Q&A: The Science of Fat

July 2, 2007 — -- Scientists at Georgetown University Medical Center have found a natural chemical in mice that seems to control the formation of fat. While the scientists have many more years of work ahead of them, they said the same chemicals may very well work in humans.

The researchers, who have published their findings in this week's edition of the journal Nature Medicine, told ABC News they discovered that a compound called neuropeptide Y -- NPY for short -- attaches itself to fat cells and promotes their growth.

Ned Potter spoke with Dr. Zofia Zukowska, Georgetown University Medical Center, senior author of the paper published in Nature Medicine, and Dr. Stephen Baker, a plastic surgeon on the faculty at Georgetown, to explain the study.

What's important about their discovery of the NPY molecule?

Zukowska: We have discovered that this molecule may be actually the molecule linking stress with obesity. Two major plagues of American culture, both on the rise.

How did they survey stress in the mice?

Zukowska: We wanted to make it like what would happen in the mouse or maybe human life. So one of the stresses we used was a daily encounter with an angry individual … and that was a Alpha mouse that we would introduce into the cage of experimental mice … And when that was combined with a high fat, high sugar diet after two weeks we found there is more fat buildup around the belly of the stressed mice but not any other groups.

Researchers then gave the mice small injections of a chemical that blocked the receptors to which NPY bonded.

Zukowska: We injected into, under the skin of the mice, into the belly and found that within two weeks that chemical, that blocker of the NPY receptor melted the fat away -- by about 50 percent.

Baker: The research that we've done at Georgetown has identified a pathway, when we use a little chemical to block a receptor (that's on people's cells) we can actually cause the fat cell to go away.

And I think the most interesting thing is we have a little mouse, I kind of call it a couch potato mouse, we give it a high fat diet, stress it a little bit. We don't give it a remote control but you know its a chubby little mouse and when we actually inject this, very very small amounts just once a day for two weeks we find that in the normal mouse where they had salt water injected you still see the big fat depot.