@article{NaglLouiRailaetal.2009, author = {Nagl, Britta and Loui, Andrea and Raila, Jens and Felderhoff-Mueser, Ursula and Obladen, Michael and Schweigert, Florian J.}, title = {Urinary vitamin A excretion in very low birth weight infants}, issn = {0931-041X}, doi = {10.1007/s00467-008-0965-0}, year = {2009}, abstract = {Vitamin A (VA) deficiency in very low birth weight (VLBW) infants is associated with an increased risk for disorders related to kidney and lung maturation and function. VA losses through increased urinary retinol (ROH) excretion might contribute to this deficiency risk. The mechanism accounting for ROH loss in the urine has not yet been clarified. The aim of this study was to assess the excretion of ROH, retinol-binding protein 4 (RBP4) and transthyretin (TTR) in urine from VLBW infants in comparison with that in term infants in relation to kidney function. Urine specimens were collected from 15 VLBW infants (birth weight < 1,500 g) as well as from 20 term infants during the first 2 days after birth. ROH in urine was detectable in 14 of the 15 VLBW infants at a median concentration of 234 nmol/g creatinine. In the group of term infants, 17 of the 20 excreted ROH, but at an approximately five-times lower concentration (P<0.001). Excretion of RBP4 and TTR was also much higher in VLBW infants (both P<0.001). The urinary ROH excretion in VLBW infants may be related to the impaired tubular handling of its carrier proteins RBP4 and TTR. Thus, ROH excretion might contribute to an increased risk of VA deficiency, especially in VLBW infants.}, language = {en} } @article{SchmiedchenLongardtBuehreretal.2014, author = {Schmiedchen, Bettina and Longardt, Ann Carolin and Buehrer, Christoph and Raila, Jens and Loui, Andrea and Schweigert, Florian J.}, title = {The relative dose response test based on retinol-binding protein 4 is not suitable to assess vitamin A status in very low birth weight infants}, series = {Neonatology : fetal and neonatal research}, volume = {105}, journal = {Neonatology : fetal and neonatal research}, number = {2}, publisher = {Karger}, address = {Basel}, issn = {1661-7800}, doi = {10.1159/000356773}, pages = {155 -- 160}, year = {2014}, language = {en} } @article{SchmiedchenLongardtLouietal.2016, author = {Schmiedchen, Bettina and Longardt, Ann Carolin and Loui, Andrea and Buehrer, Christoph and Raila, Jens and Schweigert, Florian J.}, title = {Effect of vitamin A supplementation on the urinary retinol excretion in very low birth weight infants}, series = {European journal of pediatrics : official organ of the Belgian Pediatric Association}, volume = {175}, journal = {European journal of pediatrics : official organ of the Belgian Pediatric Association}, publisher = {Springer}, address = {New York}, issn = {0340-6199}, doi = {10.1007/s00431-015-2647-9}, pages = {365 -- 372}, year = {2016}, abstract = {Despite high-dose vitamin A supplementation of very low birth weight infants (VLBW, <1500 g), their vitamin A status does not improve substantially. Unknown is the impact of urinary retinol excretion on the serum retinol concentration in these infants. Therefore, the effect of high-dose vitamin A supplementation on the urinary vitamin A excretion in VLBW infants was investigated. Sixty-three VLBW infants were treated with vitamin A (5000 IU intramuscular, 3 times/week for 4 weeks); 38 untreated infants were classified as control group. On days 3 and 28 of life, retinol, retinol-binding protein 4 (RBP4), glomerular filtration rate, proteinuria, and Tamm-Horsfall protein were quantified in urine. On day 3 of life, substantial retinol and RBP4 losses were found in both groups, which significantly decreased until day 28. Notwithstanding, the retinol excretion was higher (P<0.01) under vitamin A supplementation as compared to infants of the control group. On day 28 of life, the urinary retinol concentrations were predictive for serum retinol concentrations in the vitamin A treated (P<0.01), but not in the control group (P=0.570). Conclusion: High urinary retinol excretion may limit the vitamin A supplementation efficacy in VLBW infants. Advanced age and thus postnatal kidney maturation seems to be an important contributor in the prevention of urinary retinol losses.}, language = {en} } @misc{SchmiedchenLongardtBuehreretal.2017, author = {Schmiedchen, Bettina and Longardt, Ann Carolin and B{\"u}hrer, Christoph and Raila, Jens and Loui, Andrea and Schweigert, Florian J.}, title = {The Relative Dose Response Test Based on Retinol-Binding Protein 4 Is Not Suitable to Assess Vitamin A Status in Very Low Birth Weight Infants}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-399853}, pages = {6}, year = {2017}, abstract = {Background: The relative dose response (RDR) test, which quantifies the increase in serum retinol after vitamin A administration, is a qualitative measure of liver vitamin A stores. Particularly in preterm infants, the feasibility of the RDR test involving blood is critically dependent on small sample volumes. Objectives: This study aimed to assess whether the RDR calculated with retinol-binding protein 4 (RBP4) might be a substitute for the classical retinol-based RDR test for assessing vitamin A status in very preterm infants. Methods: This study included preterm infants with a birth weight below 1,500 g (n = 63, median birth weight 985 g, median gestational age 27.4 weeks) who were treated with 5,000 IU retinyl palmitate intramuscularly 3 times a week for 4 weeks. On day 3 (first vitamin A injection) and day 28 of life (last vitamin A injection), the RDR was calculated and compared using serum retinol and RBP4 concentrations. Results: The concentrations of retinol (p < 0.001) and RBP4 (p < 0.01) increased significantly from day 3 to day 28. On day 3, the median (IQR) retinol-RDR was 27\% (8.4-42.5) and the median RBP4-RDR was 8.4\% (-3.4 to 27.9), compared to 7.5\% (-10.6 to 20.8) and -0.61\% (-19.7 to 15.3) on day 28. The results for retinol-RDR and RBP4-RDR revealed no significant correlation. The agreement between retinol-RDR and RBP4-RDR was poor (day 3: Cohen's κ = 0.12; day 28: Cohen's κ = 0.18). Conclusion: The RDR test based on circulating RBP4 is unlikely to reflect the hepatic vitamin A status in preterm infants.}, language = {en} }