As I mentioned in my previous post about Lenny Guerente’s book “Ageless Quest,” aging research has, within the last 15 years, gone from being a scientific backwater to a mainstream field of scientific research, with new discoveries now regularly featured on the cover of Nature or Science (as in the Nature issue from June 2007 below.)
Although we now are capable of manipulating the aging process, including significantly extending the lifespan of many laboratory animals, it is still a frustrating fact that there is no consensus about the ultimate cause or causes of aging.
One viewpoint, which is probably only held by a significant minority of scientists in the field, is that the aging process is strongly connected to mitochondria, which are the power plants or batteries of our cell, converting nutrients into useful packets of energy in the form of ATP. We’re used to the idea that electronic equipment fails when the batteries go dead, so it’s not such a stretch to take a close look at the mitochondria.
What’s more, mitochondria produce much of the “pollution” in the cell in the form of the free radicals that are a by-product of the oxidative phosphorylation process (the process that turns nutrients into energy). Those free-radicals can damage proteins or DNA, particularly the mitochondrial DNA (this is special DNA, inherited from the mother, that resides in the mitochondria rather than the nucleus) that codes for a few essential mitochondrial proteins.
So one theory says that there is a kind of vicious circle, whereby old mitochondria start emitting more free radicals, which further damages the mitochondria, until the mitochondria are so damaged that they don’t produce sufficient energy and start damaging the rest of the cell. Right now, the consensus view on whether the experimental facts really fit that theory is “Maybe.”
If you want to learn more about mitochondria, I highly recommend “Power, Sex, Suicide: Mitochondria and the Meaning of Life (you’ve just got to love that title), by Nick Lane. Lane’s book is popular science, but it’s a very deep book, and actually proposes theories, including theories of aging, that you won’t see elsewhere in the literature. It’s not an easy book to read, but it’s very worthwhile.
Alternatively, you might enjoy this video of Douglas Wallace lecturing on the role of mitochondria in diseases and aging. Wallace, a professor from UC Irvine, delivers highly entertaining and persuasive lectures.