Scientists May Have Found Way to Boost Metabolism
Thu Jul 11, 5:55 PM ET

By Linda Carroll

NEW YORK (Reuters Health) - An enzyme called SCD-1 may act as a switch to turn metabolism up or down, new study findings suggest.

Researchers found that mice that were missing the enzyme tended to stay thin, even if they overate, according to the report published in Science.

The research may help scientists devise treatments for obesity, study co-author Dr. James M. Ntambi, a professor of biochemistry and nutritional sciences at the University of Wisconsin, Madison, said in an interview with Reuters Health.

The amount of SCD-1 in an animal's body appears to be regulated, at least in part, by the hormone leptin, Ntambe said. When levels of leptin increase, levels of SCD-1 decrease.

Leptin is released by fat cells. And the larger fat cells get, the more leptin they release. Normally, when the brain gets a surge of leptin, it concludes that the body has a safe store of fat and it sends out a message to dampen appetite. The hormone also appears to regulate metabolism, but until now, nobody knew how.

In 1994, when researchers discovered leptin, they thought they might have come up with a cure for obesity. But when scientists tried giving overweight people more leptin to see if it would kill appetite and cause weight loss, the experiments were a dismal failure.

"Most obese people already have high levels of leptin," study co-author Dr. Jeffrey M. Friedman, an investigator with the Howard Hughes Medical Institute at The Rockefeller University in New York City, said in an interview with Reuters Health. "For reasons we don't completely understand, leptin doesn't seem to work well enough for them."

But Friedman and his colleagues suspect that SCD-1 may give obesity researchers a way to skip past leptin and turn up metabolism, allowing people to lose weight.

In the new study, researchers compared mice that were deficient in leptin to mice that were deficient in both leptin and SCD-1. Mice with no or low levels of leptin tend to be obese.

The first thing the scientists noticed was that the SCD-1-deficient mice were thinner than those with normal levels of the enzyme. When they checked to see whether the SCD-1-deficient mice were eating less, there was a surprise. These mice, though thinner than their counterparts, were actually consuming more food.

Apparently, the body needs SCD-1 in order to store fat. Without the enzyme, most fat is burned instead of being stashed away.

There is a catch, however. The enzyme is necessary for maintenance of healthy hair and skin. Mice that were completely deficient in SCD-1 tended to lose their hair, Ntambe said.

So scientists would need to design a therapy that only cut back production of SCD-1, instead of completely knocking it out, he added.

SOURCE: Science 2002;297:240-243.


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