Sex-specific differences in the influence of maternal obesity on the oxidative and inflammatory status in the maternal-placental-fetal unit: new insights into the placental sphingolipid profile.

Although maternal obesity influences placental and fetal development, the underlying molecular mechanisms have yet to be determined. Oxidative and inflammatory status at the fetal-placental unit appear to be involved in the early fetal metabolic programming. The objective of the present study is to reveal a potential role of sphingolipids in stablishing an oxidative and inflammatory status in the maternal-placental-fetal unit, as function of fetal sex. Term placenta and maternal and fetal plasma were collected from lean (BMI 18-25 kg/m²) and obese women (BMI 30-40 kg/m²) without gestational diabetes aged from 20 to 40 having undergone a cesarean section. Firstly, key markers of oxidative stress and inflammation were studied with immunoblotting and biochemical assays. Secondly, the maternal-placental-fetal unit's sphingolipid profile was determined by mass spectrometry. Lastly, the placental samples' transcriptome was analyzed by RNA sequencing. Obese mothers showed lower plasma levels of ceramide Cer 20:0 (p = 0.02). Surprisingly, placental ceramide content was not influenced by maternal obesity. Nevertheless, male placentas from obese women showed a higher sphingomyelin content and hypo-inflammation as showed by RNAseq. Both males and female placentas from obese women showed higher levels of oxidative stress as showed by the oxidative stress markers (protein carbonylation and lipid peroxidation). However, RNAseq revealed an upregulation of oxidative stress mechanisms only in female placentas. Whatever the newborn's sex, maternal obesity was associated with higher fetal plasma oxidative stress. In conclusion, our results revealed sex-specific features in the placental transcriptome, highlighted placental metabolic adaptations, and provided insights into the underlying molecular mechanisms of fetal programming.