| Brown adipose tissue(BAT)plays an important role in energy consumption.Human BAT was once considered to only exist in infancy.However,with thedevelopment of novel imaging technology,such as positron emission tomography/computed tomography(PET/CT),it has been discovered among adults.Due to the radiation exposure and the high cost,it has been difficult to promote this method in large scale studies.Though an innovative thermal imaging technology has been developed to measure human BAT,the operation protocol was not standardized,the sample size of previous studies were small,and the information of Chinese population was missing.In addition,previous studies have associated BAT thermogenesis with obesity among adolescents;however,few studies have investigated the associations between BAT thermogenesis,BMI,fat distribution indicators,and metabolic risk factors among adults.Therefore,it is necessary to examine the value of such thermal imaging method in epidemiological screening for adult brown fat,and explore the interplay among supraclavicular brown fat thermogenesis,body composition(content and distribution),and metabolic risk factors of Chinese adults.This research adopted a cross-sectional study design.Body composition indicators were measured by dual-energy X-ray absorptiometry,and the metabolic profile was quantified by blood analysis.Thermal imaging measurements were performed to record the baseline supraclavicular region temperature(TSCR)(mean values before cool stimulus)and the △TSCR(change from baseline to peak TSCR after cool stimulus).Covariance analysis was employed to analyze sex differences in TSCR,and multivariate regression models were adopted to analyze the associations between TSCR,BMI,body composition indicators,lean indices,and metabolic risk factors.Results show clearly and marked about baseline temperature and temperature at supraclavicular area,where human brown fat main located.Those features could be quantified by thermal imaging.Men’s baseline TSCR and maximum TSCR after cold stimulation were higher than women.TSCRs were negatively correlated with age in both men and women,but TSCR declined significantly around the age of 30 years in men,whereas around the age of 50 in women.TSCR was negatively associated with BMI and body fat percentage,but positively associated with lean mass percentage.Moreover,TSCR also showed negative associations with central obesity indicators,such as waist and trunk fat to legs fat ratio;and none association with BMI.The Baseline of TSCR was also independent from BMI,negatively associated with blood lipids and blood glucose metabolism indicators,and inversely proportional to the morbidity of metabolic diseases such as diabetes and fatty liver.In conclusion,this study for the first time quantitatively estimated the characteristic of brown fat,by detecting supraclavicular area skin surface temperature using infrared thermal imaging technology in Chinese adults.Our work demonstrated the applicability of thermal imaging as a screening tool in the large-scale epidemiological research.Besides the traditional physical measurement,we also used the accurate measure of body composition to further explore the relationship between body composition(content and distribution)and adult BAT.And observed significant correlation between TSCR,centrality fat deposition,and multiple metabolic risk factors in adults.Our results indicate that BAT thermogenesis is associated with central fat distribution and metabolic risk factors,which suggested that brown fat may affect the clearance process of blood glucose and lipid,as well as in the regulation of insulin sensitivity and fat ectopic deposition.Thus,BAT thermogenesis should be considered as a predictor to evaluate body composition and metabolic risk. |
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