Fig 2: Expression of endocrine FGFs and FLRT2 in plasma. a Comparison of FGF15, FGF21, FGF23 and FLRT2 expression levels in response to fasting in male mice plasma. b Comparison of FGF15, FGF21, FGF23 and FLRT2 expression levels in response to fasting in female mice plasma. c Comparison of FGF15, FGF21, FGF23 and FLRT2 expression levels in female and male mice plasma. Data represent means ± S.E.M, n = 6; biological replicates. *P < 0.05, **P < 0.01 and ***P < 0.001 by one-way ANOVA with unpaired two-tailed Student’s t test

Fig 3: Development and validation of an AAV approach for systemic delivery of Klotho.(A) Changes in circulating Klotho levels measured via ELISA in young (3–6 months), middle-aged (10-14 months), old (21-24 months), and oldest-old (27-29 months) male (N = 41), and female (N = 47) mice (one-way ANOVAs). (B) Changes in circulating FGF23 levels in male (N = 20) and female (N = 39) mice. Red symbols represent undetectable levels and were set to zero (Kruskal-Wallis tests, KO values were excluded from statistical analysis). (C) Schematic of the AAV-Klotho plasmid design. (D) Liver expression of AAV vector genomes quantified via qPCR (N = 33, Kruskal-Wallis test). (E) Circulating Klotho levels measured via MSD-ELISA in young female (N = 33) mice injected with AAV-Klotho at varying doses (Kruskal-Wallis test). (F) Gene count normalized to library size for Klotho in the gastrocnemius muscle of female mice treated with GFP and AAV-Kl (N = 20, one-way ANOVA). (G,H,I) Serum concentration levels for insulin (N = 29), cholesterol (N = 35), and glucose (N = 20) in GFP- and Kl-treated female mice (one-way ANOVA). All data presented as mean ± SD (*p<0.05, **p<0.01, ***p<0.001, ****p<0.0001).Figure 4—source data 1.Raw Data for Figure 4A-B, D-I, and Figure 4—figure supplement 1.

Fig 4: Pemigatinib suppresses liver fibrosis induced by CCl4 in vivo. (A, B) Images of Masson trichrome-stained liver and quantification of the results in pemigatinib (0.3 mg/kg/d) treated liver fibrosis model mice induce by CCl4 (8 wk, N=4–6). Scale bar=100 μm. (C) Hydroxyproline assay results (N=8–10). (D, E) Blood test results indicating liver function (N=4–6). (F) Images of Masson trichrome-stained liver samples in pemigatinib-treated liver fibrosis model mice induced by BDL (2 wk). (G) Hydroxyproline assay results (N=6-8). (H) mRNA expression levels of COL4A2, COL8A2 and ADAM28, which are matrisome-related genes, in FGF23-treated LX-2 cells (1 ng/mL, 72 h; N=6). * p<0.05, ** p<0.01, *** p<0.001, **** p<0.0001. The data are plotted as individual points, and the bars represent means. Abbreviations: BDL, bile duct ligation; CCl4, carbon tetrachloride.

Fig 5: Serum FGF23 level is upregulated in the mouse model of liver fibrosis. (A) Images of H&E-and Masson trichrome-stained liver samples (scale bar=100 μm). (B) Hydroxyproline assay results in the CCl4-induced liver fibrosis model mice (2–8 wk, N=3–5). (C) Serum FGF23 levels in the CCl4-induced liver fibrosis model mice (N=3–5). (D) Correlations between hydroxyproline and serum FGF23 levels are obtained in B and C. (E) Hydroxyproline assay results in BDL-induced liver fibrosis model mice (0.5–2 wk, N=3–4). (F) Serum FGF23 levels in the BDL-induced liver fibrosis model mice (N=3–4). (G) Correlation between hydroxyproline and serum FGF23 levels obtained in E and F. (H) mRNA expression of Fgf23 in various tissues of CCl4-induced and BDL-induced liver fibrosis model mice (N=3). * p<0.05, ** p<0.01, **** p<0.0001. The data are plotted as individual points, and the bars represent the means. Abbreviations: BDL, bile duct ligation; CCl4, carbon tetrachloride; H&E, hematoxylin and eosin.