SIRT3与胰岛素抵抗

沉默信息调节因子(SIRT)3是哺乳动物类NAD+依赖性组蛋白去乙酰化酶家族中的一员.研究表明,SIRT3可以改善胰岛素抵抗、增加胰岛素敏感性.其通过保护胰岛β细胞、促进骨骼肌葡萄糖摄取、调节骨骼肌代谢、减轻氧化应激、抵抗高糖诱导的细胞毒性等途径发挥作用.SIRT3为治疗2型糖尿病、肥胖、线粒体功能障碍等疾病带来了新的研究方向.     

GLP-1受体激动剂呈葡萄糖依赖性刺激胰岛β细胞胰岛素分泌的机制

2型糖尿病的主要治疗目标是控制高血糖,然而传统的治疗药物如胰岛素和磺脲类药物在降低血糖的同时也可以出现低血糖.因此,应在一定的血糖范围内自我调整用药量,避免出现低血糖.低血糖会造成身心障碍,同时可引起心血管事件.因此临床用药应最大限度的降低低血糖风险.胰高血糖素样肽-1受体激动剂呈葡萄糖依赖性的刺激胰岛素分泌,在胰岛素剂量很小或者缺乏,以及血糖浓度不高时,胰高血糖素样肽-1受体激动剂则不会刺激或很少刺激胰岛素分泌.     

GLP-1受体激动剂的胰岛素增敏效应

2型糖尿病的发病机制主要涉及胰岛素抵抗张胰岛素分泌缺乏.研究表明,胰高血糖素样肽-1受体激动剂在有效改善胰岛β细胞功能,促进胰岛素分泌的同时,还能够作用于细胞信号转导,促进脂肪细胞分化和葡萄糖摄取,并通过减轻相关炎性反应因子表达,降低体重等,改善胰岛素抵抗,增加胰岛素敏感性.     

SIRT1通过AKT通路和ERK1/2通路共同调节退变髓核细胞细胞外基质的合成

目的 研究沉默信息调节因子2同源蛋白1(SIRT1/sirtuin 1)对已退变的人椎间盘髓核细胞(DNPCs)合成细胞外基质的影响.方法 对人DNPCs进行分离、培养及其细胞鉴定,第一部分取P2代细胞用白藜芦醇(RES,SIRT1激动剂)、二甲双胍(MET,SIRT1激动剂)、尼克酰胺(NAM,S1RT1抑制剂)、SIRT1-siRNA进行相应处理,采用Western印迹检测Ⅱ型胶原(COLLA2α1)、聚蛋白多糖(Aggrecan)及其p-AKT、t-AKT、p-ERK1/2、t-EKR1/2.第二部分先RES与P2代细胞共培养后分别加入PI3K与ERK的特异性抑制剂LY294002PD98059,观察COLLA2α1、Aggrecan的表达情况.结果 用SIRT1激动剂刺激以后COLLA2α1、Aggrecan的表达显著提高,AKT及其ERK1/2的磷酸化水平也相应提高,用NAM及其SIRT1-siRNA处理后COLLA2α1、Aggrecan的表达显著降低,AKT及其ERK1/2的磷酸化水平也显著降低.用LY294002和PD98059分别处理后观察到COLLA2α1、Aggrecan的表达亦显著降低.结论 SIRT1可通过AKT及其ERK1/2两条通路上调人DNPCs细胞外基质的表达,抑制椎间盘的变性,为进一步研究椎间盘退变的机制、组织工程学、基因治疗等奠定了基础.     

沉默信息调节因子1对高糖诱导的系膜细胞内皮素-1和转化生长因子β1的影响

目的探讨沉默信息调节因子1(SIRT1)对高糖诱导的系膜细胞内皮素-1(ET-1)和转化生长因子β1(TGF-β1)的影响。方法体外培养系膜细胞分为:(1)高糖组(高糖培养液);(2)SIRT1激动剂(白藜芦醇)+高糖组,含1μmol/L白藜芦醇的高糖培养液;(3)SIRT1 RNAi干扰+高糖组,加入pTRC-shSIRT1慢病毒感染;(4)正常对照(NC)组。检测各组细胞SIRT1基因表达,以及ET-1和TGF-β1水平。结果高糖组、SIRT1激动剂+高糖组、SIRT1RNAi干扰+高糖组及NC组ET-1含量分别为(56.1±6.3)、(31.9±5.1)、(105.63±8.2)和(17.3±3.4)pg/ml;TGF-β1含量分别为(43.3±5.7)、(27.5±4.9)、(87.4±7.3)和(15.6±3.6)ng/ml。高糖抑制SIRT1表达,上调ET-1和TGF-β1表达(P0.05);SIRT1激动剂可改善高糖对SIRT1的抑制,下调ET-1和TGF-β1表达(P0.05);沉默SIRT1,可上调ET-1和TGF-β1表达(P0.05)。结论 SIRT1基因对高糖诱导的系膜细胞ET-1和TGF-β1可能起负调控作用。     

2 氨基酸通过与细胞外钙敏感受体相互作用刺激胰岛素分泌(ADA 2001年会,37-OR)

波士顿的研究者报道了从INS-1胰岛素瘤细胞中克隆钙敏感受体(CaSR).β细胞CaSR与大鼠肾脏CaSR同分异构体密切相关.他们指出L-氨基酸可作为CaSR的激动剂是通过提高细胞内Ca2+浓度的信号途径来刺激葡萄糖诱导的胰岛素分泌,从而提出提高正常饮食的氨基酸水平可作为CaSR信号的生理刺激物增强葡萄糖诱导的胰岛素分泌.CaSR激动剂激活β细胞非选择性阳离子通道导致膜去极化及细胞内Ca2+浓度升高,引起ATP敏感K+通道活性的改变而调节β细胞膜的功能.故认为氨基酸作为β细胞CaSR生理性配基,通过激活非选择性阳离子通道促进了葡萄糖诱导的胰岛素分泌.     

替利帕肽在2型糖尿病治疗中的降糖机制、临床作用及不良反应研究进展

替利帕肽是由双葡萄糖依赖性促胰岛素多肽(GIP)受体和胰高血糖素样肽1(GLP-1)受体合成的激动剂,其可通过刺激胰岛素分泌、延缓胃排空、改善胰岛素敏感性和胰岛β细胞功能而发挥降糖作用,是治疗2型糖尿病的新型药物.除降糖作用外,替利帕肽还能显著减轻患者体质量,同时参与保护心血管功能.其不良反应包括胃肠道反应、食欲下降、...     

G蛋白耦联受体119激动剂的研究进展

糖尿病病程中出现的胰岛β细胞功能衰竭和降糖药物引起的低血糖已成为糖尿病治疗的难点.应用G蛋白耦联受体119(GPR119)激动剂可以降低血糖水平,保护胰岛β细胞功能,且不产生低血糖.GPR119在胰岛β细胞和肠内分泌细胞中表达,其激活可增加葡萄糖刺激的胰岛素分泌( GSIS)和胰高血糖素样肽-t(GLP-1)的分泌,并增强胰岛素启动子的活性.GPR119激动剂表现出的诸多优势提示,其作为一类新的糖尿病治疗药物有良好的应用前景.     

HIV-1蛋白酶抑制剂Nelfinavir降低大鼠胰岛素瘤INS-1细胞胰岛素释放

HIV 1蛋白酶抑制剂Nelfinavir处理 48h ,显著降低大鼠INS 1细胞基础胰岛素分泌和葡萄糖刺激的胰岛素释放 ,Nelfinavir对后者的抑制作用更强 ,提示Nelfinavir长期治疗可能导致胰岛 β细胞功能损害。     

胰高血糖素样肽1的胰腺外作用研究进展

胰高血糖素样肽1(GLP-1)是体内重要的肠肽激素,在调节体内葡萄糖稳态中起重要作用.它通过促进胰岛素分泌、抑制胰高血糖素产生以及减慢餐后胃排空降低血糖.在胰腺外组织它也可通过调节葡萄糖代谢来参与全身血糖的调节.一方面通过激活磷脂酰肌醇3激酶、蛋白激酶B、蛋白激酶C、1型蛋白磷酸酶和丝裂原活化蛋白酶等增加糖原合酶a活性,促进糖原合成和糖利用.另一方面,在脂肪组织直接促进葡萄糖利用或增强胰岛素对葡萄糖的利用.此外,GLP-1还具有其它生物学作用包括舒张血管、保护血管内皮功能并激活垂体前叶激素分泌等.exendin-4是GLP-1的长效类似物,具有比GLP-1更持久的生物学活性和更强的降血糖作用,是一种治疗2型糖尿病的新型药物.     

Effects of resveratrol on NO secretion stimulated by insulin and its dependence on SIRT1 in high glucose cultured endothelial cells

To investigate the effects of resveratrol on the secretion of NO induced by insulin in high glucose cultured primary human umbilical vein endothelial cells (HUVEC). HUVEC were treated with 1 μmol/l resveratrol for 24 h before cultured in high glucose medium for 48 h, then all cells were stimulated by 100 nmol/l insulin for 30 min. Method based on nitric acid reductase was used to analyze the NO contents in the supernatant. Cells were collected to analyze the expression of eNOS, endothelin-1, E-selectin, and SIRT1. In order to investigate the dependence of resveratrol on SIRT1, the effects of resveratrol on cells treated by SIRT1 siRNA were also examined. Compared with control cells, high glucose decreased the secretion of NO induced by insulin. Resveratrol treatment increased the expression of SIRT1 and the secretion of NO. After interfering the expression of SIRT1 using SIRT1 siRNA, the effects of resveratrol on the NO secretion induced by insulin was impaired. Resveratrol also counteracted other pro-atherosclerotic effects of high glucose, including the up-regulating roles of high glucose on the expression of endothelin-1 mRNA and E-selectin mRNA, and the down-regulating roles of high glucose on the expression of eNOS mRNA and the basal NO secretion without the stimulating of insulin. Resveratrol can improve the NO stimulating function of insulin in high glucose cultured HUVEC in SIRT1-dependent manner. Thus, our results imply that resveratrol may have the preventive roles of atherosclerosis in diabetic patients.     

The loss of Sirt1 in mouse pancreatic beta cells impairs insulin secretion by disrupting glucose sensing

Aims/hypothesis

Sirtuin 1 (SIRT1) has emerged as a key metabolic regulator of glucose homeostasis and insulin secretion. Enhanced SIRT1 activity has been shown to be protective against diabetes, although the mechanisms remain largely unknown. The aim of this study was to determine how SIRT1 regulates insulin secretion in the pancreatic beta cell.

Methods

Pancreatic beta cell-specific Sirt1 deletion was induced by tamoxifen injection in 9-week-old Pdx1CreER:floxSirt1 mice (Sirt1BKO). Controls were injected with vehicle. Mice were assessed metabolically via glucose challenge, insulin tolerance tests and physical variables. In parallel, Sirt1 short interfering RNA-treated MIN6 cells (SIRT1KD) and isolated Sirt1BKO islets were used to investigate the effect of SIRT1 inactivation on insulin secretion and gene expression.

Results

OGTTs showed impaired glucose disposal in Sirt1BKO mice due to insufficient insulin secretion. Isolated Sirt1BKO islets and SIRT1KD MIN6 cells also exhibited impaired glucose-stimulated insulin secretion. Subsequent analyses revealed impaired α-ketoisocaproic acid-induced insulin secretion and attenuated glucose-induced Ca²⁺ influx, but normal insulin granule exocytosis in Sirt1BKO beta cells. Microarray studies revealed a large cluster of mitochondria-related genes, the expression of which was dysregulated in SIRT1KD MIN6 cells. Upon further analysis, we demonstrated an explicit defect in mitochondrial function: the inability to couple nutrient metabolism to mitochondrial membrane hyperpolarisation and reduced oxygen consumption rates.

Conclusions/interpretation

Taken together, these findings indicate that in beta cells the deacetylase SIRT1 regulates the expression of specific mitochondria-related genes that control metabolic coupling, and that a decrease in beta cell Sirt1 expression impairs glucose sensing and insulin secretion.     

SIRT1 mRNA在新诊断的2型糖尿病患者脂肪组织的表达及意义

目的探讨新诊断的2型糖尿病（T2DM）患者脂肪组织SIRT1 mRNA表达水平及其与体质指数（BMI）、腰臀比（WHR）、血糖、血浆胰岛素、胰岛素抵抗指数（HOMA—IR）关系。方法采用RT—PCR方法检测了40例对照组和40例T2DM患者脂肪组织SIRT1 mRNA水平,并分析了SIRT1水平与BMI、WHR、血脂、HbA1C、血糖、血浆胰岛素和HOMA—IR等的关系。结果新诊断的T2DM患者SIRT1 mRNA水平显著低于对照组（1．49±0．47VS1．12±0．32,P〈0．01）;线性相关分析表明,SIRT1与Fins、HOMA—IR呈显著负相关（r=-0．421,P〈0．01和r=-0．511,P〈0．01）。以SIRT1为因变量,年龄、WHR、BMI、TG、TC、LDL—C、HDL—C、HbA1C、FPG、Fins和HOMA—IR为自变量,进行多元线性逐步回归分析,结果表明HOMA—IR是影响SIRT1的独立相关因素。Logistic回归分析表明控制性别、年龄、WHR、BMI、TC、TG、HDL—C、LDL—C后,发现SIRT1与T2DM发病呈负相关,OR〈1。结论脂肪组织中SIRT1 mRNA水平的变化与IR和T2DM相关。     

The Tellurium compound, AS101, increases SIRT1 level and activity and prevents type 2 diabetes

The histone deacetylase, SIRT1, plays a major role in glucose regulation and lipid metabolism. Ammonium Trichloro (dioxoethylene-o,o') Tellurate, AS101, is a potent in vitro and in vivo immunomodulator, with several potential therapeutic applications. AS101 administration resulted in upregulation of SIRT1 protein expression and activity. These effects were associated with decreased levels of serum insulin like growth factor-1 (IGF-1) and of insulin. The properties of AS101 prompted us to investigate its potential therapeutic role in rats with type 2 diabetes (T2D). T2D was induced by a high fat diet combined with a low dose of Streptozotocin (STZ). Treatment with AS101 before manifestation of hyperglycemia, resulted in increased insulin sensitivity, and decreased blood glucose levels, and prevented symptoms of diabetes including defective glucose clearance, fatty liver, and abnormal distribution of insulin-producing beta cells in the pancreas. Treatment after disease emergence resulted in partial restoration of normal glucose homeostasis. Diabetic rats showed a reduction in liver SIRT1 levels. In both treatment regimens the reduction in SIRT1 levels in the liver were blocked by AS101 consumption. Together, these findings demonstrate the therapeutic potential of AS101 for treating T2D, and for reversing impaired fat and glucose metabolism.     

Phosphoinositide 3-kinase as a novel functional target for the regulation of the insulin signaling pathway by SIRT1

The protein deacetylase SIRT1, and its activator resveratrol, exert beneficial effects on glucose metabolism. Different SIRT1 targets have been identified, including PTP1B, AMPK, FOXO, PGC-1α and IRS2. The latter may underscore a tight link between SIRT1 and insulin signaling components. However, whether SIRT1 has a direct effect on insulin resistance and whether resveratrol acts directly or indirectly in this context is still a matter of controversy and this question has not been addressed in muscle cells. Here, we show that SIRT1 protein expression is decreased in muscle biopsies and primary myotubes derived from type 2 diabetic patients, suggesting a contribution of diminished SIRT1 in the determination of muscle insulin resistance. To investigate the functional impact of SIRT1 on the insulin pathway, the activation of insulin downstream effector PKB was evaluated after SIRT1 inactivation by RNAi, SIRT1 overexpression, or resveratrol treatments. In muscle cells and HEK293 cells, downregulation of SIRT1 reduced, while overexpression increased, insulin-induced PKB activatory phosphorylation. Further molecular characterisation revealed that SIRT1 interacts in an insulin-independent manner with the PI3K adapter subunit p85. We then investigated whether resveratrol may improve insulin signaling in muscle cells via SIRT1, or alternative targets. Incubation of muscle cells with resveratrol reverted the insulin-resistant state induced by prolonged TNFα or insulin treatment. Resveratrol-dependent improvement of insulin-resistance occurred through inhibition of serine phosphorylation of IRS1/2, implicating resveratrol as a serine kinase inhibitor. Finally, a functional interaction between PI3K and SIRT1 was demonstrated in C. elegans, where constitutively active PI3K - mimicking increased IIS signaling - lead to shortened lifespan, while removal of sir-2.1 abolished PI3K-induced lifespan shortening. Our data identify SIRT1 as a positive modulator of insulin signaling in muscle cells through PI3K, and this mechanism appears to be conserved from C. elegans through humans.     

Inhibition of silent information regulator 1 induces glucose metabolism disorders of hepatocytes and enhances hepatitis C virus replication

Background and objective

Glucose metabolism disorders including insulin resistance (IR) and type 2 diabetes are frequent and important cofactors of chronic hepatitis C (CHC). Silent information regulator 1 (SIRT1) plays a key role in the regulation of hepatic glucose metabolism. We investigated the possible effect of HCV replication on glucose metabolism of hepatocytes and expression of SIRT1 using Huh-7.5 cells harboring the HCV replicon.

Methods

The level of reactive oxygen species (ROS) and value of NAD⁺/NADH and ATP/ADP were detected. Glucose uptake by hepatocytes and glucose production were measured. The activity and expression levels of SIRT1 and expression of its downstream glucose-metabolism genes were measured.

Results

In replicon cells, the level of ROS increased and the value of nicotinamide adenine dinucleotide (NAD⁺)/NADH decreased, then the activity and expression level of mRNA and protein of SIRT1 decreased. Inhibition of SIRT1 not only increased insulin receptor substrate-1 phosphorylation and decreased Akt phosphorylation, inhibited cell surface expression of glucose transporter 2 and suppressed cellular glucose uptake, but it also decreased phosphorylation of forkhead box O1, then upregulated phosphoenolpyruvate carboxykinase and glucose 6-phosphatase genes and downregulated the glucokinase gene, thus promoting glucose production. Interferon treatment restored the aforementioned changes. SIRT1 activator improved glucose metabolism disorders by an increase in glucose uptake and a decrease in glucose production, and it inhibited HCV replication.

Conclusions

HCV replication decreasing the NAD⁺/NADH ratio may downregulate the activity and expression of SIRT1, then change the expression profile of glucose metabolism-related genes, thereby causing glucose metabolism disorders of hepatocytes and promoting HCV replication. Treatment with SIRT1 activator improves glucose metabolic disorders and inhibits HCV replication, suggesting that restoration of SIRT1 activity may be a promising new therapeutic approach for CHC patients with IR.     

Skeletal muscle-specific overexpression of SIRT1 does not enhance whole-body energy expenditure or insulin sensitivity in young mice

Aims/hypothesis

The NAD⁺-dependent protein deacetylase sirtuin (SIRT)1 is thought to be a key regulator of skeletal muscle metabolism. However, its precise role in the regulation of insulin sensitivity is unclear. Accordingly, we sought to determine the effect of skeletal muscle-specific overexpression of SIRT1 on skeletal muscle insulin sensitivity and whole-body energy metabolism.

Methods

At 10 weeks of age, mice with muscle-specific overexpression of SIRT1 and their wild-type littermates were fed a standard diet with free access to chow or an energy-restricted (60% of standard) diet for 20 days. Energy expenditure and body composition were measured by indirect calorimetry and magnetic resonance imaging, respectively. Skeletal muscle insulin-stimulated glucose uptake was measured ex vivo in soleus and extensor digitorum longus muscles using a 2-deoxyglucose uptake technique with a physiological insulin concentration of 360 pmol/l (60 μU/ml).

Results

Sirt1 mRNA and SIRT1 protein levels were increased by approximately 100- and 150-fold, respectively, in skeletal muscle of mice with SIRT1 overexpression compared with wild-type mice. Despite this large-scale overexpression of SIRT1, body composition, whole-body energy expenditure, substrate oxidation and voluntary activity were comparable between genotypes. Similarly, skeletal muscle basal and insulin-stimulated glucose uptake were unaltered with SIRT1 overexpression. Finally, while 20 days of energy restriction enhanced insulin-stimulated glucose uptake in skeletal muscles of wild-type mice, no additional effect of SIRT1 overexpression was observed.

Conclusions/interpretation

These results demonstrate that upregulation of SIRT1 activity in skeletal muscle does not affect whole-body energy expenditure or enhance skeletal muscle insulin sensitivity in young mice on a standard diet with free access to chow or in young mice on energy-restricted diets.     

SIRT1功能的研究进展

SIRT1(si1ent mating-type information regulation 2 homologue 1)是Sirtuins去乙酰化酶家族中的一员,是酵母沉默信息调节因子Sir2(silence information regulator)的同源物.它参与了众多基因转录、能量代谢以及细胞衰老过程的调节...