Preservation of bone structure and function by Lithothamnion sp. derived minerals

Abstract

Progressive bone mineral loss and increasing bone fragility are hallmarks of osteoporosis. A combination of minerals isolated from the red marine algae, Lithothamnion sp. was examined for ability to inhibit bone mineral loss in female mice maintained on either a standard rodent chow (control) diet or a high-fat western diet (HFWD) for 5, 12, and 18 months. At each time point, femora were subjected to μ-CT analysis and biomechanical testing. A subset of caudal vertebrae was also analyzed. Following this, individual elements were assessed in bones. Serum levels of the 5b isoform of tartrate-resistant acid phosphatase (TRAP) and procollagen type I propeptide (P1NP) were also measured. Trabecular bone loss occurred in both diets (evident as early as 5 months). Cortical bone increased through month 5 and then declined. Cortical bone loss was primarily in mice on the HFWD. Inclusion of the minerals in the diet reduced bone mineral loss in both diets and improved bone strength. Bone mineral density was also enhanced by these minerals. Of several cationic minerals known to be important to bone health, only strontium was significantly increased in bone tissue from animals fed the mineral diets, but the increase was large (5-10 fold). Serum levels of TRAP were consistently higher in mice receiving the minerals, but levels of P1NP were not. These data suggest that trace minerals derived from marine red algae may be used to prevent progressive bone mineral loss in conjunction with calcium. Mineral supplementation could find use as part of an osteoporosis-prevention strategy.

Conflict of interest statement

Disclosure of Conflict: All authors state that they have no financial or personal conflict of interest (no disclosures).

Figures

Figure 1. Structural features of femoral bone

A: Trabecular/B: Cortical μ-CT parameters: Data are based on 5 mice at baseline (3 weeks of age), 10 mice at 5 and 12 months and 15 mice at 18 months in each diet 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<0.05 level is indicated by asterisks. * by the HFWD + minerals indicates statistically significant improvement relative to HFWD alone; ** by the HFWD + minerals indicates statistically significant improvement relative to control; *** by the control + minerals indicates statistically significant improvement relative to control. C: μ-CT images: A representative 3D μ-CT image of the trabecular region from the femur of a female mouse in each diet group is shown. D: Histological images: Hematoxylin and eosin-stained sections of decalcified bone (distal femoral condyles) from a mouse (at 18 months) in two high-fat diet groups are shown (Bars=200 μm).

Figure 2. Structural features of vertebral bone

A: Trabecular/B: Cortical μ-CT parameters: Data are based on 6 mice at 12 months in each diet group and 6 mice in each of the two high-fat diets at 18 months. 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<0.05 level is indicated by asterisks. * by the HFWD + minerals indicates statistically significant improvement relative to HFWD alone; ** by the HFWD + minerals indicates statistically significant improvement relative to control; *** by the control + minerals indicates statistically significant improvement relative to control. C: μ-CT images: Representative 3D μ-CT images of the cranial and middle region from a C8 vertebra of a mouse in each diet group at 12 month-time-point.

Figure 3. Biomechanical properties

A: Femora: Data are based on 5 mice at baseline (3 weeks of age), 10 mice at 5 and 12 months and 15 mice at 18 months in each diet group. B: Vertebrae: Data are based on 6 mice at 12 months in each diet group and 6 mice in each of the two high-fat diets at 18 months. 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<0.05 level is indicated by asterisks. * by the HFWD + minerals indicates statistically significant improvement relative to HFWD alone; ** by the HFWD + minerals indicates statistically significant improvement relative to control; *** by the control + minerals indicates statistically significant improvement relative to control.

Figure 4. Strontium levels in bone; Comparison with calcium, magnesium and potassium

Long bones from all mice in a group were pooled together, digested and analyzed by Inductively Coupled Plasma Optical Emission Spectrometry (ICP-OES) as one sample per diet group (10 mice per group at 5- and 12-months and 15 mice at 18-months). * is placed on diet groups with minerals and indicates statistically significant increase in the strontium level (using two-way factorial ANOVA) than the diet groups without minerals. (p<0.05)