Melatonin regulates the cross-talk between autophagy and apoptosis by SIRT3 in testicular Leydig cells

Dust Fall Microplastics from a Megacity of China Inhibit Autophagy via the PI3K/Akt/mTOR Pathway

The problem of microplastics (MPs) pollution has caused many health risks to residents of Chinese cities. In this study, nine kinds of MPs or microrubbers (MRs) from dust fall (DF) in Xi'an, a megacity in northwestern China, were measured by pyrolysis-gas chromatography-mass spectroscopy, namely, polyethylene, polypropylene, nylon 88, polybutylene, polytetrafluorethylene, polyisoprene, polyvinyl chloride, natural rubber, and synthesis rubber. Here, 51.20% of MPs were extracted from the original DF (samples denoted DF-O). After the subtracting procedure, MPs and their residual (DF-S samples) were divided into two parts. Our results indicated that the DF-O and MPs samples exhibited higher cytotoxicity, inflammatory, and oxidative stress levels than the DF-S samples did. The DF-O and MPs samples suppressed autophagy by decreasing expression levels of microtubule-associated protein light chain 3 (LC3B), p-phosphatidylinositol 3-kinase (p-PI3K), phosphorylated AKT protein (p-Akt), and p-mammalian target of rapamycin (p-mTOR) while increasing the level of p62. Meanwhile, DF-O and MPs samples induced apoptosis through increasing levels of Bax/Bcl-2 and Cleaved Caspase-3/Caspase-3 in Raw264.7 cells. These trends could be reversed through removing half of the MPs in DF-O. Therefore, dust fall microplastics inhibited autophagy and induced apoptosis via activating the PI3K/Akt/mTOR pathway, increasing the Bax/Bcl-2 and Cleaved Caspase-3/Caspase-3 ratios. Here we provide a comprehensive perspective into the studies of atmospheric MPs pollution status and mechanisms of inhalation toxicity for health risk assessment of MPs in DF.

Caloric Restriction and Sirtuins as New Players to Reshape Male Fertility

Over the years, caloric intake has remained a subject of profound scrutiny. Within the scientific community, there has been rigorous debate to ascertain which path is most ideal for enhancing quality of life and extending the human lifespan. Caloric restriction has been shown to be a promising contributor towards longevity and delaying the onset of age-related diseases. This diet consists of a reduction in caloric intake while maintaining essential energy and nutritional requirements to achieve optimal health while avoiding malnutrition. However, the effects of this nutritional regimen on male reproductive health have not yet been comprehensively studied. Nevertheless, such a complex process will certainly be regulated by a variety of metabolic sensors, likely sirtuins. Evidence has been gathered regarding this group of enzymes, and their ability to regulate processes such as chromatin condensation, the cell cycle, insulin signaling, and glucose and lipid metabolism, among many others. Concerning testicular function and male fertility, sirtuins can modulate certain metabolic processes through their interaction with the hypothalamic-pituitary-gonadal axis and mitochondrial dynamics, among many others, which remain largely unexplored. This review explores the impact of caloric restriction on male fertility, highlighting the emerging role of sirtuins as key regulators of male reproductive health through their influence on cellular metabolism.

DAPK3 is Essential for DBP-Induced Autophagy of Mouse Leydig Cells

Dibutyl phthalate (DBP) has been widely used in the manufacture of various daily and industrial products. As one of the most important endocrine disruptors, DBP has male reproductive toxicity and can lead to testicular dysfunction. In view of the fact that Leydig cells are important functional and structural units in the testis, their damage will affect testicular function. However, the underlying mechanism of DBP-caused damage to mouse Leydig cells remains elusive. In the study, it is confirmed that DBP can promote the expression of death-associated protein kinase 3 (DAPK3), thereby inducing autophagy of mouse Leydig cells by using in vivo and in vitro experiments. Also, bioinformatics analysis and molecular biology experimental techniques are utilized to further demonstrate that DBP-induced upregulation of DAPK3 results from both the activated transcription by specific protein 2 (Sp2) and the decreased ubiquitination and degradation by parkin RBR E3 ubiquitin-protein ligase (PRKN). Interestingly, melatonin can inhibit both Sp2/DAPK3 and PRKN/DAPK3 signaling pathways by inhibiting oxidative stress, thereby alleviating DBP-induced autophagy of mouse Leydig cells. Overall, the study unravels a novel regulatory mechanism of DBP-induced autophagy of mouse Leydig cells and identifies DAPK3 as a potential therapeutic target for DBP-caused damage to the male reproductive system.

Cadmium exposure induces Leydig cell injury via necroptosis caused by oxidative stress and TNF-α/TNFR1 signaling

Cadmium, a ubiquitous environmental pollutant, has been linked to testicular damage, primarily through mechanisms such as oxidative stress and various forms of programmed cell death. Despite extensive studies on its toxic effects, the specific role of necroptosis in cadmium-induced reproductive toxicity remains unclear. In this study, we provide critical insights into how cadmium triggers necroptosis in Leydig cells, leading to testicular dysfunction. Using both in vitro and in vivo models, we demonstrated that cadmium exposure induces necroptotic cell death in Leydig cells, with significant involvement of the TNF-α/TNFR1 signaling pathway and reactive oxygen species (ROS) generation. Co-treatment with Nec-1, a specific necroptosis inhibitor, significantly reduced elevated ROS levels and suppressed TNF-α/TNFR1-induced necroptotic cell death, suggesting that ROS and the TNF-α/TNFR1 signaling pathway contribute to necroptosis activation in cadmium-induced Leydig cell injury. In conclusion, we demonstrate that necroptosis is a key driver of cadmium-induced testicular damage, suggesting that targeting necroptosis could offer novel therapeutic strategies for mitigating reproductive toxicity caused by heavy metals.

Short-Term Treatment of Melatonin Improves the Expression of Cell Adhesion Molecules in the Testis of the Mouse Cryptorchidism Model

Melatonin plays a major role in regulating the sleep-wake cycle and enhancing testosterone production. We investigated the short-term effects of melatonin treatment for 14 consecutive days in the cryptorchidism model. We categorized experimental mice into Sham (S), Orchiopexy (O), Melatonin (Mel), and Orchiopexy + Melatonin (OMel) groups. Surgery involved inducing cryptorchidism in the left testis for seven days, followed by orchiopexy. The Mel group's testes did not descend, but they received melatonin injections after seven days of cryptorchidism. The OMel group underwent both orchiopexy and melatonin treatment. Both O and Mel groups exhibited decreased sperm and round-headed sperm in the epididymis. Significant increases were observed in the numbers of giant cells and negative Nectin-3 cells at p-value<0.05. The pattern of Cadm1 expression changed, and Nectin-2 and Nectin-3 co-expression was lacking in abnormal spermatids. Sertoli cell cytoplasm in both O and Mel groups exhibited autophagosomes and multivesicular bodies, which correlated with increased cyclooxygenase-2 expression. However, Terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL)-positive cell numbers increased significantly in all treatment groups compared to the S group. Our study found that the combination of orchiopexy and melatonin positively influenced the expression of cell adhesion molecules (Cadm1, Nectin-2, and Nectin-3) involved in spermatogenesis, while reducing giant cells, autophagosomes, and apoptosis.

Effect of exogenous melatonin implant on post-thaw semen quality of buffalo bulls

Melatonin is an intracellular antioxidant of sperm membrane that protects the cells from lipid peroxidation. Yet, its role as an antioxidant on semen quality of buffalo bulls is still obscure. The present study was undertaken to assess the effect of exogenous melatonin implant (18 mg/50 kg bodyweight) on post-thaw sperm characteristics, oxidative stress, endocrinological profiles and fertility of buffalo bulls. Six apparently healthy breeding Murrah buffalo bulls were randomly selected at bull farm, Guru Angad Dev Veterinary and Animal Sciences University for the present study and divided into two groups viz. control (n = 3) and melatonin implanted group (n = 3). A total of 120 ejaculates were collected from bulls of both groups (n = 60 each) throughout the study period. Most beneficial effects of melatonin implants were observed during post-implantation period. The percentages of post-thaw sperm total and progressive motility, viability and mitochondrial membrane potential were higher (p < .05) in melatonin implanted buffalo bulls compared to controls during post-implantation period. Following melatonin implantation, MDA production in post-thaw semen was lower (p < .05) in melatonin implanted group than in control group. Plasma melatonin and testosterone concentrations were higher (p < .05) in buffalo bulls implanted with melatonin as compared to their control counterparts. No differences (p > .05) in plasma LH concentrations were observed in both groups. First service pregnancy rate was 43.3% using semen of melatonin implanted bulls and 30.0% with semen of controls (p > .05). Thus, melatonin was able to protect sperm membrane against oxidative damage and improve post-thaw semen quality, thereby resulting in higher fertilizing potential of spermatozoa.

Sirt3 Regulates Proliferation and Progesterone Production in Leydig Cells via Suppression of Reactive Oxygen Species

Sirt3 is a mitochondrial protein deacetylase functioning in energy metabolism, regulation of intracellular reactive oxygen species (ROS) levels, and aging. Although Sirt3 loss has negative effects on fertility of oocytes during in vitro fertilization and on progesterone production in granulosa cells, Sirt3's function in Leydig cells remains unclear. Therefore, we investigated Sirt3 activity in Leydig cells, focusing on androgen production. To do so, we performed immunohistochemistry to confirm Sirt3 localization in gonads and observed strong Sirt3 immunostaining in Leydig cells of human testes and of Sirt3+/+ and Sirt3+/- mouse testes, while Sirt3-/- mouse testis tissue was negative. In human ovary, hilus cells were strongly Sirt3-positive, theca cells showed weak positivity, and granulosa cells showed very weak or almost no immunostaining. Next, we used the murine Leydig tumor cell line MA-10 as a model. We overexpressed Sirt3 but observed no changes in proliferation, expression of Star, Cyp11a1 (p450scc gene), and Hsd3b, or progesterone production in MA-10 cells. Sirt3 knockdown significantly reduced proliferation, suppressed expressions of steroidogenic enzymes and of transcription factors Ad4bp (Sf-1 gene) and Gata4, and decreased progesterone production. Sirt3 knockdown in MA-10 cells also increased intracellular ROS levels based on CM-H2DCFDA fluorescence dye analysis and increased the proportion of both early and late apoptotic (necrotic) cells based on Annexin V/7AAD assays. These results indicate that Sirt3 has a potential function in androgen production in Leydig cells by regulating intracellular ROS levels.

A narrative review on inflammaging and late-onset hypogonadism

The increasing life expectancy observed in recent years has resulted in a higher prevalence of late-onset hypogonadism (LOH) in older men. LOH is characterized by the decline in testosterone levels and can have significant impacts on physical and mental health. While the underlying causes of LOH are not fully understood, there is a growing interest in exploring the role of inflammaging in its development. Inflammaging is a concept that describes the chronic, low-grade, systemic inflammation that occurs as a result of aging. This inflammatory state has been implicated in the development of various age-related diseases. Several cellular and molecular mechanisms have been identified as contributors to inflammaging, including immune senescence, cellular senescence, autophagy defects, and mitochondrial dysfunction. Despite the extensive research on inflammaging, its relationship with LOH has not yet been thoroughly reviewed in the literature. To address this gap, we aim to review the latest findings related to inflammaging and its impact on the development of LOH. Additionally, we will explore interventions that target inflammaging as potential treatments for LOH.

Stimulation of Autophagy by Dapagliflozin Mitigates Cadmium-Induced Testicular Dysfunction in Rats: The Role of AMPK/mTOR and SIRT1/Nrf2/HO-1 Pathways

Cadmium (Cd) is a widespread environmental pollutant that triggers testicular dysfunction. Dapagliflozin is a selective sodium-glucose co-transporter-2 inhibitor with notable antioxidant and anti-apoptotic features. It has shown marked cardio-, reno-, hepato-, and neuroprotective effects. Yet, its effect on Cd-evoked testicular impairment has not been examined. Hence, the goal of the current study was to investigate the potential positive effect of dapagliflozin against Cd-induced testicular dysfunction in rats, with an emphasis on autophagy, apoptosis, and oxidative insult. Dapagliflozin (1 mg/kg/day) was given by oral gavage, and testicular dysfunction, impaired spermatogenesis, and biomolecular events were studied via immunohistochemistry, histopathology, and ELISA. The current findings demonstrated that dapagliflozin improved relative testicular weight, serum testosterone, and sperm count/motility and reduced sperm abnormalities, signifying mitigation of testicular impairment and spermatogenesis disruption. Moreover, dapagliflozin attenuated Cd-induced histological abnormalities and preserved testicular structure. The testicular function recovery was prompted by stimulating the cytoprotective SIRT1/Nrf2/HO-1 axis, lowering the testicular oxidative changes, and augmenting cellular antioxidants. As regards apoptosis, dapagliflozin counteracted the apoptotic machinery by downregulating the pro-apoptotic signals together with Bcl-2 upregulation. Meanwhile, dapagliflozin reactivated the impaired autophagy, as seen by a lowered accumulation of SQSTM-1/p62 and Beclin 1 upregulation. In the same context, the testicular AMPK/mTOR pathway was stimulated as evidenced by the increased p-AMPK (Ser487)/total AMPK ratio alongside the lowered p-mTOR (Ser2448)/total mTOR ratio. Together, the favorable mitigation of Cd-induced testicular impairment/disrupted spermatogenesis was driven by the antioxidant, anti-apoptotic, and pro-autophagic actions of dapagliflozin. Thus, it could serve as a tool for the management of Cd-evoked testicular dysfunction.

Role of Melatonin in Bovine Reproductive Biotechnology

Melatonin has profound antioxidant activity and numerous functions in humans as well as in livestock and poultry. Additionally, melatonin plays an important role in regulating the biological rhythms of animals. Combining melatonin with scientific breeding management has considerable potential for optimizing animal physiological functions, but this idea still faces significant challenges. In this review, we summarized the beneficial effects of melatonin supplementation on physiology and reproductive processes in cattle, including granulosa cells, oocytes, circadian rhythm, stress, inflammation, testicular function, spermatogenesis, and semen cryopreservation. There is much emerging evidence that melatonin can profoundly affect cattle. In the future, we hope that melatonin can not only be applied to cattle, but can also be used to safely and effectively improve the efficiency of animal husbandry.

Resveratrol inhibits LPS-induced apoptosis in bovine mammary epithelial cells: the role of PGC1α-SIRT3 axis

Resveratrol (Res) is a bioactive dietary component and alleviates apoptosis in multiple cell types. However, its effect and mechanism on lipopolysaccharide (LPS)-induced bovine mammary epithelial cells (BMEC) apoptosis, which commonly happens in dairy cows with mastitis, is unknown. We hypothesized that Res would inhibit LPS-induced apoptosis in BMEC through SIRT3, a NAD + -dependent deacetylase activated by Res. To test the dose-response effect on apoptosis, 0-50 μM Res were incubated with BMEC for 12 h, followed by 250 μg/mL LPS treatment for 12 h. To investigate the role of SIRT3 in Res-mediated alleviation of apoptosis, BMEC were pretreated with 50 μM Res for 12 h, then incubated with si-SIRT3 for 12 h and were finally treated with 250 μg/mL LPS for 12 h. Res dose-dependently promoted the cell viability and protein levels of Bcl-2 (Linear P < 0.001) but decreased protein levels of Bax, Caspase-3 and Bax/Bcl-2 (Linear P < 0.001). TUNEL assays indicated that cellular fluorescence intensity declined with the rising doses of Res. Res also dose-dependently upregulated SIRT3 expression, but LPS had the opposite effect. SIRT3 silencing abolished these results with Res incubation. Mechanically, Res enhanced the nuclear translocation of PGC1α, the transcriptional cofactor for SIRT3. Further molecular docking analysis revealed that Res could directly bind to PGC1α by forming a hydrogen bond with Tyr-722. Overall, our data suggested that Res relieved LPS-induced BMEC apoptosis through the PGC1α-SIRT3 axis, providing a basis for further in vivo investigations of applying Res to relieve mastitis in dairy cows.

Topiramate Reprofiling for the Attenuation of Cadmium-Induced Testicular Impairment in Rats: Role of NLRP3 Inflammasome and AMPK/mTOR-Linked Autophagy

Topiramate, a promising drug classically used for the management of neurological disorders including epilepsy and migraine, has demonstrated marked anti-inflammatory and anti-apoptotic actions in murine models of cardiac post-infarction inflammation, wound healing, and gastric/intestinal injury. However, its potential impact on cadmium-induced testicular injury remains to be elucidated. Herein, the present study aimed to explore the effect of topiramate against cadmium-invoked testicular impairment with emphasis on the molecular mechanisms linked to inflammation, apoptosis, and autophagy. Herein, administration of topiramate (50 mg/kg/day, by gavage) continued for 60 days and the testes were examined by histology, immunohistochemistry, and biochemical assays. The present data demonstrated that serum testosterone, sperm count/abnormalities, relative testicular weight, and histopathological aberrations were improved by topiramate administration to cadmium-intoxicated rats. The rescue of testicular dysfunction was driven by multi-pronged mechanisms including suppression of NLRP3/caspase-1/IL-1β cascade, which was evidenced by dampened caspase-1 activity, lowered IL-1β/IL-18 production, and decreased nuclear levels of activated NF-κBp65. Moreover, curbing testicular apoptosis was seen by lowered Bax expression, decreased caspase-3 activity, and upregulation of Bcl-2. In tandem, testicular autophagy was activated as seen by diminished p62 SQSTM1 accumulation alongside Beclin-1 upregulation. Autophagy activation was associated with AMPK/mTOR pathway stimulation demonstrated by decreased mTOR (Ser2448) phosphorylation and increased AMPK (Ser487) phosphorylation. In conclusion, combating inflammation/apoptosis and enhancing autophagic events by topiramate were engaged in ameliorating cadmium-induced testicular impairment.

Melatonin alleviates renal injury by activating mitophagy in diabetic nephropathy

Diabetic nephropathy (DN) causes serious renal tubule and interstitial damage, but effective prevention and treatment measures are lacking. Abnormal mitophagy may be involved in the progression of DN, but its upstream and downstream regulatory mechanisms remain unclear. Melatonin, a pineal hormone associated with circadian rhythms, is involved in regulating mitochondrial homeostasis. Here, we demonstrated abnormal mitophagy in the kidneys of DN mice or high glucose (HG)-treated HK-2 cells, which was accompanied by increased oxidative stress and inflammation. At the same time, the melatonin treatment alleviated kidney damage. After mitochondrial isolation, we found that melatonin promoted AMPK phosphorylation and accelerated the translocation of PINK1 and Parkin to the mitochondria, thereby activating mitophagy, reducing oxidative stress, and inhibiting inflammation. Interestingly, the renal protective effect of melatonin can be partially blocked by downregulation of PINK1 and inhibition of AMPK. Our studies demonstrated for the first time that melatonin plays a protective role in DN through the AMPK-PINK1-mitophagy pathway.

Repositioning Linagliptin for the Mitigation of Cadmium-Induced Testicular Dysfunction in Rats: Targeting HMGB1/TLR4/NLRP3 Axis and Autophagy

Cadmium, a ubiquitous environmental toxicant, disrupts testicular function and fertility. The dipeptidyl peptidase-4 inhibitor linagliptin has shown pronounced anti-inflammatory and anti-apoptotic features; however, its effects against cadmium-evoked testicular impairment have not been examined. Herein, the present study investigated targeting inflammation, apoptosis, and autophagy by linagliptin for potential modulation of cadmium-induced testicular dysfunction in rats. After 60 days of cadmium chloride administration (5 mg/kg/day, by gavage), testes, epididymis, and blood were collected for analysis. The present findings revealed that linagliptin improved the histopathological lesions, including spermatogenesis impairment and germ cell loss. Moreover, it improved sperm count/motility and serum testosterone. The favorable effects of linagliptin were mediated by curbing testicular inflammation seen by dampening of HMGB1/TLR4 pathway and associated lowering of nuclear NF-κBp65. In tandem, linagliptin suppressed the activation of NLRP3 inflammasome/caspase 1 axis with consequent lowering of the pro-inflammatory IL-1β and IL-18. Jointly, linagliptin attenuated testicular apoptotic responses seen by Bax downregulation, Bcl-2 upregulation, and suppressed caspase 3 activity. With respect to autophagy, linagliptin enhanced the testicular autophagy flux seen by lowered accumulation of p62 SQSTM1 alongside upregulation of Beclin 1. The observed autophagy stimulation was associated with elevated AMPK (Ser487) phosphorylation and lowered mTOR (Ser2448) phosphorylation, indicating AMPK/mTOR pathway activation. In conclusion, inhibition of testicular HMGB1/TLR4/NLRP3 pro-inflammatory axis and apoptosis alongside stimulation of autophagy were implicated in the favorable actions of linagliptin against cadmium-triggered testicular impairment.

Antifibrotic effect of AD-1 on lipopolysaccharide-mediated fibroblast injury in L929 cells and bleomycin-induced pulmonary fibrosis in mice

20(R)-25-methoxyl-dammarane-3β,12β,20-triol (25-OCH₃-PPD, AD-1) is a dammarane ginsenoside that is isolated from Panax notoginseng. The present study aimed to explore its anti-pulmonary fibrosis (PF) effect in vitro and in vivo. L929 cells were treated with 10 μg mL^-1 lipopolysaccharide (LPS) to establish a PF model in vitro and mice were administered with 3.5 mg kg^-1 bleomycin (BLM) by endotracheal intubation to establish a PF model in vivo for investigating the anti-PF effect and its potential mechanism. The results demonstrated that AD-1 reduced the injury, extracellular matrix (ECM) buildup and α-smooth muscle actin (α-SMA) protein expression levels of L929 induced by LPS. Oral administration of AD-1 downregulated the expression of interleukins (such as IL-1β, IL-6 and IL-18), increased the expression of superoxide dismutase (SOD) and glutathione (GSH), reduced the lung coefficient and the content of hydroxyproline (HYP), and mediated the Bax/Bcl-2 protein ratio and P-p53, β-catenin and SIRT3 expression in the lung tissue of mice. Furthermore, AD-1 inhibited the expression levels of TGF-β1, TIMP-1 and α-SMA and reduced inflammatory cell infiltration and collagen deposition in the lung tissue of PF mice. These results indicated that AD-1 could alleviate PF both in vitro and in vivo, and the underlying mechanism may be related to the decrease in ECM deposition and inflammation, the enhancement of antioxidant capacity, and the mediation of lung cell apoptosis and the TGF-β1/TIMP-1/α-SMA signaling pathway, which provide a theoretical basis for the rehabilitation treatment of PF.

Melatonin inhibits autophagy in TM3 cells via AKT/FOXO1 pathway

BACKGROUND

Melatonin can regulate apoptosis and autophagy of mouse Leydig cells, but its specific mechanism is still unclear.

METHODS

In this study, we used the TM3 cell line as the research object, and used H2O2 to induce autophagy. After adding 10 ng/ml melatonin, we used qRT-PCR and western-blot to detect autophagy-related gene and protein expression, and flow cytometry to detect cellular ROS level.

RESULTS

The results showed that melatonin can significantly inhibit the occurrence of autophagy, accompanied by a significant decrease in the expression of Becn1, LC3, and FOXO1 (P < 0.05), a significant increase in the expression of p62 and pAKT (P < 0.05), and a significant decrease in ROS level (P < 0.05). After added the inhibitor of AKT perifosine, the effect of melatonin on inhibiting autophagy was reversed. On this basis, we used small RNA interference technology to knock down the expression of FOXO1, and found that there was no significant change of the expression of genes and proteins related to autophagy and ROS level.

CONCLUSIONS

In summary, melatonin can inhibit H2O2-induced autophagy in TM3 cells through the AKT/FOXO1 pathway.

Hallmarks of Testicular Aging: The Challenge of Anti-Inflammatory and Antioxidant Therapies Using Natural and/or Pharmacological Compounds to Improve the Physiopathological Status of the Aged Male Gonad

The evolutionary theory of aging supports a trade-off relationship between reproduction and aging. Aging of the male reproductive system primarily affects the testes, leading to a decrease in the levels of sexual hormones, alterations in sperm quality and production, and a decline in fertility that does not necessarily involve a complete cessation of spermatogenesis. Inflammation, oxidation, and apoptosis are events considered as predictors of pathogenesis and the development of age-related diseases that are frequently observed in aged testes. Although the molecular mechanisms are still poorly understood, accumulating evidence points toward pro-inflammatory molecules and reactive oxygen species as primary contributing factors for testicular aging. However, the real impact of aging-related testicular alterations on fertility, reproductive health, and life span is far from being fully revealed. This work discusses the current knowledge on the impact of aging in the testis, particularly of aging-related dysregulated inflammation and oxidative damage on the functioning of its different cell populations. More interestingly, this review covers the potential benefits of anti-aging interventions and therapies using either pharmacological compounds (such as non-selective non-steroidal anti-inflammatory medication) or more natural alternatives (such as various nutraceuticals or even probiotics) that exhibit anti-inflammatory, antioxidant, and anti-apoptotic properties. Some of these are currently being investigated or are already in clinical use to delay or prevent testicular aging.

Mitochondrial Sirtuins in Reproduction

Mitochondria act as hubs of numerous metabolic pathways. Mitochondrial dysfunctions contribute to altering the redox balance and predispose to aging and metabolic alterations. The sirtuin family is composed of seven members and three of them, SIRT3-5, are housed in mitochondria. They catalyze NAD+-dependent deacylation and the ADP-ribosylation of mitochondrial proteins, thereby modulating gene expression and activities of enzymes involved in oxidative metabolism and stress responses. In this context, mitochondrial sirtuins (mtSIRTs) act in synergistic or antagonistic manners to protect from aging and aging-related metabolic abnormalities. In this review, we focus on the role of mtSIRTs in the biological competence of reproductive cells, organs, and embryos. Most studies are focused on SIRT3 in female reproduction, providing evidence that SIRT3 improves the competence of oocytes in humans and animal models. Moreover, SIRT3 protects oocytes, early embryos, and ovaries against stress conditions. The relationship between derangement of SIRT3 signaling and the imbalance of ROS and antioxidant defenses in testes has also been demonstrated. Very little is known about SIRT4 and SIRT5 functions in the reproductive system. The final goal of this work is to understand whether sirtuin-based signaling may be taken into account as potential targets for therapeutic applications in female and male infertility.