US researchers claim that high level of the “hunger hormone” ghrelin have an antidepressant effects.
Suggested as a weight loss treatment because it blocks the body’s response to ghrelin, it may also produce unintended effects on mood, they said.
Fewer signs of depression and anxiety were discovered on mice in which the Nature Neuroscience study found an increased levels of the hormone.
The idea was interesting even though further studies were needed, experts say.
The empty stomach releases ghrelin into the bloodstream, which then moves to the brain where it triggers feelings of hunger.
Both people who are eating too little, like cancer patients, or those who eat too much, might be helped by the treatment with the hormone itself, or a drug designed to cancel its effects, researchers believe.
Lower levels of depression
The food intake of laboratory mice has been restricted for 10 days in the latest study of Dr Jeffrey Zigman and colleagues, which caused their ghrelin levels to quadruple.
When compared with mice who had free access to food, the calorie-restricted mice showed lower levels of depression and anxiety, when subjected to mazes and other behaviour tests.
The team also looked at mice genetically engineered to be unable to respond to ghrelin.
Mice did not experience the antidepressant or anti-anxiety effects when they were fed a restricted-calorie diet.
The same thing was found by researchers when, by subjecting the mice to stress, they induced higher ghrelin levels.
The mice that were unable to respond to ghrelin had greater levels of depression-like symptoms than the normal mice.
“Our findings in mice suggest that chronic stress causes ghrelin levels to go up, and that behaviours associated with depression and anxiety decrease when ghrelin levels rise”, said Dr Zigman, a researcher at UT Southwestern Medical Center in Dallas.
“An unfortunate side effect, however, is increased food intake and body weight”, he added.
The results made sense from an evolutionary stanpoint, he said, because hunter-gatherers may have had a survival advantage, in remaining calm and collected in times of hunger, in order for them to successfully find food.
Now, the researchers are hoping to look at the antidepressant effect of the hormone, in conditions such as anorexia.
Professor Stephen Bloom, an expert in appetite regulation at Imperial College London, judged it reasonable to believe that ghrelin had an impact on behavioural responses, other than just hunger.
But he said that before it could be confirmed that the hormone released in the stomach can have an effect on mood in the brain, a lot of research still had to be done.
“The role of ghrelin in the gut and in the brain are likely to be completely different”, he said.