ABSTRACT
Theories of oxidative damage are elegant and attractive, but some of the experimental results seem almost to mock the predictions of the theory. Physical activity generates copious free radicals and yet high levels of physical activity are generally associated with longer, not shorter average lifespans. Hanson and Hakimi [3] report on a genetically modified mouse that has extra mitochondria. These mice are phenomenally active, eat much more than wild type and burn it all up, yet they live almost two years longer than wild type and remain reproductively active two years longer. Two of the body’s most essential antioxidants are superoxide dismutase (SOD) and unbiquinone. Mice in which one copy of the gene for SOD has been knocked out have half as much SOD in their tissues and measurements of oxidative damage to DNA show that it is far higher than controls; yet the heterozygous Sod2+/– mice lived slightly longer than controls [69]. SOD knockout worms also have extended lifespan, coupled with enhanced markers of oxidative stress [70].
