Computational models based on the metabolism of stable isotope tracers can yield valuable insight into the metabolic basis of disease. The complexity of these models is limited by the number of tracers and the ability to characterize tracer labeling in downstream metabolites. NMR spectroscopy is ideal for multiple tracer experiments since it precisely detects the position of tracer nuclei in molecules, but it lacks sensitivity for detecting low-concentration metabolites. GC-MS detects stable isotope mass enrichment in low-concentration metabolites, but lacks nuclei and positional specificity. We performed liver perfusions and in vivo infusions of ²H and ¹³C tracers, yielding complex glucose isotopomers that were assigned by NMR and fit to a newly developed metabolic model. Fluxes regressed from ²H and ¹³C NMR positional isotopomer enrichments served to validate GC-MS-based flux estimates obtained from the same experimental samples. NMR-derived fluxes were largely recapitulated by modeling the mass isotopomer distributions of six glucose fragment ions measured by GC-MS. Modest differences related to limited fragmentation coverage of glucose C1–C3 were identified, but fluxes such as gluconeogenesis, glycogenolysis, cataplerosis and TCA cycle flux were tightly correlated between the methods. Most importantly, modeling of GC-MS data could assign fluxes in primary mouse hepatocytes, an experiment that is impractical by ²H or ¹³C NMR.

基于稳定同位素示踪剂代谢的计算模型可以对疾病的代谢基础产生有价值的见解。这些模型的复杂性受限于示踪剂的数量以及表征下游代谢产物中示踪剂标记的能力。NMR光谱法是多种示踪剂实验的理想选择，因为它可以精确检测分子中示踪剂核的位置，但缺乏检测低浓度代谢物的灵敏度。GC-MS在低浓度代谢物中检测到稳定的同位素质量富集，但缺乏核和位置特异性。我们进行了² H和^13的肝灌注和体内灌注C示踪剂，产生复杂的葡萄糖异构体，由NMR分配并适合新开发的代谢模型。从² H和¹³ C NMR位置异构体富集返回的通量用于验证从相同实验样品获得的基于GC-MS的通量估计值。通过对通过GC-MS测量的六个葡萄糖片段离子的质量同位素异构体分布进行建模，可以大致概括NMR衍生的通量。鉴定了与有限的C1–C3葡萄糖碎片覆盖范围相关的适度差异，但方法之间的通量，如糖异生，糖原分解，卡特彼勒病和TCA循环通量紧密相关。最重要的是，GC-MS数据建模可以分配原代小鼠肝细胞中的通量，这一实验在²年前是不切实际的1 H或¹³ C NMR。