Folmes Clifford D L, Wagg Cory S, Shen Mei, Clanachan Alexander S, Tian Rong, Lopaschuk Gary D
Cardiovascular Research Group and Department of Pediatrics and Pharmacology, University of Alberta, Edmonton, Alberta, Canada.
Am J Physiol Heart Circ Physiol. 2009 Jul;297(1):H313-21. doi: 10.1152/ajpheart.01298.2008. Epub 2009 May 8.
Activation of 5'-AMP-activated protein kinase (AMPK) may benefit the heart during ischemia-reperfusion by increasing energy production. While AMPK stimulates glycolysis, mitochondrial oxidative metabolism is the major source of ATP production during reperfusion of ischemic hearts. Stimulating AMPK increases mitochondrial fatty acid oxidation, but this is usually accompanied by a decrease in glucose oxidation, which can impair the functional recovery of ischemic hearts. To examine the relationship between AMPK and cardiac energy substrate metabolism, we subjected isolated working mouse hearts expressing a dominant negative (DN) alpha(2)-subunit of AMPK (AMPK-alpha(2) DN) to 20 min of global no-flow ischemia and 40 min of reperfusion with Krebs-Henseleit solution containing 5 mM [U-(14)C]glucose, 0.4 mM [9, 10-(3)H]palmitate, and 100 microU/ml insulin. AMPK-alpha(2) DN hearts had reduced AMPK activity at the end of reperfusion (82 +/- 9 vs. 141 +/- 7 pmol.mg(-1).min(-1)) with no changes in high-energy phosphates. Despite this, AMPK-alpha(2) DN hearts had improved recovery of function during reperfusion (14.9 +/- 0.8 vs. 9.4 +/- 1.4 beats.min(-1).mmHg.10(-3)). During reperfusion, fatty acid oxidation provided 44.0 +/- 2.8% of total acetyl-CoA in AMPK-alpha(2) DN hearts compared with 55.0 +/- 3.2% in control hearts. Since insulin can inhibit both AMPK activation and fatty acid oxidation, we also examined functional recovery in the absence of insulin. Functional recovery was similar in both groups despite a decrease in AMPK activity and a decreased reliance on fatty acid oxidation during reperfusion (66.4 +/- 9.4% vs. 85.3 +/- 4.3%). These data demonstrate that the suppression of cardiac AMPK activity does not produce an energetically compromised phenotype and does not impair, but may in fact improve, the recovery of function after ischemia.
5'-AMP激活蛋白激酶（AMPK）的激活可能通过增加能量产生而在心肌缺血再灌注过程中对心脏有益。虽然AMPK刺激糖酵解，但线粒体氧化代谢是缺血心脏再灌注期间ATP产生的主要来源。刺激AMPK可增加线粒体脂肪酸氧化，但这通常伴随着葡萄糖氧化的减少，这可能损害缺血心脏的功能恢复。为了研究AMPK与心脏能量底物代谢之间的关系，我们将表达AMPK显性负性（DN）α(2)亚基（AMPK-α(2) DN）的离体工作小鼠心脏进行20分钟的全心无血流缺血，并在含有5 mM [U-(14)C]葡萄糖、0.4 mM [9, 10-(3)H]棕榈酸酯和100微单位/毫升胰岛素的Krebs-Henseleit溶液中再灌注40分钟。再灌注结束时，AMPK-α(2) DN心脏的AMPK活性降低（82±9对141±7皮摩尔·毫克(-1)·分钟(-1)），高能磷酸盐无变化。尽管如此，AMPK-α(2) DN心脏在再灌注期间功能恢复有所改善（14.9±0.8对9.4±1.4次/分钟·毫米汞柱·10(-3)）。再灌注期间，脂肪酸氧化在AMPK-α(2) DN心脏中提供了总乙酰辅酶A的44.0±2.8%，而在对照心脏中为55.0±3.2%。由于胰岛素可抑制AMPK激活和脂肪酸氧化，我们还研究了无胰岛素情况下的功能恢复。尽管再灌注期间AMPK活性降低且对脂肪酸氧化的依赖性降低，但两组的功能恢复相似（66.4±9.4%对85.3±4.3%）。这些数据表明，心脏AMPK活性的抑制不会产生能量受损的表型，不会损害但实际上可能改善缺血后功能的恢复。
