High fat diet subverts hepatocellular iron uptake determining dysmetabolic iron overload

PLoS One. 2015 Feb 3;10(2):e0116855. doi: 10.1371/journal.pone.0116855. eCollection 2015.

Abstract

Increased serum ferritin associated with mild hepatic iron accumulation, despite preserved upregulation of the iron hormone hepcidin, is frequently observed in patients with dysmetabolic overload syndrome (DIOS). Genetic factors and Western diet represent predisposing conditions, but the mechanisms favoring iron accumulation in DIOS are still unclear. Aims of this study were to assess the effect a high-fat diet (HFD) on hepatic iron metabolism in an experimental model in rats, to further characterize the effect of free fatty acids on iron metabolism in HepG2 hepatocytes in vitro, and to assess the translational relevance in patients with fatty liver with and without iron accumulation. Despite decreased uptake of dietary iron, rats fed HFD accumulated more hepatic iron than those fed regular diet, which was associated with steatosis development. Hepatic iron accumulation was paralleled by induction of ferritin, in the presence of preserved upregulation of hepcidin, recapitulating the features of DIOS. HFD was associated with increased expression of the major iron uptake protein Transferrin receptor-1 (TfR-1), consistently with upregulation of the intracellular iron sensor Iron regulated protein-1 (IRP1). Supplementation with fatty acids induced TfR-1 and IRP1 in HepG2 hepatocytes, favoring intracellular iron accumulation following exposure to iron salts. IRP1 silencing completely abrogated TfR-1 induction and the facilitation of intracellular iron accumulation induced by fatty acids. Hepatic TfR-1 mRNA levels were upregulated in patients with fatty liver and DIOS, whereas they were not associated with liver fat nor with inflammation. In conclusion, increased exposure to fatty acids subverts hepatic iron metabolism, favoring the induction of an iron uptake program despite hepatocellular iron accumulation.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Biological Transport / drug effects
  • Diet, High-Fat / adverse effects*
  • Fatty Acids / metabolism
  • Fatty Acids / pharmacology
  • Female
  • Gene Silencing
  • Hep G2 Cells
  • Hepatocytes / drug effects
  • Hepatocytes / metabolism
  • Humans
  • Iron / metabolism*
  • Iron Overload / etiology*
  • Iron Overload / metabolism*
  • Iron Regulatory Protein 1 / deficiency
  • Iron Regulatory Protein 1 / genetics
  • Liver / drug effects*
  • Liver / metabolism*
  • Liver / pathology
  • Male
  • Middle Aged
  • Non-alcoholic Fatty Liver Disease / etiology
  • Non-alcoholic Fatty Liver Disease / metabolism
  • Rats
  • Rats, Sprague-Dawley
  • Receptors, Transferrin / genetics
  • Receptors, Transferrin / metabolism
  • Up-Regulation / drug effects

Substances

  • Fatty Acids
  • Receptors, Transferrin
  • Tfrc protein, rat
  • Iron
  • Iron Regulatory Protein 1

Grants and funding

This paper was supported by the following grants: Bando Giovani Ricercatori Ricerca Finalizzata 2007, Ministero della Salute e delle Politiche Sociali (Italian ministry of Health grant; GR-2007-683265) to LV. Paola Dongiovanni was financed by Italian fiscal contribution 5X1000—2010 devolved to Fondazione IRCCS Cà Granda Ospedale Maggiore Policlinico. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. (JS 1-12-2015, SF 03738010)