@misc{HocherOberthuerSlowinskietal.2017, author = {Hocher, Berthold and Oberth{\"u}r, Dominik and Slowinski, Torsten and Querfeld, Uwe and Schaefer, Franz and Doyon, Anke and Tepel, Martin and Roth, Heinz J. and Gr{\"o}n, Hans J. and Reichetzeder, Christoph and Betzel, Christian and Armbruster, Franz Paul}, title = {Modeling of oxidized PTH (oxPTH) and non-oxidized PTH (n-oxPTH) receptor binding and relationship of oxidized to non-oxidized PTH in children with chronic renal failure, adult patients on hemodialysis and kidney transplant recipients}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-399980}, pages = {12}, year = {2017}, abstract = {Background: The biological properties of oxidized and non-oxidized PTH are substantially different. Oxidized PTH (oxPTH) loses its PTH receptor-stimulating properties, whereas non-oxidized PTH (n-oxPTH) is a full agonist of the receptor. This was described in more than 20 well published studies in the 1970(s) and 80(s). However, PTH oxidation has been ignored during the development of PTH assays for clinical use so far. Even the nowadays used third generation assay systems do not consider oxidation of PTH. We recently developed an assay to differentiate between oxPTH and n-oxPTH. In the current study we established normal values for this assay system. Furthermore, we compare the ratio of oxPTH to n-oxPTH in different population with chronic renal failure: 620 children with renal failure stage 2-4 of the 4C study, 342 adult patients on dialysis, and 602 kidney transplant recipients. In addition, we performed modeling of the interaction of either oxPTH or n-oxPTH with the PTH receptor using biophysical structure approaches. Results: The children had the highest mean as well as maximum n-oxPTH concentrations as compared to adult patients (both patients on dialysis as well as kidney transplant recipients). The relationship between oxPTH and n-oxPTH of individual patients varied substantially in all three populations with renal impairment. The analysis of n-oxPTH in 89 healthy control subjects revealed that n-oxPTH concentrations in patient with renal failure were higher as compared to healthy adult controls (2.25-fold in children with renal failure, 1.53-fold in adult patients on dialysis, and 1.56-fold in kidney transplant recipients, respectively). Computer assisted biophysical structure modeling demonstrated, however, minor sterical- and/or electrostatic changes in oxPTH and n-oxPTH. This indicated that PTH oxidation may induce refolding of PTH and hence alters PTH-PTH receptor interaction via oxidation induced three-dimensional structure alteration of PTH. Conclusion: A huge proportion of circulating PTH measured by current state-of-the-art assay systems is oxidized and thus not biologically active. The relationship between oxPTH and n-oxPTH of individual patients varied substantially. Non-oxidized PTH concentrations are 1.5 - 2.25 fold higher in patients with renal failure as compared to health controls. Measurements of n-oxPTH may reflect the hormone status more precise. The iPTH measures describes most likely oxidative stress in patients with renal failure rather than the PTH hormone status. This, however, needs to be demonstrated in further clinical studies.}, language = {en} } @inproceedings{ScholzePetersenHocheretal.2014, author = {Scholze, Alexandra and Petersen, Lise and Hocher, Berthold and Rasmussen, Lars M. and Tepel, Martin}, title = {Role of fibroblast growth factor-23 and soluble alpha klotho in chronic kidney disease}, series = {Nephrology, dialysis, transplantation}, volume = {29}, booktitle = {Nephrology, dialysis, transplantation}, publisher = {Oxford Univ. Press}, address = {Oxford}, issn = {0931-0509}, pages = {120 -- 121}, year = {2014}, language = {en} } @article{ScholzeLiuPedersenetal.2014, author = {Scholze, Alexandra and Liu, Ying and Pedersen, Lise and Xia, Shengqiang and Roth, Heinz J. and Hocher, Berthold and Rasmussen, Lars Melholt and Tepel, Martin}, title = {Soluble alpha-Klotho and its relation to kidney function and fibroblast growth factor-23}, series = {The journal of clinical endocrinology \& metabolism}, volume = {99}, journal = {The journal of clinical endocrinology \& metabolism}, number = {5}, publisher = {Endocrine Society}, address = {Washington}, issn = {0021-972X}, doi = {10.1210/jc.2013-4171}, pages = {E855 -- E861}, year = {2014}, abstract = {Context: Relations between fibroblast growth factor-23 (FGF-23), soluble alpha-klotho (s-alpha-klotho), and kidney function in chronic kidney disease (CKD) are still unclear. Especially the role of s-alpha-klotho requires further study. Objectives: Our objectives were to analyze the relation of s-alpha-klotho to estimated glomerular filtration rate (eGFR), FGF-23, and other parameters of calcium-phosphate metabolism and to investigate the response of s-alpha-klotho to cholecalciferol. Patients, Design, and Setting: Twenty-four CKD (stage 1-5) patients participated in this 8-week randomized controlled trial (vitamin D and chronic renal insufficiency). Interventions: Interventions included 40 000 IU cholecalciferol or placebo weekly. Main Outcome Measure: S-alpha-klotho was determined by ELISA with antihuman klotho antibodies 67G3 and 91F1. Results: For all patients, s-alpha-klotho concentrations did not differ between CKD stages. When patients were subdivided based on FGF-23 concentrations, a positive association of s-alpha-klotho with eGFR became apparent in patients with lower than median FGF-23 concentrations but not in those above median value. Patients with s-alpha-klotho below 204 pg/mL showed higher age, lower phosphate clearance, and lower bone-specific alkaline phosphatase compared with patients with higher s-alpha-klotho. Treatment with cholecalciferol significantly increased 1,25-dihydroxyvitamin D. The increase of FGF-23 had only borderline significance. There was no significant effect of high-dose cholecalciferol administration for 8 weeks on plasma s-alpha-klotho. Conclusions: CKD patients with s-alpha-klotho below 204 pg/mL had higher age, lower phosphate clearance, and lower bone-specific alkaline phosphatase. An association of s-alpha-klotho with eGFR was observed only in the presence of close to normal, but not high, FGF-23 concentrations. Cholecalciferol treatment did not change s-alpha-klotho concentrations.}, language = {en} } @article{HocherOberthuerSlowinskietal.2013, author = {Hocher, Berthold and Oberth{\"u}r, Dominik and Slowinski, Torsten and Querfeld, Uwe and Sch{\"a}fer, Franz and Doyon, Anke and Tepel, Martin and Roth, Heinz J. and Gr{\"o}n, Hans J. and Reichetzeder, Christoph and Betzel, Christian and Armbruster, Franz Paul}, title = {Modeling of Oxidized PTH (oxPTH) and Non-oxidized PTH (n-oxPTH) Receptor Binding and Relationship of Oxidized to Non-Oxidized PTH in Children with Chronic Renal Failure, Adult Patients on Hemodialysis and Kidney Transplant Recipients}, series = {Kidney \& blood pressure research : official organ of the Gesellschaft f{\"u}r Nephrologie}, volume = {37}, journal = {Kidney \& blood pressure research : official organ of the Gesellschaft f{\"u}r Nephrologie}, number = {4-5}, publisher = {Karger}, address = {Basel}, issn = {1420-4096}, doi = {10.1159/000350149}, pages = {240 -- 251}, year = {2013}, abstract = {Background: The biological properties of oxidized and non-oxidized PTH are substantially different. Oxidized PTH (oxPTH) loses its PTH receptor-stimulating properties, whereas non-oxidized PTH (n-oxPTH) is a full agonist of the receptor. This was described in more than 20 well published studies in the 1970(s) and 80(s). However, PTH oxidation has been ignored during the development of PTH assays for clinical use so far. Even the nowadays used third generation assay systems do not consider oxidation of PTH. We recently developed an assay to differentiate between oxPTH and n-oxPTH. In the current study we established normal values for this assay system. Furthermore, we compare the ratio of oxPTH to n-oxPTH in different population with chronic renal failure: 620 children with renal failure stage 2-4 of the 4C study, 342 adult patients on dialysis, and 602 kidney transplant recipients. In addition, we performed modeling of the interaction of either oxPTH or n-oxPTH with the PTH receptor using biophysical structure approaches. Results: The children had the highest mean as well as maximum n-oxPTH concentrations as compared to adult patients (both patients on dialysis as well as kidney transplant recipients). The relationship between oxPTH and n-oxPTH of individual patients varied substantially in all three populations with renal impairment. The analysis of n-oxPTH in 89 healthy control subjects revealed that n-oxPTH concentrations in patient with renal failure were higher as compared to healthy adult controls (2.25-fold in children with renal failure, 1.53-fold in adult patients on dialysis, and 1.56-fold in kidney transplant recipients, respectively). Computer assisted biophysical structure modeling demonstrated, however, minor sterical- and/or electrostatic changes in oxPTH and n-oxPTH. This indicated that PTH oxidation may induce refolding of PTH and hence alters PTH-PTH receptor interaction via oxidation induced three-dimensional structure alteration of PTH. Conclusion: A huge proportion of circulating PTH measured by current state-of-the-art assay systems is oxidized and thus not biologically active. The relationship between oxPTH and n-oxPTH of individual patients varied substantially. Non-oxidized PTH concentrations are 1.5 - 2.25 fold higher in patients with renal failure as compared to health controls. Measurements of n-oxPTH may reflect the hormone status more precise. The iPTH measures describes most likely oxidative stress in patients with renal failure rather than the PTH hormone status. This, however, needs to be demonstrated in further clinical studies.}, language = {en} } @inproceedings{HenzeRailaScholzeetal.2013, author = {Henze, Andrea and Raila, Jens and Scholze, Alexandra and Schweigert, Florian J. and Tepel, Martin}, title = {Administration of N-Acetylcyteine causes beneficial posttranslationalmodifications of transthyretin in hemodialysis patients}, series = {Nephrology, dialysis, transplantation}, volume = {28}, booktitle = {Nephrology, dialysis, transplantation}, number = {2}, publisher = {Oxford Univ. Press}, address = {Oxford}, issn = {0931-0509}, pages = {164 -- 164}, year = {2013}, language = {en} } @inproceedings{HocherArmbrusterScholzeetal.2013, author = {Hocher, Berthold and Armbruster, Franz Paul and Scholze, Alexandra and Marckmann, Peter and Reichetzeder, Christoph and Roth, Heinz J{\"u}rgen and Tepel, Martin}, title = {Non-oxidized, biological active parathyroid hormone determines motality in hemodialsysis patients}, series = {Nephrology, dialysis, transplantation}, volume = {28}, booktitle = {Nephrology, dialysis, transplantation}, publisher = {Oxford Univ. Press}, address = {Oxford}, issn = {0931-0509}, pages = {33 -- 33}, year = {2013}, language = {en} } @article{HenzeRailaScholzeetal.2013, author = {Henze, Andrea and Raila, Jens and Scholze, Alexandra and Zidek, Walter and Tepel, Martin and Schweigert, Florian J.}, title = {Does N-Acetylcysteine modulate post-translational modifications of transthyretin in hemodialysis patients?}, series = {Antioxidants \& redox signaling}, volume = {19}, journal = {Antioxidants \& redox signaling}, number = {11}, publisher = {Liebert}, address = {New Rochelle}, issn = {1523-0864}, doi = {10.1089/ars.2012.5125}, pages = {1166 -- 1172}, year = {2013}, abstract = {It is assumed that effects of the thiol antioxidant N-acetylcysteine (NAC) are mediated by interaction with protein-associated cysteine residues, however, information on protein level in vivo are missing. Therefore, we analyzed NAC-induced modifications of the protein transthyretin (TTR) in plasma of hemodialysis patients in a randomized, placebo-controlled study. TTR was selected due to its low molecular weight and the free cysteine residue in the polypeptide chain, which is known to be extensively modified by formation of mixed disulfides. The intravenous application of NAC during a hemodialysis session resulted in a substantial increase of native TTR from median 15\% (range 8.8\%-30\%) to median 40\% (37-50) and reduction of S-cysteinylated TTR [51\% (44-60) vs. 6.6\% (2.4-10)]. Additionally the pronounced formation of a TTR-NAC adduct was detected. However, all these modifications seemed to be reversible. Additionally, in vitro incubation of plasma with NAC confirmed the in vivo results and indicated that changes in post-translational modification pattern of TTR were a function of NAC concentration. Based on these observations and the essential metabolic and biochemical role of protein-associated cysteine residues we hypothesize that the interaction of NAC with proteins may explain altered protein functions due to modification of cysteine residues. Antioxid. Redox Signal. 19, 1166-1172.}, language = {en} } @article{TepelArmbrusterGroenetal.2013, author = {Tepel, Martin and Armbruster, Franz Paul and Groen, Hans Juergen and Scholze, Alexandra and Reichetzeder, Christoph and Roth, Heinz J{\"u}rgen and Hocher, Berthold}, title = {Nonoxidized, biologically active parathyroid hormone determines mortality in hemodialysis patients}, series = {The journal of clinical endocrinology \& metabolism}, volume = {98}, journal = {The journal of clinical endocrinology \& metabolism}, number = {12}, publisher = {Endocrine Society}, address = {Chevy Chase}, issn = {0021-972X}, doi = {10.1210/jc.2013-2139}, pages = {4744 -- 4751}, year = {2013}, abstract = {Background: It was shown that nonoxidized PTH (n-oxPTH) is bioactive, whereas the oxidation of PTH results in a loss of biological activity. Methods: In this study we analyzed the association of n-oxPTH on mortality in hemodialysis patients using a recently developed assay system. Results: Hemodialysis patients (224 men, 116 women) had a median age of 66 years. One hundred seventy patients (50\%) died during the follow-up period of 5 years. Median n-oxPTH levels were higher in survivors (7.2 ng/L) compared with deceased patients (5.0 ng/L; P = .002). Survival analysis showed an increased survival in the highest n-oxPTH tertile compared with the lowest n-oxPTH tertile (chi(2), 14.3; P = 0008). Median survival was 1702 days in the highest n-oxPTH tertile, whereas it was only 453 days in the lowest n-oxPTH tertile. Multivariable-adjusted Cox regression showed that higher age increased odds for death, whereas higher n-oxPTH reduced the odds for death. Another model analyzing a subgroup of patients with intact PTH (iPTH) concentrations at baseline above the upper normal range of the iPTH assay (70 ng/L) revealed that mortality in this subgroup was associated with oxidized PTH but not with n-oxPTH levels. Conclusions: The predictive power of n-oxPTH and iPTH on the mortality of hemodialysis patients differs substantially. Measurements of n-oxPTH may reflect the hormone status more precisely. The iPTH-associated mortality is most likely describing oxidative stress-related mortality.}, language = {en} } @article{HenzeFreyRailaetal.2010, author = {Henze, Andrea and Frey, Simone K. and Raila, Jens and Scholze, Alexandra and Spranger, Joachim and Weickert, Martin O. and Tepel, Martin and Zidek, Walter and Schweigert, Florian J.}, title = {Alterations of retinol-binding protein 4 species in patients with different stages of chronic kidney disease and their relation to lipid parameters}, issn = {0006-291X}, doi = {10.1016/j.bbrc.2010.01.082}, year = {2010}, abstract = {Retinol-binding protein 4 (RBP4) is elevated in patients with chronic kidney disease (CKD) and has been discussed as marker of kidney function. In addition to an elevated concentration, the existence of truncated RBP4 species, RBP4-L (truncated at last C-terminal leucine) and RBP4-LL (truncated at both C-terminal leucines), has been reported in serum of hemodialysis patients. Since little is known about the occurrence of RBP4 species during the progression of CKD it was the aim of this study to analyse this possible association. The presence of RBP4, RBP4-L, RBP4- LL and transthyretin (TTR) was assessed in serum of 45 healthy controls and 52 patients with stage 2-5 of CKD using ELISA and RBP4 immunoprecipitation with subsequent MALDI-TOF-MS analysis. A reduction of glomerular filtration rate was accompanied by a gradual elevation of RBP4 serum levels and relative amounts of RBP4-LL. Correlation analysis revealed a strong association of the RBP4-TTR ratio with parameters of lipid metabolism and with diabetes-related factors. In conclusion, RBP4 serum concentration and the appearance of RBP4-LL seem to be influenced by kidney function. Furthermore, the RBP4-TTR ratio may provide diagnostic potential with regard to metabolic complications in CKD patients.}, language = {en} } @article{FreyHenzeNagletal.2009, author = {Frey, Simone K. and Henze, Andrea and Nagl, Britta and Raila, Jens and Scholze, Alexandra and Tepel, Martin and Schweigert, Florian J. and Zidek, Walter}, title = {Effect of renal replacement therapy on retinol-binding protein 4 isoforms}, issn = {0009-8981}, doi = {10.1016/j.cca.2008.11.008}, year = {2009}, abstract = {Background: Retinol-binding protein 4 (RBP4) levels are elevated in the serum of patients with kidney dysfunction. We recently showed that RBP4 isoforms including apo-RBP4 (RBP4 not bound to retinol) and RBP4 truncated at the C-terminus (RBP4-L, RBP4-LL) are increased in the serum of patients with kidney diseases but not in serum of patients with various liver diseases. The aim of this study was to investigate the effect of renal replacement therapy on RBP4 isoforms. Methods: We investigated serum levels of RBP4, apo-RBP4, holo-RBP4, RBP4-L, RBP4-LL, retinol and transthyretin (TTR) in 18 hemodialysis (HD) patients, 30 patients after renal transplantation (RTx) and in 35 healthy controls. RBP4 and TTR levels were measured by enzyme-linked immunosorbent assay, apo- and holo-RBP4 by native electrophoresis, retinol by high performance liquid chromatography and RBP4-L and RBP4-LL were analyzed by mass spectrometry. Results: HD and RTx patients had elevated RBP4, apo-RBP4 and RBP4-LL levels compared to controls. RTx patients had elevated amounts of RBP4-L compared to controls and elevated RBP4 and apo-RBP4 levels compared to HD patients. Conclusion: The results demonstrate a strong correlation between kidney function and RBP4 isoforms and provide data for investigating the relation of RBP4 and insulin resistance in these patients.}, language = {en} }