@article{MaaresKeilKozaetal.2018,
  author    = {Maares, Maria and Keil, Claudia and Koza, Jenny and Straubing, Sophia and Schwerdtle, Tanja and Haase, Hajo},
  title     = {In Vitro Studies on Zinc Binding and Buffering by Intestinal Mucins},
  series = {International Journal of Molecular Sciences},
  volume    = {19},
  journal   = {International Journal of Molecular Sciences},
  number    = {9},
  issn      = {1422-0067},
  doi       = {10.3390/ijms19092662},
  pages     = {20},
  year      = {2018},
  abstract  = {The investigation of luminal factors influencing zinc availability and accessibility in the intestine is of great interest when analyzing parameters regulating intestinal zinc resorption. Of note, intestinal mucins were suggested to play a beneficial role in the luminal availability of zinc. Their exact zinc binding properties, however, remain unknown and the impact of these glycoproteins on human intestinal zinc resorption has not been investigated in detail. Thus, the aim of this study is to elucidate the impact of intestinal mucins on luminal uptake of zinc into enterocytes and its transfer into the blood. In the present study, in vitro zinc binding properties of mucins were analyzed using commercially available porcine mucins and secreted mucins of the goblet cell line HT-29-MTX. The molecular zinc binding capacity and average zinc binding affinity of these glycoproteins demonstrates that mucins contain multiple zinc-binding sites with biologically relevant affinity within one mucin molecule. Zinc uptake into the enterocyte cell line Caco-2 was impaired by zinc-depleted mucins. Yet this does not represent their form in the intestinal lumen in vivo under zinc adequate conditions. In fact, zinc-uptake studies into enterocytes in the presence of mucins with differing degree of zinc saturation revealed zinc buffering by these glycoproteins, indicating that mucin-bound zinc is still available for the cells. Finally, the impact of mucins on zinc resorption using three-dimensional cultures was studied comparing the zinc transfer of a Caco-2/HT-29-MTX co-culture and conventional Caco-2 monoculture. Here, the mucin secreting co-cultures yielded higher fractional zinc resorption and elevated zinc transport rates, suggesting that intestinal mucins facilitate the zinc uptake into enterocytes and act as a zinc delivery system for the intestinal epithelium.},
  language  = {en}
}
@misc{MaaresKeilKozaetal.2018,
  author    = {Maares, Maria and Keil, Claudia and Koza, Jenny and Straubing, Sophia and Schwerdtle, Tanja and Haase, Hajo},
  title     = {In Vitro Studies on Zinc Binding and Buffering by Intestinal Mucins},
  series = {Postprints der Universit{\"a}t Potsdam : Mathematisch-Naturwissenschaftliche Reihe},
  journal   = {Postprints der Universit{\"a}t Potsdam : Mathematisch-Naturwissenschaftliche Reihe},
  number    = {1079},
  issn      = {1866-8372},
  doi       = {10.25932/publishup-46907},
  url       = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-469078},
  pages     = {22},
  year      = {2018},
  abstract  = {The investigation of luminal factors influencing zinc availability and accessibility in the intestine is of great interest when analyzing parameters regulating intestinal zinc resorption. Of note, intestinal mucins were suggested to play a beneficial role in the luminal availability of zinc. Their exact zinc binding properties, however, remain unknown and the impact of these glycoproteins on human intestinal zinc resorption has not been investigated in detail. Thus, the aim of this study is to elucidate the impact of intestinal mucins on luminal uptake of zinc into enterocytes and its transfer into the blood. In the present study, in vitro zinc binding properties of mucins were analyzed using commercially available porcine mucins and secreted mucins of the goblet cell line HT-29-MTX. The molecular zinc binding capacity and average zinc binding affinity of these glycoproteins demonstrates that mucins contain multiple zinc-binding sites with biologically relevant affinity within one mucin molecule. Zinc uptake into the enterocyte cell line Caco-2 was impaired by zinc-depleted mucins. Yet this does not represent their form in the intestinal lumen in vivo under zinc adequate conditions. In fact, zinc-uptake studies into enterocytes in the presence of mucins with differing degree of zinc saturation revealed zinc buffering by these glycoproteins, indicating that mucin-bound zinc is still available for the cells. Finally, the impact of mucins on zinc resorption using three-dimensional cultures was studied comparing the zinc transfer of a Caco-2/HT-29-MTX co-culture and conventional Caco-2 monoculture. Here, the mucin secreting co-cultures yielded higher fractional zinc resorption and elevated zinc transport rates, suggesting that intestinal mucins facilitate the zinc uptake into enterocytes and act as a zinc delivery system for the intestinal epithelium.},
  language  = {en}
}
@article{MaaresDumanKeiletal.2018,
  author    = {Maares, Maria and Duman, Ayse and Keil, Claudia and Schwerdtle, Tanja and Haase, Hajo},
  title     = {The impact of apical and basolateral albumin on intestinal zinc resorption in the Caco-2/HT-29-MTX co-culture model},
  series = {Metallomics : integrated biometal science},
  volume    = {10},
  journal   = {Metallomics : integrated biometal science},
  number    = {7},
  publisher = {Royal Society of Chemistry},
  address   = {Cambridge},
  issn      = {1756-5901},
  doi       = {10.1039/c8mt00064f},
  pages     = {979 -- 991},
  year      = {2018},
  abstract  = {The molecular mechanisms of intestinal zinc resorption and its regulation are still topics of ongoing research. To this end, the application of suitable in vitro intestinal models, optimized with regard to their cellular composition and medium constituents, is of crucial importance. As one vital aspect, the impact of cell culture media or buffer compounds, respectively, on the speciation and cellular availability of zinc has to be considered when investigating zinc resorption. Thus, the present study aims to investigate the impact of serum, and in particular its main constituent serum albumin, on zinc uptake and toxicity in the intestinal cell line Caco-2. Furthermore, the impact of serum albumin on zinc resorption is analyzed using a co-culture of Caco-2 cells and the mucin-producing goblet cell line HT-29-MTX. Apically added albumin significantly impaired zinc uptake into enterocytes and buffered its cytotoxicity. Yet, undigested albumin does not occur in the intestinal lumen in vivo and impairment of zinc uptake was abrogated by digestion of albumin. Interestingly, zinc uptake, as well as gene expression studies of mt1a and selected intestinal zinc transporters after zinc incubation for 24 h, did not show significant differences between 0 and 10\% serum. Importantly, the basolateral application of serum in a transport study significantly enhanced fractional apical zinc resorption, suggesting that the occurrence of a zinc acceptor in the plasma considerably affects intestinal zinc resorption. This study demonstrates that the apical and basolateral medium composition is crucial when investigating zinc, particularly its intestinal resorption, using in vitro cell culture.},
  language  = {en}
}
@misc{ZeiherDuchKrolletal.2019,
  author    = {Zeiher, Johannes and Duch, M. and Kroll, Lars Eric and Mensink, Gerhardus Bernardus Maria and Finger, Jonas David and Keil, Thomas},
  title     = {Domain-specific physical activity patterns and cardiorespiratory fitness among adults in Germany},
  series = {The European Journal of Public Health},
  volume    = {29},
  journal   = {The European Journal of Public Health},
  number    = {Supplement. 4},
  publisher = {Oxford Univ. Press},
  address   = {Oxford},
  issn      = {1101-1262},
  pages     = {1},
  year      = {2019},
  abstract  = {Background Studies show that occupational physical activity (OPA) has less health-enhancing effects than leisure-time physical activity (LTPA). The spare data available suggests that OPA rarely includes aerobic PAs with little or no enhancing effects on cardiorespiratory fitness (CRF) as a possible explanation. This study aims to investigate the associations between patterns of OPA and LTPA and CRF among adults in Germany. Methods 1,204 men and 1,303 women (18-64 years), who participated in the German Health Interview and Examination Survey 2008-2011, completed a standardized sub-maximal cycle ergometer test to estimate maximal oxygen consumption (VO2max). Job positions were coded according to the level of physical effort to construct an occupational PA index and categorized as low vs. high OPA. LTPA was assessed via questionnaires and dichotomized in no vs. any LTPA participation. A combined LTPA/OPA variable was used (high OPA/ LTPA, low OPA/LTPA, high OPA/no LTPA, low OPA/no LTPA). Information on potential confounders was obtained via questionnaires (e.g., smoking and education) or physical measurements (e.g., waist circumference). Multi-variable logistic regression was used to analyze associations between OPA/LTPA patterns and VO2max. Results Preliminary analyses showed that less-active men were more likely to have a low VO2max with odds ratios (ORs) of 0.80 for low OPA/LTPA, 1.84 for high OPA/no LTPA and 3.46 for low OPA/no LTPA compared to high OPA/LTPA. The corresponding ORs for women were 1.11 for low OPA/LTPA, 3.99 for high OPA/no LTPA and 2.44 for low OPA/no LTPA, indicating the highest likelihood of low fitness for women working in physically demanding jobs and not engaging in LTPA. Conclusions Findings confirm a strong association between LTPA and CRF and suggest an interaction between OPA and LTPA patterns on CRF within the workforce in Germany. Women without LTPA are at high risk of having a low CRF, especially if they work in physically demanding jobs. Key messages Women not practicing leisure-time physical activity are at risk of having a low cardiorespiratory fitness, especially if they work in physically demanding jobs. Different impact of domains of physical activity should be considered when planning interventions to enhance fitness among the adult population.},
  language  = {en}
}
@article{SchmitzSchmidtWellenburgWitteetal.2020,
  author    = {Schmitz, Andreas and Schmidt-Wellenburg, Christian and Witte, Daniel and Keil, Maria},
  title     = {In welcher Gesellschaft forschen wir eigentlich?},
  series = {Zeitschrift f{\"u}r theoretische Soziologie},
  volume    = {8},
  journal   = {Zeitschrift f{\"u}r theoretische Soziologie},
  number    = {2},
  publisher = {Beltz Juventa},
  address   = {Weinheim},
  issn      = {2195-0695},
  doi       = {10.3262/ZTS1902245},
  pages     = {245 -- 281},
  year      = {2020},
  language  = {de}
}