NEW YORK, Oct 21 (Reuters Health) -- Mutations in the DNA found in mitochondria -- the tiny "powerhouses" that generate energy in cells -- accumulate over time and may contribute to the aging process, report researchers.
Comparing mitochondrial DNA from healthy young individuals to that of healthy older people, the investigators found that key mutations are more common with age. Scientists led by Dr. Yuichi Michikawa from the California Institute of Technology in Pasadena report the finding in the October 22nd issue of the journal Science.
The researchers found it "most striking" that one specific mutation occurred in 8 of 14 (or 57%) of individuals over the age of 65, but in none of the mitochondrial DNA from 13 younger individuals.
Results of a separate analysis of mitochondrial DNA from two sets of stored cells taken 9 to 19 years apart from nine individuals supports the role of age in the accumulation of mitochondrial DNA damage. In at least 3 of the 9 individuals, mitochondrial DNA mutations were evident in the cells taken later in life, but not cells from the same person when they were young.
According to Michikawa and colleagues, these mutations are not inherited but may be caused by free-radicals, unstable compounds formed during normal cell processes. Alternatively, the mutations may be due to cell enzymes that build DNA, or by problems with DNA repair mechanisms.
In an accompanying editorial, Elizabeth Pennisi says the findings provide "the first hard evidence that mitochondria do deteriorate as people age." Just how this deterioration affects the functioning or survival of cells remains to be determined, she adds.
