Prevalence and factors associated with brown adipose tissue detected by 18F-FDG PET/CT in Hong Kong Chinese

Abstract

Objectives: Brown adipose tissue (BAT) has been suggested to hold a potential role in adult human metabolism, and in protecting against obesity by increased energy expenditure. This study aims to evaluate the prevalence of BAT, as detected by 18F-FDG PET/CT, in a Hong Kong Chinese population, and determine the factors associated with it, in particular, its relationship with obesity and other metabolic disorders, i.e. diabetes mellitus.

Methods: We retrospectively analyzed 1265 consecutive PET-CT scans of 1079 Chinese patients performed between January 2009 to September 2009 for the presence of BAT. BAT was considered positive if there was a hypermetabolic region corresponding to negative Hounsfield number in CT image. Age, sex, BMI, blood glucose level at the time of scanning and history of diabetes were recorded. Data was analyzed using SPSS (version 18.0). Comparison of the variables between positive and negative BAT scans was performed using Student’s t-test. The predictors of observed BAT were analyzed by logistic regression to determine the significant predictors of positive BAT. P < 0.05 was considered to be statistically significant.

Results: BAT was detected in 41/1079 (3.8%) scans, mostly in the supraclavicular region and lower neck. The incidence was 3.3% (18/543) in men and 4.6% (23/495) in women, and age range was 22 to 68 years old (mean 45.1, SD 13.7). Significant differences were found between positive and negative scans for BAT in age (+BAT: mean 45.1 y±13.7y, -BAT: mean 61.1 y±14.1y, p<0.001), BMI (+BAT: mean 21.2±3.1, -BAT: mean 22.4±3.7, p=0.048) and history of DM (p=0.033). There were no significant differences in gender and blood glucose level. Age was the only predictor of observed BAT (p<0.0001).

Conclusions: The prevalence of BAT in the Hong Kong Chinese population was relatively low (3.8%) compared to subjects in temperate climes, and this may be related to the relatively warmer climate in this sub-tropical region. Its occurrence was found to be associated with age, BMI and history of DM