Here's the AP version of the CBS report:
By Daniel Q. Haney
The Associated Press
B O S T O N, Feb. 19 - Scientists believe they have
found the brain's hunger hormone, the stuff that
triggers the overwhelming urge to say, "Another
helping of mashed potatoes, please. And lots of
gravy!"
The discovery is likely to start a stampede of research
intended to find medicines that can rein in this substance and
help people say no to food.
The researchers were led by Dr. Masashi Yanagisawa of
Howard Hughes Medical Institute at the University of Texas
Southwestern Medical Center. They are reporting the finding
in Friday's issue of the journal Cell.
The scientists called their discovery "orexin," a play on
"orexis," the Greek word for hunger.
"We believe that orexin is one of the important pathways
in the regulation of hunger," said Yanagisawa.
Come From Familiar Part of Brain
The researchers found that two varieties of orexin are made
by nerve cells in the lateral hypothalamus, a part of the brain
already known to play a role in appetite.
"It's an absolutely beautiful piece of work," said Dr.
Jeffrey Friedman of Rockefeller University, "a very thorough
and technically elegant set of studies that identify two new
players in the system that controls weight."
The work suggests that the brain churns out orexin when it
senses a need to eat, such as after a drop in sugar levels in
the blood.
The same substance appears to be at work in rats as well
as probably many other creatures. This allows the scientists
to test its effects.
They gave orexin to lab rats and found it made them
ravenous. For an hour or two, they ate eight to 10 times more
food than they ordinarily would.
They also checked the brains of rats that had not eaten in
a day and found that their orexin levels had gone up.
An Eat-Don't Eat Feedback Loop
"It really makes a nice feedback loop to regulate your
appetite," said Yanagisawa.
He said the possibility of harnessing this discovery to
combat eating problems-both lack of appetite and its far
more common opposite-are already being investigated by
scientists at SmithKline Beecham Pharmaceuticals, which
collaborated on the discovery.
He said it should be possible to create drugs that mimic
orexin and make people eat more. This could be helpful for
cancer patients and others who have illnesses that rob their
appetites.
Even more important, perhaps, would be using this
discovery to make drugs for treating obesity. The scientists
know the exact spot on the surface of cells in the brain where
orexin does its business. So it should also be possible to
create medicines that block these spots, called receptors, so
orexin cannot get in and trigger the munchies.
The scientists believe many hormones besides orexin are
involved in both creating and suppressing appetite.
Leptin Already Known to be Factor
One of these is leptin, an appetite-suppressing protein made
by fat-filled adipose cells. While leptin is supposed to signal
the brain to stop eating, the signal somehow does not get
through properly in overweight people.
Yanagisawa said that leptin-or the lack of it-could be
one of the signals that triggers the brain to make orexin and
whet the appetite.
The discovery was made through a relatively new process
called reverse endocrinology.
Traditionally, scientists discover a hormone and then try to
figure out what it does by searching for the receptor that it
attaches to. In this case, however, the scientists discovered
the receptor but had no idea what hormone acted on it or
what it did.
Working with the receptor, they figured out which protein
fit into it. Still, they did not know at first that it was involved in
appetite. Their first clue was the discovery that the protein
was a hormone made by particular nerve cells in the
hippocampus.
"As soon as we saw the striking distribution of these
neurons in that part of the brain, we guessed these hormones
were doing something important in determining how much
you eat," he said. |
