In vivo animal models of body composition in aging

Area of Science:

• Biomedical science
• Animal models
• Aging research

Background:

• Assessing body elemental composition is crucial for understanding physiological changes.
• Aging in rats affects body composition, including protein and skeletal mass.
• Non-invasive in vivo techniques are needed to study these changes.

Purpose of the Study:

• To develop and apply in vivo techniques for measuring body elemental composition in aging rats.
• To investigate age-related changes in total body protein, skeletal mass, and bone microstructure.
• To correlate whole-body elemental data with regional bone analysis.

Main Methods:

• Whole-body counting for total body potassium (40K).
• In vivo neutron activation analysis for total body calcium, sodium, and chloride.
• Photon activation analysis for total body phosphorus and nitrogen.
• Computed microtomography (CMT) and synchrotron-radiation induced X-ray emission (SRIXE) for femur analysis.

Main Results:

• Total body nitrogen (protein) decreased significantly by 24 months.
• Computed microtomography showed increased bone cavities in the femur cortex with age.
• Synchrotron-radiation induced X-ray emission revealed a decreased endosteal Ca/P ratio in aging femurs.
• Total body calcium and phosphorus showed no significant age-related changes.

Conclusions:

• Aging in rats leads to substantial loss of total body protein.
• Despite stable total skeletal mass, bone microstructure and regional elemental composition significantly alter with age.
• In vivo elemental analysis combined with advanced imaging provides comprehensive insights into aging-related body composition changes.