title: Retinol, retinol-binding protein 4, abdominal fat mass, peak bone mineral density, and markers of bone metabolism in men: the Northern Osteoporosis and Obesity (NO2) Study.
abstract: BACKGROUND
  The association between retinol and bone mineral density (BMD) in males after puberty has not been fully investigated previously.
  
  
  OBJECTIVE
  To investigate the association between retinol, retinol-binding protein-4 (RBP-4), BMD (g/cm(2)), abdominal fat mass, and markers of bone metabolism in young men.
  
  
  METHODS
  Longitudinal study.
  
  
  METHODS
  Seventy-eight healthy males with a mean age of 22.6+/-0.7 years at baseline. A follow-up was conducted in 73 of the participants 2.0+/-0.4 years later.
  
  
  METHODS
  Associations between serum concentrations of retinol and RBP-4, and BMD of the total body, lumbar spine, and hip, serum concentrations of osteocalcin, and carboxy terminal telopeptide of type 1 collagen (CTX), were investigated.
  
  
  RESULTS
  Both retinol and RBP-4 showed an inverse relationship with that of osteocalcin (r=-0.23 to -0.25, P<0.05). Levels of RBP-4 (r=0.26, P=0.02) and osteocalcin (r=-0.23, P=0.04) were also related to abdominal fat mass, and the relationship between RBP-4, retinol, and osteocalcin disappeared after adjusting for this influence of abdominal fat mass. Neither retinol nor RBP-4 concentrations were associated with BMD at any site, CTX as baseline, or changes in BMD during the 2-year follow-up period. Levels of RBP-4 showed a strong association with levels of retinol (r=0.61, P<0.001).
  
  
  CONCLUSIONS
  We found a negative association between the bone formation marker osteocalcin with retinol and RBP-4. The association disappeared when adjusting for the influence of abdominal fat mass. Neither retinol nor RBP-4 were associated with peak BMD in young men.
authors.affiliation: Sports Medicine, Department of Surgical and Perioperative Science, Umeå University, S-901 85 Umeå, Sweden.
authors.forename: Magnus
authors.initials: M
authors.lastname: Högström
authors.forename: Anna
authors.initials: A
authors.lastname: Nordström
authors.forename: Peter
authors.initials: P
authors.lastname: Nordström
mesh_terms: D050153:Abdominal Fat / Q000378:metabolism*; D000328:Adult; D015415:Biomarkers; D015519:Bone Density / Q000502:physiology*; D001842:Bone and Bones / Q000378:metabolism; D015331:Cohort Studies; D024042:Collagen Type I / Q000378:metabolism; D005500:Follow-Up Studies; D006801:Humans; D008297:Male; D015233:Models, Statistical; D009765:Obesity / Q000378:metabolism*; D015675:Osteocalcin / Q000378:metabolism; D010024:Osteoporosis / Q000378:metabolism*; D010455:Peptides / Q000378:metabolism; D011237:Predictive Value of Tests; D054839:Retinol-Binding Proteins, Plasma / Q000378:metabolism*; D014801:Vitamin A / Q000097:blood*
chemical_list: D015415:Biomarkers; D024042:Collagen Type I; D010455:Peptides; C101326:RBP4 protein, human; D054839:Retinol-Binding Proteins, Plasma; C052929:collagen type I trimeric cross-linked peptide; D015675:Osteocalcin; D014801:Vitamin A