“One of these is called target of rapamycin, or TOR, a complex of proteins that regulates growth and metabolism. Like sirtuins, scientists have found TOR—called mTOR in mammals—in every organism in which they’ve looked for it. Like that of sirtuins, mTOR activity is exquisitely regulated by nutrients. And like the sirtuins, mTOR can signal cells in stress to hunker down and improve survival by boosting such activities as DNA repair, reducing inflammation caused by senescent cells, and, perhaps its most important function, digesting old proteins.27”