What if you could roll up your sleeve and get a shot that would make you eat less? Such an idea is not that far-fetched, say researchers from Portugal.
“An anti-ghrelin vaccine may become an alternate treatment for obesity, to be used in combination with diet and exercise,” said Mariana Monteiro, MD, PhD, an associate professor at the University of Porto in Portugal and lead investigator in the study.
Currently, there are few drugs available to help combat obesity. Last October, Abbott Laboratories and the U.S. Food and Drug Administration (FDA) announced Meridia, also known as sibutramine, was being withdrawn from the U.S. market because of clinical trial data indicating an increased risk of heart attack and stroke.
The popular weight-loss drug fen-phen was taken off the market in 1997 after clinical trials showed it to cause heart valve damage.
The new obesity vaccine works by suppressing the appetite-stimulating hormone ghrelin. In tests, it decreased food intake and increased calorie burning in mice.
Ghrelin is a stomach hormone that promotes weight gain by increasing appetite and food intake while decreasing energy expenditure, or calorie burning. Recent research shows that bariatric surgeries, such as gastric bypass, suppress ghrelin.
“This suggests that there is a hormonal mechanism underlying the weight loss attained by the surgical procedures,” Monteiro said.
Monteiro’s group developed the vaccine using a noninfectious virus carrying ghrelin, which was designed to provoke an immune response—development of antibodies against ghrelin—that would suppress the hormone.
They then vaccinated normal-weight mice and mice with diet-induced obesity three times and compared them with control mice that received only saline injections.
More energy, less food
Compared with unvaccinated controls, vaccinated mice — both normal-weight and obese mice — developed increasing amounts of specific anti-ghrelin antibodies, increased their energy expenditure and decreased their food intake, the authors reported.
Within 24 hours after the first vaccination injection, obese mice ate 82 percent of the amount that control mice ate, and after the final vaccination shot they ate only 50 percent of what unvaccinated mice ate, Monteiro said.
The effects of each vaccination lasted for the two months of the study, which for the normal 18-month lifespan of mice, corresponds to four human years, she said.