A mouse study presented this week at Obesity 2012, the annual scientific meeting of the Obesity Society, offers an enticing hint that an obesity vaccine targeting the hormone somatostatin may one day help humans to modulate body weight.
“The original impetus was to look at vaccines against the hormone somatostatin to produce lean meat in pigs and increase milk production in dairy cows,” Dr Keith Haffer (Braasch Biotech, Garretson, SD) said in an interview. “Extrapolation showed we could use a similar vaccine mechanism to fight obesity in an obese mouse model.”
Researchers gave a vaccine containing purified chimeric somatostatin protein to obese mice on high-fat diets on day 1, followed by a smaller dose on day 22, and compared six-week outcomes with a control group. “While the control mice continued to gain weight, vaccinated mice lost up to 20% of their body weight within the first week and maintained the weight loss over the three-week period. We gave them two vaccinations, and each vaccination caused weight loss.”
According to Haffer, the vaccine works like any other vaccine in that the body produces immune responses against the antigen contained in the vaccine. What’s different, however, is that the new vaccine’s effect tapers off rather quickly. “Every vaccination is considered to be its own vaccine,” Haffer said. “There’s no memory response to the somatostatin antigen, which makes it totally unique in vaccines. By the intramuscular route, which is how most vaccinations are given, the maximum response occurred about two weeks after vaccination. And it’s gone by four weeks. So a second dose is administered at that time.”
Haffer says his first study, published online July 9, 2012 in the Journal of Animal Science and Biotechnology, prompted worldwide media attention. Some outlets “called it ‘the flab jab,’ which we think is derogatory, but it certainly gets the point across that there could be a vaccine against obesity.”
Haffer said he thinks human trials could be ready within a year, although he also believes an intermediate animal model will be needed for toxicology studies.
One corollary to the weight loss is that insulin levels are unaffected. “We checked insulin levels, and all the mice insulin levels were the same after vaccinations. That’s a very interesting concept.”
Commenting on the study, Dr Sabyasachi Sen (Baystate Medical Center, Amherst, MA) cautioned: “One-shot solutions for complex human diseases rarely work. A vaccine may be possible, but diabetes and obesity are multifaceted diseases. . . . The issue is that this vaccine may not just target one entity, [insulinlike growth factor-1] IGF-1. Somatostatin will affect all the hormones in the body, including the good ones, like normal growth hormone. It’s going to reduce tons of other hormones that we need for everyday living. That’s the problem: it may not be reducing only one of the peaks of the total iceberg.”
But Dr Erik Hemmingsson (Karolinska Institutet, Stockholm, Sweden) thought that antiobesity vaccines may be exactly what the field needs, calling them a “hot topic.”
“We need this kind of outside-the-box thinking. We can’t continue these increasing rates of bariatric surgery, which is a measure of our desperation that we don’t have better therapies. Perhaps this is one more therapy for individualized treatment that might be different for me and for you and for everyone else.”