• Molecules and Cells
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• v.28 no.5
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• pp.407-415
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• 2009

The sirtuins are a protein family named after the first identified member, S. cerevisiae Sir2p. Sirtuins are protein deacetylases whose activity is dependent on $NAD^+$ as a cosubstrate. They are structurally defined by two central domains that together form a highly conserved catalytic center, which catalyzes the transfer of an acetyl moiety from acetyllysine to $NAD^+$, yielding nicotinamide, the unique metabolite O-acetyl-ADP-ribose and deacetylated lysine. One or more sirtuins are present in virtually all species from bacteria to mammals. Here we describe a phylogenetic analysis of sirtuins. Based on their phylogenetic relationship, sirtuins can be grouped into over a dozen classes and subclasses. Humans, like most vertebrates, have seven sirtuins: SIRT1-SIRT7. These function in diverse cellular pathways, regulating transcriptional repression, aging, metabolism, DNA damage responses and apoptosis. We show that these seven sirtuins arose early during animal evolution. Conserved residues cluster around the catalytic center of known sirtuin family members.

• Parasites, Hosts and Diseases
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• v.58 no.1
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• pp.7-14
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• 2020

Toxoplasma gondii is an intracellular protozoan parasite that infects approximately one third of the human population worldwide. Considering the toxicity and side effects of anti-toxoplasma medications, it is important to develop effective drug alternatives with fewer and less severe off-target effects. In this study, we found that 4-hydroxybenzaldehyde (4-HBA) induced autophagy and the expression of NAD-dependent protein deacetylase sirtuin-1 (SIRT1) in primary murine bone marrow-derived macrophages (BMDMs). Interestingly, treatment of BMDMs with 4-HBA significantly reduced the number of macrophages infected with T. gondii and the proliferation of T. gondii in infected cells. This effect was impaired by pretreating the macrophages with 3-methyladenine or wortmannin (selective autophagy inhibitors) or with sirtinol or EX527 (SIRT1 inhibitors). Moreover, we found that pharmacological inhibition of SIRT1 prevented 4-HBA-mediated expression of LC3-phosphatidylethanolamine conjugate (LC3-II) and the colocalization of T. gondii parasitophorous vacuoles with autophagosomes in BMDMs. These data suggest that 4-HBA promotes antiparasitic host responses by activating SIRT1-mediated autophagy, and 4-HBA might be a promising therapeutic alternative for the treatment of toxoplasmosis.

• Development and Reproduction
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• v.23 no.2
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• pp.129-138
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• 2019

In many cases, obesity is associated with metabolic disorders. Recently, natural compounds that may be beneficial for improving obesity have received increasing attention. Bitter melon has received attention as a diabetes treatment. $NAD^+$-dependent deacetylase (Sirtuin 1, SIRT1) has emerged as a novel therapeutic target for metabolic diseases. In this study, ethanol extract of bitter melon (BME) suppressed adipocyte differentiation and significantly increased the expression of SIRT1 in fully differentiated 3T3-L1 cells. Moreover, it enhanced the activation of AMP-activated protein kinase (AMPK). In high-fat diet (HFD)-fed induced-obesity mice, BME suppressed HFD-induced increases in body weight and white adipose tissue (WAT) weight. BME also increased the expression of SIRT1 and suppressed peroxisome proliferator-activated receptor and sterol regulatory element binding protein 1 expressions of WAT from HFD-fed mice. These findings suggest that BME prevents obesity by activating the SIRT1 and AMPK pathway and that it may be a useful dietary supplement for preventing obesity.

• Asian Pacific Journal of Cancer Prevention
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• v.15 no.23
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• pp.10151-10156
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• 2015

4-Hydroxynonenal (4-HNE) is a stable end product of lipid peroxidation, which has been shown to play an important role in cell signal transduction, while increasing cell growth and differentiation. 4-HNE could inhibit phosphatase and tensin homolog (PTEN) activity in hepatocytes and increased levels have been found in human invasive breast cancer. Here we report that 4-HNE increased the cell growth of breast cancer cells as revealed by colony formation assay. Moreover, vascular endothelial growth factor (VEGF) expression was elevated, while protein levels of hypoxia inducible factor 1 alpha (HIF-$1{\alpha}$) were up-regulated. Sirtuin-3 (SIRT3), a major mitochondria NAD+-dependent deacetylase, is reported to destabilize HIF-$1{\alpha}$. Here, 4-HNE could inhibit the deacetylase activity of SIRT3 by thiol-specific modification. We further demonstrated that the regulation by 4-HNE of levels of HIF-$1{\alpha}$ and VEGF depends on SIRT3. Consistent with this, 4-HNE could not increase the cell growth in SIRT3 knockdown breast cancer cells. Additionally, 4-HNE promoted angiogenesis and invasion of breast cancer cells in a SIRT3-dependent manner. In conclusion, we propose that 4-HNE promotes growth, invasion and angiogenesis of breast cancer cells through the SIRT3-HIF-$1{\alpha}$-VEGF axis.

• Journal of Life Science
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• v.25 no.3
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• pp.317-322
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• 2015

Alcohol-induced fatty liver (steatosis) results from excessive generation of reducing equivalents by ethanol metabolism. Generally, chronic ethanol treatment causes hepatosteatosis by regulating sterol regulatory element-binding protein 1c (SREBP-1c), which increases the synthesis of hepatic lipids. The effect of ethanol on SREBP-1c is mediated through mammalian sirtuin-1 (SIRT-1), a NAD⁺-dependent protein deacetylase that regulates hepatic lipid metabolism. Ginseng is a widely used herbal medicine that is used in Asia for its anti-diabetes and anti-obesity effects. The pharmacological and therapeutic effects of ginseng are primarily produced by bioactive constituents known as ginsenosides. Here, we examined the regulatory effects of Korean red ginseng (KRG) extracts on SREBP-1c and SIRT-1 on lipid homeostasis in AML-12 mouse hepatocytes. AML-12 cells were treated with ethanol and/or KRG extracts (0 - 1,000 μg/ml). Lipid droplets were assayed using Oil red O staining, and western blotting was used to measure SIRT-1 and SREBP-1 expression. Treatment with KRG extracts restored SIRT-1 expression and reduced SREBP-1c expression in ethanol-treated cells. We also showed that KRG extract and ginsenosides Rb₂ and Rd significantly decreased SREBP-1 acetylation in ethanol-treated cells. These results show that treatment with KRG extract and its active ginsenoside constituents Rb₂ and Rd protected against alcohol-related hepatosteatosis via regulation of SIRT-1 and downstream acetylation of SREBP-1c, which altered hepatic lipid metabolism.

• The Korean Journal of Physiology and Pharmacology
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• v.19 no.5
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• pp.451-460
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• 2015

Sirtuin 1 (SIRT1) is a mammalian $NAD^+$-dependent protein deacetylase that regulates cellular metabolism and inflammatory response. The organ-specific deletion of SIRT1 induces local inflammation and insulin resistance in dietary and genetic obesity. Macrophage-mediated inflammation contributes to insulin resistance and metabolic syndrome, however, the macrophage-specific SIRT1 function in the context of obesity is largely unknown. C57/BL6 wild type (WT) or myeloid-specific SIRT1 knockout (KO) mice were fed a high-fat diet (HFD) or normal diet (ND) for 12 weeks. Metabolic parameters and markers of hepatic steatosis and inflammation in liver were compared in WT and KO mice. SIRT1 deletion enhanced HFD-induced changes on body and liver weight gain, and increased glucose and insulin resistance. In liver, SIRT1 deletion increased the acetylation, and enhanced HFD-induced nuclear translocation of nuclear factor kappa B (NF-${\kappa}B$), hepatic inflammation and macrophage infiltration. HFD-fed KO mice showed severe hepatic steatosis by activating lipogenic pathway through sterol regulatory element-binding protein 1 (SREBP-1), and hepatic fibrogenesis, as indicated by induction of connective tissue growth factor (CTGF), alpha-smooth muscle actin (${\alpha}$-SMA), and collagen secretion. Myeloid-specific deletion of SIRT1 stimulates obesity-induced inflammation and increases the risk of hepatic fibrosis. Targeted induction of macrophage SIRT1 may be a good therapy for alleviating inflammation-associated metabolic syndrome.