Bone structure and function in male C57BL/6 mice: Effects of a high-fat Western-style diet with or without trace minerals

Abstract

Purpose: Osteoporosis occurs in both women and men, but most of what we know about the condition comes from studies in females. The present study examined bone structure and function over an 18-month period in male C57BL/6 mice maintained on either a rodent chow diet (AIN76A) or a high-fat, Western-style diet (HFWD). Effects of mineral supplementation were assessed in both diets.

Methods: Trabecular and cortical bone structure in femora and vertebrae were assessed by micro-CT analysis. Following this, bone stiffness and strength measurements were made. Finally, bone levels of several cationic trace elements were quantified, and serum biomarkers of bone metabolism evaluated.

Results: Bone loss occurred over time in both diets but was more rapid and extensive in mice on the HFWD. Dietary mineral supplementation reduced bone loss in both diets and increased bone stiffness in the femora and bone stiffness and strength in the vertebrae. Bone content of strontium was increased in response to mineral supplementation in both diets.

Conclusions: Bone loss was more severe in mice on the HFWD and mineral supplementation mitigated the effects of the HFWD. In comparison to previous findings with female C57BL/6 mice, the present studies indicate that males are more sensitive to diet and benefited from a healthy diet (AIN76A), while females lost as much bone on the healthy diet as on the HFWD. Male mice benefited from mineral supplementation, just as females did in the previous study.

Keywords: Bone; calcium; cationic minerals; male mice; osteoporosis; strontium.

Figures

Fig. 1

Femoral bone: Structural features of trabecular bone. Structural features were assessed in the trabecular ROI by micro-CT as described in the Materials and Methods. Data are based on 5 mice at baseline (4 weeks of age), 10 mice at the 5 and 12 month time-points and 15 mice at the 18 month time-point in each group. Values are means and standard deviations. Statistical significance of each parameter was assessed by ANOVA followed by paired group comparisons. Statistical significance at the p 

Fig. 2

Femoral bone: Structural features of cortical bone. Structural features were assessed in the cortical ROI by micro-CT as described in the Materials and Methods. Data are based on 5 mice at baseline (4 weeks of age), 10 mice at the 5 and 12 month time-points and 15 mice at the 18 month time-point in each group. Values are means and standard deviations. Statistical significance of each parameter was assessed by ANOVA followed by paired group comparisons. Statistical significance at the p 

Fig. 3

Femoral bone: Biomechanical properties. Femoral stiffness and strength were assessed in the 4-point bending assay as described in the Materials and Methods. Data are based on 5 mice at baseline (4 weeks of age), 10 mice at the 5 and 12 month time-points and 15 mice at the 18 month time-point in each group. Values are means and standard deviations. Statistical significance of each parameter was assessed by ANOVA followed by paired group comparisons. Statistical significance at the p 

Fig. 4

Vertebral bone structure and function. A: Structural features of trabecular bone. B: Structural features of cortical bone. C: Biomechanical properties. Data are based on 10 mice at the 18-month time-point in each group. Values are means and standard deviations. Statistical significance of each parameter was assessed using the Student t-test. Statistical significance at the p < 0.05 level is indicated by the letter “a” above the HFWD + AQ bar, which indicates statistically significant improvement relative to HFWD alone. The right lower panel (scatter plot) shows the positive correlation between stiffness and strength in individual mice. All of the C8 vertebral micro-CT trabecular/cortical bone parameters and biomechanical properties measured at the 18 month time-point are presented in Supplement Tables 6 and 7. Insert: A representative 3D micro-CT image of trabecular (surface) and cortical (diaphysis) region from the C8 caudal vertebrae of a mouse in each diet group at zero time and 18 month (magnification bar = 1 mm). Vertebral bone structure and function. A: Structural features of trabecular bone. B: Structural features of cortical bone. C: Biomechanical properties. Data are based on 10 mice at the 18-month time-point in each group. Values are means and standard deviations. Statistical significance of each parameter was assessed using the Student t-test. Statistical significance at the p < 0.05 level is indicated by the letter “a” above the HFWD + AQ bar, which indicates statistically significant improvement relative to HFWD alone. The right lower panel (scatter plot) shows the positive correlation between stiffness and strength in individual mice. All of the C8 vertebral micro-CT trabecular/cortical bone parameters and biomechanical properties measured at the 18 month time-point are presented in Supplement Tables 6 and 7. Insert: A representative 3D micro-CT image of trabecular (surface) and cortical (diaphysis) region from the C8 caudal vertebrae of a mouse in each diet group at zero time and 18 month (magnification bar = 1 mm).