Copper and selenium status as biomarkers of neonatal infections.

Neonatal infections are a major risk factor for neonatal mortality. A reliable diagnosis of early-onset sepsis (EOS) is hampered by the variable clinical presentations of the children. We hypothesized that changes in the Se or Cu status, or the biomarkers selenoprotein P (SELENOP) or ceruloplasmin (CP) alone or in combination may be informative of EOS. We generated a new human CP-specific non-competitive immunoassay (ELISA) suitable of analysing small sample volumes and validated the method with a commercial CP source. Using this novel CP assay, we analysed a case-control study of EOS (n = 19 control newborns, n = 18 suspected cases). Concentrations of Se, Cu, SELENOP, CP, interleukin-6 (IL-6), and C-reactive protein (CRP) along with the Cu/Se and CP/SELENOP ratios were evaluated by correlation analyses as biomarkers for EOS. Diagnostic value was estimated by receiver operating characteristic (ROC) curve analyses. The new CP-ELISA displayed a wide working range (0.10-6.78 mg CP/L) and low sample requirement (2 µL of serum, EDTA-, heparin- or citrate-plasma). Plasma CP correlated positively with Cu concentrations in the set of all samples (Pearson r = 0.8355, p < 0.0001). Three of the infected neonates displayed particularly high ratios of Cu/Se and CP/SELENOP, i.e., 3.8- to 6.9-fold higher than controls. Both the Cu/Se and the CP/SELENOP ratios correlated poorly with the early infection marker IL-6, but strongly and positively with the acute-phase protein CRP (Cu/Se-CRP: Spearman ϱ = 0.583, p = 0.011; CP/SELENOP-CRP: ϱ = 0.571, p = 0.013). The ROC curve analyses indicate that a combination of biomarkers for the Se and Cu status do not improve the early identification of EOS considerably. This study established a robust, highly precise, partly validated and scalable novel CP sandwich ELISA suitable for basic and clinical research, requiring minute amounts of sample. The ratio of circulating CP/SELENOP constitutes a promising new composite biomarker for detection of EOS, at least in a subset of severely diseased children.

Aminoglycoside-driven biosynthesis of selenium-deficient Selenoprotein P.

Selenoprotein biosynthesis relies on the co-translational insertion of selenocysteine in response to UGA codons. Aminoglycoside antibiotics interfere with ribosomal function and may cause codon misreading. We hypothesized that biosynthesis of the selenium (Se) transporter selenoprotein P (SELENOP) is particularly sensitive to antibiotics due to its ten in frame UGA codons. As liver regulates Se metabolism, we tested the aminoglycosides G418 and gentamicin in hepatoma cell lines (HepG2, Hep3B and Hepa1-6) and in experimental mice. In vitro, SELENOP levels increased strongly in response to G418, whereas expression of the glutathione peroxidases GPX1 and GPX2 was marginally affected. Se content of G418-induced SELENOP was dependent on Se availability, and was completely suppressed by G418 under Se-poor conditions. Selenocysteine residues were replaced mainly by cysteine, tryptophan and arginine in a codon-specific manner. Interestingly, in young healthy mice, antibiotic treatment failed to affect Selenop biosynthesis to a detectable degree. These findings suggest that the interfering activity of aminoglycosides on selenoprotein biosynthesis can be severe, but depend on the Se status, and other parameters likely including age and general health. Focused analyses with aminoglycoside-treated patients are needed next to evaluate a possible interference of selenoprotein biosynthesis by the antibiotics and elucidate potential side effects.

Selenium status in neonates with connatal infection.

Infectious diseases impair Se metabolism, and low Se status is associated with mortality risk in adults with critical disease. The Se status of neonates is poorly characterised, and a potential impact of connatal infection is unknown. We hypothesised that an infection negatively affects the Se status of neonates. We conducted an observational case-control study at three intensive care units at the Charité-Universitätsmedizin Berlin, Germany. Plasma samples were collected from forty-four neonates. On the basis of clinical signs for bacterial infection and concentrations of IL-6 or C-reactive protein, neonates were classified into control (n 23) and infected (n 21) groups. Plasma Se and selenoprotein P (SePP) concentrations were determined by X-ray fluorescence and ELISA, respectively, at day of birth (day 1) and 48 h later (day 3). Se and SePP showed a positive correlation in both groups of neonates. Se concentrations indicative of Se deficit in adults (500 ng/l). During antibiotic therapy, SePP increased significantly from day 1 (1·03 (sd 0·10) mg/l) to day 3 (1·34 (sd 0·10) mg/l), indicative of improved hepatic Se metabolism. We conclude that both Se and SePP are suitable biomarkers for assessing Se status in neonates and for identifying subjects at risk of deficiency.