Thymine glycol (5,6-dihydroxy-5,6-dihydrothymine) is one of the principal DNA lesions that can be induced by oxidation and ionizing radiation.[1]
Aging, stroke
The rate at which oxidative reactions generate thymine glycol and thymidine glycol in the DNA of humans is estimated to be about 300 per cell per day.[2]Oxidized DNA bases that are excised by DNA repair processes are excreted in urine. On a body weight basis, mice excrete 18 times more thymine glycol plus thymidine glycol than humans, and monkeys four times more than humans.[2] It was proposed that rate of occurrence of oxidative DNA damages correlates with metabolic rate, and that a higher rate of oxidative damage might cause a higher rate of cellular aging.[2]
Base excision repair is a major DNA repair pathway for removal of oxidative DNA damages. The rate of repair of thymine glycol damage in human fibroblasts was found to decrease with age.[3] Brain samples from humans who died of stroke were found to be deficient in base excision repair of thymine glycol as well as other types of oxidative damages.[4] It was suggested that impaired base excision repair is a risk factor for ischemic brain injury.[4]