Aging and high concentrations of glucose potentiate injury to mitochondrial DNA

Deletions of mitochondrial DNA (mtDNA) are associated with aging and severa l chronic diseases. We have reported heterogeneous mutations between base p air 8468 and 13446 in mtDNA, the region known as the "common" deletion, in muscle of older humans with impaired glucose tolerance or diabetes mellitus . To further characterize potential effects of age and glycemia on mtDNA in tegrity, we studied corpulent JCR:LA-cp rats that are characterized by insu lin resistance, hyperinsulinemia, and hyperlipidemia, factors strongly asso ciated with both aging and cardiovascular disease. In addition to skeletal muscle, we isolated vascular smooth muscle cells (VSMC) from aortas of 6-, 12-, and 17-month-old rats and exposed them to 5-, 25-, 62-, and 100-mM glu cose or a combination of hypoxanthine (100 mu M) and xanthine oxidase (0.02 5 U/ml) to generate reactive oxygen species in separate cultures. Long- and short-fragment and nested polymerase chain reaction was used to detect mut ations in the common deletion region. The data demonstrate that aging and t he cp genotype confer susceptibility to mtDNA deletions in vivo and that hi gh glucose concentrations can induce mtDNA mutations in vitro. Accordingly, aging and glucose-related oxidative stress and possibly hyperinsulinemia m ay contribute to alterations in mitochondrial gene integrity and the cp gen otype appears to increase the susceptibility of muscle to the age-related a ccumulation of mtDNA mutations. (C) 1999 Elsevier Science Inc.