Androgen receptor CAG repeat length is associated with ovarian reserve but not with ovarian response

Investigation of the role of X chromosome inactivation and androgen receptor CAG repeat polymorphisms in patients with recurrent pregnancy loss: a prospective case-control study

BACKGROUND

Previous research has revealed that skewed X chromosome inactivation (SXCI) and androgen receptor (AR) CAG polymorphisms are associated with increased risk of recurrent pregnancy loss (RPL); however, the results are conflicting, and the underlying mechanisms remain unclear. This study investigated the role of SXCI and AR CAG polymorphisms in patients with RPL and explored whether the underlying mechanisms were related to the ovarian reserve and preimplantation embryo aneuploidy.

METHODS

This was a prospective case-control study carried out in a tertiary hospital-based reproductive medicine center. An external validation RPL cohort was recruited during the study period. Data on baseline and cycle characteristics were collected. X-chromosome inactivation (XCI) was measured using a human AR assay. AR polymorphisms were assessed using quantitative fluorescent polymerase chain reactions and direct sequencing. Blastocysts of the patients with RPL were tested by single nucleotide polymorphism microarray based preimplantation genetic testing for aneuploidy.

RESULTS

In total, 131 patients with idiopathic RPL and 126 controls were included for the case-control study. Patients with RPL exhibited a significantly more skewed XCI distribution pattern (67.71 ± 10.50 vs. 64.22 ± 10.62, p = 0.011), as well as significantly shorter bi-allelic mean (18.56 ± 1.97 vs. 19.34 ± 2.38, p = 0.005) and X-weighted bi-allelic mean (18.46 ± 2.02 vs. 19.38 ± 2.53, p = 0.001) of AR CAG repeats. Multivariate logistic regression models indicated that CAG repeat < 20, SXCI, and duration of stimulation were independently associated with the risk of RPL. However, SXCI and AR CAG polymorphisms were not associated with ovarian reserve or preimplantation embryo aneuploidy in the RPL group, and the same results were attained in a separate validation cohort of 363 patients with RPL.

CONCLUSION

SXCI and AR CAG polymorphisms are related to RPL; however, these two factors do not lead to RPL by affecting the ovarian reserve or increasing embryo aneuploidy. The roles of SXCI and AR CAG in RPL may involve other mechanisms that require further investigation.

TRIAL REGISTRATION

NCT02504281, https://www.

CLINICALTRIALS

gov (Date of registration, 21/07/2015; date of enrolment of the first subject, 30/07/2015).

AOP key event relationship report: Linking decreased androgen receptor activation with decreased granulosa cell proliferation of gonadotropin-independent follicles

We recently proposed to formally recognize Key Event Relationships (KERs) as building blocks of Adverse Outcome Pathways (AOPs) that can be independently developed and peer-reviewed. Here, we follow this approach and provide an independent KER from AOP345, which describes androgen receptor (AR) antagonism leading to decreased female fertility. This KER connects AR antagonism to reduced granulosa cell proliferation of gonadotropin-independent follicles (KER2273). We have developed both the KER and the two adjacent Key Events (KEs). A systematic approach was used to ensure that all relevant supporting evidence for KER2273 was retrieved. Supporting evidence for the KER highlights the importance of AR action during the early stages of follicular development. Both biological plausibility and empirical evidence are presented, with the latter also assessed for quality. We believe that tackling isolated KERs instead of whole AOPs will accelerate the AOP development. Faster AOP development will lead to the development of simple test methods that will aid screening of chemicals, endocrine disruptor identification, risk assessment, and subsequent regulation.

An in silico model using prognostic genetic factors for ovarian response in controlled ovarian stimulation: A systematic review

PURPOSE

To study the use of in silica model to better understand and propose new markers of ovarian response to controlled ovarian stimulation before IVF.

METHODS

A systematic review and in silica model using bioinformatics. After the selection of 103 papers from a systematic review process, we performed a GRADE qualification of all included papers for evidence-based quality evaluation. We included 57 genes in the silica model using a functional protein network interaction. Moreover, the construction of protein-protein interaction network was done importing these results to Cytoscape. Therefore, a cluster analysis using MCODE was done, which was exported to a plugin BINGO to determine Gene Ontology. A p value of < 0.05 was considered significant, using a Bonferroni correction test.

RESULTS

In silica model was robust, presenting an ovulation-related gene network with 87 nodes (genes) and 348 edges (interactions between the genes). Related to the network centralities, the network has a betweenness mean value = 102.54; closeness mean = 0.007; and degree mean = 8.0. Moreover, the gene with a higher betweenness was PTPN1. Genes with the higher closeness were SRD5A1 and HSD17B3, and the gene with the lowest closeness was GDF9. Finally, the gene with a higher degree value was UBB; this gene participates in the regulation of TP53 activity pathway.

CONCLUSIONS

This systematic review demonstrated that we cannot use any genetic marker before controlled ovarian stimulation for IVF. Moreover, in silica model is a useful tool for understanding and finding new markers for an IVF individualization.

PROSPERO

CRD42020197185.

A pharmacogenetic approach to improve low ovarian response: The role of CAG repeats length in the androgen receptor gene

The AR (androgen receptor) polymorphism is associated with POR risk. Furthermore, the use of androgens in POR remains controversial. Our data could clarify the effectiveness of androgen pretreatment. AR genotyping could help us to identify patients at risk for POR and POR patients that will be benefited of androgen pretreatment.

OBJECTIVE

The aim of this project was to investigate if the AR (androgen receptor) polymorphism could be used to identify patients at risk for POR and that will benefit from androgens pretreatment.

STUDY DESIGN

To evaluate the POR risk we performed a cohort study including 231 patients (54 POR and 177 control). Moreover, we included 88 IVF-cycles performed by 44 POR-patients to assess the effect on ovarian response. All patients performed two cycles: a standard ovarian stimulation and a second one with androgen preparation. We compare the results in pair from each.

RESULTS

POR showed the highest frequency of CAG repeats at 24 vs 22 in controls. Only 33% of POR have alleles with a repeat number below 23, compared with 50% of controls (p < 0.05). According to AR polymorphism ovarian response differences were shown. Patients that carried CAG repeats in AR gene between 22 and 24 showed an increased in the number of oocytes (2.61 in cycles without androgens vs 5.11 when they were pretreated with androgens; p < 0.05). For the patients that carried repeats lower than 22 and higher than 24, no differences were reported in the number of oocytes obtained in the cycle with or without androgens (2.94 vs 2.56; p = 0.88). Similar results were obtained for mature oocytes in patients that carry a number of CAG repeats between 22 and 24 (1.86 MII in cycles without androgens vs 4.04 MII when they were pretreated with androgens; p < 0.05). No differences in the number of MII oocytes were found in patients that get out of 22 and 24 repeats between the two cycles (2.31 vs 2.13; p = 0.88).

CONCLUSION

The AR polymorphism is associated with POR risk, patients with repeats greater than 22 show a higher risk. Our data suggest that AR genotype could play a role in natural ovarian aging. Furthermore, the use of androgens in POR remains controversial. Our data suggest that the AR genotype could clarify the effectiveness of the androgen pretreatment. AR genotyping could help us to identify patients at risk of POR and POR patients that could benefit from transdermal testosterone pretreatment.

Basal serum testosterone levels correlate with ovarian reserve and ovarian response in cycling women undergoing in vitro fertilization

This study aimed to investigate the association between basal serum testosterone levels and in vitro fertilization (IVF) parameters in cycling women. A retrospective cohort study was performed at a clinical IVF center, and 495 women with regular menstruation were enrolled. Serum testosterone levels were measured before the start of IVF treatment cycle. We found that basal serum testosterone levels were negatively associated with female age and FSH/LH ratios. In contrast, we found a positive correlation between serum testosterone levels and the number of oocytes and available embryos. However, there was no significant association between testosterone levels and pregnancy outcome. Our results suggest that basal serum testosterone levels were significantly related to certain classic indicators of ovarian reserve, such as age and FSH/LH ratios. Increased testosterone levels improved ovarian response in cycling women, but they fail to predict pregnancy and miscarriage rate.

Androgen receptor (AR) gene CAG trinucleotide repeat length associated with body composition measures in non-syndromic obese, non-obese and Prader-Willi syndrome individuals

PURPOSE

Total body mass impacts reproductive health and infertility which has increased in the United States with rising rates of obesity. Overlapping genetic and environmental factors contribute to obesity and infertility including the androgen receptor (AR), a steroid hormone-activated transcription factor that is key in regulating androgen activity and sensitivity to sex hormones, weight and body composition in both males and females. The AR gene which is X-linked contains a polymorphic CAG trinucleotide repeat which varies in length and inversely correlated with gene expression.

METHODS

We examined the AR gene CAG repeat length and measures of weight and body mass index (BMI) in 27 non-syndromic obese and 33 lean controls and for the first time compared with 28 individuals with Prader-Willi syndrome (PWS), a rare obesity-related genetic disorder with natural sex hormone deficits to examine the effects of AR gene CAG repeat length on androgen-mediated response and obesity-related factors relevant to human infertility and reproduction.

RESULTS

Mean CAG repeat length in base pairs (278 ± 7.9) did not significantly differ by subject group (F = 2.6, p = 0.08) but was strongly positively correlated with height standard deviation (SD) among males (r = 0.31, p < 0.05), mainly lean and obese, but not PWS (r = 0.02, p = 0.94). A negative correlation was observed for weight SD among females (r = -0.29, p < 0.04) when grouped together.

CONCLUSIONS

The results were consistent with an androgen-mediated effect on height and weight negligible in PWS and supporting the role of sex hormones and AR gene interaction in obesity and infertility, both cardinal features of PWS. CAG repeat length of the AR gene is a marker for increased androgen sensitivity with shorter lengths predicting smaller stature in non-PWS adult males possibly due to accelerating fusion of bone growth plates and reducing the growth phase. Increased androgen effects from shorter CAG repeat lengths in non-PWS females could impact pregnancy-related weight gain and pregnancy outcomes.