title: Oxidative stress, vitamin e, and antioxidant capacity in knee osteoarthritis.
abstract: BACKGROUND
  Osteoarthritis (OA) is a chronic progressive degenerative joint disorder which is characterised by strongly age-related regressive changes in articular cartilage. The objective of this study was to evaluate oxidative stress and antioxidant parameters in plasma and synovial fluid of patients with primary knee osteoarthritis.
  
  
  METHODS
  Thirty-five OA patients and 35 healthy controls were recruited for this study. Nitrite, malondialdehyde (MDA), vitamin E, Trolox Equivalent Antioxidant Capacity (TEAC), and Ferric Reducing Antioxidant Power (FRAP) levels in plasma and synovial fluid were determined.
  
  
  RESULTS
  Plasma nitrite levels in OA patients were significantly higher than those in healthy controls (p = 0.037). Furthermore, plasma MDA levels were significantly higher in OA patients than those in healthy controls (p < 0.001). Moreover, plasma vitamin E levels in OA patients were significantly lower than those in healthy controls (p < 0.001). Synovial fluid vitamin E levels of OA patients were significantly lower than paired plasma samples (p < 0.001). The total antioxidant capacities, as were measured by TEAC and FRAP assays in plasma of OA patients, were significantly lower than those in healthy controls (p < 0.01). MDA concentrations were positively correlated with nitrite concentrations but they were negatively associated with vitamin E and TEAC levels in synovial fluid of OA patients.
  
  
  CONCLUSIONS
  The increased plasma levels of nitrite and MDA and the decreased plasma levels of vitamin E, TEAC, and FRAP indicated that oxidative stress was present in OA patients. These findings suggest that oxidative stress plays a potential role in pathophysiology of knee osteoarthritis.
authors.affiliation: Lecturer, Department of Biochemistry, Faculty of Medicine, Chulalongkorn University, King Chulalongkorn Memorial Hospital, Thai Red Cross Society , Bangkok 10330, Thailand .
authors.forename: Tanyawan
authors.initials: T
authors.lastname: Suantawee
authors.forename: Saran
authors.initials: S
authors.lastname: Tantavisut
authors.forename: Sirichai
authors.initials: S
authors.lastname: Adisakwattana
authors.forename: Aree
authors.initials: A
authors.lastname: Tanavalee
authors.forename: Pongsak
authors.initials: P
authors.lastname: Yuktanandana
authors.forename: Wilai
authors.initials: W
authors.lastname: Anomasiri
authors.forename: Benjamad
authors.initials: B
authors.lastname: Deepaisarnsakul
authors.forename: Sittisak
authors.initials: S
authors.lastname: Honsawek
keywords: Antioxidant capacity; knee osteoarthritis; oxidative stress; synovial fluid; vitamin E