Review Analysis of the Association between the Prevalence of Activated Brown Adipose Tissue and Outdoor Temperature

Abstract

Brown adipose tissue (BAT) is important for regulating body weight. Environmental temperature influences BAT activation. Activated BAT is identifiable using 18F-fluorodeoxyglucose positron emission tomography/computed tomography (18F-FDG PET/CT). 18F-FDG PET/CT scans done between June 2005 and May 2009 in our institution in tropical southern Taiwan and BAT studies from PubMed (2002–2011) were reviewed, and the average outdoor temperatures during the study periods were obtained. A simple linear regression was used to analyze the association between the prevalence of activated BAT (P) and the average outdoor temperature (T). The review analysis for 9 BAT studies (n = 16, 765) showed a significant negative correlation (r = −0.741, P = 0.022) between the prevalence of activated BAT and the average outdoor temperature. The equation of the regression line is P(%) = 6.99 − 0.20 × T (°C). The prevalence of activated BAT decreased by 1% for each 5°C increase in average outdoor temperature. In a neutral ambient temperature, the prevalence of activated BAT is low and especially rare in the tropics. There is a significant linear negative correlation between the prevalence of activated BAT and the average outdoor temperature.

Prevalence, Mass, and Glucose-Uptake Activity of 18F-FDG-Detected Brown Adipose Tissue in Humans Living in a Temperate Zone of Italy

“…This value is halfway the prevalence reported in other studies involving large cohorts of patients, that ranges from 1.72% to 6.8% [16]. Although the exact characteristics of the study populations of the previous studies in terms of age, male to female ratio, BMI, fasting plasma glucose and exposure to drugs are not known, a possible explanation for these differences might reside in the outdoor temperature and day length.…”

“…Environmental temperature is of great importance for the outcome of a 18 F-FDG-PET study. Interestingly, the average temperatures of the metropolitan area of Rome during all time of year were higher than the temperatures recorded in the latitudes where the other large cohort studies, lasting at least one year and reporting higher prevalence of BAT, were conducted [16]. Accordingly, when the average outdoor temperature was higher compared with Rome, the prevalence of BAT was lower [13], [16] and, on the contrary, when the average outdoor temperature was lower compared to Rome, the prevalence of BAT was higher [4], [9]–[11], [14], [15].…”

“…In adults, the prevalence of 18 F-FDG positive BAT is variable, ranging between 1.72% and 6.85% in studies involving cancer patients [4], [9]–[16], whereas in cold-exposed subjects, the prevalence was reported to be close to 100% [5], [6]. Ambient temperature at the time of the PET/CT assessment is a critical factor to detect BAT [4]–[6], [8]–[10], [14], [16].…”

“…Ambient temperature at the time of the PET/CT assessment is a critical factor to detect BAT [4]–[6], [8]–[10], [14], [16]. Furthermore, factors such as sex [4], [9], [10], [13], [14], [17], [18], age [4], [7]–[9], [13], [14], [17], [18], body mass index (BMI) [5], [7], [8], [18], plasma glucose [4], and day length [10] are all important determinants of 18 F-FDG uptake in BAT although their relative importance is still controversial.…”

MECHANISMS IN ENDOCRINOLOGY: Brown adipose tissue in humans: regulation and metabolic significance

“…There is a higher prevalence of BAT in scans undertaken in winter than in summer (25,26,27,28). BAT FDG uptake is increased when subjects are precooled before scanning (3,4,29) and lower with pre-warming (30,31,32).…”