The Johns Hopkins researchers who first identified myostatin as a key restrictor of muscle growth in animals now report that excessive amounts of the protein in mice cause rapid and dramatic loss of both muscle and fat, without affecting appetite.
The results, obtained by implanting cells engineered to make extra myostatin into adult mice, support the idea of targeting myostatin to find potential new treatments for muscle-wasting diseases like muscular dystrophy, the team from Johns Hopkins and pharmaceutical company Wyeth report in the May 24 issue of Science.
"We now know that myostatin can affect muscle growth and maintenance in adult animals and that it acts throughout the body," says Se-Jin Lee, M.D., Ph.D., professor of molecular biology and genetics in the School of Medicine's Institute for Basic Biomedical Sciences. "These are key pieces of information, because agents interfering with myostatin could only help if the protein normally acts postnatally."
The situation observed in mice is similar to a common and largely untreatable complication of certain cancers, AIDS and other diseases in humans -- extreme loss of both muscle and fat, even while food consumption is normal. However, the researchers caution that it's still unknown whether myostatin is involved in the human wasting syndrome, called cachexia (ka-KEX-ee-a).
"We don't know whether myostatin is a key mediator in human wasting syndromes, but our findings raise the possibility that blocking myostatin activity may have beneficial effects in patients with cachexia," says Teresa Zimmers, Ph.D., who carried out the studies as a graduate student at Hopkins. "At the very least the finding will help clarify aspects of muscle wasting in general."
Previous studies had proved that myostatin normally limits muscle growth; mice without a working myostatin gene develop more muscle than normal mice, making them so-called "mighty mice." Until now the researchers weren't
Contact: Joanna Downer
Johns Hopkins Medical Institutions