Mitochondrial respiration and ROS emission during β-oxidation in the heart: An experimental-computational study.
Mitochondrial respiration and ROS emission during β-oxidation in the heart: An experimental-computational study.
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DOI：
10.1371/journal.pcbi.1005588
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发表时间：
2017-06
影响因子：
4.3
通讯作者：
Aon MA
中科院分区：
文献类型：
--
作者：
Cortassa S;Sollott SJ;Aon MA
脂质是细胞能量的主要燃料，线粒体是其主要氧化位点。然而，尚不清楚脂质的燃料作用在多大程度上受到其解偶联效应的影响，以及这如何影响线粒体能量学，氧化还原平衡和活性氧（ROS）的排放。采用实验-计算相结合的方法，我们比较分析棕榈酰CoA（PCoA）的β-氧化分离心脏线粒体从假和链脲佐菌素（STZ）诱导的1型糖尿病（T1 DM）豚鼠（GP）。并行高通量测量的耗氧率（VO 2）和过氧化氢（H2 O2）的排放作为PCoA浓度的函数，在L-肉碱和苹果酸的存在下，进行。我们发现PCoA浓度< 200 nmol/mg mito蛋白导致低H2 O2排放通量，此后在状态4和3呼吸下的Sham和T1 DM GP中增加，糖尿病线粒体释放更大量的ROS。在对照和糖尿病动物中，PCoA > 600 nmol/mg mito prot时发生呼吸解偶联和ROS过量。此外，第一次，我们表明，一个完整的两室线粒体模型的β-氧化的长链脂肪酸和主要的能量-氧化还原过程是能够模拟VO 2和H2 O2排放之间的关系作为脂质浓度的函数。模型和实验结果表明，PCoA的氧化和浓度依赖性的解偶联效应，连同部分脂质依赖性的超氧化物生成速率的降低，调节H2 O2排放的VO 2的函数。结果表明，保持低水平的细胞内脂质对于线粒体和细胞将ROS维持在与信号传导和可靠的能量供应相容的生理水平内至关重要。脂质是肝脏、心肌和骨骼肌的主要能量来源。线粒体是脂质氧化的主要场所，在心脏中，线粒体提供其血液泵送功能所需的大部分能量。然而，奇怪的是，脂质过度供应损害线粒体功能，导致代谢综合征、胰岛素抵抗和糖尿病。在这种情况下，科学辩论集中在脂质和线粒体功能对人类健康，营养和疾病的各个方面的影响。为了阐明这个问题的潜在机制，同时考虑脂质作为能量来源的基本作用以及它们潜在的有害影响，我们利用了一种结合实验和计算的方法。我们的线粒体计算模型包括β-氧化，脂质降解的主要途径，以及其他途径，包括氧自由基的产生和消耗。在来自1型糖尿病和对照豚鼠的心脏线粒体中进行研究。模型和实验结果表明，在浓度阈值以下，脂质燃料化在不破坏线粒体功能的情况下进行;在阈值以上，脂质解偶联线粒体呼吸，触发氧化剂的过量排放，同时损害抗氧化系统和线粒体能量供需响应。这些贡献直接用于解释和预测与脂质循环水平增加相关的代谢紊乱中的功能障碍以及脂质利用、储存和细胞内信号传导中的代谢改变。
Lipids are main fuels for cellular energy and mitochondria their major oxidation site. Yet unknown is to what extent the fuel role of lipids is influenced by their uncoupling effects, and how this affects mitochondrial energetics, redox balance and the emission of reactive oxygen species (ROS). Employing a combined experimental-computational approach, we comparatively analyze β-oxidation of palmitoyl CoA (PCoA) in isolated heart mitochondria from Sham and streptozotocin (STZ)-induced type 1 diabetic (T1DM) guinea pigs (GPs). Parallel high throughput measurements of the rates of oxygen consumption (VO2) and hydrogen peroxide (H2O2) emission as a function of PCoA concentration, in the presence of L-carnitine and malate, were performed. We found that PCoA concentration < 200 nmol/mg mito protein resulted in low H2O2 emission flux, increasing thereafter in Sham and T1DM GPs under both states 4 and 3 respiration with diabetic mitochondria releasing higher amounts of ROS. Respiratory uncoupling and ROS excess occurred at PCoA > 600 nmol/mg mito prot, in both control and diabetic animals. Also, for the first time, we show that an integrated two compartment mitochondrial model of β-oxidation of long-chain fatty acids and main energy-redox processes is able to simulate the relationship between VO2 and H2O2 emission as a function of lipid concentration. Model and experimental results indicate that PCoA oxidation and its concentration-dependent uncoupling effect, together with a partial lipid-dependent decrease in the rate of superoxide generation, modulate H2O2 emission as a function of VO2. Results indicate that keeping low levels of intracellular lipid is crucial for mitochondria and cells to maintain ROS within physiological levels compatible with signaling and reliable energy supply. Lipids are main sources of energy for liver and cardiac and skeletal muscle. Mitochondria are the main site of lipid oxidation which, in the heart, supplies most of the energy required for its blood pumping function. Paradoxically, however, lipids over supply impair mitochondrial function leading to metabolic syndrome, insulin resistance and diabetes. In this context, scientific debate centers on the impact of lipids and mitochondrial function on diverse aspects of human health, nutrition and disease. To elucidate the underlying mechanisms of this issue, while accounting for both the fundamental role of lipids as energy source as well as their potential detrimental effects, we utilized a combined experimental and computational approach. Our mitochondrial computational model includes β-oxidation, the main route of lipid degradation, among other pathways that include oxygen radical generation and consumption. Studies were performed in heart mitochondria from type 1 diabetic and control guinea pigs. Model and experimental results show that, below a concentration threshold, lipids fueling proceeds without disrupting mitochondrial function; above threshold, lipids uncouple mitochondrial respiration triggering excess emission of oxidants while impairing antioxidant systems and the mitochondrial energy supply-demand response. These contributions are of direct use for interpreting and predicting functional impairments in metabolic disorders associated with increased circulating levels of lipids and metabolic alterations in their utilization, storage and intracellular signaling.