Substrate Selection and Oxidative Stress in Heart Failure

衰竭的心脏表现出代谢表型的改变，特征是游离脂肪酸的下调 氧化、糖酵解和葡萄糖氧化增强以及线粒体吸氧能力受损 消耗和ATP的产生。这些代谢变化是适应性的还是非适应性的 从代偿性心力衰竭发展到失代偿性心力衰竭的机制和作用 仍然是悬而未决的问题。我们最近发现了碳水化合物增加之间的潜在联系 新陈代谢和衰竭心脏细胞损伤的一个主要机制，即氧化应激。在……里面 失代偿性心衰，心肌葡萄糖-6-磷酸脱氢酶(G6PDH)上调， 因此，更多的葡萄糖被输送到磷酸戊糖氧化途径中。这导致了一个 胞质NADPH的合成增加，NADPH是细胞通常用来再生的电子供体 抗氧化剂系统，但衰竭心肌中的抗氧化剂可以为产生超氧化物歧化酶提供燃料，如 NADPH氧化酶和解偶联的一氧化氮合酶。因此，我们提供了第一个证据来证明原因- 葡萄糖利用增强与NADPH供应增加之间的效应关系 衰竭心脏中的磷酸戊糖途径和更高的超氧化物生成。该计划的总体目标 目前的项目是验证这一假设，即HF增加了心肌葡萄糖进入氧化的流量 磷酸戊糖途径，增加NADPH对超氧化物产生酶的供应，并加速 氧化应激和功能损伤。研究将在慢性仪器犬身上进行， 起搏诱发的心衰。具体目标1是确定改变的底物新陈代谢是否增加 心力衰竭时的心肌氧化应激。健康人和心力衰竭患者循环中游离脂肪酸和葡萄糖的变化 模拟生理条件，如禁食和餐后状态，并评估它们的影响 在基线和儿茶酚胺应激期间心脏氧化应激的影响。具体目标2：确定 磷酸戊糖氧化途径是否在促进超氧化物生成中起关键作用 衰竭心脏中的酶。在心力衰竭的发展过程中，心肌G6PDH将被 运送编码短干扰RNA的DNA，并由病毒载体携带。或者，G6PDH基因 将通过病毒载体传递以诱导其过度表达。具体目标#3：确定

The failing heart displays an altered metabolic phenotype, characterized by downregulation of free fatty acid oxidation, enhanced glycolysis and glucose oxidation and impaired mitochondrial capacity for oxygen consumption and ATP generation. Whether these metabolic alterations are adaptive or maladaptive mechanisms and contribute to the progression from compensated to decompensated heart failure (HF) remain open questions. We have recently identified a potential link between increased carbohydrate metabolism and a major mechanism of cellular damage in the failing heart, namely oxidative stress. In decompensated HF, myocardial glucose-6-phosphate dehydrogenase (G6PDH) is upregulated and, consequently, more glucose is channeled into the oxidative pentose phosphate pathway. This leads to an increased synthesis of cytosolic NADPH, an electron donor normally utilized by cells to regenerate antioxidant systems, but that in the failing myocardium can fuel superoxide-producing enzymes such as NADPH oxidase and uncoupled NO synthase. We therefore provided the first evidence to suggest a cause- effect relationship linking enhanced glucose utilization, increased NADPH supply by upregulation of the pentose phosphate pathway and higher superoxide production in the failing heart. The overall goal of the present project is to test the hypothesis that HF increases myocardial flux of glucose into the oxidative pentose phosphate pathway, enhances NADPH supply to superoxide-generating enzymes, and accelerates oxidative stress and functional damage. Studies will be performed on chronically instrumented dogs with pacing-induced HF. Specific Aim #1 is to determine whether the altered substrate metabolism increases myocardial oxidative stress in HF. Circulating free fatty acids and glucose will be altered in healthy and HF dogs to simulate physiological conditions such as fasting and post-prandial state and to assess their effects on cardiac oxidative stress at baseline and during catecholamine stress. Specific Aim #2: is to determine whether the oxidative pentose phosphate pathway plays a critical role in fueling superoxide-generating enzymes in the failing heart. During development of HF, myocardial G6PDH will be knocked down by delivering DNA encoding for short interfering RNA and carried by viral vectors. Alternatively, G6PDH gene will be delivered via viral vectors to induce its overexpression. Specific Aim #3: is to determine whether the