Searching for female reproductive aging and longevity biomarkers

A Molecular Perspective and Role of NAD+ in Ovarian Aging

The decline in female fecundity is linked to advancing chronological age. The ovarian reserve diminishes in quantity and quality as women age, impacting reproductive efficiency and the aging process in the rest of the body. NAD+ is an essential coenzyme in cellular energy production, metabolism, cell signaling, and survival. It is involved in aging and is linked to various age-related conditions. Hallmarks associated with aging, diseases, and metabolic dysfunctions can significantly affect fertility by disturbing the delicate relationship between energy metabolism and female reproduction. Enzymes such as sirtuins, PARPs, and CD38 play essential roles in NAD+ biology, which actively consume NAD+ in their enzymatic activities. In recent years, NAD+ has gained much attention for its role in aging and age-related diseases like cancer, Alzheimer's, cardiovascular diseases, and neurodegenerative disorders, highlighting its involvement in various pathophysiological processes. However, its impact on female reproduction is not well understood. This review aims to bridge this knowledge gap by comprehensively exploring the complex interplay between NAD+ biology and female reproductive aging and providing valuable information that could help develop plans to improve women's reproductive health and prevent fertility issues.

Altered brain morphology and functional connectivity in postmenopausal women: automatic segmentation of whole-brain and thalamic subnuclei and resting-state fMRI

The transition to menopause is associated with various physiological changes, including alterations in brain structure and function. However, menopause-related structural and functional changes are poorly understood. The purpose of this study was not only to compare the brain volume changes between premenopausal and postmenopausal women, but also to evaluate the functional connectivity between the targeted brain regions associated with structural atrophy in postmenopausal women. Each 21 premenopausal and postmenopausal women underwent magnetic resonance imaging (MRI). T1-weighted MRI and resting-state functional MRI data were used to compare the brain volume and seed-based functional connectivity, respectively. In statistical analysis, multivariate analysis of variance, with age and whole brain volume as covariates, was used to evaluate surface areas and subcortical volumes between the two groups. Postmenopausal women showed significantly smaller cortical surface, especially in the left medial orbitofrontal cortex (mOFC), right superior temporal cortex, and right lateral orbitofrontal cortex, compared to premenopausal women (p < 0.05, Bonferroni-corrected) as well as significantly decreased functional connectivity between the left mOFC and the right thalamus was observed (p < 0.005, Monte-Carlo corrected). Although postmenopausal women did not show volume atrophy in the right thalamus, the volume of the right pulvinar anterior, which is one of the distinguished thalamic subnuclei, was significantly decreased (p < 0.05, Bonferroni-corrected). Taken together, our findings suggest that diminished brain volume and functional connectivity may be linked to menopause-related symptoms caused by the lower sex hormone levels.

Age at natural or surgical menopause, all-cause mortality, and lifespan among postmenopausal women in the United States

OBJECTIVE

This study investigated the association of age at natural menopause with or without undergoing hysterectomy and/or bilateral oophorectomy after menopause and age at surgical menopause with all-cause mortality and lifespan in postmenopausal women.

METHODS

The data stemmed from the National Health and Nutrition Examination Survey (NHANES) (1999-2018) and NHANES III (1988-1994), including 14,161 postmenopausal women over 40. Cox proportional hazard models were used to estimate unadjusted and adjusted hazard ratios (HRs) (95% confidence intervals [CIs]). We also used Cox proportional hazard models with penalized splines to depict the association between continuous age at menopause and all-cause mortality and nonparametric regression with smoothing splines to illustrate the association between age at menopause and lifespan in deceased participants.

RESULTS

The adjusted HRs (95% CIs) for age at natural menopause of <40, 40 to 44, and 55+ years in women without undergoing hysterectomy or bilateral oophorectomy after menopause were 1.48 (1.15-1.91), 1.16 (1.00-1.35), and 0.91 (0.77-1.07) compared with age at natural menopause of 45 to 54, respectively. The respective HRs (95% CIs) for age at surgical menopause were 1.39 (1.11-1.75), 1.09 (0.86-1.38), and 0.83 (0.53-1.32). However, no significant association was found between age at natural menopause and all-cause mortality among women undergoing hysterectomy and/or bilateral oophorectomy after menopause. When treated as continuous variables, age at natural menopause without undergoing hysterectomy or bilateral oophorectomy after menopause presented inverse and nonlinear associations with all-cause mortality, whereas age at surgical menopause was linearly inversely associated with all-cause mortality. The association between age at menopause and lifespan was linearly positive regardless of menopausal type.

CONCLUSION

Young age at menopause was associated with increased risks of all-cause mortality. The later menopause age was related to a longer lifespan.

Unraveling the Clinical Relevance of Ferroptosis-Related Genes in Human Ovarian Aging

Ferroptosis, a recently discovered form of cell death, has been implicated in various diseases. However, the genetic relationship between ferroptosis and ovarian aging has not been thoroughly investigated through informatics analysis. In this study, we conducted bioinformatics analysis using ovarian aging and ferroptosis datasets to identify potential ferroptosis-related genes using R software. The expression levels of these genes at different ages were analyzed using the GTEx public database. To validate these findings at the genetic level, we performed clinical infertility biopsies. Bioinformatics analysis of a mouse ovary dataset revealed significantly higher expression of Tfrc, Ncoa4, and Slc3a2 in the aging group compared to the young group, while Gpx4 showed the opposite pattern. Consistent results were observed in biopsies from clinically aged infertile patients. This study is the first to identify a ferroptosis-related gene associated with ovarian aging, highlighting its potential as a diagnostic biomarker.

Epigenetic aging of mammalian gametes

The process of aging refers to physiological changes that occur to an organism as time progresses and involves changes to DNA, proteins, metabolism, cells, and organs. Like the rest of the cells in the body, gametes age, and it is well established that there is a decline in reproductive capabilities in females and males with aging. One of the major pathways known to be involved in aging is epigenetic changes. The epigenome is the multitude of chemical modifications performed on DNA and chromatin that affect the ability of chromatin to be transcribed. In this review, we explore the effects of aging on female and male gametes with a focus on the epigenetic changes that occur in gametes throughout aging. Quality decline in oocytes occurs at a relatively early age. Epigenetic changes constitute an important part of oocyte aging. DNA methylation is reduced with age, along with reduced expression of DNA methyltransferases (DNMTs). Histone deacetylases (HDAC) expression is also reduced, and a loss of heterochromatin marks occurs with age. As a consequence of heterochromatin loss, retrotransposon expression is elevated, and aged oocytes suffer from DNA damage. In sperm, aging affects sperm number, motility and fecundity, and epigenetic changes may constitute a part of this process. 5 methyl-cytosine (5mC) methylation is elevated in sperm from aged men, but methylation on Long interspersed nuclear elements (LINE) elements is reduced. Di and trimethylation of histone 3 lysine 9 (H3K9me2/3) is reduced in sperm from aged men and trimethylation of histone 3 lysine 27 (H3K27me3) is elevated. The protamine makeup of sperm from aged men is also changed, with reduced protamine expression and a misbalanced ratio between protamine proteins protamine P1 and protamine P2. The study of epigenetic reproductive aging is recently gaining interest. The current status of the field suggests that many aspects of gamete epigenetic aging are still open for investigation. The clinical applications of these investigations have far-reaching consequences for fertility and sociological human behavior.

Association of reproductive factors and exogenous hormone use with distal sensory polyneuropathy among postmenopausal women in the United States: results from 1999 to 2004 NHANES

Postmenopausal status is a risk factor for distal sensory polyneuropathy-the most common type of peripheral neuropathy. We aimed to investigate associations between reproductive factors and history of exogenous hormone use with distal sensory polyneuropathy among postmenopausal women in the United States using data from the National Health and Nutrition Examination Survey 1999-2004, and to explore the modifying effects of ethnicity on these associations. We conducted a cross-sectional study among postmenopausal women aged ≥ 40 years. Women with a history of diabetes, stroke, cancer, cardiovascular disease, thyroid disease, liver disease, weak or failing kidneys, or amputation were excluded. Distal sensory polyneuropathy was measured using a 10-g monofilament test, and a questionnaire was used to collect data on reproductive history. Multivariable survey logistic regression was used to test the association between reproductive history variables and distal sensory polyneuropathy. In total, 1144 postmenopausal women aged ≥ 40 years were included. The adjusted odds ratios were 8.13 [95% confidence interval (CI) 1.24-53.28] and 3.18 (95% CI 1.32-7.68) for age at menarche < 11 years and time since menopause > 20 years, respectively, which were positively associated with distal sensory polyneuropathy; adjusted odds ratios were 0.45 for the history of breastfeeding (95% CI 0.21-0.99) and 0.41 for exogenous hormone use (95% CI 0.19-0.87) were negatively associated. Subgroup analysis revealed ethnicity-based heterogeneity in these associations. Age at menarche, time since menopause, breastfeeding, and exogenous hormone use were associated with distal sensory polyneuropathy. Ethnicity significantly modified these associations.

Age-Related Hormones Changes and Its Impact on Health Status and Lifespan

The increase in life expectancy is accompanied with an increased consultation of age-related pathologies including endocrine disorders. Two main areas are focusing the attention of medical and social research in older population: the diagnosis and care of this heterogeneous population, and the interventional measures potentially useful to mitigate age-related functional declines and to increase health and quality of lifespan. Thus, better understanding the physiopathology of aging and establishing accurate diagnostic and personalized approaches are a priority and currently an unmet need of the medical community. The endocrine system plays a major role in survival and lifespan through regulating vital processes such as energy consumption and optimizing the stress response among others. The aim of this paper is to review the physiological evolution of the main hormonal functions in aging and its clinical translation to improve our approach to the aging patient.

Biomarkers of aging

Aging biomarkers are a combination of biological parameters to (i) assess age-related changes, (ii) track the physiological aging process, and (iii) predict the transition into a pathological status. Although a broad spectrum of aging biomarkers has been developed, their potential uses and limitations remain poorly characterized. An immediate goal of biomarkers is to help us answer the following three fundamental questions in aging research: How old are we? Why do we get old? And how can we age slower? This review aims to address this need. Here, we summarize our current knowledge of biomarkers developed for cellular, organ, and organismal levels of aging, comprising six pillars: physiological characteristics, medical imaging, histological features, cellular alterations, molecular changes, and secretory factors. To fulfill all these requisites, we propose that aging biomarkers should qualify for being specific, systemic, and clinically relevant.

17β-estradiol plays the anti-osteoporosis role via a novel ESR1-Keap1-Nrf2 axis-mediated stress response activation and Tmem119 upregulation

Increased oxidative stress and decreased osteoblastic bone formation contribute to estrogen deficiency-induced osteoporosis. However, the role and mechanism of estrogen-deficiency in regulating oxidative stress and osteoblastic activity remain unclear. Here, we showed that estrogen-deficient bone marrow stromal/stem cells (BMSCs) exhibited impaired capacity to combat stress, characterized by increased oxidative stress, shortened cell survival and reduced osteogenic differentiation and bone formation, which were due to a decrease of nuclear factor erythroid 2-related factor 2 (Nrf2). Nrf2 re-activation induced by the pyrazinyl dithiolethione oltipraz significantly rescued the cell phenotype of estrogen-deficient BMSCs in vitro and ex vivo. Mechanistically, we found that 17β-estradiol/ESR1 (Estrogen Receptor 1) facilitated Nrf2 accumulation, and activated its target genes by competing with Nrf2 for binding to Kelch-like ECH-associated protein 1 (Keap1) via ESR1 containing a highly conserved DLL motif. Of note, oltipraz, an Nrf2 activator, rescued ovariectomy-induced osteoporosis partly by inhibiting oxidative stress and promoting osteoblastic bone formation via Nrf2-induced antioxidant signaling activation and Tmem119 (transmembrane protein 119) upregulation. Conversely, Nrf2 knockout largely blocked the bone anabolic effect of 17β-estradiol in vivo and ex vivo. This study provides insight into the mechanisms whereby estrogen prevents osteoporosis through promoting osteoblastic bone formation via Nrf2-mediated activation of antioxidant signaling and upregulation of Tmem119, and thus provides evidence for Nrf2 as a potential target for clinical prevention and treatment of menopause-related osteoporosis.

Association Between Breastfeeding and Reduced Distal Sensory Polyneuropathy in Postmenopausal Women Aged 40-70 Years: Analysis of Data from the 1999-2004 National Health and Nutrition Examination Survey

Background: Distal sensory polyneuropathy (DSP) is a common peripheral neuropathy subtype. We aimed to determine the association between breastfeeding and DSP among postmenopausal women aged 40-70 years, and the effect modification of obesity on this association. Methods: A cross-sectional study was conducted using data from the National Health and Nutrition Examination Survey 1999-2004. Postmenopausal women aged 40-70 years were included. Women with diabetes, stroke, cancer, cardiovascular disease, thyroid disease, liver disease, weak/failing kidneys, or amputation were excluded. Binary logistic regression was used to analyze the association between breastfeeding and DSP. Results: Among 798 participants, 386 (44.30%) reported breastfeeding history and 51 (5.29%) were defined as having DSP using the monofilament test. A significant inverse association was observed between breastfeeding and DSP (odds ratio [OR] = 0.29; 95% confidence interval [CI]: 0.11-0.79; p = 0.017) after adjusting for other confounding variables. In subgroup analysis, this adjusted association was observed only in the obese group (OR = 0.21; 95% CI: 0.06-0.73, p = 0.013). Conclusions: Breastfeeding was found to have potential benefits in the presence of DSP in postmenopausal women aged 40-70 years, and obesity modified the association between breastfeeding and DSP. Promoting breastfeeding may reduce the burden of peripheral neuropathy in middle-aged postmenopausal women.

Identification of Common and Specific Genes Involved in Mouse Models of Age-Related and Cyclophosphamide-Induced Diminished Ovarian Reserve

Diminished ovarian reserve (DOR) is an etiologically heterogeneous disorder that usually leads to poor reproductive outcomes. Does a specific or common pathogenesis exist for DOR subtypes with different etiologies? Two frequently used mouse models, age-related DOR (AR-DOR) and cyclophosphamide (CTX)-induced DOR (CTX-DOR), were successfully established, and RNA sequencing was performed on ovarian tissue samples. Differentially expressed genes (DEGs) in each subtype and common DEGs (co-DEGs) in the two subtypes were identified. Subsequently, we performed comprehensive bioinformatics analyses, including an evaluation of immune cell infiltration. Finally, the genes of interest were further validated by performing RT-qPCR and immunohistochemistry. In AR-DOR mice, functional enrichment analyses showed that upregulated DEGs were mainly involved in the inflammatory/immune response, while downregulated DEGs were involved in DNA damage repair. In CTX-DOR mice, the inflammatory/immune response and cell apoptosis played significant roles. Meanwhile, 406 co-DEGs were identified from the two models. The biological functions of these co-DEGs were associated with inflammatory/immune responses. The analysis of immune cell infiltration showed reduced infiltration of Treg cells, as well as increased infiltration of M0 macrophages, NK resting, and T cells CD4 follicular in both DOR subtypes. The results of the validation experiments were consistent with the RNA sequencing data. In conclusion, the inflammatory/immune response might be the common pathogenesis for the two DOR subtypes, while DNA repair and cell apoptosis may have different roles in the two subtypes. These results may provide potential insights for mechanistic research and therapeutic targets of DOR.

Stem Cell-Based Therapeutic Strategies for Premature Ovarian Insufficiency and Infertility: A Focus on Aging

Reproductive aging is on the rise globally and inseparable from the entire aging process. An extreme form of reproductive aging is premature ovarian insufficiency (POI), which to date has mostly been of idiopathic etiology, thus hampering further clinical applications and associated with enormous socioeconomic and personal costs. In the field of reproduction, the important functional role of inflammation-induced ovarian deterioration and therapeutic strategies to prevent ovarian aging and increase its function are current research hotspots. This review discusses the general pathophysiology and relative causes of POI and comprehensively describes the association between the aging features of POI and infertility. Next, various preclinical studies of stem cell therapies with potential for POI treatment and their molecular mechanisms are described, with particular emphasis on the use of human induced pluripotent stem cell (hiPSC) technology in the current scenario. Finally, the progress made in the development of hiPSC technology as a POI research tool for engineering more mature and functional organoids suitable as an alternative therapy to restore infertility provides new insights into therapeutic vulnerability, and perspectives on this exciting research on stem cells and the derived exosomes towards more effective POI diagnosis and treatment are also discussed.

Resveratrol Treatment Induces Mito-miRNome Modification in Follicular Fluid from Aged Women with a Poor Prognosis for In Vitro Fertilization Cycles

Advanced maternal age impairs reproductive performance, influencing the quantity and the quality of oocytes. Mitochondria dysfunction seems to play a decisive role in conditioning the quality of the female gamete. Different in vitro and in vivo studies, demonstrated the antioxidant and anti-inflammatory activities of Resveratrol and its ability to improve mitochondria function even if the exact mechanism of action has not yet been demonstrated in human oocytes. In this paper, by retrospective analysis, we evaluated follicular fluid (FF) miRNome modification in aged women with a poor ovarian reserve receiving a resveratrol-based supplement the three months before the in vitro Fertilization (IVF) cycle. We found 13 differentially expressed microRNAs (miRNAs) in women treated with resveratrol and specifically miR-125b-5p, miR-132-3p, miR-19a-3p, miR-30a-5p and miR-660-5p, regulating mitochondrial proteins, are able to control metabolism and mitochondrial biogenesis. MiRNA expression differences, observed after resveratrol treatment in FF from women with a poor prognosis for IVF, demonstrated that resveratrol may act on mitomiRNAs to improve follicular microenvironment by transcriptomic and proteomic modifications in granulosa cells.

Expression of the histone lysine methyltransferases SETD1B, SETDB1, SETD2, and CFP1 exhibits significant changes in the oocytes and granulosa cells of aged mouse ovaries

Histone methylation is one of the main epigenetic mechanisms by which methyl groups are dynamically added to the lysine and arginine residues of histone tails in nucleosomes. This process is catalyzed by specific histone methyltransferase enzymes. Methylation of these residues promotes gene expression regulation through chromatin remodeling. Functional analysis and knockout studies have revealed that the histone lysine methyltransferases SETD1B, SETDB1, SETD2, and CFP1 play key roles in establishing the methylation marks required for proper oocyte maturation and follicle development. As oocyte quality and follicle numbers progressively decrease with advancing maternal age, investigating their expression patterns in the ovaries at different reproductive periods may elucidate the fertility loss occurring during ovarian aging. The aim of our study was to determine the spatiotemporal distributions and relative expression levels of the Setd1b, Setdb1, Setd2, and Cxxc1 (encoding the CFP1 protein) genes in the postnatal mouse ovaries from prepuberty to late aged periods. For this purpose, five groups based on their reproductive periods and histological structures were created: prepuberty (3 weeks old; n = 6), puberty (7 weeks old; n = 7), postpuberty (18 weeks old; n = 7), early aged (52 weeks old; n = 7), and late aged (60 weeks old; n = 7). We found that Setd1b, Setdb1, Setd2, and Cxxc1 mRNA levels showed significant changes among postnatal ovary groups (P < 0.05). Furthermore, SETD1B, SETDB1, SETD2, and CFP1 proteins exhibited different subcellular localizations in the ovarian cells, including oocytes, granulosa cells, stromal and germinal epithelial cells. In general, their levels in the follicles, oocytes, and granulosa cells as well as in the germinal epithelial and stromal cells significantly decreased in the aged groups when compared the other groups (P < 0.05). These decreases were concordant with the reduced numbers of the follicles at different stages and the luteal structures in the aged groups (P < 0.05). In conclusion, these findings suggest that altered expression of the histone methyltransferase genes in the ovarian cells may be associated with female fertility loss in advancing maternal age.

Microcystin-leucine arginine exposure induced intestinal lipid accumulation and MC-LR efflux disorder in Lithobates catesbeianus tadpoles

Few studies exist on the toxic effects of chronic exposure to microcystins (MCs) on amphibian intestines, and the toxicity mechanisms are unclear. Here, we evaluated the impact of subchronic exposure (30 days) to environmentally realistic microcystin-leucine arginine (MC-LR) concentrations (0 μg/L, 0.5 μg/L and 2 μg/L) on tadpole (Lithobates catesbeianus) intestines by analyzing the histopathological and subcellular microstructural damage, the antioxidative and oxidative enzyme activities, and the transcriptome levels. Histopathological results showed severe damage accompanied by inflammation to the intestinal tissues as the MC-LR exposure concentration increased from 0.5 μg/L to 2 μg/L. RNA-sequencing analysis identified 634 and 1,147 differentially expressed genes (DEGs) after exposure to 0.5 μg/L and 2 μg/L MC-LR, respectively, compared with those of the control group (0 μg/L). Biosynthesis of unsaturated fatty acids and the peroxisome proliferator-activated receptor (PPAR) signaling pathway were upregulated in the intestinal tissues of the exposed groups, with many lipid droplets being observed on transmission electron microscopy, implying that MC-LR may induce lipid accumulation in frog intestines. Moreover, 2 μg/L of MC-LR exposure inhibited the xenobiotic and toxicant biodegradation related to detoxification, implying that the tadpoles' intestinal detoxification ability was weakened after exposure to 2 μg/L MC-LR, which may aggravate intestinal toxicity. Lipid accumulation and toxin efflux disorder may be caused by MC-LR-induced endoplasmic reticular stress. This study presents new evidence that MC-LR harms amphibians by impairing intestinal lipid metabolism and toxin efflux, providing a theoretical basis for evaluating the health risks of MC-LR to amphibians.