Cardiovascular Division, King's College London, London, UK.
Cardiovascular Research Group, Department of Medical Biology, University of Tromsø, Tromsø, Norway.
Lancet. 2015 Feb 26;385 Suppl 1:S73. doi: 10.1016/S0140-6736(15)60388-9.
The mechanisms that determine whether the heart adapts to overload stress, or fails, are poorly understood. NADPH oxidase (NOX) proteins produce reactive oxygen species (ROS) involved in redox signalling, and our recent studies have found that an increase in Nox4 during pressure overload protects the heart against failure. We aimed to identify novel Nox4-driven cardioprotective mechanisms that promote adaptive cardiac remodelling.
We first undertook a proteomic comparison of heart tissue from cardiac-targeted Nox4-overexpressing mice and controls. The Nox4 cardiac metabolome was then investigated by (1)H nuclear magnetic resonance (NMR) spectroscopy. Effects on cardiac metabolism were assessed by ex-vivo working heart perfusions and isolated mitochondrial respiration studies. Ex-vivo cardiac energetics were assessed by (31)P NMR. Alterations to cardiac fatty acid oxidation were explored in primary cardiomyocytes (extracellular flux analysis).
Cardiac-targeted Nox4 overexpression profoundly remodelled the cardiac proteome in an isoform-specific manner, both in the unstressed and stressed heart. Glycolysis and fatty acid oxidation were identified as the most enriched pathways that were altered by Nox4. Metabolomic analysis showed a 2·2 times increase in acetylcarnitine concentrations (p=0·002). Ex-vivo heart perfusions demonstrated a profound increase in palmitate oxidation relative to wild-type hearts (3·6 times increase, p=0·01), with opposite findings observed in primary cardiomyocytes with a knockdown of Nox4. A preference for fatty acid oxidation in Nox4 hearts correlated with a better energetic state (phosphocreatine:ATP ratio) when subjected to increasing doses of isoprenaline stress under baseline and pressure-overload.
In this study we identified a novel role for Nox4 in the regulation of cardiac fatty acid oxidation. Cardiomyocyte-targeted Nox4 hearts preferentially oxidised fatty acids for energy provision, improving myocardial energetics under stress. Enhancing fatty acid oxidation might have an adaptive role in the setting of pressure-overload hypertrophy. These data provide novel insights into ROS-dependent metabolic programming.
UK Medical Research Council, British Heart Foundation.
决定心脏是否适应超负荷压力或衰竭的机制尚未完全阐明。NADPH 氧化酶（NOX）蛋白产生涉及氧化还原信号的活性氧（ROS），我们最近的研究发现，压力超负荷时 Nox4 的增加可保护心脏免受衰竭。我们旨在确定促进适应性心脏重塑的新的 Nox4 驱动的心脏保护机制。
我们首先对心脏靶向过表达 Nox4 的小鼠和对照的心脏组织进行了蛋白质组比较。然后通过（1）H 核磁共振（NMR）光谱法研究 Nox4 心脏代谢组。通过离体工作心脏灌流和分离线粒体呼吸研究评估对心脏代谢的影响。通过（31）P NMR 评估离体心脏能量代谢。在原代心肌细胞（细胞外通量分析）中探索心脏脂肪酸氧化的变化。
心脏靶向 Nox4 过表达以同工型特异性方式深刻重塑了心脏蛋白质组，无论是在未受应激的心脏还是应激的心脏中。糖酵解和脂肪酸氧化被确定为被 Nox4 改变的最丰富的途径。代谢组学分析显示乙酰肉碱浓度增加了 2.2 倍（p=0.002）。离体心脏灌流显示与野生型心脏相比，棕榈酸氧化显著增加（增加 3.6 倍，p=0.01），而在 Nox4 敲低的原代心肌细胞中则观察到相反的结果。在基线和压力超负荷下，当受到递增剂量的异丙肾上腺素应激时，Nox4 心脏中对脂肪酸氧化的偏好与更好的能量状态（磷酸肌酸：ATP 比）相关。
在这项研究中，我们确定了 Nox4 在调节心脏脂肪酸氧化中的新作用。心肌细胞靶向 Nox4 优先氧化脂肪酸提供能量，在应激下改善心肌能量代谢。增强脂肪酸氧化在压力超负荷肥大的情况下可能具有适应性作用。这些数据为 ROS 依赖性代谢编程提供了新的见解。
英国医学研究理事会，英国心脏基金会。
