Metformin Inhibits Trophoblast Ferroptosis by Suppressing ATF2 and Activating the PI3K/Akt/Nrf2 Pathway to Improve Gestational Diabetes Mellitus.

Gestational diabetes mellitus (GDM) is a common metabolic disorder during pregnancy. Metformin (MET) has emerged as a promising alternative to insulin, but its mechanism of action in the placenta remains incompletely understood. In this study, we aimed to examine whether MET counteracts high-glucose-induced ferroptosis by regulating activating transcription factor 2 (ATF2) and to delineate the underlying molecular mechanism in GDM. We established in vitro GDM cell models using HTR-8/SVneo trophoblast cells and an in vivo STZ-induced hyperglycemic rat model, followed by treatments including ATF2 lentiviral manipulation and MET administration. We evaluated cell viability, ferroptosis markers (ROS, MDA, GSH, iron deposition), and PI3K/Akt signaling pathway activity. Our results demonstrated that in GDM patients and high-glucose-challenged HTR-8/SVneo cells, MET promoted cell viability by suppressing ATF2, reactivating PI3K/Akt signaling, enhancing nuclear Nrf2 translocation, and upregulating GPX4, while concurrently lowering ROS and MDA levels, elevating GSH, and reducing iron deposition. These protective effects were reversed by ATF2 overexpression or pathway inhibitors. In STZ-induced hyperglycemic rats, MET decreased placental ATF2 expression, restored the PI3K/Akt-Nrf2-GPX4 axis, alleviated ferroptosis, and reduced fetal weight. Collectively, our findings indicate that MET suppresses ATF2, activates PI3K/Akt, drives Nrf2 nuclear import, upregulates GPX4, and curbs high-glucose-induced trophoblast ferroptosis, offering new mechanistic insight and therapeutic avenues for GDM.