Clinically relevant doses of vitamin A decrease cortical bone mass in mice

Area of Science:

• Nutritional Science
• Bone Biology
• Toxicology

Background:

• Excess vitamin A is linked to reduced bone thickness and increased fracture risk.
• Previous rodent studies used high vitamin A doses for short durations.

Purpose of the Study:

• To investigate the bone phenotype in mice after prolonged exposure to clinically relevant vitamin A doses.
• To assess the impact of varying vitamin A intake levels on bone parameters.

Main Methods:

• Mice were fed control, upper tolerable limit (UTL), or 3x UTL vitamin A diets for 1, 4, and 10 weeks.
• Bone phenotype was analyzed using micro-computed tomography, three-point bending, and dynamic histomorphometry.
• Effects were assessed in the presence and absence of bisphosphonate treatment.

Main Results:

• Supplemented vitamin A doses led to time-dependent decreases in periosteal circumference and bone mineral content.
• Cortical bone reductions resulted in decreased predicted bone strength.
• Trabecular bone remained unaffected; vitamin A decreased periosteal bone formation and endocortical circumference.

Conclusions:

• Clinically relevant doses of vitamin A negatively impact cortical bone mass.
• Osteoclast activity appears important for vitamin A's effects on cortical bone.
• Prolonged vitamin A intake poses a risk to cortical bone health.