Endocrine Abstracts

Background: Vitamin B12 is crucial for placental development and fetal growth. B12 deficiency is associated with maternal obesity and adverse pregnancy outcomes. B12 is essential for the synthesis of S-Adenosyl methionine (SAM) which serves as a methyl donor in various cellular processes including DNA and RNA methylation. Pregnant women with low B12 have higher triglycerides, lower HDL and lower DNA methylation of cholesterol transcription factor. However, the influence of B12 on m6A (N6-methyladenosine) methylation of mRNA has not been explored. M6A methylation, the most prevalent modification of mRNA in mammals is regulated by methyltransferase complex including writers, erasers and readers. Here we aim to investigate whether low B12 affects m6A levels and gene expression involved in methylation in mRNA.

Methods: Human placental explants derived from 10 healthy pregnant women and trophoblastic cells (BeWo) were cultured for 7 days in CMRL or DMEM media, respectively, supplemented with sufficient (500nM-Control) and low B12 (25pM-low B12). RNA isolation, cDNA synthesis and qRT-PCR assays were performed to assess the expression of genes and m6A levels by Epiquick m6A RNA methylation kit.

Results: Placental trophoblasts cultured in low B12 showed decreased levels of m6A in total RNA. Placental explants and trophoblasts cultured in low B12 showed a significant increase in expression of m6A methylation genes: (1)writers that catalyse mRNA methylation (METLL3, METLL5, WTAP), (2)erasers that catalyse demethylation process (FTO, ALKBH5), and (3)readers that captures m6A methylation sites (YTHDF1, YTHDF3), when compared to control (P<0.05).

Conclusion: Our novel data show that low B12 status in placenta significantly impacts m6A levels in mRNA and the expression of genes including writers, readers, and erasers. Modulation of m6A methylation levels and understanding the underlying mechanisms of its regulation may offer new avenues for developing novel therapeutic strategies for preventing adverse metabolic programming due to B12 deficiency.