Evidence for a Common Mechanism of SIRT1 Regulation by Allosteric Activators

Department of Genetics, Harvard Medical School, Boston, MA 02115, USA.
Science (Impact Factor: 33.61). 03/2013; 339(6124):1216-9. DOI: 10.1126/science.1231097
Source: PubMed


A molecule that treats multiple age-related diseases would have a major impact on global health and economics. The SIRT1 deacetylase
has drawn attention in this regard as a target for drug design. Yet controversy exists around the mechanism of sirtuin-activating
compounds (STACs). We found that specific hydrophobic motifs found in SIRT1 substrates such as PGC-1α and FOXO3a facilitate
SIRT1 activation by STACs. A single amino acid in SIRT1, Glu230, located in a structured N-terminal domain, was critical for activation by all previously reported STAC scaffolds and a new
class of chemically distinct activators. In primary cells reconstituted with activation-defective SIRT1, the metabolic effects
of STACs were blocked. Thus, SIRT1 can be directly activated through an allosteric mechanism common to chemically diverse

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    • "De-aceylation has been shown to be much more likely when substrates contain large, mainly hydrophobic residues at several positions C-terminal to the acetyl-lysine. These naturally hydrophobic residues can be mimicked by activators in a so-called " assisted allosteric " mechanism (Hubbard et al. 2013). SRT1720 and resveratrol can therefore induce quite different levels of de-acetylation with resveratrol being much weaker than SRT1720 (Schutkowski et al. 2014). "
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    ABSTRACT: Silent information regulators (SIRT)s have been shown to deacetylate a range of metabolic enzymes, including those in glycolysis and the Krebs cycle, and thus alter their activity. SIRTs require NAD+ for their activity; this linking cellular energy status to enzyme activity. Here, to examine the impact of SIRT1 modulation on oxidative metabolism, we tested the effect of ligands which are either SIRT activating compounds (STACs; resveratrol and SRT1720) or inhibitors (STICs; EX527) on the metabolism of 13C-enriched substrates by Guinea pig brain cortical tissue slices using 13C and 1H NMR spectroscopy. Resveratrol increased lactate labelling but decreased incorporation of 13C into Krebs cycle intermediates consistent with effects on AMP-activated protein kinase (AMPK) and inhibition of the F0/F1ATPase. Testing resveratrol directly applied to astrocytes using a Seahorse analyzer found increased glycolytic shift and increased mitochondrial proton leak due to interactions of resveratrol with the mitochondrial electron transport chain. SRT1720, by contrast, stimulated incorporation of 13C into Krebs cycle intermediates and reduced incorporation into lactate, while the inhibitor EX527 paradoxically also increased Krebs cycle 13C incorporation. In summary, the various SIRT1 modulators show distinct, acute effects on oxidative metabolism. The strong effects of resveratrol on the mitochondrial respiratory chain and on glycolysis suggest caution should be used in attempts to increase bioavailability of this compound in the central nervous system.
    Journal of Neuroscience Research 02/2015; 93:1147-1156. DOI:10.1002/jnr.23570 · 2.59 Impact Factor
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    • "Beher et al.[29] reported that Res could increase Sirt1 activity in fluorophore-tagged substrates but not the corresponding nontagged peptides in vitro. More recently, Hubbard et al.[30] argued that sirtuin-activating compounds (STACs, resveratrol including) directly activate Sirt1 through an allosteric mechanism, moreover, the metabolic effects of STACs are blocked in cells reconstituted with inactive Sirt1, suggesting Sirt1 directly mediates STACs regulation in vivo. Despite of these inconsistent mechanistic investigations, Sirt1 was appeared to be involved in regulating energy homeostasis, food intake, body weight and substance metabolism [31]. "
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    ABSTRACT: Background The exact mechanism of the protective role of Resveratrol (Res) in lipid metabolism and oxidative stress is not well elucidated. The present study aimed to investigate the potential benefits and possible mechanisms of Res on the amelioration of oxidative stress and hepatic steatosis in a KKAy mouse model. Methods A total of 30 KKAy male mice were randomly divided into three groups: a normal chow group, a low resveratrol group and a high resveratrol group. After a 12-wk study period, serum levels of TG, TC, LDL-C and HDL-C, the liver content of TG and TC, ROS, GSH, GPx, SOD and MDA levels were measured. Ectopic lipid deposition was observed in sectioned frozen liver tissues. The mRNA levels of ATGL and HSL in the liver tissues were determined via real-time PCR. Furthermore, the protein expression of p47phox, gp91phox, ATGL, HSL, Sirt1, AMPK and FOXO1 were analyzed using western blotting. Results Following Res supplementation, serum levels of TG and MDA were decreased, while the HDL-C and SOD levels were increased in KKAy mice. Furthermore, Res treatment increased GSH and GPx in liver tissues, while it decreased ROS. In addition, Res significantly reduced hepatic steatosis. After Res treatment, concentrations of p47phox (membrane) and gp91phox proteins were reduced, while p-HSL, HSL and ATGL protein expression levels were increased. Mechanistically, the levels of Sirt1, p-AMPK and p-FOXO1 expression in the liver tissues were up-regulated following supplementation with Res, and FOXO1 protein was released from the nucleus into the cytoplasm. Conclusions Res is able to attenuate hepatic steatosis and lipid metabolic disorder and enhance the antioxidant ability in KKAy mice, possibly by up-regulating Sirt1 expression and the phosphorylation of AMPK.
    Nutrition & Metabolism 08/2014; 11(1):35. DOI:10.1186/1743-7075-11-35 · 3.26 Impact Factor
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    • "Interestingly, SRT1720 is essential for the proper regulation of circadian rhythm in the liver of SD-fed mice through a SIRT1-dependent mechanism (Bellet et al., 2013). Although some controversy exists concerning the specificity of SRT1720 toward SIRT1 (Huber et al., 2010; Pacholec et al., 2010), the notion that SIRT1 is a target of SRT1720 is supported by recent data showing that it activates SIRT1 via a direct allosteric mechanism (Hubbard et al., 2013). Taken together, these results illustrate the involvement of multiple SIRT1-dependent mechanisms in the biological actions of SRT1720. "
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    ABSTRACT: The prevention or delay of the onset of age-related diseases prolongs survival and improves quality of life while reducing the burden on the health care system. Activation of sirtuin 1 (SIRT1), an NAD(+)-dependent deacetylase, improves metabolism and confers protection against physiological and cognitive disturbances in old age. SRT1720 is a specific SIRT1 activator that has health and lifespan benefits in adult mice fed a high-fat diet. We found extension in lifespan, delayed onset of age-related metabolic diseases, and improved general health in mice fed a standard diet after SRT1720 supplementation. Inhibition of proinflammatory gene expression in both liver and muscle of SRT1720-treated animals was noted. SRT1720 lowered the phosphorylation of NF-κB pathway regulators in vitro only when SIRT1 was functionally present. Combined with our previous work, the current study further supports the beneficial effects of SRT1720 on health across the lifespan in mice.
    Cell Reports 02/2014; 6(5). DOI:10.1016/j.celrep.2014.01.031 · 8.36 Impact Factor
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