We performed a genome-wide association scan to search for sequence variants conferring risk of prostate cancer using 1,501 Icelandic men with prostate cancer and 11,290 controls. Follow-up studies involving three additional case-control groups replicated an association of two variants on chromosome 17 with the disease. These two variants, 33 Mb apart, fall within a region previously implicated by family-based linkage studies on prostate cancer. The risks conferred by these variants are moderate individually (allele odds ratio of about 1.20), but because they are common, their joint population attributable risk is substantial. One of the variants is in TCF2 (HNF1beta), a gene known to be mutated in individuals with maturity-onset diabetes of the young type 5. Results from eight case-control groups, including one West African and one Chinese, demonstrate that this variant confers protection against type 2 diabetes.

To date, concentrations of the promising biomarker hepcidin have only been assessed in serum of relatively small series of healthy volunteers and patients. We assessed age-and sex-stratified reference ranges of serum hepcidin concentration in a selected reference set and performed regression analyses to study associations between hepcidin and (biochemical) variables in a large, wellphenotyped sample of the general population (n ‫؍‬ 2998). All participants filled out a questionnaire on lifestyle, health status, and medical history. Serum measurements of iron parameters, liver enzyme alanine aminotransferase, creatinine and C-reactive protein were available. Serum hepcidin concentrations were lower for premenopausal than for postmenopausal women (median, 4.1nM vs 8.5nM, respectively). Hepcidin concentrations in men were constant over age (median, 7.8nM).

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SummaryHFE C282Y-homozygosity has been associated with low hepcidin expression, leading to increased ferritin levels. However, serum hepcidin protein levels have not been documented in humans. In the current study, we compared serum hepcidin levels of newly diagnosed HFE C282Y-homozygotes with (N = 15) and without (N = 7) elevated serum ferritin levels to levels of 40 controls (20 heterozygotes and 20 wild types). In addition, hepcidin levels of four C282Y homozygotes were investigated during the course of all phlebotomy treatment phases. Serum hepcidin levels were lower in HFE C282Y-homozygotes (median; 25th-75th percentile: 1AE88; 0AE78-2AE77 nmol/l) compared to controls (2AE74; 1AE45-5AE39). Hepcidin/ferritin ratios were also lower in homozygotes. Homozygotes with an elevated serum ferritin had a higher serum hepcidin but a lower hepcidin/ferritin ratio than those with normal ferritin (2AE28; 1AE62-3AE23 nmol/l hepcidin vs. 0AE80; 0AE60-1AE29 and 3AE63; 2AE72-7AE59 pmol hepcidin/lg ferritin vs. 13AE2; 5AE15-14AE2). Serum hepcidin decreased during the depletion phase of phlebotomy and remained low during maintenance. This study showed that serum hepcidin is innately low in HFE-related haemochromatosis. Elevated ferritin levels were associated with increased hepcidin levels while erythropoiesis lead to lower hepcidin levels. During depletion, therefore, hepcidin levels are decreased, which may exacerbate intestinal iron absorption.

Mass spectrometry (MS)-based assays for the quantification of the iron regulatory hormone hepcidin are pivotal to discriminate between the bioactive 25-amino acid form that can effectively block the sole iron transporter ferroportin and other naturally occurring smaller isoforms without a known role in iron metabolism. Here we describe the design, validation and use of a novel stable hepcidin-25+40 isotope as internal standard for quantification. Importantly, the relative large mass shift of 40 Da makes this isotope also suitable for easy-to-use medium resolution linear time-of-flight (TOF) platforms. As expected, implementation of hepcidin-25+40 as internal standard in our weak cation exchange (WCX) TOF MS method yielded very low inter/intra run coefficients of variation. Surprisingly, however, in samples from kidney disease patients, we detected a novel peak (m/z 2673.9) with low intensity that could be identified as hepcidin-24 and had previously remained unnoticed due to peak interference with the formerly used internal standard. Using a cell-based bioassay it was shown that synthetic hepcidin-24 was, like the -22 and -20 isoforms, a significantly less potent inducer of ferroportin degradation than hepcidin-25. During prolonged storage of plasma at room temperature, we observed that a decrease in plasma hepcidin-25 was paralleled by an increase in the levels of the hepcidin-24, -22 and -20 isoforms. This provides first evidence that all determinants for the conversion of hepcidin-25 to smaller inactive isoforms are present in the circulation, which may contribute to the functional suppression of hepcidin-25, that is significantly elevated in patients with renal impairment. The present update of our hepcidin TOF MS assay together with improved insights in the source and preparation of the internal standard, and sample stability will further improve our understanding of circulating hepcidin and pave the way towards further optimization and standardization of plasma hepcidin assays.