The Speculist

Scientists had a mystery on their hands.

In 1999 Japanese scientists discovered the "ghrelin" hormone.  And in 2000 American researches discovered that this hormone drives appetite.

[Seattle endocrinologist Dr. David Cummings] showed off a test tube.

"At the bottom of this tube is a little tiny fleck of stuff, which is pure dried ghrelin," he says.

[CBS Reporter:] What would happen to someone who ate that tiny bit of ghrelin?

"You’d want to eat," says Cummings. "You’d want to eat right away."

Ghrelin is still the only hormone known to directly affect appetite this way.  With the developed world getting fatter every year, scientists rushed to learn everything they could about the hormone. 

They were able to track the hormone back to a gene, and then they produced a mouse without the ghrelin gene.  They expected to have a skinny, emaciated mouse.  But the mouse appeared normal.

This remained a mystery until yesterday's announcement by a group of scientists at Stanford.  These scientists have discovered another hormone, obestatin, that sends out a signal to eat less or stop eating.  It is the anti-ghrelin.  But, amazingly, it is coded by the same gene as ghrelin:

The scientists were surprised to find that the two hormones were products of the same gene. The gene directs cells to make one protein molecule, which breaks into two smaller ones, called peptides. One is ghrelin, and the other is obestatin.

So when they knocked out the gene for the hunger hormone ghrelin, they were also knocking out the fullness hormone obestatin.  The net effect was an apparently normal mouse.

Scientists are excited about these discoveries, in part, because both hormones are produced in the stomach instead of some more problematic area like the brain.  It is thought that an oral medication could be developed to either inhibit ghrelin or boost obestatin (or do both).  Johnson & Johnson sponsored the obestatin research and has the rights to that discovery.

Part of the ghrelin/obestatin mystery remains:

[Dr. Rudolph Leibel, an obesity researcher at Columbia University] said having two hormones with opposite effects embedded in the same molecule was like driving with one foot on the brake and one on the gas.

"One might wonder, why would you do this?" he said. "Why design a system like this?"