Prevalence Of Brown Adipose Tissue Research Articles

Prevalence and Associated Factor of Brown Adipose Tissue: Systematic Review and Meta-Analysis

Background Brown adipose tissue generates heat instead of storing energy. It is important in the regulation of body weight, and individual variation in adaptive thermogenesis can be attributed to variations in the amount or activity of BAT. Objective The objective of this study was to systematically review different articles to assess the prevalence of BAT and its associated factors and relation with obesity and diabetes mellitus. Methods A systematic review and meta-analysis were employed on published research works from different electronic databases using keywords. Cross-sectional studies and a few experimental studies were included for systematic review, and only studies done on human population were used for quantitative analysis. Twenty-two peer-reviewed papers were included in the systematic review, and eight papers were used for the meta-analysis for estimation of pooled prevalence of brown adipose tissue using selection criteria. Results The pooled prevalence of brown adipose tissue among adults was 6.97% (95% CI: 6.51–7.43), and it was 7.4% (95% CI 6.51-7.43) after sequential omission of a single study. The heterogeneity in estimating the pooled prevalence among the studies was statistically significant (Cochran Q test, P < 0.001, I2 = 71.2%), and after sequential omission of a single study, it becomes Cochran Q test, P = 0.065, I2 = 49.4%. The brown adipose tissue activity was significantly lower in overweight or obese subjects than in lean subjects. Conclusion The percentage of adult individuals with brown adipose tissue was high, and its activity was reduced in obese individuals. Although it is reduced in amount, still it presents in obese individuals. So, activation of the brown adipose tissue in adult and older individuals should be a target for the treatment of obesity.

The Influence of Cancer-Related Characteristics on Brown Adipose Tissue at [18 F] DG PET/CT

Background: The present study aimed at investigating the influence of cancer related characteristics in association with environmental factors and patients demographics and on the prevalence of brown adipose tissue at 2-deoxy-2-[18F] fluoro-Dsglucose (18F-FDG) as well as the level of metabolic activity. Methods: A total 3762 [18 F] DG PET/CT scans were retrospectively reviewed to identify BAT related [18 F] DG uptake. Demographics, anthropometrics, outdoor temperature, daylight exposure in addition to cancer related characteristics including type of cancer, reason for referral, history of recent treatment, the presence of malignant lesion were recorded. Anatomical distribution of FDG detectable BAT and related SUVmax were also determined. Control groups consisted of patients without FDG detectable BAT was randomly selected and matched for age, gender and mean outdoor temperature for all groups and for type of cancer, reason for referral and presence of active disease, as appropriate. 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 (SPSS ver.23) were used as appropriate (P value < .05). Results: One-hundred eighteen studies were recognized to demonstrate foci of FDG BAT uptake (3.1%, mean age: 22.7 years). There were statistically significant higher rate of BAT occurrence in female, younger patients, normal/low BMI and Body Fat-based categorical weight, lower temperature and shorter daylight duration. In the context of cancer related characteristics, lymphoma and evaluation of treatment response were found as the most prevalent cancer type and reason for referral, respectively. Univariate analysis demonstrated strong correlation between the prevalence of FDG-detectable BAT and associated metabolic activity and age, gender, BMI and BF-based categorical weight, daylight as well as the nonactive underlying malignancy and recent history of treatment. Multivariate analysis revealed age, gender, daylight duration and recent history of treatment as independent influencing factors on BAT recruitment and the level of metabolic activity. Conclusions: Recent treatment, in addition to age, gender and daylight duration were proved as strong independent determinants on BAT development and the level of metabolic activity at [18 F] DG PET/CT and should be considered as an important confounding factor in future researches.

Prevalence and Factors Associated with Brown Adipose Tissue Detected by 18F-fluorodeoxyglucose Positron Emission Tomography/Computed Tomography in Southern Chinese

Objectives: This study aimed to evaluate the prevalence of brown adipose tissue, as detected by fluorine 18-fluorodeoxyglucose positron emission tomography combined with computed tomography (18F-FDG PETCT), in a Southern Chinese population. It also set out to determine associated factors with brown adipose tissue, and particularly its relationship with being overweight and having other metabolic disorders such as diabetes mellitus. Methods: We analysed 1765 consecutive 18F-FDG PET-CT scans of 1442 Chinese subjects for the presence of brown adipose tissue. Comparison of variables in subjects with positive and negative brown adipose tissue scans was performed using Student’s t test. The predictors of observed brown adipose tissue were analysed by multiple logistic regressions. Any p < 0.05 was considered statistically significant. Results: Brown adipose tissue was detected in 66 (4.6%) out of 1442 subjects. There were significant differences in age, gender, body mass index, blood glucose levels, and history of diabetes in subjects positive and negative for brown adipose tissue. In the multiple logistic regression test, age and mean monthly temperatures were both independent predictors of the presence of brown adipose tissue (p ≤ 0.001), which was itself a significant independent predictor of being overweight (p = 0.001). Conclusions: Age was the most important factor associated with the prevalence of brown adipose tissue in humans. Lower outdoor temperatures in winter can increase the prevalence of brown adipose tissue, even in subtropical climates. There was also an association of brown adipose tissue with being overweight and having higher blood sugar levels, supporting the notion that brown adipose tissue may be a potential therapeutic target for obesity and diabetes.

High Prevalence of Brown Adipose Tissue in Adult Humans

Positron emission tomography (PET)-computed tomography (CT) has identified metabolically active supraclavicular fat in adult humans based on uptake of labeled glucose and confirmed to be brown adipose tissue (BAT) histologically. However, PET-CT has estimated a prevalence of BAT as low as 5% in adult humans, casting doubt on its significance. The true prevalence of BAT is unknown because of the suboptimal sensitivity of standard PET-CT. The objective of the study was to determine whether BAT is present in PET-negative supraclavicular fat. This was a prospective cohort study. The study was conducted at a tertiary referral hospital. Seventeen patients who underwent preoperative PET-CT for staging of head and neck malignancy participated in the study. The main outcome was signature BAT gene transcripts and protein in biopsies of supraclavicular fat with sc fat as negative control. PET-CT was positive in three and negative in 14 patients. PET-positive fat harbored multilobulated lipid droplets and stained strongly for uncoupling protein 1 (UCP1). These features are absent in sc fat. By contrast, PET-negative fat contained a predominance of cells with unilobulated lipid droplets, with scattered cells containing multilobulated lipid droplets and variable UCP1 staining. Molecular analyses of fat biopsies showed lower but clear expression of UCP1, NDUFS3 (NADH dehydrogenase (ubiquinone) iron-sulfur protein 3), β₃-adrenoceptor, and PRDM16 (PR domain containing 16) transcripts. BAT is present in supraclavicular fat, regardless of PET status. BAT is highly prevalent in adult humans, and its abundance determines PET status.

Three years with adult human brown adipose tissue

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 antagonists-inhibit 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.

Brown adipose tissue in cancer patients: possible cause of cancer-induced cachexia.

Cachexia is a common manifestation of advanced cancer and frequently contributes to physical disability and mortality. An increased metabolic rate has been suggested to be one of the causes of cancer-induced cachexia, although the mechanisms producing this hypermetabolism remain unclear. The presence and activation of brown adipose tissue, a highly thermogenic tissue, may result in a hypermetabolic state and be partially responsible for weight loss in cancer patients. To investigate this hypothesis, we examined necropsy samples of peri-adrenal tissues using light microscopy to identify the prevalence of brown adipose tissue in 25 cachectic patients who died from cancer and 15 age-matched subjects who died from other illnesses. Brown adipose tissue was observed in 20 of the cancer patients (80%) compared to 2 of the age-matched subjects (13%). Therefore, our preliminary results indicate that a high prevalence of brown adipose tissue is associated with cancer-induced cachexia and may reflect an abnormal mechanism responsible for profound energy expenditure and weight loss.

Prevalence of brown adipose tissue in chronic congestive heart failure secondary to coronary heart disease

Brown adipose tissue, a highly metabolic form of fat, is used by some mammals to regulate body temperature. 1 In humans, brown adipose tissue is an important source of nonshivering thermogenesis for the neonate 1 and has recently been identified in variable amounts in adults. 2–4 Brown adipose tissue is located in definite anatomic sites of humans primarily during fetal and infantile stages of life and gradually diminishes with age until it disappears and is replaced by white adipose tissue. 2,3 However, a recent autopsy study has shown a high prevalence of brown adipose tissue in “coldexposed” adult humans, suggesting that this tissue may be important for thermorégulation in these older persons. 4