‘Obesity and thinness are not solely determined by feeding behavior,’ scientists say

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Friday, June 06, 2008 6:36 am Email this article
"Obesity and thinness are not solely determined by feeding behavior," concluded Kaveh Ashrafi, PhD, assistant professor of physiology, and his colleagues from the University of California, San Fransisco.

"Rather, feeding behavior and fat metabolism are coordinated but independent responses of the nervous system to the perception of nutrient availability."

"It is widely believed that environments that encourage excessive food intake and little physical activity promote development of obesity. However, extensive studies have revealed that body weight is not merely a passive consequence of environmental conditions but that a physiological system coordinates the complex mechanisms that regulate food intake and energy expenditure," Ashrafi says. Serotonin

Serotonin controls appetite and regulates fat metabolism separately

They found that that the neurotransmitter serotonin not only controls appetite, but also sends a signal that regulates fat metabolism, at least in the microscopic C. elegans worm that they were looking at.

They found that serotonin controls feeding by docking with receptors on neurons that are distinct from those that control fat.

In turn, these fat-controlling neurons send signals to sites of fat storage to rev up metabolism.

 

New Drugs To Target Fat Metabolism?

New drugs may be developed that block fat storage?

“If the ‘separate-channel’ mechanism is also found in humans, weight-loss drugs might be developed to attack just the fat-deposition channel rather than the hunger-dampening pathway that has met with limited success,” says Ashrafi.

“It’s not that feeding isn’t important,” Ashrafi says. “But serotonin’s control of fat is distinct from feeding. A weight-loss strategy that focuses only on eating can only go so far. It may be one reason why diets fail.”

“Various weight-loss drugs have been developed to boost serotonin and thereby suppress appetite. But the cutback in eating tends to be short-term—often a matter of days, based on animal research,” Ashrafi says.

“Drugs that block the brain’s separate fat-deposition signaling pathway might be a boon to controlling obesity, type 2 diabetes, cardiovascular disease and other threats,” he adds.

REFERENCE

Srinivasan S, Sadegh L, Elle I, Christensen A, Faergeman N, Ashrafi K. Serotonin regulates c. Elegans fat and feeding through independent molecular mechanisms. Cell Metab. 2008 Jun, 7(6):533-44.

AUTHOR’S CONTACT INFORMATION

Kaveh Ashrafi, PhD
Department of Physiology and UCSF Diabetes Center
University of California, San Francisco
San Francisco, CA 94158-2517, USA

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• Genes and genetics