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

The association between retinol and bone mineral density (BMD) in males after puberty has not been fully investigated previously. 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. Longitudinal study. 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. 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. 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). 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.