A critical appraisal of the prevalence and metabolic significance of brown adipose tissue in adult humans

2010 ◽  
Vol 299 (4) ◽  
pp. E601-E606 ◽  
Author(s):  
Paul Lee ◽  
Jerry R. Greenfield ◽  
Ken K. Y. Ho ◽  
Michael J. Fulham
Keyword(s):  
Adipose Tissue ◽  
Brown Adipose Tissue ◽  
Energy Homeostasis ◽  
Fasting Glucose ◽  
Apparent Prevalence ◽  
Positron Emission ◽  
Brown Adipose ◽  
Pet Ct ◽  
Adult Humans ◽  
Average Probability

Brown adipose tissue (BAT) plays a major role in energy homeostasis in animals. Detection of BAT using positron emission tomography (PET)-CT in humans has challenged the view that BAT disappears after infancy. Several recent studies, based on analysis of single scans, have reported a low prevalence of only 5–10% in humans, casting doubt on its significance. We undertook a critical analysis of the sensitivity, reproducibility, and accuracy of PET-CT to deduce the prevalence of BAT and factors associated with its detection in adult humans. In a retrospective evaluation of PET-CT, using [18F]fluorodeoxyglucose, performed in 2,934 patients, BAT was identified in 250 patients, yielding an apparent prevalence of 8.5%. Among those patients with BAT, 145 were scanned more than once. The frequency of another scan being positive increased from 8 to 65% for one to more than four additional studies. The average probability of obtaining another positive scan among patients with BAT is 13%, from which the prevalence of BAT is estimated at 64%. BAT was more commonly detected in women, in younger (36 ± 1 vs. 52 ± 1 years, P < 0.001) and leaner (20.1 ± 0.9 vs. 24.9 ± 0.9 kg/m2, P < 0.01) individuals. Fasting glucose was lower in those with BAT than those without (4.9 ± 0.1 vs. 5.5 ± 0.1 mmol/l, P < 0.01). Among patients scanned more than once, BAT was detected when body weight and fasting glucose were lower (54.9 ± 0.5 vs. 58.2 ± 0.8 kg, P < 0.001 and 4.9 ± 0.3 vs. 5.5 ± 0.3 mmol/l, P = 0.03). We conclude that BAT is present in the majority of adult humans. Presence of BAT correlates negatively with body mass index and glucose concentration. BAT may play an important role in energy homeostasis in adults.

scholarly journals Brown adipose tissue: what have we learned since its recent identification in human adults

2014 ◽  
Vol 58 (9) ◽  
pp. 889-899 ◽  
Author(s):  
Bruno Halpern ◽  
Marcio Correa Mancini ◽  
Alfredo Halpern
Keyword(s):  
Adipose Tissue ◽  
Brown Adipose Tissue ◽  
Mitochondrial Uncoupling ◽  
Positron Emission ◽  
Brown Adipose ◽  
Adult Humans ◽  
Human Adults ◽  
Real Importance ◽  
Diet Induced Thermogenesis ◽  
Fluorodeoxyglucose Pet

Brown adipose tissue, an essential organ for thermoregulation in small and hibernating mammals due to its mitochondrial uncoupling capacity, was until recently considered to be present in humans only in newborns. The identification of brown adipose tissue in adult humans since the development and use of positron emission tomography marked with 18-fluorodeoxyglucose (PET-FDG) has raised a series of doubts and questions about its real importance in our metabolism. In this review, we will discuss what we have learnt since its identification in humans as well as both new and old concepts, some of which have been marginalized for decades, such as diet-induced thermogenesis. Arq Bras Endocrinol Metab. 2014;58(9):889-99

scholarly journals Imaging Metabolically Active Fat: A Literature Review and Mechanistic Insights

2019 ◽  
Vol 20 (21) ◽  
pp. 5509
Author(s):  
Joseph Frankl ◽  
Amber Sherwood ◽  
Deborah J. Clegg ◽  
Philipp E. Scherer ◽  
Orhan K. Öz
Keyword(s):  
Adipose Tissue ◽  
Brown Adipose Tissue ◽  
Cancer Surveillance ◽  
Mitochondrial Uncoupling ◽  
Positron Emission ◽  
Brown Adipose ◽  
Pet Ct ◽  
Brown Adipose Tissue Activity ◽  
Magnetic Resonance Imaging Mri ◽  
Fdg Pet Ct

Currently, obesity is one of the leading causes death in the world. Shortly before 2000, researchers began describing metabolically active adipose tissue on cancer-surveillance 18F-fluorodeoxyglucose (FDG) positron emission tomography/computed tomography (PET/CT) in adult humans. This tissue generates heat through mitochondrial uncoupling and functions similar to classical brown and beige adipose tissue in mice. Despite extensive research, human brown/beige fat’s role in resistance to obesity in humans has not yet been fully delineated. FDG uptake is the de facto gold standard imaging technique when studying brown adipose tissue, although it has not been rigorously compared to other techniques. We, therefore, present a concise review of established and emerging methods to image brown adipose tissue activity in humans. Reviewed modalities include anatomic imaging with CT and magnetic resonance imaging (MRI); molecular imaging with FDG, fatty acids, and acetate; and emerging techniques. FDG-PET/CT is the most commonly used modality because of its widespread use in cancer imaging, but there are mechanistic reasons to believe other radiotracers may be more sensitive and accurate at detecting brown adipose tissue activity. Radiation-free modalities may help the longitudinal study of brown adipose tissue activity in the future.

scholarly journals Activated Brown Adipose Tissue and Its Relationship to Adiposity and Metabolic Markers (P21-073-19)

2019 ◽  
Vol 3 (Supplement_1) ◽  
Author(s):  
Malini Soundarrajan ◽  
Jie Deng ◽  
Mary Kwasny ◽  
Nicholas Rubert ◽  
Paige Nelson ◽  
...  
Keyword(s):  
Adipose Tissue ◽  
Glucose Metabolism ◽  
Brown Adipose Tissue ◽  
Fasting Glucose ◽  
Young Men ◽  
Fibroblast Growth Factor 21 ◽  
Metabolic Markers ◽  
Bat Activity ◽  
Brown Adipose ◽  
Pet Ct

Abstract Objectives To explore potential relationships between PET/CT imaging characteristics of cold-activated brown adipose tissue (BAT), measures of adiposity and metabolic markers in young men. Methods We conducted a post-hoc analysis of a study designed to compare magnetic resonance imaging (MRI) techniques to the reference standard, PET/CT, in characterizing BAT. A total of 25 healthy male participants ages 18–24 and body mass index (BMI) ranging from 19.4 to 35.9 Kg/m2 were included in the study. A physical exam and fasting lab draw were performed, including measurement of hemoglobin A1c (HbA1c), lipid panel, thyroid function tests, leptin, adiponectin, FGF-21 and IL-6. Body composition was measured using dual energy X-ray absorptiometry (DXA). An individualized cooling protocol was utilized to activate BAT. Subjects were wrapped in a water-infused suit (CritiCool® System, Mennen Medical, Israel) and cooled to achieve non-shivering thermogenesis prior to imaging. Measures of cold-activated BAT, including mean standardized uptake value adjusted for lean mass (SUVlean mean), maximum SUV (SUVlean max), total BAT activity, and BAT volume were determined from PET/CT images. Pearson's and Spearman's rank correlations were employed to relate measures of active BAT to adiposity and metabolic parameters. Results There was an inverse relationship between fasting serum glucose and BAT volume (r = −0.40, P = 0.048). In addition, a positive correlation was observed for serum fibroblast growth factor 21 (FGF-21) and SUVlean max (r = 0.45, P = 0.04). Marginally significant inverse relationships were noted between fasting glucose and total BAT activity (r = −0.39, P = 0.05) and leptin and SUVlean mean (r = −0.42, P = 0.05). However, no significant correlations were noted for measures of BAT activity or volume and other indicators of adiposity or glucose metabolism. Conclusions Data from this exploratory study suggest that BAT volume and activity may be inversely associated with fasting glucose in healthy young men. BAT activity was also correlated with an insulin sensitizer, FGF-21, suggesting BAT may lower glucose levels via an FGF-21 dependent pathway. Further studies are needed to clarify the potential mechanisms by which active BAT may impact glucose metabolism and the relationship between BAT and adiposity. Funding Sources NIDDK.

Unexpected evidence for active brown adipose tissue in adult humans

2007 ◽  
Vol 293 (2) ◽  
pp. E444-E452 ◽  
Author(s):  
Jan Nedergaard ◽  
Tore Bengtsson ◽  
Barbara Cannon
Keyword(s):  
Human Physiology ◽  
Adipose Tissue ◽  
Brown Adipose Tissue ◽  
Tracer Uptake ◽  
Interscapular Brown Adipose Tissue ◽  
Positron Emission ◽  
Brown Adipose ◽  
Adult Humans ◽  
Brown Adipose Tissue Activity ◽  
Diet Induced Thermogenesis

The contention that brown adipose tissue is absent in adult man has meant that processes attributed to active brown adipose tissue in experimental animals (mainly rodents), i.e., classical nonshivering thermogenesis, adaptive adrenergic thermogenesis, diet-induced thermogenesis, and antiobesity, should be either absent or attributed to alternative (unknown) mechanisms in man. However, serendipidously, as a consequence of the use of fluorodeoxyglucose positron emission tomography (FDG PET) to trace tumor metastasis, observations that may change that notion have recently been made. These tomography scans have visualized symmetrical areas of increased tracer uptake in the upper parts of the human body; these areas of uptake correspond to brown adipose tissue. We examine here the published observations from a viewpoint of human physiology. The human depots are somewhat differently located from those in rodents, the main depots being found in the supraclavicular and the neck regions with some additional paravertebral, mediastinal, para-aortic, and suprarenal localizations (but no interscapular). Brown adipose tissue activity in man is acutely cold induced and is stimulated via the sympathetic nervous system. The prevalence of active brown adipose tissue in normal adult man can be only indirectly estimated, but it would seem that the prevalence of active brown adipose tissue in the population may be at least in the range of some tens of percent. We conclude that a substantial fraction of adult humans possess active brown adipose tissue that thus has the potential to be of metabolic significance for normal human physiology as well as to become pharmaceutically activated in efforts to combat obesity.

Recent advances in the detection of brown adipose tissue in adult humans: a review

2018 ◽  
Vol 132 (10) ◽  
pp. 1039-1054 ◽  
Author(s):  
Frank J. Ong ◽  
Basma A. Ahmed ◽  
Stephan M. Oreskovich ◽  
Denis P. Blondin ◽  
Tahniyah Haq ◽  
...  
Keyword(s):  
Computed Tomography ◽  
Positron Emission Tomography ◽  
Adipose Tissue ◽  
Brown Adipose Tissue ◽  
Metabolic Activity ◽  
Cold Exposure ◽  
Emission Tomography ◽  
Positron Emission ◽  
Brown Adipose ◽  
Pet Ct

The activation of brown adipose tissue (BAT) is associated with reductions in circulating lipids and glucose in rodents and contributes to energy expenditure in humans indicating the potential therapeutic importance of targetting this tissue for the treatment of a variety of metabolic disorders. In order to evaluate the therapeutic potential of human BAT, a variety of methodologies for assessing the volume and metabolic activity of BAT are utilized. Cold exposure is often utilized to increase BAT activity but inconsistencies in the characteristics of the exposure protocols make it challenging to compare findings. The metabolic activity of BAT in response to cold exposure has most commonly been measured by static positron emission tomography of 18F-fluorodeoxyglucose in combination with computed tomography (18F-FDG PET-CT) imaging, but recent studies suggest that under some conditions this may not always reflect BAT thermogenic activity. Therefore, recent studies have used alternative positron emission tomography and computed tomography (PET-CT) imaging strategies and radiotracers that may offer important insights. In addition to PET-CT, there are numerous emerging techniques that may have utility for assessing BAT metabolic activity including magnetic resonance imaging (MRI), skin temperature measurements, near-infrared spectroscopy (NIRS) and contrast ultrasound (CU). In this review, we discuss and critically evaluate the various methodologies used to measure BAT metabolic activity in humans and provide a contemporary assessment of protocols which may be useful in interpreting research findings and guiding the development of future studies.

scholarly journals Characterizing active and inactive brown adipose tissue in adult humans using PET-CT and MR imaging

2016 ◽  
Vol 311 (1) ◽  
pp. E95-E104 ◽  
Author(s):  
Aliya Gifford ◽  
Theodore F. Towse ◽  
Ronald C. Walker ◽  
Malcolm J. Avison ◽  
E. Brian Welch
Keyword(s):  
Adipose Tissue ◽  
Brown Adipose Tissue ◽  
Fdg Pet ◽  
Whole Body ◽  
Subcutaneous White Adipose Tissue ◽  
Brown Adipose ◽  
Pet Ct ◽  
Adult Humans ◽  
Mri Scans ◽  
Whole Body Metabolism

Activated brown adipose tissue (BAT) plays an important role in thermogenesis and whole body metabolism in mammals. Positron emission tomography (PET)-computed tomography (CT) imaging has identified depots of BAT in adult humans, igniting scientific interest. The purpose of this study is to characterize both active and inactive supraclavicular BAT in adults and compare the values to those of subcutaneous white adipose tissue (WAT). We obtained [18F]fluorodeoxyglucose ([18F]FDG) PET-CT and magnetic resonance imaging (MRI) scans of 25 healthy adults. Unlike [18F]FDG PET, which can detect only active BAT, MRI is capable of detecting both active and inactive BAT. The MRI-derived fat signal fraction (FSF) of active BAT was significantly lower than that of inactive BAT (means ± SD; 60.2 ± 7.6 vs. 62.4 ± 6.8%, respectively). This change in tissue morphology was also reflected as a significant increase in Hounsfield units (HU; −69.4 ± 11.5 vs. −74.5 ± 9.7 HU, respectively). Additionally, the CT HU, MRI FSF, and MRI R2* values are significantly different between BAT and WAT, regardless of the activation status of BAT. To the best of our knowledge, this is the first study to quantify PET-CT and MRI FSF measurements and utilize a semiautomated algorithm to identify inactive and active BAT in the same adult subjects. Our findings support the use of these metrics to characterize and distinguish between BAT and WAT and lay the foundation for future MRI analysis with the hope that some day MRI-based delineation of BAT can stand on its own.

Functional characterization of human brown adipose tissue metabolism

2020 ◽  
Vol 477 (7) ◽  
pp. 1261-1286 ◽  
Author(s):  
Marie Anne Richard ◽  
Hannah Pallubinsky ◽  
Denis P. Blondin
Keyword(s):  
Adipose Tissue ◽  
Brown Adipose Tissue ◽  
Functional Characterization ◽  
Human Infants ◽  
Positron Emission ◽  
Brown Adipose ◽  
Treatment Of Obesity ◽  
And Function

Brown adipose tissue (BAT) has long been described according to its histological features as a multilocular, lipid-containing tissue, light brown in color, that is also responsive to the cold and found especially in hibernating mammals and human infants. Its presence in both hibernators and human infants, combined with its function as a heat-generating organ, raised many questions about its role in humans. Early characterizations of the tissue in humans focused on its progressive atrophy with age and its apparent importance for cold-exposed workers. However, the use of positron emission tomography (PET) with the glucose tracer [18F]fluorodeoxyglucose ([18F]FDG) made it possible to begin characterizing the possible function of BAT in adult humans, and whether it could play a role in the prevention or treatment of obesity and type 2 diabetes (T2D). This review focuses on the in vivo functional characterization of human BAT, the methodological approaches applied to examine these features and addresses critical gaps that remain in moving the field forward. Specifically, we describe the anatomical and biomolecular features of human BAT, the modalities and applications of non-invasive tools such as PET and magnetic resonance imaging coupled with spectroscopy (MRI/MRS) to study BAT morphology and function in vivo, and finally describe the functional characteristics of human BAT that have only been possible through the development and application of such tools.

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