Aging is a fascinating and highly important topic because of its great social relevance and scientific complexity. One of the most important theories to explain this multifactorial process is the free radical theory. Such theory involves the damaging role of reactive oxygen species (ROS) on mitochondrial molecular components as lipids, proteins and mitochondrial DNA (mtDNA). Several studies have demonstrated an age-related accumulation of the number of deleted species of mtDNA as well as of the amount of a specific 4834 bp mtDNA deletion, homologue of the human mtDNA "common deletion", in different tissues of rat (liver, brain and skeletal muscle) (1-3). The tissue-specificity of age-related mechanisms is supported by the different degrees of effect of the so-far only known treatment able to delay the aging degeneration namely caloric restriction (CR). CR treatment has been reported to decrease the number of mtDNA deleted species in rat skeletal muscle (3), but nothing is known about in other tissues. Therefore, we decided to evaluate by quantitative Real Time PCR the level of the 4834 bp mtDNA deletion in tissues of aging rats treated and not with CR. The chosen tissues include some clearly sensitive to the effect of CR in reducing mitochondrial oxidative stress that is liver and skeletal muscle (4), while brain has also been included in our study because of the CR efficacy shown by microarray approach (5). Data concerning the level of the 4834 bp mtDNA deletion in liver from adults fed ad libitum (AL), old fed ad libitum (OL) and old lifelong 40% calories-restricted (OR) Fischer animals are presented. The level of the 4834 bp mtDNA deletion has been determined with respect to the mitochondrial D-loop level, using specific primers and TaqMan probes for each target. The method has been validated by measurements in previously assayed samples and evaluating the equal reaction efficiency of the two amplicons. We found an age-related increase of the deletion level in OL animals (the mean value is a two-fold increase) that was reversed and brought back to the adult level by long term CR.
1.Gadaleta M.N., Rainaldi G., Lezza A.M.S., Milella F., Fracasso F., Cantatore P. (1992), Mutat. Res., 275: 181-193.
2.Gadaleta M.N., Rainaldi G., Lezza A.M.S., Marangi L.C., Milella F., Daddabbo L., Fracasso F., Loguercio Polosa P., Cantatore P. (1995), In: Progress in Cell Research (F. Palmieri et al. eds), Elsevier Science, Amsterdam, vol. 5 pp. 231-235.
3.Aspnes L., Lee C.M., Weindruch R., Chung S., Roecher E., Aiken J. (1997), FASEB J., 11, 573-581.
4.Gredilla R., Barja G., Lopez-Torres M. (2001), J. Bioenerg. Biomembr., 33: 279-287
5.Drew B., Phaneuf S., Kirks A., Selman C., Gredilla R., Lezza A., Barja G., Leeuwenburgh C. (2002), Am. J. Physiol. Regul. Integr. Comp. Physiol., 284: R474-480.
6.Lee C.-K, Weindruch R., Prolla T.A. (2000), Nature Genetics, 25: 294-297