title: Chronic Hyperphosphatemia and Vascular Calcification Are Reduced by Stable Delivery of Soluble Klotho.
abstract: αKlotho (αKL) regulates mineral metabolism, and diseases associated withαKL deficiency are characterized by hyperphosphatemia and vascular calcification (VC).αKL is expressed as a membrane-bound protein (mKL) and recognized as the coreceptor for fibroblast growth factor-23 (FGF23) and a circulating soluble form (cKL) created by endoproteolytic cleavage of mKL. The functions of cKL with regard to phosphate metabolism are unclear. We tested the ability of cKL to regulate pathways and phenotypes associated with hyperphosphatemia in a mouse model of CKD-mineral bone disorder and αKL-null mice. Stable delivery of adeno-associated virus (AAV) expressing cKL to diabetic endothelial nitric oxide synthase-deficient mice or αKL-null mice reduced serum phosphate levels. Acute injection of recombinant cKL downregulated the renal sodium-phosphate cotransporter Npt2a in αKL-null mice supporting direct actions of cKL in the absence of mKL. αKL-null mice with sustained AAV-cKL expression had a 74%-78% reduction in aorta mineral content and a 72%-77% reduction in mineral volume compared with control-treated counterparts (P<0.01). Treatment of UMR-106 osteoblastic cells with cKL + FGF23 increased the phosphorylation of extracellular signal-regulated kinase 1/2 and induced Fgf23 expression. CRISPR/Cas9-mediated deletion of fibroblast growth factor receptor 1 (FGFR1) or pretreatment with inhibitors of mitogen-activated kinase kinase 1 or FGFR ablated these responses. In summary, sustained cKL treatment reduced hyperphosphatemia in a mouse model of CKD-mineral bone disorder, and it reduced hyperphosphatemia and prevented VC in mice without endogenousαKL. Furthermore, cKL stimulated Fgf23 in an FGFR1-dependent manner in bone cells. Collectively, these findings indicate that cKL has mKL-independent activity and suggest the potential for enhancing cKL activity in diseases of hyperphosphatemia with associated VC.
authors.affiliation: Department of Medical and Molecular Genetics, Division of Molecular Genetics and Gene Therapy, Indiana University School of Medicine, Indianapolis, Indiana.
authors.forename: Julia M
authors.initials: JM
authors.lastname: Hum
authors.affiliation: Biotechnology Discovery Research, Lilly Research Laboratories.
authors.forename: Linda M
authors.initials: LM
authors.lastname: O'Bryan
authors.affiliation: Lead Optimization Toxicology and Pharmacology, Covance Inc., Greenfield, Indiana.
authors.forename: Arun K
authors.initials: AK
authors.lastname: Tatiparthi
authors.affiliation: Department of Medical and Molecular Genetics, Division of Molecular Genetics and Gene Therapy, Indiana University School of Medicine, Indianapolis, Indiana.
authors.forename: Taryn A
authors.initials: TA
authors.lastname: Cass
authors.affiliation: Department of Medical and Molecular Genetics, Division of Molecular Genetics and Gene Therapy, Indiana University School of Medicine, Indianapolis, Indiana.
authors.forename: Erica L
authors.initials: EL
authors.lastname: Clinkenbeard
authors.affiliation: Biotechnology Discovery Research, Lilly Research Laboratories.
authors.forename: Martin S
authors.initials: MS
authors.lastname: Cramer
authors.affiliation: Investigational Pathology, and.
authors.forename: Manoj
authors.initials: M
authors.lastname: Bhaskaran
authors.affiliation: Investigational Pathology, and.
authors.forename: Robert L
authors.initials: RL
authors.lastname: Johnson
authors.affiliation: Tailored Therapeutics, Eli Lilly and Company, Indianapolis, Indiana; and.
authors.forename: Jonathan M
authors.initials: JM
authors.lastname: Wilson
authors.affiliation: Biotechnology Discovery Research, Lilly Research Laboratories, smith_rosamund_c@lilly.com kenewhit@iupui.edu.
authors.forename: Rosamund C
authors.initials: RC
authors.lastname: Smith
authors.affiliation: Department of Medical and Molecular Genetics, Division of Molecular Genetics and Gene Therapy, Indiana University School of Medicine, Indianapolis, Indiana; smith_rosamund_c@lilly.com kenewhit@iupui.edu.
authors.forename: Kenneth E
authors.initials: KE
authors.lastname: White
mesh_terms: D000818:Animals; D001842:Bone and Bones / Q000378:metabolism; D002908:Chronic Disease; D003928:Diabetic Nephropathies / Q000150:complications; D004195:Disease Models, Animal; D005260:Female; D000089703:Fibroblast Growth Factor-23; D005966:Glucuronidase / Q000008:administration & dosage / Q000502:physiology / Q000627:therapeutic use*; D054559:Hyperphosphatemia / Q000188:drug therapy* / Q000209:etiology; D000090265:Klotho Proteins; D008297:Male; D051379:Mice; D018345:Mice, Knockout; D061205:Vascular Calcification / Q000188:drug therapy*
chemical_list: C000717428:Fgf23 protein, mouse; D000089703:Fibroblast Growth Factor-23; D005966:Glucuronidase; D000090265:Klotho Proteins
keywords: FGF23; alpha-klotho; bone; db/db-eNOS; hyperphosphatemia; osteocyte