Nieminen Petteri, Mustonen Anne-Mari, Asikainen Juha, Hyvärinen Heikki
University of Joensuu, Department of Biology, Finland.
J Biol Rhythms. 2002 Apr;17(2):155-63. doi: 10.1177/074873040201700206.
The raccoon dog (Nyctereutes procyonoides, Canidae, Carnivora) is a middle-sized omnivore with excessive autumnal fattening and winter sleep. We studied seasonal weight regulation of the species by following the plasma leptin, ghrelin, and growth hormone (GH) levels of farm-bred raccoon dogs (n = 32) for 6 months. In August, half of the raccoon dogs received continuous-release melatonin implants, and in November, half of the animals of both the sham-operated and melatonin-treated groups were fasted for 2 months. In the autumn, the plasma leptin and GH levels were low, but the ghrelin levels were relatively high and correlated positively with energy intake. This represents the period of energy storage. Leptin and GH levels peaked simultaneously in late October, and melatonin advanced the peaks by 1 week. Thereafter, the levels rapidly declined, representing the transition period from autumnal anabolism to wintertime catabolism. In the winter, the leptin and GH levels rose to high levels, but the ghrelin-leptin ratio was very low. This is the period of winter sleep, with fat accumulated in the autumn as the principal metabolic fuel. In the winter, leptin, ghrelin, and GH may work in synergy to increase lipolysis. GH may also induce winter sleep to the raccoon dog. Fasting had no effect on the hormone levels, unlike in humans and rodents. Instead of the amount of fat in the body, the main regulators of the levels of these hormones in the raccoon dog are presumably seasonal rhythms entrained by melatonin.
貉（Nyctereutes procyonoides，犬科，食肉目）是一种中型杂食动物，有秋季过度育肥和冬眠的习性。我们通过跟踪32只养殖貉6个月的血浆瘦素、胃饥饿素和生长激素（GH）水平，研究了该物种的季节性体重调节。8月，一半的貉接受了缓释褪黑素植入，11月，假手术组和褪黑素处理组的一半动物禁食2个月。秋季，血浆瘦素和GH水平较低，但胃饥饿素水平相对较高，且与能量摄入呈正相关。这代表了能量储存期。瘦素和GH水平在10月下旬同时达到峰值，褪黑素使峰值提前了1周。此后，水平迅速下降，代表从秋季合成代谢到冬季分解代谢的过渡期。冬季，瘦素和GH水平升至高位，但胃饥饿素与瘦素的比值非常低。这是冬眠期，秋季积累的脂肪是主要的代谢燃料。冬季，瘦素、胃饥饿素和GH可能协同作用以增加脂肪分解。GH也可能诱导貉进入冬眠。与人类和啮齿动物不同，禁食对激素水平没有影响。貉体内这些激素水平的主要调节因素可能是由褪黑素调节的季节性节律，而非体内脂肪量。
