Unexpected evidence for active brown adipose tissue in adult humans (original) (raw)
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Three years with adult human brown adipose tissue
Annals of the New York Academy of Sciences, 2010
The presence of active brown adipose tissue in adult humans has been recognized in general physiology only since 2007. The intervening three years established that the depots originally observed by 18 F-fluoro-deoxy-glucose positron emission tomography (FDG PET) scanning techniques really are brown adipose tissue depots because they are enriched for uncoupling protein 1 (UCP1). Reports of low apparent prevalence of brown adipose tissue based on retrospective studies of hospital records of FDG PET scans markedly underestimate true prevalence because such studies only reflect acute activity state; consequently, such retrospective studies cannot be conclusively analysed for factors influencing activity and amount of brown adipose tissue. Dedicated studies show that the true prevalence is 30-100%, depending on cohort. Warm temperature during the investigation-as well as adrenergic antagonistsinhibit tissue activity. There is probably no sexual dimorphism in the prevalence of brown adipose tissue. Outdoor temperature may affect the amount of brown adipose tissue, and the amount is negatively correlated with age and obesity. The presence of brown adipose tissue is associated with cold-induced nonshivering thermogenesis, and the tissue may be a major organ for glucose disposal. The decline in brown adipose tissue amount with increasing age may account for or aggravate middle-age obesity. Maintained activation of brown adipose tissue throughout life may thus protect against obesity and diabetes.
Identification and Importance of Brown Adipose Tissue in Adult Humans
New England Journal of Medicine, 2009
BACKGROUND-Obesity results from an imbalance between energy intake and expenditure. In rodents and newborn humans, brown adipose tissue helps regulate energy expenditure by thermogenesis mediated by the expression of uncoupling protein 1 (UCP1), but brown adipose tissue has been considered to have no physiologic relevance in adult humans.
Recent advances in the detection of brown adipose tissue in adult humans: a review
Clinical science (London, England : 1979), 2018
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 F-fluorodeoxyglucose in combination with computed tomography (F-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 po...
Iranian Journal of Radiology
Background: The effect of various environmental and intrinsic stimulators on the development of brown adipose tissue (BAT) has been widely investigated by PET-based researches. However, evidence regarding the influencing factors on the level of BAT metabolic activity is scarce. Objectives: The aim of the present study was to evaluate the frequency of cancer-related characteristics in addition to anthropometrics and demographics in BAT-bearing cancer patients at 18F-fluorodeoxyglucose positron emission tomography/computed tomography (18F-FDG PET/CT) scan and any correlation between the level of BAT metabolic activity and the influencing factors. Patients and Methods: Reports from a total of 3762 F-18 FDG PET/CT scans were retrospectively reviewed to identify BAT-bearing cancer population. Demographic, anthropometric and cancer related characteristics were recorded. Maximum standardized uptake values (SUVmax) was measured separately for each anatomical region. Descriptive quantitative variables were expressed as either frequency or mean. Independent T test, Mann-Withney U test, Pearson correlation coefficients, one-way analysis of variance and linear regression test (IBM SPSS version 23) were used as appropriate (P value <0.05) Results: Sixty-two F-18 FDG PET/CT studies demonstrated BAT related 18-F FDG uptake (1.6%, 32% male, 68% female, P = 0.007, mean age 22.9). Lymphoma (43.5%) and treatment response evaluation (54.54%) were the most frequent type of cancer and reason for referral, respectively. Most patients were in status partial or complete metabolic response to treatment. Fifty-four point eight percent of patients had at least one metabolically active cancer-related lesion. BAT detection rate was higher in females in all adult age groups, younger age (< 40 years old), body mass index (BMI) and body fat (BF) below the obesity cut off and autumn/winter seasons. The dominant distribution pattern of BAT depots was neck, mediastinum, paravertebral (33.87%) with the highest level of metabolic activity in the axillary region. SUVmax demonstrated a weak inverse correlation with age (0.015), evidence of active malignant disease and no recent treatment. Linear regression test demonstrated that age (P = 0.021) and recent treatment (P = 0.033) have independent correlation with BAT SUVmax. Conclusion: The present study provided evidence for age and chemotherapeutic agents on the level of BAT metabolism. In addition, there is a suggestion for different pathways involved in BAT development and regulation of the level of metabolic activity.
Molecular imaging of brown adipose tissue in health and disease
European Journal of Nuclear Medicine and Molecular Imaging, 2014
Brown adipose tissue (BAT) has transformed from an interfering tissue in oncological 18 F-fluorodeoxyglucose (FDG) positron emission tomography (PET) to an independent imaging research field. This review takes the perspective from the imaging methodology on which human BAT research has come to rely on heavily. Methods This review analyses relevant PubMed-indexed publications that discuss molecular imaging methods of BAT. In addition, reported links between BAT and human diseases such as obesity are discussed, and the possibilities for imaging in these fields are highlighted. Radiopharmaceuticals aiming at several different biological mechanisms of BAT are discussed and evaluated. Results Prospective, dedicated studies allow visualization of BAT function in a high percentage of human subjects. BAT dysfunction has been implicated in obesity, linked with diabetes and associated with cachexia and atherosclerosis. Presently, 18 F-FDG PET/CT is the most useful tool for evaluating therapies aiming at BAT activity. In addition to 18 F-FDG, other radiopharmaceuticals such as 99m Tc-sestamibi, 123 Imetaiodobenzylguanidine (MIBG), 18 F-fluorodopa and 18 F-14(R,S)-[ 18 F]fluoro-6-thia-heptadecanoic acid (FTHA) may have a potential for visualizing other aspects of BAT activity. MRI methods are under continuous development and provide the prospect of functional imaging without ionizing radiation. Conclusion Molecular imaging of BAT can be used to quantitatively assess different aspects of BAT metabolic activity.
Journal of Nuclear Medicine, 2010
Brown adipose tissue (BAT) densities assessed as CT Hounsfield units (HUs) were evaluated in a rodent model and in patients to determine whether HUs changed in relation to BAT activity. Methods: Serial 18 F-FDG PET/CT was performed on rats under both room temperature control conditions and after 4 h of coldstimulation, which is known to activate BAT. The maximum standardized uptake values and CT HUs of BAT were measured, and tissues were examined in the laboratory. Image records from cancer patients who underwent PET/CT were reviewed, and 23 patients were identified who displayed both high and low 18 F-FDG uptake into BAT on serial 18 F-FDG PET/CT scans. The maximum standardized uptake values and CT HUs of BAT were compared in these scans. Results: The mean (6SD) CT HUs of cold-activated BAT (212.4 6 22.4) were significantly higher than those (227.9 6 9.6) of the controls in the rat model. The CT HUs of BAT (271.6 6 18.0) in the patients with high 18 F-FDG uptake were significantly higher than those (2104.4 6 16.8) of the patients with low 18 F-FDG uptake . A decrease in relative lipid content is seen in activated BAT in rats on histology. Conclusion: The CT HUs of BAT increased in activated conditions in both animals and patients, likely because of lipid consumption by activated BAT.
Brown Adipose Tissue in Humans
Methods in Enzymology, 2014
Research with the aim to translate findings of the beneficial effects induced by brown adipose tissue (BAT) on metabolism, as seen in various non-human experimental systems to also include human metabolism requires tools that accurately measure how BAT influences human metabolism. This review sets out to discuss such techniques, how they can be used, what they can measure and also some of their limitations. The focus is on detection and functional analysis of human BAT and how this can be facilitated by applying advanced imaging technology such as: PET (Positron Emission Tomography), MRI (Magnetic Resonance Imaging), and DECT (Dual Energy Computed Tomography).
Brown Adipose Tissue—A Translational Perspective
Endocrine Reviews
Brown adipose tissue (BAT) displays the unique capacity to generate heat through uncoupled oxidative phosphorylation that makes it a very attractive therapeutic target for cardiometabolic diseases. Here, we review BAT cellular metabolism, its regulation by the central nervous and endocrine systems and circulating metabolites, the plausible roles of this tissue in human thermoregulation, energy balance, and cardiometabolic disorders, and the current knowledge on its pharmacological stimulation in humans. The current definition and measurement of BAT in human studies relies almost exclusively on BAT glucose uptake from positron emission tomography with 18F-fluorodeoxiglucose, which can be dissociated from BAT thermogenic activity, as for example in insulin-resistant states. The most important energy substrate for BAT thermogenesis is its intracellular fatty acid content mobilized from sympathetic stimulation of intracellular triglyceride lipolysis. This lipolytic BAT response is inter...