Role for Oxytocin in Bone Remodelling

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oxytocinResearch recently published in the journal PNAS describes a new role for the hormone, oxytocin. This nine-residue peptide is best known for its role in female reproduction and in mediating trusting behaviours and emotional experiences, but the new study reports a key role in bone metabolism. Deletion of oxytocin or the oxytocin receptor caused osteoporosis in both male and female mice. The underlying mechanism in osteoporosis is an imbalance between bone formation and bone resorption. Under normal physiological conditions, bone undergoes constant remodelling by osteoclasts which resorb bone, and osteoblasts which deposit new bone. Oxytocin was found to stimulate differentiation of osteoblasts to a mineralising phenotype by up-regulating bone morphogenic protein 2. The effect of oxytocin on osteoclasts was found to be more complex – on the one hand, osteoclast formation was stimulated but, on the other hand, bone resorption by mature osteoclasts was inhibited. The discovery that oxytocin plays a role in regulating bone mass could have implications for the treatment of osteoporosis, a condition that affects one in three women and one in twelve men. Oxytocin itself is not orally bioavailable and is administered either by injection or as a nasal spray but a number of groups are developing orally bioavailable non-peptidic oxytocin agonists.


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