Autism-like behaviors and abnormality of glucose metabolism in offspring derived from aging males with epigenetically modified sperm

Future in the past: paternal reprogramming of offspring phenotype and the epigenetic mechanisms

That certain preconceptual paternal exposures reprogram the developmental phenotypic plasticity in future generation(s) has conceptualized the "paternal programming of offspring health" hypothesis. This transgenerational effect is transmitted primarily through sperm epigenetic mechanisms-DNA methylation, non-coding RNAs (ncRNAs) and associated RNA modifications, and histone modifications-and potentially through non-sperm-specific mechanisms-seminal plasma and circulating factors-that create 'imprinted' memory of ancestral information. The epigenetic landscape in sperm is highly responsive to environmental cues, due to, in part, the soma-to-germline communication mediated by epididymosomes. While human epidemiological studies and experimental animal studies have provided solid evidences in support of transgenerational epigenetic inheritance, how ancestral information is memorized as epigenetic codes for germline transmission is poorly understood. Particular elusive is what the downstream effector pathways that decode those epigenetic codes into persistent phenotypes. In this review, we discuss the paternal reprogramming of offspring phenotype and the possible underlying epigenetic mechanisms. Cracking these epigenetic mechanisms will lead to a better appreciation of "Paternal Origins of Health and Disease" and guide innovation of intervention algorithms to achieve 'healthier' outcomes in future generations. All this will revolutionize our understanding of human disease etiology.

Advanced parental age affects cardiometabolic risk in offspring

Advanced age at conception usually refers to human mothers aged 35 years plus and fathers aged 40 years plus. Advanced parental age may be responsible for genetic and/or epigenetic alterations and may affect the health of offspring. Limited epidemiological and experimental studies have addressed the effect of advanced parental age on cardio-metabolic functions in human and rodent offspring. This mini review aimed to present the knowledge by focusing on adverse and favourable outcomes related to sex-specific risks and intergenerational inheritance. The outcomes identified by this review were mainly negative, but there were also some positive results.

The Role of Advanced Parental Age in Reproductive Genetics

The increase of parental reproductive age is a worldwide trend in modern society in recent decades. In general, older parents have a significant impact on reproductive genetics and the health of offspring. In particular, advanced parental age contributes to the increase in the risk of adverse neurodevelopmental outcomes in offspring. However, it is currently under debate how and to what extent the health of future generations was affected by the parental age. In this review, we aimed to (i) provide an overview of the effects of age on the fertility and biology of the reproductive organs of the parents, (ii) highlight the candidate biological mechanisms underlying reproductive genetic alterations, and (iii) discuss the relevance of the effect of parental age on offspring between animal experiment and clinical observation. In addition, we think that the impact of environmental factors on cognitive and emotional development of older offspring will be an interesting direction.

Preeclampsia promotes autism in offspring via maternal inflammation and fetal NFκB signaling

Preeclampsia (PE) is a risk factor for autism spectrum disorder (ASD) in offspring. However, the exact mechanisms underlying the impact of PE on progeny ASD are not fully understood, which hinders the development of effective therapeutic approaches. This study shows the offspring born to a PE mouse model treated by Nω-nitro-L-arginine methyl ester (L-NAME) exhibit ASD-like phenotypes, including neurodevelopment deficiency and behavioral abnormalities. Transcriptomic analysis of the embryonic cortex and adult offspring hippocampus suggested the expression of ASD-related genes was dramatically changed. Furthermore, the level of inflammatory cytokines TNFα in maternal serum and nuclear factor kappa B (NFκB) signaling in the fetal cortex were elevated. Importantly, TNFα neutralization during pregnancy enabled to ameliorate ASD-like phenotypes and restore the NFκB activation level in the offspring exposed to PE. Furthermore, TNFα/NFκB signaling axis, but not L-NAME, caused deficits in neuroprogenitor cell proliferation and synaptic development. These experiments demonstrate that offspring exposed to PE phenocopies ASD signatures reported in humans and indicate therapeutic targeting of TNFα decreases the likelihood of bearing children with ASD phenotypes from PE mothers.

Sperm epigenetics landscape: correlation with embryo quality, reproductive outcomes and offspring's health

Epigenetics refers to how gene expression and function are modulated without modifying the DNA sequence but through subtle molecular changes or interactions with it. As spermatogenesis progresses, male germ cells suffer plenty of epigenetic modifications, resulting in the definitive epigenome of spermatozoa conditioning its functionality, and this process can be altered by several internal and external factors. The paternal epigenome is crucial for sperm function, fertilization, embryo development, and offspring's health, and altered epigenetic states are associated with male infertility with or without altered semen parameters, embryo quality impairment, and worse ART outcomes together with the future offspring's health risks mainly through intergenerational transmission of epigenetic marks. Identifying epigenetic biomarkers may improve male factor diagnosis and the development of targeted therapies, not only to improve fertility but also to allow an early detection of risk and disease prevention in the progeny. While still there is much research to be done, hopefully in the near future, improvements in high-throughput technologies applied to epigenomes will permit our understanding of the underlying epigenetic mechanisms and the development of diagnostics and therapies leading to improved reproductive outcomes. In this review, we discuss the mechanisms of epigenetics in sperm and how epigenetics behave during spermatogenesis. Additionally, we elaborate on the relationship of sperm epigenetics with sperm parameters and male infertility, and highlight the impact of sperm epigenetic alterations on sperm parameters, embryo quality, ART outcomes, miscarriage rates and offspring's health. Furthermore, we provide insights into the future research of epigenetic alterations in male infertility.

4-hydroxyisoleucine mediated IGF-1/GLP-1 signalling activation prevents propionic acid-induced autism-like behavioural phenotypes and neurochemical defects in experimental rats

Autism is a neuropsychiatric disorder characterized by a neurotransmitter imbalance that impairs neurodevelopment processes. Autism development is marked by communication difficulties, poor socio-emotional health, and cognitive impairment. Insulin-like growth factor-1 (IGF-1) and glucagon-like growth factor-1 (GLP-1) are responsible for regular neuronal growth and homeostasis. Autism progression has been linked to dysregulation of IGF-1/GLP-1 signalling. 4-hydroxyisoleucine (HI), a pharmacologically active amino acid produced from Trigonella foenum graecum, works as an insulin mimic and has neuroprotective properties. The GLP-1 analogue liraglutide (LRG) was employed in our investigation to compare the efficacy of 4-HI in autism prevention. The current study explores the protective effects of 4-HI 50 and 100 mg/kg orally on IGF-1/GLP-1 signalling activation in a PPA-induced experimental model of autism. Propionic acid (PPA) injections to rats by intracerebroventricular (ICV) route for the first 11 days of the experiment resulted in autism-like neurobehavioral, neurochemical, gross morphological, and histopathological abnormalities. In addition, we investigated the dose-dependent neuroprotective effects of 4-HI on the levels of several neurotransmitters and neuroinflammatory cytokines in rat brain homogenate and blood plasma. Neuronal apoptotic and anti-oxidant cellular markers were also studied in blood plasma and brain homogenate samples. Furthermore, the luxol fast blue (LFB) staining results demonstrated significant demyelination in the brains of PPA-induced rats reversed by 4-HI treatment. Rats were assessed for spontaneous locomotor impairments, neuromuscular coordination, stress-like behaviour, learning, and memory to assess neurobehavioral abnormalities. The administration of 4-HI and LRG significantly reversed the behavioural, gross and histological abnormalities in the PPA-treated rat brains. After treatment with 4-HI and LRG, LFB-stained photomicrographs of PPA-treated rats' brains demonstrated the recovery of white matter loss. Our findings indicate that 4-HI protects neurons in rats with autism by enhancing the IGF-1 and GLP-1 protein levels.

Age-associated epigenetic changes in mammalian sperm: implications for offspring health and development

BACKGROUND

Modern reproductive behavior in most developed countries is characterized by delayed parenthood. Older gametes are generally less fertile, accumulating and compounding the effects of varied environmental exposures that are modified by lifestyle factors. Clinicians are primarily concerned with advanced maternal age, while the influence of paternal age on fertility, early development and offspring health remains underappreciated. There is a growing trend to use assisted reproductive technologies for couples of advanced reproductive age. Thus, the number of children born from older gametes is increasing.

OBJECTIVE AND RATIONALE

We review studies reporting age-associated epigenetic changes in mammals and humans in sperm, including DNA methylation, histone modifications and non-coding RNAs. The interplay between environment, fertility, ART and age-related epigenetic signatures is explored. We focus on the association of sperm epigenetics on epigenetic and phenotype events in embryos and offspring.

SEARCH METHODS

Peer-reviewed original and review articles over the last two decades were selected using PubMed and the Web of Science for this narrative review. Searches were performed by adopting the two groups of main terms. The first group included 'advanced paternal age', 'paternal age', 'postponed fatherhood', 'late fatherhood', 'old fatherhood' and the second group included 'sperm epigenetics', 'sperm', 'semen', 'epigenetic', 'inheritance', 'DNA methylation', 'chromatin', 'non-coding RNA', 'assisted reproduction', 'epigenetic clock'.

OUTCOMES

Age is a powerful factor in humans and rodent models associated with increased de novo mutations and a modified sperm epigenome. Age affects all known epigenetic mechanisms, including DNA methylation, histone modifications and profiles of small non-coding (snc)RNA. While DNA methylation is the most investigated, there is a controversy about the direction of age-dependent changes in differentially hypo- or hypermethylated regions with advanced age. Successful development of the human sperm epigenetic clock based on cross-sectional data and four different methods for DNA methylation analysis indicates that at least some CpG exhibit a linear relationship between methylation levels and age. Rodent studies show a significant overlap between genes regulated through age-dependent differentially methylated regions and genes targeted by age-dependent sncRNA. Both age-dependent epigenetic mechanisms target gene networks enriched for embryo developmental, neurodevelopmental, growth and metabolic pathways. Thus, age-dependent changes in the sperm epigenome cannot be described as a stochastic accumulation of random epimutations and may be linked with autism spectrum disorders. Chemical and lifestyle exposures and ART techniques may affect the epigenetic aging of sperm. Although most epigenetic modifications are erased in the early mammalian embryo, there is growing evidence that an altered offspring epigenome and phenotype is linked with advanced paternal age due to the father's sperm accumulating epigenetic changes with time. It has been hypothesized that age-induced changes in the sperm epigenome are profound, physiological and dynamic over years, yet stable over days and months, and likely irreversible.

WIDER IMPLICATIONS

This review raises a concern about delayed fatherhood and age-associated changes in the sperm epigenome that may compromise reproductive health of fathers and transfer altered epigenetic information to subsequent generations. Prospective studies using healthy males that consider confounders are recommended. We suggest a broader discussion focused on regulation of the father's age in natural and ART conceptions is needed. The professional community should be informed and should raise awareness in the population and when counseling older men.

Interaction between social behavior and paternal age in offspring of the same paternal mice

AIM

Previous studies reported that advanced paternal age (APA) may increase the risk of autism spectrum disorder (ASD) in offspring. However, effects of APA on behaviors have not been investigated in offspring of the same paternal mice. The present study sought to identify behavioral differences in mouse offspring of the same fathers at different paternal ages.

METHODS

We assessed locomotor activity, anxiety-like behavior, and social behavior in male mouse offspring that were born from the same fathers at three different paternal ages (3, 12, and 15 months old).

RESULTS

No differences in locomotor activity or anxiety-like behavior were observed among any of the offspring groups. In the three-chamber test, although the control group (3-month-old paternal age) exhibited significantly higher approach behavior toward the novel mouse compared with the novel object, the APA groups (12- and 15-month-old paternal ages) did not exhibit significant approach toward the novel mouse.

CONCLUSION

Offspring of 3-month-old fathers but not 12- or 15-month-old APA fathers exhibited social preference behavior. Although the present study was only exploratory, it demonstrated an interaction between social behavior and paternal age in offspring of the same paternal mice.

Influence of Prenatal Drug Exposure, Maternal Inflammation, and Parental Aging on the Development of Autism Spectrum Disorder

Autism spectrum disorder (ASD) affects reciprocal social interaction and produces abnormal repetitive, restrictive behaviors and interests. The diverse causes of ASD are divided into genetic alterations and environmental risks. The prevalence of ASD has been rising for several decades, which might be related to environmental risks as it is difficult to consider that the prevalence of genetic disorders related to ASD would increase suddenly. The latter includes (1) exposure to medications, such as valproic acid (VPA) and selective serotonin reuptake inhibitors (SSRIs) (2), maternal complications during pregnancy, including infection and hypertensive disorders of pregnancy, and (3) high parental age. Epidemiological studies have indicated a pathogenetic role of prenatal exposure to VPA and maternal inflammation in the development of ASD. VPA is considered to exert its deleterious effects on the fetal brain through several distinct mechanisms, such as alterations of γ-aminobutyric acid signaling, the inhibition of histone deacetylase, the disruption of folic acid metabolism, and the activation of mammalian target of rapamycin. Maternal inflammation that is caused by different stimuli converges on a higher load of proinflammatory cytokines in the fetal brain. Rodent models of maternal exposure to SSRIs generate ASD-like behavior in offspring, but clinical correlations with these preclinical findings are inconclusive. Hypertensive disorders of pregnancy and advanced parental age increase the risk of ASD in humans, but the mechanisms have been poorly investigated in animal models. Evidence of the mechanisms by which environmental factors are related to ASD is discussed, which may contribute to the development of preventive and therapeutic interventions for ASD.

Delayed parenthood and its influence on offspring health: What have we learned from the mouse model

Delayed parenthood is constantly increasing worldwide due to various socio-economic factors. In the last decade, a growing number of epidemiological studies have suggested a link between advanced parental age and an increased risk of diseases in the offspring. Also, poor reproductive outcome has been described in pregnancies conceived by aged parents. Similarly, animal studies showed that aging negatively affects gametes, early embryonic development, pregnancy progression and the postnatal phenotype of resulting offspring. However, how and to what extent parental age is a risk factor for the health of future generations is still subject to debate. Notwithstanding the limitation of an animal model, the mouse model represents a useful tool to understand not only the influence of parental age on offspring phenotype but also the biological mechanisms underlying the poor reproductive outcome and the occurrence of diseases in the descendants. The present review aims at i) providing an overview of the current knowledge from mouse model about the risks associated with conception at advanced age (e.g. neurodevelopmental and metabolic disorders), ii) highlighting the candidate biological mechanisms underlying this phenomenon, and iii) discussing on how murine-derived data can be relevant to humans.

Changes in Phenotypes and DNA Methylation of In Vitro Aging Sperm in Common Carp Cyprinus carpio

The purpose of the current study was to analyze phenotypic and functional characteristics of common carp (Cyprinus carpio) spermatozoa during in vitro aging and to investigate whether global DNA methylation is affected by sperm aging. Milt was collected from five individual males, stored in vitro on ice in a refrigerator for up to 96 h post stripping (HPS) and used to fertilize eggs with intervals of 1, 24 and 96 h. Computer-assisted sperm analysis and a S3e Cell Sorter was employed to determine the spermatozoa phenotypic characteristics (motility, velocity, concentration and viability). In addition, pH and osmolality of the seminal fluid and the capacity of the spermatozoa to fertilize, hatching rate and health of the resulting embryos were examined at different aging times. Whole-genome bisulfite sequencing was used to compare the global and gene-specific DNA methylation in fresh and aged spermatozoa. The results demonstrated that spermatozoa aging in common carp significantly affects their performance and thus the success of artificial fertilization. The methylation level at the cytosine-phosphate-guanine (CpG) sites increased significantly with 24 HPS spermatozoa compared to the fresh group at 1 HPS and then decreased significantly at 96 HPS. A more detailed investigation of gene specific differences in the DNA methylation was hindered by incomplete annotation of the C. carpio genome in the public databases.

Association Between Paternal Age and Birth Weight in Preterm and Full-Term Birth: A Retrospective Study

PURPOSE

While it is well documented that maternal adverse exposures contribute to a series defects on offspring health according to the Developmental Origins of Health and Disease (DOHaD) theory, paternal evidence is still insufficient. Advanced paternal age is associated with multiple metabolism and psychiatric disorders. Birth weight is the most direct marker to evaluate fetal growth. Therefore, we designed this study to explore the association between paternal age and birth weight among infants born at term and preterm (<37 weeks gestation).

METHODS

A large retrospective study was conducted using population-based hospital data from January 2015 to December 2019 that included 69,964 cases of singleton infant births with complete paternal age data. The primary outcome was infant birth weight stratified by sex and gestational age including small for gestational age (SGA, 10th percentile) and large for gestational age (LGA, 90th percentile). Birth weight percentiles by gestational age were based on those published in the INTERGROWTH-21st neonatal weight-for gestational-age standard. Logistic regression analysis and linear regression model were used to estimate the association between paternal age and infant birth weight.

RESULTS

Advanced paternal age was associated with a higher risk for a preterm birth [35-44 years: adjusted odds ratio (OR) = 1.13, 95%CI (1.03 to 1.24); >44 years: OR = 1.36, 95%CI (1.09 to 1.70)]. Paternal age exerted an opposite effect on birth weight with an increased risk of SGA among preterm infants (35-44years: OR = 1.85, 95%CI (1.18 to 2.89) and a decreased risk among term infant (35-44years: OR = 0.81, 95%CI (0.68 to 0.98); >44 years: OR = 0.50, 95%CI (0.26 to 0.94). U-shaped associations were found in that LGA risk among term infants was higher in both younger (<25 years) (OR = 1.32; 95%CI, 1.07 to 1.62) and older (35-44 years) (OR = 1.07; 95% CI, 1.01 to 1.14) fathers in comparison to those who were 25 to 34 years old at the time of delivery.

CONCLUSIONS

Our study found advanced paternal age increased the risk of SGA among preterm infants and for LGA among term infants. These findings likely reflect a pathophysiology etiology and have important preconception care implications and suggest the need for antenatal monitoring.