Hyperferritinaemia is a common laboratory finding that is often associated with metabolic dysfunction and fatty liver. Metabolic hyperferritinaemia reflects alterations in iron metabolism that facilitate iron accumulation in the body and is associated with an increased risk of cardiometabolic and liver diseases. Genetic variants that modulate iron homeostasis and tissue levels of iron are the main determinants of serum levels of ferritin in individuals with metabolic dysfunction, raising the hypothesis that iron accumulation might be implicated in the pathogenesis of insulin resistance and the related organ damage. However, validated criteria for the non-invasive diagnosis of metabolic hyperferritinaemia and the staging of iron overload are still lacking, and there is no clear evidence of a benefit for iron depletion therapy. Here, we provide an overview of the literature on the relationship between hyperferritinaemia and iron accumulation in individuals with metabolic dysfunction, and on the associated clinical outcomes. We propose an updated definition and a provisional staging system for metabolic hyperferritinaemia, which has been agreed on by a multidisciplinary global panel of expert researchers. The goal is to foster studies into the epidemiology, genetics, pathophysiology, clinical relevance and treatment of metabolic hyperferritinaemia, for which we provide suggestions on the main unmet needs, optimal design and clinically relevant outcomes. Sections MethodologyGiven the high prevalence of hyperferritinaemia in clinical practice, combined with a growing understanding of the underlying pathophysiology and clinical implications, an updated definition and grading system is warranted. The overall goal of this Consensus Statement was therefore to provide a proposal for a more accurate diagnosis and classification of MHF, to be validated by prospective studies, to provide suggestions on the design of these studies and to highlight some of the main unmet research needs in the field. Owing to the current absence of robust evidence to support the recommendation to screen for and diagnose MHF and then to treat this condition with a specific approach (such as iron depletion), the current Consensus Statement is mainly directed at clinicians who work in tertiary referral centres and clinical and basic researchers. The updated MHF definition will enable larger collaborative studies on the clinical implications, pathophysiology and therapy of this condition, although it will still require prospective validation and further refinement. The long-term goal is the improvement of clinical management of patients with MHF. On the basis of current evidence, we also provide expert recommendations for clinicians on the diagnosis, management, follow-up and treatment of this condition (presented in the Supplementary material).Consensus was reached by a multidisciplinary global panel of expert researchers with an interest in MHF from five continents and 14 countries working in the fields of iron metabolism, clinical endocrinology, ...

JAK2-V617F mutation causes myeloproliferative neoplasms (MPN) that can manifest as polycythemia vera (PV), essential thrombocythemia (ET) or primary myelofibrosis (PMF). PV patients at diagnosis already exhibited iron deficiency, whereas ET patients had normal iron stores. We examined the influence of iron availability on MPN phenotype in mice expressing JAK2-V617F and in mice expressing JAK2 with a N542-E543del mutation in exon 12 (E12). At baseline on control diet, all JAK2-mutant mouse models with PV-like phenotype displayed iron deficiency, although E12 mice maintained more iron for augmented erythropoiesis than JAK2-V617F mutant mice. In contrast, JAK2-V617F mutant mice with an ET-like phenotype had normal iron stores comparable to wildtype (WT) mice. On low-iron diet, JAK2-mutant mice and WT controls increased platelet production at the expense of erythrocytes. Mice with PV phenotype responded to parenteral iron injections by decreasing platelet counts and further increasing hemoglobin and hematocrit, whereas no changes were observed in WT controls. Alterations of iron availability primarily affected the pre-megakaryocyte erythrocyte progenitors (pre-MegE), which constitute the iron-responsive stage of hematopoiesis in JAK2-mutant mice. The orally administered ferroportin inhibitor vamifeport and the minihepcidin PR73 normalized hematocrit and hemoglobin levels in JAK2-V617F and E12 mutant mouse models of PV, suggesting that ferroportin inhibitors and minihepcidins could be used in the treatment of PV patients.

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