"And in the past couple of years, researchers have produced strong evidence that this is indeed the case, that the decline of mitochondria determines when our bodies begin to crumble."

So said New Scientist in Janurary 2006. And I'm fairly certain this has been mentioned in my lectures before- I'm pretty familiar with the idea, at any rate.

However. I've just discovered (embaressing, considering it was published in Nature Genetics at the start of March- but you try reading any other papers when you've got nine years of the proteasome to cover. In fact, try reading anything other than the very, very specefic things you study: do you know how complex biochemistry is?) that Loeb et al did a study of mutations in mitochondria DNA in normal aging mice compared to mice that have a 500-fold greater mutation burden. They found that wild type mice did show an increase (aprox 11 fold) of mutations in mitochondrial DNA with age, the mutant mice showed no signs of accelerated ageing suggesting that the small amount of mutation in WT mice has no contribution to the ageing process. Interesting. I like it when something comes along to prove everyone wrong, as it constantly does with my subject with better and more accurat methods being developed all the time.
However- it needs to be pointed out that large deletions in mitochondrial DNA could still have an affect and that there is apparently evidence for this. This seems pretty interesting and might be something to look at when I've finished my dissertation.