title: Circulatory osteoprotegerin is related to osteoporosis of the hip in patients with COPD.
abstract: BACKGROUND
  Osteoprotegerin (OPG), a potent inhibitor of osteoclastogenesis, decreases bone resorption and has protective effects on bone mineral density (BMD). Recently we have shown that the adipose-tissue derived OPG relates to BMD in patients with chronic obstructive pulmonary disease (COPD), a condition associated with increased risk of osteoporosis.
  
  
  OBJECTIVE
  Here we aimed to investigate the potential of circulatory OPG to reflect hip BMD in patients with COPD.
  
  
  METHODS
  In 56 subjects with COPD [age, 61.7 ± 6.7 years; forced expiratory volume in 1 s (FEV1), 53.6 ± 19.2% predicted], total femur BMD was assessed by dual energy X-ray absorptiometry, serum OPG and β-crosslaps, a marker of increased bone resorption, by commercially available assays.
  
  
  RESULTS
  From patients with normal hip BMD (n = 32, T-score 0.1 ± 0.8) to those with osteopenia (n = 14, T-score -1.6 ± 0.4) and osteoporosis (n = 10, T-score -3.4 ± 0.7) serum OPG levels significantly increased (6.6 ± 1.8 versus 7.2 ± 2.9 and versus 8.6 ± 1.5 pmol/l, p = 0.036). In addition, hip T-scores were directly related to FEV1, and inversely to β-crosslaps (R = 0.40, p = 0.002; R = 0.38, p = 0.01, respectively). In multivariate analysis, OPG independently predicted hip T-scores after adjustments for age, gender, FEV1, and β-crosslaps (p = 0.011, adjusted R(2) = 0.354). Area under receiver operator curve for OPG as a discriminator of osteoporosis was 0.787 (95% CI, 0.653-0.921) (p = 0.005).
  
  
  CONCLUSIONS
  Present results suggest that osteoporosis of the hip is associated with increased circulatory levels of OPG in patients with COPD. OPG might serve as a biomarker of this COPD-related comorbidity.
authors.affiliation: Department of Respiratory Medicine, Faculty of Medicine, PJ Safarik University and L Pasteur University Hospital, Rastislavova 43, Kosice 041 90, Slovakia.
authors.forename: Pavol
authors.initials: P
authors.lastname: Pobeha
authors.affiliation: Institute of Experimental Medicine, Faculty of Medicine, PJ Safarik University, Trieda SNP 1, Kosice 041 90, Slovakia.
authors.forename: Darina
authors.initials: D
authors.lastname: Petrasova
authors.affiliation: Department of Respiratory Medicine, Faculty of Medicine, PJ Safarik University and L Pasteur University Hospital, Rastislavova 43, Kosice 041 90, Slovakia.
authors.forename: Ruzena
authors.initials: R
authors.lastname: Tkacova
authors.affiliation: Department of Respiratory Medicine, Faculty of Medicine, PJ Safarik University and L Pasteur University Hospital, Rastislavova 43, Kosice 041 90, Slovakia. Electronic address: joppapavol@gmail.com.
authors.forename: Pavol
authors.initials: P
authors.lastname: Joppa
mesh_terms: D000368:Aged; D015415:Biomarkers / Q000097:blood; D001823:Body Composition / Q000502:physiology; D015519:Bone Density / Q000502:physiology; D003430:Cross-Sectional Studies; D005260:Female; D005541:Forced Expiratory Volume / Q000502:physiology; D006621:Hip Joint / Q000503:physiopathology*; D006801:Humans; D008159:Lumbar Vertebrae / Q000503:physiopathology; D008297:Male; D008875:Middle Aged; D010024:Osteoporosis / Q000175:diagnosis* / Q000209:etiology / Q000503:physiopathology; D053244:Osteoprotegerin / Q000097:blood*; D029424:Pulmonary Disease, Chronic Obstructive / Q000150:complications* / Q000503:physiopathology; D053245:RANK Ligand / Q000097:blood; D012129:Respiratory Function Tests / Q000379:methods
chemical_list: D015415:Biomarkers; D053244:Osteoprotegerin; D053245:RANK Ligand; C506030:TNFRSF11B protein, human; C505688:TNFSF11 protein, human
keywords: Biomarker; Bone resorption; Chronic obstructive pulmonary disease; Osteoporosis; Osteoprotegerin