小鼠海马内HDAC2的表达及其与NMDA受体、PSD-95的共定位

目的探讨组蛋白去乙酰化酶2（HDAC2）在成年C57BL/6小鼠海马内的分布及其与突触后致密区（PSD）蛋白成员的共定位,为揭示HDAC2与PSD蛋白复合物之间的内在联系及在海马相关的学习记忆过程中可能起到的调控作用提供形态学依据。方法应用免疫组化方法观察HDAC2在C57BL/6小鼠海马各区的表达分布。应用免疫荧光双标技术研究HDAC2与PSD蛋白成员N-甲基-D-天冬氨酸（NMDA）受体亚单位1（NR1）、PSD-95之间是否存在共定位。结果 HDAC2在小鼠海马CA1～CA3区锥体细胞和齿状回颗粒细胞均具有明显表达,而在各区的始层、辐射层、腔隙-分子层以及齿状回多形细胞层表达均较少。免疫荧光双标染色图片的重叠表明,HDAC2与NR1、PSD-95在小鼠海马CA1～CA3区锥体细胞层和齿状回颗粒细胞层内均可见显著共表达现象,其他区域偶见散在分布的双染神经元。结论 HDAC2在小鼠海马锥体细胞层和颗粒细胞层表达丰富,并与PSD蛋白成员间存在共定位现象。本实验结果为探讨HDAC2对谷氨酸能突触后神经元依赖的突触可塑性的调节机制提供了形态学依据。     

SIRT1介导的K-Ras、FoxOs和DLC1的表达及翻译后修饰调控癌细胞的增殖和凋亡

SIRT1是一种NAD+依赖的组蛋白去乙酰化酶,可通过其去乙酰化酶活性介导下游蛋白,如K-Ras、FoxOs和DLC1的翻译后修饰来调节细胞增殖和细胞凋亡。在体外培养的癌细胞、异种移植癌细胞的裸鼠或是转基因小鼠中,K-Ras的乙酰化、FoxOs的乙酰化和磷酸化及DLC1的磷酸化对癌细胞的增殖或凋亡均发挥双重作用,研究SIRT1介导的翻译后修饰对于癌症的治疗具有重要的意义。     

SIRT1的生物学功能及其在胰岛素抵抗中的作用

SIRT1是NAD+依赖的组蛋白去乙酰化酶,通过使底物发生去乙酰化作用参与了DNA修复、细胞凋亡/细胞生存、细胞分化、内分泌信号通路和衰老等生命过程的调节.SIRT1在胰岛素敏感的组织器官中,通过调节胰岛素相关蛋白之间的相互作用与胰岛素信号转导途径,改善胰岛素敏感性和胰岛素抵抗,并且SIRT1在线粒体损伤中的作用与胰岛素抵抗发生有着密切的联系.     

SIRT3与细胞代谢及心血管疾病的相关性

蛋白去乙酰化酶在细胞生理过程中发挥着极为重要的作用。人蛋白去乙酰化酶包括HDACⅠ、HDACⅡ、HDACⅢ和HDACⅣ4个家族。其中第Ⅲ类即Sir2(Silent information regulator 2)家族包括7个成员——SIRT1~ SIRT7,每个成员都具有不同的细胞定位,并且发挥不同的生物学功能。作为主要定位于线粒体的组蛋白去乙酰化酶,SIRT3不仅调节细胞的能量代谢,并在细胞凋亡、肿瘤生长和一些疾病中发挥作用。文章综述了SIRT3在细胞代谢中的生物学功能以及其在心血管疾病中的研究进展。     

SIRT7在肿瘤发生发展中的研究进展

Sirtuins蛋白家族是一类高度保守的烟酰胺腺嘌呤二核苷酸(NAD+)依赖的组蛋白去乙酰化酶。哺乳动物中的Sirtuins包括七种亚型:SIRT1-SIRT7,作为Sirtuins蛋白家族成员之一,SIRT7定位于核仁,是一种高度特异性的H3K18Ac(组蛋白H3的乙酰化赖氨酸残基18)去乙酰化酶。SIRT7的作用底物包括组蛋白和非组蛋白,底物的多样性决定着它参与体内多种细胞活动,如:细胞增殖、细胞新陈代谢、DNA损伤和应激反应等,并与肿瘤的发生发展密切相关。SIRT7在乳腺癌、甲状腺癌、卵巢癌、宫颈癌、胃癌、结直肠癌和肝细胞癌等多种肿瘤中高表达;而在头颈部鳞癌和胰腺癌中的低表达又提示其可作为抑癌基因发挥作用。本文旨从SIRT7的基因组组成、作用底物及相关肿瘤作用机制等方面阐述SIRT7的研究进展,而其致癌或抑癌作用有可能使其成为肿瘤治疗的新靶点。     

老龄小鼠卵母细胞发育过程中组蛋白乙酰化修饰的改变

分别取年轻C57/B6雌性小鼠(3-4周龄)与老龄C57/B6雌性小鼠(40-42周龄)不同发育时期的卵母细胞,利用免疫荧光技术观察其组蛋白不同赖氨酸位点乙酰化的变化,并用RT-PCR法检测年轻小鼠与老龄小鼠卵母细胞不同发育时期Hdac1与Hdac3(组蛋白去乙酰化酶)mRNA的相对表达量。结果显示:(1)年轻小鼠和老龄小鼠卵母细胞组蛋白H4/K12、H4/K16、H4/K5及H3/K14的乙酰化水平均随发育进程逐渐升高,在完全生长期乙酰化水平达到峰值,至MⅡ期,除H4/K12外,其它三个位点的乙酰化全部消失;与年轻小鼠相比,完全生长期时老龄小鼠卵母细胞组蛋白乙酰化水平较低;(2)在完全生长期之前,年轻小鼠和老龄小鼠卵中Hdac-1与Hdac-3 mRNA的表达量呈逐渐降低趋势,但老龄小鼠在MⅡ期有所升高。与年轻小鼠相比,老龄小鼠完全生长期前各时期卵母细胞中Hdac1 mRNA的表达量均极显著降低(P<0.01);而Hdac3 mRNA的表达量二者之间无显著差异。结果表明:老龄小鼠卵母细胞中组蛋白乙酰化和组蛋白去乙酰化酶表达出现了异常变化。     

沉默信息调节因子1在消化系统肿瘤中的作用

沉默信息调节因子1(SIRT1)是Sirtuin 家族中的一员,属于烟酰胺（NAD⁺）依赖的Ⅲ类组蛋白去乙酰化酶,能通过对多种非组蛋白及组蛋白赖氨酸残基进行去乙酰化修饰调节基因表达。近来的研究发现,SIRT1不仅能使肿瘤抑制因子去乙酰化,促进肿瘤发生,还能使肿瘤促进因子去乙酰化,抑制肿瘤发生。SIRT1与肿瘤的生物学特性密切相关,影响肿瘤分期及患者预后。在消化系统肿瘤中,SIRT1具有双面性,既可作为抑癌因子,也可发挥癌因子的作用。近年来,许多研究对SIRT1在肿瘤中的作用靶点及相关信号通路做了深入研究,关于SIRT1在肿瘤中作用机制的新研究不断出现。SIRT1已成为人们攻克肿瘤的一个研究热点。本文通过对SIRT1在肿瘤中的双重作用,尤其是在消化系统肿瘤中的不同作用靶点和参与的信号通路作一综述,希望为临床上治疗消化系统肿瘤提供更有说服力的证据。     

SIRT6在能量代谢中的作用

SIRT6是沉默信息调节蛋白家族成员之一,是一种依赖于烟酰胺腺嘌呤二核苷酸(NAD+)的组蛋白去乙酰化酶及ADP-核糖基转移酶的蛋白酶。其在机体的生理、病理过程中具有重要的调控作用,参与调控机体寿命与衰老、癌症、肥胖、胰岛素抵抗及炎症反应等过程。近期研究发现,SIRT6在脂代谢、糖代谢过程中具有重要的调控作用。SIRT6基因敲除小鼠具有严重的低血糖、脂肪肝等。此外,SIRT6具有保护高脂饮食引起的肥胖及胰岛素抵抗的作用。该综述主要概述了SIRT6在能量代谢中的作用。     

Sirtuin1:抗炎治疗新靶点

Sirtuin 1(SIRT1)是组蛋白去乙酰化酶的代表性成员,除可调节代谢、衰老、凋亡外,SIRT1还可通过催化组蛋白及核因子κB(NF-κB)、激活蛋白1(AP-1)等的去乙酰化,从而改变染色质构象、降低转录因子活性、下调炎症基因转录。临床研究已揭示SIRT1在某些炎症性疾病中含量明显降低,而动物实验证实白藜芦醇、SRT1720等SIRT1激活剂可有效减轻炎症损伤。因而,SIRT1有望成为抗炎治疗的新靶点。     

去乙酰化酶SIRT1的表达及活性调控机制

SIRT1是哺乳动物中重要的NAD+依赖性去乙酰化酶,参与许多重要的生理和病理过程,如衰老、细胞死亡和肿瘤发生。如何精确调节SIRT1的表达和活性对SIRT1执行其生物学功能至关重要。文章以基因表达的不同阶段为切入点,对调控SIRT1表达及活性的机制进行了论述。     

SIRT2 negatively regulates insulin resistance in C2C12 skeletal muscle cells

SIRT2 is primarily a cytoplasmic protein deacetylase and is abundantly expressed in metabolically active tissues like adipocytes and brain. However, its role, if any, in regulating insulin signaling in skeletal muscle cells, is not known. We have examined the role of SIRT2 in insulin-mediated glucose disposal in normal and insulin resistant C2C12 skeletal muscle cells in vitro. SIRT2 was over expressed in insulin resistant skeletal muscle cells. Pharmacological inhibition of SIRT2 increased insulin-stimulated glucose uptake and improved phosphorylation of Akt and GSK3β in insulin resistant cells. Knockdown of endogenous SIRT2 and over expression of catalytically-inactive SIRT2 mutant under insulin-resistant condition showed similar amelioration of insulin sensitivity. Our results suggest that down-regulation of SIRT2 improved insulin sensitivity in skeletal muscle cells under insulin-resistant condition. Previously it has been reported that down-regulation of SIRT1 and SIRT3 in C2C12 cells results in impairment of insulin signaling and induces insulin resistance. However, we have observed an altogether different role of SIRT2 in skeletal muscle. This implicates a differential regulation of insulin resistance by sirtuins which otherwise share a conserved catalytic domain. The study significantly directs towards future approaches in targeting inhibition of SIRT2 for therapeutic treatment of insulin resistance which is the major risk factor in Type 2 diabetes.     

SIRT6在缺血再灌注损伤中的作用机制及研究进展

缺血性损伤后恢复血液供应会导致缺血再灌注（ischemia reperfusion, IR）损伤,这会导致组织损伤进一步加剧。IR损伤伴随着一系列机制,包括谷氨酸兴奋性毒性、钙超载、氧化应激、炎症和细胞凋亡,最终导致细胞死亡。IR损伤过程均由Sirtuins家族调控,在Sirtuins家族中,特异性定位于细胞核中的SIRT6可以促进对DNA损伤和氧化应激的抵抗,抑制基因组的不稳定性,在代谢稳态中发挥作用,同时SIRT6在人重要脏器中处于高度表达状态。但SIRT6在IR损伤中研究较少,结合国内外最新的研究进展,对SIRT6在IR损伤中的作用进行了回顾性的总结和分析,希望对国内外学者对于SIRT6在IR损伤中的研究提供一些参考依据。     

SIRT1 attenuates palmitate-induced endoplasmic reticulum stress and insulin resistance in HepG2 cells via induction of oxygen-regulated protein 150

Endoplasmic reticulum (ER) stress has been implicated in the pathology of type 2 diabetes mellitus (T2DM). Although SIRT1 has a therapeutic effect on T2DM, the mechanisms by which SIRT1 ameliorates insulin resistance (IR) remain unclear. In this study, we investigated the impact of SIRT1 on palmitate-induced ER stress in HepG2 cells and its underlying signal pathway. Treatment with resveratrol, a SIRT1 activator significantly inhibited palmitate-induced ER stress, leading to the protection against palmitate-induced ER stress and insulin resistance. Resveratrol and SIRT1 overexpression induced the expression of oxygen-regulated protein (ORP) 150 in HepG2 cells. Forkhead box O1 (FOXO1) was involved in the regulation of ORP150 expression because suppression of FOXO1 inhibited the induction of ORP150 by SIRT1. Our results indicate a novel mechanism by which SIRT1 regulates ER stress by overexpression of ORP150, and suggest that SIRT1 ameliorates palmitate-induced insulin resistance in HepG2 cells via regulation of ER stress.     

Trifolium pratense (Red Clover) Improve SIRT1 Expression and Glycogen Content in High Fat Diet‐Streptozotocin Induced Type 2 Diabetes in Rats

Flowering tops of Trifolium pratense L. (Fabaceae) are known for its traditional medicinal values. In present study, our aim was to investigate effect of standardized aqueous extract of flowering tops of Trifolium pratense L. on insulin resistance and SIRT1 expression in type 2 diabetic rats. Type 2 diabetes was induced by feeding high fat diet and administering low dose of streptozotocin. Diabetic animals were treated with standardized aqueous extract at three different doses. Parameters such as blood glucose, lipid profile, glycohemoglobin, insulin sensitivity, HOMA‐IR and liver glycogen content were measured. Changes in morphology and expression of SIRT1 in pancreatic tissue were measured in histopathological and immunohistological studies. Aqueous extract treatment showed reduction in hyperglycemia and improved insulin sensitivity. Extract treatment also showed reduction in formation of glycated hemoglobin and improved liver glycogen level. Histopathological study revealed protecting effect of extract in pancreatic tissue against hyperglycemia induced damage. Treatment increased expression of SIRT1 in rat pancreatic tissue. Results indicate that the aqueous extract of Trifolium pratense had beneficial role in improving insulin sensitivity and SIRT1 expression.     

Metformin overcomes high glucose-induced insulin resistance of podocytes by pleiotropic effects on SIRT1 and AMPK

Podocyte insulin sensitivity is critical for glomerular function, and the loss of appropriate insulin signaling leads to alterations and disorders featuring diabetic nephropathy. Energy-sensing pathways, such as AMP-dependent protein kinase (AMPK) and protein deacetylase SIRT1, have been shown to play an important role in insulin resistance. The absence of a stimulating effect of insulin on glucose uptake into podocytes after exposure to hyperglycemic conditions has been demonstrated to be related to a decreased level and activity of SIRT1 protein, leading to reduced AMPK phosphorylation.The present work was undertaken to investigate metformin's ability to restore the insulin responsiveness of podocytes by regulating SIRT1 and AMPK activities.Primary rat podocytes cultured with standard or high glucose concentrations for 5 days were transfected with siRNAs targeting SIRT1, AMPKα1, or AMPKα2. SIRT1 activity was measured by a fluorometric method. Insulin-stimulated changes in glucose uptake were used to detect insulin resistance. Podocyte permeability was measured by a transmembrane albumin flux assay to examine podocytes functioning.Our results demonstrated that metformin activated SIRT1 and AMPK, prevented hyperglycemia-induced reduction of SIRT1 protein levels, ameliorated glucose uptake into podocytes, and decreased glomerular filtration barrier permeability. Furthermore, metformin activated AMPK in a SIRT1-independent manner, as the increase in AMPK phosphorylation after metformin treatment was not affected by SIRT1 downregulation. Therefore, the potentiating effect of metformin on insulin-resistant podocytes seemed to be dependent on AMPK, as well as SIRT1 activity, establishing multilateral effects of metformin action.     

姜黄素后处理通过SIRT1/FOXO1信号通路拮抗小鼠脑缺血再灌注损伤

目的:探究姜黄素后处理是否通过激活SIRT1/FOXO1信号通路抵抗小鼠脑缺血再灌注损伤。方法:小鼠脑缺血30 min,再灌注24 h建立脑缺血再灌注模型。手术前脑室内注射SIRT1特异性抑制剂EX527。再灌注后腹腔注射姜黄素。小鼠随机分为以下6组:假手术组;单纯姜黄素后处理组;缺血再灌注组;缺血再灌注+姜黄素后处理组;EX527预处理+缺血再灌注+姜黄素后处理组;EX527预处理+脑缺血再灌注组。再灌注24 h检测脑梗体积、Complex I活性、ROS含量以及SIRT1、Ac-FOXO1、Bax、Bcl-2、Caspase-3蛋白表达情况。结果:与手术组相比,姜黄素后处理组梗死区脑组织SIRT1的表达量及活性明显增加,脑梗体积降低,ROS含量降低而Complex I活性增高,Bcl-2的表达增高而Bax和Caspase-3的表达量降低(均P0.05)。阻断SIRT1信号通路后上述姜黄素脑保护作用均减弱(P0.05)。结论:我们的研究首次证实姜黄素后处理通过激活SIRT1/FOXO1信号通路,进而降低氧化应激与凋亡,最终减轻脑缺血再灌注损伤。     

SIRT6 Deficiency Results in Severe Hypoglycemia by Enhancing Both Basal and Insulin-stimulated Glucose Uptake in Mice

Glucose homeostasis in mammals is mainly regulated by insulin signaling. It was previously shown that SIRT6 mutant mice die before 4 weeks of age, displaying profound abnormalities, including low insulin, hypoglycemia, and premature aging. To investigate mechanisms underlying the pleiotropic phenotypes associated with SIRT6 deficiency, we generated mice carrying targeted disruption of SIRT6. We found that 60% of SIRT6^−/− animals had very low levels of blood glucose and died shortly after weaning. The remaining animals, which have relatively higher concentrations of glucose, survived the early post-weaning lethality, but most died within one year of age. Significantly, feeding the mice with glucose-containing water increased blood glucose and rescued 83% of mutant mice, suggesting that the hypoglycemia is a major cause for the lethality. We showed that SIRT6 deficiency results in more abundant membrane association of glucose transporters 1 and 4, which enhances glucose uptake. We further demonstrated that SIRT6 negatively regulates AKT phosphorylation at Ser-473 and Thr-308 through inhibition of multiple upstream molecules, including insulin receptor, IRS1, and IRS2. The absence of SIRT6, consequently, enhances insulin signaling and activation of AKT, leading to hypoglycemia. These data uncover an essential role of SIRT6 in modulating glucose metabolism through mediating insulin sensitivity.     

Reduced expression of SIRT1 is associated with diminished glucose-induced insulin secretion in islets from calorie-restricted rats

Alterations in food intake such as caloric restriction modulate the expression of SIRT1 and SIRT4 proteins that are involved in pancreatic β-cell function. Here, we search for a possible relationship between insulin secretion and the expression of SIRT1, SIRT4, PKC and PKA in islets from adult rats submitted to CR for 21 days. Rats were fed with an isocaloric diet (CTL) or received 60% (CR) of the food ingested by CTL. The dose-response curve of insulin secretion to glucose was shifted to the right in the CR compared with CTL islets (EC₅₀ of 15.1±0.17 and 10.5±0.11 mmol/L glucose). Insulin release by the depolarizing agents arginine and KCl was reduced in CR compared with CTL islets. Total islet insulin content and glucose oxidation were also reduced in CR islets. Leucine-stimulated secretion was similar in both groups, slightly reduced in CR islets stimulated by leucine plus glutamine but higher in CR islets stimulated by ketoisocaproate (KIC). Insulin secretion was also higher in CR islets stimulated by carbachol, compared with CTL islets. No differences in the rise of cytosolic Ca²⁺ concentrations stimulated by either glucose or KCl were observed between groups of islets. Finally, SIRT1, but not SIRT4, protein expression was lower in CR compared with CTL islets, whereas no differences in the expression of PKC and PKA proteins were observed. In conclusion, the lower insulin secretion in islets from CR rats was, at least in part, due to an imbalance between the expression of SIRT1 and SIRT4.     

褪黑素通过激活SIRT1信号通路发挥抗肺缺血再灌注损伤作用

目的:研究褪黑素(Melatonin,Mel)在肺缺血再灌注损伤中的作用,明确沉默信息调控因子1(Silent information regulator 1,SIRT1)信号通路在这一过程中的关键作用。方法:建立大鼠肺缺血再灌注损伤(IR)模型,实验分为Control、IR、IR+10 mg/Kg Mel、IR+20 mg/Kg Mel、IR+30 mg/Kg Mel五组,通过检测支气管肺泡灌洗液中白细胞数目、蛋白含量和肺组织中丙二醛(MDA)水平、干湿重比等指标明确肺组织损伤程度,Western blot检测SIRT1通路相关分子及凋亡相关蛋白的表达水平,研究其作用机制。结果:与IR组相比,Mel处理显著降低了支气管肺泡灌洗液中白细胞数量、蛋白含量和肺组织MDA含量、干湿重比(P0.05);Mel还显著上调了SIRT1表达,降低了Ac-FOXO1表达(P0.05);此外,Mel显著提高了抗凋亡蛋白Bcl-2表达,下调了凋亡蛋白Bax表达(P0.05)。结论:Mel具有明确的抗肺缺血再灌注损伤的作用,SIRT1信号通路在该过程中可能扮演重要角色。