# Sexually dimorphic responses in androgen metabolism and signalling in the non-human primate placenta to moderate maternal undernutrition

## TL;DR

Male primate placentas respond differently to maternal undernutrition than female placentas, which may explain why male fetuses are more vulnerable to poor growth outcomes.

## Contribution

This study reveals sex-specific molecular responses in placental androgen signaling under maternal undernutrition in non-human primates.

## Key findings

- Male placentae had higher androgen production genes and cytoplasmic AR-45, while females had higher placental function genes.
- Maternal undernutrition increased testosterone metabolism in female placentae but suppressed it in males.
- Sex differences in androgen signaling may explain poorer male fetal outcomes during pregnancy stressors.

## Abstract

Maternal nutrient restriction (MNR) can increase maternal androgen concentrations during pregnancy and cause placental dysfunction leading to reduced fetal growth, especially in males. Placental androgen metabolism, as well as differential expression and subcellular localisation of androgen receptor (AR) variants, modulates androgen signalling, which may benefit placental function; however, the impact of MNR on these adaptations remains undefined. We characterised the impact of MNR and fetal sex on placental androgen signalling in a non-human primate model of pregnancy.

Pregnant baboons (Papio spp.) were randomly assigned to control diet (Ctrl; offspring female n = 5, male n = 6) or MNR diet (70% of global Ctrl; offspring female n = 5, male n = 5) at 0.16 gestation (term = ~ 180 days). Fetuses were delivered by Caesarean section at 0.9 gestation and placenta collected. Molecular measures of sex steroid signalling and placental function were quantified using established LC-MS/MS assays, Western blot, and qRT-PCR. Data were analysed using two-way ANOVA (factors: diet, sex) with Tukey’s multiple comparison test.

CYP17A1, SRD5A1, and PGF expression was higher, whereas HSD3B1, CYP19A1, and ANGPT2 was lower in male compared to female placentae, independent of diet. KDR expression and CYP19A1 activity increased in MNR versus Ctrl in females only. Cytoplasmic expression of the antagonistic AR variant, AR-45, was higher in males, whereas MNR increased cytoplasmic and nuclear AR-45 expression independent of sex.

Differences in placental steroidogenic and angiogenic genes, as well as androgen metabolism and signalling, may explain sex-specific placental responses to MNR. Better understanding of molecular regulators of androgen signalling may lead to novel, targetable therapeutics that improve placental function in complicated pregnancies associated with increased androgen concentrations.

The placenta is a transient organ that plays several key biological roles throughout pregnancy, all of which are needed to ensure fetal growth and survival. Sex differences in placental function are known. Male placentae generally prioritise growth pathways at the expense of adaptation to any current pregnancy stressors compared with female placentae. Pregnancies that are complicated by maternal undernutrition (MNR) are associated with sex-specific fetal growth and survival outcomes, with male fetuses displaying poorer outcomes than females. The underlying mechanisms that contribute to these sex-specific outcomes are not known but may partly be explained by changes to placental androgen signalling, a pathway that if dysregulated can contribute to impaired placental function and poor fetal outcomes. Therefore, in this study we characterised the effect of sex and/or MNR on placental androgen signalling in the non-human primate (baboon) placenta. Independent of maternal diet, female placentae had higher gene expression of enzymes and other factors that support placental function, whereas male placentae had higher gene expression of enzymes involved in androgen production. Intriguingly, in response to MNR, female placentae increased androgen metabolism whereas male placentae suppressed this response. Our study indicates sex differences in placental androgen signalling may contribute to poorer outcomes for males in response to pregnancy stressors.

Pregnancies complicated by maternal nutrient restriction (MNR) are associated with sex-specific fetal growth and survival outcomes, with males generally displaying poorer outcomes.The mechanisms that contribute to these sex-specific outcomes may be partly regulated by changes to placental androgen signalling, a pathway mediated by the full-length androgen receptor (AR-FL). Therefore, advanced understanding of this pathway is needed to improve placental function and reduce the prevalence of associated risks.Independent of maternal diet, female placentae had higher expression of CYP19A1, HSD3B1, and ANGPT2, whereas male placentae had higher CYP17A1, SRD5A1, PGF expression, and greater cytoplasmic sequestration of the antagonistic androgen receptor (AR) isoform, AR-45.In response to MNR, female placentae had higher activity of enzymes involved in testosterone metabolism, as well as markers of angiogenesis, whereas male placentae suppressed testosterone metabolism.Sex differences in placental androgen signalling pathways may contribute to poorer outcomes for males in response to pregnancy stressors.

Pregnancies complicated by maternal nutrient restriction (MNR) are associated with sex-specific fetal growth and survival outcomes, with males generally displaying poorer outcomes.

The mechanisms that contribute to these sex-specific outcomes may be partly regulated by changes to placental androgen signalling, a pathway mediated by the full-length androgen receptor (AR-FL). Therefore, advanced understanding of this pathway is needed to improve placental function and reduce the prevalence of associated risks.

Independent of maternal diet, female placentae had higher expression of CYP19A1, HSD3B1, and ANGPT2, whereas male placentae had higher CYP17A1, SRD5A1, PGF expression, and greater cytoplasmic sequestration of the antagonistic androgen receptor (AR) isoform, AR-45.

In response to MNR, female placentae had higher activity of enzymes involved in testosterone metabolism, as well as markers of angiogenesis, whereas male placentae suppressed testosterone metabolism.

Sex differences in placental androgen signalling pathways may contribute to poorer outcomes for males in response to pregnancy stressors.