Investigating the effects of dietary folic acid on sperm count, DNA damage and mutation in Balb/c mice

Effect of Low Dietary Folate on Mouse Spermatogenesis and Spindle Assembly Checkpoint Dysfunction May Contribute to Folate Deficiency-Induced Chromosomal Instability in Cultured Mouse Spermatogonia

Folate, as the initial substrate in one-carbon metabolism, is involved in the synthesis of important substances such as DNA, RNA, and protein. Folate deficiency (FD) is associated with male subfertility and impaired spermatogenesis, yet the underlying mechanisms are poorly understood. In the present study, we established an animal model of FD to investigate the effect of FD on spermatogenesis. GC-1 spermatogonia were used as a model to investigate the effect of FD on proliferation, viability, and chromosomal instability (CIN). Furthermore, we explored the expression of core genes and proteins of spindle assembly checkpoint (SAC), a signaling cascade ensuring accurate chromosome segregation and preventing CIN during mitosis. Cells were maintained in medium containing 0, 20, 200, or 2000 nM folate for 14 days. CIN was measured by using a cytokinesis-blocked micronucleus cytome assay. We found that sperm counts decreased significantly (p < 0.001) and the rate of sperm with defects in the head increased significantly (p < 0.05) in FD diet mice. We also found, relative to the folate-sufficient conditions (2000 nM), cells cultured with 0, 20, or 200 nM folate exhibited delayed growth and increased apoptosis in an inverse dose-dependent manner. FD (0, 20, or 200 nM) significantly induced CIN (p < 0.001, p < 0.001, and p < 0.05, respectively). Moreover, FD significantly and inverse dose dependently increased the mRNA and protein expression of several key SAC-related genes. The results indicate that FD impairs SAC activity, which contributes to mitotic aberrations and CIN. These findings establish a novel association between FD and SAC dysfunction. Thus, FD-impaired spermatogenesis may be partly due to genomic instability and proliferation inhibition of spermatogonia.

Exposure to environmental contaminants and folic acid supplementation intergenerationally impact fetal skeleton development through the paternal lineage in a rat model

Persistent organic pollutants (POPs) are ubiquitous in the environment, which is of concern since they are broadly toxic for wildlife and human health. It is generally accepted that maternal prenatal folic acid supplementation (FA) may beneficially impact offspring development, but it has been recently shown that the father's exposures also influence the health of his offspring. Bone is an endocrine organ essential for whole-body homeostasis and is susceptible to toxicants. Herein, we tested the hypotheses that prenatal paternal exposure to POPs induces developmental bone disorders in fetuses across multiple generations and that FA supplementation attenuates these disorders. We used a four-generation rat model, in which F0 founder females were divided into four treatment groups. F0 females were gavaged with corn oil or an environmentally-relevant POPs mixture and fed either a control diet (2 mg FA/kg), or FA supplemented diet (6 mg FA/kg) before mating and until parturition (four treatments in total). After the birth of the F1 litters, all F0 females and subsequent generations received the FA control diet. Staining with alcian blue and alizarin red S of male and female fetal skeletons was performed at Gestational Day 19.5. Paternal direct and ancestral exposure to POPs delayed bone ossification and decreased the length of long limb bones in fetuses. Maternal FA supplementation did not counteract the POPs-associated delayed fetal ossification and reduced long bone length. In conclusion, prenatal paternal POPs exposure causes developmental bone abnormalities over multiple generations, which were not corrected by maternal FA supplementation.

The association between serum estradiol levels and sperm DNA integrity

In men from the general population, BMI has been associated with a lower sperm DNA fragmentation index (DFI). We wondered whether this could be due to estradiol, which is associated with BMI and reported important for sperm function. Our objective was to investigate the association between estradiol and DFI. In 2008-2010, we recruited 284 young men from the general population to deliver samples of semen and blood and answer questionnaires. Serum concentrations of reproductive hormones and DFI were analyzed, the latter using the Sperm Chromatin Structure Assay. Associations were studied using general linear models. The first model utilized metric values of estradiol, whereas the second model compared men with high and low levels, dichotomized by the median value. A possible interaction between estradiol and testosterone was also examined. When investigating metric estradiol levels and DFI, an inverse association was seen without adjustments (p = .02), but the statistical significance was lost at adjustments for potential confounders (p = .08). Men with lower estradiol levels (<88 pmol/L, mean 71 pmol/L) had a statistically significantly higher DFI than men with higher levels of estradiol (≥88 pmol/L, mean 110 pmol/L). Mean ratio difference was 1.21 (p = .002) without adjustments and 1.18 (p = .01) with adjustments. A statistically significant difference in DFI was observed in men with testosterone levels below median when comparing high and low estradiol (p < .001). This study supports the idea that serum estradiol levels are protective for sperm DNA integrity, at least at lower testosterone levels.

Parental folate deficiency induces birth defects in mice accompanied with increased de novo mutations

Dietary folate deficiency (FD) is associated with the occurrence of birth defects. However, the mechanisms underlying this association remain elusive. In particular, how FD affects genome stability is unknown. To examine whether a folate-deficient diet can affect genome stability, C57BL/6 mice were maintained on a synthetic diet lacking of folic acid (FA) for two generations. F0 mice received the FD diet beginning at 3 weeks of age, and their offspring (F1) began the FD diet after weaning. Both male and female F1 mice fed the FD diet were intentionally crossed with F1 mice fed the normal diet to produce F2 mice. F2 embryos were dissected and collected at E14.5 and E18.5. The malformation ratio was significantly increased in F2 embryos fed the FD diet for two generations compared to those fed the normal diet. Whole-genome sequencing of multiple sibship with F1 males on the FD diet showed that the de novo mutation (DNM) rate in F2 embryos was three times of the reported spontaneous rate in mice. Furthermore, many DNMs observed in the F2 mice exhibited an allele ratio of 1:3 instead of 2:2, suggesting that these mutations are likely to accumulate in gamete cells as a form of mismatch in the DNA duplex. Our study indicated that FD for two generations significantly enhances DNM accumulation during meiosis, which might contribute to the increased negative birth outcomes among F2 mice. Not only maternal but also paternal FA supplementation is probably also necessary and beneficial to prevent birth defects.

Studying the mechanism of sperm DNA damage caused by folate deficiency

Sperm DNA injury is one of the common causes of male infertility. Folic acid deficiency would increase the methylation level of the important genes, including those involved in DNA double-strand break (DSB) repair pathway. In the early stages, we analysed the correlation between seminal plasma folic acid concentration and semen parameters in 157 infertility patients and 91 sperm donor volunteers, and found that there was a significant negative correlation between seminal folic acid concentration and sperm DNA Fragmentation Index (DFI; r = -0.495, p < 0.01). Then through reduced representation bisulphite sequencing, global DNA methylation of sperm of patients in the low folic acid group and the high folic acid group was analysed, it was found that the methylation level in Rad54 promoter region increased in the folic acid deficiency group compared with the normal folic acid group. Meanwhile, the results of animal model and spermatocyte line (GC-2) also found that folic acid deficiency can increase the methylation level in Rad54 promoter region, increased sperm DFI in mice, increased the expression of γ-H2AX, that is, DNA injury marker protein, and increased sensitivity of GC-2 to external damage and stimulation. The study indicates that the expression of Rad54 is downregulated by folic acid deficiency via DNA methylation. This may be one of the mechanisms of sperm DNA damage caused by folate deficiency.

Folic acid deficiency damages male reproduction via endoplasmic reticulum stress-associated PERK pathway induced by Caveolin-1 in mice

Folic acid is critical to maintaining normal male reproductive function. Endoplasmic reticulum (ER) stress plays a crucial role in folic acid deficiency. Studies have shown that Caveolin-1 (Cav-1) is involved in ER stress, but the specific mechanism in male reproduction is still unclear. This study aimed to investigate the effects of folic acid deficiency on spermatogenesis and elucidate the underlying mechanisms. C57BL/6 mice fed with folic acid deficiency induced diet(0.3 mg/kg) were used. A significant decrease in the sperm concentration in the folic acid deficiency group was observed. Meanwhile, folic acid deficiency decreased Cav-1 expression in the testis tissue and increased endoplasmic reticulum stress-related PERK, eIF2α, ATF4, CHOP gene expression. Our results suggest that folic acid deficiency can affect male reproduction through the Cav-1-PERK-eIFα-ATF4-CHOP pathway.Abbreviations: ATF4: activating transcription factor 4; Ca2+: calcium ion; Cav-1: Caveolin-1; CCK-8: cell counting kit-8; CHOP: CCAAT-enhancer-binding protein homologous protein; DNA: Deoxyribonucleic acid; DSB: double strand breakage; eIF2α: eukaryotic Initiation Factor 2 alpha; ER: endoplasmic reticulum; FD: folic acid deficiency; FITC: fluorescein isothiocyanate; HE: hematoxylin and eosin; H3K4me3: histone H3 lysine 4 trimethylation; PERK: protein kinase RNA-like endoplasmic reticulum kinase; PI: propidium iodide; RT-qPCR: quantitative reverse transcription PCR; TUNEL: TdT mediated dUTP Nick End Labeling.

Consequences of Paternal Nutrition on Offspring Health and Disease

It is well established that the maternal diet during the periconceptional period affects the progeny’s health. A growing body of evidence suggests that the paternal diet also influences disease onset in offspring. For many years, sperm was considered only to contribute half of the progeny’s genome. It now appears that it also plays a crucial role in health and disease in offspring’s adult life. The nutritional status and environmental exposure of fathers during their childhood and/or the periconceptional period have significant transgenerational consequences. This review aims to describe the effects of various human and rodent paternal feeding patterns on progeny’s metabolism and health, including fasting or intermittent fasting, low-protein and folic acid deficient food, and overnutrition in high-fat and high-sugar diets. The impact on pregnancy outcome, metabolic pathways, and chronic disease onset will be described. The biological and epigenetic mechanisms underlying the transmission from fathers to their progeny will be discussed. All these data provide evidence of the impact of paternal nutrition on progeny health which could lead to preventive diet recommendations for future fathers.

The effect of micronutrient supplementation on spermatozoa DNA integrity in subfertile men and subsequent pregnancy rate

BACKGROUND

Male infertility has been related to an increased sperm DNA fragmentation index (DFI). Nutritional factors may improve sperm nuclear DNA integrity and thus pregnancy rates. Objective: To evaluate the effect of micronutrient supplementation on sperm DNA integrity in subfertile men and subsequent pregnancy rates.

METHODS

In this retrospective comparative study 339 subfertile males were included on whom a sperm chromatin dispersion test (SCD) was performed as a method to detect DNA fragmentation, as well as an initial semen analysis. Of all, n = 162 received a nutritional management program for three months, consisting of two daily capsules of a standardized combined micronutrient formulation together with a guidance to diet modification and to lifestyle changes (study group). Each capsule contained L-carnitine, L-arginine, coenzyme Q10, zinc, vitamin E, folic acid, glutathione, and selenium. The control group consisted of those patients who did not receive the active treatment (n = 177), yet were instructed to engage in a healthy lifestyle, including a modification of their regular diet. The SCD test was repeated for both groups after three months. As part of the routine follow up, pregnancy rate was assessed six months after the second SCD test. Males with complete follow up and healthy female partners (aged 18 to 40 years) where included.

RESULTS

Data of men with an initial mean DFI of >15% were analyzed first (n = 81;46 study and 35 control patients). After three months, both groups displayed a significant decrease of mean DFI values; however, the mean percent difference was higher in the study group (10.46 ± 1.20 % vs. 5.29 ± 0.57 %; p < .001). Then, the entire population was considered (n = 339). After three months, only the study group displayed a significant decrease of mean DFI initial values (10.48 ± 7.76 % to 6.51 ± 4.61%; p < .001); and the percent difference was higher in the study group (3.97 ± 0.28 % vs. 0.91 ± 0.28 %; p < .001). At six months follow-up, pregnancy rate was higher in the study group (27.78% vs. 15.25%, p = .002).

CONCLUSION

Both regimes significantly reduced sperm DNA fragmentation among subfertile men with a DFI >15%; however, when any baseline DFI value was considered, only micronutrient supplementation achieved a better result on DFI and thus pregnancy rate was higher.

ChIP-seq protocol for sperm cells and embryos to assess environmental impacts and epigenetic inheritance

In the field of epigenetic inheritance, delineating molecular mechanisms implicated in the transfer of paternal environmental conditions to descendants has been elusive. This protocol details how to track sperm chromatin intergenerationally. We describe mouse model design to probe chromatin states in single mouse sperm and techniques to assess pre-implantation embryo chromatin and gene expression. We place emphasis on how to obtain high-quality and quantifiable data sets in sperm and embryos, as well as highlight the limitations of working with low input.

For complete details on the use and execution of this protocol, please refer to Lismer et al. (2021).

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Assessment of paternal environmental exposure effects on sperm chromatin by ChIP-seq

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Tracking chromatin changes in sperm to embryos using ultra-low-input (ULI)-ChIP-seq

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Identification of gene expression changes in embryos using low-input mRNA-seq

Estimation of folic acid/micro nutrients levels; Does it reflect sperm parameters

OBJECTIVE

To study the impact of vitamin B12, folic acid (FA) and methylmalonic acid (MMA) on sperm parameters; count, motility and morphology leading to male fertility.

METHODS

The cross-sectional study comprised of one hundred and eighty-six subjects with normal sperm parameters (fertile) and 88 subjects with abnormal sperm parameters labelled as "infertile" from a sample population of Karachi, Pakistan. Vitamin B12, FA and MMA levels in serum were analysed by enzyme linked immune sorbent assay. Unadjusted and adjusted prevalence ratio with their 95% CI were reported by using cox regression algorithm to assess the association of Vitamin B12, FA and MMA and other factors with male Infertility. Unadjusted and adjusted beta coefficients with 95% CI were reported by using linear regression analysis for assessing relationship of Vitamin B12, FA and MMA and other factors with semen parameters (count, motility and morphology); P value of <.05 was considered significant.

RESULTS

It was declared that with every 1 unit increase in vitamin B12, FA and MMA the prevalence of infertility was decreased by 1%, 17% and 74%, respectively. Multivariate analysis revealed that vitamin B12, FA and MMA had a significant association with total sperm count, motility and morphology. The sperm parameters were also affected by increase in; LH, BMI and body fat %. There was a significant positive correlation of; LH with Vitamin B12 and FA (0.423 < 0.001, 0.338 < 0.001) and testosterone with vitamin B12 and FA (0.326 < 0.001, 0.291 < 0.001), respectively.

CONCLUSION

All the studied micronutrients; Vitamin B12, FA and MMA had a positive effect on sperm parameters; count, motility and morphology and the associated reproductive hormones which explains their role on reproductive functions required to acquire fertility.

Cell non-autonomy amplifies disruption of neurulation by mosaic Vangl2 deletion in mice

Post-zygotic mutations that generate tissue mosaicism are increasingly associated with severe congenital defects, including those arising from failed neural tube closure. Here we report that neural fold elevation during mouse spinal neurulation is vulnerable to deletion of the VANGL planar cell polarity protein 2 (Vangl2) gene in as few as 16% of neuroepithelial cells. Vangl2-deleted cells are typically dispersed throughout the neuroepithelium, and each non-autonomously prevents apical constriction by an average of five Vangl2-replete neighbours. This inhibition of apical constriction involves diminished myosin-II localisation on neighbour cell borders and shortening of basally-extending microtubule tails, which are known to facilitate apical constriction. Vangl2-deleted neuroepithelial cells themselves continue to apically constrict and preferentially recruit myosin-II to their apical cell cortex rather than to apical cap localisations. Such non-autonomous effects can explain how post-zygotic mutations affecting a minority of cells can cause catastrophic failure of morphogenesis leading to clinically important birth defects.

Brucella abortus RB51 ΔleuB expressing Salmonella FliC conjugated gonadotropins reduces mouse fetal numbers: A possible feral swine brucellosis immunocontraceptive vaccine

Population and health management of wildlife is a key to environmental health, domestic herd health, and ultimately public health. Many different methods including: surgical sterilization, poison baits, and sponsored hunting programs have been used in the attempt to control populations of various nuisance animal species. Particular interest has been given to immunocontraception through wildlife vaccination protocols. This study specifically looked at the potential immunocontraceptive and protective properties of a Brucella abortus RB51 ΔleuB vaccine expressing Salmonella typhimurium FliC conjugated to porcine follicle stimulating hormone beta subunit (FSHβ) or gonadotropin releasing hormone (GnRH) DNA sequences. B. abortus RB51 ΔleuB pNS4-TrcD-FliC- FSH_β (RB51LFSHβ) and B. abortus RB51 ΔleuB pNS4-TrcD-FliC-GnRH (RB51LGnRH) were tested in a pilot breeding study with BALB/c mice, and a significant reduction in fertility characteristics was observed in both male and female mice. Ultimately, this study provides support to test these vaccine candidates in feral swine, a destructive invasive species in the United States of America.

Moderate maternal folic acid supplementation ameliorates adverse embryonic and epigenetic outcomes associated with assisted reproduction in a mouse model

STUDY QUESTION

Could clinically-relevant moderate and/or high dose maternal folic acid supplementation prevent aberrant developmental and epigenetic outcomes associated with assisted reproductive technologies (ART)?

SUMMARY ANSWER

Our results demonstrate dose-dependent and sex-specific effects of folic acid supplementation in ART and provide evidence that moderate dose supplements may be optimal for both sexes.

WHAT IS KNOWN ALREADY

Children conceived using ART are at an increased risk for growth and genomic imprinting disorders, often associated with DNA methylation defects. Folic acid supplementation is recommended during pregnancy to prevent adverse offspring outcomes; however, the effects of folic acid supplementation in ART remain unclear.

STUDY DESIGN, SIZE, DURATION

Outbred female mice were fed three folic acid-supplemented diets, control (rodent daily recommended intake or DRI; CD), moderate (4-fold DRI; 4FASD) or high (10-fold DRI; 10FASD) dose, for six weeks prior to ART and throughout gestation. Mouse ART involved a combination of superovulation, in vitro fertilisation, embryo culture and embryo transfer.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Midgestation embryos and placentas (n = 74-99/group) were collected; embryos were assessed for developmental delay and gross morphological abnormalities and embryos and placentas were examined for epigenetic defects. We assessed methylation at four imprinted genes (Snrpn, Kcnq1ot1, Peg1 and H19) in matched midgestation embryos and placentas (n = 31-32/group) using bisulfite pyrosequencing. In addition, we examined genome-wide DNA methylation patterns in placentas (n = 6 normal placentas per sex/group) and embryos (n = 6 normal female embryos/group; n = 3 delayed female embryos/group) using reduced representation bisulfite sequencing (RRBS).

MAIN RESULTS AND THE ROLE OF CHANCE

Moderate, but not high dose supplementation, was associated with a decrease in the proportion of developmentally delayed embryos. Although moderate dose folic acid supplementation reduced DNA methylation variance at certain imprinted genes in embryonic and placental tissues, high dose supplementation exacerbated the negative effects of ART at imprinted loci. Furthermore, folic acid supplements resolved female-biased aberrant imprinted gene methylation. Supplementation was more effective at correcting ART-induced genome-wide methylation defects in male versus female placentas; however, folic acid supplementation also led to additional methylation perturbations which were more pronounced in males.

LARGE-SCALE DATA

The RRBS data from this study have been submitted to the NCBI Gene Expression Omnibus under the accession number GSE123143.

LIMITATIONS REASONS FOR CAUTION

Although the combination of mouse ART utilised in this study consisted of techniques commonly used in human fertility clinics, there may be species differences. Therefore, human studies, designed to determine the optimal levels of folic acid supplementation for ART pregnancies, and taking into account foetal sex, are warranted.

WIDER IMPLICATIONS OF THE FINDINGS

Taken together, our findings support moderation in the dose of folic acid supplements taken during ART.

STUDY FUNDING/COMPETING INTEREST(S)

This work was funded by the Canadian Institutes of Health Research (FDN-148425). The authors declare no conflict of interest.

Paternal Folate Status and Sperm Quality, Pregnancy Outcomes, and Epigenetics: A Systematic Review and Meta-Analysis

SCOPE

The effectiveness of maternal folate in reducing the risk of congenital malformations during pregnancy is well established. However, the role of the paternal folate status is scarcely investigated. The aim of this study is to investigate the evidence of associations between the paternal folate status and sperm quality, sperm epigenome, and pregnancy outcomes.

METHODS AND RESULTS

Databases are searched up to December 2017 resulting in 3682 articles, of which 23 are retrieved for full-text assessment. Four out of thirteen human and two out of four animal studies show positive associations between folate concentrations and sperm parameters. An additional meta-analysis of four randomized controlled trials in subfertile men shows that the sperm concentration increases (3.54 95% confidence interval (CI) [-1.40 to 8.48]) after 3-6 months of 5 mg folic acid use per day compared to controls. Moreover, two out of two animal and one out of three human studies show significant alterations in the overall methylation of the sperm epigenome. One animal and one human study show associations between low folate intake and an increased risk of congenital malformations.

CONCLUSIONS

This systematic review and meta-analysis shows evidence of associations between paternal folate status and sperm quality, fertility, congenital malformations, and placental weight.

Prenatal Exposure to Environmentally-Relevant Contaminants Perturbs Male Reproductive Parameters Across Multiple Generations that are Partially Protected by Folic Acid Supplementation

The paternal environment is thought to influence sperm quality and future progeny may also be impacted. We hypothesized that prenatal exposure to environmentally-relevant contaminants impairs male reproduction, altering embryo gene expression over multiple generations. Folic acid (FA) can improve sperm quality and pregnancy outcomes, thus we further hypothesized that FA mitigates the contaminants. Sprague-Dawley F0 female rats treated with persistent organic pollutants (POPs) or corn oil and fed basal or supplemented FA diets, then used to yield four generations of litters. Only F0 females received POPs and/or FA treatments. In utero POPs exposure altered sperm parameters in F1, which were partly rescued by FA supplementation. Paternal exposure to POPs reduced sperm quality in F2 males, and the fertility of F3 males was modified by both POPs and FA. Ancestral FA supplementation improved sperm parameters of F4 males, while the POPs effect diminished. Intriguingly, F3 males had the poorest pregnancy outcomes and generated the embryos with the most significantly differentially expressed genes. Early-life exposure to POPs harms male reproduction across multiple generations. FA supplementation partly mitigated the impact of POPs. The two-cell embryo transcriptome is susceptible to paternal environment and could be the foundation for later pregnancy outcomes.

Maternal folic acid supplementation does not counteract the deleterious impact of prenatal exposure to environmental pollutants on lipid homeostasis in male rat descendants

Prenatal exposure to persistent organic pollutants (POPs) has been associated with the development of metabolic syndrome-related diseases in offspring. According to epidemiological studies, father’s transmission of environmental effects in addition to mother’s can influence offspring health. Moreover, maternal prenatal dietary folic acid (FA) may beneficially impact offspring health. The objective is to investigate whether prenatal FA supplementation can overcome the deleterious effects of prenatal exposure to POPs on lipid homeostasis and inflammation in three generations of male rat descendants through the paternal lineage. Female Sprague-Dawley rats (F0) were exposed to a POPs mixture (or corn oil) +/− FA supplementation for 9 weeks before and during gestation. F1 and F2 males were mated with untreated females. Plasma and hepatic lipids were measured in F1, F2, and F3 males after 12-h fast. Gene expression of inflammatory cytokines was determined by qPCR in epididymal adipose tissue. In F1 males, prenatal POPs exposure increased plasma lipids at 14 weeks old and hepatic lipids at 28 weeks old and prenatal FA supplementation decreased plasma total cholesterol at 14 weeks old. Prenatal POPs exposure decreased plasma triglycerides at 14 weeks old in F2 males. No change was observed in inflammatory markers. Our results show an impact of the paternal lineage on lipid homeostasis in rats up to the F2 male generation. FA supplementation of the F0 diet, regardless of POPs exposure, lowered plasma cholesterol in F1 males but failed to attenuate the deleterious effects of prenatal POPs exposure on plasma and hepatic lipids in F1 males.

Measured with Sperm Chromatin Dispersion (SCD) Technique: Will DNA Integrity in Spermatozoa Increase After Micronutrient Supplementation? Comparative Controlled Study

Background: An elevated DNA Fragmentation Index (DFI) has been associated with male infertility; therefore measuring the sperm nuclear DNA integrity appears to be useful in predicting the ability of spermatozoa to fertilize oocytes.

Aim: To evaluate the effect of micronutrient supplementation over DFI values in subfertile men.

Methods: This was a retrospective/comparative study that included a total of 306 subfertile males consulting the clinic from March 2011 to November 2017, who had performed the Sperm Chromatin Dispersion test (SCD) — a method used to detect DNA fragmentation — along with the initial semen analysis. Of the included population, [Formula: see text] 146 had received two daily oral capsules of a standardized combined micronutrient compound ([Formula: see text], Lenus Pharma, Vienna, Austria) for three months plus lifestyle change (study group). Each capsule contains L-carnitine, L-arginine, coenzyme Q10, zinc, vitamin E, folic acid, glutathione and selenium. Those who did not receive the active treatment ([Formula: see text] 160) but only engaged with lifestyle changes were considered controls. The SCD test was performed in both groups at baseline and after 3 months.

Results: For the first statistical analysis, patients with an initial mean DFI of >15% were considered ([Formula: see text] 66 [37 were study and 29 were controls]). After 3 months, both groups displayed a significant decrease of mean DFI values. However, this decrease was more evident in the study group as compared to controls (10.54% vs. 14.48%, [Formula: see text] 0.05; [Formula: see text] 0.013). For the second statistical approach the entire population was considered ([Formula: see text] 306). After 3 months, only the study group displayed a significant decrease of the mean initial DFI value (10.16% to 6.49%, [Formula: see text] < 0.0001); decrease that was more evident as compared to controls (6.49% vs. 8.82%, [Formula: see text] 0.05; [Formula: see text] 0.000020).

Conclusions: Among subfertile men with a DFI >15%, both regimes significantly decreased sperm DNA fragmentation; however, when any baseline DFI value was considered, only treatment with the active standardized micronutrient compound achieved a significant better result.

Folate deficiency increases chromosomal damage and mutations in hematopoietic cells in the transgenic mutamouse model

Folate deficiency causes megaloblastic anemia and neural tube defects, and is also associated with some cancers. In vitro, folate deficiency increases mutation frequency and genome instability, as well as exacerbates the mutagenic potential of known environmental mutagens. Conversely, it remains unclear whether or not elevated folic acid (FA) intakes are beneficial or detrimental to the induction of DNA mutations and by proxy human health. We used the MutaMouse transgenic model to examine the in vivo effects of FA deficient, control, and supplemented diets on somatic DNA mutant frequency (MF) and genome instability in hematopoietic cells. We also examined the interaction between FA intake and exposure to the known mutagen N-ethyl-N-nitrosourea (ENU) on MF. Male mice were fed the experimental diets for 20 weeks from weaning. Half of the mice from each diet group were gavaged with 50 mg/kg body weight ENU after 10 weeks on diet and remained on their respective diet for an additional 10 weeks. Mice fed a FA-deficient diet had a 1.3-fold increase in normochromatic erythrocyte micronucleus (MN) frequency (P = 0.034), and a doubling of bone marrow lacZ MF (P = 0.035), compared to control-fed mice. Mice exposed to ENU showed significantly higher bone marrow lacZ and Pig-a MF, but there was no effect of FA intake on ENU-induced MF. These data indicate that FA deficiency increases mutations and MN formation in highly proliferative somatic cells, but that FA intake does not mitigate ENU-induced mutations. Also, FA intake above adequacy had no beneficial or detrimental effect on mutations or MN formation. Environ. Mol. Mutagen. 59:366-374, 2018. © 2018 Her Majesty the Queen in Right of Canada 2018.

Dose-response mutation and spectrum analyses reveal similar responses at two microsatellite loci in benzo(a)pyrene-exposed mouse spermatogonia

Identifying chemical exposures that can cause germline mutations is important as these mutations can be inherited, impacting both individual and population health. However, germline mutations are extremely rare and difficult to detect. Chemically induced germline mutations can be detected through analysis of highly unstable tandem repeat DNA. We recently developed a single-molecule PCR (SM-PCR) approach to quantify mutations at a mouse microsatellite locus (Mm2.2.1) in sperm for such purposes. In this study, we refine this approach through the combined analysis of mouse microsatellites Mm2.2.1 and Mm19.2.3. Mice were exposed to 0, 25, 50 or 100 mg/kg/day benzo(a)pyrene (BaP) by oral gavage for 28 days and sperm sampled 42 days after the end of exposure to measure effects on dividing spermatogonia. DNA was diluted to a single genome per PCR well for amplification of microsatellites in singleplex and multiplex reactions, and alleles were sized to identify mutations using capillary electrophoresis. Analysis of ~300-500 molecules per animal at both microsatellite loci, when tested individually, showed a ~2-fold increase in mutations relative to the controls at both the 50 and 100 mg/kg/day BaP doses. Multiplex SM-PCR revealed similar increases in mutation frequencies in both microsatellites. Comparison with results from a previous lacZ mutation assay conducted on the same mice revealed that although microsatellite mutations are a sensitive endpoint for detecting changes in mutation frequencies at lower doses, they appear to be saturable and thus have a reduced dynamic range. These results confirm that BaP is a male germ cell mutagen that broadly impacts tandem repeat DNA. Likewise, addition of a second hypervariable microsatellite increases the sensitivity of this assay.

Intergenerational impact of paternal lifetime exposures to both folic acid deficiency and supplementation on reproductive outcomes and imprinted gene methylation

STUDY QUESTION

Do paternal exposures to folic acid deficient (FD), and/or folic acid supplemented (FS) diets, throughout germ cell development adversely affect male germ cells and consequently offspring health outcomes?

SUMMARY ANSWER

Male mice exposed over their lifetimes to both FD and FS diets showed decreased sperm counts and altered imprinted gene methylation with evidence of transmission of adverse effects to the offspring, including increased postnatal-preweaning mortality and variability in imprinted gene methylation.

WHAT IS KNOWN ALREADY

There is increasing evidence that disruptions in male germ cell epigenetic reprogramming are associated with offspring abnormalities and intergenerational disease. The fetal period is the critical time of DNA methylation pattern acquisition for developing male germ cells and an adequate supply of methyl donors is required. In addition, DNA methylation patterns continue to be remodeled during postnatal spermatogenesis. Previous studies have shown that lifetime (prenatal and postnatal) folic acid deficiency can alter the sperm epigenome and increase the incidence of fetal morphological abnormalities.

STUDY DESIGN, SIZE, DURATION

Female BALB/c mice (F0) were placed on one of four amino-acid defined diets for 4 weeks before pregnancy and throughout pregnancy and lactation: folic acid control (Ctrl; 2 mg/kg), 7-fold folic acid deficient (7FD; 0.3 mg/kg), 10-fold high FS (10FS, 20 mg/kg) or 20-fold high FS (20FS, 40 mg/kg) diets. F1 males were weaned to their respective prenatal diets to allow for diet exposure during all windows of germline epigenetic reprogramming: the erasure, re-establishment and maintenance phases.

PARTICIPANTS/MATERIALS, SETTINGS, METHODS

F0 females were mated with chow-fed males to produce F1 litters whose germ cells were exposed to the diets throughout embryonic development. F1 males were subsequently mated with chow-fed female mice. Two F2 litters, unexposed to the experimental diets, were generated from each F1 male; one litter was collected at embryonic day (E)18.5 and one delivered and followed postnatally. DNA methylation at a global level and at the differentially methylated regions of imprinted genes (H19, Imprinted Maternally Expressed Transcript (Non-Protein Coding)-H19, Small Nuclear Ribonucleoprotein Polypeptide N-Snrpn, KCNQ1 Opposite Strand/Antisense Transcript 1 (Non-Protein Coding)-Kcnq1ot1, Paternally Expressed Gene 1-Peg1 and Paternally Expressed Gene 3-Peg3) was assessed by luminometric methylation analysis and bisulfite pyrosequencing, respectively, in F1 sperm, F2 E18.5 placenta and F2 E18.5 brain cortex.

MAIN RESULTS AND THE ROLE OF CHANCE

F1 males exhibited lower sperm counts following lifetime exposure to both folic acid deficiency and the highest dose of folic acid supplementation (20FS), (both P < 0.05). Post-implantation losses were increased amongst F2 E18.5 day litters from 20FS exposed F1 males (P < 0.05). F2 litters derived from both 7FD and 20FS exposed F1 males had significantly higher postnatal-preweaning pup death (both P < 0.05). Sperm from 10FS exposed males had increased variance in methylation across imprinted gene H19, P < 0.05; increased variance at a few sites within H19 was also found for the 7FD and 20FS groups (P < 0.05). While the 20FS diet resulted in inter-individual alterations in methylation across the imprinted genes Snrpn and Peg3 in F2 E18.5 placenta, ≥50% of individual sites tested in Peg1 and/or Peg3 were affected in the 7FD and 10FS groups. Inter-individual alterations in Peg1 methylation were found in F2 E18.5 day 10FS group brain cortex (P < 0.05).

LARGE SCALE DATA

Not applicable.

LIMITATIONS REASONS FOR CAUTION

The cause of the increase in postnatal-preweaning mortality was not investigated post-mortem. Further studies are required to understand the mechanisms underlying the adverse effects of folic acid deficiency and supplementation on developing male germ cells. Genome-wide DNA and histone methylome studies as well as gene expression studies are required to better understand the links between folic acid exposures, an altered germ cell epigenome and offspring outcomes.

WIDER IMPLICATIONS OF THE FINDINGS

The findings of this study provide further support for paternally transmitted environmental effects. The results indicate that both folic acid deficiency and high dose supplementation can be detrimental to germ cell development and reproductive fitness, in part by altering DNA methylation in sperm.

STUDY FUNDING AND COMPETING INTERESTS

This study was supported by a grant to J.M.T. from the Canadian Institutes of Health Research (CIHR #89944). The authors declare they have no conflicts of interest.

Effect of folate deficiency on promoter methylation and gene expression of Esr1, Cav1, and Elavl1, and its influence on spermatogenesis

This study aims to investigate the effect of folate deficiency on the male reproductive function and the underlying mechanism. A total of 269 screened participants from 421 recruitments were enrolled in this study. An animal model of folate deficiency was constructed. Folate concentration was measured in the ejaculate, and its association with semen parameters was then determined. The expression and promoter methylation status of ESR1, CAV1, and ELAVL1 were also evaluated. Results showed that seminal plasma folate level was significantly lower among subjects with azoospermia than those with normozoospermia. Low folate level was significantly correlated with low sperm concentration in men with normozoospermia. Folate deficiency significantly reduced the expression of ESR1, CAV1, and ELAVL1, which are critical to spermatogenesis. However, low folate levels did not increase the methylation levels of the promoter regions of ESR1, CAV1, and ELAVL1 in human sperm DNA. Thus, folate deficiency impairs spermatogenesis may partly due to inhibiting the expression of these genes. Thus future research should determine the significance of sufficient folate status in male fertilization and subsequent pregnancy outcomes.

Programmed for sex: Nutrition–reproduction relationships from an inter-generational perspective

Reproduction is our biological reason for being. Our physiology has been shaped via countless millennia of evolution with this one purpose in mind, so that at birth we are ‘programmed for sex’, although this will not kick-start functionally until puberty. Our development from an early embryo is focused on making us fit to reproduce and is intimately connected to nutrition and energy stores. Fluctuations in food supply has probably been a key evolutionary shaper of the reproductive process, and this review hypothesizes that we have developed rapid, non-genomic adaptive mechanisms to such fluctuations to better fit offspring to their perceived (nutritional) environment, thus giving them a reproductive advantage. There is abundant evidence for this notion from ‘fetal programming’ studies and from experimental ‘inter-generational’ studies involving manipulation of parental (especially paternal) diet and then examining metabolic changes in resulting offspring. It is argued that the epigenetic reprogramming of germ cells that occurs during fetal life, after fertilisation and during gametogenesis provides opportunities for sensing of the (nutritional) environment so as to affect adaptive epigenetic changes to alter offspring metabolic function. In this regard, there may be adverse effects of a modern Western diet, perhaps because it is deficient in plant-derived factors that are proven to be capable of altering the epigenome, folate being a prime example; we have evolved in tune with such factors. Therefore, parental and even grandparental diets may have consequences for health of future generations, but how important this might be and the precise epigenetic mechanisms involved are unknown.

Role of Antioxidants in Assisted Reproductive Techniques

Oxidative stress (OS) has been recognized as a significant cause of suboptimal assisted reproductive outcome. Many of the sperm preparation and manipulation procedures that are necessary in the in vitro environment can result in excessive production of reactive oxygen species (ROS) thereby exposing the gametes and growing embryos to significant oxidative damage. Antioxidants have long been utilized in the management of male subfertility as they can counterbalance the elevated levels of ROS inducing a high state of OS. Few studies have looked into the clinical effectiveness of antioxidants in patients undergoing assisted reproduction. While an overall favorable outcome has been perceived, the specific clinical indication and optimal antioxidant regimen remain unknown. The goal of our review is to explore the sources of ROS in the in vitro environment and provide a clinical scenario-based approach to identify the circumstances where antioxidant supplementation is most beneficial to enhance the outcome of assisted reproduction.

The basis for folinic acid treatment in neuro-psychiatric disorders

Multiple factors such as genetic and extraneous causes (drugs, toxins, adverse psychological events) contribute to neuro-psychiatric conditions. In a subgroup of these disorders, systemic folate deficiency has been associated with macrocytic anemia and neuropsychiatric phenotypes. In some of these, despite normal systemic levels, folate transport to the brain is impaired in the so-called cerebral folate deficiency (CFD) syndromes presenting as developmental and psychiatric disorders. These include infantile-onset CFD syndrome, infantile autism with or without neurologic deficits, a spastic-ataxic syndrome and intractable epilepsy in young children expanding to refractory schizophrenia in adolescents, and finally treatment-resistant major depression in adults. Folate receptor alpha (FRα) autoimmunity with low CSF N(5)-methyl-tetrahydrofolate (MTHF) underlies most CFD syndromes, whereas FRα gene abnormalities and mitochondrial gene defects are rarely found. The age at which FRα antibodies of the blocking type emerge, determines the clinical phenotype. Infantile CFD syndrome and autism with neurological deficits tend to be characterized by elevated FRα antibody titers and low CSF MTHF. In contrast, in infantile autism and intractable schizophrenia, abnormal behavioral signs and symptoms may wax and wane with fluctuating FRα antibody titers over time accompanied by cycling changes in CSF folate, tetrahydrobiopterin (BH4) and neurotransmitter metabolites ranging between low and normal levels. We propose a hypothetical model explaining the pathogenesis of schizophrenia. Based on findings from clinical, genetic, spinal fluid and MRI spectroscopic studies, we discuss the neurochemical changes associated with these disorders, metabolic and regulatory pathways, synthesis and catabolism of neurotransmitters, and the impact of oxidative stress on the pathogenesis of these conditions. A diagnostic algorithm and therapeutic regimens using high dose folinic acid, corticosteroids and milk-free diet is presented which has proven to be beneficial in providing adequate folate to the brain and decreasing the FRα autoantibody titer in those positive for the antibody.

Development of the adverse outcome pathway "alkylation of DNA in male premeiotic germ cells leading to heritable mutations" using the OECD's users' handbook supplement

The Organisation for Economic Cooperation and Development's (OECD) Adverse Outcome Pathway (AOP) programme aims to develop a knowledgebase of all known pathways of toxicity that lead to adverse effects in humans and ecosystems. A Users' Handbook was recently released to provide supplementary guidance on AOP development. This article describes one AOP-alkylation of DNA in male premeiotic germ cells leading to heritable mutations. This outcome is an important regulatory endpoint. The AOP describes the biological plausibility and empirical evidence supporting that compounds capable of alkylating DNA cause germ cell mutations and subsequent mutations in the offspring of exposed males. Alkyl adducts are subject to DNA repair; however, at high doses the repair machinery becomes saturated. Lack of repair leads to replication of alkylated DNA and ensuing mutations in male premeiotic germ cells. Mutations that do not impair spermatogenesis persist and eventually are present in mature sperm. Thus, the mutations are transmitted to the offspring. Although there are some gaps in empirical support and evidence for essentiality of the key events for certain aspects of this AOP, the overall AOP is generally accepted as dogma and applies broadly to any species that produces sperm. The AOP was developed and used in an iterative process to test and refine the Users' Handbook, and is one of the first publicly available AOPs. It is our hope that this AOP will be leveraged to develop other AOPs in this field to advance method development, computational models to predict germ cell effects, and integrated testing strategies.

Dietary folic acid protects against genotoxicity in the red blood cells of mice

Folate is an essential B vitamin required for the de novo synthesis of purines, thymidylate and methionine. Folate deficiency can lead to mutations and genome instability, and has been shown to exacerbate the genotoxic potential of environmental toxins. We hypothesized that a folic acid (FA) deficient diet would induce genotoxicity in mice as measured by the Pig-a mutant phenotype (CD24-) and micronuclei (MN) in reticulocytes (RET) and red blood cells/normochromatic erythrocytes (RBC/NCE). Male Balb/c mice were fed a FA deficient (0 mg/kg), control (2 mg/kg) or supplemented (6 mg/kg) diet from weaning for 18 wk. Mice fed the deficient diet had 70% lower liver folate (p < 0.001), 1.8 fold higher MN-RET (p < 0.001), and 1.5 fold higher MN-NCE (p < 0.001) than mice fed the control diet. RET(CD24-) and RBC(CD24-) frequencies were not different between mice fed the deficient and control diets. Compared to mice fed the FA supplemented diet, mice fed the deficient diet had 73% lower liver folate (p < 0.001), a 2.0 fold increase in MN-RET (p < 0.001), a 1.6 fold increase in MN-NCE (p < 0.001) and 3.8 fold increase in RBC(CD24-) frequency (p = 0.011). RET(CD24-) frequency did not differ between mice fed the deficient and supplemented diets. Our data suggest that FA adequacy protects against mutagenesis at the Pig-a locus and MN induction in the red blood cells of mice.

Single-molecule PCR analysis of an unstable microsatellite for detecting mutations in sperm of mice exposed to chemical mutagens

Single-molecule PCR (SM-PCR) analysis of long and repetitive DNA sequences, known as expanded simple tandem repeats (ESTRs), has been the most efficient method for studying germline mutation induction in endogenous sequences to date. However, the long length of these sequences makes mutation detection imprecise and laborious, and they have been characterized only in mice. Here, we explore the use of unstable microsatellite sequences that can be typed with high precision by capillary electrophoresis as alternative loci for detecting germline mutations. We screened 24 microsatellite loci across inbred mouse strains and identified Mm2.2.1 as the most polymorphic microsatellite locus. We then optimized SM-PCR of Mm2.2.1 to detect mutations in sperm. SM-PCR analysis of sperm from untreated B6C3F1 and Muta(™)Mouse samples revealed mutation frequencies that are consistent with rates derived from family pedigree analysis (∼ 5 × 10(-3)). To determine whether this locus can be used to detect chemically induced germline mutations, Muta(™)Mouse males were exposed by oral gavage to a single dose of 100mg/kg of N-ethyl-N-nitrosourea (ENU) or to 100mg/kg of benzo(a)pyrene (BaP) for 28 days alongside vehicle treated controls. Sperm were collected 10 weeks post-ENU exposure to sample sperm exposed as spermatogonial stem cells and 6 weeks post-BaP exposure to sample sperm that were dividing spermatogonia when the exposure was terminated. Both treatments resulted in a significant (approximately 2-fold) increase in mutation frequency in sperm compared to the control animals. The work establishes the utility of this microsatellite for studying mutation induction in the germ cells of mice. Because microsatellites are found in virtually every species, this approach holds promise for other organisms, including humans.

Parental diet, pregnancy outcomes and offspring health: metabolic determinants in developing oocytes and embryos

The periconceptional period, embracing the terminal stages of oocyte growth and post-fertilisation development up to implantation, is sensitive to parental nutrition. Deficiencies or excesses in a range of macro- and micronutrients during this period can lead to impairments in fertility, fetal development and long-term offspring health. Obesity and genotype-related differences in regional adiposity are associated with impaired liver function and insulin resistance, and contribute to fatty acid-mediated impairments in sperm viability and oocyte and embryo quality, all of which are associated with endoplasmic reticulum stress and compromised fertility. Disturbances to maternal protein metabolism can elevate ammonium concentrations in reproductive tissues and disturb embryo and fetal development. Associated with this are disturbances to one-carbon metabolism, which can lead to epigenetic modifications to DNA and associated proteins in offspring that are both insulin resistant and hypertensive. Many enzymes involved in epigenetic gene regulation use metabolic cosubstrates (e.g. acetyl CoA and S-adenosyl methionine) to modify DNA and associated proteins, and so act as 'metabolic sensors' providing a link between parental nutritional status and gene regulation. Separate to their genomic contribution, spermatozoa can also influence embryo development via direct interactions with the egg and by seminal plasma components that act on oviductal and uterine tissues.

The micronutrient supplements, zinc sulphate and folic acid, did not ameliorate sperm functional parameters in oligoasthenoteratozoospermic men

We investigated the effects of folic acid and zinc sulphate supplementation on the improvement of sperm function in subfertile oligoasthenoteratozoospermic (OAT) men. Eighty-three OAT men participated in a 16-week intervention randomised, double-blind clinical trial with daily treatment of folic acid (5 mg day(-1) ) and zinc sulphate (220 mg day(-1) ), or placebo. Before and after treatment, semen and blood samples were obtained for determining sperm concentration, motility, and morphology, sperm viability, sperm mitochondrial function, sperm chromatin status using toluidine blue, aniline blue, acridine orange and chromomycin A3 staining; and semen and blood folate, zinc, B12 , total antioxidant capacity (TAC) and malondialdehyde (MDA) concentrations. Sperm concentration (×10(6)  ml(-1) ) increased in subfertile men receiving the combined treatment of folic acid and zinc sulphate and also in the group receiving only folic acid treatment; however, it was not statistically significant (P = 0.056 and P = 0.05, respectively). Sperm chromatin integrity (%) increased significantly in subfertile men receiving only zinc sulphate treatment (P = 0.048). However, this improvement in sperm quality was not significant after adjusting placebo effect. This study showed that zinc sulphate and folic acid supplementation did not ameliorate sperm quality in infertile men with severely compromised sperm parameters, OAT. Male infertility is a multifactorial disorder, and also nutritional factors play an important role in results of administration of supplementation on sperm parameters. However, these results should be confirmed by multiple studies in larger populations of OAT men.