肥胖治疗新希望：白色脂肪棕色化

哺乳动物体内有两种脂肪组织,白色脂肪和棕色脂肪。白色脂肪以储存能量为主,棕色脂肪则以消耗能量产热,维持体温恒定。棕色脂肪组织约占体重的2％以下,棕色脂肪细胞富含大量线粒体和解偶联蛋白1（UCP-1）,线粒体产生大量的ATP,通过UCP-1的解偶联作用,转换成热量释放。棕色脂肪细胞也有大量的脂滴,与白色脂肪细胞不同,它们以多房小脂滴形式存在,更方便于被氧化利用。     

白色脂肪棕色化的研究进展

随着经济的发展,生活水平的提高,营养状况的改善,伴随能量摄入过剩而导致的肥胖已成为威胁健康的重要问题。肥胖又与心血管疾病密切相关~([1])。减轻和控制体重已成为医疗公共卫生事业亟待研究和解决的问题。人体中分布白色脂肪组织(WAT)和棕色脂肪组织(BAT)2种脂肪组织。WAT以三酰甘油的形式存储人体内摄入的过多能量,BAT则以产生热量的形式消耗体内的能量~([2])。     

生长分化因子11在白色脂肪细胞棕色化中的作用研究

目的 探讨生长分化因子11（GDF11）在白色脂肪细胞棕色化中的作用。方法 由C3H10T1/2细胞诱导分化而来的成熟白色脂肪细胞随机分为正常对照组，GDF11组；Western blot检测GDF11孵育成熟白色脂肪细胞后UCP1蛋白的表达；实时PCR检测GDF11对棕色脂肪标志基因表达的影响。结果 分别加入浓度为25 ng/ml、50 ng/ml、100 ng/ml 的GDF11，与正常对照组相比加入100 ng/ml的GDF11能够明显促进UCP1的表达（P<0.05），而25 ng/ml和50 ng/ml的GDF11可以在一定程度上诱导UCP1的表达却无显著统计学差异；同时，100 ng/ml的GDF11能够促进棕色脂肪标志基因ucp1、cidea、cox7α、dio2和elovl3的表达（P<0.05）和线粒体DNA拷贝数的增加（P<0.05）。结论 GDF11可显著促进白色脂肪细胞向棕色脂肪细胞转化。     

敲低GPM6B促进白色脂肪细胞向棕色脂肪表型转变

目的 研究糖蛋白M6B(GlycoproteinM6B,GPM6B)在白色脂肪细胞向棕色脂肪表型转变中的作用.方法 ①Western blot和qPCR检测小鼠白色脂肪组织(white adipose tissue,WAT)和棕色脂肪组织(brown adipose tissue,BAT)中GPM6B的表达.②分别用对...     

过氧化物酶体增殖物激活受体γ激动剂对肥胖小鼠非肾上腺素能原代棕色脂肪功能和分化的影响

目的探索过氧化物酶体增殖物激活受体γ（PPAR-γ）激动剂吡格列酮（PGZ）对肥胖小鼠非肾上腺素能条件下原代棕色脂肪分化和功能的影响,为2型糖尿病和肥胖的治疗提供新依据。方法高脂饮食诱导的4周龄雄性C57BL／6J肥胖小鼠20只,取肩胛间区棕色脂肪组织,分离并培养C57小鼠原代棕色脂肪细胞,等量分人10个培养皿中,等分为对照组和PGZ干预组,每组5皿,使用PGZ干预细胞,建立PGZ干预的细胞模型,使用和PGZ溶液等量的生理盐水处理对照组细胞。实时定量聚合酶链反应（RT-PCR）检测细胞模型的棕色脂肪基因：解偶联蛋白1（UCP-J）、超长链脂肪酸延长酶3（ELOVL3）、PPAR-γ共激活因子α和β（PGCI-α、PGCI-β）、PR包含域16区（PRDM16）、CCAAT增强子结合蛋白β（CEBP/β）、脂联素、脂肪细胞脂质结合蛋白2（AP2）、细胞色素C1氧化酶（CYC1）、线粒体转录因子A（TFAM）等表达水平;使用油红染色定量法检测细胞模型的棕色脂肪成脂功能;Western blotting法检测PGZ干预组UCP-1蛋白表达。2组间比较采用t检验,多组间比较采用方差分析和LSD检验。结果PGZ干预组细胞的棕色脂肪特异基因（UCP-1、ELOVL3、PGCI-α、PGCI-β）、成脂基因（AP2）、线粒体功能基因（CYCI、TFAM）和脂肪分化基因（PRDM16、CESP／β）表达量均显著高于对照组（相对表达量分别为：UCP-1：1100．0±612．0、2．0±0．4;ELOVL3：1461．0±617．0、2．0±1．2;PGCI-α：8．1±2．8、2．0±1．1;PGCI-β：8．3±2．8、2．0±1．3;脂联素：2．6±0．8、1．04±0．7;AP2：5．1±2．2、1．00±0．24;CYCI：3．1±0．8、1．0±0．4;TFAM：1．2±0．4、1．00±0．25;PRDM16：4．8±2．6、2．0±0．3;CEBP／β：6×10^8±5×10^8、2．0±0．6;t=2．45～5．22,均P〈0．05）;油红定量亦发现干预组成脂功能高于对照组（染色定量：1．2±0．2比1．0±0．1,t=2．45,P〈0．05）。Westernblotting检测PGZ干预组UCP-1表达高于对照组（灰度分析相对定量分别为1．24±0．25和1．00±0．14,t=2．63,P〈0．05）。结论PGZ可能通过增强棕色脂肪特异基因表达、促进细胞分化成脂、提高线粒体功能等方面增强棕色脂肪细胞功能,这可能是其改善机体代谢的原因之一。     

解偶联蛋白2基因表达对游离脂肪酸升高所致β细胞功能障碍的影响

目的观察血浆游离脂肪酸（FFA）水平短期升高对β细胞胰岛素分泌功能的影响,探讨线粒体氧化应激在其中的作用及机制。方法将24只8周龄体重160-170g雄性SD大鼠采用随机数字表法分为脂肪乳输注组（FFA组,12只）和生理盐水输注组（NS组,12只）。分别输注48h,检测以下指标：（1）采静脉血检测胰岛素和FFA水平;（2）静脉葡萄糖耐量实验,评价活体胰岛β细胞分泌功能;（3）胰岛细胞表面灌注实验,评价离体胰岛β细胞动态分泌功能;（4）实时荧光定量聚合酶链反应（PCR）方法检测胰岛细胞胰岛素受体底物1和2（IRS-1、IRS-2）和解偶联蛋白-2（UCP-2）mRNA表达的变化。两组间差异比较采用独立样本t检验。结果FFA组血胰岛素水平较NS组增高[（25．2±2．3）比（18．6±1．7）mU／L,t=7．9,P〈0．05],FFA水平也显著高于Ns组[（1．39±0．18）比（0．64±0．10）mmol／L,t=12．8,P〈0．05]。FFA刺激后,FFA组活体和离体的胰岛β细胞分泌功能均较NS组增强[活体分别为（137±24）、（80±16）mU／L,t=6．8,P〈0．05;离体分别为（272±4）、（227±4）mU／L,t=28．6,P〈0．05]。与NS组相比,FFA组胰岛细胞IRS-1mRNA表达增加了29．3％4-2．6％（t=2．2,P〈0．05）,IRS-2mRNA及UCP-2mRNA表达分别增加了345．1％±4．7％、228．4％±4．2％（t=3．4、3．0,均P〈0．05）。结论血浆FFA水平短期升高对β细胞胰岛素分泌有刺激作用,但同时激活线粒体氧化应激,使UCP-2表达相应增加。     

解偶联蛋白的产热机制及调控的研究进展

棕色脂肪组织（ＢＡＴ） 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。位于ＢＡＴ 线粒体内膜的解偶联蛋白（ＵＣＰ） 是决定ＢＡＴ 功能的关键因素。线粒体内膜的ＵＣＰ 作为质子通道驱散氧化呼吸时形成的Ｈ＋ 梯度，从而增加呼吸，阻止ＡＴＰ 形成。去甲肾上腺素、胰岛素、甲状腺激素、视黄酸等因素调控着ＵＣＰ 的浓度和活性。     

肾上腺素和葡萄糖对3T3-L1脂肪细胞水孔蛋白mRNA表达的影响

目的：通过细胞培养研究肾上腺素、葡萄糖对成熟脂肪细胞水孔蛋白（aquaporin adipose,AQPap）基因表达的影响。了解AQPap基因表达的影响因素，探讨其在肥胖及糖尿病发病中所起作用。方法：用不同浓度（10^-6mol/L、10^－7mol/L、10^-8mol/L、10^-9mol/L）的肾上腺素刺激诱导分化第9天的3T3－L1细胞6h，另以不同浓度的葡萄糖（5．6mmol/L、11．2mmol/L、16．8mmol/L、33．6mmol/L）刺激细胞48h。提取细胞RNA。运用半定量RT－PCR技术检测AQPap mRNA表达量的变化。结果：与对照组相比，给予不同浓度的肾上腺素刺激分化成熟的3T3－L1细胞，其AQPap mRNA的表达量变化，差异无显著性意义（P＞0．05）。 葡萄糖浓度的升高使培养细胞AQPap mRNA的表达量显著增强（P＜0．05，16．8mmol/L葡萄糖刺激培养细胞48h,AQPap mRNA表达量约是对照组（葡萄糖浓度为5．6mmol/L）的3倍。结论：肾上腺素是一种脂解激素，它对脂肪细胞AQPap mRNA的表达无影响；高糖状态下AQPap mRNA表达明显增强。     

棕色脂肪组织与糖代谢的关系

研究证实成人体内存在有活性的棕色脂肪组织(BAT).BAT是非颤栗产热和饮食诱导产热的主要器官,其产热作用依赖线粒体内膜的解耦联蛋白1(UCP1).UCP1可使物质氧化与ATP生成解耦联(解耦联呼吸),减少ATP的生成,使能量以热量的形式释放,维持体温与能量的平衡.寒冷暴露、胰岛素、去甲肾上腺素、甲状腺激素等均可诱导UCP1表达使BAT活化,进而促进BAT摄取循环中的葡萄糖,加速循环中葡萄糖的清除.饮食因素以及可诱导BAT活化的因素均可影响BAT对葡萄糖的摄取.     

Cannabinoid type 1 receptor blockade induces transdifferentiation towards a brown fat phenotype in white adipocytes

Aim: The endocannabinoid (EC) system is a major component in the control of energy homeostasis. It mediates a positive energy balance via central and peripheral pathways. Blockade of the cannabinoid type 1 receptor induces weight reduction and improves cardiovascular risk factors in overweight patients. Cannabinoid receptor type 1 (CB1R)‐deficient mice are resistant to diet‐induced obesity. The mechanisms responsible for these effects remain only partially elucidated. We hypothesized peripheral effects via direct modulation of adipocyte function to be an integral part of EC action on energy metabolism and insulin sensitivity. Methods: SV40 immortalized murine white and brown adipocytes were used for all experiments. We investigated the effect of CB1R blockade by stimulating the cells acutely and chronically with rimonabant, a selective antagonist for the CB1R, or by knocking down the receptor with small interfering RNA (siRNA). Changes in thermogenic mRNA and protein expression as well as mitochondrial biogenesis and function were assessed by real‐time RT‐PCR, immunoblotting, fluorescent staining techniques, electron microscopy and by measuring oxygen consumption. Results: Acute and chronic blockade of the CB1R with the selective antagonist rimonabant or by siRNA in murine white adipocytes strongly induced the thermogenic uncoupling protein‐1 (UCP‐1). UCP‐1 expression was increased in a time‐ and dose‐dependent manner both at the RNA and protein level. Furthermore, this effect was paralleled by enhanced peroxisome proliferator‐activated receptor γ coactivator 1α (PGC‐1α) expression. In accordance with these findings, AMP‐activated protein kinase (AMPK) phosphorylation was also increased after rimonabant treatment. Mitochondria‐specific fluorescent staining demonstrated an augmentation in the number of mitochondria. This was confirmed by electron microscopy images. Moreover, rimonabant treatment enhanced the cytochrome c oxidase activity and increased cellular oxygen consumption. Conclusions: Taken together, our data demonstrate that inhibition of peripheral CB1R action in adipocytes directly promotes transdifferentiation of white adipocytes into a mitochondria‐rich, thermogenic brown fat phenotype. Enhanced thermogenesis and insulin sensitivity may represent a peripheral mechanism contributing to weight loss and improved glucose homeostasis in rimonabant‐treated patients.     

3,5-二碘-L-甲状腺素对白色脂肪棕色化的作用

目的 探究3,5-二碘-L-甲状腺素(T2)诱导白色脂肪棕色化的作用.方法 3T3-LI脂肪前体细胞诱导分化并用油红O染色进行鉴定;细胞分化过程中予不同浓度梯度(1 nmol/L、10 nmol/L、100 nmol/L)的T2处理,待细胞分化成熟后,分别用实时荧光定量PCR、Western印迹检测解耦联蛋白-1(UCP-1)表达水平的变化;仅予高浓度(100 nmol/L) T2处理,Western印迹法检测其他棕色脂肪功能性基因,包括诱导细胞死亡DNA片段化因子α样效应因子A(CIDEA)、过氧化物酶体增殖物活化受体γ协同刺激因子-1α(PGC-1α)蛋白表达变化.结果 3T3-L1脂肪前体细胞呈成纤维细胞样形态,胞浆中无脂滴;诱导分化成熟后光镜下油红O染色可见细胞内大量环状脂滴.在细胞分化过程中予不同浓度T2干预后,分化成熟的脂肪细胞上UCP-1 mRNA水平均有升高(t=3.97、11.77、17.7,P均＜0.05),蛋白表达水平也均有改变(t=13.31、14.55、23.62,P均＜0.05),且在高浓度(100nmoL/L)下最明显.在高浓度T2(100 nmol/L)干预下,成熟脂肪细胞的棕色脂肪其他功能性基因蛋白CIDEA、PGC-1α水平表达增加(t=15.92、17.36,P均＜0.05).结论 T2可诱导由3T3-L1脂肪前体细胞分化而来的成熟白色脂肪细胞表达棕色脂肪功能性基因.     

Thermogenic adipocytes: From cells to physiology and medicine

The identification of active brown fat in humans has evoked widespread interest in the biology of non-shivering thermogenesis among basic and clinical researchers. As a consequence we have experienced a plethora of contributions related to cellular and molecular processes in thermogenic adipocytes as well as their function in the organismal context and their relevance to human physiology. In this review we focus on the cellular basis of non-shivering thermogenesis, particularly in relation to human health and metabolic disease.     

Molecular pathways regulating the formation of brown‐like adipocytes in white adipose tissue

Adipose tissue is functionally composed of brown adipose tissue and white adipose tissue. The unique thermogenic capacity of brown adipose tissue results from expression of uncoupling protein 1 in the mitochondrial inner membrane. On the basis of recent findings that adult humans have functionally active brown adipose tissue, it is now recognized as playing a much more important role in human metabolism than was previously thought. More importantly, brown‐like adipocytes can be recruited in white adipose tissue upon environmental stimulation and pharmacologic treatment, and this change is associated with increased energy expenditure, contributing to a lean and healthy phenotype. Thus, the promotion of brown‐like adipocyte development in white adipose tissue offers novel possibilities for the development of therapeutic strategies to combat obesity and related metabolic diseases. In this review, we summarize recent advances in understanding the molecular mechanisms involved in the recruitment of brown‐like adipocyte in white adipose tissue. Copyright © 2014 John Wiley & Sons, Ltd.     

Mitochondrial uncoupling protein 2 and pancreatic cancer:A new potential target therapy

Overall 5-years survival of pancreatic cancer patients is nearly 5%,making this cancer type one of the most lethal neoplasia.Furthermore,the incidence rate of pancreatic cancer has a growing trend that determines a constant increase in the number of deceases caused by this pathology.The poor prognosis of pancreatic cancer is mainly caused by delayed diagnosis,early metastasis of tumor,and resistance to almost all tested cytotoxic drugs.In this respect,the identification of novel potential targets for new and efficient therapies should be strongly encouraged in order to improve the clinical management of pancreatic cancer.Some studies have shown that the mitochondrial uncoupling protein 2(UCP2) is over-expressed in pancreatic cancer as compared to adjacent normal tissues.In addition,recent discoveries established a key role of UCP2 in protecting cancer cells from an excessive production of mitochondrial superoxide ions and in the promotion of cancer cell metabolic reprogramming,including aerobic glycolysis stimulation,promotion of cancer progression.These observations together with the demonstration that UCP2 repression can synergize with standard chemotherapy to inhibit pancreatic cancer cell growth provide the molecular rationale to consider UCP2 as a potential therapeutic target for pancreatic cancer.In this editorial,recent advances describing the relationship between cancer development and mitochondrial UCP2 activity are critically provided.     

脂联素球状结构域对胰岛素抵抗模型脂肪细胞及胰岛素信号转导的影响

将3T3-L1前脂肪细胞诱导分化为成熟的脂肪细胞,用软脂酸制备脂肪细胞胰岛素抵抗模型,不同浓度的脂联素球状结构域(globular domain of adiponectin,gAd)干预已经产生胰岛素抵抗的3T3-L1脂肪细胞,葡萄糖氧化酶法检测培养液中葡萄糖的消耗量,实时荧光定量PCR法检测胰岛素受体底物(IRS)-1、磷脂酰肌醇3激酶(PI3K)、蛋白激酶B(PKB)基因水平的变化,Western印迹检测IRS-1酪氨酸磷酸化水平.结果显示,与对照组相比,各实验组葡萄糖消耗量均显著增加(P＜0.01),且随着gAd浓度的增加,葡萄糖消耗量也逐渐增加;500 ng/ml gAd组及1 000 ng/ml gAd组IRS-1、PI3K、PKB的mRNA表达均比对照组显著增加(P＜0.05);同时,gAd可增加3T3-L1脂肪细胞胰岛素抵抗模型IRS-1酪氨酸磷酸化水平,且呈浓度依赖性.提示gAd能够促进3T3-L1脂肪细胞胰岛素抵抗模型葡萄糖的摄取,其机制可能与促进脂肪细胞胰岛素信号转导、改善胰岛素抵抗有关.     

甘肃省东乡族UCP-2基因A55V多态性与超重肥胖、2型糖尿病相关性的研究

目的 探讨解偶联蛋白2(UCP-2)基因多态性与超重肥胖、2型糖尿病(T2DM)的关系.方法 选取甘肃东乡族人群正常对照(NC)114名及T2DM患者104例,采用聚合酶链反应和变性高效液相色谱技术筛查 UCP-2基因Ala55Val位点的基因型并测序. 结果 AA、AV、VV基因型频率和A、V等位基因频率NC组和T2DM组比较,差异无统计学意义;两组中VV型、AV型者TG水平均高于AA型者,NC组VV型者BMI明显高于AA型者,差异均有统计学意义(P均<0.05). 结论 UCP-2基因Ala55Val的多态性可能与甘肃东乡族人群的超重肥胖及血脂异常相关,而与T2DM、胰岛素抵抗关系不大.