INTENSIVE exercise boosts communication between skeletal muscles and fat tissue, fine-tuning metabolism and improving performance, research in mice and humans suggests. The finding may lead to new treatments for metabolic diseases associated with aging and obesity.
Researchers in Brazil have discovered that aerobic exercise triggers the release of signaling molecules into the bloodstream that free up more energy for use by the muscles.
Previous research has found that aging and obesity impair the production of these signaling molecules, known as microRNAs. This increases the likelihood of metabolic diseases, such as diabetes and dyslipidemia.
The good news is that exercise may help ward off these conditions by stepping up the production of certain microRNAs.
The new research appears in the journal Proceedings of the National Academy of Sciences of the United States of America.
Marcelo Mori and his colleagues at the University of Campinas Institute of Biology in São Paulo, Brazil, collaborated on a series of experiments with researchers at the University of Copenhagen in Denmark and Harvard University in Cambridge, MA.
They started by putting mice on a treadmill for 60 minutes per day for 8 weeks. As the mice became fitter, the researchers increased the speed and slope of the treadmill.
At the end of the training program, the researchers found a significant increase in the production of a protein called DICER in the animals’ fat cells. This increase correlated with reductions in the body weight of the mice and the amount of visceral fat in their abdomens.
DICER is an enzyme that allows fat cells, or adipocytes, to make microRNA signaling molecules. These in turn make more energy available to the muscles.
When the scientists repeated the experiment with genetically modified mice that were unable to make any DICER in their fat cells, the mice did not benefit as much from the training program.
“The animals did not lose weight or visceral fat, and their overall fitness did not improve,” says Mori.
Fat cells in the genetically modified mice failed to supply their muscles with the extra metabolic fuel they needed during strenuous exercise.
Without DICER, says Mori, fat cells actually consume more glucose during exercise, leaving less fuel for muscles. This can lead to hypoglycemia, or low blood sugar levels. In athletes, this can limit their performance.
