IMAGING METABOLIC FLUX WITH HYPERPOLARIZED NUCLEI

这个子项目是许多利用资源的研究子项目之一 由NIH/NCRR资助的中心拨款提供。子项目的主要支持 而子项目的主要调查员可能是由其他来源提供的， 包括其它NIH来源。 列出的子项目总成本可能 代表子项目使用的中心基础设施的估计数量， 而不是由NCRR赠款提供给子项目或子项目工作人员的直接资金。 测量某些靶分子（如谷氨酸盐）中13 C富集和同位素异构体模式的能力可以与数学建模配对，以估计完整系统中的通量。MR为进行这些测量提供了一种独特的工具，因为它可以通过观察13 C光谱中存在的j-耦合多重峰来轻松测量各种同位素异构体的存在。在体内和离体光谱方法以及器官或血液提取物的体外分析方面都取得了进展。 考虑到这一点，该资源将注意力转向用于MR灵敏度增强的超极化新领域似乎是合适的。13 C超极化是最有前途的代谢成像新模式之一。13 C同位素分析与这种新的物理技术相结合，既符合逻辑又切合实际，并服务于多个驱动项目的目标。 我们相信，通过超极化获得的增加的灵敏度将允许在临床合理的时间段内在体内使用同位素标记的化合物来评估代谢。将该技术扩展到临床取决于新的实验MR方法的开发，以及资源已经产生的代谢模型对HP技术本身施加的独特约束的适应。使用超极化稳定同位素体内测量通量的目标需要5个目标的进步： 目的1是开发一套新的示踪分子用于评估葡萄糖代谢。在此目标范围内，将用葡内酯葡萄糖类似物探测磷酸戊糖途径，并评估TR&D 1中合成的其他葡萄糖剂的效用。 目的二是发展利用超极化测量绝对通量的新方法。 我们将利用我们的专业知识与13 C NMR同位素分析和预标记组织，这将使我们能够同时测量相对通量从组织提取物和索引此信息的结果从超极化实验。 通过明智地选择可用底物的标记模式，可以产生产生[1- 13 C]和[1，2 - 13 C]乙酰辅酶A的分子。 将开发用于分析观察到的动力学的数学模型，并根据标准生理测量（如耗氧量）进行验证。 最后，我们将整合超极化研究中的预标记和动力学分析，以完全从13 C数据中获得代谢网络的完整图像。 目标3提出了一个主要挑战：通过质子检测超极化13 C信号。 将优化INEPT参数，以检测分离组织中的[1- 13 C]乳酸盐和丙氨酸，并在灌注的大鼠心脏和小鼠肝脏中测定检测阈值。 目的4是使现有的化学位移成像（CSI）技术适用于4.7T超极化核的探测。在这个目标中，CSI协议将被实现，并将评估探索偏振传输成像的方案。 目的5是将超极化CT技术转移到3 T扫描仪上.这将需要多个步骤和里程碑，包括：1）实施用于快速13 C CSI的采集加权双自旋回波EPSI，2）实施用于将极化从谷氨酸C5转移到C4和C3的FLOPSY-EPSI。3)利用WURST RF脉冲开发低SAR绝热去耦4）开发SENSE-EPSI、keyhole-EPSI和压缩EPSI。 该研发项目与其他研发项目以及多个驱动生物医学项目广泛互动。目的是在研究资源中开发一套用于评估临床相关时期体内代谢的技术。

This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. Primary support for the subproject and the subproject's principal investigator may have been provided by other sources, including other NIH sources. The Total Cost listed for the subproject likely represents the estimated amount of Center infrastructure utilized by the subproject, not direct funding provided by the NCRR grant to the subproject or subproject staff. The ability to measure 13C enrichments and isotopomer patterns in certain target molecules such as glutamate can be paired with mathematical modeling to estimate flux in intact systems. MR provides a unique tool for making these measurements since it can easily measure the presence of a variety of isotopomers by observing the j-coupled multiplets present in 13C spectra. Progress has been made with both in vivo and ex vivo spectroscopy methods, as well as in vitro analysis of extracts from organs or blood. With this in mind, it seems appropriate that the Resource turn its attention to the new field of hyperpolarization for MR sensitivity enhancement. Hyperpolarization of 13C is one of the most promising new modalities for metabolic imaging. The combination of 13C isotopomer analysis with this new physical technique is both logical and pertinent, and serves the goals of multiple driving projects. We believe that the increased sensitivity available through hyperpolarization will allow the in vivo use of isotopically labeled compounds for assessing metabolism in clinically reasonable time periods. Extending this technology to the clinic depends upon development of new experimental MR methods as well as adaptation of the metabolic models already produced by the Resource to the unique constraints imposed by the HP technology itself. The goal of in vivo measurement of flux using hyperpolarized stable isotopes demands the advancement of 5 aims: Aim 1 is to develop a new set of tracer molecules for assessing glucose metabolism. Within this Aim, the pentose phosphate pathway will be probed with a gluconolactone glucose analogue and the utility of other glucose agents, synthesized in TR&D 1, will be assessed. Aim 2 is to develop new methods for measuring absolute flux using hyperpolarization. We will take advantage of our expertise with 13C NMR isotopomer analysis and prelabel tissues that will allow us to simultaneously measure relative fluxes from tissue extracts and index this information to results from hyperpolarization experiments. By judicious selection of the labeling pattern of available substrates, molecules that produce [1-13C] and [1,2-13C]acetyl-CoA can be generated. Mathematical models for analysis of observed kinetics will be developed and validated against standard physiological measurements such as oxygen consumption. Finally, we will integrate pre-labeling and kinetic analysis from hyperpolarization studies to obtain complete pictures of metabolic networks from 13C data exclusively. Aim 3 presents a major challenge: detect hyperpolarized 13C signals through protons. INEPT parameters will be optimized to detect [1-13C] lactate and alanine in isolated tissues and the detection threshold will be determined in the perfused rat heart and mouse liver. Aim 4 is to adapt current chemical shift imaging (CSI) technologies to the detection of hyperpolarized nuclei at 4.7 T. In this Aim, CSI protocols will be implemented and schemes that explore polarization transfer imaging will be evaluated. Aim 5 is to transfer hyperpolarized BC technology to a 3 T scanner. This will require a number of steps and milestones including: 1) Implement acquisition-weighted double spin-echo EPSI for rapid 13C CSI, 2) Implement FLOPSY-EPSI for transferring polarization from glutamate C5 to C4 and C3. 3) Develop low-SAR adiabatic decoupling with WURST RF pulses 4) Develop SENSE-EPSI, keyhole-EPSI, and compressed EPSI. This TR&D project interacts extensively with the other TR&D projects as well as with multiple Driving Biomedical Projects. The intent is to develop in the Research Resource a suite of technologies for assessing in vivo metabolism in periods that are clinically relevant.