Link Between Obesity And Memory? Researchers Examine Hormone That Turns Off Hunger

"Leptin is a hormone secreted by fat cells that tells us to stop eating. In obese people, it doesn't cross into the brain to help regulate appetite," says Susan A. Farr, Ph.D., principal investigator and associate research professor in the division of geriatric medicine at Saint Louis University School of Medicine.

"We've now found leptin affects the brain in other ways, compromising learning and memory. Low levels of leptin also could be related to cognitive deficits in disorders like type two diabetes."

Farr and her research team tested the role of leptin in learning and memory using an animal model. They found that mice navigated a maze better after they received leptin.

"We found that this drug affected the processes going into the brain," says Farr, who also is a researcher at Veterans Affairs Medical Center in St. Louis. "The mice that got the drug at the appropriate dose had improved learning and long-term memory."

Mice with elevated levels of amyloid-beta protein, the brain plaques believed to cause Alzheimer's disease, and impaired learning and memory were "super sensitive" to leptin, Farr adds.

"In the older mice that have Alzheimer's disease, leptin worked even better and at a lower dose than it did in younger mice."