Resveratrol has been claimed to be an activator of Sirtuin 1
activators. Alca?FJ et al. Sirtuin 1-7 (SIRT1-7) are deacetylases that are dependent on NAD(+) for their activity. SIRT1 down-regulates p53 activity, increasing lifespan, cell survival, and neuroprotection; it also deacetylates peroxisome proliferator-activated receptor-gamma and its coactivator 1alpha, promoting fat mobilization, increasing mitochondrial size and number, and positively regulating insulin secretion. Sirtuins link nutrient availability and energy metabolism. Calorie restriction, which increases lifespan and is beneficial in age-related disorders, activates sirtuin. Major efforts are thus focused to developing sirtuin activators.
However, the role of resveratrol as a sirtuin activator has been disputed. On the other hand, studies show that resveratrol increases the expression level of SIRT1.
SIRT1 improves insulin sensitivity under insulin-resistant conditions by repressing PTP1B. Sun C et al. Insulin resistance is often characterized as the most critical factor contributing to the development of type 2 diabetes. SIRT1 has been reported to be involved in the processes of glucose metabolism and insulin secretion. However, whether SIRT1 is directly involved in insulin sensitivity is still largely unknown. Here we show that SIRT1 is downregulated in insulin-resistant cells and tissues and that knockdown or inhibition of SIRT1 induces insulin resistance. Furthermore, increased expression of SIRT1 improved insulin sensitivity, especially under insulin-resistant conditions. Similarly, resveratrol, a SIRT1 activator, enhanced insulin sensitivity in vitro in a SIRT1-dependent manner and attenuated high-fat-diet-induced insulin resistance in vivo at a dose of 2.5 mg/kg/day. Further studies demonstrated that the effect of SIRT1 on insulin resistance is mediated by repressing PTP1B transcription at the chromatin level. Taken together, the finding that SIRT1 improves insulin sensitivity has implications toward resolving insulin resistance and type 2 diabetes.
Resveratrol, an effective regulator of ovarian development and oocyte apoptosis. Kong XX et al. Resveratrol, a phytopolyphenol compound found chiefly in grapes and wine, has been reported to have a variety of anti-inflammatory, anti-platelet, and anti-carcinogenic effects. However, little is known about the effects of resveratrol on ovarian development and oocyte apoptosis. We investigated the effects of resveratrol on ovarian development in rats with different ages [from postnatal day (PD) 1 to 15 months], as well as on oocyte apoptosis in PD1 and PD2 rat ovaries. We show that: (1) intraperitoneal (ip) injection of resveratrol (20 mg/kg/day) increased the percentage of unassembled follicles and the total number of oocytes in PD1 and PD2 rat ovaries. Similar results were obtained when mothers were treated with resveratrol (20 mg/kg/day) by intragastric administration from the day 11, after the detection of vaginal plug, until delivery. In PD4 rat ovaries, the total number of oocytes was significantly increased in the groups treated with reveratrol. Moreover, more unassembled follicles and fewer primary follicles were present in the groups treated with resveratrol than in the controls; (2) in 15-month-old rat ovaries, resveratrol increased the number of resting follicles and total oocytes, and decreased the number of developing follicles and atretic follicles; (3) the percentage of TUNEL positive oocytes decreased in PD1 and PD2 rat ovaries after resveratrol treatment, and the number of oocytes positive for Foxo3a, Bim, and p27KIP1 in PD2 rat ovaries was lower in the resveratrol treatment group than in controls. These results suggest that resveratrol may delay oocyte nest breakdown and inhibit both the primordial-to-developing-follicle transition and apoptosis by decreasing the activation of Foxo3a, Bim, and p27KIP1, thus augmenting the resting follicle reserves, maintaining regular estrous cycles of early aged rats and delaying climacterium.
NCBI Summary:
This gene encodes a member of the sirtuin family of proteins, homologs to the yeast Sir2 protein. Members of the sirtuin family are characterized by a sirtuin core domain and grouped into four classes. The functions of human sirtuins have not yet been determined; however, yeast sirtuin proteins are known to regulate epigenetic gene silencing and suppress recombination of rDNA. Studies suggest that the human sirtuins may function as intracellular regulatory proteins with mono-ADP-ribosyltransferase activity. The protein encoded by this gene is included in class I of the sirtuin family. Alternative splicing results in multiple transcript variants. [provided by RefSeq, Dec 2008]
SIRT1, 2, 3 protect mouse oocytes from postovulatory aging. Zhang T et al. (2016) The quality of metaphase II oocytes will undergo a time-dependent deterioration following ovulation as the result of the oocyte aging process. In this study, we determined that the expression of sirtuin family members (SIRT1, 2, 3) was dramatically reduced in mouse oocytes aged in vivo or in vitro. Increased intracellular ROS was observed when SIRT1, 2, 3 activity was inhibited. Increased frequency of spindle defects and disturbed distribution of mitochondria were also observed in MII oocytes aged in vitro after treatment with Nicotinamide (NAM), indicating that inhibition of SIRT1, 2, 3 may accelerate postovulatory oocyte aging. Interestingly, when MII oocytes were exposed to caffeine, the decline of SIRT1, 2, 3 mRNA levels was delayed and the aging-associated defective phenotypes could be improved. The results suggest that the SIRT1, 2, 3 pathway may play a potential protective role against postovulatory oocyte aging by controlling ROS generation.//////////////////
Effects of plant polyphenols on ovarian follicular reserve in aging rats. Chen ZG et al. The pool of ovarian primordial follicles is established during embryonic development or at birth. During the development from primordial to primary, secondary, and antral follicles, only a small portion of follicles can mature and successfully ovulate; the others are destined to degenerate through apoptotic or atretic loss. As aging advances, females ultimately enter the cessation phase of the estrous cycle and are no longer capable of fertilization. The presumption is that if we can slow down the process of folliculogenesis or decrease follicle loss, females may have a larger ovarian follicular reserve and a longer reproductive lifespan. In our study, rats underwent intragastric administration with tea polyphenols, quercetin (meletin), genistein, or resveratrol, once a day for 4 months (from age 12 to 15 months), to test whether they have positive effects on follicular reserve or ovarian functions. The results showed that rats treated with tea polyphenols (27.8 +/- 3.2) and quercetin (36.5 +/- 4.1) had a comparable number of healthy follicles to those of controls (26.9 +/- 3.8), although significantly fewer atretic follicles were observed in the tea polyphenol group (43.4 +/- 5.9 vs 79.7 +/- 7.5; p < 0.001). Remarkably, both genistein- and resveratrol-treated rats had more healthy follicles (respectively, 42.8 +/- 3.9, p < 0.05; and 51.9 +/- 6.4, p < 0.001) and fewer atretic follicles (respectively, 58.4 +/- 8.0, p < 0.05; and 51.0 +/- 6.2, p < 0.01) than controls. These results indicate that genistein and resveratrol can increase the ovarian follicular reserve and prolong the ovarian lifespan in rats, and their positive effects may be not only due to their intervention in the transition from primordial to primary follicle, but also due to the inhibiting effect on follicular atresia.
Aryl hydrocarbon receptor antagonists attenuate the deleterious effects of benzopyrene on isolated rat follicle development. Neal MS et al. It has been shown that benzopyrene, a key component of cigarette smoke and an aryl hydrocarbon receptor (AhR) ligand, reduced growth of isolated rat follicles in vitro. However, the mechanism underlying the induced changes in folliculogenesis is unknown. This study proposed that the reported adverse effects of benzopyrene on follicle growth are mediated through AhR activation. The objective was to investigate the effect of benzopyrene with and without AhR antagonists (resveratrol or 3',4'-dimethoxyflavone (3,4-DMF)) on follicle growth, oestradiol output, anti-M?an hormone (AMH) concentration and cell proliferation in isolated rat follicles cultured in vitro. Benzopyrene treatment significantly inhibited follicle growth and cell proliferation at concentrations of 1.5 ng/ml and higher (P < 0.05), an effect attenuated by co-incubation with benzopyrene and resveratrol or 3,4-DMF. A significant decrease in oestradiol (P < 0.05) and AMH output (P < 0.001) by cultured follicles was induced by benzopyrene treatment, an effect attenuated by co-incubation with 3,4-DMF. The results suggest that the adverse effects of benzopyrene on follicle growth, steroidogenesis and AMH output are mediated through activation of the AhR. Moreover, AhR antagonists such as resveratrol and 3,4-DMF may have therapeutic benefit in protecting the ovary against the adverse effects of AhR ligands, including benzopyrene.Effects of resveratrol on proliferation and apoptosis in rat ovarian theca-interstitial cells. Wong DH et al. Polycystic ovary syndrome (PCOS) is characterized by ovarian dysfunction and associated with ovarian theca-interstitial (T-I) cell hyperplasia, hyperinsulinemia, systemic inflammation and oxidative stress. This in vitro study tested whether rat T-I cell growth with or without insulin can be altered by resveratrol, a natural polyphenol with anti-carcinogenic, anti-inflammatory, anti-proliferative and antioxidant properties. Rat T-I cells were cultured with and without resveratrol and/or insulin, and the effects on DNA synthesis, number of viable cells and markers of apoptosis were evaluated. Resveratrol alone induced a potent concentration-dependent inhibition of cell growth by inhibiting DNA synthesis, decreasing the number of viable cells and increasing the activity of executioner caspases 3 and 7; these effects of resveratrol counteracted the pro-proliferative and anti-apoptotic effects of insulin. Immunofluorescence analysis of cells incubated with resveratrol showed concentration- and time-dependent morphological changes consistent with apoptosis. The present findings indicate that resveratrol promotes apoptosis to reduce rat T-I cell growth in vitro as well as inhibiting insulin-induced rat T-I cell growth. This suggests a possibility that resveratrol and/or mechanisms mediating its effect may be relevant to the development of novel treatments for PCOS, which is characterized by both excessive ovarian mesenchyma growth and hyperinsulinemia.Maternal exposure to polycyclic aromatic hydrocarbons diminishes murine ovarian reserve via induction of Harakiri. Jurisicova A et al. Maternal smoking during pregnancy is associated with a variety of adverse neonatal outcomes including altered reproductive performance. Herein we provide molecular evidence for a pathway involved in the elimination of the female germline due to prepregnancy and/or lactational exposure to polycyclic aromatic hydrocarbons (PAHs), environmental toxicants found in cigarette smoke. We show that ovaries of offspring born to mice exposed to PAHs contained only a third of the ovarian follicle pool compared with offspring of unexposed female mice. Activation of the cell death pathway in immature follicles of exposed females was mediated by the aryl hydrocarbon receptor (Ahr), as ovarian reserve was fully rescued by maternal cotreatment with the Ahr antagonist, resveratrol, or by inactivation of the Ahr gene. Furthermore, in response to PAHs, Ahr-mediated activation of the harakiri, BCL2 interacting protein (contains only BH3 domain), was necessary for execution of cell death. This pathway appeared to be conserved between mouse and human, as xenotransplanted human ovarian cortex exposed to PAHs responded by activation of the identical cell death cascade. Our data indicate that maternal exposure to PAHs prior to pregnancy and/or during lactation compromises ovarian reserve of female offspring, raising the concern about the transgenerational impact of maternal smoking on ovarian function in the human.
Cellular localization
Cytoplasmic
Comment
Effects of neonatal resveratrol exposure on adult male and female reproductive physiology and behavior. Henry LA et al. Resveratrol (RES) is a phytoestrogen that has the ability to bind to estrogen receptors (ERs) and evoke biological effects that parallel those exerted by endogenous and synthetic estrogens. We have shown in previous studies that adult female rats acutely exposed to RES exhibit estrous cycle irregularity, ovarian hypertrophy, and alterations in sociosexual behavior. The present experiment characterizes the prolonged effects of maternal RES exposure throughout the lactational period on subsequent behavior, reproductive tissues, and brain morphology of the adult offspring. During adulthood, female offspring exposed to RES throughout nursing exhibited reduced body weight and increased ovarian weight, but exhibited normal estrous cyclicity and sociosexual behavior, without changes in the volume of the sexually dimorphic nucleus of the preoptic area or the anteroventral periventricular nucleus of the hypothalamus. During adulthood, males exposed to RES throughout nursing exhibited decreased body weight and plasma testosterone concentration, increased testicular weight, and reduced sociosexual behavior. These males also had significantly smaller sexually dimorphic nucleus of the preoptic area volumes and larger anteroventral periventricular nucleus volumes compared to male controls. These data suggest that postnatal exposure to RES may affect estrogenic activity in specific peripheral tissues (e.g., the gonads), while inducing antiestrogenic effects in the brain. Thus, the present study supports recent in vitro and in vivo findings that RES differs from most other phytoestrogens by acting as a possible mixed ER agonist/antagonist, depending on the tissue-specific availability of ER subtypes that are preferentially localized in specific brain regions and throughout the reproductive tract. More importantly these data indicate that maternal consumption of phytoestrogens during lactation can have lasting effects on the offspring that may not become apparent until they reach adulthood.
Ovarian function
Preantral follicle growth, Antral follicle growth, Follicle atresia, Steroid metabolism, Oocyte maturation, Early embryo development
Comment
Resveratrol protects mitochondrial quantity by activating SIRT1/PGC-1α expression during ovarian hypoxia. Nishigaki A et al. (2020) Resveratrol is a well-known potent activator of sirtuin-1 (SIRT1). We investigated the direct effects of hypoxia and resveratrol on SIRT1/ peroxisome proliferator-activated receptor-gamma coactivator 1α (PGC-1α) pathways, vascular endothelial growth factor (VEGF), hypoxia-inducible factor (HIF)-1α, and mitochondrial quantity in a steroidogenic human ovarian granulosa-like tumor cell line (KGN) cells. KGN cells were cultured with cobalt chloride (CoCl2; a hypoxia-mimicking agent) and/or resveratrol. The mRNA and protein levels, protein secretion, and intracellular localization were assessed by real-time PCR, Western blot analysis, ELISA, and immunofluorescence staining, respectively. Mitochondrial quantity was measured based on the mitochondrial DNA (mtDNA) copy number. CoCl2 simultaneously attenuated the levels of SIRT1 and mtDNA expression, and induced the levels of VEGF protein production. In contrast, resveratrol significantly increased the levels of SIRT1 and mtDNA copy number, but reduced VEGF production in normoxia. Resveratrol could recover CoCl2-suppressed SIRT1 and mtDNA expression and antagonize CoCl2-induced VEGF production. CoCl2 treatment resulted in a downregulation of PGC-1α expression, and this effect was recovered by resveratrol. Resveratrol significantly suppressed the production of the CoCl2-induced HIF-1α and VEGF proteins. These results suggest that resveratrol improves mitochondrial quantity by activating the SIRT1/PGC-1α pathway and inhibits VEGF induction through HIF-1α under hypoxic conditions.//////////////////Epigenetic and non-epigenetic mode of SIRT1 action during oocyte meiosis progression. Nevoral J et al. (2019) SIRT1 histone deacetylase acts on many epigenetic and non-epigenetic targets. It is thought that SIRT1 is involved in oocyte maturation; therefore, the importance of the ooplasmic SIRT1 pool for the further fate of mature oocytes has been strongly suggested. We hypothesised that SIRT1 plays the role of a signalling molecule in mature oocytes through selected epigenetic and non-epigenetic regulation. We observed SIRT1 re-localisation in mature oocytes and its association with spindle microtubules. In mature oocytes, SIRT1 distribution shows a spindle-like pattern, and spindle-specific SIRT1 action decreases α-tubulin acetylation. Based on the observation of the histone code in immature and mature oocytes, we suggest that SIRT1 is mostly predestined for an epigenetic mode of action in the germinal vesicles (GVs) of immature oocytes. Accordingly, BML-278-driven trimethylation of lysine K9 in histone H3 in mature oocytes is considered to be a result of GV epigenetic transformation. Taken together, our observations point out the dual spatiotemporal SIRT1 action in oocytes, which can be readily switched from the epigenetic to non-epigenetic mode of action depending on the progress of meiosis.//////////////////
SIRT1 induces resistance to apoptosis in human granulosa cells by activating the ERK pathway and inhibiting NF-κB signaling with anti-inflammatory functions. Han Y et al. (2017) SIRT1, a member of the sirtuin family, has recently emerged as a vital molecule in controlling ovarian function. The aims of the present study were to investigate SIRT1 expression and analyze SIRT1-mediated apoptosis in human granulosa cells (GCs). Human ovarian tissues were subjected to immunohistochemistry for localization of SIRT1 expression. SIRT1 knockdown in a human ovarian GC tumor line (COV434) was achieved by small interfering RNA, and the relationship between apoptosis and SIRT1 was assessed by quantitative reverse transcription polymerase chain reaction and western blotting. We further detected SIRT1 expression in human luteinized GCs. Associations among SIRT1 knockdown, SIRT1 stimulation (resveratrol) and expression of ERK1/2 and apoptotic regulatory proteins were analyzed in cell lines and luteinized GCs. Resveratrol downregulated the levels of nuclear factor (NF)-κB/p65, but this inhibitory effect was attenuated by suppressing SIRT1 activity. The NF-κB/p65 inhibitor pyrrolidine dithiocarbamate achieved similar anti-apoptosis effects. These results suggest that SIRT1 might play an anti-apoptotic role in apoptosis processes in GCs, possibly by sensing and regulating the ERK1/2 pathway, which has important clinical implications. Thus, our study provides a mechanistic link, whereby activation of SIRT1 function might help to sustain human reproduction by maintaining GCs as well as oocytes, offering a novel approach for developing a new class of therapeutic anti-inflammatory agents.//////////////////
Expression of SIRT1 in the ovaries of rats with polycystic ovary syndrome before and after therapeutic intervention with exenatide. Tao X et al. (2015) To investigate the expression of silent information regulator 1 (SIRT1) in rats with polycystic ovary syndrome (PCOS) and its alteration after exenatide treatment. PCOS rat model was established by dehydroepiandrosterone induction. The animals were randomly divided into exenatide treatment group (EX group, n = 10), metformin treatment group (MF group, n = 10), PCOS group (PCOS group, n = 9) and normal control group (NC group, n = 10). Histological changes of the ovarian tissues were examined by HE staining. SIRT1 expression in the ovarian tissue was detected by RT-PCR and immunohistochemistry. Rats in the PCOS group lost their estrous cycle. Histological observation of the ovary showed saccular dilatation of the follicle, decreased number of corpora lutea, fewer layers of granulosa cells aligned loosely, and thickened layer of theca cells. The changes in reproductive hormones and the development of insulin resistance suggested the successful establishment of the animal models. Immunohistochemistry and Q-PCR detected the mRNA and protein expressions of SIRT1 in the ovary tissues of rats in the normal control group. The SIRT1 expression was significantly lower in PCOS group than in control group (P < 0.05); after drug intervention, the SIRT1 expression significantly increased in EX and MF groups (compared with the PCOS group), whereas no significant difference was noted between the EX group and MF group. The SIRT1 expression in the ovary tissue decreases in PCOS rats (compare with the normal rats) but can be up-regulated after Ex or MF treatment. These drugs may affect the process and development of PCOS by regulating the SIRT1 expression. Exenatide may be therapeutic for PCOS by up-regulating the SITR1 expression.//////////////////Resveratrol-induced mitochondrial synthesis and autophagy in oocytes derived from early antral follicles of aged cows. Sugiyama M et al. (2015) Mitochondrial numbers increase during oocyte growth. In this study, we collected oocytes and granulosa cell complexes (OGCs) from early antral follicles (EAFs) of aged cows (>120 months of age) and examined the effects of resveratrol on mitochondrial generation, degradation, and quality in oocytes grown in vitro. We also examined the effects of resveratrol on gene expression of the granulosa cells. Resveratrol (20 µM) enhanced the expression of SIRT1 and induced autophagy in both granulosa cells and oocytes derived from aged cows. Culturing the OGCs with resveratrol increased mitochondrial DNA copy numbers in oocytes grown in vitro. Furthermore, resveratrol increased the ATP content in oocytes and improved the developmental ability of the oocytes to the blastocyst stage. Gene expression profiles in granulosa cells, as evaluated by next-generation sequencing technology, revealed that resveratrol enhanced the expression of EIF2-related genes but downregulated the expression of mammalian target of rapamycin (mTOR)-, inflammation-, and cholesterol homeostasis-related genes in granulosa cells. In conclusion, resveratrol affected both oocytes and granulosa cells derived from aged cows and improved the quality of oocytes grown in vitro through upregulation of mitochondrial biogenesis and degradation in growing oocytes and conditioning of granulosa cells.//////////////////
Resveratrol improves the quality of pig oocytes derived from early antral follicles through sirtuin 1 activation. Itami N et al. (2015) During oocyte growth, the number of mitochondria drastically increases and mitochondrial function profoundly affects the oocyte competence. Resveratrol is a well-known activator of sirtuin 1 (SIRT1), which has a role in cellular energy homeostasis and mitochondrial biogenesis. The main aim of the present study was to examine the effect of supplementation of culture media with resveratrol on oocyte development and mitochondrial number and functions. Lipid contents and developmental ability of the oocytes grown in vitro were also examined. Oocyte-granulosa cell complexes were collected from early antral follicles of gilt ovaries and were cultured in medium containing 0 or 2 μM resveratrol for 14 days. Immunostaining revealed that resveratrol enhanced SIRT1 expression in oocytes. Antrum formation during the culture period and survivability of the granulosa cells surrounding the developed oocytes did not differ between the two concentrations of resveratrol. In addition, the ability of oocytes to complete meiotic maturation did not differ between the two concentrations of resveratrol, whereas the ability of oocytes to develop to the blastocyst stage was improved significantly by resveratrol (7.4% vs. 1.6%; P < 0.05). Resveratrol upregulated the ATP content in oocytes grown in vitro, and the addition of 2 μM of the SIRT1 inhibitor 6-Chloro-2,3,4,9-tetrahydro-1H-carbazole-1-carboxamide (EX527) diminished this effect although EX527 alone had no effect on ATP content. The mitochondrial DNA copy number in oocytes determined by quantitative real-time polymerase chain reaction increased during in vitro oocyte development, but resveratrol did not affect the kinetics of the mitochondrial DNA copy number. We found that resveratrol also increased the expression level of phospho-5'-adenosine monophosphate-activated protein kinase in oocytes but decreased the lipid content in oocytes grown in vitro. These results suggest that resveratrol increased the ATP content in oocytes via energy homeostasis and improved the developmental ability of oocytes grown in vitro.//////////////////
Sirt1 protects pig oocyte against in vitro aging. Ma R et al. (2015) Sirtuins have been widely reported to be involved in multiple biological processes. However, their function during pig oocyte aging has not been reported yet. Here, we first identify that sirt1 expression is dramatically reduced in pig in vitro-aged oocytes. Furthermore, by confocal scanning and quantitative analysis, we find the increased frequency of spindle defects and chromosome misalignment, disturbed redistribution of cortical granules and mitochondria during oocyte in vitro-aging. Importantly, these aging-associated defective phenotypes can be ameliorated through resveratrol (sirt1 activator) treatment during pig oocyte maturation, providing the evidence for the hypothesis that decreased sirt1 is one of a number of factors contributing to oocyte in vitro-aging. In summary, our data indicate a role for sirt1 in pig oocytes and uncover a striking beneficial effect of sirt1 expression on aged oocytes.//////////////////
Roles of SIRT1 in granulosa cell apoptosis during the process of follicular atresia in porcine ovary. Zhao F et al. (2014) Ovarian follicular atresia is characterized by granulosa cell apoptosis, however, the exact mechanism is still unclear. Sirtuin 1 (SIRT1) is a NAD(+)-dependent deacetylase, which is associated with apoptosis in several of cell types, but its exact role in ovarian granulosa cell apoptosis is not clearly defined. In present study, we identified the involvement of SIRT1 in the process of follicle degeneration, which is known as "follicular atresia", both from in vivo models and cell culture data. The results of immunohistochemistry showed that SIRT1 was widely detected in non-apoptotic granulosa cells of follicles, but significantly decreased during the process of granulosa cell apoptosis. Quantitative real-time PCR and Western blot analysis showed that the expression levels of SIRT1 mRNA and protein were increased (P<0.05) during follicular atresia. In order to provide more evidences elucidating the roles of SIRT1 during the process of follicular atresia, granulosa cells were cultured in vitro with resveratrol which acts as a potent activator of SIRT1. Results showed that resveratrol caused a dose-dependent increase in both SIRT1 mRNA and protein levels. Meanwhile, apoptotic rate of granulosa cell was increased (P<0.01) in a dose-dependent manner. Additionally, resveratrol significantly increased the expression levels of Caspase-3 (P<0.01) and Bax mRNA (P<0.01), while Bcl-2 mRNA level was significantly decreased (P<0.01). Thus, our results suggest that SIRT1 may play important roles in the regulation of granulosa cell apoptosis during follicular atresia in porcine ovary.//////////////////
Interrelationships between sirtuin 1 and transcription factors p53 and NF-?B (p50/p65) in the control of ovarian cell apoptosis and proliferation. Sirotkin AV 2014 et al.
The roles of the mTOR system enzyme sirtuin 1 (SIRT1), the transcription factor p53 and the nuclear factor kappaB (NF-?B) and their interrelationships in the control of ovarian function have not been well studied. We examine, in vitro, the involvement of SIRT1, p53 and the p65 and p50 subunits of NF?B and their interrelationships in the control of the apoptosis and proliferation of porcine ovarian granulosa cells. Monolayers of primary granulosa cells were transfected with cDNA constructs encoding SIRT1, p53, p65 or p50 alone or were co-transfected with gene constructs for SIRT1 together with p53, p65 or p50. The accumulation of SIRT1, markers of proliferation (mitogen-activated protein kinase or extracellular-signal-regulated kinases 1,2) and a marker of apoptosis (caspase 3) was detected by immunocytochemistry. Transfection of cells with a SIRT1 gene construct alone promoted the accumulation of SIRT1 and decreased the accumulation of proliferation markers but did not affect the marker of apoptosis. Transfection of cells with gene constructs encoding p53, p50 or p65 decreased the expression of proliferation markers but not the apoptosis marker. Co-transfection of cells with SIRT1 cDNA changed the action of p65 on cell proliferation from inhibitory to stimulatory. SIRT1 overexpression induced the pro-apoptotic action of p53 and p50 but not of p65 constructs. Thus, SIRT1, p53 and NF-?B are involved in the control of both the proliferation and the apoptosis of ovarian cells. These novel data on the cross-talk between the mTOR/SIRT1 system and the transcription factors p53 and NF-?B show both the inhibitory (proliferation) and stimulatory (apoptosis) influences of SIRT1 on transcription factor action in ovarian cells.
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Serum sirtuin 1 levels in patients with polycystic ovary syndrome. Kiyak Caglayan E et al. (2014) Objective of the study is to determine the human nicotinamide adenine dinucleotide-dependent deacetylase sirtuin 1 level in women with polycystic ovary syndrome (PCOS). This cross-sectional study included 24 patients aged 20-38 years, who were diagnosed to have PCOS (patient group). The control group included 16 age- and body mass index-matched healthy female volunteers. The patients and controls were compared in terms of pre-prandial blood glucose, the homoeostatic model assessment for insulin resistance (HOMA-IR) index, and cholesterol, triglyceride, high-density lipoprotein (HDL), low-density lipoprotein (LDL), C-reactive protein (CRP) and sirtuin 1 levels. The mean sirtuin 1 level in the patient group (6.67 ± 2.29 ng mL(-1)) was significantly higher than that in the control group (4.69 ± 1.85 ng mL(-1)) (P = 0.007). Correlation analysis showed that there were no significant differences between the groups in fasting blood glucose, HOMA-IR index or cholesterol, triglyceride, HD, LDL and CRP levels. The sirtuin 1 level, which is associated with inflammation, the immune system and insulin metabolism, was higher in the PCOS patients than in the healthy controls.//////////////////
Interrelationships between sirtuin 1 and transcription factors p53 and NF-?B (p50/p65) in the control of ovarian cell apoptosis and proliferation. Sirotkin AV 2014 et al.
The roles of the mTOR system enzyme sirtuin 1 (SIRT1), the transcription factor p53 and the nuclear factor kappaB (NF-?B) and their interrelationships in the control of ovarian function have not been well studied. We examine, in vitro, the involvement of SIRT1, p53 and the p65 and p50 subunits of NF?B and their interrelationships in the control of the apoptosis and proliferation of porcine ovarian granulosa cells. Monolayers of primary granulosa cells were transfected with cDNA constructs encoding SIRT1, p53, p65 or p50 alone or were co-transfected with gene constructs for SIRT1 together with p53, p65 or p50. The accumulation of SIRT1, markers of proliferation (mitogen-activated protein kinase or extracellular-signal-regulated kinases 1,2) and a marker of apoptosis (caspase 3) was detected by immunocytochemistry. Transfection of cells with a SIRT1 gene construct alone promoted the accumulation of SIRT1 and decreased the accumulation of proliferation markers but did not affect the marker of apoptosis. Transfection of cells with gene constructs encoding p53, p50 or p65 decreased the expression of proliferation markers but not the apoptosis marker. Co-transfection of cells with SIRT1 cDNA changed the action of p65 on cell proliferation from inhibitory to stimulatory. SIRT1 overexpression induced the pro-apoptotic action of p53 and p50 but not of p65 constructs. Thus, SIRT1, p53 and NF-?B are involved in the control of both the proliferation and the apoptosis of ovarian cells. These novel data on the cross-talk between the mTOR/SIRT1 system and the transcription factors p53 and NF-?B show both the inhibitory (proliferation) and stimulatory (apoptosis) influences of SIRT1 on transcription factor action in ovarian cells.
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SIRT1 signalling protects mouse oocytes against oxidative stress and is deregulated during aging. Di Emidio G 2014 et al.
STUDY QUESTION
Is SIRT1 involved in the oxidative stress (OS) response in mouse oocytes?
SUMMARY ANSWER
SIRT1 plays a pivotal role in the adaptive response of mouse germinal vesicle (GV) oocytes to OS and promotes a signalling cascade leading to up-regulation of the MnSod gene.
WHAT IS KNOWN ALREADY
OS is known to continuously threaten acquisition and maintenance of oocyte developmental potential during in vivo processes and in vitro manipulations. Previous studies in somatic cells have provided strong evidence for the role of SIRT1 as a sensor of the cell redox state and a protector against OS and aging.
STUDY DESIGN, SIZE, DURATION
GV oocytes obtained from young (4-8 weeks) and reproductively old (48-52 weeks) CD1 mice were blocked in the prophase stage by 0.5 ?M cilostamide. Groups of 30 oocytes were exposed to 25 ?M H2O2 and processed following different times for the analysis of intracellular localization of SIRT1 and FOXO3A, and evaluation of Sirt1, miRNA-132, FoxO3a and MnSod gene expression. Another set of oocytes was cultured in the presence or absence of the SIRT1-specific inhibitor Ex527, and exposed to H2O2 in order to assess the involvement of SIRT1 in the activation of a FoxO3a-MnSod axis and ROS detoxification. In the last part of this study, GV oocytes were maturated in vitro in the presence of different Ex527 concentrations (0, 2.5, 5, 10, 20 ?M) and assessed for maturation rates following 16 h. Effects of Ex527 on spindle morphology and ROS levels were also evaluated.
PARTICIPANTS/MATERIALS, SETTING, METHODS
SIRT1 and FOXO3A intracellular distribution in response to OS was investigated by immunocytochemistry. Real-time RT-PCR was employed to analyse Sirt1, miR-132, FoxO3a and MnSod gene expression. Reactive oxygen species (ROS) production was evaluated by in vivo measurement of carboxy-H2DCF diacetate labelling. Spindle and chromosomal distribution in in vitro matured oocytes were analysed by immunocytochemistry and DNA fluorescent labelling, respectively.
MAIN RESULTS AND THE ROLE OF CHANCE
Specific changes in the intracellular localization of SIRT1 and up-regulation of Sirt1 gene were detected in mouse oocytes in response to OS. Moreover, increased intracellular ROS were observed when SIRT1 activity was inhibited by Ex527. In aged oocytes Sirt1 was expressed more than in young oocytes but SIRT1 protein was undetectable. Upon OS, significant changes in miR-132 micro-RNA, a validated Sirt1 modulator, were observed. A negative correlation between Sirt1 mRNA and miR-132 levels was observed when young oocytes exposed to OS were compared with young control oocytes, and when aged oocytes were compared with young control oocytes. FoxO3a and MnSod transcripts were increased upon OS with the same kinetics as Sirt1 transcripts, and up-regulation of MnSod gene was prevented by oocyte treatment with Ex527, indicating that SIRT1 acts upstream to the FoxO3a-MnSod axis. Finally, the results of the in vitro maturation assay suggested that SIRT1 might be involved in oocyte maturation by regulating the redox state and ensuring normal spindle assembly.
LIMITATIONS, REASONS FOR CAUTION
The main limitation of this study was the absence of direct quantification of SIRT1 enzymatic activity due to the lack of an appropriately sensitive method.
WIDER IMPLICATIONS OF THE FINDINGS
The present findings may provide a valuable background for studying the regulation of SIRT1 during oogenesis and its relevance as a sensor of oocyte redox state and energy status. The antioxidant response orchestrated by SIRT1 in oocytes seems to decrease with aging. This suggests that SIRT1 could be an excellent pharmacological target for improving oocyte quality and IVF outcome in aging or aging-like diseases.
STUDY FUNDING/COMPETING INTERESTS
The work was supported by the Ministero dell'Universit? della Ricerca Scientifica (MIUR) to C.T., F.A., C.D., A.M.D. The authors declare no conflict of interest.
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Relationship between mitochondrial DNA Copy Number and SIRT1 Expression in Porcine Oocytes. Sato D 2014 et al.
The present study assessed the effect of resveratrol on the expression of SIRT1 and mitochondrial quality and quantity in porcine oocytes. Supplementing the maturation medium with 20 ?M resveratrol increased the expression of SIRT1, and enhanced mitochondrial functions, as observed from the increased ATP content and mitochondrial membrane potential. Addition of resveratrol also improved the ability of oocytes to develop into the blastocyst stage following activation. The effects of resveratrol on mitochondrial number were examined by comparing the mitochondrial DNA copy number (Mt number) between group of oocytes collected from the same donor gilt ovaries. Supplementing the maturation medium with only resveratrol did not affect the Mt number in the oocytes. However, supplementing the maturation medium with 10 ?M MG132, a proteasome inhibitor, significantly increased the amount of ubiquitinated proteins and Mt number by 12 and 14%, respectively. In addition, when resveratrol was added to the medium containing MG132, the Mt number increased significantly by 39%, this effect was diminished by the addition of the SIRT1 inhibitor EX527. Furthermore, supplementing the medium with MG132 and EX527 did not affect Mt number. The mean SIRT1 expression in 20 oocytes was significantly and positively correlated with the Mt number in oocytes collected from the same donor. This study suggests that the expression of SIRT1 is associated with the Mt number in oocytes. In addition, activation of SIRT1 by resveratrol enhances the biosynthesis and degradation of mitochondria in oocytes, thereby replenishing and improving mitochondrial function and the developmental ability of oocytes.
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Beneficial effect of resveratrol on bovine oocyte maturation and subsequent embryonic development after in?vitro fertilization. Wang F 2013 et al.
OBJECTIVE
To analyze the potential beneficial effects and mechanisms of action of resveratrol on the maturation of bovine oocytes that were incubated in different concentrations of resveratrol (0.1, 1.0, or 10.0??M) as germinal vesicle-stage oocytes.
DESIGN
In?vitro prospective study.
SETTING
University research laboratory.
ANIMAL(S)
Animal models for human studies.
INTERVENTION(S)
In?vitro culture in the presence of various concentrations of the antioxidant resveratrol.
MAIN OUTCOME MEASURE(S)
Parameters of hormone levels, oocyte nuclear maturation, cumulus expansion, levels of intracellular glutathione and reactive oxygen species, embryonic cleavage, blastocyst formation, gene expression associated with mature bovine oocytes and cumulus cells, and level of sirtuin 1 gene expression.
RESULT(S)
Resveratrol statistically significantly increased progesterone secretion and decreased estradiol-17?secretion by cumulus cells. The elevated levels of progesterone activated the Mos/MEK/p42 mitogen-activated protein kinase (MAPK) cascade in the oocytes. At a concentration of 1.0??M, resveratrol statistically significantly improved cumulus expansion, polar body formation, the (hatched) blastocyst rate, and the mean number of cells/blastocysts. Meanwhile, resveratrol statistically significantly reduced the level of reactive oxygen species (ROS) and increased the level of glutathione (GSH). For the first time, the expression of the sirtuin-1 gene was identified in granulosa cells, cumulus cells, oocytes, and blastocysts. Further studies revealed that resveratrol promoted sirtuin-1 gene expression.
CONCLUSION(S)
Resveratrol promoted bovine oocyte maturation and subsequent post-in?vitro fertilization embryonic development by inducing progesterone secretion and an antioxidant effect, probably in a manner dependent on sirtuin-1.
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The involvement of SIRT1 and transcription factor NF-?B (p50/p65) in regulation of porcine ovarian cell function. Pavlov? 2013 et al.
The role of either mTOR system/enzyme sirtuin1 (SIRT1) or transcription factor NF-?B in the direct control of ovarian function has not been estabished. The aim of our in vitro experiments was to examine the involvement of SIRT1 and the p65 and p50 subunits of NF?B in control of porcine ovarian granulosa cell functions and the interrelationships between SIRT1, NF?B (p65, p50) 30 and FSH in the ovary. Monolayers of primary granulosa cells were transfected with gene constructs encoding either SIRT1 or p65 and p50, and thereafter cultured with, or without, addition of FSH. The accumulation of markers of proliferation (cyclin B1 and cyclin-dependent protein kinase Cdc2/p34) and proteins p50, p65 and SIRT1 in the cells was detected by using SDS-PAGE/Western immunoblotting and immunocytochemistry. The secretion of progesterone (P4) and insulin-like growth factor I (IGF-I) was measured by using radioimmunoassay. It was observed that transfection of cells with a SIRT1 gene construct promoted accumulation of proliferation markers, Cdc2/p34, cyclin B1, decreased accumulation of p50 and p65 and stimulated release of P4 and IGF-I. Co-transfection of cells with cDNA p50 and cDNA p65 enhanced the accumulation of SIRT1 and the release of P4 but did not influence the release of IGF-I. Adding FSH to the culture medium stimulated accumulation of both subunits of NF-?B, as well as accumulation of Cdc2/p34, cyclin B1 and release of both P4 and IGF-I. The ability of FSH to promote NF-?B accumulation, the similarity of the main effects of FSH, SIRT1 and NF-?B, as well as the inability of NF-?B to substantially modify the the majority of FSH effects suggest that SIRT1/NF-?B system could be a mediator of FSH action on ovarian cell functions. On the other hand, SIRT1 was able to inhibit NF-?B and to change stimulatory the effect of FSH on NF-?B from stimulatory to inhibitory. This could suggest the existence of negative feedback control of FSH/NF-?B system by high amounts of SIRT1. Our observations (1) confirm the previous data on proliferation, P4 and IGF-I release in ovarian cells and their up-regulation by FSH, (2) demonstrate the presence of SIRT1, NF-?B/p50 and NF-?B/p65 in these cells, (3) show for the first time the involvement of SIRT1 and NF-?B in direct control of proliferation and secretory activity of ovarian cells, (4) represent the first data on interrelationships between FSH, SIRT1 and NF-?B within the ovary.
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Transcription factor FOXL2 protects granulosa cells from stress and delays cell cycle: role of its regulation by the SIRT1 deacetylase. Benayoun BA et al. FOXL2 is a transcription factor essential for ovarian function and maintenance, whose germline mutations are responsible for the Blepharophimosis syndrome (BPES), often associated with premature ovarian failure/ageing. Recent evidence has linked FOXL2 downregulation or somatic mutation (p.Cys134Trp) to cancer, though underlying molecular mechanisms remain unclear. Using a functional genomics approach, we find that FOXL2 modulates cell cycle regulators in a way which should lead to G1 arrest. Indeed, FOXL2 upregulation promotes cell accumulation in the G1 phase and protects cells from oxidative damage, notably by promoting oxidized DNA repair and by increasing the amounts of anti-oxidant agent Glutathione. In agreement with clinical observations, we find that FOXL2 mutated versions leading to BPES along with ovarian dysfunction mostly fail to transactivate cell-cycle and DNA repair targets, whereas mutations leading to isolated craniofacial defects (and normal ovarian function) activate them correctly. Interestingly, these assays revealed a mild promoter-specific hypomorphy of the tumor-associated mutation (p.Cys134Trp). Finally, the SIRT1 deacetylase suppresses FOXL2 activity on targets linked to cell cycle and DNA-repair in a dose-dependent manner. Accordingly, we find that SIRT1 inhibition by nicotinamide limits proliferation, notably by increasing endogenous FOXL2 amount/activity. The body of evidence presented here supports the idea that FOXL2 plays a key role in granulosa cell homeostasis, the failure of which is central to ovarian ageing and tumorigenesis. Since granulosa cell tumors respond poorly to conventional chemotherapy, our findings on the deacetylase inhibitor nicotinamide provide an interesting option for targeted therapy.
Expression regulated by
LH
Comment
increased expression in a DNA microarray.//////The cAMP pathway promotes sirtuin-1 expression in human granulosa-lutein cells. Szymanska M et al. (2020) Sirtuin-1 (SIRT1), a NAD+-dependent deacetylase, is present in the ovarian granulosa cells (GCs) of various species. This study examined the regulation of SIRT1 expression in human granulosa-lutein cells (hGLCs). Two different, structurally unrelated SIRT1 activators, SRT2104 and resveratrol, dose- and time-dependently enhanced SIRT1 (∼2- and 1.5-fold increase at 50 μmol/L for mRNA and protein levels, respectively), whereas EX-527, an inhibitor of SIRT1 deacetylase activity, significantly suppressed SIRT1 protein induced by these activators. Transfecting cells with SIRT1 siRNA molecules efficiently silenced SIRT1 (∼70 % decrease in 48 h post-transfection). Furthermore, the stimulatory effects of SRT2104 on SIRT1 expression observed in non-transfected or in scrambled siRNA-transfected cells were diminished with SIRT1 silencing. The findings described above imply that SIRT1 autoregulates its own expression. Interestingly, SRT2104 elevated cAMP accumulation (1.4-fold) in the culture media of hGLCs which was further augmented in the presence of hCG (2.2-fold); these effects were evident after 12 h of incubation. This additive effect of hCG and SRT2104 on cAMP accumulation may explain the incremental outcome observed on SIRT1 expression (∼3-fold increase from basal level and ∼1.6-fold stimulation for each compound alone) with these two compounds. SIRT1 knockdown diminished SIRT1 induced by forskolin, providing additional evidence that cAMP promotes SIRT1. These findings imply that by activating adenylyl cyclase (hCG or forskolin) and inhibiting phosphodiesterases (SIRT1 activators), these two signals converge to produce an incremental, positive feedback loop on SIRT1 expression. Such a mechanism highlights the importance of maintaining high SIRT1 levels in human luteinized GCs.//////////////////FSH, oxytocin and IGF-I regulate the expression of sirtuin 1 in porcine ovarian granulosa cells. Sirotkin AV et al. (2020) The involvement of the mTOR system/enzyme sirtuin 1 (SIRT1) intracellular signaling system in the control of ovarian functions and its role in mediating hormonal action on the ovary has been proposed, but this hypothesis should be supported by a demonstrated influence of hormones on mTOR/SIRT1. Therefore, the aim of our in vitro experiments was to examine the effect of the known hormonal regulators of ovarian functions, such as follicle-stimulating hormone (FSH), oxytocin (OT) and insulin-like growth factor I (IGF-I), on mTOR/SIRT1. The accumulation of SIRT1 in porcine ovarian granulosa cells cultured with and without these hormones (at doses of 1, 10 or 100 ng.ml-1) was evaluated using immunocytochemistry. It was observed that the addition of FSH (at 10 ng.ml-1 but not at 1 or 100 ng/ml) and OT (at all tested doses) increased the expression of SIRT1 in ovarian cells. In addition, 100 ng.ml-1, but not at 1 or 10 ng.ml-1, of IGF-I decreased SIRT1 accumulation. Our observations are the first demonstration that hormones can directly regulate the ovarian mTOR/SIRT1 system and that this system could mediate the action of hormonal regulators on the ovary.//////////////////
Ovarian localization
Oocyte, Cumulus, Granulosa
Comment
SA1/SA2 cohesion proteins and SIRT1-NAD+ deacetylase modulate telomere homeostasis in cumulus cells and are eligible biomarkers of ovarian aging. Valerio D et al. (2018) Are cohesins SA1/SA2 and the NAD-dependent deacetylase SIRT1 involved in telomere homeostasis of cumulus cells and thus eligible as biomarkers of follicular physiology and ovarian aging? SA1/SA2 cohesins and SIRT1 are associated with telomere length in cumulus cells and may be eligible biomarkers of follicular physiology and ovarian aging. In somatic cells, cohesins SA1/SA2 mediate sister chromatid cohesion at the telomere termini (for SA1) and along chromatid arms (for SA2). The NAD+-dependent protein deacetylase Sirtuin 1 (SIRT1), which preserves DNA integrity from oxidative stress, may also modulate genome stability and telomere length. Collectively 280 cumulus/oocyte complex samples were recovered from a total of 50 women undergoing in vitro fertilization. Cumulus cells were separated from the oocyte-cumulus complex. DNA and total mRNA were extracted from cumulus cells and assayed for telomere length and for SA1, SA2 and SIRT1 gene expression profiling. Telomere length was determined by quantitave PCR and analyzed relative to the single copy of the housekeeping gene (albumin) to generate a T/S ratio (Telomere/single copy gene). Gene expression levels of SA1, SA2 and SIRT1 mRNA were assayed by quantitative RT-PCR and confirmed by western blotting and immunofluorescent studies (SIRT1). SA1/SA2 and SIRT1 gene expression levels and telomere length analysis of patients/samples were ranked in relation to their clinical setting parameters (BMI, age) and to the number of oocyte retrieved. SA1 and SA2 transcripts were both detected in all cumulus cells analyzed and the relative amount showed a clear decreasing trend according to the age of patients. A significant increase in SA1 and SA2 was disclosed in high responder women (>6 oocytes retrieved) compared to poor responders (<4 oocytes) (P < 0.05). Furthermore, statistically significant positive correlations were also recorded between the transcripts levels of the two cohesin molecules (r = 0.89; P < 0.05) and, to a lesser extent, between telomere length and SA1 (r = 0.42; P < 0.001) and SA2 (r = 0.36; P < 0.001) mRNA levels. SIRT1 expression was also significantly increased in high responders (>6 oocytes) compared to poor responders. Significant correlations were found between SIRT1 and SA1 (r = 0.69; P < 0.001), between SIRT1 and SA2 (r = 0.78; P < 0.001), and between SIRT1 and telomere length (r = 0.36; P < 0.001). However, in the older patient group (>38 years), SIRT1 mRNA levels were twice as high as the levels recorded in the younger patient cohort (<34 years). Western blot analysis and immunofluorescent studies confirmed the increments in SIRT1 protein levels in patients over 38 years old. N/A. Cumulus/oocyte complexes were retrieved by patients undergoing ovarian stimulation protocol for IVF. We cannot exclude the possibility that different stimulation protocols affect the correlations highlighted in this study. Future investigations should shed light on cumulus cells molecular profile according to different stimulation protocols. The overall results of our study point to the involvement of cohesins SA1/SA2 and SIRT1 deacetylase in telomere homeostasis in cumulus cells and highlight their possible eligibility as biomarkers of follicular physiology and ovarian aging. Merck Serono S.P.A Italy sponsored the study with financial support. There are no competing interests to declare.//////////////////
Resveratrol promotes expression of SIRT1 and StAR in rat ovarian granulosa cells: an implicative role of SIRT1 in the ovary. Morita Y et al. ABSTRACT: BACKGROUND: Resveratrol is a natural polyphenolic compound known for its beneficial effects on energy homeostasis, and it also has multiple properties, including anti-oxidant, anti-inflammatory, and anti-tumor activities. Recently, silent information regulator genes (Sirtuins) have been identified as targets of resveratrol. Sirtuin 1 (SIRT1), originally found as an NAD+-dependent histone deacetylase, is a principal modulator of pathways downstream of calorie restriction, and the activation of SIRT1 ameliorates glucose homeostasis and insulin sensitivity. To date, the presence and physiological role of SIRT1 in the ovary are not known. Here we found that SIRT1 was localized in granulosa cells of the human ovary. METHODS: The physiological roles of resveratrol and SIRT1 in the ovary were analyzed. Immunohistochemistry was performed to localize the SIRT1 expression. SIRT1 protein expression of cultured cells and luteinized human granulosa cells was investigated by Western blot. Rat granulosa cells were obtained from diethylstilbestrol treated rats. The cells were treated with increasing doses of resveratrol, and subsequently harvested to determine mRNA levels and protein levels. Cell viability was tested by MTS assay. Cellular apoptosis was analyzed by caspase 3/7 activity test and Hoechst 33342 staining. RESULTS: SIRT1 protein was expressed in the human ovarian tissues and human luteinized granulosa cells. We demonstrated that resveratrol exhibited a potent concentration-dependent inhibition of rat granulosa cells viability. However, resveratrol-induced inhibition of rat granulosa cells viability is independent of apoptosis signal. Resveratrol increased mRNA levels of SIRT1, LH receptor, StAR, and P450 aromatase, while mRNA levels of FSH receptor remained unchanged. Western blot analysis was consistent with the results of quantitative real-time RT-PCR assay. In addition, progesterone secretion was induced by the treatment of resveratrol. CONCLUSIONS: These results suggest a novel mechanism that resveratrol could enhance progesterone secretion and expression of luteinization-related genes in the ovary, and thus provide important implications to understand the mechanism of luteal phase deficiency.
Positive and negative feedback regulates the transcription factor FOXL2 in response to cell stress: evidence for a regulatory imbalance induced by disease-causing mutations. Benayoun BA et al. FOXL2 is a Forkhead transcription factor, essential for ovarian function, whose mutations are responsible for the Blepharophimosis Syndrome, characterized by craniofacial defects, often associated with premature ovarian failure. Here, we show that cell stress upregulates FOXL2 expression in an ovarian granulosa cell model. Increased FOXL2 transcription might be mediated at least partly by self-activation. Moreover, using 2D-western blot, we show that the response of FOXL2 to stress correlates with a dramatic remodeling of its post-translational modification profile. Upon oxidative stress, we observe an increased recruitment of FOXL2 to several stress-response promoters, notably that of the mitochondrial Superoxide Dismutase (MnSOD). Using several reporter systems, we show that FOXL2 transactivation is enhanced in this context. Models predict that gene upregulation in response to a signal should eventually be counterbalanced to restore the initial steady state. In line with this, we find that FOXL2 activity is repressed by the SIRT1 deacetylase. Interestingly, we demonstrate that SIRT1 transcription is, in turn, directly upregulated by FOXL2, which closes a negative-feedback loop. The regulatory relationship between FOXL2 and SIRT1 prompted us the test action of nicotinamide, an inhibitor of sirtuins, on FoxL2 expression/activity. According to our expectations, nicotinamide treatment increases FoxL2 transcription. Finally, we show that 11 disease-causing mutations in the ORF of FOXL2 induce aberrant regulation of FOXL2 and/or regulation of the FOXL2 stress-response target gene MnSOD. Taken together, our results establish that FOXL2 is an actor of the stress response, and provide new insights into the pathogenic consequences of FOXL2 mutations.
Follicle stages
Comment
Effects of caloric restriction and a high-fat diet on the ovarian lifespan in rats and the expression of SIRT1 and SIRT6 proteins. Luo LL et al. Background and Aims: Caloric restriction (CR) extends the mammal lifespan and suppresses ovary development. Sirtuins are involved in the mechanisms of lifespan extension of CR. However, whether, as well as to what extent, CR affects ovary lifespan or the ovarian follicle development is largely unknown. We investigated the effects of moderate and severe caloric restriction on the ovarian follicle reserves in rats compared with a high-fat dietary regimen. Methods: Female Sprague-Dawley rats (n=48) were randomly divided into four groups: normal control (NC), 25% caloric restriction (MCR), 45% CR (SCR) and high-fat diet (HF). They were maintained on these regimens for 2 months. Results: Histological analysis showed that both the 25 and 45% CR rats had a significantly higher percentage of primordial follicles and greater number of healthy follicles than the NC rats, whereas the HF rats did not differ significantly from the NC rats. Immunohistochemical analysis revealed that SIRT1 and SIRT6 proteins were present in the nucleus and cytoplasm of the oocyte. The 25% CR diet increased the expression of both SIRT1 and SIRT6 in the ovary, whereas the 45% CR and HF diets caused a decrease in SIRT1 expression. The level of SIRT6 protein did not change with the 45% CR diet, and it appeared slightly lower in the HF than in the NC groups. Conclusions: Thus, caloric restriction may inhibit the transition from primordial to developing follicles and extend the entire growth phase of a follicle to preserve the reserve of germ cells. SIRT1 and SIRT6 are both associated with these effects.
Phenotypes
Mutations
3 mutations
Species: mouse
Mutation name: None
type: null mutation fertility: infertile - ovarian defect Comment: The mammalian SIR2alpha protein has a role in embryogenesis and gametogenesis. McBurney MW et al. The yeast Sir2p protein has an essential role in maintaining telomeric and mating type genes in their transcriptionally inactive state. Mammalian cells have a very large proportion of their genome inactive and also contain seven genes that have regions of homology with the yeast sir2 gene. One of these mammalian genes, sir2alpha, is the presumptive mammalian homologue of the yeast sir2 gene. We set out to determine if sir2alpha plays a role in mammalian gene silencing by creating a strain of mice carrying a null allele of sir2alpha. Animals carrying two null alleles of sir2alpha were smaller than normal at birth, and most died during the early postnatal period. In an outbred background, the sir2alpha null animals often survived to adulthood, but both sexes were sterile. We found no evidence for failure of gene silencing in sir2alpha null animals, suggesting that either SIR2alpha has a different role in mammals than it does in Saccharomyces cerevisiae or that its role in gene silencing in confined to a small subset of mammalian genes. The phenotype of the sir2alpha null animals suggests that the SIR2alpha protein is essential for normal embryogenesis and for normal reproduction in both sexes. Animals have no corpora lutea.
Species: mouse
Mutation name: type: targeted overexpression fertility: fertile Comment: SIRT1 knock-in mice preserve ovarian reserve resembling caloric restriction. Long GY et al. (2018) Previous studies have proposed that caloric restriction (CR) regulates many cell functions and prolongs the lifespan of an organism. Our previous studies proposed that CR also prevents follicular activation and preserves the ovarian reserve in mice by activating SIRT1. To test if SIRT1 preserves the ovarian reserve and prolongs the ovarian longevity, we generated SIRT1 knock-in mice that can overexpress SIRT1 in oocytes of the mouse. Ovaries of the mice at ages 35 days and 15 months were collected, and the follicular development and follicular reserve were examined. The vaginal opening and onset of estrus of transgenic female mice (both the homozygous and heterozygous for SIRT1 overexpression) were later than that of wild-type mice. Both the homozygous and heterozygous SIRT1-overexpressing mice had a larger and stronger reproductive capacity than wild-type mice. Moreover, 35-day-old and 15-month-old homozygous and heterozygous SIRT1-overexpressing mice also had a higher mean number and percentage of healthy follicles, fewer atretic follicles than wild-type mice, and the mean number and percentage of primordial follicles in both the homozygous and heterozygous SIRT1-overexpressing mice were higher than wild-type mice at the same age. However, the phenotypes of heterozygous and homozygous transgenic mice came no difference. Immunohistochemistry showed increased expression of SIRT1 and FOXO3a, and decreased expression of mTOR in both the homozygous and heterozygous SIRT1-overexpressing mice compared with wild-type mice. Thus, oocyte-specific SIRT1-overexpressing mice continuously activate FOXO3a and suppress mTOR and have a larger reproductive capacity, larger follicle reserve and longer ovarian lifespan.//////////////////
Species: mouse
Mutation name: type: null mutation fertility: subfertile Comment: Sirt1 sustains female fertility by slowing age-related decline in oocyte quality required for post-fertilization embryo development. Iljas JD et al. (2020) The NAD+ -dependent sirtuin deacetylase, Sirt1, regulates key transcription factors strongly implicated in ageing and lifespan. Due to potential confounding effects secondary to loss of Sirt1 function from the soma in existing whole-animal mutants, the in vivo role of Sirt1 in oocytes (oocyte-Sirt1) for female fertility remains unknown. We deleted Sirt1 specifically in growing oocytes and study how loss of oocyte-Sirt1 affects a comprehensive range of female reproductive parameters including ovarian follicular reservoir, oocyte maturation, oocyte mitochondrial abundance, oxidative stress, fertilization, embryo development and fertility during ageing. Surprisingly, eliminating this key sirtuin from growing oocytes has no effect in young females. During a 10-month-long breeding trial, however, we find that 50% of females lacking oocyte-Sirt1 become prematurely sterile between 9 and 11 months of age when 100% of wild-type females remain fertile. This is not due to an accelerated age-related decline in oocyte numbers in the absence of oocyte-Sirt1 but to reduced oocyte developmental competence or quality. Compromised oocyte quality does not impact in vivo oocyte maturation or fertilization but leads to increased oxidative stress in preimplantation embryos that inhibits cleavage divisions. Our data suggest that defects emerge in aged females lacking oocyte-Sirt1 due to concurrent age-related changes such as reduced NAD+ and sirtuin expression levels, which compromise compensatory mechanisms that can cover for Sirt1 loss in younger oocytes. In contrast to evidence that increasing Sirt1 activity delays ageing, our data provide some of the only in vivo evidence that loss of Sirt1 induces premature ageing.//////////////////