Regulation of P21 during diabetes-associated stress of the endoplasmic reticulum

Endoplasmic reticulum (ER) stress plays a major role in the pathogenesis of diabetes by inducing β-cell apoptosis in the islets of Langerhans. In this study, we show that the transcription factor CHOP, which is instrumental for the induction of ER-stress-associated apoptosis and the pancreatic dysfunction in diabetes, regulates the expression of P21 (WAF1), a cell cycle regulator with anti-apoptotic activity that promotes cell survival. Deficiency of P21 sensitizes pancreatic β-cells to glucotoxicity, while in mice genetic ablation of P21 accelerates experimental diet-induced diabetes, results indicative of a protective role for P21 in the development of the disease. Conversely, pharmacological stimulation of P21 expression by nutlin-3a, an inhibitor of P53-MDM2 interaction, restores pancreatic function and facilitates glucose homeostasis. These findings indicate that P21 acts as an inhibitor of ER-stress-associated tissue damage and that stimulation of P21 activity can be beneficial for the management of diabetes and probably of other conditions in which ER-stress-associated death is undesirable.