Identifying windows of susceptibility to essential elements for semen quality among 1428 healthy men screened as potential sperm donors

BACKGROUND

Essential elements such as iron (Fe), cobalt (Co), copper (Cu), zinc (Zn), selenium (Se), rubidium (Rb), strontium (Sr), and molybdenum (Mo) are necessary for reproductive health. However, their associations with human semen quality remain inconclusive.

OBJECTIVES

To investigate the associations of urinary Fe, Co, Cu, Zn, Se, Rb, Sr, and Mo concentrations with semen quality in healthy men screened as potential sperm donors and identify critical windows of susceptibility.

METHODS

1428 healthy men provided 3766 urine and 6527 semen samples, which were measured for urinary essential element concentrations and sperm quality parameters, respectively. Linear mixed models and cubic spline curves were used to evaluate associations between urinary essential elements and semen quality. Multiple informant models were used to identify potential critical windows of susceptibility.

RESULTS

Linear mixed models and cubic spline curves showed positive dose-response relationships between urinary Zn and sperm concentration and total count and between urinary Mo and total sperm count [all False Discovery Rate (FDR) adjusted p-value for trend < 0.05]. In the multiple-element linear mixed models, the men in the highest versus lowest quartiles of urinary Zn and Mo had a higher sperm concentration of 17.5% (95% CI: 2.8%, 34.2%; p-value for trend = 0.006) and total sperm count of 18.3% (95% CI: 1.4%, 38.0%; p-value for trend = 0.027), respectively. Urinary Zn was also positively associated with total sperm count in a dose-dependent manner (p-value for trend = 0.036), though the percentile difference in total sperm count between men in the highest and lowest quartile was not statistically significant (16.4%, 95% CI: -1.7%, 37.9%). These associations appeared to be stronger when urinary Zn and Mo were measured at 0-9 days before the date of semen examination (i.e., corresponding to epididymal storage).

CONCLUSIONS

Higher urinary Zn and Mo, particularly during the period of epididymal storage, were associated with greater sperm production.

Gendering gametes: The unequal contributions of sperm and egg donors

This paper compares three groups of gestational mothers who relied on gametes from donors they did not know. The three groups are women who have conceived with donor sperm and their own eggs, women who have conceived with donor eggs and a partner's sperm, and women who have conceived with embryos composed of both donor eggs and donor sperm. The paper explores three issues. First, it considers whether intending parents select sperm and egg donors for different attributes both when they are chosen as the only donor and when they are chosen as donors contributing to an entire embryo. Second, it examines how women imagine the donor. Finally, it looks at how women conceptualize the donor as an individual who contributes to their child's characteristics. Two significant findings emerged in this analysis of survey data. First, the data show that gametes are gendered with different attributes both when those gametes are separate and even more so when seen as complementary parts of a whole. Second, the data show that women minimize the impact of the egg donor (both when a sole contribution and especially when part of the complementary whole) and thus ignore the influence or impact of the egg donor relative to how they make sense of the influence or impact of the sperm donor. The data for this study comes from an online survey developed by the authors.

Decline of semen quality over the last 30 years in Uruguay

BACKGROUND

Over the last years, there has been an increasing concern about a global decline in men's fertility. Specifically, some evidence indicates that sperm quality has decreased over the last years. However, reports showing the changes in sperm quality with time are inconsistent. Part of the contradictions between studies is attributed to geographical differences. Surprisingly, few studies include data from South American countries, creating a bias in the conclusions. This study aims to determine how sperm quality has evolved over the past 30 years in Uruguay. For this purpose, 317 medical records from allegedly healthy sperm donor candidates, aged between 18 and 36 years old, who voluntarily requested to be considered as sperm donors between 1988 and 2019, were analyzed. The studied variables were the following sperm parameters: semen volume, sperm cell concentration, total sperm number, progressive motility, vitality, and sperm morphology. A correlative statistical analysis was performed between seminal parameter values and the year data were collected.

RESULTS

We found a statistically significant decrease in sperm concentration and normal sperm morphology during the studied period. There was no decrease in vitality, seminal volume, and total progressive motility. Semen parameters were not associated with tobacco, drugs, or alcohol consumption.

CONCLUSIONS

We conclude that the sperm quality of donor candidates in Uruguay decreased during this period. Further studies should be carried out to verify the occurrence of this phenomenon in the general population and find its possible causes.

Genetic testing of sperm donors for cystic fibrosis and spinal muscular atrophy: evaluation of clinical utility

OBJECTIVE

To evaluate the clinical utility of genetic testing for cystic fibrosis (CF) and spinal muscular atrophy (SMA) in sperm donors.

STUDY DESIGN

We studied the results of the genetic tests for CF and SMA applied to 372 sperm donor candidates. The CF carrier screening test analysed 32 mutations on the CFTR gene. Regarding SMA, the carrier test studied possible deletions of SMN1/2 by Multiplex Ligation-dependent Probe Amplification (MLPA) methodology.

RESULTS

The carrier frequency obtained was greater for SMA than for CF. After adjusting the results obtained for the sensitivity of the tests, and taking into account the prevalence of female carriers in our population, the probability of transmission of the disease to the child from a donor with a negative genetic test was about five times lower in the case of SMA than in CF, although this difference was not statistically significant. The number of donors needed to screen (NNS) to avoid the occurrence of a child being affected by CF and SMA in our population was similar in both cases (1591 vs. 1536).

CONCLUSIONS

This study demonstrates the need to include SMA among the diseases for which genetic screening is performed in the process of sperm donor selection. We believe that testing donors for SMA is as important and as useful as doing so for CF.

Blood trihalomethane concentrations in relation to sperm mitochondrial DNA copy number and telomere length among 958 healthy men

BACKGROUND

In animal and human studies, exposure to trihalomethanes (THMs) has been associated with reduced semen quality. However, the underlying mechanisms remain poorly understood.

OBJECTIVE

To investigate the associations of blood THM concentrations with sperm mitochondrial DNA copy number (mtDNAcn) and telomere length (TL) among healthy men.

METHODS

We recruited 958 men who volunteered as potential sperm donors. A single blood sample was collected from each participant at recruitment and measured for chloroform (TCM), bromodichloromethane (BDCM), dibromochloromethane (DBCM), and bromoform (TBM) concentrations. Within a 90-day follow-up, the last semen sample provided by each participant was quantified for sperm mtDNAcn and TL. We used multivariable linear regression models to assess the associations between blood THM concentrations and sperm mtDNAcn and TL. We also performed stratified analyses according to the time intervals between baseline blood THM determinations and semen collection (i.e., 0-9, 10-14, 15-69, or >69 days) to explore potential windows of susceptibility.

RESULTS

After adjusting for potential confounders, we found inverse associations between quartiles (or categories) of blood TBM, brominated THM (Br-THM, the sum of BDCM, DBCM, and TBM), and total THM (TTHM, the sum of all four THMs) concentrations and sperm mtDNAcn (all P for trend≤0.03). Besides, we found inverse associations between quartiles of blood TCM, Br-THM, chlorinated THM (Cl-THM, the sum of TCM, BDCM, and DBCM), and TTHM concentrations and sperm TL (all P for trend<0.10). Stratified analyses showed stronger associations between Br-THM concentrations and sperm mtDNAcn determined 15-69 days since baseline exposure determinations, and between blood TCM and TTHM concentrations and sperm TL determined >69 days since baseline exposure determinations.

CONCLUSION

Exposure to THMs may be associated with sperm mitochondrial and telomeric dysfunction.

[Seasonal variations influenced the semen quality of the sperm donor in Beijing area]

OBJECTIVE

To investigate the change trends of sperm quality with seasonal variations among the volunteers of sperm donors in Beijing area, as well as the relationship between two parameters.

METHODS

Semen data from the volunteers of sperm donors in Human Sperm Bank of Peking University Third Hospital were collected using a retrospective study method. The subjects were divided into 4 seasonal groups based on the lunar solar terms and the time of sperm donation. The data were assessed to find whether there were differences in semen parameters among different seasonal groups, and to analyze the change trends and the influence of seasonal factors on semen parameters.

RESULTS

A total of 21 174 semen parameter data were analyzed. Firstly, to analyze all data as a whole, in spring, summer, autumn and winter groups, sperm concentration was (106.04±59.67)×10⁶/mL, (97.61±47.41)×10⁶/mL, (100.18±47.17)×10⁶/mL, (100.59±38.68)×10⁶/mL, respectively, and the spring group was significantly higher than the other 3 seasonal groups (P < 0.001); proportion of progressive motility sperm (PR) was 56.49%±12.76%, 58.02%±13.65%, 58.05%±12.36%, and 57.66%±12.61%, respectively, spring group was lower than the other three seasonal groups, and summer group was better among the latter (P < 0.001). There was no difference in normal rate of sperm morphology among the four seasonal groups. The qualified rate of sperm donors in the winter group was higher than that in the other three seasons groups (P < 0.01), while the qualified rate in the summer group was lower than that in the other three seasons groups. In addition, the semen parameters of the volunteers during the screening period and the official sperm donation period were analyzed respectively, which revealed that sperm concentration of spring group was higher than that of summer and winter groups, and PR was lower than that of summer and autumn groups. On account of the semen parameters of official sperm donation period, multiple linear regression analysis found that season was the main factor affecting sperm concentration, the average sperm concentration in spring group was about 6×10⁶/mL higher than in winter group, but PR was 2.9% lower in spring group compared with autumn group (all P < 0.05).

CONCLUSION

Season was the influencing factor of semen quality of sperm donors in Beijing area. We recommend spring and winter may be the preferred seasons for sperm donation.

[Seasonal variations influenced the semen quality of the sperm donor in Beijing area]

OBJECTIVE

To investigate the change trends of sperm quality with seasonal variations among the volunteers of sperm donors in Beijing area, as well as the relationship between two parameters.

METHODS

Semen data from the volunteers of sperm donors in Human Sperm Bank of Peking University Third Hospital were collected using a retrospective study method. The subjects were divided into 4 seasonal groups based on the lunar solar terms and the time of sperm donation. The data were assessed to find whether there were differences in semen parameters among different seasonal groups, and to analyze the change trends and the influence of seasonal factors on semen parameters.

RESULTS

A total of 21 174 semen parameter data were analyzed. Firstly, to analyze all data as a whole, in spring, summer, autumn and winter groups, sperm concentration was (106.04±59.67)×106/mL, (97.61±47.41)×106/mL, (100.18±47.17)×106/mL, (100.59±38.68)×106/mL, respectively, and the spring group was significantly higher than the other 3 seasonal groups (P < 0.001); proportion of progressive motility sperm (PR) was 56.49%±12.76%, 58.02%±13.65%, 58.05%±12.36%, and 57.66%±12.61%, respectively, spring group was lower than the other three seasonal groups, and summer group was better among the latter (P < 0.001). There was no difference in normal rate of sperm morphology among the four seasonal groups. The qualified rate of sperm donors in the winter group was higher than that in the other three seasons groups (P < 0.01), while the qualified rate in the summer group was lower than that in the other three seasons groups. In addition, the semen parameters of the volunteers during the screening period and the official sperm donation period were analyzed respectively, which revealed that sperm concentration of spring group was higher than that of summer and winter groups, and PR was lower than that of summer and autumn groups. On account of the semen parameters of official sperm donation period, multiple linear regression analysis found that season was the main factor affecting sperm concentration, the average sperm concentration in spring group was about 6×106/mL higher than in winter group, but PR was 2.9% lower in spring group compared with autumn group (all P < 0.05).

CONCLUSION

Season was the influencing factor of semen quality of sperm donors in Beijing area. We recommend spring and winter may be the preferred seasons for sperm donation.