Mechanistic insights into osteotoxicity induced by early-life lead exposure: Evidence from metabolomics and network toxicology.

Early-life lead (Pb) exposure is associated with long-term skeletal deficits, but the underlying metabolic mechanisms remain unclear. This study investigated chronic osteotoxicity and its mechanisms in Sprague-Dawley rats exposed to lead acetate (2 or 4 mmol/L) in drinking water for four weeks from postnatal day 28. Samples were collected at 2, 6, and 12 months of age. Bone mass and trabecular microarchitecture were assessed by micro-computed tomography and histopathology. Pb and calcium levels in blood and bone were quantified, and serum metabolic profiles were characterized using untargeted liquid chromatography-mass spectrometry. Metabolite-target-pathway interactions were analyzed through network toxicology. Results showed that Pb exposure caused time- and dose-dependent skeletal injury, characterized by progressive bone mass loss, trabecular rarefaction, and marrow vacuolization. Bone Pb exhibited a dynamic "deposition-remobilization" pattern, peaking after exposure, declining at 6 months, and rebounding at 12 months. Metabolomics identified glycerophospholipid and arachidonic acid (AA) metabolism as primarily perturbed pathways. The log₂(PGD₂/TXB₂) ratio was markedly reduced in the high-dose group at 12 months, indicating a shift toward pro-osteoclastic signaling. Network toxicology highlighted PI3K-Akt, FoxO, and HIF-1 pathways as potential downstream mediators of Pb-induced osteotoxicity, and femoral RT-qPCR showed increased Akt1 and Sod2 mRNA expression in the high-dose group, supporting PI3K-Akt/FoxO-related responses. Overall, early-life Pb exposure disrupts lipid homeostasis and the "glycerophospholipid-AA-eicosanoid" axis, uncoupling bone formation and resorption and leading to long-term bone loss. These findings provide novel mechanistic insights into Pb-induced osteotoxicity and suggest potential targets for early preventive interventions.