Hiroki Yokota¹, João F. Raposo², Andy Chen³, Chang Jiang¹ and Hugo G. Ferreira⁴

¹Department of Biomedical Engineering, Indiana University Purdue University Indianapolis, Indianapolis, IN 46202, USA. ²Endocrinology Department of the Portuguese Cancer Institute, 1099-023 Lisboa, Portugal. ³Department of Bioengineering, University of California San Diego, La Jolla, CA 92092, USA. ⁴REQUIMTE, Department of Chemistry, New University of Lisbon, 2829-516 Caparica, Portugal.

Abstract

Fibroblast growth factor 23 (FGF23) has recently been identified as a critical regulatory factor in phosphate (P) metabolism. Although the exact molecular mechanism of FGF23 synthesis through sensing the concentration of P is yet to be determined, experimental and clinical data indicate the influential role of FGF23 in P and calcium (Ca) homeostasis. Here, we extended our previous mathematical model in calcium regulation and examined the conceivable roles of FGF23 in mineral metabolism. We assumed that the level of FGF23 was controlled through the concentrations of P and calcitriol in serum, and its actions such as lowering of the renal threshold for P, inhibition of the production of calcitriol in the kidney tubule, and inhibition of the production of parathyroid hormone (PTH) were included. Comparisons between the models with and without FGF23 demonstrate a complex interplay of FGF23 with calcitriol and PTH. In consistent with the model, our in vitro experimentation indicates that expression of FGF23 is activated in the presence of P though a G-protein linked receptor. We expect that further efforts on modeling and experimental evaluation would contribute to diagnosing patients with metabolic diseases such as osteoporosis and chronic kidney diseases, and developing FGF23-linked treatment strategies.