@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}
}
@article{RailaEnjalbertMothesetal.2012,
  author    = {Raila, Jens and Enjalbert, Francis and Mothes, Ralf and Hurtienne, Andrea and Schweigert, Florian J.},
  title     = {Validation of a new point-of-care assay for determination of ss-carotene concentration in bovine whole blood and plasma},
  series = {Veterinary clinical pathology},
  volume    = {41},
  journal   = {Veterinary clinical pathology},
  number    = {1},
  publisher = {Wiley-Blackwell},
  address   = {Malden},
  issn      = {0275-6382},
  doi       = {10.1111/j.1939-165X.2012.00400.x},
  pages     = {119 -- 122},
  year      = {2012},
  abstract  = {Background: beta-Carotene is an important precursor of vitamin A, and is associated with bovine fertility. beta-Carotene concentrations in plasma are used to optimize beta-carotene supplementation in cattle, but measurement requires specialized equipment to separate plasma and extract and measure beta-carotene, either using spectrophotometry or high performance liquid chromatography (HPLC). Objective: The objective of this study was to validate a new 2-step point-of-care (POC) assay for measuring beta-carotene in whole blood and plasma. Methods: beta-carotene concentrations in plasma from 166 cows were measured using HPLC and compared with results obtained using a POC assay, the iCheck-iEx-Carotene test kit. Whole blood samples from 23 of these cattle were also evaluated using the POC assay and compared with HPLC-plasma results from the same 23 animals. The POC assay includes an extraction vial (iEx Carotene) and hand-held photometer (iCheck Carotene). Results: Concentrations of beta-carotene in plasma measured using the POC assay ranged from 0.40 to 15.84 mg/L (n = 166). No differences were observed between methods for assay of plasma (mean +/- SD; n = 166): HPLC-plasma 4.23 +/- 2.35 mg/L; POC-plasma 4.49 +/- 2.36 mg/L. Similar good agreement was found when plasma analyzed using HPLC was compared with whole blood analyzed using the POC system (n = 23): HPLC-plasma 3.46 +/- 2.12 mg/L; POC-whole blood 3.67 +/- 2.29 mg/L. Conclusions: Concentrations of beta-carotene can be measured in blood and plasma from cattle easily and rapidly using a POC assay, and results are comparable to those obtained by the highly sophisticated HPLC method. Immediate feedback regarding beta-carotene deficiency facilitates rapid and appropriate optimization of beta-carotene supplementation in feed.},
  language  = {en}
}
@misc{MorrisSaltRailaetal.2012,
  author    = {Morris, Penelope J. and Salt, Carina and Raila, Jens and Brenten, Thomas and Kohn, Barbara and Schweigert, Florian J. and Zentek, J{\"u}rgen},
  title     = {Safety evaluation of vitamin A in growing dogs},
  series = {Potsprints der Universit{\"a}t Potsdam : Mathematisch-Naturwissenschaftliche Reihe},
  journal   = {Potsprints der Universit{\"a}t Potsdam : Mathematisch-Naturwissenschaftliche Reihe},
  number    = {686},
  doi       = {10.25932/publishup-41492},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-414929},
  pages     = {10},
  year      = {2012},
  abstract  = {The safe upper limit for inclusion of vitamin A in complete diets for growing dogs is uncertain, with the result that current recommendations range from 5.24 to 104.80 mu mol retinol (5000 to 100 000 IU vitamin A)/4184 kJ (1000 kcal) metabolisable energy (ME). The aim of the present study was to determine the effect of feeding four concentrations of vitamin A to puppies from weaning until 1 year of age. A total of forty-nine puppies, of two breeds, Labrador Retriever and Miniature Schnauzer, were randomly assigned to one of four treatment groups. Following weaning at 8 weeks of age, puppies were fed a complete food supplemented with retinyl acetate diluted in vegetable oil and fed at 1ml oil/100 g diet to achieve an intake of 5.24, 13.10, 78.60 and 104.80 mu mol retinol (5000, 12 500, 75 000 and 100 000 IU vitamin A)/4184 kJ (1000 kcal) ME. Fasted blood and urine samples were collected at 8, 10, 12, 14, 16, 20, 26, 36 and 52 weeks of age and analysed for markers of vitamin A metabolism and markers of safety including haematological and biochemical variables, bone-specific alkaline phosphatase, cross-linked carboxyterminal telopeptides of type I collagen and dual-energy X-ray absorptiometry. Clinical examinations were conducted every 4 weeks. Data were analysed by means of a mixed model analysis with Bonferroni corrections for multiple endpoints. There was no effect of vitamin A concentration on any of the parameters, with the exception of total serum retinyl esters, and no effect of dose on the number, type and duration of adverse events. We therefore propose that 104.80 mu mol retinol (100 000 IU vitamin A)/4184 kJ (1000 kcal) is a suitable safe upper limit for use in the formulation of diets designed for puppy growth.},
  language  = {en}
}
@article{KuhlAurichWulfetal.2012,
  author    = {Kuhl, Juliane and Aurich, J{\"o}rg E. and Wulf, Manuela and Hurtienne, A. and Schweigert, Florian J. and Aurich, Christine},
  title     = {Effects of oral supplementation with beta-carotene on concentrations of beta-carotene, vitamin A and alpha-tocopherol in plasma, colostrum and milk of mares and plasma of their foals and on fertility in mares},
  series = {Journal of animal physiology and animal nutrition},
  volume    = {96},
  journal   = {Journal of animal physiology and animal nutrition},
  number    = {3},
  publisher = {Wiley-Blackwell},
  address   = {Malden},
  issn      = {0931-2439},
  doi       = {10.1111/j.1439-0396.2011.01150.x},
  pages     = {376 -- 384},
  year      = {2012},
  abstract  = {In this study, effects of oral beta-carotene supplementation to mares (beta-carotene group: 1000 mg/day, n = 15; control group: n = 15) from 2 weeks before foaling until 6 weeks thereafter on concentrations of beta-carotene, vitamin A and a-tocopherol in plasma, colostrum and milk and plasma of their foals were determined. In addition, effects on fertility were studied. Beta-carotene concentrations increased in plasma and colostrum of beta-carotene-supplemented mares compared to control mares (p < 0.05). In mares of both groups, beta-carotene concentrations were higher in colostrum than in milk (p < 0.05). In foals, beta-carotene concentrations increased with colostrum uptake and were higher in foals born to supplemented mares (p < 0.05; control group: 0.0003 +/- 0.0002 mu g/ml on day 0, 0.008 +/- 0.0023 mu g/ml on day 1; beta-carotene group: 0.0005 +/- 0.0003 mu g/ml on day 0, 0.048 +/- 0.018 mu g/ml on day 1). Concentrations of vitamin A and a-tocopherol were higher in colostrum than in milk (p < 0.05) but did not differ between groups. Concentration of a-tocopherol in plasma of mares decreased over time and in foals, increased markedly within 4 days after birth. All but one mare (control group) showed oestrus within 2 weeks post-partum. Occurrence of oestrus did not differ between groups. More mares of the control group (7/7 vs. 5/12 in the beta-carotene group) became pregnant after being bred in first post-partum oestrus (p < 0.05). In conclusion, beta-carotene supplementation to mares increased beta-carotene concentrations in plasma, colostrum and milk of mares and plasma of their foals but had no positive effects on fertility.},
  language  = {en}
}
@article{GarciaRailaKoebnicketal.2006,
  author    = {Garcia, Ada Lizbeth and Raila, Jens and Koebnick, Corinna and Eulenberger, Klaus and Schweigert, Florian J.},
  title     = {Great apes show highly selective plasma carotenoids and have physiologically high plasma retinyl esters compared to humans},
  series = {American journal of physical anthropology},
  volume    = {131},
  journal   = {American journal of physical anthropology},
  number    = {2},
  publisher = {Wiley},
  address   = {Hoboken},
  issn      = {0002-9483},
  doi       = {10.1002/ajpa.20428},
  pages     = {236 -- 242},
  year      = {2006},
  abstract  = {Great apes are the closest living relatives of humans. Physiological similarities between great apes and humans provide clues to identify which biological features in humans are primitive or derived from great apes. Vitamin A (VA) and carotenoid metabolism have been only partially studied in great apes, and comparisons between great apes and humans are not available. We aimed to investigate VA and carotenoid intake and plasma concentrations in great apes living in captivity, and to compare them to healthy humans. Dietary intakes of humans (n = 20) and, among the great apes, chimpanzees (n = 15) and orangutans (n = 5) were calculated. Plasma retinol (ROH), retinol-binding protein (RBP), retinyl esters, and major carotenoids were analyzed. The great ape diet was higher in VA than in humans, due to high intake of provitamin A carotenoids. Plasma ROH concentrations in great apes were similar to those in humans, but retinyl esters were higher in great apes than in humans. Differences in plasma carotenoid concentrations were observed between great apes and humans. Lutein was the main carotenoid in great apes, while P-carotene was the main carotenoid for humans. RBP concentrations did not differ between great apes and humans. The molar ratio of ROH to RBP was close to 1.0 in both great apes and humans. In conclusion, great apes show homeostatic ROH regulation, with high but physiological retinyl esters circulating in plasma. Furthermore, great apes show great selectivity in their plasmatic carotenoid concentration, which is not explained by dietary intake.},
  language  = {en}
}
@article{ChupeerachHarnroongrojPhonratetal.2011,
  author    = {Chupeerach, Chaowanee and Harnroongroj, Talabporn and Phonrat, Benjaluck and Tungtrongchitr, Anchalee and Schweigert, Florian J. and Tungtrongchitr, Rungsunn and Preutthipan, Sangchai},
  title     = {Decreased retinol transport proteins in thai post-menopausal women with Osteporosis},
  series = {The Southeast Asian journal of tropical medicine and public health : official publication of the SEAMEO Regional Tropical Medicine and Public Health Project (TROPMED)},
  volume    = {42},
  journal   = {The Southeast Asian journal of tropical medicine and public health : official publication of the SEAMEO Regional Tropical Medicine and Public Health Project (TROPMED)},
  number    = {6},
  publisher = {SEAMEO},
  address   = {Bangkok},
  issn      = {0125-1562},
  pages     = {1515 -- 1520},
  year      = {2011},
  abstract  = {High vitamin A ingestion or high serum retinol have been postulated to increase the risk of fractures and osteoporosis by reduced bone mineral density (BMD). Retinol is carried and transported to the tissues bound to retinol binding protein 4 (RBP4) and transthyretin (TTR). The relationships between retinol, retinol transport protein, retinol binding protein 4 (RBP4) and transthyretin (TTR) and BMD and osteoporosis are unclear. To examine the association between retinol and RBP4 and TTR and osteoporosis, 73 osteoporotic and 71 normal Thai postmenopausal women were studied. RBP4 and retinol levels did not differ between the groups. Serum TTR was significantly higher in control than osteoporotic subjects (89.47 and 144.53 mu g/ml, respectively, p=0.003, Mann-Whitney U test). TTR was positively correlated with BMD at several sites, such as the total radius bone (r=0.172, p=0.008, Spearman rank test). Osteoporosis risk was analyzed with binary logistic regression. Lean elderly Thais with lower TTR levels had a higher risk of osteoporosis. RBP4 and retinol levels had no relationship with disease status among Thai post-menopausal women. These results suggest calcium, minerals, vitamins and the retinol transport protein, transthyretin may be involved in the pathogenesis of osteoporosis.},
  language  = {en}
}
@misc{BrentenMorrisSaltetal.2014,
  author    = {Brenten, Thomas and Morris, Penelope J. and Salt, Carina and Raila, Jens and Kohn, Barbara and Brunnberg, Leo and Schweigert, Florian J. and Zentek, J{\"u}rgen},
  title     = {Energy intake, growth rate and body composition of young Labrador Retrievers and Miniature Schnauzers fed different dietary levels of vitamin A},
  series = {Postprints der Universit{\"a}t Potsdam : Mathematisch-Naturwissenschaftliche Reihe},
  journal   = {Postprints der Universit{\"a}t Potsdam : Mathematisch-Naturwissenschaftliche Reihe},
  number    = {603},
  issn      = {1866-8372},
  doi       = {10.25932/publishup-41568},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-415681},
  pages     = {8},
  year      = {2014},
  abstract  = {Research in rodents has shown that dietary vitamin A reduces body fat by enhancing fat mobilisation and energy utilisation; however, their effects in growing dogs remain unclear. In the present study, we evaluated the development of body weight and body composition and compared observed energy intake with predicted energy intake in forty-nine puppies from two breeds (twenty-four Labrador Retriever (LAB) and twenty-five Miniature Schnauzer (MS)). A total of four different diets with increasing vitamin A content between 5.24 and 104.80 mu mol retinol (5000-100 000 IU vitamin A)/4184 kJ (1000 kcal) metabolisable energy were fed from the age of 8 weeks up to 52 (MS) and 78 weeks (LAB). The daily energy intake was recorded throughout the experimental period. The body condition score was evaluated weekly using a seven-category system, and food allowances were adjusted to maintain optimal body condition. Body composition was assessed at the age of 26 and 52 weeks for both breeds and at the age of 78 weeks for the LAB breed only using dual-energy X-ray absorptiometry. The growth curves of the dogs followed a breed-specific pattern. However, data on energy intake showed considerable variability between the two breeds as well as when compared with predicted energy intake. In conclusion, the data show that energy intakes of puppies particularly during early growth are highly variable; however, the growth pattern and body composition of the LAB and MS breeds are not affected by the intake of vitamin A at levels up to 104.80 mu mol retinol (100 000 IU vitamin A)/4184 kJ (1000 kcal).},
  language  = {en}
}
@article{BechirSchellingKraemeretal.2012,
  author    = {Bechir, Mahamat and Schelling, E. and Kr{\"a}mer, K. and Schweigert, Florian J. and Bonfoh, Bassirou and Crump, L. and Tanner, M. and Zinsstag, J.},
  title     = {Retinol assessment among women and children in sahelian mobile pastoralists},
  series = {EcoHealth : conservation medicine, human health, ecosystem sustainability},
  volume    = {9},
  journal   = {EcoHealth : conservation medicine, human health, ecosystem sustainability},
  number    = {2},
  publisher = {Springer},
  address   = {New York},
  issn      = {1612-9202},
  doi       = {10.1007/s10393-012-0781-7},
  pages     = {113 -- 121},
  year      = {2012},
  abstract  = {Micronutrient deficiencies are widespread in developing countries, particularly in remote communities such as mobile pastoralists. The nutritional and vitamin A status of this population is not well-documented in Chad. This study assessed serum retinol levels among women and children under five-year-old in nomadic and semi-nomadic pastoralist and rural-settled communities, who are similarly exposed to risk factors such as gastrointestinal parasitic infection, anaemia and emaciation. The novel method of portable fluorometry was used for the first time to measure beta-carotene and retinol levels in a pastoral nomadic area. Moderate level blood retinol deficiency (< 0.7 mu mol/L) was observed in 5\% (CI 1-11) of nomadic, 29\% (CI 13-45) of semi-nomadic and 22\% (CI 8-35) of sedentary women. In children, 1\% (CI 0.1-4), 17\% (CI 9-25) and 28\% (CI 18-39), respectively, had moderate level blood retinol deficiency. In nomadic communities, women and children had blood retinol levels close to normal. Deficiency of retinol was strongly linked with lifestyle (nomadic, semi-nomadic and settled) among women and lifestyle and age among children. The results support an ecological linkage between human retinol levels and livestock milk retinol. This study shows the feasibility of portable retinol and beta-carotene measurement in human blood as well as human and animal milk under remote field conditions, but the approach requires further validation.},
  language  = {en}
}