High-fat diet causes iron deficiency via hepcidin-independent reduction of duodenal iron absorption
ABSTRACT Obesity is often associated with disorders of iron homeostasis; however, the underlying mechanisms are not fully understood. Hepcidin is a key regulator of iron metabolism and may be responsible for obesity-driven iron deficiency. Herein, we used an animal model of diet-induced obesity to study high-fat-diet-induced changes in iron homeostasis. C57BL/6 mice were fed a standard (SD) or high-fat diet (HFD) for 8 weeks, and in addition, half of the mice received high dietary iron (Fe+) for the last 2 weeks. Surprisingly, HFD led to systemic iron deficiency which was traced back to reduced duodenal iron absorption. The mRNA and protein expressions of the duodenal iron transporters Dmt1 and Tfr1 were significantly higher in HFD- than in SD-fed mice, indicating enterocyte iron deficiency, whereas the mRNA levels of the duodenal iron oxidoreductases Dcytb and hephaestin were lower in HFD-fed mice. Neither hepatic and adipose tissue nor serum hepcidin concentrations differed significantly between SD- and HFD-fed mice, whereas dietary iron supplementation resulted in increased hepatic hepcidin mRNA expression and serum hepcidin levels in SD as compared to HFD mice. Our study suggests that HFD results in iron deficiency which is neither due to intake of energy-dense nutrient poor food nor due to increased sequestration in the reticulo-endothelial system but is the consequence of diminished intestinal iron uptake. We found that impaired iron absorption is independent of hepcidin but rather results from reduced metal uptake into the mucosa and discordant oxidoreductases expressions despite enterocyte iron deficiency.
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ABSTRACT: Curcumin has been shown to have many potentially health beneficial properties in vitro and in animal models with clinical studies on the toxicity of curcumin reporting no major side effects. However, curcumin may chelate dietary trace elements and could thus potentially exert adverse effects. Here, we investigated the effects of a 6 month dietary supplementation with 0.2% curcumin on iron, zinc, and copper status in C57BL/6J mice. Compared to non-supplemented control mice, we observed a significant reduction in iron, but not zinc and copper stores, in the liver and the spleen, as well as strongly suppressed liver hepcidin and ferritin expression in the curcumin-supplemented mice. The expression of the iron-importing transport proteins divalent metal transporter 1 and transferrin receptor 1 was induced, while hepatic and splenic inflammatory markers were not affected in the curcumin-fed mice. The mRNA expression of other putative target genes of curcumin, including the nuclear factor (erythroid-derived 2)-like 2 and haem oxygenase 1 did not differ between the groups. Most of the published animal trials with curcumin-feeding have not reported adverse effects on iron status or the spleen. However, it is possible that long-term curcumin supplementation and a Western-type diet may aggravate iron deficiency. Therefore, our findings show that further studies are needed to evaluate the effect of curcumin supplementation on iron status.02/2014; 2:563-9. DOI:10.1016/j.redox.2014.01.018
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ABSTRACT: Hemojuvelin (Hjv) is a membrane protein that controls body iron metabolism by enhancing signalling to hepcidin. Hjv mutations cause juvenile hemochromatosis, a disease of systemic iron overload. Excessive iron accumulation in the liver progressively leads to inflammation and disease, such as fibrosis, cirrhosis or hepatocellular cancer. Fatty liver (steatosis) may also progress to inflammation (steatohepatitis) and liver disease, and iron is considered as pathogenic cofactor. The aim of this study was to investigate the pathological implications of parenchymal iron overload due to Hjv ablation in the fatty liver. Wild-type (wt) and Hjv-/- mice on C57BL/6 background were fed a standard chow, a high fat diet (HFD) or a HFD supplemented with 2% carbonyl iron (HFD+Fe) for 12 weeks. The animals were analyzed for iron and lipid metabolism. As expected, all Hjv-/- mice manifested higher serum and hepatic iron, and diminished hepcidin levels compared to wt controls. The HFD reduced iron indices and promoted liver steatosis in both wt and Hjv-/- mice. Notably, steatosis was attenuated in Hjv-/- mice on the HFD+Fe regimen. Hjv-/- animals gained less body weight and exhibited reduced serum glucose and cholesterol levels. Histological and ultrastructural analysis revealed absence of iron-induced inflammation or liver fibrosis, despite early signs of liver injury (expression of α smooth muscle actin). We conclude that parenchymal hepatic iron overload does not suffice to trigger progression of liver steatosis to steatohepatitis or fibrosis in C57BL/6 mice. Copyright © 2014, American Journal of Physiology- Gastrointestinal and Liver Physiology.AJP Gastrointestinal and Liver Physiology 12/2014; 308(4):ajpgi.00137.2014. DOI:10.1152/ajpgi.00137.2014 · 3.74 Impact Factor
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ABSTRACT: Elevated iron stores as indicated by hyperferritinemia with normal or mildly elevated transferrin saturation and mostly mild hepatic iron deposition are a characteristic finding in subjects with non-alcoholic fatty liver disease (NAFLD). Excess iron is observed in approximately one third of NAFLD patients and is commonly referred to as the “dysmetabolic iron overload syndrome”. Clinical evidence suggests that elevated body iron stores aggravate the clinical course of NAFLD with regard to liver-related and extrahepatic disease complications which relates to the fact that excess iron catalyses the formation of toxic hydroxylradicals subsequently resulting in cellular damage. Iron removal improves insulin sensitivity, delays the onset of type 2 diabetes mellitus, improves pathologic liver function tests and likewise ameliorates NAFLD histology. Several mechanisms contribute to pathologic iron accumulation in NAFLD. These include impaired iron export from hepatocytes and mesenchymal Kupffer cells as a consequence of imbalances in the concentrations of iron regulatory factors, such as hepcidin, cytokines, copper or other dietary factors. This review summarizes the knowledge about iron homeostasis in NAFLD and the rationale for its therapeutic implications.