a protein has been found in the body's main weight-regulating system that could be targeted to develop obesity drugs. Gregory Barsh and his colleagues at Standford University School of Medicine, California, usa, have named the protein as aguoti-related protein ( agrp ).

In 1994, researchers had discovered leptin, a protein that is targeted to prevent obesity. Leptin is produced by fat cells as an indication that the body has sufficient energy stores. When laboratory mice are injected with high levels of leptin, they initially decrease their food intake, increase their metabolic rate and become much thinner. However, after a due course of time, their body adapts to high levels of leptin and becomes resistant to its effects. In such cases, the newly identified protein may prove to be an ideal target, says Barsh.

The researchers discovered agrp after receiving a clue from hairs of a yellow mouse. They were looking for proteins similar to agouti that are normally produced in skin. When a pulse of agouti alters pigment production in hair cells, the black hairs of a mouse get a tiny yellow stripe. The mouse looks brown from a distance.

When they isolated the mouse and human genes coding for agouti in 1992, they found that some mice with a mutation in this gene produced agouti continuously and throughout the body. This made the mutant mice both yellow and obese. While the colour of the mice were on expected lines, their obesity came as a surprise to the researchers.

They got a hint that a protein similar to agouti was being produced elsewhere in the body that was regulating weight. Then then started a search for a dna -sequence database and found that agrp is produced in the adrenal gland and the hypothalamus