Friedman of Rockefeller University discovered leptin, a hormone secreted by fat cells that acts in the brain to suppress eating, keeping weight gain in check. Mice lacking the leptin gene are grossly overweight and can’t stop eating. And when normal animals (or people) lose weight, leptin levels drop as fat cells disappear, so the individuals get hungrier, often leading to weight gain once again. Leptin acts over days and weeks. But what makes us hungry for lunch mere hours after breakfast, when we haven’t lost any significant fat stores between the two meals? Six years after leptin’s discovery, researchers led by Masayasu Kojima of Kurume University found a clue: the so-called hunger hormone, ghrelin.
by Jyoti Madhusoodanan, Special to C&EN |
March 21, 2017