New hormone mimics the effects of physical exercise
By Jan Belezina
January 18, 2012
A group of researchers at Dana-Farber Cancer Institute and Harvard Medical School, led by Bruce Spiegelman and Pontus Boström, have discovered a hormone that mimics some of the results of a workout by facilitating the transformation of white fat into brown fat. While the purpose of the former is to accumulate excess calories, the latter is used to produce heat. Irisin, named after the Greek goddess Iris, could one day help address obesity and diabetes. However, there is still a long way to go before the hormone is made into an actual drug.
Irisin occurs naturally both in humans and in mice, and its levels surge with physical exercise. Mice have to spend three weeks running on a wheel for the hormone to accumulate in their blood. For humans, the same happens after ten weeks of systematic exercising. A placebo-controlled study showed that boosting the levels of the hormone artificially in mice may induce some of the benefits that would normally be caused by a workout. The cells of the mice injected with irisin needed more oxygen and burned more calories. Obese mice lost several grams within the first ten days from the injection.
The treatment also had a positive effect on the regulation of blood sugar levels, which links the hormone to diabetes prevention. What's more, Spiegelman's team plans to investigate the potential of irisin to advance the treatment of diseases such as muscular dystrophy and muscle wasting. "We are hopeful, though we have no evidence, that this hormone may embody some of the other benefits of exercise, perhaps in the neuromuscular system," he says.
This sounds very promising, but there is still a lot to be done before an irisin-based drug comes to a pharmacy near you. First, whether or not irisin will have the same beneficial effects on humans still remains to be seen. Second, making it into an actual drug may turn out to be very challenging, as pointed out by MIT professor Harvay Lodish. Adiponectin, a hormone Lodish discovered back in the early 1990s, also seems to play a role in staving off obesity and diabetes. It is correlated with the body mass index (BMI) and it increases the metabolic rate in mice without raising the food intake. Still, so far all the attempts at converting the full size adiponectin protein into a viable drug have failed.
Professor Spiegelman, however, is optimistic. In fact, he's optimistic enough to have set up a separate company, called Ember Therapeutics, to conduct brown fat-related research that includes studies on the effects of irisin. Supported by Third Rock Ventures, the company raised US$34 million in the first round of financing. We do hope that all this money and brain power will eventually lead to a treatment for obesity and diabetes. That said, we do recognize that there might be more to it than just swallowing a pill.
We are far from advocating the medicalization of serious social issues, and we warmly encourage our readers to exercise on a regular basis (at least until the magic pill is out, that is).