Fibroblast growth factor-23 (FGF23) is a critical factor in
chronic kidney disease (CKD), with elevated levels causing alterations in
mineral metabolism and increased odds for mortality. Patients with CKD develop
anemia as the kidneys progressively lose the ability to produce
erythropoietin (EPO).
Anemia is a potent driver of FGF23 secretion; therefore, a
hypoxia-inducible factor
prolyl hydroxylase inhibitor (HIF-PHI) currently in clinical trials to elevate endogenous EPO to resolve
anemia was tested for effects on
iron utilization and FGF23-related parameters in a CKD mouse model. Mice were fed either a
casein control diet or an
adenine-containing diet to induce CKD. The CKD mice had markedly elevated iFGF23 and blood
urea nitrogen (BUN),
hyperphosphatemia, and
anemia. Cohorts of mice were then treated with a patient-equivalent dose of
BAY 85-3934 (BAY;
Molidustat), which elevated EPO and completely resolved aberrant complete blood counts (CBCs) in the CKD mice. iFGF23 was elevated in vehicle-treated CKD mice (120-fold), whereas circulating iFGF23 was significantly attenuated (>60%) in the BAY-treated CKD mice. The BAY-treated mice with CKD also had reduced BUN, but there was no effect on renal
vitamin D metabolic
enzyme expression. Consistent with increased EPO, bone marrow Erfe,
Transferrin receptor (Tfrc), and EpoR mRNAs were increased in BAY-treated CKD mice, and in vitro hypoxic marrow cultures increased FGF23 with direct EPO treatment. Liver
Bmp-6 and
hepcidin expression were downregulated in all BAY-treated groups. Femur trabecular parameters and cortical porosity were not worsened with BAY administration. In vitro, differentiated osteocyte-like cells exposed to an
iron chelator to simulate
iron depletion/
hypoxia increased FGF23; repletion with holo-
transferrin completely suppressed FGF23 and normalized Tfrc1. Collectively, these results support that resolving
anemia using a HIF-PHI during CKD was associated with lower BUN and reduced FGF23, potentially through direct restoration of
iron utilization, thus providing modifiable outcomes beyond improving
anemia for this patient population. © 2021 American Society for Bone and
Mineral Research (ASBMR).