title: Lower P1NP serum levels: a predictive marker of bone loss after 1 year follow-up in premenopausal systemic lupus erythematosus patients.
abstract: CONCLUSIONS
  Predictors of bone mineral density (BMD) loss are additional tools in the management of osteoporosis in premenopausal women with systemic lupus erythematosus (SLE). This study provides original evidence that N-terminal propeptide of type 1 collagen (P1NP), the most specific bone formation marker, is a predictor of BMD loss in this group of women.
  
  
  BACKGROUND
  SLE is associated with a high risk of low bone mass/fractures but this risk is still controversial in premenopausal women. Our aim was to determine the 1 year incidence of BMD loss in premenopausal SLE women and the value of bone turnover markers as predictors of this complication.
  
  
  METHODS
  This study enrolled a convenience sample of 63 premenopausal SLE patients. BMD was evaluated by dual X-ray absorptiometry at lumbar spine and hip at baseline and after 12 months. BMD changes above the least significant change were considered significant. Serum levels of P1NP and CTX (electrochemiluminescence), OPG, and RANKL (ELISA) were determined at baseline.
  
  
  RESULTS
  Mean age was 31.1±6.8 years, and disease duration was 5.25±3.8 years. 36.5 % of patients presented BMD loss and 17.5 % BMD gain at lumbar spine and/or hip. Patients were divided in three groups: BMD loss (BL), no BMD change (NC), and BMD gain (BG). Patients with BL and NC received similar cumulative/mean/maximum glucocorticoid doses during the study, but patients with BG received lower doses (p<0.05). Baseline P1NP levels were different in the groups (BL: 36.95±23.37 vs. NC: 54.63±30.82 vs. BG: 84.09±43.85 ng/mL; p=0.031 BL vs. NC, p<0.001 BL vs. BG, and p=0.039 NC vs. BG). There was no difference in CTX, OPG, or RANKL levels. After multivariate analysis, P1NP remained as an independent risk factor for BMD loss (p<0.03).
  
  
  CONCLUSIONS
  This study provides original evidence that lower levels of P1NP, the most specific bone formation marker, are predictive of BMD loss over 12 months in premenopausal SLE patients.
authors.affiliation: Rheumatology Division, Faculdade de Medicina da Universidade de São Paulo, São Paulo, Brazil.
authors.forename: L P C
authors.initials: LP
authors.lastname: Seguro
authors.forename: C B
authors.initials: CB
authors.lastname: Casella
authors.forename: V F
authors.initials: VF
authors.lastname: Caparbo
authors.forename: R M
authors.initials: RM
authors.lastname: Oliveira
authors.forename: A
authors.initials: A
authors.lastname: Bonfa
authors.forename: E
authors.initials: E
authors.lastname: Bonfa
authors.forename: R M R
authors.initials: RM
authors.lastname: Pereira
mesh_terms: D015502:Absorptiometry, Photon; D000328:Adult; D015415:Biomarkers / Q000097:blood; D015519:Bone Density / Q000502:physiology*; D016723:Bone Remodeling / Q000502:physiology*; D024042:Collagen Type I / Q000097:blood; D005260:Female; D005500:Follow-Up Studies; D006615:Hip / Q000000981:diagnostic imaging; D006801:Humans; D008159:Lumbar Vertebrae / Q000000981:diagnostic imaging; D008180:Lupus Erythematosus, Systemic / Q000097:blood*; D008875:Middle Aged; D053244:Osteoprotegerin / Q000097:blood; D010446:Peptide Fragments / Q000097:blood; D010455:Peptides / Q000097:blood; D011347:Procollagen / Q000097:blood; D053245:RANK Ligand / Q000097:blood; D055815:Young Adult
chemical_list: D015415:Biomarkers; D024042:Collagen Type I; D053244:Osteoprotegerin; D010446:Peptide Fragments; D010455:Peptides; D011347:Procollagen; D053245:RANK Ligand; C052929:collagen type I trimeric cross-linked peptide; C047202:procollagen Type I N-terminal peptide