Using a technique first employed to battle drug addiction, chemist Kim Janda at the Scripps Research Institute and his colleagues synthesized a vaccine that would convince a rat's immune system that ghrelin--a hormone secreted by the stomach in humans and thought to induce hunger--was an invading antigen. By manipulating the ghrelin molecule and hitching it to a carrier protein and adjuvant, the team succeeded in crafting three different versions of the potential vaccine.
After four inoculations, 10 rats given either of two of those vaccines gained less weight than four rats on the third version and three control rats--despite the same food intake. "All worked well in terms of getting an immune response but only two impacted basic weight processes," Janda says. "They slowed the rate of weight gain and decreased the amount of [fat] tissue."
Postmortem analysis proved that the vaccinated rats gained lean mass rather than fat and raised hopes that a vaccine for obesity might one day be available. That day is not likely to come anytime soon, Janda cautions, as the vaccines must first prove their efficacy in larger trials as well as experiments with clinically obese animals and rats fed a high-fat diet similar to the one thought to be driving the unprecedented weight gain worldwide. The paper presenting this initial research appears online this week in the Proceedings of the National Academy of Sciences.