Hepcidin Expression Is Correlated with Erythropoietic Indexes and Non-Transferrin-Bound Iron Levels in Patients with Thalassemia Major.
Abstract Hepcidin plays a central role in iron homeostasis. Hepcidin seems to be the common final mediator of both erythroid and stores regulators, and coordinates intestinal iron absorption and iron release from reticuloendothelial macrophages. The erythroid regulator probably dominates over the stores regulator. Iron overload in thalassemia major is attributed mainly to blood transfusions and partly to increased iron absorption. Urine hepcidin levels in regularly-transfused thalassemia patients are inappropriately low in regards to their iron stores. Liver hepcidin expression is suppressed in the murine model of human thalassemia (Hbbth3/+). We evaluated the correlation between indexes of iron stores and of erythropoiesis and liver hepcidin expression in patients with thalassemia major. Nineteen transfusion-dependent thalassemic patients (14 females) of 20±7.2 years of age underwent liver biopsy. Fourteen patients were seronegative for hepatitis C. Liver iron concentration (LIC) was estimated by atomic absorption spectrometry. Hepcidin mRNA expression levels were estimated by quantitative Real-Time PCR (Lightcycler, Roche) from isolated RNA from liver tissue. Hematologic and blood chemistry parameters were determined by standard methods. NTBI was measured in 13 patients by atomic absorption spectrometry. Statistical analysis was performed using non-parametric tests. Hepcidin expression ranged from 0.08 to 38.4 (median 1.13) arbitrary units. The most significant correlations between hepcidin and indexes of erythropoesis and of iron load are shown on the table. Variable median (range) hepcidin LIC NTBI r = Spearman’s rho, n.s. = non statistical Ferritin (μg/L) 2174 (990–5963) n.s. n.s. n.s. Hb (g/dL) 12 (11.2 – 13.4) r:0.55, P:.017 r:-0.43, P:.071 n.s. sTfR (mg/L) 2.64 (0.75 – 5.75) r:-0.59, P:.01 r:0.51, P:.03 r:0.71, P:.006 EPO (IU/L) 21.6 (2.9 – 106) r:-0.61, P:.007 r:0.56, P:.015 r:0.63, P:.02 NTBI (μmol/L) 3.1 (0.9 – 4.5) r:0.56, P:.047 r:0.67, P:.012 LIC (μg Fe/d.w.tissue) 8.3 (3.1 – 18.9) n.s. The correlations between hepcidin and Hb, sTfR, EPO were stronger when patients with infectious hepatitis were excluded from analysis. Hepcidin did not correlate with any indexes of iron load, including LIC, ferritin, serum iron, transferrin saturation and annual transfusional iron load. Our results provide additional evidence that increased erythropoietic activity down-regulates hepcidin expression. The lack of correlation between iron stores and hepcidin expression is in consistency with the hypothesis that increased erythropoietic activity dominates over iron stores in the regulation of hepcidin expression in patients with thalassemia major. Furthermore, the negative correlation between NTBI and hepcidin RNA levels underlies the role of hepcidin in iron body trafficking even in hemosiderotic patients.
