THURSDAY, Jan. 19, 2006 (HealthDay News) -- The hormone leptin, thought to be key to weight loss, might also improve your mood even if you're not overweight.
Leptin, which is believed to control feelings of hunger, also helps prevent stressed-out mice from falling into despair, a condition comparable to depression in people, a new study suggests.
Leptin appears to be like other hormones that play more than one role in the brain, said Richard Simerly, director of the Neuroscience Program at the Saban Research Institute of Children's Hospital Los Angeles. "They alter the way brain circuits function, and they do this not in just the areas that you'd expect."
It's too early to know if leptin would help people recover from depression. But it's good news for a hormone that was unknown until its discovery about a decade ago, Simerly said.
Leptin, which is produced by fat cells, tells the brain that people need to start eating. "Some people refer to it as a starvation signal," Simerly said. "It means your energy stores and fats are getting depleted, and you really need to start taking in calories."
If your leptin levels are naturally low -- as is the case for some people with genetic mutations -- the body continuously thinks it's hungry. "If you don't have it, you get obese," said study author Dr. Xin-Yun Lu, an assistant professor at the University of Texas Health Science Center.
Researchers have suspected that leptin does other things, too. In the new study, the scientists performed several tests on mice to measure whether leptin affects emotion.
The findings appear in this week's issue of the Proceedings of the National Academy of Sciences.
In one test, the researchers stressed the mice in a way designed to create effects similar to human stress. The researchers exposed the mice to electric shocks, water immersion, restraints, solitary confinement and overcrowding. The leptin levels in the mice dropped, suggesting it has some connection to stress.
In another test, also designed to cause stress, the researchers forced the mice to swim long distances, a grueling task that can induce a kind of hopelessness similar to depression in humans. The mice given leptin were less likely to give up and fall into "despair."
The next step: Figuring out if leptin actually helps depressed people get better. If it does, there may be an added benefit to its use as an antidepressant, Lu said -- high levels of leptin might make people lose weight, too.
Learn about leptin from Duke University.