I'm done reading
the article you proposed. I've also been searching for some of the articles it links to, namely the experiment with rats placed in cold water
(holloszy, j.o. and smith e.k. : Longevity of cold-exposed rats: a reevaluation of the" rate-of-living theory" ) and a few articles by Selmann which seemed promising too, but all but one of those weren't free (scientific litterature
... ).
It seems that although the rate of living theory still has proponents, it has been for the most part ruled out, at the very least in it naive 1900's formulation. This doesn't mean that reduced metabolism (or more efficient metabolism, which blurs with being augmented metabolism in the mitochondrial uncoupling experiments) isn't positively correlated to a longer life expectancy.
Holloszy's experiment where rats were put in cold water only shows (as far as I can tell from the abstract) that indeed rats are endotherms and as such didn't see their temperature lower as that of, say, flies, and so too had an increase in their metabolism to fuel that endothermy. Conclusion : rats put in cold water don't live longer as flies do, because they don't see their temperature or metabolism fall... for what it's worth.
I'd be interested to see the same experiment conducted on animals whose thermoregulation has been shut down, or maybe whose metabolism has been impaired in some way or the other (hydrogen sulfide coming to mind, since it can inhibit cellular respiration).
The articles by Selman were interesting because it seemed like they linked exposure to cold to analyses of how different parts of the proteome were influenced. Clearly, I believe that a lower body temperature has the potential to lower the rate of all chemical reactions in the body (err if I'm not wrong, that's essentially what's happening in cryonics, the temperature is set low enough to practically put all chemical reactions/interactions in the body almost to a standstill ?). And all reactions in the body are slowed down, then at least naively you'd be induced to believe that the body will age at a slower rate (wear and tear theory withstanding).
Now I suppose there are a lot of negative practical considerations, and I'm immediately interested in two of them : whether there are regulation mechanisms which would attempt to counteract the effect of cold in the body (obviously there are, in endotherms, but I'd like to know about more than just temperature adjustment, for instance, how do lower temperatures affect genes expression and regulation ?).
Secondly, I'd be curious to know if the decrease in reaction rates/speed are the same for all reactions in the body; it seems to me it shouldn't be the case, and so what may be perfectly balanced in homeostasis at, say, 37° C for a human being, may not be so at a lower temperature, which may lead to serious issues (tocic byproducts accumulation, cellular repair impaired faster than cellular damage is lowered, etc.). If it is so, then up to which point would it be safe to lower the temperature of a living warm blooded organism, for short or long term exposure ?
People with experience/knowledge in cryonics, do you know any idea or relevant litterature about this ? Does it sound even sound, promising, or already tried and proved worthless ?
As for castration, I couldn't find the article with regards to mice, but I could get
this article (which I'm going to read now) and this abstract.