Photoperiod, sex, gonadal steroids, and housing density affect body fat in hamsters
Photoperiod, sex, gonadal steroids, and housing density affect body fat in hamsters
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DOI：
10.1016/s0031-9384(96)80027-8
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发表时间：
1996-08-01
影响因子：
2.9
通讯作者：
Bartness, TJ
中科院分区：
文献类型：
--
作者：
Bartness, TJ
西伯利亚仓鼠（Phodopus sungorus sungorus）的体重表现出季节性周期，夏季体重最高，冬季体重最低。这些自然发生的体重变化是由光周期的变化触发的，并在实验室中通过将雄性或雌性仓鼠从长的“夏季”天（LD）转移到短的“冬季”天（SD）来模拟。在SD的初始暴露期间（1-6周），体脂的减少并不均匀，并且与位于内部的腹膜内白色脂肪组织（WAT）垫相比，位于外部的皮下WAT垫相对优先消耗相关。这种脂质消耗模式仅发生在雄性动物中。本实验的目的是通过回答以下问题来进一步探索SD诱导的脂肪垫质量的性别特异性和脂肪垫特异性相对减少：1）与SD诱导的脂肪垫质量变化相关的脂肪组织细胞结构的潜在改变是什么？2)饲养密度是否会影响脂肪垫质量的减少？3）WAT质量的这些变化是否可以通过性腺类固醇控制而改变？在实验1中，成年雄性和雌性性腺完整的西伯利亚仓鼠单独饲养或每笼10只仓鼠。在实验2中，成年雄性和雌性仓鼠保持性腺完整或性腺切除。去势雄性动物接受胆固醇控制（CHOL）、睾酮（T）或双氢睾酮（DHT）植入，而卵巢切除雌性动物接受CHOL或雌二醇植入。手术和植入后6周，两个实验中每组中一半的动物被转移到SD再持续6周，而其他动物仍留在LD中。结果发现：1）SD诱导的脂肪垫质量减少主要反映为脂肪细胞大小减少，2）SD诱导的脂质耗竭的相对模式仅见于单笼雄性，3）T或雌二醇处理逆转了两种光周期中性腺切除术的影响，4）尽管两种激素的LD血清浓度恢复，但T仅逆转了SD诱导的体重和摄食量减少，而雌二醇仅逆转SD引起的RWAT垫质量的减少; 5）DHT处理加重了SD引起的体重和食物摄入的减少。总的来说，这些结果表明：a）短光周期介导的脂肪垫质量变化仅是由于脂肪细胞大小的波动，B）饲养密度影响雄性SD诱导的脂质耗竭的相对模式，而大多数其他光敏反应在单养和群养仓鼠之间没有差异，c）许多SD诱导的反应是性腺类固醇无关的。
Siberian hamsters (Phodopus sungorus sungorus) show seasonal cycles in body mass with the peak mass occurring in the summer and the nadir in the winter. These naturally occurring changes in body mass are triggered by changes in the photoperiod and are mimicked in the laboratory by transferring male or female hamsters from long ''summer-like'' days (LDs) to short ''winter-like'' days (SDs). During the initial exposure to SDs (1-6 weeks), the decreases in body fat are not uniform and are associated with the relative preferential depletion of internally located intraperitoneal white adipose tissue (WAT) pads compared with the more externally located subcutaneous WAT pads. This pattern of lipid depletion only occurs in males. The purpose of the present experiments was to explore further the SD-induced gender- and fat pad-specific relative decreases in fat pad mass by answering the following questions: 1) What are the underlying alterations in adipose tissue cellularity associated with the SD-induced changes in fat pad mass? 2) Does housing density affect these decreases in fat pad mass? and 3) Can these changes in WAT mass be altered by gonadal steroid manipulation? In Experiment 1, adult male and female gonadally intact Siberian hamsters were housed singly or 10 hamsters per cage. In Experiment 2, adult male and female hamsters were left gonadally intact or gonadectomized. Castrated males received a cholesterol control (CHOL), testosterone (T), or dihydrotestosterone (DHT) implant, whereas ovariectomized females received CHOL or estradiol implant. Six weeks after surgery and implantation, half the animals in each group in both experiments were transferred to SDs for an additional 6 weeks, whereas the others remained in LDs. It was found that: 1) the SD-induced decrease in fat pad mass was reflected primarily as decreased fat cell size, 2) the relative pattern of SD-induced lipid depletion only was seen in single-housed males, 3) T or estradiol treatment reversed the effects of gonadectomy in both photoperiods, 4) despite the restoration of LD serum concentrations for both hormones, T only reversed the SD-induced decrease in body mass and food intake, whereas estradiol only reversed the SD-induced decrease in RWAT pad mass, and 5) DHT treatment exaggerated the SD-induced decreases in body mass and food intake. Collectively, these results showed that: a) short photoperiod-mediated changes in fat pad mass are due to fluctuations only in fat cell size, b) housing density affected the relative pattern of SD-induced lipid depletion in males, whereas most other photosensitive responses did not differ between single- and group-housed hamsters, and c) many of the SD-induced responses were gonadal steroid independent.