FGF19 Regulates Cell Proliferation, Glucose and Bile Acid Metabolism via FGFR4-Dependent and Independent Pathways

Fibroblast growth factor 19 (FGF19) is a hormone-like protein that regulates carbohydrate, lipid and bile acid metabolism. At supra-physiological doses, FGF19 also increases hepatocyte proliferation and induces hepatocellular carcinogenesis in mice. Much of FGF19 activity is attributed to the activation of the liver enriched FGF Receptor 4 (FGFR4), although FGF19 can activate other FGFRs in vitro in the presence of the coreceptor βKlotho (KLB). In this report, we investigate the role of FGFR4 in mediating FGF19 activity by using Fgfr4 deficient mice as well as a variant of FGF19 protein (FGF19v) which is specifically impaired in activating FGFR4. Our results demonstrate that FGFR4 activation mediates the induction of hepatocyte proliferation and the suppression of bile acid biosynthesis by FGF19, but is not essential for FGF19 to improve glucose and lipid metabolism in high fat diet fed mice as well as in leptin-deficient ob/ob mice. Thus, FGF19 acts through multiple receptor pathways to elicit pleiotropic effects in regulating nutrient metabolism and cell proliferation

A precise measurement of the Z -boson double-differential transverse momentum and rapidity distributions in the full phase space of the decay leptons with the ATLAS experiment at √s = 8 TeV

This paper presents for the first time a precise measurement of the production properties of the Z boson in the full phase space of the decay leptons. This is in contrast to the many previous precise unfolded measurements performed in the fiducial phase space of the decay leptons. The measurement is obtained from proton–proton collision data collected by the ATLAS experiment in 2012 at s=8 TeV at the LHC and corresponding to an integrated luminosity of 20.2 fb-1. The results, based on a total of 15.3 million Z-boson decays to electron and muon pairs, extend and improve a previous measurement of the full set of angular coefficients describing Z-boson decay. The double-differential cross-section distributions in Z-boson transverse momentum pT and rapidity y are measured in the pole region, defined as 80<mℓℓ<100 GeV, over the range |y|<3.6. The total uncertainty of the normalised cross-section measurements in the peak region of the pT distribution is dominated by statistical uncertainties over the full range and increases as a function of rapidity from 0.5–1.0% for |y|<2.0 to 2-7% at higher rapidities. The results for the rapidity-dependent transverse momentum distributions are compared to state-of-the-art QCD predictions, which combine in the best cases approximate N4LL resummation with N3LO fixed-order perturbative calculations. The differential rapidity distributions integrated over pT are even more precise, with accuracies from 0.2–0.3% for |y|<2.0 to 0.4–0.9% at higher rapidities, and are compared to fixed-order QCD predictions using the most recent parton distribution functions. The agreement between data and predictions is quite good in most cases

Antibody-mediated activation of FGFR1 induces FGF23 production and hypophosphatemia.

The phosphaturic hormone Fibroblast Growth Factor 23 (FGF23) controls phosphate homeostasis by regulating renal expression of sodium-dependent phosphate co-transporters and cytochrome P450 enzymes involved in vitamin D catabolism. Multiple FGF Receptors (FGFRs) can act as receptors for FGF23 when bound by the co-receptor Klotho expressed in the renal tubular epithelium. FGFRs also regulate skeletal FGF23 secretion; ectopic FGFR activation is implicated in genetic conditions associated with FGF23 overproduction and hypophosphatemia. The identity of FGFRs that mediate the activity of FGF23 or that regulate skeletal FGF23 secretion remains ill defined. Here we report that pharmacological activation of FGFR1 with monoclonal anti-FGFR1 antibodies (R1MAb) in adult mice is sufficient to cause an elevation in serum FGF23 and mild hypophosphatemia. In cultured rat calvariae osteoblasts, R1MAb induces FGF23 mRNA expression and FGF23 protein secretion into the culture medium. In a cultured kidney epithelial cell line, R1MAb acts as a functional FGF23 mimetic and activates the FGF23 program. siRNA-mediated Fgfr1 knockdown induced the opposite effects. Taken together, our work reveals the central role of FGFR1 in the regulation of FGF23 production and signal transduction, and has implications in the pathogenesis of FGF23-related hypophosphatemic disorders

mTOR regulates skeletal muscle regeneration in vivo through kinase-dependent and kinase-independent mechanisms

Rapamycin-sensitive signaling is required for skeletal muscle differentiation and remodeling. In cultured myoblasts, the mammalian target of rapamycin (mTOR) has been reported to regulate differentiation at different stages through distinct mechanisms, including one that is independent of mTOR kinase activity. However, the kinase-independent function of mTOR remains controversial, and no in vivo studies have examined those mTOR myogenic mechanisms previously identified in vitro. In this study, we find that rapamycin impairs injury-induced muscle regeneration. To validate the role of mTOR with genetic evidence and to probe the mechanism of mTOR function, we have generated and characterized transgenic mice expressing two mutants of mTOR under the control of human skeletal actin (HSA) promoter: rapamycin-resistant (RR) and RR/kinase-inactive (RR/KI). Our results show that muscle regeneration in rapamycin-administered mice is restored by RR-mTOR expression. In the RR/KI-mTOR mice, nascent myofiber formation during the early phase of regeneration proceeds in the presence of rapamycin, but growth of the regenerating myofibers is blocked by rapamycin. Igf2 mRNA levels increase drastically during early regeneration, which is sensitive to rapamycin in wild-type muscles but partially resistant to rapamycin in both RR- and RR/KI-mTOR muscles, consistent with mTOR regulation of Igf2 expression in a kinase-independent manner. Furthermore, systemic ablation of S6K1, a target of mTOR kinase, results in impaired muscle growth but normal nascent myofiber formation during regeneration. Therefore, mTOR regulates muscle regeneration through kinase-independent and kinase-dependent mechanisms at the stages of nascent myofiber formation and myofiber growth, respectively

R1MAb2 induces FGF23 production.

<p>(<b>A and B</b>) Serum FGF23 (A) and PTH (B) levels in male C57BL/6 mice intraperioneally injected with R1MAb2 or isotype control (Control IgG) at 1 mg/kg. The same animals described in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0057322#pone-0057322-g001" target="_blank">Figure 1C</a> and <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0057322#pone-0057322-g002" target="_blank">Figure 2</a> were analyzed at 48 hour post injection. N = 8 mice/group. (<b>C</b>) Serum FGF23 levels in female <i>db/db</i> mice intraperioneally injected with R1MAb1 or isotype control (Control IgG) at 2 mg/kg. The samples were collected at 7 days post injection. N = 6 mice/group. (<b>D and E</b>) Serum FGF23 levels (D) and phosphate levels (E) in male C57BL/6 mice intraperioneally injected with an indicated antibody at 1 mg/kg. The samples were collected at 3 days post injection. N = 8 mice/group. (<b>F</b>) FGF23 levels in culture medium after treatment of differentiate rat osteoblast with vitamin D (100 nM), R1MAb1, or isotype control IgG (26.7 nM). The cells were incubated for 48 hours in the presence of the indicated ligand. N = 6 samples/treatment. (A–F) * p<0.05, **G) Differentiated rat osteoblasts were treated with R1MAb2, or isotype control IgG (26.7 nM), for 1 hour and subjected to Western blot analysis to examine phosphorylation of MAPK pathway proteins, CREB and STAT3.</p

R1MAb2 activates the FGF23 pathway in kidney epithelial cells.

<p>(<b>A</b>) OK cells were treated with vehicle (Mock), R1MAb2 (0.5, 5, or 50 nM), or isotype control IgG (50 nM) for 24 hours, and the mRNA expression of indicated genes were determined by qPCR. The expression of each gene was normalized by the expression of <i>actin</i> in the same sample and shown as relative expression. N = 3. (<b>B</b>) Similar gene expression analysis in OK cells after treatment with an indicated antibody at 50 nM. N = 6. (<b>C</b>) mRNA expression in OK cells treated with scrambled or FGFR1 siRNA oligos, determined by qPCR. N = 6. (<b>D</b>) <i>Cyp24a1</i> gene expression in OK cells after treatment with siRNA oligos and an indicated ligand. N = 6. The data represents means ± SEM. * p<0.05 or *** p<0.001 compared with the control group.</p

A model for the mechanism of perturbation of phosphate homeostasis by anti-FGFR1 agonists.

<p>See text for explanations.</p

Bone effects of R1MAb2 treatment.

<p>(<b>A</b>) Blood glucose levels of female <i>db/db</i> mice (N = 8 mice/group) during the study. The mice received intraperitoneal injection of R1MAb1 or control IgG at 3 mg/kg doses on day 0 and day 42 (Arrow). Statistical significance in glucose reduction (p<0.05) was observed between day 3–31 and day 43–49. (<b>B</b>) Serum FGF23 levels of mice in (A) on day 49. p<0.01, N = 7–8 mice/group. (*# p<0.05, versus Control IgG (*) or versus Control IgG, PF (#)) (<b>C</b>) Bone phenotype of mice described in (A–B). The bones were dissected on day 49, and subjected to μCT analysis. Statistical significance (p<0.05) was observed only for total volume, but not other parameters shown. # p<0.05 (versus Control IgG, PF).</p

Gene expression in differentiated osteoblasts.

<p>(<b>A</b>) mRNA was isolated from differentiated osteoblasts treated with the indicated ligands (vitamin D (100 nM), R1MAb2, or isotype control IgG (26.7 nM)) for 48 hours, and subjected to qPCR analysis. Data represent means ± SEM (N = 3). *P<0.05, **P<0.01, versus mock (for vitamin D) or versus control IgG (for R1MAb2). (<b>B</b>) Schematic summary of the data presented in (A). Vitamin D and R1MAb2 induce overlapping, but distinct sets of target genes.</p