Using Deuteromics to Measure Lipid Kinetics
Two approaches have been proposed for quantifying lipid synthesis rates in vivo. One approach is to administer a carbon labeled precursor such as 13C-acetate during a continuous infusion and determining enrichment in lipids. The Deuteromic approach uses a bolus oral dose of labeled water, deuterium oxide (D2O), to enrich lipids.
When 13C-labeled tracers are used, there are some serious limitations:
- Continuous infusions require special facilities
- Infusion protocols are over short time periods
- Subjects are confined
- True precursor enrichment is difficult to measure
- Experiments are costly due to sterile IV solutions
- Difficult to test many subjects at once
Labeling with deuterated water is a more convenient and less costly alternative for measuring lipid kinetics. The basis of the technique is that deuterium oxide rapidly equilibrates with total body water. The deuterium atom labels acetyl-CoA through various enzymatic reactions in the Krebs cycle.
Deuteromic studies are easy to conduct. Only a single oral dose of deuterium oxide (1 gram/kg BW) is required. Blood samples are collected for lipid enrichment prior to dosing and after 4-24 hours. The precursor enrichment of total body water is easily measured with plasma, saliva or urine.
Gas chromatography combustion isotope ratio mass spectrometry (GCC-IRMS) is used to measure very low levels of deuterium in plasma or tissue lipids. The GCC-IRMS separates derivatized fatty acids and cholesterol by gas chromatography. The lipid peaks are then combusted to hydrogen gas at 1450°C, which is analyzed by isotope ratio mass spectrometry. We can detect enrichment levels of 0.001% of deuterium with accuracy and precision. The fractional de novo lipogenesis rate is calculated from the average enrichment of deuterium in fatty acids or cholesterol.
Please contact us with your questions about Deuteromic tracer studies.