Non‐invasive methods for the assessment of brown adipose tissue in humans

Abstract

Brown adipose tissue (BAT) is a recently rediscovered tissue in people that has shown promise as a potential therapeutic target against obesity and its metabolic abnormalities. Reliable non-invasive assessment of BAT volume and activity is critical to allow its importance in metabolic control to be evaluated. Positron emission tomography/computed tomography (PET/CT) in combination with 2-deoxy-2-[ F]fluoroglucose administration is currently the most frequently used and most established method for the detection and quantification of activated BAT in humans. However, it involves radiation exposure and can detect activated (e.g. after cold exposure), but not quiescent, BAT. Several alternative methods that overcome some of these limitations have been developed including different PET approaches, single-photon emission imaging, CT, magnetic resonance based approaches, contrast-enhanced ultrasound, near infrared spectroscopy, and temperature assessment of fat depots containing brown adipocytes. The purpose of this review is to summarize and critically evaluate the currently available methods that non-invasively probe various aspects of BAT biology in order to assess BAT volume and/or metabolism. Although several of these methods show promise for the non-invasive assessment of BAT volume and function, further research is needed to optimize them to enable an accurate, reproducible and practical means for the assessment of human BAT content and its metabolic function.

Exercise training alters lipoprotein particles independent of brown adipose tissue metabolic activity

“…This study is one of the first clinical intervention trials to investigate BAT metabolism during cold after exercise training. This study design maximized BAT detection by applying gold standard PET-scanning methodology, cold exposure and well-controlled laboratory conditions (39). As expected, exercise training increased aerobic capacity and decreased visceral fat mass.…”

Whole Body and Regional Quantification of Active Human Brown Adipose Tissue Using ¹⁸F-FDG PET/CT

“…Though we believe that this rigorous method is more precise than automated methods 26,28 and methods that use a simplified, single ROI to estimate total BAT volume 9,30 , it is not without limitations. There is no ideal method to non-invasively quantify BAT in humans, and 18 F-FDG represents only glucose uptake, which is not the same as glucose metabolism 11 . However, even though other radioactive tracers have been used 31,32,33 , 18 F-FDG is the most prominent tracer used to study human BAT.…”

“…To overcome these challenges, BAT volume and activity are commonly quantified by coupling computed tomography (CT) and positron emission tomography (PET). The radiolabeled glucose analog 18 F-Fluourodeoxyglucose ( 18 F-FDG) is the most widely used tracer to study BAT metabolic activity 18 . Adipose tissue can be differentiated from other tissue and air based on density information provided by the CT image in Hounsfield units (HU).…”

Infrared Thermography for Estimating Supraclavicular Skin Temperature and BAT Activity in Humans: A Systematic Review

“…Alternative techniques for quantifying human BAT in vivo include PET/CT measurement of the uptake of 18 F-fluoro-6thia-heptadecanoic acid (8), 15 O-O 2 (9), 11 C-acetate (10), or adenosine (11), magnetic resonance imaging (12), and magnetic resonance spectroscopy (MRS) (13), but these are expensive, and some also expose individuals to radiation. A safe, inexpensive, reliable gold standard for human BAT quantification in vivo is thus lacking, as are alternative techniques (6).…”

“…F-FDG-PET/CT scanning is currently the technique most used for quantifying human BAT activity(6). However, it suffers the drawbacks of being expensive, invasive, and exposing individuals to radiation.…”