The effect of feeding a renal diet on plasma fibroblast growth factor 23 concentrations in cats with stable azotemic chronic kidney disease.

Abstract

BACKGROUND: Fibroblast growth factor 23 (FGF-23) is a phosphatonin, which is increased in cats with azotemic CKD. Dietary phosphate restriction decreases FGF-23 concentrations in humans and rodents, but this relationship has not previously been examined in the cat. OBJECTIVES: To investigate the effect of feeding renal diet on plasma FGF-23 concentrations in cats with stable azotemic CKD. ANIMALS: Azotemic, client-owned cats (≥ 9 years); 33 cats ate renal diet (RD group) and 11 cats did not eat renal diet (comparator group) over 28-56 days. METHODS: Retrospective longitudinal study: Plasma FGF-23, PTH, and phosphate concentrations were measured at baseline and after 28-56 days. Cats in the RD group were classified as hyperphosphatemic (HP) or normophosphatemic (NP) based on the International Renal Interest Society targets for plasma phosphate concentration. Nonparametric tests were performed. RESULTS: In the HP group (n = 15), feeding renal diet was associated with a significant decrease in plasma phosphate (P = .001), PTH (P = .007), and FGF-23 (P = .008), but not creatinine concentrations (P = .91). In the NP group (n = 18), feeding renal diet was associated with a significant decrease in plasma FGF-23 (P = .006), but not phosphate (P = .48), PTH (P = .35), or creatinine concentrations (P = .10). No significant changes were seen in any parameters in the comparator group during the study period. CONCLUSIONS AND CLINICAL IMPORTANCE: Feeding renal diet is associated with reductions in plasma FGF-23 concentrations in hyper- and normophosphatemic cats with stable azotemic CKD, suggesting that dietary phosphate restriction may enable cats with CKD to maintain normal plasma phosphate concentrations in association with lower plasma FGF-23 concentrations.