Hepatic UDP-glucose 13C isotopomers from [U-13C]glucose: A simple analysis by 13C NMR of urinary menthol glucuronide
✍ Scribed by Ana C. Mendes; M. Madalena Caldeira; Claudia Silva; Shawn C. Burgess; Matthew E. Merritt; Filipe Gomes; Cristina Barosa; Teresa C. Delgado; Fatima Franco; Pedro Monteiro; Luis Providencia; John G. Jones
- Publisher
- John Wiley and Sons
- Year
- 2006
- Tongue
- English
- Weight
- 107 KB
- Volume
- 56
- Category
- Article
- ISSN
- 0740-3194
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✦ Synopsis
Abstract
Menthol glucuronide was isolated from the urine of a healthy 70‐kg female subject following ingestion of 400 mg of peppermint oil and 6 g of 99% [U‐^13^C]glucose. Glucuronide ^13^C‐excess enrichment levels were 4–6% and thus provided high signal‐to‐noise ratios (SNRs) for confident assignment of ^13^C‐^13^C spin‐coupled multiplet components within each ^13^C resonance by ^13^C NMR. The [U‐^13^C]glucuronide isotopomer derived via direct pathway conversion of [U‐^13^C]glucose to [U‐^13^C]UDP‐glucose was resolved from [1,2,3‐^13^C~3~]‐ and [1,2‐^13^C~2~]glucuronide isotopomers derived via Cori cycle or indirect pathway metabolism of [U‐^13^C]glucose. In a second study, a group of four overnight‐fasted patients (63 ± 10 kg) with severe heart failure were given peppermint oil and infused with [U‐^13^C]glucose for 4 hr (14 mg/kg prime, 0.12 mg/kg/min constant infusion) resulting in a steady‐state plasma [U‐^13^C]glucose enrichment of 4.6% ± 0.6%. Menthol glucuronide was harvested and glucuronide ^13^C‐isotopomers were analyzed by ^13^C NMR. [U‐^13^C]glucuronide enrichment was 0.6% ± 0.1%, and the sum of [1,2,3‐^13^C~3~] and [1,2‐^13^C~2~]glucuronide enrichments was 0.9% ± 0.2%. From these data, flux of plasma glucose to hepatic UDPG was estimated to be 15% ± 4% that of endogenous glucose production (EGP), and the Cori cycle accounted for at least 32% ± 10% of GP. Magn Reson Med, 2006. © 2006 Wiley‐Liss, Inc.