Brown adipose tissue and lipid metabolism imaging.

Abstract

Brown adipose tissue (BAT) research has evolved from an underestimated to a fast developing field. Its assumed curing properties for the world wide epidemic obesity, and its related diseases, makes this tissue an interesting target for a broad amount of non-invasive molecular BAT tracers. Apart from 18F-FDG PET/CT there are several methods to detect BAT and measure its metabolism in a more appropriate way. Especially interesting is the measure of lipid turnover, because fatty acids comprise the main fuel for active BAT. This review outlines different imaging modalities suitable for BAT imaging with the overall goal to explain the yet not completely understood mechanism in BAT and its quantitative contribution to whole body lipid and energy metabolism. Publications with focus on brown adipose tissue and lipid metabolism imaging are analyzed, different imaging approaches are introduced and promising BAT tracers are presented. Radiolabelled and fluorescent fatty acids, labelled particles, 3H-Triolein and ADIFAB staining can give information about the inflow and therefore about the utilization of fatty acids which represents the activation state in vivo/in vitro. Non-invasive scanning with CT or MRI is a useful addition to those techniques. Lipid metabolism imaging offers the opportunity to visualize and quantify yet undiscovered aspects of BAT metabolic activities and is key to completely clarify its role in whole body lipid and energy metabolism.