From the Burnett School of Biomedical Sciences, Division of Metabolic and Cardiovascular Sciences, University of Central Florida, College of Medicine, Orlando, Florida 32827.
the Department of Anesthesiology, University of Rochester Medical Center, Rochester, New York 14620, and.
J Biol Chem. 2018 May 4;293(18):6925-6941. doi: 10.1074/jbc.RA118.002566. Epub 2018 Mar 14.
Cardiac energy demands during early embryonic periods are sufficiently met through glycolysis, but as development proceeds, the oxidative phosphorylation in mitochondria becomes increasingly vital. Adrenergic hormones are known to stimulate metabolism in adult mammals and are essential for embryonic development, but relatively little is known about their effects on metabolism in the embryonic heart. Here, we show that embryos lacking adrenergic stimulation have ∼10-fold less cardiac ATP compared with littermate controls. Despite this deficit in steady-state ATP, neither the rates of ATP formation nor degradation was affected in adrenergic hormone-deficient hearts, suggesting that ATP synthesis and hydrolysis mechanisms were fully operational. We thus hypothesized that adrenergic hormones stimulate metabolism of glucose to provide chemical substrates for oxidation in mitochondria. To test this hypothesis, we employed a metabolomics-based approach using LC/MS. Our results showed glucose 1-phosphate and glucose 6-phosphate concentrations were not significantly altered, but several downstream metabolites in both glycolytic and pentose-phosphate pathways were significantly lower compared with controls. Furthermore, we identified glyceraldehyde-3-phosphate dehydrogenase and glucose-6-phosphate dehydrogenase as key enzymes in those respective metabolic pathways whose activity was significantly ( < 0.05) and substantially (80 and 40%, respectively) lower in adrenergic hormone-deficient hearts. Addition of pyruvate and to a lesser extent ribose led to significant recovery of steady-state ATP concentrations. These results demonstrate that without adrenergic stimulation, glucose metabolism in the embryonic heart is severely impaired in multiple pathways, ultimately leading to insufficient metabolic substrate availability for successful transition to aerobic respiration needed for survival.
胚胎早期的心脏能量需求可以通过糖酵解充分满足，但随着发育的进行，线粒体中的氧化磷酸化变得越来越重要。肾上腺素激素已知可以刺激成年哺乳动物的新陈代谢，对胚胎发育至关重要，但关于它们对胚胎心脏代谢的影响相对知之甚少。在这里，我们表明，缺乏肾上腺素刺激的胚胎与同窝对照相比，心脏 ATP 减少了约 10 倍。尽管在稳态 ATP 方面存在这种不足，但肾上腺素激素缺乏的心脏中 ATP 形成和降解的速率均不受影响，这表明 ATP 合成和水解机制完全有效。因此，我们假设肾上腺素激素刺激葡萄糖代谢，为线粒体氧化提供化学底物。为了验证这一假设，我们采用了基于代谢组学的方法，使用 LC/MS。我们的结果表明，葡萄糖 1-磷酸和葡萄糖 6-磷酸的浓度没有明显改变，但糖酵解和戊糖磷酸途径中的几个下游代谢物的浓度明显低于对照。此外，我们确定了甘油醛-3-磷酸脱氢酶和葡萄糖-6-磷酸脱氢酶作为这些代谢途径中的关键酶，其活性在肾上腺素激素缺乏的心脏中显著（<0.05）且大幅度（分别为 80%和 40%）降低。丙酮酸的添加，在较小程度上还有核糖的添加，导致稳态 ATP 浓度的显著恢复。这些结果表明，在没有肾上腺素刺激的情况下，胚胎心脏中的葡萄糖代谢在多个途径中严重受损，最终导致用于成功过渡到生存所需的有氧呼吸的代谢底物供应不足。
