Decoding the Epigenetics of Infertility: Mechanisms, Environmental Influences, and Therapeutic Strategies

Infertility is a complex condition caused by a combination of genetic, environmental, and lifestyle factors. Recent advances in epigenetics have highlighted the importance of epigenetic changes in fertility regulation. This review aims to provide a comprehensive overview of the epigenetic mechanisms involved in infertility, with a focus on DNA methylation, histone modification, and non-coding RNAs. We investigate the specific epigenetic events that occur during gametogenesis, with a focus on spermatogenesis and oogenesis as distinct processes. Furthermore, we investigate how environmental factors such as diet, stress, and toxin exposure can influence these epigenetic changes, potentially leading to infertility. The second part of the review explores epigenetic changes as therapeutic targets for infertility. Emerging therapies that modulate epigenetic marks present promising opportunities for fertility restoration, particularly in spermatogenesis. By summarizing current research findings, this review emphasizes the importance of understanding epigenetic contributions to infertility. Our discussion aims to lay the groundwork for future research directions and clinical applications in reproductive health.

The Impacts of Periconceptional Alcohol on Neonatal Ovaries and Subsequent Adult Fertility in the Rat

Maternal exposures during pregnancy can impact the establishment of the ovarian reserve in offspring, the lifetime supply of germ cells that determine a woman's reproductive lifespan. However, despite alcohol consumption being common in women of reproductive age, the impact of prenatal alcohol on ovarian development is rarely investigated. This study used an established rat model of periconceptional ethanol exposure (PCEtOH; 12.5% v/v ethanol) for 4 days prior to 4 days post-conception. Ovaries were collected from neonates (day 3 and day 10), and genes with protein products involved in regulating the ovarian reserve analyzed by qPCR. Adult offspring had estrous cycles monitored and breeding performance assessed. PCEtOH resulted in subtle changes in expression of genes regulating apoptosis at postnatal day (PN) 3, whilst those involved in regulating growth and recruitment of primordial follicles were dysregulated at PN10 in neonatal ovaries. Despite these gene expression changes, there were no significant impacts on breeding performance in adulthood, nor on F2-generation growth or survival. This contributes additional evidence to suggest that a moderate level of alcohol consumption exclusively around conception, when a woman is often unaware of her pregnancy, does not substantially impact the fertility of her female offspring.

Pregnancy characteristics and outcomes among birthing individuals with a diagnosis of fetal alcohol syndrome

BACKGROUND

Fetal alcohol syndrome (FAS) can have adverse effects on health outcomes throughout the life course. Adults with FAS have an increased risk of chronic and infectious diseases. Although these conditions can affect reproductive health, few have described perinatal outcomes among individuals with an FAS diagnosis.

METHODS

We analyzed data from the Study of Mothers and Infants, an administrative birth cohort derived from California birth certificates linked with a hospital discharge database. The cohort consisted of 7.3 million singleton, live births between 2005 and 2021. FAS was identified by International Classification of Diseases (ICD) codes in maternal hospital discharge records. Pregnancy and birth outcomes were captured via ICD codes in maternal or infant records. We performed descriptive analyses for pregnancy and birth outcomes by maternal FAS diagnosis.

RESULTS

There were 35 babies born to 30 individuals with an FAS diagnosis between 2005 and 2021 (0.5/100,000 live births). The prevalence of births to individuals with an FAS diagnosis increased over the period. Individuals with an FAS diagnosis were more likely to identify as non-Hispanic White, or "other/multiple" race, and less likely to be Hispanic than those without FAS. They were also more likely to be publicly insured and less than 18 years old. Birthing individuals with FAS were also more likely to use nicotine during pregnancy and to have diagnoses of mental health disorders, epilepsy, substance use disorders, preexisting or gestational hypertension, and sexually transmitted infections or other infections complicating pregnancy. Infants of individuals with FAS were more likely to be born prematurely or small for gestational age and be admitted to the neonatal intensive care unit.

CONCLUSIONS

These findings highlight the need for improved recognition of FAS among birthing people. The results suggest that individuals with FAS would benefit from early and sustained medical care prior to pregnancy to optimize perinatal outcomes.

Effects of prenatal alcohol exposure on infant lung function, wheeze, and respiratory infections in Australian children

BACKGROUND

Prenatal alcohol exposure (PAE) is a known risk factor for a range of adverse outcomes, such as facial dysmorphism, adverse birth outcomes, and neurodevelopmental changes. Preclinical research shows that PAE also inhibits lung development, lowers surfactant protein expression, has detrimental effects on alveolar macrophages, and decreases both T and B cell numbers. However, clinical evidence of respiratory impacts from PAE is limited. This study explored whether lung function, wheeze, and incidence of respiratory infections differ in children with PAE compared with unexposed children.

METHODS

Data from the Barwon Infant Study (n = 1074) were examined. PAE data were extracted from maternal questionnaires at trimesters 1 and 2 (combined), and trimester 3, and included as "total standard drinks" during each trimester and total pregnancy intake, a binary yes/no for PAE, and binge drinking (>5 standard drinks in one session). Respiratory outcomes were parent-reported wheeze, lung function (measured by multiple breath washout), and parent report and medical record indicators of health service attendances for respiratory conditions. Linear and logistic regressions were performed to quantify relationships between PAE and respiratory outcomes, controlling for socioeconomic status, birthweight, sex, gestational age, and maternal smoking.

RESULTS

Binge drinking was associated with increased health service attendance for respiratory condition(s) in the first 12 months of life (OR = 5.0, 95% CI (1.7, 20.7), p = 0.008). We did not find a relationship between binary PAE and binge drinking with lung function at 4 weeks of age or wheeze at 12 months. The number of standard drinks consumed in trimester two was associated with a lower lung clearance index (β = -0.011 turnovers, 95% CI (-0.0200, -0.0013), p = 0.03), and a small increase in functional residual capacity (β = 0.34 mL, 95% CI (0.02, 0.66), p = 0.04).

CONCLUSIONS

We found an association between binge drinking and health service utilization for respiratory conditions in infancy, but no evidence that low-level PAE was associated with adverse respiratory outcomes.

Factors to be considered as part of a holistic assessment for fetal alcohol spectrum disorder: A scoping review

We undertook a scoping review to identify the factors outside of current fetal alcohol spectrum disorder (FASD) diagnostic criteria to be considered as part of a holistic assessment process. This included physical, social, cultural, mental health and wellbeing factors to inform targeted recommendations and supports to improve outcomes for individuals with FASD. Evidence from this review will be used to inform the revision of the Australian Guide to the Diagnosis of FASD. Six electronic databases were searched. Studies were eligible if they included factors outside of the diagnostic criteria that cover dysmorphology, growth restriction, neurodevelopmental impairments. Data charting and content analysis were performed to synthesize the results. One hundred twenty-one studies were included that spanned 12 key areas These included physical health, sleep, adverse postnatal experiences, substance use/other risk-taking behaviors, contact with the criminal justice system, mental health, First Nations cultural considerations, transition to adult roles, involvement with the out-of-home care system, feeding and eating, strengths/interests/external resources and incontinence. Areas to be considered as part of a holistic assessment and diagnostic process spanned individual, family, and system level factors. Results provide guidance for clinicians on the wide range of factors that could influence long-term health, development, and wellbeing for individuals with prenatal alcohol exposure and FASD. In practice, this guidance can be used to inform an individualized assessment process to facilitate tailored recommendations and supports to best meet the complex needs of individuals living with FASD and their families.

Serum Levels of Hormones Regulating Appetite in Patients with Fetal Alcohol Spectrum Disorders

Prenatal alcohol exposure is the cause of impaired growth and a wide range of developmental and behavioral disorders in the child. Improper eating patterns are commonly associated with fetal alcohol spectrum disorders (FASD) and may contribute to poor nutrition and growth restriction. To date, there have been only a few studies investigating the hormonal regulation of appetite in patients with FASD. We analyzed the levels of neuropeptide Y (NPY), Agouti signaling protein (ASP), alpha-melanocyte-stimulating hormone (α-MSH), and kisspeptin (KISS1) in 57 patients with FASD and 23 healthy controls. A comparison of the hormone levels studied was also performed in subgroups of fetal alcohol syndrome (FAS) and neurobehavioral disorder associated with prenatal alcohol exposure (ND PAE), as well as in males and females. We have found no differences in hormone levels tested between affected individuals and the controls and between FASD subgroups. In addition, sex had no effect on hormone levels. However, we identified some associations between hormone concentrations and parameters describing the clinical status of patients with FASD. Most of them concerned ASP, which has shown a positive correlation with age and hormones involved in appetite and metabolism, such as proopiomelanocortin (POMC) and adrenocorticotropic hormone (ACTH). We have also found a negative correlation of α-MSH with age, BMI percentile, and glycated hemoglobin (HbA1c). Furthermore, we found a weak negative correlation of NPY with HbA1c. Although FASD has been associated with impaired child growth and development, including nutrition and puberty onset, we did not identify differences in the levels of the hormones studied, which may suggest that prenatal alcohol exposure does not affect the levels of these metabolites.

Maternal alcohol intake in early pregnancy and biomarkers of fecundity in adult sons: A cohort study

Male fecundity may be largely determined through fetal programming and therefore potentially be sensitive to exposure to maternal alcohol intake during pregnancy. We investigated whether maternal alcohol intake in early pregnancy was associated with biomarkers of fecundity in adult sons. In total, 1058 sons from the Fetal Programming of Semen Quality (FEPOS) cohort nested in the Danish National Birth Cohort (DNBC) provided blood and semen samples at around 19 years of age. Information on maternal weekly average alcohol intake (0 drinks [ref], >0-1 drinks, >1-3 drinks, >3 drinks) and binge drinking episodes (intake of ≥5 drinks on one occasion: (0 [ref], 1-2, ≥3 episodes)) was self-reported at around gestational week 17. Outcomes included semen characteristics, testes volume and reproductive hormones. We found some small tendencies towards lower semen characteristics and an altered hormone level profile in sons of mother who had an intake of > 3 drinks/week in early pregnancy and sons of mother who had ≥ 3 episodes of binge drinking in pregnancy. However, the effect estimates were overall small and inconsistent and with no indication of a dose dependent association. Due to the limited number of mothers with a high weekly alcohol intake, we cannot exclude whether prenatal exposure to higher doses than 4.5 drinks/week of alcohol in early pregnancy might have a detrimental effect on the biomarkers of fecundity in adult sons..

Environmental toxicants and male fertility

Semen quality has declined especially among Western men. Experimental and epidemiological studies have shown potential links between exposure to environmental toxicants and poor male fertility. Some environmental exposures in utero can disrupt fetal testicular function and result in cryptorchidism, low semen quality, low serum testosterone levels, and low fertility. Environmental exposure in childhood and adulthood can also adversely affect germ cells, Sertoli cells, Leydig cells, or the hypothalamic-pituitary-testicular axis, resulting in impaired male fertility. In this review, we report the latest results from human studies that investigated the role of endocrine disrupting chemicals, heavy metals, tobacco smoking, alcohol drinking, and use of marijuana in low semen quality and impaired male fertility. Current evidence suggests the relationship between these environmental factors and low male fertility; however, some factors showed conflicting results which need further investigation.

Altered bone and body composition in children and adolescents with confirmed prenatal alcohol exposure

Prenatal alcohol exposure can contribute to long term adverse health outcomes. Development of the skeletal system begins at the early embryonic stage and continues into early adulthood but the effect of prenatal alcohol exposure on skeletal growth is relatively unexplored in a clinical population. Here, we performed dual X-ray absorptiometry to examine bone, fat, and muscle accrual in children and adolescents diagnosed with, or at risk of, fetal alcohol spectrum disorders (FASDs). Children (aged 4-9 years) with FASD or at risk of FASD (n = 10) had similar growth to age matched controls (n = 27). By adolescence (aged ≥10 years), those with FASDs (n = 13) were shorter and had lower areal bone mineral density and lean tissue mass than typically developing peers (n = 29). Overall, adolescents diagnosed with FASDs had greater odds of impairments to bone and body composition. These findings highlight the importance of early FASD diagnosis and appropriate post-diagnostic medical follow-up to enable timely, effective interventions to optimize bone and body composition during paediatric growth.

Fibroblast growth factor 2: Role in prenatal alcohol-induced stimulation of hypothalamic peptide neurons

Prenatal alcohol exposure (PAE) increases alcohol consumption and risk for alcohol use disorder. This phenomenon in rodents is suggested to involve a stimulatory effect of PAE, in female more than male offspring, on neurogenesis and density of neurons expressing neuropeptides in lateral hypothalamus (LH), including melanin-concentrating hormone (MCH), known to promote alcohol intake. With evidence suggesting a role for fibroblast growth factor 2 (FGF2) and its receptor FGFR1 in stimulating neurogenesis and alcohol drinking, we investigated here whether the FGF2-FGFR1 system is involved in the PAE-induced increase in MCH neurons, in postnatal offspring of pregnant rats given ethanol orally (embryonic day 10-15) at a low-moderate (2 g/kg/day) or high (5 g/kg/day) dose. Our results demonstrate that PAE at the low-moderate but not high dose stimulates FGF2 and FGFR1 gene expression and increases the density of MCH neurons co-expressing FGF2, only in females, but FGFR1 in both sexes. PAE induces this effect in the dorsal but not ventral area of the LH. Further analysis of FGF2 and FGFR1 transcripts within individual MCH neurons reveals an intracellular, sex-dependent effect, with PAE increasing FGF2 transcripts positively related to FGFR1 in the nucleus as well as cytoplasm of females but transcripts only in the cytoplasm of males. Peripheral injection of FGF2 itself (80 μg/kg, s.c.) in pregnant rats mimics these effects of PAE. Together, these results support the involvement of the FGF2-FGFR1 system in mediating the PAE-induced, sex dependent increase in density of MCH neurons, possibly contributing to increased alcohol consumption in the offspring.

Impact of Alcohol Consumption on Male Fertility Potential: A Narrative Review

Alcohol abuse disorder is a serious condition, implicating more than 15 million people aged 12 years and older in 2019 in the United States. Ethanol (or ethyl alcohol) is mainly oxidized in the liver, resulting in the synthesis of acetaldehyde and acetate, which are toxic and carcinogenic metabolites, as well as in the generation of a reductive cellular environment. Moreover, ethanol can interact with lipids, generating fatty acid ethyl esters and phosphatidylethanol, which interfere with physiological cellular pathways. This narrative review summarizes the impact of excessive alcohol consumption on male fertility by describing its metabolism and how ethanol consumption may induce cellular damage. Furthermore, the impact of alcohol consumption on hormonal regulation, semen quality, and genetic and epigenetic regulations is discussed based on evidence from animal and human studies, focusing on the consequences on the offspring. Finally, the limitations of the current evidence are discussed. Our review highlights the association between chronic alcohol consumption and poor semen quality, mainly due to the development of oxidative stress, as well as its genotoxic impact on hormonal regulation and DNA integrity, affecting the offspring’s health. New landscapes of investigation are proposed for the identification of molecular markers for alcohol-associated infertility, with a focus on advanced OMICS-based approaches applied to the analysis of semen samples.

The effect of heavy prenatal alcohol exposure on adolescent body mass index and waist-to-height ratio at 12-13 years

BACKGROUND

Growing evidence suggests that prenatal alcohol exposure (PAE) has the potential to impact on a wide range of physical outcomes in offspring, including metabolism and body composition, although the evidence to-date is primarily from preclinical studies. The current clinical study examined the association between heavy PAE and indirect measures of adiposity in adolescence.

METHODS

Analyses drew on data from the Longitudinal Study of Australian Children, a national prospective cohort of children and their families from birth to adolescence. Participants included children with heavy PAE (≥70 g/week; n = 46), measured via maternal self-report of alcohol use during pregnancy and a comparison group of children without any PAE (n = 782), frequency matched on sex, ethnicity and socio-economic position. Body mass index (BMI) z-scores, waist-to-height ratios and proportion overweight/obese were calculated from height, weight and waist circumference measured at age 12-13 years. Two (PAE) × two (sex) ANCOVA and logistic regression models were performed, controlling for matching variables, adolescent age, pubertal status and birthweight; maternal age at birth and smoking during pregnancy.

RESULTS

Female adolescents with heavy PAE during late pregnancy had significantly higher BMI z-scores (M = 0.75, SD = 0.69) and proportion overweight/obese (38.5%) than females not exposed to any prenatal alcohol (M = 0.29, SD = 1.07, P = 0.04; 23.8%, P = 0.03, respectively). There was no significant effect of heavy PAE on male adolescent BMI z-scores and proportion overweight/obese or adolescent waist-to-height ratios (all P > 0.05).

CONCLUSIONS

Heavy PAE had a sex-specific effect on measures of adiposity in early adolescence, with girls more likely to have increased BMI and overweight/obesity status. Further longitudinal follow-up of children exposed to PAE is required to confirm if maternal alcohol consumption is a risk factor for later life obesity.

Prevention of Alcohol-Exposed Pregnancies and Fetal Alcohol Spectrum Disorder Among Pregnant and Postpartum Women: A Systematic Review

BACKGROUND

Prenatal alcohol exposure can result in a wide range of adverse health outcomes, including in some cases fetal alcohol spectrum disorder (FASD), a lifelong neurodevelopmental disorder. Thus, there is pressing need for effective interventions to prevent alcohol-exposed pregnancies (AEPs).

METHODS

A systematic review was undertaken to provide an up-to-date analysis of the current prevention literature. PubMed, Embase, CINAHL, and PsycINFO were searched for relevant English-language articles published from 1970 onward. Studies were eligible for the current systematic review if the interventions included pregnant and postpartum women and/or their support networks to prevent AEPs and FASD. Outcomes of interest included alcohol consumption, knowledge, contraceptive use, neonatal outcomes, family well-being or functioning, economics, and healthcare utilization outcomes.

RESULTS

Thirty-four peer-reviewed studies met the inclusion criteria. Fifteen studies employed brief intervention (BI) methods, 6 used long-term/intensive strategies, and 5 were educational interventions. A further 3 studies assessed counseling approaches, 2 evaluated multicomponent interventions, and 3 assessed nutritional supplementation interventions.

CONCLUSIONS

The current review identified variable results from available interventions to prevent alcohol use among pregnant and postpartum women. Preliminary evidence demonstrated that BIs may be effective among subgroups of pregnant women with higher initial alcohol consumption, those with partner involvement, and those who used alcohol and other substances concurrently. Some preliminary evidence relating to long-term interventions with pregnant women with polysubstance use emerged, specifically case management that not only focused on reduction in substance use, but also on addressing the complex interplay between health and social well-being of families. Overall, additional research is required to improve the effectiveness of preventative approaches during pregnancy and the postpartum period.

Caregiver-reported physical health status of children and young people with fetal alcohol spectrum disorder

While fetal alcohol spectrum disorder (FASD) has primarily been thought of as a neurodevelopmental condition, research is beginning to highlight its 'whole-body' implications. Accordingly, the current study sought to provide a snapshot of potential health issues. Caregivers of children (median age of 12 years) with an FASD diagnosis were invited to participate in an online survey. Information relating to sample demographics, FASD status of the child and health outcomes were collected. The prevalence of health conditions reported in the FASD sample was compared against national prevalence data. Multiple linear regression utilising a stepwise approach was used to investigate potential predictors of the number of diagnosed health conditions. Survey data were from an international cohort (n = 197), with the majority of respondents based in Australia (40.2%) or the United States (27.7%). The most commonly reported diagnosed health conditions were eye conditions (44.7%), asthma (34.5%), heart conditions (34.0%) and skin conditions (27.4%). Binomial testing indicated the proportion of children diagnosed with these disorders was generally higher in the current FASD population, compared to national prevalence data. Indicators of metabolic dysfunction including diabetes and obesity were not significantly different compared to national prevalence data. Age of FASD diagnosis, existence of comorbid mental health conditions and the primary caregiver being in paid work were identified as being associated with the prevalence of diagnosed health conditions. Overall, the study has provided an up-to-date snapshot of health problems reported in a sample of children with FASD, confirming their increased risk of adverse health outcomes.

Adverse health outcomes associated with fetal alcohol exposure: A systematic review focused on immune-related outcomes

Prenatal alcohol exposure (PAE) has well-known teratogenic effects on the developing fetus, potentially resulting in neurologic impairments. However, there is increasing interest regarding other potential adverse health outcomes related to prenatal alcohol exposure. The objective of this study was to undertake a systematic review to identify all the available clinical and preclinical literature investigating immune-related outcomes in offspring with PAE. A systematic review searching four electronic databases (PubMed, CINAHL, Web of Science, and Embase) was conducted. Potential articles were screened against strict inclusion/exclusion criteria. This review specifically focused on evaluating studies related to immune-related outcomes following PAE. Twelve clinical studies were included in the current review. Six included allergy outcomes, four included infection outcomes, and two studies included both. Thirty-nine preclinical studies were identified examining a wide range of immune outcomes. The current review provides some preliminary clinical evidence that PAE can influence immune function, including atopic allergy and infection outcomes. However, there was variability in results across studies, particularly in the atopy area. Preclinical studies demonstrated some changes in lymphocytes and cytokines in offspring following PAE. More research investigating the effects of PAE on immune responses is warranted.