From ScienceWeek, a grab bag of mainstream scientific thoughts on the mechanisms of aging; Klotho, oxidative damage, and senescence. "A defect in Klotho gene expression in mice accelerates the degeneration of multiple age-sensitive traits. The authors demonstrate that overexpression of Klotho in mice extends life span. ... overexpression of human catalase in the mitochondria of mice extends median and maximal lifespan by about 20%. Catalase prevents the formation of reactive oxygen species (ROS) that can damage cellular constituents. ... Cellular senescence is also thought to contribute to aging, although how it does so is poorly understood. In addition to arresting growth, senescent cells show changes in function. Because senescent cells accumulate with age, they may contribute to age-related declines in tissue function."

Link: http://scienceweek.com/2005/sw051111-5.htm