Assessment of postprandial carbohydrate oxidation with stable carbon isotopes (13C)

Abstract

The use of stable isotopes for mapping human metabolism is a very safe and noninvasive technique. It basically consists of enriching organic molecules with stable carbon, hydrogen, or oxygen isotopes, which are then ingested by the patient in a solid or fluid medium. Isotopes differ in the number of neutrons they contain. They are safe, easy to detect and trace in the body, and can be recovered from exhaled air, blood, urine, or body tissues. Different nutrients can be enriched with stable isotopes, such as carbohydrates, proteins, fats, and vitamins. These isotopes can be measured by different methods, but the most common is isotope-ratio mass spectrometry (IRMS). The objective of this study is to assess the kinetics of postprandial simple and complex carbohydrate oxidation in adults with different body mass indices (BMI) by measuring the 13CO2 exhaled after consumption of compounds that have been naturally enriched by plants that use the C4 carbon fixation pathway. A total of 36 adults with normal weight, class II obesity, or class III obesity will participate in the study. They will be asked to consume a meal rich in 13C and aliquots of their exhaled CO2 will be collected postprandially for IRMS. The study aims to prove that carbohydrates naturally enriched with 13C can be used as tracers of postprandial energy metabolism and that this metabolism depends on carbohydrate molecule size and body size. (AU)