Health briefs

By Compiled from Times wires

© St. Petersburg Times, published August 11, 2000

Muscle or fat? Protein makes the call

WASHINGTON -- In America's endless search for a magic pill to shrink the waistline, researchers have found a "fat switch" -- a protein that causes developing cells to become either muscle or fat.

But the "fat switch" protein does not offer the promise of an eternally slim body, say University of Michigan Medical School researchers.

"If you could see my midriff, you would know that breaks my heart," says Ormond A. MacDougald, one of the scientists.

In a study appearing today in the journal Science, co-authors MacDougald and Sarah E. Ross report that a protein called Wnt 10b acts as a molecular switch to determine which developing cells become fat and which become muscle.

MacDougald said that both fat and muscle cells evolve from what are called precursor cells. The destiny in the body of some of these precursor cells is determined by a family of 18 proteins called Wnts.

MacDougald and Ross found that one of these proteins, Wnt 10b, appears to regulate production of muscle cells. When Wnt 10b links with certain precursor cells, they develop into muscle. When the Wnt protein is missing, the same cells turn into fat.

"We used muscle precursor cells and showed that if you inhibit the Wnt signal then they turn into fat cells," said MacDougald. "Wnt has to be suppressed for adipocytes (cells that turn into fat) to form."

In effect, he said, Wnt 10b appears to act as "a molecular switch to turn on either fat or muscle."

The action of Wnt 10b was discovered in test tube experiments, but the role of the protein was proven when precursor cells with or without Wnt 10b were implanted in lab mice.

Precursor cells with the Wnt protein continued to evolve toward mature muscle cells, while those lacking Wnt "are redirected from muscle cells toward fat cells," said MacDougald.

MacDougald said the action of the Wnt protein is very local, affecting only a few cells in its vicinity. It does not work like a hormone, which travels through the blood and affects billions of cells. As a result, Wnt 10b is unlikely to be developed into an anti-fat pill.

"Our findings will be important in learning how obesity develops, but the Wnt protein will not be a target for an anti-obesity drug," said MacDougald.

FDA to require tissue bank registration

WASHINGTON -- The U.S. Food and Drug Administration will speed adoption of a rule to require the registration of all human tissue banks and companies making medical products out of donated body parts, according to Health and Human Services Secretary Donna Shalala.

The accelerated regulation is one of several steps the department is taking amid reports of lax government oversight, profiteering and other abuses in the nearly $1-billion-a-year human tissue industry.

"Although FDA believes the safety of tissue products is satisfactory, this medical sector has grown rapidly, with a need for clearer standards and improved accountability," Shalala wrote in a letter delivered this week to Sen. Dick Durbin, D-Ill.

Human tissue is considered anything that is not a vital organ. It can include bone, skin, tendons, heart valves, corneas and dozens of other items that can be taken from a dead person's body.

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