title: Galactose-Deficient IgA1 as a Candidate Urinary Polypeptide Marker of IgA Nephropathy?
abstract: In patients with IgA nephropathy (IgAN), circulatory IgA1 and IgA1 in mesangial deposits contain elevated amounts of galactose-deficient IgA1 (Gd-IgA1). We hypothesized that a fraction of Gd-IgA1 from the glomerular deposits and/or circulation may be excreted into the urine and thus represent a disease-specific biomarker. Levels of urinary IgA and Gd-IgA1 were determined in 207 patients with IgAN, 205 patients with other renal diseases, and 57 healthy controls, recruited in USA, Japan, and Italy. Urinary IgA was similarly elevated in patients with IgAN and renal-disease controls compared with healthy controls. However, urinary Gd-IgA1 levels were higher in patients with IgAN (IgAN, 28.0 ± 17.9; disease controls, 20.6 ± 17.4 units/mg urinary creatinine; P < 0.0001). Lectin western blotting data confirmed these results. In IgAN patients, levels of urinary Gd-IgA1 correlated with proteinuria (P < 0.001). When we purified IgA from serum and urine of an IgAN patient, the relative proportion of Gd-IgA1 to total IgA1 was higher in the urine compared with serum, suggesting selective excretion of Gd-IgA1 in IgAN. In summary, urinary excretion of Gd-IgA1 was elevated in patients with IgAN and the urinary Gd-IgA1 levels correlated with proteinuria. Urinary Gd-IgA1 may thus represent a disease-specific biomarker of IgAN.
authors.affiliation: Division of Nephrology, Juntendo University Faculty of Medicine, Tokyo 113-8421, Japan; University of Alabama at Birmingham, Birmingham, AL 35294, USA.
authors.forename: Hitoshi
authors.identifier: 0000-0002-1901-2111
authors.initials: H
authors.lastname: Suzuki
authors.affiliation: University of Parma, 43100 Parma, Italy.
authors.forename: Landino
authors.initials: L
authors.lastname: Allegri
authors.affiliation: Division of Nephrology, Juntendo University Faculty of Medicine, Tokyo 113-8421, Japan.
authors.forename: Yusuke
authors.identifier: 0000-0002-4077-9747
authors.initials: Y
authors.lastname: Suzuki
authors.affiliation: University of Alabama at Birmingham, Birmingham, AL 35294, USA.
authors.forename: Stacy
authors.initials: S
authors.lastname: Hall
authors.affiliation: University of Alabama at Birmingham, Birmingham, AL 35294, USA.
authors.forename: Zina
authors.identifier: 0000-0002-5372-5262
authors.initials: Z
authors.lastname: Moldoveanu
authors.affiliation: University of Tennessee Health Sciences Center, Memphis, TN 38103, USA.
authors.forename: Robert J
authors.initials: RJ
authors.lastname: Wyatt
authors.affiliation: University of Alabama at Birmingham, Birmingham, AL 35294, USA.
authors.forename: Jan
authors.identifier: 0000-0002-9211-6670
authors.initials: J
authors.lastname: Novak
authors.affiliation: University of Alabama at Birmingham, Birmingham, AL 35294, USA.
authors.forename: Bruce A
authors.identifier: 0000-0001-5781-1021
authors.initials: BA
authors.lastname: Julian
mesh_terms: D015415:Biomarkers / Q000652:urine*; D015153:Blotting, Western; D016022:Case-Control Studies; D004797:Enzyme-Linked Immunosorbent Assay; D005690:Galactose / Q000172:deficiency*; D005922:Glomerulonephritis, IGA / Q000175:diagnosis* / Q000652:urine; D006031:Glycosylation; D006801:Humans; D007070:Immunoglobulin A / Q000652:urine*; D037102:Lectins / Q000378:metabolism; D010446:Peptide Fragments / Q000652:urine*; D011379:Prognosis
chemical_list: D015415:Biomarkers; D007070:Immunoglobulin A; D037102:Lectins; D010446:Peptide Fragments; D005690:Galactose