Glucose Metabolism in Brown Adipose Tissue (BAT) in Young Healthy Men Evaluated by Deuterium Metabolic Imaging (DMI)

In this study the investigators wish to evaluate the glucose metabolism in brown adipose tissue (BAT) in young healthy men (aged 18-35). The investigators wish to validate a novel MR modality - Deuterium Metabolic Imaging (DMI), which is a non-radioactive, non-invasive method that allows for spatial as well as metabolic imaging after oral administration of deuterium-labelled glucose. Deuterium is a stable isotope of hydrogen that can be bound to different metabolites, in this case glucose. This method allows for metabolic imaging and production of 2H MR spectra of metabolites downstream from glucose uptake that can be quantified. DMI has not yet been used to evaluate BAT in humans. Currently, FDG PET/CT is the most widely used method for BAT evaluation in humans, but due to the radiation-exposure associated with FDG PET/CT repetitive studies of BAT in healthy subjects are limited. Therefore, new in vivo methods (preferably non-invasive) are warranted. However, since FDG PET/CT is the most widely used method, the investigators wish to use this modality as reference. The investigators plan to screen 10-12 subjects with an individualized cooling protocol and FDG PET/CT. Only the BAT positive subjects will be included in the DMI study. In the DMI study, the BAT positive subjects will enter in a randomized two-phased cross-over study. The subjects will have 2 DMI scans performed after ingestion of deuterium-labelled glucose; one after 2h of cooling, another in thermoneutrality. Primary outcome is the differences in glucose metabolites between cooling and thermoneutrality. The investigators hypothesize that during cooling uptake of glucose and its metabolites such as glutamine/glutamate and water may be enhanced. Moreover, glucose metabolism may shift towards anaerobic metabolism with increased lactate production as observed in a previous rodent study by the investigators group.