The study conducted by Matthias Tschop, MD, UC, associate professor of psychiatry from the University of Cincinnati, and co-authored by scientists at the German Institute of Human Nutrition, found that the melanocortin system, controls fat metabolism and the way it accumulates in the body completely independently of food intake.
The researchers believe that the finding could lead to the development of new and urgently needed medications to treat the growing, worldwide obesity epidemic.
The melanocortin system was previously identified as a "control loop" in the central nervous system (CNS) that receives signals from hunger and "satiety" hormones, like those given off by 'such as ghrelin and leptin', and responds to these sensations of hunger or fullness by causing the body to either ingest or burn calories.
Tschop and colleagues say that beyond responding to signals of hunger or satiety, the melanocortin system also controls whether extra energy (glucose) will be converted to fat and whether it will be stored or metabolized.
"Understanding how specific CNS circuits directly control fat storage and metabolism is essential in order to achieve a breakthrough in this important area of research," the authors write.
The group studied the melanocortin system at the molecular level in rodents. They found that when the system is stimulated to increase activity, fat is metabolized. When activity in the system is reduced—either pharmacologically or genetically—fat accumulation increases.
"We were able, in essence, to change traffic signals in so-called nutrient highways in the body so that calories were metabolized, and not dumped into fat cells. And we did this without changing the rate of food intake," said Tschop.
"These findings are relevant for human obesity, since mutations in the system we studied here are the most common known reason for genetically caused obesity in humans," Tschop added.
The study authors also reported clinical data from co-authors I. Sadaf Farooqi and Stephen O'Rahilly.
Their studies in humans with activity-reducing genetic variations in the melanocortin system indicate that fat metabolism may be "remote controlled" by the human brain similar to the way it is in rodents.
The study appears in the Sept. 20, 2007, online edition of the Journal of Clinical Investigation.