• International journal of thyroidology
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• v.11 no.2
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• pp.143-151
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• 2018

Background and Objectives: Sirtuins (SIRTs) play important roles in cellular and organismal homeostasis. They have distinct gene expression patterns in various cancers; however, the relationship between SIRT expression and the progression of thyroid cancer is unclear. We investigated the expression of SIRTs in patients with papillary thyroid carcinoma (PTC) and their role as biomarkers for predicting the aggressiveness of this disease. Materials and Methods: We used immunohistochemical staining to evaluate the expression of SIRT1 and SIRT3 in tumor specimens from 270 patients with PTC. We also evaluated the potential association between SIRT expression and diverse clinicopathological features. Results: High SIRT1 expression was negatively correlated with lymphovascular invasion, central lymph node metastasis, and lateral lymph node metastasis. Multivariate analyses revealed that high SIRT1 expression was a negative independent risk factor for lateral lymph node metastasis. By contrast, high SIRT3 expression was positively correlated with locoregional recurrence. Interestingly, when patients were grouped by tumor SIRT expression patterns, the group with low SIRT1 expression and high SIRT3 expression was correlated with more aggressive cancer phenotypes including central lymph node metastasis and lateral lymph node metastasis. Conclusion: Our results suggest that SIRTs play dual roles in tumor progression, and the combination of decreased SIRT1 expression and increased SIRT3 expression is significantly associated with a poor prognosis in patients with PTC.

• BMB Reports
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• v.45 no.8
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• pp.458-463
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• 2012

We investigated the mechanisms involved in KHG26377 regulation of glutamate dehydrogenase (GDH) activity, focusing on the roles of SIRT4 and SIRT3. Intraperitoneal injection of mice with KHG26377 reduced GDH activity with concomitant repression of glucose-induced insulin secretion. Consistent with their known functions, SIRT4 ribosylated GDH and reduced its activity, and SIRT3 deacetylated GDH, increasing its activity. However, KHG26377 did not affect SIRT4-mediated ADP-ribosylation/inhibition or SIRT3-mediated deacetylation/activation of GDH. KHG26377 had no effect on SIRT4 protein levels, and did not alter total GDH, acetylated GDH, or SIRT3 protein levels in pancreatic mitochondrial lysates. These results suggest that the mechanism by which KHG26377 inhibits GDH activity and insulin secretion does not involve ADP-ribosylation of GDH by SIRT4 or deacetylation of GDH by SIRT3.

• Reproductive and Developmental Biology
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• v.39 no.2
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• pp.43-47
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• 2015

Sirtuin proteins are evolutionary conserved Sir2-related $NAD^+$-dependent deacetylases and regulate many of cellular processes such as metabolism, inflammation, transcription, and aging. Sirtuin contains activity of either ADP-ribosyltransferase or deacetyltranfease and their activity is dependent on the localization in cells. However, the expression pattern of Sirtuins has not been well studied. To examine the expression levels of Sirtuins, RT-PCR was performed using total RNAs from various tissues including liver, small intestine, heart, brain, kidney, lung, spleen, stomach, uterus, ovary, and testis. Sirtuins were highly expressed in most of tissues including the testis. Immunostaining assay showed that Sirt1 and Sirt6 were mainly located in the nucleus of germ cells, spermatocytes, and spermatids in the seminiferous tubules, whereas Sirt2 and Sirt5 were exclusively present in the cytoplasm of germ cells and spermatocytes. Our results indicate that Sirtuins may function as regulators of spermatogenesis and their activities might be dependent on their location in the seminiferous tubules.

• Journal of Gastric Cancer
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• v.10 no.3
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• pp.91-98
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• 2010

Purpose: Silent mating-type information regulation 2 homologue 1 (SIRT1) is a nicotinamide adenine dinucleotide-dependent deacetylase. SIRT1 plays an important role in the regulation of cell death/survival and stress response in mammals. The aim of this study was to investigate whether the SIRT1 gene is involved in the development or progression of gastric cancers. Materials and Methods: SIRT1 and p53 genes in 86 gastric cancers were examined for genetic alterations by PCR-single strand conformation polymorphism sequencing, as well as SIRT1 protein expression in 170 gastric cancers by immunohistochemistry. Results: In the genetic analysis, we found SIRT1 and p53 mutations in two and 12 cases, respectively. Two missense mutations, c.599 C>T (T200I) and c.1258 G>A (E420K), were detected in the SIRT1 gene coding region. The SIRT1 and p53 mutation were found in mutually exclusive gastric cancers. The immunohistochemistry revealed that SIRT1 overexpression was found in 95 (55.9%) of 170 gastric cancers. Altered SIRT1 expression was not statistically associated with clinicopathological parameters, including tumor differentiation, location, lymph node metastasis, or p53 expression. Two cases with an SIRT1 mutation showed increased SIRT1 expression. Conclusions: These results suggest that genetic alterations and overexpression of the SIRT1 gene may contribute to gastric cancer development.

• BMB Reports
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• v.57 no.2
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• pp.98-103
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• 2024

The mammalian sirtuin family (SIRT1-SIRT7) has shown diverse biological roles in the regulation and maintenance of genome stability under genotoxic stress. SIRT7, one of the least studied sirtuin, has been demonstrated to be a key factor for DNA damage response (DDR). However, conflicting results have proposed that Sirt7 is an oncogenic factor to promote transformation in cancer cells. To address this inconsistency, we investigated properties of SIRT7 in hepatocellular carcinoma (HCC) regulation under DNA damage and found that loss of hepatic Sirt7 accelerated HCC progression. Specifically, the number, size, and volume of hepatic tumor colonies in diethylnitrosamine (DEN) injected Sirt7-deficient liver were markedly enhanced. Further, levels of HCC progression markers and pro-inflammatory cytokines were significantly elevated in the absence of hepatic Sirt7, unlike those in the control. In chromatin, SIRT7 was stabilized and colocalized to damage site by inhibiting the induction of γH2AX under DNA damage. Together, our findings suggest that SIRT7 is a crucial factor for DNA damage repair and that hepatic loss-of-Sirt7 can promote genomic instability and accelerate HCC development, unlike early studies describing that Sirt7 is an oncogenic factor.

• Molecules and Cells
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• v.39 no.2
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• pp.87-95
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• 2016

Sirt1 is the most prominent and extensively studied member of sirtuins, the family of mammalian class III histone deacetylases heavily implicated in health span and longevity. Although primarily a nuclear protein, Sirt1's deacetylation of Peroxisome proliferator-activated receptor Gamma Coactivator-$1{\alpha}$ (PGC-$1{\alpha}$) has been extensively implicated in metabolic control and mitochondrial biogenesis, which was proposed to partially underlie Sirt1's role in caloric restriction and impacts on longevity. The notion of Sirt1's regulation of PGC-$1{\alpha}$ activity and its role in mitochondrial biogenesis has, however, been controversial. Interestingly, Sirt1 also appears to be important for the turnover of defective mitochondria by mitophagy. I discuss here evidences for Sirt1's regulation of mitochondrial biogenesis and turnover, in relation to PGC-$1{\alpha}$ deacetylation and various aspects of cellular physiology and disease.

• Journal of Life Science
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• v.23 no.1
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• pp.131-136
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• 2013

Sirtuin proteins have emerged as important modulators of several age-associated diseases. These include cancer and diabetes, as well as cardiovascular and neurodegenerative diseases. Among the sirtuin family members, SIRT2 mRNA is strongly expressed. To investigate the pathophysiological significance of SIRT2 as a primary regulator of angiogenesis, we focused on the biological role of SIRT2 under hypoxic conditions, examining the gene expression pattern of sirtuin family members in human umbilical vein endothelial cells (HUVECs). SIRT2 was expressed primarily in the cytoplasm, but it was dynamically trans-localized in the nuclear by hypoxia stimuli. Interestingly, both SIRT2 and the pro-angiogenic factor, VEGF, were up- regulated by hypoxia. A Matrigel assay demonstrated that the HUVECs formed a tube-like structure under hypoxia. The SIRT2 inhibitor, AK-1, significantly decreased the tube-forming activity of the HUVECs under either normoxia or hypoxia conditions. These findings suggest that SIRT2 might be a key regulator of angiogenesis.

• Asian Pacific Journal of Cancer Prevention
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• v.16 no.8
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• pp.3573-3577
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• 2015

Background: Sirtuin7 (SIRT7) is a type of nicotinamide adenine dinucleotide oxidized form (NAD+)-dependent deacetylase and the least understood member of the sirtuins family; it is implicated in various processes, such as aging, DNA damage repair and cell signaling transduction. There is some evidence that SIRT7 may function as a tumor trigger for human malignancy. Here, we aimed to explore the biological function of SIRT7 in ovarian carcinoma cells and its potential mechanism. Materials and Methods: Expression of SIRT7 in ovarian cancer cell lines was detected by western blotting. Transduced cell lines with SIRT7 knockdown or overexpression were constructed. Cell viability, cologenic, apoptosis-associated and motility assays were performed to elucidate the biological function of SIRT7 in ovarian cancer cells. Results: SIRT7 demonstrated a higher level in ovarian cancer cell lines compared with normal cells. On the one hand, down-regulation of SIRT7 significantly reduced ovarian cancer cell growth, repressed colony formation and increased cancer cell apoptosis; on the other hand, up-regulation promoted the migration of cancer cells. Additionally, repression of SIRT7 also induced change in apoptosis-related molecules and subunits of the NF-${\kappa}B$ family. Conclusions: In the present study, our data indicated that SIRT7 might play a role of oncogene in ovarian malignancy and be a potential therapeutic target.

• Journal of Obesity & Metabolic Syndrome
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• v.27 no.4
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• pp.248-253
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• 2018

Background: Sirtuins mediate metabolic responses to nutrient availability and slow aging and accompanying decline in health. This study was designed to assess the expressions of sirtuin1 (SIRT1) and sirtuin3 (SIRT3) in the liver and hypothalamus after duodenal-jejunal bypass (DJB) surgery in rats. Methods: A total of 38 rats were randomly assigned to either sham group (n=8) or DJB group (n=30). DJB group was again divided into three groups according to the elapsed time after surgery (10 weeks, DJB10; 16 week, DJB16; 28 week, DJB28). The mRNA and protein expressions of SIRT1 and SIRT3 in the liver and hypothalamus were measured by reverse transcription polymerase chain reaction, Western blot, and immunohistochemistry analyses. $NAD^+/NADH$ ratio was also measured. Results: We found increased mRNA and protein expression levels of SIRT1 in the liver of DJB16 and DJB28 groups compared with those of sham group. The mRNA and protein expressions of SIRT3 in the liver of DJB group increased proportionally to the elapsed time after DJB surgery. The mRNA expression levels of SIRT1 in the hypothalamus increased in DJB16 and DJB28 groups and protein expression levels of SIRT1 in the hypothalamus increased in DJB10, DBJ16, and DJB28 groups compared with sham group. We observed that mRNA and protein levels of SIRT3 in the hypothalamus of DJB group were not changed. Conclusion: This study proves that DJB increases SIRT1 and SIRT3 expressions in the liver and SIRT1 expression in the hypothalamus. These results suggest the possibility of sirtuins being involved in bypass surgery-induced metabolic changes.

• Food Science of Animal Resources
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• v.40 no.1
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• pp.106-117
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• 2020

Cellular senescence is associated with age-related vascular disorders and has been implicated in vascular dysfunctions. Here, we show that duck oil-loaded nanoemulsion (DO-NE) attenuates premature senescence of vascular smooth muscle cells (VSMCs) triggered by angiotensin II (Ang II). Compared with control nanoemulsion (NE), DO-NE significantly inhibited the activity of senescence-associated β-galactosidase, which is a biomarker of cellular senescence, in Ang II-treated VSMCs. SIRT1 protein expression was dose- and time-dependently induced in VSMCs exposed to DO-NE, but not in those exposed to NE, and SIRT1 promoter activity was also elevated. Consistently, DO-NE also dose-dependently rescued Ang II-induced repression of SIRT1 expression, indicating that SIRT1 is linked to the anti-senescence action of DO-NE in VSMCs treated with Ang II. Furthermore, the SIRT1 agonist resveratrol potentiated the effects of DO-NE on VSMCs exposed to Ang II, whereas the SIRT1 inhibitor sirtinol elicited the opposite effect. These findings indicate that DO-NE inhibits senescence by upregulating SIRT1 and thereby impedes vascular aging triggered by Ang II.