冷暴露下下丘脑调节脂肪组织褐变产热研究进展

冷暴露是导致畜禽生产力低下的应激源之一，是负责非颤抖性产热的棕色脂肪组织（BAT）和诱导性棕色脂肪（iBAT）主要生理激活因子。下丘脑是机体脂肪储存和消耗中的主要控制中心。文章综述下丘脑不同区域和神经元参与调节白色脂肪组织（WAT）褐变和BAT产热的研究进展、下丘脑通过交感神经系统作用于脂肪细胞的腺苷酸活化蛋白激酶（AMPK）信号通路、调控脂肪细胞褐变及产热机理，旨在深入了解冷暴露下畜禽产热机制，为在生产中降低其维持能量、提高生产性能和动物福利水平提供参考。     

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。     

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.     

日粮鱼油对高脂日粮饲喂小鼠发情周期和机体产热的影响

本研究旨在探讨鱼油对高脂日粮饲喂小鼠发情周期和机体代谢产热的影响。试验选用36只4周龄C57BL/6 J雌性小鼠,随机分成3组（n=12）：对照组、高脂组和高脂+鱼油组。对照组饲喂标准啮齿动物饲料（AIN-93G）,高脂组和高脂+鱼油组分别饲喂高脂日粮（脂肪提供60%能量）和添加5%鱼油（等能替代猪油）的高脂日粮。试验期间,对小鼠体组成（12周龄）、整体代谢（16周龄）、褐色脂肪温度（18周龄）、体核温度（直肠温度,18周龄）和发情周期（20周龄）等进行检测。试验结束后,眼球采血分离血清,检测促卵泡激素（follicle-stimulating hormone,FSH）和雌二醇（estradiol,E2）的水平。此外,采集皮下脂肪、腹部脂肪和肩胛间褐色脂肪,称重并使用Western blot检测脂肪组织中产热相关基因的蛋白表达（UCP1、Cyto C）,使用实时荧光定量PCR检测褐色脂肪组织中产热基因的mRNA表达（UCP1, PRDM16,PGC1α,Cidea,Elovl3）。结果显示,与对照组相比,高脂日粮显著增加了小鼠的体脂含量（12周龄）及皮下和腹部脂肪的沉积量（21周龄）（P<0.05）,而添加鱼油显著降低了高脂饮食引起的体脂含量增加（P<0.05）。另外,高脂日粮导致小鼠的发情周期紊乱,伴随着周期延长、发情期缩短,以及血清中FSH和E2的水平降低（P<0.05）,而添加鱼油可缓解高脂日粮导致的小鼠发情周期紊乱,提高血清中FSH和E2的水平（P<0.05）。同时,添加鱼油可增加高脂饲喂小鼠肩胛间褐色脂肪（interscapular brown adipose tissue,iBAT）和腹股沟白色脂肪（inguinal white adipose tissue,iWAT）中产热相关基因的表达（P<0.05）,进而促进iBAT激活/产热和iWAT褐色化。结果提示,日粮鱼油可缓解高脂日粮导致的发情周期紊乱,可能与BAT激活和WAT褐色化造成的机体代谢产热增强有关。     

胸腺上皮细胞中雌激素诱导lncRNA的鉴定分析及表达载体构建

为研究胸腺上皮细胞(thymic epithelial cells,TECs)中雌激素(estradiol,E2)对长链非编码RNA(long non-coding RNA,lncRNA)表达的调节作用,本研究首先培养小鼠胸腺髓质上皮细胞系1(medullary thymic epithelial cell line 1,MTEC1),经50 nmol/L E2作用24 h后,观察对细胞表型变化的影响,并用CCK-8试剂盒检测细胞活力;提取细胞总RNA,运用实时荧光定量PCR技术验证E2对lncRNA-2410006H16Rik表达的调节作用;最后运用RT-PCR技术扩增其目的基因,构建pEGFP-N1-lncRNA-2410006H16Rik重组过表达载体。结果显示,50 nmol/L E2能够明显抑制MTEC1的增殖,且相较于对照组细胞,50 nmol/L E2处理组细胞的D450 nm值极显著降低(P<0.01),表明其细胞活力极显著下降。实时荧光定量PCR结果显示,在E2作用下,lncRNA-2410006H16Rik在MTEC1细胞中的表达极显著上调(P<0.01),约是对照组的2倍,与高通量测序结果一致。经RT-PCR、双酶切及测序结果分析显示,试验成功构建pEGFP-N1-lncRNA-2410006H16Rik表达载体。结果表明,TECs中lncRNA-2410006H16Rik的表达与E2作用密切相关,为后续在细胞水平上进一步验证lncRNA-2410006H16Rik的调节功能奠定了基础。     

胸腺上皮细胞中雌激素诱导lncRNA的鉴定分析及表达载体构建

为研究胸腺上皮细胞（thymic epithelial cells,TECs）中雌激素（estradiol,E₂）对长链非编码RNA（long non-coding RNA,lncRNA）表达的调节作用,本研究首先培养小鼠胸腺髓质上皮细胞系1（medullary thymic epithelial cell line 1,MTEC1）,经50 nmol/L E₂作用24 h后,观察对细胞表型变化的影响,并用CCK-8试剂盒检测细胞活力;提取细胞总RNA,运用实时荧光定量PCR技术验证E₂对lncRNA-2410006H16Rik表达的调节作用;最后运用RT-PCR技术扩增其目的基因,构建pEGFP-N1-lncRNA-2410006H16Rik重组过表达载体。结果显示,50 nmol/L E₂能够明显抑制MTEC1的增殖,且相较于对照组细胞,50 nmol/L E₂处理组细胞的D_{450 nm}值极显著降低（P<0.01）,表明其细胞活力极显著下降。实时荧光定量PCR结果显示,在E₂作用下,lncRNA-2410006H16Rik在MTEC1细胞中的表达极显著上调（P<0.01）,约是对照组的2倍,与高通量测序结果一致。经RT-PCR、双酶切及测序结果分析显示,试验成功构建pEGFP-N1-lncRNA-2410006H16Rik表达载体。结果表明,TECs中lncRNA-2410006H16Rik的表达与E₂作用密切相关,为后续在细胞水平上进一步验证lncRNA-2410006H16Rik的调节功能奠定了基础。     

脂蛋白脂酶(LPL)生理功能及特异表达

脂蛋白脂酶(lipoprotein lipase,LPL)是甘油三酯降解为甘油和游离脂肪酸(FFA)反应的限速酶,与机体的脂质代谢及肥胖与否密切相关.白色脂肪组织(WAT)中的LPL活性升高有助于机体脂质的贮存,棕色脂肪组织(BAT)的LPL活性与机体产热有关,而骨骼肌的LPL活性升高有利于机体利用能量.动物饥饿或禁食,下调控LPLmRNA;动物补饲,上调控脂肪-LPL活力.胰岛素可增加脂肪细胞内LPL活性,轻度降低骨骼肌LPL活性;儿茶酚胺和β-肾上腺素能制剂(AMP)在脂肪组织或脂肪细胞中抑制LPL活性,在心肌和骨骼肌却是提高LPL活性.     

绵羊褐色脂肪活性影响因素的研究进展

褐色脂肪细胞的结构和功能都与白色脂肪不同,其细胞富含线粒体,能够利用过剩的能量代谢底物进行产热,是幼龄哺乳动物非颤抖性产热的主要热量来源,在维持机体能量平衡方面具有重要作用。其产热过程由细胞线粒体内膜上的解偶联蛋白1(UCP1)介导,机体所处环境以及对激素的响应都可以影响褐色脂肪的活性。受到刺激后,褐色脂肪细胞表面的肾上腺素受体得到激活,激发细胞内的级联反应,同时使产热相关基因表达增强,增加能量消耗,减少脂肪沉积。褐色脂肪已经成为治疗肥胖以及能量代谢相关疾病的潜在靶点。鉴于褐色脂肪在脂肪沉积以及能量代谢方面的作用,关于畜禽褐色脂肪的研究也越来越深入。作者归纳了绵羊褐色脂肪的相关研究,主要包括影响绵羊褐色脂肪活性的环境因素如冷刺激、营养限制、长期缺氧和饲喂添加剂,以及激素因子(催乳素及其受体、甲状腺激素、瘦素、生殖激素),以期为绵羊产热脂肪的应用研究提供一定的理论依据。     

脂肪细胞的分化作用及其调控

白色脂肪组织 (WAT)是体内贮能的主要场所 ,主要由脂肪细胞组成 ,对维持体内能量平衡发挥重要作用。脂肪细胞的生长包括其体积的增大和新脂肪细胞的生成。新生动物脂肪组织的增长主要是新脂肪细胞的生长 ,即通过脂肪细胞分化 ,成年动物以脂肪细胞的体积变化为主 ,但也保留有脂肪细胞的分化能力。脂肪细胞增殖、分化异常 ,会引起脂肪组织过多堆积 ,导致肥胖 ,进而由肥胖引起的一系列心血管和代谢疾病。本文就细胞分化及其调控机理的研究状况做一概述。1　脂肪细胞的分化程序脂肪细胞分化的过程大致为 :1 )前脂肪细胞发生克隆性增生 ,细胞数…     

猪甘油三酯水解酶和激素敏感脂酶基因表达规律的研究

利用半定量RT-PCR法分析比较了甘油三酯水解酶(Triacylglycerol hydrolase,TGH)和激素敏感脂酶(Hormone-sensitive lipase,HSL)基因在不同猪种、不同发育阶段及不同部位脂肪组织中转录表达的差异,探讨其在猪脂肪组织的表达规律。结果显示,脂肪型个体TGHmRNA表达丰度显著低于瘦肉型和杂交型个体,成年猪较初生仔猪低,皮下、腹膜和内脏脂肪组织中TGH表达量依次递增;其变化规律与HSL相同。此外,对分离培养的原代前体脂肪细胞通过诱导分化和油红O染色区分分化状态,分析TGHmRNA表达的时序变化,发现TGH在前脂肪细胞中不转录表达,诱导分化后开始表达,且在诱导分化第4天表达量最高,分化第10天表达量下降,达到峰值的时间较HSL早。结果表明,TGH的表达与个体肥胖程度、年龄、脂肪组织部位以及脂肪细胞分化程度相关,同时,在脂肪细胞分化过程中,TGH表达峰值早于HSL,提示TGH在脂肪细胞发育过程中可能较早承担基础脂解作用。     

The response of adipose tissues to Mycoplasma pulmonis and Sendai virus infection in C57BL/6 and DBA/2 mice

Adipose tissues in mammals are categorized into white and brown adipose tissues in which cellular morphology, cell functions, and tissue distribution are different. White adipose tissue (WAT) plays a major role in energy reservation, while brown adipose tissue (BAT) mainly relates to the thermoregulation of the body. One interesting function of adipose tissue is the response to the infection, especially the pathogens that cause pneumonia. We have previously reported that DBA/2 (D2) mice are susceptible to pathogens causing pneumonia, Mycoplasma (M.) pulmonis and Sendai virus (SeV), whereas C57BL/6 (B6) mice are resistant to them. Furthermore, morphological alteration of mediastinal fat tissue (MFT) was seen after infection of M. pulmonis in D2 mice but not in B6 mice. In this study, we aimed to exhibit the difference in adipose tissue response in other areas, including interscapular brown adipose tissue (iBAT), inguinal white adipose tissue (ingWAT), and perigonadal WAT (perigoWAT) between resistant strain, B6 and susceptible strain, D2 after challenging them with M. pulmonis and SeV. Compared with B6 mice, D2 mice showed an increase in fat-associated lymphoid cluster in MFT, an increase in BAT in both iBAT and ingWAT after M. pulmonis and SeV infection. The results of this study indicate that pneumonia caused by M. pulmonis and SeV infection induces browning of adipocyte, suggesting that BAT plays a role in pathogen infection and inflammation.     

解偶联蛋白与动物的冷适应

动物的脂肪组织为棕色脂肪组织(brow n ad ipose tissue,BAT)和白色脂肪组织(w h ite ad ipose tissue,W AT)。棕色脂肪组织中含有大量线粒体,是哺乳动物非颤抖产热的主要器官,对动物的体温控制和能量平衡调节起重要作用,位于线粒体内膜的解偶联蛋白(uncoup ling prote in,UCP)的含量和活性是决定其功能的关键因素。作者综述了UCP的结构、UCP基因的多态性及其与肥胖的关系、影响UCPmRNA表达的因素,并对UCP进行了讨论与展望。     

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.     

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。     

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.     

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.     

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。     

Pathology of congenital generalized lipodystrophy in Agpat2-/- mice

Congenital generalized lipodystrophy (CGL) comprises a heterogeneous group of rare diseases associated with partial or total loss of adipose tissue. Of these, autosomal recessive Berardinelli-Seip congenital lipodystrophy (BSCL) is characterized by the absence of metabolically active subcutaneous and visceral adipose tissues. Metabolic abnormalities associated with lipodystrophy include insulin resistance, hypertriglyceridemia, hepatic steatosis, and diabetes. One form of BSCL has been linked to genetic mutations affecting the lipid biosynthetic enzyme 1-acyl-sn-glycerol 3-phosphate O-acyltransferase 2 (AGPAT2), which is highly expressed in adipose tissue. Precisely how AGPAT2 deficiency causes lipodystrophy remains unresolved, but possible mechanisms include impaired lipogenesis (triglyceride synthesis and storage), blocked adipogenesis (differentiation of preadipocytes to adipocytes), or apoptosis/necrosis of adipocytes. Agpat2(-/-) mice share important pathophysiologic features of CGL previously reported in humans. However, the small white adipose tissue (WAT) depots consisting largely of amoeboid adipocytes with microvesiculated basophilic cytoplasm showed that adipogenesis with deficient lipogenesis was present in all usual locations. Although well-defined lobules of brown adipose tissue (BAT) were present, massive necrosis resulted in early ablation of BAT. Although necrotic or apoptotic adipocytes were not detected in WAT of 10-day-old Agpat2(-/-), the absence of adipocytes in aged mice indicates that these cells must undergo necrosis/apoptosis at some point. Another significant finding in aged lipodystrophic mice was massive pancreatic islet hypertrophy in the face of chronic hyperglycemia, which suggests that glucotoxicity is insufficient by itself to cause β-cell loss and that adipocyte-derived factors help regulate total β-cell mass.