ABSTRACT
Unresolved ER stress followed by cell death is recognized as the main cause of a multitude of pathologies including neonatal diabetes. A systematic analysis of the mechanisms of ß-cell loss and dysfunction in Akita mice, in which a mutation in the proinsulin gene causes a severe form of permanent neonatal diabetes, showed no increase in ß-cell apoptosis throughout life. Surprisingly, we found that the main mechanism leading to ß-cell dysfunction is marked impairment of ß-cell growth during the early postnatal life due to transient inhibition of mTORC1, which governs postnatal ß-cell growth and differentiation. Importantly, restoration of mTORC1 activity in neonate ß-cells was sufficient to rescue postnatal ß-cell growth, and to improve diabetes. We propose a scenario for the development of permanent neonatal diabetes, possibly also common forms of diabetes, where early-life events inducing ER stress affect ß-cell mass expansion due to mTOR inhibition.