Determination of a glucose-dependent futile recycling rate constant from an intraperitoneal glucose tolerance test.

Abstract

Increased glucose cycling between glucose and glucose-6-phosphate is characteristic of insulin resistance and hyperglycemia seen with Type II diabetes. Traditionally, glucose cycling is determined by the difference between hepatic glucose output measured with separate [2-3H]glucose and [6-3H]glucose infusions. We demonstrate a novel method for determining hepatic glucose recycling from an intraperitoneal glucose tolerance test (IPGTT). A single tracer, [1, 2-13C(2)]glucose (a M2 glucose isotopomer), was administered at 1mg/g body weight to 4-month-old C57BL/6 mice. Hepatic glucose recycling was monitored by the appearance of a plasma M1 isotopomer of glucose, which is produced by the action of the pentose cycle on the M2 glucose isotopomer in the liver. The initial M2 enrichment was 56% and decreased to 13% at the end of 3 h, and the M1 enrichment peaked at 2 h. The ratio of plasma M1/M2 glucose increased linearly with time to approximately 25%, and the regression of the M1/M2 ratio against time gives a slope, termed the in vivo glucose-dependent futile recycling rate constant k(HR). k(HR) estimates glucose/glucose-6-phosphate futile cycling, along with glucose recycling through the pentose cycle. These observations demonstrate complex substrate cycling during an IPGTT using a single stable isotope tracer.

• Authors: Jun Xu, W N Paul Lee, Gary Xiao, Chuck Trujillo, Vicky Chang, Lilia Blanco, Felicia Hernandez, Beau Chung, Sahar Makabi, Sayed Ahmed, Sara Bassilian, Mohammed Saad, Irwin J Kurland
• Journal: Analytical biochemistry (Anal Biochem) Vol. 315 Issue 2 Pg. 238-46 (Apr 15 2003) ISSN: 0003-2697 [Print] United States
• PMID: 12689833 (Publication Type: Journal Article, Research Support, U.S. Gov't, P.H.S.)
• Copyright: Copyright 2003 Elsevier Science (USA)

Chemical References

• Blood Glucose
• Carbon Isotopes
• Insulin
• Glycogen
• Glucose

Topics

• Animals
• Blood Glucose (analysis)
• Blotting, Western
• Carbon Isotopes
• Gas Chromatography-Mass Spectrometry
• Glucose (administration & dosage, metabolism)
• Glucose Tolerance Test
• Glycogen (metabolism)
• Glycolysis
• Injections, Intraperitoneal
• Insulin (blood, metabolism)
• Isotope Labeling
• Kinetics
• Liver (metabolism)
• Male
• Mice
• Mice, Inbred C57BL
• Time Factors