Seasonal regulations of energetics, serum concentrations of leptin, and uncoupling protein 1 content of brown adipose tissue in root voles (Microtus oeconomus) from the Qinghai-Tibetan plateau

Survival of small mammals in winter requires proper adjustments in physiology, behavior and morphology. The present study was designed to examine the changes in serum leptin concentration and the molecular basis of thermogenesis in seasonally acclimatized root voles (Microtus oeconomus) from the Qinghai-Tibetan plateau. In January root voles had lower body mass and body fat mass coupled with higher nonshivering thermogenesis (NST) capacity. Consistently, cytochrome c oxidase activity and mitochondrial uncoupling protein-1 (UCP1) protein contents in brown adipose tissues were higher in January as compared to that in July. Circulating level of serum leptin was significantly lower in winter and higher in July. Correlation analysis showed that serum leptin levels were positively related with body mass and body fat mass while negatively correlated with UCP1 protein contents. Together, these data provided further evidence for our previous findings that root voles from the Qinghai-Tibetan plateau mainly depend on higher NST coupled with lower body mass to enhance winter survival. Further, fat deposition was significantly mobilized in cold winter and leptin was potentially involved in the regulation of body mass and thermogenesis in root voles. Serum leptin might act as a starvation signal in winter and satiety signal in summer.     

Regulation of body weight and thermogenesis in seasonally acclimatized Brandt's voles (Microtus brandti)

Seasonal changes in an animal's morphology, physiology, and behavior are considered to be an adaptive strategy for survival and reproductive success. In the present study, we examined body weight and several behavioral, physiological, hormonal, and biochemical markers in seasonally acclimatized Brandt's voles (Microtus brandti) to test our hypothesis that Brandt's voles can decrease energy intake associated with decrease in body weight, body fat content, serum leptin level, and increasing thermogenesis in winter conditions. We found that the body weight of Brandt's voles was lowest in winter (December to February) and highest in spring and early summer (May to June). This seasonal variation in body weight was associated with changes in other markers examined. For example, the winter decrease in body weight was accompanied by increased energy intake and enhanced nonshivering thermogenesis (NST) as well as by decreased body fat mass and reduced levels of circulating leptin. Further, circulating levels of leptin were positively correlated with body weight and body fat mass, and negatively correlated with energy intake and uncoupling protein 1 contents. Together, these data do not support our hypothesis and suggest that leptin may be involved in this process and serve as a starvation signal in Brandt's voles.     

Effects of photoperiod on energy budgets and thermogenesis in Mongolian gerbils (Meriones unguiculatus)

(1)

To investigate the role of photoperiod on the regulation of energy budgets and thermogenesis in Mongolian gerbils, body mass (BM), body fat mass (BFM), basal metabolic rate (BMR), nonshivering thermogenesis (NST), gross energy intake (GEI), mitochondrial cytochrome c oxidase (COX) activity and uncoupling protein1 (UCP1) content of brown adipose tissue (BAT), and serum tri-iodothyronine (T₃), thyroxine (T₄) and leptin levels were measured.     

Energy metabolism, thermogenesis and body mass regulation in Brandt's voles (Lasiopodomys brandtii) during cold acclimation and rewarming

Environmental cues play important roles in the regulation of an animal's physiology and behavior. The purpose of the present study was to test the hypothesis that ambient temperature was a cue to induce adjustments in body mass, energy intake and thermogenic capacity, associated with changes in serum leptin levels in Brandt's voles (Lasiopodomys brandtii). We found that Brandt's voles increased resting metabolic rate (RMR) and energy intake and kept body mass stable when exposed to the cold while showed a significant increase in body mass after rewarming. The increase in body mass after rewarming was associated with the higher energy intake compared with control. Uncoupling protein 1 (UCP1) content in brown adipose tissue (BAT) increased in the cold and reversed after rewarming. Serum leptin levels decreased in the cold while increased after rewarming, associated with the opposite changes in energy intake. Further, serum leptin levels were positively correlated with body mass and body fat mass. Together, these data supported our hypothesis that ambient temperature was a cue to induce changes in body mass and metabolism. Serum leptin, as a starvation signal in the cold and satiety signal in rewarming, was involved in the processes of thermogenesis and body mass regulation in Brandt's voles.     

Seasonal adjustments in body mass and thermogenesis in Mongolian gerbils (<Emphasis Type="Italic">Meriones unguiculatus</Emphasis>): the roles of short photoperiod and cold

Seasonal adjustments in body mass and thermogenesis are important for the survival of small mammals during acclimatization in the temperate zone. To determine the contributions of short photoperiod and cold temperatures to seasonal changes in thermogenesis and body mass in Mongolian gerbils (Meriones unguiculatus), body mass, basal metabolic rate (BMR), nonshivering thermogenesis (NST), energy intake and energy digestibility were determined in seasonally acclimatized and laboratory acclimated animals. Body mass showed significant seasonal changes and decreased to a minimum in winter. Both BMR and NST increased in winter, and these changes were mimicked by exposing animals to short photoperiod or cold temperatures in the animal house. Digestible energy intake also increased significantly in winter, and also during exposure of housed animals to both short photoperiod and cold. These results suggest that Mongolian gerbils overcome winter thermoregulatory challenges by increasing energy intake and thermogenesis, and decreasing body mass to reduce total energy requirements. Short photoperiod and cold can serve as effective environmental cues during seasonal acclimatization.     

Seasonal changes in body mass and thermogenesis in tree shrews (Tupaia belangeri): The roles of photoperiod and cold

Environmental factors play an important role in the seasonal adaptation of body mass and thermogenesis in small, wild mammals. To determine the contributions of photoperiod and cold on seasonal changes in energy metabolism and body mass, the resting metabolic rates (RMR), nonshivering thermogenesis (NST), energy intake and gut morphology of the tree shrews were determined in winter and summer and in laboratory acclimated animals. Body mass, RMR and NST increased in winter, and these changes were mimicked by exposing animals to short-day photoperiod or cold in the animal house. Energy intake and digested energy also increased significantly in winter, and also during exposure of housed animals to both short-day photoperiod and cold. The lengths and weights of small intestine increased in winter. These results indicated that Tupaia belangeri overcomes winter thermoregulatory challenges by increasing energy intake and thermogenesis, and adjusted gut morphology to balance the total energy requirements. Short-day photoperiod and cold can serve as environmental cues during seasonal acclimatization.     

不同社会等级雄性根田鼠对自身和同性陌生气味的辨别

采用两两遭遇法确定雄性根田鼠的社会等级,然后以新鲜尿作气味源,在行为选择箱中观察不同社会等级雄性根田鼠对自身气味和非自身气味的行为响应模式,结果表明:种群中从属个体对自身尿液存在明显偏好,其对自身尿液的接近潜伏期显著短于非自身尿液,而访问时间、自我修饰频次都显著高于非自身尿液;种群中优势个体则优先访问非自身尿液,其对非自身尿液的访问时间、嗅舔时间、自我修饰及反标记均显著高于自身尿液;对非自身尿液,不同社会等级雄性个体之间存在明显不同的行为反应模式。这说明,不同社会等级雄性根田鼠具有自我识别的能力且模式不同,同时其对非自身尿气味响应模式的差异也与自身的社会等级有关。     

Metabolism and thermoregulation in Maximowiczi's voles (Microtus maximowiczii) and Djungarian hamsters (Phodopus campbelli)

1 Metabolic rates (Vo₂), body temperature (T_b), and thermal conductance (C) were first determined in newly captured Maximowiczi's voles (Microtus maximowiczii) and Djungarian hamsters (Phodopus campbelli) from the Inner Mongolian grasslands at a temperature range from 5 to 35 °C.

2 The thermal neutral zone (TNZ) was between 25 and 32.5 °C for Maximowiczi's voles and between 25 and 30 °C for Djungarian hamsters. Mean T_b was 37.0±0.1 °C for voles and 36.2±0.1 °C for hamsters. Minimum thermal conductance was 0.172±0.004 ml O₂/g h °C for voles and 0.148±0.003 ml O₂/g h °C for hamsters.

3 The mean resting metabolic rate within TNZ was 2.21±0.05 ml O₂/g h in voles and 2.01±0.07 ml O₂/g h in hamsters. Nonshivering thermogenesis was 5.36±0.30 ml O₂/g h for voles and 6.30±0.18 ml O₂/g h for hamsters.

4 All these thermal physiological properties are adaptive for each species and are shaped by both macroenvironmental and microenvironmental conditions, food habits, phylogeny and other factors.

建巢行为提高雄性根田鼠的个体发育和存活

为研究建巢行为对室内繁育根田鼠的可能影响,共设计两个实验:(1)选择30 对配对根田鼠分成两组,即15 对建巢根田鼠(建巢组)和15 对不建巢根田鼠(不建巢组),每对根田鼠提供5. 3 g 左右的棉花作巢材,持续30 d。记录两组有无实验动物时的巢内、巢上温度变化情况。(2)记录24 窝后代的出生时体重、断奶时体重、杀婴的数量和日龄。结果表明,建巢组巢内温度显著高于不建巢组巢内温度,相反的是,建巢组的巢上温度比不建巢组的巢上温度低。两组间后代出生时的平均体重没有显著差异但断奶时的体重存在显著差异。而且,在2 ～ 14 日龄间,建巢组和不建巢组雄性后代体重之间存在显著差异。建巢组的杀婴数量极显著低于不建巢组的杀婴数量。因此,建巢行为可以显著提高雄性后代的个体发育和后代的存活。     

光周期和高脂食物对布氏田鼠能量代谢和产热的影响

为了研究光周期和高脂食物对小型哺乳动物能量代谢和产热的影响,将成年雌性布氏田鼠(Lasiopodomys brandtii)分别驯化于长光照低脂、高脂食物和短光照低脂、高脂食物,7周后测定动物的体重、能量摄入、产热、血清瘦素浓度以及褐色脂肪组织解偶联蛋白1(BAT-UCP1)含量等参数.结果发现:1)短光照抑制体重增长、降低体脂重量和血清瘦素水平,增加非颤抖性产热(NST)和UCP1含量;2)高脂食物使摄入能减少和消化率提高,但未显著影响体重、基础代谢率、NST、UCP1含量和血清瘦素;3)血清瘦素与摄入能不相关,但与体脂含量正相关.结果暗示:短光照下瘦素作用敏感性增加和产热能力增强,可能介导了抵抗高脂食物诱导的肥胖.在野外条件下草食性的布氏田鼠能通过能量代谢和产热的适应性调节避免体重的过度增长,有利于降低捕食风险,增强生存能力.同时布氏田鼠是研究食物诱导肥胖机理的一个好模型     

围栏条件下母体密度应激对根田鼠 F1代性器官指数的影响

为探讨自然条件下母体密度应激对根田鼠F1代性器官指数的影响,通过在围栏内建立不同密度的母体种群获得相应的F1代个体,以此建立了不同密度的子代种群,并测定了母体种群建群者的血浆皮质酮含量,将建立子代种群后剩余的F1代个体带回实验室饲养.实验结束后,测定了全部F1代个体的性器官指数及皮质酮含量.结果表明,高密度母体种群建群者的皮质酮含量显著高于低密度母体种群建群者;出生于高密度母体种群的F1代个体处于高密度子代种群,其性器官指数显著低于出生于低密度母体种群且处于低密度子代种群的F1代个体,而皮质酮含量显著高于后者;出生于高密度母体种群的F1代个体处于低密度子代种群,其性器官指数及皮质酮含量与出生于低密度母体种群且处于低密度子代种群的F1代个体间无显著差异.此外,实验室饲养条件下,出生于高密度和低密度母体种群的F1代个体间的睾丸指数无显著差异.本研究结果说明,在根田鼠种群中,单一的母体密度应激对子代的性器官指数无影响,但生前应激子代在性成熟后,当再次遭遇密度应激时,其性器官指数显著降低,母体密度应激和当前环境对种群的未来繁殖能力具有耦合效应.     

Effects of temperature and photoperiod on thermogenesis in plateau pikas (Ochotona curzoniae) and root voles (Microtus oeconomus)

We examined the effects of temperature and photoperiod on metabolic thermogenesis and the thermogenic characteristics of brown adipose tissue in plateau pikas (Ochotona curzoniae) and root voles (Microtus oeconomus), the dominant species of small mammals in the alpine meadow ecosystems on the Qinghai-Tibetan Plateau. Pikas and voles were acclimated in the following groups: (1) Long day – warm temperature (16L:8D, 23 °C), (2) Long day – cold temperature (16L:8D, 5 °C), (3) short day – warm temperature (8L:16D, 23 °C), and (4) short day – cold temperature (8L:16D, 5 °C). Both temperature and photoperiod were important environmental cues for changes in thermogenesis for both species. Low temperature and short photoperiod induced increases in metabolic rate, nonshivering thermogenesis (NST), mitochondrial protein contents of brown adipose tissue, and cytochrome C oxidase activity of brown adipose tissue mitochondria in both species. Plateau pikas were more sensitive to cold (79% of the total NST response) than to short photoperiod (21%), while root voles were more sensitive to short photoperiod (60% of the total NST response) than to cold (40%), although cold clearly enhanced thermogenesis. Their thermogenic characteristics correlated with their preferred habitats: plateau pikas are found mainly in more exposed microhabitats in open sunny meadow, while root voles live in more sheltered microhabitats in relatively closed shrub. Our results also showed that temperature and photoperiod combined induce thermogenic adjustments in both species in seasonal acclimatization in their alpine meadow macrohabitat. Accepted: 10 November 1998     

根田鼠对不同亲属关系异性尿气味的识别

根为检验根田鼠对不同亲属关系异性成体尿气味的识别能力,通过一雄两雌配对实验建立实验种群,从而产生同胞、父系半同胞和陌生个体。在行为选择箱中记录了雌、雄根田鼠对亲属系数分别为0、0.25 和0.5 异性尿气味的行为响应模式。结果如下:雌性根田鼠对3 种不同亲属关系雄鼠气味的接近潜伏期的差异达到极显著水平(P < 0.01),嗅闻时间的差异也达到显著水平(P <0.05),而嗅闻频次和反标记的差异均未达到显著水平(P >0.05)。雄性根田鼠对3 种不同亲属关系雌鼠气味的接近潜伏期和嗅闻时间的差异都未达到显著水平(P >0.05)。对不同亲属关系的气味嗅闻频次和反标记的比较分析表明,三者间的差异也未达到显著水平(P >0.05)。因此,雌性根田鼠能够识别不同亲属关系异性气味并对不同气味表现出不同的行为响应模式;而雄鼠不能识别3 种气味并对其表现出类似的行为模式。     

根田鼠粪便皮质酮的检测效能

为验证根田鼠粪便皮质酮的可检测效能,本研究检测根田鼠粪便皮质酮含量的昼夜变化,并检测急性应激后和慢性应激期间根田鼠粪便皮质酮含量变化,及其慢性应激个体的HPA 轴负反馈功能。结果表明,根田鼠粪便皮质酮水平具有明显的似昼夜节律,粪便中皮质酮含量的最高点出现在08:00 和24:00,最低点在12:00 和16:00;在终止急性应激12 h 后,根田鼠粪便皮质酮含量显著增加,且有性别间差异;慢性应激根田鼠粪便皮质酮含量始终保持在高水平;再次急性应激,慢性应激根田鼠个体的粪便皮质酮含量较对照个体升高的时间延后。上述结果说明,根田鼠的粪便皮质酮含量能够反映机体所处的生理状态及应激水平,因此,该方法可用于野外根田鼠种群的相关研究并具有可靠性。     

Short photoperiod influences energy intake and serum leptin level in Brandt's voles (Microtus brandtii)

Photoperiod cues play important roles in the regulation of seasonal variations in body mass (BM) and energy balance for many small mammals. The present study was designed to examine the effects of photoperiod acclimation on BM, energy intake, and serum leptin levels in Brandt's voles (Microtus (Lasiopodomys) brandtii). After 4 weeks of acclimation to either long (LD; light:dark, 16:8) or short (SD; 8:16) photoperiod, SD voles had lower BM, body fat mass, and dry mass of liver and kidneys, but higher digestible energy intake in comparison to LD voles. SD voles also showed a lower level of serum leptin than did LD voles. Furthermore, the level of serum leptin was correlated positively with body fat mass and negatively with gross energy intake. Together, these data suggest that Brandt's voles employ a strategy of minimizing body growth, increasing energy intake, and mobilizing fat deposition in response to cues associated with short photoperiod. Furthermore, leptin seems to be involved in the regulation of BM and energy balance mediated by photoperiod.     

根田鼠几种觅食功能反应模型的比较

植物组织空间排列对植食性哺乳动物功能反应的作用,是觅食生态学的热点问题之一。以新鲜紫花苜蓿叶片为食物,改变苜蓿叶片大小调控根田鼠口量,改变叶片间距调控叶片密度,设置叶片空间异质性斑块。在空间异质性斑块上测定根田鼠的觅食行为及其参数,检验植食性哺乳动物4种功能反应模型的预测性。除复合模型参数Rmax、h和Vmax及口量模型参数Rmax的最大似然估计值与测定值近似外,其它模型参数的估计值与测定值均存在较大差异。根田鼠摄入率测定值与4种模型预测值的线性回归均显著(P0.01),但与复合模型预测值的线性拟合效果最佳。表明,复合模型能很好地解释根田鼠觅食与行走的竞争对摄入率调节的动态。根田鼠复合模型存在调节其功能反应机制转变的距离临界值(d)。叶片间距大于该值时,叶片密度调节摄入率;叶片间距小于该值时,口量调节摄入率。结果充分地验证了提出的特定假设:在植物密集条件下,植物大小能调节植食性小型哺乳动物根田鼠的摄入率;在植物稀疏条件下,植物密度调节其摄入率。     

Effects of fasting and refeeding on body mass,thermogenesis and serum leptin in Brandt's voles (Lasiopodomys brandtii)

(1)

To investigate the effect of fasting and refeeding on the body mass, thermogenesis and serum leptin in Brandt's voles, the changes in body and body fat mass, resting metabolic rate (RMR), mitochondrial cytochrome c oxidase (COX) activity in liver and brown adipose tissue (BAT), uncoupling protein 1 (UCP1) content of BAT, serum leptin level and post-fasting food intake were monitored and measured.     

Effects of photoperiod on energy intake, thermogenesis and body mass in Eothenomys miletus in Hengduan Mountain region

The present study was designed to examine whether photoperiod alone was effective to induce seasonal changes in physiology in voles (Eothenomys.) from the Hengduan Mountain region. Eothenomys miletus were randomly assigned into either long photoperiod (LD; 16L: 8D) or short photoperiod (SD; 8L: 16D) for 4 weeks at constant temperature (25 °C). At the end of acclimation, SD voles showed lower body mass and body fat coupled with higher energy intake than LD voles. SD greatly enhanced the thermogenic capacity of E. miletus, as indicated by an elevated nonshivering thermogenesis (NST), mitochondrial protein in brown adipose tissue (BAT); basal metabolic rate (BMR) was also raised. Although no variations in serum leptin levels were found between SD and LD voles, serum leptin levels were positively correlated with body mass and body fat mass, and negatively correlated with energy intake and UCP1 content in BAT, respectively. To summarize, SD alone is effective in inducing higher thermogenic capacities and energy intake coupled with lower body mass and body fat mass in root voles. Leptin is potentially involved in the photoperiod induced body mass regulation and thermogenesis in E. miletus. Our study shows that SD alone is effective.     

单宁酸对高原鼠兔和根田鼠生殖激素的影响

高原鼠兔和根田鼠是生存于青藏高原的小哺乳动物,它们所取食的高原植物含有多种次生化合物。为了证明食物中的次生化合物对高原鼠兔和根田鼠繁殖相关激素的影响,探讨它们与取食植物间的协同进化,分别对两种动物灌服0、5、10 和20 mg/ kg BW 剂量单宁酸1 d、3 d 及5 d 后,测定其下丘脑促性腺激素释放激素、血浆中睾酮和血浆雌二醇的含量。结果表明,单宁酸对高原鼠兔的LD₅₀ 为112 ±27.72 mg/ kg BW,对根田鼠的LD₅₀ 为117 ± 17.37 mg/ kg BW;单宁酸可以使高原鼠兔和根田鼠血浆睾酮和雌二醇水平升高,但对下丘脑促性腺激素释放激素水平没有明显的影响。说明单宁酸可能会促进这两种动物的性成熟,有利于它们的繁殖。