Liver Hepcidin mRNA Is down Regulated at High Liver Iron Burdens and up Regulated in HCV Infection in Thalassaemia.

Rationale. Hepcidin is an important negative regulator of iron absorption from the gut and iron release from macrophages. Synthesis is increased by inflammation and decreased in iron deficiency. Iron overload conditions might be predicted to up-regulate hepcidin synthesis, thereby decreasing dietary iron absorption. However in adult onset herediditary hemochromatosis, there is paradoxical down regulation of liver hepcidin mRNA (Bridle et al.,Lancet 2003). Urinary hepcidin is decreased thalassaemia major (Papanikolaou et al., Blood 2005) but expression of mRNA has not been described. However, hepcidin mRNA may be increased in iron overloaded in patients with chronic HCV infection (Aoki, et al., J Clin Gasteroenterol 2005).

Methodology. mRNA was extracted on 20 liver biopsies from thalassaemia patients and RT PCR performed from cDNA as described by Leung et al., Blood 2005. 14 biopsies were obtained from thalassaemia major (TM) patients on regular transfusion programmes and the remaining 6 from thalassaemia intermedia (TI) patients, 2 of whom were not currently receiving transfusion, 3 were on exchange transfusion regimes and one was on 6–8 weekly top up transfusions. All samples were calculated as the hepcidin/actin ratio and were measured simultaneously with liver biopsies obtained from healthy control subjects at the time of surgery. Hepcidin mRNA was then expressed relative to control values from normal liver tissue in healthy control subjects.

Results. Mean hepcidin mRNA was significantly lower in patients with liver iron concentrations >10mg/g/dw compared to those with lower burdens (85 vs 131%, p=0.05). Hepcidin mRNA did not vary significantly with anaemia, with ferritin > 3000ng/ml or <1500ng/ml (p=0.99). Hepcidin mRNA was not significantly different between the 2 thalassemia groups; TI (123 ± 47%) compared to (110 ± 73%)TM. 3 patients with high transaminase levels (>80 iu/ml) all had low hepcidin mRNA levels (77 ± 16 %) and increased levels of fibrosis compared to those with lower transaminase levels (106 ± 55%) and only mild fibrosis. 4 patients who were HCV antibody positive but with only modestly elevated transaminase levels (<160iu/ml) and mild/moderate fibrosis had raised hepcidin mRNA (163 + 70 %) p=0.02. There was no difference in the HCV positive and HCV negative groups for ferritin (2530 ng/ml: 2483 ng/ml), ALT (61 iu/l :53 iu/l) or liver iron (7.5 mg/g/dw versus 8.2 mg/g/dw).

Conclusions. This suggests a critical level of iron burden (LIC) above which hepcidin expression becomes dysregulated, failing to increase with further elevations in the iron burden and paradoxically decreases. This could lead to inappropriately high iron absorption in heavily iron-loaded patients. Of other interacting factors affecting hepcidin synthesis, this study suggests that active HCV may increase hepcidin synthesis.