Assessment of Serum Vitamin B12 Levels and Other Metabolic Parameters in Subjects With Different Values of Bone Mineral Density

BACKGROUND: Controversial experimental and clinical evidences have raised questions regarding the role of B12 and insulin-like growth factor 1 (IGF-1) on osteoblast function and bone health. In this study, we aimed to determine if the serum levels of B12, IGF-1 and procollagen type 1 N-terminal propeptide (P1NP) are associated with different degrees of bone mineral density (BMD). METHODS: A total of 287 subjects (190 women and 97 men; mean age 53 years) volunteered for evaluation of BMD and serum levels of B12, IGF-1 and P1NP; BMD at lumbar spine and proximal femur was evaluated by means of dual-energy X-ray absorption (DEXA) and expressed as T-score; serum concentrations of vitamin B12 and IGF1 were measured with a chemiluminescent immunoassay on Access II Beckman Coulter and DiaSorin Liaison XL analyzers, respectively; P1NP was assessed in 61 women and 35 men with reduced T-score on Roche Modular platform. RESULTS: A total of 101 subjects (66 women and 35 men) had a reduced BMD (T-score < -1) or osteoporosis with a T-score < -2.5, while 186 (124 women and 62 men) had a normal BMD. No significant difference in the B12 levels was observed between the subjects with reduced BMD (mean 265.15 pg/mL, 95% CI: 236 - 294.25) and those with normal BMD (mean 243.91, 95% CI: 225.78 - 262.03) (P = 0.1990); lower levels of IGF-1 were observed in the group with reduced BMD (mean 138.7 pg/mL, 95% CI: 126.75 - 150.83) than in that with normal BMD (mean 167.34, 95% CI: 136.49 - 198.18) (P< 0.001); serum levels of P1NP were significantly lower in 22 subjects younger than 50 years (mean 44.8 ng/mL, 95% CI: 36.4 - 53.1) vs. 74 subjects > 50 years old (mean 53.3, 95% CI: 34.3 - 72.3) (P < 0.001), and in women (mean 45.3, 95% CI: 37.6 - 52.9) vs. men (mean 62, 95% CI: 23 - 101) (P < 0.001). CONCLUSION: We found no significant association between B12 levels and BMD, but significant associations of lower levels of IGF1 with reduced BMD and lower levels of P1NP with younger age and female sex were found; additional studies to further investigate the association of serum levels of B12, growth factors and biochemical turnover markers with human bone health are needed.