Mitochondrial Hormesis in Pancreatic beta Cells: Does Uncoupling Protein 2 Play a Role?

In pancreatic beta cells, mitochondrial metabolism translates glucose sensing into signals regulating insulin secretion. Chronic exposure of beta cells to excessive nutrients, namely, glucolipotoxicity, impairs beta-cell function. This is associated with elevated ROS production from overstimulated mitochondria. Mitochondria are not only the major source of cellular ROS, they are also the primary target of ROS attacks. The mitochondrial uncoupling protein UCP2, even though its uncoupling properties are debated, has been associated with protective functions against ROS toxicity. Hormesis, an adaptive response to cellular stresses, might contribute to the protection against beta-cell death, possibly limiting the development of type 2 diabetes. Mitochondrial hormesis, or mitohormesis, is a defense mechanism observed in ROS-induced stress-responses by mitochondria. In beta cells, mitochondrial damages induced by sublethal exogenous H2O2 can induce secondary repair and defense mechanisms. In this context, UCP2 is a marker of mitohormesis, being upregulated following stress conditions. When overexpressed in nonstressed naive cells, UCP2 confers resistance to oxidative stress. Whether treatment with mitohormetic inducers is sufficient to restore or ameliorate secretory function of beta cells remains to be determined.