Lifestyle factors associated with histologically derived human ovarian non-growing follicle count in reproductive age women

Conditional loss of Brca1 in oocytes causes reduced litter size, ovarian reserve depletion and impaired oocyte in vitro maturation with advanced reproductive age in mice

BACKGROUND

An estimated 1 in 350 women carry germline BRCA1/2 mutations, which confer an increased risk of developing breast and ovarian cancer, and may also contribute to subfertility. All mature, sex steroid-producing ovarian follicles are drawn from the pool of non-renewable primordial follicles, termed the 'ovarian reserve'. The clinical implications of early ovarian reserve exhaustion extend beyond infertility, to include the long-term adverse health consequences of loss of endocrine function and premature menopause. We aimed to determine whether conditional loss of Brca1 in oocytes impacts ovarian follicle numbers, oocyte quality and fertility in mice with advancing maternal age. We also aimed to determine the utility of AMH as a marker of ovarian function, by assessing circulating AMH levels in mice and women with BRCA1/2 mutations, and correlating this with ovarian follicle counts.

METHODS

In this study, we addressed a longstanding question in the field regarding the functional consequences of BRCA1 inactivation in oocytes. To recapitulate loss of BRCA1 protein function in oocytes, we generated mice with conditional gene deletion of Brca1 in oocytes using Gdf9-Cre recombinase (WT: Brca1fl/flGdf9+/+; cKO: Brca1fl/flGdf9cre/+).

FINDINGS

While the length of the fertile lifespan was not altered between groups after a comprehensive breeding trial, conditional loss of Brca1 in oocytes led to reduced litter size in female mice. Brca1 cKO animals had a reduced ovarian reserve and oocyte maturation was impaired with advanced maternal age at postnatal day (PN)300, compared to WT animals. Serum anti-Müllerian hormone (AMH) concentrations (the gold-standard indirect marker of the ovarian reserve used in clinical practice) were not predictive of reduced primordial follicle number in Brca1 cKO mice versus WT. Furthermore, we found no correlation between follicle number or density and serum AMH concentrations in matched samples from a small cohort of premenopausal women with BRCA1/2 mutations.

INTERPRETATION

Together, our data demonstrate that BRCA1 is a key regulator of oocyte number and quality in females and suggest that caution should be used in relying on AMH as a reliable marker of the ovarian reserve in this context.

FUNDING

This work was made possible through Victorian State Government Operational Infrastructure Support and Australian Government NHMRC IRIISS. This work was supported by funding from the Australian Research Council (ALW - DE21010037 and KJH - FT190100265), as well as the National Breast Cancer Foundation (IIRS-22-092) awarded to ALW and KJH. LRA, YML, LT, EOKS and MG were supported by Australian Government Research Training Program Scholarships. LRA, YML and LT were also supported by a Monash Graduate Excellence Scholarship. YC, SG and XC were supported by Monash Biomedicine Discovery Institute PhD Scholarships. LRA was also supported by a Monash University ECPF24-6809920940 Fellowship. JMS was supported by NHMRC funding (2011299). MH was supported by an NHMRC Investigator Grant (1193838).

A systematic review of the association between modifiable lifestyle factors and circulating anti-Müllerian hormone

BACKGROUND

Levels of anti-Müllerian hormone (AMH) are known to be associated with lifestyle determinants such as smoking and oral contraception (OC) use. When measuring AMH in clinical practice, it is essential to know which factors may influence circulating levels or ovarian reserve in general.

OBJECTIVE AND RATIONALE

To date, there is no systematic review or summarizing consensus of the nature and magnitude of the relation between AMH and modifiable lifestyle factors. The purpose of this review was to systematically assess the evidence on association of lifestyle behaviors with circulating AMH levels.

SEARCH METHODS

We performed a pre-registered systematic review of publications in Embase and PubMed on the lifestyle factors BMI, smoking, OC use, alcohol consumption, caffeine consumption, physical activity, and waist-hip ratio (WHR) in relation to circulating AMH levels up to 1 November 2023. The search strategy included terms such as 'Anti-Mullerian hormone', 'lifestyle', and 'women'. Studies were considered eligible if the association between at least one of the lifestyle factors of interest and AMH was assessed in adult women. The quality of included studies was assessed using the Study Quality Assessment Tools of the National Heart, Lung, and Blood Institute. The results were presented as ranges of the most frequently used association measure for studies that found a significant association in the same direction.

OUTCOMES

A total of 15 072 records were identified, of which 65 studies were eligible for inclusion, and 66.2% of the studies used a cross-sectional design. The majority of studies investigating BMI, smoking, OC use, and physical activity reported significant inverse associations with AMH levels. For WHR, alcohol, and caffeine use, the majority of studies did not find an association with AMH. For all determinants, the effect measures of the reported associations were heterogeneous. The mean difference in AMH levels per unit increase in BMI ranged from -0.015 to -0.2 ng/ml in studies that found a significant inverse association. The mean difference in AMH levels for current smokers versus non-smokers ranged from -0.4 to -1.1 ng/ml, and -4% to -44%, respectively. For current OC use, results included a range in relative mean differences in AMH levels of -17% to -31.1%, in addition to a decrease of 11 age-standardized percentiles, and an average decrease of 1.97 ng/ml after 9 weeks of OC use. Exercise interventions led to a decrease in AMH levels of 2.8 pmol/l to 13.2 pmol/l after 12 weeks in women with polycystic ovary syndrome or a sedentary lifestyle.

WIDER IMPLICATIONS

Lifestyle factors are associated with differences in AMH levels and thus should be taken into account when interpreting individual AMH measurements. Furthermore, AMH levels can be influenced by the alteration of lifestyle behaviors. While this can be a helpful tool for clinical and lifestyle counseling, the nature of the relation between the observed differences in AMH and the true ovarian reserve remains to be assessed.

REGISTRATION NUMBER

PROSPERO registration ID: CRD42022322575.

Tobacco or marijuana use and infertility: a committee opinion

In the United States, approximately 21% of adults report some form of tobacco use, although 18% report marijuana use. Although the negative impact of tobacco use in pregnancy is well documented, the impact of tobacco and marijuana on fertility and reproduction is less clear. This committee opinion reviews the potential deleterious effects of tobacco, nicotine, and marijuana use on conception, ovarian follicular dynamics, sperm parameters, gamete mutations, early pregnancy, and assisted reproductive technology outcomes. It also reviews the current status of tobacco smoking cessation strategies. This document replaces the 2018 American Society for Reproductive Medicine Practice Committee document entitled Smoking and Infertility: a committee opinion (Fertil Steril 2018).

The dose-response relationship of pre-menopausal alcohol consumption with age at menopause: a population study of 280 497 women in Norway

BACKGROUND

Previous research suggests that alcohol consumption is associated with high age at menopause. Yet, knowledge about the dose-response relationship is inconsistent. Thus, we studied the pattern of the association of pre-menopausal alcohol consumption with age at natural menopause.

METHODS

We performed a retrospective population-based study using self-reported data from 280 497 women aged 50-69 years attending the Norwegian breast cancer screening programme (BreastScreen Norway) during 2006-15. Associations of weekly alcohol consumption between the age of 20 and 49 years with age at menopause were estimated as hazard ratios (HRs) using Cox proportional hazard models with restricted cubic splines to allow for non-linear associations. We adjusted for year and place of birth, number of childbirths, educational level, body mass index and smoking habits.

RESULTS

Mean age at natural menopause was 51.20 years (interquartile range: 49-54 years). The adjusted HR of reaching menopause was highest for women with no alcohol consumption (reference) and the HR decreased by alcohol consumption up to 50 grams per week (adjusted HR 0.87; 95% CI: 0.86-0.88). Above 50 grams, there was no further decrease in the HR of reaching menopause (P for non-linearity of <0.001).

CONCLUSIONS

Women who did not consume alcohol were youngest at menopause. The lack of a dose-response association among alcohol consumers implies virtually no relation of alcohol consumption with age at menopause. Our findings may suggest that characteristics of the women who did not consume alcohol, not accounted for in the data analyses, explain their younger age at menopause.

Making a good egg: human oocyte health, aging, and in vitro development

Mammalian eggs (oocytes) are formed during fetal life and establish associations with somatic cells to form primordial follicles that create a store of germ cells (the primordial pool). The size of this pool is influenced by key events during the formation of germ cells and by factors that influence the subsequent activation of follicle growth. These regulatory pathways must ensure that the reserve of oocytes within primordial follicles in humans lasts for up to 50 years, yet only approximately 0.1% will ever be ovulated with the rest undergoing degeneration. This review outlines the mechanisms and regulatory pathways that govern the processes of oocyte and follicle formation and later growth, within the ovarian stroma, through to ovulation with particular reference to human oocytes/follicles. In addition, the effects of aging on female reproductive capacity through changes in oocyte number and quality are emphasized, with both the cellular mechanisms and clinical implications discussed. Finally, the details of current developments in culture systems that support all stages of follicle growth to generate mature oocytes in vitro and emerging prospects for making new oocytes from stem cells are outlined.

Beverage intake and ovarian reserve among women from a fertility center

OBJECTIVE

To evaluate the associations of caffeinated, alcoholic, and sweetened beverage intakes with antral follicle count (AFC), a well-accepted biomarker of ovarian reserve.

DESIGN

Observational prospective cohort study.

SETTING

Fertility center at an academic hospital.

PATIENTS

This study includes 567 women seeking fertility care at the Massachusetts General Hospital who participated in the Environment and Reproductive Health Study.

INTERVENTION

None. Women self-reported consumption of caffeinated (coffee, tea, soda), alcoholic (wine, beer, liquor), sugar-sweetened, and artificially sweetened beverages using a validated food-frequency questionnaire.

MAIN OUTCOME MEASURE

Antral follicle count was assessed using a transvaginal ultrasound performed on the 3rd day of an unstimulated menstrual cycle or on the 3rd day of a progesterone withdrawal bleed.

RESULTS

Median (interquartile range) age and AFC were 35.0 (32.0-38.0) years and 13.0 (9.0-18.0), respectively. Median (range) intake of caffeinated, alcoholic, sugar-sweetened, and artificially sweetened beverages in servings/day were 1.08 (0-7.08), 0.35 (0-3.84), 0.04 (0-4.80), and 0.04 (0-7.50), respectively. All examined beverages were unrelated to AFC. The multivariable adjusted mean AFC (95% confidence interval) for women in the top and bottom quartiles of intake were 13.8 (13.0-14.7) and 13.8 (12.9-14.7) for caffeinated beverages; 13.8 (13.0-14.7) and 13.8 (13.0-14.6) for alcoholic beverages; 13.5 (12.6-14.4) and 13.3 (12.4-14.2) for sugar-sweetened beverages; and 13.2 (12.4-14.1) and 13.4 (12.6-14.3) for artificially sweetened beverages.

CONCLUSION

Low-to-moderate intakes of caffeinated, alcoholic, sugar-sweetened, and artificially sweetened beverages were unrelated to ovarian reserve, as measured by AFC, in a cohort of women seeking fertility care.

Optimizing natural fertility: a committee opinion

This committee opinion provides practitioners with suggestions for optimizing the likelihood of achieving pregnancy in couples or individuals attempting conception who have no evidence of infertility. This document replaces the document of the same name previously published in 2013 (Fertil Steril 2013;100:631-7).

Effects of environmental, social and surgical factors on ovarian reserve: Implications for age-relative female fertility

OBJECTIVE

To investigate new risk factors for female fertility by analyzing the effects of environmental, social, and surgical factors on antral follicle counts (AFC) and anti-Müllerian hormone (AMH) levels.

METHODS

A total of 1513 women aged 20-47 years who underwent in vitro fertilization/intracytoplasmic injection treatment in Southwest Hospital from December 2017 to December 2019 were included. Women were assessed for AFC and AMH levels, and completed a questionnaire. Ordinal logistic regression analyses with generalized linear mixed models were used to calculate the adjusted odds ratio (OR) for diminished ovarian reserve.

RESULTS

Adnexal surgery was the only risk factor associated with low AFC in women aged 20-30 years. Younger age at menarche, alcohol drinking, and adnexal surgery are three independent risk factors for AMH decline in women aged 20-30 years. Intense exercise, sleep quality, and adnexal surgery are three independent risk factors for a low AFC in women aged 31-36 years. Alcohol drinking and adnexal surgery are two independent risk factors for AMH decline in women aged 31-36 years.

CONCLUSION

With age, female fertility becomes sensitive to high-intensity exercise and poor sleep quality. Adnexal surgery and alcohol drinking are two important risk factors for female fertility in women under age 37 years.

The Effects of Negative Elements in Environment and Cancer on Female Reproductive System

With the development of human society, factors that contribute to the impairment of female fertility is accumulating. Lifestyle-related risk factors, occupational risk factors, and iatrogenic factors, including cancer and anti-cancer treatments, have been recognized with their negative effects on the function of female reproductive system. However, the exact influences and their possible mechanism have not been elucidated yet. It is impossible to accurately estimate the indexes of female fertility, but many researchers have put forward that the general fertility has inclined through the past decades. Thus the demand for fertility preservation has increased more and more dramatically. Here we described some of the factors which may influence female reproductive system and methods for fertility preservation in response to female infertility.

Improving Prediction of Age at Menopause Using Multiple Anti-Müllerian Hormone Measurements: the Tehran Lipid-Glucose Study

CONTEXT

Several statistical models were introduced for the prediction of age at menopause using a single measurement of anti-müllerian hormone (AMH); however, individual prediction is challenging and needs to be improved.

OBJECTIVE

The objective of this study was to determine whether multiple AMH measurements can improve the prediction of age at menopause.

DESIGN

All eligible reproductive-age women (n = 959) were selected from the Tehran Lipid and Glucose Study. The serum concentration of AMH was measured at the time of recruitment and twice after that at an average of 6-year intervals. An accelerated failure-time model with Weibull distribution was used to predict age at menopause, using a single AMH value vs a model that included the annual AMH decline rate. The adequacy of these models was assessed using C statistics.

RESULTS

The median follow-up period was 14 years, and 529 women reached menopause. Adding the annual decline rate to the model that included single AMH improved the model's discrimination adequacy from 70% (95% CI: 67% to 71%) to 78% (95% CI: 75% to 80%) in terms of C statistics. The median of differences between actual and predicted age at menopause for the first model was -0.48 years and decreased to -0.21 in the model that included the decline rate. The predicted age at menopause for women with the same amount of age-specific AMH but an annual AMH decline rate of 95 percentiles was about one decade lower than in those with a decline rate of 5 percentiles.

CONCLUSION

Prediction of age at menopause could be improved by multiple AMH measurements; it will be useful in identifying women at risk of early menopause.

Ovarian Reserve Testing: A Review of the Options, Their Applications, and Their Limitations

Ovarian reserve refers to the number of oocytes remaining in a woman's ovaries that have the potential to yield a pregnancy. This is a concept based on the fact that the number of oocytes within a woman's ovaries and her ability to achieve pregnancy decline over time. There are 2 overlapping but distinct interpretations and utilizations of ovarian reserve testing (ORT)-biological and clinical. Given the increasing incorporation of ORT into clinical practice, care must be taken to ensure that patients and providers understand the limitations affecting ORT interpretation. Here, we will review commonly used tests of ovarian reserve and offer guidance on interpretation (biology) and application (clinical practice) of results.

Smoke, alcohol and drug addiction and female fertility

BACKGROUND

Considerable interest has been gathered on the relevant impact of preventable factors, including incorrect lifestyle and unhealthy habits, on female fertility. Smoking, alcohol and addictive drugs consumption represent a major concern, given the broad range of diseases which might be favored or exacerbated by these dependable attitudes. Despite the well-characterized effects of prenatal exposure on pregnancy outcomes and fetus health, a substantial proportion of women of reproductive age is still concerned with these habits. At present, the impact of smoke, alcohol and addictive drugs on women fertility, and, particularly, the specific targets and underlying mechanisms, are still poorly understood or debated, mainly due to the scarcity of well-designed studies, and to numerous biases.

OBJECTIVE

The current review will provide a comprehensive overview of clinical and experimental studies in humans and animals addressing the impact of smoke, alcohol and addictive drugs on female fertility, by also embracing effects on ovary, oviduct, and uterus, with particular reference to primary endpoints such as ovarian reserve, steroidogenesis, ovulation and menstrual cycle, oviduct function and uterus receptivity and implantation. A brief focus on polycystic ovary syndrome and endometriosis will be also included.

METHODS

A Pubmed literature search was performed with selected keywords; articles were individually retrieved by each author. No limitation was set for publication date. Articles in languages other than English were excluded. Additional articles were retrieved from references list of selected manuscripts.

RESULTS AND CONCLUSIONS

Currently, the most consistent evidences of a detrimental effect of smoke, alcohol and addictive drugs on specific domains of the female reproductive function are provided by experimental studies in animals. Overall, clinical studies suggest that smoking is associated to decreased fertility, although causal inference should be further demonstrated. Studies addressing the effect of alcohol consumption on female fertility provide conflicting results, although the majority reported lack of a correlation. Extremely scarce studies investigated the effects of addictive drugs on female fertility, and the specific actions of selected drugs have been difficult to address, due to multidrug consumption.

Do BRCA1 and BRCA2 gene mutation carriers have a reduced ovarian reserve? Protocol for a prospective observational study

INTRODUCTION

BRCA1/2 gene mutations increase risk of breast and/or ovarian cancer and may have implications for reproductive health. Indirect biomarkers of the ovarian primordial follicle pool (anti-Müllerian hormone (AMH)) and one small study in female cadavers suggest that ovarian reserve may be reduced in BRCA mutation carriers, but findings are conflicting and association between circulating AMH and primordial follicle number is not established. The aim of this study is to measure primordial follicle density in premenopausal ovarian tissue samples from women with BRCA1/2 gene mutations versus age-matched comparison group.

METHODS AND ANALYSIS

Prospective observational study measuring associations between BRCA gene mutation status, premenopausal ovarian primordial follicle density and serum AMH concentrations versus age-matched premenopausal women from the general population. Primordial follicle density will be measured in cortical sections from ovarian tissue collected at the time of risk-reducing bilateral salpingo-oophorectomy (RRBSO) in 88 BRCA1 gene mutation carriers, 65 BRCA2 gene mutation carriers and 157 non-mutation carriers. Primordial follicle density will be determined by counting follicles in a known volume of ovarian cortical tissue using light microscopy. Follicles will be identified by immunohistochemical staining for oocyte marker mouse vasa homologue. To inform the mechanisms underlying reduced ovarian reserve, the proportion of follicles containing oocytes with DNA damage will be determined by immunohistochemical staining for phosphorylated histone H2AX and terminal deoxynucleotidyl transferase dUTP nick end labelling assay to identify apoptotic cells. Follicle density will be correlated with circulating AMH concentrations quantified in the same cohort, using an electrochemiluminescence immunoassay on an automated platform.

ETHICS AND DISSEMINATION

Ethics approval has been granted by Peter MacCallum Cancer Centre to access biobanks, including; The Kathleen Cuningham Foundation Consortium for Research into Familial Breast Cancer (kConFab-HREC#97_27) and the What Happens after Menopause? (HREC12PMCC24-12/90) and Melbourne IVF.

Ovarian ageing and the impact on female fertility

Female fertility decreases with increasing age, a reflection of declining oocyte quantity and quality. The menopausal transition occurs when the oocyte quantity falls below a threshold level. The pattern of follicular depletion as well as the factors, timing and mechanisms surrounding both declining oocyte number and oocyte quality remain incompletely understood. Further studies are needed to examine the factors involved and develop predictive models and biomarkers to assist in the management of age-related subfertility. This review summarises the current knowledge addressing the ageing ovary and its impact on fertility.

Environmental pollutants, a possible etiology for premature ovarian insufficiency: a narrative review of animal and human data

BACKGROUND

Because only 25% of cases of premature ovarian insufficiency (POI) have a known etiology, the aim of this review was to summarize the associations and mechanisms of the impact of the environment on this pathology. Eligible studies were selected from an electronic literature search from the PUBMED database from January 2000 to February 2016 and associated references in published studies. Search terms included ovary, follicle, oocyte, endocrine disruptor, environmental exposure, occupational exposure, environmental contaminant, pesticide, polyaromatic hydrocarbon, polychlorinated biphenyl PCB, phenol, bisphenol, flame retardant, phthalate, dioxin, phytoestrogen, tobacco, smoke, cigarette, cosmetic, xenobiotic. The literature search was conducted in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. We have included the human and animal studies corresponding to the terms and published in English. We have excluded articles that included results that did not concern ovarian pathology and those focused on ovarian cancer, polycystic ovary syndrome, endometriosis or precocious puberty. We have also excluded genetic, auto-immune or iatrogenic causes from our analysis. Finally, we have excluded animal data that does not concern mammals and studies based on results from in vitro culture. Data have been grouped according to the studied pollutants in order to synthetize their impact on follicular development and follicular atresia and the molecular pathways involved. Ninety-seven studies appeared to be eligible and were included in the present study, even though few directly address POI. Phthalates, bisphenol A, pesticides and tobacco were the most reported substances having a negative impact on ovarian function with an increased follicular depletion leading to an earlier age of menopause onset. These effects were found when exposure occured at different times throughout the lifetime from the prenatal to the adult period, possibly due to different mechanisms. The main mechanism seemed to be an increase in atresia of pre-antral follicles.

CONCLUSION

Environmental pollutants are probably a cause of POI. Health officials and the general public must be aware of this environmental effect in order to implement individual and global preventive actions.