Effects of calcium sources and soluble silicate on bone metabolism and the related gene expression in mice

Abstract

Objective The effects of five calcium (Ca) sources were compared for bone biochemical and mechanical properties and the related gene expression using mice, from the viewpoint of their soluble silicon (Si) content. Methods Weanling male mice were fed diets containing 1% Ca supplemented with CaCO 3 as the control (CT), coral sand (CS), fossil stony coral (FSC), fish bone (FC) and eggshell (EC) powders, and 50 ppm of Si in the CT diet for 6 mo. The mRNA expressions related to bone remodeling were quantified by real-time polymerase chain reaction. Results Soluble Si content was 9.83, 7.17, 2.48, 0.29, and 0.20 ppm for the CS, FC, FSC, EC, and Ca-deficient basal diets, respectively. Si, CS, and FSC, in order, significantly increased dry and ash weights, Ca and hydroxyproline contents, and alkaline phosphatase and decreased tartrate-resistant acid phosphatase and urinary excretion of hydroxyproline compared with the CT group. Si significantly increased and FC decreased femoral strength and stiffness. In the mRNA expression related to osteoblastogenesis, Si and CS significantly increased runt-related transcription factor 2. Si, CS, and FSC, in order, significantly decreased and FC and EC increased peroxisome proliferator-activated receptor-γ. In the mRNA expression related to osteoclastogenesis, Si and CS significantly increased and FC and EC decreased the osteoprotegerin/receptor activator of nuclear factor-κB ligand ratio, whereas Si and CS decreased transforming growth factor-β. Conclusion The results indicated that soluble silicate and CS, with the highest Si content among Ca sources, improved bone biochemical and mechanical properties through stimulation of gene expression related to osteoblastogenesis and suppression of that related to osteoclastogenesis.