Iron homeostasis. Mechanisms of absorption, uptake and regulation

Iron is an essential nutrient required by every living being. This transition metal is involved in the majority of the metabolic processes, partly because of its ability to reversibly and readily cycle between ferrous (Fe2+) and ferric (Fe3+) oxidation states, Iron must be transported and stored as a component of protein complexes. Ferric ions circulate bound to plasma protein transferrin and accumulate within cells in the form of ferritin or hemosiderin. This is due to the fact that iron as a free cation can participate in a number of reactions to produce free radical species, which in turn can severely damage organs. Taking into account that both iron deficiency and iron overload are deleterious, a strict balance between iron absorption and utilization is required. In this work, the distinct pathways of gastrointestinal absorption and cellular uptake of iron are reviewed, giving details of the mechanisms involved in iron homeostasis under different conditions. Condition of iron deficiency and overload are discussed in terms of mechanisms leading to restoration of iron homeostasis.