Muscle mass maintenance under scrutiny

When muscles are not pressed into service, they begin to lose mass.

Sometimes, that can’t be helped, such as when people or animals age. Other times, atrophy might occur due to bed rest, diseases such as multiple sclerosis (MS), or even space flight.

Could there be a way to reverse this process? That’s what Troy Hornberger, an assistant professor of physiology at the University of Wisconsin–Madison School of Veterinary Medicine, is trying to find out.

His long-term goal is to develop a drug that can prevent muscle atrophy.

This would benefit people, especially the elderly, suffering from injuries that require a long recovery period.

“For example, when an individual older than 60 has suffered a hip fracture, they are unlikely to fully regain their walking abilities,” he says. “This is due in part to the large extent of muscle loss that occurs during the recovery process. Muscles simply don’t recover as quickly when we age.”

Knowing that somehow muscles convert weight-bearing “mechanical” signals into biochemical events that regulate muscle mass suggests that a drug could be developed to mimic this process.

With receipt of a $1.1 million, five-year grant from the National Institutes of Health, Hornberger is exploring this possibility with a variety of molecular techniques, including live cell imaging. Live cell imaging uses tiny molecular probes to visualize where mechanically induced signaling events are being activated within the cell (such as the nucleus or membrane).

Already, his studies have led to identification of a target molecule that, when activated, can cause skeletal muscle fibers to enlarge 60 percent within seven days.

“If we can pharmacologically reproduce the biochemical signal that tells muscle to increase its size when mechanical loads are applied, then we can potentially prevent the atrophy that occurs in the absence of mechanical loads such as during bed rest,” he says.