Vitamin B(12) deficiency stimulates osteoclastogenesis via increased homocysteine and methylmalonic acid

The risk of nutrient deficiencies increases with age in our modern Western society, and vitamin B(12) deficiency is especially prevalent in the elderly and causes increased homocysteine (Hcy) and methylmalonic acid (MMA) levels. These three factors have been recognized as risk factors for reduced bone mineral density and increased fracture risk, though mechanistic evidence is still lacking. In the present study, we investigated the influence of B(12), Hcy, and MMA on differentiation and activity of bone cells. B(12) deficiency did not affect the onset of osteoblast differentiation, maturation, matrix mineralization, or adipocyte differentiation from human mesenchymal stem cells (hMSCs). B(12) deficiency caused an increase in the secretion of Hcy and MMA into the culture medium by osteoblasts, but Hcy and MMA appeared to have no effect on hMSC osteoblast differentiation. We further studied the effect of B(12), Hcy, and MMA on the formation of multinucleated tartrate-resistant acid phosphatase-positive osteoclasts from mouse bone marrow. We observed that B(12) did not show an effect on osteoclastogenesis. However, Hcy as well as MMA were found to induce osteoclastogenesis in a dose-dependent manner. On the basis of these results, we conclude that B(12) deficiency may lead to decreased bone mass by increased osteoclast formation due to increased MMA and Hcy levels.

Vitamin B-12 status is associated with bone mineral content and bone mineral density in frail elderly women but not in men

Subclinical vitamin B-12 deficiency is common in the elderly. Encouraged by early indications, we investigated the plasma vitamin B-12 status in association with bone mineral content (BMC) and bone mineral density (BMD) in frail elderly people. Data of 194 free-living Dutch frail elderly (143 women and 51 men) were available. BMC and BMD were measured by dual energy X-ray analysis. Biochemical analyses were performed on plasma or serum including vitamin B-12, methylmalonic acid, homocysteine, 25-hydroxy vitamin D and parathyroid hormone. Women had higher plasma vitamin B-12 (288 and 238 pmol/L, respectively) and lower plasma homocysteine levels (15.8 and 21.3 micro mol/L, respectively) than men. Of the total explained variance of BMC and BMD in women (46 and 22%, respectively), 1.3-3.1% was explained by plasma vitamin B-12, in addition to weight and height or energy intake. In men, the variance of BMC and BMD was explained by weight, smoking and/or height (total R(2) was 53 and 25%, respectively), but not by plasma vitamin B-12. Osteoporosis occurred more often among women whose vitamin B-12 status was considered marginal or deficient than in women with a normal status, i.e., the prevalence odds ratios (after adjustment for weight, age and calcium intake) (95% confidence intervals) were 4.5 (0.8;24.8) and 6.9 (1.2;39.4), respectively. These results suggest that vitamin B-12 status is associated with bone health in elderly women. Future studies on bone health should take into account a possible role of vitamin B-12 status in different populations.