title: Circulating fibroblast activation protein and dipeptidyl peptidase 4 in rheumatoid arthritis and systemic sclerosis.
abstract: OBJECTIVE
  To quantify circulating fibroblast activation protein (cFAP) and dipeptidyl peptidase 4 (cDPP4) protease activities in patients with rheumatoid arthritis (RA), systemic sclerosis (SSc), and a control group with mechanical back pain and to correlate plasma levels with disease characteristics.
  
  
  METHODS
  Plasma was collected from patients with RA (n = 73), SSc (n = 37) and control subjects (n = 26). DPP4 and FAP were quantified using specific enzyme activity assays.
  
  
  RESULTS
  Median cDPP4 was significantly lower in the RA group (P = 0.02), and SSc group (P = 0.002) compared with controls. There were no significant differences in median cFAP between the three groups. DPP4 and FAP demonstrated a negative correlation with inflammatory markers and duration of disease. There were no associations with disease subtypes in RA, including seropositive and erosive disease. Decreased cDPP4 was found in SSc patients with myositis. Plasma FAP was lower in RA patients receiving prednisone (P = 0.001) or leflunomide (P = 0.04), but higher with biologic agents (P = 0.01). RA patients receiving leflunomide also had decreased cDPP4 (P = 0.014). SSc patients receiving prednisone (P = 0.02) had lower cDPP4 but there was no association with cFAP.
  
  
  CONCLUSIONS
  No association was found between cFAP and RA or SSc. Plasma DPP4 was decreased in RA and SSc when compared with controls. cDPP4 and cFAP correlated negatively with inflammatory markers and there were no significant correlations with disease characteristics in this RA cohort.
authors.affiliation: Rheumatology Department, Westmead Hospital, Westmead, New South Wales, Australia.
authors.forename: Premarani
authors.initials: P
authors.lastname: Sinnathurai
authors.affiliation: Rheumatology Department, Westmead Hospital, Westmead, New South Wales, Australia.
authors.forename: Wendy
authors.initials: W
authors.lastname: Lau
authors.affiliation: Sydney Medical School, The University of Sydney, Sydney, New South Wales, Australia.|Centenary Institute, Sydney, New South Wales, Australia.
authors.forename: Ana Julia
authors.initials: AJ
authors.lastname: Vieira de Ribeiro
authors.affiliation: Sackler School of Biomedical Sciences, Tufts University School of Medicine, Boston, Massachusetts, USA.
authors.forename: William W
authors.initials: WW
authors.lastname: Bachovchin
authors.affiliation: Rheumatology Department, Westmead Hospital, Westmead, New South Wales, Australia.|Sydney Medical School, The University of Sydney, Sydney, New South Wales, Australia.
authors.forename: Helen
authors.initials: H
authors.lastname: Englert
authors.affiliation: Rheumatology Department, Westmead Hospital, Westmead, New South Wales, Australia.
authors.forename: Graydon
authors.initials: G
authors.lastname: Howe
authors.affiliation: Rheumatology Department, Westmead Hospital, Westmead, New South Wales, Australia.|Sydney Medical School, The University of Sydney, Sydney, New South Wales, Australia.
authors.forename: David
authors.initials: D
authors.lastname: Spencer
authors.affiliation: Rheumatology Department, Westmead Hospital, Westmead, New South Wales, Australia.|Sydney Medical School, The University of Sydney, Sydney, New South Wales, Australia.
authors.forename: Nicholas
authors.initials: N
authors.lastname: Manolios
authors.affiliation: Sydney Medical School, The University of Sydney, Sydney, New South Wales, Australia.|Centenary Institute, Sydney, New South Wales, Australia.
authors.forename: Mark D
authors.identifier: http://orcid.org/0000-0002-0528-2604
authors.initials: MD
authors.lastname: Gorrell
mesh_terms: D000368:Aged; D001172:Arthritis, Rheumatoid / Q000097:blood* / Q000175:diagnosis / Q000188:drug therapy / Q000201:enzymology; D001688:Biological Products / Q000627:therapeutic use; D015415:Biomarkers / Q000097:blood; D016022:Case-Control Studies; D018819:Dipeptidyl Peptidase 4 / Q000097:blood*; D010450:Endopeptidases; D005260:Female; D018093:Gelatinases / Q000097:blood*; D005938:Glucocorticoids / Q000627:therapeutic use; D006801:Humans; D007166:Immunosuppressive Agents / Q000627:therapeutic use; D018836:Inflammation Mediators / Q000097:blood; D008297:Male; D008565:Membrane Proteins / Q000097:blood*; D008875:Middle Aged; D012595:Scleroderma, Systemic / Q000097:blood* / Q000175:diagnosis / Q000188:drug therapy / Q000201:enzymology; D012697:Serine Endopeptidases / Q000097:blood*; D000099167:Fibroblast Activation Protein Alpha
chemical_list: D001688:Biological Products; D015415:Biomarkers; D018819:Dipeptidyl Peptidase 4; D010450:Endopeptidases; D018093:Gelatinases; D005938:Glucocorticoids; D007166:Immunosuppressive Agents; D018836:Inflammation Mediators; D008565:Membrane Proteins; D012697:Serine Endopeptidases; D000099167:Fibroblast Activation Protein Alpha; C042807:DPP4 protein, human
keywords: biomarkers; enzymes; fibroblasts; inflammation; lymphocytes; proteases