The Mitochondrial Free Radical Theory of Aging - Supernova: Pliki

CHAPTER 1
Introduction
1.1. What Is Aging?
It has been said that aging is a difficult thing to define, but in fact a relatively uncontentious
definition is possible. Masoro’s1 is as good as any:
deteriorative changes with time during postmaturational life that underlie an
increasing vulnerability to challenges, thereby decreasing the ability of the
organism to survive.
This definition encapsulates a number of important features which the gerontologist, as
well as the non-specialist, benefits from keeping in mind:
1. Aging is bad for us. One might think this is so obvious as not to be worth saying, but
it goes unsaid so much that gerontologists often seem to have forgotten it.
2. Aging is not an extension of development, but a decay: thus, one can only weakly
extrapolate from development when seeking its mechanisms.
3. Aging doesn’t kill us: it “only” makes us steadily more killable. Thus, by this definition,
strokes are not part of aging but atherosclerosis (which predisposes us to them) is.
Aging also, clearly, needs to be defined descriptively as a prerequisite to its study; here it
becomes justified to be less general and to limit the description—at least of the macroscopic
features—to a single species, which in this book will be humans. Chapter 5 is devoted to
such a description; it is a purposely superficial one, since excellent comprehesive treatments
have been published in recent years and are referenced there. Chapter 5 also probes a little
way into the proximate causes of these gross symptoms of aging, preparing the ground for
the proposed ultimate cause which is the book’s central topic.
What about Chapters 2, 3 and 4? Perhaps regrettably, it is in the nature of biology that
one must master a fearsome quantity of background information before one can really
make sense of a research area. This is, arguably, truer in gerontology than in any other
biological field. Hence these three chapters are devoted to providing that background
information (on, respectively: mitochondria, free radicals and lipid metabolism), and aging
does not feature in them at all; I must ask the reader to have patience with this and to trust
that it is a prerequisite for understanding the rest of the book.
1.2. Subjectivity and Vocabulary
There is a good deal more use of the first person singular in this book than is typical in
academic work. I chose to write it in this style for one central reason: it is a book about a
theory. Consequently, much of the thinking that I shall describe has yet to achieve such
widespread support that it can be presented as fact. If there were less material in that category,
it might have been satisfactory to couch it in language which combined the impersonal with
the unauthoritative, but that necessitates a good deal of circumlocution, which, above a
certain density, becomes more irritating and flow-breaking than it is worth. I have therefore
The Mitochondrial Free Radical Theory of Aging, by Aubrey D.N.J. de Grey.
©1999 R.G. Landes Company.