Manganese Deficiency and Mn2O3 Nanoparticles Supplementation Disrupt Bone Remodeling and Mineral Matrix Maturation in Rats

This study aimed to investigate the effects of dietary manganese deficiency and compare the impact of manganese macroparticles (MnCO₃) and nanoparticles (Mn₂O₃NPs) on bone remodeling and metabolism. Twenty-seven male Wistar rats were divided into three groups (n = 9): control (standard MnCO₃, 65 mg Mn/kg), manganese-deficient, and Mn₂O₃NPs-supplemented (65 mg Mn/kg). After a 12-week feeding period, bone-related markers and gene expression were analyzed in the femur and blood. Mn-deficient rats showed reduced plasma levels of bone-specific alkaline phosphatase (BALP), tartrate-resistant acid phosphatase 5b (TRAP5b), interferon-β (IFN-β), RANKL glycoprotein, 1,25-dihydroxyvitamin D₃ (1,25-(OH)₂D₃), vitamin K₂, and collagen turnover markers (PINP, CTX-1, NTX). Femur levels of BALP, TRAP5b, interferon-γ (IFN-γ), osteonectin, calcitonin, PICP, PINP, and CTX-1 were also decreased. Replacing MnCO₃ with Mn₂O₃NPs increased IFN-γ but lowered IFN-β and 1,25-(OH)₂D₃ levels in plasma. This treatment also decreased the femur level of BALP and calcitonin, and the RANKL:OPG ratio, while increasing the expression level of <i>Sp7</i> and <i>Ctsk</i> genes. To conclude, our results suggest that manganese deficiency is associated with suppressed bone turnover and altered mineral metabolism. Furthermore, replacing MnCO₃ with Mn₂O₃ nanoparticles did not yield the anticipated benefits for bone remodeling, as evidenced by the observed imbalances in osteogenic and resorptive markers, indicating a need for cautious evaluation of nanoparticle-based supplementation.