cron-web.org

[A1CR]

[Posted on behalf of MR and Dean]

On Mon, 5 Feb 2001
Dean wrote:

> MR wrote:
> > [lots of interesting data suggesting that cold exposure may not
> > be bad (or any worse) for people (or animals) on long term CR
> > vs. AL controls]
>
> But what the studies you cite do not appear to address is the effect of long
> term cold exposure on the longevity of CR'ed animals. As I've noted several
> times, AL animals exposed to cold for their entire life ("rats with cold
> feet") eat 40% more than warm controls, but don't appear to live any shorter
> lives [1].

True. It'd be a very interesting experiment.

> It would be very interesting to know if cold exposure + CR
> results in longer, equal or shorter lifespans than CR alone. To my reading,
> Aubrey seemed to imply in his sci.l-e post that cold exposure shortened the
> lifespan of CR'ed mice to be equal to that of AL controls, which would be a
> very interesting finding.

I'm pretty sure he didn't mean to imply that. To my reading, he was just
giving one possible example of a mechanism whereby CR might aggravate a
problem to which lab animals are adapted but WTM are not, thus resulting
in no LS extension (as Austad has preliminarily reported).

-MR
>
> [1] TITLE: Longevity of cold-exposed rats: a reevaluation of the
> "rate-of-living theory".
> AUTHORS: Holloszy JO; Smith EK
> SOURCE: J Appl Physiol 1986 Nov;61(5):1656-60
> CITATION IDS: PMID: 3781978 UI: 87056780
> ABSTRACT: It has been postulated that increased energy expenditure results
> in shortened survival. To test this "rate-of-living theory" we examined the
> effect of raising energy expenditure by means of cold exposure on the
> longevity of rats. Male 6-mo-old SPF Long-Evans rats were gradually
> accustomed to immersion in cool water (23 degrees C). After 3 mo they were
> standing in the cool water for 4 h/day, 5 days/wk. They were maintained on
> this program until age 32 mo. The cold exposure resulted in a 44% increase
> in food intake (P less than 0.001). Despite their greater food intake, the
> cold-exposed rats' body weights were significantly lower than those of
> control animals from age 11 to 32 mo. The average age at death of the
> cold-exposed rats was 968 +/- 141 days compared with 923 +/- 159 days for
> the controls. The cold exposure appeared to protect against neoplasia,
> particularly sarcomas; only 24% of the necropsied cold-exposed rats had
> malignancies compared with 57% for the controls. The results of this study
> provide no support for the concept that increased energy expenditure
> decreases longevity.
>