Understanding hunger and satiety is crucial to understanding obesity and metabolic disorders. Researchers from The Rockefeller University have discovered an important new component of the process that appears to be responsible for regulating food intake.
Called amylin, it is a hormone in the brain that is tasked with controlling consumption. A complex circuit regulates how much a person eats and understanding the process requires that all molecules involved be identified, said Jeffrey Friedman, Rockefeller's Laboratory of Molecular Genetics head.
According to the researchers, amylin caught their attention while they profiling neurons in the hypothalamus. Because the protein had a role in metabolizing sugar in the body, they were keen on exploring what its function in the brain would be.
In 1994, Friedman discovered leptin. Defects in the production of this hormone were associated with obesity, so earlier studies sought out to see how using leptin could be effective in treating obesity. Unfortunately, results showed that using the hormone only worked when severe leptin deficiency is in place. This hinted that other components were at play with obesity.
In a study published in the journal Cell Metabolism, Friedman and colleagues suggested that amylin and leptin are working together to control body weight and food intake.
First, the researchers identified Iselt amyloid peptide (Iapp), a precursor to amylin in the brain. They saw that Iapp was abundant in several regions across the hypothalamus.
To find out what amylin's functions are in the hypothalamus, the researchers examined the presence of the protein in mice that were obese because of leptin deficiency. When given leptin, the mice showed increased levels of Iapp, showing that the hormone regulates amylin expression.
To assess feeding behavior, the researchers administered leptin to mice and saw decreased food intake. However, when the hormone was given to mice with nonfunctional amylin, they saw no effects. This shows that amylin and leptin work together to cut back on food intake.
"These findings confirm a functional role for amylin in the central nervous system, and provide a potential mechanism to treat obesity more effectively, through combination therapy," said Friedman.
While the discovery of amylin is a big boost, it is just one piece of the puzzle. Further research is still needed to better understand the mechanisms at play on the cellular level and come up with new approaches involving better leptin sensitivity and signaling.
Photo: Steven Depolo | Flickr
