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Experimental Leptin Therapy May Eventually Aid in Weight Loss

Feb. 9, 2004 -- Increasing levels of a hormone that regulates body weight may help convert fat-storing cells into fat-burning ones, according to a new animal study.

Researchers say if the same principle holds true in humans, the findings may offer a "quick and safe solution" to obesity and aid in weight loss efforts.

The study, published in the Feb. 17 issue of the Proceedings of the National Academy of Sciences, found that increasing the levels of the hormone known as leptin in rats led to significant weight loss in the animals.

Researchers say leptin therapy caused weight loss by triggering a change in the structure and function of the rat's fat cells, from fat-storing to fat-burning. This occurred by increasing the action of mitochondria within the cells. Mitochondria are the main source of energy in cells.

Leptin Changes Fat Cells

"This is the first careful examination of the fat cells after leptin therapy," says researcher Roger Unger, MD, director of the Touchstone Center for Diabetes Research at the University of Texas Southwestern Medical Center at Dallas, in a news release.

"The structure of the cells changes from the normal appearance of a fat cell to a very novel cell that's really never been seen before," says Unger. "The ability to convert fat cells into fat-burning cells may suggest novel therapeutic strategies for obesity."

In the study, researchers looked at the effects of injecting rats with the leptin gene. Two to four days after receiving the injection, researchers found leptin levels rose to 50 times higher than those found normally in rats and then tapered off.

Compared with normal rats fed a restricted diet, the study showed that animals that got the leptin injection experienced much greater weight loss and lost an average of about 26% of their total body weight 14 days after leptin therapy began.

Researchers say the rats receiving leptin therapy were healthy and active but had a decreased appetite. But the normal rats fed a restricted diet were constantly searching for food and had lower levels of physical activity.

When the researchers examined the rats' cells under the microscope, they found that rather than storing fat, the cells were full of fat-burning mitochondria.

Researchers say the next step is to learn how to break down the body's natural defense system against leptin produced in the fat cells of humans, which is designed to prevent a wasteful loss of the body's fat stores.

"Such an effect would make obesity impossible and might lead to a quick and safe solution to the obesity problem," write the researchers.

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