The effects of erythropoetic activity and iron burden on hepcidin expression in patients with thalassemia major.

Hepcidin production is homeostatically regulated by iron stores, anemia and hypoxia. We evaluated the effect of iron overload and of ineffective erythropoeisis on hepcidin expression in patients with thalassemia major. Liver hepcidin mRNA levels correlated with hemoglobin concentration and inversely correlated with serum transferrin receptor, erythropoietin and non-transferrin-bound iron. They did not correlate with indices of iron load. Urinary hepcidin levels were disproportionably suppressed in regards to iron burden. We conclude that hepcidin expression is regulated mainly by increased erythropoietic activity rather than by iron load and that hepcidin plays a central regulatory role in iron circulation and iron toxicity in patients with thalassemia.

Hereditary hyperferritinemia cataract syndrome in three unrelated families of western Greek origin caused by the C39 > G mutation of L-ferritin IRE.

Hereditary hyperferritinemia-cataract syndrome (HHCS) is a well-characterized autosomal dominant disease caused by mutations in the iron responsive element (IRE) of ferritin L-chain (FTL) mRNA. Mutations in the IRE result in reduced binding of the trans-acting iron regulatory proteins (IRPs) and hence in upregulation of ferritin L-chain synthesis. The disease is characterized by increased L-ferritin in serum and tissues and early onset of bilateral cataracts. Iron metabolism is normal, and there is no tissue iron overload. At least 25 nucleotide substitutions and deletions in the L-ferritin IRE have been described in families with HHCS, originating from diverse European, Australian and North American populations. We studied the molecular pathogenesis of HHCS in three unrelated kinderships of western Greek origin, with 19 affected members. We identified a relatively rare C39G mutation located in the hexanucleotide loop of L-ferritin IRE. Computational analysis of mRNA folding of mutant FTL IRE predicted that the C39 > G mutation leads to a rearrangement of base pairing in this critical region, which is likely to modify the IRP binding affinity. All subjects with HHCS were heterozygotes for the same C39G mutation. Clinical and laboratory phenotypes were described. Moreover, there was evidence of an association between this FTL IRE stem-loop mutation and very high ferritin levels. Our findings broaden the list of populations where HHCS has been described.

Hepcidin in iron overload disorders.

Hepcidin is the principal regulator of iron absorption in humans. The peptide inhibits cellular iron efflux by binding to the iron export channel ferroportin and inducing its internalization and degradation. Either hepcidin deficiency or alterations in its target, ferroportin, would be expected to result in dysregulated iron absorption, tissue maldistribution of iron, and iron overload. Indeed, hepcidin deficiency has been reported in hereditary hemochromatosis and attributed to mutations in HFE, transferrin receptor 2, hemojuvelin, and the hepcidin gene itself. We measured urinary hepcidin in patients with other genetic causes of iron overload. Hepcidin was found to be suppressed in patients with thalassemia syndromes and congenital dyserythropoietic anemia type 1 and was undetectable in patients with juvenile hemochromatosis with HAMP mutations. Of interest, urine hepcidin levels were significantly elevated in 2 patients with hemochromatosis type 4. These findings extend the spectrum of iron disorders with hepcidin deficiency and underscore the critical importance of the hepcidin-ferroportin interaction in iron homeostasis.

Prevalence of the G320V mutation of the HJV gene, associated with juvenile hemochromatosis, in Greece.

Mutations of the HJV gene, which maps on chromosome 1q21, underlie most cases of juvenile hemochromatosis. We evaluated the frequency of the most common mutation (G320V) of the HJV gene in the Greek population, since 50% of cases of hereditary hemochromatosis in Greece carry mutations of the HJV gene.

The impact of the mutations of the HFE gene and of the SLC11A3 gene on iron overload in Greek thalassemia intermedia and beta(s)/beta(thal) anemia patients.

In this study, we evaluated the impact of mutations of the HFE and ferroportin gene on iron overload in thalassemia intermedia and betas/betathal patients. Neither HFE (C282Y and H63D) nor ferroportin(Val162del) mutations were determinants of total body iron status, as assessed by ferritin levels, in either group of patients.

Mutations in HFE2 cause iron overload in chromosome 1q-linked juvenile hemochromatosis.

Juvenile hemochromatosis is an early-onset autosomal recessive disorder of iron overload resulting in cardiomyopathy, diabetes and hypogonadism that presents in the teens and early 20s (refs. 1,2). Juvenile hemochromatosis has previously been linked to the centromeric region of chromosome 1q (refs. 3-6), a region that is incomplete in the human genome assembly. Here we report the positional cloning of the locus associated with juvenile hemochromatosis and the identification of a new gene crucial to iron metabolism. We finely mapped the recombinant interval in families of Greek descent and identified multiple deleterious mutations in a transcription unit of previously unknown function (LOC148738), now called HFE2, whose protein product we call hemojuvelin. Analysis of Greek, Canadian and French families indicated that one mutation, the amino acid substitution G320V, was observed in all three populations and accounted for two-thirds of the mutations found. HFE2 transcript expression was restricted to liver, heart and skeletal muscle, similar to that of hepcidin, a key protein implicated in iron metabolism. Urinary hepcidin levels were depressed in individuals with juvenile hemochromatosis, suggesting that hemojuvelin is probably not the hepcidin receptor. Rather, HFE2 seems to modulate hepcidin expression.

Arthropathy in juvenile hemochromatosis.

OBJECTIVE: To evaluate whether arthropathy is associated with juvenile hemochromatosis and, if so, to assess the relationship between this feature and other clinical features of the disease. METHODS: Clinical, laboratory, and radiologic evidence of arthropathy was studied in 8 Greek patients with genetically proven juvenile hemochromatosis. Osteopenia and osteoporosis were assessed by bone mineral density measurement. RESULTS: Seven of the 8 patients had articular manifestations. The main affected joint was the metacarpophalangeal joint, and the arthritis was progressive independent of phlebotomy therapy. Osteopenia was observed in 2 patients, and osteoporosis in 2 patients. CONCLUSION: Arthropathy may be present in patients with juvenile hemochromatosis, with features similar to those found in patients with hemochromatosis type 1.