Weight-Loss Protein Linked to Diabetes
A natural protein that some hoped would be a “magic bullet” for weight control may have a dark and dangerous side: New research links it to diabetes.
The protein, called leptin, received a flurry of publicity last year when studies showed that it caused extremely obese mice to lose up to 30% of their weight. The mice also exercised more and ate less. Some researchers raced to develop leptin or related proteins for use in humans.
But now a lab in Israel has found that leptin may play a role in the development of Type II diabetes, a serious disorder that frequently strikes obese adults.
Menachem Rubinstein, a biochemist at the Weizmann Institute of Science in Rehovot, Israel, said that when leptin is put on human liver cells in the laboratory, it disrupts a normal action of insulin, the hormone essential for control of sugar in the blood.
“We know that obese individuals have a high level of leptin and we know that obese individuals have a tendency to develop diabetes,” Rubinstein said in an interview. “There might be a linkage. It might be that leptin is one of the agents that induces Type II diabetes.”
“One should look very carefully into using leptin as a weight-reducing agent,” said Rubinstein. “It should be ruled out that a long-term treatment with leptin doesn’t induce Type II diabetes.”
Rubinstein emphasized that his experiment involved only cell cultures and that leptin could react differently in the whole body.
“The experiment would have to be repeated in whole animals because there are many systems that can counteract or compensate events that occur in individual cells,” he said.
Arthur Campfield, a researcher at Hoffmann-La Roche Inc. in Nutley, N.J., also called for more study.
“It is a big jump to conclude from this study that leptin is a cause of diabetes,” he said.
Amgen Inc. of Thousand Oaks, Calif., started human clinical trials with leptin in May to determine if the protein causes any toxic side effects.
The firm plans clinical studies next year to determine if leptin actually will control weight.
David Kaye, a spokesman for Amgen, said that so far researchers for the company have detected no harmful side effects from leptin.
