Polymorphisms in CYP1B1 modify the risk of idiopathic male infertility with abnormal semen quality

Dioxin exposure associated with fecundability and infertility in mothers and daughters of Seveso, Italy

STUDY QUESTION

Is there an association between 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) exposure and fecundability and infertility among Seveso women and their daughters?

SUMMARY ANSWER

TCDD exposure is associated with a decrease in fecundability and increased risk of infertility in women, as well as their daughters.

WHAT IS KNOWN ALREADY

In animal studies, maternal exposure to TCDD is associated with decreased fertility in offspring. Effects of TCDD are mediated by activation of the aryl hydrocarbon receptor (AHR) pathway.

STUDY DESIGN, SIZE, DURATION

The Seveso Women's Health Study (SWHS) has followed 981 women exposed to TCDD in a 1976 accident since 1996. In 2014, we initiated the Seveso Second Generation Study to follow-up their children.

PARTICIPANTS/MATERIALS, SETTING, METHODS

We obtained information on pregnancy history including time of trying to conceive from SWHS women and their daughters who were 18 years or older. We considered TCDD exposure as initial 1976 serum TCDD concentration and estimated TCDD at pregnancy. We examined relationships of TCDD exposure with time to pregnancy (TTP, the monthly probability of conception within the first 12 months of trying) and infertility (≥12 months of trying to conceive). We also assessed contributions of polymorphisms in the AHR pathway via genetic risk score.

MAIN RESULTS AND THE ROLE OF CHANCE

Among SWHS women (n = 446), median TTP was 3 months and 18% reported taking ≥12 months to conceive. Initial 1976 TCDD (log10) was associated with longer TTP (adjusted fecundability odds ratio = 0.82; 95% CI 0.68-0.98) and increased risk of infertility (adjusted relative risk = 1.35; 95% CI 1.01-1.79). TCDD at pregnancy yielded similar associations. Among SWHS daughters (n = 66), median TTP was 2 months and 11% reported taking ≥12 months to conceive. Daughters showed similar, but non-significant, associations with maternal TCDD exposure.

LIMITATIONS, REASONS FOR CAUTION

A limitation of this study is time to pregnancy was reported retrospectively, although previous studies have found women are able to recall time to conception with a high degree of accuracy many years after the fact. The number of SWHS daughters who had a live birth was small and we were unable to examine fecundability of SWHS sons.

WIDER IMPLICATIONS OF THE FINDINGS

Consistent with previous findings in animal studies, our study found that TCDD exposure may be associated with decreased fertility in Seveso mothers and potentially in their daughters exposed in utero. There may be susceptible genetic subgroups. The literature has largely considered the genetics of the AHR pathway in the context of male fertility but not female fertility, despite strong biological plausibility. These findings should be replicated in larger populations and of different ancestry. Future studies in Seveso should examine the sons and the grandchildren of exposed mothers given the animal literature suggesting potential heritable epigenetic effects.

STUDY FUNDING/COMPETING INTEREST(S)

This study was supported by grant numbers F06 TW02075-01 from the National Institutes of Health, R01 ES07171 and 2P30-ESO01896-17 from the National Institute of Environmental Health Sciences, R82471 from the U.S. Environmental Protection Agency and #2896 from Regione Lombardia and Fondazione Lombardia Ambiente, Milan, Italy. J.A. was supported by F31ES026488 from the National Institutes of Health. The authors declare they have no actual or potential competing financial interests.

TRIAL REGISTRATION NUMBER

N/A.

Lack of association between aryl hydrocarbon receptor gene Arg554Lys polymorphism and male infertility risk: A systematic review and meta-analysis

OBJECTIVES

The association between aryl hydrocarbon receptor gene (AhR) polymorphism and male infertility risk remains conflicting. We conducted a meta-analysis to examine the AhR Arg554Lys polymorphism in relation to the susceptibility to male infertility.

STUDY DESIGN

Studies concerning the association between AHR polymorphism and male infertility were searched and related information were extracted from the included studies. The STATA 12.0 software was used to perform a meta-analysis. Pooled odd ratios (ORs) and corresponding 95% confidence intervals (CIs) were calculated to estimate the association.

RESULTS

Six case-control studies with 1234 cases and 1755 controls were included after literature research and data collection. Overall, the results indicated there was no association between the AhR Arg554Lys polymorphism and male infertility risk (G versus A, OR (95%CI) = 0.958 (0.710-1.291); GG vs AA, OR (95%CI) = 0.874 (0.702-1.088); GA versus AA, OR (95%CI) = 0.911(0.477-1.740); GG + GA vs AA, OR (95%CI) = 0.891 (0.468-1.696); GG versus GA + AA, OR (95%CI) = 1.049(0.896-1.229)). Subgroup analysis by study population revealed there was no association between AhR Arg554Lys polymorphism and susceptibility to male infertility in Asian population (G versus A, OR (95%CI) = 1.099 (0.940-1.286); GG vs AA, OR (95%CI) = 0.982 (0.781-1.235); GA versus AA, OR (95%CI) = 1.220 (0.726-2.052); GG + GA vs AA, OR (95%CI) = 1.221 (0.740-1.982); GG versus GA + AA, OR (95%CI) = 1.087 (0.919-1.286)).

CONCLUSIONS

The association between AHR Arg55Lys polymorphism and male infertility risk was not confirmed in our meta-analysis. However, the results should be interpreted with caution and further studies are required.

Selection for female traits of high fertility affects male reproductive performance and alters the testicular transcriptional profile

Background

Many genes important for reproductive performance are shared by both sexes. However, fecundity indices are primarily based on female parameters such as litter size. We examined a fertility mouse line (FL2), which has a considerably increased number of offspring and a total litter weight of 180% compared to a randomly bred control line (Ctrl) after more than 170 generations of breeding. In the present study, we investigated whether there might be a parallel evolution in males after more than 40 years of breeding in this outbred mouse model.

Results

Males of the fertility mouse line FL2 showed reduced sperm motility performance in a 5 h thermal stress experiment and reduced birth rate in the outbred mouse line. Transcriptional analysis of the FL2 testis showed the differential expression of genes associated with steroid metabolic processes (Cyp1b1, Cyp19a1, Hsd3b6, and Cyp21a1) and female fecundity (Gdf9), accompanied by 150% elevated serum progesterone levels in the FL2 males. Cluster analysis revealed the downregulation of genes of the kallikrein-related peptidases (KLK) cluster located on chromosome 7 in addition to alterations in gene expression with serine peptidase activity, e.g., angiotensinogen (Agt), of the renin-angiotensin system essential for ovulation. Although a majority of functional annotations map to female reproduction and ovulation, these genes are differentially expressed in FL2 testis.

Conclusions

These data indicate that selection for primary female traits of increased litter size not only affects sperm characteristics but also manifests as transcriptional alterations of the male side likely with direct long-term consequences for the reproductive performance of the mouse line.

Electronic supplementary material

The online version of this article (10.1186/s12864-017-4288-z) contains supplementary material, which is available to authorized users.

Gene-gene and gene-environment interactions on risk of male infertility: Focus on the metabolites

Infertility affects about 17% couples, and males contribute to half of the cases. Compared with independent effects of genetic and environmental factors, interactions between them help in the understanding of the susceptibility to male infertility. Thus, we genotyped 25 polymorphisms, measured 16 urinary chemical concentrations and explored interactions between gene-gene and gene-environment in 1039 Han Chinese using metabolomic analysis. We first observed that GSTT1 might interact with GSTM1 (Pinter=6.33×10(-8)). Furthermore, an interaction between GSTM1 and 4-n-octylphenol (4-n-OP) was identified (Pinter=7.00×10(-3)), as well as a 2-order interaction among GSTT1, GSTM1 and 4-n-OP (Pinter=0.04). Subjects with GSTT1-present and GSTM1-null genotypes were susceptible to male infertility when exposed to 4-n-OP (OR=14.05, 95% CI=4.78-60.20, P=2.34×10(-5)). Most metabolites identified were involved in the tricarboxylic acid cycle. In conclusion, it is a novel study of the interaction on male infertility from the aspect of metabolomics.

Genetic polymorphisms in Cytochrome P 4501B1 and susceptibility to idiopathic preterm labor in North Indian population

OBJECTIVE

The etiology of preterm labor (PTL) is still unknown, but it may be related to a possible genetic predisposition together with involvement of environmental factors. We investigated the relation between PTL and polymorphisms in Cytochrome P4501B1 (CYP1B1) gene, which is involved in the metabolism of a wide range of environmental toxins and hormones.

DESIGN AND METHODS

Three hundred (n=300) cases of PTL and equal number of subjects of full term labor (FTL), after excluding all the known risk factors for PTL were included in the study. A two step allele specific PCR was performed for polymorphic analysis of CYP1B1 gene.

RESULTS

The homozygous variant genotype of CYP1B1*2 (OR=2.97, 95%CI=1.08-8.08, p=0.033) and heterozygous variant of CYP1B1*3 (OR=2.57, 95%CI=1.88-3.63, p=0.001), and CYP1B1*7 (OR=2.59, 95%CI=1.85-3.62, p=0.001) were found to be significantly higher in PTL cases as compared to FTL.

CONCLUSIONS

The present study demonstrates the possible association of homozygous variant of CYP1B1*2 and heterozygous variant of CYP1B1*3 and CYP1B1*7 genes with the increased risk of PTL.

MicroRNA-122 influences the development of sperm abnormalities from human induced pluripotent stem cells by regulating TNP2 expression

Sperm abnormalities are one of the main factors responsible for male infertility; however, their pathogenesis remains unclear. The role of microRNAs in the development of sperm abnormalities in infertile men has not yet been investigated. Here, we used human induced pluripotent stem cells to investigate the influence of miR-122 expression on the differentiation of these cells into spermatozoa-like cells in vitro. After induction, mutant miR-122-transfected cells formed spermatozoa-like cells. Flow cytometry of DNA content revealed a significant increase in the haploid cell population in spermatozoa-like cells derived from mutant miR-122-transfected cells as compared to those derived from miR-122-transfected cells. During induction, TNP2 and protamine mRNA and protein levels were significantly higher in mutant miR-122-transfected cells than in miR-122-transfected cells. High-throughput isobaric tags for relative and absolute quantification were used to identify and quantify the different protein expression levels in miR-122- and mutant miR-122-transfected cells. Among all the proteins analyzed, the expression of lipoproteins, for example, APOB and APOA1, showed the most significant difference between the two groups. This study illustrates that miR-122 expression is associated with abnormal sperm development. MiR-122 may influence spermatozoa-like cells by suppressing TNP2 expression and inhibiting the expression of proteins associated with sperm development.

Microarray analysis of microRNA expression patterns in the semen of infertile men with semen abnormalities

MicroRNAs (miRNAs) play a crucial role in tissue development and the pathology of many diseases, however, the effects and roles of miRNAs in the development of semen abnormalities in infertile males have not yet been investigated. In this study, we analyzed and compared the miRNA expression profiles of abnormal semen from 86 infertile males with normal semen from 86 healthy males using an miRNA microarray. In total, 52 miRNAs were differentially expressed between the abnormal semen of infertile males and the normal semen of healthy males. The differential expression of selected miRNAs was validated by real time qRT-PCR and northern blotting: miR-574-5p, miR-297, miR-122, miR-1275, miR-373, miR-185 and miR-193b were upregulated (fold change>1.5, p<0.001) and miR-100, miR-512-3p, miR-16, miR-19b, miR-23b and miR-26a were downregulated (fold change<0.667, p<0.001) in the semen of infertile males with semen abnormalities. In conclusion, this study provides new insights into specific miRNAs that are associated with semen abnormalities in infertile males.