Blondin Denis P, Daoud Amani, Taylor Taryn, Tingelstad Hans C, Bézaire Véronic, Richard Denis, Carpentier André C, Taylor Albert W, Harper Mary-Ellen, Aguer Céline, Haman François
Department of Medicine, Centre de recherche du Centre hospitalier universitaire de Sherbrooke, Université de Sherbrooke, Sherbrooke, Canada.
Faculty of Science, University of Ottawa, Ottawa, Canada.
J Physiol. 2017 Mar 15;595(6):2099-2113. doi: 10.1113/JP273395. Epub 2017 Feb 5.
Muscle-derived thermogenesis during acute cold exposure in humans consists of a combination of cold-induced increases in skeletal muscle proton leak and shivering. Daily cold exposure results in an increase in brown adipose tissue oxidative capacity coupled with a decrease in the cold-induced skeletal muscle proton leak and shivering intensity. Improved coupling between electromyography-determined muscle activity and whole-body heat production following cold acclimation suggests a maintenance of ATPase-dependent thermogenesis and decrease in skeletal muscle ATPase independent thermogenesis. Although daily cold exposure did not change the fibre composition of the vastus lateralis, the fibre composition was a strong predictor of the shivering pattern evoked during acute cold exposure.
We previously showed that 4 weeks of daily cold exposure in humans can increase brown adipose tissue (BAT) volume by 45% and oxidative metabolism by 182%. Surprisingly, we did not find a reciprocal reduction in shivering intensity when exposed to a mild cold (18°C). The present study aimed to determine whether changes in skeletal muscle oxidative metabolism or shivering activity could account for these unexpected findings. Nine men participated in a 4 week cold acclimation intervention (10°C water circulating in liquid-conditioned suit, 2 h day , 5 days week ). Shivering intensity and pattern were measured continuously during controlled cold exposure (150 min at 4 °C) before and after the acclimation. Muscle biopsies from the m. vastus lateralis were obtained to measure oxygen consumption rate and proton leak of permeabilized muscle fibres. Cold acclimation elicited a modest 21% (P < 0.05) decrease in whole-body and m. vastus lateralis shivering intensity. Furthermore, cold acclimation abolished the acute cold-induced increase in proton leak. Although daily cold exposure did not change the fibre composition of the m. vastus lateralis, fibre composition was a strong predictor of the shivering pattern evoked during acute cold. We conclude that muscle-derived thermogenesis during acute cold exposure in humans is not only limited to shivering, but also includes cold-induced increases in proton leak. The efficiency of muscle oxidative phosphorylation improves with cold acclimation, suggesting that reduced muscle thermogenesis occurs through decreased proton leak, in addition to decreased shivering intensity as BAT capacity and activity increase. These changes occur with no net difference in whole-body thermogenesis.
人类在急性冷暴露期间肌肉产生的热量由寒冷诱导的骨骼肌质子泄漏增加和颤抖共同组成。每日冷暴露会导致棕色脂肪组织氧化能力增加，同时寒冷诱导的骨骼肌质子泄漏和颤抖强度降低。冷适应后，肌电图测定的肌肉活动与全身产热之间的耦合改善，表明ATP酶依赖性产热得以维持，而骨骼肌ATP酶非依赖性产热减少。尽管每日冷暴露并未改变股外侧肌的纤维组成，但纤维组成是急性冷暴露期间诱发颤抖模式的有力预测指标。
我们之前表明，人类每日进行4周冷暴露可使棕色脂肪组织（BAT）体积增加45%，氧化代谢增加182%。令人惊讶的是，当暴露于轻度寒冷（18°C）时，我们并未发现颤抖强度相应降低。本研究旨在确定骨骼肌氧化代谢或颤抖活动的变化是否可以解释这些意外发现。9名男性参与了为期4周的冷适应干预（在液体调节服中循环10°C的水，每天2小时，每周5天）。在冷适应前后的受控冷暴露（4°C下150分钟）期间持续测量颤抖强度和模式。从股外侧肌获取肌肉活检样本，以测量透化肌纤维的氧消耗率和质子泄漏。冷适应使全身和股外侧肌的颤抖强度适度降低了21%（P<0.05）。此外，冷适应消除了急性寒冷诱导的质子泄漏增加。尽管每日冷暴露并未改变股外侧肌的纤维组成，但纤维组成是急性寒冷期间诱发颤抖模式 的有力预测指标。我们得出结论，人类在急性冷暴露期间肌肉产生的热量不仅限于颤抖，还包括寒冷诱导的质子泄漏增加。随着冷适应，肌肉氧化磷酸化效率提高，这表明除了随着BAT能力和活性增加颤抖强度降低外，肌肉产热减少还通过质子泄漏减少而发生。这些变化在全身产热方面没有净差异。
