As small, flying, mammalian endotherms, insectivorous bats are adapted to operate at high levels of energy expenditure. In response to seasonally variable challenges, we predicted that bats should balance energy budgets by flexibly adjusting aspects of their physiology or behavior in ways that elevate metabolic capacity. We examined variation in energy storage and pathways for oxidative metabolism in Brazilian free-tailed bats (Tadarida brasiliensis) related to estimated costs associated with reproduction and migration. We collected pectoral muscle and liver from female T. brasiliensis at six time points during the summer and fall and measured changes in the activity of four enzymes involved with lipid metabolism. Body mass varied substantially with life-cycle stage, suggesting that rapid accumulation and use of fat stores occurs in response to current and anticipated energy demands. Catabolic enzyme activity (carnitine palmitoyl transferase [CPT], 3-hydroxyacyl-CoA dehydrogenase [HOAD], and citrate synthase [CS]) in the muscle was increased during lactation compared with early pregnancy but exhibited no change before fall migration. While there was no temporal change in lipid biosynthetic capacity in the liver, fatty acid synthase activity was negatively correlated with body mass. Variation in body mass and enzyme activity in T. brasiliensis during the summer suggests that stored energy is mobilized and lipid oxidative capacity is increased during periods of increased demand and that lipid biosynthetic capacity is increased with depletion of fat stores. These results suggest that bats are able to flexibly adjust metabolic capacity based on energy requirement to maintain energy balance despite high levels of expenditure.

中文翻译：

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巴西自由尾蝙蝠脂质代谢和能量存储的季节性动态。

由于小型，飞行中的哺乳动物吸热，食虫蝙蝠适合在高水平的能量消耗下运行。为了应对季节性变化的挑战，我们预测蝙蝠应通过提高代谢能力的方式灵活地调整其生理或行为方面来平衡能量预算。我们检查了巴西无尾蝙蝠（Tadarida brasiliensis）的能量存储和氧化代谢途径的变化，这些变化与与繁殖和迁移相关的估计成本有关。我们在夏季和秋季的六个时间点收集了来自女性巴西布鲁氏菌的胸肌和肝脏，并测量了与脂质代谢有关的四种酶的活性变化。体重随着生命周期的阶段而变化很大，这表明，脂肪存储的快速积累和使用是对当前和预期的能量需求的响应。与哺乳期相比，泌乳期间肌肉中的分解代谢酶活性（肉碱棕榈酰转移酶[CPT]，3-羟酰基辅酶A脱氢酶[HOAD]和柠檬酸合酶[CS]）增加，但在秋季迁徙之前未表现出变化。尽管肝脏中脂质生物合成能力没有暂时变化，但脂肪酸合酶活性与体重呈负相关。夏季巴西巴西螺旋杆菌体重和酶活性的变化表明，在需求增加的时期，动员了储存的能量并增加了脂质的氧化能力，并且随着脂肪存储的减少，脂质的生物合成能力也增加了。