NRF2 Is Required for Neonatal Beta-Cell Growth by Maintaining Redox Balance and Promoting Mitochondrial Biogenesis and Function

Due to the limited expression of several antioxidant enzymes, β-cells are highly vulnerable to high ROS levels, which can lead to the reduction of functional β-cell mass. During early postnatal ages, both human and rodent β-cells go through a burst of proliferation that quickly declines with age. Here we discovered that the expression of the master antioxidant regulator, Nrf2, is increased during this postnatal burst of β-cell proliferation in humans. Additionally, data from β-cell specific Nrf2 deletion in mice demonstrated that Nrf2 is required for β-cell proliferation, β-cell survival, β-cell identity and β-cell mass expansion at early stages of life. Daily administration of antioxidant NAC to newborn mice showed that Nrf2 mechanism of action strongly relies on maintaining normal redox balance. Interestingly, RNAseq of islets isolated from β-cell specific Nrf2 deleted mice suggests that Nrf2 regulates neonatal β-cell proliferation by promoting mitochondrial ATP synthesis. Our study highlights Nrf2 as an essential transcription factor for maintaining redox balance as well as mitochondrial biogenesis and function to support neonatal β-cell growth and for maintaining functional β-cell mass in adulthood under metabolic stress. To investigate mechanisms by which Nrf2 stimulates β-cell proliferation in neonatal mice islets from 7-day old β-cell specific Nrf2 deletion mouse model (βNrf2KO) vs Nrf2lox/lox mice