Causes and consequences of AMPK activation in the heart

心脏中 AMPK 激活的原因和后果

• 批准号: 6900263
• 负责人: James Alvin Balschi
• 金额: $ 38.5万
• 依托单位: BRIGHAM AND WOMEN'S HOSPITAL
• 依托单位国家: 美国
• 财政年份: 1991
• 资助国家: 美国
• 起止时间: 1991-08-12 至 2007-06-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/6900263
• 关键词: HMG coA reductases; Krebs' cycle; acetyl coA carboxylase; acidity /alkalinity; adenosine monophosphate; adenosine triphosphate; bioenergetics; calcium flux; cytoplasm; enzyme activity; enzyme feedback; enzyme substrate; fatty acid metabolism; glycolysis; heart metabolism; heart pharmacology; isolation perfusion; laboratory mouse; myocardial ischemia /hypoxia; nuclear magnetic resonance spectroscopy; oxygen consumption; protein kinase

DESCRIPTION (provided by applicant): AMP-activated protein kinase (AMPK) acts as a cellular low fuel warning system. Increases in AMP concentration ([AMP]) activate AMPK, while high concentrations of ATP ([ATP]) antagonize AMPK activation. After this warning system is activated it initiates protective measures to either conserve ATP or promote alternative methods of ATP generation. We increased [AMP] using metabolic inhibitors and measured the relationship between AMPK activity and [AMP] in the perfused rat heart. AMPK's half maximal activating concentration of AMP was 1.8 +/- 0.3 muM and 10 to 30 muM cytosolic [AMP] resulted in a two-fold maximal increase in AMPK activity. In this study [ATP] was greater than or equal too 7 mM. These results suggest that in the heart ATP does not antagonize AMP activation as it does in test tube studies. In the ischemic rat heart we found that 10 to 30 fM cytosolic [AMP] resulted in an eight-fold increase in AMPK activity. This four times greater AMPK activation in ischemia indicates that factors other than AMP cause AMPK activation. These observations lead to our first hypothesis that the causal factors for AMPK activation are the metabolically active cytosolic [AMP] (not total AMP), reduced [ATP], and intracellular H+ ([H+]i). We propose two specific aims to test this hypothesis. First, to define the relationship between AMPK activity and the [AMP] in the isolated perfused mouse heart. The [AMP], [ATP], and [H+]i, will be altered using three manipulations of energy metabolism, metabolic inhibitors, hypoxia, and ischemia. Second, to define how long AMPK remains activated after restoration of normal [AMP] in the isolated perfused mouse heart. Our second hypothesis that the predominant consequence of AMPK activation is a shift in substrate metabolism, in particular, an acceleration of fatty acid oxidation resulting from acetyl-CoA carboxylase phosporylation by AMPK. The third specific aim will define the alteration in substrate utilization resulting from increased AMPK activity in the isolated perfused mouse heart. Our long-term objective is to determine the causes of AMPK activity and the consequences of AMPK activity for myocardial substrate metabolism during the two most dangerous cardiovascular diseases, ischemia and heart failure, in the United States.

描述（由申请人提供）：AMP 激活蛋白激酶（AMPK）充当细胞低燃料警告系统。 AMP 浓度 ([AMP]) 的增加会激活 AMPK，而高浓度的 ATP ([ATP]) 则会拮抗 AMPK 的激活。该警告系统激活后，它会启动保护措施，以保存 ATP 或促进 ATP 生成的替代方法。 我们使用代谢抑制剂增加 [AMP]，并测量灌注大鼠心脏中 AMPK 活性和 [AMP] 之间的关系。 AMPK 的 AMP 半最大激活浓度为 1.8 +/- 0.3 muM，10 至 30 muM 胞质 [AMP] 导致 AMPK 活性最大增加两倍。在本研究中，[ATP] 也大于或等于 7 mM。这些结果表明，在心脏中 ATP 并不像试管研究中那样拮抗 AMP 激活。在缺血性大鼠心脏中，我们发现 10 至 30 fM 胞质 [AMP] 导致 AMPK 活性增加八倍。缺血时 AMPK 激活增加四倍，表明除 AMP 之外的其他因素也会导致 AMPK 激活。这些观察结果得出我们的第一个假设，即 AMPK 激活的致病因素是代谢活跃的胞质 [AMP]（不是总 AMP）、还原的 [ATP] 和细胞内 H+ ([H+]i)。 我们提出了两个具体目标来检验这一假设。首先，确定离体灌注小鼠心脏中 AMPK 活性与 [AMP] 之间的关系。 [AMP]、[ATP] 和 [H+]i 将通过能量代谢、代谢抑制剂、缺氧和缺血三种操作来改变。其次，确定离体灌注小鼠心脏恢复正常 [AMP] 后 AMPK 保持激活状态的时间。 我们的第二个假设是 AMPK 激活的主要结果是底物代谢的变化，特别是 AMPK 乙酰辅酶 A 羧化酶磷酸化导致的脂肪酸氧化加速。第三个具体目标将定义离体灌注小鼠心脏中 AMPK 活性增加导致的底物利用率的变化。 我们的长期目标是确定美国两种最危险的心血管疾病（缺血和心力衰竭）期间 AMPK 活性的原因以及 AMPK 活性对心肌底物代谢的影响。