13,267 research outputs found

    Resveratrol mediated modulation of Sirt-1/Runx2 promotes osteogenic differentiation of mesenchymal stem cells: potential role of Runx2 deacetylation.

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    Osteogenic repair in response to bone injury is characterized by activation and differentiation of mesenchymal stem cells (MSCs) to osteoblasts. This study determined whether activation of Sirt-1 (a NAD(+)-dependent histone deacetylase) by the phytoestrogen resveratrol affects osteogenic differentiation. Monolayer and high-density cultures of MSCs and pre-osteoblastic cells were treated with an osteogenic induction medium with/without the Sirt-1 inhibitor nicotinamide or/and resveratrol in a concentration dependent manner. MSCs and pre-osteoblastic cells differentiated to osteoblasts when exposed to osteogenic-induction medium. The osteogenic response was blocked by nicotinamide, resulting in adipogenic differentiation and expression of the adipose transcription regulator PPAR-γ (peroxisome proliferator-activated receptor). However, in nicotinamide-treated cultures, pre-treatment with resveratrol significantly enhanced osteogenesis by increasing expression of Runx2 (bone specific transcription factor) and decreasing expression of PPAR-γ. Activation of Sirt-1 by resveratrol in MSCs increased its binding to PPAR-γ and repressed PPAR-γ activity by involving its cofactor NCoR (nuclear receptor co-repressor). The modulatory effects of resveratrol on nicotinamide-induced expression of PPAR-γ and its cofactor NCoR were found to be mediated, at least in part, by Sirt-1/Runx2 association and deacetylation of Runx2. Finally, knockdown of Sirt-1 by using antisense oligonucleotides downregulated the expression of Sirt-1 protein and abolished the inhibitory effects of resveratrol, namely nicotinamide-induced Sirt-1 suppression and Runx2 acetylation, suggesting that the acetylated content of Runx2 is related to downregulated Sirt-1 expression. These data support a critical role for Runx2 acetylation/deacetylation during osteogenic differentiation in MSCs in vitro. (242 words in abstract)

    Role of Sirtuin-1 in the pathogenesis of hypertension in spontaneously hypertensive rats : molecular mechanisms

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    Il a été démontré que la sirtuine 1 (Sirt-1), une histone désacétylase de classe III, est surexprimée dans le coeur des rats spontanément hypertendus (SHR). Nous avons récemment montré que les cellules musculaires lisses vasculaires (CMLV) des SHR présentent une expression accrue de Sirt-1 par rapport aux rats Wistar Kyoto (WKY) de même âge qui contribue à l’augmentation de la régulation de la protéine Giα impliquée dans la pathogenèse de l'hypertension. La présente étude a été effectuée pour étudier le rôle de l'augmentation de l'expression de la Sirt-1 dans la pathogenèse de l'hypertension chez les SHR et pour explorer les mécanismes moléculaires impliqués dans cette réponse. Dans cette étude, un inhibiteur sélectif de la Sirt-1, EX-527 (5 mg/kg de poids corporel), a été injecté par voie intrapéritonéale chez des rats SHR adultes de 8 semaines et des rats WKY de même âge, deux fois par semaine pendant 3 semaines. La pression artérielle (PA) et la fréquence cardiaque ont été mesurées deux fois par semaine par la méthode non invasive du brassard autour de la queue. Le traitement avec l’inhibiteur spécifique de la Sirt-1, l'EX-527, a atténué les augmentations de PA (de 76 mmHg) et de fréquence cardiaque chez les rats SHR. La surexpression de Sirt-1 et des protéines Giα dans le coeur, les CMLV et l'aorte a été atténuée au niveau des contrôles par l'inhibiteur de la Sirt-1. L'inhibition de la Sirt-1 a également atténué les niveaux accrus des anions superoxydes, l’activité de la NADPH oxydase et la surexpression des sous-unités de la NADPH oxydase ; les protéines Nox2, Nox4 et P47phox dans les CMLV isolées des SHR traités par l’EX-527. De plus, les niveaux réduits du monoxyde d'azote synthase endothélial (eNOS) et du monoxyde d'azote (NO) et les niveaux accrus de la peroxynitrite (ONOO-) dans les CMLV des SHR ont également été rétablis à des niveaux contrôles par l'inhibiteur de la Sirt-1. Ces résultats suggèrent que l'inhibition de la surexpression de la Sirt-1, en diminuant les niveaux accrus des protéines Giα et du stress nitro-oxydant, atténue la PA élevée chez les rats SHR. Il est donc possible de suggérer que les inhibiteurs de la Sirt-1 puissent être utilisés comme des agents thérapeutiques dans le traitement des complications cardiovasculaires associées à l'hypertension.Sirtuin-1 (Sirt-1), class III histone deacetylase, has been shown to be overexpressed in hearts from spontaneously hypertensive rats (SHR). We recently showed that vascular smooth muscle cells (VSMC) from SHR exhibit enhanced expression of Sirt-1 as compared to age-matched Wistar Kyoto (WKY) rats, which contributes to the upregulation of Giα protein implicated in the pathogenesis of hypertension. The present study was undertaken to investigate the role of upregulated Sirt-1 expression in the pathogenesis of hypertension in SHR and to explore the underlying molecular mechanisms involved in this response. For this study, a selective inhibitor of Sirt-1, EX-527 (5mg/kg of body weight), was injected intraperitoneally into 8-week-old adult SHR and age-matched WKY rats twice per week for 3 weeks. The blood pressure (BP) and heart rate was measured twice a week by the CODA™ non-invasive tail cuff method. Treatment of SHR with Sirt-1-specific inhibitor, EX-527, attenuated high BP by 76 mmHg and inhibited the augmented heart rate. The overexpression of Sirt-1 and Giα proteins in heart, VSMC and aorta was attenuated to the control levels by Sirt-1 inhibitor. Inhibition of Sirt-1 also attenuated the enhanced levels of superoxide anion, NADPH oxidase activity and the overexpression of NADPH oxidase subunits; Nox2, Nox4 and P47phox proteins in VSMC isolated from EX-527-treated SHR. Furthermore, the decreased levels of endothelial nitric oxide synthase (eNOS) and nitric oxide (NO) and increased levels of peroxynitrite (ONOO-) in VSMC from SHR were also restored to control levels by Sirt-1 inhibitor. These results suggest that the inhibition of overexpression of Sirt-1 through decreasing the enhanced levels of Giα proteins and nitro-oxidative stress attenuates the high BP in SHR. It may thus be suggested that inhibitors of Sirt-1 may have the potential to be used as therapeutic agents in the treatment of cardiovascular complications associated with hypertension

    Sleep, Sirtuin 1 and Alzheimer’s disease: A review

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    Sleep plays a major role in brain health, and cognition. Disrupted sleep is a well-described symptom of Alzheimer’s disease (AD). However, accumulating evidence suggests suboptimal sleep also increases AD risk. The deacetylase Sirtuin 1 (Sirt 1), encoded by the SIRT1 gene, impacts sleep via its relationship to wake-sleep neurotransmitters and somnogens. Evidence from animal and human studies supports a significant and complex relationship between sleep, Sirt 1/ SIRT1 and AD. Numerous hypotheses attempt to explain the critical impact of Sirt 1/ SIRT1 on wake- and sleep- promoting neurons, their related mechanisms and neurotransmitters. However, there is a paucity of studies assessing the interaction between sleep and Sirt 1/ SIRT1, as a principal component of sleep regulation, on AD pathology. In this review, we explore the potential association between Sirt 1/ SIRT1, sleep, and AD aetiology. Given sleep is a likely modifiable risk factor for AD, and recent studies suggest Sirt 1/ SIRT1 activation can be modulated by lifestyle or dietary approaches, further research in this area is required to explore its potential as a target for AD prevention and treatment

    Effects of niacin restriction on sirtuin and PARP responses to photodamage in human skin.

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    Sirtuins (SIRTs) and poly(ADP-ribose) polymerases (PARPs), NAD(+)-dependent enzymes, link cellular energy status with responses to environmental stresses. Skin is frequently exposed to the DNA damaging effects of UV irradiation, a known etiology in skin cancer. Thus, understanding the defense mechanisms in response to UV, including the role of SIRTs and PARPs, may be important in developing skin cancer prevention strategies. Here, we report expression of the seven SIRT family members in human skin. SIRTs gene expressions are progressively upregulated in A431 epidermoid carcinoma cells (SIRTs1 and 3), actinic keratoses (SIRTs 2, 3, 5, 6, and 7) and squamous cell carcinoma (SIRTs 1-7). Photodamage induces dynamic changes in SIRT expression with upregulation of both SIRT1 and SIRT4 mRNAs. Specific losses of SIRT proteins occur early after photodamage followed by accumulation later, especially for SIRT4. Niacin restriction, which decreases NAD(+), the sirtuin substrate, results in an increase in acetylated proteins, upregulation of SIRTs 2 and 4, increased inherent DNA damage, alterations in SIRT responses to photodamage, abrogation of PARP activation following photodamage, and increased sensitivity to photodamage that is completely reversed by repleting niacin. These data support the hypothesis that SIRTs and PARPs play important roles in resistance to photodamage and identify specific SIRTs that respond to photodamage and may be targets for skin cancer prevention


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    ABSTRAK Pendahuluan: Protein Sirtuin-1 (SIRT-1) dan Nuclear Releating Factor-2 (NRF2) berperan dalam mekanisme terjadinya Alzheimer. Secara empiris kacang merah (Phaseolus vulgaris) mengandung senyawa aktif untuk menghambat Alzheimer, namun mekanismenya terhadap SIRT-1 dan NRF2 belum pernah diteliti. Penelitian dilakukan untuk mengetahui mekanisme kacang merah mencegah Alzheimer melalui aktivasi SIRT-1 dan NRF2.Metode: Penelitian dilakukan secara In Silico dengan menggunakan docking server untuk menilai afinitas senyawa aktif biji kacang merah terhadap protein SIRT-1 dan NRF2. Uji farmakokinetik, fisikokimia dinilai dengan pkCSM (Predicting Small-Molecule Pharmacokinetic and Toxicity Properties). Analisa dilakukan dengan diskriptif analitik dengan melihat hasil afinitas senyawa aktif terhadap SIRT-1 dan NRF2 dibandingkan obat kontrol.Hasil: Didapatkan 5 senyawa aktif (beta sitosterol, sianidin, glisitein, biokanin A, dan genistein) dari 8 senyawa aktif yang diteliti memiliki afinitas tinggi terhadap protein SIRT-1 dan 5 Senyawa aktif (beta sitosterol, biokanin A, genistein, glisitein, dan formononetin) dari 20 senyawa aktif yang didockingkan memiliki afinitas yang tinggi terhadap protein NRF2. Hasil prediksi parameter fisikokimia seluruh senyawa aktif memenuhi hukum 5 Lipinski. Hasil Prediksi sifat farmakokinetik β-sitosterol adalah senyawa yang memiliki nilai paling baik.Kesimpulan: senyawa aktif biji kacang merah mempunyai potensi sebagai pencegahan alzheimer dengan mengaktifkan SIRT-1 dan NRF2 yaitu beta sitosterol. Beta sitosterol juga mempunyai afinitas, fisikokimia, farmakokinetik yg baik dan tidak bersifat toksik sehingga dapat menjadi kandidat kuat obat pencegahan Alzheimer melalui peningkatan SIRT-1 dan NRF2.Kata Kunci : Alzheimer; Phaseolus vulgaris; in silic

    Consumption of a High-Fat Meal Alters Post-Prandial SIRT mRNA Expression in Blood Leukocytes

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    Introduction. Sirtuins (SIRT) are protein deacetylases, hypothesized to regulate the transcription of various genes involved in the prevention of atherogenesis and diet induced obesity. Previous research from our laboratory has demonstrated that consumption of a single, high-fat meal increases various CVD risk factors for up to 5-h post-prandial. Given the importance of SIRT to metabolic disorders, it is reasonable to speculate that a single, high-fat meal also disrupts SIRT. Methods. The purpose of this study was to determine the effect of a high-fat meal (75% of daily kcals & 80% of daily fat needs), on SIRT mRNA expression in blood leukocytes during a 5-h post-prandial period. Men and women (N=17) were recruited to report to the lab following an overnight fast. Venous blood samples were collected prior to the meal, 1, 3, and 5-h post-meal. White buffy coat aliquot was frozen in RNALater solution. At the end of the study samples were thawed and RNA was isolated using a phenol/chloroform method. RNA was reverse transcribed and mRNA expression for SIRT 1-7 was determined using a Taqman qPCR technique with 18S rRNA as a normalizer, under standard PCR cycling conditions. An additional aliquot of serum was used to measure triglyceride, total cholesterol, and glucose responses were measured using enzymatic assays on an automated chemistry analyzer (ChemWell T; P.C., FL). Data was analyzed using a RM ANOVA with P\u3c0.05. Results. Consistent with previous results, the meal caused an increase in triglycerides, total cholesterol and glucose that reached peaked values at 3-h post-prandial. We also observed significant expression changes in the mRNA of the SIRT 1 (P=0.02) and SIRT 6 (P=0.03) during the 5-h post-prandial period. Both SIRT 1 and SIRT 6 showed the greatest decreased expression at 3-h post-prandial compared to baseline, 51.8% and 46.2% respectfully. Conclusion. To our knowledge, this is the 1st study to report that consumption of a high-fat meal transiently alters SIRT mRNA expression consistent with changes in serum triglyceride and glucose concentration. More research is needed to understand how transient, post-prandial changes in SIRT mRNA expression contribute to increased disease risk

    A role for neuronal cAMP responsive-element binding (CREB)-1 in brain responses to calorie restriction

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    Calorie restriction delays brain senescence and prevents neurodegeneration, but critical regulators of these beneficial responses other than the NAD(+)-dependent histone deacetylase Sirtuin-1 (Sirt-1) are unknown. We report that effects of calorie restriction on neuronal plasticity, memory and social behavior are abolished in mice lacking cAMP responsive-element binding (CREB)-1 in the forebrain. Moreover, CREB deficiency drastically reduces the expression of Sirt-1 and the induction of genes relevant to neuronal metabolism and survival in the cortex and hippocampus of dietary-restricted animals. Biochemical studies reveal a complex interplay between CREB and Sirt-1: CREB directly regulates the transcription of the sirtuin in neuronal cells by binding to Sirt-1 chromatin; Sirt-1, in turn, is recruited by CREB to DNA and promotes CREB-dependent expression of target gene peroxisome proliferator-activated receptor-\u3b3 coactivator-1\u3b1 and neuronal NO Synthase. Accordingly, expression of these CREB targets is markedly reduced in the brain of Sirt KO mice that are, like CREB-deficient mice, poorly responsive to calorie restriction. Thus, the above circuitry, modulated by nutrient availability, links energy metabolism with neurotrophin signaling, participates in brain adaptation to nutrient restriction, and is potentially relevant to accelerated brain aging by overnutrition and diabetes


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    Objective: Resveratrol, a trihydroxystilbene, has been claimed to be a potent activator to SIRT-1 enzyme activity, which in turn could have a useful future application in the management of many chronic conditions such as metabolic syndrome and obesity. A group of novel tetrahydroxystilbene derivatives were isolated from Kangaroo Island propolis in Australia. Due to its structural similarities with resveratrol, the aim of this research was to explore the activity of Kangaroo Island prenylated stilbenes on SIRT-1 enzyme.Methods: In vitro fluorometry measurement of SIRT-1 enzyme activity using SIRT-1 assay kit (Cayman®).Results: None of the tested compounds had shown any activation to SIRT-1 enzyme, on contrary, they produced mild inhibition to the enzyme. Compound 3 (C20H22O4, 3,5,4'-trihydroxy-3'-methoxy-2-prenyl-E-stilbene) was the most potent inhibitor.Conclusion: Compound 3, in addition to compounds 2, 4, and 6 are candidate compounds for further investigation. A discussion of the results as well as the contradictory results in the literature has been presented in this article.Â

    Human Sirt-1: Molecular Modeling and Structure-Function Relationships of an Unordered Protein

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    BACKGROUND: Sirt-1 is a NAD+-dependent nuclear deacetylase of 747 residues that in mammals is involved in various important metabolic pathways, such as glucose metabolism and insulin secretion, and often works on many different metabolic substrates as a multifunctional protein. Sirt-1 down-regulates p53 activity, rising lifespan, and cell survival; it also deacetylases peroxisome proliferator-activated receptor-gamma (PPAR-gamma) and its coactivator 1 alpha (PGC-1alpha), promoting lipid mobilization, positively regulating insulin secretion, and increasing mitochondrial dimension and number. Therefore, it has been implicated in diseases such as diabetes and the metabolic syndrome and, also, in the mechanisms of longevity induced by calorie restriction. Its whole structure is not yet experimentally determined and the structural features of its allosteric site are unknown, and no information is known about the structural changes determined by the binding of its allosteric effectors. METHODOLOGY: In this study, we modelled the whole three-dimensional structure of Sirt-1 and that of its endogenous activator, the nuclear protein AROS. Moreover, we modelled the Sirt-1/AROS complex in order to study the structural basis of its activation and regulation. CONCLUSIONS: Amazingly, the structural data show that Sirt-1 is an unordered protein with a globular core and two large unordered structural regions at both termini, which play an important role in the protein-protein interaction. Moreover, we have found on Sirt-1 a conserved pharmacophore pocket of which we have discussed the implication
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