Heavy metal exposure, oxidative stress and semen quality: Exploring associations and mediation effects in reproductive-aged men

Arsenic exposure and oxidative damage to lipid, DNA, and protein among general Chinese adults: A repeated-measures cross-sectional and longitudinal study

Arsenic-related oxidative stress and resultant diseases have attracted global concern, while longitudinal studies are scarce. To assess the relationship between arsenic exposure and systemic oxidative damage, we performed two repeated measures among 5236 observations (4067 participants) in the Wuhan-Zhuhai cohort at the baseline and follow-up after 3 years. Urinary total arsenic, biomarkers of DNA oxidative damage (8-hydroxy-2'-deoxyguanosine (8-OHdG)), lipid peroxidation (8-isoprostaglandin F2alpha (8-isoPGF2α)), and protein oxidative damage (protein carbonyls (PCO)) were detected for all observations. Here we used linear mixed models to estimate the cross-sectional and longitudinal associations between arsenic exposure and oxidative damage. Exposure-response curves were constructed by utilizing the generalized additive mixed models with thin plate regressions. After adjusting for potential confounders, arsenic level was significantly and positively related to the levels of global oxidative damage and their annual increased rates in dose-response manners. In cross-sectional analyses, each 1% increase in arsenic level was associated with a 0.406% (95% confidence interval (CI): 0.379% to 0.433%), 0.360% (0.301% to 0.420%), and 0.079% (0.055% to 0.103%) increase in 8-isoPGF2α, 8-OHdG, and PCO, respectively. More importantly, arsenic was further found to be associated with increased annual change rates of 8-isoPGF2α (β: 0.147; 95% CI: 0.130 to 0.164), 8-OHdG (0.155; 0.118 to 0.192), and PCO (0.050; 0.035 to 0.064) in the longitudinal analyses. Our study suggested that arsenic exposure was not only positively related with global oxidative damage to lipid, DNA, and protein in cross-sectional analyses, but also associated with annual increased rates of these biomarkers in dose-dependent manners.

Cr (VI)-induced ribosomal DNA copy number variation is associated with semen quality impairment: Evidence from human to animal study

OBJECTIVES

This study aimed to analyze the possible role of rDNA copy number variation in the association between hexavalent chromium [Cr (VI)] exposure and semen quality in semen donors and further confirm this association in mice.

METHODS

In this cross-sectional study, whole blood and semen samples were collected from 155 semen donors in the Zhejiang Human Sperm Bank from January 1st to April 31st, 2021. Adult C57BL/6 J male mice were treated with different doses of Cr (VI) (0, 10, or 15 mg/kg b.w./day). Semen quality, including semen volume, total spermatozoa count, sperm concentration, progressive motility, and total motility, were analyzed according to the WHO laboratory manual. Cr concentration was detected using inductively coupled plasma mass spectrometry. The rDNA copy number was measured using qPCR.

RESULTS

In semen donors, whole blood Cr concentration was negatively associated with semen concentration and total sperm counts. Semen 5 S and 45 S rDNA copy numbers were negatively associated with whole blood Cr concentration and whole blood 5.8 S rDNA copy number was negatively associated with semen Cr concentration. In mice, Cr (VI) damaged testicular tissue, decreased semen quality, and caused rDNA copy number variation. Semen quality was related to the rDNA copy number in whole blood, testicular tissue, and semen samples in mice.

CONCLUSION

Cr (VI) was associated with decreased semen quality in semen donors and mice. Our findings suggest an in-depth analysis of the role of the rDNA copy number variation in the Cr (VI)-induced impairment of semen quality.

Testicular protective effects of hesperidin against chemical and biological toxicants

Toxic agents can adversely impact the male reproductive system mainly via activating oxidative stress affecting the seminiferous epithelia, spermatogenesis, sperms, and the testis. Toxic agents lead to the excessive generation of reactive oxygen species (ROS), such as hydroxyl radicals, hydrogen peroxide, and superoxide anions. ROS exert a cytotoxic effect and oxidative damage to nucleic acids, proteins, and membrane lipids. Hesperidin is a pharmacologically active phytoflavone abundantly occurring in citrus fruits, such as oranges and lemons. It has shown various pharmacological properties such as antioxidant, anti-inflammatory, anti-carcinogenic, analgesic, antiviral, anti-coagulant, hypolipidemic, and hypoglycemic effects. Hesperidin has been found to exert protective effects against natural and chemical toxins-induced organ toxicity. Considerable evidence has implicated the testicular protective effects of hesperidin against the toxicological properties of pharmaceutical drugs as well as biological and chemical agents, and in the present review, we discussed, for the first time, the reported studies. The resultant data indicate that hesperidin can exert testicular protective effects through antioxidant properties.

MSC-derived exosomes mitigate cadmium-induced male reproductive injury by ameliorating DNA damage and autophagic flux

Cadmium, an environmental toxicant, severely impairs male reproductive functions and currently lacks effective clinical treatments. Mesenchymal stem cell-derived exosomes (MSC-Exos) are increasingly recognized as a potential alternative to whole-cell therapy for tissue injury and regeneration. This study aims to investigate the protective effects of MSC-Exos against cadmium toxicity on male reproduction. Our findings reveal that MSC-Exos treatment significantly promotes spermatogenesis, improves sperm quality, and reduces germ cell apoptosis in cadmium-exposed mice. Mechanistically, MSC-Exos dramatically mitigate cadmium-induced cell apoptosis in a spermatogonia cell line (GC-1 spg) in vitro by reducing DNA damage and promoting autophagic flux. These results suggest that MSC-Exos have a protective effect on cadmium-induced germ cell apoptosis by ameliorating DNA damage and autophagy flux, demonstrating the therapeutic potential of MSC-Exos for cadmium toxicity on male reproduction.

Cross-talk between Vimentin and autophagy regulates blood-testis barrier disruption induced by cadmium

The blood-testis barrier (BTB) plays a vital role in mammalian spermatogenesis by separating the seminiferous epithelium into an adluminal and a basal compartment. Cadmium (Cd) is a toxic heavy metal that is widely present in the environment. We observed that Cd can induce BTB disruption, leading to apoptosis of testicular cells. However, the molecular mechanisms contributing to BTB injury induced by Cd have not yet been fully clarified. Vimentin (Vim) is an important desmosome-like junction protein that mediates robust adhesion in the BTB. In this study, we investigated how Vim responds to Cd. We found that Cd treatment led to a significant decrease in Vim expression, accompanied by a marked increase in LC3-II expression and a higer number of autophagosomes. Interestingly, we also observed that Cd-induced autophagy was associated with decreased Vim activity and enhanced apoptosis of testicular cells. To further investigate the role of autophagy in Vim regulation under Cd exposure, we treated cells with an autophagy inhibitor called 3-MA. We found that 3-MA treatment enhanced Vim expression and improved the disruption of the BTB under Cd exposure. Additionally, the inhibition of Vim confirmed the role of autophagy in modulating Vim expression. These results reveal a previously unknown regulatory mechanism of Cd involving the interplay between a heavy metal and a protein.

Combined effects of polystyrene nanoplastics and lipopolysaccharide on testosterone biosynthesis and inflammation in mouse testis

Microplastics (MPs)/nanoplastics (NPs), as a source and vector of pathogenic bacteria, are widely distributed in the natural environments. Here, we investigated the combined effects of polystyrene NPs (PS-NPs) and lipopolysaccharides (LPS) on testicular function in mice for the first time. 24 male mice were randomly assigned into 4 groups, control, PS-NPs, LPS, and PS-NPs + LPS, respectively. Histological alterations of the testes were observed in mice exposed to PS-NPs, LPS or PS-NPs + LPS. Total sperm count, the levels of testosterone in plasma and testes, the expression levels of steroidogenic acute regulatory (StAR) decreased more remarkable in testes of mice treated with PS-NPs and LPS than the treatment with LPS or PS-NPs alone. Compared with PS-NPs treatment, LPS treatment induced more sever inflammatory response in testes of mice. Moreover, PS-NPs combined with LPS treatment increased the expression of these inflammatory factors more significantly than LPS treatment alone. In addition, PS-NPs or LPS treatment induced oxidative stress in testes of mice, but their combined effect is not significantly different from LPS treatment alone. These results suggest that PS-NPs exacerbate LPS-induced testicular dysfunction. Our results provide new evidence for the threats to male reproductive function induced by both NPs and bacterial infection in human health.

Associations of exposure to ambient fine particulate matter constituents from different pollution sources with semen quality: Evidence from a prospective cohort

The association between ambient fine particulate matter (PM2.5) exposure and semen quality remains inconclusive, possibly due to variations in pollution sources and PM2.5 compositions. Studies investigating the constituents of PM2.5 have been hindered by small sample sizes, and research exploring the relationships between PM2.5 pollution sources and semen quality is lacking. To address this gap, we conducted a comprehensive study based on the Anhui prospective assisted reproduction cohort to evaluate the associations between semen quality and the constituents and pollution sources of PM2.5. This study included 9013 semen samples from 4417 males in the urban districts of Hefei. The median concentrations of PM2.5 constituents, including eight metals and four water-soluble ions (WSIs), were measured for seven days per month at two monitoring stations during the 0-90-day exposure window. A linear mixed-effects model, weighted quantile sum regression, and positive matrix factorisation were used to evaluate the associations of the constituents and pollution sources of PM2.5 with semen quality. The results showed that exposure to PM2.5-bound metals (antimony, arsenic, cadmium, lead, and thallium) and WSIs (sulphate and chloride) were negatively associated with semen quality parameters. Moreover, mixtures of PM2.5-bound metals and WSIs were negatively associated with semen quality. Additionally, PM2.5 derived from traffic emissions was negatively associated with semen quality. In summary, our study revealed that ambient PM2.5 and its constituents, especially metals, were negatively associated with semen quality. Antimony, lead, and thallium emerged as the primary contributors to toxicity, and PM2.5 from traffic emissions was associated with decreased semen quality. These findings have important public health implications for the management of PM2.5 pollution in the context of male reproductive health.

Multigenerational paternal obesity enhances the susceptibility to male subfertility in offspring via Wt1 N6-methyladenosine modification

There is strong evidence that obesity is a risk factor for poor semen quality. However, the effects of multigenerational paternal obesity on the susceptibility to cadmium (a reproductive toxicant)-induced spermatogenesis disorders in offspring remain unknown. Here, we show that, in mice, spermatogenesis and retinoic acid levels become progressively lower as the number of generations exposed to a high-fat diet increase. Furthermore, exposing several generations of mice to a high fat diet results in a decrease in the expression of Wt1, a transcription factor upstream of the enzymes that synthesize retinoic acid. These effects can be rescued by injecting adeno-associated virus 9-Wt1 into the mouse testes of the offspring. Additionally, multigenerational paternal high-fat diet progressively increases METTL3 and Wt1 N6-methyladenosine levels in the testes of offspring mice. Mechanistically, treating the fathers with STM2457, a METTL3 inhibitor, restores obesity-reduced sperm count, and decreases Wt1 N6-methyladenosine level in the mouse testes of the offspring. A case-controlled study shows that human donors who are overweight or obese exhibit elevated N6-methyladenosine levels in sperm and decreased sperm concentration. Collectively, these results indicate that multigenerational paternal obesity enhances the susceptibility of the offspring to spermatogenesis disorders by increasing METTL3-mediated Wt1 N6-methyladenosine modification.

Exposure to particulate matter may affect semen quality via trace metals: Evidence from a retrospective cohort study on fertile males

Particulate matter (PM) exposure may be associated with male semen quality. Besides, PM exposure induces up and down levels of trace metals in tissues or organs. The levels of trace metals in semen are critical for adverse male semen quality. This study aims to evaluate the concentrations of seminal-level trace metals in fertile men and assess its associations with PM exposure and to explore the mediation role of trace metals in seminal plasma plays in the relationship between PM exposure and semen quality. Total 1225 fertile men who participated in a cohort study from 2014 to 2016 were finally recruited. Multivariate linear regression was applied to explore associations between each two of PM exposure, trace metals and semen parameters. 1-year PM2.5 and PM10 exposure levels were positively associated with arsenic (As), mercury (Hg), lanthanum (La), praseodymium (Pr), neodymium (Nd) but negatively associated with vanadium (V), magnesium (Mg), strontium (Sr), barium (Ba) in semen. It was also found that most of the elements were associated with total sperm number, followed by sperm concentration. Redundancy analysis (RDA) also determined several strong positive correlations or negative correlations between 1-year PM exposure and trace metals. Mediation analysis found that trace metals had a potentially compensatory or synergetic indirect effect on the total effect of the association between 1-year PM exposure and semen quality. The retrospective cohort study provides long-term PM exposure that may cause abnormal semen quality by affecting seminal plasma element levels.

Arsenic exposure caused male infertility indicated by testis and sperm metabolic dysfunction in SD rats

Arsenic containment is one of the most severe environmental problems. It has been reported that arsenic exposure could cause male reproductive damage. However, the evidence chain from sodium arsenite (NaAsO2) exposure to adverse male fertility outcomes has not been completed by molecular events. In this study, adult male rats were exposed to NaAsO2 for eight weeks via drinking water for verifying their reproductive capacity by checking the phenotypes of testis damage, sperm quality, and female pregnancy rate. H&E staining indicated testicular cells had atrophied, and necrosis was observed under transmission electron microscopy. Sperm viability tended to decrease, and sperm malformation increased. Notably, metabolites in the testes and sperm showed substantial disruption, especially sperm metabolites. The pregnancy rate tests showed that arsenic decreased male rats' reproduction, with some adverse outcomes of the increased numbers of unpregnant females. However, the fetal crown-rump length remained unaltered, indicating that the pregnancy rate was impacted by arsenic exposure but not fetal growth. On arsenic toxicometabolomics analysis, docosahexaenoic acid (DHA) in sperm was the clearest metabolic sign to correlate with the unpregnant rate. In summary, arsenic exposure can cause male infertility via the injured sperm, which results in decreased female pregnancy. The DHA information may imply the dietary intervention for improving sperm quality. Although the fetal growth of the successful pregnancy has not been affected, the changes in epigenetic phenotypes carried by sperms still need to be verified.

Like father, like daughter:Paternal cadmium exposure causes hepatic glucose metabolic disorder and phospholipids accumulation in adult female offspring

Cadmium (Cd), is a well-known reproductive toxicant. The impacts of paternal Cd exposure on offspring glucose and lipid metabolism remain unclear, despite the abundance of adverse reports following early exposure from the mother. Here, we assessed paternally acquired metabolic derailment using a mouse model. LC-MS/MS, transcriptomics and molecular experimental techniques were subsequently applied in this study to explore the potential mechanism. We found that paternal Cd exposure caused glucose intolerance, lower insulin sensitivity and abnormal hepatic glycogen storage in adult female offspring, but not in males. LC-MS/MS data showed that hepatic phospholipids accumulation was also only observed in adult female offspring after paternal Cd exposure. Gene expression data showed that the level of insulin signaling and lipid transport-related genes was decreased in Cd-treated adult female offspring livers. Meanwhile, AHR, a transcription factor that combines with phospholipids to promote insulin resistance, was increased in Cd-treated adult female offspring livers. In addition, the escalation of the afore-mentioned lipid metabolites in the liver occurred as early as fetal stages in the female pups following paternal Cd exposure, suggesting the potential for these lipid species to be selected as early markers of disease for metabolic derailment later in life. Altogether, paternal Cd exposure causes offspring glucose metabolism disorder and phospholipids accumulation in a sex-dependent manner. This study provides a theoretical framework for future understanding of paternal-originated metabolic diseases.

Loss of Atg5 in Sertoli cells enhances the susceptibility of cadmium-impaired testicular spermatogenesis in mice

Cadmium (Cd), one of the most common contaminants in diet and drinking water, impairs testicular germ cell development and spermatogenesis. Autophagy is essential for maintaining Sertoli cell function and Sertoli-germ cell communication. However, the role of Sertoli cell autophagy in Cd-caused spermatogenesis disorder remains unclear. Here, the mice of autophagy-related gene 5 (Atg5) knockouts in Sertoli cells were used to investigate the effect of autophagy deficiency on Cd-impaired spermatogenesis and its underlying mechanisms. Results showed that Sertoli cell-specific knockout of Atg5 exacerbated Cd-reduced sperm count and MVH (a specific marker for testicular germ cells) level in mice. Additionally, Sertoli cell Atg5 deficiency reduced the number of spermatocytes and decreased the level of meiosis-related proteins (SYCP3 and STRA8) in Cd-treated mouse testes. Loss of Atg5 in Sertoli cell exacerbated Cd-reduced the level of retinoic acid (RA) and retinal dehydrogenase (ALDH1A1 and ALDH1A) in mouse testes. Meanwhile, we found that the level of transcription factor WT1 was significantly downregulated in Atg5-/- plus Cd-treated testes. Further experiments showed that Wt1 overexpression restored Cd-decreased the levels of ALDH1A1 in Sertoli cells. Collectively, the above data suggest that knockout of Atg5 in Sertoli cell enhances the susceptibility of Cd-impaired testicular spermatogenesis. These findings provide new insights into autophagy of Sertoli cell preventing environmental toxicants-impaired testicular spermatogenesis.

The Palliative and Antioxidant Effects of Hesperidin against Lead-Acetate-Induced Testicular Injury in Male Wistar Rats

Lead (Pb)-induced reprotoxicity is a detrimental consequence of Pb exposure, which results in abnormal spermatogenesis, testicular degeneration, and pathogenic sperm changes. The association between impaired male reproductive function and Pb-induced oxidative stress (OS) has been demonstrated, with consequent testicular antioxidant deficiency. The current study investigated the protective role of the natural antioxidant hesperidin (HSD) against lead-acetate (PbAc)-induced testicular toxicity. Male Wistar rats (n = 40) were randomly divided into four experimental groups: Group I (negative control) received 2.0 mL/kg BW 0.9% saline; Group II received 100 mg/kg BW PbAc; Group III received 100 mg/kg BW HSD; and Group IV received HSD two hours before PbAc using the abovementioned doses. The treatments were administered daily for 30 consecutive days. The results showed that HSD treatment significantly restored PbAc-induced decrease in body, epididymal, and testicular weights as well as in semen parameters, reproductive hormones, and testicular markers of OS. Reduced MDA levels and improved testicular histopathological findings were also observed. Collectively, this study sheds light on the preventive role of HSD against PbAc-induced testicular injury, which is mediated via the suppression of OS and the modulation of reproductive hormones as well as the plausibility of HSD being used as a supplementary therapeutic option for recovery.

Zinc and selenium attenuate quaternary heavy metal mixture-induced testicular damage via amplification of the antioxidant system, reduction in metal accumulation, inflammatory and apoptotic biomarkers

Heavy metals (HMs) such as cadmium (Cd), lead (Pb), arsenic (As), and mercury (Hg) are highly toxic elements. They are often found together in nature as a heavy metal mixture (HMM) and are known to contribute to subfertility/infertility as environmental pollutants. This study aims to evaluate the potential benefits of treating HMM-induced testicular pathophysiology with zinc (Zn) and/or selenium (Se). Six-week-old male Sprague Dawley rats were grouped into 5 (n = 7). The control group received deionized water, while the other groups were treated with PbCl2 (20 mg kg-1), CdCl2 (1.61 mg kg-1), HgCl2 (0.40 mg kg-1), and Na2AsO3 (10 mg kg-1) in deionized water for 60 days. Additionally, groups III to V received Zn, Se, and Zn/Se, respectively, for 60 days. The study evaluated testis weight, metal accumulation, sperm analysis, FSH, LH, testosterone, prolactin, oxidative stress, antioxidants, pro-inflammatory and apoptotic markers, and presented structural changes in the testis as micrographs. HMM caused a significant increase in testis weight, metal accumulation, prolactin, oxidative stress, and pro-inflammatory and apoptotic markers, while significantly decreasing semen analysis, FSH, LH, and testosterone. Histology showed decreased spermatogenesis and spermiogenesis, as evidenced by the structure of the germ cells and spermatids. However, Zn, Se, or both ameliorated and reversed some of the observed damages. This study provides further evidence for the mitigative potential of Zn, Se, or both in reversing the damage inflicted by HMM in the testis, and as a countermeasure towards improving HM-induced decrease in public health fecundity.

Graphical abstract

Urinary levels of potentially toxic elements (PTEs) in female beauticians and their association with urinary biomarkers of oxidative stress/inflammation and kidney injury

The present research was aimed to assess the urinary levels of potentially toxic elements (PTEs) in female beauticians and its correlation with oxidative stress/inflammation and kidney injury. To this end, the urine samples were collected from 50 female beauticians from beauty salons (exposed group) and 35 housewives (control group), and then, the level of PTEs was determined. The mean levels of the sum of urinary PTEs (∑PTEs) biomarkers in before and after exposure and control group were 83.55, 114.27 and 13.61 μg/L, respectively. Results also showed that the urinary level of PTEs biomarkers is significantly higher in women occupationally exposed to cosmetics compared to control group. The urinary levels of arsenic (As), cadmium (Cd), lead (Pb), and chromium (Cr) biomarkers have high correlation coefficients with early oxidative stress effects such as 8-Hydroxyguanosine (8-OHdG), 8-isoprostane and Malondialdehyde (MDA). Moreover, As and Cd biomarker levels were positively and significantly associated with kidney damages such as urinary kidney injury molecule-1 (uKIM-1) and tissue inhibitor matrix metalloproteinase 1 (uTIMP-1) (P < 0.01). Therefore, women who working in beauty salons can probably be categorized as high - exposure and high-risk workers in terms of DNA oxidative and kidney damages.

Evidence of the protective role of D-Aspartate in counteracting/preventing cadmium-induced oxidative stress in the rat testis

Cadmium (Cd), by producing oxidative stress and acting as an endocrine disruptor, is known to cause severe testicular injury, documented by histological and biomolecular alterations, such as decreased serum testosterone (T) level and impairment of spermatogenesis. This is the first report on the potential counteractive/preventive action of D-Aspartate (D-Asp), a well-known stimulator of T biosynthesis and spermatogenesis progression by affecting hypothalamic-pituitary-gonadal axis, in alleviating Cd effects in the rat testis. Our results confirmed that Cd affects testicular activity, as documented by the reduction of serum T concentration and of the protein levels of steroidogenesis (StAR, 3β-HSD, and 17β-HSD) and spermatogenesis (PCNA, p-H3, and SYCP3) markers. Moreover, higher protein levels of cytochrome C and caspase 3, together with the number of cells positive to TUNEL assay, indicated the intensification of the apoptotic process. D-Asp administered either simultaneously to Cd, or for 15 days before the Cd-treatment, reduced the oxidative stress induced by the metal, alleviating the consequent harmful effects. Interestingly, the preventive action of D-Asp was more effective than its counteractive effect. A possible explanation is that giving D-Asp for 15 days induces its significant uptake in the testes, reaching the concentrations necessary for optimum function. In summary, this report highlights, for the first time, the beneficial role played by D-Asp in both counteracting/preventing the adverse Cd effects in the rat testis, strongly encouraging further investigations to consider the potential value of D-Asp also in improving human testicular health and male fertility.

Urinary neonicotinoid insecticides and adiposity measures among 7-year-old children in northern China: A cross-sectional study

BACKGROUND

Neonicotinoid insecticides (NEOs) are emerging synthetic insecticides used in various pest management regimens worldwide. Toxicology studies have indicated the obesogenic potential of NEOs, but their associations with adiposity measures are largely unknown.

OBJECTIVES

We aimed to assess urinary levels of NEOs/metabolites and their associations with children's adiposity measures, and to further investigate the potential role of oxidative stress.

METHODS

This study included 380 children who participated in the 7th year's follow-up of the Laizhou Wan Birth Cohort in northern China. Urinary levels of seven NEOs and two metabolites and a biomarker of lipid peroxidation named 8-iso-prostaglandin-F2α (8-iso-PGF2α) were detected. A total of nine indicators of adiposity were measured. Body mass index (BMI) z-score ≥85th percentile was defined as overweight/obesity, and waist-to-height ratio (WHtR) ≥0.5 was considered as abdominal obesity. Multiple linear regression, binary logistic regression and mediation analysis were performed.

RESULTS

Six NEOs [imidacloprid (IMI, 99.7%), clothianidin (CLO, 98.9%), dinotefuran (DIN, 97.6%), thiamethoxam (THM, 95.5%), acetamiprid (ACE, 82.9%), thiacloprid (THD, 77.6%)] and two metabolites [N-desmethyl-acetamiprid (N-DMA, 100.0%), 6-chloronicotinic acid (6-CINA, 97.9%)] exhibited high detection rates. Multiple linear regressions showed positive associations of waist circumference with urinary levels of IMI and THM, of WHtR with IMI and THM levels, and of body fat percentage with 6-CINA levels. In contrast, exposure to N-DMA was negatively associated with body fat percentage and fat mass index. Binary logistic regressions further revealed that higher IMI levels were associated with overweight/obesity (OR = 1.556, 95% CI: 1.100, 2.201) and abdominal obesity (OR = 1.478, 95% CI: 1.078, 2.026) in children. 8-iso-PGF2α demonstrated 27.92%, 69.52% and 35.37% mediating effects in the positive associations of IMI, THD and THM with WHtR, respectively. Sex modified the associations of DIN with body fat mass (p_int = 0.032), body fat percentage (p_int = 0.009), fat mass index (p_int = 0.037) and the overweight/obesity rate (p_int = 0.046), with negative associations in girls and nonsignificant positive associations in boys.

CONCLUSIONS

School-age children in northern China were widely exposed to NEOs/metabolites. Urinary levels of NEOs/metabolites were associated with adiposity measures through the mediating role of 8-iso-PGF2α. These associations were mixed, and a sex-specific effect might exist.

An Exploratory Analysis of Firefighter Reproduction through Survey Data and Biomonitoring

Firefighters are occupationally exposed to chemicals that may affect fertility. To investigate this effect, firefighters were recruited to contribute blood, urine, breast milk or semen samples to (1) evaluate chemical concentrations and semen parameters against fertility standards and the general population; (2) assess correlations between chemical concentrations and demographics, fire exposure and reproductive history; and (3) consider how occupational exposures may affect reproduction. A total of 774 firefighters completed the online survey, and 97 firefighters produced 125 urine samples, 113 plasma samples, 46 breast milk samples and 23 semen samples. Blood, urine and breast milk samples were analysed for chemical concentrations (semivolatile organic compounds, volatile organic compounds, metals). Semen samples were analysed for quality (volume, count, motility, morphology). Firefighter semen parameters were below WHO reference values across multiple parameters. Self-reported rates of miscarriage were higher than the general population (22% vs. 12-15%) and in line with prior firefighter studies. Estimated daily intake for infants was above reference values for multiple chemicals in breast milk. More frequent fire incident exposure (more than once per fortnight), longer duration of employment (≥15 years) or not always using a breathing apparatus demonstrated significantly higher concentrations across a range of investigated chemicals. Findings of this study warrant further research surrounding the risk occupational exposure has on reproduction.

Determinants of oxidative stress among indigenous populations in Northern Laos: Trace element exposures and dietary patterns

OBJECTIVES

To investigate determinants of oxidative stress in an indigenous population, we examined associations of trace element exposures and dietary patterns with three oxidative stress-related biomarkers among indigenous populations in Northern Laos.

METHODS

This cross-sectional study included 341 adults from three villages with different levels of modernization. We used three oxidative stress-related biomarkers: urinary 8-hydroxy-2'-deoxyguanosine (8-OHdG) and 8-isoprostane concentrations, which were measured using liquid chromatography-tandem mass spectrometry, and blood telomere lengths, which were measured using a quantitative polymerase chain reaction method. We used multilevel analysis to examine associations of urinary arsenic, cadmium, and selenium concentrations, their interaction terms, and wild-plant-food scores (principal component scores calculated from food consumption frequencies) with oxidative stress-related biomarkers.

RESULTS

Urinary arsenic and cadmium concentrations were positively associated with urinary 8-isoprostane concentrations. Urinary selenium concentrations were positively associated with urinary 8-OHdG concentrations. Interaction terms ([arsenic or cadmium] × selenium) showed negative associations with urinary 8-OHdG and 8-isoprostane concentrations, respectively. Urinary cadmium concentrations were negatively associated with telomere lengths. Wild-plant-food scores did not exhibit associations with oxidative stress-related biomarkers.

CONCLUSION

Our findings imply that exposure to arsenic and cadmium is associated with greater oxidative lipid damage, whereas selenium may attenuate arsenic-induced oxidative DNA damage and cadmium-induced oxidative lipid damage. Cadmium exposure may accelerate telomere attrition. Trace element exposure may be a determinant of oxidative stress among indigenous populations in Northern Laos.

Ameliorative effect of Nigella sativa conjugated silver nanoparticles against chromium-induced hepatotoxicity and renal toxicity in mice

Hexavalent chromium induces oxidative stress in the liver and kidney. Therefore an in vivo study was designed to investigate the modulatory effect of biosynthesized AgNP against Cr (VI) induced hepatotoxicity and nephrotoxicity. The organs index, serum level of ALT, AST, ALP, MDA, total protein and creatinine were measured. The histopathology and micrometry of the liver and kidney were examined. The liver index was significantly increased (0.098 ± 0.13 g) with slight increase in kidney index in Cr exposed group. The serum level of ALT (163.0 ± 5.5 U/L), AST (484.0 ± 10.7 U/L), ALP (337.6 ± 9.6 U/L), MDA (641.2 ± 29.2 U/L), and creatinine (2.9 ± 0.2 mg/dL) were significantly increased (P ≤ 0.05) with significant decrease in total protein level (2.9 ± 0.2 g/dL) (P ≤ 0.05) in chromium treated group. In histopathology, distorted hepatic cords, necrosis, damaged glomerulus and Bowman's capsule were observed. Micrometric studies of the liver and kidney showed significant increase in size of hepatocytes (1188.2 ± 467.7 µ²) and their nuclei (456.4 ± 206.7 µ²), ACSA of Bowman's capsule (11835.5 ± 336.7 µ²) and glomerulus (9051.8 ± 249.8 µ²⁾ in Cr (VI) treated group. The size of brush border (10.1 ± 3.0 µ) was significantly reduced in Cr (VI) treated group however the ACSA of lumen was not significantly changed. With the administration of NSSE and Nigella sativa AgNPs, decreased the oxidative damage caused by Cr (V).

Urinary concentrations of fungicide carbendazim's metabolite and associations with oxidative stress biomarkers in young children

Carbendazim (CBDZ) is the most widely used fungicide in China. It is ubiquitous in environment and can induce oxidative stress in mammals, while data on occurrence of its metabolite in human urine are scarce, and the relationship between CBDZ and oxidative stress biomarkers (OSBs) in young children has not been examined. The aim of this study was to measure the concentrations of methyl 5-hydroxy-2-benzimidazolecarbamate (5-HBC, the main metabolite of CBDZ in urine) in 390 urine samples collected from 130 healthy young (< 6.6 years old) children from Shenzhen and Wuhan, in south and central China, respectively, and to evaluate the associations of 5-HBC with three selected OSBs (4-HNEMA, 8-OHG, and 8-OHdG, for lipid, RNA, and DNA, respectively). 5-HBC was found in 99.2% of the urine samples at concentrations ranging from below the method detection limit (< 0.005 ng/mL) to 10.9 ng/mL (median: 0.11 ng/mL). Moderate inter-day reproducibility was found for specific gravity-adjusted 5-HBC concentrations (intraclass correlation coefficient: 0.50). The urinary 5-HBC concentrations were significantly and positively associated with 4-HNEMA (p < 0.01). An interquartile range increase in urinary 5-HBC concentrations was associated with a 42.1% increase in 4-HNEMA, which implied that CBDZ exposure might be associated with lipid peroxidation in young children without occupational exposure. As far as we know, this pilot study is the first to report urinary 5-HBC and its associations with OSBs in children.

Coenzyme Q10 enhances testicular functions and sexual behavior through regulating steroidogenic-related gene expression and inflammatory pathways of Japanese quail (Coturnix japonica) aganist cadmium

A progressively essential bird of high economic significance for meat production and commercial egg is the Japanese quail, and so more experiments are necessary to improve the productivity of these birds under stressful encounters. The current work was performed to define the influences of Coenzyme Q10 (CoQ10) on growth, sexual behavior, and testicular characteristics (size of the gonad, traits of spermatic features, levels of plasma testosterone, steroidogenic-related gene expression) of Japanese quail (Coturnix coturnix japonica) aganist cadmium (Cd) administration. Chicks of quail (n = 250), 14 days old of age were distributed into 4 groups: basal ration (Group 1), basal ration and CoQ10 at 100 mg/kg ration (Group 2), basal ration and Cd at 50 mg/kg ration (Group 3), and CoQ10 + Cd (Group 4). Several parameters relating to productive performance, such as weight of the body, weight gain, feed intake, and the conversion ratio of feed, were evaluated. Constant visual scanning of the quails was performed to observe their sexual behaviors. Sperm characteristics, plasma testosterone levels, and testicular inflammatory markers of interleukin-6 (IL-6) and tumor necrosis factor-α (TNF-α) were also determined. Oxidative-antioxidant redox status in the testes was evaluated by analyzing MDA level, GPx, and SOD activities. Steroidogenic-related gene expression in the testes (CYP17A1, StAR, 3β-HSD, and Cyp19) was also examined. In addition, testicular apoptosis was assessed by monitoring the alterations in the local expression of stress-induced (HSP70), proteins of anti-apoptotic marker (Bcl-2), and pro-apoptotic markers (caspase-3 and Bax). Cd administration hurts body performance, sexual behavior, and testicular efficiency parameters. Interestingly, CoQ10 supplementation improved reproductive performance. Moreover, it significantly increases the % of birds exhibiting sexual behavior and enhances testicular functions, which were damaged by Cd administration, by enhancing plasma testosterone level, antioxidative enzyme activity, and sperm quality traits while reducing the MDA and pro-inflammatory markers. Furthermore, downregulation of pro-apoptotic factor expression, though it increased the expression of the anti-apoptotic protein, was recorded. Correspondingly, CoQ10 revealed a marked upregulation in the expression of steroidogenic-related genes. Conclusion: It is established that the consumption of CoQ10 in the ration of Japanese quail, following a Cd adminstration, improves productive performance, sexual behavior, and several testicular function parameters as a potent antioxidant.

Seaweed polysaccharide relieves hexavalent chromium-induced gut microbial homeostasis

Heavy metals released in the environment pose a huge threat to soil and water quality, food safety and public health. Additionally, humans and other mammals may also be directly exposed to heavy metals or exposed to heavy metals through the food chain, which seriously threatens the health of animals and humans. Chromium, especially hexavalent chromium [Cr (VI)], as a common heavy metal, has been shown to cause serious environmental pollution as well as intestinal damage. Thus, increasing research is devoted to finding drugs to mitigate the negative health effects of hexavalent chromium exposure. Seaweed polysaccharides have been demonstrated to have many pharmacological effects, but whether it can alleviate gut microbial dysbiosis caused by hexavalent chromium exposure has not been well characterized. Here, we hypothesized that seaweed polysaccharides could alleviate hexavalent chromium exposure-induced poor health in mice. Mice in Cr and seaweed polysaccharide treatment group was compulsively receive K2Cr2O7. At the end of the experiment, all mice were euthanized, and colon contents were collected for DNA sequencing analysis. Results showed that seaweed polysaccharide administration can restore the gut microbial dysbiosis and the reduction of gut microbial diversity caused by hexavalent chromium exposure in mice. Hexavalent chromium exposure also caused significant changes in the gut microbial composition of mice, including an increase in some pathogenic bacteria and a decrease in beneficial bacteria. However, seaweed polysaccharides administration could ameliorate the composition of gut microbiota. In conclusion, this study showed that seaweed polysaccharides can restore the negative effects of hexavalent chromium exposure in mice, including gut microbial dysbiosis. Meanwhile, this research also lays the foundation for the application of seaweed polysaccharides.

Elemental profiling of human semen with confirmed normozoospermia: Baseline levels for 44 elements

BACKGROUND

As a consequence of the progressive decline in human semen quality in recent decades, modern epidemiological investigations have identified several trace elements that could be responsible for this phenomenon. However, their levels in semen have not been clearly elucidated, particularly for elements present in ultra-trace levels.

METHODS

We aimed to determine the levels of 39 (ultra)trace elements and 5 macroelements in human semen samples with confirmed normozoospermia using ICP-based techniques. The research was amplified by analyzing blood samples from the same participants.

RESULTS

Among the analyzed (ultra)trace elements in semen samples, Zn is the most and Tm is the least prominent. Zn levels in semen are so high that Zn should be considered as a macroelement in this matrix. The levels of Zn, Rh, Sm, Re, Ir, Tl, Na, and Ca were significantly higher in semen, while the levels of Cu, As, Rb, Gd, Sb, Tb, Tm, Lu, K, and Fe were significantly higher in blood. Correlation analysis of the levels of 44 individual elements in paired semen and blood samples revealed positive correlations between 43 of the elements, particularly for Tl and Pt. An exception was the negative correlation for Cu, which showed that its high level in semen is associated with a low level in blood and contrariwise.

CONCLUSION

The reported data can be used as baseline levels/reference values for 44 elements in human semen. Furthermore, the findings of this study could be relevant for further consideration of male infertility.

Contemporary Comprehensive Review on Arsenic-Induced Male Reproductive Toxicity and Mechanisms of Phytonutrient Intervention

Arsenic (As) is a poisonous metalloid that is toxic to both humans and animals. Drinking water contamination has been linked to the development of cancer (skin, lung, urinary bladder, and liver), as well as other disorders such as diabetes and cardiovascular, gastrointestinal, neurological, and developmental damage. According to epidemiological studies, As contributes to male infertility, sexual dysfunction, poor sperm quality, and developmental consequences such as low birth weight, spontaneous abortion, and small for gestational age (SGA). Arsenic exposure negatively affected male reproductive systems by lowering testicular and accessory organ weights, and sperm counts, increasing sperm abnormalities and causing apoptotic cell death in Leydig and Sertoli cells, which resulted in decreased testosterone synthesis. Furthermore, during male reproductive toxicity, several molecular signalling pathways, such as apoptosis, inflammation, and autophagy are involved. Phytonutrient intervention in arsenic-induced male reproductive toxicity in various species has received a lot of attention over the years. The current review provides an in-depth summary of the available literature on arsenic-induced male toxicity, as well as therapeutic approaches and future directions.

Combination of high-fat diet and cadmium impairs testicular spermatogenesis in an m6A-YTHDF2-dependent manner

Environmental cadmium (Cd) or high-fat diet (HFD) exposure alone are risk factors of male infertility. However, the effect and mechanism of co-exposure to HFD and Cd on sperm quality remain unclear. This study was aimed to explore the combined effects of HFD and Cd on spermatogenesis as well as its m6A-dependent mechanism in vivo and in vitro. As a result, co-exposure of HFD and Cd resulted in a significant decrease in the number of mature testicular seminiferous tubules and epididymis sperm quantity in mice, compared with Cd or HFD exposure alone. Correspondingly, the mRNAs expression of Smc3(spermatocytes marker), Acrv1(round spermatids marker) and Lzumo3(elongated spermatids marker) were downregulated in HFD and Cd group. Furthermore, combined exposure downregulated the expression of meiosis-related proteins (STRA8 and SYCP3), increased the m6A level of Stra8, and upregulated the expression of m6A-related proteins (METTL3 and YTHDF2) in mouse spermatocytes. Mechanistically, the above-mentioned impacts caused by co-exposure were markedly restored by Mettl3 siR and Ythdf2 siR. In addition, RNA stability assay showed that Ythdf2 siR obviously reversed co-exposure-increased Stra8 mRNA degradation rate in actinomycin-D-treated mouse spermatocytes. Meanwhile, excess ROS was observed in combined-exposure group, and a free radical scavenger N-tert-Butyl-α-phenylnitrone (PBN) attenuated co-exposure-upregulated expression of METTL3 and YTHDF2 in mouse spermatocytes. These results suggested that combination of HFD and Cd impaired spermatogenesis by degrading Stra8 in an m6A-YTHDF2-dependent manner via ROS activation.

Mechanisms of Cadmium-Induced Testicular Injury: A Risk to Male Fertility

Cadmium is a heavy toxic metal with unknown biological functions in the human body. Over time, cadmium accretion in the different visceral organs (liver, lungs, kidney, and testis) is said to impair the function of these organs, which is associated with a relatively long biological half-life and a very low rate of excretion. Recently studies have revealed that the testes are highly sensitive to cadmium. In this review, we discussed the adverse effect of cadmium on the development and biological functions of the testis. The Sertoli cells (SCs), seminiferous tubules, and Blood Testis Barrier are severely structurally damaged by cadmium, which results in sperm loss. The development and function of Leydig cells are hindered by cadmium, which also induces Leydig cell tumors. The testis's vascular system is severely disturbed by cadmium. Cadmium also perturbs the function of somatic cells and germ cells through epigenetic regulation, giving rise to infertile or sub-fertile males. In addition, we also summarized the other findings related to cadmium-induced oxidative toxicity, apoptotic toxicity, and autophagic toxicity, along with their possible mechanisms in the testicular tissue of different animal species. Consequently, cadmium represents a high-risk factor for male fertility.

Assessment for the associations of twenty-three metal(loid)s exposures with early cardiovascular damage among Chinese urban adults with five statistical methods: Insight into assessing health effect of multipollutant exposure

The topic of cardiovascular hazards from multiple metal (loid)s exposures has attracted widespread attention. Here, we measured concentrations of twenty-three urinary metal (loid)s and mean platelet volume (MPV), an early cardiovascular damage biomarker, for 3396 Chinese adults. We aimed to comprehensively assess the associations of single metal (loid) and multiple metal (loid)s (as a mixture) with MPV by combined use of five statistical methods, including general linear models, Bayesian kernel machine regression (BKMR), weight quartile sum (WQS) regression, quantile g-computation (QGC), and adaptive elastic network regression (AENR). And based on that, we hope to provide insight into assessing the health effect of multipollutant exposure. After adjustment for potential covariates, at least three methods jointly suggested that of twenty-three metal (loid)s, iron, arsenic, and antimony were positively while aluminum, tungsten, and thallium were inversely associated with MPV. The environmental risk score of metal (loid)s construed by AENR was significantly positively associated with MPV, while the association between overall twenty-three metal (loid)s mixture and MPV was neutralized to be insignificant in QGC and BKMR. Conclusively, single metal (loid) may be inversely (iron, arsenic, and antimony) and positively (aluminum, tungsten, and thallium) associated with early cardiovascular damage, while the association of overall twenty-three metal (loid)s mixture with MPV was insignificant when concurrent exposures exist. It is crucial to select appropriate statistical methods based on study purpose and principles/characteristics of statistical methods, and combined employment of multimethod is insightfully suggested when assessing health effects of multipollutant exposure.

Environmental metal exposure, seminal plasma metabolome and semen quality: Evidence from Chinese reproductive-aged men

Environmental metal exposure has been associated with decreasing semen quality, but the effects of multiple metal exposure on seminal plasma metabolome remain obscure. In this study, semen and repeated urine samples from 551 volunteers were collected in Wuhan City. Heavy metals and trace elements were measured using inductively coupled plasma mass spectrometer, and seminal plasma metabolomes were acquired using liquid chromatography coupled with high-resolution mass spectrometry. Weighted gene co-expression network analysis showed more than half of the seminal plasma metals were associated with specific metabolite modules, whereas only a few urine metals presented weak associations, indicating that seminal plasma may be an ideal biological sample for male reproductive biomarker discovery and exposure risk assessment. Seminal plasma zinc (Zn) and selenium (Se) concentrations were significantly associated with 22 metabolites (e.g., glycerophospholipids, acyl-carnitines and amino acid derivatives). Among these metabolites, acyl-carnitines were positively associated with semen quality and sperm concentration. Moreover, acyl-carnitines were associated with both Zn and Se exposure, indicating the potential role of carnitine pathway in their toxicity mechanism. Our findings suggest that seminal plasma metabolome connects Zn and Se exposure and sperm concentrations in Chinese men of reproductive age.

Association of urinary or blood heavy metals and mortality from all causes, cardiovascular disease, and cancer in the general population: a systematic review and meta-analysis of cohort studies

Amounting epidemiological evidence has shown detrimental effects of heavy metals on a wide range of diseases. However, the effect of heavy metal exposure on mortality in the general population remains unclear. The primary objective of this study was to clarify the associations between heavy metals and mortality from all causes, cardiovascular disease (CVD), and cancer based on prospective studies. We comprehensively searched Pubmed, Embase, and Web of Science electronic databases to identify studies published from their inception until 1 March 2022. Investigators identified inclusion criteria, extracted study characteristics, and assessed the methodological quality of included studies according to standardized guidelines. Meta-analysis was conducted if the effect estimates of the same outcome were reported in at least three studies. Finally, 42 original studies were identified. The results of meta-analysis showed that cadmium and lead exposure was significantly associated with mortality from all causes, CVD, and cancer in the general population. Moderate evidence suggested there was a link between arsenic exposure and mortality. The adverse effects of mercury and other heavy metals on mortality were inconclusive. Epidemiological evidence for the joint effect of heavy metal exposure on mortality was still indeterminate. In summary, our study provided compelling evidence that exposure to cadmium, lead, and arsenic were associated with mortality from all causes, CVD, and cancer, while the evidence on other heavy metals, for example mercury, was insignificant or indeterminate. Nevertheless, further prospective studies are warranted to explore the joint effects of multiple metal exposure on mortality.

Assessing oxidative stress resulting from environmental exposure to metals (Oids) in a middle Eastern population

Concentrations of metals and metalloids derived mainly from anthropogenic activities have increased considerably in the environment. Metals might be associated with increase reactive oxygen species (ROS) damage, potentially related to several health outcomes. This study has recruited 200 adult participants, including 110 males and 90 females in Shiraz (Iran), to investigate the relationship between chronic exposure to metals and ROS damage by analyzing malondialdehyde (MDA) and 8-Oxo-2'-deoxyguanosine (8-OHdG) concentrations, and has evaluated the associations between chronic metal exposure and ROS damage using regression analysis. Our findings showed participants are chronically exposed to elevate As, Ni, Hg, and Pb levels. The mean urinary concentrations of 8-OHdG and MDA were 3.8 ± 2.35 and 214 ± 134 µg/g creatinine, respectively. This study shows that most heavy metals are correlated with urinary ROS biomarkers (R ranges 0.19 to 0.64). In addition, regression analysis accounting for other confounding factors such as sex, age, smoking status, and teeth filling with amalgam highlights that Al, Cu, Si and Sn are associated with 8-OHdG concentrations, while an association between Cr and MDA and 8-OHdG is suggested. Smoking cigarettes and water-pipe is considered a significant contributory factor for both ROS biomarkers (MDA and 8-OHdG).

Heavy metal and metalloid - induced reproductive toxicity

Heavy metals and metalloid exposure are among the most common factors responsible for reproductive toxicity in human beings. Several studies have indicated that numerous metals and metalloids can display severe adverse properties on the human reproductive system. Metals like lead, silver, cadmium, uranium, vanadium, and mercury and metalloids like arsenic have been known to induce reproductive toxicity. Moderate to minute quantities of lead may affect several reproductive parameters and even affect semen quality. The ecological and industrial exposures to the various heavy metals and metalloids have disastrous effects on the reproductive system ensuing in infertility. This work emphasizes the mechanism and pathophysiology of the aforementioned heavy metals and metalloids in reproductive toxicity. Additionally, this work aims to cover the classical protective mechanisms of zinc, melatonin, chelation therapy, and other trending methods to prevent heavy metal-induced reproductive toxicity.

Identifying the dose response relationship between seminal metal at low levels and semen quality using restricted cubic spline function

Environmental exposure to metals, including essential and nonessential elements, may be related to semen quality. Our goal was to explore the continuous relationship between seminal metals and sperm parameters. A restricted cubic spline (RCS) was applied to automatic selection criteria to ascertain the optimal smoothing degree. We recruited 841 male volunteers from Henan Province, China. Eighteen seminal metals, namely Al, Cr, Mn, Cu, Zn, Se, As, Ni, Cd, Pb, Co, V, Rb, Ag, Ba, TI, Fe, and Li, and 21 semen parameters were detected. Seminal malondialdehyde (MDA) was also detected to express oxidative stress. We revealed a non-linear relationship of the vanadium and chromium exposure to semen parameters. There were inverse 'U' shapes found between seminal Cr and sperm concentrations, total sperm count, and semen quality. The best semen quality was observed when the seminal Cr concentration was 5.05 ppb, and an increase or decrease in chromium concentration led to decreased semen quality. The V concentration was associated with reduced sperm concentration, total sperm count, normal morphology, and progressive motility at high doses (V > 0.58 ppb). Seminal MDA had a strong adverse association with sperm motility parameters, such as curve line velocity (VCL) (P < 0.001), straight line velocity (VSL) (P = 0.004), velocity of average path (VAP) (P < 0.001), and lateral head movement (ALH) (P = 0.001), whereas it was adversely associated with seminal Zn (β [95% confidence interval (CI)], -0.28(-0.41-0.16), P < 0.001) after adjusting for confounding factors. Our findings represent the curves of the dose-response relationship between seminal Cr, seminal V, and semen quality, in which seminal MDA was a good indicator of sperm movement. These models provide new insight into the dose-relationship between metal exposure and semen quality, and further investigation is needed to validate this.

Individual and mixtures of metal exposures in associations with biomarkers of oxidative stress and global DNA methylation among pregnant women

BACKGROUND

Prenatal exposure to metals has been linked with adverse pregnancy outcomes. Oxidative stress and epigenetic changes are potential mechanisms of action.

OBJECTIVES

We aimed to examine the associations of individual and mixtures of metal exposures with oxidative stress and DNA methylation among pregnant women.

METHODS

We measured a panel of 16 metals and 3 oxidative stress biomarkers including 8-hydroxydeoxyguanosine (8-OHdG), 4-hydroxy-2-nonenal-mercapturic acid (HNE-MA) and 8-isoprostaglandin F2α (8-isoPGF2α) in urine from 113 pregnant women in a Chinese cohort. Biomarkers of global DNA methylation including Alu and long interspersed nucleotide element-1 (LINE-1) in cord blood were measured. Multivariable linear regression and Bayesian kernel machine regression (BKMR) models were separately applied to estimate the associations between individual and mixtures of metal exposures and biomarkers of oxidative stress and global DNA methylation.

RESULTS

In single-metal analyses, we observed positive associations between 11 metals [arsenic (As), cadmium (Cd), thallium (Tl), barium (Ba), nickel (Ni), vanadium (V), cobalt (Co), zinc (Zn), copper (Cu), selenium (Se) and molybdenum (Mo)] and at least one of oxidative stress biomarkers (all FDR-adjusted P-values < 0.05). In mixture analyses, we found positive overall associations of metal mixtures with 8-OHdG and 8-isoPGF2α, and Se was the most important predictor. There was no evidence on associations of urinary metals as individual chemicals and mixtures with Alu and LINE-1 methylation.

CONCLUSION

Urinary metals as individual chemicals and mixtures were associated with increased oxidative stress, especially Se.

Cytotoxicity of stabilized/solidified municipal solid waste incineration fly ash

Low-carbon stabilization/solidification (S/S) is of increasing importance as an option for the treatment of municipal solid waste incineration fly ash (MIFA). This study tailored four binders (e.g., ordinary Portland cement (OPC), calcium aluminate cement (CAC), phosphate-modified OPC, and phosphate-modified CAC) for S/S of MIFA and evaluated the cytotoxicity of treated MIFA by using A549 cell-based in-vitro assay. After S/S treatment, the leachability of Cr, Cu, Zn and Pb from MIFA decreased by 76.1%, 93.4%, 69.6%, and 85.5%, respectively. Spectroscopic analysis indicated that the hydration products determined the immobilization efficiencies of various binders, and strong bonding between metallic cations and phosphate enhanced the immobilization efficiency. The treated MIFA showed significantly lower cellular reactive oxygen species (ROS)-inducing abilities than original MIFA, in which with phosphate-modified OPC treated MIFA showed the lowest ROS levels. Intracellular ROS and multicytotoxicity results also revealed that the treated MIFA not only decreased the cytotoxicity-inducing capability but also enhanced the tolerant dosage of cytotoxicity, in which phosphate-modified S/S treatments showed more effective mitigation (25% less cytotoxicity) than plain cement treatments due to the high-efficiency immobilization of potentially toxic elements. This study develops a pioneering assessment protocol to measure the success of sustainable treatment of MIFA in human health perspective.

Genome-wide gene-bisphenol A, F and triclosan interaction analyses on urinary oxidative stress markers

BACKGROUND

Bisphenols and triclosan (TCS) are common endocrine disrupters (EDCs) that may induce oxidative stress. However, there is limited information as to whether these EDCs interact with genetic variants to modify the levels of oxidative stress on a genome-wide scale.

METHODS

We first performed a genome-wide scan among a Chinese population and also measured three urinary EDCs, including bisphenol A (BPA), bisphenol F (BPF) and TCS, and three urinary oxidative stress markers [4-hydroxy-2-nonenal-mercapturic acid (HNE-MA), 8-iso-prostaglandin-F_2α (8-isoPGF_2α) and 8-hydroxy-deoxyguanosine (8-OHdG)]. Subsequently, we examined interactions between three urinary EDCs and nearly 4.6 million genetic variants for three urinary oxidative stress markers by the general linear model.

RESULTS

Urinary BPA, BPF and TCS were positively associated with HNE-MA, 8-isoPGF_2α and 8-OHdG. Significant rs6855040 (4p15.32/between SNORA75B and QDPR)-BPA, rs1112943 (4q35.1/SNX25)-TCS interactions were associated with the 8-isoPGF_2α levels (all P < 5 × 10^-8). In addition, rs4656116 (1p22.3/CACL1), rs16958760 (17p11.2/between USP43 and DHRS7C) and rs11651078 (17p11.2/LOC339260) showed significant gene-TCS interactions with 8-OHdG (all P < 5 × 10^-8). The gene-level analysis found significant interaction between SNX25 and TCS for 8-isoPGF_2α levels (P < 2.12 × 10^-6).

CONCLUSION

Our results identify several gene-EDCs interactions for oxidative stress, highlighting that EDCs may modify the effect of genetic variants on oxidative stress.

Arsenic exposure and biomarkers for oxidative stress and telomere length in indigenous populations in Bolivia

BACKGROUND

Women living in the Bolivian Andes are environmentally exposed to arsenic, yet there is scarce information about arsenic-related effects in this region. Several biomarkers for telomere length and oxidative stress (mitochondrial DNA copy number, mtDNAcn; 8-Oxo-2'-deoxyguanosine, 8-oxo-dG; and 4-hydroxy nonenal mercapturic acid, 4-HNE-MA) have been previously linked to arsenic, and some of which are prospective biomarkers for cancer risk.

OBJECTIVE AND HYPOTHESIS

To evaluate associations between arsenic exposure and telomere length, mtDNAcn, 8-oxo-dG, and 4-HNE-MA in Bolivians. Arsenic exposure was hypothesized to be positively associated with all four toxicity biomarkers, particularly in individuals with a less efficient arsenic metabolism.

METHODS

The study encompassed 193 indigenous women. Arsenic exposure was assessed in urine as the sum of inorganic arsenic metabolite concentrations (U-As) measured by HPLC-HG-ICP-MS, and in whole blood as total arsenic (B-As) measured by ICP-MS. Efficiency of arsenic metabolism was evaluated by a polymorphism (rs3740393) in the main arsenic methylating gene AS3MT measured by TaqMan allelic discrimination, and by the relative fractions of urinary inorganic arsenic metabolites. Telomere length and mtDNAcn were determined in peripheral blood leukocytes by quantitative PCR, and urinary 8-oxo-dG and 4-HNE-MA by LC-MS/MS.

RESULTS

U-As and B-As were associated with longer telomeres and higher mtDNAcn, particularly in women with a less efficient arsenic metabolism. Urinary 8-oxo-dG and 4-HNE-MA were positively associated with U-As, but only 4-HNE-MA was associated with B-As. Arsenic metabolism efficiency did not have a clear effect on the concentrations of either of these biomarkers.

CONCLUSION

Bolivian women showed indications of arsenic toxicity, measured by four different biomarkers. Telomere length, mtDNAcn, and 4-HNE-MA were positively associated with both U-As and B-As. The association of arsenic exposure with telomere length and mtDNAcn was only present in Bolivian women with a less efficient metabolism. These findings call for additional efforts to evaluate and reduce arsenic exposure in Bolivia.

Combined effects of exposure to polycyclic aromatic hydrocarbons and metals on oxidative stress among healthy adults in Caofeidian, China

Exposure to polycyclic aromatic hydrocarbons (PAHs) and metals is associated with many adverse effects on human health, accompanied by oxidative stress. This study aimed to investigate the effects of co-exposure to PAHs and metals on oxidative stress in healthy adults. A preliminary longitudinal panel study was conducted between 2017 and 2018 in 45 healthy college students in Caofeidian, China. Six urinary monohydroxylated-PAHs (OH-PAHs), ten metals, 8-hydroxydeoxyguanosine (8-OHdG), and 8-iso-prostaglandin-F2α (8-iso-PGF2α) were measured. Linear mixed effects (LME) models and Bayesian kernel machine regression (BKMR) models were used to explore the associations of urinary OH-PAHs and metals with 8-OHdG and 8-iso-PGF2α. LME models showed that most urinary OH-PAHs and metals were positively associated with 8-OHdG and 8-iso-PGF2α. For example, a one-unit increase in the ln-transformed level of 1-hydroxypyrene (1-OHPyr) and vanadium (V) was associated with an increase of 143.8% (95% CI: 105.7 - 188.9%) and 105.8% (95% CI: 79.2-136.4%) in 8-OHdG; 8-iso-PGF2α increased by 118.9% (95% CI: 99.2-140.5%) and 83.9% (95% CI: 67.2-102.2%) with a one-unit increase in the ln-transformed level of 3-hydroxyphenanthrene (3-OHPhe) and aluminum (Al). BKMR models indicated the overall positive associations of the mixture of six OH-PAHs, ten metals, or six OH-PAHs and ten metals with 8-OHdG and 8-iso-PGF2α. Urinary 1-OHPyr and V were identified as the major contributors to the increased urinary 8-OHdG levels, while urinary 3-OHPhe and Al were the most vital contributors to the increased urinary 8-iso-PGF2α levels. The results revealed the longitudinal dose-response relationships of urinary OH-PAHs and metals with oxidative stress among healthy adults in Caofeidian; this finding serves as an evidence regarding the early health hazard caused by exposure to PAHs and metals and has implications for the environmental management of PAH and metal emissions in this area.

Associations of propylene oxide exposure with fasting plasma glucose and diabetes: Roles of oxidative DNA damage and lipid peroxidation

Whether propylene oxide (PO) exposure is associated with hyperglycemia were rarely explored. We aimed to determine the relationship between PO exposure and glucose metabolism, and potential role of oxidative stress. Among 3294 Chinese urban adults, urinary PO metabolite (N-Acetyl-S-(2-hydroxypropyl)-L-cysteine, 2HPMA), biomarkers of oxidative DNA damage (8-oxo-7,8-dihydro-20-deoxyguanosine, 8-OHdG) and lipid peroxidation (8-isoprostane, 8-iso-PGF_2α) in urine were determined. The associations of 2HPMA with 8-OHdG, 8-iso-PGF_2α, fasting plasma glucose (FPG), and risk of diabetes were explored. The roles of 8-OHdG and 8-iso-PGF_2α on association of 2HPMA with FPG and risk of diabetes were detected. After adjusted for potential confounders, each 1-unit increase in log-transformed concentration of 2HPMA was associated with a 0.15-mmol/L increase in FPG level, and the adjusted OR (95% CI) of diabetes by the associations of log-transformed urinary 2HPMA concentrations was 1.47 (95% CI: 1.03-2.11). Combination effects of 2HPMA with 8-OHdG or 8-iso-PGF_2α on risk of diabetes were detected, and elevated 8-iso-PGF_2α significantly mediated 34.5% of the urinary 2HPMA-associated FPG elevation. PO exposure was positively associated with FPG levels and risk of diabetes. PO exposure combined with DNA oxidative damage or lipid peroxidation may increase the risk of diabetes, and lipid peroxidation may partially mediate the PO exposure-induced FPG elevation.

OUP accepted manuscript

Over the past half-century, the world has witnessed a steep decline in fertility rates in virtually every country on Earth. This universal decline in fertility is being driven by increasing prosperity largely through the mediation of social factors, the most powerful of which are the education of women and an accompanying shift in life’s purpose away from procreation. In addition, it is clear that environmental and lifestyle factors are also having a profound impact on our reproductive competence particularly in the male where increasing prosperity is associated with a significant rise in the incidence of testicular cancer and a secular decline in semen quality and testosterone levels. On a different timescale, we should also recognize that the increased prosperity associated with the demographic transition greatly reduces the selection pressure on high fertility genes by lowering the rates of infant and childhood mortality. The retention of poor fertility genes within the human population is also being exacerbated by the increased uptake of ART. It is arguable that all of these elements are colluding to drive our species into an infertility trap. If we are to avoid the latter, it will be important to recognize the factors contributing to this phenomenon and adopt the social, political, environmental and lifestyle changes needed to bring this situation under control.

Intraperitoneal kisspeptin-10 administration ameliorates sodium arsenite-induced reproductive toxicity in adult male mice

The current study investigated the protective ameliorative effect of intraperitoneally administered kisspeptin-10 (50 nmol/day) against reproductive toxicity in adult male mice challenged with 35 days of exposure to sodium arsenite in drinking water. Mice were divided into tap water control, sodium arsenite-alone (4 ppm and 10 ppm), kisspeptin-alone (intermittent and continuous) and combined (sodium arsenite +kisspeptin-10 intermittent and continuous) treatment groups. Results revealed protective effect of both intermittent and continuous kisspeptin doses on reproductive organs against sodium arsenite-induced toxicity. This was indicated by an increase (p < 0.001) in the activity of antioxidant enzymes and a decrease (p < 0.001) in the levels of oxidative stress biomarkers. Concomitant significant increase was noticeable in the relative organ weight (p < 0.01), and serum testosterone and seminal fructose (p < 0.001), and a significant improvement in sperm parameters was also observed. A significant downregulation of lactate dehydrogenase concentration demonstrated further the protective effect of kisspeptin against tissue damage. Histologically, both treatment regimens of kisspeptin combined with sodium arsenite exposure prevented massive germ cell loss and tissue damage, a condition prominent in sodium arsenite-alone-treated mice. The study demonstrates for the first time kisspeptin's potential to mitigate the biochemical and histotoxic effects of arsenic on male reproductive system.

Inorganic elements in occupational settings: A review on the effects on telomere length and biology

The past decades have shown that telomere crisis is highly affected by external factors. Effects of human exposure to xenobiotics on telomere length (TL), particularly in their workplace, have been largely studied. TL has been shown to be an efficient biomarker in occupational risk assessment. This is the first review focusing on studies about the effects on TL from occupational exposures to metals (lead [Pb] and mixtures), and particulate matter (PM) related to inorganic elements. Data from 15 studies were evaluated regarding occupational exposure to metals and PM-associated inorganic elements and impact on TL. Potential complementary analyses and subjects' background (age, length of employment and gender) were also assessed. There was limited information on the correlations between work length and TL dynamics, and that was also true for the correlation between age and TL. Results indicated that TL is affected differently across the types of occupational exposure investigated in this review, and even within the same exposure, a variety of effects can be observed. Fifty-three percent of the studies observed decreased TL in occupational exposure among welding fumes, open-cast coal mine, Pb and PM industries workers. Two studies focused particularly on the levels of metals and association with TL, and both linear and non-linear associations were found. Interestingly, TL modifications were accompanied by increase in DNA damage in 7 out of 8 studies that investigated it, measured either by Cytokinesis-block Micronucleus Assay or Comet assay. Five studies also investigated oxidative stress parameters, and 4 of them found increased levels of oxidative damage along with TL impairment. Oxidative stress is one of the main mechanisms by which telomeres are affected due to their high guanine content. Our review highlights the need of further studies accessing TL in simultaneous occupational exposure to mixtures of xenobiotics.

Associations between depression, oxidative stress, and semen quality among 1,000 healthy men screened as potential sperm donors

OBJECTIVE

To explore the association between depression and semen quality and the mediating role of oxidative stress.

DESIGN

Cross-sectional study with repeated measures of semen quality.

SETTING

Human Sperm Bank of Hubei Province, People's Republic of China.

PATIENT(S)

From April 2017 to July 2018, we recruited 1,000 potential sperm donors who completed the Beck Depression Inventory questionnaire and had measures of oxidative stress biomarkers.

INTERVENTION(S)

None.

MAIN OUTCOME MEASURE(S)

Severity of depression was evaluated by the Beck Depression Inventory scores (0-4, no depression; 5-13, mild depression; 14-20, moderate depression; and 21 or greater, severe depression). The urinary concentrations of 8-hydroxy-2-deoxyguanosine, 4-hydroxy-2-nonenal-mercapturic acid, and 8-iso-prostaglandin F_2α (8-isoPGF_2α) were measured to reflect oxidative stress status. Repeated semen quality parameters (n = 5,880) were examined by trained professional technicians according to the World Health Organization laboratory manual. Associations between depression, oxidative stress, and repeated measures of semen quality parameters were evaluated using linear or mixed-effects models with adjustment for potential confounders. Mediation analysis was performed to test the potential mediating role of oxidative stress.

RESULT(S)

A total of 391 (39.1%) men were classified as mild depression, 67 (6.7%) as moderate depression, and 19 (1.9%) as severe depression. Inverse dose-response relationships between severity of depression and semen quality parameters were found. Compared with men without depression (n = 523), those with severe depression had a 25.26% (95% confidence interval, -38.65%, -8.93%) lower semen volume, 37.04% (-55.37%, -11.20%) lower total sperm count, 13.57% (-23.17%, -2.78%) lower total motility, and 15.08% (-25.09%, -3.72%) lower progressive motility; men with moderate depression also had a 12.28% (-21.16%, -2.40%) lower semen volume and 23.56% (-36.50%, -7.97%) lower total sperm count. We found a positive dose-response relationship between severity of depression and urinary 8-isoPGF_2α concentrations. However, we found no evidence that the associations between depression status and semen quality were mediated by oxidative stress markers.

CONCLUSION(S)

In the study of Chinese male sperm donors, men with depression had worse semen quality parameters, including semen volume, sperm concentration, total sperm count, total motility, and progressive motility. Although depression was positively associated with urinary 8-isoPGF_2α concentrations, depression-semen quality associations were not mediated by oxidative stress.

Impact of Heavy Metals on Human Male Fertility-An Overview

Heavy metals are endocrine disruptors which interfere with processes mediated by endogenous hormones of the organism, negatively affecting endocrine functions. Some studies have correlated heavy metal exposure with male infertility. However, the number of studies conducted on humans are limited. Therefore, the aim of this study is to summarize the current knowledge on how heavy metals influence human male fertility. Hence, three distinct databases were consulted—PubMed, Scopus and Web of Science—using single keywords and combinations of them. The total number of identified articles was 636. Nevertheless, by using the inclusion and exclusion criteria, 144 articles were finally included in this work. Results display that the development of adequate instruments for heavy metal assessment may play an important function in human male fertility diagnosis and treatment. Furthermore, clinical trials could be useful to confirm the role of heavy metals in human male fertility diagnosis. Overall, further research is required to fully understand the molecular and cellular basis of the influence of environmental and occupational exposure to heavy metals on human male infertility and reproductive outcomes.

The Effects of Mung Bean Peptide and Its’ Complexes on the Treatment of Lead Poisoning

Objective. To investigate the effects of mung bean peptide and its’ complexes on promoting lead excretion and neuroprotection of zebrafish. Methods. The lead poisoning models of zebrafish were established by lead acetate solution; the models were treated with high and low concentrations (58.3 and 175 μg/mL) of mung bean peptides, with high, medium, and low concentrations (27.8, 83.3, and 250 μg/mL) of mung bean peptide complexes, separately. The effects of the mung bean peptide complexes on the lead content, axonal fluorescence intensity, and peripheral motor nerve length changes were identified in the zebrafish model, and the effects of mung bean peptide and its’ complexes on zebrafish's lead excretion, axonal protection rate, and peripheral movement promotion rate of nerve regeneration were calculated. Results. The effects of high concentration of mung bean peptide (175 μg/mL) in promoting lead excretion was 29% ( $p<0.05$ ), and the effect of high concentration of mung bean peptide complexes (250 μg/mL) in promoting lead excretion was 30% ( $p<0.05$ ). The other concentrations of mung bean peptide and its’ complex groups did not show a noticeable lead excretion effect. The protective effects of mung bean peptide at concentrations of 58.3 and 175 μg/mL against zebrafish axonal injury were 98% and 101% ( $p<0.01$ ), and the peripheral nerve regeneration promotion effects were 29% ( $p>0.05$ ) and 42% ( $p<0.05$ ), respectively. The protective effects of mung bean peptide complexes at concentrations of 27.8, 83.3, and 250 μg/mL against zebrafish axonal injury were 85%, 78%, and 93% ( $p<0.01$ ); peripheral nerve regeneration promotion rates were 46%, 50%, and 50% ( $p<0.05$ ). Conclusion. The mung bean peptide and its’ complexes can effectively promote the discharge of lead in the zebrafish lead poisoning and have protective and regeneration effects on zebrafish nerves.

Quercetin mediated attenuation of cadmium-induced oxidative toxicity and apoptosis of spermatogenic cells in caprine testes in vitro

Cadmium (Cd), an environmental toxic heavy metal, has been reported to cause testicular toxicity, which contributes to the recent decline in male fertility worldwide. Quercetin (Qcn), a major dietary antioxidant, has been shown to have protective effects under various pathological conditions. However, whether Qcn provides protection against Cd-stimulated testicular toxicity remains obscured. The present study was therefore aimed at investigating the ameliorative effect of Qcn supplementation on Cd-induced toxicity in the goat testis in vitro in a dose-(10, 50, and 100 μM) and time-dependent (4 and 8 h) manner. Different cytotoxicity, genotoxicity, and biochemical analyses have been carried out using appropriate methods. Cytotoxicity in testicular cells induced by Cd treatment was apparently mitigated by Qcn treatment, evidenced by decreased apoptotic attributes or frequency in Qcn plus Cd-treated groups compared to the only Cd-treated groups. Qcn treatment provides substantial protection to the Cd-triggered aggression in oxidative (increased MDA levels) and total antioxidant capacity (reduced FRAP activity) in testicular tissue, indicating the anti-oxidative function of Qcn against Cd exposure. Moreover, Cd-induced decline in antioxidant status (CAT, SOD, and GST activity) was markedly restored by Qcn supplementation in testicular tissue. In conclusion, this study shows that Qcn treatment significantly attenuated the Cd-evoked testicular damage, suggesting its beneficial potential in preventing or at least in managing the gonadotoxicity in males induced by steadily increasing Cd contamination in the environment.

Biomarkers of effect as determined in human biomonitoring studies on hexavalent chromium and cadmium in the period 2008-2020

A number of human biomonitoring (HBM) studies have presented data on exposure to hexavalent chromium [Cr(VI)] and cadmium (Cd), but comparatively few include results on effect biomarkers. The latter are needed to identify associations between exposure and adverse outcomes (AOs) in order to assess public health implications. To support improved derivation of EU regulation and policy making, it is of great importance to identify the most reliable effect biomarkers for these heavy metals that can be used in HBM studies. In the framework of the Human Biomonitoring for Europe (HBM4EU) initiative, our study aim was to identify effect biomarkers linking Cr(VI) and Cd exposure to selected AOs including cancer, immunotoxicity, oxidative stress, and omics/epigenetics. A comprehensive PubMed search identified recent HBM studies, in which effect biomarkers were examined. Validity and applicability of the markers in HBM studies are discussed. The most frequently analysed effect biomarkers regarding Cr(VI) exposure and its association with cancer were those indicating oxidative stress (e.g., 8-hydroxy-2'-deoxyguanosine (8-OHdG), malondialdehyde (MDA), glutathione (GSH)) and DNA or chromosomal damage (comet and micronucleus assays). With respect to Cd and to some extent Cr, β-2-microglobulin (B2-MG) and N-acetyl-β-D-glucosaminidase (NAG) are well-established, sensitive, and the most common effect biomarkers to relate Cd or Cr exposure to renal tubular dysfunction. Neutrophil gelatinase-associated lipocalin (NGAL) and kidney injury molecule (KIM)-1 could serve as sensitive biomarkers of acute kidney injury in response to both metals, but need further investigation in HBM studies. Omics-based biomarkers, i.e., changes in the (epi-)genome, transcriptome, proteome, and metabolome associated with Cr and/or Cd exposure, are promising effect biomarkers, but more HBM data are needed to confirm their significance. The combination of established effect markers and omics biomarkers may represent the strongest approach, especially if based on knowledge of mechanistic principles. To this aim, also mechanistic data were collected to provide guidance on the use of more sensitive and specific effect biomarkers. This also led to the identification of knowledge gaps relevant to the direction of future research.

Associations between blood metal/ metalloid concentration and human semen quality and sperm function: A cross-sectional study in Hong Kong

BACKGROUND

The association between metal/metalloid exposure on human sperm quality is still inconclusive. There is a lack of data on the effect of metal/metalloid on sperm function.

METHODS

The aim of this study was to clarify the association between blood metal/metalloid concentration and traditional and functional sperm parameters, the blood concentration of Pb, Hg, Cd, As, Ni, Mo, Zn, Cu, Se, Fe, Mg, Cr and Ca of 288 men in Hong Kong were assessed by inductively coupled plasma-mass spectrometry, and sperm parameters including sperm concentration, motility, morphology, vitality, total sperm count, total motile sperm count, sperm DNA fragmentation and sperm acrosome reaction were measured. Demographic and lifestyle questionnaires were also provided for all participants. Multivariable linear regression analysis was performed to test the association between blood metal/ metalloid concentration and semen parameters after adjusting for relevant confounding variables.

RESULTS

The results showed that moderate to high level of blood Pb concentration (>27.19 μg/L) appeared to be negatively associated with sperm morphology (P < 0.05); high level of blood Cd concentration (>1.44 μg/L) was negatively associated with sperm acrosome reaction (P < 0.05); Mo was positively associated with semen volume (P < 0.05), however, high level of blood Mo concentration (>13.52 μg/L) was negatively associated with sperm vitality (P < 0.05); high level of blood Zn concentration (>6.20 mg/L) was positively associated with sperm vitality (P < 0.05); moderate level of blood Fe concentration (526.89-566.63 mg/L) was positively associated with sperm acrosome reaction (P < 0.05); moderate level of blood Ca concentration (55.92-66.10 mg/L) was positively associated with semen volume (P < 0.05); however, lower level of blood Ca concentration (45.90-55.92 mg/L) was negatively associated with sperm morphology (P < 0.05).

CONCLUSIONS

Our results suggested that the sperm function could be affected by blood Cd and Fe concentration and traditional sperm parameters could be affected by blood concentration of Mo, Zn, Pb and Ca.