The Choline Metabolite TMAO Inhibits NETosis and Promotes Placental Development in GDM of Humans and Mice

Choline metabolite trimethylamine N-oxide (TMAO) has been recognized as a risk factor of gestational diabetes mellitus (GDM), but its exact role in GDM has not been reported. In this study, we focused on the placenta development to reveal the role of TMAO in GDM. We found that the TMAO levels in peripheral and cord plasma were increased in women with GDM and that TMAO levels were positively correlated with newborn weight and placental thickness. Neutrophil extracellular traps (NETs) in the peripheral and cord plasma and the myeloperoxidase expression in the placenta of women with GDM also increased. NETs could inhibit the proliferation, migration, invasion, and angiogenesis of HTR-8/Svneo cells. However, TMAO not only could inhibit the formation of NETs but also could enhance the biological function of HTR-8/Svneo cells. With induction of GDM in NETs-deficient PAD4^-/- and wild-type mice, the placental weight of PAD4^-/- mice increased significantly. TMAO feeding also inhibited the formation of NETs and further increased the weight of the placenta and fetuses, and this increase did not affect the placental structure. Our data indicate that higher TMAO levels and the formation of abnormal NETs were associated with GDM. TMAO not only could promote the development of the placenta and fetuses but also could inhibit the formation of NETs.