Background: Vitamin D3 is a key regulator in calcium homeostasis. Vitamin D3 deficiency is associated with mineralisation defects and increased fracture risk and is common among elderly. Whereas short-term vitamin D3 deficiency in young animals is a widely studied phenomenon, there are relatively few in vivo experiments to investigate the effects of long-term vitamin D3 deficiency on bone tissue in older animals. The objective is to characterise the effect of long-term adult vitamin D3 deficiency in vivo on bone histomorphometric parameters in ageing mice.
Methods: Mice were exposed to either a vitamin D3 adequate diet (n=7) containing 1 IU/g Vitamin D3 or a vitamin D3 deficient diet (n=8) containing 0 IU/g Vitamin D3 from 10 months until 24 months of age. Both diets contained 0.5% calcium. Serum 25(OH)D levels were assessed by LC/MS MS. Using Goldner- and TRAP-stained undecalcified bone sections of the proximal humerus, bone volume (BV/TV), bone surface (BS), osteoclast surface (Oc.S/BS), trabecular diameter (Tb.Dm), trabecular number (Tb.N) and trabecular separation (Tb.Sp) were measured. Differences between groups were statistically tested with the Student-t test.
Results: Average serum 25-hydroxyvitamin D3 levels in control mice were 55.7 nmol/l, all deficient mice had 25-hydroxyvitamin D3 levels <4 nmol/l. No significant differences in bone structural variables between the vitamin D3 deficient and control mice were found. Mineralisation defects were not apparent on qualitative inspection in the vitamin D deficient mice.
Conclusions: Despite the long term vitamin D3 deficiency, the bone volume and structure was not different in long-term vitamin D3 deficient mice compared to control mice. Bone resorption was similar in both groups. The sufficient calcium in the diet could possibly have reversed the effects of vitamin D3 deficiency.
Disclosure: The authors declared no competing interests.