Department of Biology, Texas A&M University, College Station, TX 77843, USA.
Sable Systems International, Las Vegas, NV 89032, USA.
J Neurosci Methods. 2022 Jul 1;376:109606. doi: 10.1016/j.jneumeth.2022.109606. Epub 2022 Apr 26.
Drosophila melanogaster is a leading genetic model for studying the neural regulation of sleep. Sleep is associated with changes in behavior and physiological state that are largely conserved across species. The investigation of sleep in flies has predominantly focused on behavioral readouts of sleep because physiological measurements, including changes in brain activity and metabolic rate, are less accessible. We have previously used stop-flow indirect calorimetry to measure whole body metabolic rate in single flies and have shown that in flies, like mammals, metabolic rate is reduced during sleep.
Here, we describe a modified version of this system that allows for efficient and highly sensitive acquisition of CO output from single flies.
In this modified system, we show that sleep-dependent changes in metabolic rate are diminished in aging flies, supporting the notion that sleep quality is reduced as flies age. We also describe a modification that allows for simultaneous acquisition of CO and O levels, providing a respiratory quotient that quantifies how metabolic stores are utilized. We find that the respiratory quotient identified in flies on an all-sugar diet is suggestive of lipogenesis, where the dietary sugar provided to the flies is being converted to fat.
Taken together, the measurement of metabolic rate via indirect calorimetry not only provides a physiological readout of sleep depth, but also provides insight the metabolic regulation of nutrient utilization, with broad applications to genetic studies in flies.
黑腹果蝇是研究睡眠的神经调节的主要遗传模型。睡眠与行为和生理状态的变化有关,这些变化在物种间基本保持一致。对果蝇睡眠的研究主要集中在睡眠的行为测量上,因为生理测量,包括大脑活动和代谢率的变化,不太容易获得。我们之前使用停流间接测热法来测量单只果蝇的全身代谢率,并表明在果蝇中,与哺乳动物一样,代谢率在睡眠期间降低。
在这里,我们描述了该系统的一个改进版本,该版本允许从单只果蝇中高效且高度灵敏地获取 CO 输出。
在这个改进的系统中,我们表明代谢率在衰老果蝇中的睡眠依赖性变化减少,这支持了随着果蝇衰老,睡眠质量降低的观点。我们还描述了一种改进方法,允许同时获取 CO 和 O 水平,提供呼吸商,量化代谢物的利用情况。我们发现,在以全糖为食的果蝇中,呼吸商表明存在脂肪生成,即提供给果蝇的膳食糖被转化为脂肪。
总的来说,间接测热法测量代谢率不仅提供了睡眠深度的生理测量值,还提供了对营养物质利用的代谢调节的深入了解,这在果蝇的遗传研究中有广泛的应用。