Enrichment of hepatic glycogen and plasma glucose from H₂18O informs gluconeogenic and indirect pathway fluxes in naturally feeding mice. (22nd October 2022)

• Record Type: Journal Article
• Authors: Coelho, Margarida; Mahar, Rohit; Belew, Getachew D.; Torres, Alejandra; Barosa, Cristina; Cabral, Fernando; Viegas, Ivan; Gastaldelli, Amalia; Mendes, Vera M.; Manadas, Bruno; Jones, John G.; Merritt, Matthew E.
• Is Part Of: NMR in biomedicine. Volume 36:Number 2(2023)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2022-10-22
• Subjects: fructose -- gluconeogenesis -- glycogenesis -- isotope shift -- triose phosphates; Nuclear magnetic resonance -- Periodicals; Magnetic Resonance Spectroscopy -- Periodicals; 574
• DOI: 10.1002/nbm.4837
• Languages: English
• ISSNs: 0952-3480

Abstract

Abstract: Deuterated water ( 2 H2 O) is a widely used tracer of carbohydrate biosynthesis in both preclinical and clinical settings, but the significant kinetic isotope effects (KIE) of 2 H can distort metabolic information and mediate toxicity. 18 O‐water (H2 18 O) has no significant KIE and is incorporated into specific carbohydrate oxygens via well‐defined mechanisms, but to date it has not been evaluated in any animal model. Mice were given H2 18 O during overnight feeding and 18 O‐enrichments of liver glycogen, triglyceride glycerol (TG), and blood glucose were quantified by 13 C NMR and mass spectrometry (MS). Enrichment of oxygens 5 and 6 relative to body water informed indirect pathway contributions from the Krebs cycle and triose phosphate sources. Compared with mice fed normal chow (NC), mice whose NC was supplemented with a fructose/glucose mix (i.e., a high sugar [HS] diet) had significantly higher indirect pathway contributions from triose phosphate sources, consistent with fructose glycogenesis. Blood glucose and liver TG 18 O‐enrichments were quantified by MS. Blood glucose 18 O‐enrichment was significantly higher for HS versus NC mice and was consistent with gluconeogenic fructose metabolism. TG 18 O‐enrichment was extensive for both NC and HS mice, indicating a high turnover of liver triglyceride, independent of diet. Thus H2 18 O informs hepatic carbohydrate biosynthesis in similar detail to 2 H2 O but without KIE‐associated risks. Abstract : 18 O‐enrichment of liver glycogen, triglyceride glycerol, and blood glucose of mice given 18 O‐water during overnight feeding was quantified by 13 C NMR and MS. Glycogen 18 O‐enrichment of oxygens 3, 5, and 6 from isotope‐shifted 13 C signals informed indirect pathway contributions from different sources. Glucose 18 O‐enrichment by LC–MS/MS yielded an all‐oxygens average, while GC–MS provided average estimates of oxygens 2–5, 2–4, and 4–6, evaluating gluconeogenesis. Triglyceride glycerol 18 O‐enrichment, measured by GC–MS, indicated high liver turnover rates.