Department of Sports Medicine for Health Promotion, Tokyo Medical University, Tokyo, Japan.
Division of Preventive Medicine, National Hospital Organization Kyoto Medical Center, Clinical Research Institute, Kyoto, Japan.
Front Endocrinol (Lausanne). 2020 May 19;11:261. doi: 10.3389/fendo.2020.00261. eCollection 2020.
Brown adipose tissue (BAT) mediates adaptive thermogenesis upon food intake and cold exposure, thus potentially contributing to the prevention of lifestyle-related diseases. F-fluorodeoxyglucose (FDG)-positron emission tomography (PET) with computed tomography (CT) (FDG-PET/CT) is a standard method for assessing BAT activity and volume in humans. FDG-PET/CT has several limitations, including high device cost and ionizing radiation and acute cold exposure necessary to maximally stimulate BAT activity. In contrast, near-infrared spectroscopy (NIRS) has been used for measuring changes in O-dependent light absorption in the tissue in a non-invasive manner, without using radiation. Among NIRS, time-resolved NIRS (NIR) can quantify the concentrations of oxygenated and deoxygenated hemoglobin ([oxy-Hb] and [deoxy-Hb], respectively) by emitting ultrashort (100 ps) light pulses and counts photons, which are scattered and absorbed in the tissue. The basis for assessing BAT density (BAT-d) using NIR is that the vascular density in the supraclavicular region, as estimated using Hb concentration, is higher in BAT than in white adipose tissue. In contrast, relatively low-cost continuous wavelength NIRS (NIR) is employed for measuring relative changes in oxygenation in tissues. In this review, we provide evidence for the validity of NIR and NIR in estimating human BAT characteristics. The indicators (Ind) examined were [oxy-Hb], [deoxy-Hb], total hemoglobin [total-Hb], Hb O saturation (StO), and reduced scattering coefficient ( ) in the supraclavicular region, as determined by NIR, and relative changes in corresponding parameters, as determined by NIR. The evidence comprises the relationships between the Ind investigated and those determined by FDG-PET/CT; the correlation between the Ind and cold-induced thermogenesis; the relationship of the Ind to parameters measured by FDG-PET/CT, which responded to seasonal temperature fluctuations; the relationship of the Ind and plasma lipid metabolites; the analogy of the Ind to chronological and anthropometric data; and changes in the Ind following thermogenic food supplementation. The [total-Hb] and [oxy-Hb] determined by NIR, but not parameters determined by NIR, exhibited significant correlations with cold-induced thermogenesis parameters and plasma androgens in men in winter or analogies to FDG-PET. We conclude that NIR can provide useful information for assessing BAT-d in a simple, rapid, non-invasive way, although further validation study is still needed.
棕色脂肪组织 (BAT) 在进食和暴露于寒冷时介导适应性产热，从而可能有助于预防与生活方式相关的疾病。氟代脱氧葡萄糖 (FDG)-正电子发射断层扫描 (PET) 与计算机断层扫描 (CT)（FDG-PET/CT）是评估人类 BAT 活性和体积的标准方法。FDG-PET/CT 有几个局限性，包括设备成本高、电离辐射以及为最大限度地刺激 BAT 活性而必需的急性寒冷暴露。相比之下，近红外光谱 (NIRS) 已用于以非侵入性方式测量组织中与 O 相关的光吸收率的变化，而无需使用辐射。在 NIRS 中，时间分辨 NIRS (NIR) 可以通过发射超短 (100 ps) 光脉冲并计数在组织中散射和吸收的光子，来定量测量氧合血红蛋白 ([oxy-Hb]) 和去氧血红蛋白 ([deoxy-Hb]) 的浓度。使用 NIR 评估 BAT 密度 (BAT-d) 的基础是，使用血红蛋白浓度估算的锁骨上区域的血管密度在 BAT 中高于在白色脂肪组织中。相比之下，相对低成本的连续波长 NIRS (NIR) 用于测量组织中氧合的相对变化。在本综述中，我们提供了 NIR 和 NIR 用于估计人体 BAT 特征的有效性的证据。使用 NIR 测定的锁骨上区域的指标 (Ind) 包括 [oxy-Hb]、[deoxy-Hb]、总血红蛋白 [total-Hb]、血红蛋白氧饱和度 (StO) 和还原散射系数 ( )，以及通过 NIR 测定的相应参数的相对变化。证据包括所研究的 Ind 与 FDG-PET/CT 确定的 Ind 之间的关系；Ind 与冷诱导产热之间的相关性；Ind 与 FDG-PET/CT 测量的参数之间的关系，这些参数对季节性温度波动有反应；Ind 与血浆脂质代谢物之间的关系；Ind 与年龄和人体测量学数据的相似性；以及热原性食物补充后的 Ind 变化。NIR 测定的 [total-Hb] 和 [oxy-Hb]，而不是 NIR 测定的参数，与男性冬季冷诱导产热参数和血浆雄激素显著相关，并且与 FDG-PET 相似。我们得出结论，NIR 可以提供有用的信息，以简单、快速、非侵入性的方式评估 BAT-d，尽管仍需要进一步验证研究。
