title: Detection of FGF15 in plasma by stable isotope standards and capture by anti-peptide antibodies and targeted mass spectrometry.
abstract: Fibroblast growth factor 15 (FGF15) has been proposed as a postprandial hormone that signals from intestine to liver to regulate bile acid and carbohydrate homeostasis. However, detecting FGF15 in blood using conventional techniques has proven difficult. Here, we describe a stable isotope standards and capture by anti-peptide antibodies (SISCAPA) assay that combines immuno-enrichment with selected reaction monitoring (SRM) mass spectrometry to overcome this issue. Using this assay, we show that FGF15 circulates in plasma in an FXR and circadian rhythm-dependent manner at concentrations that activate its receptor. Consistent with the proposed endocrine role for FGF15 in liver, mice lacking hepatocyte expression of the obligate FGF15 co-receptor, β-Klotho, have increased bile acid synthesis and reduced glycogen storage despite having supraphysiological plasma FGF15 concentrations. Collectively, these data demonstrate that FGF15 functions as a hormone and highlight the utility of SISCAPA-SRM as a sensitive assay for detecting low-abundance proteins in plasma.
authors.affiliation: Department of Pharmacology, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA.
authors.forename: Takeshi
authors.initials: T
authors.lastname: Katafuchi
authors.affiliation: Department of Pharmacology, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA.
authors.forename: Daria
authors.initials: D
authors.lastname: Esterházy
authors.affiliation: Department of Biochemistry, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA.
authors.forename: Andrew
authors.initials: A
authors.lastname: Lemoff
authors.affiliation: Department of Pharmacology, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA; Department of Molecular Biology, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA.
authors.forename: Xunshan
authors.initials: X
authors.lastname: Ding
authors.affiliation: Department of Pharmacology, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA.
authors.forename: Varun
authors.initials: V
authors.lastname: Sondhi
authors.affiliation: Department of Pharmacology, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA; Department of Molecular Biology, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA. Electronic address: steven.kliewer@utsouthwestern.edu.
authors.forename: Steven A
authors.initials: SA
authors.lastname: Kliewer
authors.affiliation: Department of Biochemistry, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA. Electronic address: hamid.mirzaei@utsouthwestern.edu.
authors.forename: Hamid
authors.initials: H
authors.lastname: Mirzaei
authors.affiliation: Department of Pharmacology, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA; Howard Hughes Medical Institute, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA. Electronic address: davo.mango@utsouthwestern.edu.
authors.forename: David J
authors.initials: DJ
authors.lastname: Mangelsdorf
mesh_terms: D000818:Animals; D000906:Antibodies / Q000737:chemistry*; D005346:Fibroblast Growth Factors / Q000097:blood*; D013058:Mass Spectrometry / Q000379:methods*; D051379:Mice; D018345:Mice, Knockout; D010455:Peptides / Q000097:blood*; D011817:Rabbits
chemical_list: D000906:Antibodies; D010455:Peptides; C108526:fibroblast growth factor 15, mouse; D005346:Fibroblast Growth Factors