Lanja Saleh

Renal expression of FGF23 and peripheral resistance to elevated FGF23 in rodent models of polycystic kidney disease

Fibroblast growth factor 23 (FGF23) regulates phosphate homeostasis and is linked to cardiovascular disease and all-cause mortality in chronic kidney disease. FGF23 rises in patients with CKD stages 2-3, but in patients with autosomal dominant polycystic kidney disease, the increase of FGF23 precedes the first measurable decline in renal function. The mechanisms governing FGF23 production and effects in kidney disease are largely unknown. Here we studied the relation between FGF23 and mineral homeostasis in two animal models of PKD. Plasma FGF23 levels were increased 10-fold in 4-week-old cy/+ Han:SPRD rats, whereas plasma urea and creatinine concentrations were similar to controls. Plasma calcium and phosphate levels as well as TmP/GFR were similar in PKD and control rats at all time points examined. Expression and activity of renal phosphate transporters, the vitamin D3-metabolizing enzymes, and the FGF23 co-ligand Klotho in the kidney were similar in PKD and control rats through 8 weeks of age, indicating resistance to FGF23, although phosphorylation of the FGF receptor substrate 2α protein was enhanced. In the kidneys of rats with PKD, FGF23 mRNA was highly expressed and FGF23 protein was detected in cells lining renal cysts. FGF23 expression in bone and spleen was similar in control rats and rats with PKD. Similarly, in an inducible Pkd1 knockout mouse model, plasma FGF23 levels were elevated, FGF23 was expressed in kidneys, but renal phosphate excretion was normal. Thus, the polycystic kidney produces FGF23 but is resistant to its action.

Effect of Twice-Yearly Denosumab on Prevention of Bone Mineral Density Loss in De Novo Kidney Transplant Recipients: A Randomized Controlled Trial

We conducted an open‐label, prospective, randomized trial to assess the efficacy and safety of RANKL inhibition with denosumab to prevent the loss of bone mineral density (BMD) in the first year after kidney transplantation. Ninety kidney transplant recipients were randomized 1:1 2 weeks after surgery to receive denosumab (60 mg at baseline and 6 months) or no treatment. After 12 months, total lumbar spine areal BMD (aBMD) increased by 4.6% (95% confidence interval [CI] 3.3–5.9%) in 46 patients in the denosumab group and decreased by −0.5% (95% CI −1.8% to 0.9%) in 44 patients in the control group (between‐group difference 5.1% [95% CI 3.1–7.0%], p < 0.0001). Denosumab also increased aBMD at the total hip by 1.9% (95% CI, 0.1–3.7%; p = 0.035) over that in the control group at 12 months. High‐resolution peripheral quantitative computed tomography in a subgroup of 24 patients showed that denosumab increased volumetric BMD at the distal tibia and radius (all p < 0.05). Biomarkers of bone turnover (C‐terminal telopeptide of type I collagen, procollagen type I N‐terminal propeptide) markedly decreased with denosumab (all p < 0.0001). Episodes of cystitis and asymptomatic hypocalcemia occurred more often with denosumab, whereas graft function, rate of rejections, and incidence of opportunistic infections were similar. In conclusion, denosumab increased BMD in the first year after kidney transplantation but was associated with more frequent episodes of urinary tract infection.

Lack of Associations between Female Hormone Levels and Visuospatial Working Memory, Divided Attention and Cognitive Bias across Two Consecutive Menstrual Cycles

Background: Interpretation of observational studies on associations between prefrontal cognitive functioning and hormone levels across the female menstrual cycle is complicated due to small sample sizes and poor replicability. Methods: This observational multisite study comprised data of n = 88 menstruating women from Hannover, Germany, and Zurich, Switzerland, assessed during a first cycle and n = 68 re-assessed during a second cycle to rule out practice effects and false-positive chance findings. We assessed visuospatial working memory, attention, cognitive bias and hormone levels at four consecutive time-points across both cycles. In addition to inter-individual differences we examined intra-individual change over time (i.e., within-subject effects). Results: Estrogen, progesterone and testosterone did not relate to inter-individual differences in cognitive functioning. There was a significant negative association between intra-individual change in progesterone and change in working memory from pre-ovulatory to mid-luteal phase during the first cycle, but that association did not replicate in the second cycle. Intra-individual change in testosterone related negatively to change in cognitive bias from menstrual to pre-ovulatory as well as from pre-ovulatory to mid-luteal phase in the first cycle, but these associations did not replicate in the second cycle. Conclusions: There is no consistent association between womens hormone levels, in particular estrogen and progesterone, and attention, working memory and cognitive bias. That is, anecdotal findings observed during the first cycle did not replicate in the second cycle, suggesting that these are false-positives attributable to random variation and systematic biases such as practice effects. Due to methodological limitations, positive findings in the published literature must be interpreted with reservation.

Analytical and clinical performance of the new Fujirebio 25-OH vitamin D assay, a comparison with liquid chromatography-tandem mass spectrometry (LC-MS/MS) and three other automated assays.

Abstract Background: We evaluated the analytical and clinical performance of the new Lumipulse® G 25-OH vitamin D assay from Fujirebio, and compared it to a liquid chromatography-tandem mass spectrometry (LC-MS/MS) method and three other commercial automated assays. Methods: Total 25 hydroxy vitamin D (25(OH)D) levels were measured in 100 selected serum samples from our routine analysis with Fujirebio 25(OH)D assay. The results were compared with those obtained with LC-MS/MS and three other automated 25(OH)D assays (Abbott, Beckman, and Roche). The accuracy of each assay tested was evaluated against a Labquality reference serum panel for 25(OH)D (Ref!25OHD; University of Ghent). Results: Intra- and inter-day imprecision of the Fujirebio 25(OH)D assay was <5%. Fujirebio 25(OH)D assay showed the highest correlation among the assays tested with the LC-MS/MS method (R=0.986). The mean relative bias obtained was –15.6% (Fujirebio), –12.7% (Beckman), –2.1% (Abbott) and 9.7% (Roche) as compared to LC-MS/MS. Comparison with the Labquality certified reference serum panel yielded a mean bias of –11.8% (Fujirebio), –14.1% (Beckman), 4.4% (Abbott) and 3.2% (Roche), respectively. Compared to LC-MS/MS, the sensitivity of different methods in detecting vitamin D insufficiency (<50 nmol/L) varied from 100% for the Fujirebio assay to 72.7% for Roche, and specificity ranged from 94.4% for Roche to 87.6% for Beckman. Conclusions: The Lumipulse G 25-OH vitamin D assay from Fujirebio demonstrated a good correlation with LC-MS/MS and some immunoassays. The performance of the assay is well-suited for routine 25(OH)D measurement in clinical serum samples. A correction for the observed negative bias vs. LC-MS/MS could be considered.

N-terminal pro-B-type natriuretic peptide-ratio predicts mortality after transcatheter aortic valve replacement

We studied the prognostic value of plasma N‐terminal pro‐brain natriuretic peptide (NT‐proBNP)‐ratio, which is independent of individual cutoff levels, in predicting mortality in patients undergoing transcatheter aortic valve replacement (TAVR). Background: Elevated levels of natriuretic peptides are associated with adverse outcomes across a wide spectrum of cardiovascular diseases. However, cutoff values differ according to age, gender, and body weight. Methods: 244 TAVR patients with preprocedural NT‐proBNP levels were analyzed, and the predictive value of NT‐proBNP‐ratio (measured NT‐proBNP/maximal normal NT‐proBNP values specific for age and gender) on all‐cause‐mortality was assessed in a multivariate model. Results: Median NT‐proBNP‐ratio was 4.2 [IQR 1.8–9.7]. All‐cause mortality at 30 days was 3.4% in patients with less than median NT‐proBNP‐ratio, and 14.0% in patients with more than median NT‐proBNP‐ratio (P = 0.02). All‐cause mortality at 1 year was 8.5% in patients with less than median NT‐proBNP‐ratio, and 32.1% in those with more than median NT‐proBNP‐ratio (P = 0.001). Cumulative survival declined with increasing quartiles of NT‐proBNP‐ratio (log rank P = 0.001). All patients with a NT‐proBNP‐ratio below 1.5 survived at 1‐year follow‐up. In ROC analysis, NT‐proBNP‐ratio significantly predicted 30‐day (AUC = 0.72; P = 0.002) and 1‐year all‐cause mortality (AUC = 0.72; P < 0.001). By multivariate Cox regression analysis, NT‐proBNP‐ratio, chronic obstructive pulmonary disease, and serum creatinine were the only independent predictors of all‐cause mortality. Conclusions: Elevated NT‐proBNP‐ratio was associated with increased short‐ and long‐term mortality after TAVR, and independently predicted all‐cause mortality. NT‐proBNP‐ratio should be considered in the risk stratification of patients undergoing TAVR.

Quantification of teicoplanin in plasma by LC-MS with online sample clean-up and comparison with QMS assay.

Abstract Background: Teicoplanin is a glycopeptide antibiotic used for the treatment of infections caused by Gram-positive bacteria. There is a good correlation between trough levels and clinical outcome, therefore therapeutic drug monitoring is recommended. Here we present a liquid chromatography-mass spectrometry (LC-MS) method with online extraction based on turbulent flow chromatography for the quantification of the five main components of teicoplanin, A2–1, A2–2, A2–3, A2–4, and A2–5. Methods: After online extraction, analytical chromatography was performed on a Hypersil Gold C8 column under acidic conditions. As mass spectrometer, a Q Exactive hybrid instrument was used. Samples were prepared by adding internal standard and subsequent centrifugation. Patient samples (n=125) that had previously been analyzed using a commercially available immunoassay (QMS® teicoplanin) were re-analyzed by LC-MS. Results: The imprecision was <6.9%, inaccuracy between 99.6% and 109%, for both, within- and between-day analysis. The method was shown to be free of matrix effects in the relevant time ranges and was compared to a commercially available immunoassay, QMS® teicoplanin from Thermo Fisher Scientific. The LC-MS assay produced comparable results to the QMS® assay, the correlation coefficient was 0.856 (95% confidence interval 0.800–0.896). LC-MS yielded lower concentrations than the immunoassay as could be demonstrated by the bias of −1.16 mg/L (95% confidence interval −1.90–0.43 mg/L) in the Bland-Altman analysis. Conclusions: This specific, automated, LC-MS assay for teicoplanin is suitable for therapeutic drug monitoring.

Evaluation of the new restandardized Abbott Architect 25-OH Vitamin D assay in vitamin D-insufficient and vitamin D-supplemented individuals

Recently, Abbott Diagnostics has restandardized the Architect 25(OH)D assay against the NIST SRM 2972. We have evaluated the analytical and clinical performance of the restandardized Architect 25(OH)D assay and compared its performance with a NIST‐traceable liquid chromatography‐tandem mass spectrometry (LC‐MS/MS) method and the Roche total 25(OH)D assay in vitamin D‐insufficient individuals before and after vitamin D3 supplementation.

Reference intervals for 24 laboratory parameters determined in 24-hour urine collections

Abstract Background: Reference intervals for many laboratory parameters determined in 24-h urine collections are either not publicly available or based on small numbers, not sex specific or not from a representative sample. Methods: Osmolality and concentrations or enzymatic activities of sodium, potassium, chloride, glucose, creatinine, citrate, cortisol, pancreatic α-amylase, total protein, albumin, transferrin, immunoglobulin G, α1-microglobulin, α2-macroglobulin, as well as porphyrins and their precursors (δ-aminolevulinic acid and porphobilinogen) were determined in 241 24-h urine samples of a population-based cohort of asymptomatic adults (121 men and 120 women). For 16 of these 24 parameters creatinine-normalized ratios were calculated based on 24-h urine creatinine. The reference intervals for these parameters were calculated according to the CLSI C28-A3 statistical guidelines. Results: By contrast to most published reference intervals, which do not stratify for sex, reference intervals of 12 of 24 laboratory parameters in 24-h urine collections and of eight of 16 parameters as creatinine-normalized ratios differed significantly between men and women. For six parameters calculated as 24-h urine excretion and four parameters calculated as creatinine-normalized ratios no reference intervals had been published before. For some parameters we found significant and relevant deviations from previously reported reference intervals, most notably for 24-h urine cortisol in women. Ten 24-h urine parameters showed weak or moderate sex-specific correlations with age. Conclusions: By applying up-to-date analytical methods and clinical chemistry analyzers to 24-h urine collections from a large population-based cohort we provide as yet the most comprehensive set of sex-specific reference intervals calculated according to CLSI guidelines for parameters determined in 24-h urine collections.

Voluntary intake of paracetamol-enriched drinking water and its influence on the success of embryo transfer in mice

Embryo transfer (ET) in mice is a key technique in biomedical research, and is carried out mostly via surgery by transferring founder embryos into pseudo-pregnant recipient females. To cover post-operative analgesic requirements in surrogate mothers, oral self-administration of painkillers has several advantages, but its effectiveness has also been criticized as voluntary ingestion of the drug can be uncertain. Additionally, concerns about potential negative side effects of analgesics on embryo viability and development have been raised. In this regard, we investigated the impact of orally administered analgesia by comparing the outcome of ET with and without paracetamol in the drinking water (3.5mg/ml) of surrogate mothers. Water intake increased significantly when paracetamol, as a sweet-tasting formulation (childrens syrup), was added to the drinking water. Measurements of paracetamol concentrations in blood serum confirmed reasonable drug uptake. Success rate of ETs and the body weight of newborn offspring were not different whether paracetamol was administered for two days after surgery or not. In conclusion, paracetamol in drinking water was consumed voluntarily in substantial doses, without detectable side-effects, by freshly operated surrogate mothers, and can therefore be recommended as a feasible method for providing analgesic treatment for surgical ET in mice.

Head to head evaluation of the analytical performance of two commercial methotrexate immunoassays and comparison with liquid chromatography-mass spectrometry and the former fluorescence polarization immunoassay

Abstract Background: Monitoring of plasma drug levels is mandatory in patients receiving high-dose methotrexate. This study evaluated the analytical performance of the novel Architect and the established ARK™ methotrexate immunoassay (running on the Roche Cobas© c502 analyzer) in comparison with liquid chromatography-mass spectrometry (LC-MS) and the TDx/TDxFLx Methotrexate II assay. Methods: Imprecision and linearity were verified for the Architect and ARK assay according to CLSI EP15-A3 and EP6-A guidelines, respectively. The reported limit of quantitation (0.04 μmol/L) was tested for both assays according to the CLSI EP17-A2 guideline. Correlation and agreement between the different assays were evaluated using residual plasma samples (n=153). Results: Total imprecision was <6.3% and <9.5% for the Architect and ARK assay, respectively. The claimed linearity and limit of quantitation were confirmed for the Architect assay. For the ARK assay, imprecision at the limit of quantitation was <18% with a positive bias resulting in a high total error up to 58%, and hence the linearity could not be confirmed. Both assays showed strong correlations with the TDX assay and LC-MS but a positive bias of 12.2% and 20.5% in comparison to LC-MS for the Architect and ARK assay, respectively. For the ARK assay this bias increased dramatically for samples with concentrations towards the limit of quantitation. Conclusions: The Architect assay is suitable for monitoring plasma methotrexate, but the ARK assay showed unsatisfactory performance in the analysis of low concentrated samples. Unlike the TDX assay, both assays require manual dilution of samples at higher concentrations, which delays sample processing in clinical routine.