Hormone Could Serve as an Antidepressant

New York Times Syndicate - January 19, 2006

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, says 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 says.

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 says. "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," says 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 says: high levels of leptin might make people

lose weight, too.