title: Increased serum levels of β₂-GPI-Lp(a) complexes and their association with premature atherosclerosis in patients with rheumatoid arthritis.
abstract: BACKGROUND
  Our recent study found the existence of complexes of β₂-glycoprotein I (β₂-GPI) with lipoprotein(a)[Lp(a)] in circulation and the complex concentrations were increased in sera of systemic lupus erythematosus patients. The concentration of β₂-GPI-Lp(a) and its relationship with premature atherosclerosis were evaluated in rheumatoid arthritis (RA) patients.
  
  
  METHODS
  Serum concentrations of β₂-GPI-Lp(a) were measured in 53 active RA patients and 40 healthy controls by a "sandwich" ELISA. β₂-GPI-ox-LDL, ox-Lp(a), ox-LDL and anti-β₂-GPI were also measured by ELISAs. In addition, inflammatory markers were examined.
  
  
  RESULTS
  Serum β₂-GPI-Lp(a) (1.12±0.25 U/ml vs. 0.87±0.19 U/ml, P<0.0001) and β₂-GPI-ox-LDL (1.01±0.20 U/ml vs. 0.80±0.08 U/ml, P<0.0001) concentrations in RA were both significantly higher than those of controls. Ox-Lp(a) (8.38±6.69 mg/l vs. 5.49±4.31 mg/l, P<0.05) and ox-LDL (0.68±0.65 mg/l vs. 0.37±0.13 mg/l, P=0.001) were also higher in RA than in controls. The area under the ROC curve (AUC) for β₂-GPI-Lp(a) (0.787) was larger than for ox-Lp(a) (0.731). AUC of β₂-GPI-ox-LDL (0.858) was also larger than for ox-LDL (0.785). β₂-GPI-Lp(a) and β₂-GPI-ox-LDL were positively correlated with ox-Lp(a), ox-LDL and CRP, respectively.
  
  
  CONCLUSIONS
  β₂-GPI-Lp(a) complex concentrations increased in active RA. Inflammation and oxidative stress in RA contribute to the increase of ox-Lp(a) and subsequently the formation of β₂-GPI-Lp(a).
authors.affiliation: Department of Biochemistry, Jinling Hospital, Clinical School of Medical College, Nanjing University, 210002 Nanjing, PR China.
authors.forename: Chunni
authors.initials: C
authors.lastname: Zhang
authors.forename: Xiaojun
authors.initials: X
authors.lastname: Li
authors.forename: Dongmei
authors.initials: D
authors.lastname: Niu
authors.forename: Ruifeng
authors.initials: R
authors.lastname: Zi
authors.forename: Cheng
authors.initials: C
authors.lastname: Wang
authors.forename: Aizhong
authors.initials: A
authors.lastname: Han
authors.forename: Xiangdong
authors.initials: X
authors.lastname: Wang
authors.forename: Ke
authors.initials: K
authors.lastname: Li
authors.forename: Junjun
authors.initials: J
authors.lastname: Wang
mesh_terms: D001172:Arthritis, Rheumatoid / Q000097:blood / Q000150:complications* / Q000378:metabolism; D050197:Atherosclerosis / Q000097:blood* / Q000150:complications*; D015415:Biomarkers / Q000097:blood; D005260:Female; D006801:Humans; D017270:Lipoprotein(a) / Q000097:blood*; D008297:Male; D008875:Middle Aged; D018384:Oxidative Stress; D053482:beta 2-Glycoprotein I / Q000097:blood*
chemical_list: D015415:Biomarkers; D017270:Lipoprotein(a); D053482:beta 2-Glycoprotein I