June 17, 2008 — If you are treating patients for weight management, you might want to considerable a stress-relief program as a first step.
New research at UT (University of Texas) Southwestern Medical Center may explain why some people who are stressed or depressed overeat.
While levels of the so-called “hunger hormone” ghrelin are known to increase when a person doesn’t eat, findings by UT Southwestern scientists suggest that the hormone might also help defend against symptoms of stress-induced depression and anxiety.
“Our findings in mice suggest that chronic stress causes ghrelin levels to go up and that behaviors associated with depression and anxiety decrease when ghrelin levels rise. An unfortunate side effect, however, is increased food intake and body weight,” said Jeffrey Zigman, MD, PhD, assistant professor of internal medicine and psychiatry at UT Southwestern and senior author of a study appearing online and in a future print edition of Nature Neuroscience.
Michael Lutter, MD, PhD, instructor of psychiatry at UT Southwestern and lead author of the study, said, “Our findings support the idea that these hunger hormones don’t do just one thing; rather, they coordinate an entire behavioral response to stress and probably affect mood, stress and energy levels.”
It is known that fasting causes ghrelin to be produced in the gastrointestinal tract, and that the hormone then plays a role in sending hunger signals to the brain. Research groups including Zigman’s have suggested that blocking the body’s response to ghrelin signals might be one way to help control weight by decreasing food intake and increasing energy expenditure.
“However, this new research suggests that if you block ghrelin signaling, you might actually increase anxiety and depression, which would be bad,” Zigman said.
To determine how ghrelin affects mood, Zigman and his colleagues restricted the food intake of laboratory mice for 10 days. This caused their ghrelin levels to quadruple. As compared to the control mice, which were allowed free access to food, the calorie-restricted mice displayed decreased levels of anxiety and depression when subjected to mazes and other standard behavior tests for depression and anxiety.
In addition, mice genetically engineered to be unable to respond to ghrelin were also fed a restricted-calorie diet. Unlike their calorie-restricted wild-type counterparts, these mice did not experience the antidepressant-like or anti-anxiety-like effects.
In future studies, the researchers hope to determine which area in the brain ghrelin may be acting on to cause these antidepressant-like effects.
The work was supported by the National Institutes of Health, the Foundation for Prader-Willi Research, the National Alliance for Research on Schizophrenia, and Depression and the Disease-Oriented Clinical Scholars Program at UT Southwestern.
Source: University of Texas Southwestern Medical Center, www.utsouthwestern.edu