Leucine Potentiates Glucose-mediated (18)F-FDG Uptake in Brown Adipose Tissue via β-Adrenergic Activation

Significant depots of brown adipose tissue (BAT) have been identified in many adult humans through positron emission tomography (PET), with the amount of BAT being inversely correlated with obesity. As dietary activation of BAT has implications for whole body glucose metabolism, leucine was used in the present study to determine its ability to promote BAT activation resulting in increased glucose uptake. In order to assess this, 2-deoxy-2-(fluorine-18)fluoro-d-glucose ((18)F-FDG) uptake was measured in C57BL/6 mice using microPET after treatment with leucine, glucose, or both in interscapular BAT (IBAT). Pretreatment with propranolol (PRP) was used to determine the role of β-adrenergic activation in glucose and leucine-mediated (18)F-FDG uptake. Analysis of maximum standardized uptake values (SUV(MAX)) determined that glucose administration increased (18)F-FDG uptake in IBAT by 25.3%. While leucine did not promote (18)F-FDG uptake alone, it did potentiate glucose-mediated (18)F-FDG uptake, increasing (18)F-FDG uptake in IBAT by 22.5%, compared to glucose alone. Pretreatment with PRP prevented the increase in IBAT (18)F-FDG uptake following the combination of glucose and leucine administration. These data suggest that leucine is effective in promoting BAT (18)F-FDG uptake through β-adrenergic activation in combination with glucose.