Transferrin Deficiency Leads To Specific and Partially Reversible Iron Overload

Studies in hpx mice, a model of inherited transferrin deficiency, have demonstrated that transferrin is essential for iron delivery to the erythron and regulation of expression of hepcidin, a hormone that inhibits dietary iron absorption. Here we address two other putative roles for s transferrin. First, we determined if transferrin is essential for metabolism of metals other than iron. Metal content analysis of fractionated mouse sera indicated that iron was the most abundant metal in transferrin-rich fractions. Organ metal content analysis demonstrated severe imbalances for iron and minimal to moderate imbalances for copper, zinc and manganese in hpx tissues. Analysis of metal-dependent gene expression and organ metal content in a mouse model of inherited hepcidin excess suggested that hpx tissue imbalances in copper, zinc and manganese levels were not all physiologic or specific to primary transferrin deficiency. Second, we tested if transferrin modulates the mobilization of tissue iron stores. Transferrin treatment of hpx mice decreased iron levels in most tissues analyzed. Iron mobilization was independent of hepcidin, as iron levels decreased in hpx mice deficient in hemojuvelin, a membrane protein essential for hepcidin expression. Iron mobilization led to decreased ferritin iron and heavy chain levels. The decrease in liver ferritin iron stores did not match the decrease in total liver iron stores, suggesting that iron was mobilized from multiple storage sites. Overall, our analysis suggests that the primary consequences of transferrin deficiency are largely specific to iron and that transferrin can modulate the mobilization of tissue iron stores.