Combined effects of protein deficiency and hypoxia on bone mechanical properties in growing rats

Background: Protein deficiency and chronic exposure to hypoxia produce negative effects on body mass and bone mechanical properties. Objective: To explore the combined effect on body mass and bone mechanical properties of high altitude (SHA) and isocaloric protein-deficient diets in growing rats. Methods: Young female rats were assigned to 8 groups with different protein concentration (20, 15, 10, and 5%) under normoxic/hypoxic conditions. Bone structural properties were evaluated in the femoral media diaphysis using the 3-point bending test. Architectural and material properties were calculated, including the degree of mineralization. Results: Body mass growth rate was negatively affected in rats exposed to SHA following protein deficiency. Similar results were observed for structural and architectural properties whereas material properties showed no statistical difference. Interaction was found between protein deficiency and hypoxia. Conclusions: The effects are non-additive, but they show saturation, that is, the combined negative effect of hypoxia and malnutrition is lower than separate treatments. Intrinsic quality of the material is not altered by the treatments.