Stable isotopes in clinical studies—advancements in doubly labeled water and labeled glucose and free fatty acids analyses

Thursday, October 27, 2011 — Core Poster Session
10:00 a.m. – Noon	South Lobby of Building 10	NIDDK	CORE-22

Authors

• P Walter
• M Shrestha

Abstract

Clinical studies using stable isotopes involve administering a subject with substances labeled with rare isotopes, collecting samples, and monitoring production or decay in the isotopic ratio of the labeled product. Rare stable isotopes are advantageous for clinical studies as they are chemically and physically indistinguishable from the predominant natural isotope of the same element, however, they are readily distinguished and quantitated by isotope ratio mass spectrometers (IRMS). Additionally, stable isotopes are not radioactive and do not have the safety and disposal restrictions associated with radioactive tracers. Metabolic studies with stable isotopes covers a vast range. Currently we are developing the use of stable isotope labeled glucose as a measure of glucose metabolism. Labeled glucose can either be done with deuterium or with 13carbon. Development of the measurement of deuterium or carbon labeled glucose will be presented. The doubly labeled water method was developed to measure total energy expenditure. A patient is dosed with water labeled with rare stable isotopes of hydrogen and oxygen. Once equilibrated, the loss of labeled hydrogen and oxygen relates to carbon dioxide production and a measure of total energy expenditure. This technique requires a very high accuracy and precision measurement of the isotopic ratios by IRMS.

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