Scientists discover hormone that helps curb people's appetites
JOSEPH B. VERRENGIA, AP Science Writer
Wednesday, August 7, 2002
©2002 Associated Press
URL: sfgate.com
(08-07) 22:30 PDT (AP) --
Scientists have isolated a hormone that makes us feel full when we eat, and they demonstrated its potential as a new weight-loss drug by
injecting volunteers with the substance before a big buffet lunch.
The participants injected with the so-called "third helping hormone" ate one-third less than usual and resisted snacking for up to 12 hours,
scientists reported.
The hormone infusion was "sort of a fake meal," said the study's senior author, Steven Bloom of the Imperial College of London. "The brain
was fooled into thinking that it had already eaten."
The experiment offers a preliminary but promising opportunity to develop a new drug to curb obesity, researchers said.
Still, some cautioned that treating overweight people with direct hormone injections has not been proven effective and may be dangerous.
Public health officials have been warning of an obesity epidemic in the United States, and the problem is spreading around the globe. The
International Obesity Taskforce estimates 300 million people worldwide are obese.
In the United States, obesity is implicated in the deaths of 300,000 people annually from heart disease, stroke, diabetes and cancer.
The hormone experiment was reported in Thursday's issue of the journal Nature. Scientists in England and Oregon isolated the hormone
PYY3-36 that is secreted by cells lining the intestines. Levels of the hormone rise in the blood after eating and remain high between meals.
Using mice, researchers first identified its effect on the hypothalamus, a part of the brain that regulates appetite.
Then, 12 people of normal weight -- 6 men and six women in their 20s -- were injected with extra hormone or a placebo saline solution. Two
hours later, they were offered an Indian curry buffet lunch -- chicken or vegetarian, spicy or mild.
The volunteers who received the hormone boost ate one-third less than they did at previous meals.
However, other scientists in the study said the one-time experiment does not by itself prove that the injections can safely control appetite or
reverse obesity. How the body might respond to elevated PYY3-36 levels over time is unclear.
"It would not make a suitable weight loss drug due to its potential effect on other important systems of the body," said Oregon Health Science
University neurobiologist Roger Cone. "Scientists still have a long way to go before the development of a drug that can help Americans fighting
obesity."
Researchers who did not participate in the experiment were intrigued by the findings.
"Everyone decreased their food intake, so that's pretty significant," said Dr. Richard Atkinson, president of the American Obesity Association.
Among the hurdles to developing a "third helping" drug: proving whether the hormone safely reduces body weight and fat over the long term,
and finding a more tolerable method than intravenous infusion.
"If you raise the levels of some hormones, the body becomes tolerant and it stops working," Atkinson said. "They need to give this every day
for months and see if it results in significant weight loss."
Previous studies have focused on limiting the effects of ghrelin, a hormone made by stomach cells that boosts appetite.
New non-hormonal prescription weight control drugs are coming on the market, including Meridia, which influences brain chemistry associated
with appetite.
But Meridia and similar drugs usually result only in modest weight loss, Atkinson said. Combinations of new drugs might be more effective, he
said.
Over-the-counter weight loss treatments are a $40 billion industry. Yet scientists still are untangling the body's complex chemical signaling
system known as the adipostat, which continually adjusts food intake and energy expenditure.
Some hormones, like insulin, act over the long term to regulate levels of body fat. Other short-term hormones like PYY3-36 are released to
trigger hunger pangs or communicate satiation.
The human metabolism evolved millions of years ago to store energy for times when man's ancestors returned from the hunt empty-handed.
Today, many people have an abundance of food and get little exercise, and yet our adipostat has not adjusted.
"Ordinary folk feel hungry more often than they should," Bloom said "We now need a hunger regulator to stay at a normal weight."
On the Net:
Nature: www.nature.com
American Obesity Association: www.obesity.org |
