Possible solution to long-standing breastfeeding mystery discovered

A newly discovered hormone discovered in mice may solve a long-standing mystery about how adult bones stay strong under the stress of breastfeeding, a discovery that could lead to new treatments for osteoporosis, a disease that causes bones to become weak and brittle.

For decades, it was unclear how bones maintain their strength during breastfeeding. Breastfeeding removes calcium from bones to produce nutritious breast milk. Breastfeeding also reduces levels of estrogen, a hormone essential for bone health. Temporary loss of bone mass This will resolve within 6-12 months after breastfeeding ends.

While conducting research unrelated to this conundrum, Holly Ingraham Researchers at the University of California, San Francisco have found that targeting receptors in the hypothalamus of the brain to inhibit estrogen production actually strengthens the bones of female mice.

“It's a bit of a paradox that we're eliminating estrogen signaling, which is thought to be beneficial for bone, and then creating women with extremely dense bones,” Ingraham said.

To find out why, they bred female mice that lacked estrogen receptors and had unusually strong bones, then surgically mated these animals with other female mice that had the receptors, linking their circulatory systems.

After 17 weeks, the mice that had been attached to the strong-bone mice had an average 152 percent increase in bone mass, suggesting that a bone-strengthening substance was circulating in the blood and being transferred from the mice that didn't have the receptor to the ones that did. Subsequent experiments revealed that this substance was a brain hormone called CCN3.

The researchers then measured CCN3 in the brains of female mice before and after pregnancy and found that it is only produced during lactation. Moreover, blocking the hormone caused bone loss in lactating mice, suggesting that it may be the mysterious molecule that prevents bone loss during lactation. This finding suggests that CCN3 may be used to repair bone in other situations as well.

To explore this further, the researchers placed patches containing CCN3 on four male mice that had suffered fractures. An equal number of animals received patches that did not contain the hormone. All rodents were 2 years old. 69 years in humans.

After three weeks, mice with the CCN3 patch had an average of 240% more bone mass than mice without the patch, suggesting that CCN3 may be useful in treating or preventing osteoporosis, which affects more than one million people. 12 percent Among U.S. adults age 50 and older.

But it's unclear whether these findings apply to humans, Ingraham said. She and her colleagues are developing a blood test for CCN3 that will allow them to test whether levels of the hormone increase in breastfeeding women.