Figure 2. FGF23-FGFR4 signaling does not contribute to hypoferremia following dietary Pi overload.

(A) Serum FGF23 and serum Pi levels. (B, C) Quantitative polymerase chain reaction (qPCR) analysis of Il1b, Il6, and Saa1 expression levels in liver tissue. (D) Scatter plots showing correlations between liver Pi and serum Pi levels. (E) Scatter plots showing correlations between liver Hamp expression and liver Pi levels (a = slopes are significantly different from each other). (F) CBC analysis. (G) Representative gross pathology of Perls’ Prussian blue-stained spleen sections (scale bar, 50 μm). Larger magnification is shown in supplementary figure and legends. All values are mean ± standard error of the mean (SEM; n = 8 mice/group; *p ≤ 0.05 vs. Fgfr4^+/+ + 0.7% Pi diet, ^#p ≤ 0.05 vs. Fgfr4^−/− + 0.7% Pi diet, ^$p ≤ 0.05 vs. Fgfr4^+/+ + 2% Pi diet, ^@p ≤ 0.05 vs. Fgfr4^−/− + 2% Pi diet, ^&p ≤ 0.05 vs. Fgfr4^+/+ + 3% Pi diet) where statistical analyses were calculated by two-way analysis of variance (ANOVA) followed by Tukey’s multiple comparison post hoc test. Dotted lines indicate median Fgfr4^+/+ + 0.7% Pi diet measurements. Scatter plot shadows indicate 95% confidence interval.

Figure 2—figure supplement 1. FGF23-FGFR4 signaling does not contribute to hypoferremia following dietary Pi overload.

(A) Serum calcium analysis from Fgfr4^+/+ and Fgfr4^−/− mice, fed either a 0.7% Pi diet or an escalating Pi diet (2% Pi diet or 3% Pi diet). (B, C) BUN and serum creatinine analysis from Fgfr4^+/+ and Fgfr4^−/− mice, fed either a 0.7% Pi diet or an escalating Pi diet (2% Pi diet or 3% Pi diet). (D) Representative gross pathology of H&E-stained kidney sections (original magnification, ×20; scale bar, 50 μm) from Fgfr4^+/+ and Fgfr4^−/− mice, fed either a 0.7% Pi diet or an escalating Pi diet (2% Pi diet or 3% Pi diet). No pathologic changes were detected in sections stained with H&E, as Fgfr4^+/+ and Fgfr4^−/− mice on a 2% Pi or 3% Pi diet display similar results to Fgfr4^+/+ mice fed a 0.7% Pi diet. (E) Representative gross pathology of Masson’s trichrome-stained kidney sections (original magnification, ×20; scale bar, 50 μm) from Fgfr4^+/+ and Fgfr4^−/− mice, fed either a 0.7% Pi diet or an escalating Pi diet (2% Pi diet or 3% Pi diet). No interstitial fibrosis was detected in sections stained with Masson’s trichrome, as Fgfr4^+/+ and Fgfr4^−/− mice on a 2% Pi or 3% Pi diet display similar results to Fgfr4^+/+ mice fed a 0.7% Pi diet. (F) Representative gross pathology of Perls’ Prussian blue-stained spleen sections (original magnification, ×40; scale bar, 20 μm). All values are mean ± standard error of the mean (SEM; n = 8 mice/group). Dotted lines indicate corresponding median measurements from Fgfr4^+/+ mice on 0.7% Pi diet.

Figure 2—figure supplement 2. Liver injury marker and hematological analyses in Fgfr4^+/+ and Fgfr4^−/− mice fed a graded Pi diet.

(A, B) Quantitative polymerase chain reaction (qPCR) analysis of liver tissue shows expression levels of alanine aminotransferase (Alt1) and aspartate aminotransferase (Ast1) are not significantly elevated in Fgfr4^+/+ and Fgfr4^−/− mice, fed either a 2% Pi diet or 3% Pi diet, when compared to Fgfr4^+/+ mice on a 0.7% Pi diet. (C) Hematocrit percentage (HCT%) and mean corpuscular hematocrit (MCH) analysis in Fgfr4^+/+ and Fgfr4^−/− mice, fed either a 0.7% Pi diet or an escalating Pi diet (2% Pi diet or 3% Pi diet). All values are mean ± standard error of the mean (SEM; n = 8 mice/group; *p ≤ 0.05 vs. Fgfr4^+/+ + 0.7% Pi diet, ^#p ≤ 0.05 vs. Fgfr4^−/− + 0.7% Pi diet, ^#p ≤ 0.05 vs. Fgfr4^+/+ + 2% Pi diet, ^@p ≤ 0.05 vs. Fgfr4^−/− + 2% Pi diet) where statistical analyses were calculated by two-way analysis of variance (ANOVA) followed by Tukey’s multiple comparison post hoc test. Dotted lines indicate corresponding median measurements from Fgfr4^+/+ mice on 0.7% Pi diet.