【作者】 王璐；

【导师】 朱善宽；

【作者基本信息】 浙江大学 ， 营养与食品卫生， 2017， 博士

【摘要】 棕色脂肪组织(Brown adipose tissue,BAT)在能量消耗中的发挥着重要作用。人类棕色脂肪曾被认为只存在于婴儿期,随着正电子发射断层显像/X线计算机体层成像仪(Positron emission tomography/computed tomography,PET/CT)等影像学技术发展,发现成人体内也存在部分棕色脂肪分布。但限于辐射安全和高昂的成本,难以在大范围人群调查中推广该技术。尽管已有研究开始将红外热成像技术用于人类棕色脂肪的检测,但相关操作尚未标准化,研究样本量较小,且未见中国人群数据。此外,既往研究发现棕色脂肪的生热作用与青少年肥胖相关;但有关成年人棕色脂肪生热作用与体质指数(Body mass index,BMI)、体成分,以及肥胖相关代谢性疾病的关系尚缺乏足够的证据。因此,有必要考察热成像法在成人棕色脂肪的流行病学筛查中的应用价值,并探讨中国成年人锁骨上棕色脂肪生热作用与人体组成(含量和分布)和代谢危险因素的相关性。本研究采用横断面调查设计,应用双能X线吸收法(Dual energy X-ray absorptiometry,DXA)测量体成分数据,通过血液学分析检测代谢指标,并使用红外线热像仪量化评估锁骨上区域皮肤的基线温度(冷刺激前)和温度变化(基线温度与冷刺激后最高温度的差值)。采用协方差分析锁骨上温度的性别差异,采用多元回归模型分析锁骨上温度与BMI、体成分指标和代谢危险因素之间的关系。结果表明,人类棕色脂肪所在位置——锁骨上区域皮肤的基线温度及温度变化十分清晰和显著,并能够通过热成像检测探查和定量化。分析不同性别和年龄人群锁骨上区域棕色脂肪的分布特征发现,男性锁骨上区域基线温度和冷刺激后最高温度高于女性;男性和女性锁骨上区域温度与年龄均呈负相关,但男性锁骨上区域温度出现明显下降的分界点在30岁左右,而女性则在50岁左右。锁骨上区域温度与BMI,体脂百分比等肥胖指标呈负相关,与瘦软组织百分比呈正相关;同时,锁骨上区域温度与腰围、躯干下肢脂肪比等中心性肥胖指标呈负相关,且独立于BMI。锁骨上基线温度与血脂、血糖相关代谢指标呈负相关,且独立于BMI。锁骨上基线温度与糖尿病、脂肪肝等代谢性疾病的患病概率成反比,且独立于BMI。综上,本研究首次在中国人群中采用红外热成像技术,通过对锁骨上区域皮肤表面温度的定量检测来评估成年人棕色脂肪的特征。证实热成像法在实际工作中具有较强的可操作性,适宜作为大规模人群流行病学的筛查工具。在传统体格测量的基础上,采用更精确的体成分指标,测量进一步探索了脂肪、肌肉等体成分含量和分布与成人棕色脂肪的关系。证明了成人的锁骨上区域温度与中心性脂肪沉积和多种代谢危险因素之间存在显著的相关性。以上研究结果提示成人棕色脂肪可能影响血糖和脂质清除过程,以及胰岛素敏感性和脂肪的异位沉积,有望作为评估及预测人体成分及代谢风险的指标。更多还原

【Abstract】 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.更多还原