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Protein that creates big muscles discovered

Kathleen Blanchard's picture
Mouse study shows protein responsible for powerful muscles.

Researchers at the Dana Farber Cancer Institute have discovered a protein that is important for strong muscles. The finding could have implications for helping us stay stronger with aging as well as for patients undergoing cancer therapy or suffer from other chronic debilitating illnesses.

The protein was previously unknown and is responsible for increased muscle growth that follows resistance training. When researchers gave mice extra doses of the protein they gained muscle mass. Rodents with cancer that were given the protein were less likely to become frail and thin – something that often happens to cancer patients.

Jorge Ruas, PhD, first author of the report said the discovery is basic, but notes it would be "exciting" if ways could be discovered to elevate levels of the protein.

The finding could mean ways to help patients on prolonged bed rest in the hospital, elders and even people with muscular dystrophy.

The protein that was discovered by lead researcher Bruce Spiegelman, PhD, is PGC-1 alpha-4 that is present in skeletal muscle.

Weight lifting and other resistance exercises trigger the release of PGC-1 alpha-4 causing muscles to become larger and more powerful.

PGC-1 alpha-4 increases activity of a protein called IGF1 (insulin-like growth factor 1), which makes muscles bigger.

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Other types of exercise, like running, turns on the activity of the protein variant - PGC-1 alpha – that increases muscle endurance rather than size.

“It’s pretty amazing that two proteins made by a single gene regulate the effects of both types of exercise,” commented Spiegelman in a press release.

The researchers used viruses to inject the PGC-1 alpha-4 protein into leg muscles of mice being tested. After several days, their leg muscles were 60 percent bigger.

“All of our muscles have both positive and negative influences on growth,” Spiegelman explained. “This protein (PGC-1 alpha-4) turns down myostatin and turns up IGF1.” Myostatin inhibits muscle growth and IGF-1 promotes bigger muscles.

The researchers also engineered mice with higher levels of the protein. Compared to normal mice, they were 20 percent stronger and more resistant to fatigue. They also had a ‘dramatic’ resistance to muscle wasting caused by cancer, losing just 10 percent of muscle mass, compared to 29 percent muscle loss in mice that did not have the extra protein.

The new discovery showing the protein PGC-1 alpha-4 leads to larger and more powerful muscles could someday help cancer patients; help us stay stronger with aging and more. The study authors suggest there may be ways to artificially raise the protein levels.

Dana Farber Cancer Institute

"A PGC-1α Isoform Induced by Resistance Training Regulates Skeletal Muscle Hypertrophy"
Jorge L. Ruas, et al.
December 7, 2012

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