Department of Animal and Poultry Sciences, Virginia Tech, Blacksburg, VA, USA.
Adv Nutr. 2013 May 1;4(3):267-76. doi: 10.3945/an.112.003376.
Energy metabolism is a highly coordinated process, and preferred fuel(s) differ among tissues. The hierarchy of substrate use can be affected by physiological status and environmental factors including high ambient temperature. Unabated heat eventually overwhelms homeothermic mechanisms resulting in heat stress, which compromises animal health, farm animal production, and human performance. Various aspects of heat stress physiology have been extensively studied, yet a clear understanding of the metabolic changes occurring at the cellular, tissue, and whole-body levels in response to an environmental heat load remains ill-defined. For reasons not yet clarified, circulating nonesterified fatty acid levels are reduced during heat stress, even in the presence of elevated stress hormones (epinephrine, glucagon, and cortisol), and heat-stressed animals often have a blunted lipolytic response to catabolic signals. Either directly because of or in coordination with this, animals experiencing environmental hyperthermia exhibit a shift toward carbohydrate use. These metabolic alterations occur coincident with increased circulating basal and stimulated plasma insulin concentrations. Limited data indicate that proper insulin action is necessary to effectively mount a response to heat stress and minimize heat-induced damage. Consistent with this idea, nutritional interventions targeting increased insulin action may improve tolerance and productivity during heat stress. Further research is warranted to uncover the effects of heat on parameters associated with energy metabolism so that more appropriate and effective treatment methodologies can be designed.
能量代谢是一个高度协调的过程，不同组织对首选燃料也有所不同。底物利用的层次结构可能受到生理状态和环境因素的影响，包括环境温度较高。持续的高温最终会使恒温机制不堪重负，导致热应激，从而损害动物健康、农场动物生产和人类表现。热应激生理学的各个方面已经得到了广泛的研究，但对于环境热负荷下细胞、组织和全身水平发生的代谢变化，仍缺乏明确的认识。由于尚未阐明的原因，即使在应激激素（肾上腺素、胰高血糖素和皮质醇）升高的情况下，循环非酯化脂肪酸水平在热应激期间也会降低，而且热应激动物对分解代谢信号的脂肪分解反应通常较为迟钝。要么是因为直接的原因，要么是因为与之协调的原因，处于环境过热环境中的动物表现出对碳水化合物利用的转变。这些代谢变化与循环基础和刺激后血浆胰岛素浓度的增加同时发生。有限的数据表明，适当的胰岛素作用对于有效应对热应激和最小化热诱导损伤是必要的。基于这个想法，针对增加胰岛素作用的营养干预可能会提高热应激期间的耐受性和生产力。需要进一步的研究来揭示热对与能量代谢相关参数的影响，以便设计更合适和有效的治疗方法。
