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Molecule found to trim fat in mice

WASHINGTON -- A new approach used to fight cancer may also help fight fat, US researchers said yesterday.

They said blocking a certain protein seems to remove fat from mice.

When fat mice were injected with the new "fat-zapper" every day for a month, all slimmed down to normal weight with no visible side effects, the researchers reported in the June issue of Nature Medicine.

They stressed the experiment is in its very early stages, and it affects a function found in virtually all cells, meaning it has a high potential for serious side effects.

"I am trying to unhype this," said Dr. Wadih Arap of the M. D. Anderson Cancer Center in Houston, who led the research.

A new class of cancer drugs called angiogenesis inhibitors starve tumors by cutting off their blood supply.

Arap and colleagues have turned this approach against fat.

It makes sense, Arap argues -- fat cells grow and proliferate quickly, as cancer cells do. Like tumors, they build themselves a scaffold of tiny blood vessels called capillaries for sustenance.

Cancer drugs tackle different proteins involved in building blood vessels. Arap's team looked for a protein that might be found only in the blood vessels that feed fat cells.

The one the team found, prohibitin, is active on the surface of fat-feeding blood vessels. The team also found a monoclonal antibody, a synthetic immune system molecule, that finds and attaches to prohibitin alone.

"If even a fraction of what we found in mice relates to human biology, then we are cautiously optimistic that there may be a new way to think about reversing obesity," said Renata Pasqualini, Arap's research partner and wife.

Arap's team did not measure how long their mice lived, and it did not measure lean body mass to see whether the mice lost healthy muscle tissue, too.

Next, the researchers plan to test baboons, which tend to put on weight the way humans do.

Arap said that other research in which fat rodents have lost weight has not translated to humans. Also, prohibitin is found inside cells, which means that accidentally disrupting it there could cause severe side effects.

"I think it will be a while before we know whether this will be duplicated in humans," he said.