Later, tissue of all of the rats was examined for fat content. Unger said the normal rats lost fat, but only about half the amount shed by the leptin rodents. Also, the normal rats retained fat in their muscle cells. The study suggested that leptin may be useful in the control of Type II diabetes, the form of the disease that often develops in older, overweight people. The rat study showed that by burning fat in the cells, the excess leptin also lowered blood sugar and made the cells more sensitive to insulin, the hormone that controls sugar levels, Unger said.
Diabetes develops when the body stops making or becomes insensitive to insulin.
Unger cautioned, however, that the rat study may not apply to humans. An artificial form of leptin is now being tested as a weight-control drug in humans, but the results are still unknown, he said.