Studies show that a range of strategies to reduce the level of reactive oxygen species produced by mitochondria extend life in lesser mammals - pointing to the operation of mitochondria as an important determinant of aging. One of these strategies is to increase uncoupling protein 2 (UCP2) expression, which causes mitochondria to generate more heat rather than packaged chemical energy for use in the cell. "The long-term effects of uncoupled mitochondrial respiration by uncoupling protein 2 (UCP2) in mammalian physiology remains controversial. Here we show that increased mitochondrial uncoupling activity of different tissues predicts longer lifespan of rats compared to mice. UCP2 reduces reactive oxygen species (ROS) production and oxidative stress throughout the aging process in different tissues in mice. The absence of UCP2 shortens life span in wild type mice ... Thus, UCP2 has a beneficial influence on cell and tissue function leading to increased lifespan."