SLC40A1 and hyperinsulinemic hypoglycemia, familial, 4: A physiological relationship between apoE and iron was further evidenced by mice studies that showed that apoE deficiency induces an age-dependent accumulation of iron in liver and spleen due to an imbalance between iron absorption via transferrin receptor 1 (TfR1) and export via ferroportin 1 (Fpn1) [83].