Low-density lipoprotein receptor-5 contributes to whole body metabolism by regulating fatty acid metabolism in the osteoblast

Wnt signaling is critical for normal skeletal development as well as whole-body metabolic function. In this study, we described a previously unrecognized function for Wnt-Lrp5 signaling in the osteoblast that allows bone to acquire the resources necessary to fuel bone formation. Mice lacking the Lrp5 co-receptor specifically in osteoblasts and osteocytes exhibit the expected reductions in postnatal bone mass and also develop peripheral adiposity with corresponding reductions in energy expenditure. Conversely, mice expressing a high-bone mass mutant Lrp5 allele are leaner with reduced plasma triglyceride and free fatty acid levels. In this context, Wnt-initiated signals downstream of Lrp5, but not Lrp6, regulate the expression of key enzymes required for fatty acid β-oxidation. These results suggest that Wnt-Lrp5 signaling regulates basic cellular activities beyond those associated with fate-specification and differentiation in bone and that the skeleton influences global energy homeostasis via mechanisms independent of osteocalcin and glucose metabolism Total RNA isolated from cultures of Lrp5-deficient osteoblasts differentiated for 7 days in vitro compared to control osteoblasts