Loss of muscle mass makes a bad situation worse for individuals coping with immobility, cancer, other illnesses, and more than 500 genetic conditions. When muscle fibres fail to maintain their normal cycle of growth and regeneration, inactivity and atrophy can trigger devastating consequences such as pneumonia, pressure ulcers, falls, and permanent immobility.
Research announced today shows that a protein whose roles in many of the body’s systems are already understood is also vital in maintaining muscle mass. This opens up a new research pathway for prevention and treatment of muscle atrophy in many inherited conditions and acquired illnesses, says lead author Dr. Ronald D. Cohn. He is head of the Division of Clinical & Metabolic Genetics and co-director of the new Centre for Genetic Medicine at The Hospital for Sick Children (SickKids), and Associate Professor of Paediatrics at University of Toronto. The study appears today in the Early View edition of EMBO Molecular Medicine.
Clues in hibernation
Dr. Cohn and his international co-investigators first identified the critical role of the SGK1 protein in animals’ resumption of normal activity following hibernation. The team then studied the protein’s effects on muscle tissue. While SGK1 (serum glucocorticoid-induced kinase-1) is widely known for its complex roles in cardiovascular, kidney, and other functions, the fact that it also plays a vital role in regulating muscle mass in mammals has not been known until now.
“Previous research of hibernating animals has yielded important insights into many aspects of metabolism,” says Dr. Cohn. “Our team is engaged in the question of how animals recover full use of skeletal muscles that atrophy due to illness, decreased caloric needs, or inactivity.
We found that SGK1 is critical in hibernating ground squirrels. Building on that insight, we wondered if SGK1 plays a role in the muscle cells of non-hibernating mammals. We now confirm that, along with the protein Akt, it plays a vital role in muscle homeostasis – that is, maintaining functional muscle mass and preventing muscle loss in conditions leading to muscle atrophy.”
The researchers showed that leg muscles in mice that do not have normal levels of SGK1 develop more severe atrophy compared to normal mice. On the other hand, when mice are inactive or on a calorie-reduced diet, a boost of SGK1 protects them from muscle loss or atrophy.
“Until now, we have understood the protein Akt to be the primary muscle-mass regulator,” Dr. Cohn says. The discovery that SKG1 also plays a critical role opens up the potential for research that could help to sustain muscle mass in old age, illness, immobility, spinal cord injury, and some neuromuscular conditions.
“It’s much too soon to predict a clinical impact for this research. At the same time, we are optimistic about the potential for eventual applications that could make a difference in the physical status and quality of life of people who suffer from muscle loss,” says Dr. Cohn. “Our next projects will focus on applying this new understanding of SKG1 to conditions associated with denervation (such as spinal cord injury) and genetic conditions such as the many types of muscular dystrophy,” he adds.
The project was an international effort involving 23 researchers in Spain, France, and several centres in the U.S. and Germany. Dr. Cohn and partners initiated and completed this research when he was at Johns Hopkins University School of Medicine in Baltimore.
Funding support included the (U.S.) National Institutes of Health and the Dana and Albert R. Broccoli Charitable Foundation for Research.
About The Hospital for Sick Children
The Hospital for Sick Children (SickKids) is recognized as one of the world’s foremost paediatric health-care institutions and is Canada’s leading centre dedicated to advancing children’s health through the integration of patient care, research and education. Founded in 1875 and affiliated with the University of Toronto, SickKids is one of Canada’s most research-intensive hospitals and has generated discoveries that have helped children globally. Its mission is to provide the best in complex and specialized family-centred care; pioneer scientific and clinical advancements; share expertise; foster an academic environment that nurtures health-care professionals; and champion an accessible, comprehensive and sustainable child health system. SickKids is proud of its vision of Healthier Children. A Better World.™ For more information, please visit www.sickkids.ca.
About SickKids Centre for Research and Learning
The SickKids Centre for Research and Learning will bring together researchers from different scientific disciplines and a variety of clinical perspectives, to accelerate discoveries, new knowledge and their application to child health — a different concept from traditional research building designs. The facility will physically connect SickKids science, discovery and learning activities to its clinical operations. Designed by award-winning architects Diamond + Schmitt Inc. and HDR Inc. with a goal to achieve LEED® Gold Certification for sustainable design, the Centre will create an architectural landmark as the eastern gateway to Toronto’s Discovery District. The SickKids Centre for Research and Learning is funded by a grant from the Canada Foundation for Innovation, the Government of Ontario, philanthropist Peter Gilgan and community support for the ongoing fundraising campaign. For more information, please visit www.sickkidsfoundation.com/bepartofit.
For more information, please contact:
The Hospital for Sick Children
Phone: 416-813-7654 ext. 2059
The Hospital for Sick Children