The Nijmegen Biomedical Study is a population-based cross-sectional study conducted in the eastern part of the Netherlands. As part of the overall study, we provide reference values of estimated glomerular filtration rate (GFR) for this Caucasian population without expressed risk. Age-stratified, randomly selected inhabitants received a postal questionnaire on lifestyle and medical history. In a large subset of the responders, serum creatinine was measured. The GFR was then measured using the abbreviated Modification of Diet in Renal Disease (MDRD) formula. To limit possible bias, serum creatinine was calibrated against measurements performed in the original MDRD laboratory. The study cohort included 2823 male and 3274 female Caucasian persons aged 18-90 years. A reference population of apparently healthy subjects was selected by excluding persons with known hypertension, diabetes, cardiovascular- or renal diseases. This healthy study cohort included 1660 male subjects and 2072 female subjects, of which 869 of both genders were 65 years or older. The median GFR was 85 ml/min/1.73 m(2) in 30-to 34-year-old men and 83 ml/min/1.73 m(2) in similar aged women. In these healthy persons, GFR declined approximately 0.4 ml/min/year. Our study provides age- and gender-specific reference values of GFR in a population of Caucasian persons without identifiable risk.

Although iron is essential for living organisms to survive, its reactive properties require strict regulation in order to prevent toxic effects. Hepcidin, a liver produced peptide hormone, is thought to be the central regulator of body iron metabolism. Its production is mainly controlled by the erythropoietic activity of the bone-marrow, the amount of circulating and stored body iron, and inflammation. Recent reports, however, provide new hypotheses on how hepcidin might exert its regulatory function. Although hepcidin was first discovered in human urine and serum, most of our understanding of hepcidin regulation and action comes from in vitro and mice studies that often use hepcidin mRNA expression as a read out. The difficulties in carrying out studies in humans have mostly been due to the lack of suitable hepcidin assay. The recent development of assays to measure hepcidin in serum and urine has offered new opportunities to study hepcidin regulation in humans. However, for the moment, only a small number of laboratories are able to perform these assays. The aim of this review is to discuss insights into hepcidin regulation obtained from recent clinical studies in the light of findings from in vitro and mice studies. Ongoing studies in humans should provide us with more information on the etiology of iron metabolism disorders in order to create new therapeutic strategies and improve differential diagnosis protocols for these diseases.

The hepatic peptide hormone hepcidin is the central regulator of iron metabolism and mediator of anemia of inflammation. To date, only one specific immuno-dot assay to measure hepcidin in urine had been documented. Here we report an alternative approach for quantification of hepcidin in urine by surface-enhanced laser desorption/ionization time-of-flight mass spectrometry (SELDI-TOF-MS). Peptide peaks were detected corresponding to the 3 forms of hepcidin normally found in urine. The identity of the peptide peak equivalent to hepcidin-25 was confirmed using synthetic human hepcidin-25. Validation of our MS data on samples with various hepcidin levels showed a strong correlation with previous immuno-dot assay results (Spearman R ‫؍‬ 0.9275, P < .001). Most importantly, this hepcidin assay clearly discriminates between relevant clinical iron disorders. In conclusion, this novel MS urine hepcidin assay is easy to perform and available to a wide audience. This enables the implementation of hepcidin measurements in large clinical studies. ( IntroductionHepcidin is a small, cysteine-rich cationic peptide produced by hepatocytes, 1-3 secreted into plasma, and excreted in urine. Hepcidin expression is induced by iron stores and inflammation 3 and suppressed by hypoxia and anemia. 4 Hepcidin is proposed to be the key regulator of iron metabolism and its discovery has changed our understanding of the pathophysiology of iron disorders. It now appears that hepcidin deficiency is the cause of most types of hereditary hemochromatosis and that hepcidin excess mediates anemia of inflammation. 5 Measurements of hepcidin concentrations could therefore be useful in diagnosis of iron disorders and would provide further insight into hepcidin regulation in vivo. However, assays for hepcidin detection and quantification in plasma or urine have not been generally available, and the development of reagents has been hampered by technical difficulties. 6,7 The development of immunochemical methods based on the production of specific antihepcidin antibodies is difficult due to the small size of hepcidin (25 amino acids), conservation between animal species, 8 and the limited availability of the antigen, as the production of synthetic hepcidin in its native conformation 9 or the isolation of hepcidin from urine 2 involves complex, time-consuming procedures. To date, only one immunochemical assay was successfully used to quantify urinary hepcidin in clinical studies. 10 We sought to develop a more widely available, high-throughput assay. Here we report a new quantification method for hepcidin in urine by the use of surface-enhanced laser desorption/ionization time-of-flight mass spectrometry (SELDI-TOF-MS). This provides a fast assay with increased simplicity and accessibility that circumvents the difficulties encountered with antibody and antigen production. Moreover, this assay has also the potential to provide insight in the proportional contribution of the 3 known hepcidin isoforms that can be found in urine (hepcidin-20, -22, and -25)....

The human bowel contains a large and dynamic bacterial population that is not only essential for intestinal health, but also critical for the development of diseases such as cancer. In this respect, the Gram-positive bacterium Streptococcus bovis has been associated with colon cancer for many years. To investigate the clinical importance of this association, an immunocapture mass spectrometry assay was developed that can generate infection-related protein profiles. The composition of these profiles is governed by the capture of specific antigens by serum antibodies from colon cancer patients. This assay showed that S. bovis antigen profiles could distinguish 11 out of 12 colon cancer patients from 8 control subjects, whereas antigen profiles derived from the gut bacterium Escherichia coli were not diagnostic for colon cancer. Moreover, S. bovis antigen profiles were also detected in polyp patients, indicating that infection with this bacterium does occur early during carcinogenesis. Highly accurate tandem mass spectrometry was used to identify one of the diagnostic antigens as a surface-exposed heparin-binding protein, which might be involved in attachment of S. bovis to tumor cells. Together, these findings corroborate the hypothesis that colonic lesions provide a specific niche for S. bovis, resulting in tumor-associated ''silent'' infections. These infections, however, only become apparent in colon cancer patients with a compromised immune system (bacteremia) or coincidental cardiac valve lesions (endocarditis). This makes profiling of the humoral immune response against ''silent'' S. bovis infections a promising diagnostic tool for the early detection of human colon cancer, which is crucial for the effective treatment of this disease. ' 2006 Wiley-Liss, Inc. Key words: colon cancer; early detection; diagnostic bacterial antigens; Streptococcus bovisThe human bowel is the natural habitat for a large and dynamic bacterial community, which is essential for the control of intestinal epithelial homeostasis and human health.1,2 However, gut flora might also be an essential factor in certain diseases, including multisystem organ failure, inflammatory bowel diseases, and colon cancer.3 Although bacterial infections were originally not considered to be a major cause of cancer, accumulating evidence suggests that bacteria can induce or promote cancer by inflammation. In this model, tumor formation is caused or promoted by induction of cell proliferation and the production of mutagenic free radicals and n-nitroso compounds. In this respect, Helicobacter pylori has been the first invasive bacterium to be identified as a definite cause of gastric cancer. 4 Similarly, an association between Streptococcus bovis infection and colon cancer has been known for at least 25 years. Moreover, recent research has shown that S. bovis can promote intestinal carcinogenesis in a rat model for colon cancer.6 Certain cell surface proteins of this bacterium can induce inflammation, supporting a linkage between S. bovis, inflammation and ...