It is well known that CD38, an enzyme that takes away NAD+, increases with age. The gradual depletion of this core metabolic molecule is, as expected, linked to multiple problems, one of which is a loss in bone-building osteoblasts [1]. Instead, CD38 contributes to the formation of osteoclasts, the cells that wear away bone [2].
Why Bone Destruction Is Accelerated with Aging | Lifespan.io
Maybe both contribute?
I think one is causal. The other perhaps is downstream.