Transgenerational inheritance of behavioral and metabolic effects of paternal exposure to traumatic stress in early postnatal life: evidence in the 4th generation

Cardiometabolic disease management: influences from epigenetics

Epigenomics is a rapidly emerging field that has gathered significant attention as a "non-genetic determinant" implicated in the manifestation of non-communicable diseases. Exploring epigenetic modifications provides novel insights into the management of cardiometabolic disease (CMD). Epigenetics signatures are influenced by environmental stressors such as air pollution, toxins, and urban noises as well as by established cardiovascular risk factors including smoking, sedentary lifestyle, obesity, and diabetes. Understanding how epigenetic alterations lead to CMD as well as inter-individual differences in epigenetic makeup could unveil new molecular targets and new epi-drugs to be employed for precision medicine approaches in the growing population of patients with cardiometabolic disease to reduce cardiovascular risk. Herein, we provide an overview of the latest advancements in epigenetic mechanisms implicated in CMD and possible therapeutic opportunities.

The paternal contribution to shaping the health of future generations

Paternal health and exposure to adverse environments in the period prior to conception have a profound impact on future generations. Adversities such as stress, diet, and toxicants influence offspring health. Emerging evidence indicates that epigenetic mechanisms including noncoding RNA, DNA methylation, and chromatin remodelling mediate these effects. Preclinical studies have contributed to advancing mechanistic understanding in the field; however, human research is limited and primarily observational. Here, we discuss the evidence linking paternal to offspring health and advocate for further research in this area, which may ultimately inform policy and healthcare guidelines to improve paternal preconception health and offspring outcomes.

On the role of epigenetic modifications of HPA axis in posttraumatic stress disorder and resilience

Stress is a fundamental adaptive response that invokes amygdala and hypothalamus-pituitary-adrenal (HPA) axis along with other brain regions. Extreme or chronic stress, however, can result in a multitude of neuropsychiatric disorders, including anxiety, paranoia, bipolar disorder (BP), major depressive disorder (MDD), and posttraumatic stress disorder (PTSD). Despite widespread exposure to trauma (70.4%), the incidence of PTSD is relatively low (6.8%), suggesting that either individual susceptibility or adaptability driven by epigenetic and genetic mechanisms are likely at play. PTSD takes hold from exposure to traumatic events, such as death threats or severe abuse, with its severity being impacted by the magnitude of trauma, its frequency, and the nature. This comprehensive review examines how traumatic experiences and epigenetic modifications in hypothalamic-pituitary axis (HPA), such as DNA methylation, histone modifications, noncoding RNAs, and chromatin remodeling, are transmitted across generations, and impact genes such as FKBP prolyl isomerase 5 (FKBP5), nuclear receptor subfamily 3 group C member 1 (NR3C1), brain-derived neurotrophic factor (BDNF), and solute carrier family 6 member 4 (SLC6A4). It also provides a comprehensive overview on trauma reversal, resilience mechanisms, and pro-resilience factors such as histone acetyltransferases (HATs)/histone deacetylases (HDACs) ratio, dehydroepiandrosterone (DHEA)/cortisol ratio, testosterone levels, and neuropeptide Y, thus highlighting potential therapeutic approaches for trauma-related disorders. The studies highlighted here underscore the narrative, for the first time, that the examination and treatment of PTSD and other depressive disorders must invoke a multitude of approaches to seek out the most effective and personalized strategies. We also hope that the discussion emanating from this review will also inform government policies directed toward intergenerational trauma and PTSD.

Prenatal maternal stress in rats alters the epigenetic and transcriptomic landscape of the maternal-fetal interface across four generations

Prenatal maternal stress (PNMS) determines lifetime mental and physical health. Here, we show in rats that PNMS has consequences for placental function and fetal brain development across four generations (F0-F3). Using a systems biology approach, comprehensive DNA methylation (DNAm), miRNA, and mRNA profiling revealed a moderate impact of PNMS in the F1 generation, but drastic changes in F2 and F3 generations, suggesting compounding effects of PNMS with each successive generation. Both maternal and placental miRNA gene targets included de novo DNA methyltransferases, indicating robust PNMS-induced disruption in the complex epigenetic regulatory network between miRNAs and DNAm. Transgenerational programming mainly involved genes and biological pathways associated with neurological and psychiatric diseases which were linked to maternal-fetal crosstalk facilitated by the placenta. The highly correlated placenta-brain profiles support the use of placenta as a noninvasive biomarker resource to predict pathological changes in the neonatal brain. The transgenerational persistence of critical DNAm, miRNA and mRNA signatures may explain familial non-genetic disease risks.

Early life stress shifts critical periods and causes precocious visual cortex development

The developing nervous system displays remarkable plasticity in response to sensory stimulation during critical periods of development. Critical periods may also increase the brain's vulnerability to adverse experiences. Here we show that early-life stress (ELS) in mice shifts the timing of critical periods in the visual cortex. ELS induced by animal transportation on postnatal day 12 accelerated the opening and closing of the visual cortex critical period along with earlier maturation of visual acuity. Staining of a molecular correlate that marks the end of critical period plasticity revealed premature emergence of inhibitory perineuronal nets (PNNs) following ELS. ELS also drove lasting changes in visual cortex mRNA expression affecting genes linked to psychiatric disease risk, with hemispheric asymmetries favoring the right side. NMR spectroscopy and a metabolomics approach revealed that ELS was accompanied by activated energy metabolism and protein biosynthesis. Thus, ELS may accelerate visual system development, resulting in premature opening and closing of critical period plasticity. Overall, the data suggest that ELS desynchronizes the orchestrated temporal sequence of regional brain development potentially leading to long-term functional deficiencies. These observations provide new insights into a neurodevelopmental expense to adaptative brain plasticity. These findings also suggest that shipment of laboratory animals during vulnerable developmental ages may result in long lasting phenotypes, introducing critical confounds to the experimental design.

A Survey of Fatty Acid Content of the Male Reproductive System in Mice Supplemented With Arachidonic Acid

Paternal exposure to high-fat diets or individual fatty acids (FAs) including arachidonic acid (AA) modifies progeny traits by poorly understood mechanisms. Specific male reproductive system FAs may be involved in paternal inheritance, as they can modify a range of cellular components, including the epigenome. Our objective was to determine FAs in compartments of the male reproductive system that potentially affect ejaculate composition-right and left testicular interstitial fluid (TIF), vesicular gland fluid (VGF), and epididymal adipose tissue (EAT)-in mice exposed to AA or vehicle daily for 10 days (n = 9-10/group). Whole blood (WB) and interscapular brown adipose tissue (IBAT) FA profiles were used as reference. AA significantly affected only VGF FAs relative to vehicle, that is, increased and decreased levels of arachidic and docosahexaenoic acid, respectively, versus vehicle (0.28% ± 0.01% and 0.23% ± 0.03%, respectively, p = 0.049, and 2.42% ± 0.47% and 3.00% ± 0.58%, respectively, p = 0.041). AA affected distinct FAs in WB. Additionally, we uncovered AA-dependent and AA-independent FA laterality. Myristic acid was higher in AA-exposed left versus right TIF (0.68% ± 0.35% and 0.60% ± 0.11%, respectively, p = 0.004). Right TIF contained higher oleic and linoleic acid and lower stearic acid than left TIF (29.01% ± 3.07% and 24.00% ± 2.18%, respectively, p = 0.005; 9.14% ± 1.88% and 7.05% ± 1.36%, respectively, p = 0.005; and 21.90% ± 2.92% and 26.01% ± 2.46%, respectively, p = 0.036), irrespective of exposure to AA. The TIF oleic/stearic acid ratio suggested higher Stearoyl-CoA Desaturase 1 activity in the right versus the left testis (1.35 ± 0.32 and 1.00 ± 0.17, respectively, p = 1.0 × 10-4). Multitissue comparisons revealed that TIF and VGF FA profiles were distinct from WB, EAT, or IBAT counterparts, suggesting tissue-specific FA fingerprints. In conclusion, AA modulated selected VGF long-chain FAs that may impact on uterine inflammation and subsequent embryonic development. AA altered local FA synthesis or selective uptake, rather than eliciting passive uptake from WB. Additionally, we uncover a significant laterality of testis FAs that may result in asymmetric sperm cell phenotypes.

Paternal adverse childhood experiences are associated with a low risk of atopy in the offspring

AIM

Parental adverse childhood experiences (ACE) might affect the offspring health through intergenerational inheritance. The aim of this study was to investigate how paternal ACE associate with offspring sensitisation and allergic rhinitis (AR).

METHODS

The study included 590 Finnish father-child dyads from the FinnBrain Birth Cohort Study. Outcomes were offspring sensitisation against allergens and AR at age 5.5 years. Paternal ACE up to 18 years were assessed using the Trauma and Distress Scale (TADS) with the lowest quarter as the reference group.

RESULTS

Of the children, 317 (54%) were males. Sensitisation occurred in 162/533 (30%) and AR in 122/590 (21%). Paternal TADS (median 17 points; interquartile range 11-27) was inversely associated with the risk of sensitisation. Children whose fathers scored the highest quarter had the lowest risk of sensitisation (adjusted odds ratio 0.42; 95% confidence interval 0.24-0.75), followed by those in the second highest quarter (0.58; 0.34-0.99). The association between the highest quarter and reduced risk of AR was similar.

CONCLUSION

Paternal ACE were associated with a low risk of offspring sensitisation and AR, suggesting paternal childhood stress might influence immune responses in their offspring.

Early-life prefrontal cortex inhibition and early-life stress lead to long-lasting behavioral, transcriptional, and physiological impairments

Early-life stress has been linked to multiple neurodevelopmental and neuropsychiatric deficits. Our previous studies have linked maternal presence/absence from the nest in developing rat pups to changes in prefrontal cortex (PFC) activity. Furthermore, we have shown that these changes are modulated by serotonergic signaling. Here we test whether changes in PFC activity during early life affect the developing cortex leading to behavioral alterations in the adult. We show that inhibiting the PFC of mouse pups leads to cognitive deficits in the adult comparable to those seen following maternal separation. Moreover, we show that activating the PFC during maternal separation can prevent these behavioral deficits. To test how maternal separation affects the transcriptional profile of the PFC we performed single-nucleus RNA-sequencing. Maternal separation led to differential gene expression almost exclusively in inhibitory neurons. Among others, we found changes in GABAergic and serotonergic pathways in these interneurons. Interestingly, both maternal separation and early-life PFC inhibition led to changes in physiological responses in prefrontal activity to GABAergic and serotonergic antagonists that were similar to the responses of more immature brains. Prefrontal activation during maternal separation prevented these changes. These data point to a crucial role of PFC activity during early life in behavioral expression in adulthood.

Transgenerational effects of early life stress on the fecal microbiota in mice

Stress in early life can affect the progeny and increase the risk to develop psychiatric and cardiometabolic diseases across generations. The cross-generational effects of early life stress have been modeled in mice and demonstrated to be associated with epigenetic factors in the germline. While stress is known to affect gut microbial features, whether its effects can persist across life and be passed to the progeny is not well defined. Here we show that early postnatal stress in mice shifts the fecal microbial composition (binary Jaccard index) throughout life, including abundance of eight amplicon sequencing variants (ASVs). Further effects on fecal microbial composition, structure (weighted Jaccard index), and abundance of 16 ASVs are detected in the progeny across two generations. These effects are not accompanied by changes in bacterial metabolites in any generation. These results suggest that changes in the fecal microbial community induced by early life traumatic stress can be perpetuated from exposed parent to the offspring.

The effects of paternal dietary fat versus sugar on offspring body composition and anxiety-related behavior

Increasing evidence suggests that the pre-conception parental environment has long-term consequences for offspring health and disease susceptibility. Though much of the work in this field concentrates on maternal influences, there is growing understanding that fathers also play a significant role in affecting offspring phenotypes. In this study, we investigate effects of altering the proportion of dietary fats and carbohydrates on paternal and offspring body composition and anxiety-related behavior in C57Bl/6-JArc mice. We show that in an isocaloric context, greater dietary fat increased body fat and reduced anxiety-like behavior of studs, whereas increased dietary sucrose had no significant effect. These dietary effects were not reflected in offspring traits, rather, we found sex-specific effects that differed between offspring body composition and behavioral traits. This finding is consistent with past paternal effect studies, where transgenerational effects have been shown to be more prominent in one sex over the other. Here, male offspring of fathers fed high-fat diets were heavier at 10 weeks of age due to increased lean body mass, whereas paternal diet had no significant effect on female offspring body fat or lean mass. In contrast, paternal dietary sugar appeared to have the strongest effects on male offspring behavior, with male offspring of high-sucrose fathers spending less time in the closed arms of the elevated plus maze. Both high-fat and high-sugar paternal diets were found to reduce anxiety-like behavior of female offspring, although this effect was only evident when offspring were fed a control diet. This study provides new understanding of the ways in which diet can shape the behavior of fathers and their offspring and contribute to the development of dietary guidelines to improve obesity and mental health conditions, such as anxiety.

Effects of paternal arachidonic acid supplementation on offspring behavior and hypothalamus inflammation markers in the mouse

Arachidonic acid (AA) is involved in inflammation and plays a role in growth and brain development in infants. We previously showed that exposure of mouse sires to AA for three consecutive generations induces a cumulative change in fatty acid (FA) involved in inflammation and an increase in body and liver weight in the offspring. Here, we tested the hypothesis that paternal AA exposure changes the progeny's behavioral response to a proinflammatory insult, and asked whether tissue-specific FA are associated with that response. Male BALB/c mice were supplemented daily with three doses of AA for 10 days and crossed to non-supplemented females (n = 3/dose). Two-month-old unsupplemented male and female offspring (n = 6/paternal AA dose) were exposed to Gram-negative bacteria-derived lipopolysaccharides (LPS) or saline control two hours prior to open field test (OFT) behavioral analysis and subsequent sacrifice. We probed for significant effects of paternal AA exposure on: OFT behaviors; individual FA content of blood, hypothalamus and hypothalamus-free brain; hypothalamic expression profile of genes related to inflammation (Tnfa, Il1b, Cox1, Cox2) and FA synthesis (Scd1, Elovl6). All parameters were affected by paternal AA supplementation in a sex-specific manner. Paternal AA primed the progeny for behavior associated with increased anxiety, with a marked sex dimorphism: high AA doses acted as surrogate of LPS in males, realigning a number of OFT behaviors that in females were differential between saline and LPS groups. Progeny hypothalamic Scd1, a FA metabolism enzyme with documented pro-inflammatory activity, showed a similar pattern of differential expression between saline and LPS groups at high paternal AA dose in females, that was blunted in males. Progeny FA generally were not affected by LPS, but displayed non-linear associations with paternal AA doses. In conclusion, we document that paternal exposure to AA exerts long-term behavioral and biochemical effects in the progeny in a sex-specific manner.

The developmental origins of health and disease and intergenerational inheritance: a scoping review of multigenerational cohort studies

Epidemiologic research has increasingly acknowledged the importance of developmental origins of health and disease (DOHaD) and suggests that prior exposures can be transferred across generations. Multigenerational cohorts are crucial to verify the intergenerational inheritance among human subjects. We carried out this scoping review aims to summarize multigenerational cohort studies' characteristics, issues, and implications and hence provide evidence to the DOHaD and intergenerational inheritance. We adopted a comprehensive search strategy to identify multigenerational cohorts, searching PubMed, EMBASE, and Web of Science databases from the inception of each dataset to June 20th, 2022, to retrieve relevant articles. After screening, 28 unique multigenerational cohort studies were identified. We classified all studies into four types: population-based cohort extended three-generation cohort, birth cohort extended three-generation cohort, three-generation cohort, and integrated birth and three-generation cohort. Most cohorts (n = 15, 53%) were categorized as birth cohort extended three-generation studies. The sample size of included cohorts varied from 41 to 167,729. The study duration ranged from two years to 31 years. Most cohorts had common exposures, including socioeconomic factors, lifestyle, and grandparents' and parents' health and risk behaviors over the life course. These studies usually investigated intergenerational inheritance of diseases as the outcomes, most frequently, obesity, child health, and cardiovascular diseases. We also found that most multigenerational studies aim to disentangle genetic, lifestyle, and environmental contributions to the DOHaD across generations. We call for more research on large multigenerational well-characterized cohorts, up to four or even more generations, and more studies from low- and middle-income countries.

Inter- and transgenerational heritability of preconception chronic stress or alcohol exposure: Translational outcomes in brain and behavior

Chronic stress and alcohol (ethanol) use are highly interrelated and can change an individual's behavior through molecular adaptations that do not change the DNA sequence, but instead change gene expression. A recent wealth of research has found that these nongenomic changes can be transmitted across generations, which could partially account for the "missing heritability" observed in genome-wide association studies of alcohol use disorder and other stress-related neuropsychiatric disorders. In this review, we summarize the molecular and behavioral outcomes of nongenomic inheritance of chronic stress and ethanol exposure and the germline mechanisms that could give rise to this heritability. In doing so, we outline the need for further research to: (1) Investigate individual germline mechanisms of paternal, maternal, and biparental nongenomic chronic stress- and ethanol-related inheritance; (2) Synthesize and dissect cross-generational chronic stress and ethanol exposure; (3) Determine cross-generational molecular outcomes of preconception ethanol exposure that contribute to alcohol-related disease risk, using cancer as an example. A detailed understanding of the cross-generational nongenomic effects of stress and/or ethanol will yield novel insight into the impact of ancestral perturbations on disease risk across generations and uncover actionable targets to improve human health.

Chronically high stress hormone levels dysregulate sperm long noncoding RNAs and their embryonic microinjection alters development and affective behaviours

Previous studies on paternal epigenetic inheritance have shown that sperm RNAs play a role in this type of inheritance. The microinjection of sperm small noncoding RNAs into fertilised mouse oocytes induces reprogramming of the early embryo, which is thought to be responsible for the differences observed in adult phenotype. While sperm long noncoding RNAs (lncRNAs) have also been investigated in a previous study, their microinjection into fertilised oocytes did not yield conclusive results regarding their role in modulating brain development and adult behavioural phenotypes. Therefore, in the current study we sought to investigate this further. We used our previously established paternal corticosterone (stress hormone) model to assess sperm lncRNA expression using CaptureSeq, a sequencing technique that is more sensitive than the ones used in other studies in the field. Paternal corticosterone exposure led to dysregulation of sperm long noncoding RNA expression, which encompassed lncRNAs, circular RNAs and transposable element transcripts. Although they have limited functional annotation, bioinformatic approaches indicated the potential of these lncRNAs in regulating brain development and function. We then separated and isolated the sperm lncRNAs and performed microinjections into fertilised oocytes, to generate embryos with modulated lncRNA populations. We observed that the resulting adult offspring had lower body weight and altered anxiety and affective behavioural responses, demonstrating roles for lncRNAs in modulating development and brain function. This study provides novel insights into the roles of lncRNAs in epigenetic inheritance, including impacts on brain development and behaviours of relevance to affective disorders.

The influence of intergenerational trauma on epigenetics and obesity in Indigenous populations - a scoping review

Background: Research has recently begun to examine the potential intergenerational impacts of trauma on obesity.Objective: This scoping review examines the literature on the interactions between intergenerational trauma, epigenetics, and obesity in Indigenous populations. The review was conducted to identify what is known from the literature about how intergenerational trauma may epigenetically influence obesity in Indigenous populations.Methods: Following the PRISMA-ScR guidelines for scoping reviews, online databases were used to identify studies that included discussion of the four focus topics: trauma, epigenetics, obesity, and Indigeneity. The review resulted in six studies that examined those themes. The focus and findings of the selected studies varied from cultural to biological mechanisms and from discussion regarding trauma, epigenetics, obesity, or Indigeneity, but they support three broad statements. First, they support that obesity has genetic and epigenetic factors. Second, intergenerational trauma is prevalent in Indigenous communities. Finally, intergenerational trauma has cultural and biological influences on obesity.Conclusions: Current literature illustrates that intergenerational trauma has behavioural and epigenetic influences that can lead to increased obesity. This scoping review provides a preliminary map of the current literature and understandings of these topics. This review calls for continued studies regarding the connection between trauma, obesity, and epigenetics in Indigenous communities. Future research is vital for practice and policy surrounding individual and communal healing.

Epigenetic inheritance of phenotypes associated with parental exposure to cocaine

Parental exposure to drugs of abuse induces changes in the germline that can be transmitted across subsequent generations, resulting in enduring effects on gene expression and behavior. This transgenerational inheritance involves a dynamic interplay of environmental, genetic, and epigenetic factors that impact an individual's vulnerability to neuropsychiatric disorders. This chapter aims to summarize recent research into the mechanisms underlying the inheritance of gene expression and phenotypic patterns associated with exposure to drugs of abuse, with an emphasis on cocaine. We will first define the epigenetic modifications such as DNA methylation, histone post-translational modifications, and expression of non-coding RNAs that are impacted by parental cocaine use. We will then explore how parental cocaine use induces heritable epigenetic changes that are linked to alterations in neural circuitry and synaptic plasticity within reward-related circuits, ultimately giving rise to potential behavioral vulnerabilities. This discussion will consider phenotypic differences associated with gestational as well as both maternal and paternal preconception drug exposure and will emphasize differences based on offspring sex. In this context, we explore the complex interactions between genetics, epigenetics, environment, and biological sex. Overall, this chapter consolidates the latest developments in the multigenerational effects and long-term consequences of parental substance abuse.

Effects of acute maternal stress induced by predator cues on spatial learning and memory of offspring in the subterranean rodent Ctenomys talarum

One of the main selection pressures to which animals are exposed in nature is predation, which affects a wide variety of biological traits. When the mother experiences this stressor during pregnancy and/or lactation, behavioral and physiological responses may be triggered in the offspring as well. Thus, in order to broaden and deepen knowledge on the transgenerational effects of predation stress, we evaluated how maternal stress experienced during pregnancy and/or lactation affects the spatial abilities of progeny at the onset of adulthood in the subterranean rodent Ctenomys talarum. The results showed that, contrary to what was observed in other rodent species, maternal exposure to predator cues during pregnancy and lactation did not negatively affect the spatial abilities of the offspring, even registering some minor positive effects. Concomitantly, no effects of predatory cues on physiological parameters associated with stress were observed in the progeny. This difference in results between the present study and previous works on maternal stress highlights the importance of considering the species to be evaluated (strain, age and origin-wild or captive-) and the type of stressor used (artificial or natural, intensity of exposure) in the evaluation of the possible transgenerational effects of maternal stress.

Increased paternal corticosterone exposure influences offspring behaviour and expression of urinary pheromones

BACKGROUND

Studies have shown that paternal stress prior to conception can influence the innate behaviours of their offspring. The evolutionary impacts of such intergenerational effects are therefore of considerable interest. Our group previously showed in a model of daily stress that glucocorticoid treatment of adult male mouse breeders prior to conception leads to increased anxiety-related behaviours in male offspring. Here, we aimed to understand the transgenerational effects of paternal stress exposure on the social behaviour of progeny and its potential influence on reproductive success.

RESULTS

We assessed social parameters including social reward, male attractiveness and social dominance, in the offspring (F1) and grand-offspring (F2). We report that paternal corticosterone treatment was associated with increased display of subordination towards other male mice. Those mice were unexpectedly more attractive to female mice while expressing reduced levels of the key rodent pheromone Darcin, contrary to its conventional role in driving female attraction. We investigated the epigenetic regulation of major urinary protein (Mup) expression by performing the first Oxford Nanopore direct methylation of sperm DNA in a mouse model of stress, but found no differences in Mup genes that could be attributed to corticosterone-treatment. Furthermore, no overt differences of the prefrontal cortex transcriptome were found in F1 offspring, implying that peripheral mechanisms are likely contributing to the phenotypic differences. Interestingly, no phenotypic differences were observed in the F2 grand-offspring.

CONCLUSIONS

Overall, our findings highlight the potential of moderate paternal stress to affect intergenerational (mal)adaptive responses, informing future studies of adaptiveness in rodents, humans and other species.

Biological Embedding of Early-Life Adversity and a Scoping Review of the Evidence for Intergenerational Epigenetic Transmission of Stress and Trauma in Humans

Severe or chronic stress and trauma can have a detrimental impact on health. Evidence suggests that early-life adversity can become biologically embedded and has the potential to influence health outcomes decades later. Epigenetics is one mechanism that has been implicated in these long-lasting effects. Observational studies in humans indicate that the effects of stress could even persist across generations, although whether or not epigenetic mechanisms are involved remains under debate. Here, we provide an overview of studies in animals and humans that demonstrate the effects of early-life stress on DNA methylation, one of the most widely studied epigenetic mechanisms, and summarize findings from animal models demonstrating the involvement of epigenetics in the transmission of stress across generations. We then describe the results of a scoping review to determine the extent to which the terms intergenerational or transgenerational have been used in human studies investigating the transmission of trauma and stress via epigenetic mechanisms. We end with a discussion of key areas for future research to advance understanding of the role of epigenetics in the legacy effects of stress and trauma.

Addressing Structural Racism in Pediatric Clinical Practice

Structural racism is the inequitable allocation of various social determinants of health to different communities. Exposure to this and other discrimination levied from intersectional identities is the primary driver of disproportionately adverse health outcomes for minoritized children and their families. Pediatric clinicians must vigilantly identify and mitigate racism in health care systems and delivery, assess for any impact of patient and family exposure to racism and direct them to appropriate health resources, foster an environment of inclusion and respect, and ensure that all care is delivered through a race-conscious lens with the utmost cultural humility and shared decision-making.

Strain-specific changes in nucleus accumbens transcriptome and motivation for palatable food reward in mice exposed to maternal separation

Introduction

In humans, adversity in childhood exerts enduring effects on brain and increases the vulnerability to psychiatric diseases. It also leads to a higher risk of eating disorders and obesity. Maternal separation (MS) in mice has been used as a proxy of stress during infancy. We hypothesized that MS in mice affects motivation to obtain palatable food in adulthood and changes gene expression in reward system.

Methods

Male and female pups from C57Bl/6J and C3H/HeN mice strains were subjected to a daily MS protocol from postnatal day (PND) 2 to PND14. At adulthood, their motivation for palatable food reward was assessed in operant cages.

Results

Compared to control mice, male and female C3H/HeN mice exposed to MS increased their instrumental response for palatable food, especially when the effort required to obtain the reward was high. Importantly, this effect is shown in animals fed ad libitum. Transcriptional analysis revealed 375 genes differentially expressed in the nucleus accumbens of male MS C3H/HeN mice compared to the control group, some of these being associated with the regulation of the reward system (e.g., Gnas, Pnoc). Interestingly, C57Bl/6J mice exposed to MS did not show alterations in their motivation to obtain a palatable reward, nor significant changes in gene expression in the nucleus accumbens.

Conclusion

MS produces long-lasting changes in motivation for palatable food in C3H/HeN mice, but has no impact in C57Bl/6J mice. These behavioral alterations are accompanied by drastic changes in gene expression in the nucleus accumbens, a key structure in the regulation of motivational processes.

Maternal repetitive hypoxia prior to mating confers epigenetic resilience to memory impairment in male progeny

We showed previously in a mouse model of vascular cognitive impairment and dementia involving chronic cerebral hypoperfusion (CCH) that repetitive hypoxic conditioning (RHC) of both parents results in the epigenetic, intergenerational transmission of resilience to recognition memory loss in adult progeny, as assessed by the novel object recognition test. The present study was undertaken in the same model to determine whether RHC treatment of one or both parents is required to confer dementia resilience intergenerationally. We found inherited resilience to 3 months of CCH in males is maternally mediated (p = .006). Statistically, we observed a strong trend for the paternal germline to contribute as well (p = .052). We also found that, in contrast to what is widely observed in males, females display intact recognition memory (p = .001) after 3 months of CCH, revealing a heretofore unidentified sexual dimorphism with respect to cognitive impact during disease progression. Overall, results of our study strongly implicate epigenetic changes in maternal germ cells, induced by our repetitive systemic hypoxic stimulus, contributing to a modified differentiation program capable of establishing a dementia-resilient phenotype in adult male first-generation progeny. (PsycInfo Database Record (c) 2023 APA, all rights reserved).

Preconception paternal mental disorders and child health: Mechanisms and interventions

Mental illness is a significant global health issue with a steady prevalence. High heritability is suspected, but genome-wide association studies only identified a small number of risk genes associated with mental disorders. This 'missing inheritance' can be partially explained by epigenetic heredity. Evidence from numerous animal models and human studies supports the possibility that preconception paternal mental health influences their offspring's mental health via nongenetic means. Here, we review two potential pathways, including sperm epigenetics and seminal plasma components. The current review highlights the role of sperm epigenetics and explores epigenetic message origination and susceptibility to chronic stress. Meanwhile, possible spatiotemporal windows and events that induce sexually dimorphic modes and effects of paternal stress transmission are inferred in this review. Additionally, we discuss emerging interventions that could potentially block the intergenerational transmission of paternal psychiatric disorders and reduce the incidence of mental illness. Understanding the underlying mechanisms by which preconception paternal stress impacts offspring health is critical for identifying strategies supporting healthy development and successfully controlling the prevalence of mental illness.

Paternal transmission of behavioural and metabolic traits induced by postnatal stress to the 5th generation in mice

Life experiences and environmental conditions in childhood can change the physiology and behaviour of exposed individuals and, in some cases, of their offspring. In rodent models, stress/trauma, poor diet, and endocrine disruptors in a parent have been shown to cause phenotypes in the direct progeny, suggesting intergenerational inheritance. A few models also examined transmission to further offspring and suggested transgenerational inheritance, but such multigenerational inheritance is not well characterized. Our previous work on a mouse model of early postnatal stress showed that behaviour and metabolism are altered in the offspring of exposed males up to the 4th generation in the patriline and up to the 2nd generation in the matriline. The present study examined if symptoms can be transmitted beyond the 4th generation in the patriline. Analyses of the 5th and 6th generations of mice revealed that altered risk-taking and glucose regulation caused by postnatal stress are still manifested in the 5th generation but are attenuated in the 6th generation. Some of the symptoms are expressed in both males and females, but some are sex-dependent and sometimes opposite. These results indicate that postnatal trauma can affect behaviour and metabolism over many generations, suggesting epigenetic mechanisms of transmission.

Psychosocial family-level mediators in the intergenerational transmission of trauma: Protocol for a systematic review and meta-analysis

INTRODUCTION

Family-level psychosocial factors appear to play a critical role in mediating the intergenerational transmission of trauma; however, no review article has quantitatively synthesized causal mechanisms across a diversity of trauma types. This study aims to systematically consolidate the epidemiological research on family-level psychosocial mediators and moderators to ultimately produce causal diagram(s) of the intergenerational transmission of trauma.

METHODS

We will identify epidemiological peer-reviewed publications, dissertations, and conference abstracts that measure the impact of at least one psychosocial family-level factor mediating or moderating the relationship between parental trauma exposure and a child mental health outcome. English, French, Kinyarwanda, and Spanish articles will be eligible. We will search MEDLINE, PsycINFO, PTSDpubs, Scopus, and ProQuest Dissertations and Theses and will conduct forward citation chaining of included documents. Two reviewers will perform screening independently. We will extract reported mediators, moderators, and relevant study characteristics for included studies. Findings will be presented using narrative syntheses, descriptive analyses, mediation meta-analyses, moderating meta-analyses, and causal diagram(s), where possible. We will perform a risk of bias assessment and will assess for publication bias.

DISCUSSION

The development of evidence-based causal diagram(s) would provide more detailed understanding of the paths by which the psychological impacts of trauma can be transmitted intergenerationally at the family-level. This review could provide evidence to better support interventions that interrupt the cycle of intergenerational trauma.

TRIAL REGISTRATION

Systematic review registration: PROSPERO registration ID #CRD42021251053.

Mechanisms by which adverse childhood experiences, other traumas and PTSD influence the health and well-being of individuals with eating disorders throughout the life span

BACKGROUND

Multiple published sources from around the world have confirmed an association between an array of adverse childhood experiences (ACEs) and other traumatic events with eating disorders (EDs) and related adverse outcomes, including higher morbidity and mortality.

METHODS

In keeping with this Special Issue's goals, this narrative review focuses on the ACEs pyramid and its purported mechanisms through which child maltreatment and other forms of violence toward human beings influence the health and well-being of individuals who develop EDs throughout the life span. Relevant literature on posttraumatic stress disorder (PTSD) is highlighted when applicable.

RESULTS

At every level of the pyramid, it is shown that EDs interact with each of these proclaimed escalating mechanisms in a bidirectional manner that contributes to the predisposition, precipitation and perpetuation of EDs and related medical and psychiatric comorbidities, which then predispose to early death. The levels and their interactions that are discussed include the contribution of generational embodiment (genetics) and historical trauma (epigenetics), social conditions and local context, the ACEs and other traumas themselves, the resultant disrupted neurodevelopment, subsequent social, emotional and cognitive impairment, the adoption of health risk behaviors, and the development of disease, disability and social problems, all resulting in premature mortality by means of fatal complications and/or suicide.

CONCLUSIONS

The implications of these cascading, evolving, and intertwined perspectives have important implications for the assessment and treatment of EDs using trauma-informed care and trauma-focused integrated treatment approaches. This overview offers multiple opportunities at every level for the palliation and prevention of EDs and other associated trauma-related conditions, including PTSD.

Trans- and Multigenerational Maternal Social Isolation Stress Programs the Blood Plasma Metabolome in the F3 Generation

Metabolic risk factors are among the most common causes of noncommunicable diseases, and stress critically contributes to metabolic risk. In particular, social isolation during pregnancy may represent a salient stressor that affects offspring metabolic health, with potentially adverse consequences for future generations. Here, we used proton nuclear magnetic resonance (¹H NMR) spectroscopy to analyze the blood plasma metabolomes of the third filial (F3) generation of rats born to lineages that experienced either transgenerational or multigenerational maternal social isolation stress. We show that maternal social isolation induces distinct and robust metabolic profiles in the blood plasma of adult F3 offspring, which are characterized by critical switches in energy metabolism, such as upregulated formate and creatine phosphate metabolisms and downregulated glucose metabolism. Both trans- and multigenerational stress altered plasma metabolomic profiles in adult offspring when compared to controls. Social isolation stress increasingly affected pathways involved in energy metabolism and protein biosynthesis, particularly in branched-chain amino acid synthesis, the tricarboxylic acid cycle (lactate, citrate), muscle performance (alanine, creatine phosphate), and immunoregulation (serine, threonine). Levels of creatine phosphate, leucine, and isoleucine were associated with changes in anxiety-like behaviours in open field exploration. The findings reveal the metabolic underpinnings of epigenetically heritable diseases and suggest that even remote maternal social stress may become a risk factor for metabolic diseases, such as diabetes, and adverse mental health outcomes. Metabolomic signatures of transgenerational stress may aid in the risk prediction and early diagnosis of non-communicable diseases in precision medicine approaches.

Canada's Colonial Genocide of Indigenous Peoples: A Review of the Psychosocial and Neurobiological Processes Linking Trauma and Intergenerational Outcomes

The policies and actions that were enacted to colonize Indigenous Peoples in Canada have been described as constituting cultural genocide. When one considers the long-term consequences from the perspective of the social and environmental determinants of health framework, the impacts of such policies on the physical and mental health of Indigenous Peoples go well beyond cultural loss. This paper addresses the impacts of key historical and current Canadian federal policies in relation to the health and well-being of Indigenous Peoples. Far from constituting a mere lesson in history, the connections between colonialist policies and actions on present-day outcomes are evaluated in terms of transgenerational and intergenerational transmission processes, including psychosocial, developmental, environmental, and neurobiological mechanisms and trauma responses. In addition, while colonialist policies have created adverse living conditions for Indigenous Peoples, resilience and the perseverance of many aspects of culture may be maintained through intergenerational processes.

Paternal diet induces transgenerational epigenetic inheritance of DNA methylation signatures and phenotypes in sheep model

Transgenerational epigenetic inheritance (TEI) requires transmission of environmentally induced epigenetic changes and associated phenotypes to subsequent generations without continued exposure to the environmental factor that originated the change. TEI is well-established in plants and Caenorhabditis elegans; however, occurrence in mammals is debated and poorly understood. Here, we examined whether paternal diet from weaning to puberty-induced changes in sperm DNA methylation that were transmitted to subsequent generations. Over 100 methylated cytosines, environmentally altered in the F0 generation, were inherited by the F1 and F2 generations. Furthermore, the F0 paternal diet was associated with growth and male fertility phenotypes in subsequent generations. Differentially methylated cytosines were correlated with gene expression. Our results demonstrate that some sperm methylation sites may escape DNA methylation erasure and are transmitted to subsequent generations despite the 2 waves of epigenetic programming: in primordial germ cells and in embryos after fertilization. These results advance our understanding of the complex relationships between nature and nurture.

Transgenerational Effects of Prenatal Ethanol Exposure in Prepubescent Mice

Background: Fetal alcohol spectrum disorders (FASD) represent a leading cause of non-genetic neuropathologies. Recent preclinical evidence from suggests that prenatal ethanol exposure (PrEE), like other environmental exposures, may have a significant, transgenerational impact on the offspring of directly exposed animals, including altered neocortical development at birth and behavior in peri-pubescent mice. How these adverse behavioral outcomes are manifested within the brain at the time of behavioral disruption remains unknown.

Methods: A transgenerational mouse model of FASD was used to generate up to a third filial generation of offspring to study. Using a multi-modal battery of behavioral assays, we assessed motor coordination/function, sensorimotor processing, risk-taking behavior, and depressive-like behavior in postnatal day (P) 20 pre-pubescent mice. Additionally, sensory neocortical area connectivity using dye tracing, neocortical gene expression using in situ RNA hybridization, and spine density of spiny stellate cells in the somatosensory cortex using Golgi-Cox staining were examined in mice at P20.

Results: We found that PrEE induces behavioral abnormalities including abnormal sensorimotor processing, increased risk-taking behavior, and increased depressive-like behaviors that extend to the F3 generation in 20-day old mice. Assessment of both somatosensory and visual cortical connectivity, as well as cortical RZRβ expression in pre-pubescent mice yielded no significant differences among any experimental generations. In contrast, only directly-exposed F1 mice displayed altered cortical expression of Id2 and decreased spine density among layer IV spiny stellate cells in somatosensory cortex at this pre-pubescent, post weaning age.

Conclusion: Our results suggest that robust, clinically-relevant behavioral abnormalities are passed transgenerationally to the offspring of mice directly exposed to prenatal ethanol. Additionally, in contrast to our previous findings in the newborn PrEE mouse, a lack of transgenerational findings within the brain at this later age illuminates the critical need for future studies to attempt to discover the link between neurological function and the described behavioral changes. Overall, our study suggests that multi-generational effects of PrEE may have a substantial impact on human behavior as well as health and well-being and that these effects likely extend beyond early childhood.

Health inequities and the inappropriate use of race in nephrology

Chronic kidney disease is an important clinical condition beset with racial and ethnic disparities that are associated with social inequities. Many medical schools and health centres across the USA have raised concerns about the use of race - a socio-political construct that mediates the effect of structural racism - as a fixed, measurable biological variable in the assessment of kidney disease. We discuss the role of race and racism in medicine and outline many of the concerns that have been raised by the medical and social justice communities regarding the use of race in estimated glomerular filtration rate equations, including its relationship with structural racism and racial inequities. Although race can be used to identify populations who experience racism and subsequent differential treatment, ignoring the biological and social heterogeneity within any racial group and inferring innate individual-level attributes is methodologically flawed. Therefore, although more accurate measures for estimating kidney function are under investigation, we support the use of biomarkers for determining estimated glomerular filtration rate without adjustments for race. Clinicians have a duty to recognize and elucidate the nuances of racism and its effects on health and disease. Otherwise, we risk perpetuating historical racist concepts in medicine that exacerbate health inequities and impact marginalized patient populations.

Association of Parental Famine Exposure With Offspring Depression and Cognition Function

BACKGROUND

The effect of early exposure to famine on depression and cognition in adulthood has been shown, but the intergenerational association of famine remain to be explored. This study focused on exploring the association of parental famine exposure with depression and cognition in the offspring.

METHODS

Based on the Chinese Family Panel Studies database, which is a longitudinal survey, we included 5,150 individuals born between 1959 and 1961 and divided them into fetal-exposed, infancy-exposed (birth year = 1957-1958), school-age-exposed (birth year = 1949-1956), adolescent-exposed (birth year = 1946-1948), and unexposed groups. We used one-way analysis of variance, multiple linear regression, and one follow-up measurement to analyze the association between parental famine exposure and offspring depression and cognitive function.

RESULTS

Compared with the unexposed group, the correlations between parental famine exposure during fetal period and their cognitive function (mother: β = -1.614, 95% CI: -2.535, -0.693; p = 0.001; father: β = -2.153, 95% CI: -3.104, -1.202, p < 0.001) were significant. For the offspring, there was a negative correlation between famine exposure of fathers during the fetal period and depression in their offspring (β = -0.477, 95% CI: -0.907, -0.047; p = 0.030). There was a negative correlation between maternal famine exposure during the infant and adolescent period and cognitive function in the offspring (math test: β = -0.730, 95% CI: -1.307, -0.153; p = 0.013; word test: β = -2.346, 95% CI: -4.067, -0.625; p = 0.008).

LIMITATIONS

Not all variables related to depression and cognition function were included in the CFPS database, and the other unknown or unmeasured confounders may explain our results.

Alternative models for transgenerational epigenetic inheritance: Molecular psychiatry beyond mice and man

Mental illness remains the greatest chronic health burden globally with few in-roads having been made despite significant advances in genomic knowledge in recent decades. The field of psychiatry is constantly challenged to bring new approaches and tools to address and treat the needs of vulnerable individuals and subpopulations, and that has to be supported by a continuous growth in knowledge. The majority of neuropsychiatric symptoms reflect complex gene-environment interactions, with epigenetics bridging the gap between genetic susceptibility and environmental stressors that trigger disease onset and drive the advancement of symptoms. It has more recently been demonstrated in preclinical models that epigenetics underpins the transgenerational inheritance of stress-related behavioural phenotypes in both paternal and maternal lineages, providing further supporting evidence for heritability in humans. However, unbiased prospective studies of this nature are practically impossible to conduct in humans so preclinical models remain our best option for researching the molecular pathophysiologies underlying many neuropsychiatric conditions. While rodents will remain the dominant model system for preclinical studies (especially for addressing complex behavioural phenotypes), there is scope to expand current research of the molecular and epigenetic pathologies by using invertebrate models. Here, we will discuss the utility and advantages of two alternative model organisms-Caenorhabditis elegans and Drosophila melanogaster-and summarise the compelling insights of the epigenetic regulation of transgenerational inheritance that are potentially relevant to human psychiatry.

Paternal and/or maternal preconception-induced neurobehavioral teratogenicity in animal and human models

Prenatal insult exposure effects on the offspring, have and are still considered the main interest of most teratological studies, while paternal and maternal preconception effects have received relatively little interest. Once thought to be a myth, paternal exposure to insults leading to numerous detrimental effects in the offspring, has been confirmed on several occasions and is gaining increased attention. These effects could be demonstrated molecularly, biochemically and/or behaviorally. Different epigenetic mechanisms have been proposed for these effects to occur, including DNA methylation, histone modification and sperm RNA transmission. Paternal insult exposure has been shown to cause several neurobehavioral and developmental defects in the offspring. Findings on parental insult exposure effects on the progeny will be discussed in this review, with the main focus being on neurobehavioral effects after parental preconceptional exposure. The exposure to the insults induced long-lasting, mostly marked, defects. A few pioneering, prevention and reversal studies were published. Interestingly, most studies were conducted on paternal exposure and, at the present state of this field, on animal models. Clinical translation remains the subsequent challenge.

Pre-reproductive stress in adolescent female rats alters oocyte microRNA expression and offspring phenotypes: pharmacological interventions and putative mechanisms

Pre-reproductive stress (PRS) to adolescent female rats alters anxiogenic behavior in first (F1)- and second-generation (F2) offspring and increases mRNA expression of corticotropin-releasing factor receptor type 1 (Crhr1) in oocytes and in neonate offspring brain. Here, we ask whether the expression of Crhr1 and Crhr1-targeting microRNA is altered in brain, blood, and oocytes of exposed females and in the brain of their neonate and adult F1 and F2 offspring. In addition, we inquire whether maternal post-stress drug treatment reverses PRS-induced abnormalities in offspring. We find that PRS induces a selective increase in Crhr1-targeting mir-34a and mir-34c in blood and oocytes, while non-Crhr1 microRNA molecules remain unaltered. PRS induces similar microRNA changes in prefrontal cortex of F1 and F2 neonates. In adult animals, cortical Crhr1, but not mir-34, expression is affected by both maternal and direct stress exposure. Post-PRS fluoxetine (FLX) treatment increases pup mortality, and both FLX and the Crhr1 antagonist NBI 27914 reverse some of the effects of PRS and also have independent effects on F1 behavior and gene expression. PRS also alters behavior as well as gene and miRNA expression patterns in paternally derived F2 offspring, producing effects that are different from those previously found in maternally derived F2 offspring. These findings extend current knowledge on inter- and trans-generational transfer of stress effects, point to microRNA changes in stress-exposed oocytes as a potential mechanism, and highlight the consequences of post-stress pharmacological interventions in adolescence.

Epigenome-wide association study for atrazine induced transgenerational DNA methylation and histone retention sperm epigenetic biomarkers for disease

Atrazine is a common agricultural herbicide previously shown to promote epigenetic transgenerational inheritance of disease to subsequent generations. The current study was designed as an epigenome-wide association study (EWAS) to identify transgenerational sperm disease associated differential DNA methylation regions (DMRs) and differential histone retention regions (DHRs). Gestating female F0 generation rats were transiently exposed to atrazine during the period of embryonic gonadal sex determination, and then subsequent F1, F2, and F3 generations obtained in the absence of any continued exposure. The transgenerational F3 generation males were assessed for disease and sperm collected for epigenetic analysis. Pathology was observed in pubertal onset and for testis disease, prostate disease, kidney disease, lean pathology, and multiple disease. For these pathologies, sufficient numbers of individual males with only a single specific disease were identified. The sperm DNA and chromatin were isolated from adult one-year animals with the specific diseases and analyzed for DMRs with methylated DNA immunoprecipitation (MeDIP) sequencing and DHRs with histone chromatin immunoprecipitation (ChIP) sequencing. Transgenerational F3 generation males with or without disease were compared to identify the disease specific epimutation biomarkers. All pathologies were found to have disease specific DMRs and DHRs which were found to predominantly be distinct for each disease. No common DMRs or DHRs were found among all the pathologies. Epimutation gene associations were identified and found to correlate to previously known disease linked genes. This is one of the first observations of potential sperm disease biomarkers for histone retention sites. Although further studies with expanded animal numbers are required, the current study provides evidence the EWAS analysis is effective for the identification of potential pathology epimutation biomarkers for disease susceptibility.

Involvement of circulating factors in the transmission of paternal experiences through the germline

Environmental factors can change phenotypes in exposed individuals and offspring and involve the germline, likely via biological signals in the periphery that communicate with germ cells. Here, using a mouse model of paternal exposure to traumatic stress, we identify circulating factors involving peroxisome proliferator-activated receptor (PPAR) pathways in the effects of exposure to the germline. We show that exposure alters metabolic functions and pathways, particularly lipid-derived metabolites, in exposed fathers and their offspring. We collected data in a human cohort exposed to childhood trauma and observed similar metabolic alterations in circulation, suggesting conserved effects. Chronic injection of serum from trauma-exposed males into controls recapitulates metabolic phenotypes in the offspring. We identify lipid-activated nuclear receptors PPARs as potential mediators of the effects from father to offspring. Pharmacological PPAR activation in vivo reproduces metabolic dysfunctions in the offspring and grand-offspring of injected males and affects the sperm transcriptome in fathers and sons. In germ-like cells in vitro, both serum and PPAR agonist induce PPAR activation. Together, these results highlight the role of circulating factors as potential communication vectors between the periphery and the germline.

Mapping the past, present and future research landscape of paternal effects

BACKGROUND

Although in all sexually reproducing organisms an individual has a mother and a father, non-genetic inheritance has been predominantly studied in mothers. Paternal effects have been far less frequently studied, until recently. In the last 5 years, research on environmentally induced paternal effects has grown rapidly in the number of publications and diversity of topics. Here, we provide an overview of this field using synthesis of evidence (systematic map) and influence (bibliometric analyses).

RESULTS

We find that motivations for studies into paternal effects are diverse. For example, from the ecological and evolutionary perspective, paternal effects are of interest as facilitators of response to environmental change and mediators of extended heredity. Medical researchers track how paternal pre-fertilization exposures to factors, such as diet or trauma, influence offspring health. Toxicologists look at the effects of toxins. We compare how these three research guilds design experiments in relation to objects of their studies: fathers, mothers and offspring. We highlight examples of research gaps, which, in turn, lead to future avenues of research.

CONCLUSIONS

The literature on paternal effects is large and disparate. Our study helps in fostering connections between areas of knowledge that develop in parallel, but which could benefit from the lateral transfer of concepts and methods.

Impact of Parental Exposure on Offspring Health in Humans

The possibility that parental life experiences and environmental exposures influence mental and physical health across generations is an important concept in biology and medicine. Evidence from animal models has established the existence of a non-genetic mode of inheritance. This form of heredity involves transmission of the effects of parental exposure to the offspring through epigenetic changes in the germline. Studying the mechanisms of epigenetic inheritance in humans is challenging because it is difficult to obtain multigeneration cohorts, to collect reproductive cells in exposed parents, and to exclude psychosocial and cultural confounders. Nonetheless, epidemiological studies in humans exposed to famine, stress/trauma, or toxicants have provided evidence that parental exposure can impact the health of descendants, in some cases, across several generations. A few studies have also started to reveal epigenetic changes in the periphery and sperm after certain exposures. This article reviews these studies and evaluates the current evidence for the potential contribution of epigenetic factors to heredity in humans. The challenges and limitations of this fundamental biological process, its implications, and its societal relevance are also discussed.

Paternal bloodlines sculpting seminal concepts: circulating factors as mediators of transgenerational 'epigenopathy' and 'epigenetic resilience'

Accumulating evidence, particularly from rodent and human studies, shows that the environmental exposures and experience of a father prior to conception can modulate sperm epigenetics and subsequent offspring phenotypes. In this issue of The EMBO Journal, van Steenwyk and colleagues (2020) provide important new insights into how one form of paternal experience (early-life stress or trauma) may impact sperm epigenetics via circulating factors, presenting novel experimental evidence from a mouse model and an analogous human cohort.

Intermittent Hypoxia Promotes Functional Neuroprotection from Retinal Ischemia in Untreated First-Generation Offspring: Proteomic Mechanistic Insights

Purpose

Stress can lead to short- or long-term changes in phenotype. Accumulating evidence also supports the transmission of maladaptive phenotypes, induced by adverse stressors, through the germline to manifest in subsequent generations, providing a novel mechanistic basis for the heritability of disease. In the present study in mice, we tested the hypothesis that repeated presentations of a nonharmful conditioning stress, demonstrated previously to protect against retinal ischemia, will also provide ischemic protection in the retinae of their untreated, first-generation (F1) adult offspring.

Methods

Swiss-Webster ND4 outbred mice were mated following a 16-week period of brief, every-other-day conditioning exposures to mild systemic hypoxia (repetitive hypoxic conditioning, RHC). Retinae of their 5-month-old F1 progeny were subjected to unilateral ischemia. Scotopic electroretinography quantified postischemic outcomes. The injury-resilient retinal proteome was revealed by quantitative mass spectrometry, and bioinformatic analyses identified the biochemical pathways and networks in which these differentially expressed proteins operate.

Results

Significant resilience to injury in both sexes was documented in F1 mice derived from RHC-treated parents, relative to matched F1 adult progeny derived from normoxic control parents. Ischemia-induced increases and decreases in the expression of many visual transduction proteins that are integral to photoreceptor function were abrogated by parental RHC, providing a molecular basis for the observed functional protection.

Conclusions

Our proteomic analyses provided mechanistic insights into the molecular manifestation of the inherited, injury-resilient phenotype. To our knowledge, this is the first study in a mammalian model documenting the reprogramming of heritability to promote disease resilience in the next generation.

The relevance of a rodent cohort in the Consortium on Individual Development

One of the features of the Consortium on Individual Development is the existence of a rodent cohort, in parallel with the human cohorts. Here we give an overview of the current status. We first elaborate on the choice of rat and mouse models mimicking early life adverse or beneficial conditions during development. We performed a systematic literature search on early life adversity and adult social behavior to address the status quo. Next, we describe the behavioral tasks we used and designed to examine behavioral control and social competence in rodents. The results so far indicate that manipulation of the environment in the first postnatal week only subtly affects social behavior. Stronger effects were seen in the model that targeted early adolescence; once adult, these rats are characterized by increased attention, a higher degree of impulsiveness and reduced social interest in peers. Many experiments in our rodent models with tightly controlled conditions were inspired by findings in human cohorts, and now allow in-depth mechanistic investigations. Vice versa, some of the findings in rodents are currently followed up by dedicated investigations in the human cohorts. This exemplifies the added value of animal investigations in a consortium encompassing primarily human developmental cohorts.

Epigenetic Transgenerational Inheritance of Obesity Susceptibility

The prevalence of obesity and associated diseases has reached pandemic levels. Obesity is often associated with overnutrition and a sedentary lifestyle, but clearly other factors also increase the susceptibility of metabolic disease states. Ancestral and direct exposures to environmental toxicants and altered nutrition have been shown to increase susceptibility for obesity and metabolic dysregulation. Environmental insults can reprogram the epigenome of the germline (sperm and eggs), which transmits the susceptibility for disease to future generations through epigenetic transgenerational inheritance. In this review, we discuss current evidence and molecular mechanisms for epigenetic transgenerational inheritance of obesity susceptibility. Understanding ancestral environmental insults and epigenetic transgenerational impacts on future generations will be critical to fully understand the etiology of obesity and to develop preventative therapy options.

Natural cryptic variation in epigenetic modulation of an embryonic gene regulatory network

Gene regulatory networks (GRNs) that direct animal embryogenesis must respond to varying environmental and physiological conditions to ensure robust construction of organ systems. While GRNs are evolutionarily modified by natural genomic variation, the roles of epigenetic processes in shaping plasticity of GRN architecture are not well understood. The endoderm GRN in Caenorhabditis elegans is initiated by the maternally supplied SKN-1/Nrf2 bZIP transcription factor; however, the requirement for SKN-1 in endoderm specification varies widely among distinct C. elegans wild isotypes, owing to rapid developmental system drift driven by accumulation of cryptic genetic variants. We report here that heritable epigenetic factors that are stimulated by transient developmental diapause also underlie cryptic variation in the requirement for SKN-1 in endoderm development. This epigenetic memory is inherited from the maternal germline, apparently through a nuclear, rather than cytoplasmic, signal, resulting in a parent-of-origin effect (POE), in which the phenotype of the progeny resembles that of the maternal founder. The occurrence and persistence of POE varies between different parental pairs, perduring for at least 10 generations in one pair. This long-perduring POE requires piwi-interacting RNA (piRNA) function and the germline nuclear RNA interference (RNAi) pathway, as well as MET-2 and SET-32, which direct histone H3K9 trimethylation and drive heritable epigenetic modification. Such nongenetic cryptic variation may provide a resource of additional phenotypic diversity through which adaptation may facilitate evolutionary changes and shape developmental regulatory systems.

Transgenerational inheritance of fetal alcohol exposure adverse effects on immune gene interferon-ϒ

Background

Alcohol exposures in utero have been shown to alter immune system functions in the offspring which persists into adulthood. However, it is not apparent why the in utero alcohol effect on the immune system persists into adulthood of fetal alcohol-exposed offspring. The objective of this study was to determine the long-term effects of fetal alcohol exposure on the production of interferon-ϒ (IFN-ϒ), a cytokine known to regulate both innate and adaptive immunity.

Methods

Isogenic Fisher 344 rats were bred to produce pregnant dams, which were fed with a liquid diet containing 6.7% alcohol between gestation days 7 and 21 and pair-fed with an isocaloric liquid diet or fed ad libitum with rat chow; their male and female offspring were used for the study. F1-F3 generation rats were used when they were 2 to 3 months old. Fetal alcohol exposure effects on the Ifn-ɣ gene was determined by measuring the gene promoter methylation and mRNA and protein expression in the spleen. Additionally, transgenerational studies were conducted to evaluate the germline-transmitted effects of fetal alcohol exposure on the Ifn-ɣ gene.

Results

Fetal alcohol exposure reduced the expression of Ifn-ɣ mRNA and IFN-ϒ protein while it increased the proximal promoter methylation of the Ifn-ɣ gene in both male and female offspring during the adult period. Transgenerational studies revealed that the reduced levels of Ifn-ɣ expression and increased levels of its promoter methylation persisted only in F2 and F3 generation males derived from the male germ line.

Conclusion

Overall, these findings provide the evidence that fetal alcohol exposures produce an epigenetic mark on the Ifn-ɣ gene that passes through multiple generations via the male germ line. These data provide the first evidence that the male germ line transmits fetal alcohol exposure's adverse effects on the immune system.

Epigenetic-sensitive pathways in personalized therapy of major cardiovascular diseases

The complex pathobiology underlying cardiovascular diseases (CVDs) has yet to be explained. Aberrant epigenetic changes may result from alterations in enzymatic activities, which are responsible for putting in and/or out the covalent groups, altering the epigenome and then modulating gene expression. The identification of novel individual epigenetic-sensitive trajectories at single cell level might provide additional opportunities to establish predictive, diagnostic and prognostic biomarkers as well as drug targets in CVDs. To date, most of studies investigated DNA methylation mechanism and miRNA regulation as epigenetics marks. During atherogenesis, big epigenetic changes in DNA methylation and different ncRNAs, such as miR-93, miR-340, miR-433, miR-765, CHROME, were identified into endothelial cells, smooth muscle cells, and macrophages. During man development, lipid metabolism, inflammation and homocysteine homeostasis, alter vascular transcriptional mechanism of fundamental genes such as ABCA1, SREBP2, NOS, HIF1. At histone level, increased HDAC9 was associated with matrix metalloproteinase 1 (MMP1) and MMP2 expression in pro-inflammatory macrophages of human carotid plaque other than to have a positive effect on toll like receptor signaling and innate immunity. HDAC9 deficiency promoted inflammation resolution and reverse cholesterol transport, which might block atherosclerosis progression and promote lesion regression. Here, we describe main human epigenetic mechanisms involved in atherosclerosis, coronary heart disease, ischemic stroke, peripheral artery disease; cardiomyopathy and heart failure. Different epigenetics mechanisms are activated, such as regulation by circular RNAs, as MICRA, and epitranscriptomics at RNA level. Moreover, in order to open new frontiers for precision medicine and personalized therapy, we offer a panoramic view on the most innovative bioinformatic tools designed to identify putative genes and molecular networks underlying CVDs in man.

Exploring the Stress Impact in the Paternal Germ Cells Epigenome: Can Catecholamines Induce Epigenetic Reprogramming?

Spermatogenesis is characterized by unique epigenetic programs that enable chromatin remodeling and transcriptional regulation for proper meiotic divisions and germ cells maturation. Paternal lifestyle stressors such as diet, drug abuse, or psychological trauma can directly impact the germ cell epigenome and transmit phenotypes to the next generation, pointing to the importance of epigenetic regulation during spermatogenesis. It is established that environmental perturbations can affect the development and behavior of the offspring through epigenetic inheritance, including changes in small non-coding RNAs, DNA methylation, and histones post-translational modifications. But how male germ cells react to lifestyle stressors and encode them in the paternal epigenome is still a research gap. Most lifestyle stressors activate catecholamine circuits leading to both acute and long-term changes in neural functions, and epigenetic mechanisms show strong links to both long-term and rapid, dynamic gene expression regulation during stress. Importantly, the testis shares a molecular and transcriptional signature with the brain tissue, including a rich expression of catecholaminergic elements in germ cells that seem to respond to stressors with similar epigenetic and transcriptional profiles. In this minireview, we put on stage the action of catecholamines as possible mediators between paternal stress responses and epigenetic marks alterations during spermatogenesis. Understanding the epigenetic regulation in spermatogenesis will contribute to unravel the coding mechanisms in the transmission of the biological impacts of stress between generations.