microRNAs——脂质代谢调控新机制

综述了近年来microRNAs,尤其是miR-33在脂质代谢调控方面的功能研究进展.脂质代谢在细胞水平进行有规律的调控,主要参与者有肝X受体(LXRs)和固醇调节元件结合蛋白(SREBPs)等.最近研究发现,非编码RNAs家族成员microRNAs在转录后水平调节脂质代谢相关基因表达,参与胆固醇、甘油三酯和脂肪酸代谢.其中miR-33可靶向沉默三磷酸脂苷结合盒(ABC)转运体家族成员ABCA1和ABCG1,抑制胆固醇流出和高密度脂蛋白(HDL)合成;通过靶向沉默脂肪酸β-氧化相关基因,如CPT1A、CROT和HADHB表达,抑制脂肪酸氧化;还可沉默AMPK和RIP140的表达,影响甘油三酯代谢.其他microRNAs如miR-122、miR-370、miR-125a-5p、miR-27、miR-320等,也参与调控胆固醇、甘油三脂、脂肪酸代谢及脂肪细胞分化.     

Leptin介导的JAK/STAT信号通路对脂类代谢调节的研究进展

Leptin介导的JAK/STAT信号通路主要参与脂类代谢的调节。JAK/STAT信号通路激活后,CPT-1的表达水平升高,通过促进脂肪酸分解而参与脂类代谢的调节。本文主要介绍了近年来关于leptin介导的JAK/STAT信号通路的组成、作用机制、活性调节和leptin与受体结合激活细胞内多个信号通路如JAK/STAT、PI3K/Akt、MAPK等,以及这些信号通路对脂类代谢调节的最新研究进展。     

固醇调节元件结合蛋白与脂质代谢

固醇调节元件结合蛋白(sterol regulatory element-binding proteins,SREBPs)是脊椎动物细胞脂质稳态的转录调节物,可直接激活多个参与胆固醇、脂肪酸、甘油三酯、磷脂合成和摄取,以及辅助因子NADPH等基因的表达,从而调控胆固醇及脂肪酸等脂类的代谢过程。本文综述了SREBPs转运和活化的过程,以及调节细胞脂质稳态功能的分子机制,并探讨了其在脂代谢紊乱相关疾病发生中的重要作用。     

miRNAs与脂蛋白酯酶

miRNAs是一类具有调控基因功能的非编码RNAs,它在细胞核中合成,可转运至细胞质,调控脂质代谢相关性疾病的发生发展。脂蛋白酯酶(lipoprotein lipase,LPL)作为甘油三酯水解的限速酶,由心肌、脂肪、骨骼肌、乳腺及巨噬细胞等实质细胞合成和分泌,在脂蛋白转运和脂质代谢过程中发挥重要作用。近期研究证实多种miRNAs,包括miR-29、miR-467b、miR-590、miR-27、miR-134和miR-186,可通过调控脂蛋白酯酶LPL的表达,进而影响脂质代谢。为了深入探讨miRNAs对LPL的影响,本文以miRNAs对LPL的调控作用进行综述,期望以miRNAs为靶点,为脂质代谢相关性疾病的防治提供治疗方案。     

microRNAs与TP53基因调控网络研究进展

TP53基因(编码p53蛋白)作为一个重要的抑瘤基因,通过调控一系列信号转导通路广泛参与了多种恶性肿瘤的发生发展,一直是肿瘤分子生物学研究领域的热点.最近的研究发现,microRNAs(miRNAs)参与了TP53的信号通路,它们之间存在着复杂的调控网络.一方面,p53通过调控一些miRNAs的转录及转录后成熟,促进细胞周期阻滞、诱导细胞凋亡和衰老,抑制肿瘤发生.另一方面,许多miRNAs,如miR-25、miR-30d、miR-125b和miR-504等可直接调控p53的表达与活性,参与TP53信号通路的调节,还有一些miRNAs则通过调节p53上下游基因,发挥重要的生物学功能.其中,最具有代表性的是miR-34家族,它们受p53直接调控并参与TP53信号通路,通过靶向抑制多个TP53信号通路关键分子的表达,发挥抑瘤作用.此外,它们还可以通过抑制沉默信息调节子,增强p53的活性,反馈调节TP53信号通路.miRNAs与TP53之间调控网络的研究,是对TP53抑瘤机制的重要补充.     

涉及脂质代谢的miRNA及其对动脉粥样硬化发展和治疗的进展

MicroRNA是一类长度为18～24碱基的非编码小分子RNA,作为基因表达转录后调控因子,涉及多种生理、病理过程,包括调节脂质代谢和动脉粥样硬化。通过机体代谢,miR-126、miR-155、miR-221/222、miR-124、miR-145、miR-133、miR-663、miR-29等可参与动脉粥样硬化的形成和发展。目前有超过30种miRNA,包括miR-33、miR-122、miR-223和miR-27a/b也在调节脂肪酸生物合成及氧化,胆固醇的流出等脂质代谢中起重要作用。此外,"循环miRNA"的发现为其成为动脉粥样硬化性疾病的新型生物标志物提供可能。本综述通过探讨miRNA调节脂质代谢途径,参与动脉粥样硬化的发生、发展过程,为动脉粥样硬化疾病提供新的分子学观点并为深入研究其治疗靶点提供理论依据。     

饲料硒含量对黄颡鱼肠系膜脂肪组织中脂类代谢和miRNAs表达水平的影响

使用3种不同硒含量的饲料饲养黄颡鱼12周, 研究饲料硒含量对黄颡鱼(Pelteobagrus fulvidraco)肠系膜脂肪组织脂类代谢和miRNAs表达水平的影响, 饲料硒含量分别为0.03(低硒组)、0.25(适宜硒组)和6.39 mg Se/kg饲料(高硒组)。结果表明, 相比较于适宜硒组, 高硒和低硒组中甘油三酯(TG)含量显著升高(P<0.05), 葡萄糖-6-磷酸脱氢酶(G6PD)和6-磷酸葡萄糖脱氢酶(6PGD)的酶活性在低硒组中活性显著下降(P<0.05), 在高硒组中活性显著上升(P<0.05); 异柠檬酸脱氢酶(ICDH)的酶活性在低硒组中没有显著性变化(P>0.05), 在高硒组中显著下降(P<0.05); 苹果酸酶(ME)和脂肪酸合成酶(FAS)的酶活性在低硒和高硒组中均显著上升(P<0.05)。相比于适宜硒组, 在高硒组miR-26a、miR-183、miR-135、let-7b、let-7c和let-7g的表达量显著上升(P<0.05), 而在低硒组中没有显著性差异(P>0.05); miR-181a-5p和let-7e在低硒组中显著上升(P<0.05), 在高硒组中没有显著性差异(P>0.05); miR-130和miR-203a在低硒和高硒组中表达量均显著上升(P<0.05); miR-200a、miR-143、let-7d和let-7f在低硒组中表达量显著下降同时在高硒组中表达量上升(P<0.05)。miR-143、miR-203a和miR-130在脂肪组织中高表达, 且对硒产生强响应, 通过TargetScanFish6.2和miRwalk3.0共预测3个miRNA的靶基因, 并对靶基因进行KEGG富集分析, 结果显示, miR-143的靶基因在矿物盐吸收、不饱和脂肪酸生物合成、胰岛素通路、自噬、脂肪酸代谢、鞘脂类代谢、调节脂肪细胞脂肪分解和甘油磷脂代谢等途径中显著富集(P<0.05, FDR≤0.05); miR-203a的靶基因在胰岛素抵抗、胰岛素通路、调节脂肪细胞脂肪分解和自噬等代谢途径、信号通路中显著富集(P<0.05, FDR≤0.05); miR-130的靶基因在胰岛素通路、胰岛素抵抗、自噬、鞘脂类代谢、调节脂肪细胞脂肪分解和mTOR通路中显著富集(P<0.05, FDR≤0.05)。综合分析发现, miR-143、miR-203a和miR-130的靶基因共同富集在脂肪酸合成、调节脂肪细胞脂肪分解、胰岛素抵抗等脂代谢相关的通路中, 选取共富集通路中的靶基因进行qPCR检测, 结果显示fas、碳水化合物反应元件结合蛋白α(chrebpα)、肉碱棕榈酰转移酶1α(cpt1α)、激素敏感酯酶(hsl)、固醇调节元件结合蛋白(srebp1)、过氧化物酶体增殖剂激活受体α(pparα)和脂肪组织甘油三酯酶(atgl)的表达趋势与miR-143、miR-203a和miR-130的表达趋势相符合, 推测饲料硒缺乏和过量诱导黄颡鱼肠系膜脂肪组织脂质沉积是通过诱导miR-143、miR-203a和miR-130的表达量上调, 进而负调控靶基因chrebpa、cpt1a、hsl、srebp1、ppara和atgl的表达实现。     

微小RNA与细胞凋亡的研究进展

微小RNA(miRNAs)是最近发现的由18~24个核苷酸组成的RNA,通过对目标mRNA的抑制而发挥重要的调节作用。目前所有已研究的多细胞真核生物表明它们是通过miRNAs来调节细胞基本的生理功能,这些功能包括细胞的增殖、分化和死亡。本文讨论了miRNAs在调节细胞增殖和凋亡方面的功能:其中,抗凋亡的miRNAs有miR-17家族、miR-21、bantam和miR-14;促凋亡的miRNAs有let-7、miR-15a和miR-16。     

调节小鼠胰腺发育中Ptf1a基因表达的microRNAs的鉴定研究

Ptf1a,又名p48,是Ptf1转录因子的一个亚基,为胰腺命运决定与细胞分化必需的转录因子．最近研究发现,Ptf1a表达的丰度变化与发育中胰腺细胞生长、分化和胰岛?茁细胞数量密切相关．然而,胰腺细胞中Ptf1a的表达调节机制还不清楚．MicroRNAs(miRNAs)是一类约22nt的非编码小RNA,它们通过切割靶mRNA或抑制靶mRNA的翻译调节基因的表达．一些研究提示,miRNAs参与调控胰腺发育的多个过程．因而推测,miRNAs可能在胰腺发育中参与调控Ptf1a的表达变化．为了验证这一假设,结合两个靶基因预测算法的结果,获得4个可能调控Ptf1a表达的miRNAs．随后,利用双荧光素酶报告系统研究发现,预测得到miRNAs中的miR-18a,miR-145 和miR-495能通过结合到小鼠Ptf1a mRNA的3′UTR而有效抑制其表达．还利用qRT-PCR和免疫荧光染色实验研究了miR-18a、miR-145和miR-495与Ptf1a在小鼠胰腺发育过程中的表达模式．结果表明,miR-18a,miR-145和miR-495与Ptf1a mRNA及蛋白质的表达成负相关,进一步说明miR-18a, miR-145和miR-495可能在小鼠胰腺发育中调节Ptf1a的表达．     

miR-17-92基因簇microRNAs对哺乳动物器官发育及肿瘤发生的调控

microRNAs(miRNAs)是近年发现的一种高度保守的非编码小RNA, 它们通过抑制靶基因mRNA的翻译或将其降解, 在转录后水平调控基因的表达, 参与调控哺乳动物多个器官的发育过程和人类疾病的发生。miR-17-92基因簇是一个高度保守的基因簇, 编码miR-17-5p、miR-17-3p、miR-18a、miR-19a、miR-20a、miR-19b-1和miR-92-1等7个miRNAs。大量证据表明, miR-17-92基因簇miRNAs参与了心、肺、免疫系统的发育、血管生长及前脂肪细胞的分化等过程。此外, miR-17-92基因簇miRNAs在多种肿瘤中高表达, 能作为致癌基因诱发淋巴瘤和血管化肿瘤的发生, 但它也可以作为抑癌基因抑制乳腺癌细胞的增殖。文章对miR-17-92基因簇miRNAs在哺乳动物器官发育及肿瘤发生中的作用进行综述     

细菌不饱和脂肪酸合成研究进展

脂肪酸不仅是细菌细胞膜组分，还是许多生物活性物质的合成原料。不饱和脂肪酸(unsaturated fatty acid, UFA)具有更低的相变温度，是细菌调节细胞膜流动性的重要分子，因此UFA合成途径是重要的抗菌药物筛选靶点。细菌可利用厌氧途径合成UFA，其中模式生物大肠杆菌利用经典的FabA-FabB途径合成UFA，但不同细菌中UFA合成的厌氧途径具有多样性，相关催化酶类也不尽相同；细菌还可以利用需氧途径合成UFA，利用脂肪酸脱饱和酶直接将饱和脂肪酸(saturated fatty acid, SFA)转化为不饱和脂肪酸，而不同脱饱和酶会生成不同结构的UFA，在逆境耐受、致病力等多方面发挥重要作用；细菌还可以利用单加氧酶，将脂肪酸合成途径中癸酰酰基载体蛋白(acyl carrier protein, ACP)转化为顺-3-癸烯酰ACP，并最终合成UFA。细菌脂肪酸合成相关的其他酶类在UFA合成或不同种类UFA调节中也发挥着重要作用。本文系统地总结了细菌UFA合成途径与相关酶类的多样性研究进展，旨在为进一步了解细菌UFA合成机制，并以此为靶点开发抗菌药物等方面提供理论支撑。     

The role of Coenzyme A in lipid synthesis by a particulate fraction from germinating peas

The effect of CoA on fatty acid synthesis by the microsomal fraction from germinating pea (Pisum sativum) was examined. Increasing concentrations of CoA progressively decreased total fatty acid synthesis from [¹⁴C]malonyl-CoA. However, the synthesis of very long chain fatty acids was relatively unaffected so that their proportion in the reaction products increased. Other CoA-esters also decreased total fatty acid synthesis while increasing the relative accumulation of radioactivity in very long chain fatty acids. The addition of CoA also altered the distribution of newly synthesized fatty acids in different lipid fractions. Complex lipid labelling was relatively increased while that of acyl-acyl carrier proteins was decreased. Very long chain fatty acids accumulated in lipids rather than thioesters. The role of CoA in controlling fatty acid synthesis in the pea microsomal fraction is discussed.     

Effect of long chain fatty acids on triacylglycerol accumulation,fatty acid composition and related gene expression in primary cultured bovine satellite cells

Abstract

This study was conducted to determine the effects of long chain fatty acids (LCFAs) on triacylglycerol (TAG) content, as well as on genes associated with lipid synthesis and fatty acid composition in bovine satellite cells. Both saturated (palmitic and stearic) and unsaturated (oleic and linoleic) fatty acids stimulated the TAG accumulation at a concentration of 100?µM and oleate increased it significantly more than stearate and palmitate. The results revealed that the lipid droplet formation was markedly stimulated by linoleate and oleate at 100?µM. Compared to control, the expressions of adipose triglyceride lipase, carnitine acyltransferase 1 and the fatty acid translocase 36 were upregulated by LCFAs. All the fatty acids also significantly increased diacylglycerol acyltransferase 2 than the untreated control (p?<?0.05). The monounsaturated fatty acids significantly increased (p?<?0.05) in response to oleate and linoleate compared to the control as did the polyunsaturated fatty acids (p?<?0.05), in addition to stearate, linoleate and oleate. In contrast, saturated fatty acids were significantly decreased in the oleate and linoleate-treated groups. The study results contribute to our enhanced understanding of LCFAs’ regulatory roles on the bovine cell lipid metabolism.     

Die Gefriertrocknung von Rinderkot

Fatty acids in fish can arise from two sources: synthesis de novo from non‐lipid carbon sources within the animal, or directly from dietary lipid. Acetyl‐CoA derived mainly from protein can be converted to saturated fatty acids via the combined action of acetyl‐CoA carboxylase and fatty acid synthetase. The actual rate of fatty acid synthesis de novo is inversely related to the level of lipid in the diet. Freshwater fish can de‐saturate endogenously‐synthesized fatty acids to monounsaturated fatty acids via a A9 desaturase but lack the necessary enzymes for complete de novo synthesis of polyunsaturated fatty acids which must therefore be obtained preformed from the diet. Most freshwater fish species can desaturate and elongate 18:2(n‐6) and 18:3(n‐3) to their C20 and C22 homologues but the pathways involved remain ill‐defined. Cyclooxygenase and lipoxygenase enzymes can convert C20 polyunsaturated fatty acids to a variety of eicosanoid products. The dietary ratio of (n‐3) to (n‐6) polyunsaturated fatty acids influences the pattern of eicosanoids formed. The ß‐oxidation of fatty acids can occur in both mitochondria and peroxisomes but mi‐tochondrial ß‐oxidation is quantitatively more important and can utilise a wide range of fatty acid substrates.     

Fatty acid activation and utilization by Alistipes finegoldii,a representative Bacteroidetes resident of the human gut microbiome

Members of the Bacteroidetes phylum, represented by Alistipes finegoldii, are prominent anerobic, Gram-negative inhabitants of the gut microbiome. The lipid biosynthetic pathways were analyzed using bioinformatic analyses, lipidomics, metabolic labeling and biochemistry to characterize exogenous fatty acid metabolism. A. finegoldii only produced the saturated fatty acids. The most abundant lipids were phosphatidylethanolamine (PE) and sulfonolipid (SL). Neither phosphatidylglycerol nor cardiolipin are present. PE synthesis is initiated by the PlsX/PlsY/PlsC pathway, whereas the SL pathway is related to sphingolipid biosynthesis. A. finegoldii incorporated medium-chain fatty acids (≤14 carbons) into PE and SL after their elongation, whereas long-chain fatty acids (≥16 carbons) were not elongated. Fatty acids >16 carbons were primarily incorporated into the 2-position of phosphatidylethanolamine at the PlsC step, the only biosynthetic enzyme that utilizes long-chain acyl-ACP. The ability to assimilate a broad-spectrum of fatty acid chain lengths present in the gut environment is due to the expression of two acyl-acyl carrier protein (ACP) synthetases. Acyl-ACP synthetase 1 had a substrate preference for medium-chain fatty acids and synthetase 2 had a substrate preference for long-chain fatty acids. This unique combination of synthetases allows A. finegoldii to utilize both the medium- and long-chain fatty acid nutrients available in the gut environment to assemble its membrane lipids.     

Relationship between fatty acid binding proteins,acetyl-CoA formation and fatty acid synthesis in developing human placenta

The relationship between fatty acid binding proteins, ATP citrate lyase activity and fatty acid synthesis in developing human placenta has been studied. Fatty acid binding proteins reverse the inhibitory efect of palmitoyl-CoA and oleate on ATP citrate lyase and fatty acid synthesis. In the absence of these inhibitors fatty acid binding proteins activate ATP citrate lyase and stimulate [ 1-¹⁴ C] acetate incorporation into placental fatty acids indicating binding of endogenous inhibitors by these proteins. Thus these proteins regulate the supply of acetyl-CoA as well as the synthesis of fatty acids from that substrates. As gestation proceeds and more lipids are required by the developing placenta fatty acid binding protein content, activity of ATP citrate lyase and rate of fatty acid synthesis increase indicating a cause and efect relationship between the demand of lipids and supply of precursor fatty acids during human placental development.     

Metabolic profiles of fish nodavirus infection in vitro: RGNNV induced and exploited cellular fatty acid synthesis for virus infection

Red‐spotted grouper nervous necrosis virus (RGNNV), the causative agent of viral nervous necrosis disease, has caused high mortality and heavy economic losses in marine aquaculture worldwide. However, changes in host cell metabolism during RGNNV infection remain largely unknown. Here, the global metabolic profiling during RGNNV infection and the roles of cellular fatty acid synthesis in RGNNV infection were investigated. As the infection progressed, 71 intracellular metabolites were significantly altered in RGNNV‐infected cells compared with mock‐infected cells. The levels of metabolites involved in amino acid biosynthesis and metabolism were significantly decreased, whereas those that correlated with fatty acid synthesis were significantly up‐regulated during RGNNV infection. Among them, tryptophan and oleic acid were assessed as the most crucial biomarkers for RGNNV infection. In addition, RGNNV infection induced the formation of lipid droplets and re‐localization of fatty acid synthase (FASN), indicating that RGNNV induced and required lipogenesis for viral infection. The exogenous addition of palmitic acid (PA) enhanced RGNNV infection, and the inhibition of FASN and acetyl‐CoA carboxylase (ACC) significantly decreased RGNNV replication. Additionally, not only inhibition of palmitoylation and phospholipid synthesis, but also destruction of fatty acid β‐oxidation significantly decreased viral replication. These data suggest that cellular fatty acid synthesis and mitochondrial β‐oxidation are essential for RGNNV to complete the viral life cycle. Thus, it has been demonstrated for the first time that RGNNV infection in vitro overtook host cell metabolism and, in that process, cellular fatty acid synthesis was an essential component for RGNNV replication.     

Lipid Auxotrophy and the Effect on Lipid Composition of Entamoeba invadens*†

SYNOPSIS. A medium for the axenic cultivation of Entamoeba invadens has been developed. Serum, an essential constituent of conventional media, has been replaced by a mixture of albumin, unsaturated fatty acids, Tween, and cholesterol to control the lipid composition of the medium. Entamoeba invadens requires both cholesterol and unsaturated fatty acids for growth. The fatty acid composition of the phospholipids of the ameba reflects that of the medium to a great extent, especially with regard to the unsaturated fatty acids. The amount of membrane bounded cholesterol depends on the cholesterol concentration in the medium.     

Substrate Specificity and Regioselectivity of Δ12 and ω3 Fatty Acid Desaturases from Saccharomyces kluyveri

Δ12 and ω3 fatty acid desaturases are key enzymes in the synthesis of polyunsaturated fatty acids (PUFAs), which are important constituents of membrane glycerolipids and also precursors to signaling molecules in many organisms. In this study, we determined the substrate specificity and regioselectivity of the Δ12 and ω3 fatty acid desaturases from Saccharomyces kluyveri (Sk-FAD2 and Sk-FAD3). Based on heterologous expression in Saccharomyces cerevisiae, it was found that Sk-FAD2 converted C16–20 monounsaturated fatty acids to diunsaturated fatty acids by the introduction of a second double bond at the ν+3 position, while Sk-FAD3 recognized the ω3 position of C18 and C20. Furthermore, fatty acid analysis of major phospholipids suggested that Sk-FAD2 and Sk-FAD3 have no strong substrate specificity toward the lipid polar head group or the sn-positions of fatty acyl groups in phospholipids.