CIC通过激活棕色脂肪组织逆转高脂膳食诱导的肥胖

摘要 目的：探讨慢性间歇性冷暴露（Chronic intermittent cold exposure,CIC）干预对小鼠棕色脂肪组织的影响及其作用机制。方法：利用高脂饲料喂养C57BL/6小鼠,建立肥胖小鼠模型,同时给予CIC处理。将动物随机分为4组：对照组（Con组）、慢性间歇性冷暴露组（CIC组）、高脂组（HF组）、高脂冷暴露组（HF+CIC组）,每组6只小鼠;CIC干预过程中,检测小鼠体重、肛温等数据。CIC处理16周后,麻醉处死小鼠取肩胛部位棕色脂肪组织, HE染色法观察棕色脂肪组织的形态学改变,Western blotting和q-PCR 检测棕色脂肪组织Cirbp、PPAR-γ、C/EBPα、PGC-1α、UCP-1等信号分子表达情况。结果：肛温变化结果显示,干预初期小鼠冷暴露前后肛温差较大,冷适应后各组无显著性差异;与Con组相比,HF组小鼠体重升高、棕色脂肪占体重的比例下降,棕色脂肪组织中Cirbp、PPAR-γ、C/EBPα表达增高,PGC-1α、UCP-1表达下降（P<0.05）;与HF组相比,HF+CIC组小鼠体重下降、棕色脂肪占体重的比例增高,棕色脂肪组织中Cirbp、PPAR-γ、C/EBPα表达下调,PGC-1α、UCP-1表达上调（P<0.05）。结论：CIC可能是通过激活Cirbp,影响PPAR-γ-PGC-1α-UCP-1信号通路的表达变化从而对棕色脂肪组织的活化产生影响,起到防治肥胖的作用。     

肥胖相关基因FTO、FNDC5、PRDM16的研究进展

脂肪量及肥胖相关基因(FTO)被认定为肥胖关联最强最确切的基因,其单核苷酸多态性变异是导致肥胖的主要原因,通常来讲,其通过与其他肥胖相关基因、细胞因子发生相互作用,从而影响体内脂质的代谢,达到调控体脂量的目的。但是,FTO的很多作用机制尚未得到确切证实。本文综述了FTO通过调控IRX3、IRX5的表达,致使白色脂肪细胞内UCP1增多,变成米色脂肪细胞,从而影响能量代谢反应的相关生理机制。FNDC5是新近发现的肌肉相关因子,受到细胞因子PGC-1的诱导激活后,可表达Irisin蛋白,从而促使棕色脂肪细胞的UCP-1表达增加,同时促进细胞转化,提高解偶联呼吸作用的产热耗能反应。PRDM16被冠以"棕色脂肪细胞开关"一名,可激活棕色脂肪细胞关键特征,增强线粒体作用、解耦连呼吸作用及调控PGC-1a和UCP1等的表达;抑制富集白脂肪的几种基因的m RNA水平如resistin和serpin3ak的表达,达到强有力地干预棕色脂肪细胞的分化、代谢及转化反应的效果。     

EPO对高脂喂养小鼠棕色脂肪组织PRDM16、FGF21表达及STAT3磷酸化水平的影响

目的：探索促红细胞生成素（EPO）对高脂饲料（HFD）喂养小鼠血糖和血浆胰岛素水平、胰岛素抵抗指数（HOMA-IR）、糖耐量,以及棕色脂肪组织中含PR结构域蛋白16（PRDM16）、信号转导与转录激活因子3（STAT3）磷酸化水平（p-STAT3/STAT3）、成纤维细胞生长因子21（FGF21）mRNA以及蛋白质表达的影响,为肥胖及其并发症的发生机制提供线索。方法：20只高脂饲料喂养的C57BL/6J雄性小鼠随机分为对照组（HFD-Con）和EPO组（HFD-EPO）,两组分别腹腔注射生理盐水和EPO（200 IU/kg）,每周3次,连续4周。4周后检测两组动物的体重、血糖与血浆胰岛素水平、HOMA-IR及糖耐量的变化;分别使用实时定量PCR法和Western blot法检测棕色脂肪组织中PRDM16、STAT3、FGF21 mRNA和蛋白质水平。结果：腹腔注射EPO 4周后,HFD-EPO组小鼠体重为（26.65±0.85）g,HFD-Con组体重为（31.50±1.60）g,P<0.01。HFD-Con组血糖为（91.06±9.86）mg/dl,HFD-EPO组为（62.79±8.09）mg/dl,P<0.01;HFD-EPO组小鼠血浆胰岛素水平为（10.56±1.06）μU/ml,HFD-Con组为（13.2±1.1）μU/ml,P<0.01。与HFD-Con组比较,HFD-EPO组的糖耐量水平显著改善,胰岛素抵抗指数下降;HFD-EPO组动物棕色脂肪组织中PRDM16、FGF21mRNA以及蛋白质表达,p-STAT/STAT3水平均显著增加,两组小鼠肝脏中FGF21 mRNA含量、血浆中FGF21含量无明显差异。结论：EPO可能通过增加棕色脂肪组织中PRDM16表达促进棕色脂肪组织的分化,降低高脂喂养小鼠的血糖水平、改善高脂喂养小鼠的糖代谢状态。     

CTRP6基因缺失对小鼠白色脂肪组织“棕色化”的影响

补体C1q/肿瘤坏死因子相关蛋白6(CTRP6)是一种新型脂肪分泌因子,在动物脂代谢中发挥重要作用。作者前期研究发现,利用慢病毒敲减CTRP6能够保护小鼠免于发生饮食诱导型肥胖。该文以CTRP6缺失的杂合子(KO)小鼠为材料,结合冷刺激手段,来确认CTRP6对小鼠体重和白脂"棕色化"的影响。首先通过Real-time PCR分析KO小鼠CTRP6表达水平,与野生型(WT)小鼠相比, KO小鼠各组织中CTRP6表达显著降低。然后,取4周龄雄性KO小鼠,随机分为两组(5只/组):4°C冷刺激组和25°C室温组,分别以WT小鼠为对照。6周后对小鼠体重、体脂进行分析。与WT小鼠相比,两个温度下KO小鼠体重和白色脂肪的质量均显著下降,棕色脂肪的质量显著上升。对脂肪组织基因表达分析发现, KO小鼠白色脂肪的UCP1、PGC1、PRDM16(棕色脂肪标志基因)以及Cyt c、NRF1、TFAM(线粒体标志基因)的表达显著升高。上述数据表明, CTRP6缺失能够抑制小鼠白色脂肪积累,促进白色脂肪"棕色化"。该研究为揭示CTRP6基因生物学功能奠定了基础,为人类肥胖及其相关代谢疾病的治疗提供了理论借鉴。     

组蛋白H3甲基转移酶Ezh2与小鼠脂肪细胞分化关系研究

目的:探索组蛋白H3K27me3甲基转移酶Ezh2对小鼠白色、棕色和米色脂肪细胞分化的影响。方法:构建诱导型Ezh2全身敲除小鼠(Ezh2~(flox/flox) CAGcre)并于6周龄时腹腔注射他莫昔芬诱导敲除,以同窝、同性别、相同基因型假诱导(腹腔注射玉米油)小鼠作为对照。诱导完成后在光镜下观察脂肪细胞形态,采用Western Blot法检测脂肪组织中H3K27me3、Ezh2和Ucp1的蛋白表达量。采用Realtime PCR法检测不同部位脂肪组织的脂肪分化相关基因(Pparγ、Adipoq和Fabp4)、棕色脂肪标志基因(Ucp1、Cidea和Prdm16)和米色脂肪标志基因(CD137、Tmem26和Tbx1)的表达。检测敲除组小鼠的冷耐受能力,并予以高脂饮食诱导肥胖,观察小鼠体重增长情况、诱导结束后小鼠的糖耐量和胰岛素敏感性指标。结果:Ezh2敲除小鼠Ezh2和H3K27me3的蛋白含量降低,背部棕色脂肪细胞脂滴明显小于对照组,Ucp1的基因和蛋白表达明显高于对照组(P0.05);敲除组小鼠白色脂肪细胞分化较差,米色脂肪分化增加,米色脂肪的Ucp1和Tbx1基因表达增加(P0.05)。敲除小鼠可以更好地耐受冷刺激,并抵抗高脂饮食诱导的肥胖和胰岛素抵抗。结论:Ezh2在体内促进白色脂肪细胞的分化,抑制棕色和米色脂肪细胞分化。     

脂肪细胞Npy4r促进高脂饮食诱导肥胖

脂肪组织的神经支配与调节在能量代谢稳态的维持中发挥重要作用。神经肽Y(neuropeptide Y, NPY)及其脂肪细胞受体信号通路促进高脂饮食诱导的肥胖,其中NPY受体1(NPY receptor Y1,NPY1R)与受体2(NPY2R)是主要的NPY外周受体。NPY受体4(NPY4R)也在脂肪组织表达,然而尚不清楚其是否参与肥胖的发生发展机制。本研究建立了NPY及其受体的免疫荧光成像技术和脂肪细胞回复性表达Npy4r小鼠。根据对不同部位脂肪组织的荧光显微术观察,发现NPY在肩胛间棕色脂肪和皮下脂肪的围绕血管区域以点状形式表达,NPY系统的各受体在脂肪组织的空间分布上具有明显的组织特异性：NPY1R在棕色脂肪、主动脉周围脂肪和性腺脂肪较为富集,NPY2R在棕色脂肪和主动脉周围脂肪较为富集,NPY4R在棕色脂肪与性腺脂肪较为富集。继而通过比较脂肪细胞回复性表达Npy4r小鼠与全身Npy4r基因静默小鼠在高脂喂食下的体重与糖代谢,发现脂肪细胞Npy4r促进高脂饮食诱导的肥胖(P <0.0001)。本研究明确了NPY及其受体NPY1R、 NPY2R和NPY4R在不同部位脂肪组织的蛋...     

组胺刺激棕色和米色脂肪产热

3-肾上腺素受体激动剂能够刺激棕色脂肪适应性产热,并能促进白色脂肪米色化。然而到目前为止,有哪些代谢产物参与介导β3-肾上腺素受体激动剂促进脂肪产热作用尚不清楚。本研究通过给予8周龄C57/BL6J雄性小鼠腹腔注射β3-肾上腺素受体激动剂CL316,243,分离提取小鼠脂肪组织进行RNA-Seq检测,结果显示组胺合成限速酶组氨酸脱羧酶(histidine decarboxylase, HDC)在脂肪中被CL316,243强烈诱导,因此推测HDC的代谢产物组胺可能参与了脂肪组织的产热过程。通过给予正常饮食与高脂饮食C57BL/6J小鼠静脉注射组胺,以明确组胺促进脂肪产热的生理作用和机制。结果显示,组胺可刺激正常饮食小鼠棕色脂肪和皮下白色脂肪中产热基因的表达,包括过氧化物酶体增殖物激活受体γ-辅活化因子-1α(peroxisome proliferator-activated receptor gamma coactivator-1α, PGC-1α)和解耦联蛋白1 (uncoupling protein 1, UCP1)。HE染色表明,组胺处理降低了脂肪细胞中脂滴的大小。此外,组胺还可以促进高脂饮食诱导的肥胖小鼠脂肪产热,改善糖耐量和脂肪肝表型。最后,我们通过脂肪原代前体细胞实验验证了组胺促进产热是细胞的自主特性。本研究结果表明,组胺可能参与介导了β3-肾上腺素受体激动剂促进脂肪的产热。     

乳源性复合益生菌促进db/db糖尿病小鼠白色脂肪棕色化的研究

目的研究乳源性复合益生菌对db/db糖尿病小鼠白色脂肪棕色化细胞因子解偶联蛋白1(UCP1)、过氧化物酶体增殖物激活受体γ共激活因子1α(PGC1α)、R结构域蛋白16(PRDM16)表达的影响。方法将6周龄的SPF级db/db糖尿病雄性小鼠适应性喂养1周,随机分为糖尿病模型组、罗格列酮组及复合益生菌高剂量组和低剂量组,SC57BL/Ks雄性小鼠为正常对照组,每组8只。血糖仪检测不同时段空腹血糖(FBG)水平,ELISA法检测糖化血红蛋(HbA1c)含量,取各组小鼠皮下白色脂肪组织,HE染色观察脂肪组织形态,用Real time-PCR检测各组白色脂肪组织中UCP1、PGC1α、PRDM16 mRNA表达水平以及Western Blot检测各组脂肪组织中UCP1的表达。结果与模型组相比,复合益生菌组FBG、HbA1c水平明显下降,并且复合益生菌能够明显增加脂肪组织多室脂肪细胞数量,具有棕色化的趋向,并能够显著提高UCP1、PGC1α、PRDM16的mRNA表达和UCP1表达量。结论本研究发现乳源性复合益生菌能够促进白色脂肪棕色化从而改善胰岛素抵抗。     

干预GPR1通路对实验性小鼠脂肪累积的影响

一直以来,肥胖是令人担忧和烦恼的健康问题,可导致包括2型糖尿病在内的代谢综合征发生.与肥胖相关疾病的发病机制是多因子影响的结果,但是,越来越多的证据表明,脂肪组织分泌的细胞因子(脂联素、瘦素、TNF-α等)的改变,以及局部的炎症反应对于这些疾病的发生具有重要作用.Chemerin(也被称为他扎罗汀诱导基因2或者视黄酸受体反应子2),是近年来发现的一种脂肪细胞因子,是G蛋白偶联受体1(GPR1)的配体,在调节代谢、先天免疫等方面具有重要的作用.为了研究Chemerin及其受体GPR1对小鼠脂肪累积的影响,本课题组通过高脂饲料喂养,成功建立小鼠肥胖模型,利用si RNA干扰技术沉默小鼠和分化前3T3-L1细胞中Chemerin或GPR1基因的表达发现:a.Chemerin及其受体GPR1在高脂饲料喂养小鼠的腹股沟脂肪以及肩胛下脂肪中的表达高于正常饲料组;b.沉默C57BL/6小鼠体内Chemerin或GPR1基因的表达后,肝脏以及腹股沟脂肪组织中脂质的累积受到抑制;c.3T3-L1细胞在体外分化成熟过程中,Chemerin和GPR1也呈高表达的趋势,沉默分化前3T3-L1细胞中Chemerin或GPR1基因的表达后,3T3-L1细胞向脂肪细胞的分化受到影响,降低了脂肪细胞中脂质的累积以及与脂质代谢相关基因的表达,改变了成熟脂肪细胞中新陈代谢功能.这些结果提示,Chemerin及其受体GPR1可能在小鼠脂肪累积中具有调控作用.综上所述,Chemerin/GPR1可能是一种调节脂肪组织中脂质累积的潜在信号通路,为肥胖症等代谢紊乱疾病的治疗提供了可能的作用靶点.     

乙酸可通过增强脂肪酸β氧化治疗小鼠肥胖

目的：探讨乙酸对高脂饮食诱导的肥胖小鼠体重及脂肪酸β氧化的影响。方法：3~4w龄C57BL/6J雄性小鼠分别给予正常饲料和高脂饲料喂养4个月以诱导肥胖,然后对肥胖小鼠实施乙酸治疗5w。喂养过程结束后,心脏采血,取结肠、肝脏和性腺周围脂肪。检测血浆葡萄糖、甘油三酯（TG）、总胆固醇（TCH）和胰岛素浓度,同时检测结肠G蛋白偶联受体（GPR43、GPR41）、酪酪肽（PYY）、胰高血糖素样肽1（GLP-1）以及肝脏和脂肪肉碱脂酰转移酶（cpt）基因mRNA表达水平。结果：高脂诱导的肥胖小鼠给予乙酸治疗5w后,体重显著性下降,但日均进食量和能量摄入却显著增加（P<0.05）。肥胖小鼠的血浆葡萄糖、TG和TCH较正常小鼠,均显著升高（P<0.05）,给予乙酸治疗后,血浆TG和TCH水平均显著降低（P<0.05）。与正常小鼠相比,肥胖小鼠结肠中GPR43、GPR41、PYY和GLP1的mRNA表达量均显著性升高（P<0.05）,脂肪和肝脏中cpt1a、cpt1c、cpt2的mRNA表达显著性降低（P<0.05）;肥胖小鼠给予乙酸治疗后,结肠中上述基因mRNA表达量均显著性降低（P<0.05）,脂肪中cpt基因mRNA表达均显著性升高（P<0.05）。结论：乙酸对小鼠肥胖有较好的治疗效果,其作用机制可能是通过特异性促进脂肪组织中脂肪酸β氧化。     

Milk fat globule membrane and its component phosphatidylcholine induce adipose browning both in vivo and in vitro

The functional induction of brown-like adipocytes in white adipose tissue (WAT) provides a defense against obesity. The aim of this study was to analyze the effects of milk fat globule membrane (MFGM) and its component phosphatidylcholine (PC) on the brown remodeling of WAT. Male C57BL/6 J mice were fed a high-fat diet (HFD) for 8 weeks and then fed HFD for another 8 weeks with MFGM. In vitro studies were performed in C3H10T1/2 pluripotent stem cells, 3T3-L1 pre-adipocytes and differentiated inguinal WAT stromal vascular cells (SVCs) to determine the role of MFGM and PC on the formation of brown-like adipocytes. MFGM decreased fasting glucose and serum insulin levels in HFD-fed mice. MFGM improved glucose tolerance and insulin sensitivity, and induced browning of inguinal WAT. MFGM and its component PC stimulated transformation of brown-like adipocytes in C3H10T1/2 pluripotent stem cells, 3T3-L1 adipocytes and SVCs by increasing the protein expression of UCP1, PGC-1α, PRDM16 as well as the mRNA expression of other thermogenic genes and beige cell markers. MFGM and PC also increased mitochondrial DNA (mtDNA) copy number, mitochondrial density and oxygen consumption rate and up-regulated the mRNA expression of mitochondria-biogenesis-related genes in vitro. PPARα inhibitor GW6471 treatment or knockdown of PPARα using lentivirus-expressing shRNA inhibited the PC-induced increase in the protein expression of UCP1, PGC-1α and PRDM16 in C3H10T1/2 pluripotent stem cells and 3T3-L1 adipocytes, indicating the potential role of PPARα in PC-mediated brown-like adipocyte formation. In conclusion, MFGM and milk PC induced adipose browning, which has major protective effects against obesity and metabolic dysfunction.     

Grape pomace extract induced beige cells in white adipose tissue from rats and in 3T3-L1 adipocytes

This study investigated the effects of a grape pomace extract (GPE) rich in phenolic compounds on brown-like adipocyte induction and adiposity in spontaneously hypertensive (SHR) and control normotensive Wistar–Kyoto (WKY) rats fed a high-fat diet (HFD). HFD consumption for 10 weeks significantly increased epididymal white adipose tissue (eWAT) in WKY but not in SHR rats. Supplementation with GPE (300 mg/kg body weight/day) reduced adipocyte diameter and increased levels of proteins that participate in adipogenesis and angiogenesis, i.e., peroxisome-proliferator activated receptor gamma (PPARγ), vascular endothelial grow factor-A (VEGF-A) and its receptor 2 (VEGF-R2), and partially increased the uncoupling protein 1 (UCP-1) in WKY. In both strains, GPE attenuated adipose inflammation. In eWAT from SHR, GPE increased the expression of proteins involved in adipose tissue “browning,” i.e., PPARγ-coactivator-1α (PGC-1α), PPARγ, PR domain containing 16 (PRDM16) and UCP-1. In primary cultures of SHR adipocytes, GPE-induced UCP-1 up-regulation was dependent on p38 and ERK activation. Accordingly, in 3T3-L1 adipocytes treated with palmitate, the addition of GPE (30 μM) activated the β-adrenergic signaling cascade (PKA, AMPK, p38, ERK). This led to the associated up-regulation of proteins involved in mitochondrial biogenesis (PGC-1α, PPARγ, PRDM16 and UCP-1) and fatty acid oxidation (ATGL). These effects were similar to those exerted by (−)-epicatechin and quercetin, major phenolic compounds in GPE. Overall, in HFD-fed rats, supplementation with GPE promoted brown-like cell formation in eWAT and diminished adipose dysfunction. Thus, winemaking residues, rich in bioactive compounds, could be useful to mitigate the adverse effects of HFD-induced adipose dysfunction.     

PPARγ agonists induce a white-to-brown fat conversion through stabilization of PRDM16 protein

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Highlights? PPARγ full agonists induce a brown fat phenotype in subcutaneous WAT ? PRDM16 is required for the development of PPARγ agonist-inducible brow adipocytes ? PRDM16 and PPARγ agonists synergistically activate the brown fat gene program ? Browning effect is mediated through the enhanced stability of the PRDM16 protein     

Thermogenic Capacity Is Antagonistically Regulated in Classical Brown and White Subcutaneous Fat Depots by High Fat Diet and Endurance Training in Rats: IMPACT ON WHOLE-BODY ENERGY EXPENDITURE*

This study investigated the regulation of thermogenic capacity in classical brown adipose tissue (BAT) and subcutaneous inguinal (SC Ing) white adipose tissue (WAT) and how it affects whole-body energy expenditure in sedentary and endurance-trained rats fed ad libitum either low fat or high fat (HF) diets. Analysis of tissue mass, PGC-1α and UCP-1 content, the presence of multilocular adipocytes, and palmitate oxidation revealed that a HF diet increased the thermogenic capacity of the interscapular and aortic brown adipose tissues, whereas exercise markedly suppressed it. Conversely, exercise induced browning of the SC Ing WAT. This effect was attenuated by a HF diet. Endurance training neither affected skeletal muscle FNDC5 content nor circulating irisin, but it increased FNDC5 content in SC Ing WAT. This suggests that locally produced FNDC5 rather than circulating irisin mediated the exercise-induced browning effect on this fat tissue. Importantly, despite reducing the thermogenic capacity of classical BAT, exercise increased whole-body energy expenditure during the dark cycle. Therefore, browning of subcutaneous WAT likely exerted a compensatory effect and raised whole-body energy expenditure in endurance-trained rats. Based on these novel findings, we propose that exercise-induced browning of the subcutaneous WAT provides an alternative mechanism that reduces thermogenic capacity in core areas and increases it in peripheral body regions. This could allow the organism to adjust its metabolic rate to accommodate diet-induced thermogenesis while simultaneously coping with the stress of chronically increased heat production through exercise.