P1396effect of Mixed Versus Animal-Based Low Phosphorus Diets in Dialysis Patients on Intact Fgf23 Levels: A Randomized Clinical Trial

Abstract

Background and Aims The FGF23-lowering effect of different phosphate-sources (vegetable versus animal) in low-phosphorus diets are scarcely known. In this trial, we assess the effect on intact FGF23 (iFGF23) of two low-phosphorus diets, animal versus mixed (vegetable + animal), in dialysis patients. Method A randomized, two-center, open-label, clinical trial was performed. Subjects on stable dialysis for >6 months with P>4.5 mg/dL were randomized into a mixed-based (3 ounces equivalent of animal protein + 3 ounces equivalent of legumes) vs. animal-based (6 ounce equivalent of animal protein) low phosphorus diet with equivalent nutrients (phosphorus <1000 mg/day; protein=1.3 g/kg/day). The primary outcome was the difference in serum iFGF23 change (ELISA) after 12 wks. We excluded patients who modified their dialysis dose, phosphate binder, or vitamin D prescription during trial. Results 556 subjects were screened, only 57 subjects (37 hemodialysis[HD] and 18 peritoneal dialysis[PD]) were randomized. Age, sex, phosphate-binders use, and other baseline characteristics were similar between groups. Baseline iFGF23 levels were 7394 (IQR 2379-16629) and 6859 (1543-17521) ng/mL in mixed-based and animal-based groups respectively (p=0.62). Both groups had a significant decrease in iFGF23 after 12 weeks of intervention (iFGF23 change: -285 [IQR -3002 to 227] ng/mL, p<0.001, and -182 [IQR -9323 to 228] ng/mL, p<0.001); there were not significant differences in iFGF23-decrease between both diets (Figure, p:0.78). Serum phosphorus in the mixed-based and the animal-based declined by -0.66 (95% confidence interval [95% IC], -1.39 to -0.04] mg/dL and -0.21 (95% IC -0.81 to 0.38) respectively (p=0.14). There was a trend between the decrease in observed phosphorus and iFGF23 (rho = 0.265, p=0.058). There were no differences between groups in the change of serum Ca, albumin, PTH, and other biochemical parameters. Conclusion Dietary phosphorus restriction for 12 weeks with animal-based or mixed-based phosphorus sources similarly decreases iFGF23 concentration in HD or PD patients.