Hunger hormone 'helps depression'16th June 2008
The hunger hormone ghrelin has been shown to be linked to an anti-depressive effect, a recent study in the United States has shown.
While ghrelin is already known to increase when a person does not eat, researchers at the University of Texas' Southwestern Medical Center say the hormone might also help defend against symptoms of stress-induced depression and anxiety.
Research findings in mice suggest that chronic stress causes ghrelin levels to go up and that behaviour associated with depression and anxiety decrease when ghrelin levels rise, according to senior study author Jeffrey Zigman, assistant professor of internal medicine and psychiatry at UT Southwestern.
Published in the journal Nature Neuroscience, the study shows that hunger hormones have more than one function, and that they coordinate an entire behavioural response to stress and probably affect mood, stress and energy levels.
Ghrelin is produced in the gastrointestinal tract when a person is fasting, and plays a role in sending hunger signals to the brain.
One focus of ghrelin research has been on how to block the body's response to ghrelin signals as a way to control weight by decreasing food intake and increasing energy expenditure.
But the study suggests that this might in fact lead to increased anxiety and depression.
Zigman's team restricted the food intake of laboratory mice for 10 days, causing their ghrelin levels to quadruple. A control group was meanwhile allowed free access to food.
The calorie-restricted mice displayed decreased levels of anxiety and depression when subjected to mazes and other standard behaviour tests for depression and anxiety.
They also exposed the mice to stress from aggressive individual mice, and found that this led to increased ghrelin levels that lasted at least four weeks from the stressful encounter.
A group of genetically altered mice, who were unable to respond to ghrelin, showed an exacerbation of depression-like symptoms.
The link, Zigman said, could be evolutionary in nature, meaning that hunger would override anxiety about potential predators prompting our ancestors to venture out in search of food.
Experts said the findings might be relevant in understanding conditions such as anorexia nervosa.
In future studies, the researchers hope to determine which area in the brain ghrelin may be acting on to cause these antidepressant-like effects.
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Title: Hunger hormone 'helps depression'
Author: Luisetta Mudie
Article Id: 7134
Date Added: 16th Jun 2008