title: Levels of serum and synovial fluid pyridinium crosslinks in patients with rheumatoid arthritis.
abstract: OBJECTIVE
  To elucidate the major source of pyridinium crosslinks in rheumatoid arthritis (RA).
  
  
  METHODS
  Serum samples were collected from 75 patients with RA and 41 healthy controls, and synovial fluid (SF) samples were collected from 20 patients with RA and 13 with osteoarthritis (OA). Paired samples of serum and SF were collected at the same time from 26 patients with RA. Levels of pyridinium crosslinks were determined by a recently developed high sensitivity assay method using high pressure liquid chromatography.
  
  
  RESULTS
  The levels of serum pyridinoline (PYD) and serum deoxypyridinoline (DPD) were significantly higher in patients with RA than in healthy controls, and significantly correlated with laboratory variables indicating disease activity and severity. The levels of SF DPD, but not SF PYD, were significantly higher in patients with RA than in patients with OA. The levels of SF PYD and SF DPD both showed a significantly positive correlation with those of either SF interleukin 1beta or SF interleukin 6 in patients with RA. Finally, the levels of PYD, but not DPD, were higher in SF than in serum in all paired RA samples collected at the same time, with significant correlation between the members of each pair.
  
  
  CONCLUSIONS
  These observations suggest than an increase of PYD in RA serum may originate mostly from affected joints and that an increase of DPD in RA serum may be influenced more by systemic bone resorption.
authors.affiliation: Yukioka Hospital, Second Department of Internal Medicine, Osaka City University Medical School, Japan.
authors.forename: Y
authors.initials: Y
authors.lastname: Furumitsu
authors.forename: M
authors.initials: M
authors.lastname: Inaba
authors.forename: K
authors.initials: K
authors.lastname: Yukioka
authors.forename: M
authors.initials: M
authors.lastname: Yukioka
authors.forename: Y
authors.initials: Y
authors.lastname: Kumeda
authors.forename: Y
authors.initials: Y
authors.lastname: Azuma
authors.forename: T
authors.initials: T
authors.lastname: Ohta
authors.forename: T
authors.initials: T
authors.lastname: Ochi
authors.forename: Y
authors.initials: Y
authors.lastname: Nishizawa
authors.forename: H
authors.initials: H
authors.lastname: Morii
mesh_terms: D000328:Adult; D000368:Aged; D000596:Amino Acids / Q000032:analysis* / Q000097:blood; D001172:Arthritis, Rheumatoid / Q000378:metabolism*; D015415:Biomarkers / Q000032:analysis / Q000097:blood; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D013582:Synovial Fluid / Q000737:chemistry*
chemical_list: D000596:Amino Acids; D015415:Biomarkers; C015484:pyridinoline; C036020:deoxypyridinoline