Methionine Supply during Late-Gestation Triggers Sex-Specific Divergent Trajectories of Metabolism and Epigenetic Systems in Bovine Placenta

In non-ruminant species, males and females respond differently to gestational nutrition, and placenta, as a widely recognized programming agent, contributes to the underlying processes. According to our previous findings, methionine (a methyl donor) supply during late pregnancy increases calves’ body weight at birth, at least in part through upregulation of nutrient transporters. However, the effects of methionine on placenta metabolism and epigenetic signatures are not clear. Thus, we further investigated the impact of methionine supply during late gestation and the calf’s sex on metabolism and DNA methylation in bovine placenta. Multiparous cows were fed during the last 28 days of pregnancy with a control (CTR) or methionine-supplemented (MET; Mepron®, Evonik Nutrition & Care GmbH, Germany) diet. Mepron was supplied at a rate of 0.09% of the dry matter of the diet to ensure a ratio of Lysine to Methionine close to 2.8:1 in the metabolizable protein. Placentome samples were collected from 15 cows per treatment. Samples were organized according to diet and offspring sex, so as to obtain four groups: Male CTR (n = 7), Male MET (n = 7), Female CTR (n = 8), and Female MET (n = 8). Targeted metabolomics were performed to quantify 32 metabolites related to the TCA cycle, C1 metabolism and transsulfuration pathway. The enzyme activity of betaine-homocysteine methyltransferase (BHMT), methionine synthase (MTR) and cystathionine-β-synthase (CBS) was measured using radioisotopes. The global DNA methylation was assessed using a commercial kit. The mRNA expression of the DNA methyltransferases (DNMT) 1 and 3a was measured by RT-PCR. No interaction diet × sex was observed for any of the parameters measured. Compared with Male CTR, the placenta from Male MET had greater concentrations of metabolites related to the TCA cycle (isocitrate acid, vitamin B12, and NAD+) and transsulfuration pathway (cysteinesulfinic acid and glutathione). Male MET had lower MTR activity compared with Male CTR, while BHMT and CBS were not affected. No differences in global DNA methylation and mRNA expression of the DNMTs were observed between Male CTR and Male MET. Female MET had greater concentrations of metabolites related to C1 metabolism (methionine and S-adenosyl-methionine) and TCA cycle (glutamine) than Female CTR. The enzyme activity in the female placentas was not affected by the diet. DNMT3a was upregulated in Female MET compared with Female CTR, while DNMT1 was not affected by the diet. Interestingly, the global DNA methylation was higher in Female CTR than Female MET. Overall, our findings suggest that diet affects placental metabolism and DNA methylation, and also highlight the importance of studying sex-specific responses to dietary interventions.