Five different roads lead to the same destination: a long life. Some mice received drugs, others ate 40% less. After eight months, seven tissues were taken from all of them: brain, liver, muscle, kidney, fat, blood. Each tissue is like a witness who sees the event from its own angle.
Scientists ran a computer program that compared molecules in the tissues a thousand times. It found shared changes in all the long-lived mice. In the brain and blood, ergothioneine increased, a substance from mushrooms that the mice get from their food. In muscle, cardiolipin rose, a fat that helps cells produce energy.
Now it is clear that different ways of extending life leave a common trace. You can measure these molecules in a person's blood after a short course of a drug and tell whether it slows aging.
Ergothioneine is an antioxidant that mammals cannot synthesize themselves. It is produced by fungi, and mice obtain it from food via a special transporter, OCTN1.
Not published on arXiv. Here are its page, the PDF and the formalization: you can check it yourself, not only read our account.