Fruit bats (Pteropodidae) fuel their metabolism rapidly and directly with exogenous sugars
Fruit bats (Pteropodidae) fuel their metabolism rapidly and directly with exogenous sugars
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DOI：
10.1242/jeb.043505
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发表时间：
2010-08-01
影响因子：
2.8
通讯作者：
Voigt, C. C.
中科院分区：
文献类型：
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作者：
Amitai, O.;Holtze, S.;Voigt, C. C.
以前的研究报告说，喂养蝙蝠和鸟类大多使用最近获得的外源性营养作为飞行燃料，而不是内源性燃料，如脂质或糖原。然而，这种燃料使用模式可能是一个简单的大小相关的现象，因为迄今为止，只有小型鸟类和蝙蝠已经研究了代谢燃料的来源，因为小动物携带相对较小的能量储备，考虑到它们的高质量特定代谢率。我们假设，类似于150克埃及果蝠（Rousettus aegyptiacus Pteropodidae），比以前研究的蝙蝠重一个数量级以上，也分解代谢膳食糖直接和专门燃料休息和飞行代谢。我们的期望是基于这样的观察，即这些动物快速运输摄入的膳食糖，这些糖通过肠道中的被动细胞旁途径被吸收到高能量需求的器官。我们使用稳定的碳同位素比呼出的二氧化碳（三角洲C-13（呼吸）），以评估16个埃及果蝠，保持在实验前的C3植物的饮食代谢底物的来源。首先，我们预测，在休息蝙蝠三角洲C-13（呼吸）保持不变，当蝙蝠摄入C3蔗糖，但增加和收敛的饮食同位素签名时，C4蔗糖和C4葡萄糖摄入。第二，如果飞果蝠只使用外源性营养物质来为飞行提供燃料，我们预测飞果蝠的δ C-13（呼吸）将集中在它们喂食的C4蔗糖的同位素特征上。事实上，休息和飞行的埃及果蝠都直接用新鲜摄入的外源底物来促进它们的新陈代谢。果蝠氧化膳食糖的速度与10克花蜜喂养的蝙蝠和5克蜂鸟一样快。我们的研究结果支持这样一种观点，即飞行蝙蝠，无论其大小，直接分解代谢膳食糖，并可能专门为飞行提供燃料。
Previous studies reported that fed bats and birds mostly use recently acquired exogenous nutrients as fuel for flight, rather than endogenous fuels, such as lipids or glycogen. However, this pattern of fuel use may be a simple size-related phenomenon because, to date, only small birds and bats have been studied with respect to the origin of metabolized fuel, and because small animals carry relatively small energy reserves, considering their high mass-specific metabolic rate. We hypothesized that similar to 150 g Egyptian fruit bats (Rousettus aegyptiacus Pteropodidae), which are more than an order of magnitude heavier than previously studied bats, also catabolize dietary sugars directly and exclusively to fuel both rest and flight metabolism. We based our expectation on the observation that these animals rapidly transport ingested dietary sugars, which are absorbed via passive paracellular pathways in the intestine, to organs of high energy demand. We used the stable carbon isotope ratio in exhaled CO2 (delta C-13(breath)) to assess the origin of metabolized substrates in 16 Egyptian fruit bats that were maintained on a diet of C3 plants before experiments. First, we predicted that in resting bats delta C-13(breath) remains constant when bats ingest C3 sucrose, but increases and converges on the dietary isotopic signature when C4 sucrose and C4 glucose are ingested. Second, if flying fruit bats use exogenous nutrients exclusively to fuel flight, we predicted that delta C-13(breath) of flying bats would converge on the isotopic signature of the C4 sucrose they were fed. Both resting and flying Egyptian fruit bats, indeed, directly fuelled their metabolism with freshly ingested exogenous substrates. The rate at which the fruit bats oxidized dietary sugars was as fast as in 10 g nectar-feeding bats and 5 g hummingbirds. Our results support the notion that flying bats, irrespective of their size, catabolize dietary sugars directly, and possibly exclusively, to fuel flight.