Host defense peptide hepcidin 1 and iron overload differentially modulate energy, lipid, and hepatic–biliary metabolic pathways in gilthead seabream (Sparus aurata) blood

Hepcidin 1 (a host defense peptide with antimicrobial and iron-regulating properties) and iron overload are relevant in fish physiology; however, the in vivo effects of their increase in healthy fish are poorly characterised. This study evaluated the effects of intraperitoneal injections of hepcidin 1, iron (iron-dextran), and sequential treatment (iron and hepcidin 1) on the blood metabolome of gilthead seabream ( Sparus aurata ) after 10 days. Multivariate analyses revealed weak metabolomic changes in all three conditions. In all treatments, 15 chemical superclasses were conserved, with the predominance of lipids, indicating quantitative reorganisation. Energy metabolism and immune response were activated, involving lipids, fatty acids, acyl-CoA/acylcarnitines, and one‑carbon metabolism (folate/serine/methionine) linked to NAD(H)/NADP(H) and redox balance, although several associations lost robustness (non-significant FDR), consistent with the return to the homeostasis. Hepcidin 1 was associated with increased abundance of adenosine, Lys-Glu-Leu tripeptide, dodecanoylcarnitine, and phosphoethanolamines/phosphocholines (LysoPE/PE/LysoPC), and decreased levels of exogenous compounds (e.g. erythromycin C, harzianopyridone), suggesting modulation of the gut–microbiota–barrier axis or hepatic-biliary clearance. Iron overload-induced reprogramming is compatible with reactive oxygen species management, lipid remodelling, and mitochondrial fatty acid mobilisation, without markers of peroxidation, liver damage, or inflammation; herbicides (bensulfuron/sulfometuron methyl) were reduced. In the iron-hepcidin 1 group, PCA separation was not significant ( p = 0.247), suggesting an overlap or no unidirectional shift in the metabolome. In conclusion, hepcidin 1 and iron modulate energy and lipid metabolism in gilthead seabream blood, providing biomarkers for interpreting immunometabolic adaptations, although targeted validation of annotations and higher temporal resolution are required for this purpose.