title: Association of Irisin and CRP Levels with the Radiographic Severity of Knee Osteoarthritis.
abstract: OBJECTIVE
  Irisin, a recently identified myokine, is implicated in protecting mice from obesity. This study was designed to examine the relation of irisin levels in serum and synovial fluid (SF) with the radiographic severity of osteoarthritis (OA).
  
  
  METHODS
  Our study included 215 patients with knee OA. Irisin levels in serum and SF were evaluated using an enzyme-linked immunosorbent assay. The progression of OA was assessed using Kellgren-Lawrence grading system.
  
  
  RESULTS
  Knee OA patients had lower serum irisin concentrations and increased serum C-reactive protein (CRP) levels compared with healthy controls. There were markedly decreased irisin levels in both the serum and the SF, as well as increased serum CRP levels of knee OA patients with Kellgren and Lawrence (KL) grade 4 compared with patients classified as KL grade 2 and 3. Furthermore, patients with KL grade 3 showed markedly reduced serum and SF levels of irisin, as well as increased serum CRP levels compared with patients classified as KL grade 2. Irisin levels in serum and SF of knee OA patients were negatively correlated with disease severity evaluated by KL grading criteria.
  
  
  CONCLUSIONS
  Irisin levels in the serum and SF of knee OA patients were negatively correlated with disease severity evaluated by the radiographic KL grading criteria.
authors.affiliation: Department of Orthopeadic Surgery, The Second Affiliated Hospital of Soochow University , Suzhou, People's Republic of China .
authors.forename: Yongtao
authors.initials: Y
authors.lastname: Mao
authors.affiliation: Department of Orthopeadic Surgery, The Second Affiliated Hospital of Soochow University , Suzhou, People's Republic of China .
authors.forename: Wei
authors.initials: W
authors.lastname: Xu
authors.affiliation: Department of Orthopeadic Surgery, The Second Affiliated Hospital of Soochow University , Suzhou, People's Republic of China .
authors.forename: Zonggang
authors.initials: Z
authors.lastname: Xie
authors.affiliation: Department of Orthopeadic Surgery, The Second Affiliated Hospital of Soochow University , Suzhou, People's Republic of China .
authors.forename: Qirong
authors.initials: Q
authors.lastname: Dong
mesh_terms: D000368:Aged; D000818:Animals; D002097:C-Reactive Protein / Q000378:metabolism*; D005260:Female; D005353:Fibronectins / Q000097:blood*; D006801:Humans; D008297:Male; D051379:Mice; D008875:Middle Aged; D020370:Osteoarthritis, Knee / Q000097:blood* / Q000000981:diagnostic imaging*; D011859:Radiography
chemical_list: C577593:FNDC5 protein, human; D005353:Fibronectins; D002097:C-Reactive Protein