Zinc decrease and bone metabolism in the femoral-metaphyseal tissues of rats with skeletal unloading

Area of Science:

• Bone biology
• Nutritional biochemistry
• Skeletal physiology

Background:

• Skeletal unloading, such as hindlimb suspension in rats, is a model for studying bone loss.
• Zinc is an essential trace element crucial for various cellular processes, including bone metabolism.

Purpose of the Study:

• To investigate the role of decreased zinc content in femoral-metaphyseal tissues during skeletal unloading.
• To determine if zinc deficiency contributes to altered bone metabolism in unloaded rats.

Main Methods:

• Hindlimb suspension model in rats for 4 days.
• Measurement of metaphyseal zinc content, serum zinc concentration, alkaline phosphatase activity, and deoxyribonucleic acid (DNA) content.
• In vitro experiments with metaphyseal tissues, zinc sulfate, beta-alanyl-L-histidinato zinc (AHZ), cycloheximide, and dipicolinate.

Main Results:

• Skeletal unloading significantly decreased zinc content in metaphyseal tissues.
• Zinc accumulation in metaphyseal tissues was impaired by unloading, despite higher serum zinc.
• Unloading decreased alkaline phosphatase activity and DNA content, which were restored by zinc compounds in vitro.
• Zinc's effect in vitro was dependent on newly synthesized protein and could be blocked by a zinc-chelating agent.

Conclusions:

• Reduced zinc content in femoral-metaphyseal tissues contributes to the deterioration of bone metabolism during skeletal unloading.
• Zinc plays a critical role in maintaining bone cell activity and proliferation.
• Targeting zinc levels may offer a therapeutic strategy for conditions involving skeletal unloading and bone loss.