Fat Hormone May Protect Against Alzheimer's

Dec. 16 -- TUESDAY, Dec. 15 (HealthDay News) -- High blood levels of leptin, a hormone that regulates appetite, may guard against Alzheimer's disease, new research suggests.

"Hopefully, in 10 or 15 years this may be one of many agents that we use to reduce the risk of Alzheimer's disease," said senior study author Dr. Sudha Seshadri, an associate professor of neurology at Boston University School of Medicine. "Or it may be one of many markers that we measure in combination to predict risk."

But many more studies of different population groups are needed to determine whether leptin can play such a pivotal role in predicting the risk of Alzheimer's, Seshadri said.

The research, which was reported in the Dec. 16 issue of the Journal of the American Medical Association, was done because "there has been some data relating body weight to the risk of Alzheimer's disease," Seshadri said. "When we looked at animal studies, we found some data to indicate that leptin not only produces a feeling of satiety but also has a beneficial effect on the hippocampus. It was important to see if that was true in humans."

The hippocampus is a portion of the brain that plays a role in important aspects of memory.

Some human studies have shown that people with Alzheimer's disease have lower levels of leptin, but those studies didn't show which came first, the lower leptin levels or the decline in mental function, Seshadri said. So she and her colleagues turned to the Framingham Heart Study, which has followed residents of a Massachusetts community for decades.

Leptin levels had been measured in 785 Framingham participants in the early 1990s. For the new study, 198 of them had MRI scans that measured brain volume an average of 7.7 years after leptin was measured. The study authors also kept track of new Alzheimer's diagnoses among the study participants.

The researchers found that higher leptin levels were associated with a lower incidence of Alzheimer's and all other forms of dementia. The 25 percent of participants with the lowest leptin levels had a 25 percent risk of developing Alzheimer's over a 12-year period; the incidence was only 6 percent for those with the highest leptin levels. And lower leptin levels were associated with a greater decrease in total brain size.