A high-fat diet modulates iron metabolism but does not promote liver fibrosis in hemochromatotic Hjv-/- mice

Hemojuvelin (Hjv) is a membrane protein that controls body iron metabolism by enhancing signaling 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 wk. 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 with WT controls. The HFD reduced iron indexes 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 alpha-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.