及乙酰辅酶A羧化酶（ACC）磷酸化的短暂下调同时发生，而脂肪酸摄取保持不变。同样，小鼠短期经主动脉缩窄导致心脏中磷酸化AMPK（P-AMPK）和磷酸化ACC（P-ACC）下调，但GLUT4膜转位上调。用AMPK激动剂5-氨基咪唑-4-甲酰胺-1-β-D-呋喃核糖苷（AICAR；1毫摩尔，4小时）预孵育心肌细胞可完全阻止血管紧张素II诱导的心肌细胞肥大。此外，AICAR逆转了血管紧张素II的代谢作用：GLUT4转位减少，但ACC磷酸化和TSC磷酸化增加。总之，血管紧张素II诱导的心肌细胞肥大伴随着AMPK激活降低、葡萄糖摄取增加和mTOR抑制减弱。用AMPK激活剂AICAR刺激可逆转这些代谢变化，增加脂肪酸利用，并抑制心肌细胞肥大。
