[New insights on a long-known element - iron, hepcidin and inflammation].

Iron (Fe) is an essential trace element. In daily veterinary practice, it plays a pivotal role e. g. due to its role in Fe deficiency anaemia. The bioavailability of Fe, for example for heme and hemoglobin synthesis, sets high demands on Fe homeostasis. The discovery of hepcidin as being an important regulative protein made a hormone-like regulation of the Fe metabolism evident. Hepcidin is synthesized by the liver and regulates the trans-membranous Fe-transporter ferroportin. An increase of hepcidin leads to a decrease of Fe export from the cell into the extracellular space, the consequence being an internalisation of Fe in the reticuloendothelial system as well as in mononuclear cells. Additionally, enteral Fe uptake decreases. The induction of hepatic hepcidin synthesis seems to be caused by high Fe- and transferrin concentrations in plasma. In addition to this, an increase of cytokines during inflammation similarly triggers hepatic hepcidin synthesis. This finding offers an explanation for the frequently observed decrease of Fe in serum/plasma during acute inflammation, the mechanism thus being termed as cytokine-hepcidin-link. Based on the fact that numerous pathogens require Fe for their own metabolism, internalisation of Fe into the intracellular compartment during inflammation has hence been categorised as being a part of the innate immunity. Iron supplementation, initiated by the veterinarian or the farmer, interferes with this regulation. Currently however, there is a lack of knowledge regarding the clinical and metabolic impacts of parenteral or oral Fe supplementation to farm animals. Therefore, the acquisition of added scientific data via prospective studies is warranted. In consequence, novel findings may lead to a reassessment of Fe supplementation strategies for ruminants, pigs and/or horses.