Hyperpolarized [U-²H, U-¹³C]Glucose reports on glycolytic and pentose phosphate pathway activity in EL4 tumors and glycolytic activity in yeast cells

Abstract

A resonance at ∼181 ppm in the (13) C spectra of tumors injected with hyperpolarized [U-(2) H, U-(13) C]glucose was assigned to 6-phosphogluconate (6PG), as in previous studies in yeast, whereas in breast cancer cells in vitro this resonance was assigned to 3-phosphoglycerate (3PG). These peak assignments were investigated here using measurements of 6PG and 3PG (13) C-labeling using liquid chromatography tandem mass spectrometry (LC-MS/MS) METHODS: Tumor-bearing mice were injected with (13) C6 glucose and the (13) C-labeled and total 6PG and 3PG concentrations measured. (13) C MR spectra of glucose-6-phosphate dehydrogenase deficient (zwf1Δ) and wild-type yeast were acquired following addition of hyperpolarized [U-(2) H, U-(13) C]glucose and again (13) C-labeled and total 6PG and 3PG were measured by LC-MS/MS RESULTS: Tumor (13) C-6PG was more abundant than (13) C-2PG/3PG and the resonance at ∼181 ppm matched more closely that of 6PG. (13) C MR spectra of wild-type and zwf1Δ yeast cells showed a resonance at ∼181 ppm after labeling with hyperpolarized [U-(2) H, U-(13) C]glucose, however, there was no 6PG in zwf1Δ cells. In the wild-type cells 3PG was approximately four-fold more abundant than 6PG CONCLUSION: The resonance at ∼181 ppm in (13) C MR spectra following injection of hyperpolarized [U-(2) H, U-(13) C]glucose originates predominantly from 6PG in EL4 tumors and 3PG in yeast cells.

Reprogramming glucose metabolism in cancer: can it be exploited for cancer therapy?

“…The oxidative branch generates NADPH and ribulose-5-phosphate in three irreversible reactions. The non-oxidative branch generates pentose phosphates for ribonucleotide synthesis in a series of reversible reactions that also recruit additional metabolites, such as fructose-6-phosphate (F6P) and glyceraldehyde-3-phosphate (G3P) (reviewed in REFS 11,12 ) (FIG. 2a).…”

“…2a), it has a pivotal role in cancer metabolism. The PPP is modulated by several metabolites, and in proliferating cancer cells both the oxidative and non-oxidative branches of the PPP are increased by several oncogenic drivers (reviewed in REFS 11,12 ). The extent to which the oxidative branch versus the non-oxidative branch is modulated depends on the redox and metabolic status of the cell.…”

Hyperpolarized Sodium [1-13C]-Glycerate as a Probe for Assessing Glycolysis In Vivo

“…Previous reports have observed a chemical shift of [1- 13 C]-PEP ([ 13 C]-PEP) in a similar region as [ 13 C]-Pyr with a 1.7 ppm difference in the respective signals. 30 In our study at 3 T, spectral overlap of these metabolites cannot be discounted, which could result in potential contribution of [ 13 C]-PEP to the [ 13 C]-Pyr signal. Since the interconversion between pyruvate and lactate catalyzed by lactate dehydrogenase is generally in a fast chemical equilibrium, the lactate/pyruvate ratio has traditionally been employed in the evaluation of intracellular redox states.…”

Applications of NMR spectroscopy to systems biochemistry

“…However, 13 C carbonyl resonance assignments of metabolites based only on chemical shift and biochemical intuition could be problematic. Recently it was shown that a particular signal was assigned to 6-phosphogluconate (6PG) in tumors, but 3PGA in yeast and potentially in other systems [338]. The biochemical interpretation of these assignments is distinct, as 3PGA relates to glycolytic flux while 6PG reflects flux through the oxidative branch of the pentose phosphate pathway.…”