Researchers have found that a drug used to prevent transplant rejection reduces body fat and appetite in older rats, a discovery which may lead to new treatments for age-related obesity in humans.
University of Florida Health researchers found that Rapamycin, a pharmaceutical used to coat coronary stents and prevent transplant rejection, can reduce obesity and preserve lean body mass when given to older rats.
Although the current findings are limited to rats, rapamycin has potential as a treatment for age-related obesity since it is already being used to treat other conditions in people, researchers said.
“We need to be able to intervene with treatments for older adults. They’re going to have health care issues, and not everyone can get up and exercise. So if you can give them a jump-start or combine rapamycin with other therapies, you could have better health outcomes,” said Christy S Carter, an assistant professor in the Department of Ageing and Geriatric Research in the University of Florida College of Medicine.
Carter and Drake Morgan, an assistant professor in the department of Psychiatry, are the co-lead authors of the study which found that rapamycin reduced food consumption and body weight.
Using 25-month-old rats, which are about equivalent to 65-year-old people, researchers found that body weight dropped by approximately 13 per cent after the rats were treated with rapamycin.
The drug targets the production of leptin, a hormone that affects hunger and metabolism. The researchers believe that normalising the typical age-related spike in leptin results in the reduction of eating.
Rapamycin’s ability to stabilise the rats’ leptin level made them lighter, researchers found.
Rapamycin selectively targeted the fat in rats, allowing the animals to retain lean mass. It worked so well that the older rats ultimately developed a lean-to-fat ratio similar to that of their younger counterparts, researchers said.
In another study, researchers found that small, intermittent amounts of rapamycin produced the desired slimming effect in both young and old rats.
The study determined that the drug works by inhibiting a signalling mechanism known as mTORC1, a protein complex that is an energy and nutrient sensor.
This triggers a response in the brain that curbs eating, effectively reducing age-related fat until the older animals resemble much younger ones.
The second study was led by Philip J Scarpace, a professor in the Department of Pharmacology, and Nihal Tumer, pharmacologist in the geriatric centre at the Malcom Randall Veterans Affairs Medical Center.
While rapamycin works best in older, obese rats, researchers were encouraged that it also had an effect on certain younger animals.
“One point that is common is that it seems to work better in animals, old or young, that have more fat,” Scarpace said.