There's a toolbox in an old house, but it's locked. Aging cells tell a similar story: they hold plenty of the enzyme NAMPT, which makes fuel for the cell, a molecule called NAD+. But old cells barely burn through that fuel, so the enzyme sits idle.
Then the compound was added to the food of old mice along with vitamin B3, because the compound quickly used up the vitamin in their blood. The mice aged more slowly and held on longer to a spinning rod. That means aging cells carry a hidden stockpile of the enzyme that can be woken up. If we learn to open a toolbox like this in human cells, we could clear out old cells and extend healthy life.
Senescent cells, despite their "old age," contain more of the enzyme NAMPT than young ones, but use it less efficiently, like a library with a huge collection and a closed reading room.
Not published on arXiv. Here are its page, the PDF and the formalization: you can check it yourself, not only read our account.