Acetylation, catalyzed by acetyltransferases that transfer an acetyl residue from acetyl-CoA to the ε-amino group of specific lysine residues in histones and other proteins, is responsible for chromatin activation and regulation of metabolic pathways. The authors declare that they have no conflict of interest in the publication. The authors thank Sharda University, Greater Noida, India for support. Emerging research has recently recognised their role in a wide range of ailments.
Shirane et al. indicated that regulation of SIRT1 can determine the initial step of endometrial/uterine receptivity by controlling E-cadherin expression on endometrial carcinoma cell lines. RSV reduces androgen concentration (e.g., testosterone) produced at too high amounts by ovaries and the adrenals by more than 20%, and it decreases fasting insulin levels by 32% . Banaszewska et al. documented that in women with PCOS resveratrol, applied over a period of 3 months, significantly reduced ovarian and adrenal androgens. The authors documented that the levels of miR-152, miR-24, and SIRT1 significantly decreased, while the levels of miR-205, miR-222, and miR-150 were significantly higher in patients when compared to the healthy subjects. As a mitochondrial histone deacetylase, SIRT3 is involved in the regulation of mitochondrial function in cancers.
Bartosch et al. underlined that the obtained results show that sirtuins are deregulated in EC, and that this observed diversity of expression patterns suggests that sirtuins may have distinctive roles in endometrial cancer, similarly to what has been described for other cancer models. The authors observed that SIRT3 positively regulates the expression of folliculogenesis- and luteinization-related genes and progesterone secretion in human ovarian tissues by manipulating OS in human luteinized granulosa cells. In a study verifying the expression of seven sirtuin genes (SIRT1-SIRT7) in mouse ovaries, isolated oocytes, and cumulus cells, Okamoto et al. found the expression of all sirtuins regulated in a cell-specific manner. Authors observed decreased SIRT5 mRNA, protein, and desuccinylation activity in granulosa and cumulus cells, which resulted in an accumulation of follicular-fluid ammonium in women with reduced ovarian reserve or advanced maternal age. They examined SIRT5 mRNA, protein, and protein activity in samples of surplus follicular fluid, granulosa, and cumulus cells derived from women of different maternal ages and ovarian reserves who were undergoing routine IVF treatment. However, the expression of SIRT3 mRNA and active protein was decreased in women below 35 with reduced ovarian reserve, as well as in women of an advanced maternal age (above 40) and reduced ovarian reserve, and it was confirmed both in granular cells and cumulus cells (CSs). In this light, the role of sirtuins, which can modulate various proteins and cellular routs, seems to be important.
In a recent clinical trial, the pan-sirtuin inhibitor niacinamide was reported to improve therapeutic outcome when in combination with HDAC inhibition for treatment of human aggressive B-cell lymphomas.173 However, these inhibitors are neither potent enough nor specific enough, and their in vivo effect is also limited.122 In addition, a specific SIRT1 inhibitor EX-527 is in a Phase II clinical trial for treating Huntington’s disease,174 although its effect on cancer remains unclear. In-depth understanding of the roles of individual sirtuins in a particular type of cancer would thus be necessary to better guide a therapeutic strategy with sirtuin modulation. However, in HNSCC, SIRT7 mRNA expression level is lower.143 An antiproliferative role of SIRT7 has been demonstrated by using SIRT7 knockout or overexpressing cells, and an inverse correlation with tumorigenic potential has been shown in several murine cell lines.165 In HeLa, Hep3B, MDA-MB-231, and HEK293T cells, a negative transcriptional regulation of HIF1 and HIF2 by SIRT7 was established, suggesting that SIRT7 may function as a tumor suppressor through HIF signaling.166 In a conditional SIRT6 knockout mouse model, SIRT6 deletion increased the number, size, and aggressiveness of tumors.60 In a genetic mouse model specific for liver cancer initiation, SIRT6 represses Survivin expression by reducing histone H3K9 acetylation and NF-κB activation, and the increased SIRT6 expression at the liver cancer initiation stage markedly impairs liver cancer development.158 Overexpression of SIRT6 leads to massive apoptosis in a variety of cancer cell lines but not in non-transformed cells.159
According to research, expression of SIRT4 is considerably downregulated in hepatocellular carcinoma tumour tissues (Li et al. 2019) and esophageal squamous cell carcinoma (Nakahara et al. 2016). It also prevents cancer cell metabolic reprogramming by destabilising HIF1α (Finley et al. 2011). The deacetylase activity of SIRT3 is required for viral suppression, during infection it keeps membrane potential and mitochondrial pH stable (Sheng and Cristea 2021). The smaller domain consists of a helical bundle and a zinc binding region, which is created by two extending loops from the large domain The smaller domain consists of a helical bundle and a zinc binding region, which is created by two extending loops from the large domain. HIF-1 protein stability and transcriptional activity are both negatively influenced by SIRT2 (Seo et al. 2015). Down regulation of SIRT1 was found to be important in the senescence of different type of endothelial cells (Arunachalam et al. 2014; Vassallo et al. 2014).
For the first time sirtuin was recognised in yeast and named as sir2 (Michan and Sinclair 2007; Ivy et al. 1986). We have also discussed about the various natural and synthetic regulators of sirtuin activities like resveratrol. Their role is particularly important and well documented in the course of cancer developing within the female reproductive organs; however, they are also widely investigated in terms of disturbances observed in the ovary and oocyte as well as in follicular fluid. It is important because follicular metabolism is essential for the development of a competent oocyte, and therefore alterations in SIRT3 as well as its targets in granulosa and cumulus cells may alter the follicular environment and impact oocyte health. These disorders, e.g., GDH activity, may have a negative effect on cell function—in this case, oocyte viability . Pacelle-Ince et al. examined the degree of acetylation of glutamate dehydrogenase (GDH), which is a mitochondrial enzyme that participates in the urea cycle (it converts glutamate to α-ketoglutarate and vice versa). The application of an SIRT1 activator, resveratrol, elevated E-cadherin expression in a dose-dependent manner, while SIRT1 repressors (nicotinamide and sirtinol) exhibited a dose-dependent reduction of E-cadherin expression.
The involvement of sirtuins in the control of ovarian functions at various regulatory levels was also described by Sirotkin . Luo et al. made an attempt to identify the microRNAs (miRNAs) in granulosa cells from the follicular fluid of patients with various levels of ovarian reserve function and the potential regulatory function of miR-23a in granulosa cell apoptosis also in terms of the role of SIRT1. However, the involvement of sirtuins in the regulation of oocyte quality with aging has yet not been determined, but their role in the modulation of appropriate proteins responsible for the proper action of oocyte and folliculogenesis is indicated 66,67,68. In young women (aged below 35), an increased concentration of mRNA and SIRT3 concentration as well as its mitochondrial localization in granulosa cells (GCs) were observed, compared to cumulus oophorus cells in follicular cells taken from the same young women with normal ovarian reserve.
Recently, researchers have been interested in the role and usefulness of resveratrol in the normalization of disorders related to aging of the ovaries or impairment of their function. Mimics of miR-152 and miR-24 induced autophagy by increasing the level of SIRT1, which deacetylated LC3. Tong et al. examined the levels of serum miR-152, miR-205, miR-222, miR-24, miR-150, and SIRT1 in patients with uterine sarcoma and healthy subjects by quantitative real-time polymerase chain reaction (qRT-PCR). It was documented that the Bcl-2 inhibitor ABT737 can significantly improve the effect of cisplatin and induce mitochondrial pathway apoptosis. The authors observed significantly lower SIRT4 concentration in endometrioid adenocarcinoma than in non-neoplastic tissue counterpart.
There are a total of seven human sirtuins that have been identified namely, SIRT1, SIRT2, SIRT3, SIRT4, SIRT5, SIRT6 and SIRT7. Concluding, despite many studies, sirtuins are still an interesting research target, also in the context of women’s gynecological health. Knowledge about such perturbations may lead to novel therapies for improving mitochondrial metabolism that would specifically target the deacetylation of GDH in the oocyte and follicular cells of women undergoing IVF treatment . Furthermore, resveratrol enhanced E-cadherin and protein glycodelin expression at sites of intercellular contact, suggesting an additive role of resveratrol in promoting implantation and its future application as a protective agent . SIRT1 was expressed in endometriotic stromal cells (ESC) and normal endometrial stromal cells (NEC) and resveratrol suppressed TNF-α-induced IL-8 released from the ESC in a dose-dependent manner, while sirtinol increased IL-8 release. However, the mechanism of ABT737 increasing sensitivity to cisplatin in ovarian cancer cells remains unclear. They found that as a downstream target gene of HIF-1α, SIRT1 was involved in the promotion of cancer stem cell-like features in ovarian cancer cells by hypoxia.

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