Noninvasive liquid diet delivery of stable isotopes into mouse models for deep metabolic network tracing

Abstract

Delivering isotopic tracers for metabolic studies in rodents without overt stress is challenging. Current methods achieve low label enrichment in proteins and lipids. Here, we report noninvasive introduction of 13C6-glucose via a stress-free, ad libitum liquid diet. Using NMR and ion chromatography-mass spectrometry, we quantify extensive 13C enrichment in products of glycolysis, the Krebs cycle, the pentose phosphate pathway, nucleobases, UDP-sugars, glycogen, lipids, and proteins in mouse tissues during 12 to 48 h of 13C6-glucose feeding. Applying this approach to patient-derived lung tumor xenografts (PDTX), we show that the liver supplies glucose-derived Gln via the blood to the PDTX to fuel Glu and glutathione synthesis while gluconeogenesis occurs in the PDTX. Comparison of PDTX with ex vivo tumor cultures and arsenic-transformed lung cells versus xenografts reveals differential glucose metabolism that could reflect distinct tumor microenvironment. We further found differences in glucose metabolism between the primary PDTX and distant lymph node metastases.

Acute loss of iron–sulfur clusters results in metabolic reprogramming and generation of lipid droplets in mammalian cells

“…IC-UHR-FTMS analyses were performed as described previously (66,67) to assess 13 C incorporation into various metabolites. For metabolites quantified with purified standards, data are expressed as nmol/mg protein.…”

Translating In Vitro T Cell Metabolic Findings to In Vivo Tumor Models of Nutrient Competition

“…Thus, during commonly used isolation procedures and before any assay can be performed in vitro , metabolic changes are occurring (Fig 2B). Alternative approaches such as utilizing isotopic tracers are highly compatible with in vivo models, can be easily administered, and may better recapitulate in vivo biology (Hensley et al, 2016; Sun et al, 2017). …”

Integrated Analysis of Acetyl-CoA and Histone Modification via Mass Spectrometry to Investigate Metabolically Driven Acetylation

“…Here, we briefly outline a simplified protocol for the quantification of labeled acetyl-CoA from either [ 13 C]-glucose or [ 13 C]-acetate in mice. Note that a “stress-free” protocol for efficient and reliable tracing of metabolites in vivo has very recently been proposed [19]. Also, glucose can more conveniently administered by IP injection or gavage [20].…”