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bioRxiv · 10.1101/2025.07.11.664289

Estrogens protect bone mass by inhibiting NAD+ metabolism in osteoclasts

Kim, H.-N.·Marques-Carvalho, A.·Adam, G. O.·Chalke, A.·Resende-Coelho, A.·Reyes-Castro, O.·Warren, A.·Grilo, L.·Chini, C. N.·Stronach, B.·Alturkmani, F.·Ambrogini, E.·Chini, E. N.·Almeida, M.
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Abstract

Estrogens protect against bone loss by reducing osteoclast number and bone resorption, primarily via direct actions on osteoclast precursors. In these cells, estrogens attenuate RANKL-induced stimulation of mitochondrial complex I, which is crucial for ATP generation through NADH oxidation. NAD+ promotes redox reactions and activates NAD+-dependent enzymes, including the mitochondrial deacetylase SIRT3. However, the contribution of NAD+ to the skeletal effects of estrogens remains unknown. We show that NAD+ levels and SIRT3 activity are upregulated by RANKL and inhibited by 17{beta}-estradiol (E2) in mouse and human osteoclast precursors. Increasing NAD+ or the mitochondrial NAD+/NADH ratio reverses the inhibitory effects of E2 on SIRT3 activity and osteoclastogenesis in vitro. Deletion of Nampt, a key NAD salvage enzyme, reduces NAD+ and prevents bone loss in ovariectomized mice. Similarly, deletion of Sirt3 in osteoclast precursors mitigates estrogen deficiency-induced bone resorption. These findings indicate that suppression of NAD+ levels and mitochondrial redox metabolism by estrogens contributes to their anti-resorptive effects via inhibition of SIRT3.

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Kim, H.-N., Marques-Carvalho, A., Adam, G. O., Chalke, A., Resende-Coelho, A., Reyes-Castro, O., Warren, A., Grilo, L., Chini, C. N., Stronach, B., Alturkmani, F., Ambrogini, E., Chini, E. N., Almeida, M.. 2025-07-16. Estrogens protect bone mass by inhibiting NAD+ metabolism in osteoclasts. https://doi.org/10.1101/2025.07.11.664289

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