UCDHSC Anesthesiology Research - Clinical Nutrition Research Unit

The CNRU Mass Spectrometry Core Facility is equipped with today's most advanced scientific equipment.

Applications in Glucose/Glycerol Metabolism Research

The CNRU Mass Spectrometry Core Facility offers assistance in methods development and mass spectrometry analysis to help researchers study glucose and glycerol metabolism using stable isotope methods. The infusion of stable isotope-labeled glucose has been extensively and reliably utilized to quantify glucose kinetics. This approach is particularly useful for exploring whole body glucose homeostasis under perturbations such as infusions of glucose and insulin.

TYPES OF GLUCOSE METABOLISM APPLICATIONS

GLUCOSE PRODUCTION RATE
Glucose production rates and flux can be calculated when a known amount of glucose tracer is administered.

GLUCOSE RECYCLING
The measured rates of cycling in glycosis and gluconeogenesis represents the total substrate cycling rates between glucose and glucose-6-phosphate and fructose-6-phosphate and fructose-1,6-diphosphate.

GLUCOSE OXIDATION
¹³C-labeled glucose is used to compute the rate of glucose oxidation. Samples of blood are collected to determine the plateau level of 13C-blood while expired breath samples are used to measure ¹³CO₂ enrichment.

GLUCOSE SYNTHESIS FROM PRECURSORS
¹³C stable isotope tracers are used to quantify the rate of gluconeogenesis. For example, the incorporation of alanine carbon into glucose determines the glucose-alanine relationship. By infusing [2,3-13C2]-alanine and 6,6-D2-glucose as tracers, the role of alanine in glucose synthesis can be quantitatively measured. When lactate is enriched the impact of alanine on lactate production can also be calculated.

GLYCEROL TURNOVER
Despite active lipolysis, re-esterification of fatty acids within adipocytes will prevent release of fatty acids into the bloodstream. Therefore, a measurement of fatty acid flux can underestimate the rate of lipolysis except under fasting conditions. However, glycerol cannot be reincorporated into triglycerides because glycerol kinase is absent in adipocytes. We use the rate of appearance of glycerol as a direct index of lipolysis.

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