被毛在黑线仓鼠能量代谢、产热和体温调节中的作用

为阐明小型哺乳动物被毛的季节性变化及其在能量代谢和体温调节中的作用,测定了季节性驯化,以及不同光周期和温度驯化的黑线仓鼠的被毛重量、体温和能量收支。结果显示: (1)冬季黑线仓鼠的被毛重量和产热显著高于夏季;(2)短光照(8L∶16D)和低温(5℃ ) 对被毛生长的影响不显著; (3)与室温组(21℃ )相比,低温组(5℃ )摄入能、基础代谢率(BMR)、非颤抖性产热(NST) 、褐色脂肪组织细胞色素c 氧化酶活性和热传导率显著增加,而暖温组(30℃ )显著降低; (4)室温和低温下,剃毛导致摄入能、BMR、NST 和热传导率显著增加;结果表明:被毛的作用与环境温度有关,低温下被毛降低了能量需求,增强了动物应对低温环境的适应能力;被毛的适应性变化是独居的野生小型哺乳动物应对环境温度季节性波动的主要适应策略之一,在其能量代谢和体温调节中具有重要作用和意义。     

Photoperiod and temperature can regulate body mass, serum leptin concentration, and uncoupling protein 1 in Brandt's voles (Lasiopodomys brandtii) and Mongolian gerbils (Meriones unguiculatus)

Environmental factors play an important role in the seasonal adaptation of body mass and thermogenesis in wild small mammals. In this study, we performed a factorial experiment (temperature x photoperiod) in which Brandt's voles and Mongolian gerbils were acclimated to different photoperiods (long photoperiod, 16L : 8D; short photoperiod, 8L : 16D) and temperatures (warm, 23 degrees C; cold, 5 degrees C) to test the hypothesis that photoperiod, temperature, or both together can trigger seasonal changes in serum leptin level, body mass, thermogenesis, and energy intake. Our data demonstrate that Brandt's voles showed a remarkable decrease in body mass in both the cold and a short photoperiod. However, no significant changes in body mass were found for gerbils exposed to similar conditions. The short photoperiod induced a decrease in serum leptin levels for both voles and gerbils that might contribute to an increase in energy intake. Furthermore, the short photoperiod induced an increase of uncoupling protein 1 (UCP1) content for both voles and gerbils, and cold can further enhance the increase in voles. No interactions between photoperiod and temperature were detected for the two species. Brandt's voles can decrease their body mass through changes in energy intake and expenditure, while Mongolian gerbils can keep body mass relatively stable by balancing energy metabolism under winterlike conditions. Leptin was potentially involved in the regulation of body mass and thermogenic capacity for the two species.     

Photoperiod and temperature affect reproductive and nonreproductive functions in male prairie voles (Microtus ochrogaster)

Adult male prairie voles (Microtus ochrogaster) were housed for 10 wk and exposed to long (16L:8D) or short (8L:16D) photoperiods at 21 degrees or 5 degrees C. Maintenance in short day lengths reduced testicular, epididymal, and seminal vesicle mass and also significantly depressed spermatogenic activity. Cold ambient temperature further suppressed gonadal size in voles exposed to short days. Several pelage characteristics were affected by photoperiod, but not by temperature. Increased fur density, fur depth, and length of guard hair and underhair were observed in voles exposed to short days. Intrascapular brown fat and gonadal fat pad mass as well as body mass were significantly less in voles housed in cold temperatures than in voles exposed to warm ambient temperatures; photoperiod did not affect these parameters. Approximately 30% of the male voles exposed to short days maintained their reproductive systems, yet they clearly processed photoperiodic information; all short-day males, regardless of reproductive condition, had comparable winter pelage development. Our results suggest that in prairie voles, photoperiod may be a predictive cue for reproductive function in nature; however, it appears that pelage development is a more obligatory response to photoperiod than is reproduction.     

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.     

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     

Photoperiod and ambient temperature as environmental cues for seasonal thermogenic adaptation in the Djungarian hamster,Phodopus sungorus

For their seasonal control of thermogenesis Djungarian hamsters rely on environmental cueing by both photoperiod and ambient temperature. Their total potential for adaptive improvements of nonshivering thermogenesis is constant in summer and winter. The shortening of photoperiod in fall is used to anticipate about half of the total improvement in thermogenesis, in advance of any experience of cold, as can be concluded from the photoperiodic control of thermogenesis, cold resistance, and the protein content, cyctochrome oxidase activity and content of mitochondria in brown adipose tissue. The remainder of the seasonal thermogenic adaptation is due to stimulatory responses to chronic exposure to cold.This research was supported by the Deutsche Forschungsgemeinschaft, Schwerpunktprogramm Mechanismen der Temperaturregulation und -Adaptation.     

Serum leptin, energy budget, and thermogenesis in striped hamsters exposed to consecutive decreases in ambient temperatures

Leptin has been found to be a direct participant in the regulation of both energy intake and energy expenditure in small mammals showing seasonal declines in body mass (M(b)) and fat mass, but its roles in an animal exhibiting seasonally increased thermogenesis and unchanged M(b) remain unclear. Serum leptin levels, energy budget, and thermogenesis were measured in striped hamsters exposed to consecutive decreases in ambient temperatures ranging from 23° to -23°C. Cold-exposed hamsters had significant increases in gross energy intake (GEI), the rate of basal metabolism, nonshivering thermogenesis, and activity of cytochrome c oxidase (COX) in brown adipose tissue (BAT), compared with control hamsters, indicating a cold-induced elevation of thermogenesis. Body mass and fat content were decreased in cold-exposed animals, and serum leptin levels were increased in hamsters exposed to temperatures of -8°C and below in inverse proportion to body fat content. Serum leptin levels were positively correlated with GEI and BAT COX activity in cold-exposed hamsters, but no such relationships were observed in control animals. These findings suggest that cold-exposed hamsters increase food consumption to meet the energy requirements for increased BAT thermogenesis. The increases in serum leptin levels are likely involved in increased thermogenesis in hamsters under cold stress. Cold-exposed hamsters may become leptin resistant, which is associated with impaired regulation of food intake. This new natural model of leptin resistance may also provide insight into the dynamic long-term control of energy homeostasis for animals that do not exhibit seasonal decline in M(b).     

Photoperiodic regulation in energy intake, thermogenesis and body mass in root voles (Microtus oeconomus)

The present study was designed to examine whether photoperiod alone was effective to induce seasonal regulations in physiology in root voles (Microtus oeconomus) from the Qinghai-Tibetan plateau noted for its extreme cold environment. Root voles were randomly assigned into either long photoperiod (LD; 16L:8D) or short photoperiod (SD; 8L:16D) for 4 weeks at constant temperature (20 degrees 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 thermogenic capacities in root voles, as indicated by elevated basal metabolic rate (BMR), nonshivering thermogenesis (NST), mitochondrial protein content and uncoupling protein-1 (UCP1) content in brown adipose tissue (BAT). 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 root voles.     

暖温经历对雌性黑线仓鼠能量代谢、产热和体脂含量的影响

能量代谢的生理调节是小型哺乳动物应对不同环境温度的重要策略之一,为探讨暖温下代谢产热在体重和体脂适应性调节中的作用和机理,本研究将雌性黑线仓鼠(Cricetulus barabensis)暴露于暖温(30°C)1个月、3个月和4个月,测定体重、摄入能、代谢产热、体脂含量、褐色脂肪组织(BAT)细胞色素c氧化酶(COX)活性和解偶联蛋1 (UCP1) mRNA表达等。结果显示,暖温对黑线仓鼠体重无显著影响,但使脂肪含量显著增加。与室温组相比(21°C),暖温组消化率显著升高,但摄入能和消化能显著降低;暖温下非颤抖性产热(NST)显著降低,脑、肝脏和心脏COX活性、BAT COX活性和UCP1 mRNA的表达显著下调。结果表明,暖温下降低代谢产热补偿了能量摄入的减少,机体处于正能量平衡状态,是脂肪含量显著增加的主要原因之一。脑、肝脏、心脏和BAT代谢活性降低是代谢产热降低的主要机制,与脂肪累积有关。     

Photoperiod and pinealectomy do not affect cold-induced deposition of brown adipose tissue in the long-evans rat

Brown adipose tissue is a major thermogenic effector of cold-induced nonshivering thermogenesis. Previous studies indicate that melatonin and/or short photo-period are involved in the increase in brown fat deposition seen in certain cold-acclimated rodents. The present study was undertaken, in part, to determine whether the pineal is a necessary component in the cold-induced increase in thermogenic capacity characteristic of the cold-acclimated laboratory rat. Under a 12L:12D light cycle, pinealectomized rats did not differ from sham-operated rats in their ability to increase brown fat deposition in the cold (5 °C). Moreover, in a subsequent set of experiments performed at 9 °C, intact rats maintained at a short photoperiod (9L:15D) exhibited the same degree of brown fat hypertrophy/hyperplasia as did those kept at a long photoperiod (15L:9D). These data thus indicate that: (a) the intact pineal is not necessary for the cold-induced increase in brown adipose tissue occurring in the cold-acclimated rat; and (b) photoperiod does not significantly modulate the magnitude of this increase.     

Increased nonshivering thermogenesis, brown fat cytochrome-c oxidase activity, GDP binding, and uncoupling protein mRNA levels after short daily cold exposure of Phodopus sungorus

In their natural environment, burrowing rodents experience rather fluctuating ambient temperatures and are acutely cold exposed only for short periods outside their burrows. The effect of short daily cold exposure on basal metabolic rate, nonshivering thermogenesis, brown fat thermogenesis, and uncoupling protein mRNA was studied in the Djungarian hamster, Phodopus sungorus. They were kept at 23 degrees C and exposed to 5 degrees C daily either for one 4-h period or twice for 2 h (in 12-h intervals). At the same time control hamsters were kept continuously either at thermoneutrality (23 degrees C) or at 5 degrees C. Two 2-h cold exposures daily were sufficient to increase basal metabolic rate and nonshivering thermogenesis to the same level as continuous cold exposure, whereas one 4-h cold period per day did not result in a significant increase of both parameters. Brown fat thermogenesis (as measured by cytochrome-c oxidase activity and GDP binding to the mitochondrial uncoupling protein) increased to the same extent by both treatments with short daily cold exposure. However, this increase was less than in the chronically cold-exposed hamsters. A similar result was found for uncoupling protein mRNA: both short-term cold-exposed hamsters increased uncoupling protein mRNA levels to a similar extent, but less than after chronic cold treatment. It is concluded that short daily cold exposures are sufficient to cause adaptive increases of the capacity of metabolic heat production as well as brown fat thermogenic properties.     

温度和高脂食物对黑线仓鼠代谢产热和体脂累积的影响

能量代谢的适应性调节是小型哺乳动物应对环境季节性变化的主要策略之一。为探讨不同温度下动物在代谢产热能量支出与脂肪累积之间的权衡策略,以成年雄性黑线仓鼠为研究对象开展了3 个实验:实验1 将动物驯化于高脂和低脂食物;实验2 将动物暴露于低温(5℃)和暖温(30℃);实验3 将饲喂高脂食物的动物暴露于低温。以食物平衡法测定摄食量、摄入能和消化率,以开放式氧气分析仪测定代谢产热,以索氏抽提法测定脂肪含量。结果发现,取食高脂食物的黑线仓鼠摄食量显著减少,但脂肪累积显著增加;暖温下摄食量显著减少,但体脂含量显著增加,低温下摄食量显著升高,但体脂含量显著减少;饲喂高脂食物的黑线仓鼠在低温下摄入能显著增加,非颤抖性产热增强,但体脂含量显著降低。结果表明高脂食物对黑线仓鼠体脂累积的影响与环境温度有关,低温诱导脂肪动员,暖温促进脂肪贮存;低温下黑线仓鼠增加能量摄入不能完全补偿用于产热的能量支出,导致脂肪动员增加;暖温下代谢产热降低是脂肪累积的主要因素;与能量摄入相比代谢产热的能量支出在体脂累积的适应性变化中发挥更重要的作用。     

Biological distribution and significance of brown adipose tissue

1. The structure, location, identification and thermogenic function of brown adipose tissue is discussed before describing its distribution in animals. 2. With a few interesting exceptions, brown fat occurs almost exclusively in mammals. 3. This tissue has been positively identified in thirteen orders, but more thorough investigations are required before its absence can be confirmed in the remaining eight mammalian orders. 4. Factors influencing the amount and activity of brown fat seen between and within species are numerous, but some of the most important are body size, diet, environmental temperature, age and reproductive state. 5. The role brown fat, and the effects of impairments in its function, are described in relation to thermoregulation and the control of energy balance and body composition.     

晚成性哺乳动物体温调节能力的胎后发育

按照体温调节能力的发育情况,哺乳动物的生长发育可分为早成性、晚成性和未成熟性3类。本文主要综述了晚成性哺乳动物体温调节能力的发育特点。这类动物的幼体出生时一般身体裸露,热传导率较高,产热能力较差,不能进行有效的体温调节。当环境温度低于热中性区时,单独的个体不能维持较高的恒定体温。但晚成性幼体也具有一定的体温调节能力,当受低温刺激时,即使新生幼体也会具有增加代谢率的反应;同时结合亲体关怀和幼体之间的聚群效应以及巢的保温作用等方式,仍能使其体温维持在一个较高的水平。晚成性幼体生理性产热的不足,也可看作是一种有利的特点,这样可以减少能量在体温调节方面的消耗,从而增加用于生长发育的能量。文章最后对可能的发展方向进行了展望。     

光照和温度对根田鼠褐色脂肪组织产热能力的影响

测定了根田鼠在室内驯化2周后褐色脂肪组织（BAT）的蛋白含量、线粒体蛋白含量和细胞色素C氧化酶活性的变化。动物进行如下4种处理:23℃,16L:8D;23℃,8L：16D;5℃,16L：8D和5℃,8L:16D.。结果表明,短光照可刺激根田鼠的BAT线粒体细胞色素C氧化酶的活性增加;低温驯化可导致根田鼠的BAT线粒体蛋白含量增加;短光照加低温可进一步促进酶的活性增加。结合个体水平的产热特点,说明根田鼠在产热能力的季节驯化过程中,光周期是一主要的季节调节信号,环境温度进一步增强光照的作用,环境温度和光周期共同作用以诱导其产热能力等方面的生理调节。研究结果支持了环境温度和光周期共同作用以调节动物产热变化的学说。     

Thermogenesis, energy intake and serum leptin in Apodemus chevrieri in Hengduan Mountains region during cold acclimation

Environmental factors play an important role in the seasonal adaptation of body mass and thermogenesis in small, wild mammals. The purpose of the present study was to test the hypothesis that ambient temperature was a cue to trigger the adjustments in body mass, energy intake, and serum leptin level in Apodemus chevrieri during 42 days of cold exposure. Our data demonstrated that cold acclimation induced a decrease in body mass and a significant increase in energy intake in A. chevrieri. Serum leptin levels were positively correlated with body mass and fat mass. These data suggest that A. chevrieri reduced the body mass and increased energy intake and thermogenic capacity under cold acclimation. Further, serum leptin appears to be involved in the energy intake regulation and thermoregulation.     

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.     

Seasonal changes in body mass, energy intake and thermogenesis in Maximowiczi’s voles (Microtus maximowiczii) from the Inner Mongolian grassland

Small mammals inhabiting temperate and arctic regions exhibit annual adaptive adjustments in physiology, anatomy, and behavior. No data on the physiology of Maximowicz’s voles (Microtus maximowiczii) are available at present. Here we examined the seasonal changes in body mass, food intake, thermogenic capacity, serum leptin and thyroid hormone levels in wild-captured individuals from Inner Mongolian grassland, China. We further examined the effects of photoperiod on these parameters. Energy intake, resting metabolic rate, nonshivering thermogenesis (NST), and serum tri-iodothyronine (T3) levels increased while serum leptin and body mass decreased in the cold seasons. Serum T3 levels were positively correlated with NST and uncoupling protein 1 (UCP1) contents in brown adipose tissue, and leptin levels were negatively correlated with energy intake and resting metabolic rate. Furthermore, laboratory data showed these changes could be induced by short photoperiod alone. Taken together, our results indicate that Maximowicz’s voles can increase thermogenic capacity and energy intake to cope with cold stress. Serum leptin seems to be involved in the regulation of energy intake and changes in T3 level may be important for the variations in NST and/or UCP1. Short photoperiod can serve as a seasonal cue for the winter acclimatization of energy balance in free-living Maximowicz’s voles.     

Photoperiod perception in the blind mole rat (Spalax ehrenbergi, Nehring): involvement of the Harderian gland, atrophied eyes, and melatonin

The involvement of the Harderian gland, atrophied eyes, and melatonin in the perception of photoperiodic changes has been studied in the mole rat, a fossorial blind mammal the thermoregulatory capacity of which is photoperiod-dependent. When transferred from a long photoperiod to a short one, mole rats increase their resistance to cold, a perfectly reversible phenomenon. After 2 weeks under short photoperiod the thermoregulatory capacities of animals without Harderian glands are less than those of the controls. The Harderian gland appears thus to be implicated in the detection of photoperiodic changes. After 5 weeks, however, the Harderianectomized animals had perfectly integrated the photoperiodic change, so demonstrating that other photoreceptor organs exist. The atrophied eyes, which, under these conditions, do not seem to play an important role, are involved when the animals are transferred from short photoperiod to long photoperiod. Melatonin, but not 5-methoxytryptamine, appears to be a crucial compound in such a phenomenon. These results, which demonstrate that in mammals (at least in the mole rat, as in nonmammalian vertebrates), nonocular photoreceptors exist, suggest that the mechanism by which mammals integrate photoperiodic changes is not the same when the animals are transferred from long to short photoperiod as when transferred from short photoperiod to long photoperiod.     

光周期和高脂食物对雌性高山姬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,将成年雌性高山姬鼠分别驯化于长光照低脂、高脂食物和短光照低脂、高脂食物条件下,7周后测定动物的体重、能量摄入、产热、身体组成、血清瘦素浓度以及体脂含量等参数。结果发现:1)短光照抑制体重增长,降低血清瘦素浓度,增加非颤抖性产热;2)高脂食物使摄入能减少,消化率和体脂含量提高,但未显著影响体重、基础代谢率、非颤抖性产热和血清瘦素浓度;3)血清瘦素浓度与摄入能不相关,但与体脂重量正相关。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,高山姬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。