Data from: Oxidation of linoleic and palmitic acid in pre-hibernating and hibernating common noctule bats revealed by 13C breath testing

Mammals fuel hibernation by oxidizing saturated and unsaturated fatty acids from triacylglycerols in adipocytes, yet the relative importance of these two categories as an oxidative fuel may change during hibernation. We studied the selective use of fatty acids as an oxidative fuel in noctule bats (<i>Nyctalus noctula</i>). Pre-hibernating noctule bats that were fed 13C-enriched linoleic acid (LA) showed 12 times higher tracer oxidation rates compared to conspecifics fed 13C-enriched palmitic acid (PA). After this experiment, we supplemented the diet of bats with the same fatty acids on 5 subsequent days to enrich their fat depots with the respective tracer. We then compared the excess 13C enrichment (APE) in breath of bats for torpor and arousal events during early and late hibernation. We observed higher APE values in breath of bats fed 13C-enriched LA than in bats fed 13C-enriched PA for both states, torpor and arousal, and also for both periods. Thus, hibernating bats oxidized selectively endogenous LA instead of PA, most likely because of faster transportation rates of PUFA compared with SFA. We did not observe changes in APE values in the breath of torpid animals between early and late hibernation. Skin temperature of torpid animals increased by 0.7oC between early and late hibernation in bats fed PA, whereas it decreased by -0.8oC in bats fed LA, highlighting that endogenous LA may fulfil two functions when available in excess: serving as an oxidative fuel and supporting cell membrane functionality.哺乳动物通过氧化脂肪细胞（adipocytes）内三酰甘油（triacylglycerols）释放的饱和脂肪酸与不饱和脂肪酸为冬眠供能，但这两类脂肪酸作为氧化供能底物的相对重要性可能在冬眠进程中发生改变。我们以普通夜蝠（*Nyctalus noctula*）为研究对象，探究其对脂肪酸作为氧化供能底物的选择性利用情况。预冬眠期的普通夜蝠在喂食13C标记亚油酸（linoleic acid, LA）后，其示踪剂氧化速率是喂食13C标记棕榈酸（palmitic acid, PA）的同种个体的12倍。本实验结束后，我们在后续5天内为蝙蝠补充饲喂上述两种脂肪酸，以使它们的脂肪储备中富集对应标记物。随后我们比较了蝙蝠在冬眠早期与晚期的蛰伏（torpor）和觉醒（arousal）阶段呼出气体中的过量13C富集度（excess 13C enrichment, APE）。我们观察到，无论是蛰伏与觉醒两种状态，还是冬眠早期与晚期两个阶段，喂食13C标记LA的蝙蝠呼出气体中的APE值均高于喂食13C标记PA的个体。由此可见，冬眠的普通夜蝠会选择性地氧化内源性亚油酸而非棕榈酸，这一现象很可能源于多不饱和脂肪酸（polyunsaturated fatty acid, PUFA）相较于饱和脂肪酸（saturated fatty acid, SFA）具有更快的转运速率。我们未观察到蛰伏个体在冬眠早期与晚期的呼出气体APE值存在变化。喂食PA的蝙蝠，其蛰伏个体的皮肤温度在冬眠早期至晚期间升高了0.7℃；而喂食LA的蝙蝠，其蛰伏个体的皮肤温度则下降了0.8℃，这一结果表明，当内源性亚油酸供应充足时，其可发挥两项功能：作为氧化供能底物，以及支持细胞膜的正常功能。