Hepcidin-22 (human)

Background: The peptide hormone hepcidin plays a central role in regulating dietary iron absorption and body iron distribution. Many human diseases are associated with alterations in hepcidin concentrations. The measurement of hepcidin in biological fluids is therefore a promising tool in the diagnosis and management of medical conditions in which iron metabolism is affected. Content: We describe hepcidin structure, kinetics, function, and regulation. We moreover explore the therapeutic potential for modulating hepcidin expression and the diagnostic potential for hepcidin measurements in clinical practice. Summary: Cell-culture, animal, and human studies have shown that hepcidin is predominantly synthesized by hepatocytes, where its expression is regulated by body iron status, erythropoietic activity, oxygen tension, and inflammatory cytokines. Hepcidin lowers serum iron concentrations by counteracting the function of ferroportin, a major cellular iron exporter present in the membrane of macrophages, hepatocytes, and the basolateral site of enterocytes. Hepcidin is detected in biologic fluids as a 25 amino acid isoform, hepcidin-25, and 2 smaller forms, i.e., hepcidin-22 and -20; however, only hepcidin-25 has been shown to participate in the regulation of iron metabolism. Reliable assays to measure hepcidin in blood and urine by use of immunochemical and mass spectrometry methods have been developed. Results of proof-of-principle studies have highlighted hepcidin as a promising diagnostic tool and therapeutic target for iron disorders. However, before hepcidin measurements can be used in routine clinical practice, efforts will be required to assess the relevance of hepcidin isoform measurements, to harmonize the different assays, to define clinical decision limits, and to increase assay availability for clinical laboratories.

Background: Hepcidin-25 is a potential marker for iron disorders with a demand for accessible assays. This study aimed to evaluate a commercial competitive enzyme-linked immunosorbent assay (cELISA) for hepcidin quantitation. Methods: Serum samples; 95 healthy subjects (HS), six patients with iron deficiency (ID), 84 patients with liver disorders (LD) and 220 hemodialysis patients (HD), were analyzed. Controls were used for imprecision, while accuracy was evaluated by quantitating hepcidin-25 with LC-MS/MS in 149 samples. Cross-reactivity for hepcidin-20 and hepcidin-22 was tested. Hepcidin-mRNA expression in 37 liver biopsies was measured. Results: S-hepcidin ranged from 8-76 and 2-31 μg/L in healthy men and women. Levels in ID, LD and HD significantly differed from HS. Total coefficients of variation (CV) for controls were 24% and 22%. Within-sample CV was 10%. Despite a good correlation with LC-MS/MS (r = 0.89), the cELISA showed higher values and detected hepcidin-20 and hepcidin-22. Hepcidin-mRNA correlated well with S-hepcidin using cELISA and LC-MS/MS (r = 0.69 and 0.64). Conclusions: The correlation with LC-MS/MS is good and the examined kit can differentiate between patient groups although it is not specific for hepcidin-25. Considering ELISA's capacity to readily be set up, the investigated kit can be applied. Specific reference ranges are required.

Hepcidin, the iron regulatory hormone, has three isoforms; -20, -22 and -25. While hepcidin-25 has been studied extensively, the physiological significance of other isoforms remains poorly understood. Using a quantitative method based on liquid chromatography-tandem mass spectrometry (LC-tandem MS) developed by our group, we quantified hepcidin isoforms in human serum to elucidate their characteristics, and investigated the role of hepatocytes in isoform processing. Hepcidin isoforms in serum obtained from 40 healthy volunteers were quantified. Synthetic hepcidin peptides were added to healthy serum, and to HepG2 culture media, and hepcidin isoform concentrations determined. All three hepcidin isoforms were detected in human serum; however, hepcidin-25 concentrations were highest. The three hepcidin isoforms showed a strong positive correlation with each other and with serum ferritin. Additionally, while hepcidin-20 was strongly correlated with serum creatinine, the other isoforms were not. Hepcidin-20 and -25 levels were also increased in chronic kidney disease (CKD) serum. Hepcidin-22 rapidly degraded into hepcidin-20, whereas hepcidin-25 remained relatively stable. Finally, hepcidin-22 degradation into hepcidin-20 was accelerated in the presence of HepG2. This method has enabled us to reveal fundamental characteristics of the three hepcidin isoforms in serum and may be a powerful tool for quantifying hepcidin isoform expression and processing.