Scientists discover hormone that helps curb people's appetites
Wednesday, August 7th 2002, 12:00 am
By: News On 6
To help rescue us from our super-sized appetites, scientists say they have isolated the hormone that makes people feel full.
In a small experiment in London, people who had injections of the so-called ``third helping hormone'' before chowing down at a buffet lunch reduced the amount of food they ate by one-third.
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.''
Bloom said a medication based on boosting levels of the hormone might reduce overeating as well as between-meal snacking. However, other researchers said the results were too limited. Details appear in the current issue of the journal Nature.
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 that 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 cancers.
In the experiments, scientists in England and Oregon isolated the short-term hormone PPY3-36 that is secreted by cells lining the intestines. Levels of the hormone rise in the blood after eating and remain high between meals.
First, researchers identified the hormone's effect on certain neurons in the brains of mice associated with appetite and weight control.
Then, 12 people of normal weight at Imperial College were injected with extra hormone or a placebo saline solution for 90 minutes. Two hours later, they were offered a buffet lunch.
Results show the subjects who received the hormone boost ate one-third less. They reported feeling less hungry for another 12 hours and did not make up the ``missing'' calories by snacking.
However, other scientists in the study said the experiment does not by itself prove that injections of the ``third helping hormone'' can safely control appetite or reverse obesity. How the body might respond to elevated PPY3-36 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.''
Still, harnessing the dietary role of hormones is an important step in developing effective weight control therapies, experts said.
Previous studies have focused limiting the effects of ghrelin, a hormone made by stomach cells that boosts appetite.
``If we are to combat the global obesity epidemic, such breakthroughs are urgently needed,'' said University of Washington endocrinologist Michael W. Schwartz, who did not contribute to the Nature report.
Weight loss schemes and food supplements are a $40 billion industry. Yet scientists still are untangling the complex chemical signals controlling appetite _ how the body tells the brain it needs energy and how the brain tells the body how much to eat.
Its part of a chemical system called the adipostat, which continually adjusts food intake and energy expenditure like a thermostat.
Some hormones, like insulin, act over the long-term to regulate body fat stores. Other short-term hormones like PPY3-36 are released to trigger hunger pangs or communicate satiation.
Our metabolism evolved millions of years ago to store energy when prehuman ancestors hunted and gathered nourishment, but often returned home empty-handed. Today we live in a caloric extravaganza, but our adipostat _ along with a sedentary lifestyle and other factors _ hasn't adjusted.
``Ordinary folk feel hungry more often than they should,'' Bloom said ``We have too much hunger for a civilized society where too much food is about. We now need a hunger regulator to stay at a normal weight.''