Dietary zinc supplementation increased TNFα and IL1β-induced RANKL expression, resulting in a decrease in bone...

Area of Science:

• Bone Metabolism
• Nutritional Biochemistry
• Mineral Metabolism

Background:

• Dietary zinc is essential for bone health.
• High zinc intake effects on bone are not fully understood.
• Understanding zinc's role in bone resorption is crucial for preventing bone loss.

Purpose of the Study:

• To investigate the impact of varying dietary zinc levels on bone metabolism in rats.
• To determine the relationship between zinc supplementation and bone mineral density.
• To elucidate the molecular mechanisms underlying zinc-induced changes in bone resorption.

Main Methods:

• Wistar rats were fed diets with 30, 300, or 3000 mg zinc/kg for 4 weeks.
• Femur zinc content, bone mineral density, and gene expression (metallothioneins, zinc transporters, inflammatory cytokines, osteoclastogenesis markers) were analyzed.
• Quantitative real-time PCR was used to assess mRNA expression levels.

Main Results:

• Femur zinc content increased with dietary zinc levels.
• Bone mineral density significantly decreased in high zinc groups (300 and 3000 mg/kg).
• Expression of metallothioneins, tumor necrosis factor α, Interleukin-1β, and key osteoclastogenesis genes (e.g., receptor activator of nuclear factor-κB ligand) were upregulated in high zinc groups.

Conclusions:

• Dietary zinc supplementation, particularly at high levels, can negatively impact bone health by decreasing bone mineral density.
• Increased bone resorption, mediated by elevated tumor necrosis factor α and Interleukin-1β, appears to be a key mechanism.
• These findings suggest a potential threshold for beneficial zinc intake in bone metabolism, with excessive intake promoting bone loss.