Reduced leptin concentrations are permissive for display of torpor in Siberian hamsters
Reduced leptin concentrations are permissive for display of torpor in Siberian hamsters
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DOI：
10.1152/ajpregu.00716.2003
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发表时间：
2004-07-01
影响因子：
2.8
通讯作者：
Dark, J
中科院分区：
文献类型：
--
作者：
Freeman, DA;Lewis, DA;Dark, J
短光期的光周期诱导西伯利亚仓鼠出现冬季表型，包括摄食量和体质量的进行性减少和生殖器官的退化，以及以短期麻木形式出现的可逆低温。昏迷极大地减少了能量的利用，直到体重、脂肪储存和血清瘦素浓度降到最低点时才开始。因为依赖光周期的麻木会延迟到脂肪储备最低时，瘦素浓度可能是麻木发作的一个允许因素。这一猜想是通过向表现出自发麻木的西伯利亚仓鼠植入渗透性小泵来验证的；这些动物接受了持续14天的瘦素或载体释放。外源性瘦素治疗消除了相当大比例的治疗仓鼠的麻木，而使用赋形剂治疗则没有。类似地，在所有每日昏迷的动物中，内源性血清瘦素浓度显著降低。虽然简单地将瘦素浓度降低到阈值以下并不足以引发麻木，但降低瘦素浓度似乎仍然是麻木发生的必要条件。有人提出，瘦素浓度的急剧下降为介导麻木启动的一种尚未确定的中枢机制提供了“饥饿信号”。
A photoperiod with a short photophase induces a winterlike phenotype in Siberian hamsters that includes a progressive decrease in food intake and body mass and reproductive organ regression, as well as reversible hypothermia in the form of short-duration torpor. Torpor substantially reduces energy utilization and is not initiated until body mass, fat stores, and serum leptin concentrations are at their nadir. Because photoperiod-dependent torpor is delayed until fat reserves are lowest, leptin concentrations may be a permissive factor for torpor onset. This conjecture was tested by implanting osmotic minipumps into Siberian hamsters manifesting spontaneous torpor; the animals received a constant release of leptin or vehicle for 14 days. Exogenous leptin treatment eliminated torpor in a significant proportion of treated hamsters, whereas treatment with the vehicle did not. Similarly, endogenous serum leptin concentrations were markedly reduced in all animals undergoing daily torpor. Although simply reducing leptin concentrations below a threshold value is not sufficient for torpor initiation, reduced leptin concentrations nevertheless appear necessary for its occurrence. It is proposed that drastically reduced leptin concentrations provide a "starvation signal" to an as yet unidentified central mechanism mediating torpor initiation.