The mouse bone metabolome is sexually dimorphic and is associated with whole bone strength

Abstract

AbstractThe material properties of bone tissue depend on the activity of remodeling bone cells, but the impact of bone cell metabolism on bone tissue is uncertain. To date, the metabolome of bone has not been evaluated for cortical bone, bone marrow, or whole bone including both tissue types. Furthermore, it is of particular interest whether the cortical bone metabolome reflects the sexual dimorphism observed in cortical bone material properties. We hypothesized that the metabolome of cortical bone differs from that of bone marrow, and that the cortical bone metabolome is sexually dimorphic. We first evaluated the metabolic profiles of isolated cortical bone, bone marrow, and whole bone for 20-week female C57Bl/6 mice (n = 10). We then compared metabolic profiles for isolated cortical bone from a separate group of 20-week female and male C57Bl6/mice (n = 10 / sex). Femurs from the same mice were evaluated for flexural material properties. Strength groupings (high strength males, high strength females, low strength males) were utilized to inform comparisons in the isolated humerus cortical bone metabolome. The metabolome of isolated cortical bone, bone marrow, and whole bone are distinct. The isolated cortical bone metabolome is also distinct between males and females. The female mice show evidence of lipid metabolism, whereas male mice show evidence of amino acid metabolism. Finally, 12 metabolic pathways were differentially regulated between bones that differed in strength. High-strength bones from both male and female mice included metabolites associated with tryptophan and purine metabolism. Taken together, these data demonstrate the power of metabolomics to provide insight into the effects of metabolism on bone physiology. These data add to an intricate picture of bone as an organ that is sexually dimorphic both in material and metabolomic profiles.