Hasn't metformin increased lifespan in humans though? Or just average lifespan in diabetic humans?
DING-DING-DING-DING-DING!
Slightly low blood glucose does improve the appearance of skin and slow the accumulation of visible aging, in synergy with other vectors it can make the benefits permanent. Diabetics still die in their 60s, even taking metformin in my personal observation... still as a CR mimetic, it's going to be better for health and youthspan in non diabetics and improve the efficacy of other interventions.
It's not a CR-mimetic: that's a mechanistic hypothesis refuted by the lifespan studies and human data — see studies cited in the post I linked. It's also not known that metformin will give low-normal glucose levels to a normoglycemic person (as opposed to give (more) normal levels in an hyperglycemic person) — and even if it did, it's also not clear that low-normal (as opposed to normal) blood glucose is even good for you: see here, and also look through (1-9), which shows you that
the HbA1C-mortality association data are really all over the map: everything from J-shaped curves with a mortality "sweet spot" around HbA1c 5.3 (like (1,8,9)), to mortality curves that are flat up to and including 5.0 and then rise steadily above that point, to classic, continuous relationships across the board. I haven't yet seen any serious effort to reconcile these disparate findings, but we certainly can't say at this point that truly low glucose levels are good for one.
References
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Edited by Michael, 27 December 2017 - 11:48 PM.