San Francisco: US researchers, led by the University of California, San Francisco (UCSF), have discovered a new hormone in female mice that promotes the growth of exceptionally strong and dense bones. This hormone, named the maternal brain hormone (MBH), prevents mothers’ skeletons from weakening despite the significant calcium drain caused by milk production.
The study, which highlights the importance of studying both male and female animals across their lifespans, was led by pharmacologist Holly Ingraham. “It underscores just how important it is to look at both male and female animals across the lifespan to get a full understanding of biology,” Ingraham said.
MBH, a protein called CCN3, is secreted by neurons in the brain’s arcuate nucleus, a region involved in reproduction and puberty. During lactation in mice, MBH production surges as estrogen levels fall, stimulating stem cell activity in bone tissue and boosting bone remodeling and fracture repair.
The discovery is particularly significant for female mice, which lose nearly 30 percent of their bone density while feeding large litters. MBH helps counteract this loss, ensuring both the mother and her pups remain healthy.
When MBH production was artificially inhibited in experiments, mother mice experienced greater bone density loss, and their pups rapidly lost weight. Conversely, introducing extra MBH into young adult and older mice resulted in substantial increases in bone mass and strength.
Thomas Ambrosi, a stem cell biologist from the University of California Davis, remarked, “When we tested these bones, they turned out to be much stronger than usual. We’ve never been able to achieve this kind of mineralization and healing outcome with any other strategy.”
Researchers also found that applying MBH directly to a fractured bone in older mice promoted bone growth at the fracture site. Further research is needed to determine if these results can be replicated in humans, who lose about 10 percent of bone density while breastfeeding.
“It would be incredibly exciting if [MBH] could increase bone mass in all these scenarios,” Ingraham said, noting potential applications for post-menopausal women, breast cancer survivors, elite female athletes, and older men.
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