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Scientists Confirm Leptin Link to Sexual Maturity in Swine

By Jill Lee
January 7, 1999

Leptin, a protein long associated with obesity and its control, has also been linked to sexual maturity in female mammals. Now scientists with the Agricultural Research Service and the University of Georgia have even stronger evidence that leptin helps cue reproduction in swine. ARS is the chief scientific wing of the U.S. Department of Agriculture.

ARS and university researchers in Athens, Ga., found estrogen triggers leptin production by fat cells when pigs reach reproductive age. The study also suggests leptin stimulated the brain and pituitary gland to produce two hormones that allow pigs to ovulate.

The scientists studied female pigs at 90, 150 and 210 days of age. Only the pigs at 210 days of age--the ones on the verge of reproductive age--demonstrated the estrogen effect. Estrogen in those pigs caused a two-and-a-half fold increase in messenger RNA for leptin.

So what do these results mean? Leptin is secreted by fat cells. In obesity research, scientists think leptin is the body cue that enough food has been eaten. In reproduction, leptin may send the brain a message that there is enough energy--in the form of fat--to start reproduction.

It may be that estrogen is a first cue of sexual maturity and triggers leptin increases, which in turn tell the brain and the pituitary gland to release those key reproductive hormones.

If further research confirms these scenarios, it might be possible to speed sexual maturity in pigs. Sows that have more piglets in their lifetime give pork producers more profit.

Researchers caution, however, that these biological chemicals are part of a natural balance. They found a threshold where increased leptin no longer speeds sexual maturity. And it may be that diet alone could turn on leptin’s benefits sooner for farmers.

Scientific contact: C. Richard Barb, ARS Animal Physiology Research Unit, Russell Research Center, Athens, Ga., phone (706) 546-3226, fax: (706) 546-3586,