The intracellular concentration of homocysteine and related thiols is negatively correlated to sperm quality after highly effective method of sperm lysis

Machine learning approach to assess the association between anthropometric, metabolic, and nutritional status and semen parameters

Many lifestyle factors, such as nutritional imbalance leading to obesity, metabolic disorders, and nutritional deficiency, have been identified as potential risk factors for male infertility. The aim of this study was to evaluate the relationship between semen parameters and anthropometric, metabolic and nutritional parameters. Relationship was first assessed individually, then after the application of a previously constructed and validated machine learning score that allows their combination. Anthropometric, metabolic, antioxidant, micronutrient, and sperm parameters from 75 men suffering from idiopathic infertility from four infertility centers in France (Jean-Verdier ART Center Hospital, Bondy; North Hospital ART Center, Saint-Étienne; Navarre Polyclinic ART Center, Pau; and Cochin Hospital ART Center, Paris) between September 2009 and December 2013 were collected. After assessing standard correlation analysis, a previously built machine learning model, providing a score ranging from 0 (the poorest) to 1 (the most favorable), was calculated for each man in the study cohort. This machine learning model, which separates infertile/fertile men with unexplained infertility on the basis of their bioclinical signature, provides a more holistic evaluation of the influence of the considered markers (anthropometric, metabolic, and oxidative status). We observed a significant correlation of some anthropometric, metabolic, and nutritional disorders with some sperm characteristics. Moreover, an unfavorable machine learning score was associated with a high level of sperm DNA fragmentation. Favorable anthropometric, metabolic, and oxidative patterns, which may reflect an appropriate lifestyle, appear to positively impact overall health, in particular reproductive function. This study, consistent with previous publications, suggests that beyond semen quality parameters, in an essential assessment of male fertility, other key factors should be taken into account. In this regard, the application of emerging artificial intelligence techniques may provide a unique opportunity to integrate all these parameters and deliver personalized care.

Study of Correlation between Serum Vitamin B12 Level and Aberrant DNA Methylation in Infertile Males

Introduction

Altered DNA methylation pattern in sperms has been associated with infertility in males demonstrating defective spermatogenesis or low semen quality. Vitamin B-12, by affecting 1-carbon metabolism pathways, might alter the DNA methylation pattern. We aimed to study the correlation of serum vitamin B12 levels with aberrant DNA methylation in infertile male patients.

Methods

A cross-sectional study was conducted on 17 oligozoospermic infertile males (WHO criteria, 2010) and 10 healthy fertile males. Serum vitamin B12 levels were estimated using the chemiluminescence method. Global methylation was determined using the ELISA system (Imprint Methylated DNA Quantification Kit, Sigma-Aldrich). The levels of global DNA methylation were calculated and compared relative to the methylated (100%) control DNA provided with the kit.

Results

Mean serum vitamin B12 concentration in the control group was higher than that of the case group. This difference in serum vitamin B12 concentration in both groups was found statistically significant. Although the results of this study show that oligozoospermic men have relatively lower global DNA methylation as compared to normozoospermic control, the values could not reach a statistically significant level. A small positive correlation was found between serum vitamin B12 levels and percent methylation defect (r = 0.14) but was statistically insignificant.

Conclusion

Our study concludes that oligozoospermic infertile males have a significant deficiency of vitamin B12 as compared to normozoospermic fertile males. This study did not find any significant difference in global DNA methylation between the two groups. The present study does not suggest any correlation between serum vitamin B12 level and percent DNA methylation.

Identification of genes related to sexual differentiation and sterility in embryonic gonads of Mule ducks by transcriptome analysis

The key genes of avian gonadal development are of great significance for sex determination. Transcriptome sequencing analysis of Mule duck gonad as potential sterile model is expected to screen candidate genes related to avian gonad development. In this study, the embryonic gonadal tissues of Mule ducks, Jinding ducks, and Muscovy ducks were collected and identified. Six sample groups including female Mule duck (A), male Mule duck (B), female Jinding duck (C), male Jinding duck (D), female Muscovy duck (E), and male Muscovy duck (F) were subjected to RNA sequencing analysis. A total of 9,471 differential genes (DEGs) and 691 protein-protein interaction pairs were obtained. Totally, 12 genes (Dmrt1, Amh, Sox9, Tex14, Trim71, Slc26a8, Spam1, Tdrp, Tsga10, Boc, Cxcl14, and Hsd17b3) were identified to be specifically related to duck testicular development, and 11 genes (Hsd17b1, Cyp19a1, Cyp17a1, Hhipl2, Tdrp, Uts2r, Cdon, Axin2, Nxph1, Brinp2, and Brinp3) were specifically related to duck ovarian development. Seven genes (Stra8, Dmc1, Terb1, Tex14, Tsga10, Spam1, and Plcd4) were screened to be specifically involved in the female sterility of Mule ducks; eight genes (Gtsf1, Nalcn, Tat, Slc26a8, Kmo, Plcd4, Aldh4a1, and Hgd) were specifically involved in male sterility; and five genes (Terb1, Stra8, Tex14 Tsga10 and Spam1) were involved in both female and male sterility. This study provides an insight into the differential development between male and female gonads of ducks and the sterility mechanism of Mule ducks through function, pathway, and protein interaction analyses. Our findings provide theoretical basis for the further research on sex determination and differentiation of birds and the sterility of Mule ducks.

Boar semen cryopreserved with trehalose-containing liposomes: disaccharide determination and rheological behaviour

This study aimed to detect intracellular trehalose in boar sperm that were cryopreserved with liposomes and conduct an analysis of its effects on some characteristics of thawed sperm, including rheological properties. First, soybean lecithin cholesterol-based liposomes were produced and characterized in the presence of 300 mM trehalose. Next, semen samples were frozen in two freezing media: a control medium with 300 mM trehalose and an experimental medium supplemented with 300 mM trehalose and 10% liposomes, both of which were thawed and then studied to ascertain their integrity, motility, rheological response, and trehalose quantities by testing two methods of spermatic lysis via high-performance liquid chromatography with an evaporative light-scattering detector (HPLC-ELSD). The results found spherical liposomes measuring 357 nm that were relatively stable in an aqueous medium and had an entrapment efficiency of 73%. An analysis of the cryopreserved ejaculates showed that their viability and motility did not significantly differ between groups (P > 0.05). The viscous response of the samples was influenced by the extracellular medium rather than by the freezing–thawing process, which resulted in a loss of interaction between the cells and cryoprotectants. Finally, intracellular trehalose levels were determined using HPLC-ELSD, with no differences observed (P > 0.05) when comparing both sperm lysis methods. The use of liposomes with trehalose appears to be a promising option for boar semen cryopreservation, with a marked effect on rheological properties. The proposed HPLC-ELSD method was effective for measuring trehalose in cryopreserved cell samples.

Association of methyltetrahydrofolate reductase gene mutation, homocysteine level with semen quality of Iraqi infertile males

Background

Infertility is very common condition and almost 50% of cases are due to male factors. Several genetic and environmental factors are responsible for the poor quality and reduced number of sperms in several cases of infertility. The present study was designed to investigate the association between semen parameters, homocysteine, and the risk of C677T polymorphism of MTHFR gene in infertile males of Iraqi population.

Methods

This Case–control study has been conducted from February 2019 to July 2021 at a molecular laboratory in the Anatomy and Histology Department/college of Medicine/University of Kufa/Najaf/Iraq. It was composed of 353 infertile male patients. They were divided into five groups: 90 azoospermic, 84 oligospermia, 64 asthenospermic, 50 oligoasthenospermic, and 65 teratospermic with an age range 20–46 years compared with 100 fertile males as control with age range 21–49 years. In order to detect homocysteine levels, we used Hcy ELISA Kit. C677T mutation of MTHFR gene was employed by PCR–RFLP technique.

Results

Our data revealed three genotypes of MTHFR C677T, 167 (47.3%) subjects had CC genotype, 116 (32.9%) subjects had CT genotype and 70 (21.1%) subjects had TT genotype. Furthermore, T allele was associated with higher risk of infertility in all patients groups for any genetic model. In total infertile subjects (codominant model: CT vs. CC, OR = 2.0, 95% C.I = 1.2–3.3, P = 0.011; TT vs. CC, OR = 4.8, 95% C.I = 3.3–8.2, P = 0.0003; dominant model: CT + TT vs. CC, OR = 2.8, 95% C.I = 1.7–4.5, P = 0.0001). Oligoasthenospermic patients associated with higher risk in CT heterozygous genotype (OR = 2.8, 95% C.I = 1.0–4.9, P = 0.03) and TT homozygous of mutant allele (OR = 6.3, 95% C.I = 1.9–9.2, P = 0.002). Homocystein level was elevated in all infertile groups when compared with control group (P < 0.01), but the elevation was marked in oligoasthenospermia group. As well as, the level of Serum Hcy exhibited the highest value in TT mutant genotype (39.7 µmol/ml) followed by CT genotype (28.5 µmol/ml) while the lowest level of Hcy recorded in CC genotype (14.6 µmol/ml) for oligoasthenospermia group.

Conclusions

By relating the MTHFR C677T gene mutation with a higher homocystein level, the results showed that Iraqi males with this mutation are more likely to suffer from infertility.

Sperm DNA damage and seminal antioxidant activity in subfertile men

Supraphysiological ROS levels can lead to apoptosis, lipid peroxidation, and DNA and protein damage. This pilot study aimed to investigate the sperm oxidative damage in subfertile men, to describe the relationship between the antioxidant system and ROS. Sixty-four semen samples were categorised according to the evaluated routine parameters (WHO, WHO laboratory manual for the examination and processing of human semen, 2010). Results were cross-referenced with the DNA damage [Comet (n = 53) and TUNEL (n = 49) assays], antioxidant enzyme activity [SOD (n = 51), CAT (n = 48) and GST (n = 48)], and content of total thiols (n = 36), lipid hydroperoxides (n = 35) and MDA (n = 31). Compared to pathospermic samples, normozoospermic presented 40%-45% fewer spermatozoa with fragmented DNA, 19% fewer hydroperoxides, and slightly higher total thiols and MDA levels. Asthenozoospermic/asthenoteratozoospermic samples had the lowest GST activity. SOD and CAT showed a similar trend. Our results evidenced significant positive correlations between DNA damage and immotile spermatozoa; SOD and CAT, GST and total thiols; CAT and GST; total thiols and sperm concentration; and MDA levels and head/midpiece abnormalities and hydroperoxides. This work contributes to the existing body of knowledge by showing that the oxidative status correlates with the classic sperm analysis parameters. Oxidative stress and DNA damage evaluation might be a valuable diagnostic and prognostic tool in cases of idiopathic male subfertility.

Nutrition, genetic variation and male fertility

Infertility affects nearly 50 million couples worldwide, with 40-50% of cases having a male factor component. It is well established that nutritional status impacts reproductive development, health and function, although the exact mechanisms have not been fully elucidated. Genetic variation that affects nutrient metabolism may impact fertility through nutrigenetic mechanisms. This review summarizes current knowledge on the role of several dietary components (vitamins A, B₁₂, C, D, E, folate, betaine, choline, calcium, iron, caffeine, fiber, sugar, dietary fat, and gluten) in male reproductive health. Evidence of gene-nutrient interactions and their potential effect on fertility is also examined. Understanding the relationship between genetic variation, nutrition and male fertility is key to developing personalized, DNA-based dietary recommendations to enhance the fertility of men who have difficulty conceiving.

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.

Antioxidant-Based Therapies in Male Infertility: Do We Have Sufficient Evidence Supporting Their Effectiveness?

Under physiological conditions, reactive oxygen species (ROS) play pivotal roles in various processes of human spermatozoa. Indeed, semen requires the intervention of ROS to accomplish different stages of its maturation. However, ROS overproduction is a well-documented phenomenon occurring in the semen of infertile males, potentially causing permanent oxidative damages to a vast number of biological molecules (proteins, nucleic acids, polyunsaturated fatty acids of biological membrane lipids), negatively affecting the functionality and vitality of spermatozoa. ROS overproduction may concomitantly occur to the excess generation of reactive nitrogen species (RNS), leading to oxidative/nitrosative stress and frequently encountered in various human pathologies. Under different conditions of male infertility, very frequently accompanied by morpho-functional anomalies in the sperm analysis, several studies have provided evidence for clear biochemical signs of damages to biomolecules caused by oxidative/nitrosative stress. In the last decades, various studies aimed to verify whether antioxidant-based therapies may be beneficial to treat male infertility have been carried out. This review analyzed the results of the studies published during the last ten years on the administration of low-molecular-weight antioxidants to treat male infertility in order to establish whether there is a sufficient number of data to justify antioxidant administration to infertile males. An analysis of the literature showed that only 30 clinical studies tested the effects of the administration of low-molecular-weight antioxidants (administered as a single antioxidant or as a combination of different antioxidants with the addition of vitamins and/or micronutrients) to infertile males. Of these studies, only 33.3% included pregnancy and/or live birth rates as an outcome measure to determine the effects of the therapy. Of these studies, only 4 were case–control studies, and only 2 of them found improvement of the pregnancy rate in the group of antioxidant-treated patients. Additionally, of the 30 studies considered in this review, only 43.3% were case–control studies, 66.7% enrolled a number of patients higher than 40, and 40% carried out the administration of a single antioxidant. Therefore, it appears that further studies are needed to clearly define the usefulness of antioxidant-based therapies to treat male infertility.

Association between serum homocysteine level and unexplained infertility in in vitro fertilization/intracytoplasmic sperm injection (IVF/ICSI): A retrospective, hospital-based, case-control study

Background

Lower serum homocysteine (Hcy) levels are found to correlate with a better chance of clinical pregnancy and better embryo grades in assisted reproductive technology (ART). However, there is little knowledge on the association between Hcy level and unexplained infertility until now.

Methods

A total of 388 infertile women undergoing IVF/ICSI treatments were recruited, including 129 women with unexplained causes (case group) and 259 women with known causes (control group), and the case group was further divided into subgroups A (≤8 μmol/L), B (>8 and <15 μmol/L), and C (≥15 μmol/L) based on the serum Hcy level. The associations between serum Hcy level and IVF/ICSI pregnancy outcomes were examined in infertile women with unknown causes.

Results

A significantly higher serum Hcy level was measured in the case group than in the control group (P = .008). Subgroup analysis revealed a significant difference in the total number of oocytes retrieved among subgroups A, B, and C (P = .031), and no significant difference was seen among these three groups in terms of age, BMI, E₂ level on the hCG day, number of M‐II oocytes, number of fertilized oocytes, or total number of high‐quality embryos (P > .05). Spearman correlation analysis revealed a negative correlation between serum Hcy level and total number of oocytes retrieved (r = −.406, P = .019). Univariate and multivariate linear regression analyses revealed that serum Hcy level had no correlations with any IVF/ICSI outcomes.

Conclusion

Serum Hcy level has no associations with IVF/ICSI pregnancy outcomes.

Correlation between methylenetetrahydrofolate reductase gene polymorphism and oligoasthenospermia and the effects of folic acid supplementation on semen quality

Background

The present study investigated the correlation between 5,10-methylenetetrahydrofolate reductase (MTHFR) C677T polymorphism and oligoasthenospermia, as well as the effects of folic acid supplementation on semen quality.

Methods

The present study was a case control study. The PCR-chip assay was applied to analyze the distribution characteristics of the frequencies and genotypes of the MTHFR C677T allele in 167 Han Chinese patients with idiopathic male infertility (including 86 patients with oligospermia and 81 patients with asthenospermia) and in 78 males with normal semen parameters. Moreover, homocysteine (Hcy) levels were assessed for the different groups. Semen quality was measured following three months of folic acid supplementation for the oligospermia and asthenospermia groups.

Results

The cytosine-thymine (CT) genotype (50% vs. 39.5%) and the thymine-thymine (TT) genotype (51.2% vs. 7.7%) carriers in the oligospermia group exhibited significantly higher percentages compared with those of the control group. The percentage of the CT genotype carriers in the asthenospermia group was significantly higher compared with that of the control group (59.3% vs. 50%), while the frequency of the TT genotype was significantly increased (22.2% vs. 7.7%). Furthermore, serum Hcy levels in the oligospermia and asthenospermia groups were significantly higher compared with those of the control group. The data also demonstrated that sperm density increased significantly following three months of folic acid supplementation to patients with oligospermia or asthenospermia. In these patients, the highest increase was noted for the subjects carrying the TT genotype.

Conclusions

The MTHFR C677T mutation and the elevated Hcy levels are important risk factors for the development of oligoasthenospermia. Folic acid supplementation can significantly improve sperm density.

Effect of cysteine, glutamate and glycine supplementation to in vitro fertilization medium during bovine early embryo development

Glutathione (GSH) is an antioxidant synthesized from three constitutive amino acids (CAA): cysteine (Cys), glycine (Gly) and glutamate (Glu). Glutathione plays an important role in oocyte maturation, fertilization and early embryo development. This study aimed to investigate the effect of Cys (0.6 mM), Gly (0.6 mM) and Glu (0.9 mM) supplementation during in vitro fertilization (IVF) of cattle oocytes. In a Pilot Experiment, de novo synthesis of GSH in bovine zygote was evaluated using a modified TALP medium prepared without MEM-essential and MEM-non-essential amino acids (mTALP): mTALP + CAA (constitutive amino acids); mTALP + CAA+5 mMBSO (buthionine sulfoximide); mTALP + Cys + Gly; mTALP + Cys + Glu and mTALP + Gly + Glu. This evidence led us to investigate the impact of CAA supplementation to TALP medium (with essential and non-essential amino acids) on zygote viability, lipid peroxidation, total intracellular GSH content (include reduced and oxidized form; GSH-GSSG), pronuclear formation in zygotes and subsequent embryo development. IVF media contained a) TALP; b) TALP + Cys + Gly + Glu (TALP + CAA); c) TALP + Cys + Gly; d) TALP + Cys + Glu; e) TALP + Gly + Glu, were used. Total GSH-GSSG concentration was increased in TALP, TALP + CAA, and TALP + Cys + Gly. The viability of zygote was similar among treatments. Lipid peroxidation was increased in zygote fertilized with TALP + Cys + Gly; TALP + Cys + Glu; TALP + Gly + Glu and TALP + CAA. The percentage of penetrated oocytes decreased in TALP + CAA and TALP + Cys + Gly. The cleavage rate was lower in TALP + CAA and TALP + Gly + Glu. The percentage of embryos developing to the blastocyst stage was lower in TALP + Cys + Glu and TALP + CAA. In conclusion, we have demonstrated the synthesis of GSH during IVF. However, Cys, Gly and Glu supplementation to TALP medium had negative effects on embryonic development.

The dynamic metabolomic changes throughout mouse epididymal lumen fluid potentially contribute to sperm maturation

Epididymal lumen fluids are directly responsible for sperm maturation. However, very little is known about the molecular details of small molecule metabolites in the epididymal lumen fluids until now. Here we identified and compared the metabolic profiles of mouse caput and cauda epididymal lumen fluids using GC-MS technique. Among 236 metabolites identified in caput and cauda epididymis, 36 were significantly enriched in caput epididymis while 18 were significantly enriched in cauda epididymis. Pathway analysis identified ascorbate and aldarate metabolism and beta-alanine metabolism as most relevant pathways in caput and cauda epididymis, respectively. Ascorbate, dehydroascorbic acid and beta-alanine associated with these two pathways were firstly reported in mouse epididymal lumen fluids and might play important roles in sperm maturation.

Reactive oxygen species as mediators of sperm capacitation and pathological damage

Oxidative stress plays a major role in the life and death of mammalian spermatozoa. These gametes are professional generators of reactive oxygen species (ROS), which appear to derive from three potential sources: sperm mitochondria, cytosolic L-amino acid oxidases, and plasma membrane Nicotinamide adenine dinucleotide phosphate oxidases. The oxidative stress created via these sources appears to play a significant role in driving the physiological changes associated with sperm capacitation through the stimulation of a cyclic adenosine monophosphate/Protein kinase A phosphorylation cascade, including the activation of Extracellular signal regulated kinase-like proteins, massive up-regulation of tyrosine phosphorylation in the sperm tail, as well as the induction of sterol oxidation. When generated in excess, however, ROS can induce lipid peroxidation that, in turn, disrupts membrane characteristics that are critical for the maintenance of sperm function, including the capacity to fertilize an egg. Furthermore, the lipid aldehydes generated as a consequence of lipid peroxidation bind to proteins in the mitochondrial electron transport chain, triggering yet more ROS generation in a self-perpetuating cycle. The high levels of oxidative stress created as a result of this process ultimately damage the DNA in the sperm nucleus; indeed, DNA damage in the male germ line appears to be predominantly induced oxidatively, reflecting the vulnerability of these cells to such stress. Extensive evaluation of antioxidants that protect the spermatozoa against oxidative stress while permitting the normal reduction-oxidation regulation of sperm capacitation is therefore currently being undertaken, and has already proven efficacious in animal models.

Vitamin B12 and Semen Quality

Various studies have revealed the effects of vitamin B₁₂, also named cobalamin, on semen quality and sperm physiology; however, these studies collectively are still unsummarized. Here, we systematically discuss and summarize the currently understood role of vitamin B₁₂ on semen quality and sperm physiology. We searched the Web of Science, PubMed, and Scopus databases for only English language articles or abstracts from September 1961 to March 2017 (inclusive) using the key words “vitamin B₁₂” and “cobalamin” versus “sperm”. Certain relevant references were included to support the empirical as well as the mechanistic discussions. In conclusion, the mainstream published work demonstrates the positive effects of vitamin B₁₂ on semen quality: first, by increasing sperm count, and by enhancing sperm motility and reducing sperm DNA damage, though there are a few in vivo system studies that have deliberated some adverse effects. The beneficial effects of vitamin B₁₂ on semen quality may be due to increased functionality of reproductive organs, decreased homocysteine toxicity, reduced amounts of generated nitric oxide, decreased levels of oxidative damage to sperm, reduced amount of energy produced by spermatozoa, decreased inflammation-induced semen impairment, and control of nuclear factor-κB activation. However, additional research, mainly clinical, is still needed to confirm these positive effects.