Bone structure is largely unchanged in growing male CD-1 mice fed lower levels of vitamin D and calcium than in the AIN-93G diet

C Brent Wakefield; Jenalyn L Yumol; Sandra M Sacco; Philip J Sullivan; Elena M Comelli; Wendy E Ward

doi:10.1016/j.bonr.2018.100191

Bone structure is largely unchanged in growing male CD-1 mice fed lower levels of vitamin D and calcium than in the AIN-93G diet

Bone Rep. 2018 Dec 30:10:100191. doi: 10.1016/j.bonr.2018.100191. eCollection 2019 Jun.

Authors

C Brent Wakefield¹, Jenalyn L Yumol², Sandra M Sacco¹, Philip J Sullivan¹, Elena M Comelli^{1

3

4}, Wendy E Ward^{1

2

3}

Affiliations

¹ Kinesiology, Brock University, St. Catharines, Ontario, Canada.
² Health Sciences, Brock University, St. Catharines, Ontario, Canada.
³ Nutritional Sciences, University of Toronto, Toronto, Ontario, Canada.
⁴ Joannah and Brian Lawson Centre for Child Nutrition, University of Toronto, Toronto, Ontario, Canada.

Abstract

Background: Calcium (Ca) and vitamin D (vit D) in the AIN-93G diet may be higher than required for healthy bone development, and mask the potential benefit of a dietary intervention.

Objective: The objective was to determine if lower levels of Ca and vit D than is present in the AIN-93G diet supports bone development in growing male CD-1 mice.

Methods: Weanling male CD-1 mice were randomized to modified AIN-93G diets containing either 100 (Trial 1) or 400 (Trial 2) IU vit D/kg diet within one of two or three Ca levels (0.35, 0.30, or 0.25% Ca diet in Trial 1 or 0.35% or 0.25% in Trial 2) or the AIN-93G diet (1000 IU/kg vit D and 0.5% Ca) from weaning to 4 months of age (n = 13-15/group). At 2 and 4 months of age, BMD and structural properties of the tibia were analyzed in vivo. Structure of lumbar vertebra 4 (L4) and mandible, and femur strength were assessed ex vivo at age 4 months.

Results: There were no differences in tibia, L4, and mandible structure between the AIN-93G diet and the 0.35% Ca groups at either vit D level. A few structure outcomes were compromised with the 0.25 and/or 0.3% Ca diets but there were no differences in femur biomechanical strength compared to AIN-93G group in either Trial.

Conclusion: At 400 or 100 IU vit D/kg diet, Ca can be lowered to 0.35% without detriment to BMD or bone structure while bone strength is not altered at lower Ca (0.25%) compared to CD-1 mice fed AIN-93G diet. Because of genetic variation in CD-1 mice among different breeding facilities, results in CD-1 mice from other facilities may differ from the present study.

Keywords: AIN-93G; BMD, bone mineral density; BV/TV, percent bone volume; Bone mineral density; Bone structure; Ca, calcium; Calcium; Conn.D, connectivity density; Ct.Ar/Tt.Ar, cortical area fraction; Ct.Th, cortical thickness; DA, degree anisotropy; Ec.Pm, endocortical perimeter; Ecc., eccentricity; L4, lumbar vertebra 4; Ma.Ar, medullary area; Ps.Pm, periosteal perimeter; ROI, region of interest; Rodent diet; Tb.N, trabecular number; Tb.Sp, trabecular separation; Tb.Th, trabecular thickness; Vitamin D; vit D, vitamin D; μCT, micro-computed tomography.