CR and rate of maturation
Aubrey de Grey
ag24 at mole.bio.cam.ac.uk
Thu Oct 1 11:30:25 EST 1998
In continuation of this thread:
ADG>The mice used for typical CR
ADG>experiments have been bred in captivity for many generations, and may
ADG>therefore have been quite heavily selected for rapid maturation.
BR > Stop right there! Walford, Weindruch, Spindler and everyone else who
BR > does CR experiments use special, long-lived hybrid mice for CR
BR > experiments. These mice are unusually resistant to the diseases of
BR > aging and live a long, long time for mice.
ADG>Yes, but I'm not sure that that completely rebuts the challenge, since
ADG>these mice may still have been quite substantially selected for fast
ADG>maturation and short lifespan, just less so than typical lab strains.
ADG>Do these mice live close to the maximum lifespan potential of wild Mus
ADG>musculus? How accurately is the MLSP of wild Mus musculus known?
(which I summarise since it lost some groups mid-way), Brian Rowley wrote:
> I don't know what the lifespan of wild Mus musculus is. However, it's
> the sort of thing Alex Comfort has published in his books on aging.
> It seems most unlikely that wild Mus musculus would have a longer
> maximal lifespan than Walford's long-lived hybrids. There are fierce
> selective pressures in the wild for early reproduction. Rapid
> senescence almost invariably goes along with early reproduction (Jay
> Olshansky and Robin Holliday are references). Since the rate of
> attrition is high in the wild, there is little evolutionary pressure
> for longevity. Therefore I see no reason why wild Mus musculus would
> live as long as Walford's carefully selected, longevous hybrids.
I'm not at all sure about that. The link between rate of maturation and
rate of aging is indeed very clear -- that's where my question began --
but the pressure for early reproduction in the lab is also fierce, very
fierce. I can see no clear argument that it is less fierce than that in
the wild; if it is fiercer, the difference may not have been outweighed
by Walford's selection. I'll explore more, and would be grateful for
pointers from those who know this literature well (eg Brian D or Steve).
This question is made rather more interesting by the finding you noted
that McCay got a bigger life extension than is found with the longevous
hybrids. McCay's work of course predated the development of the modern
and sophisticated protocols for avoiding artifacts. Have *all* recent
studies used the longevous hybrids? If not, and if modern studies with
typical lab strains also get bigger life-extension than those with the
longevous hybrids, then it becomes positively parsimonious (rather than
just plausible) to speculate that lifespan of *species* (as opposed to
strains) with very long lifespan may be less increased by CR than that
of those with short lifespan, despite the many biochemical similarities.
This is why I think it may be very valuable to find reasonably accurate
data on this, and why I'd be surprised if it's not readily to hand.
Aubrey de Grey
More information about the Ageing