Cerebral Metabolic Flux Mapping Using Oxygen 17 NMR

氧是最丰富的元素之一，几乎存在于所有生物相关分子中。在 过去，由于弛豫时间短和低，NMR活性同位素17 O很少受到关注。 灵敏度然而，随着更高磁场强度的可用性，使用17 O富集的底物 有利的T2 */T1比率，任何灵敏度问题都可以快速解决， MRSI数据在几秒钟内。此外，宽的化学位移分散允许检测到 广泛的代谢物。在这里，我们建议开发17 O NMR结合17 O富集底物 注入到一个快速，灵敏和强大的方法，空间映射代谢通量在大鼠大脑中的体内。 在1、2或3位富集的17 O-葡萄糖的代谢提供了糖酵解、三羧酸 循环或丙酮酸脱氢酶活性。星形胶质细胞代谢和丙酮酸羧化酶活性 可以用富含17 O的乙酸盐和碳酸氢盐进行评估。17 O各营业额特征 底物可以通过代谢模型来描述，其中一些需要额外输入，例如再循环 其他器官的17 O标记水。在这里，我们将开发方法来测量所有需要的输入， 以可靠地获得所需的代谢通量。在优化17 O底物合成后， 17 O NMR和17 O标记动力学特性将在体外进行研究。建立的1H-[13 C]-NMR 技术结合13 C标记的葡萄糖和2-脱氧葡萄糖输注将用于验证 大鼠三羧酸循环和糖酵解中的17 O脑代谢通量 11.7T.

Oxygen is one of the most abundant elements and is present in almost all biologically relevant molecules. In the past the NMR active isotope 17O has received little attention, due to short relaxation times and low sensitivity. However, with the availability of higher magnetic field strengths, the use of 17O-enriched substrates and the favorable T2 */T1 ratio, any sensitivity concerns are quickly overcome, allowing the acquisition of 3D MRSI data in the span of seconds. Furthermore, the wide chemical shift dispersion allows the detection of a wide range of metabolites. Here we propose to develop 17O NMR in combination with 17O-enriched substrate infusion into a fast, sensitive and robust method to spatially map metabolic fluxes in the rat brain in vivo. Metabolism of 17O-glucose enriched in the 1, 2 or 3 positions gives information on glycolytic, tricarboxylic acid cycle or pyruvate dehydrogenase activity, respectively. Astroglial metabolism and pyruvate carboxylase activity can be assessed with 17O-enriched acetate and bicarbonate. The 17O turnover characteristics of each substrate can be described by a metabolic model, some of which require additional inputs such as recirculated 17O-labeled water from other organs. Here we will develop the methods to measure all required inputs in order to reliably obtain the desired metabolic fluxes. Following the optimization of 17O substrate synthesis, the characteristics of 17O NMR and 17O label dynamics will be studied in vitro. The established 1H-[13C]-NMR technique in combination with 13C-labeled glucose and 2-deoxyglucose infusions will be used to validate the 17O-based cerebral metabolic fluxes through the tricarboxylic acid cycle and glycolysis, respectively, in the rat brain in vivo at 11.7 T.