This biochemical pathway is exploited as a trade off between longevity and sex; something first suggested by a British gerontologist by the name of Tom Kirkwood:
- Kirkwood pictured exactly such a 'choice', on the grounds that energy is limited and everything has a cost. The energetic cost of bodily maintenance must be subtracted from the energetic cost of sex, and organisms that try to do both simultaneously will fare less well than organisms that apportion their resources.
So as with the trade off between elite fitness, health and longevity, we see another three-way trade-off between sex, maintenance and the rearing of offspring, which Lane tells us, is controlled by insulin.
There are mutations in life-extending genes that are called gerontogenes (any genetic elements that are involved in the regulation of aging and life span), which act to prolong life, but which have a default setting of 'shorter life'. Sexual maturation is costly and so there is no point maturing in an infavourable environment, better to put life on hold until things improve. So here is the rub - what we call ageing has more to do with sexual maturation and also has a role in obesity,
There are mutations in life-extending genes that are called gerontogenes (any genetic elements that are involved in the regulation of aging and life span), which act to prolong life, but which have a default setting of 'shorter life'. Sexual maturation is costly and so there is no point maturing in an infavourable environment, better to put life on hold until things improve. So here is the rub - what we call ageing has more to do with sexual maturation and also has a role in obesity,
- Mutations in the gerontogenes simulate silence. They disable the signal of plenty, and instead rouse the genes concerned with bodily maintenance. Even when food is abundant, the mutant geontogenes fail to respond.....they resist the sirens' beckoning of insulin. The irony is that insulin resistance in humans doesn't confer longevity but adult-onset diabetes. The problem is that overeating, coupled with a physiological determination to hoard scant resources for better times, leads to weight gain, diabetes and earlier mortality. A second irony: the penalty for prolonging life, deferring sex, remains resolutely in place. It's expressed as infertility. So it's no fluke that diabetes is linked to infertility. Diabetes and infertility are caused by the same hormonal swing. Disabling insulin prolongs life only if we're hungry for much of the time, and at the potential cost of not having any children.
- ...blocking TOR represses immune and inflammatory activity, which could be beneficial, because many age-related diseases have a persistent inflammatory component.
- By lowering free radical leak, bolstering mitochondrial membranes against damage, and boosting the number of mitochondria, calorie restriction effectively 'resets' the colic of life back to 'youth'. In doing so it switches off hundreds of inflammatory genes, returning genes to their youthful chemical environment, while fortifying cells against programmed cell death.
Nick Lane's Live Ascending is an excellent read. Highly recommended not least for the Chapter 10, Death - which I have drawn from above (and very heavily too, I might add). The other nine chapters are equally fascinating. Please read it!
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