title: Effect of a 16 weeks weight loss program on osteoarthritis biomarkers in obese patients with knee osteoarthritis: a prospective cohort study.
abstract: OBJECTIVE
  Changes in biomarkers for bone and cartilage in knee osteoarthritis (KOA) may reflect changes in tissue turnover induced by interventions. The aim of this study was to assess the effect on osteoarthritis biomarkers of an intensive weight loss intervention in obese KOA patients.
  
  
  METHODS
  192 obese KOA patients followed a 16 weeks weight loss intervention (ClinicalTrials.gov: NCT00655941). Serum Cartilage Oligomeric Matrix Protein (sCOMP), Urine C-terminal telopeptide of collagen type II (uCTX-II) and type I (uCTX-I) were determined by enzyme-linked immunoassay (ELISA) at baseline and after 16 weeks. Patient-reported symptoms were assessed by the Knee Injury and Osteoarthritis Outcome Score (KOOS) Questionnaire without the sports and recreation score (KOOS-4). Change from baseline was analyzed using Analysis of CoVariance (ANCOVA) adjusting for sex, age, and body mass index (BMI). Bivariate associations were analyzed using Spearman's test of rank correlation.
  
  
  RESULTS
  175 patients completed the treatment and lost mean 13.4 (95% CI: 12.5-14.4) kg. sCOMP concentration decreased on average 1.1 (95% CI: -1.5 to -0.8) U/L with a correlation to weight loss (r = -0.17, P = 0.028), but not to change in KOOS-4 (r = -0.13, P = 0.091). uCTX-II increased significantly, mean 69 (95% CI: 31-106) ng/mmol creatinine, with no relation to weight loss (P = 0.14). Change in uCTX-II was reversely related to change in KOOS-4 (r = -0.28, P = 0.0003). uCTX-I increased, mean 67 (95% CI: 47-87) μg/mmol creatinine, and correlated to weight loss (r = 0.22, P = 0.0007), while not to KOOS-4 (P = 0.93).
  
  
  CONCLUSIONS
  A rapid substantial weight loss in obese KOA patients was weakly, while significantly associated with a reduction in sCOMP, and increases in both uCTX-II and uCTX-I.
authors.affiliation: The Parker Institute, Department of Rheumatology, Copenhagen University Hospital Bispebjerg and Frederiksberg, Denmark. Electronic address: else.marie.bartels@regionh.dk.
authors.forename: E M
authors.initials: EM
authors.lastname: Bartels
authors.affiliation: The Parker Institute, Department of Rheumatology, Copenhagen University Hospital Bispebjerg and Frederiksberg, Denmark; Institute of Sports Science and Clinical Biomechanics, University of Southern Denmark, Odense M, Denmark. Electronic address: robin.daniel.kjersgaard.christensen@regionh.dk.
authors.forename: R
authors.initials: R
authors.lastname: Christensen
authors.affiliation: The Parker Institute, Department of Rheumatology, Copenhagen University Hospital Bispebjerg and Frederiksberg, Denmark; Department of Nutrition, Exercise and Sports, University of Copenhagen, Denmark. Electronic address: piach@life.ku.dk.
authors.forename: P
authors.initials: P
authors.lastname: Christensen
authors.affiliation: The Parker Institute, Department of Rheumatology, Copenhagen University Hospital Bispebjerg and Frederiksberg, Denmark. Electronic address: marius.henriksen@regionh.dk.
authors.forename: M
authors.initials: M
authors.lastname: Henriksen
authors.affiliation: Immunodiagnostic Systems Limited (IDS), UK. Electronic address: alex.bennett@idsplc.com.
authors.forename: A
authors.initials: A
authors.lastname: Bennett
authors.affiliation: The Parker Institute, Department of Rheumatology, Copenhagen University Hospital Bispebjerg and Frederiksberg, Denmark; Knowledgecentre for Telemedicine, The Capital Region of Denmark, Denmark; Department of Rheumatology, Copenhagen University Hospitals, Glostrup, Frederiksberg and Bispebjerg, Denmark. Electronic address: rindelgudbergsen@gmail.com.
authors.forename: H
authors.initials: H
authors.lastname: Gudbergsen
authors.affiliation: The Parker Institute, Department of Rheumatology, Copenhagen University Hospital Bispebjerg and Frederiksberg, Denmark; Department of Radiology, Copenhagen University Hospital Bispebjerg and Frederiksberg, Denmark. Electronic address: mikael.ploug.boesen@regionh.dk.
authors.forename: M
authors.initials: M
authors.lastname: Boesen
authors.affiliation: The Parker Institute, Department of Rheumatology, Copenhagen University Hospital Bispebjerg and Frederiksberg, Denmark; Faculty of Health Science, University of Copenhagen, Denmark; SMI, Aalborg University, Denmark. Electronic address: henning.bliddal@regionh.dk.
authors.forename: H
authors.initials: H
authors.lastname: Bliddal
mesh_terms: D015415:Biomarkers / Q000097:blood*; D015992:Body Mass Index; D064236:Cartilage Oligomeric Matrix Protein / Q000097:blood; D024043:Collagen Type II / Q000097:blood; D003404:Creatinine / Q000097:blood; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D007719:Knee Joint; D008297:Male; D008875:Middle Aged; D009765:Obesity / Q000097:blood / Q000150:complications*; D020370:Osteoarthritis, Knee / Q000097:blood / Q000209:etiology / Q000534:rehabilitation*; D011446:Prospective Studies; D013997:Time Factors; D016896:Treatment Outcome; D015431:Weight Loss / Q000502:physiology*; D061217:Weight Reduction Programs / Q000379:methods*
chemical_list: D015415:Biomarkers; D064236:Cartilage Oligomeric Matrix Protein; D024043:Collagen Type II; D003404:Creatinine
keywords: COMP; CTX-I; CTX-II; Knee; Osteoarthritis; Weight loss