ANN ARBORResearchers in the Life Sciences Institute at the University of Michigan have challenged a long-held belief that whitening of skeletal muscle in diabetes is harmful.
In fact, the white muscle that increases with resistance training, age and diabetes helps keep blood sugar in check, the researchers showed.
In addition, the insights from the molecular pathways involved in this phenomenon and identified in the study may point the way to potential drug targets for obesity and metabolic disease.
"We wanted to figure out the relationship between muscle types and body metabolism, how the muscles were made, and also what kind of influence they have on diseases like type 2 diabetes," said Jiandie Lin, Life Sciences Institute faculty member and associate professor at the U-M Medical School.
Lin's findings are scheduled to be published online April 7 in Nature Medicine.
Much like poultry has light and dark meat, mammals have a range of muscles: red, white and those in between. Red muscle, which gets its color in part from mitochondria, prevails in people who engage in endurance training, such as marathon runners. White muscle dominates in the bodies of weightlifters and sprinterspeople who require short, intense bursts of energy.
"Most people are in the middle and have a mix of red and white," Lin said.
When you exercise, nerves signal your muscles to contract, and the muscle needs energy. In response to a signal to lift a heavy weight, white muscles use glycogen to generate adenosine triphosphate (ATP)energy the cells can use to complete the task. While this process, called glycolysis, can produce a lot of power for a short time, the glycogen fuel soon depletes.
However, if the brain tells the muscle to run a slow and steady long-distance race, the mitochondria in red muscles primarily use fat oxidation instead of glycogen breakdown to generate ATP. The supply of energy lasts much l
|Contact: Laura J. Williams|
University of Michigan