Injected in rats, the vaccine led to losing body weight and fat even if the animals ate normally

Aug 2, 2006 07:17 GMT  ·  By

Scientists at the Scripps Research Institute in La Jolla, California announced yesterday in a report published in the Proceedings of the National Academy of Sciences that they have developed the first anti-obesity vaccine. The vaccine is meant to inhibit one of the hunger hormones in our body, called ghrelin.

By administering the vaccine in overweight people, the levels of ghrelin hormone in their bodies will be considerably reduced and they will gain less extra kilos. The good news is that obese people can go on eating as much as they want to and preserve the same eating habits, because they will lose weight and body fat anyway.

The vaccine has been tested on rats and it proved to be working. Scientists split a number of rats into two groups - one was formed of rats that received food and were injected with the anti-obesity vaccine, while the other group consisted in rats that were simply given the same amount of food as their injected counterparts.

Rats that did not receive any shot gained weight, while those vaccinated lost both weight and body fat. The trial period lasted for 13 weeks, during which rats in the group of vaccinated ones were given 4 shots with the anti-obesity serum. Taking into account the fact that one week in a rat's life is the equivalent of one year in a human's life, the vaccine proved to be long-term efficient.

The vaccine works by activating the immune system to track down and destroy the ghrelin hormone in the body. When injected into the rats, the serum activated antibodies that prevented ghrelin from forming and rats could eat as much as their un-vaccinated counterparts, but they still lost weight. At the end of the testing period, mice receiving the anti-obesity shot reduced their body weight with 20-30%.

"We have enabled the immune system to recognize a molecule that it ordinarily won't recognize. We're training the immune system to recognize ghrelin." The vaccinated mice "were eating the same, but still losing weight -- which is pretty cool," said research leader Kim D. Janda, professor of chemistry at Scripps.

However, activating the immune against ghrelin is not the most recommended solution to treat obesity. Though the vaccine would excellently work against excessive body fat, we should not forget that the ghrelin hormone is also present in the brain and other important areas of the body. Therefore, neutralizing the hormone in the body could lead to serious health disorders.

Ghrelin hormone is primarily found in the cells of the stomach epithelial tissue, but also in various areas of the brain and hypothalamus. Before we eat the levels of ghrelin in our bodies are very high and stimulate brain cells, that "let us know" that we should eat. After we eat, the levels of the hunger hormone decrease considerably.

But besides making us hungry, the hunger hormone is tightly connected with the growth hormone, therefore enhances body's physical development. Recent studies carried out in February this year have also shown that high levels or ghrelin in the body stimulate and improve memory and concentration.

It is important then to take into account these facts before proceeding to use the vaccine on obese people. "What is surprising about this study is that by producing antibodies to block ghrelin it works as well as it does. This is an important proof of principle but there are problems. For example if you develop antibodies against something you can't get rid of them very easily, so if there's anything bad you can't undo it. And since ghrelin is present in the brain you might start an immune system response against the brain. It's not necessarily a very safe thing to do - I wouldn't want to be a volunteer," stated Stephen Bloom, professor of Investigative Science at Imperial College London.

Researchers that carried out the study are also aware of the negative consequences the vaccine could develop. This is why they are very cautious: "We want to do real basic work and make sure we do all our homework before we look at it in humans. We could do it quickly, but it's prudent to know exactly what's going on," professor Janda pointed out.