Severely impaired adipsin expression in genetic and acquired obesity

Adipsin, a serine protease homolog, is synthesized and secreted by adipose cells and is found in the bloodstream. The expression of adipsin messenger RNA (mRNA) and protein was analyzed in rodents during metabolic perturbations and in several experimental models of obesity. Adipsin mRNA abundance is increased in adipose tissue during fasting in normal rats and in diabetes due to streptozotocin-induced insulin deficiency. Adipsin mRNA abundance decreased during the continuous infusion of glucose, which induces a hyperglycemic, hyperinsulinemic state that is accompanied by an increased adipose mass; it is suppressed (greater than 100-fold) in two strains of genetically obese mice (db/db and ob/ob), compared to their congenic counterparts, and is also reduced when obesity is induced chemically by injection of monosodium glutamate into newborn mice. Circulating adipsin protein is decreased in these animal models of obesity, as determined by immunoblotting with antisera to adipsin. Little change in adipsin expression is observed in a model of obesity obtained by pure overfeeding of normal rats (cafeteria model). These data suggest a possible role for adipsin in the above-mentioned disordered metabolic states, and raise the possibility that adipsin expression may be used to distinguish obesities that arise from certain genetic or metabolic defects from those that result from pure overfeeding.     

Adipsin and complement factor D activity: an immune-related defect in obesity

Adipsin is a serine protease that is secreted by adipocytes into the bloodstream; it is deficient in several animal models of obesity, representing a striking example of defective gene expression in this disorder. Recombinant mouse adipsin was purified and its biochemical and enzymatic properties were studied in order to elucidate the function of this protein. Activated adipsin has little or no proteolytic activity toward most substrates but has the same activity as human complement factor D, cleaving complement factor B when it is complexed with activated complement component C3. Like authentic factor D, adipsin can activate the alternative pathway of complement, resulting in red blood cell lysis. Decreased (58 to 80 percent) complement factor D activity, relative to lean controls, was observed as a common feature of several experimental models of obesity, including the ob/ob, db/db, and monosodium glutamate (MSG)-injected mouse and the fa/fa rat. These results suggest that adipsin and the alternative pathway of complement may play an unexpected but important role in the regulation of systemic energy balance in vivo.     

Cell cycle-dependent regulation of phosphorylation of the human retinoblastoma gene product

The human retinoblastoma gene (RB1) encodes a protein (Rb) of 105 kilodaltons that can be phosphorylated. Analysis of Rb metabolism has shown that the protein has a half-life of more than 10 hours and is synthesized at all phases of the cell cycle. Newly synthesized Rb is not extensively phosphorylated (it is "underphosphorylated") in cells in the G0 and G1 phases but is phosphorylated at multiple sites at the G1/S boundary and in S phase. HL-60 cells that were induced to terminally differentiate by various chemicals lost their ability to phosphorylate newly synthesized Rb at multiple sites when cell growth was arrested. These findings suggest that underphosphorylated Rb may restrict cell proliferation.     

A circadian rhythm orchestrated by histone deacetylase 3 controls hepatic lipid metabolism

Disruption of the circadian clock exacerbates metabolic diseases, including obesity and diabetes. We show that histone deacetylase 3 (HDAC3) recruitment to the genome displays a circadian rhythm in mouse liver. Histone acetylation is inversely related to HDAC3 binding, and this rhythm is lost when HDAC3 is absent. Although amounts of HDAC3 are constant, its genomic recruitment in liver corresponds to the expression pattern of the circadian nuclear receptor Rev-erbα. Rev-erbα colocalizes with HDAC3 near genes regulating lipid metabolism, and deletion of HDAC3 or Rev-erbα in mouse liver causes hepatic steatosis. Thus, genomic recruitment of HDAC3 by Rev-erbα directs a circadian rhythm of histone acetylation and gene expression required for normal hepatic lipid homeostasis.     

PPARγ对脂类代谢和脂肪细胞分化的调控

 过氧化物酶体增殖物激活受体γ是一种配体活化的核转录因子,具有多种生物学效应。除能调节脂肪细胞分化、脂代谢,细胞增殖、细胞周期外,还能调控细胞因子生成,增强机体对胰岛素的敏感性等作用。主要就PPARγ对脂类代谢和脂肪细胞分化调控作用的最新研究进展进行综述。     

Krüppel-Like Factor 3（KLF3）基因对牛脂肪沉积的作用

【目的】通过研究牛KLF3基因对牛脂肪分化和脂肪酸代谢关键基因表达量的作用,进而探讨KLF3 基因对脂质沉积的影响。【方法】合成干扰siRNA,筛选得到KLF3基因干扰效率最高SiRNA,分离培养秦川牛肉用新品系新生牛前脂肪细胞生长至70%-90%汇合度时转染筛选得到的KLF3基因SiRNA和阴性对照SiRNA（NC）,并进行诱导分化培养至第0天和第4 天时,利用荧光定量PCR方法研究分化标志基因过氧化物酶体增殖物激活受体γ（peroxisome proliferator activated receptor γ, PPARγ）、CCAAT增强子结合蛋白（CCAAT/enhancer-binding proteins α, C/EBPα）,脂肪酸代谢关键基因脂肪酸合成酶（fatty acid synthase,FAS）、乙酰辅酶A羧化酶（acetyl-CoA carboxylase α, ACCα）和脂肪酸结合蛋白4（fatty acid binding protein 4, FABP4）基因在牛脂肪细胞分化不同时期干扰KLF3基因处理组和对照组之间表达量的变化,同时在干扰KLF3基因处理并进行诱导脂肪细胞分化的第 4天采用油红O染色法观察干扰KLF3基因处理组和对照组之间脂滴差异及采用酶联免疫吸附测定(enzyme-linked immunosorbent assay,ELISA)方法测定甘油三酯含量进一步确定KLF3基因对牛脂肪细胞分化和脂肪酸代谢的作用。【结果】KLF3-Si2 具有最高的干扰效率达到73%。转染KLF3-Si2后PPARγ的表达量在牛脂肪细胞诱导分化的第0天 和第4 天与对照组相比分别下调了58% 和37%,达到了差异极显著（P<0.01）,C/EBPα 的表达量也分别下调了64% 和41%,达到了差异极显著（P<0.01）。脂质代谢的关键基因FABP4的表达量与对照组相比在牛脂肪细胞诱导分化的第0天和第4 天分别下调了89% 和60%,而ACCα的表达量干扰KLF3处理组与对照组相比在脂肪细胞诱导分化第0天和第4天分别下调了50% 和37%, 而FAS的表达量则分别下调了73% 和19%,都分别达到了差异极显著（P<0.01）。在牛脂肪细胞诱导分化第4天油红O染色和甘油三酯含量测定也发现干扰KLF3基因处理组与对照组相比脂滴减少,甘油三酯含量显著下降（P<0.05）。【结论】干扰牛KLF3基因可以抑制牛脂肪细胞分化和脂肪酸代谢关键基因表达量下调,进而影响脂肪的沉积。     

育成期高能饲喂下开产与未开产蛋鸡肝脏miRNA表达谱差异分析

【目的】对育成期高能饲喂下开产与未开产蛋鸡的肝脏进行miRNA高通量测序分析,探明高能饮食状态下蛋鸡肝脏中影响其开产的miRNA,为提高产蛋性能打下基础。【方法】以代谢能水平为12.14 MJ/kg的高能饲粮饲喂育成期蛋鸡,通过Illumina NextSeq500高通量测序平台对开产与未开产蛋鸡肝脏进行small RNA测序,使用DESeq分析miRNA表达量,并以实时荧光定量PCR进行验证;采用miRanda对差异表达miRNA进行靶基因和靶位点预测,同时以超几何分布对差异表达的靶基因进行GO功能注释分析和KEGG信号通路富集分析。【结果】 6个样本（3个开产蛋鸡样本,3个未开产蛋鸡样本）能注释到的miRNA均超过300个,约占miRBase中已鉴定鸡miRNA的30.00%,且前体鉴定结果显示各样本注释到的miRNA有部分定位在同一前体上。与未开产组样本相比,开产组样本有9个miRNA表达上调、3个miRNA表达下调。其中,gga-miR-132c-5p、gga-miR-132b-5p、gga-miR-2184a-5p、gga-miR-132c-3p、gga-miR-132b-3p及gga-miR-2184a-3p属于同一miRNA基因簇,且gga-miR-1682、gga-miR-132b-3p和gga-miR-2184a-3p等3个上调miRNA在未开产蛋鸡样本中不表达。通过miRanda共预测得到129个差异表达潜在靶基因,以miR-203a预测得到的靶基因最多,为32个;其次是gga-miR-2184a-5p、gga-miR-148a-5p和gga-miR-12211-5p,分别预测到30、25和23个靶基因;而miR-132c-5p预测得到的靶基因最少,仅为9个。129个靶基因显著注释到8条GO功能条目上,生物学过程（Biological process）主要注释到脂质代谢过程、细胞脂质代谢过程、脂质生物合成过程、磷脂生物合成过程、磷脂代谢过程、甘油磷脂生物合成过程和解剖学结构发育,分子功能（Molecular funcion）仅注释到1条GO功能条目,即利钠肽受体活性,未发现涉及细胞组分（Cellular component）的GO功能条目;在注释到的8条GO功能条目中有6条与脂质代谢相关,涉及的靶基因有22个,占总潜在靶基因的17.10%。KEGG信号通路富集分析结果显示共显著富集到7条KEGG信号通路,其中脂肪酸降解、脂肪酸生物合成、酮体合成与降解及PPAR信号通路等4条信号通路与脂质代谢相关。【结论】育成期高能饲喂下开产与未开产蛋鸡中共存在12个差异表达miRNA,涉及129个差异表达潜在靶基因,且主要富集在肝脏脂质代谢相关过程和信号通路,说明miRNA是通过调控脂质代谢及其相关基因表达而影响蛋鸡开产。     

Cloning of complementary DNA for GAP-43, a neuronal growth-related protein

GAP-43 is one of a small subset of cellular proteins selectively transported by a neuron to its terminals. Its enrichment in growth cones and its increased levels in developing or regenerating neurons suggest that it has an important role in neurite growth. A complementary DNA (cDNA) that encodes rat GAP-43 has been isolated to study its structural characteristics and regulation. The predicted molecular size is 24 kilodaltons, although its migration in SDS-polyacrylamide gels is anomalously retarded. Expression of GAP-43 is limited to the nervous system, where its levels are highest during periods of neurite outgrowth. Nerve growth factor or adenosine 3',5'-monophosphate induction of neurites from PC12 cells is accompanied by increased GAP-43 expression. GAP-43 RNA is easily detectable, although at diminished levels, in the adult rat nervous system. This regulation of GAP-43 is concordant with a role in growth-related processes of the neuron, processes that may continue in the mature animal.     

The 36-kilodalton substrate of pp60v-src is myristylated in a transformation-sensitive manner

A primary intracellular substrate for pp60v-src kinase in a variety of avian and mammalian cells is a protein of 34 to 39 kilodaltons (kD). After incubation of chicken embryo fibroblasts (CEF) with [3H]myristic acid for 4 hours, the 36-kD protein contained covalently bound myristic acid by several criteria: (i) the radioactively labeled material comigrated with the 36-kD protein on sodium dodecyl sulfate-polyacrylamide gels in one and two dimensions, (ii) the labeled material was insoluble in chloroform-methanol, and (iii) radioactively labeled myristate could be recovered from the purified 36-kD protein. The resistance of the acyl fatty acid moiety to hydrolysis by hydroxylamine suggested that the covalent linkage to the 36-kD protein may be through an amide linkage. The [3H]myristic-acid labeling of the 36-kD protein in Rous sarcoma virus-transformed CEF showed a reduction of up to 45 percent when compared to an identical amount of 36-kD protein derived from normal cells; this reduction was not due to general changes in myristic acid metabolism in transformed cells.     

土壤干旱对小麦根系蛋白组分变化的影响

在土壤干旱条件下,小麦幼苗根系组织含水量降低,可溶蛋白质含量增加.SDS—PAGE扫描图谱表明,陕合6号出现46、59及60KD3种新蛋白质峰值,郑引1号产生24、46、61、63、65、69、及72KD7种新蛋白质峰值.两个品种在15～72KD间的多数蛋白质含量显著增加,而15KD以下的蛋白质含量大幅度下降.复水后,新蛋白质消失,15KD以下的蛋白质含量接近对照水平,而15～72KD间的蛋白质含量明显低于对照.     

莱茵衣藻“细菌型”pepc2基因叶绿体表达及其对油脂蛋白质含量的影响

磷酸烯醇式丙酮酸羧化酶(Phosphoenolpyruvate carboxylase,PEPC,EC 4.1.1.31)在植物碳代谢中有重要作用,高等植物中PEPC可以调控蛋白质和脂肪酸含量,但是对绿藻PEPC的研究还较少.莱茵衣藻是绿藻中的模式生物,其基因工程中外源基因的转化以叶绿体转化效率最高,为了提高外源蛋白表达和获得高产油莱茵衣藻,利用叶绿体转化法能进一步提高表达效率.因此,本研究首先克隆了莱茵衣藻“细菌型”PEPCCS Ⅰ (conserved sequence Ⅰ)的639 bp,构建了pASapI-reve-Crpepc2和pASapI-forw-Crpepc2正反向叶绿体表达载体,并用基因枪法转化莱茵衣藻cc-400获得了空质粒型,正向型和反向型转基因藻株.其次,应用RT-qPCR方法检测Crpepc2的相对表达量,结果表明反向型Crpepc2的表达量减少了89.97％,而正向型增加了201.16％.最后,检测了总蛋白和脂质含量的变化,正向型突变株的总蛋白增加了37.03％;而反向型突变株的脂质含量增加了70.32％,且不饱和脂肪酸含量明显增加.以上结果证明莱茵衣藻“细菌型”PEPC的叶绿体表达不仅可以进一步提高蛋白质与脂肪酸含量,也可为今后外源蛋白的表达和高产油工程藻的应用做贡献.     

细胞脂滴的物理结构及影响其稳定的因素

脂滴是储存中性脂质的细胞器,对能量代谢至关重要,它们广泛存在于存在于动物、植 物、真菌,甚至细菌中。脂滴是油包水乳液在细胞水溶液中的分散相,乳液的基本生物物理原理 对于脂滴生物学的重要性正在被人们所重视。由于其存在于分散油相和水胞质之间的独特结 构,其形成,生长和收缩的具体机制尤为复杂,这种机制使细胞能够在代谢能量或膜合成需求发 生变化时使用乳化油,有利于为细胞新陈代谢提供更有利的途径。此外,脂滴表面的磷脂作为 表面活性剂组成的调控对脂滴的稳态和表面蛋白靶向至关重要。在这里,我们回顾脂滴的乳液 结构及其在     

动物脂肪代谢与调控

动物脂肪代谢受到多种因素的调控 ,碳水化合物、蛋白质、多不饱和脂肪酸和共轭亚油酸等营养因素 ,生长激素、胰岛素、胰岛素样生长因子、β-肾上腺素能受体兴奋剂、腺苷及其核苷酸和肿瘤坏死因子 - α等激素都对脂肪代谢产生影响。动物脂肪细胞膜免疫也对脂肪代谢产生调控作用     

C-terminal signal sequence promotes virulence factor secretion in Mycobacterium tuberculosis

Mycobacterium tuberculosis uses the ESX-1/Snm system [early secreted antigen 6 kilodaltons (ESAT-6) system 1/secretion in mycobacteria] to deliver virulence factors into host macrophages during infection. Despite its essential role in virulence, the mechanism of ESX-1 secretion is unclear. We found that the unstructured C terminus of the CFP-10 substrate was recognized by Rv3871, a cytosolic component of the ESX-1 system that itself interacts with the membrane protein Rv3870. Point mutations in the signal that abolished binding of CFP-10 to Rv3871 prevented secretion of the CFP-10 (culture filtrate protein, 10 kilodaltons)/ESAT-6 virulence factor complex. Attachment of the signal to yeast ubiquitin was sufficient for secretion from M. tuberculosis cells, demonstrating that this ESX-1 signal is portable.     

TRB3 links the E3 ubiquitin ligase COP1 to lipid metabolism

During fasting, increased concentrations of circulating catecholamines promote the mobilization of lipid stores from adipose tissue in part by phosphorylating and inactivating acetyl-coenzyme A carboxylase (ACC), the rate-limiting enzyme in fatty acid synthesis. Here, we describe a parallel pathway, in which the pseudokinase Tribbles 3 (TRB3), whose abundance is increased during fasting, stimulates lipolysis by triggering the degradation of ACC in adipose tissue. TRB3 promoted ACC ubiquitination through an association with the E3 ubiquitin ligase constitutive photomorphogenic protein 1 (COP1). Indeed, adipocytes deficient in TRB3 accumulated larger amounts of ACC protein than did wild-type cells. Because transgenic mice expressing TRB3 in adipose tissue are protected from diet-induced obesity due to enhanced fatty acid oxidation, these results demonstrate how phosphorylation and ubiquitination pathways converge on a key regulator of lipid metabolism to maintain energy homeostasis.     

Fat metabolism links germline stem cells and longevity in C. elegans

Fat metabolism, reproduction, and aging are intertwined regulatory axes; however, the mechanism by which they are coupled remains poorly understood. We found that germline stem cells (GSCs) actively modulate lipid hydrolysis in Caenorhabditis elegans, which in turn regulates longevity. GSC arrest promotes systemic lipolysis via induction of a specific fat lipase. Subsequently, fat mobilization is promoted and life span is prolonged. Constitutive expression of this lipase in fat storage tissue generates lean and long-lived animals. This lipase is a key factor in the lipid hydrolysis and increased longevity that are induced by decreased insulin signaling. These results suggest a link between C. elegans fat metabolism and longevity.     

Microbodies (peroxisomes) containing catalase in myocardium: morphological and biochemical evidence

Microbodies characterized by a single limiting membrane and finely granular matrix occur in mouse myocardium and appear in close spatial relation to mitochondria and sarcoplasmic reticulum. The presence of catalase in the microbodies is revealed cytochemically and confirmed biochemically by direct measurement of its activity in myocardial tissue fractions. It is suggested that the microbodies may play an important role in myocardial lipid metabolism.     

The elastin receptor: a galactoside-binding protein

The elastin receptor complex contains a component of 67 kilodaltons that binds to a glycoconjugate affinity column containing beta-galactoside residues and is eluted from this column with lactose. This protein component is also released from the surface of cultured chondroblasts by incubation with lactose, and its association with immobilized elastin is inhibited by lactose. Since lactose also blocks elastic fiber formation by cultured chondroblasts, the galactoside-binding property of the elastin receptor is implicated in this process.