title: Body mass index (BMI) and parameters of bone formation and resorption in postmenopausal women.
abstract: OBJECTIVE
  Aim of this study was to evaluate increased body mass index (BMI) as an anthropometric factor, predisposing to lower rates of bone turnover or changes in bone balance after menopause.
  
  
  METHODS
  For this purpose, we calculated BMI, and measured spinal (BMD(SP)) and femoral bone mineral density (BMD(FN)) and biochemical markers of bone formation (serum osteocalcin (S-OC), serum procollagen type I C propeptide (S-PICP), serum bone-specific alkaline phosphatase (S-B-ALP)) and resorption (urine N- and C-terminal cross-linking telopeptide of type I collagen (U-NTX-I and U-CTX-I), pyridinoline (U-PYD) and deoxypyridinoline (U-DPD)) in 130 healthy postmenopausal women, aged 46-85 years. Bone balance indices were calculated by subtracting z-scores of resorption markers from z-scores of formation markers, to evaluate bone balance.
  
  
  RESULTS
  S-PICP ( r = -0.297, P = 0.002), S-OC ( r = -0.173, P = 0.05) and bone balance indices (zPICP-zDPD) and (zPICP-zPYD) were negatively correlated with BMI (r = -0.25, P = 0.01 and r = -0.25, P = 0.01 and r = -0.21, P = 0.037) and with BMD(SP) (r = -0.196, P = 0.032 and r = -0.275 and P = 0.022). Women were grouped according to their BMI, in normals (BMI < 25 kg/m2), overweight (BMI = 25-30 kg/m2, and obese (BMI > 30 kg/m2). Overweight and obese women had approximately 30% lower levels of S-PICP compared to normals (68.11 +/- 24.85 and 66.41 ng/ml versus 97.47 +/- 23.36 ng/ml, respectively; P = 0.0001). zPICP-zDPD, zPICP-zCTX-I and zPICP-zPYD were significantly declined in obese women compared to normals (P = 0.0072, 0.02 and 0.0028).
  
  
  CONCLUSIONS
  We conclude that in postmenopausal women, BMI is inversely associated with levels of collagen I formation marker, serum PICP. In obesity formation of collagen I was reduced, in favor of degradation, but since this finding is not followed by simultaneous decrease in bone mineral density, it seems that increased body weight may have different effects on mature estrogen-deficient bone and extraskeletal tissues containing collagen I.
authors.affiliation: Center for the Study of Osteoporotic Fractures, University of Crete, Heraklion, Crete, Greece. kdret@her.forthnet.gr
authors.forename: E F
authors.initials: EF
authors.lastname: Papakitsou
authors.forename: A N
authors.initials: AN
authors.lastname: Margioris
authors.forename: K E
authors.initials: KE
authors.lastname: Dretakis
authors.forename: G
authors.initials: G
authors.lastname: Trovas
authors.forename: U
authors.initials: U
authors.lastname: Zoras
authors.forename: G
authors.initials: G
authors.lastname: Lyritis
authors.forename: E K
authors.initials: EK
authors.lastname: Dretakis
authors.forename: K
authors.initials: K
authors.lastname: Stergiopoulos
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D000469:Alkaline Phosphatase / Q000097:blood; D000596:Amino Acids / Q000652:urine; D000704:Analysis of Variance; D015415:Biomarkers; D015992:Body Mass Index; D015519:Bone Density / Q000502:physiology; D001862:Bone Resorption / Q000378:metabolism*; D001842:Bone and Bones / Q000378:metabolism / Q000502:physiology*; D003094:Collagen / Q000652:urine; D024042:Collagen Type I; D005260:Female; D005272:Femur Neck / Q000502:physiology; D006801:Humans; D016014:Linear Models; D016015:Logistic Models; D008159:Lumbar Vertebrae / Q000502:physiology; D008875:Middle Aged; D015675:Osteocalcin / Q000097:blood; D010012:Osteogenesis / Q000502:physiology*; D010446:Peptide Fragments / Q000097:blood; D010455:Peptides / Q000652:urine; D017698:Postmenopause / Q000502:physiology*; D011347:Procollagen / Q000097:blood
chemical_list: D000596:Amino Acids; D015415:Biomarkers; D024042:Collagen Type I; D010446:Peptide Fragments; D010455:Peptides; D011347:Procollagen; C052929:collagen type I trimeric cross-linked peptide; C042813:procollagen type I carboxy terminal peptide; D015675:Osteocalcin; C015484:pyridinoline; C036020:deoxypyridinoline; D003094:Collagen; D000469:Alkaline Phosphatase