They affect the storage of fat. They help to replenish the linings of the gut and skin, replacing damaged and dying cells with new ones. They ensure the sanctity of the blood–brain barrier – a web of tightly packed cells that lets nutrients and small molecules pass from blood to brain, but bars the way to larger substances and living cells. They even influence the relentless remodelling of skeletons, in which fresh bone is deposited and old stuff is reabsorbed.
