Scientists Find a New Molecular Link Between Exercise and Health

In some not-so-shocking news, it turns out that exercise is good for you.

But, what is rather shocking is that a natural hormone that’s increased by exercise was found by Dana-Farber researchers to improve blood sugar control, suppress inflammation, and burn fat—in mice.

In a new study published in the journal, Cell, the researchers said that when Metrnl, a hormone that can be made in a lab, was injected into mice, it achieved some of the same effects as exercise. “It decreased their body fat by 25 percent and caused them to lose weight, even on a high-fat diet. It improved their blood sugar control, stimulated conversion of chemical energy to heat, and turned on anti-inflammatory genes,” the study says.

So, did Dana-Farber scientist just find the weight loss Holy Grail?

Its health-promoting properties make it a promising candidate for treating obesity and other metabolic diseases, inflammation, and possibly other disorders, said principal investigator Bruce Spiegelman, of Dana-Farber’s Cancer Biology department.

“This might have interesting therapeutic potential for several diseases,” Spiegelman says. “Because it targets the immune cells involved in tissue repair it will also be interesting to see if this protein affects muscle repair in certain neuromuscular diseases.”

The researchers say that although the Metrnl protein had previously been identified, this new study is the first to reveal its role as a hormone involved in metabolism and energy balance. In addition, the study revealed that Metrnl helps maintain core heat production which leads to extra fat burning in mice exposed to cold temperatures. The researchers said in the study that this indicates that Metrnl is part of the body’s mechanism for adapting to environmental changes.

According to the report:

Unlike other exercise-related proteins that stimulate “thermogenesis” – burning calories to create heat – Metrnl works mainly through the immune system, rather than directly on fat cells, said Spiegelman. The scientists found that Metrnl activates an alternative molecular pathway by which immune cells are recruited to enter fatty tissue, where they trigger the fat-burning process.

The Metrnl findings come two years after the Spiegelman group isolated a different protein, irisin, produced in muscles by endurance as opposed to resistance exercise, which stimulates Metrnl secretion. Irisin also promotes the browning of fat to release energy and caused mice to lose weight; like Metrnl, irisin improves glucose tolerance, which helps prevent diabetes.

From the viewpoint of developing therapies, “it is a good thing to have molecules that work through different pathways,” said Spiegelman. Irisin is being studied as a potential treatment for obesity and type 2 diabetes and has been licensed commercially.

“The idea of a protein acting primarily through the immune cells in the fat is pretty amazing, at least in our view,” Spiegelman says.