PROFITH "PRO-moting FITness and Health Through Physical Activity" Research Group, Department of Physical and Sports Education, Sport and Health University Research Institute (iMUDS), Faculty of Sports Science, University of Granada, Granada, Spain; Turku PET Centre, University of Turku, Turku, Finland; Turku PET Centre, Turku University Hospital, Turku, Finland.
PROFITH "PRO-moting FITness and Health Through Physical Activity" Research Group, Department of Physical and Sports Education, Sport and Health University Research Institute (iMUDS), Faculty of Sports Science, University of Granada, Granada, Spain; Pennington Biomedical Research Center, Baton Rouge, LA, USA.
Clin Nutr. 2021 Oct;40(10):5311-5321. doi: 10.1016/j.clnu.2021.08.010. Epub 2021 Aug 24.
Harnessing cold-induced thermogenesis (CIT) and brown adipose tissue (BAT) activity has been proposed as a means of counteracting a positive energy balance, and thus of combating obesity and its related comorbidities. However, it has remained unclear whether CIT and BAT activity show diurnal variation in humans - knowledge that might allow treatments based on these factors to be time-optimized.
A randomized crossover experiment was designed to examine whether CIT shows morning/evening variation in young, healthy adults (n = 14, 5 women). On the first experimental day, subjects' shivering thresholds were determined following a cooling protocol. After ≈96 h had elapsed, the subjects then returned on two further days (approx. 48 h apart) at 08:00 h or 18:00 in random order. On both the latter days, the resting energy expenditure (REE) was measured before the subjects underwent personalized cold exposure (i.e., according to their shivering threshold). CIT was then assessed for 60 min by indirect calorimetry. In an independent cross-sectional study (n = 133, 88 women), subjects came to the laboratory between 8:00 and 18:00 h and their BAT F-fluordeoxyglucose (F-FDG) uptake was assessed after personalized cold stimulation.
Both the REE and CIT were similar in the morning and evening (all P > 0.05). Indeed, 60 min of personalized-mild cold exposure in the morning or evening elicited a similar change in energy expenditure (16.8 ± 12.8 vs. 15.7 ± 15.1% increase above REE, P = 0.72). BAT F-FDG uptake was also similar in the morning, evening and afternoon (all P > 0.05).
CIT does not appear to show morning/evening variation in young healthy adults, with the current study design and methodology. BAT F-FDG uptake appears not to change across the day either, although experiments with a within-subject study design are needed to confirm these findings. Registered under ClinicalTrials.gov Identifier no. NCT02365129.
利用冷诱导产热（CIT）和棕色脂肪组织（BAT）的活性已被提出作为对抗正能 量平衡的一种手段，从而对抗肥胖及其相关的合并症。然而，CIT 和 BAT 活性是否在人体中存在昼夜变化仍不清楚——这一知识可能使基于这些因素的治疗能够进行时间优化。
设计了一项随机交叉实验，以检查年轻健康成年人的 CIT 是否存在早晨/晚上的变化（n=14，女性 5 人）。在第一个实验日，根据冷却方案确定受试者的颤抖阈值。约 96 小时后，受试者在随机顺序的另外两天（约相隔 48 小时）在 08:00 或 18:00 返回。在这两天的后两天，在受试者接受个性化冷暴露（即根据他们的颤抖阈值）之前，测量静息能量消耗（REE）。然后通过间接测热法评估 CIT 60 分钟。在一项独立的横断面研究（n=133，女性 88 人）中，受试者在 8:00 至 18:00 之间来到实验室，并在个性化冷刺激后评估 BAT F-氟脱氧葡萄糖（F-FDG）摄取。
在早晨和晚上，REE 和 CIT 相似（均 P>0.05）。事实上，在早晨或晚上进行 60 分钟的个性化轻度冷暴露会引起能量消耗相似的变化（REE 增加 16.8±12.8%与 15.7±15.1%，P=0.72）。BAT F-FDG 摄取在早晨、晚上和下午也相似（均 P>0.05）。
在当前的研究设计和方法学下，年轻健康成年人的 CIT 似乎没有出现早晨/晚上的变化。BAT F-FDG 摄取似乎也不会随时间变化，尽管需要进行个体内研究设计的实验来证实这些发现。在 ClinicalTrials.gov 注册号 NCT02365129 下注册。
