Newly Discovered Hormone Cuts Appetite

Nov. 10, 2005 -- Scientists at Stanford University have discovered a stomach hormone that cuts appetite.

The hormone, called obestatin, "could have potential as an appetite-suppressing drug," possibly by injection or nasal spray, says researcher Aaron Hsueh, PhD.

"In addition, identification of the receptor for obestatin will allow us to screen for new drugs that can also suppress appetite," Hsueh continues.

However, much more work is needed first. Researchers don't know everything about obestatin yet, and it's not certain that the hormone would thwart obesity.

"There are so many factors involved in the obesity regulation of body weight," says Hsueh. "I think we just provide one of the factors, and more data are really needed to figure out exactly what's going on."

Experts Speak Out

Here's a first look at obestatin from Hsueh and Matthias Tschop, MD. They both spoke to reporters in the same conference call.

Hsueh is a professor and heads the Hsueh Lab in the reproductive biology division of Stanford's department of gynecology and obstetrics. He and his colleagues discovered obestatin.

Tschop works in the German Institute of Human Nutrition's pharmacology department. He didn't work on Hsueh's study, but he wrote an editorial about it for Science.

What Is Obestatin?

"What we have discovered is a stomach hormone that suppresses food intake," Hsueh says.

Obestatin shares the same gene as another appetite-focused hormone, ghrelin. The two hormones have opposing effects on appetite. Obestatin cuts appetite; ghrelin boosts appetite.

Hsueh's team not only discovered obestatin and its gene, they also found the receptor where obestatin can dock to do its work.

That's a "spectacular" achievement, Tschop says, calling the findings "very, very intriguing."

How Did the Hormone Fare in Tests?

Hsueh's team made synthetic obestatin in a lab and tested it on healthy rats that weren't obese.

After getting obestatin, the rats ate half as much food as before. The rats' weight also dropped 20% over eight days, Hsueh says.

That figure -- a 20% weight drop -- may not tell the whole story. "It's a difference of less than 1 gram in the mouse and it's not clear how much we can translate into humans," Tschop says.

"Although the effects on food intake seem to be impressive, there's not much change in body weight, and we don't yet know if fat mass is actually changed," he says.

How Does the Hormone Work?

No one knows the answer to that question yet.

Obestatin may have cut appetite by making the rats "a little sick and therefore a little bit less willing to eat," Tschop says. Or it might be a specific mechanism to decrease food intake.

A third possibility is that it affects the contraction of muscles in the intestines. "If the intestines do not move adequately, you will feel full," Hsueh says. He adds that his team found obestatin receptors in the brain's hypothalamus region, which could be another place for obestatin to work.