Upregulation Of Hepcidin Expression By Lactoferrin Administration To Pre-Weanling Mice

Hepcidin is a peptide hormone produced in hepatocytes which regulates dietary iron absorption and systemic iron distribution. The hepatic expression of the hepcidin gene is regulated by signals which reflect body iron status and erythropoietic activity. The regulation of hepcidin by iron status includes a signal from the circulating transferrin via hepatocellular transferrin receptor (TfR2). Lactoferrin is a member of the transferrin family of iron-binding glycoproteins found in high concentrations in milk. Lactoferrin has a well described role in host defense; however, its in iron metabolism is less clear. Like transferrin, lactoferrin will deliver iron to hepatocytes but unlike transferrin, lactoferrin cannot deliver iron to erythroid cells. Lactoferrin does not interact with TfR1 or TfR2. We took advantage of these properties of lactoferrin to determine if delivering iron to the liver (but not erythron) in a form which is independent on transferrin and its receptors could regulate hepcidin.

To take advantage of the naturally-occuring low iron and low hepcidin states at this developmental stage, experiments were performed on pre-weanling mice. Mice at 12-14d (pre-weanling) were administered human lactoferrin equivalent to 2 mg/kg iron (n=10) or carrier (n=10) intraperitoneally (IP) and sacrificed 6 h later. Other mice were administered a comparable IP dose of transferrin (n=5) or carrier (n=4). Additional groups of mice were delivered Lf (n=8) or carrier (n=7) enterally (by orogastric tube), and the sacrificed 6h or 24h later. Liver hepcidin (Hamp1) mRNA was measured by real-time RT-PCR, normalized to beta actin expression, and analyzed by commercial software (Rest 2007, Qiagen). Liver iron distribution was determined histochemically in tissue sections by modified Perls' staining.

Parenteral administration of lactoferrin in pre-weanling mice was associated with a 32-fold increase in liver Hamp1 expression after 6 hours (P<0.001). This compares with an only 4.5 fold increase in Hamp1 expression 6h after a comparable dose of transferrin. Enteral lactoferrin likewise resulted in a ∼30-fold increase in Hamp1 expression (P<0.005) after 24 hours. Iron delivered to the liver from lactoferrin was distributed in sinusoidal lining cells as well as hepatocytes.

Exogenously administered iron-rplete lactoferrin increases liver Hamp1 expression in pre-weanling mice. These observations demonstrate that iron delivery to the liver in a form not dependent upon transferrin or its receptors upregulates hepcidin expression. These findings moreover raise the possibility that lactoferrin-mediated changes in hepcidin expression may contribute to reported benefits of supplemental lactoferrin on host defense.

No relevant conflicts of interest to declare.