冷环境中解偶联蛋白对动物体温的调节作用

解偶联蛋白属线粒体内膜栽体蛋白,存在动物体的棕色脂肪组织(brown adiposetissue,BAT)、白色脂肪组织(white adipose tissue,WAT)、骨胳肌以及各种器官中.这些组织器官是哺乳动物及禽类非颤抖产热(NST)及其它产热作用的主要点位,对动物的体温维持乖能量平衡调节起重要作用.     

影响棕色脂肪代谢的调控因素及其应用

脂肪组织分为两类,一类是白色脂肪组织,而另一类则是棕色脂肪组织。棕色脂肪组织(BAT)呈棕色,含有丰富的毛细血管,脂肪细胞内分散着大量小脂滴,线粒体大而丰富,细胞中央有圆形的核。棕色脂肪与白色脂肪之间存在着相互转化的关系,棕色脂肪对扩大动物生态位和增强动物适应外界环境突然改变的能力以及保障幼畜的成活具有重要作用。它还可为治疗人类肥胖以及调节畜禽动物肌内脂肪含量提供研究思路和参考。文章综述了国内外棕色脂肪组织的研究进展,主要从发现过程、调控因素和应用等三个方面进行总结,并对棕色脂肪在未来对人类健康以及动物在肉质和生长代谢方面的育种应用进行展望。     

解偶联蛋白mRNA研究进展

解偶联蛋白（UCPs）是机体组织特异表达的线粒体内膜蛋白质，有阻止肥胖的作用。UCPs有5种同族体，UCP1在啮齿类动物调节动物体重、维持体温有重要作用。UCP2主要存在于成年大型动物和人类，与糖尿病有关，UCP3主要存在于骨骼肌一啮齿类动物的棕色脂肪组织中，提供非颤抖的生热作用。UCP4是小鼠和非人类的灵长目动物大脑特有的线粒体UCPs同族体，可能与控制食欲有关。UCP5存在于人和小鼠的多 , 大脑和附睾特别丰富，受寒冷和绝食的影响，在UCPs转基因或基因敲出的实验动物可改善肥胖症，UCPs同族体受到多种因子调控。食物调节影响UCPs mRNA同族体在不同组织的特异表达。高等植物线粒体UCPs同族体PUMP、stUCP也有同样的解偶联作用。     

棕色脂肪组织的生理功能及影响因素

棕色脂肪组织是哺乳动物体内非颤栗产热的主要来源,对于维持动物的体温和能量平衡起重要作用,对幼龄哺乳动物尤为重要。文中阐述了棕色脂肪组织的产热机制,介绍了影响棕色脂肪细胞的分化、决定棕色脂肪组织生理功能的关键因素解偶联蛋白和PPARγ的辅助激活因子PGC-1α,讨论了影响棕色脂肪组织功能的因素。棕色脂肪组织生理功能和影响因素的研究,对扩大动物生态位和提高动物对环境骤然变化的适应能力以及提高幼畜的成活率十分重要。     

棕色脂肪和米黄色脂肪研究进展

脂肪组织不仅是机体能量储存的主要场所,也是重要的内分泌器官。根据脂肪颜色的不同,动物脂肪组织可分为白色脂肪(WAT)、棕色脂肪(BAT)和米黄色脂肪(Beige)。WAT以甘油三酯的形式储存能量,而BAT是动物非颤抖性产热的主要场所。在一定外界环境刺激下,WAT可以生成一种与BAT功能类似的细胞,称之为Beige细胞。论文对棕色脂肪和米黄色脂肪的功能、增殖与分化机制进行了综述,并对其在畜牧业中的应用进行了展望。     

ZICI、UCP1、LEP基因在成年水牛和黄牛肌肉和脂肪组织中的表达模式比较

为探讨不同类型脂肪细胞在水牛和黄牛肌肉和脂肪组织中的差异,本研究检测了成年槟榔江水牛和夏南牛(黄牛)背最长肌、皮下及肾周脂肪组织中3类脂肪细胞标志基因(ZICI、UCP1、LEP)的mRNA表达水平。结果表明:棕色脂肪标志基因ZIC1在育肥水牛皮脂中的表达量显著高于育肥黄牛和未育肥水牛;米色脂肪标志基因UCP1在育肥水牛皮下脂肪和内脏脂肪中的表达量均显著高于育肥黄牛和未育肥水牛;白色脂肪标志基因LEP主要在脂肪中表达,黄牛肌肉和皮脂中LEP表达量显著或极显著高于水牛。结果提示,育肥可促进水牛白色脂肪棕色化,育肥水牛白色脂肪棕色化水平高于育肥黄牛,育肥水牛皮脂中可能存在棕色脂肪细胞;与黄牛相比,水牛可能具有更强的抗寒潜力,黄牛肌内脂肪和皮下脂肪沉积能力可能高于水牛。     

小鼠棕色脂肪转基因过表达miR-155损坏棕色脂肪细胞的分化

为探究microRNA-155(miR-155)对小鼠棕色脂肪组织分化的影响,收集广泛过表达miR-155的转基因小鼠(RL-m155小鼠)棕色脂肪组织,离体棕色脂肪大体拍照,然后收集部分组织固定、石蜡包埋和切片,并行HE染色,观察棕色脂肪细胞的大小和形态;同时RT-qPCR检测棕色脂肪组织中分化相关基因的表达水平。结果表明,RL-m155小鼠的体重、体型与对照小鼠无显著差异;与对照小鼠相比,RL-m155小鼠棕色脂肪组织中miR-155表达水平显著升高,而棕色脂肪组织体积及棕色脂肪细胞的大小均显著减小;棕色脂肪中特异表达基因(UCP1和SCA-1)、棕色脂肪分化调控因子(BMP2、BMP6、Smad1、Smad5、C/EBPB、MYO10和PTEN)、棕色脂肪分化诱导因子(PPARγ、PGC-1α、BMP2、BMP4、BMP7、BMPR1A和Sirt1)等棕色脂肪分化相关功能基因的mRNA表达水平均显著降低(P<0.05)。表明RL-m155小鼠棕色脂肪组织中miR-155过表达,导致棕色脂肪组织分化受损。     

UCPs基因多态性与脂肪代谢的相关性研究

解偶联蛋白(uncoupling protein,UCPs)是线粒体内膜上具有调节质子跨膜转运作用的载体蛋白,在调节动物能量代谢、脂肪沉积及脂肪酸氧化等方面起着重要作用。到目前为止,至少有5种(UCP1、UCP2、UCP3、UCP4和UCP5)这个家族的蛋白质已经在人类、哺乳动物、禽类、鱼甚至在植物的不同组织线粒体的内膜上被发现。UCPs在能量代谢动态平衡中、机体生热作用、肥胖、糖尿病及自由基代谢中起到重要的作用,解偶联蛋白基因已经被列为参与能量代谢和体温调节的候选基因。大量的研究报道了人类UCPs基因突变对脂肪代谢、糖尿病及其并发症、肥胖症的影响。作者从UCP1、UCP2及UCP3基因的定位、结构、分布、基因的多态突变与脂肪代谢、糖尿病及肥胖症之间的相关性研究进行了综述。     

动物脂肪组织的分化起源

动物脂肪组织是机体重要的器官,主要负责能量的储存和代谢,同时分泌多种脂肪细胞因子(adipokines)参与机体生理功能的调控。脂肪组织的功能紊乱与人类的肥胖病、糖尿病以及代谢综合症密切相关,多年以来动物脂肪组织的细胞分化起源一直是研究的热点。白色脂肪、棕色脂肪和肌肉组织都来源于机体的间充质干细胞(mesenchymal stem cells,MSCs),长期以来,人们一直以为白色脂肪和棕色脂肪的分化起源更加亲近,但随着对棕色脂肪分化机制的深入研究,发现白色脂肪和棕色脂肪在早期发育阶段有着不同的前体细胞,而棕色脂肪组织与肌肉组织的分化支系更加亲近。以往的脂肪分化研究往往利用基质血管组分(stromal vascular fractions,SVF)或肌卫星细胞等混合细胞群作为实验材料,随着流式细胞仪、转基因动物模型和干细胞表面标志抗原识别等技术的发展,使我们可以从这样的混合细胞群中分离得到纯的前体脂肪细胞系,从而提示我们之前的研究可能过高的估计了这样的混合细胞群体的活体分化潜能。进一步深入研究动物脂肪组织的分化起源,有助于我们理解机体脂肪沉积的具体机制,从而为治疗脂肪代谢相关疾病以及提高动物肉品品质提供理论依据。     

冷环境中解偶联蛋白对动物体温的调节作用

解偶联蛋白属线粒体内膜载体蛋白,存在动物体的棕色脂肪组织（brown adipose tissue,BAT）、白色脂肪组织（white adipose tissue,WAT）、骨胳肌以及各种器官中。这些组织器官是哺乳动物及禽类非颤抖产热（NST）及其它产热作用的主要点位,对动物的体温维持和能量平衡调节起重要作用。     

Uncoupling proteins and energy expenditure in mice divergently selected for heat loss

The objective of this study was to determine whether variation in energy expenditure created by selection on heat loss is mediated by uncoupling protein-1 (UCP1) in brown adipose tissue. Divergent selection for heat loss developed lines of mice with high (MH) and low (ML) maintenance energy expenditure. Concentration of UCP1 mRNA in brown adipose tissue (BAT) was 93% greater in ML than in MH mice (P < 0.02). Two new lines of mice, KH and KL, were bred by backcrossing a UCP1 knockout gene into the MH and ML lines, respectively; KH and KL with both knock-out (-/-) and wild type (+/+) UCP1 genotypes were generated. At 13 wk of age, KH mice exhibited greater heat loss (166 kcal x kg(0.75) x d(-1)) than KL mice (126.4 kcalkg(0.75) x d(-1)) regardless of the UCP1 knockout (P < 0.0001). Concentration of UCP2 mRNA in BAT was 74% greater in UCP1 knockout mice (-/-) than in wild type (+/+; P = 0.0001). We conclude that response to selection for increased energy expenditure was not mediated by increased expression or function of UCP1.     

Brown adipose tissue development and metabolism in ruminants

We conducted several experiments to better understand the relationship between brown adipose tissue (BAT) metabolism and thermogenesis. In Exp. 1, we examined perirenal (brown) and sternum s.c. adipose tissue in 14 Wagyu x Angus neonates infused with norepinephrine (NE). Perirenal adipocytes contained numerous large mitochondria with well-differentiated cristae; sternum s.c. adipocytes contained a few, small mitochondria, with poorly developed cristae. Lipogenesis from acetate was high in BAT but barely detectable in sternum s.c. adipose tissue. In Exp. 2, we compared perirenal and tailhead adipose tissues between NE-infused Angus (n = 6) and Brahman (n = 7) newborn calves. Brahman BAT contained two-to-three times as many total beta-receptors as Angus BAT. The mitochondrial UCP1:28S rRNA ratio was greater in Brahman BAT than in BAT from Angus calves. Lipogenesis from acetate and glucose again was high, but lipogenesis from palmitate was barely detectable. Tail-head s.c. adipose tissue from both breed types contained adipocytes with distinct brown adipocyte morphology. In Exp. 3, three fetuses of each breed type were taken at 96, 48, 24, 14, and 6 d before expected parturition, and at parturition. Lipogenesis from acetate and glucose in vitro decreased 97% during the last 96 d of gestation in both breed types, whereas the UCP1 gene expression tripled during gestation in both breed types. At birth, palmitate esterification was twice as high in Angus than in Brahman BAT and was at least 100-fold higher than in BAT from NE-infused calves from Exp. 2. Uncoupling protein-1 mRNA was readily detectable in tailhead s.c. adipose tissue in all fetal samples. In Exp. 4, male Brahman and Angus calves (n = 5 to 7 per group) were assigned to 1) newborn treatment (15 h of age), 2) 48 h of warm exposure (22 degrees C) starting at 15 h of age, or 3) 48 h of cold exposure (4 degrees C) starting at 15 h of age. Brahman BAT adipocytes shrank with cold exposure, whereas Angus BAT adipocytes did not. Similarly, BAT from neonatal lambs (Exp. 5; n = 6 per group) was depleted of lipid in response to cold exposure, although UCP1 gene expression persisted. In Exp. 4, NE stimulated lipogenesis from palmitate in BAT incubated in vitro. Lipogenesis from palmitate was higher in Angus than in Brahman BAT, and increased with both warm and cold exposure. These studies suggest that BAT from Brahman calves may be exhausted of lipid shortly after birth during times of cold exposure.     

Molecular and histological evidence of brown adipose tissue in adult cats

Brown adipose tissue (BAT) can influence glucose, lipid, and energy metabolism in rodents. Active BAT is now known to be present in adult humans, and interventions targeting BAT are being investigated for the treatment of human obesity and disorders of glucose and lipid metabolism. Domestic cats, like humans, are at increasing risk for obesity and diabetes but little is known about the presence and role of BAT in adult cats. The purpose of this study was to determine if brown adipocytes, identifiable by histological features and molecular markers, were present in the fat depots of adult cats. Adipose tissue samples from intrascapular, perirenal, and subcutaneous depots of eleven 8–12 year old cats (6 lean, 5 obese), were analyzed by real-time PCR for brown adipocyte markers uncoupling protein 1 (UCP1) and Type II iodothyronine 5′deiodinase (D2), by histological examination and by immunohistochemistry for UCP1.UCP1 mRNA was detectable in interscapular and subcutaneous depots in all cats, and in the perirenal depot in 10/11 cats. D2 mRNA was detectable in all depots from all cats. Multilocular adipocytes were identified in the interscapular depots of 4/11 cats and these were positive for UCP1 immunoreactivity. The results demonstrate that UCP1-expressing brown adipocytes are present in multiple depots of adult lean and long-term obese cats, even at 8–12 years of age. It is possible that dietary components or pharmacological agents that influence brown fat activity could exert a relevant biological effect in cats.     

Metabolism and morphology of brown adipose tissue from Brahman and Angus newborn calves

The objective of this study was to compare adipocyte morphology and lipogenesis between breed types (Angus vs Brahman) in brown adipose tissue (BAT) and white adipose tissue (WAT) from newborn calves. The Brahman calves (n = 7) were born during the fall season, whereas the Angus calves were born in fall (n = 6) or the following spring (n = 4). At parturition, Brahman cows were lighter than fall Angus cows, but were heavier than spring Angus cows (P < .05). Birth weights and perirenal BAT weights were greater in spring-born, but not in fall-born Angus calves, than in Brahman calves (P < .05). Fall-born Angus BAT contained 63% more (P < .05) adipocytes/100 mg tissue and contained a greater proportion (P < .05) of adipocytes with mean diameters of 40 to 50 microm, and fewer adipocytes with diameters of 60 microm or greater, than Brahman BAT. Brahman BAT contained two-to-three times as many beta-receptors as Angus BAT (P < .05), although the dissociation constant (Kd) was not different between breed types. Mitochondria in Brahman BAT were primarily spherical, whereas Angus BAT mitochondria were elongated, and mitochondrial cross-sectional area tended (P = .08) to be greater in Brahman BAT than in Angus BAT. The mitochondrial uncoupling protein (UCP) mRNA concentration (per 10(6) cells) was greater in Brahman BAT than in BAT from fall-born Angus calves. Lipogenesis from acetate was greater in Angus BAT than in Brahman BAT (P < .05), and glucose and palmitate contributed a greater proportion of carbon to lipogenesis in Brahman BAT than in Angus BAT. These differences in lipogenesis between breed types were not observed in s.c. WAT. The WAT from both breed types contained adipocytes with distinct brown adipocyte morphology, suggesting an involution of BAT to WAT in utero. We conclude that differences in UCP gene expression cannot cause the greater peak thermogenesis of Angus calves; however, differences between breed types in lipid metabolism and(or) mitochondrial morphology may contribute to this phenomenon.     

冷刺激小鼠脂肪组织差异表达长链非编码RNA的初步研究

脂肪组织主要有白色脂肪组织(WAT)和褐色脂肪组织(BAT)两种类型;WAT储存能量,BAT通过特异性表达解耦联蛋白1(uncoupling protein 1,UCP1)消耗能量产热。与BAT不同,WAT具有很强的可塑性,在寒冷刺激下,呈现褐色脂肪表型、获得褐色脂肪的产热活性("褐色化")。根据对冷刺激组(6℃)和对照组(28℃)小鼠的肩胛区褐色脂肪组织(iBAT)和皮下白色脂肪组织(sWAT)的RNA转录组测序分析结果,初步筛选出1个差异明显的长链非编码RNA (lncRNA-6030408B16Rik)。通过qRT-PCR检测lncRNA-6030408B16Rik在野生型小鼠的脾脏、肌肉、肾脏、十二指肠、大脑、肝脏、sWAT和iBAT中的表达;24只雄性C57BL/6野生型小鼠随机分成冷刺激组(6℃)和对照组(28℃),两组小鼠分别在6和28℃环境下处理10 d,分别采集两组的iBAT和sWAT;并分离出生1 d的野生型小鼠褐色前脂肪细胞,诱导分化后,收集0、1、3、5 d的细胞,检测UCP1基因和lncRNA-6030408B16Rik在分化过程中的时空表达。qRT-PCR结果显示iBAT和sWAT中lncRNA-6030408B16Rik的表达量均明显高于其他组织;与对照组相比,冷刺激组iBAT中lncRNA-6030408B16Rik的表达量极显著上调(P<0.01),冷刺激组sWAT中lncRNA-6030408B16Rik的表达量显著上调(P<0.05);前脂肪细胞诱导分化的过程中,lncRNA-6030408B16Rik的表达量呈先上调后下调的趋势。lncRNA-6030408B16Rik在脂肪组织中特异性高表达。lncRNA-6030408B16Rik可能对白色脂肪组织"褐色化"及褐色前脂肪细胞的分化具有重要的调控作用。     

Ontogenic development of brown adipose tissue in Angus and Brahman fetal calves

Brahman calves experience greater neonatal mortality than Angus calves if cold-stressed. To establish a developmental basis for this, three fetuses of each breed type were taken at 96, 48, 24, 14, and 6 d before expected parturition, and at parturition. Overall fetal BW tended (P = 0.08) to be greater for Angus than for Brahman fetuses. There was no difference between breed types in total brown adipose tissue (BAT) mass or grams of BAT/kg BW. Brown adipocyte density decreased 56%, whereas lipogenesis from acetate and glucose in vitro decreased 97% during the last 96 d of gestation in both breed types. Glycerolipid synthesis from palmitate declined by 85% during the last trimester but still contributed 98% to total lipid synthesis at birth. The fetal age x breed interaction was significant for lipogenesis from glucose (P = 0.05) and palmitate (P = 0.005); rates were higher at 96 d before birth in Brahman BAT but declined to similar rates by birth. Uncoupling protein-1 (UCP1) mRNA tripled during gestation in both breed types (P = 0.002), whereas mitochondrial cross-sectional area did not change (P = 0.14) during gestation. Neither the breed nor the age x breed effect was significant (P > or = 0.24) for UCP1 mRNA concentration or mitochondrial cross-sectional area. In both breed types, a marked decrease in BAT UCP1 mRNA between 24 and 14 d prepartum was associated with a similar reduction in lipogenesis from palmitate and a noticeable change in BAT mitochondrial morphology, as the mitochondria became more elongated and the cristae became more elaborate. Uncoupling protein-1 mRNA initially was elevated in Angus tailhead s.c. adipose tissue, but was barely detectable by birth, and tended to be greater overall (P = 0.09) in Angus than in Brahman BAT. If uncoupling protein activity in s.c. adipose tissue persists after birth, then s.c. adipose tissue may contribute more to thermogenesis in Angus newborn calves than in Brahman calves. In contrast, we did not observe differences in ontogenic development of perirenal BAT that could explain the documented differences in thermogenic capacity between Angus and Brahman newborn calves.     

Molecular cloning and tissue distribution of uncoupling protein 1 (UCP1) in plateau pika (Ochotona dauurica)

Uncoupling protein 1 (UCP1) is present exclusively in brown adipose tissue, and contributes to body temperature control during cold exposure. We cloned UCP1 cDNA of plateau pika (Ochotona dauurica), a small, non-hibernating, diurnal lagomorph that inhabits in relatively cold climates and at high altitudes in Mongolia and in northern China. The nucleotide sequence of pika UCP1 was highly homologous to UCP1 of other species, and the deduced amino acid sequence had some common domains for UCP, including six mitochondrial carrier protein motifs and a putative purine-nucleotide binding site. RT-PCR and Western blot analyses revealed that both UCP1 mRNA and protein were expressed exclusively in the interscapular adipose tissue. These results suggest that pika UCP1 contributes to heat production in brown adipose tissue, as do those in other species.     

苏尼特羔羊褐色脂肪鉴定及特征研究

哺乳动物脂肪组织主要可以分为白色脂肪组织和褐色脂肪组织,无论细胞形态还是功能,褐色脂肪与白色脂肪都有较大差别。褐色脂肪在哺乳动物产热以及能量平衡方面发挥着重要作用。为探究绵羊褐色脂肪分布特点,本研究采集了出生1、7和30 d苏尼特羊的肾周、颈部、背部、尾部、胸部、腹股沟和心包脂肪,通过HE染色、透射电镜和免疫组织化学鉴定脂肪组织类型,并通过实时荧光定量PCR和Western blot探究苏尼特羔羊不同日龄以及不同部位褐色脂肪的特点。结果发现,苏尼特羔羊体内存在两种不同类型的脂肪细胞,多室小脂滴的褐色脂肪细胞和空泡状脂滴的白色脂肪细胞。褐色脂肪细胞内有嵴的线粒体较多,并检测到褐色脂肪组织特异性蛋白UCP1的表达。而白色脂肪细胞内很少有带规则嵴的线粒体,不表达UCP1。出生1和7 d时褐色脂肪细胞数量及UCP1表达无显著差异,但出生30 d时明显下降。本研究通过形态学观察和标记基因以及蛋白检测鉴定了苏尼特羔羊的褐色脂肪和白色脂肪,证明了肾周脂肪和尾部脂肪分别是褐色脂肪以及白色脂肪的主要来源部位。出生1和7 d时苏尼特羔羊体内褐色脂肪较多,出生30 d时褐色脂肪的表型变化较大,呈现下降的趋势。本文探究了苏尼特羔羊褐色脂肪的特点,为反刍动物褐色脂肪研究提供了一定的基础。