Fetal sex modulates placental microRNA expression, potential microRNA-mRNA interactions, and levels of amino acid transporter expression and substrates: INFAT study subpopulation analysis of n-3 LCPUFA intervention during pregnancy and associations with offspring body composition

Abstract

Background Previously, we revealed sexually dimorphic mRNA expression and responsiveness to maternal dietary supplementation with n-3 long-chain polyunsaturated fatty acids (LCPUFA) in placentas from a defined INFAT study subpopulation. Here, we extended these analyses and explored the respective placental microRNA expression, putative microRNA-mRNA interactions, and downstream target processes as well as their associations with INFAT offspring body composition. Results We performed explorative placental microRNA profiling, predicted microRNA-mRNA interactions by bioinformatics, validated placental target microRNAs and their putative targets by RT-qPCR and western blotting, and measured amino acid levels in maternal and offspring cord blood plasma and placenta. microRNA, mRNA, protein, and amino acid levels were associated with each other and with offspring body composition from birth to 5 years of age. Forty-six differentially regulated microRNAs were found. Validations identified differential expression for microRNA-99a (miR-99a) and its predicted target genes mTOR, SLC7A5, encoding L-type amino acid transporter 1 (LAT1), and SLC6A6, encoding taurine transporter (TauT), and their prevailing significant sexually dimorphic regulation. Target mRNA levels were mostly higher in placentas from control male than from female offspring, whereas respective n-3 LCPUFA responsive target upregulation was predominantly found in female placentas, explaining the rather balanced expression levels between the sexes present only in the intervention group. LAT1 and TauT substrates tryptophan and taurine, respectively, were significantly altered in both maternal plasma at 32 weeks’ gestation and cord plasma following intervention, but not in the placenta. Several significant associations were observed for miR-99a, mTOR mRNA, SLC7A5 mRNA, and taurine and tryptophan in maternal and cord plasma with offspring body composition at birth, 1 year, 3 and 5 years of age. Conclusions Our data suggest that the analyzed targets may be part of a sexually dimorphic molecular regulatory network in the placenta, possibly modulating gene expression per se and/or counteracting n-3 LCPUFA responsive changes, and thereby stabilizing respective placental and fetal amino acid levels. Our data propose placental miR-99, SLC7A5 mRNA, and taurine and tryptophan levels in maternal and fetal plasma as potentially predictive biomarkers for offspring body composition.

Sex at the interface: the origin and impact of sex differences in the developing human placenta

“…Both datasets highlighted the mTOR pathway as upregulated in males. This matches with observations by Sedlmeier et al [ 28 , 72 ] as well as in a meta-analysis of human placenta which found mTOR to be a consistent point of sex differences at term [ 27 ]. The mTORC1 and mTORC2 complexes are master regulators of anabolic growth and organism size, and this consistent trend toward male elevation likely contributes to the establishment and maintenance of sexual dimorphism.…”

“…Guo et al [ 97 ] found 32 miRNA differentially expressed, with the male-selective transcripts annotated as evolutionarily younger and enriched in endocrine functions, and female selective transcripts enriched for the imprinted miR-379 cluster on Chr14 (C14MC) which linked to estradiol, glucocorticoids, and brain-specific mRNA targets. In their study of the interaction of placental sex and maternal n-3 LCPUFA dietary supplementation, Sedlmeier et al [ 72 ] highlighted miR-99a as differentially expressed by sex and modulated by maternal diet, linking its expression to sex differences in mTOR-related mRNA expression. The link to mTOR may help to explain the mechanisms underlying sexual dimorphism in fetal growth.…”

Placental Endocrine Activity: Adaptation and Disruption of Maternal Glucose Metabolism in Pregnancy and the Influence of Fetal Sex

“…The influence of maternal environment on placental function is well documented from conception to birth and epigenetic mechanisms, i.e., DNA methylation and regulation by microRNAs seem to be a major contributor. These mechanisms add another level to the sexual dimorphism of the human placenta as they are also modulated by fetal sex [ 140 , 141 , 142 ].…”

Changes in PPAR-γ Expression Are Associated with microRNA Profiles during Fetal Programming due to Maternal Overweight and Obesity

“…Expression of several microRNAs shows differences between men and women in association with several diseases [32]; these differences can be attributed to hormonal and genetic factors. Also, there are differences in placental expression of some microRNAs between pregnancies with male and female infants [33]. Additional studies are required to assess the relevance of gender-driven differences in mi-croRNA expression.…”