Osteoprotegerin affects the responsiveness of fibroblast growth factor-23 to high oral phosphate intake

Both fibroblast growth factor-23 (FGF-23) and osteoprotegerin (OPG) are associated with phosphate metabolism, and are produced by bone tissue.

In order to clarify the influence of bone turnover on phosphate metabolism, we examined the response of FGF-23 to an oral phosphate load in 4 groups of mice (2 OPG knockout (KO) and 2 wild-type (WT) groups) given either a high-phosphate diet or a normal diet by performing serum and urinary biochemical assays.

Although there was no significant difference in serum phosphate/ calcium levels between the groups, the decrease in tubular reabsorption rate of phosphate (%TRP) by oral phosphate load was smaller in the OPG KO mice than in the WT mice. FGF-23 level was significantly increased by a high-phosphate diet in WT mice, but not in OPG KO mice. However, there was no significant difference of intact PTH and calcitriol levels between the OPG KO and WT mice.

Therefore, OPG may play a key role in mediating the response of FGF-23 to an oral phosphate load in bone cells.