Dietary Selenium Supplementation Ameliorates Female Reproductive Efficiency in Aging Mice

Towards prolonging ovarian reproductive life: Insights into trace elements homeostasis

Ovarian aging is marked by a reduction in the quantity and quality of ovarian follicles, leading to a decline in female fertility and ovarian endocrine function. While the biological characteristics of ovarian aging are well-established, the exact mechanisms underlying this process remain elusive. Recent studies underscore the vital role of trace elements (TEs) in maintaining ovarian function. Imbalances in TEs can lead to ovarian aging, characterized by reduced enzyme activity, hormonal imbalances, ovulatory disorders, and decreased fertility. A comprehensive understanding of the relationship between systemic and cellular TEs balance and ovarian aging is critical for developing treatments to delay aging and manage age-related conditions. This review consolidates current insights into TEs homeostasis and its impact on ovarian aging, assesses how altered TEs metabolism affects ovarian aging, and suggests future research directions to prolong ovarian reproductive life. These studies are expected to offer novel approaches for mitigating ovarian aging.

Genetic Determinants of Selenium Availability, Selenium-Response, and Risk of Polycystic Ovary Syndrome

Selenium is a trace element and its deficiency has been associated with the risk of PCOS, a multifactorial syndrome that affects a large number of women worldwide. Several databases and literature were searched to find out genetic variants of the genes involved in selenium uptake, metabolism, and regulation which may be significantly associated with the risk of PCOS through Se-related pathways. Genes that require selenium for their biological actions to perform were also shortlisted. A total of eighteen significantly associated genes with forty-four variants were identified as candidate variants that could play a potential role in the modulation of PCOS risk among the study population. The genetic variant distribution data was available in-house and was obtained through a GWAS study of the North India population. In silico tools were applied to understand the functional impact of these variants. Three variants namely LDLR (rs2228671), TNF (rs1041981), and SAA2 (rs2468844) are strongly associated with PCOS risk and have a functional impact on encoded protein. Certain variants of Se uptake genes such as DIO1, GPX2, TXNRD1, DIO2 and GPX3 are also significantly associated with the risk of PCOS development. "C" allele of the Se transporter gene SELENOP (rs9686343) significantly increases PCOS risk. Other potential genes require selenium for their biological actions and are involved in the inflammatory, antioxidant response, and energy homeostasis signaling pathways. Thus, genetic variants of the population may affect the Se availability in the body. Also, deficiency of Se effects may get modulated due to underlying genetic polymorphism of Se-associated genes. This information may be helpful in dosage adjustment of Se supplementation for a population in order to get maximum benefits.

Se-Enriched Cardamine violifolia Improves Laying Performance and Regulates Ovarian Antioxidative Function in Aging Laying Hens

As a selenium-enriched plant, Cardamine violifolia (SEC) has an excellent antioxidant function. The edibility of SEC is expected to develop new sources of organic Se supplementation for human and animal nutrition. This study was conducted to investigate the effects of SEC on laying performance and ovarian antioxidant capacity in aging laying hens. A total of 450 laying hens were assigned to five treatments. Dietary treatments included the following: a basal diet (diet without Se supplementation, CON) and basal diets supplemented with 0.3 mg/kg Se from sodium selenite (SS), 0.3 mg/kg Se from Se-enriched yeast (SEY), 0.3 mg/kg Se from SEC, or 0.3 mg/kg Se from SEC and 0.3 mg/kg Se from SEY (SEC + SEY). Results showed that supplementation with SEC tended to increase the laying rate, increased the Haugh unit of eggs, and reduced the FCR. SEC promoted ovarian cell proliferation, inhibited apoptosis, and ameliorated the maintenance of follicles. SEC, SEY, or SEC + SEY increased ovarian T-AOC and decreased MDA levels. SEC increased the mRNA abundance of ovarian selenoproteins. SEC and SEC + SEY increased the mRNA abundance of Nrf2, HO-1, and NQO1, and decreased the mRNA abundance of Keap1. These results indicate that SEC could potentially to improve laying performance and egg quality via the enhancement of ovarian antioxidant capacity. SEC exerts an antioxidant function through the modulation of the Nrf2/Keap1 signaling pathway.

Single-nucleus RNA Sequencing reveals the mechanism of cigarette smoke exposure on diminished ovarian reserve in mice

The systematic toxicological mechanism of cigarette smoke (CS) on ovarian reserve has not been extensively investigated. Female 8-week-old C57BL/6 mice at peak fertility were exposed to CS or indoor air only for 30 days (100 mice per group) and the effects of CS on ovarian reserve were assessed using Single-Nucleus RNA Sequencing (snRNA-seq). In addition, further biochemical experiments, including immunohistochemical staining, ELISA, immunofluorescence staining, transmission electron microscopy, cell counting kit-8 assay, flow cytometry analysis, senescence-associated β-galactosidase staining, and western blotting, were accomplished to confirm the snRNA-seq results. We identified nine main cell types in adult ovaries and the cell-type-specific differentially expressed genes (DEGs) induced by CS exposure. Western blot results verified that down-regulation of antioxidant genes (Gpx1 and Wnt10b) and the steroid biosynthesis gene (Fdx1) occurred in both ovarian tissue and human granulosa cell-like tumor cell line (KGN cells) after CS exposure. Five percent cigarette smoke extract (CSE) effectively stimulated the production of reactive oxygen species (ROS), DNA damage, cellular senescence and markedly inhibited KGN cell proliferation by inducing G1-phase cell cycle arrest. Moreover, down-regulation of Gja1, Lama1 and the Ferroptosis indicator (Gpx4) in granulosa cells plays a significant role in ultrastructural changes in the ovary induced by CS exposure. These observations suggest that CS exposure impaired ovarian follicle reserve might be caused by REDOX imbalance in granulosa cells. The current study systematically determined the damage caused by CS in mouse ovaries and provides a theoretical basis for early clinical prediction, diagnosis and intervention of CS exposure-associated primary ovarian insufficiency (POI), and is of great significance in improving female reproductive health.

Female infertility and diet, is there a role for a personalized nutritional approach in assisted reproductive technologies? A Narrative Review

Female infertility is a major public health concern and a global challenge. It is a disorder of the reproductive system, defined as the inability to achieve a clinical pregnancy. Nutrition and other environmental factors are found to impact reproductive health in women as well as the outcome of assisted reproductive technologies (ART). Dietary factors, such as polyunsaturated fatty acids (PUFA), fiber as well as the intake of Mediterranean diet appear to exert beneficial effects on female reproductive outcomes. The exact mechanisms associating diet to female fertility are yet to be identified, although genomic, epigenomic, and microbial pathways may be implicated. This review aims to summarize the current knowledge on the impact of dietary components on female reproduction and ART outcomes, and to discuss the relevant interplay of diet with genome, epigenome and microbial composition.

The Use of Dietary Supplements and Amino Acid Restriction Interventions to Reduce Frailty in Pre-Clinical Models

Frailty is a state of accelerated aging that increases susceptibility to adverse health outcomes. Due to its high societal and personal costs, there is growing interest in discovering beneficial interventions to attenuate frailty. Many of these interventions involve the use of lifestyle modifications such as dietary supplements. Testing these interventions in pre-clinical models can facilitate our understanding of their impact on underlying mechanisms of frailty. We conducted a narrative review of studies that investigated the impact of dietary modifications on measures of frailty or overall health in rodent models. These interventions include vitamin supplements, dietary supplements, or amino acid restriction diets. We found that vitamins, amino acid restriction diets, and dietary supplements can have beneficial effects on frailty and other measures of overall health in rodent models. Mechanistic studies show that these effects are mediated by modifying one or more mechanisms underlying frailty, in particular effects on chronic inflammation. However, many interventions do not measure frailty directly and most do not investigate effects in both sexes, which limits their applicability. Examining dietary interventions in animal models allows for detailed investigation of underlying mechanisms involved in their beneficial effects. This may lead to more successful, translatable interventions to attenuate frailty.

Dysregulation of Transcription Profile of Selenoprotein in Patients with Kashin-Beck Disease and Its Effect on Se Deficiency-Induced Chondrocyte Apoptosis

Kashin-Beck disease (KBD) is a chronic, degenerative osteoarthropathy related to selenium (Se) deficiency. Se participates in the synthesis of selenoprotein in the form of selenocysteine. In total, 25 selenoproteins, encoded by 25 genes, are currently found in humans; however, the effects of selenoprotein genes on chondrocyte apoptosis, particularly in apoptosis-related genes, remain poorly elucidated. Therefore, in the current study, the expression of selenoprotein genes and apoptosis-related genes were determined by RT-qPCR in patients and chondrocytes and the correlations between them were analyzed using Pearson and Spearman's rank correlation, and the chondrocyte apoptosis rate was detected by Annexin V-FITC/PI. The results showed that the mRNA levels of 17 selenoprotein genes were downregulated, whereas two genes were upregulated in patients with KBD. The BAX/BCL2 ratio and the mRNA levels of BAX and P53 were increased, but the mRNA levels of BCL2 and NF-κB p65 were decreased in patients with KBD. The mRNA levels of GPX2, GPX3, DIO1, TXNRD1, TXNRD3, and SPS2 were most closely associated with apoptosis-related genes in patients with KBD. Moreover, in the Se deficiency group, the mRNA levels of GPX3, DIO1, and TXNRD1 were downregulated and GPX activity was decreased, but the late apoptosis rate, the mRNA levels of BAX and P53, and the BAX/BCL2 ratio were increased; the opposite trend was observed in the Se supplement group. Collectively, these results indicate that selenoprotein transcription profile is dysregulated in patients with KBD. Furthermore, the expression of GPX3, DIO1, and TXNRD1 genes might be involved in the development of chondrocyte apoptosis by affecting antioxidant capacity.

Role for Selenium in Metabolic Homeostasis and Human Reproduction

Selenium (Se) is a micronutrient essential for life. Dietary intake of Se within the physiological range is critical for human health and reproductive functions. Selenium levels outside the recommended range have been implicated in infertility and variety of other human diseases. However, presently it is not clear how different dietary Se sources are processed in our bodies, and in which form or how much dietary Se is optimum to maintain metabolic homeostasis and boost reproductive health. This uncertainty leads to imprecision in published dietary guidelines and advice for human daily intake of Se and in some cases generating controversies and even adverse outcomes including mortality. The chief aim for this review is to describe the sources of organic and inorganic Se, the metabolic pathways of selenoproteins synthesis, and the critical role of selenprotenis in the thyroid gland homeostasis and reproductive/fertility functions. Controversies on the use of Se in clinical practice and future directions to address these challenges are also described and discussed herein.

Protective effects of selenium on Bisphenol A-induced oxidative stress in mouse testicular mitochondria and sperm motility

OBJECTIVE

This study aimed to explore the impact of selenium (SE) on Bisphenol-A (BPA)-exposed sperm and isolated testicular mitochondria of mice.

METHODS

Mouse sperm and isolated mitochondria were exposed to BPA (0.8 mM) and different concentrations of SE (50, 100, and 200 μM) for four hours. The viability of sperm and isolated mitochondria as well as the mitochondrial membrane potential (MMP) were evaluated. SOD (superoxide dismutase), GSH (glutathione), MDA (malondialdehyde), and ROS (reactive oxygen species) levels in testicular mitochondria were also examined.

RESULTS

BPA concentration-dependently enhanced ROS and MDA levels in isolated mitochondria, while MMP and acclivity of GSH and SOD significantly reduced. BPA also considerably impaired spermatozoa survival and motility. SE concentration-dependently reduced mitochondrial oxidative stress, MMP, sperm survival, and total sperm motility.

CONCLUSIONS

Our findings collectively suggested that SE concentration-dependently reversed BPA-caused mitochondrial toxicity and reduced sperm motility by suppressing oxidative stress.

Combination of Quercetin and Vitamin E Supplementation Promotes Yolk Precursor Synthesis and Follicle Development in Aging Breeder Hens via Liver-Blood-Ovary Signal Axis

Simple Summary

This study evaluated the capacity of dietary quercetin, vitamin E and their combination to promote follicle development and attenuate organ inflammation by improving the antioxidant capacity of the liver–blood–ovary signal axis of aging broiler breeder hens. The results from this study showed that the combination of quercetin and vitamin E synergistically improved the chicken’s reproductive organ characteristics, and also showed protective effects on liver morphology and histology. Moreover, the antioxidant parameters, reproductive hormones and receptors, liver lipid synthesis, and the levels of mRNAs related to yolk precursor synthesis (very low density apolipoprotein-II and vitellogenin-II), lipid transport (microsomal triglyceride transport protein), lipogenesis (fatty acid synthase), and follicle developments were increased remarkably by the combination of quercetin and vitamin E. The results obtained in this study provide an important reference for the combination of quercetin and vitamin E as a functional feed additive for promoting the functions of the liver–blood–ovary axis, and also as a potential chemopreventive and chemotherapeutic agent for improving liver and ovary functions in chickens by acting as a hepatoprotective and oviprotective agent. This could facilitate the transport and exchange of synthetic substances (including hormones, yolk precursors, and other biochemical substances) among the liver–blood–ovary alliances to ensure the synchronous development and functional coordination between the liver and ovary in aging breeder hens.

Abstract

The fertility of female animals is negatively correlated with increasing chronological age. In aging broiler breeder hens, there is a decline in the functionality of the ovary and liver accompanied by hormonal or endocrine changes, a reduction in antioxidant capacity, and a decrease in folliculogenesis. Therefore, improving the reproductive function in aging breeder hens using dietary strategies is of great concern to the poultry breeder. This study evaluated the capacity of dietary quercetin (Q), vitamin E (VE), and their combination (Q + VE) to promote follicle development and attenuate organ inflammation by improving the antioxidant capacity of aging breeder hens. In this study, 400 broiler breeder hens (Tianfu broilers breeder hens, 435 days old) were allotted into four groups (100 birds each) with four replicates each (25 birds each). They were fed diets containing Q (0.4 g/kg), VE (0.2 g/kg), Q + VE (0.4 g/kg + 0.2 g/kg), and a basal diet for 10 weeks. The results showed that Q + VE improved the organ characteristics (p < 0.05), and also that Q + VE showed protective effects on the liver against injury, as well as increasing the antioxidant capacity of the liver, serum, and ovary (p < 0.05). Furthermore, liver lipid synthesis was increased remarkably, as indicated by the changes in triglyceride levels in hens fed Q + VE (p < 0.05). Levels of E2, FSH, and LH, their receptors, and mRNAs related to yolk precursor synthesis were increased by the Q + VE (p < 0.05). Therefore, the combination of quercetin and vitamin E synergistically promotes and regulates the transportation and exchange of synthetic substances among the liver–blood–ovary alliances to ensure the synchronous development and functional coordination between the liver and ovary in aging breeder hens.

The Protective Effect of Aspirin Eugenol Ester on Oxidative Stress to PC12 Cells Stimulated with H2O2 through Regulating PI3K/Akt Signal Pathway

Aspirin eugenol ester (AEE) is a new pharmaceutical compound esterified by aspirin and eugenol, which has anti-inflammatory, antioxidant, and other pharmacological activities. This study is aimed at identifying the protective effect of AEE against H₂O₂-induced apoptosis in rat adrenal pheochromocytoma PC12 cells and the possible mechanisms. The results of cell viability assay showed that AEE could increase the viability of PC12 cells stimulated by H₂O₂, while AEE alone had no significant effect on the viability of PC12 cells. Compared with the control group, the activities of superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GSH-Px) were significantly decreased, and the content of malondialdehyde (MDA) was significantly increased in the H₂O₂ group. By AEE pretreatment, the level of MDA was reduced and the levels of SOD, CAT, and GSH-Px were increased in H₂O₂-stimulated PC12 cells. In addition, AEE could reduce the apoptosis of PC12 cells induced by H₂O₂ via reducing superoxide anion, intracellular ROS, and mitochondrial ROS (mtROS) and increasing the levels of mitochondrial membrane potential (ΔΨm). Furthermore, the results of western blotting showed that compared with the control group, the expression of p-PI3K, p-Akt, and Bcl-2 was significantly decreased, while the expression of Caspase-3 and Bax was significantly increased in the H₂O₂ group. In the AEE group, AEE pretreatment could upregulate the expression of p-PI3K, p-Akt, and Bcl-2 and downregulate the expression of Caspase-3 and Bax in PC12 cells stimulated with H₂O₂. The silencing of PI3K with shRNA and its inhibitor-LY294002 could abrogate the protective effect of AEE in PC12 cells. Therefore, AEE has a protective effect on H₂O₂-induced PC12 cells by regulating the PI3K/Akt signal pathway to inhibit oxidative stress.

Characterization of Glutathione Peroxidase 4 in Rat Oocytes, Preimplantation Embryos, and Selected Maternal Tissues during Early Development and Implantation

This study aimed to describe glutathione peroxidase 4 (GPx4) in rat oocytes, preimplantation embryos, and female genital organs. After copulation, Sprague Dawley female rats were euthanized with anesthetic on the first (D1), third (D3), and fifth days of pregnancy (D5). Ovaries, oviducts, and uterine horns were removed, and oocytes and preimplantation embryos were obtained. Immunohistochemical, immunofluorescent, and Western blot methods were employed. Using immunofluorescence, we detected GPx4 in both the oocytes and preimplantation embryos. Whereas in the oocytes, GPx4 was homogeneously diffused, in the blastomeres, granules were formed, and in the blastocysts, even clusters were present mainly around the cell nuclei. Employing immunohistochemistry, we detected GPx4 inside the ovary in the corpus luteum, stroma, follicles, and blood vessels. In the oviduct, the enzyme was present in the epithelium, stroma, blood vessels, and smooth muscles. In the uterus, GPx4 was found in the endometrium, myometrium, blood vessels, and stroma. Moreover, we observed GPx4 positive granules in the uterine gland epithelium on D1 and D3 and cytoplasm of fibroblasts forming in the decidua on D5. Western blot showed the highest GPx4 levels in the uterus and the lowest levels in the ovary. Our results show that the GPx4 is necessary as early as in the preimplantation development of a new individual because we detected it in an unfertilized oocyte in a blastocyst and not only after implantation, as was previously thought.

Selenium alleviates the negative effect of heat stress on myogenic differentiation of C2C12 cells with the response of selenogenome

With the globe warming, heat stress (HS) has frequently affected animal production. Selenium (Se) is an essential trace element for animals and exerts most of its biological functions through selenoproteins. We previously demonstrated that the damage to C2C12 cells by HS accompanied with the response of selenoprotein encoding genes and proteins. The objective of this study was to investigate whether selenium supplementation (sodium selenite, SS and selenomethionine, SeMet) could alleviate the negative effect of heat stress on the differentiation of C2C12 cells, and interpret the potential corresponding selenoproteins response. The differentiated cells were cultured for 4 and 8 days under different condition: at 37 °C, 41.5 °C and 41.5 °C with 0.5 μmol Se/L SS or SeMet, and the HSP70, cell apoptosis, selenoproteins and cell differentiation-related gene or protein were detected. The result showed that HS up-regulated (P < 0.05) mRNA and protein levels of HSP70 and gene expression of AMPKα1 and AMPKα2, and down-regulated (P < 0.05) mRNA or protein levels of MYOGENIN and MYOD. Meanwhile, up to 15 and 17 selenoprotein genes expression were significantly changed response to 4-and 8-days HS challenge, respectively. Relative to the HS group, SS and SeMet supplementation down-regulated the mRNA and protein abundance of HSP70 to different degrees, and partly recovered (P < 0.05) the mRNA or protein abundance of MYOGENIN and MYOD at 4th and 8th day. Especially, 16 and 10 selenoprotein genes expression in cells affected by HS were altered by SS and SeMet supplementation, respectively. Both SS and SeMet supplementation modestly increased (P < 0.05) protein levels of GPX1 and SELENON in cells under HS. In summary, Se supplementation partly alleviated the negative impact of HS on myogenic differentiation of C2C12 cells and the process may associate with the alternation of selenoprotein expression pattern, and SeMet exhibits better effect than SS.

Impact of Dietary Selenium on Modulation of Expression of Several Non-Selenoprotein Genes Related to Key Ovarian Functions, Female Fertility, and Proteostasis: a Transcriptome-Based Analysis of the Aging Mice Ovaries

Female reproductive (ovarian) aging is characterized by a marked decline in quantity and quality of follicles and oocytes, as well as alterations in the surrounding ovarian stroma. In our previous report, we have shown that dietary selenium (Se) insufficiency and supplementation differentially impacted the reproductive efficiency in aging mice; however, the precise understanding of such modulation is still incomplete. In the present study, we sought to determine the impact of low (mildly low level) and moderately high (medium level) Se diets on expression profile of non-selenoprotein genes in the ovaries of aging mice. For this purpose, the aged mice were divided in two groups and fed either a low Se (Se-L; 0.08 mg Se/kg) diet or a moderately high Se (Se-M; 0.33 mg Se/kg) diet. RNA-seq analysis revealed that a total of 168 genes were differentially expressed between the two groups. From these, 72 and 96 differentially expressed genes (DEGs) were found to be upregulated and downregulated, respectively. Gene Ontology (GO) and pathways enrichment (KEGG) analyses revealed that these DEGs were enriched in several key GO terms and biological pathways including PI3K-Akt signaling pathway, steroid hormone biosynthesis, signaling pathways regulating pluripotency of stem cells, Hippo signaling pathway, ovarian steroidogenesis, and Wnt signaling pathway. Further filtering of RNA-seq data revealed that several DEGs such as Star, Hsd3b6, Scd1, Bmp7, Aqp8, Gas1, Fzd1, and Wwc1 were implicated in key ovarian- and fertility-related functions. In addition, some of the DEGs were related to ER homeostasis and/or proteostasis. These results highlight that dietary low and moderately high (medium level) Se diets, in addition to modulation of selenoproteins, can also have an impact on expression of several non-selenoprotein genes in the ovaries of aging mice. To sum up, these findings add more value to our understanding of Se modulation of ovarian functions and female fertility and will pave a way for the focused mechanistic and functional studies in this domain.

Dietary selenium deficiency and supplementation differentially modulate the expression of two ER-resident selenoproteins (selenoprotein K and selenoprotein M) in the ovaries of aged mice: Preliminary data

In the present report, we determined the impact of dietary selenium (Se) deficiency and supplementation on the expression of two ER-resident selenoproteins i.e., Selenok and Selenom in the ovaries of aging mice. The mRNA expression of Selenok and Selenom (RT-qPCR) was significantly higher in the ovaries of mice fed diets supplemented with inorganic (ISe-S: 0.33 mg Se/kg) and organic (OSe-S: 0.33 mg Se/kg) Se compared to those fed a Se-deficient (Se-D: 0.08 mg Se/kg) diet and both Se-adequate (ISe-A: 0.15 mg Se/kg and OSe-A: 0.15 mg Se/kg) diets. Similarly, the protein signals of SELENOK (immunofluorescence assay) were also significantly higher in the Se-supplemented groups compared to those fed Se-D and Se-adequate (ISe-A and OSe-A) diets. Meanwhile, the rate of in vitro-produced blastocysts developing from MII oocytes was also evaluated and it was revealed that this rate was significantly higher in the Se-supplemented mice compared to those fed a Se-D diet. Altogether, the dietary Se supplementation increased the expression of Selenok (also its protein expression) and Selenom in the ovaries of aging mice, potentially contributing to an improved developmental potential of in vitro-matured M II oocytes.