Positive association between serum silicon levels and bone mineral density in female rats following oral silicon supplementation with monomethylsilanetriol

Observational (epidemiological) studies suggest the positive association between dietary silicon intake and bone mineral density may bemediated by circulating estradiol level. Here, we report the results of a silicon supplementation study in rats that strongly support these observations and suggest an interaction between silicon and estradiol. Introduction Epidemiological studies report strong positive associations between dietary silicon (Si) intake and bone mineral density (BMD) in premenopausal women and indicate that the association may be mediated by estradiol. We have tested this possibility in a mixed-gender rodent intervention study. Methods Tissue samples were obtained from three groups of 20-week-old Sprague Dawley rats (five males and five females per group) that had been supplemented ad libitum for 90 days in their drinking water with (i) <0.1 mg SiL (vehicle control), (ii) 115 mg SiL (moderate dose) or (iii) 575 mg SiL (high dose). All rats received conventional laboratory feed, whilst supplemental Si was in the form of monomethylsilanetriol, increasing dietary Si intakes by 18 and 99 %, for the moderate-and high-dose groups, respectively. Results Fasting serum and tissue Si concentrations were increased with Si supplementation (p<0.05), regardless of gender. However, only for female rats was there (i) a trend for a dose-responsive increase in serum osteocalcin concentration with Si intervention and (ii) strong significant associations between serum Si concentrations and measures of bone quality (p<0.01). Correlations were weaker or insignificant for tibia Si levels and absent for other serum or tibia elemental concentrations and bone quality measures. Conclusions Our findings support the epidemiological observations that dietary Si positively impacts BMD in younger females, and this may be due to a Si-estradiol interaction. Moreover, these data suggest that the Si effect is mediated systemically, rather than through its incorporation into bone.