NRF2 deficiency leads to inadequate beta cell adaptation during pregnancy and gestational diabetes

Abstract

The late stages of mammalian pregnancy are accompanied by a mild increase in insulin resistance likely due to enhanced glucose demand of the growing fetus. Therefore, as an adaptive process to maintain euglycemia during pregnancy, maternal β-cell mass expands leading to increased insulin release. Defects in functional β-cell adaptive expansion during pregnancy can lead to gestational diabetes mellitus (GDM). While the exact mechanisms that promote GDM are poorly understood, GDM is associated with inadequate functional β-cell mass expansion and with a systematic increase of oxidative stress. Here, we show that NRF2 levels are upregulated in mouse β-cells at gestational day 15 (GD15). Inducible β-cell-specific Nrf2 deleted (βNrf2KO) mice display reduced β-cell proliferation, increased β-cell oxidative stress and lipid peroxidation, compromised β-cell function, and elevated β-cell death, leading to impaired β-cell mass expansion and dysregulated glucose homeostasis towards the end of pregnancy. Importantly, the gestational hormone 17-β-estradiol (E2) increases NRF2 levels, and downregulation of NRF2 suppresses E2-induced protection of β-cells against oxidative stress, suggesting that E2 exerts its antioxidant effects through activation of NRF2 signaling in β-cells. Collectively, these data highlight the critical role of NRF2 in regulating oxidative stress during the adaptive response of β-cells in pregnancy and identify NRF2 as a potential therapeutic target for GDM treatment.