myostatin blocker might slow muscle wasting

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Gene mutation makes tot super strong

Thursday, June 24, 2004 Posted: 11:01 AM EDT (1501 GMT)

(AP) -- Somewhere in Germany is a baby Superman, born in Berlin with

bulging arm and leg muscles. Not yet 5, he can hold seven-pound weights

with arms extended, something many adults cannot do. He has muscles

twice the size of other kids his age and half their body fat.

DNA testing showed why: The boy has a genetic mutation that boosts

muscle growth.

The discovery, reported in Thursday's New England Journal of Medicine,

represents the first documented human case of such a mutation.

Many scientists believe the find could eventually lead to drugs for

treating people with muscular dystrophy and other muscle-destroying

conditions. And athletes would almost surely want to get their hands on

such a drug and use it like steroids to bulk up.

The boy's mutant DNA segment was found to block production of a protein

called myostatin that limits muscle growth. The news comes seven years

after researchers at s Hopkins University in Baltimore created buff

" mighty mice " by " turning off " the gene that directs cells to produce

myostatin.

" Now we can say that myostatin acts the same way in humans as in

animals, " said the boy's physician, Dr. Markus Schuelke, a professor in

the child neurology department at Charite/University Medical Center

Berlin. " We can apply that knowledge to humans, including trial

therapies for muscular dystrophy. "

Disease relief

Given the huge potential market for such drugs, researchers at

universities and pharmaceutical companies already are trying to find a

way to limit the amount and activity of myostatin in the body. Wyeth has

just begun human tests of a genetically engineered antibody designed to

neutralize myostatin.

Dr. Lou Kunkel, director of the genomics program at Boston Children's

Hospital and professor of pediatrics and genetics at Harvard Medical

School, said success is possible within several years.

" Just decreasing this protein by 20, 30, 50 percent can have a profound

effect on muscle bulk, " said Kunkel, who is among the doctors

participating in the Wyeth research.

Muscular dystrophy is the world's most common genetic disease. There is

no cure and the most common form, Duchenne's, usually kills before

adulthood. The few treatments being tried to slow its progression have

serious side effects.

Muscle wasting also is common in the elderly and patients with diseases

such as cancer and AIDS.

" If you could find a way to block myostatin activity, you might slow the

wasting process, " said Dr. Se-Jin Lee, the s Hopkins professor whose

team created the " mighty mice. "

Lee said he believes a myostatin blocker also could suppress fat

accumulation and thus thwart the development of diabetes. Lee and s

Hopkins would receive royalties for any myostatin-blocking drug made by

Wyeth.

Boy's background, future

Dr. Hoffman, director of Children's National Medical Center's

Research Center for Genetic Medicine, said he believes a muscular

dystrophy cure will be found, but he is unsure whether it will be a

myostatin-blocking drug, another treatment or a combination, because

about a dozen genes have some effect on muscles.

He said a mystotatin-blocking drug could help other groups of people,

including astronauts and others who lose muscle mass during long stints

in zero gravity or when immobilized by illness or a broken limb.

Researchers would not disclose the German boy's identity but said he was

born to a somewhat muscular mother, a 24-year-old former professional

sprinter. Her brother and three other close male relatives all were

unusually strong, with one of them a construction worker able to unload

heavy curbstones by hand.

In the mother, one copy of the gene is mutated and the other is normal;

the boy has two mutated copies. One almost definitely came from his

father, but no information about him has been disclosed. The mutation is

very rare in people.

The boy is healthy now, but doctors worry he could eventually suffer

heart or other health problems.

In the past few years, scientists have seen great potential in

myostatin-blocking strategies.

Internet marketers have been hawking " myostatin-blocking " supplements to

bodybuilders, though doctors say the products are useless and perhaps

dangerous.

Some researchers are trying to turn off the myostatin gene in chickens

to produce more meat per bird. And several breeds of cattle have natural

variations in the gene that, aided by selective breeding, give them far

more muscle and less fat than other steer.