Thioredoxin‐interacting protein deficiency induces Akt/Bcl‐xL signaling and pancreatic beta‐cell mass and protects against diabetes

Abstract

Pancreatic beta‐cell loss through apoptosis represents a key factor in the pathogenesis of diabetes;however, no effective approaches to block this process and preserve endogenous beta‐cell mass are currently available. To study the role of thioredoxin‐interacting protein (TXNIP), a proapoptotic beta‐cell factor we recently identified, we used HcB‐19 (TXNIP nonsense mutation) and beta‐cell‐specific TXNIP knockout (bTKO) mice. Interestingly, HcB‐19 mice demonstrate increased adiposity, but have lower blood glucose levels and increased pancreatic beta‐cell mass (as assessed by morphometry). Moreover, HcB‐19 mice are resistant to streptozotocin‐induced diabetes. When intercrossed with obese, insulin‐resistant, and diabetic mice, double‐mutant BTBRlep ob/ob txnip hcb/hcb are even more obese, but are protected against diabetes and beta‐cell apoptosis, resulting in a 3‐fold increase in beta‐cell mass. Beta‐cell‐specific TXNIP deletion also enhanced beta‐cell mass (P< 0.005) and protected against diabetes, and terminal deoxynucleotidyl transferase‐mediated nick end labeling (TUNEL) revealed a ~50‐fold reduction in beta‐cell apoptosis in streptozotocin‐treated bTKO mice. We further discovered that TXNIP deficiency induces Akt/Bcl‐xL signaling and inhibits mitochondrial beta‐cell death, suggesting that these mechanisms may mediate the beta‐cell protective effects of TXNIP deficiency. These results suggest that lowering beta‐cell TXNIP expression could serve as a novel strategy for the treatment of type 1 and type 2 diabetes by promoting endogenous beta‐cell survival.—Chen, J., Hui, S. T., Couto, F. M., Mungrue, I. N., Davis, D. B., Attie, A. D., Lusis, A. J., Davis, R. A., Shalev, A. Thioredoxin‐interacting protein deficiency induces Akt/ Bcl‐xL signaling and pancreatic beta‐cell mass and protects against diabetes. FASEB J. 22, 3581–3594 (2008)