Jefimow Małgorzata, Ostrowski Maciej, Jakubowska Anna, Wojciechowski Michał S
Department of Animal Physiology, Nicolaus Copernicus University, ul. Lwowska 1, 87-100 Toruń, Poland; 2Department of Biochemistry, Nicolaus Copernicus University, ul. Gagarina 7, 87-100 Toruń, Poland.
Physiol Biochem Zool. 2014 Jul-Aug;87(4):527-38. doi: 10.1086/676319. Epub 2014 May 28.
The concentrations of fatty acids in the diet influence torpor in numerous species of mammals. Much less is known, however, about the potential effects of other types of dietary lipids. One study demonstrated that increasing dietary cholesterol levels during fall feeding increased torpor bout length and also decreased minimum body temperatures during hibernation by chipmunks. Another hibernation study with ground squirrels revealed that the cholesterol contents of both the cerebral cortex and the microsomes were significantly greater during arousal episodes than during torpor bouts, suggesting that cholesterol plays a role in preserving brain function during torpor. We thus predicted that dietary cholesterol enhances daily torpor in mammals as well. We also predicted that the level of cholesterol found in mammalian brain tissues during daily torpor increases with that of the diet. These hypotheses were tested in a series of laboratory feeding and daily torpor experiments involving Siberian hamsters (Phodopus sungorus) maintained on semisynthetic diets varying only in cholesterol content. Hamsters that were maintained on diets with cholesterol contents of 0.3%-2.5% during the summer entered winter daily torpor spontaneously, whereas those that were fed diets that contained no cholesterol did not. This is the first study to demonstrate the effects of a cholesterol-free diet on mammalian torpor. The presence of cholesterol in the summer diet also increased the level of cholesterol found in the brains of hamsters during the winter daily torpor period, but it did not during the summer. These findings support our hypotheses that dietary cholesterol is permissive for daily torpor in mammals and that it also increases brain cholesterol levels during the winter.
饮食中脂肪酸的浓度会影响众多哺乳动物的蛰伏状态。然而，对于其他类型膳食脂质的潜在影响，我们了解得要少得多。一项研究表明，在秋季喂食期间提高膳食胆固醇水平，会增加花栗鼠的蛰伏时长，同时也会降低其冬眠期间的最低体温。另一项针对地松鼠的冬眠研究显示，在苏醒期，大脑皮层和微粒体中的胆固醇含量均显著高于蛰伏期，这表明胆固醇在蛰伏期间对维持大脑功能发挥着作用。因此，我们推测膳食胆固醇同样会增强哺乳动物的日常蛰伏。我们还预测，在日常蛰伏期间，哺乳动物脑组织中发现的胆固醇水平会随饮食中的胆固醇水平升高而增加。在一系列实验室喂养和日常蛰伏实验中，我们对这些假设进行了验证，实验对象是饲养在仅胆固醇含量不同的半合成饮食中的西伯利亚仓鼠（Phodopus sungorus）。夏季以胆固醇含量为0.3%-2.5%的饮食饲养的仓鼠会自发进入冬季日常蛰伏状态，而那些喂食不含胆固醇饮食的仓鼠则不会。这是第一项证明无胆固醇饮食对哺乳动物蛰伏有影响的研究。夏季饮食中胆固醇的存在，也会增加仓鼠在冬季日常蛰伏期大脑中的胆固醇水平，但在夏季则不会。这些发现支持了我们的假设，即膳食胆固醇有利于哺乳动物的日常蛰伏，并且在冬季还会增加大脑中的胆固醇水平。
